Sample records for underlying soil substrate
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Bitterlich, Michael; Franken, Philipp; Graefe, Jan
2018-01-01
Arbuscular mycorrhizal fungi (AMF) proliferate in soils and are known to affect soil structure. Although their contribution to structure is extensively investigated, the consequences of those processes for soil water extractability and transport has, so far, gained surprisingly little attention. Therefore we asked, whether AMF can affect water retention and unsaturated hydraulic conductivity under exclusion of root ingrowth, in order to minimize plant driven effects. We carried out experiments with tomato inoculated with Rhizoglomus irregulare in a soil substrate with sand and vermiculite that created variation in colonization by mixed pots with wild type (WT) plants and mycorrhiza resistant (RMC) mutants. Sampling cores were introduced and used to assess substrate moisture retention dynamics and modeling of substrate water retention and hydraulic conductivity. AMF reduced the saturated water content and total porosity, but maintained air filled porosity in soil spheres that excluded root ingrowth. The water content between field capacity and the permanent wilting point (6-1500 kPa) was only reduced in mycorrhizal substrates that contained at least one RMC mutant. Plant available water contents correlated positively with soil protein contents. Soil protein contents were highest in pots that possessed the strongest hyphal colonization, but not significantly affected. Substrate conductivity increased up to 50% in colonized substrates in the physiologically important water potential range between 6 and 10 kPa. The improvements in hydraulic conductivity are restricted to substrates where at least one WT plant was available for the fungus, indicating a necessity of a functional symbiosis for this effect. We conclude that functional mycorrhiza alleviates the resistance to water movement through the substrate in substrate areas outside of the root zone.
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Jia, Xiaohong; Zhou, Xuhui; Luo, Yiqi; Xue, Kai; Xue, Xian; Xu, Xia; Yang, Yuanhe; Wu, Liyou; Zhou, Jizhong
2014-01-01
Regulatory mechanisms of soil respiratory carbon (C) release induced by substrates (i.e., plant derived substrates) are critical for predicting ecosystem responses to climate change, but the mechanisms are not well understood. In this study, we sampled soils from a long-term field manipulative experiment and conducted a laboratory incubation to explore the role of substrate supply in regulating the differences in soil C release among the experimental treatments, including control, warming, clipping, and warming plus clipping. Three types of substrates (glucose, C3 and C4 plant materials) were added with an amount equal to 1% of soil dry weight under the four treatments. We found that the addition of all three substrates significantly stimulated soil respiratory C release in all four warming and clipping treatments. In soils without substrate addition, warming significantly stimulated soil C release but clipping decreased it. However, additions of glucose and C3 plant materials (C3 addition) offset the warming effects, whereas C4 addition still showed the warming-induced stimulation of soil C release. Our results suggest that long-term warming may inhibit microbial capacity for decomposition of C3 litter but may enhance it for decomposition of C4 litter. Such warming-induced adaptation of microbial communities may weaken the positive C-cycle feedback to warming due to increased proportion of C4 species in plant community and decreased litter quality. In contrast, clipping may weaken microbial capacity for warming-induced decomposition of C4 litter but may enhance it for C3 litter. Warming- and clipping-induced shifts in microbial metabolic capacity may be strongly associated with changes in plant species composition and could substantially influence soil C dynamics in response to global change. PMID:25490701
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Jia, Xiaohong; Zhou, Xuhui; Luo, Yiqi; Xue, Kai; Xue, Xian; Xu, Xia; Yang, Yuanhe; Wu, Liyou; Zhou, Jizhong
2014-01-01
Regulatory mechanisms of soil respiratory carbon (C) release induced by substrates (i.e., plant derived substrates) are critical for predicting ecosystem responses to climate change, but the mechanisms are not well understood. In this study, we sampled soils from a long-term field manipulative experiment and conducted a laboratory incubation to explore the role of substrate supply in regulating the differences in soil C release among the experimental treatments, including control, warming, clipping, and warming plus clipping. Three types of substrates (glucose, C3 and C4 plant materials) were added with an amount equal to 1% of soil dry weight under the four treatments. We found that the addition of all three substrates significantly stimulated soil respiratory C release in all four warming and clipping treatments. In soils without substrate addition, warming significantly stimulated soil C release but clipping decreased it. However, additions of glucose and C3 plant materials (C3 addition) offset the warming effects, whereas C4 addition still showed the warming-induced stimulation of soil C release. Our results suggest that long-term warming may inhibit microbial capacity for decomposition of C3 litter but may enhance it for decomposition of C4 litter. Such warming-induced adaptation of microbial communities may weaken the positive C-cycle feedback to warming due to increased proportion of C4 species in plant community and decreased litter quality. In contrast, clipping may weaken microbial capacity for warming-induced decomposition of C4 litter but may enhance it for C3 litter. Warming- and clipping-induced shifts in microbial metabolic capacity may be strongly associated with changes in plant species composition and could substantially influence soil C dynamics in response to global change.
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Bitterlich, Michael; Sandmann, Martin; Graefe, Jan
2018-01-01
Arbuscular mycorrhizal fungi (AMF) proliferate in soil pores, on the surface of soil particles and affect soil structure. Although modifications in substrate moisture retention depend on structure and could influence plant water extraction, mycorrhizal impacts on water retention and hydraulic conductivity were rarely quantified. Hence, we asked whether inoculation with AMF affects substrate water retention, water transport properties and at which drought intensity those factors become limiting for plant transpiration. Solanum lycopersicum plants were set up in the glasshouse, inoculated or not with Funneliformis mosseae , and grown for 35 days under ample water supply. After mycorrhizal establishment, we harvested three sets of plants, one before (36 days after inoculation) and the second (day 42) and third (day 47) within a sequential drying episode. Sampling cores were introduced into pots before planting. After harvest, moisture retention and substrate conductivity properties were assessed and water retention and hydraulic conductivity models were fitted. A root water uptake model was adopted in order to identify the critical substrate moisture that induces soil derived transpiration limitation. Neither substrate porosity nor saturated water contents were affected by inoculation, but both declined after substrates dried. Drying also caused a decline in pot water capacity and hydraulic conductivity. Plant available water contents under wet (pF 1.8-4.2) and dry (pF 2.5-4.2) conditions increased in mycorrhizal substrates and were conserved after drying. Substrate hydraulic conductivity was higher in mycorrhizal pots before and during drought exposure. After withholding water from pots, higher substrate drying rates and lower substrate water potentials were found in mycorrhizal substrates. Mycorrhiza neither affected leaf area nor root weight or length. Consistently with higher substrate drying rates, AMF restored the plant hydraulic status, and increased plant transpiration when soil moisture declined. The water potential at the root surface and the resistance to water flow in the rhizosphere were restored in mycorrhizal pots although the bulk substrate dried more. Finally, substrates colonized by AMF can be more desiccated before substrate water flux quantitatively limits transpiration. This is most pronounced under high transpiration demands and complies with a difference of over 1,000 hPa in substrate water potential.
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Fungal Taxa Target Different Carbon Substrates in Harvard Forest Soils
NASA Astrophysics Data System (ADS)
Hanson, C. A.; Allison, S. D.; Wallenstein, M. D.; Mellilo, J. M.; Treseder, K. K.
2006-12-01
The mineralization of soil organic carbon is a major component of the global carbon cycle and is largely controlled by soil microbial communities. However, little is known about the functional roles of soil microbes or whether different microbial taxa target different carbon substrates under natural conditions. To examine this possibility, we assessed the community composition of active fungi by using a novel nucleotide analog technique in soils from the Harvard Forest. We hypothesized that fungal community composition would shift in response to the addition of different substrates and that specific fungal taxa would respond differentially to particular carbon sources. To test this hypothesis, we added a nucleotide analog probe directly to soils in conjunction with one of five carbon compounds of increasing recalcitrance: glycine, sucrose, cellulose, tannin-protein complex, and lignin. During 48 hour incubations, the nucleotide analog was incorporated into newly replicated DNA of soil organisms that proliferated following the addition of the substrates. In this way, we labeled the DNA of microbes that respond to a particular carbon source. Labeled DNA was isolated and fungal Internal Transcribed Spacer (ITS) regions of ribosomal DNA (rDNA) were sequenced and analyzed to identify active fungi to near-species resolution. Diversity analyses at the ≥97% sequence similarity level indicated that taxonomic richness was greater under cellulose (Shannon Index: 3.23 ± 0.11 with ± 95% CI) and lignin (2.87 ± 0.15) additions than the other treatments (2.34 ± 0.16 to 2.64 ± 0.13). In addition, community composition of active fungi shifted under glycine, sucrose, and cellulose additions. Specifically, the community under glycine was significantly different from communities under control, cellulose, and tannin-protein (P<0.05). Additionally, the sucrose and cellulose communities were marginally different from the control community (P = 0.059 and 0.054, respectively) and each other (P = 0.058). Together these results support our hypothesis that fungal communities change in response to different carbon sources. We found 11 fungal operational taxonomic units (OTUs) whose relative abundances differed at least marginally significantly among substrates. One OTU related to Mortierella increased in abundance under cellulose, but was absent or rare under the other substrates. Another OTU related to an unidentified Basidiomycete was only present under lignin addition, while yet another OTU closely related to Mortierella macrocystis greatly increased in abundance under tannin-protein and slightly increased in response to lignin and sucrose. This confirms our hypothesis that particular taxa respond differently to specific carbon substrates and suggests that some fungal taxa may specialize in the break-down of particular carbon sources in soils. Overall, our results imply that microbes have varying roles in the mineralization of soil carbon, and thus microbial community composition may be an important control over ecosystem carbon dynamics and storage, especially in relation to global change.
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NASA Astrophysics Data System (ADS)
Cyle, K. T.; Martinez, C. E.
2017-12-01
Recent experimental work has elevated the importance of microbial processing for the stabilization of fresh carbon inputs within the soil mineral matrix. Enhancing our understanding of soil carbon and nitrogen dynamics therefore requires a better understanding of how efficiently microbial metabolism can process low molecular weight carbon substrates (carbon use efficiency, CUE) under environmentally relevant conditions. One approach to better understanding microbial uptake rates and CUE is the ecophysiological study of soil isolates in liquid media culture consisting of soil-extracted solubilized organic matter (SESOM). We are using SESOM from an Oa horizon under hemlock hardwood vegetation in upstate New York as liquid media for the growth of 12 isolates from the Oa and B horizon of the same site. Here we seek to test the uptake rates as well as CUE of 5 different low molecular weight substrates spanning compound class and nominal oxidation state (glucose, acetate, formate, glycine, valine) by isolates differing in phylogeny and physiology. The use of a spike of each of the 13C-labeled substrates into SESOM, along with a 0.2 μm filtration step, allows accurate partitioning of labeled carbon between biomass, gaseous CO2 as well as the exometabolome. Coupled UHPLC-MS measurements are being used to identify and determine uptake rates of over 80 potential C substrates present in the extract as well as our labeled substrate of interest along the course of the isolate growth curve. This work seeks to utilize a gradient in substrate class as well as microbial physiologies to inform our understanding of C and N cycling under relevant soil solution conditions. Future experiments may also use labeled biomass from stationary phase to investigate the stabilization potential of anabolic products formed from each substrate with a clay fraction isolated from the same site.
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Bitterlich, Michael; Sandmann, Martin; Graefe, Jan
2018-01-01
Arbuscular mycorrhizal fungi (AMF) proliferate in soil pores, on the surface of soil particles and affect soil structure. Although modifications in substrate moisture retention depend on structure and could influence plant water extraction, mycorrhizal impacts on water retention and hydraulic conductivity were rarely quantified. Hence, we asked whether inoculation with AMF affects substrate water retention, water transport properties and at which drought intensity those factors become limiting for plant transpiration. Solanum lycopersicum plants were set up in the glasshouse, inoculated or not with Funneliformis mosseae, and grown for 35 days under ample water supply. After mycorrhizal establishment, we harvested three sets of plants, one before (36 days after inoculation) and the second (day 42) and third (day 47) within a sequential drying episode. Sampling cores were introduced into pots before planting. After harvest, moisture retention and substrate conductivity properties were assessed and water retention and hydraulic conductivity models were fitted. A root water uptake model was adopted in order to identify the critical substrate moisture that induces soil derived transpiration limitation. Neither substrate porosity nor saturated water contents were affected by inoculation, but both declined after substrates dried. Drying also caused a decline in pot water capacity and hydraulic conductivity. Plant available water contents under wet (pF 1.8–4.2) and dry (pF 2.5–4.2) conditions increased in mycorrhizal substrates and were conserved after drying. Substrate hydraulic conductivity was higher in mycorrhizal pots before and during drought exposure. After withholding water from pots, higher substrate drying rates and lower substrate water potentials were found in mycorrhizal substrates. Mycorrhiza neither affected leaf area nor root weight or length. Consistently with higher substrate drying rates, AMF restored the plant hydraulic status, and increased plant transpiration when soil moisture declined. The water potential at the root surface and the resistance to water flow in the rhizosphere were restored in mycorrhizal pots although the bulk substrate dried more. Finally, substrates colonized by AMF can be more desiccated before substrate water flux quantitatively limits transpiration. This is most pronounced under high transpiration demands and complies with a difference of over 1,000 hPa in substrate water potential. PMID:29503655
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The Use of Arbuscular Mycorrhizal Fungi to Improve Strawberry Production in Coir Substrate
Robinson Boyer, Louisa; Feng, Wei; Gulbis, Natallia; Hajdu, Klara; Harrison, Richard J.; Jeffries, Peter; Xu, Xiangming
2016-01-01
Strawberry is an important fruit crop within the UK. To reduce the impact of soil-borne diseases and extend the production season, more than half of the UK strawberry production is now in substrate (predominantly coir) under protection. Substrates such as coir are usually depleted of microbes including arbuscular mycorrhizal fungi (AMF) and consequently the introduction of beneficial microbes is likely to benefit commercial cropping systems. Inoculating strawberry plants in substrate other than coir has been shown to increase plants tolerance to soil-borne pathogens and water stress. We carried out studies to investigate whether AMF could improve strawberry production in coir under low nitrogen input and regulated deficit irrigation. Application of AMF led to an appreciable increase in the size and number of class I fruit, especially under either deficient irrigation or low nitrogen input condition. However, root length colonization by AMF was reduced in strawberry grown in coir compared to soil and Terragreen. Furthermore, the appearance of AMF colonizing strawberry and maize roots grown in coir showed some physical differences from the structure in colonized roots in soil and Terragreen: the colonization structure appeared to be more compact and smaller in coir. PMID:27594859
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NASA Astrophysics Data System (ADS)
Nii-Annang, S.; Rodionov, A.; Dilly, O.; Bens, O.; Raab, T.; Hüttl, R. F.
2009-04-01
The search for viable re-cultivation techniques for the reclamation of large scale soil disturbances induced by mining of mineral resources has increasingly received attention in recent times. These techniques should favour plant growth under dry conditions and under nutrient-poor substrates; a problem in the lignite mining district in Lusatia, Germany. Substrates with basal respiration around 0.04 µg CO2 g-1 h-1, which is relatively low compared to mature soils, were amended with two nutrient rich commercial soil additives (CSA 1 and CSA 2). The CSA 1 is a synthetic-mineral mixture and CSA 2 an organo-mineral mixture. The amendment stimulated basal respiration based on both carbon dioxide evolution and oxygen uptake by 150 and 125 % for SCA 1 and CSA 2, respectively when 1 % of each additive was thoroughly mixed with substrate in a laboratory study. The stimulating effect was evident after glucose addition to CSA 2. The CSA 1 application in the field at lower rates still showed apparent stimulation of soil respiratory activities after one year. Similarly, the organo-mineral-mixture has prominent effects on basal respiration and substrate-induced respiration when glucose was added. We concluded that the commercial additives used as long-term amelioration techniques increased both nutrient preservation and, to some extent, soil microbial activity.
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Impact of glycerin and lignosulfonate on biodegradation of high explosives in soil.
Won, Jongho; Borden, Robert C
2016-11-01
Soil microcosms were constructed and monitored to evaluate the impact of substrate addition and transient aerobic and anaerobic conditions on TNT, RDX and HMX biodegradation in grenade range soils. While TNT was rapidly biodegraded under both aerobic and anaerobic conditions with and without organic substrate, substantial biodegradation of RDX, HMX, and RDX daughter products was not observed under aerobic conditions. However, RDX and HMX were significantly biodegraded under anaerobic conditions, without accumulation of TNT or RDX daughter products (2-ADNT, 4-ADNT, MNX, DNX, and TNX). In separate microcosms containing grenade range soil, glycerin and lignosulfonate addition enhanced oxygen consumption, increasing the consumption rate >200% compared to untreated soils. Mathematical model simulations indicate that oxygen consumption rates of 5 to 20g/m 3 /d can be achieved with reasonable amendment loading rates. These results indicate that glycerin and lignosulfonate can be potentially used to stimulate RDX and HMX biodegradation by increasing oxygen consumption rates in soil. Copyright © 2016 Elsevier B.V. All rights reserved.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Bradford, M A; Melillo, J M; Reynolds, J F
2010-06-10
The central objective of the proposed work was to develop a genomic approach (nucleic acid-based) that elucidates the mechanistic basis for the observed impacts of experimental soil warming on forest soil respiration. The need to understand the mechanistic basis arises from the importance of such information for developing effective adaptation strategies for dealing with projected climate change. Specifically, robust predictions of future climate will permit the tailoring of the most effective adaptation efforts. And one of the greatest uncertainties in current global climate models is whether there will be a net loss of carbon from soils to the atmosphere asmore » climate warms. Given that soils contain approximately 2.5 times as much carbon as the atmosphere, a net loss could lead to runaway climate warming. Indeed, most ecosystem models predict that climate warming will stimulate microbial decomposition of soil carbon, producing such a positive feedback to rising global temperatures. Yet the IPCC highlights the uncertainty regarding this projected feedback. The uncertainty arises because although warming-experiments document an initial increase in the loss of carbon from soils, the increase in respiration is short-lived, declining to control levels in a few years. This attenuation could result from changes in microbial physiology with temperature. We explored possible microbial responses to warming using experiments and modeling. Our work advances our understanding of how soil microbial communities and their activities are structured, generating insight into how soil carbon might respond to warming. We show the importance of resource partitioning in structuring microbial communities. Specifically, we quantified the relative abundance of fungal taxa that proliferated following the addition of organic substrates to soil. We added glycine, sucrose, cellulose, lignin, or tannin-protein to soils in conjunction with 3-bromo-deoxyuridine (BrdU), a nucleotide analog. Active microbes absorb BrdU from the soil solution; if they multiply in response to substrate additions, they incorporate the BrdU into their DNA. After allowing soils to incubate, we extracted BrdU-labeled DNA and sequenced the ITS regions of fungal rDNA. Fungal taxa that proliferated following substrate addition were likely using the substrate as a resource for growth. We found that the structure of active fungal communities varied significantly among substrates. The active fungal community under glycine was significantly different from those under other conditions, while the active communities under sucrose and cellulose were marginally different from each other and the control. These results indicate that the overall community structure of active fungi was altered by the addition of glycine, sucrose, and cellulose and implies that some fungal taxa respond to changes in resource availability. The community composition of active fungi is also altered by experimental warming. We found that glycine-users tended to increase under warming, while lignin-, tannin/protein-, and sucrose-users declined. The latter group of substrates requires extracellular enzymes for use, but glycine does not. It is possible that warming selects for fungal species that target, in particular, labile substrates. Linking these changes in microbial communities and resource partitioning to soil carbon dynamics, we find that substrate mineralization rates are, in general, significantly lower in soils exposed to long-term warming. This suggests that microbial use of organic substrates is impaired by warming. Yet effects are dependent on substrate identity. There are fundamental differences in the metabolic capabilities of the communities in the control and warmed soils. These differences might relate to the changes in microbial community composition, which appeared to be associated with groups specialized on different resources. We also find that functional responses indicate temperature acclimation of the microbial community. There are distinct seasonal patterns and to long-term soil warming, with higher-temperature optima for soils exposed to warmer temperatures. To relate these changes within the microbial community to potential positive feedbacks between climate warming and soil respiration, we develop a microbial-enzyme model to simulate the responses of soil carbon to warming. We find that declines in microbial biomass and degradative enzymes can explain the observed attenuation of soil-carbon emissions in response to warming. Specifically, reduced carbon-use efficiency limits the biomass of microbial decomposers and mitigates loss of soil carbon. However, microbial adaptation or a change in microbial communities could lead to an upward adjustment of the efficiency of carbon use, counteracting the decline in microbial biomass and accelerating soil-carbon loss. We conclude that the soil-carbon response to climate warming depends on the efficiency of soil microbes in using carbon.« less
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Reduced substrate supply limits the temperature response of soil organic carbon decomposition
Cinzia Fissore; Christian P. Giardina; Randall K. Kolka
2013-01-01
Controls on the decomposition rate of soil organic carbon (SOC), especially the more stable fraction of SOC, remain poorly understood, with implications for confidence in efforts to model terrestrial C balance under future climate. We investigated the role of substrate supply in the temperature sensitivity of SOC decomposition in laboratory incubations of coarse-...
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The effects of substrate supply on the temperature sensitivity of soil carbon decomposition
Cinzia Fissore; Christian P. Giardina; Randall K. Kolka
2013-01-01
Controls on the decomposition rate of soil organic carbon (SOC), especially the more stable fraction of SOC, remain poorly understood, with implications for confidence in efforts to model terrestrial C balance under future climate. We investigated the role of substrate supply in the temperature sensitivity of SOC decomposition in laboratory incubations of coarse-...
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Substrate Diffusion Heterogeneity Controls Bacterial Competition and Coexistence
NASA Astrophysics Data System (ADS)
Dechesne, A.; Or, D.; Smets, B. F.
2005-12-01
Diffusion has long been recognized as a key process affecting bacterial physiological functions ranging from nutrient uptake to removal of metabolic waste products. In the vadose zone, significant convective flows are limited and bacteria rely primarily on diffusion for nutrient supply. Even under relatively "wet" conditions (e.g. matric potentials -20 J/kg), soil water is fragmented and exists as thin liquid films or held in crevices imposing constraints on substrate diffusion. Our objective was to investigate the role of diffusion on soil microbial diversity, by focusing on one of the processes that shapes the structure of bacterial communities: competitive interactions. We used a simplified setup, in which the substrate (citrate) fluxes were controlled by different agar gels thicknesses and spatially heterogeneous diffusive pathways were created by an impermeable film with prescribed hole sizes and patterns. Our competition experiments involved two soil bacteria: Burkholderia xenovorans LB400 and Pseudomonas putida KT2440, which were tagged with different constitutive fluorescent markers, allowing for their on line microscopic detection. The growth parameters on citrate of these strains were thoroughly assessed. B. xenovorans LB400 is the weaker competitor. As a result, this strain was outcompeted by KT2440 under high substrate diffusivity and homogeneous conditions. Conversely, the disadvantage of the weakest competitor was not so marked under low substrate diffusivity condition. These results suggest that dry conditions in soil would provide conditions allowing the sustaining of weak bacterial competitors, resulting in the maintenance of high bacterial diversity.
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Tikhomirov, A A; Ushakova, S A; Gribovskaya, I A; Tirranen, L S; Manukovsky, N S; Zolotukhin, I G; Karnachuk, R A; Gros, J B; Lasseur, Ch
2003-01-01
To increase the degree of closure of biological life support systems of a new generation, we used vermicomposting to involve inedible phytomass in the intra-system mass exchange. The resulting product was a soil-like substrate, which was quite suitable for growing plants (Manukovsky et al. 1996, 1997). However, the soil like substrate can be regarded as a candidate for inclusion in a system only after a comprehensive examination of its physical, chemical, and other characteristics. An important criterion is the ability of the soil-like substrate to supply the necessary mineral elements to the photosynthesizing component under the chosen cultivation conditions. Thus, the purpose of this work was to study the feasibility of enhancing the production activity of wheat and radish crops by varying the intensity of photosynthetically active radiation, without decreasing the harvest index. The increase of light intensity from 920 to 1150 micromoles m-2 s-1 decreased the intensity of apparent photosynthesis of the wheat crops and slightly increased the apparent photosynthesis of the radish crops The maximum total and grain productivity (kg/m2) of the wheat crops was attained at the irradiance of 920 micromoles m-2 s-1. Light intensity of 1150 micromoles m-2 s-1 decreased the productivity of wheat plants and had no significant effect on the productivity of the radish crops (kg/m2) as compared to 920 micromoles m-2 s-1. The qualitative and quantitative composition of microflora of the watering solution and substrate was determined by the condition of plants, developmental phase and light intensity. By the end of wheat growth under 1150 micromoles m-2 s-1 the numbers of bacteria of the coliform family and phytopathogenic bacteria in the watering solution and substrate were an order of magnitude larger than under other illumination conditions. The obtained data suggest that the cultivation of plants in a life support system on soil-like substrate from composts has a number of advantages over the cultivation on neutral substrates, which require continual replenishment of the plant nutrient solution from the system's store to complement the macro- and micro-elements. Yet, a number of problems arise, including those related to the controlling of the production activity of the plants by the intensity of photosynthetically active radiation. It is essential to understand why the intensity of production processes is limited at higher irradiation levels and to overcome the factors responsible for this, so that the soil-like substrate could have an even better chance in the competition for the best plant cultivation technology to be used in biological life support systems. c2003 COSPAR. Published by Elsevier Science Ltd. All rights reserved.
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NASA Astrophysics Data System (ADS)
María Foronda, Ana; Pueyo, Yolanda; Castillejo, José Miguel; Alados, Conceción L.
2017-04-01
Degraded areas such as quarries or dumps are devoid of vegetation where the spontaneous vegetation recovery is a very slow process that requires restoration actions, especially under harsh environmental conditions such as arid conditions and special substrates. Specifically, gypsum substrates have physical and chemical limitations such as surface crusts, poor water availability or high concentrations of SO4 and Ca. Some plants, the so called gypsophytes, are adapted to tolerate such limitations and thus, might be able to establish in gypsum bare soils. Thus, well adapted gypsophytes might play an important role in vegetation recovery by acting as ecosystem engineers, improving the environmental conditions under their canopy and facilitating the establishment of other species. Facilitation is being recently considered as a key process in restoration practices because it might enhance restoration effectiveness by favoring the plant establishment and therefore, plant succession. The aim of this study was to test the effectiveness of a gypsophyte (Gypsophila struthium) in facilitating the establishment and development of other species and thus in vegetation recovery of degraded gypsum substrates. To address this objective, a sowing and planting experiment was set in November 2014 in a gypsum dump located in Andorra municipality (Teruel, NE Spain). Forty well-established adults of G. struthium previously planted in that dump were employed as nurse plants in the experiment. Two species were used as test species in the experiment: Helianthemum squamatum (gypsophyte) and Stipa lagascae (non-gypsophyte). Seeds and seedlings of those test species were sowed and planted in two different microsites: under the canopy and in the surrounding bare soil of each G. struthium individual (n=80 per test species). Germination, survival and growth of test species were surveyed twice a year during two years. Soil compaction and soil temperature were seasonally measured at both microsites during two years to test the role of G. struthium plants as ecosystem engineers by changing abiotic conditions under their canopy. Preliminary results showed that planted seedlings of H. squamatum grew in volume and seedlings of S.lagascae grew in height significantly more under the canopy of G. struthium than in bare soil, while germination and survival rates were similar at both microsites. Additionally, abiotic data showed that soil compaction decreased and extreme temperatures were softened under the canopy of G. struthium plants. Our study suggests that G. struthium can play an important role in restoration effectiveness of areas degraded by quarrying because it improves micro-environmental conditions under its canopy, favoring the development of other species in gypsum substrates.
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Pareniuk, O; Shavanova, K; Laceby, J P; Illienko, V; Tytova, L; Levchuk, S; Gudkov, I; Nanba, K
2015-11-01
After nuclear accidents, such as those experienced in Chernobyl and Fukushima, microorganisms may help purify contaminated soils by changing the mobility of radionuclides and their availability for plants by altering the physical and chemical properties of the substrate. Here, using model experiments with quartz sand as a substrate we investigate the influence of microorganisms on (137)Cs transfer from substrate to plants. The highest transition of (137)Cs from substrate to plants (50% increase compared to the control) was observed after Brassica napus L. seeds were inoculated by Azotobacter chroococcum. The best results for reducing the accumulation of (137)Cs radionuclides (30% less) were noted after the inoculation by Burkholderia sp.. Furthermore, Bacillus megaterium demonstrated an increased ability to accumulate (137)Cs. This research improves our prediction of the behavior of radionuclides in soil and may contribute towards new, microbiological countermeasures for soil remediation following nuclear accidents. Copyright © 2015 Elsevier Ltd. All rights reserved.
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Acidotolerant Bacteria and Fungi as a Sink of Methanol-Derived Carbon in a Deciduous Forest Soil
Morawe, Mareen; Hoeke, Henrike; Wissenbach, Dirk K.; Lentendu, Guillaume; Wubet, Tesfaye; Kröber, Eileen; Kolb, Steffen
2017-01-01
Methanol is an abundant atmospheric volatile organic compound that is released from both living and decaying plant material. In forest and other aerated soils, methanol can be consumed by methanol-utilizing microorganisms that constitute a known terrestrial sink. However, the environmental factors that drive the biodiversity of such methanol-utilizers have been hardly resolved. Soil-derived isolates of methanol-utilizers can also often assimilate multicarbon compounds as alternative substrates. Here, we conducted a comparative DNA stable isotope probing experiment under methylotrophic (only [13C1]-methanol was supplemented) and combined substrate conditions ([12C1]-methanol and alternative multi-carbon [13Cu]-substrates were simultaneously supplemented) to (i) identify methanol-utilizing microorganisms of a deciduous forest soil (European beech dominated temperate forest in Germany), (ii) assess their substrate range in the soil environment, and (iii) evaluate their trophic links to other soil microorganisms. The applied multi-carbon substrates represented typical intermediates of organic matter degradation, such as acetate, plant-derived sugars (xylose and glucose), and a lignin-derived aromatic compound (vanillic acid). An experimentally induced pH shift was associated with substantial changes of the diversity of active methanol-utilizers suggesting that soil pH was a niche-defining factor of these microorganisms. The main bacterial methanol-utilizers were members of the Beijerinckiaceae (Bacteria) that played a central role in a detected methanol-based food web. A clear preference for methanol or multi-carbon substrates as carbon source of different Beijerinckiaceae-affiliated phylotypes was observed suggesting a restricted substrate range of the methylotrophic representatives. Apart from Bacteria, we also identified the yeasts Cryptococcus and Trichosporon as methanol-derived carbon-utilizing fungi suggesting that further research is needed to exclude or prove methylotrophy of these fungi. PMID:28790984
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Holocene Substrate Influences on Plant and Fire Response to Climate Change
NASA Astrophysics Data System (ADS)
Briles, C.; Whitlock, C. L.
2011-12-01
The role of substrates in facilitating plant responses to climate change in the past has received little attention. Ecological studies, documenting the relative role of fertile and infertile substrates in mediating the effects of climate change, lack the temporal information that paleoecological lake studies provide on how plants have responded under equal, larger and more rapid past climate events than today. In this paper, pollen and macroscopic charcoal preserved in the sediments of eight lakes surrounded by infertile ultramafic soils and more fertile soils in the Klamath Mountains of northern California were analyzed. Comparison of late-Quaternary paleoecological sites suggests that infertile and fertile substrates supported distinctly different plant communities. Trees and shrubs on infertile substrates were less responsive to climate change than those on fertile substrates, with the only major compositional change occurring at the glacial/interglacial transition (~11.5ka), when temperature rose 5oC. Trees and shrubs on fertile substrates were more responsive to climate changes, and tracked climate by moving along elevational gradients, including during more recent climate events such as the Little Ice Age and Medieval Climate Anomaly. Fire regimes were similar until 4ka on both substrate types. After 4ka, understory fuels on infertile substrates became sparse and fire activity decreased, while on fertile substrates forests became increasingly denser and fire activity increased. The complacency of plant communities on infertile sites to climate change contrasts with the individualistic and rapid adjustments of species on fertile sites. The findings differ from observations on shorter time scales that show the most change in herb cover and richness in the last 60 years on infertile substrates. Thus, the paleorecord provides unique long-term ecological data necessary to evaluate the response of plants to future climate change under different levels of soil fertility.
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He, Y.; Zhuang, Q.; Harden, Jennifer W.; McGuire, A. David; Fan, Z.; Liu, Y.; Wickland, Kimberly P.
2014-01-01
The large amount of soil carbon in boreal forest ecosystems has the potential to influence the climate system if released in large quantities in response to warming. Thus, there is a need to better understand and represent the environmental sensitivity of soil carbon decomposition. Most soil carbon decomposition models rely on empirical relationships omitting key biogeochemical mechanisms and their response to climate change is highly uncertain. In this study, we developed a multi-layer microbial explicit soil decomposition model framework for boreal forest ecosystems. A thorough sensitivity analysis was conducted to identify dominating biogeochemical processes and to highlight structural limitations. Our results indicate that substrate availability (limited by soil water diffusion and substrate quality) is likely to be a major constraint on soil decomposition in the fibrous horizon (40–60% of soil organic carbon (SOC) pool size variation), while energy limited microbial activity in the amorphous horizon exerts a predominant control on soil decomposition (>70% of SOC pool size variation). Elevated temperature alleviated the energy constraint of microbial activity most notably in amorphous soils, whereas moisture only exhibited a marginal effect on dissolved substrate supply and microbial activity. Our study highlights the different decomposition properties and underlying mechanisms of soil dynamics between fibrous and amorphous soil horizons. Soil decomposition models should consider explicitly representing different boreal soil horizons and soil–microbial interactions to better characterize biogeochemical processes in boreal forest ecosystems. A more comprehensive representation of critical biogeochemical mechanisms of soil moisture effects may be required to improve the performance of the soil model we analyzed in this study.
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Wang, Hui; Boutton, Thomas W.; Xu, Wenhua; Hu, Guoqing; Jiang, Ping; Bai, Edith
2015-01-01
Changes in biogeochemical cycles and the climate system due to human activities are expected to change the quantity and quality of plant litter inputs to soils. How changing quality of fresh organic matter (FOM) might influence the priming effect (PE) on soil organic matter (SOM) mineralization is still under debate. Here we determined the PE induced by two 13C-labeled FOMs with contrasting nutritional quality (leaf vs. stalk of Zea mays L.). Soils from two different forest types yielded consistent results: soils amended with leaf tissue switched faster from negative PE to positive PE due to greater microbial growth compared to soils amended with stalks. However, after 16 d of incubation, soils amended with stalks had a higher PE than those amended with leaf. Phospholipid fatty acid (PLFA) results suggested that microbial demand for carbon and other nutrients was one of the major determinants of the PE observed. Therefore, consideration of both microbial demands for nutrients and FOM supply simultaneously is essential to understand the underlying mechanisms of PE. Our study provided evidence that changes in FOM quality could affect microbial utilization of substrate and PE on SOM mineralization, which may exacerbate global warming problems under future climate change. PMID:25960162
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Wang, Hui; Boutton, Thomas W; Xu, Wenhua; Hu, Guoqing; Jiang, Ping; Bai, Edith
2015-05-11
Changes in biogeochemical cycles and the climate system due to human activities are expected to change the quantity and quality of plant litter inputs to soils. How changing quality of fresh organic matter (FOM) might influence the priming effect (PE) on soil organic matter (SOM) mineralization is still under debate. Here we determined the PE induced by two (13)C-labeled FOMs with contrasting nutritional quality (leaf vs. stalk of Zea mays L.). Soils from two different forest types yielded consistent results: soils amended with leaf tissue switched faster from negative PE to positive PE due to greater microbial growth compared to soils amended with stalks. However, after 16 d of incubation, soils amended with stalks had a higher PE than those amended with leaf. Phospholipid fatty acid (PLFA) results suggested that microbial demand for carbon and other nutrients was one of the major determinants of the PE observed. Therefore, consideration of both microbial demands for nutrients and FOM supply simultaneously is essential to understand the underlying mechanisms of PE. Our study provided evidence that changes in FOM quality could affect microbial utilization of substrate and PE on SOM mineralization, which may exacerbate global warming problems under future climate change.
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NASA Astrophysics Data System (ADS)
Wang, Hui; Boutton, Thomas W.; Xu, Wenhua; Hu, Guoqing; Jiang, Ping; Bai, Edith
2015-05-01
Changes in biogeochemical cycles and the climate system due to human activities are expected to change the quantity and quality of plant litter inputs to soils. How changing quality of fresh organic matter (FOM) might influence the priming effect (PE) on soil organic matter (SOM) mineralization is still under debate. Here we determined the PE induced by two 13C-labeled FOMs with contrasting nutritional quality (leaf vs. stalk of Zea mays L.). Soils from two different forest types yielded consistent results: soils amended with leaf tissue switched faster from negative PE to positive PE due to greater microbial growth compared to soils amended with stalks. However, after 16 d of incubation, soils amended with stalks had a higher PE than those amended with leaf. Phospholipid fatty acid (PLFA) results suggested that microbial demand for carbon and other nutrients was one of the major determinants of the PE observed. Therefore, consideration of both microbial demands for nutrients and FOM supply simultaneously is essential to understand the underlying mechanisms of PE. Our study provided evidence that changes in FOM quality could affect microbial utilization of substrate and PE on SOM mineralization, which may exacerbate global warming problems under future climate change.
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Effect of differently pelletized digestate on the plant growth of spring wheat
NASA Astrophysics Data System (ADS)
Dietrich, Nils; Knoop, Christine; Raab, Thomas
2017-04-01
In Germany, biowaste is used in more than 100 biogas plants and has increasing potential as a fermentation substrate. To optimise waste cycle management organic digestates should be redistributed and innovative products for soil amendment of agricultural areas could be developed. The BMBF-funded VeNGA project seeks to find answers on how to improve the properties of soil amendments produced from fermentation residues. Here, we report findings from our study that focuses on plant growth and soil development. Within a three-month rhizotron experiment, the influence of differently prepared fermentation residues on the root development of summer wheat was investigated. The four variants of the prepared digestate (rolled pellet, pressed pellet, shredded, loose) were tested under constant conditions in the greenhouse on two soils with different textures (sandy and loamy-sand). All fermentation residues originated from the same batch and were composted before the preparation to ensure adequate hygienisation. Depending on preparation type and soil substrate significant differences in root growth and root development have been observed. Plant growth was most intense in the rhizotron experiment with the loose digestate, indicating high nutrient availability due to the large surface area of the organic matter. Plant growth in the substrate with the rolled and pressed pellets was less pronounced, indicating a more persistent stability of the pellets. In rhizotrons applied with rolled and pressed pellets root growth into the mineral fabric was significantly lower in sandy substrate than in the loamy-sand. However, in the sandy substrate root growth within the rolled pellets was more intense than in the substrate with the pressed pellets. Obviously, the different production techniques of the pellets seem to have an influence on the rooting of the pellets and facilitate the long term stability of soil organic carbon. Furthermore, the comparison of the two different textures indicate, that sandy substrates benefit more from the positive effects of soil amendments on increased water retention than loamy substrates.
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Effects of Soil Temperature and Moisture on Soil Respiration on the Tibetan Plateau
Chang, Xiaofeng; Wang, Shiping; Xu, Burenbayin; Luo, Caiyun; Zhang, Zhenhua; Wang, Qi; Rui, Yichao; Cui, Xiaoying
2016-01-01
Understanding of effects of soil temperature and soil moisture on soil respiration (Rs) under future warming is critical to reduce uncertainty in predictions of feedbacks to atmospheric CO2 concentrations from grassland soil carbon. Intact cores with roots taken from a full factorial, 5-year alpine meadow warming and grazing experiment in the field were incubated at three different temperatures (i.e. 5, 15 and 25°C) with two soil moistures (i.e. 30 and 60% water holding capacity (WHC)) in our study. Another experiment of glucose-induced respiration (GIR) with 4 h of incubation was conducted to determine substrate limitation. Our results showed that high temperature increased Rs and low soil moisture limited the response of Rs to temperature only at high incubation temperature (i.e. 25°C). Temperature sensitivity (Q10) did not significantly decrease over the incubation period, suggesting that substrate depletion did not limit Rs. Meanwhile, the carbon availability index (CAI) was higher at 5°C compared with 15 and 25°C incubation, but GIR increased with increasing temperature. Therefore, our findings suggest that warming-induced decrease in Rs in the field over time may result from a decrease in soil moisture rather than from soil substrate depletion, because warming increased root biomass in the alpine meadow. PMID:27798671
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Biodegradation kinetics of the nitramine explosive CL-20 in soil and microbial cultures.
Panikov, N S; Sizova, M V; Ros, D; Christodoulatos, C; Balas, W; Nicolich, S
2007-06-01
The cyclic nitramine explosive CL-20 (C(6)H(6)N(12)O(12), 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12 -hexaazaisowurtzitane) is a relatively new energetic compound which could be a persistent organic pollutant. To follow its biodegradation dynamics, CL-20 was added to soil alone or together with organic co-substrates and N-source and incubated under oxic and anoxic conditions. Without co-substrates, the CL-20 degradation was detectable only under anoxic conditions. The highest degradation rate was found under aerobic conditions and with the addition of co-substrates, succinate and pyruvate being more efficient than acetate, glucose, starch or yeast extract. When added to intact soil, CL-20 degradation was not affected by the N content, but in soil serially diluted with N-free succinate-mineral medium, the process became N-limited. About 40% of randomly selected bacterial colonies grown on succinate agar medium were able to decompose CL-20. Based on 16S rDNA gene sequence and cell morphology, they were affiliated to Pseudomonas, Rhodococcus, Ochrobactrum, Mycobacterium and Ralstonia. In the pure culture of Pseudomonas sp. MS-P grown on the succinate-mineral N(+) medium, the degradation kinetics were first order with the same apparent kinetic constant throughout growth and decline phases of the batch culture. The observed kinetics agreed with the model that supposes co-metabolic transformation of CL-20 uncoupled from cell growth, which can be carried out by several constitutive cellular enzymes with wide substrate specificity.
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Feng, Wenting; Liang, Junyi; Hale, Lauren E.; ...
2017-06-09
Quantifying soil organic carbon (SOC) decomposition under warming is critical to predict carbon–climate feedbacks. According to the substrate regulating principle, SOC decomposition would decrease as labile SOC declines under field warming, but observations of SOC decomposition under warming do not always support this prediction. This discrepancy could result from varying changes in SOC components and soil microbial communities under warming. This study aimed to determine the decomposition of SOC components with different turnover times after subjected to long-term field warming and/or root exclusion to limit C input, and to test whether SOC decomposition is driven by substrate lability under warming.more » Taking advantage of a 12-year field warming experiment in a prairie, we assessed the decomposition of SOC components by incubating soils from control and warmed plots, with and without root exclusion for 3 years. We assayed SOC decomposition from these incubations by combining inverse modeling and microbial functional genes during decomposition with a metagenomic technique (GeoChip). The decomposition of SOC components with turnover times of years and decades, which contributed to 95% of total cumulative CO 2 respiration, was greater in soils from warmed plots. But the decomposition of labile SOC was similar in warmed plots compared to the control. The diversity of C-degradation microbial genes generally declined with time during the incubation in all treatments, suggesting shifts of microbial functional groups as substrate composition was changing. Compared to the control, soils from warmed plots showed significant increase in the signal intensities of microbial genes involved in degrading complex organic compounds, implying enhanced potential abilities of microbial catabolism. These are likely responsible for accelerated decomposition of SOC components with slow turnover rates. Overall, the shifted microbial community induced by long-term warming accelerates the decomposition of SOC components with slow turnover rates and thus amplify the positive feedback to climate change.« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Feng, Wenting; Liang, Junyi; Hale, Lauren E.
Quantifying soil organic carbon (SOC) decomposition under warming is critical to predict carbon–climate feedbacks. According to the substrate regulating principle, SOC decomposition would decrease as labile SOC declines under field warming, but observations of SOC decomposition under warming do not always support this prediction. This discrepancy could result from varying changes in SOC components and soil microbial communities under warming. This study aimed to determine the decomposition of SOC components with different turnover times after subjected to long-term field warming and/or root exclusion to limit C input, and to test whether SOC decomposition is driven by substrate lability under warming.more » Taking advantage of a 12-year field warming experiment in a prairie, we assessed the decomposition of SOC components by incubating soils from control and warmed plots, with and without root exclusion for 3 years. We assayed SOC decomposition from these incubations by combining inverse modeling and microbial functional genes during decomposition with a metagenomic technique (GeoChip). The decomposition of SOC components with turnover times of years and decades, which contributed to 95% of total cumulative CO 2 respiration, was greater in soils from warmed plots. But the decomposition of labile SOC was similar in warmed plots compared to the control. The diversity of C-degradation microbial genes generally declined with time during the incubation in all treatments, suggesting shifts of microbial functional groups as substrate composition was changing. Compared to the control, soils from warmed plots showed significant increase in the signal intensities of microbial genes involved in degrading complex organic compounds, implying enhanced potential abilities of microbial catabolism. These are likely responsible for accelerated decomposition of SOC components with slow turnover rates. Overall, the shifted microbial community induced by long-term warming accelerates the decomposition of SOC components with slow turnover rates and thus amplify the positive feedback to climate change.« less
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Feng, Wenting; Liang, Junyi; Hale, Lauren E; Jung, Chang Gyo; Chen, Ji; Zhou, Jizhong; Xu, Minggang; Yuan, Mengting; Wu, Liyou; Bracho, Rosvel; Pegoraro, Elaine; Schuur, Edward A G; Luo, Yiqi
2017-11-01
Quantifying soil organic carbon (SOC) decomposition under warming is critical to predict carbon-climate feedbacks. According to the substrate regulating principle, SOC decomposition would decrease as labile SOC declines under field warming, but observations of SOC decomposition under warming do not always support this prediction. This discrepancy could result from varying changes in SOC components and soil microbial communities under warming. This study aimed to determine the decomposition of SOC components with different turnover times after subjected to long-term field warming and/or root exclusion to limit C input, and to test whether SOC decomposition is driven by substrate lability under warming. Taking advantage of a 12-year field warming experiment in a prairie, we assessed the decomposition of SOC components by incubating soils from control and warmed plots, with and without root exclusion for 3 years. We assayed SOC decomposition from these incubations by combining inverse modeling and microbial functional genes during decomposition with a metagenomic technique (GeoChip). The decomposition of SOC components with turnover times of years and decades, which contributed to 95% of total cumulative CO 2 respiration, was greater in soils from warmed plots. But the decomposition of labile SOC was similar in warmed plots compared to the control. The diversity of C-degradation microbial genes generally declined with time during the incubation in all treatments, suggesting shifts of microbial functional groups as substrate composition was changing. Compared to the control, soils from warmed plots showed significant increase in the signal intensities of microbial genes involved in degrading complex organic compounds, implying enhanced potential abilities of microbial catabolism. These are likely responsible for accelerated decomposition of SOC components with slow turnover rates. Overall, the shifted microbial community induced by long-term warming accelerates the decomposition of SOC components with slow turnover rates and thus amplify the positive feedback to climate change. © 2017 John Wiley & Sons Ltd.
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Environmental Controls of Microbial Resource Partitioning in Soils
NASA Astrophysics Data System (ADS)
Kandeler, Ellen; Poll, Christian; Kramer, Susanne; Mueller, Karolin; Marhan, Sven
2015-04-01
The mineralization and flow of plant-derived carbon in soils is relevant to global carbon cycling. Current models of organismic carbon fluxes in soil assume that separate bacterial and fungal energy channels exist in soil. Recent studies disentangle the herbivore and detritivore pathways of microbial resource use, identify the key players contributing to these two different pathways, and determine to what extent microbial substrate use is affected by environmental controls. To follow the kinetics of litter and root decomposition and to quantify the contribution of key players, it is necessary to use isotopic approaches like PLFA-SIP and ergosterol-SIP. It was shown that bacteria and sugar consuming fungi initiated litter decomposition in an incubation experiment during the first two weeks, whereas higher fungi started to grow after the depletion of low molecular weight substrates. Analyses of PLFA-SIP revealed, for example, that fungi assimilated C directly from the litter, whereas bacteria took up substrates in the soil and therefore depended more on external transport processes than fungi. In addition, we will present data from a field experiment showing the incorporation of root and shoot litter C into organic and microbial C pools under field conditions over a period of two years. Similar amounts of C derived from the two resources differing in substrate quality and amount were incorporated into microbial C and ergosterol pools over time, indicating the importance of root-derived C for the soil food web. High incorporation of maize C (up to 76%) into ergosterol suggests fast and high assimilation of maize C into fungal biomass. Nevertheless, there is still a debate whether bacteria, archaea and fungi start feeding on new substrates at the same time or if their activity occurs at different successional stages. This presentation gives a summery of current knowledge on microbial resource partitioning under lab and field conditions.
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Gavazov, Konstantin; Ingrisch, Johannes; Hasibeder, Roland; Mills, Robert T E; Buttler, Alexandre; Gleixner, Gerd; Pumpanen, Jukka; Bahn, Michael
2017-07-15
Seasonal snow cover provides essential insulation for mountain ecosystems, but expected changes in precipitation patterns and snow cover duration due to global warming can influence the activity of soil microbial communities. In turn, these changes have the potential to create new dynamics of soil organic matter cycling. To assess the effects of experimental snow removal and advanced spring conditions on soil carbon (C) and nitrogen (N) dynamics, and on the biomass and structure of soil microbial communities, we performed an in situ study in a subalpine grassland in the Austrian Alps, in conjunction with soil incubations under controlled conditions. We found substantial winter C-mineralisation and high accumulation of inorganic and organic N in the topsoil, peaking at snowmelt. Soil microbial biomass doubled under the snow, paralleled by a fivefold increase in its C:N ratio, but no apparent change in its bacteria-dominated community structure. Snow removal led to a series of mild freeze-thaw cycles, which had minor effects on in situ soil CO 2 production and N mineralisation. Incubated soil under advanced spring conditions, however, revealed an impaired microbial metabolism shortly after snow removal, characterised by a limited capacity for C-mineralisation of both fresh plant-derived substrates and existing soil organic matter (SOM), leading to reduced priming effects. This effect was transient and the observed recovery in microbial respiration and SOM priming towards the end of the winter season indicated microbial resilience to short-lived freeze-thaw disturbance under field conditions. Bacteria showed a higher potential for uptake of plant-derived C substrates during this recovery phase. The observed temporary loss in microbial C-mineralisation capacity and the promotion of bacteria over fungi can likely impede winter SOM cycling in mountain grasslands under recurrent winter climate change events, with plausible implications for soil nutrient availability and plant-soil interactions. Copyright © 2017 Elsevier B.V. All rights reserved.
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NASA Astrophysics Data System (ADS)
Farji-Brener, Alejandro G.; Lescano, María Natalia
2017-11-01
In arid environments, the high availability of sunlight due to the scarcity of trees suggests that plant competition take place mainly belowground for water and nutrients. However, the occurrence of soil disturbances that increase nutrient availability and thereby promote plant growth may enhance shoot competition between neighboring plants. We conducted a greenhouse experiment to evaluate the influence of the enriched soil patches generated by the leaf-cutting ant, Acromyrmex lobicornis, on the performance of the alien forb Carduus thoermeri (Asteraceae) under different intraspecific competition scenarios. Our results showed that substrate type and competition scenario affected mainly aboveground plant growth. As expected, plants growing without neighbors and in nutrient-rich ant refuse dumps showed more aboveground biomass than plants growing with neighbors and in nutrient-poor steppe soils. However, aboveground competition was more intense in nutrient-poor substrates: plants under shoot and full competition growing in the nutrient-rich ant refuse dumps showed higher biomass than those growing on steppe soils. Belowground biomass was similar among focal plants growing under different substrate type. Our results support the traditional view that increments in resource availability reduce competition intensity. Moreover, the fact that seedlings in this sunny habitat mainly compete aboveground illustrates how limiting factors may be scale-dependent and change in importance as plants grow.
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NASA Astrophysics Data System (ADS)
Lenhart, Katharina; Keppler, Frank
2017-04-01
Typically, aerated soil are net sinks of atmospheric methane (CH4), being highest in native ecosystems (pristine forests > managed forests > grasslands > crop fields). However, this does not exclude a simultaneous endogenic CH4 production in the plant-soil system, which cannot be detected simply via CH4 flux measurements. Methanogenic archaea producing CH4 under anoxic conditions were thought to be the only biotic source of CH4 in the soil. However, until recently a non-archaeal pathway of CH4 formation is known where CH4 is produced under oxic conditions in plants (Keppler et al. 2006) and fungi (Lenhart et al. 2012). Additionally, abiotic formation of CH4 from soil organic matter was reported (Jugold et al. 2012) and may be ubiquitous in terrestrial ecosystems. The major goal of this project was to determine soil endogenic CH4 sources and to estimate their contribution to the endogenic CH4 production. Especially the effect of plants and fungi on soil CH4 production was investigated. Therefore, a series of experiments was carried out on field fresh soil collected in a grassland and a forest ecosystem under controlled laboratory conditions. By combining selective inhibitors and 13C labelling, CH4 production rates of several CH4 sources were quantified. The major difficulty was to detect the comparatively small flux of CH4 production against the background of the high CH4 consumption rates due to methanotrophic bacteria. Therefore, we supplemented bare soil and soil with vegetation with selective inhibitors and 13C labelled substrates in a closed chamber system. In a first step, CH4 production was determined by the inhibition of CH4 oxidizing bacteria with Difluoromethane (DFM, 2ml l-1). In the following, a 13C labelled substrate (either CO2, Acetate, or Methionine -S-CH3 labelled) was added in combination with a specific inhibitor -either for archaeal methanogenesis (Bromoethanesulfonate), bacteria (Streptomycin), or fungi (Captan, Cycloheximide). Gas samples were taken during the incubation for CH4 and CO2 concentration measurements and isotope ratio mass spectrometry (CH4, CO2). Grassland and forest soils showed differences in CO2 and CH4 production rates. Based on the 13C-CH4 signature we found that all substrates were metabolized to CH4, but to a different degree. Inhibitors reduced CH4 production and conversion of certain substrates to a different degree. Using the example of acetate and cycloheximide, in both soils acetate increased respiration, whereas cycloheximide reduced respiration by 56 and 62 %, respectively. For CH4 production, however, no effect was visible for the grassland soil, but in the forest soil CH4 production increased by 69 %. Cycloheximide inhibited the substrate-induced CH4 production by 63 %, indicating that fungi were responsible for this pathway. Moreover, the finding that fungi use the methyl group of acetate to produce CH4 was also verified with a sterile culture. References Lenhart, K. et al. Evidence for methane production by saprotrophic fungi. Nat Commun 3, 1046, (2012). Keppler, F., et al. Methane emissions from terrestrial plants under aerobic conditions. Nature 439, 187-191 (2006). Jugold, A. et al. Non-microbial methane formation in oxic soils. Biogeosciences 9, 5291-5301, (2012).
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Nianpeng, He; Ruomeng, Wang; Yang, Gao; Jingzhong, Dai; Xuefa, Wen; Guirui, Yu
2013-12-01
Understanding the temperature sensitivity (Q 10) of soil organic matter (SOM) decomposition is important for predicting soil carbon (C) sequestration in terrestrial ecosystems under warming scenarios. Whether Q 10 varies predictably with ecosystem succession and the ways in which the stoichiometry of input SOM influences Q 10 remain largely unknown. We investigate these issues using a grassland succession series from free-grazing to 31-year grazing-exclusion grasslands in Inner Mongolia, and an incubation experiment performed at six temperatures (0, 5, 10, 15, 20, and 25°C) and with four substrates: control (CK), glucose (GLU), mixed grass leaf (GRA), and Medicago falcata leaf (MED). The results showed that basal soil respiration (20°C) and microbial biomass C (MBC) logarithmically decreased with grassland succession. Q 10 decreased logarithmically from 1.43 in free-grazing grasslands to 1.22 in 31-year grazing-exclusion grasslands. Q 10 increased significantly with the addition of substrates, and the Q 10 levels increased with increase in N:C ratios of substrate. Moreover, accumulated C mineralization was controlled by the N:C ratio of newly input SOM and by incubation temperature. Changes in Q 10 with grassland ecosystem succession are controlled by the stoichiometry of newly input SOM, MBC, and SOM quality, and the combined effects of which could partially explain the mechanisms underlying soil C sequestration in the long-term grazing-exclusion grasslands in Inner Mongolia, China. The findings highlight the effect of substrate stoichiometry on Q 10 which requires further study.
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Soil Nitrification and N2O Production: the connection with N concentration and Soil Water Content
NASA Astrophysics Data System (ADS)
Zhu-Barker, X.; Horwath, W. R.
2016-12-01
The development of mitigation strategies to reduce nitrous oxide (N2O) emission from soils is dependent on explicating the biophysical factors affecting different N2O production pathways. Ammonia oxidation and heterotrophic denitrification are the main pathways of N2O production, depending on soil conditions such as soil moisture content, oxygen (O2) content and N substrate. Many researchers have reported that N2O production increased as substrate concentration and soil moisture content increased. However, less understood is how N fertilizer concentration and moisture content interact to affect N2O production pathways. To investigate interaction and its effect on O2 consumption, we incubated three agricultural soils (clay, sandy loam, and peat) with different concentrations of (NH4)2SO4 (0-1000 µg N g-1) under 50 %, 75%, and 100% of water holding capacity. All treatments received 15N -KNO3 to bring the concentrations of NO3-_N in soils to 50 mg kg-1 soil and the NO3- pool to an enrichment of 10 atom% 15N. In all soils, the total amount of O2 consumption and N2O production increased as soil ammonical N concentration increased. The increased soil moisture significantly promoted N2O production in sandy loam and clay loam soils, compared to the peat soil. These results indicate that N2O production increased as substrate concentration increased likely due to the onset of O2 limitation caused by ammonia oxidation.
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Zhu, Q.; Riley, W. J.; Tang, J.; ...
2016-01-18
Soil is a complex system where biotic (e.g., plant roots, micro-organisms) and abiotic (e.g., mineral surfaces) consumers compete for resources necessary for life (e.g., nitrogen, phosphorus). This competition is ecologically significant, since it regulates the dynamics of soil nutrients and controls aboveground plant productivity. Here we develop, calibrate and test a nutrient competition model that accounts for multiple soil nutrients interacting with multiple biotic and abiotic consumers. As applied here for tropical forests, the Nutrient COMpetition model (N-COM) includes three primary soil nutrients (NH 4 +, NO 3 − and PO x; representing the sum of PO 4 3−, HPOmore » 4 2− and H 2PO 4 −) and five potential competitors (plant roots, decomposing microbes, nitrifiers, denitrifiers and mineral surfaces). The competition is formulated with a quasi-steady-state chemical equilibrium approximation to account for substrate (multiple substrates share one consumer) and consumer (multiple consumers compete for one substrate) effects. N-COM successfully reproduced observed soil heterotrophic respiration, N 2O emissions, free phosphorus, sorbed phosphorus and NH 4 + pools at a tropical forest site (Tapajos). The overall model uncertainty was moderately well constrained. Our sensitivity analysis revealed that soil nutrient competition was primarily regulated by consumer–substrate affinity rather than environmental factors such as soil temperature or soil moisture. Our results also imply that under strong nutrient limitation, relative competitiveness depends strongly on the competitor functional traits (affinity and nutrient carrier enzyme abundance). We then applied the N-COM model to analyze field nitrogen and phosphorus perturbation experiments in two tropical forest sites (in Hawaii and Puerto Rico) not used in model development or calibration. Under soil inorganic nitrogen and phosphorus elevated conditions, the model accurately replicated the experimentally observed competition among nutrient consumers. Although we used as many observations as we could obtain, more nutrient addition experiments in tropical systems would greatly benefit model testing and calibration. In summary, the N-COM model provides an ecologically consistent representation of nutrient competition appropriate for land BGC models integrated in Earth System Models.« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Zhu, Q.; Riley, W. J.; Tang, J.
Soil is a complex system where biotic (e.g., plant roots, micro-organisms) and abiotic (e.g., mineral surfaces) consumers compete for resources necessary for life (e.g., nitrogen, phosphorus). This competition is ecologically significant, since it regulates the dynamics of soil nutrients and controls aboveground plant productivity. Here we develop, calibrate and test a nutrient competition model that accounts for multiple soil nutrients interacting with multiple biotic and abiotic consumers. As applied here for tropical forests, the Nutrient COMpetition model (N-COM) includes three primary soil nutrients (NH 4 +, NO 3 − and PO x; representing the sum of PO 4 3−, HPOmore » 4 2− and H 2PO 4 −) and five potential competitors (plant roots, decomposing microbes, nitrifiers, denitrifiers and mineral surfaces). The competition is formulated with a quasi-steady-state chemical equilibrium approximation to account for substrate (multiple substrates share one consumer) and consumer (multiple consumers compete for one substrate) effects. N-COM successfully reproduced observed soil heterotrophic respiration, N 2O emissions, free phosphorus, sorbed phosphorus and NH 4 + pools at a tropical forest site (Tapajos). The overall model uncertainty was moderately well constrained. Our sensitivity analysis revealed that soil nutrient competition was primarily regulated by consumer–substrate affinity rather than environmental factors such as soil temperature or soil moisture. Our results also imply that under strong nutrient limitation, relative competitiveness depends strongly on the competitor functional traits (affinity and nutrient carrier enzyme abundance). We then applied the N-COM model to analyze field nitrogen and phosphorus perturbation experiments in two tropical forest sites (in Hawaii and Puerto Rico) not used in model development or calibration. Under soil inorganic nitrogen and phosphorus elevated conditions, the model accurately replicated the experimentally observed competition among nutrient consumers. Although we used as many observations as we could obtain, more nutrient addition experiments in tropical systems would greatly benefit model testing and calibration. In summary, the N-COM model provides an ecologically consistent representation of nutrient competition appropriate for land BGC models integrated in Earth System Models.« less
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NASA Astrophysics Data System (ADS)
Zhu, Q.; Riley, W. J.; Tang, J.; Koven, C. D.
2016-01-01
Soil is a complex system where biotic (e.g., plant roots, micro-organisms) and abiotic (e.g., mineral surfaces) consumers compete for resources necessary for life (e.g., nitrogen, phosphorus). This competition is ecologically significant, since it regulates the dynamics of soil nutrients and controls aboveground plant productivity. Here we develop, calibrate and test a nutrient competition model that accounts for multiple soil nutrients interacting with multiple biotic and abiotic consumers. As applied here for tropical forests, the Nutrient COMpetition model (N-COM) includes three primary soil nutrients (NH4+, NO3- and POx; representing the sum of PO43-, HPO42- and H2PO4-) and five potential competitors (plant roots, decomposing microbes, nitrifiers, denitrifiers and mineral surfaces). The competition is formulated with a quasi-steady-state chemical equilibrium approximation to account for substrate (multiple substrates share one consumer) and consumer (multiple consumers compete for one substrate) effects. N-COM successfully reproduced observed soil heterotrophic respiration, N2O emissions, free phosphorus, sorbed phosphorus and NH4+ pools at a tropical forest site (Tapajos). The overall model uncertainty was moderately well constrained. Our sensitivity analysis revealed that soil nutrient competition was primarily regulated by consumer-substrate affinity rather than environmental factors such as soil temperature or soil moisture. Our results also imply that under strong nutrient limitation, relative competitiveness depends strongly on the competitor functional traits (affinity and nutrient carrier enzyme abundance). We then applied the N-COM model to analyze field nitrogen and phosphorus perturbation experiments in two tropical forest sites (in Hawaii and Puerto Rico) not used in model development or calibration. Under soil inorganic nitrogen and phosphorus elevated conditions, the model accurately replicated the experimentally observed competition among nutrient consumers. Although we used as many observations as we could obtain, more nutrient addition experiments in tropical systems would greatly benefit model testing and calibration. In summary, the N-COM model provides an ecologically consistent representation of nutrient competition appropriate for land BGC models integrated in Earth System Models.
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Paetsch, Lydia; Mueller, Carsten W; Kögel-Knabner, Ingrid; von Lützow, Margit; Girardin, Cyril; Rumpel, Cornelia
2018-05-01
Biochar (BC) amendments may be suitable to increase the ecosystems resistance to drought due to their positive effects on soil water retention and availability. We investigated the effect of BC in situ ageing on water availability and microbial parameters of a grassland soil. We used soil containing 13 C labeled BC and determined its water holding capacity, microbial biomass and activity during a 3 months incubation under optimum and drought conditions. Our incubation experiment comprised three treatments: soil without BC (Control), soil containing aged BC (BC aged ) and soil containing fresh BC (BC fresh ), under optimum soil water (pF 1.8) and drought conditions (pF 3.5). Under optimum water as well as drought conditions, soils containing BC showed higher soil organic carbon (SOC) mineralization as compared to control soil. Moreover, BC effects on the soil water regime increase upon in situ aging. Native SOC mineralization increased most for soils containing BC aged . The BC aged led to improved C use under drought as compared to the other treatments. We conclude that BC addition to soils can ameliorate their water regime, especially under drought conditions. This beneficial effect of BC increases upon its aging, which also improved native substrate availability.
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Nitrogen-fixing legume tree species for the reclamation of severely degraded lands in Brazil.
Chaer, Guilherme Montandon; Resende, Alexander Silva; Campello, Eduardo Francia Carneiro; de Faria, Sergio Miana; Boddey, Robert Michael
2011-02-01
The main challenges faced in the reclamation of severely degraded lands are in the management of the systems and finding plant species that will grow under the harsh conditions common in degraded soils. This is especially important in extremely adverse situations found in some substrates from mining activities or soils that have lost their upper horizons. Under these conditions, recolonization of the area by native vegetation through natural succession processes may be extremely limited. Once the main physical and chemical factors restrictive to plant growth are corrected or attenuated, the introduction of leguminous trees able to form symbioses with nodulating N₂-fixing bacteria and arbuscular mycorrhizal fungi constitutes an efficient strategy to accelerate soil reclamation and initiate natural succession. These symbioses give the legume species a superior capacity to grow quickly in poor substrates and to withstand the harsh conditions presented in degraded soils. In this article we describe several successful results in Brazil using N₂-fixing legume tree species for reclamation of areas degraded by soil erosion, construction and mining activities, emphasizing the potential of the technique to recover soil organic matter levels and restore ecosystem biodiversity and other environmental functions.
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Soil organic matter content: a non-liner control on microbial respiration in soils
NASA Astrophysics Data System (ADS)
Schnecker, Jörg; Grandy, Stuart
2016-04-01
It is widely assumed that microbial activity and respiration rates respond linearly to substrate concentrations, irrespective of substrate chemical characteristics, but this assumption remains largely untested. We know that microbial decomposition of soil organic matter (SOM) and the amount of CO2 respired from soil depends on substrate availability. While soils with high SOM concentrations will have higher respiration rates than soils with low SOM concentrations, the specific relationship between substrate quantity and CO2 respired and its underlying mechanisms has robust theoretical, modeling, and management implications. In a lab incubation experiment, we amended a mixture of agricultural soil and sand with increasing amounts of one of three plant residues differing in their C/N ratio (clover C/N 14; rye C/N 23 and wheat straw C/N 110). Keeping the soil/sand mixture at a constant ratio, we obtained 9 levels of organic carbon (OC) content ranging from 0.25% to 5.7%. The sand-soil-residue mixtures were then incubated at constant temperature and water contents for a total of 63 days. Our results show that across substrates CO2 production increased with increasing OC content following a sigmoidal curve function instead of the expected linear one. A breakpoint analysis for the respiration curve of rye revealed two significant break points at 1.3 and 3.8 % OC. The three individual linear relations might be shaped by spatial separation of substrate and microbes and the interaction of the microbes themselves. In the first "survival" phase up to 1.3 % OC, more substrate leads to the survival of more microbes. However, microbial growth does not result in the discovery of new resources. In the "expansion" phase (1.3 % OC to 3.8 % OC), microbial growth is successful and microbes can exploit new resources. Finally, in the "competition" phase microbes start to compete for space and resources, which leads to a decrease in decomposition and respiration. While the results for clover were similar to rye, different amounts of straw resulted in an almost linear relationship between OC content and respiratory loss. The low N content of straw may explain this, limiting microbial growth and the exploration for new resources. Microbes in the straw treatment likely remained in the "survival" phase. Our findings of a non-linear decrease of CO2 production with decreasing OC content indicate that spatial separation as an inherent property of SOM content is an important control on decomposition of soil organic matter. Knowledge of this controlling effect might be beneficial in many ways. For example, even small additions of plant residues to agricultural systems might strongly enhance N availability to microbes and plants. Further, the spatial distribution of new C inputs may regulate its potential to be decomposed or stabilized. Finally, our results will help to improve model parameterization and predictions about microbial limitations and potential changes in decomposition under a future climate.
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Elevated atmospheric CO2 increases microbial growth rates and enzymes activity in soil
NASA Astrophysics Data System (ADS)
Blagodatskaya, Evgenia; Blagodatsky, Sergey; Dorodnikov, Maxim; Kuzyakov, Yakov
2010-05-01
Increasing the belowground translocation of assimilated carbon by plants grown under elevated CO2 can cause a shift in the structure and activity of the microbial community responsible for the turnover of organic matter in soil. We investigated the long-term effect of elevated CO2 in the atmosphere on microbial biomass and specific growth rates in root-free and rhizosphere soil. The experiments were conducted under two free air carbon dioxide enrichment (FACE) systems: in Hohenheim and Braunschweig, as well as in the intensively managed forest mesocosm of the Biosphere 2 Laboratory (B2L) in Oracle, AZ. Specific microbial growth rates (μ) were determined using the substrate-induced respiration response after glucose and/or yeast extract addition to the soil. We evaluated the effect of elevated CO2 on b-glucosidase, chitinase, phosphatase, and sulfatase to estimate the potential enzyme activity after soil amendment with glucose and nutrients. For B2L and both FACE systems, up to 58% higher μ were observed under elevated vs. ambient CO2, depending on site, plant species and N fertilization. The μ-values increased linearly with atmospheric CO2 concentration at all three sites. The effect of elevated CO2 on rhizosphere microorganisms was plant dependent and increased for: Brassica napus=Triticum aestivum
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Soil texture and climatc conditions for biocrust growth limitation: a meta analysis
NASA Astrophysics Data System (ADS)
Fischer, Thomas; Subbotina, Mariia
2015-04-01
Along with afforestation, attempts have been made to combat desertification by managing soil crusts, and is has been reported that recovery rates of biocrusts are dependent on many factors, including the type, severity, and extent of disturbance; structure of the vascular plant community; conditions of adjoining substrates; availability of inoculation material; and climate during and after disturbance (Belnap & Eldridge 2001). Because biological soil crusts are known to be more stable on and to prefer fine substrates (Belnap 2001), the question arises as to how successful crust management practices can be applied to coarser soil. In previous studies we observed similar crust biomasses on finer soils under arid and on coarser soils under temperate conditions. We hypothesized that the higher water holding capacity of finer substrates would favor crust development, and that the amount of silt and clay in the substrate that is required for enhanced crust development would vary with changes in climatic conditions. In a global meta study, climatic and soil texture threshold values promoting BSC growth were derived. While examining literature sources, it became evident that the amount of studies to be incorporated into this meta analysis was reversely related to the amount of common environmental parameters they share. We selected annual mean precipitaion, mean temperature and the amount of silt and clay as driving variables for crust growth. Response variable was the "relative crust biomass", which was computed per literature source as the ratio between each individual crust biomass value of the given study to the study maximum value reported. We distinguished lichen, green algal, cyanobacterial and moss crusts. To quantify threshold conditions at which crust biomass responded to differences in texture and climate, we (I) determined correlations between bioclimatic variables, (II) calculated linear models to determine the effect of typical climatic variables with soil clay content and with study site as a random effect. (III) Threshold values of texture and climatc effects were identified using a regression tree. Three mean annual temperature classes for texture dependent BSC growth limitation were identified: (1) <9 °C with a threshold value of 25% silt and clay (limited growth on coarser soils), (2) 9-19 °C, where texture did have no influence on relative crust biomass, and (3) >19 °C at soils with <4 or >17% silt and clay. Because biocrust development is limited under certain climatic and soil texture conditions, it is suggested to consider soil texture for biocrust rehabilitation purposes and in biogeochemical modeling of cryptogamic ground covers. References Belnap, J. & Eldridge, D. 2001. Disturbance and Recovery of Biological Soil Crusts. In: Belnap, J. & Lange, O. (eds.) Biological Soil Crusts: Structure, Function, and Management, Springer, Berlin. Belnap, J. 2001. Biological Soil Crusts and Wind Erosion. In: Belnap, J. & Lange, O. (eds.) Fischer, T., Subbotina, M. 2014. Climatic and soil texture threshold values for cryptogamic cover development: a meta analysis. Biologia 69/11:1520-1530,
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Lead toxicity thresholds in 17 Chinese soils based on substrate-induced nitrification assay.
Li, Ji; Huang, Yizong; Hu, Ying; Jin, Shulan; Bao, Qiongli; Wang, Fei; Xiang, Meng; Xie, Huiting
2016-06-01
The influence of soil properties on toxicity threshold values for Pb toward soil microbial processes is poorly recognized. The impact of leaching on the Pb threshold has not been assessed systematically. Lead toxicity was screened in 17 Chinese soils using a substrate-induced nitrification (SIN) assay under both leached and unleached conditions. The effective concentration of added Pb causing 50% inhibition (EC50) ranged from 185 to >2515mg/kg soil for leached soil and 130 to >2490mg/kg soil for unleached soil. These results represented >13- and >19-fold variations among leached and unleached soils, respectively. Leaching significantly reduced Pb toxicity for 70% of both alkaline and acidic soils tested, with an average leaching factor of 3.0. Soil pH and CEC were the two most useful predictors of Pb toxicity in soils, explaining over 90% of variance in the unleached EC50 value. The relationships established in the present study predicted Pb toxicity within a factor of two of measured values. These relationships between Pb toxicity and soil properties could be used to establish site-specific guidance on Pb toxicity thresholds. Copyright © 2016. Published by Elsevier B.V.
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NASA Astrophysics Data System (ADS)
Tománková, Klára; Sněhota, Michal; Jelínková, Vladimíra
2016-04-01
Extensive green roofs with a thin growing medium require minimal maintenance, and in general no irrigation. The proper functioning of such systems rests with their structural constituents, especially with the substrate used for planting. An extensive green roof with poorly developed vegetation and with a soil layer of a maximum thickness of 5 cm mixed with local stripped topsoil with crushed bricks and green waste was studied with respect to the hydrological behavior. The substrate classified as loam comprises a significant proportion of very fine particles and thus it is prone to clogging up of soil pores and forming of fissures on the surface. The green roof studied is well equipped for measuring meteorological data including air temperature, wind speed and direction, net radiation, relative humidity, and rainfall intensity. The meteorological information on the site is completed by soil temperature measurement. The 12 m long transect is equipped with eight time domain reflectometry probes (TDR) to monitor soil water content. Soil physical properties (bulk density, porosity, grain size distribution) and soil hydraulic characteristics (soil water retention curve) were obtained. The numerical modeling of transient soil water movement in the green roof substrate was performed using a two-dimensional model based on the Richards' equation. Results were compared with the soil water content data acquired. Six alternative scenarios were formulated to discuss possible improvement of green roof functioning and four selected scenarios were simulated. The study helped us to improve our understanding of the flow processes through the green roof soil system under study. The alternative scenario simulations allowed hydrological assessment of roof construction amendments. The research was realized as a part of the University Centre for Energy Efficient Buildings supported by the EU and with financial support from the Czech Science Foundation under project number 14-10455P.
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Plant-microbe interactions driven by exometabolite preferences of rhizosphere bacteria
NASA Astrophysics Data System (ADS)
Zhalnina, K.; Louie, K. B.; Mansoori, N.; Hao, Z.; Gao, J.; Cho, H. J.; Karaoz, U.; Loqué, D.; Bowen, B.; Firestone, M.; Brodie, E.; Northen, T.
2016-12-01
It is known that rhizosphere bacteria can impact important processes during plant development. In `return' plants release substantial quantities of soluble C into the soil surrounding its roots, attracting bacteria and other soil organisms. Given the potential beneficial and detrimental consequences of stimulating high densities of organisms adjacent to newly formed root, regulating the chemical composition of exudates would represent a potential means of plant selection for beneficial microorganisms. If exudate resource composition functions to select specific microorganisms, then one would expect that substrate specialization exists within the rhizosphere microbiome. Here we provide evidence that in the rhizosphere of wild oats (Avena barbata), specific metabolites are exuded that are preferentially used by selected bacteria in rhizosphere and this substrate specialization, together with the changing composition of root exudates, drives the observed successional patterns. To investigate the relationship between exudates and rhizosphere bacteria we first analyzed exudate composition of hydroponically grown plants using LC-MS/MS based metabolomics. We then designed a medium to simulate plant exudates and using this medium we examined the substrate preferences of a diversity of rhizosphere bacterial isolates. We then assessed the ability of soil isolates to consume exudate components by LC-MS/MS based metabolomics. These substrate preferences were then related to genomic features and successional patterns of bacteria in the Avena rhizosphere. The major fraction of plant exudates was found to be composed of amino- and carboxylic acids, sugars, nucleosides, quaternary amines and plant hormones. Amino acids, sugars and nucleosides were consumed by all analyzed isolates. However, isolates that were preferentially stimulated by plant growth, revealed substrate utilization preferences towards aromatic organic acids, while those not responding to growing roots did not utilize these compounds under these conditions. This substrate partitioning among rhizosphere bacteria can be suggested as a potential mechanism for how plants influence the structure of their rhizosphere microbiome and provides a key insight into the mechanisms underlying patterns of ecological succession in soil.
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NASA Astrophysics Data System (ADS)
Anissimova, Marina; Heinze, Stefanie; Chen, Yona; Tarchitzky, Jorge; Marschner, Bernd
2014-05-01
Irrigation of soils with treated wastewater (TWW) directly influences microbial processes of soil. TWW contains easily decomposable organic material, which can stimulate the activity of soil microorganisms and, as a result, lead to the excessive consumption of soil organic carbon pool. We investigated the effects of irrigation with TWW relative to those of irrigation with freshwater (FW) on the microbial parameters in soils with low (7%) and medium (13%) clay content in a lysimeter experiment. The objectives of our study were to (i) determine the impact of water quality on soil respiration and enzymatic activity influenced by clay content and depth, and (ii) work out the changes in the turnover of soil organic matter (PE, priming effects). Samples were taken from three soil depths (0-10, 10-20, and 40-60 cm). Soil respiration and PE were determined in a 21-days incubation experiment after addition of uniformly 14C-labeled fructose. Activity of 10 extracellular enzymes (EEA, from C-, N-, P-, and S-cycle), phenol oxidase and peroxidase activity (PO+PE), and dehydrogenase activity (DHA) were assayed. Microbial Community-Level Physiological Profiles (CLPP) using four substrates, and microbial biomass were determined. The results showed that the clay content acted as the main determinative factor. In the soil with low clay content the water quality had a greater impact: the highest PE (56%) was observed in the upper layer (0-10cm) under FW irrigation; EEA of C-, P-, and S-cycles was significantly higher in the upper soil layer under TWW irrigation. Microbial biomass was higher in the soil under TWW irrigation and decreased with increasing of depth (50 μg/g soil in the upper layer, 15 μg/g soil in the lowest layer). This tendency was also observed for DHA. Contrary to the low clay content, in the soil with medium clay content both irrigation types caused the highest PE in the lowest layer (65% under FW irrigation, 48% under TWW irrigation); the higher substrate mineralization (10%) and the highest phosphatase activity (in the case of FW irrigation) was observed. The PO+PE activity was two to three times higher than in the soil with low clay content and increased clearly with increasing of soil depth. The last tendency was also valid generally for the enzymes of C-, N-, and P-cycles under both types of irrigation. The upper layer in the soil under TWW irrigation was characterized by the highest microbial biomass value (74 μg/g soil). DHA in all soil depths under both types of irrigation was significantly higher than in the corresponding depths of soil with low clay content. CLPP data showed the highest consumption of ascorbic acid and D-glucosamine hydrochloride in comparison to consumption of D-glucose and L-glutamine in both irrigation types.
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Venkata Mohan, S; Ramakrishna, M; Shailaja, S; Sarma, P N
2007-09-01
The influence of soil-water ratio was studied on the performance of the slurry phase bioreactor operated in sequencing batch mode (anoxic-aerobic-anoxic microenvironments) during the bioremediation of soil contaminated with pendimethalin. The performance of the reactors was evaluated at different soil-water ratios (1:5-1:25; at soil loading rate (60 kg of soil/cum-day to 12 kg of soil/cum-day)) keeping the loading rate of pendimethalin constant (133.2 g/kg of soil-day) in six reactors and variable (66.6 g/kg of soil-day to 166.6 g/kg of soil-day) in other four reactors. At 1:20 soil-water ratio, the slurry phase system showed enhanced degradation of substrate (629 microg pendimethalin/g soil). The removal efficiency of pendimethalin in the reactors was dependent on the mass-transfer rates of the substrate from the soil to the aqueous phase. Soil-water ratio and substrate loading rates showed significant influence on the substrate portioning, substrate degradation efficiency and substrate desorption rate.
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Warming accelerates decomposition of decades-old carbon in forest soils
Hopkins, F. M.; Torn, M. S.; Trumbore, S. E.
2012-06-11
Global climate carbon-cycle models predict acceleration of soil organic carbon losses to the atmosphere with warming, but the size of this feedback is poorly known. The temperature sensitivity of soil carbon decomposition is commonly determined by measuring changes in the rate of carbon dioxide (CO 2) production under controlled laboratory conditions. We added measurements of carbon isotopes in respired CO 2 to constrain the age of carbon substrates contributing to the temperature response of decomposition for surface soils from two temperate forest sites with very different overall rates of carbon cycling. Roughly one-third of the carbon respired at any temperaturemore » was fixed from the atmosphere more than 10 y ago, and the mean age of respired carbon reflected a mixture of substrates of varying ages. Consistent with global ecosystem model predictions, the temperature sensitivity of the carbon fixed more than a decade ago was the same as the temperature sensitivity for carbon fixed less than 10 y ago. However, we also observed an overall increase in the mean age of carbon respired at higher temperatures, even correcting for potential substrate limitation effects. The combination of several age constraints from carbon isotopes showed that warming had a similar effect on respiration of decades-old and younger (<10 y) carbon but a greater effect on decomposition of substrates of intermediate (between 7 and 13 y) age. Our results highlight the vulnerability of soil carbon to warming that is years-to-decades old, which makes up a large fraction of total soil carbon in forest soils globally.« less
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Warming accelerates decomposition of decades-old carbon in forest soils.
Hopkins, Francesca M; Torn, Margaret S; Trumbore, Susan E
2012-06-26
Global climate carbon-cycle models predict acceleration of soil organic carbon losses to the atmosphere with warming, but the size of this feedback is poorly known. The temperature sensitivity of soil carbon decomposition is commonly determined by measuring changes in the rate of carbon dioxide (CO(2)) production under controlled laboratory conditions. We added measurements of carbon isotopes in respired CO(2) to constrain the age of carbon substrates contributing to the temperature response of decomposition for surface soils from two temperate forest sites with very different overall rates of carbon cycling. Roughly one-third of the carbon respired at any temperature was fixed from the atmosphere more than 10 y ago, and the mean age of respired carbon reflected a mixture of substrates of varying ages. Consistent with global ecosystem model predictions, the temperature sensitivity of the carbon fixed more than a decade ago was the same as the temperature sensitivity for carbon fixed less than 10 y ago. However, we also observed an overall increase in the mean age of carbon respired at higher temperatures, even correcting for potential substrate limitation effects. The combination of several age constraints from carbon isotopes showed that warming had a similar effect on respiration of decades-old and younger (<10 y) carbon but a greater effect on decomposition of substrates of intermediate (between 7 and 13 y) age. Our results highlight the vulnerability of soil carbon to warming that is years-to-decades old, which makes up a large fraction of total soil carbon in forest soils globally.
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Energizing marginal soils: A perennial cropping system for Sida hermaphrodita
NASA Astrophysics Data System (ADS)
Nabel, Moritz; Poorter, Hendrik; Temperton, Vicky; Schrey, Silvia D.; Koller, Robert; Schurr, Ulrich; Jablonowski, Nicolai D.
2017-04-01
As a way to avoid land use conflicts, the use of marginal soils for the production of plant biomass can be a sustainable alternative to conventional biomass production (e.g. maize). However, new cropping strategies have to be found that meet the challenge of crop production under marginal soil conditions. We aim for increased soil fertility by the use of the perennial crop Sida hermaphrodita in combination with organic fertilization and legume intercropping to produce substantial biomass yield. We present results of a three-year outdoor mesocosm experiment testing the perennial energy crop Sida hermaphrodita grown on a marginal model substrate (sand) with four kinds of fertilization (Digestate broadcast, Digestate Depot, mineral NPK and unfertilized control) in combination with legume intercropping. After three years, organic fertilization (via biogas digestate) compared to mineral fertilization (NPK), reduced the nitrate concentration in leachate and increased the soil carbon content. Biomass yields of Sida were 25% higher when fertilized organically, compared to mineral fertilizer. In general, digestate broadcast application reduced root growth and the wettability of the sandy substrate. However, when digestate was applied locally as depot to the rhizosphere, root growth increased and the wettability of the sandy substrate was preserved. Depot fertilization increased biomass yield by 10% compared to digestate broadcast fertilization. We intercropped Sida with various legumes (Trifolium repens, Trifolium pratense, Melilotus spp. and Medicago sativa) to enable biological nitrogen fixation and make the cropping system independent from synthetically produced fertilizers. We could show that Medicago sativa grown on marginal substrate fixed large amounts of N, especially when fertilized organically, whereas mineral fertilization suppressed biological nitrogen fixation. We conclude that the perennial energy crop Sida in combination with organic fertilization has great potential to increase the soil fertility of marginal substrates and produce substantial biomass yields.
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Recycling vs. stabilisation of soil sugars - a long-term laboratory incubation experiment
NASA Astrophysics Data System (ADS)
Basler, A.; Dippold, M.; Helfrich, M.; Dyckmans, J.
2015-06-01
Independent of its chemical structure carbon (C) persists in soil for several decades, controlled by stabilisation and recycling. To disentangle the importance of the two factors on the turnover dynamics of soil sugars, an important compound of soil organic matter (SOM), a three year incubation experiment was conducted on a silty loam soil under different types of land use (arable land, grassland and forest) by adding 13C-labeled glucose. The compound specific isotope analysis of soil sugars was used to examine the dynamics of different sugars during incubation. Sugar dynamics were dominated by a pool of high mean residence times (MRT) indicating that recycling plays an important role for sugars. However, this was not substantially affected by soil C content. Six months after label addition the contribution of the label was much higher for microbial biomass than for CO2 production for all examined soils, corroborating that substrate recycling was very effective within the microbial biomass. Two different patterns of tracer dynamics could be identified for different sugars: while fucose (fuc) and mannose (man) showed highest label contribution at the beginning of the incubation with a subsequent slow decline, galactose (gal) and rhamnose (rha) were characterised by slow label incorporation with subsequently constant levels, which indicates that recycling is dominating the dynamics of these sugars. This may correspond to (a) different microbial growing strategies (r and K-strategist) or (b) location within or outside the cell membrane (lipopolysaccharides vs. exopolysaccharides) and thus be subject of different re-use within the microbial food web. Our results show how the microbial community recycles substrate very effectively and that high losses of substrate only occur during initial stages after substrate addition.
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Monitoring the Soil Water Availability of Young Urban Trees in Hamburg, Germany
NASA Astrophysics Data System (ADS)
Titel, Selina; Gröngröft, Alexander; Eschenbach, Annette
2017-04-01
In large cities numerous trees have to be planted each year to replace died off or cut down trees or for greening of constructed roads and newly built quarters. The typical age of planted trees is between five and fifteen years. Often the planting takes place in special planting pits to stimulate the tree growth under the restricted urban conditions. Consequently, trees are surrounded by different soil substrates: the soil from the nursery in the root ball, the special planting pit substrate and the surrounding urban soil which is often anthropogenic influenced. Being relocated in the city, trees have to cope with the warmer urban climate, the soil sealing and compaction and the low water storage capacity of the substrate. All factors together increase the probability of dry phases for roadside trees. The aim of this study is to monitor the soil water availability at sites of planted roadside trees during the first years after planting. Therefore, a measuring design was developed, which works automatically and takes the complex below ground structure of the soil into account. This approach consists of 13 soil water tension sensors inside and outside of each planting pit up to one meter depth connected to a data logger. The monitoring devices will finally be installed at 20 roadside trees (amongst others Quercus cerris, Quercus robur, Acer platanoides 'Fairview') in Hamburg, Germany, to identify phases of drought stress. The young trees were mainly planted in spring 2016. Data of the first year of measurements show, that the water tension varied between the different soil substrates and the depth. In the first year of tree growth in the city, soil in the tree root ball became significantly drier than the surrounding soil material. In late summer 2016 the water tension in the topsoil had the potential to cause drought stress below some trees.
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NASA Astrophysics Data System (ADS)
Toosi, E. R.; Yu, J.; Doane, T. A.; Guber, A.; Rivers, M. L.; Marsh, T. L.; Ali, K.; Kravchenko, A. N.
2015-12-01
Enduring challenges in understanding soil organic matter (SOM) stability and emission of greenhouse gases (GHGs) from soil stem from complexities of soil processes, many of which occur at micro-scales. The goal of this study is to evaluate the interactive effects soil pore characteristics, soil moisture levels, inherent SOM levels and properties, and substrate quality, on GHGs emission, and accelerated decomposition of native SOM following addition of fresh substrate i.e. priming. Our core hypothesis is that soil pore characteristics play a major role as a mediator in (i) the decomposition of organic matter regardless of its source (i.e. litter vs. native SOM) or substrate quality, as well as in (ii) GHGs emissions. Samples with prevalence of small (<10 μm) vs. large (>30 μm) pores were prepared from soils with similar properties but under long-term contrasting management. The samples were incubated (110 d) at low and optimum soil moisture conditions after addition of high quality (13C-soybean) and low quality (13C-corn) substrate. Headspace gas was analyzed for 13C-CO2 and GHGs on a regularly basis (day 1, 3, 7, 14, 24, 36, 48, 60, 72, 90, and 110). Selected samples were scanned at the early stage of decomposition (7, 14, 24 d) at 2-6 μm resolutions using X-ray computed μ tomography in order to: (1) quantify soil pore characteristics; (2) visualize and quantify distribution of soil moisture within samples of different pore characteristics; and (3) to visualize and measure losses of decomposing plant residue. Initial findings indicate that, consistent with our hypotheses, pore characteristics influenced GHGs emission, and intensity and pattern of plant residue decomposition. The importance of pores was highly pronounced in presence of added plant residue where greater N2O emission occurred in samples with dominant large pores, in contrast to CO2. Further findings will be discussed upon completion of the study and analysis of the results.
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Aridity and plant uptake interact to make dryland soils hotspots for nitric oxide (NO) emissions
Blankinship, Joseph C.; Marchus, Kenneth; Lucero, Delores M.; Sickman, James O.; Schimel, Joshua P.
2016-01-01
Nitric oxide (NO) is an important trace gas and regulator of atmospheric photochemistry. Theory suggests moist soils optimize NO emissions, whereas wet or dry soils constrain them. In drylands, however, NO emissions can be greatest in dry soils and when dry soils are rewet. To understand how aridity and vegetation interact to generate this pattern, we measured NO fluxes in a California grassland, where we manipulated vegetation cover and the length of the dry season and measured [δ15-N]NO and [δ18-O]NO following rewetting with 15N-labeled substrates. Plant N uptake reduced NO emissions by limiting N availability. In the absence of plants, soil N pools increased and NO emissions more than doubled. In dry soils, NO-producing substrates concentrated in hydrologically disconnected microsites. Upon rewetting, these concentrated N pools underwent rapid abiotic reaction, producing large NO pulses. Biological processes did not substantially contribute to the initial NO pulse but governed NO emissions within 24 h postwetting. Plants acted as an N sink, limiting NO emissions under optimal soil moisture. When soils were dry, however, the shutdown in plant N uptake, along with the activation of chemical mechanisms and the resuscitation of soil microbial processes upon rewetting, governed N loss. Aridity and vegetation interact to maintain a leaky N cycle during periods when plant N uptake is low, and hydrologically disconnected soils favor both microbial and abiotic NO-producing mechanisms. Under increasing rates of atmospheric N deposition and intensifying droughts, NO gas evasion may become an increasingly important pathway for ecosystem N loss in drylands. PMID:27114523
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Enzymatic activity inside and outside of water-stable aggregates in soils under different land use
NASA Astrophysics Data System (ADS)
Garbuz, S. A.; Yaroslavtseva, N. V.; Kholodov, V. A.
2016-03-01
A method is presented for assessing the distribution of enzymatic activity inside and outside of water-stable aggregates. Two samples of water-stable aggregates >1 mm have been isolated from dry aggregates of 1-2 mm. To determine the enzymatic activity, a substrate has been added to one of the samples without disaggregation; the other sample has been preliminarily disaggregated. Enzymatic activity within waterstable aggregates has been assessed from the difference between the obtained results under the supposition that the penetration of substrate within the water-saturated aggregates is hampered, and enzymatic reactions occur only at the periphery. The levels and distributions of enzymatic (peroxidase, polyphenol oxidase, and catalase) activities in water-stable aggregates of soddy-podzolic soils under forest and plowland and typical chernozems of long-term field experiments have been studied. The peroxidase, polyphenol oxidase, and catalase activities of water-stable aggregates vary from 6 to 23, from 7 to 30, and from 5 to 7 mmol/(g h), respectively. The ratio between the enzymatic activities inside and outside of soil aggregates showed a higher dependence on soil type and land use, as well as on the input of organic matter and the structural state, than the general activity level in water-stable aggregates.
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Mäkipää, Raisa; Rajala, Tiina; Schigel, Dmitry; Rinne, Katja T; Pennanen, Taina; Abrego, Nerea; Ovaskainen, Otso
2017-01-01
We investigated the interaction between fungal communities of soil and dead wood substrates. For this, we applied molecular species identification and stable isotope tracking to both soil and decaying wood in an unmanaged boreal Norway spruce-dominated stand. Altogether, we recorded 1990 operational taxonomic units, out of which more than 600 were shared by both substrates and 589 were found to exclusively inhabit wood. On average the soil was more species-rich than the decaying wood, but the species richness in dead wood increased monotonically along the decay gradient, reaching the same species richness and community composition as soil in the late stages. Decaying logs at all decay stages locally influenced the fungal communities from soil, some fungal species occurring in soil only under decaying wood. Stable isotope analyses suggest that mycorrhizal species colonising dead wood in the late decay stages actively transfer nitrogen and carbon between soil and host plants. Most importantly, Piloderma sphaerosporum and Tylospora sp. mycorrhizal species were highly abundant in decayed wood. Soil- and wood-inhabiting fungal communities interact at all decay phases of wood that has important implications in fungal community dynamics and thus nutrient transportation. PMID:28430188
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Mäkipää, Raisa; Rajala, Tiina; Schigel, Dmitry; Rinne, Katja T; Pennanen, Taina; Abrego, Nerea; Ovaskainen, Otso
2017-09-01
We investigated the interaction between fungal communities of soil and dead wood substrates. For this, we applied molecular species identification and stable isotope tracking to both soil and decaying wood in an unmanaged boreal Norway spruce-dominated stand. Altogether, we recorded 1990 operational taxonomic units, out of which more than 600 were shared by both substrates and 589 were found to exclusively inhabit wood. On average the soil was more species-rich than the decaying wood, but the species richness in dead wood increased monotonically along the decay gradient, reaching the same species richness and community composition as soil in the late stages. Decaying logs at all decay stages locally influenced the fungal communities from soil, some fungal species occurring in soil only under decaying wood. Stable isotope analyses suggest that mycorrhizal species colonising dead wood in the late decay stages actively transfer nitrogen and carbon between soil and host plants. Most importantly, Piloderma sphaerosporum and Tylospora sp. mycorrhizal species were highly abundant in decayed wood. Soil- and wood-inhabiting fungal communities interact at all decay phases of wood that has important implications in fungal community dynamics and thus nutrient transportation.
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Influence of biochar and terra preta substrates on wettability and erodibility of soils
NASA Astrophysics Data System (ADS)
Smetanova, A.; Dotterweich, M.; Diehl, D.; Ulrich, U.; Fohrer, N.
2012-04-01
Biochar (BC) and terra preta substrates (TPS) have recently been promoted as soil amendments suitable for soil stabilization, soil amelioration and long-term carbon sequestration. BC is a carbon-enriched substance produced by thermal decomposition of organic material. TPS is composed of liquid and solid organic matter, including BC, altered by acid-lactic fermentation. Their effect on wettability, soil erodibility and nutrient discharge through overland flow was studied by laboratory experiments. At water contents between 0 and 100% BC is water repellent, while TPS changes from a wettable into a repellent state. The 5 and 10 vol % mixtures of BC and 10 and 20 vol% mixtures of TPS with sand remain mainly wettable during drying but repellency maxima are shifted to higher water contents with respect to pure sand and are mainly of subcritical nature. The runoff response was dominated by infiltration properties of the substrates rather than their wettability.Only one mixtures (20% TPS) produced more runoff than sandy-loamy soil on a 15% slope at an intensity of 25 mm•h-1. The 10% BC decreased runoff by up to 40%. At higher rainfall intensities (45 and 55 mm•h-1) the 10% TPS7 was up to 35% less erodible than 10% BC. Despite the TPS containing more nutrients, nutrient discharge varied between types of nutrients, slopes, rainfall intensities and mixtures. The application of a 1 cm layer onto the soil surface instead of 10% mixtures is not recommended due to high nutrient concentrations in the runoff and the wettability of pure substrates. The usage of 10% BC in lowland areas with low frequency and low-intensity precipitation and 10% TPS7 in areas with higher rainfall intensities appears to be appropriate and commendable according to current results. However, together with reversibility of repellency, it needs to undergo further examination in the field under different environmental and land use conditions Key words: biochar, terra preta substrate, wettability, erodibility, nutrient discharge
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Soil functional diversity analysis of a bauxite-mined restoration chronosequence.
Lewis, Dawn E; White, John R; Wafula, Denis; Athar, Rana; Dickerson, Tamar; Williams, Henry N; Chauhan, Ashvini
2010-05-01
Soil microorganisms are sensitive to environmental perturbations such that changes in microbial community structure and function can provide early signs of anthropogenic disturbances and even predict restoration success. We evaluated the bacterial functional diversity of un-mined and three chronosequence sites at various stages of rehabilitation (0, 10, and 20 years old) located in the Mocho Mountains of Jamaica. Samples were collected during the dry and wet seasons and analyzed for metal concentrations, microbial biomass carbon, bacterial numbers, and functional responses of soil microbiota using community-level physiological profile (CLPP) assays. Regardless of the season, un-mined soils consisted of higher microbial biomass and numbers than any of the rehabilitated sites. Additionally, the number and rate of substrates utilized and substrate evenness (the distribution of color development between the substrates) were significantly greater in the un-mined soils with carbohydrates being preferentially utilized than amino acids, polymers, carboxylic acids, and esters. To some extent, functional responses varied with the seasons but the least physiological activity was shown by the site rehabilitated in 1987 indicating long-term perturbation to this ecosystem. Small subunit ribosomal DNA (SSUrDNA)-denaturing gradient-gel electrophoresis analyses on the microbiota collected from the most preferred CLPP substrates followed by taxonomic analyses showed Proteobacteria, specifically the gamma-proteobacteria, as the most functionally active phyla, indicating a propensity of this phyla to out-compete other groups under the prevailing conditions. Additionally, multivariate statistical analyses, Shannon's diversity, and evenness indices, principal component analysis, biplot and un-weighted-pair-group method with arithmetic averages dendrograms further confirmed that un-mined sites were distinctly different from the rehabilitated soils.
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NASA Astrophysics Data System (ADS)
Holland, Elisabeth A.; Neff, Jason C.; Townsend, Alan R.; McKeown, Becky
2000-12-01
Tropical ecosystems play a central role in the global carbon cycle. Large changes in tropical temperature over geologic time and the significant responses of tropical ecosystems to shorter-term variations such as El Niño/La Niña argue for a robust understanding of the temperature sensitivity of tropical decomposition. To examine the responsiveness of heterotrophic respiration to temperature, we measured rates of heterotrophic respiration from a wide range of tropical soils in a series of laboratory incubations. Under conditions of optimal soil water and nonlimiting substrate availability, heterotrophic respiration rose exponentially with rising temperature. The meanQ10measured across all temperature ranges in these short-term incubations was 2.37, but there was significant variation inQ10s across sites. The source of this variation could not be explained by soil carbon or nitrogen content, soil texture, site climate, or lignin to nitrogen ratio. At the beginning of the incubation, heterotrophic respiration increased exponentially with temperature for all sites, despite the fact that the fluxes differed by an order of magnitude. When substrate availability became limiting later in the incubation, the temperature response changed, and heterotrophic response declined above 35°C. The documented changes in temperature sensitivity with substrate availability argue for using temperature relationships developed under optimal conditions of substrate availability for models which include temperature regulation of heterotrophic respiration. To evaluate the significance of this natural variation in temperature control over decomposition, we used the Century ecosystem model gridded for the areas between the tropics of Cancer and Capricorn. These simulations used the mean and upper and lower confidence limits of the normalized exponential temperature response of our experimental studies. We found that systems with the lowest temperature sensitivity accumulated a total of 70 Pg more carbon in soil organic carbon and respired 5.5 Pg yr-1 less carbon compared to the systems with the highest sensitivity.
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Short-term incubation studies on degradation of biochar in soil
NASA Astrophysics Data System (ADS)
Lanza, Giacomo; Wirth, Stephan; Geßler, Arthur; Kern, Jürgen; Mumme, Jan
2014-05-01
Biochar is considered a stable, recalcitrant substance, which holds potential to store carbon in soils for prolonged time and therefore would provide a long-term carbon sink. Furthermore, biochar is discussed to enhance soil fertility and plant productivity, and may improve water and nutrient holding capacity. However, mineralisation to CO2 may occur, as for any soil organic carbon pool, depending on char composition, soil properties and environmental conditions. Therefore, it is important to gain insight into the stability of its carbon structure and the dynamics of decay processes in soil. The evaluation of biochar stability in soil is complicated by the impact of external factors thus as soil moisture and temperature, soil nutrient status and moreover by extended decay timescales. To overcome these difficulties, we performed dynamic incubation experiments under laboratory conditions, using a multi-channel, automated infra-red gas analysis system at 20°C for up to 10 days to detect CO2 emission over time. Our aim was to compare the decay dynamics of different biochar preparations added to soil, i.e. HTC-char and pyrochar from maize silage with and without biological post-processing (anaerobic digestion), as compared to unmodified maize straw. Digestate from a maize silage-fed anaerobic biogas reactor was also tested. As a result, the addition of charred or digested materials to soil resulted in much lower CO2 emission rates as compared to the unmodified maize straw, proving stability of biochar carbon compounds. Pyrochar showed to be the most stable of all substrates added, as the CO2 emission was hardly distinguishable from that of the control soil. Soil enriched with HTC-char emitted significantly more CO2 compared to soil enriched with pyrochar, but the post-processing was effective in reducing the emissions. Furthermore, HTC-char showed a two-step decay kinetics, which cannot apparently be explained with a simple double-pool model. In conclusion, the short-term incubation approach was effective to highlight differences in decomposition dynamics between the considered substrates in soil, and confirmed the effectiveness of the charring process to increase the stability of organic substrates in soil. More investigations are necessary to reveal the impact of readily available substrates and nutrients on degradation of biochar in soil, and to clarify the mechanisms responsible for the observed kinetics in order to derive a suitable process model.
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Activity and stability of a complex bacterial soil community under simulated Martian conditions
NASA Astrophysics Data System (ADS)
Hansen, Aviaja Anna; Merrison, Jonathan; Nørnberg, Per; Aagaard Lomstein, Bente; Finster, Kai
2005-04-01
A simulation experiment with a complex bacterial soil community in a Mars simulation chamber was performed to determine the effect of Martian conditions on community activity, stability and survival. At three different depths in the soil core short-term effects of Martian conditions with and without ultraviolet (UV) exposure corresponding to 8 Martian Sol were compared. Community metabolic activities and functional diversity, measured as glucose respiration and versatility in substrate utilization, respectively, decreased after UV exposure, whereas they remained unaffected by Martian conditions without UV exposure. In contrast, the numbers of culturable bacteria and the genetic diversity were unaffected by the simulated Martian conditions both with and without UV exposure. The genetic diversity of the soil community and of the colonies grown on agar plates were evaluated by denaturant gradient gel electrophoresis (DGGE) on DNA extracts. Desiccation of the soil prior to experimentation affected the functional diversity by decreasing the versatility in substrate utilization. The natural dominance of endospores and Gram-positive bacteria in the investigated Mars-analogue soil may explain the limited effect of the Mars incubations on the survival and community structure. Our results suggest that UV radiation and desiccation are major selecting factors on bacterial functional diversity in terrestrial bacterial communities incubated under simulated Martian conditions. Furthermore, these results suggest that forward contamination of Mars is a matter of great concern in future space missions.
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NASA Astrophysics Data System (ADS)
McMillan, Mica Franklin
Soil water repellency (SWR) negatively affects turfgrass growth and quality and impedes uniform distribution of water, particularly in sand-based rootzones. Surfactants and soil amendments such as calcined clay are two approaches to improving soil hydrological properties affected by SWR. However, studying SWR in the field is difficult due to the extreme spatial variability in the soil profile. An objective of this dissertation was to assess two methods to impart SWR on sand and examine SWR amelioration strategies using these procedures under a plant environment and deficit irrigation. To determine effectiveness of artificial hydrophobicity, two methods produced severely hydrophobic substrates: stearic acid sand (HSS) and sand:peat (90:10 sand:peat v/v)(HSP). Greenhouse studies compared the effects of substrates HSS, HSP, 100% sand (SAND), sand:peat (90:10 v/v) (SP), sand:calcined clay (90:10 v/v) (CC) and naturally water repellent sand (NWRS) on bermudagrass [Cynodon dactylon (L.) Pers. x C. transvaalensis Burtt Davy] establishment and growth. Results indicate that HSS and HSP were not toxic to turfgrass but initially, hindered bermudagrass growth. At trials end, SWR had declined in both soils. A second greenhouse study assessed surfactant chemistry on substrates. After three dry downs, surfactants generally improved turfgrass quality in SAND and CC but had no significant effect in HSP and SP. Water drop penetration tests deemed CC and SAND wettable and HSP and SP nonwettable. Contact angle analysis found CC and SAND to be subcritically water repellent while HSP and SP were water repellent. Both HSP and HSS could be used to evaluate the influence of SWR on plant growth. However, both methods have disadvantages. CC remained wettable after several dry downs. In another greenhouse study, perennial ryegrass (Lolium perenne) seeds coated with 10% w/w alkyl-terminated block copolymer surfactant seed coating (SC) were evaluated as an amelioration strategy. Seed treated with surfactant yielded similar or greater percent coverage, shoot growth, root weight and increased volumetric water in the majority of substrates when compared to substrates sown with untreated seed. Coating seeds with surfactant may be used as a method to improve seed germination, establishment and enhance soil moisture, particularly under deficit irrigation.
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Detection of soil microorganism in situ by combined gas chromatography mass spectrometry
NASA Technical Reports Server (NTRS)
Alexander, M.; Duxbury, J. M.; Francis, A. J.; Adamson, J.
1972-01-01
Experimental tests were made to determine whether analysis of volatile metabolic products, formed in situ, is a viable procedure for an extraterrestrial life detection system. Laboratory experiments, carried out under anaerobic conditions with addition of carbon source, extended to include a variety of soils and additional substrates. In situ experiments were conducted without amendment using a vacuum sampling system.
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Álvarez-Martín, Alba; Sánchez-Martín, María Jesús; Pose-Juan, Eva; Rodríguez-Cruz, María Sonia
2016-04-15
Physicochemical methods to immobilize pesticides in vulnerable soils are currently being developed to prevent water contamination. Some of these methods include the use of different organic residues to modify soils because they could limit the transport of pesticides and/or facilitate their dissipation. Spent mushroom substrate (SMS) may be used for these purposes. Accordingly a study was conducted under laboratory conditions to know the dissipation and bioavailability of the fungicides cymoxanil and tebuconazole over time in a vineyard soil amended with two rates of spent mushroom substrate (SMS) (5% and 50% (w/w)), selected to prevent the diffuse or point pollution of soil. The dissipation of cymoxanil was more rapid than that of tebuconazole in the different soils studied. The dissipation rate was higher in the amended soil than in the unamended one for both compounds, while no significant differences were observed between the amended soils in either case. An apparent dissipation occurred in the amended soil due to the formation of non-extractable residues. Bound residues increased with incubation time for tebuconazole, although a proportion of this fungicide was bioavailable after 303days. The major proportion of cymoxanil was tightly bound to the amended soil from the start, although an increasing fraction of bound fungicide was bioavailable for mineralization. Soil dehydrogenase activity was significantly affected by SMS application and incubation time; however, it was not significantly modified by fungicide application. The significance of this research suggests that SMS applied at a low or high rate to agricultural soil can be used to prevent both the diffuse or point pollution of soil through the formation of non-extractable residues, although more research is needed to discover the time that fungicides remain adsorbed into the soil decreasing either bioavailability (tebuconazole) or mineralization (cymoxanil) in SMS-amended soils. Copyright © 2016 Elsevier B.V. All rights reserved.
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NASA Astrophysics Data System (ADS)
Zhang, Pingjiu; Li, Lianqing; Pan, Genxing; Ren, Jingchen
2006-12-01
Not only the nutritional status and biological activity but also the soil ecological functioning or soil health has been impacted profoundly by land degradation in the karst area of southwest China where the karst ecosystems are generally considered as extremely vulnerable to land degradation under intensified land-use changes. The objectives of this study are to elucidate the changes in overall soil quality by a holistic approach of soil nutritional, biological activity, and soil health indicators in the karst area as impacted by intense cultivation and vegetation degradation. Topsoil samples were collected on selected eco-tesserae in a sequence of land degradation in a karst area of southwest Guizhou in 2004. The soil nutrient pools of organic carbon (Corg), extractable extracellular carbon (Cext), total soil nitrogen (Nt), alkali-hydrolyzable nitrogen (Nah), total phosphorus (Pt), available phosphorus (Pa) were analyzed by wet soil chemistry. The soil biological properties were studied by means of measurements of microbial biomass carbon (both by fumigation-extraction, FE-Cmic, and by calculation from substrate-incubation respiration, SIR-Cmic) of respiration [respiration without addition of substrates, basal respiration (BR), and potential respiration (PR) with substrate-incubation] and of soil enzyme activities (invertase, urease, and alkaline phosphatase). Soil health status was assessed by simple indices of Cmic/Corg and BR/Cmic in conjunction with bacterial community structures determined by polymerase chain reaction and denaturing gradient gel electrophoresis. While the nutritional pool parameters, such as Corg and Cext, described basically the changes in soil life-supporting capacity with cultivation interference and vegetation declined, those parameters of biological activity such as FE-Cmic, SIR, and SIR-Cmic as well as bacterial community structures measured by molecular method evidenced well the changes in soil functioning for ecosystem health with the land degradation.
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Influence of Vegetations' Metabolites on the Composition and Functioning of Soil Microbial Complex
NASA Astrophysics Data System (ADS)
Biryukov, Mikhail
2013-04-01
Microbiota is one of the major factors of soils fertility. It transforms organic substances in soil and, therefore, serves as the main component in the cycles of carbon and nitrogen. Microbial communities (MC) are characterized as highly diverse and extremely complex structures. This allows them to adapt to any affection and provide all the necessary biospheric functions. Hence, the study of their functional diversity and adaptivity of microbiota provides the key to the understanding of the ecosystems' functioning and their adaptivity to the human impact. The formation of MC at the initial stage is regulated by the fluxes of substrates and biologically active substances (BAS), which vary greatly in soils under different vegetations. These fluxes are presented by: low molecular weights organic substances (LMWOS), which can be directly included in metabolism of microbes; polymers, that can be decomposed to LMWOS by exoenzymes; and more complex compounds, having different "drug effects" (e.g. different types of phenolic acids) and regulating growth and enzymatic properties of microbiota. Therefore, the main hypothesis of the research was formulated as follows: penetration of different types of substrates and BAS into soil leads to the emergence of MC varying in enzymatic properties and structure. As a soil matrix we used the soil from the untreated variant of the lysimeter model experiment taking place in the faculty of Soil Science of the MSU for over the last 40 years. It was sieved with a 2mm sieves, humidified and incubated at 25C during one week. Subsequently, the samples were air-dried with occasional stirring for one more week. Thereafter, aliquots of the prepared soil were taken for the different experimental variants. The samples were rewetted with solutions of various substrates (glucose, cellulose, starch, etc.) and thoroughly mixed. The control variant was established with addition of deionised water. The samples were incubated at the 25C. During the incubation the rate of mineralisation of organic substances was assessed with CO2 measurements. In 5, 10 and 21 days of incubation the enzymatic properties of the formed MC were studied by the hydrolysis of fluorogenic substrates. The influence of BAS on enzymatic properties of MC were researched by addition of different concentrations of phenolic acids (e.g. salicylic, vanillic, benzoic, etc.) to the samples from various substrates treatments. The acute toxicity of BAS was studied with bacterial luminescent test. After the last measurement, the isolations of microorganisms on elective nutrient medias were made. The dominant microorganisms were collected to the library for further identification and physiological tests. MeOH-chloroform extraction of phospholipids were performed with the remaining samples. Finally, they were stored for subsequent FAME identifications. The obtained data prove that penetration of various substrates into the soil determines the formation of MC different in structure and properties. It was found, that EC50 of the most studied phenolic acids are similar to naturally occurring concentrations. This means that they can be the real drivers of forming endemical MC under various vegetations along with the plant-specific fluxes of nutrients.
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NASA Astrophysics Data System (ADS)
Basler, A.; Dippold, M.; Helfrich, M.; Dyckmans, J.
2015-10-01
Independent of its chemical structure carbon (C) persists in soil for several decades, controlled by stabilization and recycling. To disentangle the importance of the two factors on the turnover dynamics of soil sugars, an important compound of soil organic matter (SOM), a 3-year incubation experiment was conducted on a silty loam soil under different types of land use (arable land, grassland and forest) by adding 13C-labelled glucose. The compound-specific isotope analysis of soil sugars was used to examine the dynamics of different sugars during incubation. Sugar dynamics were dominated by a pool of high mean residence times (MRT) indicating that recycling plays an important role for sugars. However, this was not substantially affected by soil C content. Six months after label addition the contribution of the label was much higher for microbial biomass than for CO2 production for all examined land use types, corroborating that substrate recycling was very effective within the microbial biomass. Two different patterns of tracer dynamics could be identified for different sugars: while fucose and mannose showed highest label contribution at the beginning of the incubation with a subsequent slow decline, galactose and rhamnose were characterized by slow label incorporation with subsequently constant levels, which indicates that recycling is dominating the dynamics of these sugars. This may correspond to (a) different microbial growing strategies (r and K-strategist) or (b) location within or outside the cell membrane (lipopolysaccharides vs. exopolysaccharides) and thus be subject of different re-use within the microbial food web. Our results show how the microbial community recycles substrate very effectively and that high losses of substrate only occur during initial stages after substrate addition. This study indicates that recycling is one of the major processes explaining the high MRT observed for many SOM fractions and thus is crucial for understanding the global soil C cycle.
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Strigul, Nikolay; Braida, Washington; Christodoulatos, Christos; Balas, Wendy; Nicolich, Steven
2006-01-01
CL-20 is a relatively new energetic compound with applications in explosive and propellant formulations. Currently, information about the fate of CL-20 in ecological systems is scarce. The aim of this study is to evaluate the biodegradability of CL-20 in soil environments. Four soils were used where initial CL-20 concentrations (above water solubility) ranged from 125 to 1500 mg of CL-20 per kg dry soil (corresponding to the concentrations derived from unexploded ordnance, low order detonation, or manufacturing spills). CL-20 appears to be biodegradable in soil under anaerobic conditions, and additions of organic substrates can substantially accelerate this process. However, CL-20 is not degraded in soil under aerobic conditions kept in the dark at temperatures up to 30 degrees C without organic amendments. Additions of starch or cellulose promote the biodegradation of CL-20 under aerobic conditions. Soil microbial community mediated biodegradation and plant uptake appears to enhance CL-20 biodegradation, the latter suggesting a possible route for CL-20 to entry in the food chain.
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Application of spatial time domain reflectometry measurements in heterogeneous, rocky substrates
NASA Astrophysics Data System (ADS)
Gonzales, C.; Scheuermann, A.; Arnold, S.; Baumgartl, T.
2016-10-01
Measurement of soil moisture across depths using sensors is currently limited to point measurements or remote sensing technologies. Point measurements have limitations on spatial resolution, while the latter, although covering large areas may not represent real-time hydrologic processes, especially near the surface. The objective of the study was to determine the efficacy of elongated soil moisture probes—spatial time domain reflectometry (STDR)—and to describe transient soil moisture dynamics of unconsolidated mine waste rock materials. The probes were calibrated under controlled conditions in the glasshouse. Transient soil moisture content was measured using the gravimetric method and STDR. Volumetric soil moisture content derived from weighing was compared with values generated from a numerical model simulating the drying process. A calibration function was generated and applied to STDR field data sets. The use of elongated probes effectively assists in the real-time determination of the spatial distribution of soil moisture. It also allows hydrologic processes to be uncovered in the unsaturated zone, especially for water balance calculations that are commonly based on point measurements. The elongated soil moisture probes can potentially describe transient substrate processes and delineate heterogeneity in terms of the pore size distribution in a seasonally wet but otherwise arid environment.
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Xu, Wenhua; Li, Wei; Jiang, Ping; Wang, Hui; Bai, Edith
2014-01-01
The roles of substrate availability and quality in determining temperature sensitivity (Q10) of soil carbon (C) decomposition are still unclear, which limits our ability to predict how soil C storage and cycling would respond to climate change. Here we determined Q10 in surface organic layer and subsurface mineral soil along an elevation gradient in a temperate forest ecosystem. Q10 was calculated by comparing the times required to respire a given amount of soil C at 15 and 25°C in a 350-day incubation. Results indicated that Q10 of the organic layer was 0.22–0.71 (absolute difference) higher than Q10 of the mineral soil. Q10 in both the organic layer (2.5–3.4) and the mineral soil (2.1–2.8) increased with decreasing substrate quality during the incubation. This enhancement of Q10 over incubation time in both layers suggested that Q10 of more labile C was lower than that of more recalcitrant C, consistent with the Arrhenius kinetics. No clear trend of Q10 was found along the elevation gradient. Because the soil organic C pool of the organic layer in temperate forests is large, its higher temperature sensitivity highlights its importance in C cycling under global warming. PMID:25270905
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Lingli Lui; John S. King; Fitzgerald L. Booker; Christian P. Giardina; H. Lee Allen; Shuijin Hu
2009-01-01
Elevated CO2 has been shown to stimulate plant productivity and change litter chemistry. These changes in substrate availability may then alter soil microbial processes and possibly lead to feedback effects on N availability. However, the strength of this feedback, and even its direction, remains unknown. Further, uncertainty remains whether...
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Zampella, Mariavittoria; Quétel, Christophe R; Paredes, Eduardo; Goitom Asfaha, Daniel; Vingiani, Simona; Adamo, Paola
2011-10-15
We propose a method for the authentication of the origin of vegetables grown under similar weather conditions, in sites less than 10 km distance from the sea and distributed over a rather small scale area (58651 km(2)). We studied how the strontium (Sr) isotopic signature and selected elemental concentrations ([Mn], [Cu], [Zn], [Rb], [Sr] and [Cd]) in early potatoes from three neighbouring administrative regions in the south of Italy were related to the geological substrate (alluvial sediments, volcanic substrates and carbonate rocks) and to selected soil chemical properties influencing the bioavailability of elements in soils (pH, cation exchange capacity and total carbonate content). Through multiple-step multivariate statistics (PLS-DA) we could assign 26 potatoes (including two already commercialised samples) to their respective eight sites of production, corresponding to the first two types of geological substrates. The other 12 potatoes from four sites of production had similar characteristics in terms of the geological substrate (third type) and these soil properties could be grouped together. In this case, more discriminative parameters would be required to allow the differentiation between sites. The validation of our models included external prediction tests with data of potatoes harvested the year before and a study on the robustness of the uncertainties of the measurement results. Annual variations between multi-elemental and Sr isotopic fingerprints were observed in potatoes harvested from soils overlying carbonate rocks, stressing the importance of testing long term variations in authentication studies. Copyright © 2011 John Wiley & Sons, Ltd. and European Union [2011].
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Li, Jing; Wang, Jun-Tao; Hu, Hang-Wei; Ma, Yi-Bing; Zhang, Li-Mei; He, Ji-Zheng
2016-01-01
Dry-rewetting (DW) disturbance frequently occurs in soils due to rainfall and irrigation, and the frequency of DW cycles might exert significant influences on soil microbial communities and their mediated functions. However, how microorganisms respond to DW alternations in soils with a history of heavy metal pollution remains largely unknown. Here, soil laboratory microcosms were constructed to explore the impacts of ten DW cycles on the soil microbial communities in two contrasting soils (fluvo-aquic soil and red soil) under three copper concentrations (zero, medium and high). Results showed that the fluctuations of substrate induced respiration (SIR) decreased with repeated cycles of DW alternation. Furthermore, the resistance values of substrate induced respiration (RS-SIR) were highest in non-copper-stressed (zero) soils. Structural equation model (SEM) analysis ascertained that the shifts of bacterial communities determined the changes of RS-SIR in both soils. The rate of bacterial community variance was significantly lower in non-copper-stressed soil compared to the other two copper-stressed (medium and high) soils, which might lead to the higher RS-SIR in the fluvo-aquic soil. As for the red soil, the substantial increase of the dominant group WPS-2 after DW disturbance might result in the low RS-SIR in the high copper-stressed soil. Moreover, in both soils, the bacterial diversity was highest in non-copper-stressed soils. Our results revealed that initial copper stress could decrease the resistance of soil microbial community structure and function to subsequent DW disturbance. Copyright © 2015. Published by Elsevier B.V.
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Wei, Hui; Yan, Wenbin; Quan, Guoming; Zhang, Jiaen; Liang, Kaiming
2017-09-12
Two Bidens species (Bidens pilosa and B. bipinnata) that originate from America have been introduced widely in pan-tropics, with the former regarded as a noxious invasive weed whereas the latter naturalized as a plant resource. Whether the two species exhibit different effects on the belowground system remains rarely studied. This study was conducted to investigate soil microbial carbon (C) utilization, enzyme activities and available nitrogen, phosphorus and potassium contents under the two species in a subtropical garden soil of southern China under different levels of light intensity. Results showed that the microbial C utilization and enzyme activities were not significantly different under the two species, implying that the strong invasiveness of B. pilosa could not be due to the plant-soil microbe interactions, at least plant-induced alterations of microbial community function to utilize C substrates. Alternatively, available soil nitrogen and potassium contents were significantly higher under B. pilosa than under B. bipinnata in full sun, indicating that the strong invasiveness of B. pilosa could result from rapid nutrient mobilizations by B. pilosa. However, the differences turned non-significant as light intensity decreased, suggesting that light availability could substantially alter the plant effects on soil nutrient mobilizations.
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NASA Astrophysics Data System (ADS)
Tang, Jin-Yun; Riley, William J.
2017-09-01
Several land biogeochemical models used for studying carbon-climate feedbacks have begun explicitly representing microbial dynamics. However, to our knowledge, there has been no theoretical work on how to achieve a consistent scaling of the complex biogeochemical reactions from microbial individuals to populations, communities, and interactions with plants and mineral soils. We focus here on developing a mathematical formulation of the substrate-consumer relationships for consumer-mediated redox reactions of the form A + BE→ products, where products could be, e.g., microbial biomass or bioproducts. Under the quasi-steady-state approximation, these substrate-consumer relationships can be formulated as the computationally difficult full equilibrium chemistry problem or approximated analytically with the dual Monod (DM) or synthesizing unit (SU) kinetics. We find that DM kinetics is scaling inconsistently for reaction networks because (1) substrate limitations are not considered, (2) contradictory assumptions are made regarding the substrate processing rate when transitioning from single- to multi-substrate redox reactions, and (3) the product generation rate cannot be scaled from one to multiple substrates. In contrast, SU kinetics consistently scales the product generation rate from one to multiple substrates but predicts unrealistic results as consumer abundances reach large values with respect to their substrates. We attribute this deficit to SU's failure to incorporate substrate limitation in its derivation. To address these issues, we propose SUPECA (SU plus the equilibrium chemistry approximation - ECA) kinetics, which consistently imposes substrate and consumer mass balance constraints. We show that SUPECA kinetics satisfies the partition principle, i.e., scaling invariance across a network of an arbitrary number of reactions (e.g., as in Newton's law of motion and Dalton's law of partial pressures). We tested SUPECA kinetics with the equilibrium chemistry solution for some simple problems and found SUPECA outperformed SU kinetics. As an example application, we show that a steady-state SUPECA-based approach predicted an aerobic soil respiration moisture response function that agreed well with laboratory observations. We conclude that, as an extension to SU and ECA kinetics, SUPECA provides a robust mathematical representation of complex soil substrate-consumer interactions and can be applied to improve Earth system model (ESM) land models.
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NASA Astrophysics Data System (ADS)
Crawford, L.; Rivera, L. D.; van Iersel, M.
2013-12-01
Moisture release curves are often used when assessing plant-water relationships in soil-less substrates. However, differences between natural soils and soilless substrates make traditional assumptions about plant available water potentially invalid. If soil-less substrates are supposed to be treated like natural soils; why do plants begin wilting at very low water potentials (-10 to -30 kPa) and there is anywhere between 20 to 40 % water left (on a volumetric basis) in the soil (Abad et al., 2005; Arguedas et al., 2006; Ristvey et al, 2008) . We hypothesize that the fault lies in the methods used and the assumption that water potential is the only limiting factor in water availability to plants. Hydraulic properties, including the relationships that exist between plant available water, water content, and hydraulic conductivity of soil-less substrates have traditionally been characterized using instrumentation such as pressure plates, hanging water columns, and tempe cells. These approaches typically take a months and only provide data on select segments of the soil moisture release curve, and in the case of pressure plates and hanging water columns hydraulic conductivity is ignored and not very well understood. Using the Wind/Schindler Evaporation method more detailed measurements of these hydraulic properties can be measured in a less than a week. A more detailed look at the hydraulic properties of soil-less substrates and how they compare with natural soils may give us more insight into soil-plant-water-relations and what limits availability of water to plants. Soil moisture release curves and hydraulic conductivity curves of different soil-less substrates were compared with curves from typical agriculture soils to give insight into how these properties compare. Results of the soil moisture release curves showed that some soil-less substrates had comparable moisture release curves to agricultural soils while others had bi-modal curves indicating gap-gradation in the pore size distribution. These soils that showed this non-typical curve had hydraulic conductivities that dropped very low (500 times lower than agricultural soils) at low water potentials (around 10 kPa). This dramatically lower hydraulic conductivity could lead to zones of depletion around the roots hindering plant water uptake.
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Donaldson, Melissa A.; Bish, David L.; Raff, Jonathan D.
2014-01-01
Nitrous acid (HONO) is an important hydroxyl (OH) radical source that is formed on both ground and aerosol surfaces in the well-mixed boundary layer. Recent studies report the release of HONO from nonacidic soils, although it is unclear how soil that is more basic than the pKa of HONO (∼3) is capable of protonating soil nitrite to serve as an atmospheric HONO source. Here, we used a coated-wall flow tube and chemical ionization mass spectrometry (CIMS) to study the pH dependence of HONO uptake onto agricultural soil and model substrates under atmospherically relevant conditions (1 atm and 30% relative humidity). Experiments measuring the evolution of HONO from pH-adjusted surfaces treated with nitrite and potentiometric titrations of the substrates show, to our knowledge for the first time, that surface acidity rather than bulk aqueous pH determines HONO uptake and desorption efficiency on soil, in a process controlled by amphoteric aluminum and iron (hydr)oxides present. The results have important implications for predicting when soil nitrite, whether microbially derived or atmospherically deposited, will act as a net source or sink of atmospheric HONO. This process represents an unrecognized mechanism of HONO release from soil that will contribute to HONO emissions throughout the day. PMID:25512517
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Donaldson, Melissa A; Bish, David L; Raff, Jonathan D
2014-12-30
Nitrous acid (HONO) is an important hydroxyl (OH) radical source that is formed on both ground and aerosol surfaces in the well-mixed boundary layer. Recent studies report the release of HONO from nonacidic soils, although it is unclear how soil that is more basic than the pKa of HONO (∼ 3) is capable of protonating soil nitrite to serve as an atmospheric HONO source. Here, we used a coated-wall flow tube and chemical ionization mass spectrometry (CIMS) to study the pH dependence of HONO uptake onto agricultural soil and model substrates under atmospherically relevant conditions (1 atm and 30% relative humidity). Experiments measuring the evolution of HONO from pH-adjusted surfaces treated with nitrite and potentiometric titrations of the substrates show, to our knowledge for the first time, that surface acidity rather than bulk aqueous pH determines HONO uptake and desorption efficiency on soil, in a process controlled by amphoteric aluminum and iron (hydr)oxides present. The results have important implications for predicting when soil nitrite, whether microbially derived or atmospherically deposited, will act as a net source or sink of atmospheric HONO. This process represents an unrecognized mechanism of HONO release from soil that will contribute to HONO emissions throughout the day.
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Groundwater quality under the influence of spent mushroom substrate weathering.
Guo, Mingxin
2005-10-01
Nitrate and other solutes resulting from field-weathering of spent mushroom substrate (SMS) percolate into underlying soils and may migrate to groundwater. A field trial was conducted to investigate the potential influences of SMS weathering on groundwater quality. Spent mushroom substrate was deposited at 90 and 150 cm pile depths over a Typic Hapludult and weathered for 2 years. Eight casing wells were installed around the SMS piles to monitor the quality changes of groundwater with a high seasonal water table of 760 cm below the surface. Although leachate solutes had moved more than 200 cm deep in soil from the surface, no significant changes of groundwater quality caused by SMS weathering were observed even one year after removal of the SMS piles (3 years total). The groundwater had pH, electrical conductivity (EC) and dissolved organic carbon (DOC) of 4.3-5.7, 0.2-0.3 dS m(-1) and 0.7-2.2 mg L(-1), respectively. The major inorganic ions were Mg(2+), Ca(2+), Na(+), Cl(-), SO(4)(2-) and NO(3)(-), with a concentration range of 2.5-68.3 mg L(-1). The results suggest that SMS leachate solutes migrated fairly slow in deep subsurface soils of the experimental field. Considering that leachate solutes may move several meters in soil through preferential flow channels, weathering of SMS in fields with a high seasonal groundwater table >or=5 m below the ground is recommended. Conservatively, SMS weathering should be conducted on compact surfaces and leachate be collected and reused as liquid fertilizers.
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Pan, Fuxia; Li, Yaying; Chapman, Stephen James; Yao, Huaiying
2016-03-01
Rice straw application and flooding are common practices in rice production, both of which can induce changes in the microbial community. This study used soil microcosms to investigate the impact of water status (saturated and nonsaturated) and straw application (10 g kg(-1) soil) on soil microbial composition (phospholipid fatty acid analysis) and activity (MicroResp(™) method). Straw application significantly increased total PLFA amount and individual PLFA components independent of soil moisture level. The amount of soil fungal PLFA was less than Gram-negative, Gram-positive, and actinomycete PLFA, except the drained treatment with rice straw application, which had higher fungal PLFA than actinomycete PLFA at the initial incubation stage. Straw amendment and waterlogging had different effects on microbial community structure and substrate-induced pattern. PLFA profiles were primarily influenced by straw application, whereas soil water status had the greater influence on microbial respiration. Of the variation in PLFA and respiration data, straw accounted for 30.1 and 16.7 %, while soil water status explained 7.5 and 29.1 %, respectively. Our results suggest that (1) the size of microbial communities in paddy soil is more limited by carbon substrate availability rather than by the anaerobic conditions due to waterlogging and (2) that soil water status is more important as a control of fungal growth and microbial community activity.
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Substrate-dependent temperature sensitivity of soil organic matter decomposition
NASA Astrophysics Data System (ADS)
Myachina, Olga; Blagodatskaya, Evgenia
2015-04-01
Activity of extracellular enzymes responsible for decomposition of organics is substrate dependent. Quantity of the substrate is the main limiting factor for enzymatic or microbial heterotrophic activity in soils. Different mechanisms of enzymes response to temperature suggested for low and high substrate availability were never proved for real soil conditions. We compared the temperature responses of enzymes-catalyzed reactions in soils. Basing on Michaelis-Menten kinetics we determined the enzymes affinity to substrate (Km) and mineralization potential of heterotrophic microorganisms (Vmax) 1) for three hydrolytic enzymes: β-1,4-glucosidase, N-acetyl- β -D-glucosaminidase and phosphatase by the application of fluorogenically labeled substrates and 2) for mineralization of 14C-labeled glucose by substrate-dependent respiratory response. Here we show that the amount of available substrate is responsible for temperature sensitivity of hydrolysis of polymers in soil, whereas monomers oxidation to CO2 does not depend on substrate amount and is mainly temperature governed. We also found that substrate affinity of enzymes (which is usually decreases with the temperature) differently responded to warming for the process of depolymerisation versus monomers oxidation. We suggest the mechanism to temperature acclimation based on different temperature sensitivity of enzymes kinetics for hydrolysis of polymers and for monomers oxidation.
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Anoxic conditions drive phosphorus limitation in humid tropical forest soil microorganisms
NASA Astrophysics Data System (ADS)
Gross, A.; Pett-Ridge, J.; Weber, P. K.; Blazewicz, S.; Silver, W. L.
2017-12-01
The elemental stoichiometry of carbon (C), nitrogen (N) and phosphorus (P) of soil microorganisms (C:N:P ratios) regulates transfers of energy and nutrients to higher trophic levels. In humid tropical forests that grow on P-depleted soils, the ability of microbes to concentrate P from their surroundings likely plays a critical role in P-retention and ultimately in forest productivity. Models predict that climate change will cause dramatic changes in rainfall patterns in the humid tropics and field studies have shown these changes can affect the redox state of tropical forest soils, influencing soil respiration and biogeochemical cycling. However, the responses of soil microorganisms to changing environmental conditions are not well known. Here, we incubated humid tropical soils under oxic or anoxic conditions with substrates differing in both C:P stoichiometry and lability, to assess how soil microorganisms respond to different redox regimes. We found that under oxic conditions, microbial C:P ratios were similar to the global optimal ratio (55:1), indicating most microbial cells can adapt to persistent aerated conditions in these soils. However, under anoxic conditions, the ability of soil microbes to acquire soil P declined and their C:P ratios shifted away from the optimal ratio. NanoSIMS elemental imaging of single cells extracted from soil revealed that under anoxic conditions, C:P ratios were above the microbial optimal value in 83% of the cells, in comparison to 41% under oxic conditions. These data suggest microbial growth efficiency switched from being energy limited under oxic conditions to P-limited under anoxic conditions, indicating that, microbial growth in low P humid tropical forests soils may be most constrained by P-limitation when conditions are oxygen-limited. We suggest that differential microbial responses to soil redox states could have important implications for productivity of humid tropical forests under future climate scenarios.
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Influence of Soil Properties on Soldierless Termite Distribution.
Bourguignon, Thomas; Drouet, Thomas; Šobotník, Jan; Hanus, Robert; Roisin, Yves
2015-01-01
In tropical rainforests, termites constitute an important part of the soil fauna biomass, and as for other soil arthropods, variations in soil composition create opportunities for niche partitioning. The aim of this study was twofold: first, we tested whether soil-feeding termite species differ in the foraging substrate; second, we investigated whether soil-feeding termites select their foraging sites to enhance nutrients intake. To do so, we collected termites and analysed the composition and structure of their feeding substrates. Although Anoplotermes-group members are all considered soil-feeders, our results show that some species specifically feed on abandoned termite nests and very rotten wood, and that this substrate selection is correlated with previous stable isotope analyses, suggesting that one component of niche differentiation among species is substrate selection. Our results show that the composition and structure of bare soils on which different termite species foraged do not differ, suggesting that there is no species specialization for a particular type of bare soil. Finally, the bare soil on which termites forage does not differ from random soil samples. Overall, our results suggest that few species of the Anoplotermes-group are specialized toward substrates rich in organic matter, but that the vast majority forage on soil independently of its structural and chemical composition, being ecologically equivalent for this factor.
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Delgadillo, Víctor; Verdejo, José; Mondaca, Pedro; Verdugo, Gabriela; Gaete, Hernán; Hodson, Mark E; Neaman, Alexander
2017-06-01
Use of avoidance tests is a quick and cost-effective method of assessing contaminants in soils. One option for assessing earthworm avoidance behavior is a two-section test, which consists of earthworms being given the choice to move between a test soil and a control substrate. For ecological relevance, tested soils should be field-contaminated soils. For practical reasons, artificial soils are commonly used as the control substrate. Interpretation of the test results compromised when the test soil and the artificial substrate differ in their physico-chemical properties other than just contaminants. In this study we identified the physico-chemical properties that influence avoidance response and evaluated the usefulness of adjusting these in the control substrate in order to isolate metal-driven avoidance of field soils by earthworms. A standardized two-section avoidance test with Eisenia fetida was performed on 52 uncontaminated and contaminated (Cu >155mgkg -1 , As >19mgkg -1 ) agricultural soils from the Aconcagua River basin and the Puchuncaví Valley in Chile. Regression analysis indicated that the avoidance response was determined by soil organic matter (OM), electrical conductivity (EC) and total soil Cu. Organic matter content of the artificial substrate was altered by peat additions and EC by NaCl so that these properties matched those of the field soils. The resultant EC 80 for avoidance (indicative of soils of "limited habitat") was 433mg Cu kg -1 (339 - 528mgkg -1 95% confidence intervals). The earthworm avoidance test can be used to assess metal toxicity in field-contaminated soils by adjusting physico-chemical properties (OM and EC) of the artificial control substrate in order to mimic those of the field-collected soil. Copyright © 2017 Elsevier Inc. All rights reserved.
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Allem, Laísa N; Gomes, Anabele S; Borghetti, Fabian
2014-10-21
Studies have identified the phytotoxicity of many native species of the Cerrado; however, most of them were conducted either in inert substrates, or using exaggerate proportions of plant material. We investigated the phytotoxicity of pequi leaves added to substrate soil in quantities compatible with the litter produced by this species. Pequi leaves were triturated and added to red latosol in concentrations of 0.75%, 1.5% and 3%; the control was constituted of leafless soil. These mixtures were added to pots and irrigated daily to keep them moist. Germinated seeds of the cultivated sorghum and sesame, of the invasive brachiaria and of the native purple ipê, were disposed in the pots to grow for five to seven days at 30°C within a photoperiod of 12 h. Seedlings of all the species presented a reduction in their initial growth in a dose-dependent way. In general, the root growth was more affected by the treatments than the shoot growth; moreover, signs of necrosis were observed in the roots of the sorghum, sesame and brachiaria. The phytotoxic effects generated by relatively small quantities of leaves, in a reasonable range of species within a soil substrate, suggest potential allelopathy of pequi leaves under natural conditions.
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Allem, Laísa N; Gomes, Anabele S; Borghetti, Fabian
2014-12-01
Studies have identified the phytotoxicity of many native species of the Cerrado; however, most of them were conducted either in inert substrates, or using exaggerate proportions of plant material. We investigated the phytotoxicity of pequi leaves added to substrate soil in quantities compatible with the litter produced by this species. Pequi leaves were triturated and added to red latosol in concentrations of 0.75%, 1.5% and 3%; the control was constituted of leafless soil. These mixtures were added to pots and irrigated daily to keep them moist. Germinated seeds of the cultivated sorghum and sesame, of the invasive brachiaria and of the native purple ipê, were disposed in the pots to grow for five to seven days at 30°C within a photoperiod of 12 h. Seedlings of all the species presented a reduction in their initial growth in a dose-dependent way. In general, the root growth was more affected by the treatments than the shoot growth; moreover, signs of necrosis were observed in the roots of the sorghum, sesame and brachiaria. The phytotoxic effects generated by relatively small quantities of leaves, in a reasonable range of species within a soil substrate, suggest potential allelopathy of pequi leaves under natural conditions.
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Likus-Cieślik, Justyna; Pietrzykowski, Marcin; Chodak, Marcin
2018-01-01
The impact of tree litter on soil chemistry leachate and sulfurous substrates of mine soils from former Jeziórko sulfur mine was investigated. Composites were used: soil substrate (less contaminated at mean 5090 mg kg -1 S or high contaminated at 42,500 mg kg -1 S) + birch or pine litter and control substrate (no litter). The composites were rinsed with distilled water over 12 weeks. In the obtained leachate, pH, EC, dissolved organic carbon, N, Ca, Mg, Al, and S were determined. Physicochemical parameters of the substrates and their basal respiration rate were determined. Rinsing and litter application lowered sulfur concentration in high contamination substrates. Pine litter application decreased EC and increased pH of the low-contaminated substrate. The substrate pH remained at low phytotoxic level (i.e., below 3.0), resulting in the low biological activity of the composites. Birch litter application increased leaching of N and Mg, indicating the possibility of an intensification of soil-forming processes in contaminated sites.
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Substrate quality alters the microbial mineralization of added substrate and soil organic carbon
NASA Astrophysics Data System (ADS)
Jagadamma, S.; Mayes, M. A.; Steinweg, J. M.; Schaeffer, S. M.
2014-09-01
The rate and extent of decomposition of soil organic carbon (SOC) is dependent, among other factors, on substrate chemistry and microbial dynamics. Our objectives were to understand the influence of substrate chemistry on microbial decomposition of carbon (C), and to use model fitting to quantify differences in pool sizes and mineralization rates. We conducted an incubation experiment for 270 days using four uniformly labeled 14C substrates (glucose, starch, cinnamic acid and stearic acid) on four different soils (a temperate Mollisol, a tropical Ultisol, a sub-arctic Andisol, and an arctic Gelisol). The 14C labeling enabled us to separate CO2 respired from added substrates and from native SOC. Microbial gene copy numbers were quantified at days 4, 30 and 270 using quantitative polymerase chain reaction (qPCR). Substrate C respiration was always higher for glucose than other substrates. Soils with cinnamic and stearic acid lost more native SOC than glucose- and starch-amended soils. Cinnamic and stearic acid amendments also exhibited higher fungal gene copy numbers at the end of incubation compared to unamended soils. We found that 270 days were sufficient to model the decomposition of simple substrates (glucose and starch) with three pools, but were insufficient for more complex substrates (cinnamic and stearic acid) and native SOC. This study reveals that substrate quality exerts considerable control on the microbial decomposition of newly added and native SOC, and demonstrates the need for multi-year incubation experiments to constrain decomposition parameters for the most recalcitrant fractions of SOC and complex substrates.
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Substrate quality alters microbial mineralization of added substrate and soil organic carbon
NASA Astrophysics Data System (ADS)
Jagadamma, S.; Mayes, M. A.; Steinweg, J. M.; Schaeffer, S. M.
2014-03-01
The rate and extent of decomposition of soil organic carbon (SOC) is dependent on substrate chemistry and microbial dynamics. Our objectives were to understand the influence of substrate chemistry on microbial processing of carbon (C), and to use model fitting to quantify differences in pool sizes and mineralization rates. We conducted an incubation experiment for 270 days using four uniformly-labeled 14C substrates (glucose, starch, cinnamic acid and stearic acid) on four different soils (a temperate Mollisol, a tropical Ultisol, a sub-arctic Andisol, and an arctic Gelisol). The 14C labeling enabled us to separate CO2 respired from added substrates and from native SOC. Microbial gene copy numbers were quantified at days 4, 30 and 270 using quantitative polymerase chain reaction (qPCR). Substrate C respiration was always higher for glucose than other substrates. Soils with cinnamic and stearic acid lost more native SOC than glucose- and starch-amended soils, despite an initial delay in respiration. Cinnamic and stearic acid amendments also exhibited higher fungal gene copy numbers at the end of incubation compared to unamended soils. We found that 270 days was sufficient to model decomposition of simple substrates (glucose and starch) with three pools, but was insufficient for more complex substrates (cinnamic and stearic acid) and native SOC. This study reveals that substrate quality imparts considerable control on microbial decomposition of newly added and native SOC, and demonstrates the need for multi-year incubation experiments to constrain decomposition parameters for the most recalcitrant fractions of SOC and added substrates.
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Bajar, Somvir; Singh, Anita; Kaushik, C P; Kaushik, Anubha
2017-05-01
Biocovers are considered as the most effective and efficient way to treat methane (CH 4 ) emission from dumpsites and landfills. Active methanotrophs in the biocovers play a crucial role in reduction of emissions through microbiological methane oxidation. Several factors affecting methane bio-oxidation (MOX) have been well documented, however, their interactive effect on the oxidation process needs to be explored. Therefore, the present study was undertaken to investigate the suitability of a dumpsite soil to be employed as biocover, under the influence of substrate concentrations (CH 4 and O 2 ) and temperature at variable incubation periods. Statistical design matrix of Response Surface Methodology (RSM) revealed that MOX rate up to 69.58μgCH 4 g -1 dw h -1 could be achieved under optimum conditions. MOX was found to be more dependent on CH 4 concentration at higher level (30-40%, v/v), in comparison to O 2 concentration. However, unlike other studies MOX was found in direct proportionality relationship with temperature within a range of 25-35°C. The results obtained with the dumpsite soil biocover open up a new possibility to provide improved, sustained and environmental friendly systems to control even high CH 4 emissions from the waste sector. Copyright © 2017 Elsevier Ltd. All rights reserved.
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Species and Media Effects on Soil Carbon Dynamics in the Landscape
Marble, S. Christopher; Prior, Stephen A.; Runion, G. Brett; Torbert, H. Allen; Gilliam, Charles H.; Fain, Glenn B.; Sibley, Jeff L.; Knight, Patricia R.
2016-01-01
Three woody shrub species [cleyera (Ternstroemia gymnanthera Thunb. ‘Conthery’), Indian hawthorn (Rhaphiolepis indica L.) and loropetalum (Loropetalum chinensis Oliv.‘Ruby’)] were container-grown for one growing season in 2008 using either pinebark (industry standard), clean chip residual or WholeTree (derived by-products from the forestry industry) as potting substrates and then transplanted into the landscape in 2008. An Automated Carbon Efflux System was used to continually monitor soil CO2 efflux from December 2010 through November 2011 in each species and substrate combination. Changes in soil carbon (C) levels as a result of potting substrate were assessed through soil sampling in 2009 and 2011 and plant biomass was determined at study conclusion. Results showed that soil CO2-C efflux was similar among all species and substrates, with few main effects of species or substrate observed throughout the study. Soil analysis showed that plots with pinebark contained higher levels of soil C in both 2009 and 2011, suggesting that pinebark decomposes slower than clean chip residual or WholeTree and consequently has greater C storage potential than the two alternative substrates. Results showed a net C gain for all species and substrate combinations; however, plants grown in pinebark had greater C sequestration potential. PMID:27140321
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Species and Media Effects on Soil Carbon Dynamics in the Landscape
NASA Astrophysics Data System (ADS)
Marble, S. Christopher; Prior, Stephen A.; Runion, G. Brett; Torbert, H. Allen; Gilliam, Charles H.; Fain, Glenn B.; Sibley, Jeff L.; Knight, Patricia R.
2016-05-01
Three woody shrub species [cleyera (Ternstroemia gymnanthera Thunb. ‘Conthery’), Indian hawthorn (Rhaphiolepis indica L.) and loropetalum (Loropetalum chinensis Oliv.‘Ruby’)] were container-grown for one growing season in 2008 using either pinebark (industry standard), clean chip residual or WholeTree (derived by-products from the forestry industry) as potting substrates and then transplanted into the landscape in 2008. An Automated Carbon Efflux System was used to continually monitor soil CO2 efflux from December 2010 through November 2011 in each species and substrate combination. Changes in soil carbon (C) levels as a result of potting substrate were assessed through soil sampling in 2009 and 2011 and plant biomass was determined at study conclusion. Results showed that soil CO2-C efflux was similar among all species and substrates, with few main effects of species or substrate observed throughout the study. Soil analysis showed that plots with pinebark contained higher levels of soil C in both 2009 and 2011, suggesting that pinebark decomposes slower than clean chip residual or WholeTree and consequently has greater C storage potential than the two alternative substrates. Results showed a net C gain for all species and substrate combinations; however, plants grown in pinebark had greater C sequestration potential.
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Soil warming alters microbial substrate use in alpine soils.
Streit, Kathrin; Hagedorn, Frank; Hiltbrunner, David; Portmann, Magdalena; Saurer, Matthias; Buchmann, Nina; Wild, Birgit; Richter, Andreas; Wipf, Sonja; Siegwolf, Rolf T W
2014-04-01
Will warming lead to an increased use of older soil organic carbon (SOC) by microbial communities, thereby inducing C losses from C-rich alpine soils? We studied soil microbial community composition, activity, and substrate use after 3 and 4 years of soil warming (+4 °C, 2007-2010) at the alpine treeline in Switzerland. The warming experiment was nested in a free air CO2 enrichment experiment using depleted (13)CO2 (δ(13)C = -30‰, 2001-2009). We traced this depleted (13)C label in phospholipid fatty acids (PLFA) of the organic layer (0-5 cm soil depth) and in C mineralized from root-free soils to distinguish substrate ages used by soil microorganisms: fixed before 2001 ('old'), from 2001 to 2009 ('new') or in 2010 ('recent'). Warming induced a sustained stimulation of soil respiration (+38%) without decline in mineralizable SOC. PLFA concentrations did not reveal changes in microbial community composition due to soil warming, but soil microbial metabolic activity was stimulated (+66%). Warming decreased the amount of new and recent C in the fungal biomarker 18:2ω6,9 and the amount of new C mineralized from root-free soils, implying a shift in microbial substrate use toward a greater use of old SOC. This shift in substrate use could indicate an imbalance between C inputs and outputs, which could eventually decrease SOC storage in this alpine ecosystem. © 2013 John Wiley & Sons Ltd.
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NASA Astrophysics Data System (ADS)
Swails, E.; Jaye, D.; Verchot, L. V.; Hergoualc'h, K.; Wahyuni, N. S.; Borchard, N.; Lawrence, D.
2015-12-01
In Indonesia, peatlands are a major and growing source of greenhouse gas emissions due to increasing pressure from oil palm and pulp wood plantations. We are using a combination of field measures, laboratory experiments, and remote sensing to investigate relationships among land use, climatic factors and biogeochemical controls, and their influence on trace gas fluxes from tropical peat soils. Analysis of soils collected from peat sites on two major islands indicated substantial variation in peat substrate quality and nutrient content among land uses and geographic location. We conducted laboratory incubations to test the influence of substrate quality and nutrient availability on CO2 production from peat decomposition. Differences in peat characteristics attributable to land use change were tested by comparison of forest and oil palm peat samples collected from the same peat dome in Kalimantan. Regional differences in peat characteristics were tested by comparison of samples from Sumatra with samples from Kalimantan. We conducted additional experiments to test the influence of N and P availability and labile carbon on CO2 production. Under moisture conditions typical of oil palm plantations, CO2 production was higher from peat forest samples than from oil palm samples. CO2 production from Sumatra and Kalimantan oil palm samples was not different, despite apparent differences in nutrient content of these soils. N and P treatments representative of fertilizer application rates raised CO2 production from forest samples but not oil palm samples. Labile carbon treatments raised CO2 production in all samples. Our results suggest that decomposition of peat forest soils is nutrient limited, while substrate quality controls decomposition of oil palm soils post-conversion. Though fertilizer application could accelerate peat decomposition initially, fertilizer application may not influence long-term CO2 emissions from oil palm on peat.
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NASA Astrophysics Data System (ADS)
Xu, Xiaoming; Ding, Hongrui; Li, Yan; Lu, Anhuai; Li, Yan; Wang, Changqiu
2018-03-01
Identification of Mn oxides in natural Mn coatings is very difficult due to their poor crystallinity, fine grains, complex chemistry and tiny amounts. In this work, we investigated three types of Mn coatings including rock varnish, dendrite and soil Fe-Mn cutan from different weathering environments in China. Optical microscope, scanning electron microscope, energy dispersive X-ray spectroscopy and micro-Raman spectrometer were employed to achieve non-destructive, sensitive, in-situ and micro analysis on their mineral assemblages, micromorphological features and elemental distribution characteristics. The observed results suggest that rock varnish and soil cutan comprise birnessite, while dendrite is mainly composed of hollandite. Rock varnish with a layered structure has a clear boundary with its substrate, and microlaminations which arise from the fluctuations in Mn content (6.42-17.07 wt%) within the sample profile are obvious on closer inspection. Branch-like dendrite is rich in Mn (32.53-42.96 wt%) but poor in Si and Al, which shows a pilotaxitic texture with its substrate. Soil Fe-Mn cutan can be further divided into an outer black Mn-rich (8.26-13.58 wt%) belt and an inner yellowish-brown Fe-rich (2.06-4.85 wt%) belt, and a clear border can be identified between these two belts. Mn in the substrate of rock varnish and soil cutan is below detection limit while it can be detected in the substrate of dendrite (1.43-7.83 wt%). Our in-situ analysis provides more precise results than traditional powder test. These mineralogical characteristics indicate that dendrite is most likely endogenic, while rock varnish and soil cutan are external accretion formed under different weathering environments.
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Moreno-Jiménez, Eduardo; Esteban, Elvira; Carpena-Ruiz, Ramón O; Lobo, María Carmen; Peñalosa, Jesús M
2012-01-30
Phytoremediation can be a suitable option to manage derelict mine soils. A pot experiment was carried out under semi-controlled conditions with a mine-impacted soil. A further contamination event was mimicked by applying 5% of pyritic sludge. Four species were planted in pots (Myrtus communis, Retama sphaerocarpa, Rosmarinus officinalis and Tamarix gallica), and some pots remained unplanted as a control. The substrates were moderately to highly contaminated, mainly with arsenic and zinc. The strong acidification induced by the pyritic sludge was buffered with lime and plants survived in all the pots. Liming provoked an effective immobilisation of metals and arsenic. Plant establishment decreased labile As in the substrate by 50%, mainly M. communis, although the levels of extractable metals were not affected by the plants. R. sphaerocarpa and M. communis increased the levels of C and N in the soil by 23% and 34% respectively, and also enhanced enzymatic activities and microbial respiration to the double in some cases. The low transfer of trace elements to shoots limited the phytoextraction rate. Our results support the use of phytostabilisation in Mediterranean mine soils and show how plants of R. sphaerocarpa and M. communis may increase soil health and quality during revegetation. Copyright © 2011 Elsevier B.V. All rights reserved.
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Tucker, Colin L.; Tamang, Shanker; Pendall, Elise; ...
2016-05-01
In sagebrush steppe, snowpack may govern soil respiration through its effect on multiple abiotic and biotic factors. Across the Intermountain West of the United States, snowpack has been declining for decades and is projected to decline further over the next century, making the response of soil respiration to snowpack a potentially important factor in the ecosystem carbon cycle. In this study, we evaluated the direct and indirect roles of the snowpack in driving soil respiration in sagebrush steppe ecosystems by taking advantage of highway snowfences in Wyoming to manipulate snowpack. An important contribution of this study is the use ofmore » Bayesian modeling to quantify the effects of soil moisture and temperature on soil respiration across a wide range of conditions from frozen to hot and dry, while simultaneously accounting for biotic factors (e.g., vegetation cover, root density, and microbial biomass and substrate-use diversity) affected by snowpack. Elevated snow depth increased soil temperature (in the winter) and moisture (winter and spring), and was associated with reduced vegetation cover and microbial biomass carbon. Soil respiration showed an exponential increase with temperature, with a temperature sensitivity that decreased with increasing seasonal temperature (Q 10 = 4.3 [winter], 2.3 [spring], and 1.7 [summer]); frozen soils were associated with unrealistic Q 10 approximate to 7989 due to the liquid-to-ice transition of soil water. Soil respiration was sensitive to soil water content; predicted respiration under very dry conditions was less than 10% of respiration under moist conditions. While higher vegetation cover increased soil respiration, this was not due to increased root density, and may reflect differences in litter inputs. Microbial substrate-use diversity was negatively related to reference respiration (i.e., respiration rate at a reference temperature and optimal soil moisture), although the mechanism remains unclear. Lastly, this study indicates that soil respiration is inhibited by shallow snowpack through multiple mechanisms; thus, future decreases in snowpack across the sagebrush steppe have the potential to reduce losses of soil C, potentially affecting regional carbon balance.« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Tucker, Colin L.; Tamang, Shanker; Pendall, Elise
In sagebrush steppe, snowpack may govern soil respiration through its effect on multiple abiotic and biotic factors. Across the Intermountain West of the United States, snowpack has been declining for decades and is projected to decline further over the next century, making the response of soil respiration to snowpack a potentially important factor in the ecosystem carbon cycle. In this study, we evaluated the direct and indirect roles of the snowpack in driving soil respiration in sagebrush steppe ecosystems by taking advantage of highway snowfences in Wyoming to manipulate snowpack. An important contribution of this study is the use ofmore » Bayesian modeling to quantify the effects of soil moisture and temperature on soil respiration across a wide range of conditions from frozen to hot and dry, while simultaneously accounting for biotic factors (e.g., vegetation cover, root density, and microbial biomass and substrate-use diversity) affected by snowpack. Elevated snow depth increased soil temperature (in the winter) and moisture (winter and spring), and was associated with reduced vegetation cover and microbial biomass carbon. Soil respiration showed an exponential increase with temperature, with a temperature sensitivity that decreased with increasing seasonal temperature (Q 10 = 4.3 [winter], 2.3 [spring], and 1.7 [summer]); frozen soils were associated with unrealistic Q 10 approximate to 7989 due to the liquid-to-ice transition of soil water. Soil respiration was sensitive to soil water content; predicted respiration under very dry conditions was less than 10% of respiration under moist conditions. While higher vegetation cover increased soil respiration, this was not due to increased root density, and may reflect differences in litter inputs. Microbial substrate-use diversity was negatively related to reference respiration (i.e., respiration rate at a reference temperature and optimal soil moisture), although the mechanism remains unclear. Lastly, this study indicates that soil respiration is inhibited by shallow snowpack through multiple mechanisms; thus, future decreases in snowpack across the sagebrush steppe have the potential to reduce losses of soil C, potentially affecting regional carbon balance.« less
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NASA Astrophysics Data System (ADS)
Glushakova, A. M.; Kachalkin, A. V.; Chernov, I. Yu.
2011-08-01
The annual dynamics of the number and taxonomic composition of yeast communities were studied in the phyllosphere, on the flowers, and on the roots of Indian balsam ( Impatiens glandulifera Royle) and in the mucky gley soil under the thickets of this plant. It was shown that typical phyllosphere yeast communities with a predominance of the red-pigmented species Rhodotorula mucilaginosa and Rhodotorula glutinis and the typical epiphyte Cryptococcus magnus are formed on the leaves of this annual hygrophyte. However, yeast groups with a predominance of the ascosporous species Saccharomyces paradoxus, Kazachstania barnettii, and Torulaspora delbrueckii, which are not typical of soils at all, were found in the mucky gley soil under the thickets of Indian balsam. Thus, the epiphytic and soil yeast complexes under the thickets of Indian balsam are represented by two entirely discrete communities without common species. In other biogeocenoses of the forest zone, the rearrangement of the structure of yeast communities in passing from the aboveground substrates to the soil proceeds gradually, and most of the species can be isolated both from the aboveground parts of plants and from the soil. The strong difference between the yeast communities in the phyllosphere of Indian balsam and in the soil under its thickets is apparently related to the fact that the annual hygrophytes are decomposed very quickly (during several days after the first frosts). Because of this, an intermediate layer between the phyllosphere and the soil (the litter layer), in which epiphytic microorganisms can develop, is not formed under these plants.
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Liu, Xian; Chen, Chengrong; Wang, Weijin; Hughes, Jane M; Lewis, Tom; Hou, Enqing; Shen, Jupei
2015-11-01
Soil biogeochemical cycles are largely mediated by microorganisms, while fire significantly modifies biogeochemical cycles mainly via altering microbial community and substrate availability. Majority of studies on fire effects have focused on the surface soil; therefore, our understanding of the vertical distribution of microbial communities and the impacts of fire on nitrogen (N) dynamics in the soil profile is limited. Here, we examined the changes of soil denitrification capacity (DNC) and denitrifying communities with depth under different burning regimes, and their interaction with environmental gradients along the soil profile. Results showed that soil depth had a more pronounced impact than the burning treatment on the bacterial community size. The abundance of 16S rRNA and denitrification genes (narG, nirK, and nirS) declined exponentially with soil depth. Surprisingly, the nosZ-harboring denitrifiers were enriched in the deeper soil layers, which was likely to indicate that the nosZ-harboring denitrifiers could better adapt to the stress conditions (i.e., oxygen deficiency, nutrient limitation, etc.) than other denitrifiers. Soil nutrients, including dissolved organic carbon (DOC), total soluble N (TSN), ammonium (NH(4)(+)), and nitrate (NO(3)(-)), declined significantly with soil depth, which probably contributed to the vertical distribution of denitrifying communities. Soil DNC decreased significantly with soil depth, which was negligible in the depths below 20 cm. These findings have provided new insights into niche separation of the N-cycling functional guilds along the soil profile, under a varied fire disturbance regime.
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In-Situ Quantification of Microbial Processes Controlling Methane Emissions From Rice Plants
NASA Astrophysics Data System (ADS)
Schroth, M. H.; Cho, R.; Zeyer, J. A.
2011-12-01
Methane is an important greenhouse gas contributing to global warming. Among other sources, rice (paddy) soils represent a major nonpoint source of biogenic methane. In flooded paddy soils methane is produced under anaerobic conditions. Conversely, methanotrophic microorganisms oxidize methane to carbon dioxide in the root zone of rice plants, thus reducing overall methane emissions to the atmosphere. We present a novel combination of methods to quantify methanogenesis and methane oxidation in paddy soils and to link methane turnover to net emissions of rice plants. To quantify methane turnover in the presence of high methane background concentrations, small-scale push-pull tests (PPTs) were conducted in paddy soils using stable isotope-labeled substrates. Deuterated acetate and 13-C bicarbonate were employed to discern and quantify acetoclastic and hydrogenotrophic methanogenesis, while 13-C methane was employed to quantify methane oxidation. During 2.5 hr-long PPTs, 140 mL of a test solution containing labeled substrates and nonreactive tracers (Ar, Br-) was injected into paddy soils of potted rice plants. After a short rest period, 480 mL of test solution/pore water mixture was extracted from the same location. Methane turnover was then computed from extraction-phase breakthrough curves of substrates and/or products, and nonreactive tracers. To link methane turnover to net emissions, methane emissions from paddy soils and rice plants were individually determined immediately preceding PPTs using static flux chambers. We will present results of a series of experiments conducted in four different potted rice plants. Preliminary results indicate substantial variability in methane turnover and net emission between different rice plants. The employed combination of methods appears to provide a robust means to quantitatively link methane turnover in paddy soils to net emissions from rice plants.
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NASA Astrophysics Data System (ADS)
Reynolds, L. L.; Lajtha, K.; Bowden, R.; Johnson, B. R.; Bridgham, S. D.
2013-12-01
The decomposition of soil organic matter is expected to increase with global warming and has been commonly described by kinetic models with at least two pools with differing turnover times. Pools characterized by rapid turnover are thought to consist of labile substrates. Meanwhile, slower turnover is attributed, in part, to greater chemical complexity and a necessarily higher activation energy which should in turn lead to a higher sensitivity (Q10) to temperature and a proportionally larger response to warming. Experimental tests of the relative Q10 of these pools have been inconclusive and contradictory in part due the fact that all pools are decomposing simultaneously and soils kept under differing conditions over long periods of time diverge in more than the Q10 response making them less comparable over time. We present here a test of the temperature response on soils from a 20 yr litter manipulation experiment incubated under an experimental regime that minimizes divergence among the soils. We hypothesize that 1) if exclusion of inputs has depleted labile substrates and 2) the remaining carbon is more chemically complex, then the input exclusion treatments should show a higher Q10 compared to the ambient or increased input treatments. The soils are taken from the Detritus Input and Removal Treatment (DIRT) plots in the Bousson Forest, Pennsylvania, US. The DIRT treatments consist of litter and root exclusion (no inputs = NI), no roots (NR), no litter (NL), double litter (DL), and ambient conditions (C). Soils were incubated at 25oC for 525 days. Periodically, replicate sets were rotated into 15oC, 35oC or remained at 25oC for 24 hr. The headspace CO2 concentration was measured before and after the 24 hr temperature treatments, and then all replicate sets were returned to 25oC. Twenty years of input exclusion decreased respiration rate, with NI < NR = NL < C = DL, and total carbon content, and thus, we conclude, labile substrates. The respiration rate at 25oC was the same for all replicate sets throughout, indicating no divergence due to the temperature rotations. Contrary to our hypothesis, our data indicates that Q10 was similar among the DIRT treatments, despite the clear differences in their carbon pools. Similar studies have examined the temperature response due to depletion labile substrate through laboratory incubation, rather beginning with presumably very different initial labile pools. Our results would suggest that soils with differing soil carbon content and presumably differing carbon quality have the same relative temperature responses. Recent studies have questioned the putative importance of chemical recalcitrance in soils, which would explain our results relative to the predictions of enzymatic kinetic theory.
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NASA Astrophysics Data System (ADS)
Liu, Yuan; He, Nianpeng
2017-04-01
How to assess the temperature sensitivity (Q10) of soil organic matter (SOM) decomposition and its regional variation with high accuracy is one of the largest uncertainties in determining the intensity and direction of the global carbon (C) cycle in response to climate change. In this study, we collected a series of soils from 22 forest sites and 30 grassland sites across China to explore regional variation in Q10 and its underlying mechanisms. We conducted a novel incubation experiment with periodically changing temperature (5-30 °C), while continuously measuring soil microbial respiration rates. The results showed that Q10 varied significantly across different ecosystems, ranging from 1.16 to 3.19 (mean 1.63). Q10 was ordered as follows: alpine grasslands (2.01) > temperate grasslands (1.81) > tropical forests (1.59) > temperate forests (1.55) > subtropical forests (1.52). The Q10 of grasslands (1.90) was significantly higher than that of forests (1.54). Furthermore, Q10 significantly increased with increasing altitude and decreased with increasing longitude. Environmental variables and substrate properties together explained 52% of total variation in Q10 across all sites. Overall, pH and soil electrical conductivity primarily explained spatial variation in Q10. The general negative relationships between Q10 and substrate quality among all ecosystem types supported the C quality temperature (CQT) hypothesis at a large scale, which indicated that soils with low quality should have higher temperature sensitivity. Furthermore, alpine grasslands, which had the highest Q10, were predicted to be more sensitive to climate change under the scenario of global warming.
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NASA Astrophysics Data System (ADS)
Liu, Y.; He, N.; Zhu, J.; Yu, G.; Xu, L.; Niu, S.; Sun, X.; Wen, X.
2017-12-01
How to assess the temperature sensitivity (Q10) of soil organic matter (SOM) decomposition and its regional variation with high accuracy is one of the largest uncertainties in determining the intensity and direction of the global carbon (C) cycle in response to climate change. In this study, we collected a series of soils from 22 forest sites and 30 grassland sites across China to explore regional variation in Q10 and its underlying mechanisms. We conducted a novel incubation experiment with periodically changing temperature (5-30 °C), while continuously measuring soil microbial respiration rates. The results showed that Q10 varied significantly across different ecosystems, ranging from 1.16 to 3.19 (mean 1.63). Q10 was ordered as follows: alpine grasslands (2.01) > temperate grasslands (1.81) > tropical forests (1.59) > temperate forests (1.55) > subtropical forests (1.52). The Q10 of grasslands (1.90) was significantly higher than that of forests (1.54). Furthermore, Q10 significantly increased with increasing altitude and decreased with increasing longitude. Environmental variables and substrate properties together explained 52% of total variation in Q10 across all sites. Overall, pH and soil electrical conductivity primarily explained spatial variation in Q10. The general negative relationships between Q10 and substrate quality among all ecosystem types supported the C quality temperature (CQT) hypothesis at a large scale, which indicated that soils with low quality should have higher temperature sensitivity. Furthermore, alpine grasslands, which had the highest Q10, were predicted to be more sensitive to climate change under the scenario of global warming.
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Soil biological attributes in arsenic-contaminated gold mining sites after revegetation.
Dos Santos, Jessé Valentim; de Melo Rangel, Wesley; Azarias Guimarães, Amanda; Duque Jaramillo, Paula Marcela; Rufini, Márcia; Marra, Leandro Marciano; Varón López, Maryeimy; Pereira da Silva, Michele Aparecida; Fonsêca Sousa Soares, Cláudio Roberto; de Souza Moreira, Fatima Maria
2013-12-01
Recovery of arsenic contaminated areas is a challenge society faces throughout the world. Revegetation associated with microbial activity can play an essential role in this process. This work investigated biological attributes in a gold mining area with different arsenic contents at different sites under two types of extant revegetation associated with cover layers of the soil: BS, Brachiaria sp. and Stizolobium sp., and LEGS, Acacia crassicarpa, A. holosericea, A. mangium, Sesbania virgata, Albizia lebbeck and Pseudosamanea guachapele. References were also evaluated, comprising the following three sites: B1, weathered sulfide substrate without revegetation; BM, barren material after gold extraction and PRNH (private reserve of natural heritage), an uncontaminated forest site near the mining area. The organic and microbial biomass carbon contents and substrate-induced respiration rates for these sites from highest to lowest were: PRNH > LEGS > BS > B1 and BM. These attributes were negatively correlated with soluble and total arsenic concentration in the soil. The sites that have undergone revegetation (LEGS and BS) had higher densities of bacteria, fungi, phosphate solubilizers and ammonium oxidizers than the sites without vegetation. Principal component analysis showed that the LEGS site grouped with PRNH, indicating that the use of leguminous species associated with an uncontaminated soil cover layer contributed to the improvement of the biological attributes. With the exception of acid phosphatase, all the biological attributes were indicators of soil recovery, particularly the following: microbial carbon, substrate-induced respiration, density of culturable bacteria, fungi and actinobacteria, phosphate solubilizers and metabolic quotient.
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Thermal and water regime of green roof segments filled with Technosol
NASA Astrophysics Data System (ADS)
Jelínková, Vladimíra; Šácha, Jan; Dohnal, Michal; Skala, Vojtěch
2016-04-01
Artificial soil systems and structures comprise appreciable part of the urban areas and are considered to be perspective for number of reasons. One of the most important lies in contribution of green roofs and facades to the heat island effect mitigation, air quality improvement, storm water reduction, etc. The aim of the presented study is to evaluate thermal and water regime of the anthropogenic soil systems during the first months of the construction life cycle. Green roof test segments filled with two different anthropogenic soils were built to investigate the benefits of such systems in the temperate climate. Temperature and water balance measurements complemented with meteorological observations and knowledge of physical properties of the soil substrates provided basis for detailed analysis of thermal and hydrological regime. Water balance of green roof segments was calculated for available vegetation seasons and individual rainfall events. On the basis of an analysis of individual rainfall events rainfall-runoff dependency was found for green roof segments. The difference between measured actual evapotranspiration and calculated potential evapotranspiration was discussed on period with contrasting conditions in terms of the moisture stress. Thermal characteristics of soil substrates resulted in highly contrasting diurnal variation of soils temperatures. Green roof systems under study were able to reduce heat load of the roof construction when comparing with a concrete roof construction. Similarly, received rainfall was significantly reduced. The extent of the rainfall reduction mainly depends on soil, vegetation status and experienced weather patterns. The research was realized as a part of the University Centre for Energy Efficient Buildings supported by the EU and with financial support from the Czech Science Foundation under project number 14-10455P.
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Ouzounidou, G; Asfi, M; Sotirakis, N; Papadopoulou, P; Gaitis, F
2008-10-30
We have studied the changes in the physiology and nutritional quality of Lycopersicon esculentum exposed to olive mill wastewater (OMW) with regard to cultivation in sand and soil. Tomato plant performance decreased with increasing concentration of OMW to both substrates. Root was more sensitive to OMW than the upper parts of the plants, grown either in sand or in soil for 10 days and 3 months, respectively, probably due to the direct OMW toxicity on roots as compared to other parts. Significant restriction on uptake and translocation of nutrients (K, Na, Fe, Ca and Mg) under OMW application was found. The decrease in the photochemical efficiency of PSII photochemistry in the light adapted state and the big decrease in photochemical quenching, indicate that OMW resulted in diminished reoxidation of Q(A)(-) and started to inactivate the reaction centers of PSII. The OMW supply on soil and sand, resulted in leaf water stress and lesser water use efficiency. Plants treated with high OMW concentration, produced fewer but bigger tomatoes as compared to plants treated with lower OMW concentration. Generally, fruit yield and nutritional value was inhibited under OMW application.
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Chen, Shuqin; Chu, Zhaosheng; Zhou, Yunqiao; Li, Qifeng; Wang, Tieyu
2018-05-08
Because of the unstable hydrodynamic conditions in the wild, the endangered aquatic plant should be cultivated first in constructed wetlands for the protection and expansion of germplasm resources. Ottelia acuminata (Gagnep.) Dandy has become extinct in Erhai Lake, Yunnan province, China. In order to optimize substrates for this species to artificial cultivation, the native substrate (sandy soils) and the other three representative ones (red paddy soils, alluvial paddy soils, and purple paddy soils) collected from Erhai lakeside were applied to cultivate O. acuminata for 50 days. Multi indicators, such as antioxidant enzymes activity, malondialdehyde and chlorophyll-α concentration, and relative growth rate of O. acuminata, were discussed and statistically analyzed to classify the substrates. The results suggested that even disregarding the physiology significance of these indicators, hierarchical clustering analysis had high efficiency on optimizing substrates. Although various single indexes suggested different optimal substrates for macrophyte growth, red paddy soil was never excluded out the optimal substrate classes. Further study is needed to assess the substrates optimization functionalities of these indicators. This study offers amounts of physiology data and an effective method to optimize substrates of O. acuminata. It is helpful for environmental scientists and ecological engineers to conduct the similar study on endangered species.
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NASA Astrophysics Data System (ADS)
Billings, S. A.; Tiemann, L. K.; Ballantyne, F., IV; Lehmeier, C. A.; Min, K.
2015-04-01
Discerning why some soil organic matter (SOM) leaves soil profiles relatively quickly while other compounds, especially at depth, can be retained for decades to millennia is challenging for a multitude of reasons. Simultaneous with soil-specific advances, multiple other disciplines have enhanced their knowledge bases in ways potentially useful for future investigations of SOM decay. In this article, we highlight observations highly relevant for those investigating SOM decay and retention but often emanating from disparate fields and residing in literature seldom cited in SOM research. We focus on recent work in two key areas. First, we turn to experimental approaches using natural and artificial aquatic environments to investigate patterns of microbially mediated OM transformations as environmental conditions change, and highlight how aquatic microbial responses to environmental change can reveal processes likely important to OM decay and retention in soils. Second, we emphasize the importance of establishing intrinsic patterns of decay kinetics for purified substrates commonly found in soils to develop baseline rates. These decay kinetics - which represent the upper limit of the reaction rates - can then be compared to substrate decay kinetics observed in natural samples, which integrate intrinsic decay reaction rates and edaphic factors essential to the site under study but absent in purified systems. That comparison permits the site-specific factors to be parsed from the fundamental decay kinetics, an important advance in our understanding of SOM decay (and thus persistence) in natural systems. We then suggest ways in which empirical observations from aquatic systems and purified substrate-enzyme reaction kinetics can be used to advance recent theoretical efforts in SOM-focused research. Finally, we suggest how the observations in aquatic and purified substrate-enzyme systems could be used to help unravel the puzzles presented by oft-observed patterns of SOM characteristics with depth, as one example of the many perplexing SOM-related problems.
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NASA Astrophysics Data System (ADS)
Hedgpeth, A.; Beilman, D.; Crow, S. E.
2014-12-01
Arctic soil organic matter (SOM) mineralization processes are fundamental to the functioning of high latitude soils in relation to nutrients, stability, and feedbacks to atmospheric CO2 and climate. The arctic permafrost zone covers 25% of the northern hemisphere and contains 1672Pg of soil carbon (C). 88% of this C currently resides in frozen soils that are vulnerable to environmental change. For instance, arctic growing seasons may be lengthened, resulting in an increase in plant productivity and rate of below ground labile C inputs as root exudates. Understanding controls on Arctic SOM dynamics requires recognition that labile C inputs have the potential to significantly affect mineralization of previously stable SOM, also known as 'priming effects'. We conducted a substrate addition incubation experiment to quantify and compare respiration in highly organic (42-48 %C) permafrost soils along a north-south transect in western Canada. Near surface soils (10-20 cm) were collected from permafrost peatland sites in the Mackenzie River Basin from 69.2-62.6°N. The surface soils are fairly young (Δ14C values > -140.0) and can be assumed to contain relatively reactive soil carbon. To assess whether addition of labile substrate alters SOM decomposition dynamics, 4.77-11.75 g of permafrost soil were spiked with 0.5 mg D-glucose g-1 soil and incubated at 5°C. A mass balance approach was used to determin substrate-induced respiration and preliminary results suggest a potential for positive priming in these C-rich soils. Baseline respiration rates from the three sites were similar (0.067-0.263 mg CO2 g-1 soil C) yet show some site-specific trends. The rate at which added substrate was utilized within these soils suggests that other factors besides temperature and soil C content are controlling substrate consumption and its effect on SOM decomposition. Microbial activity can be stimulated by substrate addition to such an extent that SOM turnover is enhanced, suggesting that soil C decay rates and processes are not constant, but depend on the inter-soil dynamics of other soil C pools. If these C rich soils contain ample C-resources to fuel extra microbial SOM decomposition, then possibly this enhanced use of SOM is not as a means of C acquisition, but to mobilize nutrients needed to meet microbial growth requirements.
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NASA Astrophysics Data System (ADS)
Zhu, Q.; Riley, W. J.; Tang, J.; Koven, C. D.
2015-03-01
Soil is a complex system where biotic (e.g., plant roots, micro-organisms) and abiotic (e.g., mineral surfaces) consumers compete for resources necessary for life (e.g., nitrogen, phosphorus). This competition is ecologically significant, since it regulates the dynamics of soil nutrients and controls aboveground plant productivity. Here we develop, calibrate, and test a nutrient competition model that accounts for multiple soil nutrients interacting with multiple biotic and abiotic consumers. As applied here for tropical forests, the Nutrient COMpetition model (N-COM) includes three primary soil nutrients (NH4+, NO3-, and POx (representing the sum of PO43-, HPO42-, and H2PO4-)) and five potential competitors (plant roots, decomposing microbes, nitrifiers, denitrifiers, and mineral surfaces). The competition is formulated with a quasi-steady-state chemical equilibrium approximation to account for substrate (multiple substrates share one consumer) and consumer (multiple consumers compete for one substrate) effects. N-COM successfully reproduced observed soil heterotrophic respiration, N2O emissions, free phosphorus, sorbed phosphorus, and free NH4+ at a tropical forest site (Tapajos). The overall model posterior uncertainty was moderately well constrained. Our sensitivity analysis revealed that soil nutrient competition was primarily regulated by consumer-substrate affinity rather than environmental factors such as soil temperature or soil moisture. Our results imply that the competitiveness (from most to least competitive) followed this order: (1) for NH4+, nitrifiers ~ decomposing microbes > plant roots, (2) for NO3-, denitrifiers ~ decomposing microbes > plant roots, (3) for POx, mineral surfaces > decomposing microbes ~ plant roots. Although smaller, plant relative competitiveness is of the same order of magnitude as microbes. We then applied the N-COM model to analyze field nitrogen and phosphorus perturbation experiments in two tropical forest sites (in Hawaii and Puerto Rico) not used in model development or calibration. Under soil inorganic nitrogen and phosphorus elevated conditions, the model accurately replicated the experimentally observed competition among different nutrient consumers. Although we used as many observations as we could obtain, more nutrient addition experiments in tropical systems would greatly benefit model testing and calibration. In summary, the N-COM model provides an ecologically consistent representation of nutrient competition appropriate for land BGC models integrated in Earth System Models.
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Exometabolite niche partitioning among sympatric soil bacteria
Baran, Richard; Brodie, Eoin L.; Mayberry-Lewis, Jazmine; ...
2015-09-22
Soils are arguably the most microbially diverse ecosystems. Physicochemical properties have been associated with the maintenance of this diversity. Yet, the role of microbial substrate specialization is largely unexplored since substrate utilization studies have focused on simple substrates, not the complex mixtures representative of the soil environment. Here we examine the exometabolite composition of desert biological soil crusts (biocrusts) and the substrate preferences of seven biocrust isolates. The biocrust's main primary producer releases a diverse array of metabolites, and isolates of physically associated taxa use unique subsets of the complex metabolite pool. Individual isolates use only 13-26% of available metabolites,more » with only 2 out of 470 used by all and 40% not used by any. An extension of this approach to a mesophilic soil environment also reveals high levels of microbial substrate specialization. In conclusion, these results suggest that exometabolite niche partitioning may be an important factor in the maintenance of microbial diversity.« less
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Exometabolite niche partitioning among sympatric soil bacteria
Baran, Richard; Brodie, Eoin L.; Mayberry-Lewis, Jazmine; Hummel, Eric; Da Rocha, Ulisses Nunes; Chakraborty, Romy; Bowen, Benjamin P.; Karaoz, Ulas; Cadillo-Quiroz, Hinsby; Garcia-Pichel, Ferran; Northen, Trent R.
2015-01-01
Soils are arguably the most microbially diverse ecosystems. Physicochemical properties have been associated with the maintenance of this diversity. Yet, the role of microbial substrate specialization is largely unexplored since substrate utilization studies have focused on simple substrates, not the complex mixtures representative of the soil environment. Here we examine the exometabolite composition of desert biological soil crusts (biocrusts) and the substrate preferences of seven biocrust isolates. The biocrust's main primary producer releases a diverse array of metabolites, and isolates of physically associated taxa use unique subsets of the complex metabolite pool. Individual isolates use only 13−26% of available metabolites, with only 2 out of 470 used by all and 40% not used by any. An extension of this approach to a mesophilic soil environment also reveals high levels of microbial substrate specialization. These results suggest that exometabolite niche partitioning may be an important factor in the maintenance of microbial diversity. PMID:26392107
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Effects of biochar amendments on soil microbial biomass and activity.
Zhang, H; Voroney, R P; Price, G W
2014-11-01
Environmental benefits reported in the literature of using biochar as a soil amendment are generally increased microbial activity and reduced greenhouse gas (GHG) emissions. This study determined the effects of amendment with biomass feedstocks (spent coffee grounds, wood pellets, and horse bedding compost) and that of biochars (700°C) produced from these feedstocks on soil microbial biomass (C and N) and activity. Soils were amended with these substrates at 0.75% by weight and incubated for up to 175 d under laboratory conditions. Biochar residual effects on soil microbial activity were also studied by amending these soils with either ammonium nitrate (NHNO, 35 mg N kg) or with glucose (864 mg C kg) plus NHNO. Soil microbial biomass C and N, net N mineralization, and CO, NO, and CH emissions were measured. Amendment with biomass feedstocks significantly increased soil microbial biomass and activity, whereas amendment with the biochars had no significant effect. Also, biochar amendment had no significant effect on either net N mineralization or NO and CH emissions from soil. These results indicate that production of biochars at this high temperature eliminated potential substrates. Microbial biomass C in biochar-amended and unamended soils was not significantly different following additions of NHNO or glucose plus NHNO, suggesting that microbial access to otherwise labile C and N was not affected. This study shows that biochars produced at 700°C, regardless of feedstock source, do not enhance soil microbial biomass or activity. Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.
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Ouyang, Wei; Huang, Weijia; Wei, Peng; Hao, Fanghua; Yu, Yongyong
2016-06-15
Herbicides are a main source of agricultural diffuse pollution due to their wide application in tillage practices. The aim of this study is to optimize the control efficiency of the herbicide atrazine with the aid of modified soil amendments. The soil amendments were composed of a combination of biochar and gravel. The biochar was created from corn straw with a catalytic pyrolysis of ammonium dihydrogen phosphate. The leaching experiments under four rainfall conditions were measured for the following designs: raw soil, soil amended with gravel, biochar individually and together with gravel. The control efficiency of each design was also identified. With the designed equipment, the atrazine content in the contaminant load layer, gravel substrate layer, biochar amendment layer and soil layer was measured under four types of rainfall intensities (1.25 mm/h, 2.50 mm/h, 5.00 mm/h and 10.00 mm/h). Furthermore, the vertical distribution of atrazine in the soil sections was also monitored. The results showed that the herbicide leaching load increased under the highest rainfall intensity in all designs. The soil with the combination of gravel and biochar provided the highest control efficiency of 87.85% on atrazine when the additional proportion of biochar was 3.0%. The performance assessment under the four kinds of rainfall intensity conditions provided the guideline for the soil amendment configuration. The combination of gravel and biochar is recommended as an efficient method for controlling diffuse herbicide pollution. Copyright © 2016 Elsevier Ltd. All rights reserved.
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[Oil degradation by basidiomycetes in soil and peat at low temperatures].
Kulikova, N A; Klein, O I; Pivchenko, D V; Landesman, E O; Pozdnyakova, N N; Turkovskaya, O V; Zaichik, B Ts; Ruzhitskii, A O; Koroleva, O V
2016-01-01
A total of 17 basidiomycete strains causing white rot and growing on oil-contaminated substrates have been screened. Three strains with high (Steccherinum murashkinskyi), average (Trametes maxima), and low (Pleurotus ostreatus) capacities for the colonization of oil-contaminated substrates have been selected. The potential for degrading crude oil hydrocarbons has been assessed with the use of fungi grown on nonsterile soil and peat at low temperatures. Candida sp. and Rhodococcus sp. commercial strains have been used as reference organisms with oil-degrading ability. All microorganisms introduced in oil-contaminated soil have proved to be ineffective, whereas the inoculation of peat with basidiomycetes and oil-degrading microorganisms accelerated the destruction of oil hydrocarbons. The greatest degradation potential of oil-aliphatic hydrocarbons has been found in S. murashlinskyi. T. maxima turned out to be the most successful in degrading aromatic hydrocarbons. It has been suggested that aboriginal microflora contributes importantly to the effectiveness of oil-destructing microorganisms. T. maxima and S. murashkinskyi strains are promising for further study as oil-oxidizing agents during bioremediation of oil-contaminated peat soil under conditions of low temperatures.
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Berthrong, Sean T; Buckley, Daniel H; Drinkwater, Laurie E
2013-07-01
We investigated how conversion from conventional agriculture to organic management affected the structure and biogeochemical function of soil microbial communities. We hypothesized the following. (1) Changing agricultural management practices will alter soil microbial community structure driven by increasing microbial diversity in organic management. (2) Organically managed soil microbial communities will mineralize more N and will also mineralize more N in response to substrate addition than conventionally managed soil communities. (3) Microbial communities under organic management will be more efficient and respire less added C. Soils from organically and conventionally managed agroecosystems were incubated with and without glucose ((13)C) additions at constant soil moisture. We extracted soil genomic DNA before and after incubation for TRFLP community fingerprinting of soil bacteria and fungi. We measured soil C and N pools before and after incubation, and we tracked total C respired and N mineralized at several points during the incubation. Twenty years of organic management altered soil bacterial and fungal community structure compared to continuous conventional management with the bacterial differences caused primarily by a large increase in diversity. Organically managed soils mineralized twice as much NO3 (-) as conventionally managed ones (44 vs. 23 μg N/g soil, respectively) and increased mineralization when labile C was added. There was no difference in respiration, but organically managed soils had larger pools of C suggesting greater efficiency in terms of respiration per unit soil C. These results indicate that the organic management induced a change in community composition resulting in a more diverse community with enhanced activity towards labile substrates and greater capacity to mineralize N.
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Key parameters and practices controlling pesticide degradation efficiency of biobed substrates.
Karanasios, Evangelos; Karpouzas, Dimitrios G; Tsiropoulos, Nikolaos G
2012-01-01
We studied the contribution of each of the components of a compost-based biomixture (BX), commonly used in Europe, on pesticide degradation. The impact of other key parameters including pesticide dose, temperature and repeated applications on the degradation of eight pesticides, applied as a mixture, in a BX and a peat-based biomixture (OBX) was compared and contrasted to their degradation in soil. Incubation studies showed that straw was essential in maintaining a high pesticide degradation capacity of the biomixture, whereas compost, when mixed with soil, retarded pesticide degradation. The highest rates of degradation were shown in the biomixture composed of soil/compost/straw suggesting that all three components are essential for maximum biobed performance. Increasing doses prolonged the persistence of most pesticides with biomixtures showing a higher tolerance to high pesticide dose levels compared to soil. Increasing the incubation temperature from 15 °C to 25 °C resulted in lower t(1/2) values, with biomixtures performing better than soil at the lower temperature. Repeated applications led to a decrease in the degradation rates of most pesticides in all the substrates, with the exception of iprodione and metalaxyl. Overall, our results stress the ability of biomixtures to perform better than soil under unfavorable conditions and extreme pesticide dose levels. Copyright © Taylor & Francis Group, LLC
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Tang, Jin-Yun; Riley, William J.
2017-09-05
Several land biogeochemical models used for studying carbon–climate feedbacks have begun explicitly representing microbial dynamics. However, to our knowledge, there has been no theoretical work on how to achieve a consistent scaling of the complex biogeochemical reactions from microbial individuals to populations, communities, and interactions with plants and mineral soils. We focus here on developing a mathematical formulation of the substrate–consumer relationships for consumer-mediated redox reactions of the form A + B E→ products, where products could be, e.g., microbial biomass or bioproducts. Under the quasi-steady-state approximation, these substrate–consumer relationships can be formulated as the computationally difficult full equilibrium chemistrymore » problem or approximated analytically with the dual Monod (DM) or synthesizing unit (SU) kinetics. We find that DM kinetics is scaling inconsistently for reaction networks because (1) substrate limitations are not considered, (2) contradictory assumptions are made regarding the substrate processing rate when transitioning from single- to multi-substrate redox reactions, and (3) the product generation rate cannot be scaled from one to multiple substrates. In contrast, SU kinetics consistently scales the product generation rate from one to multiple substrates but predicts unrealistic results as consumer abundances reach large values with respect to their substrates. We attribute this deficit to SU's failure to incorporate substrate limitation in its derivation. To address these issues, we propose SUPECA (SU plus the equilibrium chemistry approximation – ECA) kinetics, which consistently imposes substrate and consumer mass balance constraints. We show that SUPECA kinetics satisfies the partition principle, i.e., scaling invariance across a network of an arbitrary number of reactions (e.g., as in Newton's law of motion and Dalton's law of partial pressures). We tested SUPECA kinetics with the equilibrium chemistry solution for some simple problems and found SUPECA outperformed SU kinetics. As an example application, we show that a steady-state SUPECA-based approach predicted an aerobic soil respiration moisture response function that agreed well with laboratory observations. We conclude that, as an extension to SU and ECA kinetics, SUPECA provides a robust mathematical representation of complex soil substrate–consumer interactions and can be applied to improve Earth system model (ESM) land models.« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Tang, Jin-Yun; Riley, William J.
Several land biogeochemical models used for studying carbon–climate feedbacks have begun explicitly representing microbial dynamics. However, to our knowledge, there has been no theoretical work on how to achieve a consistent scaling of the complex biogeochemical reactions from microbial individuals to populations, communities, and interactions with plants and mineral soils. We focus here on developing a mathematical formulation of the substrate–consumer relationships for consumer-mediated redox reactions of the form A + B E→ products, where products could be, e.g., microbial biomass or bioproducts. Under the quasi-steady-state approximation, these substrate–consumer relationships can be formulated as the computationally difficult full equilibrium chemistrymore » problem or approximated analytically with the dual Monod (DM) or synthesizing unit (SU) kinetics. We find that DM kinetics is scaling inconsistently for reaction networks because (1) substrate limitations are not considered, (2) contradictory assumptions are made regarding the substrate processing rate when transitioning from single- to multi-substrate redox reactions, and (3) the product generation rate cannot be scaled from one to multiple substrates. In contrast, SU kinetics consistently scales the product generation rate from one to multiple substrates but predicts unrealistic results as consumer abundances reach large values with respect to their substrates. We attribute this deficit to SU's failure to incorporate substrate limitation in its derivation. To address these issues, we propose SUPECA (SU plus the equilibrium chemistry approximation – ECA) kinetics, which consistently imposes substrate and consumer mass balance constraints. We show that SUPECA kinetics satisfies the partition principle, i.e., scaling invariance across a network of an arbitrary number of reactions (e.g., as in Newton's law of motion and Dalton's law of partial pressures). We tested SUPECA kinetics with the equilibrium chemistry solution for some simple problems and found SUPECA outperformed SU kinetics. As an example application, we show that a steady-state SUPECA-based approach predicted an aerobic soil respiration moisture response function that agreed well with laboratory observations. We conclude that, as an extension to SU and ECA kinetics, SUPECA provides a robust mathematical representation of complex soil substrate–consumer interactions and can be applied to improve Earth system model (ESM) land models.« less
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Catalytic efficiency is a better predictor of arsenic toxicity to soil alkaline phosphatase.
Wang, Ziquan; Tian, Haixia; Lu, Guannan; Zhao, Yiming; Yang, Rui; Megharaj, Mallavarapu; He, Wenxiang
2018-02-01
Arsenic (As) is an inhibitor of phosphatase, however, in the complex soil system, the substrate concentration effect and the mechanism of As inhibition of soil alkaline phosphatase (ALP) and its kinetics has not been adequately studied. In this work, we investigated soil ALP activity in response to As pollution at different substrate concentrations in various types of soils and explored the inhibition mechanism using the enzyme kinetics. The results showed that As inhibition of soil ALP activity was substrate concentration-dependent. Increasing substrate concentration decreased inhibition rate, suggesting reduced toxicity. This dependency was due to the competitive inhibition mechanism of As to soil ALP. The kinetic parameters, maximum reaction velocity (V max ) and Michaelis constant (K m ) in unpolluted soils were 0.012-0.267mMh -1 and 1.34-3.79mM respectively. The competitive inhibition constant (K ic ) was 0.17-0.70mM, which was lower than K m , suggesting higher enzyme affinity for As than for substrate. The ecological doses, ED 10 and ED 50 (concentration of As that results in 10% and 50% inhibition on enzyme parameter) for inhibition of catalytic efficiency (V max /K m ) were lower than those for inhibition of enzyme activity at different substrate concentrations. This suggests that the integrated kinetic parameter, catalytic efficiency is substrate concentration independent and more sensitive to As than ALP activity. Thus, catalytic efficiency was proposed as a more reliable indicator than ALP activity for risk assessment of As pollution. Copyright © 2017 Elsevier Inc. All rights reserved.
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Colin, Verónica Leticia; Castro, María Fernanda; Amoroso, María Julia; Villegas, Liliana Beatriz
2013-10-15
In recent years, increasing interest has been shown in the use of bioemulsifiers as washing agents that can enhance desorption of soil-bound metals. However, high production costs derived from the use of expensive substrates for formulation of the fermentation media represent the main challenge for full, large-scale implementation of bioemulsifiers. This work reports on a first study of bioemulsifier production by the actinobacterium Amycolatopsis tucumanensis DSM 45259 using different carbon and nitrogen sources. Preliminary results on the potential use of these compounds as washing agents for soils contaminated with Cu(II) and Cr(VI) are also presented. The best specific production was detected using glycerol and urea as carbon and nitrogen substrates, respectively. However, with all of the substrates used during the batch assay, the bioemulsifiers showed high levels of stability at extreme conditions of pH, temperature, and salt concentration. Under the current assay conditions, the bioemulsifiers were not effective in removing Cu(II) from soil. However, they were able to mediate Cr(VI) recovery, with the removal percentage doubled compared to that seen when using deionized water. These findings appear promising for the development of remediation technologies for hexavalent chromium compounds based upon direct use of these microbial emulsifiers. Copyright © 2013 Elsevier B.V. All rights reserved.
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Undercooled water in basaltic regoliths and implications for fluidized debris flows on Mars
NASA Technical Reports Server (NTRS)
Gooding, James L.
1987-01-01
Pursuant to the past attribution of many geomorphic features on Mars to the movements of water- or ice-lubricated debris, experiments have been conducted for water freezing in wet, sand-like basaltic substrates. It is found that substantial undercooling can be achieved under Martian conditions, independently of freezing-point depressions due to soluble salts. Attention is given to results for a clay-poor soil with negligible salinity from Mauna Kea, Hawaii, which demonstrate that the degree of undercooling is essentially independent of both soil particle size and water/soil mass ratio, albeit with cooling rate variations.
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Microhabitat Effects on N2O Emissions from Floodplain Soils under Controlled Conditions
NASA Astrophysics Data System (ADS)
Ley, Martin; Lehmann, Moritz; Niklaus, Pascal; Frey, Beat; Kuhn, Thomas; Luster, Jörg
2015-04-01
Semi-terrestrial soils such as floodplain soils are considered to be potential hotspots of nitrous oxide (N2O) emissions. The quantitative assessment of N2O release from these hot spots under field conditions, and of the microbial pathways that underlie net N2O production (ammonium oxidation, nitrifier-denitrification, and denitrification) is challenging in the environment because of the high spatial and temporal variability. The production and consumption of N2O appears to be linked to the presence or absence of micro-niches, providing specific conditions that may be favorable to either of the microbial pathways that produce or consume N2O. The availability of oxygen, reactive organic carbon, and dissolved nitrogen substrates likely play key roles with regards to the net production of N2O. Previous field studies demonstrated, for example, that flooding can trigger "hot moments" of enhanced N2O emission through a close coupling of niches with high and low oxygen availabilities. Such microhabitat effects likely depend on soil aggregate formation, plant soil interactions in the rhizosphere and the degradation of organic matter accumulations. In order to assess how these factors can modulate N2O production and consumption under simulated flooding/drying conditions, we have set up a mesocosm experiment with model soils comprising various mixtures of N-rich floodplain soil aggregates (4000 - 250 µm representing large aggregates, or <250 µm representing small aggregates) and inert matrix material (glass beads of 150 - 250 µm size, or quartz sand of 2000 - 3200 µm size, respectively). Soils containing the different aggregate size groups were either planted with willow (Salix viminalis L.), mixed with leaf litter or left untreated. At several time points before, during and after a simulated flood event, we measure the net efflux rate of N2O. In addition, soil water content, redox potential as well as carbon and nitrogen substrate availability are monitored. In order to gain insight into the sources of, and biogeochemical controls on N2O production, we will measure the bulk isotopic signature of the produced N2O as well as its intramolecular 15N site preference. Changes in soil microbial communities, potentially controlling the balance between N2O production and consumption under different microhabitat conditions will be assessed using high-throughput DNA sequencing and q-PCR of key functional genes. Our study helps to increase our limited understanding of how microhabitats affect the occurrence of high N2O emissions from floodplain soils.
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Koper, Teresa E; Stark, John M; Habteselassie, Mussie Y; Norton, Jeanette M
2010-11-01
An agricultural soil was treated with dairy-waste compost, ammonium-sulfate fertilizer or no added nitrogen (control) and planted to silage corn for 6 years. The kinetics of nitrification were determined in laboratory-shaken slurry assays with a range of substrate concentrations (0-20 mM NH(4)(+)) over a 24-h period for soils from the three treatments. Determined concentrations of substrate and product were fit to Michaelis-Menten and Haldane models. For all the treatments, the Haldane model was a better fit, suggesting that significant nitrification inhibition may occur in soils under high ammonium conditions similar to those found immediately after fertilization or waste applications. The maximum rate of nitrification (V(max)) was significantly higher for the fertilized and compost-treated soils (1.74 and 1.50 mmol N kg(-1) soil day(-1)) vs. control soil (0.98 mmol kg(-1) soil day(-1)). The K(m) and K(i) values were not significantly different, with average values of 0.02 and 27 mM NH(4)(+), respectively. Our results suggest that both N sources increased nitrifier community size, but did not shift the nitrifier community structure in ways that influenced enzyme affinity or sensitivity to ammonium. The K(m) values are comparable to those determined directly in other soils, but are substantially lower than those from most pure cultures of ammonia-oxidizing bacteria. © 2010 Federation of European Microbiological Societies. Published by Blackwell Publishing Ltd. No claim to original US government works.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Huang, Chin-Pao
2001-05-31
This project will study electrochemical processes for the in situ treatment of soils contaminated by mixed wastes, i.e., organic and inorganic. Soil samples collected form selected DOE waste sites will be characterized for specific organic and metal contaminants and hydraulic permeability. The soil samples are then subject to desorption experiments under various physical-chemical conditions such as pH and the presence of surfactants. Batch electro-osmosis experiments will be conducted to study the transport of contaminants in the soil-water systems. Organic contaminants that are released from the soil substrate will be treated by an advanced oxidation process, i.e., electron-Fantan. Finally, laboratory reactormore » integrating the elector-osmosis and elector-Fantan processes will be used to study the treatment of contaminated soil in situ.« less
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NASA Astrophysics Data System (ADS)
Bateman, Amber; E Erickson, Todd; Merritt, David J.; Muñoz-Rojas, Miriam
2017-04-01
Introduction Soil health and functionality are major determining factors for restoration of degraded arid and semi-arid ecosystems. These highly nutrient impoverished soil substrates with low water retention capabilities dictate plant growth and survival in these landscapes that are subject to variable rainfall event and high temperatures (Muñoz-Rojas et al., 2016). Anthropogenic disturbances derived from mining activities have contributed to the degradation of soil functionality and have altered plant-soil-water interactions. With unknown positive or negative rehabilitation outcomes, inorganic amendments in the form of urea and gypsum are commonly added to reconstructed soil substrates disturbed by mining to replenish soil nutrients (nitrogen) and improve soil water holding capacity to improve seedling establishment and survival. Methods Using existing protocols for amendment addition to soil substrates, two experiments assessed the effects of urea and gypsum at multiple doses in reconstructed soil substrates (topsoil (TS), waste (W) and, 50:50 blend of both materials (TW) to evaluate its effectiveness as a supplement to improve seed germination, seedling recruitment and plant growth. In the first experiment, 20 species native to the resource-rich biodiverse Pilbara region of Western Australia were grown in 30 °C glasshouse facilities under well-watered conditions for three weeks with seedling emergence scored daily. At the end of the trial, seedlings were harvested and biomass was assessed. In the second experiment, five of the original 20 species (e.g. Acacia bivenosa, Gossypium robinsonii, Eucalyptus gamophylla, Triodia wiseana and, Senna notabilis) were assessed for germination in amended soils by burying nylon sachets in the reconstructed substrates. After three weeks, the sachets were retrieved and seeds were assessed for germination (i.e. radicle emergence was evident). Results and Discussion Total emergence and biomass of seedlings was negatively affected by higher doses of gypsum and urea amendments. In the lower dose treatments, however, the total biomass of seedlings showed a positive effect for species from the Amaranthaceae. There was no apparent effect on species from the Fabaceae, Malvaeceae, Myrtaceae, and Poaceae families. Small doses of the amendments had a positive impact on the seed germination for three of the five evaluated species (Acacia bivenosa, Triodia wiseana and, Senna notabilis). Yet, despite the addition of soil amendments there was a high rate of mortality between the germination and emergence phases, a common occurrence in arid zone species subject to extreme environmental conditions (James et al., 2011). Seedling emergence of Acacia bivenosa and Triodia wiseana in TW and W substrates with low doses of urea achieved levels comparable to emergence in topsoil. Overall, responses to the inorganic amendments varied considerably across species and long-term field studies are required to assess plant responses in a restoration setting. Nevertheless, the findings of this suggest that the addition of these N-based inorganic amendments at low concentrations will benefit some plant species and improve arid zone restoration. References James JJ, Svejcar TJ, Rinella MJ. 2011. Demographic processes limiting seedling recruitment in arid grassland restoration. Journal of Applied Ecology, 48, 961-969 Muñoz-Rojas M, Erickson TE, Martini D, Dixon KW, Merritt DJ. 2016. Climate and soil factors influencing seedling recruitment of plant species used for dryland restoration. SOIL, 2, 1-11, DOI: 10.5194/soil-2016-25
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NASA Astrophysics Data System (ADS)
Khalil, M. I.; Richards, K. G.
2009-04-01
Denitrifier population size and potential activity combined with the relevant environmental factors regulate the rates of denitrification in terrestrial and aquatic ecosystems. Due to the high atmospheric background of di-nitrogen (N2), denitrification enzyme activity (DEA) in soils is traditionally measured using the acetylene block or stable isotope techniques under non-limiting substrates and anaerobic/saturated conditions for periods from a few hours to several days so as to estimate denitrification potential (DP). This research investigated the estimation of DEA and DP by quantifying the N2/Ar ratio changes in waters/sediments using membrane inlet mass spectrometry (MIMS). Two experiments were conducted with soils of A, B and C horizons collected from grazed grassland to obtain optimal NO3- and available carbon (C) rates. In experiment 1, 30 g soil (oven dry basis) followed by helium-flushed deionized water was taken in triplicate 160 mL glass bottles and sealed with rubber stoppers without any air entrapments. Then N as potassium nitrate (0 to 120 mg NO3 - N kg-1 soil) and readily available C as glucose (0 to 240 mg glucose-C) plus 30 mg NO3 - N, kg-1 soil were amended. Laboratory incubation was performed in the dark at 21oC under water to reduce the risk of N2 contamination. After six hours, the treated water samples were transferred into 12 mL exetainers and kept under water at 4oC before analysis using MIMS. The N2/Ar ratios, representing DEA, varied between soil horizons and declined with decreasing soil depths. The maximum peak for N2/Ar ratios were observed with the 30 mg NO3 - N kg-1 soil in all soil horizons and coupled with the 60 mg glucose-C kg-1 soil for C horizon, and 120 mg glucose-C kg-1 for A and B horizons. Experiment 2 was conducted to assess simulated unsaturated and saturated subsoil (C horizon) denitrification capacity (NO3 - Nonly amendment), and DP (both C and N amendment) using the same methodology as experiment 1 and incubated for 3 days using groundwater. The optimal substrate rates (30 mg NO3 - N
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NASA Astrophysics Data System (ADS)
Vasconcelos, Steel S.; Zarin, Daniel J.; Capanu, Marinela; Littell, Ramon; Davidson, Eric A.; Ishida, Francoise Y.; Santos, Elisana B.; Araújo, Maristela M.; AragãO, DéBora V.; Rangel-Vasconcelos, LíVia G. T.; de Assis Oliveira, Francisco; McDowell, William H.; de Carvalho, Claudio José R.
2004-06-01
Changes in land-use and climate are likely to alter moisture and substrate availability in tropical forest soils, but quantitative assessment of the role of resource constraints as regulators of soil trace gas fluxes is rather limited. The primary objective of this study was to quantify the effects of moisture and substrate availability on soil trace gas fluxes in an Amazonian regrowth forest. We measured the efflux of carbon dioxide (CO2), nitric oxide (NO), nitrous oxide (N2O), and methane (CH4) from soil in response to two experimental manipulations. In the first, we increased soil moisture availability during the dry season by irrigation; in the second, we decreased substrate availability by continuous removal of aboveground litter. In the absence of irrigation, soil CO2 efflux decreased during the dry season while irrigation maintained soil CO2 efflux levels similar to the wet season. Large variations in soil CO2 efflux consistent with a significant moisture constraint on respiration were observed in response to soil wet-up and dry-down events. Annual soil C efflux for irrigated plots was 27 and 13% higher than for control plots in 2001 and 2002, respectively. Litter removal significantly reduced soil CO2 efflux; annual soil C efflux in 2002 was 28% lower for litter removal plots compared to control plots. The annual soil C efflux:litterfall C ratio for the control treatment (4.0-5.2) was consistent with previously reported values for regrowth forests that indicate a relatively large belowground C allocation. In general, fluxes of N2O and CH4 were higher during the wet season and both fluxes increased during dry-season irrigation. There was no seasonal effect on NO fluxes. Litter removal had no significant impact on N oxide or CH4 emissions. Net soil nitrification did not respond to dry-season irrigation, but was somewhat reduced by litter removal. Overall, these results demonstrate significant soil moisture and substrate constraints on soil trace gas emissions, particularly for CO2, and suggest that climate and land-use changes that alter moisture and substrate availability are therefore likely to have an impact on atmosphere chemistry.
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Guittonny-Larchevêque, Marie; Bussière, Bruno; Pednault, Carl
2016-05-01
Tree water uptake relies on well-developed root systems. However, mine wastes can restrict root growth, in particular metalliferous mill tailings, which consist of the finely crushed ore that remains after valuable metals are removed. Thus, water stress could limit plantation success in reclaimed mine lands. This study evaluates the effect of substrates varying in quality (topsoil, overburden, compost and tailings mixture, and tailings alone) and quantity (50- or 20-cm-thick topsoil layer vs. 1-m plantation holes) on root development and water stress exposure of trees planted in low-sulfide mine tailings under boreal conditions. A field experiment was conducted over 2 yr with two tree species: basket willow ( L.) and hybrid poplar ( Moench × A. Henry). Trees developed roots in the tailings underlying the soil treatments despite tailings' low macroporosity. However, almost no root development occurred in tailings underlying a compost and tailings mixture. Because root development and associated water uptake was not limited to the soil, soil volume influenced neither short-term (water potential and instantaneous transpiration) nor long-term (δC) water stress exposure in trees. However, trees were larger and had greater total leaf area when grown in thicker topsoil. Despite a volumetric water content that always remained above permanent wilting point in the tailings colonized by tree roots, measured foliar water potentials at midday were lower than drought thresholds reported for both tested tree species. Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.
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Response of microbial community composition and function to soil climate change
Waldrop, M.P.; Firestone, M.K.
2006-01-01
Soil microbial communities mediate critical ecosystem carbon and nutrient cycles. How microbial communities will respond to changes in vegetation and climate, however, are not well understood. We reciprocally transplanted soil cores from under oak canopies and adjacent open grasslands in a California oak-grassland ecosystem to determine how microbial communities respond to changes in the soil environment and the potential consequences for the cycling of carbon. Every 3 months for up to 2 years, we monitored microbial community composition using phospholipid fatty acid analysis (PLFA), microbial biomass, respiration rates, microbial enzyme activities, and the activity of microbial groups by quantifying 13C uptake from a universal substrate (pyruvate) into PLFA biomarkers. Soil in the open grassland experienced higher maximum temperatures and lower soil water content than soil under the oak canopies. Soil microbial communities in soil under oak canopies were more sensitive to environmental change than those in adjacent soil from the open grassland. Oak canopy soil communities changed rapidly when cores were transplanted into the open grassland soil environment, but grassland soil communities did not change when transplanted into the oak canopy environment. Similarly, microbial biomass, enzyme activities, and microbial respiration decreased when microbial communities were transplanted from the oak canopy soils to the grassland environment, but not when the grassland communities were transplanted to the oak canopy environment. These data support the hypothesis that microbial community composition and function is altered when microbes are exposed to new extremes in environmental conditions; that is, environmental conditions outside of their "life history" envelopes. ?? 2006 Springer Science+Business Media, Inc.
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Akpheokhai, Leonard I; Oribhabor, Blessing J
2016-01-01
The interaction of man with the ecosystem is a major factor causing environmental pollution and its attendant consequences such as climate change in our world today. Patents relating to nematodes' relevance in soil quality management and their significance as biomarkers in aquatic substrates were reviewed. Nematodes are useful in rapid, easy and inexpensive method for testing the toxicity of substance (e.g. aquatic substrates). This review paper sets out to examine and discuss the issue of soil pollution, functions of nematodes in soil and aquatic substrates as well as bio-indicators in soil health management in terrestrial ecology. The information used were on the basis of secondary sources from previous research. It is abundantly clear that the population dynamics of plant parasitic or free-living nematodes have useful potentials as biomonitor for soil health and other forms of environmental contamination through agricultural activities, industrial pollution and oil spillage, and the analysis of nematode community structure could be used as complementary information obtained from conventional soil testing approaches.
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NASA Astrophysics Data System (ADS)
Ohte, N.; Aoki, M.; Katsuyama, C.; Suwa, Y.; Tange, T.
2012-12-01
To elucidate the mechanisms of denitrification processes in the forested catchment, microbial ecological approaches have been applied in an experimental watershed that has previously investigated its hydrological processes. The study catchment is located in the Chiba prefecture in central Japan under the temperate Asian monsoon climate. Potential activities of denitrification of soil samples were measured by incubation experiments under anoxic condition associated with Na15NO3 addition. Existence and variety of microbes having nitrite reductase genes were investigated by PCR amplification, cloning and sequencings of nirK and nirS fragments after DNA extraction. Contrary to our early expectation that the potential denitrification activity was higher at deeper soil horizon with consistent groundwater residence than that in the surface soil, denitrification potential was higher in shallower soil horizons than deeper soils. This suggested that the deficiency of NO3- as a respiratory substrate for denitrifier occurred in deeper soils especially in the summer. However, high denitrification activity and presence of microbes having nirK and nirS in surface soils usually under aerobic condition was explainable by the fact that the majority of denitrifying bacteria have been recognized as a facultative anaerobic bacterium. This also suggests the possibility of that denitrification occurs even in the surface soils if the wet condition is provided by rainwater during and after a storm event. Community structures of microbes having nirK were different between near surface and deeper soil horizons, and ones having nirS was different between saturated zone (under groundwater table) and unsaturated soil horizons. These imply that microbial communities with nisK are sensitive to the concentration of soil organic matters and ones with nirS is sensitive to soil moisture contents.
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NASA Astrophysics Data System (ADS)
Goodchild, Martin; Janes, Stuart; Jenkins, Malcolm; Nicholl, Chris; Kühn, Karl
2015-04-01
The aim of this work is to assess the use of temperature corrected substrate moisture data to improve the relationship between environmental drivers and the measurement of substrate moisture content in high porosity soil-free growing environments such as coir. Substrate moisture sensor data collected from strawberry plants grown in coir bags installed in a table-top system under a polytunnel illustrates the impact of temperature on capacitance-based moisture measurements. Substrate moisture measurements made in our coir arrangement possess the negative temperature coefficient of the permittivity of water where diurnal changes in moisture content oppose those of substrate temperature. The diurnal substrate temperature variation was seen to range from 7° C to 25° C resulting in a clearly observable temperature effect in substrate moisture content measurements during the 23 day test period. In the laboratory we measured the ML3 soil moisture sensor (ThetaProbe) response to temperature in Air, dry glass beads and water saturated glass beads and used a three-phase alpha (α) mixing model, also known as the Complex Refractive Index Model (CRIM), to derive the permittivity temperature coefficients for glass and water. We derived the α value and estimated the temperature coefficient for water - for sensors operating at 100MHz. Both results are good agreement with published data. By applying the CRIM equation with the temperature coefficients of glass and water the moisture temperature coefficient of saturated glass beads has been reduced by more than an order of magnitude to a moisture temperature coefficient of
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NASA Astrophysics Data System (ADS)
Hu, Dawei; Li, Leyuan; Liu, Hui; Zhang, Houkai; Fu, Yuming; Sun, Yi; Li, Liang
It is necessary to process inedible plant biomass into soil-like substrate (SLS) by bio-compost to realize biological resource sustainable utilization. Although similar to natural soil in structure and function, SLS often has uneven water distribution adversely affecting the plant growth due to unsatisfactory porosity, permeability and gravity distribution. In this article, SLS plant-growing facility (SLS-PGF) were therefore rotated properly for cultivating lettuce, and the Brinkman equations coupled with laminar flow equations were taken as governing equations, and boundary conditions were specified by actual operating characteristics of rotating SLS-PGF. Optimal open-control law of the angular and inflow velocity was determined by lettuce water requirement and CFD simulations. The experimental result clearly showed that water content was more uniformly distributed in SLS under the action of centrifugal and Coriolis force, rotating SLS-PGF with the optimal open-control law could meet lettuce water requirement at every growth stage and achieve precise irrigation.
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NASA Astrophysics Data System (ADS)
Cheng, X.; Wu, J.
2016-12-01
Global change greatly alters the quality and quantity of plant litter inputs to soils, and further impacts soil organic matter (SOM) dynamics and soil respiration. However, the process-based understanding of how soil respiration may change with future shift in litter input is not fully understood. The Detritus Input and Removal Treatment (DIRT) experiment was conducted in coniferous forest (Platycladus orientalis (Linn.) Franco) ecosystem of central China to investigate the impact of above- and belowground litter input on soil respiration and the carbon-isotopic signature of soil respired CO2. Short-term (1-2 years) litter input manipulation significantly affected soil respiration, based on annual flux values, soil respiration was 31.9%, 20.5% and 37.2% lower in no litter (NL), no root (NR) and no input (NRNL), respectively, compared to control (CK). Whereas double litter (DL) treatment increased soil respiration by 9.1% compared to CK. The recalcitrance index of carbon (RIC) and the relative abundance of fungi increased under litter removal or root exclusion treatment (NL, NR and NRNL) compared to CK. Basal soil respiration was positively related to liable C and microbial biomass and negatively related to RIC and fungi to bacteria (F: B) ratio. The carbon-isotopic signature of soil respired CO2 enriched under litter removal and no input treatment, and slightly depleted under litter addition treatment compared to CK. Our results suggest that short-term litter input manipulation can affect the soil respiration by altering substrate availability and microbial community structure, and also impact the carbon-isotopic signature of soil respired CO2 possibly duo to change in the component of soil respiration and soil microclimate.
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Liu, Yuan; He, Nianpeng; Zhu, Jianxing; Xu, Li; Yu, Guirui; Niu, Shuli; Sun, Xiaomin; Wen, Xuefa
2017-08-01
How to assess the temperature sensitivity (Q 10 ) of soil organic matter (SOM) decomposition and its regional variation with high accuracy is one of the largest uncertainties in determining the intensity and direction of the global carbon (C) cycle in response to climate change. In this study, we collected a series of soils from 22 forest sites and 30 grassland sites across China to explore regional variation in Q 10 and its underlying mechanisms. We conducted a novel incubation experiment with periodically changing temperature (5-30 °C), while continuously measuring soil microbial respiration rates. The results showed that Q 10 varied significantly across different ecosystems, ranging from 1.16 to 3.19 (mean 1.63). Q 10 was ordered as follows: alpine grasslands (2.01) > temperate grasslands (1.81) > tropical forests (1.59) > temperate forests (1.55) > subtropical forests (1.52). The Q 10 of grasslands (1.90) was significantly higher than that of forests (1.54). Furthermore, Q 10 significantly increased with increasing altitude and decreased with increasing longitude. Environmental variables and substrate properties together explained 52% of total variation in Q 10 across all sites. Overall, pH and soil electrical conductivity primarily explained spatial variation in Q 10 . The general negative relationships between Q 10 and substrate quality among all ecosystem types supported the C quality temperature (CQT) hypothesis at a large scale, which indicated that soils with low quality should have higher temperature sensitivity. Furthermore, alpine grasslands, which had the highest Q 10 , were predicted to be more sensitive to climate change under the scenario of global warming. © 2017 John Wiley & Sons Ltd.
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Marín-Benito, Jesús María; Rodríguez-Cruz, María Sonia; Sánchez-Martín, María Jesús; Mamy, Laure
2015-09-01
The performance of the pesticide fate model PRZM to predict the fate of two fungicides, penconazole and metalaxyl, and the major metabolite of metalaxyl (CGA-62826), in amended and unamended vineyard soils was tested from undisturbed soils columns experiments. Three different treatments were tested in two soils: control soil (unamended), and soil amended with fresh or composted spent mushroom substrates, which correspond to common agricultural practices in Spain. Leaching experiments were performed under non-saturated flow conditions. The model was parameterized with laboratory and literature data, and using pedotransfer functions. It was first calibrated for water flow against chloride breakthrough curves. The key parameter was the hydrodynamic dispersion coefficient (DISP). No leaching of penconazole, the most hydrophobic fungicide, was observed. It remained in the top 0-8 cm of the column. In any case, simulations were highly correlated to the experimental results. On the contrary, metalaxyl and its metabolite were consistently found in the leachates. A calibration step of the Kd of metalaxyl and CGA-62826 and of DISP for CGA-62826 was necessary to obtain good prediction of the leaching of both compounds. PRZM generally simulated acceptable metalaxyl vertical distribution in the soil profiles although results were overestimated for its metabolite. Nevertheless, PRZM can be reasonably used to assess the leaching (through breakthrough curves) and vertical distribution of fungicides in amended soils, knowing their DISP values. Copyright © 2015 Elsevier Ltd. All rights reserved.
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Particle transport patterns of short-distance soil erosion by wind-driven rain, rain and wind
NASA Astrophysics Data System (ADS)
Marzen, Miriam; Iserloh, Thomas; de Lima, João L. M. P.; Ries, Johannes B.
2015-04-01
Short distance erosion of soil surface material is one of the big question marks in soil erosion studies. The exact measurement of short-distance transported soil particles, prior to the occurrence of overland flow, is a challenge to soil erosion science due to the particular requirements of the experimental setup and test procedure. To approach a quantification of amount and distance of each type of transport, we applied an especially developed multiple-gutter system installed inside the Trier Portable Wind and Rainfall Simulator (PWRS). We measured the amount and travel distance of soil particles detached and transported by raindrops (splash), wind-driven rain (splash-saltation and splash-drift) and wind (saltation). The test setup included three different erosion agents (rain/ wind-driven rain/ wind), two substrates (sandy/ loamy), three surface structures (grain roughness/ rills lengthwise/ rills transversal) and three slope angles (0°/+7°/-7°). The results present detailed transport patterns of the three erosion agents under the varying soil and surface conditions up to a distance of 1.6 m. Under the applied rain intensity and wind velocity, wind-driven rain splash generates the highest erosion. The erodibility and travel distance of the two substrates depend on the erosion agent. The total erosion is slightly higher for the slope angle -7° (downslope), but for wind-driven rain splash, the inclination is not a relevant factor. The effect of surface structures (rills) changes with traveling distance. The wind driven rain splash generates a much higher amount of erosion and a further travel distance of the particles due to the combined action of wind and rain. The wind-driven rain factor appears to be much more significant than the other factors. The study highlights the effects of different erosion agents and surface parameters on short-distance particle transport and the powerful impact of wind-driven rain on soil erosion.
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Testing a biofilter cover design to mitigate dairy effluent pond methane emissions.
Pratt, Chris; Deslippe, Julie; Tate, Kevin R
2013-01-02
Biofiltration, whereby CH(4) is oxidized by methanotrophic bacteria, is a potentially effective strategy for mitigating CH(4) emissions from anaerobic dairy effluent lagoons/ponds, which typically produce insufficient biogas for energy recovery. This study reports on the effectiveness of a biofilter cover design at oxidizing CH(4) produced by dairy effluent ponds. Three substrates, a volcanic pumice soil, a garden-waste compost, and a mixture of the two, were tested as media for the biofilters. All substrates were suspended as 5 cm covers overlying simulated dairy effluent ponds. Methane fluxes supplied to the filters were commensurate with emission rates from typical dairy effluent ponds. All substrates oxidized more than 95% of the CH(4) influx (13.9 g CH(4) m(-3) h(-1)) after two months and continued to display high oxidation rates for the remaining one month of the trial. The volcanic soil biofilters exhibited the highest oxidation rates (99% removal). When the influx CH(4) dose was doubled for a month, CH(4) removal rates remained >90% for all substrates (maximum = 98%, for the volcanic soil), suggesting that biofilters have a high capacity to respond to increases in CH(4) loads. Nitrous oxide emissions from the biofilters were negligible (maximum = 19.9 mg N(2)O m(-3) h(-1)) compared with CH(4) oxidation rates, particularly from the volcanic soil that had a much lower microbial-N (75 mg kg(-1)) content than the compost-based filters (>240 mg kg(-1)). The high and sustained CH(4) oxidation rates observed in this laboratory study indicate that a biofilter cover design is a potentially efficient method to mitigate CH(4) emissions from dairy effluent ponds. The design should now be tested under field conditions.
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McDaniel, M D; Kaye, J P; Kaye, M W; Bruns, M A
2014-04-01
Forest disturbances, including whole-tree harvest, will increase with a growing human population and its rising affluence. Following harvest, forests become sources of C to the atmosphere, partly because wetter and warmer soils (relative to pre-harvest) increase soil CO2 efflux. This relationship between soil microclimate and CO2 suggests that climate changes predicted for the northeastern US may exacerbate post-harvest CO2 losses. We tested this hypothesis using a climate-manipulation experiment within a recently harvested northeastern US forest with warmed (H; +2.5 °C), wetted (W; +23% precipitation), warmed + wetted (H+W), and ambient (A) treatments. The cumulative soil CO2 effluxes from H and W were 35% (P = 0.01) and 22% (P = 0.07) greater than A. However, cumulative efflux in H+W was similar to A and W, and 24% lower than in H (P = 0.02). These findings suggest that with higher precipitation soil CO2 efflux attenuates rapidly to warming, perhaps due to changes in substrate availability or microbial communities. Microbial function measured as CO2 response to 15 C substrates in warmed soils was distinct from non-warmed soils (P < 0.001). Furthermore, wetting lowered catabolic evenness (P = 0.04) and fungi-to-bacteria ratios (P = 0.03) relative to non-wetted treatments. A reciprocal transplant incubation showed that H+W microorganisms had lower laboratory respiration on their home soils (i.e., home substrates) than on soils from other treatments (P < 0.01). We inferred that H+W microorganisms may use a constrained suite of C substrates that become depleted in their "home" soils, and that in some disturbed ecosystems, a precipitation-induced attenuation (or suppression) of soil CO2 efflux to warming may result from fine-tuned microbe-substrate linkages.
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Expanding Upon the MEMS Framework: How Temperature Impacts Organo-Mineral Interactions
NASA Astrophysics Data System (ADS)
Smith, K.; Waring, B. G.
2017-12-01
Microbial substrate use efficiency (SUE; the fraction of substrate carbon (C) incorporated into biomass vs. respired) affects the development of soil organic matter (SOM). An emerging theoretical model (the Microbial Efficiency-Matrix Stabilization (MEMS) framework) posits that microbial SUE acts as a filter for plant litter inputs, whereby a larger proportion of microbial products are synthesized from labile (and not recalcitrant) plant substrates. Thus, SOM stability depends on both the efficiency of microbial anabolism as well as the degree to which microbial products stabilize within the mineral soil matrix. In this study, we performed a laboratory microcosm experiment using diverse soils collected in Utah to test how substrate complexity, soil mineralogy, and temperature interact to control SOM formation. Prior to microcosm setup, we first removed organic C from our field soils by washing with concentrated hypochlorite solution. Microcosms were then assembled by mixing C-free soil with one of three substrates (glucose, cellulose, and lignin), and placed in incubators set to different temperatures (18°, 28°, and 38°C). Respiration rates were then estimated by periodically sampling headspace CO2 concentrations in each microcosm. Prior to C removal, we found that field soils exhibited distinct properties ranging from clay-rich vertisols (55:27:18, sand:silt:clay; 1.1% C), to loamy-sand entisols (85:11:4; 0.3% C), and organic-rich mollisols (79:17:4; 1.7% C). In the incubation experiment, consistent with enzyme kinetics theory, respiration rates increased as a function of incubation temperature (p < 0.0001), and that the temperature response of respiration was dependent on substrate (p < 0.0001), with the lignin treatment exhibiting the greatest temperature sensitivity. While respiration was significantly lower in the mollisol treatment (p < 0.0001), other soil effects (including interactions with temperature and substrate) were less clear. Together these results build upon the MEMS framework by highlighting the importance of organo-mineral interactions and temperature as controls on soil C cycling.
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NASA Astrophysics Data System (ADS)
Tong, C.; She, C. X.; Jin, Y. F.; Yang, P.; Huang, J. F.
2013-11-01
Methane production is influenced by the abundance of methanogens and the availability of terminal substrates. Sulfate-reducing bacteria (SRB) also play an important role in the anaerobic decomposition of organic matter. However, the relationships between methane production and methanogen populations, pore water terminal substrates in estuarine brackish marshes are poorly characterized, and even to our knowledge, no published research has explored the relationship between methane production rate and abundance of SRB and pore water dimethyl sulfide (DMS) concentration. We investigated methane production rate, abundances of methanogens and SRB, concentrations of pore water terminal substrates and electron acceptors at a brackish marsh landscape dominated by Phragmites australis, Cyperus malaccensis and Spatina alterniflora marshes zones in the Min River estuary. The average rates of methane production at a soil depth of 30 cm in the three marsh zones were 0.142, 0.058 and 0.067 μg g-1 d-1, respectively. The abundance of both methanogens and SRB in the soil of the P. australis marsh with highest soil organic carbon content was higher than in the C. malaccensis and S. alterniflora marshes. The abundance of methanogens and SRB in the three soil layers was statistically indistinguishable. Mean pore water DMS concentrations at a soil depth of 30 cm under the S. alterniflora marsh were higher than those in the C. malaccensis and P. australis marshes. Methane production rate increased with the abundance of both methanogens and SRB across three marsh zones together at the landscape scale, and also increased with the concentration of pore water acetate, but did not correlate with concentrations of pore water DMS and dissolved CO2. Our results suggest that, provided that substrates are available in ample supply, methanogens can continue to produce methane regardless of whether SRB are prevalent in estuarine brackish marshes.
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Content and Bioaccumulation of Nine Mineral Elements in Ten Mushroom Species of the Genus Boletus
Wang, Xue-Mei; Zhang, Ji; Li, Tao; Wang, Yuan-Zhong; Liu, Hong-Gao
2015-01-01
Concentrations and bioconcentration potential of nine elements (Ca, Cu, Fe, K, Mg, Mn, Na, P, and Zn) in ten species of wild edible Boletus and the corresponding underlying soils were analyzed. The analyses were performed using inductively coupled plasma atomic emission spectrophotometer. Boletus showed relative abundant contents of P, K, Fe, Mg, Ca, and Na and less of Zn, Cu, and Mn. Caps compared to stalks were enriched in P, K, Cu, Mg, and Zn, while stalks were enriched in Mn. The elements such as P and K were accumulated (BCF > 1), while Ca, Fe, Mg, Mn, and Na were excluded (BCF < 1) in the fruiting bodies. The correlation analysis indicated high correlations between Cu, Mn, Ca, and Fe in the mushrooms as compared to the corresponding soils. Significant correlations were also obtained between Cu-P (r = 0.775), Fe-P (r = 0.728), and Zn-P (r = 0.76) for caps and Cu-Mg (r = 0.721), Fe-Mg (r = 0.719), Zn-Mg (r = 0.824), and Zn-P (r = 0.818) for stalks. The results of this study imply that ability of fungi to accumulate elements from substrate could be influenced by mushroom species and underlying soil substrates. PMID:26146585
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Content and Bioaccumulation of Nine Mineral Elements in Ten Mushroom Species of the Genus Boletus.
Wang, Xue-Mei; Zhang, Ji; Li, Tao; Wang, Yuan-Zhong; Liu, Hong-Gao
2015-01-01
Concentrations and bioconcentration potential of nine elements (Ca, Cu, Fe, K, Mg, Mn, Na, P, and Zn) in ten species of wild edible Boletus and the corresponding underlying soils were analyzed. The analyses were performed using inductively coupled plasma atomic emission spectrophotometer. Boletus showed relative abundant contents of P, K, Fe, Mg, Ca, and Na and less of Zn, Cu, and Mn. Caps compared to stalks were enriched in P, K, Cu, Mg, and Zn, while stalks were enriched in Mn. The elements such as P and K were accumulated (BCF > 1), while Ca, Fe, Mg, Mn, and Na were excluded (BCF < 1) in the fruiting bodies. The correlation analysis indicated high correlations between Cu, Mn, Ca, and Fe in the mushrooms as compared to the corresponding soils. Significant correlations were also obtained between Cu-P (r = 0.775), Fe-P (r = 0.728), and Zn-P (r = 0.76) for caps and Cu-Mg (r = 0.721), Fe-Mg (r = 0.719), Zn-Mg (r = 0.824), and Zn-P (r = 0.818) for stalks. The results of this study imply that ability of fungi to accumulate elements from substrate could be influenced by mushroom species and underlying soil substrates.
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The Role of Microbial Community Composition in Controlling Soil Respiration Responses to Temperature
Khachane, Amit; Dungait, Jennifer A. J.; Fraser, Fiona; Hopkins, David W.; Wookey, Philip A.; Singh, Brajesh K.; Freitag, Thomas E.; Hartley, Iain P.; Prosser, James I.
2016-01-01
Rising global temperatures may increase the rates of soil organic matter decomposition by heterotrophic microorganisms, potentially accelerating climate change further by releasing additional carbon dioxide (CO2) to the atmosphere. However, the possibility that microbial community responses to prolonged warming may modify the temperature sensitivity of soil respiration creates large uncertainty in the strength of this positive feedback. Both compensatory responses (decreasing temperature sensitivity of soil respiration in the long-term) and enhancing responses (increasing temperature sensitivity) have been reported, but the mechanisms underlying these responses are poorly understood. In this study, microbial biomass, community structure and the activities of dehydrogenase and β-glucosidase enzymes were determined for 18 soils that had previously demonstrated either no response or varying magnitude of enhancing or compensatory responses of temperature sensitivity of heterotrophic microbial respiration to prolonged cooling. The soil cooling approach, in contrast to warming experiments, discriminates between microbial community responses and the consequences of substrate depletion, by minimising changes in substrate availability. The initial microbial community composition, determined by molecular analysis of soils showing contrasting respiration responses to cooling, provided evidence that the magnitude of enhancing responses was partly related to microbial community composition. There was also evidence that higher relative abundance of saprophytic Basidiomycota may explain the compensatory response observed in one soil, but neither microbial biomass nor enzymatic capacity were significantly affected by cooling. Our findings emphasise the key importance of soil microbial community responses for feedbacks to global change, but also highlight important areas where our understanding remains limited. PMID:27798702
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Auffret, Marc D; Karhu, Kristiina; Khachane, Amit; Dungait, Jennifer A J; Fraser, Fiona; Hopkins, David W; Wookey, Philip A; Singh, Brajesh K; Freitag, Thomas E; Hartley, Iain P; Prosser, James I
2016-01-01
Rising global temperatures may increase the rates of soil organic matter decomposition by heterotrophic microorganisms, potentially accelerating climate change further by releasing additional carbon dioxide (CO2) to the atmosphere. However, the possibility that microbial community responses to prolonged warming may modify the temperature sensitivity of soil respiration creates large uncertainty in the strength of this positive feedback. Both compensatory responses (decreasing temperature sensitivity of soil respiration in the long-term) and enhancing responses (increasing temperature sensitivity) have been reported, but the mechanisms underlying these responses are poorly understood. In this study, microbial biomass, community structure and the activities of dehydrogenase and β-glucosidase enzymes were determined for 18 soils that had previously demonstrated either no response or varying magnitude of enhancing or compensatory responses of temperature sensitivity of heterotrophic microbial respiration to prolonged cooling. The soil cooling approach, in contrast to warming experiments, discriminates between microbial community responses and the consequences of substrate depletion, by minimising changes in substrate availability. The initial microbial community composition, determined by molecular analysis of soils showing contrasting respiration responses to cooling, provided evidence that the magnitude of enhancing responses was partly related to microbial community composition. There was also evidence that higher relative abundance of saprophytic Basidiomycota may explain the compensatory response observed in one soil, but neither microbial biomass nor enzymatic capacity were significantly affected by cooling. Our findings emphasise the key importance of soil microbial community responses for feedbacks to global change, but also highlight important areas where our understanding remains limited.
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Natural recovery of biological soil crusts after disturbance
Weber, Bettina; Bowker, Matthew A.; Zhang, Yuanming; Belnap, Jayne
2016-01-01
Natural recovery of biological soil crusts (biocrusts) is influenced by a number of different parameters, such as climate, soil conditions, the severity of disturbance, and the timing of disturbance relative to the climatic conditions. In recent studies, it has been shown that recovery is often not linear, but a highly dynamic process directly influenced by non-linear external parameters as extraordinary climatic conditions (e.g., particularly dry or wet year). Natural recovery often follows a general succession pattern, starting out with cyanobacteria and algae, which is then followed by lichens and bryophytes at a later stage. However, this general sequence can be altered by parameters like dust deposition, fire effects, and special climatic conditions as in fog deserts and under mesic climates. Recent studies have proposed that under favorable, stable soil conditions, the initial soil-stabilizing cyanobacteria-dominated succession stages may be omitted and moss-dominated biocrusts can develop in the initial phases of biocrust development. During natural recovery of biocrusts, soil properties change, e.g., soil nutrient and organic matter contents increase. Also, silt and clay contents of encrusted soils increase with biocrust maturity, which may be caused by two mechanisms, i.e. entrapment of fine soil particles by biocrusts and the new formation of smaller particles by weathering of the existing substrate.
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Automated Microbial Metabolism Laboratory
NASA Technical Reports Server (NTRS)
1971-01-01
The effect of several environmental parameters on previously developed life detection systems is explored. Initial attempts were made to conduct all the experiments in a moist mode (high soil volume to water volume ratio). However, only labeled release and measurement of ATP were found to be feasible under conditions of low moisture. Therefore, these two life detection experiments were used for most of the environmental effects studies. Three soils, Mojave (California desert), Wyaconda (Maryland, sandy loam) and Victoria Valley (Antarctic desert) were generally used throughout. The environmental conditions studied included: incubation temperature 3 C to 80 C, ultraviolet irradiation of soils, variations in soil/liquid ratio, specific atmospheric gases, various antimetabolites, specific substrates, and variation in pH. An experiment designed to monitor nitrogen metabolism was also investigated.
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NASA Astrophysics Data System (ADS)
Stock, Svenja; Köster, Moritz; Dippold, Michaela; Boy, Jens; Matus, Francisco; Merino, Carolina; Nájera, Francisco; Spielvogel, Sandra; Gorbushina, Anna; Kuzyakov, Yakov
2017-04-01
The Chilean ecosystems provide a unique study area to investigate biotic controls on soil organic matter (SOM) decomposition and mineral weathering depending on climate (from hyper arid to temperate humid). Microorganisms play a crucial role in the SOM decomposition, nutrient release and cycling. By means of extracellular enzymes microorganisms break down organic compounds and provide nutrients for plants. Soil moisture (abiotic factor) and root carbon (biotic factor providing easily available energy source for microorganisms), are important factors for microbial decomposition of SOM and show strong gradients along the investigated climatic gradient. A high input of root carbon increases microbial activity and enzyme production, and facilitates SOM breakdown and nutrient release The aim of this study was to determine the potential enzymatic SOM decomposition and nutrient release depending on root proximity and precipitation. C and N contents, δ13C and δ15N values, and kinetics (Vmax, Km) of six extracellular enzymes, responsible for C, N, and P cycles, were quantified in vertical (soil depth) and horizontal (from roots to bulk soil) gradients in two climatic regions: within a humid temperate forest and a semiarid open forest. The greater productivity of the temperate forest was reflected by higher C and N contents compared to the semiarid forest. Regression lines between δ13C and -[ln(%C)] showed a stronger isotopic fractionation from top- to subsoil at the semiarid open forest, indicating a faster SOM turnover compared to the humid temperate forest. This is the result of more favorable soil conditions (esp. temperature and smaller C/N ratios) in the semiarid forest. Depth trends of δ15N values indicated N limitation in both soils, though the limitation at the temperate site was stronger. The activity of enzymes degrading cellulose and hemicellulose increased with C content. Activity of enzymes involved in C, N and P cycles decreased from top- to subsoil and with distance to roots. Chitinase and acid phosphatase activities increased with increasing C contents and indicated a faster substrate turnover in soil under the temperate forest compared to the semiarid forest. In contrast, Tyrosin-aminopeptidase activities indicated a faster substrate turnover under semiarid forest than the temperate forest, and strongly increased with increasing N content. We conclude that the N availability and SOM turnover under semiarid open forest is higher than under humid temperate forest. The enzyme activities are depending on depth only indirectly and are driven mainly by soil C content, which is directly affected by root carbon input.
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Seasonal variation in functional properties of microbial communities in beech forest soil
Koranda, Marianne; Kaiser, Christina; Fuchslueger, Lucia; Kitzler, Barbara; Sessitsch, Angela; Zechmeister-Boltenstern, Sophie; Richter, Andreas
2013-01-01
Substrate quality and the availability of nutrients are major factors controlling microbial decomposition processes in soils. Seasonal alteration in resource availability, which is driven by plants via belowground C allocation, nutrient uptake and litter fall, also exerts effects on soil microbial community composition. Here we investigate if seasonal and experimentally induced changes in microbial community composition lead to alterations in functional properties of microbial communities and thus microbial processes. Beech forest soils characterized by three distinct microbial communities (winter and summer community, and summer community from a tree girdling plot, in which belowground carbon allocation was interrupted) were incubated with different 13C-labeled substrates with or without inorganic N supply and analyzed for substrate use and various microbial processes. Our results clearly demonstrate that the three investigated microbial communities differed in their functional response to addition of various substrates. The winter communities revealed a higher capacity for degradation of complex C substrates (cellulose, plant cell walls) than the summer communities, indicated by enhanced cellulase activities and reduced mineralization of soil organic matter. In contrast, utilization of labile C sources (glucose) was lower in winter than in summer, demonstrating that summer and winter community were adapted to the availability of different substrates. The saprotrophic community established in girdled plots exhibited a significantly higher utilization of complex C substrates than the more plant root associated community in control plots if additional nitrogen was provided. In this study we were able to demonstrate experimentally that variation in resource availability as well as seasonality in temperate forest soils cause a seasonal variation in functional properties of soil microorganisms, which is due to shifts in community structure and physiological adaptations of microbial communities to altered resource supply. PMID:23645937
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NASA Astrophysics Data System (ADS)
Billings, S. A.; Tiemann, L. K.; Ballantyne, F., IV; Lehmeier, C.; Min, K.
2014-12-01
Investigators of soil organic matter (SOM) transformations struggle with a deceptively simple-sounding question: "Why does some SOM leave the soil profile relatively quickly, while other compounds, especially those at depth, appear to be retained on timescales ranging from the decadal to the millennial?" This question is important on both practical and academic levels, but addressing it is challenging for a multitude of reasons. Simultaneous with soil-specific advances, multiple other disciplines have enhanced their knowledge bases in ways potentially useful for future investigations of SOM decay. In this article, we highlight observations highly relevant for those investigating SOM decay and retention but often emanating from disparate fields and residing in literature seldom cited in SOM research. We focus on recent work in two key areas. First, we turn to experimental approaches using natural and artificial aquatic environments to investigate patterns of microbially-mediated OM transformations as environmental conditions change, and highlight how aquatic microbial responses to environmental change can reveal processes likely important to OM decay and retention in soils. Second, we emphasize the importance of establishing intrinsic patterns of decay kinetics for purified substrates commonly found in soils to develop baseline rates. These decay kinetics - which represent the upper limit of the reaction rates - can then be compared to substrate decay kinetics observed in natural samples, which integrate intrinsic decay reaction rates and edaphic factors essential to the site under study but absent in purified systems. That comparison permits the site-specific factors to be parsed from the fundamental decay kinetics, an important advance in our understanding of SOM decay (and thus persistence) in natural systems. We then suggest ways in which empirical observations from aquatic systems and purified enzyme-substrate reaction kinetics can be used to advance recent theoretical efforts in SOM-focused research. Finally, we suggest how the observations in aquatic and purified enzyme-substrate systems could be used to help unravel the puzzles presented by oft-observed patterns of SOM characteristics with depth, as one example of the many perplexing SOM-related problems.
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Dusza, Yann; Barot, Sébastien; Kraepiel, Yvan; Lata, Jean-Christophe; Abbadie, Luc; Raynaud, Xavier
2017-04-01
Green roofs provide ecosystem services through evapotranspiration and nutrient cycling that depend, among others, on plant species, substrate type, and substrate depth. However, no study has assessed thoroughly how interactions between these factors alter ecosystem functions and multifunctionality of green roofs. We simulated some green roof conditions in a pot experiment. We planted 20 plant species from 10 genera and five families (Asteraceae, Caryophyllaceae, Crassulaceae, Fabaceae, and Poaceae) on two substrate types (natural vs. artificial) and two substrate depths (10 cm vs. 30 cm). As indicators of major ecosystem functions, we measured aboveground and belowground biomasses, foliar nitrogen and carbon content, foliar transpiration, substrate water retention, and dissolved organic carbon and nitrates in leachates. Interactions between substrate type and depth strongly affected ecosystem functions. Biomass production was increased in the artificial substrate and deeper substrates, as was water retention in most cases. In contrast, dissolved organic carbon leaching was higher in the artificial substrates. Except for the Fabaceae species, nitrate leaching was reduced in deep, natural soils. The highest transpiration rates were associated with natural soils. All functions were modulated by plant families or species. Plant effects differed according to the observed function and the type and depth of the substrate. Fabaceae species grown on natural soils had the most noticeable patterns, allowing high biomass production and high water retention but also high nitrate leaching from deep pots. No single combination of factors enhanced simultaneously all studied ecosystem functions, highlighting that soil-plant interactions induce trade-offs between ecosystem functions. Substrate type and depth interactions are major drivers for green roof multifunctionality.
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Organic soil production from urban soil, spent mushroom substrate, and other additives
NASA Astrophysics Data System (ADS)
Pham, Nhung Thi Ha
2017-09-01
In recent years, spent mushroom substrate (SMS) is becoming the huge problem in environmental pollution issues from mushroom production. However, SMS is also a nutrient-rich ogranic material with available nutrients and high porosity. Therefore, the value of products made from SMS should be exploited to take full advantage of agricultural by-product, support organic agriculture development without environmental pollution. The research has built 5 experimental formulas (4 mixed formulas and 1 control formulas with only urban soil). The analysis results of soil samples from mixed formulas and the control formula witness a significant increase in moisture and OM of mixed formulas (moisture from 36-42%, OM from 5.5-6.9%) after 20 treatment days, and N-P-K contents are also improved remarkably. 60 days later, soil nutrients in mixed formulas continue to rise, with highest OM (8.679%) at CT1; N (0.154%) at CT4; K2O (0,698%) and P2O5 (0,172%) at CT3, in addition, heavy metal contents in all formulas are under standard limit. Synthetic assessment of all norms indicates that the best organic soil product comes from CT3. The pak choi planting experiments are performed show that the growth of plants cultivated on organic soil products made from mixed formulas are much better than plants are grown on initially soil, and they also have no pestilent insect. Specially, pak choi planted on organic soil from CT3 have sharp developing with excellent tolerance ability, quantity and area of leaves are high. Thus, CT3 is the most suitable formula to increase soil nutrients, to solve spent mushroom subtrate streament problems after harvest, and for sustainable agricultural development.
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Thin soil layer of green roof systems studied by X-Ray CT
NASA Astrophysics Data System (ADS)
Šácha, Jan; Jelínková, Vladimíra; Dohnal, Michal
2016-04-01
The popular non-invasive visualization technique of X-ray computed tomography (CT) has been used for 3D examination of thin soil layer of vegetated roof systems. The two categories of anthropogenic soils, usually used for green roof systems, were scanned during the first months after green roof system construction. First was represented by stripped topsoil with admixed crushed bricks and was well graded in terms of particle size distribution. The other category represented a commercial lightweight technogenic substrate. The undisturbed soil samples of total volume of 62.8 ccm were studied be means of X-ray Computed Tomography using X-ray Inspection System GE Phoenix Nanomex 180T with resulting spatial resolution about 57 μm in all directions. For both soil categories visible macroporosity, connectivity (described by the Euler characteristic), dimensionless connectivity and critical cross section of pore network were determined. Moreover, the temporal structural changes of studied soils were discussed together with heat and water regime of the green roof system. The analysis of CT images of anthropogenic soils was problematic due to the different X-ray attenuation of individual constituents. The correct determination of the threshold image intensity differentiating the soil constituents from the air phase had substantial importance for soil pore network analyses. However, X-ray CT derived macroporosity profiles reveal significant temporal changes notably in the soil comprised the stripped topsoil with admixed crushed bricks. The results implies that the technogenic substrate is structurally more stable over time compared to the stripped topsoil. The research was realized as a part of the University Centre for Energy Efficient Buildings supported by the EU and with financial support from the Czech Science Foundation under project number 14-10455P.
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Sorption of VX to Clay Minerals and Soils: Thermodynamic and Kinetic Studies
2012-12-01
Suspengel 200, humus , and soil substrates for use in this study. In addition, the authors gratefully acknowledge the support of the ECBC Technical...sorption profiles for VX with clay substrates ..................................55 30. Initial kinetic sorption profiles for VX with humus ...naturally derived garden soil amendment, identified as humus , was purchased from Frey Brothers (Quarryville, PA). Two natural soils, identified as MCL lot
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NASA Astrophysics Data System (ADS)
García-Gil, Juan Carlos; Soler-Rovira, Pedro Angel; García López de Sa, Esther; Polo, Alfredo
2013-04-01
Soil tillage practices exert a significant influence on the dynamic of soluble organic C and N pools, affecting nutrient cycling in agricultural systems by enhancing its mineralization through microbial activities or stabilization in soil microaggregates, which contribute to mitigate greenhouse gases emissions. The objective of the present research was to determine the influence of three different soil management systems (moldboard plowing, chisel and no-tillage) and the application of composted sludge (CS) and thermally-dried sewage sludge (TSS) obtained from wastewater treatment processes on dissolved organic C (water-soluble organic C -WSOC-, carbohydrates, phenolic compounds) and soluble N (total-N, NH4+, NO3-) pools in a long-term field experiment (27 years) conducted on a sandy-loam soil at the experimental station "La Higueruela" (40° 03'N, 4° 24'W) under semi-arid conditions. Both organic amendments were applied at a rate of 30 tonnes per hectare prior to tillage practices. Unamended soils were used as control for each tillage system. Soil sampling was performed two months after tillage practices at the following depths for each treatment: 0-10 cm, 10-20 cm and 20-30 cm. Results obtained for unamended soils showed that no-tillage management increased total-N, NH4+ and NO3- contents at the 0-10 cm depth samples, meanwhile WSC and carbohydrates contents were larger at 20-30 cm depth samples in both moldboard and no-tillage plots. CS and TSS-amended soils presented a general increase in soluble C and N compounds, being significantly higher in TSS-amended soils, as TSS contains a great amount of labile organic C and N substrates due to the lack of stabilization treatment. TSS-amended soils under no-tillage and chisel plowing showed larger N, NH4+ and NO3- content at the 0-10 cm samples, meanwhile moldboard management exhibited larger NH4+ and NO3- content at 10-20 and 20-30 cm samples, possibly due to the incorporation of TSS at deeper depths (20-40 cm). CS and TSS-amended soils in no-tillage system showed the largest content of organic C pools at 0-10 cm depth samples due to less soil disturbance and the input of organic substrates with CS and TSS on soil surface. CS and TSS-amended soils under chisel plowing exhibited similar contents of soluble organic C pools at 10-20 and 20-30 cm depth samples and only TSS-amended soils increased significantly WSOC content at 0-10 cm samples. Similarly, contents of WSOC and carbohydrates in moldboard plowing were distributed more uniformly throughout the soil profile due to the turnover of soil and CS and TSS amendments into the plow layer. Acknowledgements: this research was supported by the Spanish CICYT, Project no. CTM2011-25557.
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Determining resistance to soft-rot fungi
C. G. Duncan
1965-01-01
A laboratory procedure is outlined that incorporates techniques found to promote soft rot by several fungi. This procedure employs either an agar or a soil substrate. Also presented are the principal findings of experiments underlying the procedure. Results of tests conducted according to the suggested procedure are illustrated. The overall decay resistance of the...
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Rees, Rainer; Robinson, Brett H; Rog, Christopher J; Papritz, Andreas; Schulin, Rainer
2013-03-01
Paper mill wastes are a mixture of by-products from pulp production and on-site energy production, consisting of paper mill sludge, ash and cinders. Landfilling of these highly boron (B) and heavy metal laden waste products carries environmental risks. Poplars have been successfully employed in the phytomanagement and hydraulic control of B contaminated sites. Here, we assess the performance of hybrid poplars on a paper-mill waste landfill, investigate the accumulation of B by the trees and explore the relationship between local-scale root growth and substrate properties. Leaf and root tissue samples were collected on three plots and analyzed for their chemical properties and root traits. Additionally, we sampled four soil cores in the vicinity of each of the trees and determined chemical and physical properties. Using a principal component analysis followed by a cluster analysis, we identified three substrate types. This method delineated the soil effects on tree survival and growth, although correlations with individual soil element concentrations were weak. Despite signs of B toxicity in some leaves, B was not the key limiting factor for poplar growth. Instead, Ca deficiency caused by a Mg:Ca imbalance was the primary reason for the poor performance of some trees. Root growth was not limited by toxicity effects of soil contaminants. Our results show that hybrid poplars perform well under the harsh growing conditions on a multi-contaminated, B-laden substrate in a hemiboreal climate. Exploiting the differences in the performance of the four clones in relation to the soil types, could increase the success of revegetation on this and other landfills. Copyright © 2012 Elsevier B.V. All rights reserved.
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Rainfall simulation experiments in ecological and conventional vineyards.
NASA Astrophysics Data System (ADS)
Adrian, Alexander; Brings, Christine; Rodrigo Comino, Jesús; Iserloh, Thomas; Ries, Johannes B.
2015-04-01
In October 2014, the Trier University started a measurement series, which defines, compares and evaluates the behavior of runoff and soil erosion with different farming productions in vineyards. The research area is located in Kanzem, a traditional wine village in the Saar Valley (Rheinland-Palatinate, Germany). The test fields show different cultivation methods: ecological (with natural vegetation cover under and around the vines) and conventional cultivated rows of wine. By using the small portable rainfall simulator of Trier University it shall be proved if the assumption that there is more runoff and soil erosion in the conventional part than in the ecological part of the tillage system. Rainfall simulations assess the generation of overland flow, soil erosion and infiltration. So, a trend of soil erosion and runoff of the different cultivation techniques are noted. The objective of this work is to compare the geomorphological dynamics of two different tillage systems. Therefore, 30 rainfall simulations plots were evenly distributed on a west exposition hillside with different slope angels (8-25°), vegetation- and stone-covers. In concrete, the plot surface reaches from strongly covered soil across lithoidal surfaces to bare soil often with compacted lanes of typical using machines. In addition, by using the collected substrate, an estimation and distribution of the grain size of the eroded material shall be given. The eroded substrate is compared to soil samples of the test plots. The first results have shown that there is slightly more runoff and soil erosion in the ecological area than on the conventional part of the vineyard.
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The survival strategy of the soil microbial biomass
NASA Astrophysics Data System (ADS)
Brookes, Philip; Kemmitt, Sarah; Dungait, Jennifer; Xu, Jianming
2014-05-01
The soil microbial biomass (biomass) is defined as the sum of the masses of all soil microorganisms > 5000 µm3 (e.g. fungi, bacteria, protozoa, yeasts, actinomycetes and algae). Typically comprising about 1 to 3 % of total soil organic matter (SOM), the biomass might be though to live in a highly substrate-rich environment. However, the SOM is, normally, only exceedingly slowly available to the biomass. However the biomass can survive for months or even years on this meagre energy source. Not surprisingly, therefore, the biomass exhibits many features typical of a dormant or resting population. These include a very low rate of basal and specific respiration, a slow rate of cell division (about once every six months on average) and slow turnover rate. These are clearly adaptations to existing in an environment where substrate availability is very low. Yet, paradoxically, the biomass, in soils worldwide, has an adenosine triphosphate (ATP) concentration (around 10 to 12 µmol ATP g-1 biomass C), and an Adenylate Energy Charge (AEC = [(ATP) + (0.5 ADP)]/[(ATP)+(ADP) + (AMP)]) which are typical of microorganisms growing exponentially in a chemostat. This sets us several questions. Firstly, under the condition of extremely limited substrate availability in soil, why does the biomass not mainly exist as spores, becoming active, by increasing both its ATP concentration and AEC, when substrate (plant and animal residues) becomes available? We surmise that a spore strategy may put organisms at a competitive disadvantage, compared to others which are prepared to invest energy, maintaining high ATP and ATP, to take advantage of a 'food event' as soon as it becomes available. Secondly, since SOM is available (although only very slowly) to the biomass, why have some groups not evolved the ability to mineralize it faster, obtain more energy, and so gain a competitive advantage? We believe that the reason why organisms do not use this strategy is, simply, that they cannot. Our explanation is that the rate of mineralization of humified SOM is not, as usually believed, regulated by microbial activity but by abiotic processes which are outside of the control of the biomass. We do not yet know what these processes are. They could involve diffusion from soil aggregates, oxidation processes, free radical reactions, other mechanisms, or none of these. We will present experimental evidence in support of our hypothesis - termed "The Regulatory Gate Hypothesis". If correct this hypothesis will have serious implication for our understanding of soil organic matter dynamics, CO2 evolution from soil and climate change.
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Influence of pine bark particle size and pH on cation exchange capacity
USDA-ARS?s Scientific Manuscript database
Cation exchange capacity (CEC) describes the maximum quantity of cations a soil or substrate can hold while being exchangeable with the soil solution. While CEC has been studied for peat-based substrates, relatively little work has documented factors that affect CEC of pine bark substrates. The ob...
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Ondoño, S; Martínez-Sánchez, J J; Moreno, J L
2016-01-15
Extensive green roofs are used to increase the surface area covered by vegetation in big cities, thereby reducing the urban heat-island effect, promoting CO2 sequestration, and increasing biodiversity and urban-wildlife habitats. In Mediterranean semi-arid regions, the deficiency of water necessitates the use in these roofs of overall native plants which are more adapted to drought than other species. However, such endemic plants have been used scarcely in green roofs. For this purpose, we tested two different substrates with two depths (5 and 10 cm), in order to study their suitability with regard to adequate plant development under Mediterranean conditions. A compost-soil-bricks (CSB) (1:1:3; v:v:v) mixture and another made up of compost and bricks (CB) (1:4; v:v) were arranged in two depths (5 and 10 cm), in cultivation tables. Silene vulgaris (Moench) Garcke and Lagurus ovatus L. seeds were sown in each substrate. These experimental units were subjected, on the one hand, to irrigation at 40% of the registered evapotranspiration values (ET0) and, on the other, to drought conditions, during a nine-month trial. Physichochemical and microbiological substrate characteristics were studied, along with the physiological and nutritional status of the plants. We obtained significantly greater plant coverage in CSB at 10 cm, especially for L. ovatus (80-90%), as well as a better physiological status, especially in S. vulgaris (SPAD values of 50-60), under irrigation, whereas neither species could grow in the absence of water. The carbon and nitrogen fixation by the substrate and the aboveground biomass were also higher in CSB at 10 cm, especially under L. ovatus - in which 1.32 kg C m(-2) and 209 g N m(-2) were fixed throughout the experiment. Besides, the enzymatic and biochemical parameters assayed showed that microbial activity and nutrient cycling, which fulfill a key role for plant development, were higher in CSB. Therefore, irrigation of 40% can maintain an adequate plant cover of both endemic species, particularly in a deeper and soil-containing substrate. Copyright © 2015 Elsevier Ltd. All rights reserved.
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NASA Astrophysics Data System (ADS)
Gypser, Stella; Fischer, Thomas; Lange, Philipp; Veste, Maik
2016-04-01
Mining activities can strongly affect ecosystem properties by destruction of naturally developed soils and removal of vegetation. The unstructured substrates show high bulk densities, compaction, low water infiltration rates, reduced water holding capacities and higher susceptibility to wind and water erosion. In the initial stage of the ecosystem development, the post-mining sites are open areas without or with a low cover of higher vegetation. It is well-known that biocrusts are able to colonize the soil surface under such extreme conditions without human support and affect soil hydrological processes such as water infiltration, run-off or re-distribution. Investigations were conducted on two former lignite open-cast mining sites, an artificial sand dune on the reclaimed watershed Welzow "Neuer Lugteich" and a reforestation area in Schlabendorf (Brandenburg, north-east Germany). The aim was to relate the hydrological characteristics of the topsoil to successional stages of biological soil crusts on reclaimed soils and their influence on repellency index and water holding capacity compared to pure mining substrate. Our study emphasized the influence of changing successional stages and species composition of biological soil crusts, forming a small-scale crust pattern, on water repellency and retention on sandy soils in temperate climate. Different successional stages of soil crusts were identified from initial scattered green algae crusts, dominated by Zygogonium spec. and Ulothrix spec., and more developed soil crusts containing mosses such as Ceratodon purpureus and Polytrichum piliferum. Lichens of the Genus Cladonia were more pronouncedly contributed to biocrusts at later and mature stages of development. The repellency index on the one hand increased due to the cross-linking of sand particles by the filamentous green algae Zygogonium spec. which resulted in clogging of pores, and on the other hand decreased with the occurrence of moss plants due to absorption caused by bryophytes. The determination of the water retention curves showed an increase of the water holding capacity, especially in conjunction with the growth of green algae layer. The absorption capacity of soil crust biota as well as a decreased pore diameter in the green algae layers positively affected the water retention of crusted soil compared to pure substrate. The occurrence of bryophytes with later succession weakened the repellent behavior of the biocrusts, increased infiltration, and might have affected the run-off at small-scale on biocrusts. Certainly, the biological soil crusts showed water repellent properties but no distinctive hydrophobic characteristics. On both locations, similar trends of water repellency and retention related to crustal formation were observed, in spite of different relief, reclamation time and inhomogeneous distribution of crustal organisms. References Gypser, S., Veste, M., Fischer, T., Lange, P. (2016): Infiltration and water retention of biological soil crusts on reclaimed soils of former open-cast lignite mining sites in Brandenburg, north-east Germany, Journal of Hydrology and Hydromechanics, accepted 12. November 2015. Gypser, S., Veste, M., Fischer, T., Lange, P. (2015): Formation of soil lichen crusts at reclaimed post-mining sites, Lower Lusatia, North-east Germany. Graphis Scripta 27: 3-14.
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NASA Astrophysics Data System (ADS)
Hopkins, F. M.; Trumbore, S.
2011-12-01
The role of substrate availability on soil carbon turnover is a critical unknown in predicting future soil carbon stocks. Substrate composition and availability can be altered by land cover change, warming, and nitrogen deposition, which can in turn affect soil carbon stocks through the priming effect. In particular, little is understood about the interaction between warming and changing substrate concentration. We examined the interactions between global change factors and the priming effect using sucrose addition to incubations of soils from two forest Free Air CO2 Enrichment (FACE) sites (Duke and Aspen). In addition to the in situ global change manipulations conducted at these sites, the CO2 fertilization procedure over the decade-long experiment labeled soil carbon pools with fossil-derived carbon (depleted in 14C relative to the background isotope content of soil carbon), allowing us to determine the effect of priming on respiration of soil carbon substrates of different ages. Thus, we used the carbon-13 signature of sucrose-derived CO2 to account for losses of substrate C, and the carbon-14 signature to partition fluxes of soil-derived CO2 between pre-FACE (> 10 y) and FACE derived (< 10 y) carbon sources. At both sites, we observed a positive priming effect-an increase in the rate of soil carbon derived respiration due to sucrose addition. However, the effect of substrate addition on respiratory source pools, as measured by 14C of respiration, varied greatly. At Duke FACE, we observed an increase in 14C content of CO2 of primed soil carbon, whereas at Aspen, we observed no difference. The amount of CO2 released by priming increased with temperature, but was proportionally similar to the amount of increase in basal respiration rates (no differences in Q10). At Duke, both warming and priming served to increase the 14C of respiration, whereas only warming changed 14C of respiration at Aspen. Despite similar overall carbon stocks, differences in the source of the priming effect between the two sites may be due to inherent differences in the relative role of stabilization factors within the soil carbon stock.
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X-Ray Computed Tomography Reveals the Response of Root System Architecture to Soil Texture1[OPEN
Rogers, Eric D.; Monaenkova, Daria; Mijar, Medhavinee; Goldman, Daniel I.
2016-01-01
Root system architecture (RSA) impacts plant fitness and crop yield by facilitating efficient nutrient and water uptake from the soil. A better understanding of the effects of soil on RSA could improve crop productivity by matching roots to their soil environment. We used x-ray computed tomography to perform a detailed three-dimensional quantification of changes in rice (Oryza sativa) RSA in response to the physical properties of a granular substrate. We characterized the RSA of eight rice cultivars in five different growth substrates and determined that RSA is the result of interactions between genotype and growth environment. We identified cultivar-specific changes in RSA in response to changing growth substrate texture. The cultivar Azucena exhibited low RSA plasticity in all growth substrates, whereas cultivar Bala root depth was a function of soil hardness. Our imaging techniques provide a framework to study RSA in different growth environments, the results of which can be used to improve root traits with agronomic potential. PMID:27208237
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NASA Astrophysics Data System (ADS)
Zaidel'Man, F. R.
2010-04-01
Nowadays, three processes, namely lessivage, acid hydrolysis, and gleying, are considered as responsible for the development of loamy and clayey podzolic soils. However, as was shown earlier, lessivage is not obligatory for their origin. In view of assessing the reasons for the formation of light-colored acid eluvial horizons, this article deals with the role of acid hydrolysis under aerobic conditions against the background of a percolative water regime and of two forms of gleying in the development of the horizons mentioned above. One form of gleying occurs under permanent anaerobic conditions against the background of a stagnant water regime; the other one is formed under pulsating anaerobic-aerobic conditions against the background of a stagnant-percolative water regime. As a result, three large genetically individual groups of soils are formed: nondifferentiated brown and gley, and differentiated podzolic soils on different parent rocks. The two latter forms of gleying are identical in their effects on the mineral substrates. They cause the iron removal from the soils. Among the three processes considered, the last one (gleying under a stagnant-percolative water regime) is the single reason for the leaching of most of the metals, the formation of light-colored acid eluvial horizons and their clay depletion, and for the differentiation of the soil profile.
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Herrero-Hernández, E; Marín-Benito, J M; Andrades, M S; Sánchez-Martín, M J; Rodríguez-Cruz, M S
2015-11-01
This study reports the effect that adding spent mushroom substrate (SMS) to a representative vineyard soil from La Rioja region (Spain) has on the behaviour of azoxystrobin in two different environmental scenarios. Field dissipation experiments were conducted on experimental plots amended at rates of 50 and 150 t ha(-1), and similar dissipation experiments were simultaneously conducted in the laboratory to identify differences under controlled conditions. Azoxystrobin dissipation followed biphasic kinetics in both scenarios, although the initial dissipation phase was much faster in the field than in the laboratory experiments, and the half-life (DT50) values obtained in the two experiments were 0.34-46.3 days and 89.2-148 days, respectively. Fungicide residues in the soil profile increased in the SMS amended soil and they were much higher in the top two layers (0-20 cm) than in deeper layers. The persistence of fungicide in the soil profile is consistent with changes in azoxystrobin adsorption by unamended and amended soils over time. Changes in the dehydrogenase activity (DHA) of soils under different treatments assayed in the field and in the laboratory indicated that SMS and the fungicide had a stimulatory effect on soil DHA. The results reveal that the laboratory studies usually reported in the literature to explain the fate of pesticides in amended soils are insufficient to explain azoxystrobin behaviour under real conditions. Field studies are necessary to set up efficient applications of SMS and fungicide, with a view to preventing the possible risk of water contamination. Copyright © 2015 Elsevier Ltd. All rights reserved.
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Genetic and environmental effects on morphology and asexual reproduction in the moss, Bryum bicolor
DOE Office of Scientific and Technical Information (OSTI.GOV)
Shaw, A.J.
A distinctive form of Bryum bicolor, characterized by stoutly excurrent costae and abundant asexual gemmae, occurs on heavy metal-contaminated tailings of the Conrad Hill Mine in the Piedmont of North Carolina. Plants from two mine site populations, plus two other populations from Richmond, Virginia, were grown on three types of soil in order to determine the degree to which morphological traits, including the number of gemmae per plant, can be modified by substrate. All populations grew equally well in the mine soil, and there was no evidence that plants from the mine site populations were physiologically adapted for growth onmore » the contaminated tailings. Leaf dimensions, costa length, and number of gemmae per stem were strongly influenced by substrate, although some differences between populations were maintained under experimental conditions. Populations also differed in the efficacy with which plants regenerated from gametophytic fragments.« less
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NASA Astrophysics Data System (ADS)
Sanaullah, Muhammad; Baumann, Karen; Chabbi, Abad; Dignac, Marie-France; Maron, Pierre-Alain; Kuzyakov, Yakov; Rumpel, Cornelia
2014-05-01
Soil organic matter turnover depends on substrate quality and microbial activity in soil but little is known about how addition of freshly added organic material modifies the diversity of soil microbial communities with in a soil profile. We took advantage of a decomposition experiment, which was carried out at different soil depths under field conditions and sampled litterbags with 13C-labelled wheat roots, incubated in subsoil horizons at 30, 60 and 90 cm depth for up to 36 months. The effect of root litter addition on microbial community structure, diversity and activity was studied by determining total microbial biomass, PLFA signatures, molecular tools (DNA genotyping and pyrosequencing of 16S and 18S rDNAs) and extracellular enzyme activities. Automated ribosomal intergenic spacer analysis (ARISA) was also carried out to determine the differences in microbial community structure. We found that with the addition of root litter, total microbial biomass as well as microbial community composition and structure changed at different soil depths and change was significantly higher at top 30cm soil layer. Moreover, in the topsoil, population of both gram-positive and gram-negative bacteria increased with root litter addition over time, while subsoil horizons were relatively dominated by fungal community. Extra-cellular enzyme activities confirmed relatively higher fungal community at subsoil horizons compared with surface soil layer with bacteria dominant microbial population. Bacterial-ARISA profiling illustrated that the addition of root litter enhanced the abundance of Actinobacteria and Proteobacteria, at all three soil depths. These bacteria correspond to copiotrophic attributes, which can preferentially consume of labile soil organic C pools. While disappearance of oligotrophic Acidobacteria confirmed the shifting of microbial communities due to the addition of readily available substrate. We concluded that root litter mixing altered microbial community development which was soil horizon specific and its effects on soil microbial activity may impact on nutrient cycling.
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2013-01-01
Background Developing a quick and reliable technique to estimate floral cover in deserts will assist in monitoring and management. The present attempt was to estimate plant cover in the UAE desert using both digital photography and field sampling. Digital photographs were correlated with field data to estimate floral cover in moderately (Al-Maha) and heavily (DDCR) grazed areas. The Kruskal-Wallis test was also used to assess compatibility between the two techniques within and across grazing intensities and soil substrates. Results Results showed that photographs could be a reliable technique within the sand dune substrate under moderate grazing (r = 0.69). The results were very poorly correlated (r =−0.24) or even inversely proportional (r =−0.48) when performed within DDCR. Overall, Chi-square values for Al-Maha and DDCR were not significant at P > 0.05, indicating similarities between the two methods. At the soil type level, the Kruskal-Wallis analysis was not significant (P > 0.05), except for gravel plains (P < 0.05). Across grazing intensities and soil substrates, the two techniques were in agreement in ranking most plant species, except for Lycium shawii. Conclusions Consequently, the present study has proven that digital photography could not be used reliably to asses floral cover, while further testing is required to support such claim. An image-based sampling approach of plant cover at the species level, across different grazing and substrate variations in desert ecosystems, has its uses, but results are to be cautiously interpreted. PMID:23758667
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Time-dependent phosphate dynamics in reclaimed lignite-mine soils under Robinia pseudoacacia L.
NASA Astrophysics Data System (ADS)
Freese, Dirk; Slazak, Anna
2017-04-01
As a consequence of the opencast lignite mining activities in Lusatia/Germany, the cultivation of Short Rotation Coppice plantations (SRC) has been considered as a viable option for reclamation purposes. In this region an area of about 1000 km2 has been degraded. Owing to the unfavourable biotic and abiotic properties of the overburden mining substrate, the biogeochemical processes associated with the soil ecosystem development are in the initial phase. The substrate contains very low amount of nutrients, mainly very low total Phosphate (P) content nearly equal to zero. The lack of P is one of the main issues in reclamation of this marginal site. Therefore, the cultivation of perennial SRC with Robinia pseudoacacia L. is considered as a supporting measurement for effective soil reclamation. In this context, it is important to understand the dynamics of P in this "initial substrate" to describe the P availability and P sorption/desorption.. Iron/aluminium oxides and organic matter are the soil constituents most strongly affecting the reactions and rate of P sorption and desorption, also in post-mining soils. Therefore the interaction of these oxides and organic matter with P is essential with regard to developing effective nutrient management strategies for marginal sites. The study focused on P sorption and desorption with regard to different development stages of R. pseudoacacia L. established in a short rotation coppices on the post mining soils. to describe the P availability (Pav) in relation to total P mobility. The hypothesis is that SRC would cause significant changes in soil P dynamics over time in post lignite mining soils. The trees has been planted in between 1995 and 2007, which means that R. pseudoacacia L. was in a range of 2 to 20 years old at different sampling times. Soil was sampled in 2008 and 2015 at three depths of: 0-3cm, 3-10 cm and 10-30 cm. To characterize the P dynamics different P forms and P sorption/desorption kinetics were analysed. With increasing age of trees the ratio of available P to total P decreased in tendency for all soil layers. The total P content increased slightly over time in all soil layers. But the amount of Fe and Al oxides increased also over time and therefore the overall P sorption capacity increased, too. Hence, the ratio between available P and total P shifted more to the less available forms of P in soil. Within a period of 20 years, R. pseudoacacia L. cultivation on post mining sites increased the contents of available P and total P, repectively. The P sorption increased with time of soil development showing the maximum at the oldest site. Nevertheless, P sorption of these initial post mining soils is still rather low. The results suggest, that the SRC of R. pseudoacacia L. on post mining sites have a positive influence on the P dynamics. References Freese, D., Van Riemsdijk, W.H., Van Der Zee, S.E.A.T.M., 1995. Modelling phosphate-sorption kinetics in acid soils. European Journal of Soil Science 46(2), 239-245. Matos, E.S., Freese, D., Böhm, C., Quinkenstein, A., Hüttl, R.F., 2012. Organic Matter Dynamics in Reclaimed Lignite Mine Soils under Robinia pseudoacacia L. Plantations of Different Ages in Germany. Communications in Soil Science and Plant Analysis 43(5), 745-755.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Bailey, Vanessa L.; Fansler, Sarah J.; Smith, Jeffery L.
2011-02-01
Applying biochar to soils as an ameliorative substance and mechanism for C sequestration has received a great deal of interest in light of the sustained fertility observed in the Terra Preta soils of Brazil. The effects of synthetic biochars on biochemical processes needs to be better understood in order to determine if this is a reasonable practice in managed systems. The biochar studied was formed from the fast-pyrolysis of a switchgrass feedstock. Four soil enzymes were studied: β-glucosidase, β-N-acetylglucosaminidase, lipase, and leucine aminopeptidase. Both colorimetric and fluorescent assays were used for β-glucosidase and β-N-acetylglucosaminidase. Seven days after biochar was addedmore » to microcosms of a Palouse silt loam, the fluorescence-based assays indicated increased activities of the four enzymes, compared to non-amended soil. To clarify the mechanisms of the observed effects,in the absence of soil, purified enzymes or substrates were briefly exposed to biochar and then assayed. Except for β-N-acetylglucosaminidase, the exposure of substrate to biochar reduced the apparent activity of the remaining three enzymes in vitro, suggesting that sorption reactions between the substrate and biochar either removed the substrate from the assays or impeded the enzyme binding. The activity of purified β-N-acetylglucosaminidase increased significantly following biochar exposure, suggesting a chemical stimulation of enzyme functioning. We conclude that biochar added to soil acts as a substrate that can stimulate the soil microbial biomass and its activity. Our in vitro study suggests that biochar is not biochemically inert. Biochar amendments are likely to have effects that are currently difficult to predict, and that could impact overall soil function.« less
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Plant/soil concentration ratios of SSWRa for contrasting sites around an active U mine-mill
DOE Office of Scientific and Technical Information (OSTI.GOV)
Ibrahim, S.A.; Whicker, F.W.
Concentrations of 226Ra were determined in native vegetation and underlying substrate (soil and tailings) at various sites around a conventional open-pit, acid leach U production operation in Wyoming. Plant/soil concentration ratios (CRs) for 226Ra were estimated for various sites, including weathered tailings; a tailings impoundment shoreline; downwind from exposed tailings; a mine overburden reclamation area; and several background locations. Radium-226 concentrations for vegetation and substrate and CR values from the perturbed sites were elevated above background. The highest vegetation concentration (1.3 Bq g-1) was found in a grass which had invaded exposed, weathered tailings. Levels of 226Ra in soil andmore » vegetation and CR values decreased with distance from the tailings impoundment edge. CR values varied significantly among sites, but few differences were found between plant species groups. The observed CR values ranged from 0.07 at the background and reclamation areas to 0.4 downwind from the tailings area. Average CR values for plants growing on exposed tailings and within one meter from the impoundment edge were 0.15 and 0.3, respectively. CR values of 226Ra for plants on tailings substrates were comparatively low in contrast to other radionuclides in the U chain. We speculate that in the case of sulfuric acid leached tailings-derived material, 226Ra is sequestered as sulfate, which is highly insoluble relative to the sulfates of the other elements (e.g., U and Th) resulting in reduced availability for plant uptake.« less
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Substrate-induced respiration in Puerto Rican soils: minimum glucose amendment
Marcela Zalamea; Grizelle Gonzalez
2007-01-01
Soil microbiota âusually quantified as microbial biomass âis a key component of terrestrial ecosystems, regulating nutrient cycling and organic matter turnover. Among the several methods developed for estimating soil microbial biomass, Substrate-Induced Respiration (SIR) is considered reliable and easy to implement; once the maximum respiratory response is determined...
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Initial-phase optimization for bioremediation of munition compound-contaminated soils.
Funk, S B; Roberts, D J; Crawford, D L; Crawford, R L
1993-01-01
We examined the bioremediation of soils contaminated with the munition compounds 2,4,6-trinitrotoluene (TNT), hexahydro-1,3,5-trinitro-1,3,5-triazine, and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetraazocine by a procedure that produced anaerobic conditions in the soils and promoted the biodegradation of nitroaromatic contaminants. This procedure consisted of flooding the soils with 50 mM phosphate buffer, adding starch as a supplemental carbon substrate, and incubating under static conditions. Aerobic heterotrophs, present naturally in the soil or added as an inoculum, quickly removed the oxygen from the static cultures, creating anaerobic conditions. Removal of parent TNT molecules from the soil cultures by the strictly anaerobic microflora occurred within 4 days. The reduced intermediates formed from TNT and hexahydro-1,3,5-trinitro-1,3,5-triazine were removed from the cultures within 24 days, completing the first stage of remediation. The procedure was effective over a range of incubation temperatures, 20 to 37 degrees C, and was improved when 25 mM ammonium was added to cultures buffered with 50 mM potassium phosphate. Ammonium phosphate buffer (50 mM), however, completely inhibited TNT reduction. The optimal pH for the first stage of remediation was between 6.5 and 7.0. When soils were incubated under aerobic conditions or under anaerobic conditions at alkaline pHs, the TNT biodegradation intermediates polymerized. Polymerization was not observed at neutral to slightly acidic pHs under anaerobic conditions. Completion of the first stage of remediation of munition compound-contaminated soils resulted in aqueous supernatants that contained no munition residues or aminoaromatic compounds. PMID:8357251
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Cycoń, M; Piotrowska-Seget, Z; Kaczyńska, A; Kozdrój, J
2006-11-01
Changes in microbiological properties of a sandy loam soil in response to the addition of different concentrations of fungicide tebuconazole and pyrethroid insecticide lambda-cyhalothrin were assessed under laboratory conditions. To ascertain these changes, the potentially active soil microbial biomass, concentrations of ammonium and nitrate ions, numbers of total culturable bacteria, fungi, nitrogen-fixing bacteria, nitrifying and denitrifying bacteria were determined. Substrate-induced respiration (SIR) increased with time in both control (ranged from 13.7 to 23.7 mg/O(2)/kg(-1)/dry soil/h(-1)) and pesticide treated soil portions. For both pesticides, SIR values ranged from 12-13 to 23-25 mg/O(2)/kg(-1)/dry soil/h(-1) on days 1 and 28, respectively. Also, concentrations of nitrate and ammonium ions, numbers of total culturable bacteria, denitrifying bacteria, nitrogen-fixing bacteria (for the insecticide) and fungi (for the insecticide) were either unaffected or even stimulated by the pesticide treatments. The adverse impacts of the pesticides were observed for nitrate concentrations (on days 1 or 7), numbers of nitrifying bacteria (on day 1), denitrifying bacteria (for the insecticide on days 1 and 14), nitrogen-fixing bacteria (for tebuconazole on day 1) as well as numbers of fungi in tebuconazole-treated soil (on days 1 and 14).
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NASA Astrophysics Data System (ADS)
Muñoz-Rojas, Miriam; Raúl Román Fernández, José; Roncero Ramos, Beatriz; Cantón Castilla, Yolanda
2017-04-01
Despite the large efforts and investments to dryland ecosystems restoration worldwide, land rehabilitation in these areas has very low rates of success. Most of the challenges in landscape-scale restoration come from the lack of suitable soil substrates to support plant establishment and to ultimately achieve functional ecosystems. A common practice during extractive operations such as open-cut and strip mining is the removal of the topsoil layer that is subsequently stockpiled and respread in areas targeted for restoration. This topsoil is a crucial source of seeds, nutrients, and microorganisms but is a scarce resource which challenges the success of many restoration programs. In these conditions, the use of direct seeding of key native plant species becomes critical to reinstate biodiverse vegetation communities. Alternative soil substrates such as overburden or waste materials produced in mining operations are increasingly being used as growth media in restoration. However, these soil substrates can have inadequate levels of pH or salinity for plant growth and in most cases are depleted in organic materials and nutrients. In these conditions, the establishment of native plant species can be extremely difficult with a consequent potential loss of biodiversity. Development of appropriate soil structures such as technosols can be extremely expensive and demanding in terms of time and natural resources soils and therefore new approached need to be explored. In the last years, the potential of cyanobacteria biological crust to restore soil functionality in degraded has been highlighted because of their important role in controlling soil structure, preventing soil erosion and N and C fixation. Nevertheless, many research gaps still remain in their application to restore soil functionality in seed-based restoration practices. In this study, we test the potential of cyanobacteria inoculation to restore soil functions of soil materials used in post-mine restoration. Soil substrates consisted of topsoil retrieved from previously stockpiled material, an overburden waste material commonly used in landform reconstruction due to its erosive stability and physical competency, and a mixture of both substrates. These materials were collected from an active mine site in the mining intensive Pilbara region and inoculated with a mixture of soil cyanobacteria from three nitrogen-fixing genera (Nostoc, Scytonema and Tolypothrix). Further analyses need to be undertaken but preliminary results showed that after only 4 weeks, cyanobacteria rapidly colonized the mine substrates as cyanobacteria surface cover significantly increased during the time of study.The output of this research is the first step to effectively address the reconstruction of soil substrates that can provide support to the establishment of biodiverse vegetation communities in landscape-scale seed-based mine restoration.
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NASA Astrophysics Data System (ADS)
Ohm, H.; Marschner, B.
2009-04-01
It is expected that the biomass production and thus the input of organic carbon to the soil will increase in response to elevated CO¬2 concentrations in the atmosphere. It remains unclear whether this will lead to a long term increased carbon pool, because only little is known about the stability of the additional carbon inputs. The soil samples were taken on an agricultural field at the experimental farm of the Federal Agricultural Research Centre (FAL) in Braunschweig, Germany. A Free-Air Carbon-dioxide Enrichment (FACE) system was installed here in May 2000. It consists of rings with 20 m diameter. Two rings were operated with CO2 enriched air (550 ppm), another two rings received ambient air (370 ppm). One half of each ring received the full amount of nitrogen fertiliser, the remainder received only half of this N-amount. The soil samples were taken after 6 years of operation and were incubated with 14C-labeled fructose and alanine for 21 days. Furthermore, combined additions with the respective substrate and ammonium nitrate or ammonium nitrate alone were conducted. The microbial biomass was determined after 2 and 21 days. In the untreated controls the SOC mineralisation amounted to 0.59 to 0.68%. The addition of fructose, fructose+NH4NO3, alanine and alanine+NH4NO3 to the different soil samples increased SOC mineralization and thus caused priming effects of different extents. For NH4NO3 no priming effects occurred. The addition of fructose induced positive priming effects in all samples. The lowest priming effect was observed in the sample ambient CO2+50% N (+50%), either with fructose alone or in combination with NH4NO3. The addition of alanine caused similar priming effects in the ambient CO2+100% N and the elevated CO2+100% N samples (+92.4 and +95.6%, respectively). Again, the lowest priming effect was observed in the sample ambient CO2+50% N. The microbial biomass showed a clear increase in the substrate treated samples compared to the controls. The addition of NH4NO3 did not change the amount of Cmic. The results show, that in no treatment SOC degradation was N-limited, but always limited by easily available energy substrates. On the other hand, N-fertilization had a stronger effect on the microbial response to alanine addition than the CO2-level. Only with low N-fertilization, soils under elevated CO2 are more substrate limited than under elevated CO2, indicating that biomass C-inputs are of different quality.
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Phenoloxidase-mediated interactions of phenols and anilines with humic materials
DOE Office of Scientific and Technical Information (OSTI.GOV)
Dec, J.; Bollag, J.M.
Phenoloxidases present in terrestrial systems may contribute to the formation of humus through random coupling of a variety of aromatic compounds, including xenobiotic chemicals. Because of their structural similarity to natural substrates originating mainly from lignin decomposition, xenobiotic phenols and anilines can be readily incorporated into the soil organic matter, a phenomenon referred to as binding. The underlying mechanism of binding involves oxidation of the xenobiotic substrates to free radicals or quinone products that subsequently couple directly to humus or to naturally occurring phenols that also are subject to oxidation. The oxidation can be mediated by soil phenoloxidases as wellmore » as by abiotic catalysts. The ability of the enzymes to mediate the oxidation was demonstrated in a number of model studies, in which selected pollutants were incubated with humic monomers or natural humic acids in the presence of different phenoloxidases (laccase, peroxidase, tyrosinase). Analysis of the formed complexes by mass spectrometry and {sup 13}C nuclear magnetic resonance (NMR) spectroscopy left no doubt about the formation of covalent bonds between the pollutants and humic materials. Some bonds were formed at the chlorinated sites, leading to partial dehalogenation of the aromatic contaminants. Experimental data indicated that bound phenols and anilines were unlikely to adversely affect the environment; their release from humic complexes by soil microorganisms was very limited and once released, they were subjected to mineralization. For those reasons, phenoloxidases, which proved capable of mediating the underlying reaction, are currently considered as a tool for enhancing immobilization phenomena in soil.« less
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NASA Astrophysics Data System (ADS)
Epikhina, Anna; Vizirskaya, Mariya; Mazirov, Ilya; Vasenev, Vyacheslav; Vasenev, Ivan; Valentini, Riccardo
2014-05-01
Green lawns are the key element of the urban environment. They occupy a considerable part of the city area and locate in different urban functional zones. Urban constructed soils under green lawns have a unique spatial variability in chemical and morphogenetic features. So far, there is lack of information on the influence of morphogenetic features of urban soils on the functioning of the green lawn ecosystems especially in Moscow - the biggest megalopolis in Europe. Urban lawns perform a number of principal functions including both aesthetic and environmental. The role of the green lawn ecosystems in global carbon cycle is one of their main environmental functions. It is traditionally assessed through carbon stocks and fluxes in the basic ecosystem components. So far, such a data for the urban lawn ecosystems of the Moscow megapolis is lacking. In addition to environmental functions, green lawns perform an important ornamental role, which is also a critical criterion of their optimal functioning. Considering the variability of driving factors, influencing green lawns in urban environment, we carry out the model experiment in order to analyze "pure" effect of soil morphogenetic features. The current study aimed to analyze the influence of contrast morphogenetic features of urban constructed soils on the environmental and aesthetic functions of lawn ecosystems in Moscow megapolis basing in the model experiment. We carry out the model experiment located at the experimental field of the Russian State Agrarian University. Special transparent containers developed for the experiment, provided an option to observe soil morphogenetic features dynamics, including the depth and material of the organic transformation. At the same soil body inside the containers was united with the outside environment through the system of holes in the bottom and walls. The set of urban constructed soils includ four contrast types of the top soil (turf (T), turf-sand (TSa), turf-soil (TSo) and sand-soil (SS)) with three version of the depths (5, 10 and 20 cm). Soil construction with 10 cm organic horizon from TS top soil was taken as a reference. Grass mixture used for the green lawn including: Lolium perenne, Poa pratensis and Festuca rubra. For all the containers we measured soil CO2 emission by Li-820, soil temperature and moisture and the grass ornamental quality based on the 30-score scale (Laptev; 1988). All the measurements have been done in June-October 2013 with two-week time steps. We also observed the dynamic in soil chemical features (Corg, Ntot and pHKCl) monthly. We found high seasonal dynamics for all the observed functioning parameters. The highest CO2 emission was obtained in the beginning of July, whereas the lowest one - at the end of August. Maximal averaged CO2 emission was shown for the TSa and TSo substrates with the 20 cm depth. The lowest flux has been fixed for the more mineralized substrat. Soil moisture was shown as the main driving factor influencing CO2 emission both for the seasonal dynamics and for the averaged values for different substrates and depths (r=0.5, p<0.05). As for the aesthetic function the highest grass ornamental quality was shown for 20 cm TS and 5 cm T substrate (30 scores), whereas the lowest one was obtained for SS substrate with 5 and 20 cm depths (5 scores). We also obtained high positive correlation between the grass ornamental quality and the CO2 emissions (r=0.84, p>0.05). This outcome highlights that the standards of urban constructed soils' optimal features should be the compromise between the beauty of the green lawn and climate mitigation demands. Supported by the RF governmental grant 11.G34.31.0079
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Bhat, Nisar A.; Riar, Amritbir; Ramesh, Aketi; Iqbal, Sanjeeda; Sharma, Mahaveer P.; Sharma, Sanjay K.; Bhullar, Gurbir S.
2017-01-01
Mobilization of unavailable phosphorus (P) to plant available P is a prerequisite to sustain crop productivity. Although most of the agricultural soils have sufficient amounts of phosphorus, low availability of native soil P remains a key limiting factor to increasing crop productivity. Solubilization and mineralization of applied and native P to plant available form is mediated through a number of biological and biochemical processes that are strongly influenced by soil carbon/organic matter, besides other biotic and abiotic factors. Soils rich in organic matter are expected to have higher P availability potentially due to higher biological activity. In conventional agricultural systems mineral fertilizers are used to supply P for plant growth, whereas organic systems largely rely on inputs of organic origin. The soils under organic management are supposed to be biologically more active and thus possess a higher capability to mobilize native or applied P. In this study we compared biological activity in soil of a long-term farming systems comparison field trial in vertisols under a subtropical (semi-arid) environment. Soil samples were collected from plots under 7 years of organic and conventional management at five different time points in soybean (Glycine max) -wheat (Triticum aestivum) crop sequence including the crop growth stages of reproductive significance. Upon analysis of various soil biological properties such as dehydrogenase, β-glucosidase, acid and alkaline phosphatase activities, microbial respiration, substrate induced respiration, soil microbial biomass carbon, organically managed soils were found to be biologically more active particularly at R2 stage in soybean and panicle initiation stage in wheat. We also determined the synergies between these biological parameters by using the methodology of principle component analysis. At all sampling points, P availability in organic and conventional systems was comparable. Our findings clearly indicate that owing to higher biological activity, organic systems possess equal capabilities of supplying P for crop growth as are conventional systems with inputs of mineral P fertilizers. PMID:28928758
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Xu, Xiaofeng; Schimel, Joshua; Thornton, Peter E
2014-01-01
Microbial assimilation of soil organic carbon is one of the fundamental processes of global carbon cycling and it determines the magnitude of microbial biomass in soils. Mechanistic understanding of microbial assimilation of soil organic carbon and its controls is important for to improve Earth system models ability to simulate carbon-climate feedbacks. Although microbial assimilation of soil organic carbon is broadly considered to be an important parameter, it really comprises two separate physiological processes: one-time assimilation efficiency and time-dependent microbial maintenance energy. Representing of these two mechanisms is crucial to more accurately simulate carbon cycling in soils. In this study, amore » simple modeling framework was developed to evaluate the substrate and environmental controls on microbial assimilation of soil organic carbon using a new term: microbial annual active period (the length of microbes remaining active in one year). Substrate quality has a positive effect on microbial assimilation of soil organic carbon: higher substrate quality (lower C:N ratio) leads to higher ratio of microbial carbon to soil organic carbon and vice versa. Increases in microbial annual active period from zero stimulate microbial assimilation of soil organic carbon; however, when microbial annual active period is longer than an optimal threshold, increasing this period decreases microbial biomass. The simulated ratios of soil microbial biomass to soil organic carbon are reasonably consistent with a recently compiled global dataset at the biome-level. The modeling framework of microbial assimilation of soil organic carbon and its controls developed in this study offers an applicable ways to incorporate microbial contributions to the carbon cycling into Earth system models for simulating carbon-climate feedbacks and to explain global patterns of microbial biomass.« less
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Effect of Different Substrates and Casing Materials on the Growth and Yield of Calocybe indica.
Amin, Ruhul; Khair, Abul; Alam, Nuhu; Lee, Tae Soo
2010-06-01
Calocybe indica, a tropical edible mushroom, is popular because it has good nutritive value and it can be cultivated commercially. The current investigation was undertaken to determine a suitable substrate and the appropriate thickness of casing materials for the cultivation of C. indica. Optimum mycelial growth was observed in coconut coir substrate. Primordia initiation with the different substrates and casing materials was observed between the 13th and 19th day. The maximum length of stalk was recorded from sugarcane leaf, while diameter of stalk and pileus, and thickness of pileus were found in rice straw substrate. The highest biological and economic yield, and biological efficiency were also obtained in the rice straw substrate. Cow dung and loamy soil, farm-yard manure, loamy soil and sand, and spent oyster mushroom substrates were used as casing materials to evaluate the yield and yield-contributing characteristics of C. indica. The results indicate that the number of effective fruiting bodies, the biological and economic yield, and the biological efficiency were statistically similar all of the casing materials used. The maximum biological efficiency was found in the cow dung and loamy soil casing material. The cow dung and loamy soil (3 cm thick) was the best casing material and the rice straw was the best substrate for the commercial cultivation of C. indica.
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Effect of Different Substrates and Casing Materials on the Growth and Yield of Calocybe indica
Amin, Ruhul; Khair, Abul; Alam, Nuhu
2010-01-01
Calocybe indica, a tropical edible mushroom, is popular because it has good nutritive value and it can be cultivated commercially. The current investigation was undertaken to determine a suitable substrate and the appropriate thickness of casing materials for the cultivation of C. indica. Optimum mycelial growth was observed in coconut coir substrate. Primordia initiation with the different substrates and casing materials was observed between the 13th and 19th day. The maximum length of stalk was recorded from sugarcane leaf, while diameter of stalk and pileus, and thickness of pileus were found in rice straw substrate. The highest biological and economic yield, and biological efficiency were also obtained in the rice straw substrate. Cow dung and loamy soil, farm-yard manure, loamy soil and sand, and spent oyster mushroom substrates were used as casing materials to evaluate the yield and yield-contributing characteristics of C. indica. The results indicate that the number of effective fruiting bodies, the biological and economic yield, and the biological efficiency were statistically similar all of the casing materials used. The maximum biological efficiency was found in the cow dung and loamy soil casing material. The cow dung and loamy soil (3 cm thick) was the best casing material and the rice straw was the best substrate for the commercial cultivation of C. indica. PMID:23956634
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NASA Technical Reports Server (NTRS)
Gooding, J. L.
1987-01-01
Many geomorphic features on Mars were attributed to Earth-analogous, cold-climate processes involving movement of water or ice lubricated debris. Clearly, knowledge of the behavior of water in regolith materials under Martian conditions is essential to understanding the postulated geomorphic processes. Experiments were performed with sand-sized samples of natural basaltic regoliths in order to further elucidate how water/regolith interactions depend upon grain size and mineralogy. The data reveal important contrasts with data for clay-mineral substrates and suggest that the microphysics of water/mineral interactions might affect Martian geomorphic processes in ways that are not fully appreciated. Sand and silt sized fractions of two soils from the summit of Mauna Kea were used as Mars-analogous regolith materials. Temperatures were measured for water/ice phase transitions as wet slurries of individual soil fractions which were cooled or heated at controlled rates under a carbon dioxide atmosphere. Freezing and melting of ice was studied as a function of water/soil mass ratio, soil particle size, and thermal-cycle rate. Comparison tests were done under the same conditions with U.S. Geological Survey standard rock powders.
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Principles of soil mapping of a megalopolis with St. Petersburg as an example
NASA Astrophysics Data System (ADS)
Aparin, B. F.; Sukhacheva, E. Yu.
2014-07-01
For the first time, a soil map of St. Petersburg has been developed on a scale of 1 : 50000 using MicroStation V8i software. The legend to this map contains more than 60 mapping units. The classification of urban soils and information on the soil cover patterns are principally new elements of this legend. New concepts of the urbanized soil space and urbopedocombinations have been suggested for soil mapping of urban territories. The typification of urbopedocombinations in St. Petersburg has been performed on the basis of data on the geometry and composition of the polygons of soils and nonsoil formations. The ratio between the areas of soils and nonsoil formations and their spatial distribution patterns have been used to distinguish between six types of the urbanized soil space. The principles of classification of the soils of urban territories have been specified, and a separate order of pedo-allochthonous soils has been suggested for inclusion into the Classification and Diagnostic System of Russian Soils (2004). Six types of pedo-allochthonous soils have been distinguished on the basis of data on their humus and organic horizons and the character of the underlying mineral substrate.
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Volatile metal deposits on lunar soils: Relation to volcanism
NASA Technical Reports Server (NTRS)
Reed, G. W., Jr.; Allen, R. O., Jr.; Jovanovic, S.
1977-01-01
Parallel leaching and volatilization experiments conducted on lunar samples and similar experiments on sphalerite do not supply the information needed to resolve the question of the chemical nature of pb 204, Zn, Bi and Tl deposits on lunar soil surfaces. It is proposed that in Apollo 17 mare and terra soils and fractions of pb 204, Zn and Tl that are insoluble under mild, hot pH 5HNO3, leaching conditions and involatile at 600 C were originally surface deposits which became immobilized by migration into the silicate substrate or by chemisorption. Only Bi is predominantly indigenous. The implication is also that the soils over their respective times of evolution were exposed to heavy metal vapors or that an episodic exposure occurred after they had evolved. A sequence of events is proposed to account for orange 74220 and black 74001 glasses by lava fountaining and for soil 74241 as tephra from an explosive volcanic eruption.
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Changes in gene expression during adaptation of Listeria monocytogenes to the soil environment.
Piveteau, Pascal; Depret, Géraldine; Pivato, Barbara; Garmyn, Dominique; Hartmann, Alain
2011-01-01
Listeria monocytogenes is a ubiquitous opportunistic pathogen responsible for listeriosis. In order to study the processes underlying its ability to adapt to the soil environment, whole-genome arrays were used to analyse transcriptome modifications 15 minutes, 30 minutes and 18 h after inoculation of L. monocytogenes EGD-e in soil extracts. Growth was observed within the first day of incubation and large numbers were still detected in soil extract and soil microcosms one year after the start of the experiment. Major transcriptional reprofiling was observed. Nutrient acquisition mechanisms (phosphoenolpyruvate-dependent phosphotransferase systems and ABC transporters) and enzymes involved in catabolism of specific carbohydrates (β-glucosidases; chitinases) were prevalent. This is consistent with the overrepresentation of the CodY regulon that suggests that in a nutrient depleted environment, L. monocytogenes recruits its extensive repertoire of transporters to acquire a range of substrates for energy production.
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Tulliani, Jean-Marc; Baroni, Chiara; Zavattaro, Laura; Grignani, Carlo
2013-01-01
The aim of this work is to study the sensing behavior of Sr-doped hematite for soil water content measurement. The material was prepared by solid state reaction from commercial hematite and strontium carbonate heat treated at 900 °C. X-Ray diffraction, scanning electron microscopy and mercury intrusion porosimetry were used for microstructural characterization of the synthesized powder. Sensors were then prepared by uniaxially pressing and by screen-printing, on an alumina substrate, the prepared powder and subsequent firing in the 800–1,000 °C range. These sensors were first tested in a laboratory apparatus under humid air and then in an homogenized soil and finally in field. The results evidenced that the screen printed film was able to give a response for a soil matric potential from about 570 kPa, that is to say well below the wilting point in the used soil. PMID:24025555
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Relationship between gaseous N dynamics and the hydraulic state of hierarchically structured soils
NASA Astrophysics Data System (ADS)
Schlüter, Steffen; Dörsch, Peter; Vogel, Hans-Jörg
2017-04-01
The inherent spatial heterogeneity of soil generates spatially distributed micro-sites with different local N gas (NO, N2O, N2) production and release rates. Moreover, local micro-site conditions and the pathways between them depend on soil moisture which itself is highly dynamic close to the soil surface. These relationships need to be taken into account for a quantitative understanding of soil denitrification and associated N gas dynamics. Soil structure has been recognized as a key factor to understand the high spatial variability of N gas emissions. In particular gaseous N release from soils depends on: i) the total denitrification rate, which is related to the spatial extent and distribution of anaerobic sites and ii) the probability of N2O to escape from the soil without being further reduced to N2. This impact of soil structure is typically ignored in studies with soil slurries or repacked soil. In this project we run well-defined mesocosm experiments on N gas dynamics with hierarchically structured, artificial soils in which the spatial distribution of substrate and denitrifiers is known exactly. Sintered, porous glass pellets are inoculated with strains of Paracoccus denitrificans and/or Agrobacterium tumefaciens and amended with nutrient solution. These pellets are embedded in coarse-grained sand within gas-tight columns under O2/He atmosphere. The pellets are either places in layers or randomly to create different patterns of N gas production sites and diffusion pathways. Denitrification occurs in the anaerobic centers of the porous pellets, while the partially saturated sand matrix controls the diffusive transport of N gases towards the headspace, where all relevant gas concentrations are monitored with gas chromatography. Water saturations are adjusted such that the diffusive pathways are either fully continuous or partially discontinuous. Preliminary results indicate that the water content exert a major control on the magnitude of denitrification, whereas the onset and dynamics are mainly controlled by the position of the substrate and the denitrifiers.
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NASA Technical Reports Server (NTRS)
Gruener, John E.; Ming, Douglas W.
2000-01-01
The National Aeronautics and Space Administration (NASA) Johnson Space Center (JSC) is developing a substrate, termed zeoponics, that will slowly release all of the essential nutrients into solution for plant growth experiments in advanced life support system testbeds. This substrate is also potentially useful in the near future on the Space Shuttle and International Space Station and could eventually be used at an outpost on Mars. Chemical analyses of the Martian soil by the Viking and Mars Pathfinder missions have indicated that several of the elements required for plant growth are available in the soil. It may be possible to use the martian soil as the bulk substrate for growing food crops, while using smaller amounts of zeoponic substrate as an amendment to rectify any nutrient deficiencies.
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Chen, Nuo; Liao, Ting-ting; Wang, Rui; Zheng, Xun-hua; Hu, Rong-gui; Butterbach-Bahl, Klaus
2014-09-01
Understanding the effects of carbon and nitrogen substrates concentrations on the emissions of denitrification gases including nitrogen (N2) , nitrous oxide (N2O) and nitric oxide (NO), carbon dioxide (CO2) and methane (CH4) from anaerobic paddy soils is believed to be helpful for development of greenhouse gas mitigation strategies. Moreover, understanding the quantitative dependence of denitrification products compositions on carbon substrate concentration could provide some key parameters or parameterization scheme for developing process-oriented model(s) of nitrogen transformation. Using a silt loam soil collected from a paddy field, we investigated the influence of carbon substrate concentration on the emissions of the denitrification gases, CO2 and CH4 from anaerobically incubated soils by setting two treatments: control (CK) with initial soil nitrate and dissolved organic carbon (DOC) concentrations of ~ 50 mg.kg-1 and -28 mg kg-1 , respectively; and DOC added (C + ) with initial soil nitrate and DOC concentrations of ~50 mg.kg-1 and ~300 mg.kg-1 , respectively. The emissions of denitrification gases, CO2 and CH4, as well as concentrations of carbon and nitrogen substrates for each treatment were dynamically measured, using the gas-flow-soil-core technique and a paralleling substrate monitoring system. The results showed that CH4 emission was not observed in CK treatment while observed in C treatment. Aggregate emission of greenhouse gases for C + treatment was significantly higher comparing with the CK treatment (P <0. 01). The mass fractions of NO, N20 and N2 emissions in total nitrogen gases emissions were approximately 9% , 35% and 56% for CK treatment, respectively; and approximately 31% , 50% and 19% for C+ treatment, respectively, with significant differences between these two treatments (P < 0.01). The results indicated that carbon substrate concentrations can significantly change the composition of nitrogen gas emissions. The results also implicated that organic fertilizer should not be applied to nitrate-rich paddy soils prior to or during flooding so as to mitigate greenhouse gases emissions.
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Insights from intercomparison of microbial and conventional soil models
NASA Astrophysics Data System (ADS)
Allison, S. D.; Li, J.; Luo, Y.; Mayes, M. A.; Wang, G.
2014-12-01
Changing the structure of soil biogeochemical models to represent coupling between microbial biomass and carbon substrate pools could improve predictions of carbon-climate feedbacks. So-called "microbial models" with this structure make very different predictions from conventional models based on first-order decay of carbon substrate pools. Still, the value of microbial models is uncertain because microbial physiological parameters are poorly constrained and model behaviors have not been fully explored. To address these issues, we developed an approach for inter-comparing microbial and conventional models. We initially focused on soil carbon responses to microbial carbon use efficiency (CUE) and temperature. Three scenarios were implemented in all models at a common reference temperature (20°C): constant CUE (held at 0.31), varied CUE (-0.016°C-1), and 50% acclimated CUE (-0.008°C-1). Whereas the conventional model always showed soil carbon losses with increasing temperature, the microbial models each predicted a temperature threshold above which warming led to soil carbon gain. The location of this threshold depended on CUE scenario, with higher temperature thresholds under the acclimated and constant scenarios. This result suggests that the temperature sensitivity of CUE and the structure of the soil carbon model together regulate the long-term soil carbon response to warming. Compared to the conventional model, all microbial models showed oscillatory behavior in response to perturbations and were much less sensitive to changing inputs. Oscillations were weakest in the most complex model with explicit enzyme pools, suggesting that multi-pool coupling might be a more realistic representation of the soil system. This study suggests that model structure and CUE parameterization should be carefully evaluated when scaling up microbial models to ecosystems and the globe.
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Multisubstrate Isotope Labeling and Metagenomic Analysis of Active Soil Bacterial Communities
Verastegui, Y.; Cheng, J.; Engel, K.; Kolczynski, D.; Mortimer, S.; Lavigne, J.; Montalibet, J.; Romantsov, T.; Hall, M.; McConkey, B. J.; Rose, D. R.; Tomashek, J. J.; Scott, B. R.
2014-01-01
ABSTRACT Soil microbial diversity represents the largest global reservoir of novel microorganisms and enzymes. In this study, we coupled functional metagenomics and DNA stable-isotope probing (DNA-SIP) using multiple plant-derived carbon substrates and diverse soils to characterize active soil bacterial communities and their glycoside hydrolase genes, which have value for industrial applications. We incubated samples from three disparate Canadian soils (tundra, temperate rainforest, and agricultural) with five native carbon (12C) or stable-isotope-labeled (13C) carbohydrates (glucose, cellobiose, xylose, arabinose, and cellulose). Indicator species analysis revealed high specificity and fidelity for many uncultured and unclassified bacterial taxa in the heavy DNA for all soils and substrates. Among characterized taxa, Actinomycetales (Salinibacterium), Rhizobiales (Devosia), Rhodospirillales (Telmatospirillum), and Caulobacterales (Phenylobacterium and Asticcacaulis) were bacterial indicator species for the heavy substrates and soils tested. Both Actinomycetales and Caulobacterales (Phenylobacterium) were associated with metabolism of cellulose, and Alphaproteobacteria were associated with the metabolism of arabinose; members of the order Rhizobiales were strongly associated with the metabolism of xylose. Annotated metagenomic data suggested diverse glycoside hydrolase gene representation within the pooled heavy DNA. By screening 2,876 cloned fragments derived from the 13C-labeled DNA isolated from soils incubated with cellulose, we demonstrate the power of combining DNA-SIP, multiple-displacement amplification (MDA), and functional metagenomics by efficiently isolating multiple clones with activity on carboxymethyl cellulose and fluorogenic proxy substrates for carbohydrate-active enzymes. PMID:25028422
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Substrate and nutrient limitation of ammonia-oxidizing bacteria and archaea in temperate forest soil
J.S. Norman; J.E. Barrett
2014-01-01
Ammonia-oxidizing microbes control the rate-limiting step of nitrification, a critical ecosystem process, which affects retention and mobility of nitrogen in soil ecosystems. This study investigated substrate (NH4þ) and nutrient (K and P) limitation of ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA) in temperate forest soils at Coweeta Hydrologic...
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Microbial Diversity in Soil, Sand Dune and Rock Substrates of the Thar Monsoon Desert, India.
Rao, Subramanya; Chan, Yuki; Bugler-Lacap, Donnabella C; Bhatnagar, Ashish; Bhatnagar, Monica; Pointing, Stephen B
2016-03-01
A culture-independent diversity assessment of archaea, bacteria and fungi in the Thar Desert in India was made. Six locations in Ajmer, Jaisalmer, Jaipur and Jodhupur included semi-arid soils, arid soils, arid sand dunes, plus arid cryptoendolithic substrates. A real-time quantitative PCR approach revealed that bacteria dominated soils and cryptoendoliths, whilst fungi dominated sand dunes. The archaea formed a minor component of all communities. Comparison of rRNA-defined community structure revealed that substrate and climate rather than location were the most parsimonious predictors. Sequence-based identification of 1240 phylotypes revealed that most taxa were common desert microorganisms. Semi-arid soils were dominated by actinobacteria and alpha proteobacteria, arid soils by chloroflexi and alpha proteobacteria, sand dunes by ascomycete fungi and cryptoendoliths by cyanobacteria. Climatic variables that best explained this distribution were mean annual rainfall and maximum annual temperature. Substrate variables that contributed most to observed diversity patterns were conductivity, soluble salts, Ca(2+) and pH. This represents an important addition to the inventory of desert microbiota, novel insight into the abiotic drivers of community assembly, and the first report of biodiversity in a monsoon desert system.
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A mechanistic diagnosis of the simulation of soil CO2 efflux of the ACME Land Model
NASA Astrophysics Data System (ADS)
Liang, J.; Ricciuto, D. M.; Wang, G.; Gu, L.; Hanson, P. J.; Mayes, M. A.
2017-12-01
Accurate simulation of the CO2 efflux from soils (i.e., soil respiration) to the atmosphere is critical to project global biogeochemical cycles and the magnitude of climate change in Earth system models (ESMs). Currently, the simulated soil respiration by ESMs still have a large uncertainty. In this study, a mechanistic diagnosis of soil respiration in the Accelerated Climate Model for Energy (ACME) Land Model (ALM) was conducted using long-term observations at the Missouri Ozark AmeriFlux (MOFLUX) forest site in the central U.S. The results showed that the ALM default run significantly underestimated annual soil respiration and gross primary production (GPP), while incorrectly estimating soil water potential. Improved simulations of soil water potential with site-specific data significantly improved the modeled annual soil respiration, primarily because annual GPP was simultaneously improved. Therefore, accurate simulations of soil water potential must be carefully calibrated in ESMs. Despite improved annual soil respiration, the ALM continued to underestimate soil respiration during peak growing seasons, and to overestimate soil respiration during non-peak growing seasons. Simulations involving increased GPP during peak growing seasons increased soil respiration, while neither improved plant phenology nor increased temperature sensitivity affected the simulation of soil respiration during non-peak growing seasons. One potential reason for the overestimation of the soil respiration during non-peak growing seasons may be that the current model structure is substrate-limited, while microbial dormancy under stress may cause the system to become decomposer-limited. Further studies with more microbial data are required to provide adequate representation of soil respiration and to understand the underlying reasons for inaccurate model simulations.
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X-Ray Computed Tomography Reveals the Response of Root System Architecture to Soil Texture.
Rogers, Eric D; Monaenkova, Daria; Mijar, Medhavinee; Nori, Apoorva; Goldman, Daniel I; Benfey, Philip N
2016-07-01
Root system architecture (RSA) impacts plant fitness and crop yield by facilitating efficient nutrient and water uptake from the soil. A better understanding of the effects of soil on RSA could improve crop productivity by matching roots to their soil environment. We used x-ray computed tomography to perform a detailed three-dimensional quantification of changes in rice (Oryza sativa) RSA in response to the physical properties of a granular substrate. We characterized the RSA of eight rice cultivars in five different growth substrates and determined that RSA is the result of interactions between genotype and growth environment. We identified cultivar-specific changes in RSA in response to changing growth substrate texture. The cultivar Azucena exhibited low RSA plasticity in all growth substrates, whereas cultivar Bala root depth was a function of soil hardness. Our imaging techniques provide a framework to study RSA in different growth environments, the results of which can be used to improve root traits with agronomic potential. © 2016 American Society of Plant Biologists. All Rights Reserved.
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Karanasios, Evangelos C; Tsiropoulos, Nikolaos G; Karpouzas, Dimitrios G
2013-09-01
Biobed substrates commonly exhibit high degradation capacity. However, degradation does not always lead to detoxification and information on the metabolic pathways of pesticides in biobeds is scarce. We studied the degradation and metabolism of three pesticides in selected biomixtures and soil. Biomixtures stimulated degradation of terbuthylazine and metribuzin, whereas chlorpyrifos degraded faster in soil. The latter was attributed to the lipophilicity of chlorpyrifos which increased adsorption and limited biodegradation in organic-rich biomixtures. Although the same metabolites were detected in all substrates, qualitative and quantitative differences in the metabolic routes of pesticides in the various substrates were observed. Chlorpyrifos was hydrolyzed to 3,5,6-tricholorpyridinol (TCP) which was further degraded only in compost-biomixture CBX1. Metabolism of terbuthylazine in compost biomixtures (BX) and soil resulted in the formation of desethyl-terbuthylazine (DES) which was fully degraded only in the compost-biomixture CBX2, whereas peat-based biomixture (OBX) promoted the hydroxylation of terbuthylazine. Desamino- (DA) (dominant) and diketo- (DK) metribuzin appear as intermediate metabolites in all substrates and were further transformed to desamino-diketo-metribuzin (DADK) which was fully degraded only in compost-biomixture GSBX. Overall, lower amounts of metabolites were accumulated in biomixtures compared to soil stressing the higher depuration efficiency of biobeds. Copyright © 2013 Elsevier Ltd. All rights reserved.
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NASA Astrophysics Data System (ADS)
Karhu, Kristiina; Auffret, Marc; Dungait, Jennifer; Fraser, Fiona; Hopkins, David; Prosser, James; Singh, Brajesh; Subke, Jens-Arne; Wookey, Philip; Ågren, Göran; Hartley, Iain
2013-04-01
There are concerns that global warming may stimulate decomposition rates in soils, leading to a substantial release of CO2 to the atmosphere, and thus accelerating rates of 21st century climate change. However, there is growing recognition that adaptation of soil microbial communities to changes in their prevailing thermal regime may alter the potential rate of carbon release. Critically, recent studies have produced conflicting results in terms of whether adaptation of soil microbial communities to temperature reduces (thermal acclimation) or enhances (enhancement) the direct effects of temperature changes on decomposition rates. This lack of understanding adds considerably to uncertainty in predictions of the magnitude and direction of carbon-cycle feedbacks to climate change. Investigating the impacts of adaptation to temperature is currently only possible in controlled laboratory experiments, in which fluctuations in substrate availability can be minimised. We developed a approach which involves incubating soils at 3°C above mean annual temperature (MAT), until respiration rates stabilise, then cooling by 6°C (MAT -3 °C) and determining the potential for respiration rates to recover during extended exposure to lower temperatures. Our approach avoids the issues associated with substrate depletion in warming studies, but still tests whether adaptation enhances or reduces the direct impact of temperature on microbial activity. In contrast to many other studies, our initial research clearly demonstrated enhancement in Arctic soils. Here we present results from a new project which has extended the approach to soils sampled from contrasting Arctic, Boreal, temperate, Mediterranean and tropical ecosystems. This study represents one of the most extensive investigations undertaken into the potential for thermal acclimation, and/or enhancement, under contrasting environmental conditions. We also attempted to disentangle the mechanisms underlying the observed responses by quantifying changes in microbial biomass, microbial community structure , mass-specific activity, carbon-use efficiency, and the activities of enzymes involved in the break-down of labile versus more recalcitrant compounds. Our results from temperate, Mediterranean and tropical soils generally show little evidence of thermal acclimation, but responses were dependent on soil type and the temperature range investigated; at low temperatures and from organic soils, further evidence for enhancement was produced. The lack of evidence of acclimation suggests that there remains the potential for C losses from soils in temperate and tropical areas as the climate changes. Furthermore, results from incubations from Boreal and Arctic soils showed clear enhancement. This suggests that the long-term effect of warming on soil respiration rates in the Arctic could be larger than predicted based on short-term measurements of temperature sensitivity. Consequently, the substantial stores of carbon present in high-latitude soils may be even more vulnerable to climate warming than previously estimated. We also discuss the potential mechanisms underlying the observed patterns based on the extensive range of microbial assays carried out in this project.
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Effectiveness of T. harzianum and Humate Amendment in Soil Salinity Restoration
NASA Astrophysics Data System (ADS)
Apostolakis, Antonios; Daliakopoulos, Ioannis; Tsanis, Ioannis
2017-04-01
Soil salinity is a major soil degradation threat, especially for the water stressed parts of the Mediterranean region, where it hinders soil fertility and thus agricultural productivity. Soil salinity management can be complex and expensive, often resorting to the use of chemical amendments thus risking soil and aquifer pollution. This study quantifies the beneficial effects of (a) a commercial strain of the beneficial fungus Trichoderma harzianum (TH), and (b) a commercial humate fertilizer enhancer (HFE) approved for organic farming, against soil salinization. The treatments are tested in the context of a Solanum lycopersicum (tomato) greenhouse simulation of the cultivation conditions typical for the semi-arid coastal Timpaki basin in south-central Crete. 20 vigorous 20-day-old Solanum lycopersicum L. cv Elpida seedlings are treated either with TH or HFE, using soil substrates and irrigation treatments of two degradation states. 20 additional plants serve either as controls or guard rows. All plants are transplanted into 35 L pots under greenhouse conditions. Preliminary analysis of soil salinity and crop yield indicators suggest that both treatments are beneficial for the soil-plant system, each to a different extent depending on initial soil conditions.
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Iwaoka, Chikae; Imada, Shogo; Taniguchi, Takeshi; Du, Sheng; Yamanaka, Norikazu; Tateno, Ryunosuke
2018-05-01
Nitrogen (N) is one of the most common limiting nutrients for primary production in terrestrial ecosystems. Soil microbes transform organic N into inorganic N, which is available to plants, but soil microbe activity in drylands is sometimes critically suppressed by environmental factors, such as low soil substrate availability or high salinity. Tamarisk (Tamarix spp.) is a halophytic shrub species that is widely distributed in the drylands of China; it produces litter enriched in nutrients and salts that are thought to increase soil fertility and salinity under its crown. To elucidate the effects of tamarisks on the soil microbial community, and thus N dynamics, by creating "islands of fertility" and "islands of salinity," we collected soil samples from under tamarisk crowns and adjacent barren areas at three habitats in the summer and fall. We analyzed soil physicochemical properties, inorganic N dynamics, and prokaryotic community abundance and composition. In soils sampled beneath tamarisks, the N mineralization rate was significantly higher, and the prokaryotic community structure was significantly different, from soils sampled in barren areas, irrespective of site and season. Tamarisks provided suitable nutrient conditions for one of the important decomposers in the area, Verrucomicrobia, by creating "islands of fertility," but provided unsuitable salinity conditions for other important decomposers, Flavobacteria, Gammaproteobacteria, and Deltaproteobacteria, by mitigating salt accumulation. However, the quantity of these decomposers tended to be higher beneath tamarisks, because they were relatively unaffected by the small salinity gradient created by the tamarisks, which may explain the higher N mineralization rate beneath tamarisks.
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Chosing erosion control nets. Can't you decide? Ask the lab.
NASA Astrophysics Data System (ADS)
Simkova, Jana; Jacka, Lukas
2015-04-01
Geotextiles (GTXs) have been used to protect steep slopes against soil erosion for about 60 years and many products have become available. The choice of individual product is always based on its ratio of cost versus effectiveness. Generally applicable recommendations for specific site conditions are missing and testing the effectiveness of GTXs in the field is time consuming and costly. Due to various site conditions, results of numerous case-studies cannot be generalized. One of the major and site-specific factors affecting the erosion process, and hence the effectiveness of GTXs, is the soil. This study aimed to determine the rate of influence of three natural erosion control nets on the volume and velocity of surface runoff caused by rainfall. The nets were installed on slope under laboratory conditions and then exposed to simulated rainfall. An impermeable plastic film was used as a substrate instead of soil to simulate non-infiltrating conditions. A comparison of the influence of tested GTX samples on surface runoff may indicate to their erosion control effect. Thus, the results could help with choosing a particular product. Under real conditions, the effect of erosion control nets would be increased by the infiltration capacity of the soil, equally for all samples. Therefore, the order of effectiveness of the samples should stay unchanged. To validate this theory, a field experiment was carried out where soil loss was recorded along with runoff characteristics. The data trends of discharge culmination under natural conditions were similar to trends under laboratory conditions and corresponded to soil loss records.
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Soils as relative-age dating tools
Markewich, Helaine Walsh; Pavich, Milan J.; Wysocki, Douglas A.
2017-01-01
Soils develop at the earth's surface via multiple processes that act through time. Precluding burial or disturbance, soil genetic horizons form progressively and reflect the balance among formation processes, surface age, and original substrate composition. Soil morphology provides a key link between process and time (soil age), enabling soils to serve as both relative and numerical dating tools for geomorphic studies and landscape evolution. Five major factors define the contemporary state of all soils: climate, organisms, topography, parent material, and time. Soils developed on similar landforms and parent materials within a given landscape comprise what we term a soil/landform/substrate complex. Soils on such complexes that differ in development as a function of time represent a soil chronosequence. In a soil chronosequence, time constitutes the only independent formation factor; the other factors act through time. Time dictates the variations in soil development or properties (field or laboratory measured) on a soil/landform/substrate complex. Using a dataset within the chronosequence model, we can also formulate various soil development indices based upon one or a combination of soil properties, either for individual soil horizons or for an entire profile. When we evaluate soil data or soil indices mathematically, the resulting equation creates a chronofunction. Chronofunctions help quantify processes and mechanisms involved in soil development, and relate them mathematically to time. These rigorous kinds of comparisons among and within soil/landform complexes constitute an important tool for relative-age dating. After determining one or more absolute ages for a soil/landform complex, we can calculate quantitative soil formation, and or landform-development rates. Multiple dates for several complexes allow rate calculations for soil/landform-chronosequence development and soil-chronofunction calibration.
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NASA Astrophysics Data System (ADS)
Toledo, Diana Marcela; Arzuaga, Silvia; Dalurzo, Humberto; Zornoza, Raúl; Vazquez, Sara
2015-04-01
The objective of this work was to evaluate changes in soil organic matter in Oxisols under different crops compared to native rainforest, and to assess if acid phosphatase activity (APA) could be a good indicator for SOC changes and soil quality. The experimental design consisted of four completely randomized blocks with four treatments: subtropical rainforest (F); yerba mate crop (I) (Ilex paraguariensis SH.); citrus crop (C) (Citrus unshiu Marc); and tobacco crop (T) (Nicotiana tabacum L.). Soil samples were taken at 0-10; 10-20 and 20-30 cm depths. The variables measured were soil organic carbon (SOC), APA, clay content, pH, total nitrogen (Nt), available phosphorus (P) and CO2 emissions. All data were analyzed by ANOVA to assess the effects of land-use changes. The treatment means were compared through Duncan's multiple range tests (p<0.05). The relationship between variables was determined with a simple correlation analysis and with a multiple linear regression analysis through the stepwise method. These soils showed an acid reaction and their clay content was over 650 g kg-1 for the three depths. SOC and N contents were higher in native soils, intermediate for the citrus crop, and lower under both tobacco and yerba mate crops. CO2 emissions were higher in the rainforest (47.32 kg ha-1 of CO2) than in cultivated soils, which indicates that biological activity is enhanced in rainforest soils where substrates for soil biota and fauna are more readily available. The variability of 76% in APA was explained by total nitrogen, which is closely related to soil organic matter, and by available P. Conversion of subtropical rainforests into agricultural lands reduced SOC content and acid phosphatase activity, thereby lowering soil quality. In this study, acid phosphatase activity proved to be a sensitive indicator to detect changes from pristine to cropped soils, but it failed to distinguish differences among crop systems.
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Interactions between arbuscular mycorrhizal fungi and organic material substrates.
Hodge, Angela
2014-01-01
Arbuscular mycorrhizal (AM) associations are widespread and form between ca. two-thirds of all land plants and fungi in the phylum Glomeromycota. The association is a mutualistic symbiosis with the fungi enhancing nutrient capture for the plant while obtaining carbon in return. Although arbuscular mycorrhizal fungi (AMF) lack any substantial saprophytic capability they do preferentially associate with various organic substrates and respond by hyphal proliferation, indicating the fungus derives a benefit from the organic substrate. AMF may also enhance decomposition of the organic material. The benefit to the host plant of this hyphal proliferation is not always apparent, particularly regarding nitrogen (N) transfer, and there may be circumstances under which both symbionts compete for the N released given both have a large demand for N. The results of various studies examining AMF responses to organic substrates and the interactions with other members of the soil community will be discussed. © 2014 Elsevier Inc. All rights reserved.
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A tree from waste: Decontaminated dredged sediments for growing forest tree seedlings.
Ugolini, Francesca; Mariotti, Barbara; Maltoni, Alberto; Tani, Andrea; Salbitano, Fabio; Izquierdo, Carlos García; Macci, Cristina; Masciandaro, Graziana; Tognetti, Roberto
2018-04-01
The sediments dredged from a waterway and decontaminated through a phytoremediation process have been used as substrates alternatively to the traditional forest nursery substrate for pot productions of holm oak (Quercus ilex L.) planting stocks. The substrates, made by mixing decontaminated sediments to agricultural soil at different degrees, were tested in order to evaluate their suitability as growth substrates. The experiment was carried out at the nursery of the Department of Agricultural, Food and Forestry Systems of the University of Florence (Italy). The experimental design consisted of four randomized blocks with six pots as replicates for each of the following treatments: 100% sediments, 66% sediments, 33% sediments, 100% agronomic soil and 100% traditional peat based substrate. In each pot, one holm oak acorn was seeded. Germination and both physiological and morphological traits of the seedlings were analysed during and at the end of the first growing season. Holm oak grown in phytoremediated sediments at higher concentrations showed germination levels comparable to those in the traditional substrate, and survival capacity (especially in 66% sediments) slightly higher than in 100% soil. Physiological performance of seedlings resembled that on the traditional substrate which required the addition of fertilizer, at least for the first growing season. Seedlings grown in mixed substrates with higher sediment concentrations occasionally showed better photosynthetic capacity with improved connectivity between the units of the photosystem II. At the end of the first growing season, height as well as the number of growth flushes of the seedlings grown in sole sediment or soil-sediment substrates were similar to what generally is observed for forest nursery stock of Quercus spp.. Regarding the root-system articulation and growth in depth, results in the mixed substrates were comparable to those for seedlings grown in the traditional forest nursery media, and higher than seedlings grown in 100% agronomic soil. According to our results, the reclamation of dredged sediments can provide appropriate nursery substrate for germination beds for forestry species. Copyright © 2018 Elsevier Ltd. All rights reserved.
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NASA Astrophysics Data System (ADS)
Brock, Olaf; Kooijman, Annemieke; Vancampenhout, Karen; Muys, Bart; Jansen, Boris
2017-04-01
By storing carbon in the soil, forests can play an important role in climate mitigation. We studied how the SOM composition was affected by conversion of deciduous stands to mono-culture spruce plantations in the Mullerthal in Luxembourg and the Gaume in south-east Belgium. Both regions have a known and similar vegetation history on different lithologies, ranging from carcareous marls to decalcified sands. Lignin and cutin/suberin biomarkers were identified by using thermally assisted hydrolysis and methylation (THM) with unlabelled tetra methyl ammonium hydroxide (TMAH). Lignin was used to distinguish deciduous and coniferous litter sources, whereas cutin and suberin indicated the respective input of above- and belowground litter input. A twinplot setup was used to be able to independently evaluate the effect of edaphic factors versus input differences on SOM composition. pH values and SOC stocks reflected the lithological gradients in both study areas. The difference was more subtle in the Gaume where the gradient is much narrower. The existence of pedogenic thresholds explains why significant differences in lignin yield and SOC stocks between plots with different lithology were also found along the subtle gradient in the Gaume. Secondly, we observed differences in molecular composition and also in decomposition state of lignin that were caused solely by input differences between adjacent deciduous and coniferous forest plots. Furthermore, we found a legacy effect, a signal of former deciduous forest in the deeper soil layers (15-20 cm) under the current spruce plantations, in the loamy substrate plots of the Gaume, which was not observed in the Mullerthal, despite the similar vegetation history of both regions. This can be explained by differences in environmental conditions between both areas. Higher pH values resulting in a higher biological activity could explain the absence of a legacy effect in the Mullerthal plots. Therefore, an important conclusion of this work is that the presence of a legacy effect depends on local soil conditions and soil process domains. Lignin decomposition was found to be higher under more acid conditions, as present in spruce soils compared with the soils under deciduous trees. Moreover, the observance that in the Mullerthal the amount of lignin relative to TOC decreased with increasing depth from the surface, indicates preferential decomposition of lignin with depth. This is in line with the new paradigm that the (soil) environment rather than molecular composition is in many situations a dominant factor in determining the lignin turnover rate. Lastly, in both study areas within most twin plots SOC stocks were similar for both forest types, while SOC stocks were higher on a marl or limestone substrate than on a sandy substrate. We therefore argue that edapthic factors are of vital importance when considering forests to effectively mitigate climate change and that litter quality,and therefore the molecular composition of the organic matter, cannot be ignored when discussing organic matter persistence and carbon sequestration.
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Content and bioconcentration of mercury in mushrooms from northern Poland.
Falandysz, J; Gucia, M; Brzostowski, A; Kawano, M; Bielawski, L; Frankowska, A; Wyrzykowska, B
2003-03-01
Mercury (Hg) was quantified using cold vapour-atomic absorption spectrometry (CV-AAS) in the fruiting bodies of nine edible and five inedible mushrooms and in underlying soil substrate samples. In total, 404 samples comprising caps and stalks and 202 samples of soil substrate (0-10 cm layer) were collected in 1996 from Trójmiejski Landscape Park, northern Poland. Mean Hg concentrations in the soil substrate for different species varied between 10 +/- 3 and 780 +/- 500 ng x g(-1) dry wt (range 2.3-1700). Among edible mushroom species, Horse Mushroom (Agaricus arvensis), Brown Birch Scaber Stalk (Leccinum scabrum), Parasol Mushroom (Macrolepiota procera), King Bolete (Boletus edulis) and Yellow-cracking Bolete (Xerocomus subtomentosus) contained elevated concentrations of Hg ranging from 1600 +/- 930 to 6800 +/- 4000 ng x g(-1) dry wt in the caps. Concentrations of Hg in the stalks were 2.6 +/- 1.1 to 1.7 +/- 1.0 times lower than those in the caps. Some mushroom species investigated had high Hg levels when compared with specimens collected from the background reference sites elsewhere (located far away from the big cities) in northern Poland. Bioconcentration factors of Hg in the caps of Horse Mushroom, Parasol Mushroom and Brown Birch Scaber Stalk were between 150 +/- 58 and 230 +/- 150 ng x g(-1) dry wt, respectively, and for inedible Pestle-shaged Puffball (Claviata excipulformis) was 960 +/- 300 ng x g(-1) dry wt. Linear regression coefficients between Hg in caps and in stalks and Hg soil concentrations showed a positive relationship for A. arvensis and Horse mushroom (p < 0.05) and a negative correlation for the caps of Death Caps (Amanita phalloides) and Woolly Milk Cap (Lactarius torminosus) (p < 0.05), while for other species no clear trend was found.
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Microbial activity in the profiles of gray forest soil and chernozems
NASA Astrophysics Data System (ADS)
Susyan, E. A.; Rybyanets, D. S.; Ananyeva, N. D.
2006-08-01
Soil samples were taken from the profiles of a gray forest soil (under a forest) and southern chernozems of different textures under meadow vegetation. The microbial biomass (MB) was determined by the method of substrate-induced respiration; the basal respiration (BR) and the population density of microorganisms on nutrient media of different composition were also determined in the samples. The microbial metabolic quotient ( qCO2 = BR/MB) and the portion of microbial carbon (C mic) in C org were calculated. The MB and BR values were shown to decrease down the soil profiles. About 57% of the total MB in the entire soil profile was concentrated in the layer of 0-24 cm of the gray forest soil. The MB in the C horizon of chernozems was approximately two times lower than the MB in the A horizon of these soils. The correlation was found between the MB and the C org ( r = 0.99) and between the MB and the clay content ( r = 0.89) in the profile of the gray forest soil. The C mic/C org ratio in the gray forest soil and in the chernozems comprised 2.3-6.6 and 1.2-9.6%, respectively. The qCO2 value increased with the depth. The microbial community in the lower layers of the gray forest soil was dominated (88-96%) by oligotrophic microorganisms (grown on soil agar); in the upper 5 cm, these microorganisms comprised only 50% of the total amount of microorganisms grown on three media.
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NASA Astrophysics Data System (ADS)
Kristensen, J. A.; Metcalfe, D. B.; Rousk, J.
2017-12-01
Climate warming may increase insect herbivore ranges and outbreak intensities in arctic ecosystems. Thorough understanding of the implications of these changes for ecosystem processes is essential to make accurate predictions of surface-atmosphere carbon (C) feedbacks. Yet, we lack a comprehensive understanding of the impacts of herbivore outbreaks on soil microbial underpinnings of C and nitrogen (N) fluxes. Here, we investigate the growth responses of heterotrophic soil decomposers and C and N mineralisation to simulated defoliator outbreaks in Subarctic birch forests. In microcosms, topsoil was incubated with leaf litter, insect frass, mineral N and combinations of the three; all was added in equal amounts of N. A higher fraction of added C and N was mineralised during outbreaks (frass addition) relative to non-outbreak years (litter addition). However, under high mineral N-availability in the soil of the kind likely under longer periods of enhanced insect herbivory (litter+mineral N), the mineralised fraction of added C decreased while the mineralised fraction of N increased substantially, which suggest a shift towards more N-mining of the organic substrates. This shift was accompanied by higher fungal dominance, and may facilitate soil C-accumulation assuming constant quality of C-inputs. Thus, long-term increases of insect herbivory, of the kind observed in some areas and projected by some models, may facilitate higher ecosystem C-sink capacity in this Subarctic ecosystem.
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Comparison of Gravel Substrate vs Soil Substrate for the Construction of an Experimental Fen.
1995-12-01
1993). "Bog fens" contain many plants of northern distribution such as pitcher-plant ( Sarracenia purpurea L), tamarack (Larix lancina [DuRoi] K. Koch...Mint) SOIL 25 Carex cristatella (Crested Sedge) Sanguisorba canadensis 26 (Canadian Goldenrod) SOIL No difference Phytosegia purpurea 27...Carex cristatella (Crested Sedge) 26 Sanguisorba canadensis (Canada Buraet) 27 Physostegia purpurea (Purple Dragon-head) 28 Scirpus pendula (Drooping
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Competing for phosphors under changing redox conditions: biological versus geochemical sinks
NASA Astrophysics Data System (ADS)
Gross, A.; Pett-Ridge, J.; Silver, W. L.
2016-12-01
Competing for phosphorus under changing redox conditions: biological versus geochemical sinksAvner Gross1, Jennifer Pett-Ridge2 and Whendee L Silver1 University of California Berkeley, Department of Environmental Science, Policy, & Management, Berkeley, CA, USA. Lawrence Livermore National Laboratory, Physical and Life Science Directorate, Livermore, CA, USA. The cycling of phosphorous (P) in highly weathered, humid tropical forest soils is tightly regulated by P sorption dynamics to the surfaces of Fe(III) (hydr)oxides and root and microbial demands for P. Periods of anoxic soil conditions, which are common in humid environments, induce the reduction of Fe (III) to Fe (II) and may release sorbed P into the soil solution. The microbial demand for P is influenced by the C and nutrient composition of their available substrates. Therefore, we hypothesize that soil redox conditions and substrate quality and availability will control the partitioning of P between microbial biomass and the soil mineral phase. The aim of this study was to examine how fluctuations in soil redox conditions and changes in microbial P demand affect the fate of new P that enters the soil solution. To achieve this aim we conducted a series of soil incubation experiments using a wet tropical soil from Puerto Rico (where redox conditions and P availability naturally oscillate) with a single pulse of phosphate (PO4), altering both the microbial activity and redox conditions. To follow the fate the added P, the added phosphate was labeled with 18O. As the exchange of oxygen between phosphate and water only occurs during biological processes, P-18O labeling can be used as an indicator of microbial use. To quantify sizes of the microbial and mineral P pools we used traditional chemical extractions in the bulk scale. We used NanoSIMS isotopic imaging to map the distribution of P-16O and P-18O and co-localization with Fe minerals at the nano scale. Our results show that the amount of the added P fixed by the mineral phase was inversely correlated to the amount of P assimilated by the microbial biomass. In addition, we discovered the iron redox state did not affect the microbial or mineral P pool sizes. Overall, our results indicate the partition of the added P between the biological and mineral pools is regulated by the microbial biomass demands for P.
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Linking soil bacterial biodiversity and soil carbon stability.
Mau, Rebecca L; Liu, Cindy M; Aziz, Maliha; Schwartz, Egbert; Dijkstra, Paul; Marks, Jane C; Price, Lance B; Keim, Paul; Hungate, Bruce A
2015-06-01
Native soil carbon (C) can be lost in response to fresh C inputs, a phenomenon observed for decades yet still not understood. Using dual-stable isotope probing, we show that changes in the diversity and composition of two functional bacterial groups occur with this 'priming' effect. A single-substrate pulse suppressed native soil C loss and reduced bacterial diversity, whereas repeated substrate pulses stimulated native soil C loss and increased diversity. Increased diversity after repeated C amendments contrasts with resource competition theory, and may be explained by increased predation as evidenced by a decrease in bacterial 16S rRNA gene copies. Our results suggest that biodiversity and composition of the soil microbial community change in concert with its functioning, with consequences for native soil C stability.
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Mining lipolytic enzymes in community DNA from high Andean soils using a targeted approach.
Borda-Molina, Daniel; Montaña, José Salvador; Zambrano, María Mercedes; Baena, Sandra
2017-08-01
Microbial enrichments cultures are a useful strategy to speed up the search for enzymes that can be employed in industrial processes. Lipases have gained special attention because they show unique properties such as: broad substrate specificity, enantio- and regio-selectivity and stability in organic solvents. A major goal is to identify novel lipolytic enzymes from microorganisms living in cold extreme environments such as high Andean soils, of relevance to our study being their capability be used in industrial processes. Paramo and glacier soils from the Nevados National Park in Colombia were sampled and microbial communities enriched through a fed-batch fermentation using olive oil as an inductor substrate. After 15 days of enrichment under aerobic conditions, total DNA was extracted. Subsequently, metagenomic libraries were constructed in the cosmid vector pWEB-TNC™. After functional screening, twenty and eighteen lipolytic clones were obtained from Paramo and Glacier soil enrichments, respectively. Based on lipid hydrolysis halo dimensions, the clone (Gla1) from a glacier enrichment was selected. A gene related to lipolytic activity was subcloned to evaluate enzyme properties. Phylogenetic analysis of the identified gene showed that the encoded lipase belongs to the family GDSL from a Ralstonia-like species. Interestingly, the secreted enzyme exhibited stability at high temperature and alkaline conditions, specifically the preferred conditions at 80 °C and pH 9.0. Thus, with the identification of an enzyme with non-expected properties, in this study is shown the potential of extreme cold environments to be explored for new catalytic molecules, using current molecular biology techniques, with applications in industrial processes, which demand stability under harsh conditions.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Goldfarb, K.C.; Karaoz, U.; Hanson, C.A.
2011-04-18
Soils are immensely diverse microbial habitats with thousands of co-existing bacterial, archaeal, and fungal species. Across broad spatial scales, factors such as pH and soil moisture appear to determine the diversity and structure of soil bacterial communities. Within any one site however, bacterial taxon diversity is high and factors maintaining this diversity are poorly resolved. Candidate factors include organic substrate availability and chemical recalcitrance, and given that they appear to structure bacterial communities at the phylum level, we examine whether these factors might structure bacterial communities at finer levels of taxonomic resolution. Analyzing 16S rRNA gene composition of nucleotide analog-labeledmore » DNA by PhyloChip microarrays, we compare relative growth rates on organic substrates of increasing chemical recalcitrance of >2,200 bacterial taxa across 43 divisions/phyla. Taxa that increase in relative abundance with labile organic substrates (i.e., glycine, sucrose) are numerous (>500), phylogenetically clustered, and occur predominantly in two phyla (Proteobacteria and Actinobacteria) including orders Actinomycetales, Enterobacteriales, Burkholderiales, Rhodocyclales, Alteromonadales, and Pseudomonadales. Taxa increasing in relative abundance with more chemically recalcitrant substrates (i.e., cellulose, lignin, or tannin-protein) are fewer (168) but more phylogenetically dispersed, occurring across eight phyla and including Clostridiales, Sphingomonadalaes, Desulfovibrionales. Just over 6% of detected taxa, including many Burkholderiales increase in relative abundance with both labile and chemically recalcitrant substrates. Estimates of median rRNA copy number per genome of responding taxa demonstrate that these patterns are broadly consistent with bacterial growth strategies. Taken together, these data suggest that changes in availability of intrinsically labile substrates may result in predictable shifts in soil bacterial composition.« less
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Cao, Xian; Yu, Chunyan; Wang, Hui; Zhou, Fang; Li, Xianning
2017-04-01
In this study, the soil microbial fuel cells (MFCs) were constructed based on sandy soil to remove the refractory organic pesticide hexachlorobenzene (HCB) in topsoil by a simple method. The construction of membraneless single-chamber soil MFCs by setting up the cathode- and the anode-activated carbon, inoculating the sludge and adding the co-substrates can promote HCB removal significantly. The results showed that HCB removal efficiencies in the soils contaminated with 40, 80 and 200 mg/kg were 71.14%, 62.15% and 50.06%, respectively, which were 18.65%, 18.46% and 19.17% higher than the control, respectively. The electricity generation of soil MFCs in different HCB concentrations was analyzed. The highest power density reached was 70.8 mW/m 2 , and an internal resistance of approximately 960 Ω was obtained when an external resistance loading of 1000 Ω was connected. Meanwhile, the influences of temperature, substrate species and substrate concentrations on soil MFCs initial electricity production were investigated. The addition of the anionic surfactant sodium dodecyl sulfate (SDS) into the soil MFCs system contributed to the improvement in HCB removal efficiency.
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Native soils with their microbiotas elicit a state of alert in tomato plants.
Chialva, Matteo; Salvioli di Fossalunga, Alessandra; Daghino, Stefania; Ghignone, Stefano; Bagnaresi, Paolo; Chiapello, Marco; Novero, Mara; Spadaro, Davide; Perotto, Silvia; Bonfante, Paola
2018-02-09
Several studies have investigated soil microbial biodiversity, but understanding of the mechanisms underlying plant responses to soil microbiota remains in its infancy. Here, we focused on tomato (Solanum lycopersicum), testing the hypothesis that plants grown on native soils display different responses to soil microbiotas. Using transcriptomics, proteomics, and biochemistry, we describe the responses of two tomato genotypes (susceptible or resistant to Fusarium oxysporum f. sp. lycopersici) grown on an artificial growth substrate and two native soils (conducive and suppressive to Fusarium). Native soils affected tomato responses by modulating pathways involved in responses to oxidative stress, phenol biosynthesis, lignin deposition, and innate immunity, particularly in the suppressive soil. In tomato plants grown on steam-disinfected soils, total phenols and lignin decreased significantly. The inoculation of a mycorrhizal fungus partly rescued this response locally and systemically. Plants inoculated with the fungal pathogen showed reduced disease symptoms in the resistant genotype in both soils, but the susceptible genotype was partially protected from the pathogen only when grown on the suppressive soil. The 'state of alert' detected in tomatoes reveals novel mechanisms operating in plants in native soils and the soil microbiota appears to be one of the drivers of these plant responses. © 2018 The Authors. New Phytologist © 2018 New Phytologist Trust.
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NASA Astrophysics Data System (ADS)
Jelinkova, Vladmira; Dohnal, Michal; Picek, Tomas; Sacha, Jan
2015-04-01
Understanding the performance of technogenic substrates for green roofs is a significant task in the framework of sustainable urban planning and water/energy management. The potential retention and detention of the anthropogenic, light weight soil systems and their temporal soil structure changes are of major importance. A green roof test segment was built to investigate the benefits of such anthropogenic systems. Adaptable low-cost system allows long-term monitoring of preferred characteristics. Temperature and water balance measurements complemented with meteorological observations and knowledge of physical properties of the substrates provide basis for detailed analysis of thermal and hydrological regime in green roof systems. The first results confirmed the benefits of green roof systems. The reduction of temperature fluctuations as well as rainfall runoff was significant. Depending on numerous factors such substrate material or vegetation cover the test green roof suppressed the roof temperature amplitude for the period analyzed. The ability to completely prevent (light rainfall events) or reduce and delay (medium and heavy rainfall events) the peak runoff was also analyzed. Special attention is being paid to the assessment of soil structural properties related to possible aggregation/disaggregation, root growth, weather conditions and associated structural changes using non-invasive imaging method. X-ray computed microtomography of undisturbed soil samples (taken from experimental segments) is used for description of pore space geometry, evaluation of surface to volume ratio, additionally for description of cracks and macropores as a product of soil flora and fauna activity. The information from computed tomography imaging will be used for numerical modeling of water flow in variable saturated porous media. The research was realized as a part of the University Centre for Energy Efficient Buildings supported by the EU and with financial support from the Czech Science Foundation under project number 14-10455P.
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Mineral Control of Soil Carbon Dynamics in Forest Soils: A Lithosequence Under Ponderosa Pine
NASA Astrophysics Data System (ADS)
Heckman, K. A.; Welty-Bernard, A.; Rasmussen, C.; Schwartz, E.; Chorover, J.
2008-12-01
The role of soil organic carbon in regulating atmospheric CO2 concentration has spurred interest in both quantifying existing soil C stocks and modeling the behavior of soil C under climate change scenarios. Soil parent material exerts direct control over soil organic carbon content through its influence on soil pH and mineral composition. Soil acidity and mineral composition also influence soil microbial community composition and activity, thereby controlling soil respiration rates and microbial biomass size. We sampled a lithosequence of four parent materials (rhyolite, granite, basalt, limestone) under Pinus ponderosa to examine the effects of soil mineralogy and acidity on soil organic carbon content and soil microbial community. Three soil profiles were examined on each parent material and analyzed by X-ray diffraction, pH, selective dissolution, C and N content, and 13C signature. Soils from each of the four parent materials were incubated for 40 days, and microbial communities were compared on the basis of community composition (as determined through T-RFLP analysis), specific metabolic activity, biomass, δ13C of respired CO2, and cumulative amount of C mineralized over the course of the incubation. Soil C content varied significantly among soils of different parent material, and was strongly and positively associated with the abundance of Al-humus complexes r2 = 0.71; P < 0.0001, Fe-humus complexes r2 = 0.74; P = 0.0003, and crystalline Fe-oxide content r2 = 0.63; P = 0.0023. Microbial community composition varied significantly among soils and showed strong associations with soil pH 1:1 in KCl; r2 = 0.87; P < 0.0001, concentration of exchangeable Al r2 = 0.81; P < 0.0001, amorphous Fe oxide content r2 = 0.59; P < 0.004, and Al-humus content r2 = 0.35; P < 0.04. Mineralization rates, biomass and δ13C of respired CO2 differed among parent materials, and also varied with incubation time as substrate quality and N availability changed. The results demonstrate that within a specific ecosystem type, soil parent material exerts significant control over the lability and bioavailability of soil C and soil microbial community composition. We suggest that soil parent material and mineralogy are critical parameters for predicting soil C dynamics and recalcitrance of soil C stocks.
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Sulfate reduction in freshwater wetland soils and the effects of sulfate and substrate loading
DOE Office of Scientific and Technical Information (OSTI.GOV)
Feng, J.; Hsieh, Y.P.
1998-07-01
Elevated sulfate and organic C loadings in freshwater wetlands could stimulate dissimilatory sulfate reduction that oxidizes organic C, produces hydrogen sulfide and alkalinity, and sequesters trace metals. The authors determined the extent of sulfate reduction in two freshwater wetland soils, that is black gum (Nyssa biflona) swamp soils and titi (Cliftonia monophylla) swamp soils, in northern Florida. They also investigated the potential of sulfate reduction in the wetland soils by adding sulfate, organic substrate, and lime. Sulfate reduction was found to be an active process in both swamp soils without any amendment, where the pore water pH was as lowmore » as 3.6 and sulfate concentration was as low as 5 mg L{sup {minus}1}. Without amendment, 11 to 14% of organic C was oxidized through sulfate reduction in the swamp soils. Sulfate loading, liming, and substrate addition significantly increased sulfate reduction in the black gum swamp soil, but none of those treatments increase sulfate reduction in the titi swamp soil. The limiting factor for sulfate reduction in the titi swamp soil were likely texture and soil aggregate related properties. The results suggested that wastewater loading may increase sulfate reduction in some freshwater wetlands such as the black swamps while it has no stimulating effect on other wetlands such as the titi swamps.« less
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Strontium source and depth of uptake shifts with substrate age in semiarid ecosystems
NASA Astrophysics Data System (ADS)
Coble, Ashley A.; Hart, Stephen C.; Ketterer, Michael E.; Newman, Gregory S.; Kowler, Andrew L.
2015-06-01
Without exogenous rock-derived nutrient sources, terrestrial ecosystems may eventually regress or reach a terminal steady state, but the degree to which exogenous nutrient sources buffer or slow to a theoretical terminal steady state remains unclear. We used strontium isotope ratios (87Sr/86Sr) as a tracer and measured 87Sr/86Sr values in aeolian dust, soils, and vegetation across a well-constrained 3 Myr semiarid substrate age gradient to determine (1) whether the contribution of atmospheric sources of rock-derived nutrients to soil and vegetation pools varied with substrate age and (2) to determine if the depth of uptake varied with substrate age. We found that aeolian-derived nutrients became increasingly important, contributing as much as 71% to plant-available soil pools and tree (Pinus edulis) growth during the latter stages of ecosystem development in a semiarid climate. The depth of nutrient uptake increased on older substrates, demonstrating that trees in arid regions can acquire nutrients from greater depths as ecosystem development progresses presumably in response to nutrient depletion in the more weathered surface soils. Our results demonstrate that global and regional aeolian transport of nutrients to local ecosystems is a vital process for ecosystem development in arid regions. Furthermore, these aeolian nutrient inputs contribute to deep soil nutrient pools, which become increasingly important for maintaining plant productivity over long time scales.
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Masyagina, O V; Tokareva, I V; Prokushkin, A S
2016-12-15
Periodical ground fires of high frequency in permafrost forest ecosystems of Siberia (Russian Federation) are essential factors determining quantitative and qualitative parameters of permafrost soil organic matter. Specific changes in physical and chemical parameters and microbial activity of permafrost soil mineral horizons of northern taiga larch stands were revealed after heating at high temperatures (150-500°C) used for imitation of different burn intensities. Burning at 150-200°C resulted in decreasing of soil pH, whilst heating at 300-500°C caused increase of pH compare to unheated soils. Water-soluble organic carbon concentration in permafrost soils heated at 150-200°C was much higher than that of unheated soils. All these changes determined soil microbial activity in heated soils. In particular, in soils heated at 300-500°C there was momentary stimulating effect on substrate-induced respiration registered and on basal respiration values in soils burned at 150°C and 300-400°C. Four-month laboratory incubation of permafrost soils heated at different temperatures showed stimulation of microbial activity in first several days after inoculation due to high substrate availability after heating. Then soon after that soil microbial community started to be depleted on substrate because of decreasing water-soluble organic carbon, C and N content and it continued to the end of incubation. Copyright © 2016 Elsevier B.V. All rights reserved.
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NASA Astrophysics Data System (ADS)
Zimmermann, Claudia; Schaaf, Wolfgang
2010-05-01
In the initial phase of soil formation interactions between solid and liquid phases and processes like mineral weathering, formation of reactive surfaces and accumulation of organic matter play a decisive role in developing soil properties. As part of the Transregional Collaborative Research Centre (SFB/TRR 38) 'Patterns and processes of initial ecosystem development' in an artificial catchment, these interactions are studied at the catchment 'Chicken Creek' (Gerwin et al. 2009). To link the interactions between soil solid phase and soil solution at the micro-scale with observed processes at the catchment scale, microcosm experiments under controlled laboratory conditions were carried out. Main objectives were to determine the transformation processes of C and N from litter decomposition within the gaseous, liquid and solid phase, the interaction with mineral surfaces and its role for the establishment of biogeochemical cycles. The microcosm experiments were established in a climate chamber at constant 10 ° C. In total 48 soil columns (diameter: 14.4 cm; height: 30 cm) were filled with two different quaternary substrates (sand and loamy sand) representing the textural variation within the catchment at a bulk density of 1.4-1.5 g*cm-3. The columns were automatically irrigated four times a day with 6.6 ml each (corresponding to 600 mm*yr-1). The gaseous phase in the headspace of the microcosms was analysed continuously for CO2 and N2O contents. C and N transformation processes were studied using 13C and 15N labelled litter of two different plant species occurring at the catchment (Lotus corniculatus, Calamagrostis epigejos) that was incorporated into the microcosm surface. All treatments including a control ran with four replicates over a period of 40 weeks. Two additional microcosms act as pure litter controls where substrate was replaced by glass pearls. Litter and substrate were analysed before and after the experiment. Percolate was continuously collected and analyzed in two weeks intervals for C and N contents (including δ13C), pH and ion concentrations. The results show that the initial phase of the experiment is characterized by intensive leaching of C and N from the litter and transformation as well as leaching from the substrate. Calcium leaching is caused mainly by carbonate dissolution from the substrates. In contrast, magnesium and especially potassium are leached in initially high amounts from the litter, but are strongly retained in the soil. The addition of litter promotes microbial CO2 production as shown by a strong increase of respiration due to easily available organic substances at the beginning of the experiment. Litter of L. corniculatus induced also a high initial peak in N2O emission as well as higher nitrification and NO3-N leaching. Leaching of DOC and TDN was clearly affected by the substrate texture, illustrated by intensive DOC leaching from the sand at the beginning of the experiment but shifting later to higher leaching rates from the loamy sand. References: Gerwin W, Schaaf W, Biemelt D, Fischer A, Winter S, Hüttl RF (2009) The artificial catchment 'Chicken Creek' (Lusatia, Germany) - a landscape laboratory for interdisciplinary studies of initial ecosystem development. Ecolological Engineering 35, 1786-1796.
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Halotolerant microbial consortia able to degrade highly recalcitrant plant biomass substrate.
Cortes-Tolalpa, Larisa; Norder, Justin; van Elsas, Jan Dirk; Falcao Salles, Joana
2018-03-01
The microbial degradation of plant-derived compounds under salinity stress remains largely underexplored. The pretreatment of lignocellulose material, which is often needed to improve the production of lignocellulose monomers, leads to high salt levels, generating a saline environment that raises technical considerations that influence subsequent downstream processes. Here, we constructed halotolerant lignocellulose degrading microbial consortia by enriching a salt marsh soil microbiome on a recalcitrant carbon and energy source, i.e., wheat straw. The consortia were obtained after six cycles of growth on fresh substrate (adaptation phase), which was followed by four cycles on pre-digested (highly-recalcitrant) substrate (stabilization phase). The data indicated that typical salt-tolerant bacteria made up a large part of the selected consortia. These were "trained" to progressively perform better on fresh substrate, but a shift was observed when highly recalcitrant substrate was used. The most dominant bacteria in the consortia were Joostella marina, Flavobacterium beibuense, Algoriphagus ratkowskyi, Pseudomonas putida, and Halomonas meridiana. Interestingly, fungi were sparsely present and negatively affected by the change in the substrate composition. Sarocladium strictum was the single fungal strain recovered at the end of the adaptation phase, whereas it was deselected by the presence of recalcitrant substrate. Consortia selected in the latter substrate presented higher cellulose and lignin degradation than consortia selected on fresh substrate, indicating a specialization in transforming the recalcitrant regions of the substrate. Moreover, our results indicate that bacteria have a prime role in the degradation of recalcitrant lignocellulose under saline conditions, as compared to fungi. The final consortia constitute an interesting source of lignocellulolytic haloenzymes that can be used to increase the efficiency of the degradation process, while decreasing the associated costs.
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Influence of organic substrates on the kinetics of bacterial As(III) oxidation
NASA Astrophysics Data System (ADS)
Lescure, T.; Joulian, C.; Bauda, P.; Hénault, C.; Battaglia-Brunet, F.
2012-04-01
Soil microflora plays a major role on the behavior of metals and metalloids. Arsenic speciation, in particular, is related to the activity of bacteria able to oxidize, reduce or methylate this element, and determines mobility, bioavailability and toxicity of As. Arsenite (AsIII) is more toxic and more mobile than arsenate (AsV). Bacterial As(III)-oxidation tends to reduce the toxicity of arsenic in soils and the risk of transfer toward underlying aquifers, that would affect the quality of water resources. Previous results suggest that organic matter may affect kinetics or efficiency of bacterial As(III)-oxidation in presence of oxygen, thus in conventional physico-chemical conditions of a surface soil. Different hypothesis can be proposed to explain the influence of organic matter on As(III) oxidation. Arsenic is a potential energy source for bacteria. The presence of easily biodegradable organic matter may inhibit the As(III) oxidation process because bacteria would first metabolize these more energetic substrates. A second hypothesis would be that, in presence of organic matter, the Ars system involved in bacterial resistance to arsenic would be more active and would compete with the Aio system of arsenite oxidation, decreasing the global As(III) oxidation rate. In addition, organic matter influences the solubility of iron oxides which often act as the main pitfalls of arsenic in soils. The concentration and nature of organic matter could therefore have a significant influence on the bioavailability of arsenic and hence on its environmental impact. The influence of organic matter on biological As(III) oxidation has not yet been determined in natural soils. In this context, soil amendment with organic matter during operations of phytostabilization or, considering diffuse pollutions, through agricultural practices, may affect the mobility and bio-availability of the toxic metalloid. The objective of the present project is to quantify the influence of organic matter on the bacterial speciation of arsenic in contaminated soils. Moreover, the biogeochemical consequences of this phenomenon on the mobility and ecotoxicity of this metalloid will be studied. The first task of this program is the precise and systematic investigation of the influence of different types and concentrations of organic matters on the activity of As(III)-oxidizing pure strains. Influence of aspartate, succinate (simple substrates) and yeast extract (complex substrate) on As(III)-oxidation kinetics has been studied. For each experiment, the bacterial growth and the expression of genes involved in the speciation of arsenic, i.e. aio and ars genes, has been monitored. A direct perspective of this work will be to perform experiments with humic and fulvic acids (complex organic matter commonly found in soils), and with water-extracted organic matter from polluted soils. Then the As(III)-oxidation activity of bacterial communities extracted from contaminated soils will be followed. These assays should allow the screening of conditions which will be applied in subsequent experiments with several real contaminated soils, including a former mining site, impacted industrial sites, and a forest soil heavily contaminated after arsenical ammunitions storage. This work is co-funded by BRGM and ADEME (convention TEZ 11-16).
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Karas, Panagiotis A; Makri, Sotirina; Papadopoulou, Evangelia S; Ehaliotis, Constantinos; Menkissoglu-Spiroudi, Urania; Karpouzas, Dimitrios G
2016-02-01
Citrus fruit-packaging plants (FPP) produce large wastewater volumes with high loads of fungicides like ortho-phenylphenol (OPP) and imazalil (IMZ). No methods are in place for the treatment of those effluents and biobeds appear as a viable alternative. We employed a column study to investigate the potential of spent mushroom substrate (SMS) of Pleurotus ostreatus, either alone or in mixture with straw and soil plus a mixture of straw /soil to retain and dissipate IMZ and OPP. The role of P. ostreatus on fungicides dissipation was also investigated by studying in parallel the performance of fresh mushroom substrate of P. ostreatus (FMS) and measuring lignolytic enzymatic activity in the leachates. All substrates effectively reduced the leaching of OPP and IMZ which corresponded to 0.014-1.1% and 0.120-0.420% of their initial amounts respectively. Mass balance analysis revealed that FMS and SMS/Straw/Soil (50/25/25 by vol) offered the most efficient removal of OPP and IMZ from wastewaters respectively. Regardless of the substrate, OPP was restricted in the top 0-20cm of the columns and was bioavailable (extractable with water), compared to IMZ which was less bioavailable (extractable with acetonitrile) but diffused at deeper layers (20-50, 50-80cm) in the SMS- and Straw/Soil-columns. PLFAs showed that fungal abundance was significantly lower in the top layer of all substrates from where the highest pesticide amounts were recovered suggesting an inhibitory effect of fungicides on total fungi in the substrates tested. Our data suggest that biobeds packed with SMS-rich substrates could ensure the efficient removal of IMZ and OPP from wastewaters of citrus FPP. Copyright © 2015 Elsevier Inc. All rights reserved.
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NASA Astrophysics Data System (ADS)
Fischer, T.; Veste, M.; Wiehe, W.; Lange, P.
2009-04-01
First colonizers of new land surfaces are cryptogames which often form biological soil crusts (BSC) covering the first millimetre of the top soil in many ecosystems from polar to desert ecosystems. These BSC are assemblages of cyanobacteria, green algae, mosses, liverworts, fungi and/or lichens. The development of soil surface crusts plays a major role for the further vegetation pattern through changes to the physico-chemical conditions and influencing various ecosystem processes. We studied the development of BSC on quaternary substrate of an initial artificial water catchment in Lusatia, Germany. Due to lack of organic matter in the geological substrate, photoautotrophic organisms like green algae and cyanobacteria dominated the initial phases of ecosystem development and, hence, of organo-mineral ineractions. We combined SEM/EDX and FTIR microscopy to study the contact zone of extracellular polymeric substances (EPS) of green algae and cyanobacteria with quartz, spars and mica on a >40 µm scale in undisturbed biological soil crusts, which had a maximum thickness of approx. 2 mm. SEM/EDX microscopy was used to determine the spatial distribution of S, Ca, Fe, Al, Si and K in the profiles, organic compounds were identified using FTIR microscopy. Exudates of crust organisms served as cementing material between sand particles. The crust could be subdivided into two horizontal layers. The upper layer, which had a thickness of approx. 200 µm, is characterized by accumulation of Al and K, but absence of Fe in microbial derived organic matter, indicating capture of weathering products of feldspars and mica by microbial exudates. The pore space between mineral particles was entirely filled with organic matter here. The underlying layer can be characterized by empty pores and organo-mineral bridges between the sand particles. Contrarily to the upper layer of the crust, Fe, Al and Si were associated with organic matter here but K was absent. Highest similarity of the FTIR spectra of EPS was observed with carbohydrates, using cellulose, dextran and humic acid Na salt as controls. Obviously, humification does not play a key role during this initial phase of soil formation. It was hypothesized that biological soil crusts facilitate the weathering of mineral substrate by (I) circumventing loss of fine particles with erosion, (II) by chemical treatment of minerals and (III) by catching small mineral-particles by glutinous EPS on the soil surface from the surrounding area.
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Transformation of soil organics under extreme climate events: a project description
NASA Astrophysics Data System (ADS)
Blagodatskaya, Evgenia
2017-04-01
Recent climate scenarios predict not only continued global warming but also an increased frequency and intensity of extreme climatic events such as strong changes in temperature and precipitation with unusual regional dynamics. Weather anomalies at European territory of Russia are currently revealed as long-term drought and strong showers in summer and as an increased frequency of soil freezing-thawing cycles. Climate extremes totally change biogeochemical processes and elements cycling both at the ecosystem level and at the level of soil profile mainly affecting soil biota. Misbalance in these processes can cause a reduction of soil carbon stock and an increase of greenhouse gases emission. Our project aims to reveal the transformation mechanisms of soil organic matter caused by extreme weather events taking into consideration the role of biotic-abiotic interactions in regulation of formation, maintenance and turnover of soil carbon stock. Our research strategy is based on the novel concept considering extreme climatic events (showers after long-term droughts, soil flooding, freezing-thawing) as abiotic factors initiating a microbial succession. Study on stoichiometric flexibility of plants under climate extremes as well as on resulting response of soil heterotrophs on stoichiometric changes in substrate will be used for experimental prove and further development of the theory of ecological stoichiometry. The results enable us to reveal the mechanisms of biotic - abiotic interactions responsible for the balance between mobilization and stabilization of soil organic matter. Identified mechanisms will form the basis of an ecosystem model enabled to predict the effects of extreme climatic events on biogenic carbon cycle in the biosphere.
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NASA Astrophysics Data System (ADS)
Blagodatskaya, E.; Blagodatsky, S.; Kuzyakov, Y.
2009-04-01
The double-stranded DNA (dsDNA) content in soil can serve as a measure of microbial biomass under near steady-state conditions and quantitatively reflect the exponential microbial growth initiated by substrate addition. The yield of respired CO2 per microbial biomass unit (expressed as DNA content) could be a valuable physiological indicator reflecting state of soil microbial community. Therefore, investigations combining both analyses of DNA content and respiration of soil microorganisms under steady-state and during periods of rapid growth are needed. We studied the relationship between CO2 evolution and microbial dsDNA content in native and glucose-amended samples of root-free and rhizosphere soil under Beta vulgaris (Cambisol, loamy sand from the field experiment of the Institute of Agroecology FAL, Braunschweig, Germany). Quantity of dsDNA was determined by direct DNA isolation from soil with mechanic and enzymatic disruption of microbial cell walls with following spectrofluorimetric detection with PicoGreen (Blagodatskaya et al., 2003). Microbial biomass and the kinetic parameters of microbial growth were estimated by dynamics of the CO2 emission from soil amended with glucose and nutrients (Blagodatsky et al., 2000). The CO2 production rate was measured hourly at 22оС using an automated infrared-gas analyzer system. The overall increase in microbial biomass, DNA content, maximal specific growth rate and therefore, in the fraction of microorganisms with r-strategy were observed in rhizosphere as compared to bulk soil. The rhizosphere effect for microbial respiration, biomass and specific growth rate was more pronounced for plots with half-rate of N fertilizer compared to full N addition. The DNA content was significantly lower in bulk compared to rhizosphere soil both before and during microbial growth initiated by glucose amendment. Addition of glucose to the soil strongly increased the amount of CO2 respired per DNA unit. Without substrate addition the VCO2-to-total DNA ratios were lower than 0.1 µg CO2-C µg-1 total DNA h-1 whereas during exponential microbial growth these values increased consistently and exceeded 1 µg CO2-C µg-1 DNA h-1. Thus, the VCO2-to-total DNA ratio strongly changes along with the physiological state of soil microorganisms and can be used as valuable physiological parameter. In growing microorganisms the quantity of CO2 evolved per unit of newly formed DNA was identical in rhizosphere and root free soil and averaged for 13.5 ± 1.1 µg CO2-C µg-1 newly formed DNA. The CO2 yield per unit of newly formed DNA allows the estimation of microbial growth efficiency and validation of specific growth rates obtained during kinetic analysis of respiration curves. The study was supported by European Commission (Marie Curie IIF program, project MICROSOM) and by Alexander von Humboldt Foundation. References: Blagodatskaya EV, Blagodatskii SA, Anderson TH. 2003. Quantitative Isolation of Microbial DNA from Different Types of Soils of Natural and Agricultural Ecosystems. Microbiology 72(6):744-749. Blagodatsky SA, Heinemeyer O, Richter J. 2000. Estimating the active and total soil microbial biomass by kinetic respiration analysis. Biology and Fertility of Soils 32(1):73-81.
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W. J. Massman
2006-01-01
Advective flows within soils and snowpacks caused by pressure fluctuations at the upper surface of either medium can significantly influence the exchange rate of many trace gases from the underlying substrate to the atmosphere. Given the importance of many of these trace gases in understanding biogeochemical cycling and global change, it is crucial to quantify (as much...
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Mitigation of Cd accumulation in paddy rice (Oryza sativa L.) by Fe fertilization.
Chen, Zhe; Tang, Ye-Tao; Yao, Ai-Jun; Cao, Jian; Wu, Zhuo-Hao; Peng, Zhe-Ran; Wang, Shi-Zhong; Xiao, Shi; Baker, Alan J M; Qiu, Rong-Liang
2017-12-01
Cadmium uptake in rice is believed to be mediated by the Fe transport system. Phyto-available Cd can be changed by Fe fertilization of substrates. This work investigated whether and how Fe fertilization affects mitigation of Cd accumulation in paddy rice. A 90-d soil column experiment was conducted to study the change of Cd and Fe availability in soil after Fe fertilization (ionic and chelated Fe). A low-Cd accumulating cultivar (TY116) and a high-Cd accumulating cultivar (JY841) were grown in two Cd-polluted paddy soils amended with chelated Fe fertilizers. Additionally, both cultivars were grown in hydroponics to compare Fe-related gene expression in EDDHAFe-deficient and EDDHAFe-sufficient roots. The column experiment showed that EDTANa 2 Fe(II) and EDDHAFe(III) fertilization had a better mitigation effect on soil Cd availability compared to FeSO 4 ·7H 2 O. Moreover, the field experiment demonstrated that these two chelated fertilizations could reduce Cd concentrations in brown rice by up to 80%. Iron concentrations in the brown rice were elevated by Fe chelates. Compared to EDDHAFe(III), EDTANa 2 Fe(II) fertilization had a stronger mitigation effect by generating more EDTANa 2 Cd(II) in the soil solution to decrease phyto-available Cd in the soil. While EDDHAFe(III) fertilization could increase soil pH and decrease soil Eh which contributed to decreasing phyto-available Cd in a contaminated soil. In the hydroponic experiment, Fe sufficiency significantly reduced Cd concentrations in above-ground organs. In some cases, the expression of OsIRT1, OsNRAMP1 and OsNRAMP5 was inhibited under Fe sufficiency relative to Fe deficiency conditions. These results suggest that mitigation of rice Cd by Fe chelate fertilization results from a decrease in available Cd in substrates and the inhibition of the expression of several Fe-related genes in the IRT and NRAMP families. Copyright © 2017 Elsevier Ltd. All rights reserved.
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NASA Astrophysics Data System (ADS)
Pérez, Francisco L.
2010-04-01
Globular mosses were found in Haleakala's crater (Maui) at five locations between 2175 and 2725 m; the highest-altitude site, with abundant epilithic mosses growing on alkali-olivine basalt outcrops and a large mossball population, was studied. Mossballs form when moss cushions are dislodged from rocks but continue growing unattached to substrate; detachment agents include rainsplash, desiccation, wind, frost, and disturbance by birds (dark-rumped petrels) that burrow nests under outcrops, or by goats. When loosened, moss polsters are transported down steep (26-34°) slopes by different geomorphic processes, including frost—mainly needle ice—activity, runoff, and wind. Mossballs contained two species, Grimmia trichophylla Grev. and Grimmia torquata Drumm., growing separately or commingled. Weight, size, and various shape indices were determined for 260 specimens. Shape and size were correlated; larger mosses become less spheroidal because heavier specimens are less disturbed by needle ice, remaining immobile for increasingly longer time periods, thus becoming flattened. Distance of downslope transport from source rockwalls was measured for 330 specimens; 83% shifted ≤ 100 cm, but only ˜ 5% had moved > 200-839 cm. Heavier mossballs moved short distances, thus ˜ 88% of all biomass remained within 200 cm from outcrops. Substrate soils were compared with those within globoids; surface site soils were much coarser than mossball grains. Twelve substrate samples had, on average, 21.3% gravel (≥ 2 mm), 6.1% fines (≤ 0.063 mm) and 2.1% organic matter; in contrast, 12 mossballs contained < 0.1% gravel, 47.9% fines, and 34.1% organic matter. G. torquata polsters had slightly finer soil (53.2%) than G. trichophylla (43.5%). This significant fine-grain concentration results as mosses trap aeolian dust among stems and leaves; ˜ 91% of moss grains were ≤ 0.25 mm, but only ˜ 30% of substrate particles measured ≤ 0.25 mm. Such fine texture, along with abundant organic matter contributed by moss growth, generates greater water-storage capacity in globoids (˜ 310%) than in site soils (16.8%); this is ecologically significant for mossball development and survival during drought periods. This area is frequently subjected to freezing temperatures, while fog interception from incoming tradewinds contributes significant moisture amounts to precipitation. Ground disturbance by frost activity seemed significant. Needle ice grows frequently on this slope, as evidenced by widespread presence of miniature sorted stripes, striated soils, fine-earth flags below stones, gaps around stones, and fine-soil raised patches, observed during multiple visits. Biogeomorphic interactions between mossballs and substrate at Haleakala are briefly discussed from the perspective of self-organized criticality, and interpreted to represent a self-replicating moss-dispersal system dependent on slope geomorphic processes.
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Surface Analysis Evaluation of Handwipe Cleaning for the Space Shuttle RSRM
NASA Technical Reports Server (NTRS)
Lesley, Michael W.; Anderson, Erin L.; McCool, Alex (Technical Monitor)
2001-01-01
In this paper we discuss the role of surface-sensitive spectroscopy (electron spectroscopy for chemical analysis, or ESCA) in the selection of solvents to replace 1,1,1-trichloroethane in handwipe cleaning of bonding surfaces on NASA's Space Shuttle Reusable Solid Rocket Motor (RSRM). Removal of common process soils from a wide variety of metallic and polymeric substrates was characterized. The cleaning efficiency was usually more dependent on the type of substrate being cleaned and the specific process soil than on the solvent used. A few substrates that are microscopically rough or porous proved to be difficult to clean with any cleaner, and some soils were very tenacious and difficult to remove from any substrate below detection limits. Overall, the work showed that a wide variety of solvents will perform at least as well as 1,1,1-trichloroethane.
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Torn, M. S.; Chabbi, A.; Crill, P.; ...
2015-08-24
The soil profile encompasses a remarkably large range of biogeochemical conditions, processes, and fluxes. For example, in most soils the turnover time of soil organic carbon (SOC) varies more between the soil surface and 1m deep than between surface soils in the tropics vs. the Arctic (Torn et al., 2009). Moreover, radiocarbon observations in different soil types show that SOC decomposition rates decrease with depth, with residence times of years to decades at the soil surface to over 10 000 years at 1m deep (e.g., Torn et al., 2002). There are many competing hypotheses for this steep decline in SOCmore » turnover with depth. They can be grouped loosely into physical–chemical accessibility, energetic limits to microbial activity, microclimate and pH, and physical disconnect between decomposers and substrate. While all of these mechanisms control deep SOC cycling, data are lacking for unraveling their relative importance in different soils under different environmental conditions. However, critical knowledge for predicting soil responses to global change, because fairly rapid loss (or gain) of old and/or deep SOC stocks is possible and more than 80% of the world’s SOC is found below 20 cm depth (Jobbágy and Jackson, 2000). Currently, the soil modules within Earth system models are parameterized for surface soil and lack mechanisms important for stabilization and losses of deep SOC. We, therefore, suggest that a critical challenge is to achieve process-level understanding at the global level and the ability to predict whether, and how, the large stores of deep, old SOC are stabilized and lost under global change scenarios.« less
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NASA Astrophysics Data System (ADS)
Jin, V. L.; Schaeffer, S. M.; Ziegler, S. E.; Evans, R. D.
2011-06-01
Changes in the rates of nitrogen (N) cycling, microbial carbon (C) substrate use, and extracellular enzyme activities in a Mojave Desert ecosystem exposed to elevated atmospheric CO2 suggest shifts in the size and/or functional characteristics of microbial assemblages in two dominant soil microsites: plant interspaces and under the dominant shrub Larrea tridentata. We used ester-linked phospholipid fatty acid (PLFA) biomarkers as a proxy for microbial biomass to quantify spatial and temporal differences in soil microbial communities from February 2003 to May 2005. Further, we used the 13C signature of the fossil CO2 source for elevated CO2 plots to trace recent plant C inputs into soil organic matter (SOM) and broad microbial groups using δ13C (‰). Differences between individual δ13CPLFA and δ13CSOM for fungal biomarkers indicated active metabolism of newer C in elevated CO2 soils. Total PLFA-C was greater in shrub microsites compared to plant interspaces, and CO2 treatment differences within microsites increased under higher soil water availability. Total, fungal, and bacterial PLFA-C increased with decreasing soil volumetric water content (VWC) in both microsites, suggesting general adaptations to xeric desert conditions. Increases in fungal-to-bacterial PLFA-C ratio with decreasing VWC reflected functional group-specific responses to changing soil water availability. While temporal and spatial extremes in resource availability in desert ecosystems contribute to the difficulty in identifying common trends or mechanisms driving microbial responses in less extreme environments, we found that soil water availability and soil microsite interacted with elevated CO2 to shift fungal and bacterial biomarker abundances in Mojave Desert soils.
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The use of biochar substrates for soil reclamation - results of experiments in Northeastern Germany
NASA Astrophysics Data System (ADS)
Lukas, Stefan; Haubold-Rosar, Michael
2017-04-01
After the model of the very fertile "Terra preta do Indio" in Amazonia, the joint project "LaTerra" has been taken up a new technology for the production of organic substrates using biochar as admixture to the composting and fermentation of biomass to test its application for soil improvement, reclamation and remediation purposes. Processing organic materials or residues and the creation of high quality organic soil improving materials will close material cycles and contribute to the value added on a regional scale. This should be an essential part of a sustainable material flow management. The presentation will focus on the application of biochar substrates for the reclamation of sandy soils in Northeastern Germany. Lignite mining activities leave raw soils without humus on dumps and tips. The rapid formation and maintenance of a balanced humus and nutrient budget is of great importance. Field, lysimeter and pot experiments were part of the research program in order to find out the impact of biochar substrate application on soil functions and plant growth and to derive quality criteria and recommendations for practice. The results of the experiments show that application of biochar substrates (BCS) improved soil properties like nutrient supply, organic carbon content, water storage and cation exchange capacity. However, crop yields did not increase in the year of BCS application on the test sites or even decreased on the dumped soil with rising amounts of BCS. This is a consequence of nitrogen immobilization and sorption in the soils treated with BCS. Therefore, BCS applications should be combined with mineral fertilization of nitrogen and BCS production should be modified aiming to improve contents and release of plant available nitrogen. In the third year after BCS application variants treated with 60 t BCS ha-1 (15 Vol.-% biochar) showed highest yields, exceeding the variants with mineral fertilization. On the dumped soil, in the fourth and fifth year after application all variants exceeded yields of mineral fertilization by 5 to 15 % with maximum in variants treated with 90 t BCS (15 Vol.-% biochar) ha-1.
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Volatile metal deposits on lunar soils - Relation to volcanism
NASA Technical Reports Server (NTRS)
Reed, G. W., Jr.; Jovanovic, S.; Allen, R. O., Jr.
1977-01-01
Parallel leaching and volatilization experiments conducted on lunar samples and similar experiments on sphalerite do not supply the information needed to resolve the question of the chemical nature of Pb-204, Zn, Bi, and Tl deposits on lunar soil surfaces. It is proposed that in Apollo 17 mare and terra soils the fractions of Pb-204, Zn, and Tl that are insoluble under mild, hot pH 5 HNO3, leaching conditions and involatile at 600 C were originally surface deposits which became immobilized by migration into the silicate substrate or by chemisorption. Most of the Bi does not seem to be the result of such a deposit. The implication is also that the soils, over their respective times of evolution, were exposed to heavy metal vapors or that an episodic exposure occurred after they had evolved. A sequence of events is proposed to account for orange 74220 and black 74001 glasses by lava fountaining and for soil 74241 as tephra from an explosive volcanic eruption.
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Manzoni, S.; Katul, G.
2014-09-30
We report that soil microbial respiration rates decrease with soil drying, ceasing below water potentials around -15 MPa. A proposed mechanism for this pattern is that under dry conditions, microbes are substrate limited because solute diffusivity is halted due to breaking of water film continuity. However, pore connectivity estimated from hydraulic conductivity and solute diffusivity (at Darcy's scale) is typically interrupted at much less negative water potentials than microbial respiration (-0.1 to -1 MPa). It is hypothesized here that the more negative respiration thresholds than at the Darcy's scale emerge because microbial activity is restricted to microscale soil patches thatmore » retain some hydrological connectivity even when it is lost at the macroscale. This hypothesis is explored using results from percolation theory and meta-analyses of respiration-water potential curves and hydrological percolation points. Lastly, when reducing the spatial scale from macroscale to microscale, hydrological and respiration thresholds become consistent, supporting the proposed hypothesis.« less
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Tan, Xiangping; Liu, Yanju; Yan, Kaihong; Wang, Ziquan; Lu, Guannan; He, Yike; He, Wenxiang
2017-02-01
Dehydrogenase activity (DHA) is an important indicator of heavy metal toxicity in contaminated soils. Different instances of DHA were determined using various substrates and which could affect the description of heavy metal toxicity. Currently, too few investigations have been done on selecting appropriate substrates. This study employed indoor simulation to determine soil DHA and its response to external cadmium (Cd) using two substrates (TTC and INT). Hormesis for DHA obtained using the TTC method (DHA-TTC) in low Cd concentration was observed which was quickly inhibited in high Cd concentration. While DHA obtained using the INT method (DHA-INT) decreased slowly when Cd concentration increased. The DHA-TTC and DHA-INT in soils at Cd concentration of 500 mg kg -1 decreased 86% and 53%, respectively, compared to the control. The dose-response relationship of Cd to DHA can be well simulated using the logistic model (p < 0.01), which indicated DHA could be used to indicate soil Cd toxicity. Multiple stepwise regression analysis revealed that total organic matter (TOC) is the major factor influencing the toxicity of Cd to DHA-TTC, while TOC, pH and cation exchange capacity (CEC) are major factors influencing the toxicity of Cd to DHA-INT. The different responses of soil DHA-TTC and DHA-INT to Cd are due to the differences in electron transport chain characteristics between TTC and INT, as well as the influence of soil properties. Although both DHA-TTC and DHA-INT can monitor soil Cd contamination, DHA-INT is recommended as a superior bio-indicator to indicate and assess contamination of Cd in soil. Copyright © 2016 Elsevier Ltd. All rights reserved.
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Radiocarbon Evidence That Millennial and Fast-Cycling Soil Carbon are Equally Sensitive to Warming
NASA Astrophysics Data System (ADS)
Vaughn, L. S.; Torn, M. S.; Porras, R. C.
2017-12-01
Within the century, the Arctic is expected to shift from a sink to a source of atmospheric CO2 due to climate-induced increases in soil carbon mineralization. The magnitude of this effect remains uncertain, due in large part to unknown temperature sensitivities of organic matter decomposition. In particular, the distribution of temperature sensitivities across soil carbon pools remains unknown. New experimental approaches are needed, because studies that fit multi-pool models to CO2 flux measurements may be sensitive to model assumptions, statistical effects, and non-steady-state changes in substrate availability or microbial activity. In this study, we developed a new methodology using natural abundance radiocarbon to evaluate temperature sensitivities across soil carbon pools. In two incubation experiments with soils from Barrow, AK, we (1) evaluated soil carbon age and decomposability, (2) disentangled the effects of temperature and substrate depletion on carbon mineralization, and (3) compared the temperature sensitivities of fast- and slow-cycling soil carbon pools. From a long-term incubation, both respired CO2 and the remaining soil organic matter were highly depleted in radiocarbon. At 20 cm depth, median Δ14C values were -167‰ in respired CO2 and -377‰ in soil organic matter, corresponding to turnover times of 1800 and 4800 years, respectively. Such negative Δ14C values indicate both storage and decomposition of old, stabilized carbon, while radiocarbon differences between the mineralized and non-mineralized fractions suggest that decomposability varies along a turnover time gradient. Applying a new analytical method combining CO2 flux and Δ14C, we found that fast- and slow-cycling carbon pools were equally sensitive to temperature, with a Q10 of 2 irrespective of turnover time. We conclude that in these Arctic soils, ancient soil carbon is vulnerable to warming under thawed, aerobic conditions. In contrast to many previous studies, we found no difference in temperature sensitivity of decomposition between fast- and slow-cycling pools. These findings suggest that in these soils, carbon stabilization mechanisms other than chemical recalcitrance mediate temperature sensitivities, and even old SOC will be readily decomposable as climate warms.
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Interactions between Soil Habitat and Geographic Range Location Affect Plant Fitness
Stanton-Geddes, John; Shaw, Ruth G.; Tiffin, Peter
2012-01-01
Populations are often found on different habitats at different geographic locations. This habitat shift may be due to biased dispersal, physiological tolerances or biotic interactions. To explore how fitness of the native plant Chamaecrista fasciculata depends on habitat within, at and beyond its range edge, we planted seeds from five populations in two soil substrates at these geographic locations. We found that with reduced competition, lifetime fitness was always greater or equivalent in one habitat type, loam soils, though early-season survival was greater on sand soils. At the range edge, natural populations are typically found on sand soil habitats, which are also less competitive environments. Early-season survival and fitness differed among source populations, and when transplanted beyond the range edge, range edge populations had greater fitness than interior populations. Our results indicate that even when the optimal soil substrate for a species does not change with geographic range location, the realized niche of a species may be restricted to sub-optimal habitats at the range edge because of the combined effects of differences in abiotic and biotic effects (e.g. competitors) between substrates. PMID:22615745
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NASA Astrophysics Data System (ADS)
Hess, N. J.; Tfaily, M.; Evans, R. D.; Koyama, A.
2017-12-01
Little is known about how soils in arid ecosystems will respond to rising atmospheric CO2 concentration yet arid and semi-arid ecosystems cover more than 40% of Earth's land surface. Previous work in the Mojave Desert (Evans et al., 2014 Nature Climate Change) reported higher soil organic carbon (SOC) and total nitrogen (N) concentrations following 10 years exposure to elevated atmospheric CO2 at the Nevada Desert Free-Air-Carbon dioxide-Enrichment (FACE) Facility (NDFF). In this study, we investigated potential mechanisms that resulted in increased SOC and total N accumulation and stabilization using high resolution mass spectrometry at the NDFF site. Samples were collected from soil profiles to 1 m in depth with a 0.2 m a increment under the dominant evergreen shrub Larrea tridentata. The differences in the molecular composition and diversity of soil organic matter (SOM) were more evident in surface soils and declined with depth, and were consistent with higher SOC and total N concentrations under elevated than ambient CO2. Our molecular analysis also suggested increased root exudation and/or microbial necromass from stabilization of labile C and N contributed to SOM and N stocks. Increased microbial activity and metabolism under elevated CO2 compared to ambient plots suggested that elevated CO2 altered microbial carbon (C) use patterns, reflecting changes in the quality and quantity of SOC inputs. We found that plant-derived compounds were primary substrates for microbial activity under elevated CO2 and microbial products were the main constituents of stabilized SOM. Our results suggest that arid ecosystems are a potential large C sink under elevated CO2, give the extensive coverage of the land surface, and that labile compounds are transformed to stable SOM via microbial processes. Arid systems are limited by water, and thus may have a different C storage potential under changing climates than other ecosystems that are limited by nitrogen or phosphorus.
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Changes of soil organic matter and microbial activity in irrigated and non irrigated olive groves
NASA Astrophysics Data System (ADS)
Kavvadias, Victor; Papadopoulou, Maria; Theocharopoulos, Sideris; Vavoulidou, Evagelia; Doula, Maria; Reppas, Spiros
2014-05-01
The implementation of olive cultivation techniques in Greece has not been systematically tested under the prevailing Mediterranean conditions. A LIFE+ project was initiated (oLIVE-CLIMA; LIFE 11/ENV/000942) aiming to introduce new management practices in olive tree crops that lead to increased carbon dioxide uptake by plants as well as carbon sequestration from the atmosphere and reverse the trend of soil organic matter decline, erosion and desertification. This paper presents data on soil organic matter and microbial activity from a soil campaign in a pilot region in Greece, and particularly in the area of Chora, prefecture of Messinia, South west Peloponnese. The soil campaign took place during the period December 2012-February 2013. Twelve soil parcels of olive groves were selected (6 irrigated and 6 rainfed) and in each soil parcel six composite soil samples were taken from 0-10 cm depth at equal intervals along a straight line of the trunk of the tree to the middle of the distance from the nearest tree of the next tree series. The first three samples were under olive tree canopy. An additional composite sample was taken at depth of 10-40 cm. Soil samples were analyzed for soil physicochemical and biological properties. In this study results for total organic carbon (TOC), soil basal microbial respiration (BR), microbial biomass C (MB-C) from the region of Messinia, are presented. Organic matter was determined by dichromate oxidation. The microbial activity was measured by the amount of CO2 evolution, while microbial biomass C was determined by substrate-induced respiration, after the addition of glucose. The results showed considerable differences in TOC, BR and MB-C associated with the sampling position and soil depth. The higher TOC, BR and MB-C values, in most cases, were determined in samples taken from points under the canopy, but not close to the tree trunk compared to the sampling points outside the canopy. This indicates the positive effect of rhizosphere and the favorable soil moisture conditions under tree canopy on soil microbial activities. TOC, BR and MB-C values were considerably lower in soil depth of 10-40cm compared with 0-10 cm in both irrigated and rainfed soil parcels. Moreover BR and MB-C was higher in irrigated soil parcels compared with rainfed ones suggesting that the periodic irrigation significantly enhances the soil microbial activity. There were no considerable differences in TOC. For this the TOC and potential activity of microbial community can contribute in the soil nutrient and irrigation management guidelines in order to exploit the utilization of productive soils in the region under studied.
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Establishment and effectiveness of inoculated arbuscular mycorrhizal fungi in agricultural soils.
Köhl, Luise; Lukasiewicz, Catherine E; van der Heijden, Marcel G A
2016-01-01
Arbuscular mycorrhizal fungi (AMF) are promoted as biofertilizers for sustainable agriculture. So far, most researchers have investigated the effects of AMF on plant growth under highly controlled conditions with sterilized soil, soil substrates or soils with low available P or low inoculum potential. However, it is still poorly documented whether inoculated AMF can successfully establish in field soils with native AMF communities and enhance plant growth. We inoculated grassland microcosms planted with a grass-clover mixture (Lolium multiflorum and Trifolium pratense) with the arbuscular mycorrhizal fungus Rhizoglomus irregulare. The microcosms were filled with eight different unsterilized field soils that varied greatly in soil type and chemical characteristics and indigenous AMF communities. We tested whether inoculation with AMF enhanced plant biomass and R. irregulare abundance using a species specific qPCR. Inoculation increased the abundance of R. irregulare in all soils, irrespective of soil P availability, the initial abundance of R. irregulare or the abundance of native AM fungal communities. AMF inoculation had no effect on the grass but significantly enhanced clover yield in five out of eight field soils. The results demonstrate that AMF inoculation can be successful, even when soil P availability is high and native AMF communities are abundant. © 2015 John Wiley & Sons Ltd.
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[Limiting factors of waste land revegetation in indigenous zinc smelting areas of western Guizhou].
Lin, Wen-Jie; Xiao, Tang-Fu; Ao, Zi-Qiang; Xing, Jun; Ma, Huan-Cheng; Hu, Ting-Xing
2007-03-01
With indigenous zinc smelting waste residue, contaminated soil and background soil as test substrates, a pot experiment was conducted to study the growth characteristics of Lolium perenne and Trifolium pretense on these substrates. The results showed that the major limiting factors of waste land revegetation in indigenous zinc smelting areas of western Guizhou were the salt-alkali stress and the lower contents of organic matter, total N, available N and total K. The heavy metals in waste residue had a high concentration, but their available forms only occupied a small proportion, with low toxicity to plant but having potential harmful risk. Contaminated soil had lower concentrations of heavy metals than waste residue, but its contained heavy metals were more in available form. The constraints of revegetation on contaminated soil were the toxicity of heavy metals and the low contents of available P and K. Mixing contaminated soil with zinc smelting waste residue could be one of the effective approaches for the substrate amendment in indigenous zinc smelting areas.
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NASA Astrophysics Data System (ADS)
Billings, S. A.; Ziegler, S. E.
2012-12-01
The response of microbial resource demand to many environmental variables, including temperature and natural organic and inorganic N variability, remains poorly understood. Furthermore, we do not understand how these variables can influence CO2 release vs. C retention in cell walls, which as microbial necromass can generate long-lived soil organic matter (SOM). We explore microbial resource demand and C retention vs. release in one temperate forest and two boreal forests along a climate gradient. We characterized SOM C:N and inorganic N, extracellular enzyme activity (E), and phospholipid fatty acid (PLFA) concentration and δ13C. Experimental warming permitted us to assess how interactions between soil N status and warming influence resource demand and C flows through microbes in the two boreal soils. For all soils, we used δ13C of respired CO2 and δ13CPLFA to generate indices of C allocation to biomass vs. to respiratory costs (Δ), useful for cross-site comparisons. Decreasing values of Δ indicate a greater proportion of 13C-enriched C allocated to respiration relative to PLFA-C; changes in Δ with warming or N status thus imply that these variables can influence the physiological mechanisms determining the fate of microbial C after it is imported into the cell. We thus were able to assess the influence of soil N status and warming on substrate decay via E, the fate of microbial C from diverse substrates via Δ, and one index of microbial composition relevant to SOM formation [PLFA]. In all soils, E often varied with N status in ways predicted by stoichiometric theory. For example, the ratio of exo-enzymes associated with labile C decay to those linked to organic N decay (EC:N) increased with inorganic N, and EC:N declined as substrate C:N increased. In contrast to measures of decay, all soils exhibited distinct responses of microbial composition and C allocation to N status and warming. In the temperate forest soils, Gram+ bacteria responded positively to organic N availability and Gram- bacteria to inorganic N, while fungi responded positively to declines in both measures of soil N status. In the more northern boreal soils, actinomycete [PLFA] increased with inorganic N, while that of more southern boreal soils increased with substrate C:N; in both boreal soils, Gram+ bacteria increased with temperature. Given that cell walls of these microbes exhibit distinct propensities for forming long-lived SOM, our work illustrates how similar variation in N status and temperature can drive divergent patterns of biomass relevant to SOM formation. Sensitivity of patterns of C allocation to these variables also contrasted between these soils. In the temperate soils, Δ did not vary with soil N status nor with E, implying that microbes' C allocation patterns were not driven N status or by the C's organic precursor. In both boreal soils, Δ declined with warming, and as EC or EC:N increased. Though N status of the boreal soils drove resource demand similarly as in the temperate forest, the fate of boreal microbial C varied with N status and temperature. Because microbial C substrate use varied with warming in the boreal soils, Δ highlights how the fate of microbial C may vary with the identity of its organic precursor, which in turn is influenced by environmental conditions like temperature and soil N status.
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Effect of Contrasting Trophic Conditions on the Priming Effect in Gray Forest Soils
NASA Astrophysics Data System (ADS)
Zhuravleva, A. I.; Alifanov, V. M.; Blagodatskaya, E. V.
2018-02-01
Priming effects initiated by the addition of 14C glucose have been compared for humus horizons of soils existing under continuous input of fresh organic substrates and for buried soil horizons, in which entering of organic matter has been essentially limited. The effect of microrelief on the manifestation of priming effect in the humus horizons of gray forest soil on microhigh and in microlow has been estimated. Humus horizon in soils on microhigh, not activated by glucose, produced two times more CO2 in comparison with soils of microlow. However, the introduction of glucose canceled the effect of microrelief on CO2 emission. The intensity of absolute priming effect correlated with the Corg pool, initial microbial biomass, and enzyme activity, decreasing from humus horizons to the buried ones, and did not depend on microrelief. The effect of microrelief was observed, when assessing the priming effect relative to control (soil not activated by glucose): the value of relative priming effect was 1.5 times greater in A horizon of gray forest soil in microlow in comparison with that on microhigh being the result of increasing activity of enzymes.
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NASA Astrophysics Data System (ADS)
Kaiser, Christina; Evans, Sarah; Dieckmann, Ulf; Widder, Stefanie
2016-04-01
At the μm-scale, soil is a highly structured and complex environment, both in physical as well as in biological terms, characterized by non-linear interactions between microbes, substrates and minerals. As known from mathematics and theoretical ecology, spatial structure significantly affects the system's behaviour by enabling synergistic dynamics, facilitating diversity, and leading to emergent phenomena such as self-organisation and self-regulation. Such phenomena, however, are rarely considered when investigating mechanisms of microbial soil organic matter turnover. Soil organic matter is the largest terrestrial reservoir for organic carbon (C) and nitrogen (N) and plays a pivotal role in global biogeochemical cycles. Still, the underlying mechanisms of microbial soil organic matter buildup and turnover remain elusive. We explored mechanisms of microbial soil organic matter turnover using an individual-based, stoichiometrically and spatially explicit computer model, which simulates the microbial de-composer system at the soil microscale (i.e. on a grid of 100 x 100 soil microsites). Soil organic matter dynamics in our model emerge as the result of interactions among individual microbes with certain functional traits (f.e. enzyme production rates, growth rates, cell stoichiometry) at the microscale. By degrading complex substrates, and releasing labile substances microbes in our model continusly shape their environment, which in turn feeds back to spatiotemporal dynamics of the microbial community. In order to test the effect of microbial functional traits and organic matter input rate on soil organic matter turnover and C and N storage, we ran the model into steady state using continuous inputs of fresh organic material. Surprisingly, certain parameter settings that induce resource limitation of microbes lead to regular spatial pattern formation (f.e. moving spiral waves) of microbes and substrate at the μm-scale at steady-state. The occurrence of these pattern can be explained by the Turing mechanism. These pattern formation had strong consequences for process rates, as well as for C and N storage in the soil at the steady state: Scenarios that exhibited pattern formation were generally associated with higher C storage at steady state compared to those without pattern formation (i.e. at non-limiting conditions for microbes). Moreover, pattern formation lead to a spatial decoupling of C and N turnover processes, and to a spatial decoupling of microbial N mineralization and N immobilization. Taken together, our theoretical analysis shows that self-organisation may be a feature of the soil decomposer system, with consequences for process rates of microbial C and N turnover. Pattern formation through spatial self-organization, which has been observed on larger spatial scales in other resource-limited communities (e.g., vegetation patterns in arid or wetland eco-systems), may also occur at the soil microscale, leaving its mark on the soil's storage capacity for C and N.
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The potential for iron reduction in upland soils in Calhoun Critical Zone Observatory
NASA Astrophysics Data System (ADS)
Thompson, A.; Chen, C.; Noor, N.; Hodges, C. A.; Barcellos, D.; Richter, D. D., Jr.
2017-12-01
Fe redox cycling plays an important role in organic matter preservation and degradation, and the fate of nutrients and contaminants. Despite its importance, Fe redox cycling in non-flooded upland soils has been underappreciated, although many upland terrestrial ecosystems have episodes of low redox events and an abundance of anoxic microsites. Soil Fe reduction is generally constrained by C availability, the reactivity of Fe(III) oxyhydroxides, and the abundance of Fe reducing bacteria. The goal of this study was to determine the potential for Fe reduction in upland soils under varying land-uses (Hardwood, Pine and Cultivated soils) from Calhoun Critical Zone Observatory. Fresh field soils from multiple depths were incubated in the lab without amendments under anoxic conditions for 3 weeks to determine the native potential for soil Fe reduction and to assess the limiting factors, the soils were amended with factorial mixtures of the following: (1) organic substrates (glucose and alanine); (2) bioavailable Fe (ferrihydrite); and (3) Fe reducing bacteria (Shewanella oneidensis strain MR-1). Results showed that Fe reduction potential generally decreased with soil depth. Fe reduction potential is very minimal below 1m of soil profile. The availability of Fe(III) minerals did not constrain pine and hardwood soil Fe reduction potential. Fe(III) availability only slightly limited the potential for Fe reduction the cultivated soils, which have the lowest extractable Fe by ascorbate-citrate. Labile C constrained Fe reduction in the hardwood and cultivated soils, but not in the pine soils, which had the highest extractable C by K2SO4. In addition, we found the more energetic C source (glucose) facilitated more Fe reduction in the subsurface soil than did Alanine. Finally, the abundance of Fe-reducing bacteria limited Fe reduction potential in almost all of these soils, particularly the pine soils.
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Organic matter composition and substrate diversity under elevated CO2 in the Mojave Desert
NASA Astrophysics Data System (ADS)
Tfaily, M. M.; Hess, N. J.; Koyama, A.; Evans, R. D.
2016-12-01
Little is known about how rising atmospheric CO2 concentration will impact long-term plant biomass or the dynamics of soil organic matter (SOM) in arid ecosystems. In this study, we investigated the change in the molecular composition of SOM by high resolution mass spectrometry after 10 years exposure to elevated atmospheric CO2 concentrations at the Nevada Desert FACE Facility. Samples were collected from soil profiles from 0 to 1m in 0.2m increments under the dominant evergreen shrub (Larrea tridentata). The differences in the composition of SOM were more evident in soils close to the surface and consistent with higher bulk soil organic carbon (C) and total nitrogen (N) concentrations under elevated than ambient CO2, reflecting increased net productivity of shrubs under elevated CO2, which could be attributed to increased litter input from above-ground biomass and/or shallow roots, root exudation and/or microbial residues. This was further supported by the significant increase in the abundance of amino sugars-, protein- and carbohydrate-like compounds. These compounds are involved in diverse pathways ranging from sugars and amino-acid metabolism to lipid biosynthesis. This indicates increased activity and metabolism under elevated CO2 and suggests that elevated CO2 have altered microbial C use patterns, reflecting changes in the quality and quantity of soil C inputs. A significant increase in the mineral-bound soil organic C was also observed in the surface soils under elevated CO2. This was accompanied by increased microbial residues as identified by mass spectrometry that supports microbial lipid analysis, and reflecting accelerated microbial turnover under elevated CO2. Fungal neutral lipid fatty acids (NLFA) abundance doubled under elevated CO2. When provided with excess labile compounds, such as root exudates, and with limited supply of nutrients, fungi assimilate the excess labile C and store it as NLFA likely contributing to increased total N concentrations. This was further supported by the presence of acetyl glucosamine, a typical amino sugar, present in the chitin of fungi, under elevated than ambient CO2. Our results suggest that arid ecosystems, limited by water, may have a different C storage potential under changing climates than other ecosystems that are limited by N or P.
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Adaptability test of lettuce to soil-like substrate in bioregenerative life support system
NASA Astrophysics Data System (ADS)
Min, Yan; Liu, Professor Hong; Wenting, Fu
Plant cultivation using soil-like substrate (SLS) is considered to be a feasible option for building up matter for biological turnover in bioregenerative life support system (BLSS) by many researchers. The characteristics of SLS are different from those of true soil therefore it is very important to study the adaptability of candidate crop to SLS in BLSS. This study was carried out in three successive steps to test the adaptability of lettuce (Lactuca sativa L.) to rice straw SLS in BLSS of China. First, six Chinese specific lettuce cultivars which were selected for Chinese advanced life support system were planted into the same rice straw SLS, which was to determine the more suitable plant cultivar to do the next experiment. The results showed that Sharp Leaf lettuce and Red lettuce were more suitable for SLS than other cultivars. Second, the possibility of increasing the crop yield on the SLS was conducted by changing the soil depth and plant density. Sharp Leaf lettuce and Red lettuce were used into this experiment in order to obtain the highest yield under the smallest soil volume and weight at the same light intensity. Crop edible biomass, crop nutrition content and photosynthetic characteristics were estimated during the experiment. Red lettuce obtained higher biomass and photosynthesis capacity. Lastly, the stability of planting system of lettuce and SLS was evaluated in the closed controlled system. Red lettuce would be the test plant. In this experiment different age lettuce groups would be planted together and gas exchange would be measured. In all of these experiments soil physical and chemical characteristics were also be measured which will be the basal data for further research.
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Appalachian piedmont regolith: Relations of saprolite and residual soils to rock-type
Pavich, M.J.
1996-01-01
Saprolite is a major product of rock weathering on the Appalachian Piedmont from New Jersey to Alabama. On the Piedmont, it is the primary substrate from which residual soils are developed. Properties of saprolite and residual soils are highly related to their parent rocks. Studies of cores and outcrops illustrate that rock structure and mineralogy control upland regolith zonation. Saprolite develops by in situ chemical alteration of a wide variety of mafic to highly silicic rocks. Thickness of upland saprolite varies from a few meters on mafic rocks to tens of meters on silicic rocks. Saprolite thickness decreases with increasing slope and saprolite is generally thin or absent in valley bottoms. Massive residual subsoils and soils develop by physical and chemical processes that alter the upper few meters of saprolite. The fabric, texture and mineralogy of residual soils are distinctly different from underlying saprolite. The boundary between soil and saprolite is often gradual, and often a zone of low permeability. Geologic maps are useful guides to Piedmont regolith thickness and zonation. In regional design studies, geologic maps and regolith characteristics can be useful in environmental decision-making.
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Two-dimensional modeling of water and heat fluxes in green roof substrates
NASA Astrophysics Data System (ADS)
Suarez, F. I.; Sandoval, V. P.
2016-12-01
Due to public concern towards sustainable development, greenhouse gas emissions and energy efficiency, green roofs have become popular in the last years. Green roofs integrate vegetation into infrastructures to reach additional benefits that minimize negative impacts of the urbanization. A properly designed green roof can reduce environmental pollution, noise levels, energetic requirements or surface runoff. The correct performance of green roofs depends on site-specific conditions and on each component of the roof. The substrate and the vegetation layers strongly influence water and heat fluxes on a green roof. The substrate is an artificial media that has an improved performance compared to natural soils as it provides critical resources for vegetation survival: water, nutrients, and a growing media. Hence, it is important to study the effects of substrate properties on green roof performance. The objective of this work is to investigate how the thermal and hydraulic properties affect the behavior of a green roof through numerical modeling. The substrates that were investigated are composed by: crushed bricks and organic soil (S1); peat with perlite (S2); crushed bricks (S3); mineral soil with tree leaves (S4); and a mixture of topsoil and mineral soil (S5). The numerical model utilizes summer-arid meteorological information to evaluate the performance of each substrate. Results show that the area below the water retention curve helps to define the substrate that retains more water. In addition, the non-linearity of the water retention curve can increment the water needed to irrigate the roof. The heat propagation through the roof depends strongly on the hydraulic behavior, meaning that a combination of a substrate with low thermal conductivity and more porosity can reduce the heat fluxes across the roof. Therefore, it can minimize the energy consumed of an air-conditioner system.
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Response of nematode-trapping fungi to organic substrates in a coastal grassland soil.
Nguyen, Vi L; Bastow, Justin L; Jaffee, Bruce A; Strong, Don R
2007-07-01
To understand why Arthrobotrys oligospora and other nematode-trapping fungi are common and sometimes abundant in the coastal grassland soils of the Bodega Marine Reserve (BMR, Sonoma County, CA), we examined how resident trapping fungi responded to the addition of eight organic substrates (lupine leaves, grass leaves, dead isopods, dead moth larvae, isopod faeces, deer faeces, shrimp shells, and powdered chitin). We were especially interested in the effects of dead isopods because isopods are abundant at BMR and because previous studies had documented strong responses of A. oligospora to other arthropods (dead moth larvae). Soil from BMR was packed into vials (40 g dry mass equivalent per vial with water potential at -230 kPa and bulk density at 0.9 gcm(-3)), and one substrate or no substrate was added to the soil surface. After 30 d at 20 degrees C, trapping fungi were quantified by dilution plating and most probable number procedures. The response of A. oligospora was inversely related to substrate carbon:nitrogen (C:N) ratio: substrates with low C:N ratios (dead isopods, lupine leaves, dead moth larvae) usually caused large increases in A. oligospora whereas those with higher C:N ratios (isopod faeces, deer faeces, grass leaves) did not. An exception was chitin powder, which had a low C:N ratio, but which did not cause A. oligospora to proliferate. Responses of A. oligospora were directly related to the quantity of nitrogen added with each substrate, and those substrates that caused large increases in resident nematodes usually caused large increases in A. oligospora. Other trapping fungi did not respond as strongly as A. oligospora.
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NASA Astrophysics Data System (ADS)
Zemek, Rostislav; Konopická, Jana; Bohatá, Andrea
2018-04-01
Convenient ecological alternative to broad-spectrum chemical pesticides is the utilization of natural enemies, like predators, parasitoids and microorganisms. A substantial number of microbial biopesticides based on entomopathogenic fungi have been developed worldwide since 1960s. Beauveria bassiana (Balsamo-Crivelli) Vuillemin, Metarhizium anisopliae (Metchnikoff) Sorokin, Isaria fumosorosea (Wize), and B. brongniartii (Saccardo) Petch are the most common species used in commercially produced mycopesticides. Besides direct biological pest control, these fungi could be also used in preventive application programs, particularly in ornamental or nursery plants to provide better control against pests. The aim of the present study was to investigate potential of pre-colonization of sphagnum-based soil substrate with I. fumosorosea strain CCM 8367 which was found earlier to be highly virulent against several pest species. We developed simple laboratory apparatus for application of fungal spore suspension into the substrate. Suspension was prepared from blastospores obtained by submerged cultivation on potato dextrose broth (PDB) medium using an orbital shaker. Inoculated substrate was placed into plastic bags and stored at constant temperature for six months. Every month, samples were analyzed for concentration of colony forming units (CFU) by elution and selective medium technique. The results showed that at 20°C the fungus successfully colonized the soil substrate and persisted there although the mean concentration slightly decreased from 5.89×104 to 2.76×104 CFU per milliliter of substrate during the experiment. Temperature 30°C had negative effect on survival of the fungus and is not recommended for long-term storage of pre-inoculated substrate. We can conclude that I. fumosorosea-colonized substrate can be convenient for preventive and permanent protection of various plants against soil-dwelling pests.
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Feigl, Viktória; Ujaczki, Éva; Vaszita, Emese; Molnár, Mónika
2017-10-01
Red mud can be applied as soil ameliorant to acidic, sandy and micronutrient deficient soils. There are still knowledge gaps regarding the effects of red mud on the soil microbial community. The Biolog EcoPlate technique is a promising tool for community level physiological profiling. This study presents a detailed evaluation of Biolog EcoPlate data from two case studies. In experiment "A" red mud from Ajka (Hungary) was mixed into acidic sandy soil in soil microcosms at 5-50 w/w%. In experiement "B" red mud soil mixture was mixed into low quality subsoil in a field experiment at 5-50 w/w%. According to average well color development, substrate average well color development and substrate richness 5-20% red mud increased the microbial activity of the acidic sandy soil over the short term, but the effect did not last for 10months. Shannon diversity index showed that red mud at up to 20% did not change microbial diversity over the short term, but the diversity decreased by the 10th month. 30-50% red mud had deteriorating effect on the soil microflora. 5-20% red mud soil mixture in the low quality subsoil had a long lasting enhancing effect on the microbial community based on all Biolog EcoPlate parameters. However, 50% red mud soil mixture caused a decrease in diversity and substrate richness. With the Biolog EcoPlate we were able to monitor the changes of the microbial community in red mud affected soils and to assess the amount of red mud and red mud soil mixture applicable for soil treatment in these cases. Copyright © 2017 Elsevier B.V. All rights reserved.
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Methods to ensure the quality of excavated soil material from geogenically metalliferous sites
NASA Astrophysics Data System (ADS)
Liebhard, Peter; Sager, Manfred
2017-04-01
Soils at geogenically metalliferous sites might exceed heavy metal threshold levels with respect to agricultural use, apart from anthropogenic contamination sources. As a fundamental substrate for green plants and green plant production, soil is not easily renewable, its formation needs long time (e.g. 500 years for 20 mm). In Austria, about 10ha of soil get sealed every day, resulting in complete loss of its biological functions. Excavated soil material has been classified as waste from a legal point of view, which made 33 mill. tons resp. 48% of total waste in Austria in 2010. Recycling of excavated soil material for agricultural use will be an important task to reduce future waste and to enlarge agricultural substrate volumes, but methods to ensure proper qualities are needed to improve regulations. Within this investigation, the transfer of various metals from geogenically metalliferous soils to various crop plants will be investigated, and correlated with various simple soil test methods. Four excavated soil materials from the metalliferous schist zone within the Austrian province of Styria (Kraubath/Mur, Übelbach) and a low-metal reference sample have been taken as substrates to grow raygrass (lolium multiflorum) as a green cover, salad (Lactuca sativa) as a vegetable food item, oats (Avena sativa), maize (Zea mais) and stinging nettle (Urtica dioica) as a hyperaccumulating species. Results and recommendations will be presented.
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Janin, Agnès; Léna, Jean-Paul; Deblois, Sandrine; Joly, Pierre
2012-10-01
The influence of landscape matrix on functional connectivity has been clearly established. Now methods to assess the effects of different land uses on species' movements are needed because current methods are often biased. The use of physiological parameters as indicators of the level of resistance to animal movement associated with different land uses (i.e., matrix resistance) could provide estimates of energetic costs and risks to animals migrating through the matrix. To assess whether corticosterone levels indicate matrix resistance, we conducted experiments on substrate choice and measured levels of corticosterone before and after exposure of toads (Bufo bufo) to 3 common substrates (ploughed soil, meadow, and forest litter). We expected matrix resistance and hormone levels to increase from forest litter (habitat of the toad) to meadows to ploughed soil. Adult toads had higher corticosterone levels on ploughed soil than on forest litter or meadow substrates. Hormone levels did not differ between forest litter and meadow. Toads avoided moving onto ploughed soil. Corticosterone levels in juvenile toads were not related to substrate type; however, hormone levels decreased as humidity increased. Juveniles, unlike adults, did not avoid moving over ploughed soil. The difference in responses between adult and juvenile toads may have been due to differences in experimental design (for juveniles, entire body used to measure corticosterone concentration; for adults, saliva alone); differences in the scale of sensory perception of the substrate (juveniles are much smaller than adults); or differences in cognitive processes between adult and juvenile toads. Adults probably had experience with different substrate types, whereas juveniles first emerging from the water probably did not. As a consequence, arable lands could act as ecological traps for juvenile toads. ©2012 Society for Conservation Biology.
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Poliovirus adsorption by 34 minerals and soils.
Moore, R S; Taylor, D H; Sturman, L S; Reddy, M M; Fuhs, G W
1981-12-01
The adsorption of radiolabeled infectious poliovirus type 2 by 34 well-defined soils and mineral substrates was analyzed in a synthetic freshwater medium containing 1 mM CaCl(2) and 1.25 mM NaHCO(3) at pH 7. In a model system, adsorption of poliovirus by Ottawa sand was rapid and reached equilibrium within 1 h at 4 degrees C. Near saturation, the adsorption could be described by the Langmuir equation; the apparent surface saturation was 2.5 x 10(6) plaque-forming units of poliovirus per mg of Ottawa sand. At low surface coverage, adsorption was described by the Freundlich equation. The soils and minerals used ranged from acidic to basic and from high in organic content to organic free. The available negative surface charge on each substrate was measured by the adsorption of a cationic polyelectrolyte, polydiallyldimethylammonium chloride. Most of the substrates adsorbed more than 95% of the virus. In general, soils, in comparison with minerals, were weak adsorbents. Among the soils, muck and Genesee silt loam were the poorest adsorbents; among the minerals, montmorillonite, glauconite, and bituminous shale were the least effective. The most effective adsorbents were magnetite sand and hematite, which are predominantly oxides of iron. Correlation coefficients for substrate properties and virus adsorption revealed that the elemental composition of the adsorbents had little effect on poliovirus uptake. Substrate surface area and pH, by themselves, were not significantly correlated with poliovirus uptake. A strong negative correlation was found between poliovirus adsorption and both the contents of organic matter and the available negative surface charge on the substrates as determined by their capacities for adsorbing the cationic polyelectrolyte, polydiallyldimethylammonium chloride.
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NASA Astrophysics Data System (ADS)
Marañón-Jiménez, Sara; Soong, Jenniffer L.; Leblans, Niki I. W.; Sigurdsson, Bjarni D.; Dauwe, Steven; Fransen, Erik; Janssens, Ivan A.
2017-04-01
Increasing temperatures can accelerate soil organic matter (SOM) decomposition and release large amounts of CO2 to the atmosphere, potentially inducing climate change feedbacks. Alterations to the temperature sensitivity and metabolic pathways of soil microorganisms in response to soil warming can play a key role in these soil carbon (C) losses. Here, we present results of an incubation experiment using soils from a geothermal gradient in Iceland that have been subjected to different intensities of soil warming (+0, +1, +3, +5, +10 and +20 °C above ambient) over seven years. We hypothesized that 7 years of soil warming would led to a depletion of labile organic substrates, with a subsequent decrease of the "apparent" temperature sensitivity of soil respiration. Associated to this C limitation and more sub-optimal conditions for microbial growth, we also hypothesized increased microbial metabolic quotients (soil respiration per unit of microbial biomass), which is associated with increases in the relative amount of C invested into catabolic pathways along the warming gradient. Soil respiration and basal respiration rates decreased with soil warming intensity, in parallel with a decline in soil C availability. Contrasting to our first hypothesis, we did not detect changes in the temperature sensitivity of soil respiration with soil warming or on the availability of nutrients and of labile C substrates at the time of incubation. However, in agreement to our second hypothesis, microbial metabolic quotients (soil respiration per unit of microbial biomass) increased at warmer temperatures, while the C retained in biomass decreased as substrate became limiting. Long-term (7 years) temperature increases thus triggered a change in the metabolic functioning of the soil microbial communities towards increasing energy costs for maintenance or resource acquisition, thereby lowering the capacity of C retention and stabilization of warmed soils. These results highlight the need to incorporate the potential changes in microbial physiological functioning into models, in order to accurately predict future changes in soil C stocks in response to global warming.
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Chen, Haoming; Ma, Jinyi; Wei, Jiaxing; Gong, Xin; Yu, Xichen; Guo, Hui; Zhao, Yanwen
2018-09-01
Green roofs have increasingly been designed and applied to relieve environmental problems, such as water loss, air pollution as well as heat island effect. Substrate and vegetation are important components of green roofs providing ecosystem services and benefiting the urban development. Biochar made from sewage sludge could be potentially used as the substrate amendment for green roofs, however, the effects of biochar on substrate quality and plant performance in green roofs are still unclear. We evaluated the effects of adding sludge biochar (0, 5, 10, 15 and 20%, v/v) to natural soil planted with three types of plant species (ryegrass, Sedum lineare and cucumber) on soil properties, plant growth and microbial communities in both green roof and ground ecosystems. Our results showed that sludge biochar addition significantly increased substrate moisture, adjusted substrate temperature, altered microbial community structure and increased plant growth. The application rate of 10-15% sludge biochar on the green roof exerted the most significant effects on both microbial and plant biomass by 63.9-89.6% and 54.0-54.2% respectively. Path analysis showed that biochar addition had a strong effect on microbial biomass via changing the soil air-filled porosity, soil moisture and temperature, and promoted plant growth through the positive effects on microbial biomass. These results suggest that the applications of biochar at an appropriate rate can significantly alter plant growth and microbial community structure, and increase the ecological benefits of green roofs via exerting effects on the moisture, temperature and nutrients of roof substrates. Copyright © 2018 Elsevier B.V. All rights reserved.
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Góngora-Echeverría, Virgilio René; Martin-Laurent, Fabrice; Quintal-Franco, Carlos; Giácoman-Vallejos, German; Ponce-Caballero, Carmen
2017-04-01
Misuse of pesticides in farming activities leads to contamination of drinking water sources and is responsible for animal and human health problems. The biobeds are practicable option to minimize contamination by pesticides during preparation, use and washing of equipment for pesticide treatments. This research aimed at testing substrate mixtures to optimize biobed efficiency to remove pesticides under the climate of the Yucatan (México). Agricultural soil and 11 mixtures adding vegetable compost, sisal pulp, corn stover and seaweed were tested under controlled conditions. Each biomixture was exposed to a mixture of five pesticides (2,4-diclorophenoxyacetic acid "2,4-D" [1.08 mg cm -3 ], atrazine [2.50 mg cm -3 ], carbofuran [0.23 mg cm -3 ], diazinon [0.34 mg cm -3 ], and glyphosate [0.36 mg cm -3 ]) in a period of 41 days. Monitoring of the dissipation of pesticide residues showed that pesticides were quickly dissipated in soil at microcosm level experiment, while at two critical times of 20 and 41 days, all mixtures of substrates (biomixtures) were efficient in dissipation of high concentrations of pesticide in a short time (>99%). Time, biomixture and type of pesticide were shown to be the main parameters influencing pesticide dissipation (P < 0.05). Several other physicochemical parameters of the biomixtures, such as organic matter (OM), lignin, water holding capacity (WHC), and pH, were also significant on pesticide dissipation (P < 0.05), being pH the most significant.
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Paterson, Eric; Midwood, Andrew J; Millard, Peter
2009-01-01
For soils in carbon balance, losses of soil carbon from biological activity are balanced by organic inputs from vegetation. Perturbations, such as climate or land use change, have the potential to disrupt this balance and alter soil-atmosphere carbon exchanges. As the quantification of soil organic matter stocks is an insensitive means of detecting changes, certainly over short timescales, there is a need to apply methods that facilitate a quantitative understanding of the biological processes underlying soil carbon balance. We outline the processes by which plant carbon enters the soil and critically evaluate isotopic methods to quantify them. Then, we consider the balancing CO(2) flux from soil and detail the importance of partitioning the sources of this flux into those from recent plant assimilate and those from native soil organic matter. Finally, we consider the interactions between the inputs of carbon to soil and the losses from soil mediated by biological activity. We emphasize the key functional role of the microbiota in the concurrent processing of carbon from recent plant inputs and native soil organic matter. We conclude that quantitative isotope labelling and partitioning methods, coupled to those for the quantification of microbial community substrate use, offer the potential to resolve the functioning of the microbial control point of soil carbon balance in unprecedented detail.
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Mechanisms of microbial destabilization of soil C shifts over decades of warming
NASA Astrophysics Data System (ADS)
DeAngelis, K.; Pold, G.; Chowdhury, P. R.; Schnabel, J.; Grandy, S.; Melillo, J. M.
2017-12-01
Microbes are major actors in regulating the earth's biogeochemical cycles, with temperature-sensitive microbial tradeoffs improving ecosystem biogeochemical models. Meanwhile, the Earth's climate is changing, with decades of warming undercutting the ability of soil to store carbon. Our work explores trends of 26 years of experimental warming in temperate deciduous forest soils, which is associated with cycles of soil carbon degradation punctuated by periods of changes in soil microbial dynamics. Using a combination of biogeochemistry and molecular analytical methods, we explore the hypotheses that substrate availability, community structure, altered temperature sensitivity of microbial turnover-growth efficiency tradeoff, and microbial evolution are responsible for observations of accelerated degradation of soil carbon over time. Amplicon sequencing of microbial communities suggests a small role of changing microbial community composition over decades of warming, but a sustained suppression of fungal biomass is accompanied by increased biomass of Actinobacteria, Actinobacteria, Alphaproteobacteria, Verrucomicrobia and Planctomycetes. Substrate availability plays an important role in microbial dynamics, with depleted labile carbon in the first decade and depleted lignin in the second decade. Increased lignin-degrading enzyme activity supports the suggestion that lignin-like organic matter is an important substrate in chronically warmed soils. Metatranscriptomics data support the suggestion that increased turnover is associated with long-term warming, with metagenomic signals of increased carbohydrate-degrading enzymes in the organic horizon but decreased in the mineral soils. Finally, traits analysis of over 200 cultivated isolates of bacterial species from heated and control soils suggests an expanded ability for degradation of cellulose and hemicellulose but not chitin, supporting the hypothesis that long-term warming is exerting evolutionary pressure on microbial species. Together, these data suggest that after decades of warming both direct kinetic effects and indirect effects of altered substrate availability are affecting microbial ecology and evolution in ways that conspire to destabilize soil organic matter.
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Soil Quality Index Determination Models for Restinga Forest
NASA Astrophysics Data System (ADS)
Bonilha, R. M.; Casagrande, J. C.; Soares, R. M.
2012-04-01
The Restinga Forest is a set of plant communities in mosaic, determined by the characteristics of their substrates as a result of depositional processes and ages. In this complex mosaic are the physiognomies of restinga forests of high-stage regeneration (high restinga) and middle stage of regeneration (low restinga), each with its plant characteristics that differentiate them. Located on the coastal plains of the Brazilian coast, suffering internal influences both the continental slopes, as well as from the sea. Its soils come from the Quaternary and are subject to constant deposition of sediments. The climate in the coastal type is tropical (Köppen). This work was conducted in four locations: (1) Anchieta Island, Ubatuba, (2) Juréia-Itatins Ecological Station, Iguape, (3) Vila das Pedrinhas, Comprida Island; and (4) Cardoso Island, Cananeia. The soil samples were collect at a depths of 0 to 5, 0-10, 0-20, 20-40 and 40 to 60cm for the chemical and physical analysis. Were studied the additive and pondering additive models to evaluate soil quality. It was concluded: a) the comparative additive model produces quantitative results and the pondering additive model quantitative results; b) as the pondering additive model, the values of Soil Quality Index (SQI) for soils under forest of restinga are low and realistic, demonstrating the small plant biomass production potential of these soils, as well as their low resilience; c) the values of SQI similar to areas with and without restinga forest give quantitative demonstration of the restinga be considered as soil phase; d) restinga forest, probably, is maintained solely by the cycling of nutrients in a closed nutrient cycling; e) for the determination of IQS for soils under restinga vegetation the use of routine chemical analysis is adequate. Keywords: Model, restinga forest, Soil Quality Index (SQI).
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NASA Astrophysics Data System (ADS)
Enzhu, Hu; Nesterenko, Elena; Liu, Professor Hong; Manukovsky, N. S.; Kovalev, Vladimir; Gurevich, Yu.; Kozlov, Vladimir; Khizhnyak, Serge; Xing, Yidong; Hu, Enzhu; Enzhu, Hu
There are two ways of getting vegetable food in BLSS: in hydroponic culture and on soil substrates. In any case there is a chance that the plants will be affected by plant pathogenic microorganisms. The subject of the research was a soil-like substrate (SLS) for growing plants in a Bioregenerative Life Support System (BLSS). We estimated the fungistatic properties of SLS using test cultures of Bipolaris and Alternaria plant pathogenic fungi. Experiments were made with the samples of SLS, natural soil and sand (as control). We tested 2 samples of SLS produced by way of bioconversion of wheat and rice straw. We measured the disease severity of wheat seedlings and the incidence of common root rot in natural (non-infectious) background and man-made (infectious) conditions. The severity of disease on the SLS was considerably smaller both in non-infectious and infectious background conditions (8 and 12%) than on the natural soil (18 and 32%) and sand. It was the soil-like substrate that had the minimal value among the variants being compared (20% in non-infectious and 40% in infectious background conditions). This index in respect of the soil was 55 and 78%, correspondingly, and in respect of the sand - 60%, regardless of the background. It was found that SLS significantly suppressed conidia germination of Bipolaris soroikiniana (p<0.001). In the presence of SLS germination of conidia decreased to 9.9 - 12.2% of the control value. No significant differences were found between SLS samples obtained from wheat and rice straw.
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Effects of Warming on the Fate of Carbon Across a Hawaiian Soil Mineralogical Gradient
NASA Astrophysics Data System (ADS)
Neupane, A.
2016-12-01
Earth's surface temperature in tropical region have increased over the last century. However, relatively few studies have focused on the interacting effects of warming and soil mineralogy on the fate of carbon (C) in tropical soils. This research uses soils from three montane forest sites and two grasslands along soil age gradients on basaltic lava flows in Hawaii. The age gradient provides a range in soil mineralogies and binding site densities. We hypothesized that warming would promote microbial respiration and losses of added C more in younger soils with lower binding site density, whereas warming would have less of an impact on C losses in older soils with more reactive minerals. Soils were collected from 0-25 cm depths and incubated in the lab at 16 °C (ambient temperature), 21°C, and 26 °C. New C in the form of 13C-labeled glucose and glycine were added to replicate soils to track the fate of C with warming across sites (n = 3). Carbon dioxide (CO2) fluxes was measured every 15 to 30 days for 8 months to assess changes in heterotrophic respiration, and 13C uptake in microbial biomass was measured after 4 days and 8 months. Among the forest sites, the youngest soils (Thurston, 300 years old), had the overall lowest respiration, an intermediate aged soil (Laupahoehoe, 20,000 years old) had the highest respiration, and there was intermediate respiration from the oldest soil (Kohala, 150,000 yrs). Both the grassland sites had lower respiration compared to the forest. Soils from all sites showed increase in respiration rate at warmer temperature. Contrary to expectations, Kohala soil showed largest increase in respiration upon warming while Thurston showed the smallest increase for the forest sites. The C substrates altered respiration differently over time. Preliminary microbial 13C data show significant uptake and retention of added substrates in microbial biomass during the first 4 days of the incubation, with significantly greater retention of added substrate in microbial biomass at 16 °C versus 21 oC. These results show that warming not only increases heterotrophic respiration of C, but also decreases microbial retention of simple C substrates. These results, together with analyses across the soil mineralogical gradient, will improve our understanding of how warming may affect C storage across tropical sites.
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Dresler, Sławomir; Wójciak-Kosior, Magdalena; Sowa, Ireneusz; Stanisławski, Grzegorz; Bany, Izabela; Wójcik, Małgorzata
2017-06-01
The aim of the study was to determine the response of metallicolous and nonmetallicolous Echium vulgare L. populations to chronic multi-metal (Zn, Pb, Cd) and acute Zn (200, 400 μM) and Pb (30, 60 μM) stress. Three populations of E. vulgare, one from uncontaminated and two from metal-contaminated areas, were studied. Two types of experiments were performed - a short-term hydroponic experiment with acute Zn or Pb stress and a long-term manipulative soil experiment with the use of soils from the sites of origin of the three populations. Growth parameters, such as shoot and root fresh weight and leaf area, as well as organic acid accumulation were determined. Moreover, the concentration of selected secondary metabolites and antioxidant capacity in the three populations exposed to Pb or Zn excess were measured. Both metallicolous populations generally achieved higher biomass compared with the nonmetallicolous population cultivated under metal stress in hydroponics or on metalliferous substrates. Plants exposed to Pb or Zn excess or contaminated soil substrate exhibited higher malate and citrate concentrations compared with the reference (no metal stress) plants. It was observed that Zn or Pb stress increased accumulation of allantoin, chlorogenic and rosmarinic acids, total phenolics, and flavonoids. Moreover, it was shown that Pb sequestration in the roots or Zn translocation to the shoots may play a role in enhanced metal tolerance of metallicolous populations under acute Pb/Zn stress. Copyright © 2017 Elsevier Masson SAS. All rights reserved.
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Alvarez, Gaël; Shahzad, Tanvir; Andanson, Laurence; Bahn, Michael; Wallenstein, Matthew D; Fontaine, Sébastien
2018-04-23
Most current models of soil C dynamics predict that climate warming will accelerate soil C mineralization, resulting in a long-term CO 2 release and positive feedback to global warming. However, ecosystem warming experiments show that CO 2 loss from warmed soils declines to control levels within a few years. Here, we explore the temperature dependence of enzymatic conversion of polymerized soil organic C (SOC) into assimilable compounds, which is presumed the rate-limiting step of SOC mineralization. Combining literature review, modelling and enzyme assays, we studied the effect of temperature on activity of enzymes considering their thermal inactivation and catalytic activity. We defined the catalytic power of enzymes (E power ) as the cumulative amount of degraded substrate by one unit of enzyme until its complete inactivation. We show a universal pattern of enzyme's thermodynamic properties: activation energy of catalytic activity (EA cat ) < activation energy of thermal inactivation (EA inact ). By investing in stable enzymes (high EA inact ) having high catalytic activity (low EA cat ), microorganisms may maximize the E power of their enzymes. The counterpart of such EAs' hierarchical pattern is the higher relative temperature sensitivity of enzyme inactivation than catalysis, resulting in a reduction in E power under warming. Our findings could explain the decrease with temperature in soil enzyme pools, microbial biomass (MB) and carbon use efficiency (CUE) reported in some warming experiments and studies monitoring the seasonal variation in soil enzymes. They also suggest that a decrease in soil enzyme pools due to their faster inactivation under warming contributes to the observed attenuation of warming effect on soil C mineralization. This testable theory predicts that the ultimate response of SOC degradation to warming can be positive or negative depending on the relative temperature response of E power and microbial production of enzymes. © 2018 John Wiley & Sons Ltd.
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On the Non-Uniqueness of Sediment Yield
NASA Astrophysics Data System (ADS)
Kim, J.; Ivanov, V. Y.; Fatichi, S.
2014-12-01
There has been ample experimental evidence that soil erosion does not necessarily occur at the same rate, given the same amount of rainfall or runoff. Such a non-unique phenomenon has been often referred to in literature as due to 'natural variability'. Our recent study hypothesized that uncertainties in the distribution and properties of a sediment layer can be a potential clue to one of the reasons of the non-unique sediment yield. Specifically, numerical experimentation with a sophisticated two-dimensional model showed that a deposited layer plays two conflicting roles: it can both increase and decrease soil erosion, given the same magnitude of runoff. The difference in erodibilities of the "original, intact soil layer" and the "deposited, loose soil layer" and the composition of soil particles in the underlying layers give rise to the non-uniqueness of the amount of eroded materials. In continuing efforts, we attempt to investigate this phenomenon using a comprehensive the Universal Soil Loss Erosion (USLE) database, that contains data on paired hillslopes that show a high degree of non-uniqueness in the response, even though the hillslopes exhibit the same topography, soil type, rainfall and meteorological forcings, and landuse. An underlying hypothesis of this study is that uncertainties in the distribution of soil substrate prior to a rainfall event lead to low predictability skill, i.e., a stochastically-varying outcome. A large number of simulation cases demonstrating the proposed hypothesis are conducted using a coupled numerical model, tRIBS-VEGGIE-FEaST (Triangulated irregular network - based Real time Integrated Basin Simulator- VEGetation Generator for Interactive Evolution -Flow Erosion and Sediment Transport).
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Marín-Guirao, J I; Rodríguez-Romera, P; Lupión-Rodríguez, B; Camacho-Ferre, F; Tello-Marquina, J C
2016-10-01
The biostimulant effect of Trichoderma spp. on horticultural crops are highly variable. Thus, practical use of Trichoderma sp. requires feasible formulated products and suitable substrates. This study evaluates the survival and the growth-promotion effect of a Trichoderma saturnisporum rice formulation compared with a nonformulated conidia suspension (seven treatments in total), on tomato, pepper and cucumber seedlings grown in two substrates: (i) rich in organic matter (OM) and (ii) mineral substrate without OM. The results showed beneficial effects on seedling growth in the OM-rich substrate when T. saturnisporum rice formulation (mainly at maximum concentration) was applied, but the effects were opposite when the mineral substrate without OM was used. The effects were closely linked to the level of inoculum in the substrate, which was greater upon application of the formulated inoculum as opposed to the nonformulated one. The use of rice to prepare the inoculum of T. saturnisporum seems to be promising for seedling growth in the nursery when it is applied in a substrate that is rich in organic matter, but it must be considered that under certain conditions of food shortage, Trichoderma sp. could show pathogenicity to seedlings. This study provides evidence of the complexity inherent in the use of micro-organisms in agriculture, while also confirming that the activity of the biofertilizers based on Trichoderma depends on the type of inoculum and its concentration, as well as the properties of the medium in which the fungi develop. Further studies assessing the effectiveness or possible pathogenicity of Trichoderma in different soils under greenhouse conditions must be addressed. © 2016 The Society for Applied Microbiology.
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Biodegradation of Used Motor Oil in Soil Using Organic Waste Amendments
Abioye, O. P.; Agamuthu, P.; Abdul Aziz, A. R.
2012-01-01
Soil and surface water contamination by used lubricating oil is a common occurrence in most developing countries. This has been shown to have harmful effects on the environment and human beings at large. Bioremediation can be an alternative green technology for remediation of such hydrocarbon-contaminated soil. Bioremediation of soil contaminated with 5% and 15% (w/w) used lubricating oil and amended with 10% brewery spent grain (BSG), banana skin (BS), and spent mushroom compost (SMC) was studied for a period of 84 days, under laboratory condition. At the end of 84 days, the highest percentage of oil biodegradation (92%) was recorded in soil contaminated with 5% used lubricating oil and amended with BSG, while only 55% of oil biodegradation was recorded in soil contaminated with 15% used lubricating oil and amended with BSG. Results of first-order kinetic model to determine the rate of biodegradation of used lubricating oil revealed that soil amended with BSG recorded the highest rate of oil biodegradation (0.4361 day−1) in 5% oil pollution, while BS amended soil recorded the highest rate of oil biodegradation (0.0556 day−1) in 15% oil pollution. The results of this study demonstrated the potential of BSG as a good substrate for enhanced remediation of hydrocarbon contaminated soil at low pollution concentration. PMID:22919502
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Ruiz-González, Clara; Archambault, Esther; Laforest-Lapointe, Isabelle; Del Giorgio, Paul A; Kembel, Steven W; Messier, Christian; Nock, Charles A; Beisner, Beatrix E
2018-06-14
Freshwater bacterioplankton communities are influenced by the inputs of material and bacteria from the surrounding landscape, yet few studies have investigated how different terrestrial inputs affect bacterioplankton. We examined whether the addition of soils collected under various tree species combinations differentially influences lake bacterial communities. Lake water was incubated for 6 days following addition of five different soils. We assessed the taxonomic composition (16S rRNA gene sequencing) and metabolic activity (Biolog Ecoplates) of lake bacteria with and without soil addition, and compared these to initial soil communities. Soil bacterial assemblages showed a strong influence of tree composition, but such community differences were not reflected in the structure of lake communities that developed during the experiment. Bacterial taxa showing the largest abundance increases during incubation were initially present in both lake water and across most soils, and were related to Cytophagales, Burkholderiales and Rhizobiales. No clear metabolic profiles based on inoculum source were found, yet soil-amended communities used 60% more substrate than non-inoculated communities. Overall, we show that terrestrial inputs influence aquatic communities by stimulating the growth and activity of certain ubiquitous taxa distributed across the terrestrial-aquatic continuum, yet different forest soils did not cause predictable changes in lake bacterioplankton assemblages.
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Laccase-catalyzed oxidation of iodide and formation of organically bound iodine in soils.
Seki, Miharu; Oikawa, Jun-ichi; Taguchi, Taro; Ohnuki, Toshihiko; Muramatsu, Yasuyuki; Sakamoto, Kazunori; Amachi, Seigo
2013-01-02
Laccase oxidizes iodide to molecular iodine or hypoiodous acid, both of which are easily incorporated into natural soil organic matter. In this study, iodide sorption and laccase activity in 2 types of Japanese soil were determined under various experimental conditions to evaluate possible involvement of this enzyme in the sorption of iodide. Batch sorption experiment using radioactive iodide tracer ((125)I(-)) revealed that the sorption was significantly inhibited by autoclaving (121 °C, 40 min), heat treatment (80 and 100 °C, 10 min), γ-irradiation (30 kGy), N(2) gas flushing, and addition of reducing agents and general laccase inhibitors (KCN and NaN(3)). Interestingly, very similar tendency of inhibition was observed in soil laccase activity, which was determined using 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonate) (ABTS) as a substrate. The partition coefficient (K(d): mL g(-1)) for iodide and specific activity of laccase in soils (Unit g(-1)) showed significant positive correlation in both soil samples. Addition of a bacterial laccase with an iodide-oxidizing activity to the soils strongly enhanced the sorption of iodide. Furthermore, the enzyme addition partially restored iodide sorption capacity of the autoclaved soil samples. These results suggest that microbial laccase is involved in iodide sorption on soils through the oxidation of iodide.
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Depth and type of substrate influence the ability of Nasonia vitripennis to locate a host
Frederickx, Christine; Dekeirsschieter, Jessica; Verheggen, François J.; Haubruge, Eric
2014-01-01
Abstract The foraging behaviour of a parasitoid insect species includes the host’s habitat and subsequent location of the host. Habitats substrate, substrate moisture, and light levels can affect the host searching of different species of parasitoids. However, the depth at which parasitoids concentrate their search effort is another important ecological characteristic and plays an important role in locating a host. Here, we investigated the ability of a pupal parasitoid, Nasonia vitripennis Walker (Hymenoptera: Pteromalidae), to penetrate and kill fly pupae located at different depths of the substrate. Three different types of substrate were tested: loam soil, compost, and vermiculite substrate. In both loam soil and compost, all of the parasitism activity was restricted to pupae placed directly on the surface. Parasitism activity in vermiculite showed that the average number of pupae parasitized decreased with depth of substrate. These results suggest that fly pupae situated deeper in the substrate are less subjected to parasitism by N. vitripennis . PMID:25373205
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Effect of soil and a nonionic surfactant on BTE-oX and MTBE biodegradation kinetics.
Acuna-Askar, K; Gracia-Lozano, M V; Villarreal-Chiu, J F; Marmolejo, J G; Garza-Gonzalez, M T; Chavez-Gomez, B
2005-01-01
The biodegradation kinetics of BTE-oX and MTBE, mixed all together, in the presence of 905 mg/L VSS of BTEX-acclimated biomass was evaluated. Effects of soil and Tergitol NP-10 in aqueous samples on substrate biodegradation rates were also evaluated. Biodegradation kinetics was evaluated for 36 hours, every 6 hours. MTBE biodegradation followed a first-order one-phase kinetic model in all samples, whereas benzene, toluene and ethylbenzene biodegradation followed a first-order two-phase kinetic model in all samples. O-xylene biodegradation followed a first-order two-phase kinetic model in the presence of biomass only. Interestingly, o-xylene biodegradation was able to switch to a first-order one-phase kinetic model when either soil or soil and Tergitol NP-10 were added. The presence of soil in aqueous samples retarded benzene, toluene and ethylbenzene removal rates. O-xylene and MTBE removal rates were enhanced by soil. The addition of Tergitol NP-10 to aqueous samples containing soil had a positive effect on substrate removal rate in all samples. Substrate percent removals ranged 77-99.8% for benzene, toluene and ethylbenzene. O-xylene and MTBE percent removals ranged 50.1-65.3% and 9.9-43.0%, respectively.
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NASA Astrophysics Data System (ADS)
Sihi, D.; Davidson, E. A.; Savage, K. E.; Liang, D.
2017-12-01
Production and consumption of nitrous oxide (N2O), methane (CH4), and carbon dioxide (CO2) are affected by complex interactions of temperature, moisture, and substrate supply, that is further complicated by spatial heterogeneity of the soil matrix. This microsite heterogeneity is often invoked conceptually to explain unusual observations like consumption of atmospheric N2O (reduction) in upland soils that co-occur with CH4 uptake (oxidation). To advance numerical simulation of these belowground processes, we expanded the Dual Arrhenius and Michaelis-Menten (DAMM) model, to apply it consistently for all three greenhouse gases (GHGs) with respect to the biophysical processes of production, consumption, and diffusion within the soil, including the contrasting effects of oxygen (O2) as substrate or inhibitor for each process. Chamber-based measurements of all three GHGs at the Howland Forest (ME, USA) were used to parameterize the model. The area under a soil chamber is partitioned according to a bivariate lognormal probability distribution function of soil carbon (C) and moisture across a range of microsites, that leads to a distribution of heterotrophic respiration and O2 consumption among microsites. Linking microsite consumption of O2 with a diffusion model generates a broad range of microsite concentrations of O2 that determines the distribution of microsites that produce or consume CH4 and N2O, such that a range of microsite concentrations occur both above and below ambient values for both GHGs. At lower mean soil moisture, some microsites of methanogenesis still occur, but most become sites of methanotrophy. Likewise, concentrations of below ambient N2O (hotspots of N2O reduction) occur in microsites with high C and high moisture (further accentuated at high temperature). Net consumption and production of CH4 and N2O is simulated within a chamber based on the sum of the distribution of soil microsites. Results demonstrate that it is numerically feasible for microsites of N2O reduction and CH4 oxidation to co-occur under a single chamber. Simultaneous simulation of all three GHGs in a parsimonious modeling framework is challenging but affords confidence that agreement between simulations and measurements is based on skillful numerical representation of processes across a heterogeneous environment.
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Bioremediation of fungicides by spent mushroom substrate and its associated microflora.
Ahlawat, O P; Gupta, Pardeep; Kumar, Satish; Sharma, D K; Ahlawat, K
2010-10-01
Experiments were conducted both under in vitro and in situ conditions to determine the biodegradation potential of button mushroom spent substrate (SMS) and its dominating microbes (fungi and bacteria) for carbendazim and mancozeb, the commonly used agricultural fungicides. During 6 days of incubation at 30 ± 2°C under broth culture conditions, highest degradation of carbendazim (17.45%) was recorded with B-1 bacterial isolate, while highest degradation of mancozeb (18.05%) was recorded with Trichoderma sp. In fungicide pre-mixed sterilized SMS, highest degradation of carbendazim (100.00-66.50 μg g(-1)) was recorded with mixed inoculum of Trichoderma sp. and Aspergillus sp., whereas highest degradation of mancozeb (100.00-50.50 μg g(-1)) was with mixed inoculum of Trichoderma sp., Aspergillus sp. and B-I bacterial isolate in 15 days of incubation at 30 ± 2°C. All these microbes both individually as well as in different combinations grew well and produced extracellular lignolytic enzymes on SMS, which helped in fungicides degradation. Under in situ conditions, among three different proportions of SMS (10, 20 and 30%, w/w) mixed with fungicide pre-mixed soil (100 μg g(-1) of soil), the degradation of carbendazim was highest in 30% SMS treatment, while for mancozeb it was in 20% SMS treatment. The residue levels of both fungicides decreased to half of their initial concentration after 1 month of SMS mixing.
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Aeolian dust nutrient contributions increase with substrate age in semi-arid ecosystems
NASA Astrophysics Data System (ADS)
Coble, A. A.; Hart, S. C.; Ketterer, M. E.; Newman, G. S.
2013-12-01
Rock-derived nutrients supplied by mineral weathering become depleted over time, and without an additional nutrient source the ecosystem may eventually regress or reach a terminal steady state. Previous studies have demonstrated that aeolian dust act as parent materials of soils and important nutrients to plants in arid regions, but the relative importance of these exogenous nutrients to the function of dry ecosystems during soil development is uncertain. Here, using strontium isotopes as a tracer and a well-constrained, three million year old substrate age gradient, we show that aeolian-derived nutrients become increasingly important to plant-available soil pools and tree (Pinus edulis) growth during the latter stages of soil development in a semi-arid climate. Furthermore, the depth of nutrient uptake increased on older substrates, suggesting that trees in arid regions acquire nutrients from greater depths as ecosystem development progresses presumably in response to nutrient depletion in the more weathered surface soils. Our results contribute to the unification of biogeochemical theory by demonstrating the similarity in roles of atmospheric nutrient inputs during ecosystem development across contrasting climates.
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Studies related to the development of the Viking 1975 labeled release experiment
NASA Technical Reports Server (NTRS)
Devincenzi, D. L.; Deal, P. H.
1976-01-01
The labeled release life detection experiment on the Viking 1975 Mars mission is based on the concept that microorganisms will metabolize radioactive organic substrates in a nutrient medium and release radioactive carbon dioxide. Several experiments, using laboratory equipment, were carried out to evaluate various aspects of the concept. Results indicate: (1) label is released by sterilization-treated soil, (2) substantial quantities of label are retained in solution under basic conditions, (3) the substrate used, as well as position of label in the molecule, affect release of label, (4) label release is depressed by radiolytic decomposition of substrates, and (5) About 100,000 organisms are required to produce a detectable response. These results, suggest additional areas for testing, add to the data base for interpretation of flight results, and have significance for broader application of this technique for assessing microbial activity.
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SOIL NITROGEN TRANSFORMATIONS AND ROLE OF LIGHT FRACTION ORGANIC MATTER IN FOREST SOILS
Depletion of soil organic matter through cultivation may alter substrate availability for microbes, altering the dynamic balance between nitrogen (N) immobilization and mineralization. Soil light fraction (LF) organic matter is an active pool that decreases upon cultivation, and...
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NASA Astrophysics Data System (ADS)
Kumar, Amit; Dorodnikov, Maxim; Splettstößer, Thomas; Kuzyakov, Yakov; Pausch, Johanna
2017-04-01
Soil aggregation and microbial activities within the aggregates are important factors regulating soil carbon (C) turnover. A reliable and sensitive proxy for microbial activity is activity of extracellular enzymes (EEA). In the present study, effects of soil aggregates on EEA were investigated under three maize plant densities (Low, Normal, and High). Bulk soil was fractionated into three aggregate size classes (>2000 µm large macroaggregates; 2000-250 µm small macroaggregates; <250 µm microaggregates) by optimal-moisture sieving. Microbial biomass and EEA (β-1,4-glucosidase (BG), β-1,4-N-acetylglucosaminidase (NAG), L-leucine aminopeptidase (LAP) and acid phosphatase (acP)) catalyzing soil organic matter (SOM) decomposition were measured in rooted soil of maize and soil from bare fallow. Microbial biomass C (Cmic) decreased with decreasing aggregate size classes. Potential and specific EEA (per unit of Cmic) increased from macro- to microaggregates. In comparison with bare fallow soil, specific EEA of microaggregates in rooted soil was higher by up to 73%, 31%, 26%, and 92% for BG, NAG, acP and LAP, respectively. Moreover, high plant density decreased macroaggregates by 9% compared to bare fallow. Enhanced EEA in three aggregate size classes demonstrated activation of microorganisms by roots. Strong EEA in microaggregates can be explained by microaggregates' localization within the soil. Originally adhering to surfaces of macroaggregates, microaggregates were preferentially exposed to C substrates and nutrients, thereby promoting microbial activity.
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Evaluation of TCDD biodegradability under different redox conditions.
Kao, C M; Chen, S C; Liu, J K; Wu, M J
2001-09-01
Polychlorinated dibenzo-p-dioxins have been generated as unwanted by-products in many industrial processes. Although their widespread distribution in different environmental compartments has been recognized, little is known about their fate in the ultimate environment sinks. The highly stable dioxin isomer 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) has been called the most toxic compound known to man. In this laboratory microcosm study, TCDD bioavailability was evaluated under five reduction/oxidation (redox) conditions including aerobic biodegradation, aerobic cometabolism, methanogenesis, iron reduction, and reductive dechlorination. Activated sludge and aquifer sediments from a TCDD and a pentachlorophenol (PCP) contaminated site were used as the inocula. Acetate, sludge cake, and cane molasses were used as the primary substrates (carbon sources) in cometabolism and reductive dechlorination microcosms. After a 90-day incubation period, microcosms constructed under reductive dechlorination conditions were the only treatment showing promising remediation results. The highest TCDD degradation rate [up to 86% of TCDD removal (with an initial concentration of 96 microg/kg of soil)] was observed in the microcosms with anaerobic activated sludge as the microbial inocula and sludge cakes as the primary substrates. Except for reductive dechlorination microcosms, no significant TCDD removal was observed in the microcosms prepared under other conditions. Thus, application of an effective primary substrate to enhance the reductive dechlorination process is a feasible method for TCDD bioremediation. Bioremediation expense can be significantly reduced by the supplement of some less expensive alternative substrates (e.g., sludge cakes, cane molasses). Results would be useful in designing a scale-up in situ or on-site bioremediation system such as bioslurry reactor for field application.
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NASA Astrophysics Data System (ADS)
Achiban, Hassan; Taous, Ali; El-Khantoury, Ismail; El Mderssa, Mohamed; Amechrouq, Ali
2018-05-01
The present study proposes to evaluate the extent of erosion according to the lithology in three sub-watersheds (Ras Elma, Sebab and Tamelalet) belonging to the Tigrigra basin and evolving in humid climatic context. The methodology adopts the revised universal soil loss equation (RUSLE). The results obtained make it possible to establish erosion class maps via GIS. A clear spatial difference in soil loss is observed, between the three sub-basins and in proportion to the lithology: on average 42.15 t/ha/year on Paleozoic schistose soils, against 17.06 t/ha/year on carbonate substrates Mesozoic and 8.46 t/ha/year on quaternary basalts. Correlations between soil loss and RUSLE factors are established. Soil infiltration regimes on different substrates are studied.
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Thermal adaptation of decomposer communities in warming soils
Bradford, Mark A.
2013-01-01
Temperature regulates the rate of biogeochemical cycles. One way it does so is through control of microbial metabolism. Warming effects on metabolism change with time as physiology adjusts to the new temperature. I here propose that such thermal adaptation is observed in soil microbial respiration and growth, as the result of universal evolutionary trade-offs between the structure and function of both enzymes and membranes. I review the basis for these trade-offs and show that they, like substrate depletion, are plausible mechanisms explaining soil respiration responses to warming. I argue that controversies over whether soil microbes adapt to warming stem from disregarding the evolutionary physiology of cellular metabolism, and confusion arising from the term thermal acclimation to represent phenomena at the organism- and ecosystem-levels with different underlying mechanisms. Measurable physiological adjustments of the soil microbial biomass reflect shifts from colder- to warmer-adapted taxa. Hypothesized declines in the growth efficiency of soil microbial biomass under warming are controversial given limited data and a weak theoretical basis. I suggest that energy spilling (aka waste metabolism) is a more plausible mechanism for efficiency declines than the commonly invoked increase in maintenance-energy demands. Energy spilling has many fitness benefits for microbes and its response to climate warming is uncertain. Modeled responses of soil carbon to warming are sensitive to microbial growth efficiency, but declines in efficiency mitigate warming-induced carbon losses in microbial models and exacerbate them in conventional models. Both modeling structures assume that microbes regulate soil carbon turnover, highlighting the need for a third structure where microbes are not regulators. I conclude that microbial physiology must be considered if we are to have confidence in projected feedbacks between soil carbon stocks, atmospheric CO2, and climate change. PMID:24339821
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Influence of the lower boundary in lysimeter observations
NASA Astrophysics Data System (ADS)
Weller, Ulrich; Richter, Katja; Gubis, Jozef; Vogel, Hans-Jörg
2014-05-01
Lysimeters are a valuable tool to study the water household in soils under close to natural conditions. One major drawback is that they are cut off at the lower boundary. This influences strongly the percolation of water. As long as water is leaching down in the soil, it is stagnating at the lower boundary until saturated conditions are reached and the water can percolate through the gravel filter, and under unsaturated conditions there is no flow at all at the lower boundary. In natural soils the water potential at the same depth differs considerably from the regime in a lysimeter. If the depth of the soil or the soil forming substrate is deep enough, the lower boundary is at the potential that allows the percolation of the long term mean of percolation. In other situations, a water table may influence the matric potential in the natural soil, or a less permeable layer may impede free drainage. In all these situations the matric potential at the depth of the lower boundary of the lysimeter will differ substantially in the natural soil. The latest generation of lysimeter therefore has a controlled lower boundary. The matric potential can be actively adjusted to a desired value over a broad range. Most applications connect the suction in the lysimeter to a reference value obtained in the field at the same depth in order to mimic the correct distribution of the soil water. In this presentation we demonstrate the long term influence of the different lower boundary regimes on percolation and evaporation of water based on soil physical models, and we show first field data on the practical implementations with several months of observations.
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NASA Astrophysics Data System (ADS)
Inisheva, L. I.; Szajdak, L.; Sergeeva, M. A.
2016-04-01
The biological activity in oligotrophic peatlands at the margins of the Vasyugan Mire has been studied. It is shown found that differently directed biochemical processes manifest themselves in the entire peat profile down to the underlying mineral substrate. Their activity is highly variable. It is argued that the notion about active and inert layers in peat soils is only applicable for the description of their water regime. The degree of the biochemical activity is specified by the physical soil properties. As a result of the biochemical processes, a micromosaic aerobic-anaerobic medium is developed under the surface waterlogged layer of peat deposits. This layer contains the gas phase, including oxygen. It is concluded that the organic and mineral parts of peat bogs represent a single functional system of a genetic peat profile with a clear record of the history of its development.
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Álvarez-Martín, Alba; Sánchez-Martín, María J; Ordax, José M; Marín-Benito, Jesús M; Sonia Rodríguez-Cruz, M
2017-04-15
A study has been conducted on the leaching of two fungicides, tebuconazole and cymoxanil, in a soil amended with spent mushroom substrate (SMS), with an evaluation of how different factors influence this process. The objective was based on the potential use of SMS as a biosorbent for immobilizing pesticides in vulnerable soils, and the need to know how it could affect the subsequent transport of these retained compounds. Breakthrough curves (BTCs) for 14 C-fungicides, non-incubated and incubated over 30days, were obtained in columns packed with an unamended soil (S), and this soil amended with SMS at rates of 5% (S+SMS5) and 50% (S+SMS50) under saturated and saturated-unsaturated flows. The highest leaching of tebuconazole (>50% of the total 14 C added) was found in S when a saturated water flow was applied to the column, but the percentage of leached fungicide decreased when a saturated-unsaturated flow was applied in both SMS-amended soils. Also a significant decrease in leaching was observed for tebuconazole after incubation in the column, especially in S+SMS50 when both flows were applied. Furthermore, cymoxanil leaching was complete in S and S+SMS when a saturated flow was applied, and maximum peak concentrations were reached at 1pore volume (PV), although BTCs showed peaks with lower concentrations in S+SMS. The amounts of cymoxanil retained only increased in S+SMS when a saturated-unsaturated flow was applied. A more relevant effect of SMS for reducing the leaching of fungicide was observed when cymoxanil was previously incubated in the column, although mineralization was enhanced in this case. These results are of interest for extending SMS application on the control of the leaching of fungicides with different physicochemical characteristics after different ageing times in the soil and water flow conditions applied. Copyright © 2017 Elsevier B.V. All rights reserved.
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Ginocchio, Rosanna; De la Fuente, Luz María; Sánchez, Pablo; Bustamante, Elena; Silva, Yasna; Urrestarazu, Paola; Rodríguez, Patricio H
2009-10-01
Pollution of soil with mine wastes results in both Cu enrichment and soil acidification. This confounding effect may be very important in terms of phytotoxicity, because pH is a key parameter influencing Cu solubility in soil solution. Laboratory toxicity tests were used to assess the effect of acidification by acidic mine wastes on Cu solubility and on root elongation of barley (Hordeum vulgare L.). Three contrasting substrates (two soils and a commercial sand) and two acidic, Cu-rich mine wastes (oxidized tailings [OxT] and smelter dust [SmD]) were selected as experimental materials. Substrates were spiked with a fixed amount of either SmD or OxT, and the pH of experimental mixtures was then modified in the range of 4.0 to 6.0 and 7.0 using PIPES (piperazine-1,4-bis(2-ethanesulfonic acid)), MES (2-(N-morpholino)ethanesulfonic acid), and MOPS (3-(N-Morpholino)-propanesulfonic acid) buffers. Chemical (pore-water Cu and pH) and toxicological (root length of barley plants) parameters were determined for experimental mixtures. Addition of SmD and OxT to substrates resulted in acidification (0.11-1.16 pH units) and high levels of soluble Cu and Zn. Neutralization of experimental mixtures with MES (pH 6.0) and MOPS (pH 7.0) buffers resulted in a marked decrease in soluble Cu and Zn, but the intensity of the effect was substrate-dependent. Adjustment of soil pH above the range normally considered to be toxic to plants (pH in water extract, > 5.5) significantly reduced metal toxicity in barley, but phytotoxicity was not completely eliminated. The present results stress the importance of considering confounding effects on derivation of toxicity thresholds to plants when using laboratory phytotoxicity tests.
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Microbial Community Responses to Glycine Addition in Kansas Prairie Soils
NASA Astrophysics Data System (ADS)
Bottos, E.; Roy Chowdhury, T.; White, R. A., III; Brislawn, C.; Fansler, S.; Kim, Y. M.; Metz, T. O.; McCue, L. A.; Jansson, J.
2015-12-01
Advances in sequencing technologies are rapidly expanding our abilities to unravel aspects of microbial community structure and function in complex systems like soil; however, characterizing the highly diverse communities is problematic, due primarily to challenges in data analysis. To tackle this problem, we aimed to constrain the microbial diversity in a soil by enriching for particular functional groups within a community through addition of "trigger substrates". Such trigger substrates, characterized by low molecular weight, readily soluble and diffusible in soil solution, representative of soil organic matter derivatives, would also be rapidly degradable. A relatively small energy investment to maintain the cell in a state of metabolic alertness for such substrates would be a better evolutionary strategy and presumably select for a cohort of microorganisms with the energetics and cellular machinery for utilization and growth. We chose glycine, a free amino acid (AA) known to have short turnover times (in the range of hours) in soil. As such, AAs are a good source of nitrogen and easily degradable, and can serve as building blocks for microbial proteins and other biomass components. We hypothesized that the addition of glycine as a trigger substrate will decrease microbial diversity and evenness, as taxa capable of metabolizing it are enriched in relation to those that are not. We tested this hypothesis by incubating three Kansas native prairie soils with glycine for 24 hours at 21 degree Celsius, and measured community level responses by 16S rRNA gene sequencing, metagenomics, and metatranscriptomics. Preliminary evaluation of 16S rRNA gene sequences revealed minor changes in bacterial community composition in response to glycine addition. We will also present data on functional gene abundance and expression. The results of these analyses will be useful in designing sequencing strategies aimed at dissecting and deciphering complex microbial communities.
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Keiluweit, Marco; Bougoure, Jeremy J.; Nico, Peter S.; ...
2015-03-30
Multiple lines of existing evidence suggest that climate change enhances root exudation of organic compounds into soils. Recent experimental studies show that increased exudate inputs may cause a net loss of soil carbon. This stimulation of microbial carbon mineralization (‘priming’) is commonly rationalized by the assumption that exudates provide a readily bioavailable supply of energy for the decomposition of native soil carbon (co-metabolism). Here we show that an alternate mechanism can cause carbon loss of equal or greater magnitude. We find that a common root exudate, oxalic acid, promotes carbon loss by liberating organic compounds from protective associations with minerals.more » By enhancing microbial access to previously mineral-protected compounds, this indirect mechanism accelerated carbon loss more than simply increasing the supply of energetically more favourable substrates. Lastly, our results provide insights into the coupled biotic–abiotic mechanisms underlying the ‘priming’ phenomenon and challenge the assumption that mineral-associated carbon is protected from microbial cycling over millennial timescales.« less
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NASA Astrophysics Data System (ADS)
Velitchko, Vladimir; Tikhomirov, Alexander; Ushakova, Sofya
To increase a closure level of mass exchange processes in bioregenerative life support systems (BLSS) including a human a technology of plants cultivation on a soil-like substrate (SLS) consisting in a gradual decomposition of inedible plants biomass under its addition in the SLS was developed at the Institute of Biophysics SB RAS (Russia). In the given work the effect of periodical introduction of inedible plant biomass in the SLS on plants photosynthetic productivity and on the closure of mass exchange has been analyzed. Thereupon CO2 gas exchange and the certain vegetables' productivity under their cultivation in a conveyor regime on the SLS and on a neutral substrate with reference to the closure of mass exchange processes in BLSS have been studied in this work. The vegetables Raphanus sativus L., Brassica caulorapa L. Daucus carota L. and Beta vulgaris L. being prospective plantsrepresentatives of the BLSS phototrophic unit were taken as the research objects. The SLS was taken as an experiment substrate and an expanded clay aggregate as the control. The changeable Knop solution was used for the control, and an irrigation solution with the SLS extract was used for the experiment. Rapidity dynamics of CO2 consumption showed sharp distinctions of the ‘plants-SLS' system from the ‘plantsexpanded clay aggregate' system connected with the oxidation processes coursing in the SLS. The intensity of CO2 evolution from the SLS on average was 70% of the total plants conveyor's respiration. Thus a balance between the system's respiration and photosynthesis was often determined by the processes coursing in the SLS. Here the sharp CO2 evolution was recorded after introduction of the plants inedible biomass in the SLS. That peak was gradually coming down during 10-14 days after the beginning of every cycle of plants cultivation that was connected with intensification of plants photosynthesis and drop of decomposition intensity of the biomass introduced. Comparative estimation of plants productivity in the control and in the experiment showed that the plants grown on the SLS had amassed less of total (on 40%) and edible (on 26%) dry biomass in comparison with the control. Probably that decrease in productivity was connected with unbalance on mineral elements under introduction of mineralized straw in the amount equivalent to the mass of the plants edible part. Cultivated on the SLS the vegetable conveyor on average gave 80 g*m-2 *day-1 of dry edible biomass that approximately amounted 13% of a total daily vegetative ration of a human. The use resources of the plants cultivation methods on different substrates under study depending on the requirements to a closure level of mass exchange processes in BLSS has been discussed.
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Weathering and genesis of Soils from Ellsworth Mountains, East Antarctica
NASA Astrophysics Data System (ADS)
Karoline Delpupo Souza, Katia; Schaefer, Carlos Ernesto; Michel, Roberto; Monari, Julia; Machado, Vania
2015-04-01
Knowledge on Antarctic soils from the Ellsworth Mountains (EM) are patchy comparatively with Dry Valleys soils from the Transantartic Mountains, and could help understand the genesis of cryogenic soils under extreme dry, cold desert conditions. The EM are a slightly arcuate 350-km-long north-northwest-trending mountain chain is bordered on the west by the polar plateau of West Antarctica and on the east by Ronne Ice Shelf. The range is as much as 90 km wide and constitutes one of the largest areas of exposed bedrock in West Antarctica. The stratigraphic succession in the EM includes strata from Cambriam to Permian in age. The objective of this study is to analyze the properties of soils from EM in order to identify the main factors and processes involved in soil formation under cold desert conditions in Antarctica. The sampling design aimed to represent the different geological substrates (marble-clast conglomerate, graywacke, argillite, conglomerate, black shale, marble and quartzite) as well as altitudinal levels and landforms within the same substrate. We characterized soils from EM regarding their morphological, physics and chemical properties. Soil samples were air dried and passed through 2 mm sieves. After removal of water soluble salts, the samples were submitted to chemical and physical analyses such as: pH in water, potential acidity (H + Al), exchangeable bases, total organic carbon, electric conductivity, soil texture and color. The soils classify, for the most part, in weathering stages 1 to 2. Only in the upper parts of ridges were there traces of soils at weathering stage 3. This indicates that much of the present icefree topography has been overridden by ice within the last few hundred thousand years. Cryoturbation is a widespread phenomenon in this area resulting in intense cryoclastic weathering and patterned ground, forming sorted circles, stripes and gelifluxion lobes. The soil show low horizontation, discrete patches of salt on the surface, and salt crusts beneath the rock fragments. Despite of the low weathering stage of the soil, they have yellowish hue and high chroma values from influence by sulfide material. Boulders on moraines show staining, pitting, spalling, and some striations. All soil are alkaline in reaction, with pHs at the range between 7.5-9.2. Cryptogamic (lichens or mosses) crusts are absent, and the organic matter contents were invariably very low, ranging between 0.13 and 0.38%. Permafrost is continuous and occurs close to the surface, at between 5-15 cm down the top. The available P background is also very low (< 5.3 mg/kg), exchangeable K and Na levels are surprisingly low for Polar Desert soils. Soils are all skelletic, with a predominance of coarse materials. CEC is medium to high, and Ca-dominated, as a result of a strong limestone influence in the moraine parent materials. The main salts present are Ca and Na-sulphate forms, and less cloride forms, and clay sized materials are dominated by salts in all soils, especially below 5 cm depth.
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Enzymatic mechanisms of soil-carbon response to temperature on Mt. Kilimanjaro
NASA Astrophysics Data System (ADS)
Blagodatskaya, Evgenia; Blagodatskiy, Sergey; Kuzyakov, Yakov
2016-04-01
Short-term acceleration of soil organic matter (SOM) decomposition by increasing temperature contradicts the acclimation observed in long-term studies. We used the unique altitudinal gradient (from colline tropical zone to subalpine zone) on Mt. Kilimanjaro to demonstrate the mechanisms of short- and long-term acclimation of extra- and intracellular enzymes that decompose polymers (cellulose, chitin, phytate) and oxidize monomers (14C-glucose). Basing on Michaelis-Menten kinetics we determined the enzymes affinity to substrate (Km) and mineralization potential of heterotrophic microorganisms (Vmax) 1) for three hydrolytic enzymes: β-1,4-glucosidase, N-acetyl- β -D-glucosaminidase and phosphatase by the application of fluorogenically labeled substrates and 2) for mineralization of 14C-labeled glucose by substrate-dependent respiratory response. Here we show that the amount of available substrate is responsible for temperature sensitivity of hydrolysis of polymers in soil, whereas monomers oxidation to CO2 does not depend on substrate amount and is mainly temperature governed. We also found that substrate affinity of enzymes (which is usually decreases with the temperature) differently responded to warming for the process of depolymerisation versus monomers oxidation. We suggest the mechanism to temperature acclimation based on different temperature sensitivity of enzymes kinetics for hydrolysis of polymers and for monomers oxidation
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Preliminary assessment of soil moisture over vegetation
NASA Technical Reports Server (NTRS)
Carlson, T. N.
1986-01-01
Modeling of surface energy fluxes was combined with in-situ measurement of surface parameters, specifically the surface sensible heat flux and the substrate soil moisture. A vegetation component was incorporated in the atmospheric/substrate model and subsequently showed that fluxes over vegetation can be very much different than those over bare soil for a given surface-air temperature difference. The temperature signatures measured by a satellite or airborne radiometer should be interpreted in conjunction with surface measurements of modeled parameters. Paradoxically, analyses of the large-scale distribution of soil moisture availability shows that there is a very high correlation between antecedent precipitation and inferred surface moisture availability, even when no specific vegetation parameterization is used in the boundary layer model. Preparatory work was begun in streamlining the present boundary layer model, developing better algorithms for relating surface temperatures to substrate moisture, preparing for participation in the French HAPEX experiment, and analyzing aircraft microwave and radiometric surface temperature data for the 1983 French Beauce experiments.
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Microbial responses to chitin and chitosan in oxic and anoxic agricultural soil slurries
NASA Astrophysics Data System (ADS)
Wieczorek, A. S.; Hetz, S. A.; Kolb, S.
2014-06-01
Microbial degradation of chitin in soil substantially contributes to carbon cycling in terrestrial ecosystems. Chitin is globally the second most abundant biopolymer after cellulose and can be deacetylated to chitosan or can be hydrolyzed to N,N'-diacetylchitobiose and oligomers of N-acetylglucosamine by aerobic and anaerobic microorganisms. Which pathway of chitin hydrolysis is preferred by soil microbial communities is unknown. Supplementation of chitin stimulated microbial activity under oxic and anoxic conditions in agricultural soil slurries, whereas chitosan had no effect. Thus, the soil microbial community likely was more adapted to chitin as a substrate. In addition, this finding suggested that direct hydrolysis of chitin was preferred to the pathway that starts with deacetylation. Chitin was apparently degraded by aerobic respiration, ammonification, and nitrification to carbon dioxide and nitrate under oxic conditions. When oxygen was absent, fermentation products (acetate, butyrate, propionate, hydrogen, and carbon dioxide) and ammonia were detected, suggesting that butyric and propionic acid fermentation, along with ammonification, were likely responsible for anaerobic chitin degradation. In total, 42 different chiA genotypes were detected of which twenty were novel at an amino acid sequence dissimilarity of less than 50%. Various chiA genotypes responded to chitin supplementation and affiliated with a novel deep-branching bacterial chiA genotype (anoxic conditions), genotypes of Beta- and Gammaproteobacteria (oxic and anoxic conditions), and Planctomycetes (oxic conditions). Thus, this study provides evidence that detected chitinolytic bacteria were catabolically diverse and occupied different ecological niches with regard to oxygen availability enabling chitin degradation under various redox conditions on community level.
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Interactions between extracellular polymeric substances and clay minerals affect soil aggregation
NASA Astrophysics Data System (ADS)
Vogel, Cordula; Rehschuh, Stephanie; Kemi Olagoke, Folasade; Redmile Gordon, Marc; Kalbiltz, Karsten
2017-04-01
Soil aggregation is crucial for carbon (C) sequestration and microbial processes have been recognised as important control of aggregate turnover (formation, stability, and destruction). However, how microorganisms contribute to these processes is still a matter of debate. An enthralling mechanism determining aggregate turnover and therefore C sequestration may be the excretion of extracellular polymeric substances (EPS) as microbial glue, but effects of EPS on aggregation is largely unknown. Moreover, interdependencies between important aggregation factors like the amount of fine-sized particles (clay content), the decomposability of organic matter and the microbial community (size and composition, as well as the excretion of EPS) are still poorly understood. Therefore, we studied the complex interactions between these factors and their role in aggregate turnover. It was hypothesized that an increase in microbial activity, induced by the input of organic substrates, will stimulate EPS production and therefore the formation and stability of aggregates. To test this hypothesis, an incubation experiment has been conducted across a gradient of clay content (montmorillonite) and substrate decomposability (starch and glucose) as main drivers of the microbial activity. A combination of aggregate separation and stability tests were applied. This results will be examined with respect to the obtained microbial parameters (amount and composition of EPS, CO2 emission, microbial biomass, phospholipid fatty acid), to disentangle the mechanisms and factors controlling aggregate turnover affected by soil microorganisms. This study is expected to provide insights on the role of EPS in the stability of aggregates. Thus, the results of this study will provide an improved understanding of the underlying processes of aggregate turnover in soils, which is necessary to implement strategies for enhanced C sequestration in agricultural soils.
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Roohi, Mahnaz; Riaz, Muhammad; Arif, Muhammad Saleem; Shahzad, Sher Muhammad; Yasmeen, Tahira; Riaz, Muhammad Atif; Tahir, Shermeen; Mahmood, Khalid
2016-12-01
Wastewater is an alternative, valuable and cost effective resource for irrigation in water-scarce arid and sami-arid regions of the world including Pakistan. Soils near urban centers are cultivated for vegetable and cash crops using untreated wastewater. Current study was performed with objectives of assessing impacts of untreated textile wastewater on some soil chemical, biological and enzymatic activities. The microcosm incubation study used a clay loam soil that received 0 (distilled-water), 25, 50 and 100% wastewater concentrations and incubated for 30 and 60 days under optimum temperature and moisture conditions. Soil respiration was measured periodically throughout the experiment over 60 days. After the incubation periods of 30- and 60-d, soils were destructively analyzed for pH, electrical conductivity (EC), water extractable organic matter (WEOM), microbial biomass carbon (MBC), microbial metabolic quotient (qCO 2 ) and dehydrogenase enzymatic activity. Results revealed that wastewater and incubation time significantly altered chemical, biological and enzymatic properties of soils. The observed large surge in soil respiration, at initial stage, was stimulated by dissolved organic matter in wastewater. Dehydrogenase activity increased significantly with increasing wastewater concentrations. Increase in qCO 2 with wastewater concentration and incubation time suggested more stress to microorganisms but also enhanced microbial activity under stress to synthesize biomass. We found significant positive (R 2 = 0.64, p < 0.001) relationship between soil respiration and MBC, however, correlation between WEOM and MBC was significant negative (R 2 = 0.18, p < 0.01) indicating a dynamic mismatch between carbon substrate, soil respiration and buildup of MBC pool. Wastewater concentration and incubation time interaction had significant (p < 0.01) effect on WEOM suggesting that WEOM accumulated over time and comparatively less utilized by microorganisms. Short- and long-term effects of untreated wastewater on soil physico-chemical and biological health should be assessed before its use for crop production. Copyright © 2016 Elsevier Ltd. All rights reserved.
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Influence of crop rotation and tillage intensity on soil physical properties and functions
NASA Astrophysics Data System (ADS)
Krümmelbein, Julia
2013-04-01
Soil tillage intensity can vary concerning tillage depth, frequency, power input into the soil and degree of soil turn-over. Conventional tillage systems where a plough is regularly used to turn over the soil can be differentiated from reduced tillage systems without ploughing but with loosening the upper soil and no tillage systems. Between conventional tillage and no tillage is a wide range of more or less reduced tillage systems. In our case the different tillage intensities are not induced by different agricultural machinery or techniques, but result from varying crop rotations with more or less perennial crops and therefore lower or higher tillage frequency. Our experimental area constitutes of quite unstructured substrates, partly heavily compacted. The development of a functioning soil structure and accumulation of nutrients and organic matter are of high importance. Three different crop rotations induce varying tillage intensities and frequencies. The first crop rotation (Alfalfa monoculture) has only experienced seed bed preparation once and subsequently is wheeled once a year to cut and chaff the biomass. The second crop rotation contains perennial and annual crops and has therefore been tilled more often, while the third crop rotation consists only of annual crops with annual seedbed preparation. Our results show that reduced tillage intensity/frequency combined with the intense root growth of Alfalfa creates the most favourable soil physical state of the substrate compared to increased tillage and lower root growth intensity of the other crop rotations. Soil tillage disturbs soil structure development, especially when the substrate is mechanically unstable as in our case. For such problematic locations it is recommendable to reduce tillage intensity and/or frequency to allow the development of soil structure enhanced by root growth and thereby the accumulation of organic matter and nutrients within the rooting zone.
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Suyama, Tetsushi; Tokiwa, Yutaka; Ouichanpagdee, Pornpimol; Kanagawa, Takahiro; Kamagata, Yoichi
1998-01-01
Thirty-nine morphologically different soil bacteria capable of degrading poly(β-hydroxyalkanoate), poly(ɛ-caprolactone), poly(hexamethylene carbonate), or poly(tetramethylene succinate) were isolated. Their phylogenetic positions were determined by 16S ribosomal DNA sequencing, and all of them fell into the classes Firmicutes and Proteobacteria. Determinations of substrate utilization revealed characteristic patterns of substrate specificities. PMID:9835597
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Phosphorus contents and availability of technogenic substrates for soil construction
NASA Astrophysics Data System (ADS)
Nehls, Thomas; Lydia, Paetsch; Sarah, Rokia; Schwartz, Christophe; Wessolek, Gerd
2014-05-01
Urban areas lack of green and of soil substrates to support this green. A great variety of solid waste materials can be seen as technogenic substances (TS) for the construction of soil-similar plant substrates. Biomass production in the city and the use of waste materials as nutrient sources can help to close regional nutrient cycles. The most important waste materials have been studied for their phosphorus contents, availabilities and diffusion rates in the rhizosphere by combining their analyzed chemical and physical properties. Compost, concrete, green wastes, paper mill sludge, street-sweepings, mix of rubble, bricks, track ballasts and charcoal have (i) been analyzed their P release properties (HF extraction, Olsen-P, adsorption isotherms); (ii) the physical properties (water retention function, saturated hydraulic conductivity) were analyzed at 80 % of the proctor density; (iii) The P availability of the TMs to the roots were simulated for different pressure heads (pF = 1.3, 1.8 and 3.0) using HYDRUS 1-D. We compared the results for TS with these for agricultural soils. Ptot varies from 710 to 21 000 mg kg-1 for bricks and compost, while POlsen varies from 19 to 1 090 mg kg-1 for charcoal and green wastes. The diffusion rates of TSs (pF = 1.3) are up to 10 times higher compared to those of soils, with green wastes showing highest and bricks the lowest P diffusion rates. We conclude that the investigated TS are appropriate for construction of soil similar planting substrates because of their P delivery potential and their favourable physical properties.
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Electrokinetic transport of aerobic microorganisms under low-strength electric fields.
Maillacheruvu, Krishnanand Y; Chinchoud, Preethi R
2011-01-01
To investigate the feasibility of utilizing low strength electric fields to transport commonly available mixed cultures such as those from an activated sludge process, bench scale batch reactor studies were conducted in sand and sandy loam soils. A readily biodegradable substrate, dextrose, was used to test the activity of the transported microorganisms. Electric field strengths of 7V, 10.5V, and 14V were used. Results from this investigation showed that an electric field strength of 0.46 Volts per cm was sufficient to transport activated sludge microorganisms across a sandy loam soil across a distance of about 8 cm in 72 h. More importantly, the electrokinetically transported microbial culture remained active and viable after the transport process and was biodegrade 44% of the dextrose in the soil medium. Electrokinetic treatment without microorganisms resulted in removal of 37% and the absence of any treatment yielded a removal of about 15%.
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Wine from the Netherlands: investigating the effect of soil-type on taste
NASA Astrophysics Data System (ADS)
Vis, Geert-Jan; Maljers, Denise; Beurskens, Stan
2016-04-01
During the last decade professional viticulture has seen a strong increase in the Netherlands, reaching 270 ha in 2015. Although on a European scale this is a small area, the number of prize-winning quality wines is steadily growing. This growth can largely be ascribed to new grape varieties from Germany and Switzerland, that are better adapted to the cooler and moister climate at the northern fringe of the viticultural zone, as well as to increasing viticultural expertise. The distribution of vineyards across the Netherlands shows that they occur on a plethora of substrates. Dutch substrate is dominated by typical lowland deposits such as fluvial and marine sands and clays and aeolian sands. Unlike many European countries, bedrock is scarce. Only in the south-eastern extremity and in the east of the country, carbonate bedrock is present at or near the surface. This wide variety of substrate triggered our interest in the effect of the various soil-types on the smell and taste characteristics of wines. An effect which is often mentioned concerning well-known foreign wines. We wondered whether an Auxerrois wine from carbonate rocks tastes significantly different from a wine from the same grape variety from loess. And how about a Johanniter wine from fluvial deposits versus windblown sands? And what happens if you make wine in exactly the same way with the same grape variety and from the same vineyard, but with three different yeast types? To answer our questions, we selected ten Dutch vineyards with varying soil-types and the grape varieties Auxerrois and Johanniter. In October 2014 we harvested the grapes and wine was made under controlled identical conditions (in a double setup). The wines were scientifically tested at the institute of Viticulture and Oenology in Neustadt, Germany. The results show no significant effect of soil-type on the smell and taste of Dutch wines in our experiment. Varying yeast types (Cryarome, 3079, VL2) used on Souvignier Gris grapes from the same vineyard did show significant differences in the taste characteristics. We conclude that the effect of grape ripening and yeast on the smell and taste of Dutch wines is much stronger than the effect of soil. This implies that from virtually any soil a high-quality wine can be made. The use of geology to promote the quality of a wine is thus merely a marketing tool.
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Downie, Helen F; Valentine, Tracy A; Otten, Wilfred; Spiers, Andrew J; Dupuy, Lionel X
2014-01-01
The recently developed transparent soil consists of particles of Nafion, a polymer with a low refractive index (RI), which is prepared by milling and chemical treatment for use as a soil analog. After the addition of a RI-matched solution, confocal imaging can be carried out in vivo and without destructive sampling. In a previous study, we showed that the new substrate provides a good approximation of plant growth conditions found in natural soils. In this paper, we present further development of the techniques for detailed quantitative analysis of images of root-microbe interactions in situ. Using this system it was possible for the first time to analyze bacterial distribution along the roots and in the bulk substrate in vivo. These findings indicate that the coupling of transparent soil with light microscopy is an important advance toward the discovery of the mechanisms of microbial colonisation of the rhizosphere.
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NASA Astrophysics Data System (ADS)
Preusser, Sebastian; Poll, Christian; Marhan, Sven; Kandeler, Ellen
2017-04-01
At the global scale, soil organic carbon (SOC) represents the largest active terrestrial organic carbon (OC) pool. Carbon dynamics in subsoil, however, vary from those in topsoil with much lower C concentrations in subsoil than in topsoil horizons, although more than 50 % of SOC is stored in subsoils below 30 cm soil depth. In addition, microorganisms in subsoil are less abundant, more heterogeneously distributed and the microbial communities have a lower diversity than those in topsoil. Especially in deeper soil, the impact of changes in habitat conditions on microorganisms involved in carbon cycling are largely unexplored and consequently the understanding of microbial functioning is limited. A reciprocal translocation experiment allowed us to investigate the complex interaction effects of altered environmental and substrate conditions on microbial decomposer communities in both topsoil and subsoil habitats under in situ conditions. We conducted this experiment with topsoil (5 cm soil depth) and subsoil (110 cm) samples of an acid and sandy Dystric Cambisol from a European beech (Fagus sylvatica L.) forest in Lower Saxony, Germany. In total 144 samples were buried into three depths (5 cm, 45 cm and 110 cm) and 13C-labelled root litter was added to expose the samples to different environmental conditions and to increase the substrate availability, respectively. Samples were taken in three month intervals up to a maximum exposure time of one year to follow the temporal development over the experimental period. Analyses included 13Cmic and 13C PLFA measurements to investigate the response of microbial abundance, community structure and 13C-root decomposition activity under the different treatments. Environmental conditions in the respective soil depths such as soil temperature and water content were recorded throughout the experimental period. All microbial groups (gram+ and gram- bacteria, fungi) showed highest relative 13C incorporation in 110 cm depth and samples with root addition had generally higher microbial abundances than those with no root addition. Here, especially fungi benefited from the additional carbon source with highly increased abundances in all incorporation depths. Also the altered environmental conditions in the different incorporation depths significantly influenced the different microbial groups. The steepest decrease with depth was detected in fungal abundance, while bacteria were less affected and increased in relative abundance in soil samples incorporated into subsoil layers. The highest seasonal variability in microbial abundance, however, was determined in 5 cm incorporation depth demonstrating the higher amplitude in micro-climatic and micro-environmental conditions in this near-surface soil habitat. In summary, this experiment demonstrated that carbon quality and quantity are the main factors restricting fungal abundance in deeper soil layers, while bacterial decomposer communities are adapted to a wider range of habitat conditions.
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Senna, André M; Botaro, Vagner R
2017-08-28
To study the behavior of a biodegradable hydrogel derived from cellulose acetate and ethylenediaminetetraacetic dianhydride (EDTAD), as a reduction substrate of NPK fertilizer in soil. The biodegradable hydrogel (HEDTA) was prepared from cellulose acetate (CA) with a degree substitution (DS) 2.5 by esterification crosslinking with EDTAD catalyzed by triethylamine. We systematically investigated the performance of the HEDTA in the reducing NPK (Ammonium, phosphate and potassium) fertilizer leaching. We also compare the percentage of leaching between the HEDTA and commercial fertilizers. To characterize the esterification and crosslinking between CA and EDTAD, FTIR spectroscopy and thermogravimetric analysis (DTG) were employed. The biodegradation experiments were carried out in simulated soil (23% of sand, 23% of cattle manure, 23% of soil and 31% of water) and the HEDTA was tested in the eucalyptus planting during the dry season in the São Paulo state, Brazil. The HEDTA was able to reduce the leaching of fertilizers and improve the performance of eucalyptus seedlings and reduced the mortality of the seedlings. The HEDTA showed to be an excellent substrate for slow release and water-retention in soil, reducer of the fertilizers leaching, in addition being nontoxic, biodegradable in the soil and environmentally-friendly. Copyright © 2017 Elsevier B.V. All rights reserved.
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Campo, Julio; Merino, Agustín
2016-05-01
The effect of precipitation regime on the C cycle of tropical forests is poorly understood, despite the existence of models that suggest a drier climate may substantially alter the source-sink function of these ecosystems. Along a precipitation regime gradient containing 12 mature seasonally dry tropical forests growing under otherwise similar conditions (similar annual temperature, rainfall seasonality, and geological substrate), we analyzed the influence of variation in annual precipitation (1240 to 642 mm) and duration of seasonal drought on soil C. We investigated litterfall, decomposition in the forest floor, and C storage in the mineral soil, and analyzed the dependence of these processes and pools on precipitation. Litterfall decreased slightly - about 10% - from stands with 1240 mm yr(-1) to those with 642 mm yr(-1), while the decomposition decreased by 56%. Reduced precipitation strongly affected C storage and basal respiration in the mineral soil. Higher soil C storage at the drier sites was also related to the higher chemical recalcitrance of litter (fine roots and forest floor) and the presence of charcoal across sites, suggesting an important indirect influence of climate on C sequestration. Basal respiration was controlled by the amount of recalcitrant organic matter in the mineral soil. We conclude that in these forest ecosystems, the long-term consequences of decreased precipitation would be an increase in organic layer and mineral soil C storage, mainly due to lower decomposition and higher chemical recalcitrance of organic matter, resulting from changes in litter composition and, likely also, wildfire patterns. This could turn these seasonally dry tropical forests into significant soil C sinks under the predicted longer drought periods if primary productivity is maintained. © 2016 John Wiley & Sons Ltd.
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Soil Minerals Affect Extracellular Enzyme Activities in Cold and Warm Environments
NASA Astrophysics Data System (ADS)
Yang, Z.; Morin, M. M.; Graham, D. E.; Wullschleger, S. D.; Gu, B.
2017-12-01
Extracellular enzymes are mainly responsible for degrading and cycling soil organic matter (SOM) in both cold and warm terrestrial ecosystems. Minerals can play important roles in affecting soil enzyme activities, however, the interactions between enzyme and soil minerals remain poorly understood. In this study, we developed a model soil-enzyme system to examine the mineral effects on a hydrolytic enzyme (i.e., β-glucosidase) under both cold (4°C) and relatively warm (20 and 30°C) conditions. Minerals including iron oxides and clays (e.g., kaolinite and montmorillonite) were used to mimic different types of soils, and enzyme adsorption experiments were conducted to determine the enzyme interactions with different mineral surfaces. Time-series experiments were also carried out to measure enzymatic degradation of the organic substrates, such as cellobiose and indican. We observed that fractions of adsorbed enzyme and the hydrolytic activity were higher on iron oxides (e.g., hematite) compared to kaolinite and montmorillonite at given experimental conditions. The degradation of cellobiose was significantly faster than that of indican in the presence of minerals. We also found that the adsorption of enzyme was not dependent on the mineral surface areas, but was controlled by the mineral surface charge. In addition, temperature increase from 4 to 30°C enhanced mineral-assisted glucosidase hydrolysis by 2 to 4 fold, suggesting greater degradation under warmer environments. The present work demonstrates that the enzyme activity is influenced not only by the soil temperature but also by the surface chemistry of soil minerals. Our results highlight the need to consider the physical and chemical properties of minerals in biogeochemical models, which could provide a better prediction for enzyme-facilitated SOM transformations in terrestrial ecosystems.
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NASA Astrophysics Data System (ADS)
Gu, B.
2017-12-01
It is estimated that Arctic permafrost soils store approximately half of the global belowground organic carbon, which is susceptible to microbial decomposition under warming climate. Studies have shown that rates of soil organic carbon (SOC) decomposition are controlled not only by temperature but also SOC substrate quality or chemical composition. However, detailed molecular-scale characterization of SOC and its susceptibility to degradation are lacking, due to extremely complex nature of SOC. Here, ultrahigh resolution Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS) was utilized to determine compositional changes of SOC during a microcosm warming experiment using tundra soils that were collected from the Barrow Environmental Observatory in Alaska, USA. Soil microcosm incubation was conducted with both organic and mineral active layer soils at two temperatures (-2°C and 8°C) up to 122 days, and water-extractable SOC was analyzed. Results indicate that peptides, amino sugars, and carbohydrate-like compounds are among the most labile SOC compounds to be degraded, with nitrogen-containing compounds degrading at a much faster rate than those containing no nitrogen. Refractory SOC components are dominated by the lignin- or tannin-like compounds and, to a less extent, the aliphatic compounds. Additionally, elemental ratios of O:C, H:C, and N:C were found to decrease with incubation time, and SOC in the mineral soil exhibited lower O:C and N:C ratios than those of the organic-rich soil. A biodegradation index is proposed to facilitate the incorporation of mass spectrometry data into mechanistic models of SOC degradation and thus improved prediction model of climate feedbacks in the Arctic.
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NASA Astrophysics Data System (ADS)
Gilbert, A.; Yamada, K.; Julien, M.; Yoshida, N.; Remaud, G.; Robins, R.
2016-12-01
It is estimated that Arctic permafrost soils store approximately half of the global belowground organic carbon, which is susceptible to microbial decomposition under warming climate. Studies have shown that rates of soil organic carbon (SOC) decomposition are controlled not only by temperature but also SOC substrate quality or chemical composition. However, detailed molecular-scale characterization of SOC and its susceptibility to degradation are lacking, due to extremely complex nature of SOC. Here, ultrahigh resolution Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS) was utilized to determine compositional changes of SOC during a microcosm warming experiment using tundra soils that were collected from the Barrow Environmental Observatory in Alaska, USA. Soil microcosm incubation was conducted with both organic and mineral active layer soils at two temperatures (-2°C and 8°C) up to 122 days, and water-extractable SOC was analyzed. Results indicate that peptides, amino sugars, and carbohydrate-like compounds are among the most labile SOC compounds to be degraded, with nitrogen-containing compounds degrading at a much faster rate than those containing no nitrogen. Refractory SOC components are dominated by the lignin- or tannin-like compounds and, to a less extent, the aliphatic compounds. Additionally, elemental ratios of O:C, H:C, and N:C were found to decrease with incubation time, and SOC in the mineral soil exhibited lower O:C and N:C ratios than those of the organic-rich soil. A biodegradation index is proposed to facilitate the incorporation of mass spectrometry data into mechanistic models of SOC degradation and thus improved prediction model of climate feedbacks in the Arctic.
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Soil-plant-microbial relations in hydrothermally altered soils of Northern California
Blecker, S.W.; Stillings, L.L.; DeCrappeo, N.M.; Ippolito, J.A.
2014-01-01
Soils developed on relict hydrothermally altered soils throughout the Western USA present unique opportunities to study the role of geology on above and belowground biotic activity and composition. Soil and vegetation samples were taken at three unaltered andesite and three hydrothermally altered (acid-sulfate) sites located in and around Lassen VolcanicNational Park in northeastern California. In addition, three different types of disturbed areas (clearcut, thinned, and pipeline) were sampled in acid-sulfate altered sites. Soils were sampled (0–15 cm) in mid-summer 2010 from both under-canopy and between-canopy areas within each of the sites. Soils were analyzed for numerous physical and chemical properties along with soil enzyme assays, C and N mineralization potential, microbial biomass-C and C-substrate utilization. Field vegetation measurements consisted of canopy cover by life form (tree, shrub, forb, and grass), tree and shrub density, and above-ground net primary productivity of the understory. Overall, parameters at the clearcut sites were more similar to the unaltered sites, while parameters at the thinned and pipeline sites were more similar to the altered sites. We employed principal components analysis (PCA) to develop two soil quality indices (SQI) to help quantify the differences among the sites: one based on the correlation between soil parameters and canopy cover, and the second based on six sub-indices. Soil quality indices developed in these systems could provide a means for monitoring and identifying key relations between the vegetation, soils, and microorganisms.
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NASA Astrophysics Data System (ADS)
Kudrevatykh, Irina; Ivashchenko, Kristina; Ananyeva, Nadezhda
2016-04-01
Inflow of pollutants in terrestrial ecosystems nowadays increases dramatically, that might be led to disturbance of natural biogeochemical cycles and landscapes structure. Production of nitrogen fertilizers is one of the air pollution sources, namely by nitrogen compounds (NH4+, NO3-, NO2-). Air pollution by nitrogen compounds of terrestrial ecosystems might be affected on soil biochemical properties, which results increasing mineral nitrogen content in soil, changing soil P/N and Al/Ca ratios, and, finally, the deterioration of soil microbial community functioning. The research is focused on the assessment of anthropogenic emission of nitrogen compounds on soil properties of grassland ecosystems in European Russia. Soil samples (Voronic Chernozem Pachic, upper 10 cm mineral layer, totally 10) were taken from grassland ecosystem: near (5-10 m) nitrogen fertilizer factory (NFF), and far from it (20-30 km, served as a control) in Tula region. In soil samples the NH4+ and NO3- (Kudeyarov's photocolorimetric method), P, Ca, Al (X-ray fluorescence method) contents were measured. Soil microbial biomass carbon (Cmic) was analyzed by substrate-induced respiration method. Soil microbial respiration (MR) was assessed by CO2 rate production. Soil microbial metabolic quotient (qCO2) was calculated as MR/Cmic ratio. Near NFF the soil ammonium and nitrate nitrogen contents were a strongly varied, variation coefficient (CV) was 42 and 86This study was supported by Russian Foundation of Basic Research Grant No. 14-04-00098, 15-44-03220, 15-04-00915.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Jenkins, Stefan; Swenson, Tami L.; Lau, Rebecca
Exometabolomics enables analysis of metabolite utilization of low molecular weight organic substances by soil bacteria. Thus, environmentally-based defined media are needed to examine ecologically relevant patterns of substrate utilization. Here, we describe an approach for the construction of defined media using untargeted characterization of water soluble soil microbial metabolites from a saprolite soil collected from the Oak Ridge Field Research Center (ORFRC). To broadly characterize metabolites, both liquid chromatography mass spectrometry (LC/MS) and gas chromatography mass spectrometry (GC/MS) were used. With this approach, 96 metabolites were identified, including amino acids, amino acid derivatives, sugars, sugar alcohols, mono- and di-carboxylic acids,more » nucleobases, and nucleosides. From this pool of metabolites, 25 were quantified. Molecular weight cut-off filtration determined the fraction of carbon accounted for by the quantified metabolites and revealed that these soil metabolites have an uneven quantitative distribution (e.g., trehalose accounted for 9.9% of the < 1 kDa fraction). This quantitative information was used to formulate two soil defined media (SDM), one containing 23 metabolites (SDM1) and one containing 46 (SDM2). To evaluate the viability of the SDM, we examined the growth of 30 phylogenetically diverse soil bacterial isolates from the ORFRC field site. The simpler SDM1 supported the growth of 13 isolates while the more complex SDM2 supported 15 isolates. To investigate SDM1 substrate preferences, one isolate, Pseudomonas corrugata strain FW300-N2E2 was selected for a time-series exometabolomics analysis. Interestingly, it was found that this organism preferred lower-abundance substrates such as guanine, glycine, proline and arginine and glucose and did not utilize the more abundant substrates maltose, mannitol, trehalose and uridine. These results demonstrate the viability and utility of using exometabolomics to construct a tractable environmentally relevant media. We anticipate that this approach can be expanded to other environments to enhance isolation and characterization of diverse microbial communities.« less
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Jenkins, Stefan; Swenson, Tami L.; Lau, Rebecca; Rocha, Andrea M.; Aaring, Alex; Hazen, Terry C.; Chakraborty, Romy; Northen, Trent R.
2017-01-01
Exometabolomics enables analysis of metabolite utilization of low molecular weight organic substances by soil bacteria. Environmentally-based defined media are needed to examine ecologically relevant patterns of substrate utilization. Here, we describe an approach for the construction of defined media using untargeted characterization of water soluble soil microbial metabolites from a saprolite soil collected from the Oak Ridge Field Research Center (ORFRC). To broadly characterize metabolites, both liquid chromatography mass spectrometry (LC/MS) and gas chromatography mass spectrometry (GC/MS) were used. With this approach, 96 metabolites were identified, including amino acids, amino acid derivatives, sugars, sugar alcohols, mono- and di-carboxylic acids, nucleobases, and nucleosides. From this pool of metabolites, 25 were quantified. Molecular weight cut-off filtration determined the fraction of carbon accounted for by the quantified metabolites and revealed that these soil metabolites have an uneven quantitative distribution (e.g., trehalose accounted for 9.9% of the <1 kDa fraction). This quantitative information was used to formulate two soil defined media (SDM), one containing 23 metabolites (SDM1) and one containing 46 (SDM2). To evaluate the viability of the SDM, we examined the growth of 30 phylogenetically diverse soil bacterial isolates from the ORFRC field site. The simpler SDM1 supported the growth of 13 isolates while the more complex SDM2 supported 15 isolates. To investigate SDM1 substrate preferences, one isolate, Pseudomonas corrugata strain FW300-N2E2 was selected for a time-series exometabolomics analysis. Interestingly, it was found that this organism preferred lower-abundance substrates such as guanine, glycine, proline and arginine and glucose and did not utilize the more abundant substrates maltose, mannitol, trehalose and uridine. These results demonstrate the viability and utility of using exometabolomics to construct a tractable environmentally relevant media. We anticipate that this approach can be expanded to other environments to enhance isolation and characterization of diverse microbial communities. PMID:29312276
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Jenkins, Stefan; Swenson, Tami L.; Lau, Rebecca; ...
2017-12-22
Exometabolomics enables analysis of metabolite utilization of low molecular weight organic substances by soil bacteria. Thus, environmentally-based defined media are needed to examine ecologically relevant patterns of substrate utilization. Here, we describe an approach for the construction of defined media using untargeted characterization of water soluble soil microbial metabolites from a saprolite soil collected from the Oak Ridge Field Research Center (ORFRC). To broadly characterize metabolites, both liquid chromatography mass spectrometry (LC/MS) and gas chromatography mass spectrometry (GC/MS) were used. With this approach, 96 metabolites were identified, including amino acids, amino acid derivatives, sugars, sugar alcohols, mono- and di-carboxylic acids,more » nucleobases, and nucleosides. From this pool of metabolites, 25 were quantified. Molecular weight cut-off filtration determined the fraction of carbon accounted for by the quantified metabolites and revealed that these soil metabolites have an uneven quantitative distribution (e.g., trehalose accounted for 9.9% of the < 1 kDa fraction). This quantitative information was used to formulate two soil defined media (SDM), one containing 23 metabolites (SDM1) and one containing 46 (SDM2). To evaluate the viability of the SDM, we examined the growth of 30 phylogenetically diverse soil bacterial isolates from the ORFRC field site. The simpler SDM1 supported the growth of 13 isolates while the more complex SDM2 supported 15 isolates. To investigate SDM1 substrate preferences, one isolate, Pseudomonas corrugata strain FW300-N2E2 was selected for a time-series exometabolomics analysis. Interestingly, it was found that this organism preferred lower-abundance substrates such as guanine, glycine, proline and arginine and glucose and did not utilize the more abundant substrates maltose, mannitol, trehalose and uridine. These results demonstrate the viability and utility of using exometabolomics to construct a tractable environmentally relevant media. We anticipate that this approach can be expanded to other environments to enhance isolation and characterization of diverse microbial communities.« less
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Time and substrate dependent exudation of carboxylates by Lupinus albus L. and Brassica napus L.
Mimmo, Tanja; Hann, Stephan; Jaitz, Leonhard; Cesco, Stefano; Gessa, Carlo Emanuele; Puschenreiter, Markus
2011-11-01
Root exudates influence significantly physical, chemical and biological characteristics of rhizosphere soil. Their qualitative and quantitative composition is affected by environmental factors such as pH, soil type, oxygen status, light intensity, soil temperature, plant growth, nutrient availability and microorganisms. The aim of the present study was to assess the influence of growth substrate and plant age on the release of carboxylates from Lupinus albus L. and Brassica napus L. Both plant species were studied in continuously percolated microcosms filled with either sand, soil or sand + soil (1:1) mixture. Soil solution was collected every week at 7, 14, 21, 28 and 35 days after planting (DAP). Carboxylate concentrations were determined by reversed-phase liquid chromatography - electrospray ionization - time of flight mass spectrometry (LC-ESI-TOFMS). Oxalate, citrate, succinate, malate and maleate were detected in soil solutions of both plant species. Their concentrations were correlated with the physiological status of the plant and the growth substrate. Oxalate was the predominant carboxylate detected within the soil solution of B. napus plants while oxalate and citrate were the predominant ones found in the soil solutions of L. albus plants. The sampling determination of carboxylates released by plant roots with continuous percolation systems seems to be promising as it is a non-destructive method and allows sampling and determination of soluble low molecular weight organic compounds derived from root exudation as well as the concentration of soluble nutrients, which both might reflect the nutritional status of plants. Copyright © 2011 Elsevier Masson SAS. All rights reserved.
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Soil and substrate morphology as witnesses of present and former agricultural landscape management
NASA Astrophysics Data System (ADS)
Chartin, C.; Salvador-Blanes, S.; Hinschberger, F.; Bourennane, H.; Macaire, J.-J.
2009-04-01
Water and tillage erosion, combined with the effect of successive regrouping of the land campaigns, have sensibly modified the morphology of cultivated hillslopes. Nowadays, we can still observe over cultivated landscapes various anthropogenic structures (e.g. lynchets) that correspond to former and/or present field limits. The aim of this work is to spatially characterise the geometry of these various structures, and to assess their relation with soil variability. The 10 ha studied site corresponds to an hillslope located in a small calcareous watershed near Tours in the Parisian Basin (France). Soils are mainly Cambisols (calcaric), Epileptic cambisols (calcaric) and Colluvic cambisols. This watershed is characterised by the presence of many soil accumulation structures and has been submitted to an important regrouping of the lands since the 1960's. The existing structures were accurately located and defined through a topographical analysis (slope, profile curvature...), and then related to past and present field limits using aerial photographies and cadastral maps. Two main morphological structures, deeply marked in the topography, are identified. The most remarkable type corresponds to well developed lynchets located at the lower part of field limits. Secondary structures, less marked than lynchets, are linked to field limits which existed at least since 1836, but that disappeared from the 1960's. These secondary structures look like longitudinal bulges placed perpendicularly to the direction of the main slope. A soil survey on these two geomorphic structure types has been performed in order to determine their specific geometry. Lynchets are characterised by a large increase in the thickness of soils: from 35 cm at 24 m upslope to more than 120 cm on its top. But, in some cases, the elevation study shows a topographical discontinuity between the top of the accumulation and the field or road below, discontinuity that is more important than the maximum soil thickness observed in the lynchet. This implies that the substrate, which is mostly homogeneous, has been largely excavated below these limits certainly due to repeated tillage operations. Concerning the secondary structures, soil thickness increases slightly from 35 cm at 16 m up- and downslope the former field limit to 70 cm at the maximum of the bulges convexity. However, the slope morphology seems to show larger soil accumulation considering a regular substrate morphology along the hillslope profile. Here too, by combining soil thickness and surface topography, we show that the substrate has certainly been strongly remodelled at these former field limits by tillage erosion. The spatial variability of the various soils types is closely linked to the sequence of structures oriented perpendicularly to the direction of the main slope. Although the current topography is clearly marked by various structures linked to former and present field limits, it appears that soil thickness is not the only factor explaining these large variations in the slope morphology: long-term agricultural practices, certainly tillage, "shape" the substrate as well. It is thus important to take into account these substrate excavations for sediment budget studies. The use of tracers such as 137Cs will allow to understand the intensity of these morphological changes at the slope scale within the last decades.
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Cárcamo, Valeska; Bustamante, Elena; Trangolao, Elizabeth; de la Fuente, Luz María; Mench, Michel; Neaman, Alexander; Ginocchio, Rosanna
2012-05-01
Acidic and metal(oid)-rich topsoils resulted after 34 years of continuous operations of a copper smelter in the Puchuncaví valley, central Chile. Currently, large-scale remediation actions for simultaneous in situ immobilization of metals and As are needed to reduce environmental risks of polluted soils. Aided phytostabilization is a cost-effective alternative, but adequate local available soil amendments have to be identified and management options have to be defined. Efficacy of seashell grit (SG), biosolids (B), natural zeolite (Z), and iron-activated zeolite (AZ), either alone or in mixtures, was evaluated for reducing metal (Cu and Zn) and As solubilization in polluted soils under laboratory conditions. Perennial ryegrass was used to test phytotoxicity of experimental substrates. Soil neutralization to a pH of 6.5 with SG, with or without incorporation of AZ, significantly reduces metal (Cu and Zn) solubilization without affecting As solubilization in soil pore water; furthermore, it eliminates phytotoxicity and excessive metal(oid) accumulation in aerial plant tissues. Addition of B or Z to SG-amended soil does not further reduce metal solubilization into soil pore water, but increase As solubilization due to excessive soil neutralization (pH > 6.5); however, no significant As increase occurs in aerial plant tissues. Simultaneous in situ immobilization of metal(oid) in acidic topsoils is possible through aided phytostabilization.
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The structural bases of long-term anabiosis in non-spore-forming bacteria
NASA Astrophysics Data System (ADS)
Suzina, N. E.; Mulyukin, A. L.; Dmitriev, V. V.; Nikolaev, Yu. A.; Plakunov, V. K.; El-Registan, G. I.; Duda, V. I.
Peculiarities of the structural and functional organization related to extended and long-term anabiosis were revealed for non-spore-forming bacteria both in stored laboratory cultures and natural substrates: (1) 1-3-Myr-old Eastern Siberian permafrost, (2) tundra soils, and (3) oil slurry. Different advanced or specially designed methods were used such as (a) high-resolution electron microscopy; (b) simulation of in situ conditions in laboratory by varying of growth composition media and cultivation conditions; (c) low-temperature fractionation to isolate and concentrate microbial cells from natural substrates; (d) specimen selection and preparation; (e) comparative ultrastructural and morphometric analysis of microbial cells in model cultures and natural substrates (in situ). Under laboratory conditions, the intense formation of anabiotic (resting) cells by representatives of various taxa of eubacteria and halophilic archaea were observed in 2-9-month-old cultures grown in carbon-, nitrogen-, or phosphorus-deficient media, in starved cell suspensions in the presence of sodium silicate at environmentally occurring concentrations, or on soil agar. Among resting cells were revealed cyst-like forms possessing the complicated structure. The most common peculiarities of cyst-like resting cells were thick and distinguishable capsule; thickened and multilamellar cell wall with 1 to 3 de novo synthesized murein layers; large intramembrane particles on PF- and EF-fractures; finely granulated or coarse textured cytoplasm; condensed nucleoid. The data of morphological and ultrastructural analyses of cyst-like cells, as well as their experimentally proved resistance to prolonged desiccation, heat shock, etc. and the ability to germinate under the effect of lysozyme, gives an evidence for constitutive dormancy in the studied non-spore-forming bacteria at least. Noteworthy, it was found that the majority of microorganisms in permafrost, tundra soils, and oil slurry was presented by cyst-like cells, very similar to those in laboratory cultures and encrusted with organomineral particles. Anabiotic (resting) cyst-like cells are responsible for survival of non-spore-formers in extreme Earth habitats and may be regarded as possible analogs of extraterrestrial forms of microbial life.
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Fraser, F C; Todman, L C; Corstanje, R; Deeks, L K; Harris, J A; Pawlett, M; Whitmore, A P; Ritz, K
2016-12-01
Factors governing the turnover of organic matter (OM) added to soils, including substrate quality, climate, environment and biology, are well known, but their relative importance has been difficult to ascertain due to the interconnected nature of the soil system. This has made their inclusion in mechanistic models of OM turnover or nutrient cycling difficult despite the potential power of these models to unravel complex interactions. Using high temporal-resolution respirometery (6 min measurement intervals), we monitored the respiratory response of 67 soils sampled from across England and Wales over a 5 day period following the addition of a complex organic substrate (green barley powder). Four respiratory response archetypes were observed, characterised by different rates of respiration as well as different time-dependent patterns. We also found that it was possible to predict, with 95% accuracy, which type of respiratory behaviour a soil would exhibit based on certain physical and chemical soil properties combined with the size and phenotypic structure of the microbial community. Bulk density, microbial biomass carbon, water holding capacity and microbial community phenotype were identified as the four most important factors in predicting the soils' respiratory responses using a Bayesian belief network. These results show that the size and constitution of the microbial community are as important as physico-chemical properties of a soil in governing the respiratory response to OM addition. Such a combination suggests that the 'architecture' of the soil, i.e. the integration of the spatial organisation of the environment and the interactions between the communities living and functioning within the pore networks, is fundamentally important in regulating such processes.
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Methanogenesis at low temperatures by microflora of tundra wetland soil.
Kotsyurbenko, O R; Nozhevnikova, A N; Soloviova, T I; Zavarzin, G A
1996-01-01
Active methanogenesis from organic matter contained in soil samples from tundra wetland occurred even at 6 degrees C. Methane was the only end product in balanced microbial community with H2/CO2 as a substrate, besides acetate was produced as an intermediate at temperatures below 10 degrees C. The activity of different microbial groups of methanogenic community in the temperature range of 6-28 degrees C was investigated using 5% of tundra soil as inoculum. Anaerobic microflora of tundra wetland fermented different organic compounds with formation of hydrogen, volatile fatty acids (VFA) and alcohols. Methane was produced at the second step. Homoacetogenic and methanogenic bacteria competed for such substrates as hydrogen, formate, carbon monoxide and methanol. Acetogens out competed methanogens in an excess of substrate and low density of microbial population. Kinetic analysis of the results confirmed the prevalence of hydrogen acetogenesis on methanogenesis. Pure culture of acetogenic bacteria was isolated at 6 degrees C. Dilution of tundra soil and supply with the excess of substrate disbalanced the methanoigenic microbial community. It resulted in accumulation of acetate and other VFA. In balanced microbial community obviously autotrophic methanogens keep hydrogen concentration below a threshold for syntrophic degradation of VFA. Accumulation of acetate- and H2/CO2-utilising methanogens should be very important in methanogenic microbial community operating at low temperatures.
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Resource availability controls fungal diversity across a plant diversity gradient
Waldrop, M.P.; Zak, D.R.; Blackwood, C.B.; Curtis, C.D.; Tilman, D.
2006-01-01
Despite decades of research, the ecological determinants of microbial diversity remain poorly understood. Here, we test two alternative hypotheses concerning the factors regulating fungal diversity in soil. The first states that higher levels of plant detritus production increase the supply of limiting resources (i.e. organic substrates) thereby increasing fungal diversity. Alternatively, greater plant diversity increases the range of organic substrates entering soil, thereby increasing the number of niches to be filled by a greater array of heterotrophic fungi. These two hypotheses were simultaneously examined in experimental plant communities consisting of one to 16 species that have been maintained for a decade. We used ribosomal intergenic spacer analysis (RISA), in combination with cloning and sequencing, to quantify fungal community composition and diversity within the experimental plant communities. We used soil microbial biomass as a temporally integrated measure of resource supply. Plant diversity was unrelated to fungal diversity, but fungal diversity was a unimodal function of resource supply. Canonical correspondence analysis (CCA) indicated that plant diversity showed a relationship to fungal community composition, although the occurrence of RISA bands and operational taxonomic units (OTUs) did not differ among the treatments. The relationship between fungal diversity and resource availability parallels similar relationships reported for grasslands, tropical forests, coral reefs, and other biotic communities, strongly suggesting that the same underlying mechanisms determine the diversity of organisms at multiple scales. ?? 2006 Blackwell Publishing Ltd/CNRS.
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Goecke, Paul; Ginocchio, Rosanna; Mench, Michel; Neaman, Alexander
2011-07-01
The Puchuncaví valley, central Chile, has been exposed to aerial emissions from a copper smelter. Nowadays, soils in the surroundings are sparsely-vegetated, acidic, and metal-contaminated, and their remediation is needed to reduce environmental risks. We assessed effectiveness of lime, fly ash, compost, and iron grit as amendments to immobilize Cu in soils and promote plant growth. Amended soils were cultivated with Lolium perenne for 60 days under controlled conditions. Total dissolved Cu and Cu2+ activity in the soil solution, ryegrass biomass, and Cu accumulation in plant tissues were measured. Addition of lime and fly ash decreased Cu concentrations and Cu2+ activity in the soil solution, increased plant biomass, and reduced shoot Cu concentration below 22 mg kg(-1) (the phytotoxicity threshold for the species). The most effective amendment with respect to the shoot biomass yield was a combination of lime and compost. Water content of the substrate and the K accumulation were positively correlated with the compost application rate. Compost combined with iron grit decreased dissolved Cu concentrations during the period of highest solubility, i.e., during the first 60 days after the compost application. However, iron grit incorporation into soils amended with lime and compost decreased the shoot biomass of ryegrass.
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Assessing and mitigating the effects of windblown soil on rare and common vegetation.
Gleason, Sean M; Faucette, Dave T; Toyofuku, Mai M; Torres, Carlos A; Bagley, Calvin F
2007-12-01
Acting under the auspices of the US Endangered Species Act, we quantified wind erosion and its effects on rare and common plant species on a semi-arid military installation in Hawaii. Our goal was to develop management strategies, based on local data, to aid the conservation of rare and common indigenous plants and their habitats. We collected windblown soil coming off of roads and other disturbed soils to assess likely impacts to plants occurring at certain heights and distances from disturbed surfaces. We then subjected plants in a glasshouse to windblown dust treatments, designed from our field data to simulate erosion events, and evaluated the effect of these treatments on photosynthesis and survival. We also designed several field experiments to examine the in-situ effects of windblown soil and soil substrate on germination, growth rate, and survival of indigenous and nonindigenous plants. We conclude from these experiments that most direct effects of windblown soil to plants can be effectively mitigated by locating roads and training areas at least 40 m from sensitive plant habitats and through vegetation management to maintain at least 11% aerial cover on disturbed surfaces. Effects of soil type on germination, growth, and survival was species-specific, emphasizing the importance of species trials prior to, or during, rehabilitation efforts.
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Soil inoculation with microbial communities - can this become a useful tool in soil remediation?
NASA Astrophysics Data System (ADS)
Krug, Angelika; Wang, Fang; Dörfler, Ulrike; Munch, Jean Charles; Schroll, Reiner
2010-05-01
We artificially loaded different type of agricultural soils with model 14C-labelled chemicals, and we inoculated such soils with different microbial communities as well as isolated strains to enhance the mineralization of such chemicals. Inocula were introduced by different approaches: (i) soil inocula, (ii) application of isolated strain as well as microbial community via media, (iii) isolated strain as well as microbial community attached to a carrier material. Most of the inoculation experiments were conducted in laboratory but we also tested one of these approaches under real environmental conditions in lysimeters and we could show that the approach was successful. We already could show that inoculating soils with microbial communities attached on a specific carrier material shows the highest mineralization effectiveness and also the highest sustainability. Microbes attached on clay particles preserved their function over a long time period even if the specific microbial substrate was already degraded or at least not detectable any more. Additionally we already could show that in specific cases some soil parameters might reduce the effectiveness of such an approach. Results on isoproturon as a model for phenylurea-herbicides and 1,2,4-trichlorobenzene as an example for an industrially used chemical as well as the corresponding chemicals` degrading microbial communities and isolated strain will be presented.
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He, Ruoyang; Yang, Kaijun; Li, Zhijie; Schädler, Martin; Yang, Wanqin; Wu, Fuzhong; Tan, Bo; Zhang, Li; Xu, Zhenfeng
2017-01-01
Forest land-use changes have long been suggested to profoundly affect soil microbial communities. However, how forest type conversion influences soil microbial properties remains unclear in Tibetan boreal forests. The aim of this study was to explore variations of soil microbial profiles in the surface organic layer and subsurface mineral soil among three contrasting forests (natural coniferous forest, NF; secondary birch forest, SF and spruce plantation, PT). Soil microbial biomass, activity and community structure of the two layers were investigated by chloroform fumigation, substrate respiration and phospholipid fatty acid analysis (PLFA), respectively. In the organic layer, both NF and SF exhibited higher soil nutrient levels (carbon, nitrogen and phosphorus), microbial biomass carbon and nitrogen, microbial respiration, PLFA contents as compared to PT. However, the measured parameters in the mineral soils often did not differ following forest type conversion. Irrespective of forest types, the microbial indexes generally were greater in the organic layer than in the mineral soil. PLFAs biomarkers were significantly correlated with soil substrate pools. Taken together, forest land-use change remarkably altered microbial community in the organic layer but often did not affect them in the mineral soil. The microbial responses to forest land-use change depend on soil layer, with organic horizons being more sensitive to forest conversion.
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Dong, Zhi-Yong; Huang, Wen-Hui; Xing, Ding-Feng; Zhang, Hong-Feng
2013-09-15
Successful remediation of soil co-contaminated with high levels of organics and heavy metals is a challenging task, because that metal pollutants in soil can partially or completely suppress normal heterotrophic microbial activity and thus hamper biodegradation of organics. In this study, the benefits of integrating electrokinetic (EK) remediation with biodegradation for decontaminating soil co-contaminated with crude oil and Pb were evaluated in laboratory-scale experiments lasting for 30 days. The treated soil contained 12,500 mg/kg of total petroleum hydrocarbons (TPH) and 450 mg/kg Pb. The amendments of EDTA and Tween 80, together with a regular refreshing of electrolyte showed the best performance to remediate this contaminated soil. An important function of EDTA-enhanced EK treatment was to eliminate heavy metal toxicity from the soil, thus activating microbial degradation of oil. Although Tween 80 reduced current, it could serve as a second substrate for enhancing microbial growth and biodegradation. It was found that oil biodegradation degree and microbial numbers increased toward the anode and cathode. Microbial metabolism was found to be beneficial to metal release from the soil matrix. Under the optimum conditions, the soil Pb and TPH removal percentages after 30 days of running reached 81.7% and 88.3%, respectively. After treatment, both the residual soil Pb and TPH concentrations met the requirement of the Chinese soil environmental quality standards. Copyright © 2013 Elsevier B.V. All rights reserved.
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Ribas, L C C; de Mendonça, M M; Camelini, C M; Soares, C H L
2009-10-01
This study aimed to assess physicochemical and microbiological properties of fresh spent mushroom substrates (SMSs)--without post-crop heat treatment--from Agaricus subrufescens and Lentinula edodes production to optimize the use of these residues in the soil enrichment for lettuce growth promotion and soil remediation. Organic matter and C content of both SMSs were high. Fresh A. subrufescens SMS was a good source of N, P and K. On the other hand, L. edodes SMS presented a lower concentration of these nutrients and a high level of immaturity. Both SMSs presented high electric conductivity values (2.5-3.4 mS/cm). Microbiological analysis, based upon enumeration of culturable bacteria (thermophilic and mesophilic) and fungi, and also evolution of CO(2), showed that SMSs played higher microbial diversity than soil control. Laccase activity from A. subrufescens SMS tended to remain constant during a 2-month period, while L. edodes SMS presented low laccase activity throughout the same period. Agaricus subrufescens and L. edodes were able to grow on a PDA (Potato Dextrose Agar) media supplemented with different concentrations of atrazine (1-50 microg/ml), degraded the herbicide, attaining rates of 35% and 26%, respectively. On experiments of lettuce growth promotion using a soil-based potting media with different SMS rates, 5% and 10% (dw) rates of A. subrufescens SMS resulted in higher lettuce aerial dry weights than the rates of 25% and 40%, the chemical fertilization (NPK) and the control (soil). At 10% supplementation, lettuce aerial dry weight increased 2.2 and 1.3 times compared to the control and the NPK treatment, respectively. Protein content increased along with SMS rates. Fresh A. subrufescens SMS was an excellent supplement for lettuce growth promotion and showed potential for remediation of biocides possibly due to improved microbial diversity and enzymatic activity. Fresh L. edodes SMS was not a good fertilizer, at least under the conditions tested. However, microbiological analysis showed that promising results may be achieved when using fresh L. edodes SMS for soil remediation.
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NASA Astrophysics Data System (ADS)
Kéraval, Benoit; Alvarez, Gaël; Lehours, Anne Catherine; Amblard, Christian; Fontaine, Sebastien
2015-04-01
The mineralization of organic C requires two main steps. First, microorganisms secrete exoenzymes in soil in order to depolymerize plant and microbial cell walls and release soluble substrates for microbial assimilation. The second step of mineralization, during which C is released as CO2, implies the absorption and utilization of solubilized substrates by microbial cells with the aim to produce energy (ATP). In cells, soluble substrates are carried out by a cascade of respiratory enzymes, along which protons and electrons are transferred from a substrate to oxygen. Given the complexity of this oxidative metabolism and the typical fragility of respiratory enzymes, it is traditionally considered that respiration (second step of C mineralization process) is strictly an intracellular metabolism process. The recurrent observations of substantial CO2 emissions in soil microcosms where microbial cells have been reduced to extremely low levels challenges this paradigm. In a recent study where some respiratory enzymes have shown to function in an extracellular context in soils, Maire et al. (2013) suggested that an extracellular oxidative metabolism (EXOMET) substantially contributes to CO2 emission from soils. This idea is supported by the recent publication of Blankinship et al., 2014 who showed the presence of active enzymes involved in the Krebs cycle on soil particles. Many controversies subsist in the scientific community due to the presence of non-proliferating but morphologically intact cells after irradiation that could substantially contribute to those soil CO2 emissions. To test whether a purely extracellular oxidative metabolism contribute to soil CO2 emissions, we combined high doses of gamma irradiations to different time of soil autoclaving. The presence of active and non-active cells in soil was checked by DNA and RNA extraction and by electronic microscopy. None active cells (RNA-containing cells) were detectable after irradiation, but some morphological intact cells were observed by microscopy. These "ghost" cells were completely destroyed by the irradiation-autoclaving combination releasing large amount of soluble C. The soil respiration (O2 consumption and CO2 production) was reduced by irradiation and autoclaving but not stopped, suggesting the presence of an EXOMET. The delta 13C of CO2 released in the irradiated-autoclaved soil was strongly depleted (-70‰) indicating that this extracellular metabolism induced a substantial isotopic fractionation. Our findings suggest that two main oxidative metabolisms co-occur in soils: cell respiration and EXOMET. The isotopic fractionation induced by the EXOMET open perspectives for its quantification in non-sterilized living soils.
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Jeanbille, M; Buée, M; Bach, C; Cébron, A; Frey-Klett, P; Turpault, M P; Uroz, S
2016-02-01
Soil and climatic conditions as well as land cover and land management have been shown to strongly impact the structure and diversity of the soil bacterial communities. Here, we addressed under a same land cover the potential effect of the edaphic parameters on the soil bacterial communities, excluding potential confounding factors as climate. To do this, we characterized two natural soil sequences occurring in the Montiers experimental site. Spatially distant soil samples were collected below Fagus sylvatica tree stands to assess the effect of soil sequences on the edaphic parameters, as well as the structure and diversity of the bacterial communities. Soil analyses revealed that the two soil sequences were characterized by higher pH and calcium and magnesium contents in the lower plots. Metabolic assays based on Biolog Ecoplates highlighted higher intensity and richness in usable carbon substrates in the lower plots than in the middle and upper plots, although no significant differences occurred in the abundance of bacterial and fungal communities along the soil sequences as assessed using quantitative PCR. Pyrosequencing analysis of 16S ribosomal RNA (rRNA) gene amplicons revealed that Proteobacteria, Acidobacteria and Bacteroidetes were the most abundantly represented phyla. Acidobacteria, Proteobacteria and Chlamydiae were significantly enriched in the most acidic and nutrient-poor soils compared to the Bacteroidetes, which were significantly enriched in the soils presenting the higher pH and nutrient contents. Interestingly, aluminium, nitrogen, calcium, nutrient availability and pH appeared to be the best predictors of the bacterial community structures along the soil sequences.
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Adelaide Chapman Johnson; J. Alan Yeakley
2016-01-01
Although climate warming is generally expected to facilitate upward advance of forests, conifer seedling regeneration and survival may be hindered by low substrate moisture, high radiation, and both low and high snow accumulation. To better understand substrate-related factors promoting regeneration in the alpine treeline ecotone, this study compared 2 substrates...
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Carbon dynamics under a maize-Faidherbia albida agroforestry system in Zambia
NASA Astrophysics Data System (ADS)
Yengwe, Jones; Chipatela, Floyd; Amalia, Okky; Lungu, Obed; De Neve, Stefaan
2017-04-01
Continued crop residue removal for other competing uses such as livestock or household has exacerbated the decline of soil organic matter. Foliar litter from indigenous agroforestry trees such as Faidherbia albida (F. albida) can be a source of organic matter input in resource constrained farmers' fields to mitigate the declining fertility status of many Zambian soils. A controlled incubation study was conducted to evaluate the short term degradability of F. albida litter and maize plant residue. Further, we assessed the effect of F. albida litter and maize residue amendments on microbial biomass carbon (MBC) and enzyme activity. Soils were collected from outside and under the canopies of F. albida trees from six sites with 8, 9, 11, 15, and two sites with > 35-year old trees. Soils from under the canopies were amended with F. albida+maize residue (FMU), F. albida litter (FU), maize residue (MU) and controls were not amended (CTRU). The soils from outside the canopy were amended with maize residue (MO) and controls were not amended (CTRO). These were adjusted to 50% WFPS and incubated for twelve weeks at 27°C to assess C mineralization, microbial biomass carbon (MBC) and enzyme activity (Dehydrogenase, β-glucosidase and β-glucosaminidase activity). The material used as amendment in the incubation experiment had two pools of carbon: a labile and a recalcitrant pool. The mixed amendment FMU had a significantly (p<0.05) higher C mineralization compared to the other amendments for all incubated soils. The treatment MU had a higher net C mineralized than FU. However, C mineralization from FU treatment was generally higher in the first 20 days of the incubation period but declined thereafter for all the soils. The net C mineralized from MU did not significantly differ with MO in all except soil from 11-year old trees. Enzyme activity and MBC consistently increased due to amendments for all soils. Enzyme activity was significantly (p<0.05) positively correlated with MBC in amended soils. Net C mineralized and microbial activity were high in FMU because of large C substrate added. Indicating a high C mineralization potential, MBC and enzyme activity for soils under the canopy compared with soils outside the canopy. F. albida trees therefore could be a source of labile C in F. albida-Maize systems nevertheless, in the long term, input from other crop residue such as maize and savanna grasses which have a large recalcitrant pool of C are important in sustaining SOC on these fields.
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Wu, Xueping; Gebremikael, Mesfin Tsegaye; Wu, Huijun; Cai, Dianxiong; Wang, Bisheng; Li, Baoguo; Zhang, Jiancheng; Li, Yongshan; Xi, Jilong
2018-01-01
Microbial mechanisms associated with soil organic carbon (SOC) decomposition are poorly understood. We aim to determine the effects of inorganic and organic fertilizers on soil labile carbon (C) pools, microbial community structure and C mineralization rate under an intensive wheat-maize double cropping system in Northern China. Soil samples in 0–10 cm layer were collected from a nine-year field trial involved four treatments: no fertilizer, CK; nitrogen (N) and phosphorus (P) fertilizers, NP; maize straw combined with NP fertilizers, NPS; and manure plus straw and NP fertilizers, NPSM. Soil samples were analyzed to determine labile C pools (including dissolved organic C, DOC; light free organic C, LFOC; and microbial biomass C, MBC), microbial community composition (using phospholipid fatty acid (PLFA) profiles) and SOC mineralization rate (from a 124-day incubation experiment). This study demonstrated that the application of chemical fertilizers (NP) alone did not alter labile C fractions, soil microbial communities and SOC mineralization rate from those observed in the CK treatment. Whereas the use of straw in conjunction with chemical fertilizers (NPS) became an additional labile substrate supply that decreased C limitation, stimulated growth of all PLFA-related microbial communities, and resulted in 53% higher cumulative mineralization of C compared to that of CK. The SOC and its labile fractions explained 78.7% of the variance of microbial community structure. Further addition of manure on the top of straw in the NPSM treatment did not significantly increase microbial community abundances, but it did alter microbial community structure by increasing G+/G- ratio compared to that of NPS. The cumulative mineralization of C was 85% higher under NPSM fertilization compared to that of CK. Particularly, the NPSM treatment increased the mineralization rate of the resistant pool. This has to be carefully taken into account when setting realistic and effective goals for long-term soil C stabilization. PMID:29668702
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Li, Jing; Wu, Xueping; Gebremikael, Mesfin Tsegaye; Wu, Huijun; Cai, Dianxiong; Wang, Bisheng; Li, Baoguo; Zhang, Jiancheng; Li, Yongshan; Xi, Jilong
2018-01-01
Microbial mechanisms associated with soil organic carbon (SOC) decomposition are poorly understood. We aim to determine the effects of inorganic and organic fertilizers on soil labile carbon (C) pools, microbial community structure and C mineralization rate under an intensive wheat-maize double cropping system in Northern China. Soil samples in 0-10 cm layer were collected from a nine-year field trial involved four treatments: no fertilizer, CK; nitrogen (N) and phosphorus (P) fertilizers, NP; maize straw combined with NP fertilizers, NPS; and manure plus straw and NP fertilizers, NPSM. Soil samples were analyzed to determine labile C pools (including dissolved organic C, DOC; light free organic C, LFOC; and microbial biomass C, MBC), microbial community composition (using phospholipid fatty acid (PLFA) profiles) and SOC mineralization rate (from a 124-day incubation experiment). This study demonstrated that the application of chemical fertilizers (NP) alone did not alter labile C fractions, soil microbial communities and SOC mineralization rate from those observed in the CK treatment. Whereas the use of straw in conjunction with chemical fertilizers (NPS) became an additional labile substrate supply that decreased C limitation, stimulated growth of all PLFA-related microbial communities, and resulted in 53% higher cumulative mineralization of C compared to that of CK. The SOC and its labile fractions explained 78.7% of the variance of microbial community structure. Further addition of manure on the top of straw in the NPSM treatment did not significantly increase microbial community abundances, but it did alter microbial community structure by increasing G+/G- ratio compared to that of NPS. The cumulative mineralization of C was 85% higher under NPSM fertilization compared to that of CK. Particularly, the NPSM treatment increased the mineralization rate of the resistant pool. This has to be carefully taken into account when setting realistic and effective goals for long-term soil C stabilization.
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NASA Astrophysics Data System (ADS)
Galieva, G. Sh; Gilmutdinova, I. M.; Fomin, V. P.; Selivanovskaya, S. Yu; Galitskaya, P. Yu
2018-01-01
Conservation of soil fertility is one of the most important tasks of the present time. As microorganisms are among the key factors in forming soil fertility, monitoring their state in natural and anthropogenically changed soils is an important component of compulsory environmental monitoring. Modern methods make it possible to evaluate the diversity and the functions of soil microorganisms, however, unfortunately, not all the soils are analyzed with their help up to the present moment. The present investigation is aimed to evaluate the functional diversity of five natural soil samples in the Republic of Tatarstan (belonging to sod-podzol, sod-carbonate, alluvial, and gray types) using the method of Biolog EcoPlate according to the index of average well color development, alpha-biodiversiry Shannon index (H), amount of substrates consumed ®, and strategy of consumption of various carbon substrate groups. It was shown that the highest AWCD index was found in sample No 3 - alluvial soil type (3.159±0.460), the lowest one - in sample No 5 - gray soil type (0.572±0.230). Correlation of biological activity of microorganisms with organic matter content in soil was shown.
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Thermal shock and splash effects on burned gypseous soils from the Ebro Basin (NE Spain)
NASA Astrophysics Data System (ADS)
León, J.; Seeger, M.; Badía, D.; Peters, P.; Echeverría, M. T.
2014-03-01
Fire is a natural factor of landscape evolution in Mediterranean ecosystems. The middle Ebro Valley has extreme aridity, which results in a low plant cover and high soil erodibility, especially on gypseous substrates. The aim of this research is to analyze the effects of moderate heating on physical and chemical soil properties, mineralogical composition and susceptibility to splash erosion. Topsoil samples (15 cm depth) were taken in the Remolinos mountain slopes (Ebro Valley, NE Spain) from two soil types: Leptic Gypsisol (LP) in a convex slope and Haplic Gypsisol (GY) in a concave slope. To assess the heating effects on the mineralogy we burned the soils at 105 and 205 °C in an oven and to assess the splash effects we used a rainfall simulator under laboratory conditions using undisturbed topsoil subsamples (0-5 cm depth of Ah horizon). LP soil has lower soil organic matter (SOM) and soil aggregate stability (SAS) and higher gypsum content than GY soil. Gypsum and dolomite are the main minerals (>80%) in the LP soil, while gypsum, dolomite, calcite and quartz have similar proportions in GY soil. Clay minerals (kaolinite and illite) are scarce in both soils. Heating at 105 °C has no effect on soil mineralogy. However, heating to 205 °C transforms gypsum to bassanite, increases significantly the soil salinity (EC) in both soil units (LP and GY) and decreases pH only in GY soil. Despite differences in the content of organic matter and structural stability, both soils show no significant differences (P < 0.01) in the splash erosion rates. The size of pores is reduced by heating, as derived from variations in soil water retention capacity.
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Muhammadi; Afzal, Muhammad
2014-01-01
Optimum culture conditions, and carbon and nitrogen sources for production of water absorbing exopolysaccharide by Bacillus strain CMG1403 on local cheap substrates were determined using one variable at a time approach. Carbon source was found to be sole substrate for EPS biosynthesis in the presence of yeast extract that supported the growth only and hence, indirectly enhanced the EPS yield. Whereas, urea only coupled with carbon source could enhance the EPS production but no effect on growth. The maximum yield of EPS was obtained when Bacillus strain CMG1403 was grown statically in neutral minimal medium with 25% volumetric aeration at 30°C for 10 days. Under these optimum conditions, a maximum yield of 2.71±0.024, 3.82±0.005, 4.33±0.021, 4.73±0.021, 4.85±0.024, and 5.52±0.016 g/L culture medium was obtained with 20 g (sugar) of sweet whey, glucose, fructose, sucrose, cane molasses and sugar beet the most efficient one respectively as carbon sources. Thus, the present study showed that under optimum culture conditions, the local cheap substrates could be superior and efficient alternatives to synthetic carbon sources providing way for an economical production of water absorbing EPS by indigenous soil bacterium Bacillus strain CMG1403.
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Cardinali, Alessandra; Pizzeghello, Diego; Zanin, Giuseppe
2015-01-01
In intensive agriculture areas the use of pesticides can alter soil properties and microbial community structure with the risk of reducing soil quality. In this study the fatty acid methyl esters (FAMEs) evolution has been studied in a factorial lab experiment combining five substrates (a soil, two aged composts and their mixtures) treated with a co-application of three pesticides (azoxystrobin, chlorotoluron and epoxiconazole), with two extraction methods, and two incubation times (0 and 58 days). FAMEs extraction followed the microbial identification system (MIDI) and ester-linked method (EL). The pesticides showed high persistence, as revealed by half-life (t1/2) values ranging from 168 to 298 days, which confirms their recalcitrance to degradation. However, t1/2 values were affected by substrate and compost age down to 8 days for chlorotoluron in S and up to 453 days for epoxiconazole in 12M. Fifty-six FAMEs were detected. Analysis of variance (ANOVA) showed that the EL method detected a higher number of FAMEs and unique FAMEs than the MIDI one, whereas principal component analysis (PCA) highlighted that the monosaturated 18:1ω9c and cyclopropane 19:0ω10c/19ω6 were the most significant FAMEs grouping by extraction method. The cyclopropyl to monoenoic acids ratio evidenced higher stress conditions when pesticides were applied to compost and compost+soil than solely soil, as well as with final time. Overall, FAMEs profiles showed the importance of the extraction method for both substrate and incubation time, the t1/2 values highlighted the effectiveness of solely soil and the less mature compost in reducing the persistence of pesticides.
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Cardinali, Alessandra; Pizzeghello, Diego; Zanin, Giuseppe
2015-01-01
Introduction In intensive agriculture areas the use of pesticides can alter soil properties and microbial community structure with the risk of reducing soil quality. Materials and Methods In this study the fatty acid methyl esters (FAMEs) evolution has been studied in a factorial lab experiment combining five substrates (a soil, two aged composts and their mixtures) treated with a co-application of three pesticides (azoxystrobin, chlorotoluron and epoxiconazole), with two extraction methods, and two incubation times (0 and 58 days). FAMEs extraction followed the microbial identification system (MIDI) and ester-linked method (EL). Results and Discussion The pesticides showed high persistence, as revealed by half-life (t1/2) values ranging from 168 to 298 days, which confirms their recalcitrance to degradation. However, t1/2 values were affected by substrate and compost age down to 8 days for chlorotoluron in S and up to 453 days for epoxiconazole in 12M. Fifty-six FAMEs were detected. Analysis of variance (ANOVA) showed that the EL method detected a higher number of FAMEs and unique FAMEs than the MIDI one, whereas principal component analysis (PCA) highlighted that the monosaturated 18:1ω9c and cyclopropane 19:0ω10c/19ω6 were the most significant FAMEs grouping by extraction method. The cyclopropyl to monoenoic acids ratio evidenced higher stress conditions when pesticides were applied to compost and compost+soil than solely soil, as well as with final time. Conclusion Overall, FAMEs profiles showed the importance of the extraction method for both substrate and incubation time, the t1/2 values highlighted the effectiveness of solely soil and the less mature compost in reducing the persistence of pesticides. PMID:26694029
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NASA Astrophysics Data System (ADS)
Kuźniar, Agnieszka; Banach, Artur; Stępniewska, Zofia; Frąc, Magdalena; Oszust, Karolina; Gryta, Agata; Kłos, Marta; Wolińska, Agnieszka
2018-01-01
The aim of the study was to assess the differences in the bacterial community physiological profiles in soils contaminated with heavy metals versus soils without metal contaminations. The study's contaminated soil originated from the surrounding area of the Szopienice non-ferrous metal smelter (Silesia Region, Poland). The control was soil unexposed to heavy metals. Metal concentration was appraised by flame atomic absorption spectrometry, whereas the the community-level physiological profile was determined with the Biolog EcoPlatesTM system. The soil microbiological activity in both sites was also assessed via dehydrogenase activity. The mean concentrations of metals (Cd and Zn) in contaminated soil samples were in a range from 147.27 to 12265.42 mg kg-1, and the heavy metal contamination brought about a situation where dehydrogenase activity inhibition was observed mostly in the soil surface layers. Our results demonstrated that there is diversity in the physiological profiles of microorganisms inhabiting contaminated and colntrol soils; therefore, for assessment purposes, these were treated as two clusters. Cluster I included colntrol soil samples in which microbial communities utilised most of the available substrates. Cluster II incorporated contaminated soil samples in which a smaller number of the tested substrates was utilised by the contained microorganisms. The physiological profiles of micro-organisms inhabiting the contaminated and the colntrol soils are distinctly different.
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Iron oxidation stimulates organic matter decomposition in humid tropical forest soils.
Hall, Steven J; Silver, Whendee L
2013-09-01
Humid tropical forests have the fastest rates of organic matter decomposition globally, which often coincide with fluctuating oxygen (O2 ) availability in surface soils. Microbial iron (Fe) reduction generates reduced iron [Fe(II)] under anaerobic conditions, which oxidizes to Fe(III) under subsequent aerobic conditions. We demonstrate that Fe (II) oxidation stimulates organic matter decomposition via two mechanisms: (i) organic matter oxidation, likely driven by reactive oxygen species; and (ii) increased dissolved organic carbon (DOC) availability, likely driven by acidification. Phenol oxidative activity increased linearly with Fe(II) concentrations (P < 0.0001, pseudo R(2) = 0.79) in soils sampled within and among five tropical forest sites. A similar pattern occurred in the absence of soil, suggesting an abiotic driver of this reaction. No phenol oxidative activity occurred in soils under anaerobic conditions, implying the importance of oxidants such as O2 or hydrogen peroxide (H2 O2 ) in addition to Fe(II). Reactions between Fe(II) and H2 O2 generate hydroxyl radical, a strong nonselective oxidant of organic compounds. We found increasing consumption of H2 O2 as soil Fe(II) concentrations increased, suggesting that reactive oxygen species produced by Fe(II) oxidation explained variation in phenol oxidative activity among samples. Amending soils with Fe(II) at field concentrations stimulated short-term C mineralization by up to 270%, likely via a second mechanism. Oxidation of Fe(II) drove a decrease in pH and a monotonic increase in DOC; a decline of two pH units doubled DOC, likely stimulating microbial respiration. We obtained similar results by manipulating soil acidity independently of Fe(II), implying that Fe(II) oxidation affected C substrate availability via pH fluctuations, in addition to producing reactive oxygen species. Iron oxidation coupled to organic matter decomposition contributes to rapid rates of C cycling across humid tropical forests in spite of periodic O2 limitation, and may help explain the rapid turnover of complex C molecules in these soils. © 2013 John Wiley & Sons Ltd.
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NASA Astrophysics Data System (ADS)
Löppmann, Sebastian; Blagodatskaya, Evgenia; Kuzyakov, Yakov
2014-05-01
Rhizosphere and detritusphere are soil microsites with very high resource availability for microorganisms affecting their biomass, composition and functions. In the rhizosphere low molecular compounds occur with root exudates and low available polymeric compounds, as belowground plant senescence. In detritusphere the substrate for decomposition is mainly a polymeric material of low availability. We hypothesized that microorganisms adapted to contrasting quality and availability of substrates in the rhizosphere and detritusphere are strongly different in affinity of hydrolytic enzymes responsible for decomposition of organic compounds. According to common ecological principles easily available substrates are quickly consumed by microorganisms with enzymes of low substrate affinity (i.e. r-strategists). The slow-growing K-strategists with enzymes of high substrate affinity are better adapted for growth on substrates of low availability. Estimation of affinity of enzyme systems to the substrate is based on Michaelis-Menten kinetics, reflecting the dependency of decomposition rates on substrate amount. As enzymes-mediated reactions are substrate-dependent, we further hypothesized that the largest differences in hydrolytic activity between the rhizosphere and detritusphere occur at substrate saturation and that these differences are smoothed with increasing limitation of substrate. Affected by substrate limitation, microbial species follow a certain adaptation strategy. To achieve different depth gradients of substrate availability 12 plots on an agricultural field were established in the north-west of Göttingen, Germany: 1) 4 plots planted with maize, reflecting lower substrate availability with depth; 2) 4 unplanted plots with maize litter input (0.8 kg m-2 dry maize residues), corresponding to detritusphere; 3) 4 bare fallow plots as control. Maize litter was grubbed homogenously into the soil at the first 5 cm to ensure comparable conditions for the herbivore and detritivore communities in the soil. The kinetics (Km and Vmax) of four extracellular hydrolytic enzymes responsible for C- and phosphorous-cycle (β-glucosidase, β-xylosidase, β-cellobiohydrolase and acid phosphatase), microbial biomass, basal respiration (BR) and substrate-induced respiration (SIR) were measured in rhizosphere, detritusphere and control from 0 - 10 and 10 - 20 cm. The metabolic quotient (qCO2) was calculated as specific indicator for efficiency of microbial substrate utilization. We observed clear differences in enzymes activities at low and high concentrations of substrate. At substrate saturation enzyme activity rates of were significantly higher in rooted plots compared to litter amended plots, whereas at lower concentration no treatment effect could be found. The BR, SIR and qCO2 values were significantly higher at 0 - 10 cm of the planted treatment compared to litter and control plots, revealing a significantly higher respiration at lower efficiency of microbial substrate utilization in the rhizosphere. The Michaelis-Menten constant (Km) decreased with depth, especially for β-glucosidase, acid phosphatase and β-xylosidase, indicating higher substrate affinity of microorganisms in deeper soil and therefore different enzyme systems functioning. The substrate affinity factor (Vmax/Km) increased 2-fold with depth for various enzymes, reflecting a switch of predominantly occurring microbial strategies. Vmax/Km ratio indicated relative domination of zymogenous microbial communities (r-strategists) in 0 - 10 cm depth as compared with 10 - 20 cm depth where the K-strategists dominated.
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Radojevic, Ana A; Serbula, Snezana M; Kalinovic, Tanja S; Kalinovic, Jelena V; Steharnik, Mirjana M; Petrovic, Jelena V; Milosavljevic, Jelena S
2017-04-01
The town of Bor and its surroundings (Serbia) have been under environmental pollution for more than a century, due to exploitation of large copper deposits. Naturally present Corylus spp. were sampled in the surroundings of the mine and flotation tailings at 12 sites distributed in six zones with different pollution loads, under the assumption that all the zones were endangered except for the background. As, Cd, Co, Cr, Cu, Fe, Mn, Mo, Ni, Pb and Zn inputs from soil and the air were evaluated in plant parts, in terms of absorption, accumulation and indication abilities of Corylus spp. The obtained results showed that As and Cu were the most enriched elements in soil, and their concentration exceeded the limit and remediation values proposed by the regulation. Plant parts (root, branch, leaf and catkin) also showed enrichment of most studied elements in wide ranges. According to the enrichment factor for plant, metal/metalloid inputs, particularly in leaves, were from anthropogenic origin. Plant absorption which occurred at the soil-root interface was low, based on the bioaccumulation factor, which could be indicative of resistance mechanisms of root to abiotic stress induced by a high content of elements in soil substrate. The values of bioaccumulation coefficient suggested weak and intermediate absorption and exclusion abilities of Corylus spp. to the studied elements. Element concentrations differ in unwashed and washed leaves, as well as pollution loads in plant and soil samples from the background, traffic and the sites with clear mining-metallurgical influence. Therefore, Corylus spp. could be promising in biomonitoring studies.
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Fanin, Nicolas; Barantal, Sandra; Fromin, Nathalie; Schimann, Heidy; Schevin, Patrick; Hättenschwiler, Stephan
2012-01-01
Human-caused alterations of the carbon and nutrient cycles are expected to impact tropical ecosystems in the near future. Here we evaluated how a combined change in carbon (C), nitrogen (N) and phosphorus (P) availability affects soil and litter microbial respiration and litter decomposition in an undisturbed Amazonian rainforest in French Guiana. In a fully factorial C (as cellulose), N (as urea), and P (as phosphate) fertilization experiment we analyzed a total of 540 litterbag-soil pairs after a 158-day exposure in the field. Rates of substrate-induced respiration (SIR) measured in litter and litter mass loss were similarly affected by fertilization showing the strongest stimulation when N and P were added simultaneously. The stimulating NP effect on litter SIR increased considerably with increasing initial dissolved organic carbon (DOC) concentrations in litter, suggesting that the combined availability of N, P, and a labile C source has a particularly strong effect on microbial activity. Cellulose fertilization, however, did not further stimulate the NP effect. In contrast to litter SIR and litter mass loss, soil SIR was reduced with N fertilization and showed only a positive effect in response to P fertilization that was further enhanced with additional C fertilization. Our data suggest that increased nutrient enrichment in the studied Amazonian rainforest can considerably change microbial activity and litter decomposition, and that these effects differ between the litter layer and the underlying soil. Any resulting change in relative C and nutrient fluxes between the litter layer and the soil can have important consequences for biogeochemical cycles in tropical forest ecosystems. PMID:23272052
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Gautam, Bal K; Henderson, Gregg
2011-12-01
The uptake and potential transfer of chlorantraniliprole and fipronil by the Formosan subterranean termite, Coptotermes formosanus Shiraki, was investigated in the laboratory by using donor-recipient model bioassays. Two different types of substrates, sandy loam soil (18.6% organic matter) and sand (0.19% organic matter), were used to evaluate how these treated substrates impact the direct mortality and transfer efficiency of the two nonrepellent termiticides tested at different concentrations. Chlorantraniliprole exhibited a more delayed mortality on termites than fipronil in sand. In soil, chlorantraniliprole did not cause higher mortality to either donor or recipient termite at any of the tested concentrations during a 21-d test period when compared with controls. Compared with the controls, a greater number of donors died in the soil treated with fipronil at 14 h postinteraction, and higher death of recipients occurred at 21 d but only in the 60-ppm concentration tested. Our data showed that chlorantraniliprole performed best in substrate with low organic matter against
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BTE-OX biodegradation kinetics with MTBE through bioaugmentation.
Acuna-Askar, K; Villarreal-Chiu, J F; Gracia-Lozano, M V; Garza-Gonzalez, M T; Chavez-Gomez, B; Rodriguez-Sanchez, I P; Barrera-Saldana, H A
2004-01-01
The biodegradation kinetics of BTE-oX and MTBE, mixed all together, in the presence of bioaugmented bacterial populations as high as 880 mg/L VSS was evaluated. The effect of soil in aqueous samples and the effect of Tergitol NP-10 on substrate biodegradation rates were also evaluated. Biodegradation kinetics was evaluated for 36 hours, every 6 hours. Benzene and o-xylene biodegradation followed a first-order one-phase kinetic model, whereas toluene and ethylbenzene biodegradation was well described by a first-order two-phase kinetic model in all samples. MTBE followed a zero-order removal kinetic model in all samples. The presence of soil in aqueous samples retarded BTE-oX removal rates, with the highest negative effect on o-xylene. The presence of soil enhanced MTBE removal rate. The addition of Tergitol NP-10 to aqueous samples containing soil had a positive effect on substrate removal rate in all samples. Substrate percent removals ranged from 95.4-99.7% for benzene, toluene and ethylbenzene. O-xylene and MTBE percent removals ranged from 55.9-90.1% and 15.6-30.1%, respectively.
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NASA Astrophysics Data System (ADS)
Wu, D.; Cardenas, L. M.; Sanz, S. C.; Brueggemann, N.; Loick, N.; Liu, S.; Bol, R.
2016-12-01
Emissions of gaseous forms of nitrogen from soil, such as nitrous oxide (N2O) and nitric oxide (NO), have shown great impact on global warming and atmospheric chemistry. Although in soil both nitrification and denitrification could cause N2O and NO emissions, most recent studies demonstrated that denitrification is the dominant process responsible for the increase of atmospheric N2O, while nitrification produces most of NO. The use of nitrification inhibitors (NI) has repeatedly been shown to lower both N2O and NO emissions from agricultural soils; nevertheless, the efficiency of the mitigation effect varies greatly. It is generally assumed that nitrification inhibitors have no direct effect on denitrification. However, the indirect impact, due to the reduced substrate delivery (NO3-) to microsites where denitrification occurs, may have significant effects on denitrification product stoichiometry that may significantly lower soil born N2O emissions. In the present study, soil incubation experiments were carried out in a fully automated continuous-flow incubation system under a He/O2 atmosphere. Ammonium sulfate was applied with and without NI (DMPP) to a UK grassland soil under three different soil moisture conditions (50% WFPS, 65% WFPS, 80% WFPS). With every treatment glucose was applied to supply enough carbon for denitrification. We examined the effect of DMPP on NO, N2O and N2 emissions at different soil moisture conditions which favor nitrification, a mixture of both nitrification and denitrification, or denitrification, respectively. Generally cumulative NO emissions were about 17% of cumulative N2O emissions, while N2 emissions were only detected at high soil moisture condition (80% WFPS). Higher soil moisture increased both N2O and NO emissions. DMPP application increased N2 emissions at soil moisture condition favoring denitrification. Although the application of DMPP significantly mitigated both N2O and NO emissions in all DMPP treatments, the efficiency of the mitigation effect varied with different soil moisture conditions. Overall, DMPP application mitigated about 40- 60% N2O emissions and 50-70% NO emissions during the 44-day incubation period.
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Accumulation factors of mercury by King Bolete Boletus edulis
NASA Astrophysics Data System (ADS)
Falandysz, J.; Frankowska, A.
2003-05-01
To understand pollution picture with mercury and to examine suitability of King Bolete Boletits edulis Bull.: Fr. as possible bioindicator the total mercurv concentrations were determined both in the fruiting bodies and underlying soil substrate collected from various regions of Poland. There were quite large spatial variations of mercury concentration and some seasonal also were noted. Mercury content of the caps exceeded that of stalks (p<0.05), Nvhile Hg BCF values varied between 9 and 40, and 4 and 40, respectively.
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Visible/near-infrared spectra and two-layer modeling of palagonite-coated Basalts
Johnson, J. R.; Grundy, W.M.
2001-01-01
Fine-grained dust coatings on Martian rocks and soils obscure underlying surfaces and hinder mineralogic interpretations of both remote sensing and in-situ observations. We investigate laboratory visible/near-infrared spectra of various thicknesses of palagonite coatings on basalt substrates. We develop a two-layer Hapke scattering model incorporating porosity, grain size, and derived absorption coefficients of palagonite and basalt that reproduces the observed spectra only when the single scattering particle phase function is varied with wavelength.
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NASA Astrophysics Data System (ADS)
Loick, Nadine; Dixon, Elizabeth R.; Repullo Ruibérriz de Torres, Miguel A.; Ciganda, Veronica; Lopez-Aizpun, Maria A.; Matthews, G. Peter; Müller, Christoph; Cardenas, Laura M.
2017-04-01
Nitrous oxide (N2O) is considered to be an important greenhouse gas (GHG) accounting for approximately 6% of the current global warming. The atmospheric N2O concentration has been increasing since the Industrial Revolution, with soils representing its major source, making the understanding of its sources and removal processes very important for the development of mitigation strategies. In soils N gases are mainly produced via nitrification and denitrification. It is assumed that under dry/aerobic conditions nitrification is the dominant N consuming process, while denitrification becomes dominant under wetter conditions promoting anaerobicity. Nitrification and denitrification may occur simultaneously in different microsites of the same soil but there is often uncertainty associated with which process dominates in a particular soil under specific conditions. N2O predominantly derives from incomplete denitrification of nitrate (NO3-). The existence of different pools of NO3- in soils, namely the native soil pool, and the fertiliser-added one, has been suggested through a series of laboratory incubation experiments (Meijide et al., 2010; Bergstermann et al., 2011) using the denitrification incubation system, DENIS (Cardenas et al., 2003), in which soil cores are incubated under an N-free atmosphere, allowing direct measurements of all emitted N gases (NO, N2O and N2) as well as CO2. A third pool, NO3- produced from nitrification of applied NH4+, can also be a source of N2O via denitrification and also from nitrification. In this study labelling of substrate-N with 15N is used to quantify the underlying gross N transformation rates and link them to N-emissions to identify the production and consumption pathways and temporal dynamics of N2O. In three experiments twelve soil cores each were incubated in the DENIS to measure gaseous emissions, while parallel incubations under the same conditions were set up for destructive soil sampling at 7 time points. Using the triple labelling technique - i.e. applying NH4NO3 with either the N at the NH4+ or at the NO3-, or in both places being labelled - this study investigates the effects of a low, medium and high water filled pore space (55, 70, 85%) in a clay soil on gaseous N emissions and investigates the source and processes leading to N2O emissions. To assess the utilisation of applied NO3- vs nitrified NO3- from applied NH4+, the model developed by Müller et al. (2007) is used to calculate the immobilisation of added NO3- and NH4+, nitrification of added NH4+, mineralisation of organic N and subsequent nitrification by the analysis of the 15N in the soil. Gross transformation rates, indicating the relative importance of added NO3- and NO3- derived from nitrified added NH4+ are calculated. Bergstermann et al. (2011) Soil Biol. & Biochem. 43, 240-250. Meijide et al. (2010) Eur. J. Soil Sci. 61, 364-374. Cárdenas et al. (2003) Soil Biol. & Biochem. 35, 867-870. Müller et al. (2007) Soil Biol. & Biochem. 39, 715-726.
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Hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) degradation by Acetobacterium paludosum.
Sherburne, Leslie A; Shrout, Joshua D; Alvarez, Pedro J J
2005-12-01
Substrates and nutrients are often added to contaminated soil or groundwater to enhance bioremediation. Nevertheless, this practice may be counterproductive in some cases where nutrient addition might relieve selective pressure for pollutant biodegradation. Batch experiments with a homoacetogenic pure culture of Acetobacterium paludosum showed that anaerobic RDX degradation is the fastest when auxiliary growth substrates (yeast extract plus fructose) and nitrogen sources (ammonium) are not added. This bacterium degraded RDX faster under autotrophic (H2-fed) than under heterotrophic conditions, even though heterotrophic growth was faster. The inhibitory effect of ammonium is postulated to be due to the repression of enzymes that initiate RDX degradation by reducing its nitro groups, based on the known fact that ammonia represses nitrate and nitrite reductases. This observation suggests that the absence of easily assimilated nitrogen sources, such as ammonium, enhances RDX degradation. Although specific end products of RDX degradation were not determined, the production of nitrous oxide (N2O) suggests that A. paludosum cleaved the triazine ring.
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A straw-soil co-composting and evaluation for plant substrate in BLSS
NASA Astrophysics Data System (ADS)
Cheng, Quanyong; Guo, Shuangsheng; Ai, Weidang; Tang, Yongkang; Qin, Lifeng
2013-02-01
Material closure is important for the establishment of Bioregenerative Life Support System, and many studies have focused on transforming candidate plant residues into plant culture medium. For the limitations of using wheat straw compost as substrate for plant cultivation, a straw-soil co-composting technique was studied. The changes of pH, C/N value, germination index, cellulose, lignin and so on were monitored during the co-composting process. The maturity was evaluated by the C/N value and the germination index. The result showed that after 45 days' fermentation, the straw-soil final co-compost with inoculation (T1) became mature, while the co-compost without inoculation (T0) was not mature. In the plant culture test, the T1 substrate could satisfy the needs for lettuce's growth, and the edible biomass yield of lettuce averaged 74.42 g pot-1 at harvest. But the lettuces in T0 substrate showed stress symptoms and have not completed the growth cycle. Moreover, the results of nitrogen (N) transformation experiment showed that about 10.0% and 3.1% N were lost during the T1 co-composting and plant cultivation, respectively, 23.5% N was absorbed by lettuce, and 63.4% N remained in the T1 substrate after cultivation.
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Dracaena marginata biofilter: design of growth substrate and treatment of stormwater runoff.
Vijayaraghavan, K; Praveen, R S
2016-01-01
The purpose of this research was to investigate the efficiency of Dracaena marginata planted biofilters to decontaminate urban runoff. A new biofilter growth substrate was prepared using low-cost and locally available materials such as red soil, fine sand, perlite, vermiculite, coco-peat and Sargassum biomass. The performance of biofilter substrate was compared with local garden soil based on physical and water quality parameters. Preliminary analyses indicated that biofilter substrate exhibited desirable characteristics such as low bulk density (1140 kg/m(3)), high water holding capacity (59.6%), air-filled porosity (7.82%) and hydraulic conductivity (965 mm/h). Four different biofilter assemblies, with vegetated and non-vegetated systems, were examined for several artificial rain events (un-spiked and metal-spiked). Results from un-spiked artificial rain events suggested that concentrations of most of the chemical components in effluent were highest at the beginning of rain events and thereafter subsided during the subsequent rain events. Biofilter growth substrate showed superior potential over garden soil to retain metal ions such as Al, Fe, Cu, Cr, Ni, Zn, Cd and Pb during metal-spiked rain events. Significant differences were also observed between non-vegetated and vegetated biofilter assemblies in runoff quality, with the latter producing better results.
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NASA Astrophysics Data System (ADS)
Billings, S. A.; Ballantyne, F.; Lehmeier, C.; Min, K.
2014-12-01
Soil organic matter (SOM) transformation rates generally increase with temperature, but whether this is realized depends on soil-specific features. To develop predictive models applicable to all soils, we must understand two key, ubiquitous features of SOM transformation: the temperature sensitivity of myriad enzyme-substrate combinations and temperature responses of microbial physiology and metabolism, in isolation from soil-specific conditions. Predicting temperature responses of production of CO2 vs. biomass is also difficult due to soil-specific features: we cannot know the identity of active microbes nor the substrates they employ. We highlight how recent empirical advances describing SOM decay can help develop theoretical tools relevant across diverse spatial and temporal scales. At a molecular level, temperature effects on purified enzyme kinetics reveal distinct temperature sensitivities of decay of diverse SOM substrates. Such data help quantify the influence of microbial adaptations and edaphic conditions on decay, have permitted computation of the relative availability of carbon (C) and nitrogen (N) liberated upon decay, and can be used with recent theoretical advances to predict changes in mass specific respiration rates as microbes maintain biomass C:N with changing temperature. Enhancing system complexity, we can subject microbes to temperature changes while controlling growth rate and without altering substrate availability or identity of the active population, permitting calculation of variables typically inferred in soils: microbial C use efficiency (CUE) and isotopic discrimination during C transformations. Quantified declines in CUE with rising temperature are critical for constraining model CUE estimates, and known changes in δ13C of respired CO2 with temperature is useful for interpreting δ13C-CO2 at diverse scales. We suggest empirical studies important for advancing knowledge of how microbes respond to temperature, and ideas for theoretical work to enhance the relevance of such work to the world's soils.
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Controls of Methane Dynamics and Emissions in an Arctic Warming Experiment
NASA Astrophysics Data System (ADS)
Nielsen, C. S.; Elberling, B.; Michelsen, A.; Strobel, B. W.; Wulff, K.; Banyasz, I.
2015-12-01
Climatic changes have resulted in increasing air temperatures across the Arctic. This may increase anaerobic decomposition of soil organic matter to methane (CH4) in wetlands and increase plant growth and thereby production of substrate. Little is known about how seasonal variations in dissolved CH4 in soil water, substrate availability, and the effect of warming affect arctic wetland dynamics of CH4 production and emission. In 2013 we established two experiments in a fen at Disko Island, W Greenland; one with year round warming by open-top chambers and removal of shrubs, and one with removal of the aerenchymatous sedge Carex aquatilis ssp. stans. Throughout the growing season 2014 we measured how the treatments affected CH4 emissions, dissolved CH4 in the soil water, and substrate availability. Ecosystem CH4 emissions peaked at August 5th 2014 (7.5 μmol m-2 h-1) without coinciding with time of highest concentrations of dissolved CH4 or acetate indicating a decoupling between production and emission of CH4. The peak in dissolved CH4 concentration, at ten cm depth (1368 ppm, September 18th 2014), followed the peak in concentration of acetate in the same depth (0.30 ppm, August 30th 2014) highlighting the importance of this substance as a substrate for methanogenesis. C. aquatilis ssp. stans accounted for 60% and 77% of the ecosystem CH4 emissions in areas of the fen with water table above and below soil surface showing the importance of the presence of this species to serve as a pipe for CH4 emission which is bypassing the upper soil zone and potential methane oxidation. Throughout the season, warming increased the air temperature at soil surface by on average 0.89°C and occasionally warming and shrub removal increased soil temperature in 2 and 5 cm depth, but there was no effect of the treatments on the CH4 emissions indicating that this wetland is quite resilient towards future climate change.
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Marín-Benito, Jesús M.; Sánchez-Martín, María J.; Rodríguez-Cruz, M. Sonia
2016-01-01
Intensive crop production involves a high consumption of pesticides. This is a cause of major environmental concern because the presence of pesticides in water is becoming increasingly common. Physicochemical methods based on soil modification with organic residues have been developed to enhance the immobilization and/or degradation of pesticides in agricultural soils, which may control both the diffuse and the point pollution of soils and waters. This review summarizes the influence of spent mushroom substrate (SMS) on the environmental fate of pesticides when both are simultaneously applied in agriculture. The processes of adsorption, leaching and dissipation of these compounds in SMS-amended soils were evaluated at laboratory and field scale. Relationships were established between the experimental parameters obtained and the properties of the soils, the SMS, and the pesticides in order to determine the effect that the application of SMS in agricultural soils has on the environmental impact of pesticides. Accordingly, this review highlights the use of SMS as a strategy for the prevention and/or control of soil and water contamination by pesticides to strike a balance between agricultural development and the use of these compounds. PMID:29051422
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USDA-ARS?s Scientific Manuscript database
Inorganic and organic phosphates react strongly with soil constituents, resulting in relatively low concentrations of soluble phosphates in the soil solution. Multiple competing reactions control the solution-phase concentration and the cycling of phosphorus-containing organic substrates and the re...
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Strategies to characterize fungal lipases for applications in medicine and dairy industry.
Gopinath, Subash C B; Anbu, Periasamy; Lakshmipriya, Thangavel; Hilda, Azariah
2013-01-01
Lipases are water-soluble enzymes that act on insoluble substrates and catalyze the hydrolysis of long-chain triglycerides. Lipases play a vital role in the food, detergent, chemical, and pharmaceutical industries. In the past, fungal lipases gained significant attention in the industries due to their substrate specificity and stability under varied chemical and physical conditions. Fungal enzymes are extracellular in nature, and they can be extracted easily, which significantly reduces the cost and makes this source preferable over bacteria. Soil contaminated with spillage from the products of oil and dairy harbors fungal species, which have the potential to secrete lipases to degrade fats and oils. Herein, the strategies involved in the characterization of fungal lipases, capable of degrading fatty substances, are narrated with a focus on further applications.
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Strategies to Characterize Fungal Lipases for Applications in Medicine and Dairy Industry
Gopinath, Subash C. B.; Anbu, Periasamy; Lakshmipriya, Thangavel; Hilda, Azariah
2013-01-01
Lipases are water-soluble enzymes that act on insoluble substrates and catalyze the hydrolysis of long-chain triglycerides. Lipases play a vital role in the food, detergent, chemical, and pharmaceutical industries. In the past, fungal lipases gained significant attention in the industries due to their substrate specificity and stability under varied chemical and physical conditions. Fungal enzymes are extracellular in nature, and they can be extracted easily, which significantly reduces the cost and makes this source preferable over bacteria. Soil contaminated with spillage from the products of oil and dairy harbors fungal species, which have the potential to secrete lipases to degrade fats and oils. Herein, the strategies involved in the characterization of fungal lipases, capable of degrading fatty substances, are narrated with a focus on further applications. PMID:23865040
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Rivest, David; Lorente, Miren; Olivier, Alain; Messier, Christian
2013-10-01
Agroforestry is increasingly viewed as an effective means of maintaining or even increasing crop and tree productivity under climate change while promoting other ecosystem functions and services. This study focused on soil biochemical properties and resilience following disturbance within agroforestry and conventional agricultural systems and aimed to determine whether soil differences in terms of these biochemical properties and resilience would subsequently affect crop productivity under extreme soil water conditions. Two research sites that had been established on agricultural land were selected for this study. The first site included an 18-year-old windbreak, while the second site consisted in an 8-year-old tree-based intercropping system. In each site, soil samples were used for the determination of soil nutrient availability, microbial dynamics and microbial resilience to different wetting-drying perturbations and for a greenhouse pot experiment with wheat. Drying and flooding were selected as water stress treatments and compared to a control. These treatments were initiated at the beginning of the wheat anthesis period and maintained over 10 days. Trees contributed to increase soil nutrient pools, as evidenced by the higher extractable-P (both sites), and the higher total N and mineralizable N (tree-based intercropping site) found in the agroforestry compared to the conventional agricultural system. Metabolic quotient (qCO2) was lower in the agroforestry than in the conventional agricultural system, suggesting higher microbial substrate use efficiency in agroforestry systems. Microbial resilience was higher in the agroforestry soils compared to soils from the conventional agricultural system (windbreak site only). At the windbreak site, wheat growing in soils from agroforestry system exhibited higher aboveground biomass and number of grains per spike than in conventional agricultural system soils in the three water stress treatments. At the tree-based intercropping site, higher wheat biomass, grain yield and number of grains per spike were observed in agroforestry than in conventional agricultural system soils, but in the drought treatment only. Drought (windbreak site) and flooding (both sites) treatments significantly reduced wheat yield and 1000-grain weight in both types of system. Relationships between soil biochemical properties and soil microbial resilience or wheat productivity were strongly dependent on site. This study suggests that agroforestry systems may have a positive effect on soil biochemical properties and microbial resilience, which could operate positively on crop productivity and tolerance to severe water stress. Copyright © 2013 Elsevier B.V. All rights reserved.
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Jain, Neha; Merwyn, S; Rai, G P; Agarwal, G S
2012-05-01
Real-time polymerase chain reaction (real-time PCR) is a laboratory technique based on PCR. This technique is able to detect sequence-specific PCR products as they accumulate in "real time" during the PCR amplification, and also to quantify the number of substrates present in the initial PCR mixture before amplification begins. In the present study, real-time PCR assay was employed for rapid and real-time detection of Bacillus anthracis spores spiked in 0.1 g of soil and talcum powder ranging from 5 to 10(7) spores. DNA was isolated from spiked soil and talcum powder, using PBS containing 1 % Triton-X-100, followed by heat treatment. The isolated DNA was used as template for real-time PCR and PCR. Real-time PCR amplification was obtained in 60 min under the annealing condition at 60°C by employing primers targeting the pag gene of B. anthracis. In the present study, the detection limit of real-time PCR assay in soil was 10(3) spores and 10(2) spores in talcum powder, respectively, whereas PCR could detect 10(4) spores in soil and 10(3) spores in talcum powder, respectively.
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Incident radiation has been reported to facilitate mercury release from soils. In this study the influence of light on mercury emissions from substrates amended with pure synthetic mercury species, and from naturally and anthropogenically mercury-enriched substrates were inves...
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Accumulation of atmospheric sulfur in some Costa Rican soils
Bern, Carleton R.; Townsend, Alan R.
2013-01-01
Sulfur is one of the macronutrient elements whose sources to terrestrial ecosystems should shift from dominance by rock-weathering to atmospheric deposition as soils and underlying substrate undergo progressive weathering and leaching. However, the nature and timing of this transition is not well known. We investigated sources of sulfur to tropical rain forests growing on basalt-derived soils in the Osa Peninsula region of Costa Rica. Sulfur sources were examined using stable isotope ratios (δ34S) and compared to chemical indices of soil development. The most weathered soils, and the forests they supported, are dominated by atmospheric sulfur, while a less weathered soil type contains both rock-derived and atmospheric sulfur. Patterns of increasing δ34S with increasing soil sulfur concentration across the landscape suggest atmospheric sulfur is accumulating, and little rock-derived sulfur has been retained. Soil sulfur, minus adsorbed sulfate, is correlated with carbon and nitrogen, implying that sulfur accumulation occurs as plants and microbes incorporate sulfur into organic matter. Only the lower depth increments of the more weathered soils contained significant adsorbed sulfate. The evidence suggests a pattern of soil development in which sulfur-bearing minerals in rock, such as sulfides, weather early relative to other minerals, and the released sulfate is leached away. Sulfur added via atmospheric deposition is retained as organic matter accumulates in the soil profile. Adsorbed sulfate accumulates later, driven by changes in soil chemistry and mineralogy. These aspects of sulfur behavior during pedogenesis in this environment may hasten the transition to dominance by atmospheric sources.
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Li, Xiao-sha; Wu, Ning; Liu, Ling; Feng, Yu-peng; Xu, Xu; Han, Hui-fang; Ning, Tang-yuan; Li, Zeng-jia
2015-06-01
To explore the effects of different tillage methods and straw recycling on soil respiration and microbial activity in summer maize field during the winter wheat and summer maize double cropping system, substrate induced respiration method and CO2 release method were used to determine soil microbial biomass carbon, microbial activity, soil respiration, and microbial respiratory quotient. The experiment included 3 tillage methods during the winter wheat growing season, i.e., no-tillage, subsoiling and conventional tillage. Each tillage method was companied with 2 straw management patterns, i.e., straw recycling and no straw. The results indicated that the conservation tillage methods and straw recycling mainly affected 0-10 cm soil layer. Straw recycling could significantly improve the microbial biomass carbon and microbial activity, while decrease microbial respiratory quotient. Straw recycling could improve the soil respiration at both seedling stage and anthesis, however, it could reduce the soil respiration at filling stage, wax ripeness, and harvest stage. Under the same straw application, compared with conventional tillage, the soil respiration and microbial respiratory quotient in both subsoiling and no-tillage were reduced, while the microbial biomass carbon and microbial activity were increased. During the summer maize growing season, soil microbial biomass carbon and microbial activity were increased in straw returning with conservation tillage, while the respiratory quotient was reduced. In 0-10 cm soil layer, compared with conventional tillage, straw recycling with subsoiling and no-tillage significantly increased soil microbial biomass carbon by 95.8% and 74.3%, and increased soil microbial activity by 97.1% and 74.2%, respectively.
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Micro-scale heterogeneity of soil phosphorus depends on soil substrate and depth
Werner, Florian; Mueller, Carsten W.; Thieme, Jurgen; ...
2017-06-09
Soils comprise various heterogeneously distributed pools of lithogenic, free organic, occluded, adsorbed, and precipitated phosphorus (P) forms, which differ depending on soil forming factors. Small-scale heterogeneity of element distributions recently has received increased attention in soil science due to its influence on soil functions and soil fertility. We investigated the micro-scale distribution of total P and different specific P binding forms in aggregates taken from a high-P clay-rich soil and a low-P sandy soil by combining advanced spectrometric and spectroscopic techniques to introduce new insights on P accessibility and availability in soils. Here we show that soil substrate and soilmore » depth determine micro-scale P heterogeneity in soil aggregates. In P-rich areas of all investigated soil aggregates, P was predominantly co-located with aluminium and iron oxides and hydroxides, which are known to strongly adsorb P. Clay minerals were co-located with P only to a lesser extent. In the low-P topsoil aggregate, the majority of the P was bound organically. Aluminium and iron phosphate predominated in the quartz-rich low-P subsoil aggregate. Sorbed and mineral P phases determined P speciation in the high-P top- and subsoil, and apatite was only detected in the high-P subsoil aggregate. Lastly, our results indicate that micro-scale spatial and chemical heterogeneity of P influences P accessibility and bioavailability.« less
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Micro-scale heterogeneity of soil phosphorus depends on soil substrate and depth
DOE Office of Scientific and Technical Information (OSTI.GOV)
Werner, Florian; Mueller, Carsten W.; Thieme, Jurgen
Soils comprise various heterogeneously distributed pools of lithogenic, free organic, occluded, adsorbed, and precipitated phosphorus (P) forms, which differ depending on soil forming factors. Small-scale heterogeneity of element distributions recently has received increased attention in soil science due to its influence on soil functions and soil fertility. We investigated the micro-scale distribution of total P and different specific P binding forms in aggregates taken from a high-P clay-rich soil and a low-P sandy soil by combining advanced spectrometric and spectroscopic techniques to introduce new insights on P accessibility and availability in soils. Here we show that soil substrate and soilmore » depth determine micro-scale P heterogeneity in soil aggregates. In P-rich areas of all investigated soil aggregates, P was predominantly co-located with aluminium and iron oxides and hydroxides, which are known to strongly adsorb P. Clay minerals were co-located with P only to a lesser extent. In the low-P topsoil aggregate, the majority of the P was bound organically. Aluminium and iron phosphate predominated in the quartz-rich low-P subsoil aggregate. Sorbed and mineral P phases determined P speciation in the high-P top- and subsoil, and apatite was only detected in the high-P subsoil aggregate. Lastly, our results indicate that micro-scale spatial and chemical heterogeneity of P influences P accessibility and bioavailability.« less
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He, Ruoyang; Yang, Kaijun; Li, Zhijie; Schädler, Martin; Yang, Wanqin; Wu, Fuzhong; Tan, Bo; Zhang, Li
2017-01-01
Forest land-use changes have long been suggested to profoundly affect soil microbial communities. However, how forest type conversion influences soil microbial properties remains unclear in Tibetan boreal forests. The aim of this study was to explore variations of soil microbial profiles in the surface organic layer and subsurface mineral soil among three contrasting forests (natural coniferous forest, NF; secondary birch forest, SF and spruce plantation, PT). Soil microbial biomass, activity and community structure of the two layers were investigated by chloroform fumigation, substrate respiration and phospholipid fatty acid analysis (PLFA), respectively. In the organic layer, both NF and SF exhibited higher soil nutrient levels (carbon, nitrogen and phosphorus), microbial biomass carbon and nitrogen, microbial respiration, PLFA contents as compared to PT. However, the measured parameters in the mineral soils often did not differ following forest type conversion. Irrespective of forest types, the microbial indexes generally were greater in the organic layer than in the mineral soil. PLFAs biomarkers were significantly correlated with soil substrate pools. Taken together, forest land-use change remarkably altered microbial community in the organic layer but often did not affect them in the mineral soil. The microbial responses to forest land-use change depend on soil layer, with organic horizons being more sensitive to forest conversion. PMID:28982191
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Pittman, Charles U; He, Jinbao
2002-05-03
Na/NH3 reductions have been used to dehalogenate polychlorinated biphenyls (PCBs), chlorinated aliphatic hydrocarbons (CAHs) and pesticides at diffusion controlled rates at room temperature in model compound studies in both dry NH3 and when water was added. The rate ratio of dechlorination (aliphatic and aromatic compounds) versus reaction of the solvated electron with water is very large, allowing wet soils or sludges to be remediated without an unreasonable consumption of sodium. Several soils, purposely contaminated with 1,1,1-trichloroethane, 1-chlorooctane and tetrachloroethylene, were remediated by slurring the soils in NH3 followed by addition of sodium. The consumption of sodium per mole of chlorine removed was examined as a function of both the hazardous substrate's concentration in the soil and the amount of water present. The Na consumption per Cl removed increases as the amount of water increases and as the substrate concentration in soil decreases. However, remediation was still readily accomplished from 5000 to 3000ppm to sub ppm levels of RCl in the presence of substantial amounts of water. PCB- and dioxin-contaminated oils were remediated with Na/NH3 as were PCB-contaminated soils and sludges from contaminated sites. Ca/NH3 treatments also successfully remediated PCB-contaminated clay, sandy and organic soils but laboratory studies demonstrated that Ca was less efficient than Na when substantial amounts of water were present. The advantages of solvated electron reductions using Na/NH3 include: (1) very rapid dehalogenation rates at ambient temperature, (2) soils (even clay soils) break down into particles and slurry nicely in NH3, (3) liquid ammonia handling technology is well known and (4) removal from soils, recovery and recycle of ammonia is easy due to its low boiling point. Finally, dechlorination is extremely fast even for the 'corner' chlorines in the substrate Mirex (structure in Eq. (5)).
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NASA Astrophysics Data System (ADS)
Luna Ramos, Lourdes; Pastorelli, Roberta; Miralles Mellado, Isabel; Fabiani, Arturo; Bastida López, Felipe; Hernández Fernández, María Teresa; García Izquierdo, Carlos; Solé Benet, Albert
2015-04-01
Mining activities generate loss of the quality of the environment and landscape specially in arid and semiarid Mediterranean regions. A precondition for ecosystem reclamation in such highly disturbed mining areas is the development of functional soils with appropriate levels of organic matter. In an experimental soil restoration in limestone quarries from Sierra de Gádor (Almería), SE Spain, 9 plots 15 x 5 m were prepared to test organic amendments (compost from solid urban residues-DOW-, sludge from urban water treatment-SS-, control-NA-) and different mulches (fine gravel-GM-, wood chips-WM-, control-NM-) with the aim to improve soil/substrate properties and to reduce evaporation and erosion. In each experimental plot, 75 native plants (Macrochloa tenacissima, Anthyllis terniflora and Anthyllis cytisoides) were planted. After 5 years from the start of the experiment, we evaluated how microbial community composition responded to the organic amendments and mulches. Microbial community composition of both bacteria and fungi was determined by phospholipid fatty acid (PLFA) and polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) fingerprinting. The results of the two-way ANOVA showed that PLFAs were significantly affected by organic amendments but not by the mulches or interaction of both factors. Experimental plots with DOW showed significantly higher level of fungal PLFAs than those with SS and NA, even higher than the reference undisturbed soil. However, any plot with organic amendments did not reach the content of bacterial PLFAs of the reference soils. The bacterial diversity (evaluated by diversity indices calculated from DGGE profiles) was greater in soil samples taken under NA and GM. Comparing these indices in fungal DGGE, we found greater values for soil samples taken under DOW and without mulches. Results from UPGMA analysis showed significant differences in the structure of soil bacterial communities from the different treatments respect to that of reference soil. Fungal communities could be divided into main groups according to the organic amendment. Within each group, GM amendment generated fungal community structures with lower similarities with respect to the other mulch treatments. In contrast to PLFA results, DGGE fingerprints revealed significant influence of the combination of organic amendments and mulches on diversity and composition of soil microbial communities.
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Use of lunar regolith as a substrate for plant growth
NASA Technical Reports Server (NTRS)
Ming, D. W.; Henninger, D. L.
1994-01-01
Regenerative Life Support Systems (RLSS) will be required to regenerate air, water, and wastes, and to produce food for human consumption during long-duration missions to the Moon and Mars. It may be possible to supplement some of the materials needed for a lunar RLSS from resources on the Moon. Natural materials at the lunar surface may be used for a variety of lunar RLSS needs, including (1) soils or solid-support substrates for plant growth, (2) sources for extraction of essential, plant-growth nutrients, (3) substrates for microbial populations in the degradation of wastes, (4) sources of O2 and H2, which may be used to manufacture water, (5) feed stock materials for the synthesis of useful minerals (e.g., molecular sieves), and (6) shielding materials surrounding the outpost structure to protect humans, plants, and microorganisms from harmful radiation. Use of indigenous lunar regolith as a terrestrial-like soil for plant growth could offer a solid support substrate, buffering capacity, nutrient source/storage/retention capabilities, and should be relatively easy to maintain. The lunar regolith could, with a suitable microbial population, play a role in waste renovation; much like terrestrial waste application directly on soils. Issues associated with potentially toxic elements, pH, nutrient availability, air and fluid movement parameters, and cation exchange capacity of lunar regolith need to be addressed before lunar materials can be used effectively as soils for plant growth.
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NASA Astrophysics Data System (ADS)
Velichko, V. V.; Tikhomirov, A. A.; Ushakova, S. A.
2018-02-01
If soil-like substrate (SLS) is to be used in human life support systems with a high degree of mass closure, the rate of its gas exchange as a compartment for mineralization of plant biomass should be understood. The purpose of this study was to compare variations in CO2 gas exchange of vegetable plant communities grown on the soil-like substrate using a number of plant age groups, which determined the so-called conveyor interval. Two experimental plant communities were grown as plant conveyors with different conveyor intervals. The first plant community consisted of conveyors with intervals of 7 days for carrot and beet and 14 days for chufa sedge. The conveyor intervals in the second plant community were 14 days for carrot and beet and 28 days for chufa sedge. This study showed that increasing the number of age groups in the conveyor and, thus, increasing the frequency of adding plant waste to the SLS, decreased the range of variations in CO2 concentration in the "plant-soil-like substrate" system. However, the resultant CO2 gas exchange was shifted towards CO2 release to the atmosphere of the plant community with short conveyor intervals. The duration of the conveyor interval did not significantly affect productivity and mineral composition of plants grown on the SLS.
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Simplified MPN method for enumeration of soil naphthalene degraders using gaseous substrate.
Wallenius, Kaisa; Lappi, Kaisa; Mikkonen, Anu; Wickström, Annika; Vaalama, Anu; Lehtinen, Taru; Suominen, Leena
2012-02-01
We describe a simplified microplate most-probable-number (MPN) procedure to quantify the bacterial naphthalene degrader population in soil samples. In this method, the sole substrate naphthalene is dosed passively via gaseous phase to liquid medium and the detection of growth is based on the automated measurement of turbidity using an absorbance reader. The performance of the new method was evaluated by comparison with a recently introduced method in which the substrate is dissolved in inert silicone oil and added individually to each well, and the results are scored visually using a respiration indicator dye. Oil-contaminated industrial soil showed slightly but significantly higher MPN estimate with our method than with the reference method. This suggests that gaseous naphthalene was dissolved in an adequate concentration to support the growth of naphthalene degraders without being too toxic. The dosing of substrate via gaseous phase notably reduced the work load and risk of contamination. The result scoring by absorbance measurement was objective and more reliable than measurement with indicator dye, and it also enabled further analysis of cultures. Several bacterial genera were identified by cloning and sequencing of 16S rRNA genes from the MPN wells incubated in the presence of gaseous naphthalene. In addition, the applicability of the simplified MPN method was demonstrated by a significant positive correlation between the level of oil contamination and the number of naphthalene degraders detected in soil.
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Raman microspectroscopy for in situ examination of carbon-microbe-mineral interactions
NASA Astrophysics Data System (ADS)
Creamer, C.; Foster, A. L.; Lawrence, C. R.; Mcfarland, J. W.; Waldrop, M. P.
2016-12-01
The changing paradigm of soil organic matter formation and turnover is focused at the nexus of microbe-carbon-mineral interactions. However, visualizing biotic and abiotic stabilization of C on mineral surfaces is difficult given our current techniques. Therefore we investigated Raman microspectroscopy as a potential tool to examine microbially mediated organo-mineral associations. Raman microspectroscopy is a non-destructive technique that has been used to identify microorganisms and minerals, and to quantify microbial assimilation of 13C labeled substrates in culture. We developed a partial least squares regression (PLSR) model to accurately quantify (within 5%) adsorption of four model 12C substrates (glucose, glutamic acid, oxalic acid, p-hydroxybenzoic acid) on a range of soil minerals. We also developed a PLSR model to quantify the incorporation of 13C into E. coli cells. Using these two models, along with measures of the 13C content of respired CO2, we determined the allocation of glucose-derived C into mineral-associated microbial biomass and respired CO2 in situ and through time. We observed progressive 13C enrichment of microbial biomass with incubation time, as well as 13C enrichment of CO2 indicating preferential decomposition of glucose-derived C. We will also present results on the application of our in situ chamber to quantify the formation of organo-mineral associations under both abiotic and biotic conditions with a variety of C and mineral substrates, as well as the rate of turnover and stabilization of microbial residues. Application of Raman microspectroscopy to microbial-mineral interactions represents a novel method to quantify microbial transformation of C substrates and subsequent mineral stabilization without destructive sampling, and has the potential to provide new insights to our conceptual understanding of carbon-microbe-mineral interactions.
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Antibiotic production by soil bacteria: diversity, activity and natural functions
USDA-ARS?s Scientific Manuscript database
The living components of soils, the micro- and macrobiota, play an essential role in several life support functions as they enable soils to recycle nutrients, inactive contaminants, suppress plant pathogens and serve as a suitable substrate for plant growth. Beneficial bacteria occur naturally in s...
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USDA-ARS?s Scientific Manuscript database
Antarctica is a pristine and extreme environment that represents a unique opportunity for taxonomic, ecological and biotechnological studies of the microorganisms. In the present work, the fungal communities of rhizosphere soil of Deschampsia antarctica, soil, ornithogenic soil, marine and lake sedi...
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NASA Astrophysics Data System (ADS)
Kader, Mohammed Abdul; Yeasmin, Sabina; Akter, Masuda; Sleutel, Steven
2016-04-01
Driving controllers of nitrogen (N) mineralization in paddy soils, especially under anaerobic soil conditions, remain elusive. The influence of exogenous organic matter (OM) and fertilizer application on the activities of five relevant enzymes (β-glucosaminidase, β-glucosidase, L-glutaminase, urease and arylamidase) was measured in two long-term field experiments. One 18-years field experiment was established on a weathered terrace soil with a rice-wheat crop rotation at the Bangabandhu Sheikh Mujibur Rahman Agricultural University (BSMRAU) having five OM treatments combined with two mineral N fertilizer levels. Another 30-years experiment was established on a young floodplain soil with rice-rice crop rotation at the Bangladesh Agricultural University (BAU) having eight mineral fertilizer treatments combined with organic manure. At BSMRAU, N fertilizer and OM amendments significantly increased all enzyme activities, suggesting them to be primarily determined by substrate availability. At BAU, non-responsiveness of β-glucosidase activity suggested little effect of the studied fertilizer and OM amendments on general soil microbial activity. Notwithstanding probably equal microbial demand for N, β-glucosaminidase and L-glutaminase activities differed significantly among the treatments (P>0.05) and followed strikingly opposite trends and correlations with soil organic N mineralization. So enzymatic pathways to acquire N differed by treatment at BAU, indicating differences in soil N quality and bio-availability. L-glutaminase activity was significantly positively correlated to the aerobic and anaerobic N mineralization rates at both field experiments. Combined with negative correlations between β-glucosaminidase activity and N mineralization rates, it appears that terminal amino acid NH2 hydrolysis was a rate-limiting step for soil N mineralization at BAU. Future investigations with joint quantification of polyphenol accumulation and binding of N, alongside an array of extracellular enzymes including oxidases and peroxidases for (poly)phenols and hydrolases for N-compounds, would enable verifying the hypothesized binding and stabilization of N onto accumulating polyphenols at BAU site under SOM accumulating management.
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NASA Astrophysics Data System (ADS)
Albino, J. D.; Nambi, I. M.
2009-12-01
Microbial Enhanced Oil Recovery (MEOR) and remediation of aquifers contaminated with hydrophobic contaminants require insitu production of biosurfactants for mobilization of entrapped hydrophobic liquids. Most of the biosurfactant producing microorganisms produce them under aerobic condition and hence surfactant production is limited in subsurface condition due to lack of oxygen. Currently bioremediation involves expensive air sparging or excavation followed by exsitu biodegradation. Use of microorganisms which can produce biosurfactants under anaerobic conditions can cost effectively expedite the process of insitu bioremediation or mobilization. In this work, the feasibility of anaerobic biosurfactant production in three mixed anaerobic cultures prepared from groundwater and soil contaminated with chlorinated compounds and municipal sewage sludge was investigated. The cultures were previously enriched under complete anaerobic conditions in the presence of Tetrachloroethylene (PCE) for more than a year before they were studied for biosurfactant production. Biosurfactant production under anaerobic conditions was simulated using two methods: i) induction of starvation in the microbial cultures and ii) addition of complex fermentable substrates. Positive result for biosurfactant production was not observed when the cultures were induced with starvation by adding PCE as blobs which served as the only terminal electron acceptor. However, slight reduction in interfacial tension was noticed which was caused by the adherence of microbes to water-PCE interface. Biosurfactant production was observed in all the three cultures when they were fed with complex fermentable substrates and surface tension of the liquid medium was lowered below 35 mN/m. Among the fermentable substrates tested, vegetable oil yielded highest amount of biosurfactant in all the cultures. Complete biodegradation of PCE to ethylene at a faster rate was also observed when vegetable oil was amended to the microbial cultures. The microorganisms responsible for biosurfactant production was isolated and identified as Pseudomonas Sp (designated as Pseudomonas Sp ANBIOSURF-1, Gene bank no: FJ930079), Pseudomonas stutzeri (MTCC 10033), Pseudomonas Sp (MTCC 10032) from groundwater, soil and municipal sewage sludge enrichments respectively. This study confirms that biosurfactants can be produced under anaerobic conditions and also in sufficient quantities. The cultures were also able to cometabolically degrade PCE to Ethylene. The isolated microorganisms can be used for remediation of DNAPL contaminated sites by in-situ biosurfactant production.
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Regional mapping of soil parent material by machine learning based on point data
NASA Astrophysics Data System (ADS)
Lacoste, Marine; Lemercier, Blandine; Walter, Christian
2011-10-01
A machine learning system (MART) has been used to predict soil parent material (SPM) at the regional scale with a 50-m resolution. The use of point-specific soil observations as training data was tested as a replacement for the soil maps introduced in previous studies, with the aim of generating a more even distribution of training data over the study area and reducing information uncertainty. The 27,020-km 2 study area (Brittany, northwestern France) contains mainly metamorphic, igneous and sedimentary substrates. However, superficial deposits (aeolian loam, colluvial and alluvial deposits) very often represent the actual SPM and are typically under-represented in existing geological maps. In order to calibrate the predictive model, a total of 4920 point soil descriptions were used as training data along with 17 environmental predictors (terrain attributes derived from a 50-m DEM, as well as emissions of K, Th and U obtained by means of airborne gamma-ray spectrometry, geological variables at the 1:250,000 scale and land use maps obtained by remote sensing). Model predictions were then compared: i) during SPM model creation to point data not used in model calibration (internal validation), ii) to the entire point dataset (point validation), and iii) to existing detailed soil maps (external validation). The internal, point and external validation accuracy rates were 56%, 81% and 54%, respectively. Aeolian loam was one of the three most closely predicted substrates. Poor prediction results were associated with uncommon materials and areas with high geological complexity, i.e. areas where existing maps used for external validation were also imprecise. The resultant predictive map turned out to be more accurate than existing geological maps and moreover indicated surface deposits whose spatial coverage is consistent with actual knowledge of the area. This method proves quite useful in predicting SPM within areas where conventional mapping techniques might be too costly or lengthy or where soil maps are insufficient for use as training data. In addition, this method allows producing repeatable and interpretable results, whose accuracy can be assessed objectively.
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Spatial distribution of enzyme activities along the root and in the rhizosphere of different plants
NASA Astrophysics Data System (ADS)
Razavi, Bahar S.; Zarebanadkouki, Mohsen; Blagodatskaya, Evgenia; Kuzyakov, Yakov
2015-04-01
Extracellular enzymes are important for decomposition of many biological macromolecules abundant in soil such as cellulose, hemicelluloses and proteins. Activities of enzymes produced by both plant roots and microbes are the primary biological drivers of organic matter decomposition and nutrient cycling. So far acquisition of in situ data about local activity of different enzymes in soil has been challenged. That is why there is an urgent need in spatially explicit methods such as 2-D zymography to determine the variation of enzymes along the roots in different plants. Here, we developed further the zymography technique in order to quantitatively visualize the enzyme activities (Spohn and Kuzyakov, 2013), with a better spatial resolution We grew Maize (Zea mays L.) and Lentil (Lens culinaris) in rhizoboxes under optimum conditions for 21 days to study spatial distribution of enzyme activity in soil and along roots. We visualized the 2D distribution of the activity of three enzymes:β-glucosidase, leucine amino peptidase and phosphatase, using fluorogenically labelled substrates. Spatial resolution of fluorescent images was improved by direct application of a substrate saturated membrane to the soil-root system. The newly-developed direct zymography shows different pattern of spatial distribution of enzyme activity along roots and soil of different plants. We observed a uniform distribution of enzyme activities along the root system of Lentil. However, root system of Maize demonstrated inhomogeneity of enzyme activities. The apical part of an individual root (root tip) in maize showed the highest activity. The activity of all enzymes was the highest at vicinity of the roots and it decreased towards the bulk soil. Spatial patterns of enzyme activities as a function of distance from the root surface were enzyme specific, with highest extension for phosphatase. We conclude that improved zymography is promising in situ technique to analyze, visualize and quantify spatial distribution of enzyme activities in the rhizosphere hotspots. References Spohn, M., Kuzyakov, Y., 2013. Phosphorus mineralization can be driven by microbial need for carbon. Soil Biology & Biochemistry 61: 69-75
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Microbial Populations of Stony Meteorites: Substrate Controls on First Colonizers.
Tait, Alastair W; Gagen, Emma J; Wilson, Siobhan A; Tomkins, Andrew G; Southam, Gordon
2017-01-01
Finding fresh, sterilized rocks provides ecologists with a clean slate to test ideas about first colonization and the evolution of soils de novo. Lava has been used previously in first colonizer studies due to the sterilizing heat required for its formation. However, fresh lava typically falls upon older volcanic successions of similar chemistry and modal mineral abundance. Given enough time, this results in the development of similar microbial communities in the newly erupted lava due to a lack of contrast between the new and old substrates. Meteorites, which are sterile when they fall to Earth, provide such contrast because their reduced and mafic chemistry commonly differs to the surfaces on which they land; thus allowing investigation of how community membership and structure respond to this new substrate over time. We conducted 16S rRNA gene analysis on meteorites and soil from the Nullarbor Plain, Australia. We found that the meteorites have low species richness and evenness compared to soil sampled from directly beneath each meteorite. Despite the meteorites being found kilometers apart, the community structure of each meteorite bore more similarity to those of other meteorites (of similar composition) than to the community structure of the soil on which it resided. Meteorites were dominated by sequences that affiliated with the Actinobacteria with the major Operational Taxonomic Unit (OTU) classified as Rubrobacter radiotolerans. Proteobacteria and Bacteroidetes were the next most abundant phyla. The soils were also dominated by Actinobacteria but to a lesser extent than the meteorites. We also found OTUs affiliated with iron/sulfur cycling organisms Geobacter spp. and Desulfovibrio spp. This is an important finding as meteorites contain abundant metal and sulfur for use as energy sources. These ecological findings demonstrate that the structure of the microbial community in these meteorites is controlled by the substrate, and will not reach homeostasis with the Nullarbor community, even after ca. 35,000 years. Our findings show that meteorites provide a unique, sterile substrate with which to test ideas relating to first-colonizers. Although meteorites are colonized by microorganisms, the microbial population is unlikely to match the community of the surrounding soil on which they fall.
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Microbial Populations of Stony Meteorites: Substrate Controls on First Colonizers
Tait, Alastair W.; Gagen, Emma J.; Wilson, Siobhan A.; Tomkins, Andrew G.; Southam, Gordon
2017-01-01
Finding fresh, sterilized rocks provides ecologists with a clean slate to test ideas about first colonization and the evolution of soils de novo. Lava has been used previously in first colonizer studies due to the sterilizing heat required for its formation. However, fresh lava typically falls upon older volcanic successions of similar chemistry and modal mineral abundance. Given enough time, this results in the development of similar microbial communities in the newly erupted lava due to a lack of contrast between the new and old substrates. Meteorites, which are sterile when they fall to Earth, provide such contrast because their reduced and mafic chemistry commonly differs to the surfaces on which they land; thus allowing investigation of how community membership and structure respond to this new substrate over time. We conducted 16S rRNA gene analysis on meteorites and soil from the Nullarbor Plain, Australia. We found that the meteorites have low species richness and evenness compared to soil sampled from directly beneath each meteorite. Despite the meteorites being found kilometers apart, the community structure of each meteorite bore more similarity to those of other meteorites (of similar composition) than to the community structure of the soil on which it resided. Meteorites were dominated by sequences that affiliated with the Actinobacteria with the major Operational Taxonomic Unit (OTU) classified as Rubrobacter radiotolerans. Proteobacteria and Bacteroidetes were the next most abundant phyla. The soils were also dominated by Actinobacteria but to a lesser extent than the meteorites. We also found OTUs affiliated with iron/sulfur cycling organisms Geobacter spp. and Desulfovibrio spp. This is an important finding as meteorites contain abundant metal and sulfur for use as energy sources. These ecological findings demonstrate that the structure of the microbial community in these meteorites is controlled by the substrate, and will not reach homeostasis with the Nullarbor community, even after ca. 35,000 years. Our findings show that meteorites provide a unique, sterile substrate with which to test ideas relating to first-colonizers. Although meteorites are colonized by microorganisms, the microbial population is unlikely to match the community of the surrounding soil on which they fall. PMID:28713354
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Coupled biotic-abiotic oxidation of organic matter by biogenic MnO_{2}
NASA Astrophysics Data System (ADS)
Gonzalez, Julia; Peña, Jasquelin
2016-04-01
Some reactive soil minerals are strongly implicated in stabilising organic matter. However, others can play an active role in the oxidation of organic molecules. In natural systems, layer-type manganese oxide minerals (MnO2) typically occur as biomineral assemblages consisting of mineral particles and microbial biomass. Both the mineral and biological fractions of the assemblage can be powerful oxidants of organic C. The biological compartment relies on a set of enzymes to drive oxidative transformations of reduced C-substrates, whereas MnO2 minerals are strong, less specific abiotic oxidants that are assumed to rely on interfacial interactions between C-substrates and the mineral surface. This project aims to understand the coupling between microbial C mineralization and abiotic C oxidation mediated by MnO2 in bacterial-MnO2 assemblages. Specifically, under conditions of high C turnover, microbial respiration can significantly alter local pH, dissolved oxygen and pool of available reductants, which may modify rates and mechanism of C oxidation by biotic and abiotic components. We first investigated changes in the solution chemistry of Pseudomonas putida suspensions exposed to varying concentrations of glucose, chosen to represent readily bioavailable substrates in soils. Glucose concentrations tested ranged between 0 and 5.5mM and changes in pH, dissolved oxygen and dissolved organic and inorganic carbon were tracked over 48h. We then combined literature review and wet-chemical experiments to compile the pH dependence of rates of organic substrate oxidation by MnO2, including glucose. Our results demonstrate a strong pH dependence for these abiotic reactions. In assemblages of P. putida - MnO2, kinetic limitations for abiotic C oxidation by MnO2 are overcome by changes in biogeochemical conditions that result from bacterial C metabolism. When extrapolated to a soil solution confronted to an input of fresh dissolved organic matter, bacterial C metabolism of the labile fraction may lower solution pH into a regime that favours abiotic oxidation of recalcitrant C by MnO2. This project demonstrates that the co-occurrence of mineral particles with metabolically active cells provides a direct link between the C and Mn cycles.
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Andresen, Louise C.; Dungait, Jennifer A. J.; Bol, Roland; Selsted, Merete B.; Ambus, Per; Michelsen, Anders
2014-01-01
It is vital to understand responses of soil microorganisms to predicted climate changes, as these directly control soil carbon (C) dynamics. The rate of turnover of soil organic carbon is mediated by soil microorganisms whose activity may be affected by climate change. After one year of multifactorial climate change treatments, at an undisturbed temperate heathland, soil microbial community dynamics were investigated by injection of a very small concentration (5.12 µg C g−1 soil) of 13C-labeled glycine (13C2, 99 atom %) to soils in situ. Plots were treated with elevated temperature (+1°C, T), summer drought (D) and elevated atmospheric carbon dioxide (510 ppm [CO2]), as well as combined treatments (TD, TCO2, DCO2 and TDCO2). The 13C enrichment of respired CO2 and of phospholipid fatty acids (PLFAs) was determined after 24 h. 13C-glycine incorporation into the biomarker PLFAs for specific microbial groups (Gram positive bacteria, Gram negative bacteria, actinobacteria and fungi) was quantified using gas chromatography-combustion-stable isotope ratio mass spectrometry (GC-C-IRMS). Gram positive bacteria opportunistically utilized the freshly added glycine substrate, i.e. incorporated 13C in all treatments, whereas fungi had minor or no glycine derived 13C-enrichment, hence slowly reacting to a new substrate. The effects of elevated CO2 did suggest increased direct incorporation of glycine in microbial biomass, in particular in G+ bacteria, in an ecosystem subjected to elevated CO2. Warming decreased the concentration of PLFAs in general. The FACE CO2 was 13C-depleted (δ13C = 12.2‰) compared to ambient (δ13C = ∼−8‰), and this enabled observation of the integrated longer term responses of soil microorganisms to the FACE over one year. All together, the bacterial (and not fungal) utilization of glycine indicates substrate preference and resource partitioning in the microbial community, and therefore suggests a diversified response pattern to future changes in substrate availability and climatic factors. PMID:24454793
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Do diatoms percolate through soil and can they be used for tracing the origin of runoff?
NASA Astrophysics Data System (ADS)
De Graaf, Lenka; Cammeraat, Erik; Pfister, Laurent; Wetzel, Carlos; Klaus, Julian; Hissler, Christophe
2015-04-01
Tracers are widely used to study the movement of water in a catchment. Because of depletion of scientific possibilities with most common tracer types, we proposed the use of diatoms as a natural tracer. Paradoxical results on the contribution of surface runoff to the storm hydrograph were obtained in pioneer research on this idea. Diatom transport via the subsurface flow to the stream would explain this paradox. Prerequisite for this is vertical transport of diatoms through soils, which is the topic of this study. Emphasis is on percolation behavior (speed of percolation, speed of percolation over time, and species distribution) of Pseudostaurosira sp. and Melosira sp. (Bacillariophyceae) through undisturbed soil columns of contrasting substrates. Co-objective is to study the flowpaths of water through the soil columns. Natural undisturbed soil columns were sampled in the Attert basin (Luxembourg) on schist, marl and sandstone substrates. Rain simulation experiments were performed to study vertical diatom transport. Rhodamine dye experiments were carried out to gain insight in the active flowpaths of water, and breakthrough experiments were performed to study the responses of the soil columns to applied water. Diatoms were transported through the soil columns of the three substrates. A vast majority of diatom percolation took place within the first 15 minutes, percolation hereafter was marginal but nevertheless present. Peaks in diatom percolation corresponded with a high flux caused by the addition of the diatom culture, but seepage of diatoms along the sides is unlikely according to the species distribution and the rhodamine dye experiment. Pseudostaurosira sp. percolated significantly better than Melosira sp. Significantly more diatoms percolated through the marl columns compared to the schist columns and variance within the sandstone group was very high. Absolute differences between substrates however, were marginal. Most preferential flowpaths were observed in the marl columns, indicating highest active macroporosity in these columns. Although the sample size of this study was small, it is suspected that the highest diatom percolation percentages of the marl columns is linked to its greater macroporosity and most importantly, diatoms can percolate through soil (macro-) pores.
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NASA Astrophysics Data System (ADS)
Davidson, Eric; Sihi, Debjani; Savage, Kathleen
2017-04-01
Soil fluxes of greenhouse gases (GHGs) play a significant role as biotic feedbacks to climate change. Production and consumption of carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) are affected by complex interactions of temperature, moisture, and substrate supply, which are further complicated by spatial heterogeneity of the soil matrix. Models of belowground processes of these GHGs should be internally consistent with respect to the biophysical processes of gaseous production, consumption, and transport within the soil, including the contrasting effects of oxygen (O2) as either substrate or inhibitor. We installed automated chambers to simultaneously measure soil fluxes of CO2 (using LiCor-IRGA), CH4, and N2O (using Aerodyne quantum cascade laser) along soil moisture gradients at the Howland Forest in Maine, USA. Measured fluxes of these GHGs were used to develop and validate a merged model. While originally intended for aerobic respiration, the core structure of the Dual Arrhenius and Michaelis-Menten (DAMM) model was modified by adding M-M and Arrhenius functions for each GHG production and consumption process, and then using the same diffusion functions for each GHG and for O2. The area under a soil chamber was partitioned according to a log-normal probability distribution function, where only a small fraction of microsites had high available-C. The probability distribution of soil C leads to a simulated distribution of heterotrophic respiration, which translates to a distribution of O2 consumption among microsites. Linking microsite consumption of O2 with a diffusion model generates microsite concentrations of O2, which then determine the distribution of microsite production and consumption of CH4 and N2O, and subsequently their microsite concentrations using the same diffusion function. At many moisture values, there are some microsites of production and some of consumption for each gas, and the resulting simulated microsite concentrations of CH4 and N2O range from below ambient to above ambient atmospheric values. As soil moisture or temperature increase, the skewness of the microsite distributions of heterotrophic respiration and CH4 concentrations shifts toward a larger fraction of high values, while the skewness of microsite distributions of O2 and N2O concentrations shifts toward a larger fraction of low values. This approach of probability distribution functions for each gas simulates the importance of microsite hotspots of methanogenesis and N2O reduction at high moisture (and temperature). In addition, the model demonstrates that net consumption of atmospheric CH4 and N2O can occur simultaneously within a chamber due to the distribution of soil microsite conditions, which is consistent with some episodes of measured fluxes. Because soil CO2, N2O and CH4 fluxes are linked through substrate supply and O2 effects, the multiple constraints of simultaneous measurements of all three GHGs proved to be effective when applied to our combined model. Simulating all three GHGs simultaneously in a parsimonious modeling framework provides confidence that the most important mechanisms are skillfully simulated using appropriate parameterization and good process representation.
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An interactive survey panel regarding the effects of mice (Microtus spec.) on a young ecosystem
NASA Astrophysics Data System (ADS)
Zaplata, Markus; Maurer, Thomas; Boldt-Burisch, Katja; Schaaf, Wolfgang; Hinz, Christoph
2015-04-01
Apparent disturbance caused by soil megafauna took place for the very first time in 2014, after nine years of spontaneous vegetative succession of the constructed watershed Chicken Creek catchment (6 ha). This watershed was designed to investigate the initial phase of soil and ecosystem development under natural conditions including the detailed study of hydrologic processes and water-substrate-plant-atmosphere interactions. In autumn 2014, we recorded the primarily common vole (Microtus arvalis Pallas) activities (calamity), which altered the microtopography of the substrate surface: We counted mouse holes and diggings (for storage organs) at the same spatial units (permanent plots, >100 # of 5 m × 5 m) where we monitor the vegetation since the onset of the catchment. We are hence capable of analysing the effect of abundant vegetarian mice and biogenic macropores, e.g. on the occurrence and performance of the more than 150 vascular plant species present by comparing the respective coverage in 2013 (the pre-mice year) versus 2014, with or without accounting for the confounding effect of succession. Additionally elaborated insight on the 3-D architecture of the mice underground corridors and the nesting places (in situ) enables to extrapolate mass and volume of the moved substrate and the number of the nests of mice for the whole catchment. We report these results, anticipating a return service: Here, we ask for your expectation regarding the significance of the mice-made disturbance on the vegetation of the young ecosystem.
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NASA Astrophysics Data System (ADS)
Matteucci, M.; Cescatti, A.; Gruening, C.; Ballarin, I. G.; Guenther, S.; Magnani, F.; Nali, C.; Lorenzini, G.
2012-04-01
The response of ecosystems to environmental factors, such as temperature and rainfall, is crucial to understand the impact of climate change on the terrestrial C cycle. Forest soil respiration represents the main pathway by which photosynthetically assimilated C is released to atmosphere; its intensity depends not only on soil environmental conditions, but also on the availability of organic substrates respired by roots and microorganisms. Several techniques have been applied to partition the autotrophic and heterotrophic components of soil respiration in boreal and temperate forests; there is a general lack of information, on the contrary, on the dynamics of soil CO2 efflux in Mediterranean ecosystems. The IPCC A1B scenario highlighted the importance of the Mediterranean area since it is expected to experience a temperature increase (from 2.2 °C to 5.1 °C) and a rainfall reduction ranging from -4 to -27% on annual basis. We used the tree-girdling technique together with periodic chamber-based measurements to study the partitioning of total soil respiration (Rs) into its autotrophic (Ra) and heterotrophic (Rh) components in a 60-year old forest in Central Italy (San Rossore) dominated by Pinus pinaster. This technique has been extensively used to block the flux of photosynthates from leaves to roots, thus stopping the autotrophic root respiration in the soil. We found that two weeks after the treatment soil respiration in the girdled plots decreased by 29% and remained stable over the period of analysis, suggesting that Rh dominates total soil respiration. The anomalous low rainfall regimen of May to October 2011 (102 mm cumulated rain) associated with average air temperatures (with a mean value of 19,6 °C over the period) gave us the opportunity to investigate the decoupled response of soil respiration to water and temperature. Time series analysis performed under this severe drought conditions showed overall low values of soil respiration with three clear peaks associated with water pulses from rain events. Both total and partitioned fluxes were indeed significantly correlated with soil water content (Rs: R2=0,63, p<0,001; Rh: R2=0,45, p<0,01; Ra: R2=0,70, p<0,001) while the response to soil temperature was evident only for Ra (R2=0,27, p<0,05) and no significant for Rh and Rs (R2=0,11, p>0,05 and R2=0,03, p>0,05, respectively). The relationship with photosynthesis was subsequently evaluated analyzing the time-lagged correlation between daily gross primary productivity (GPP) derived from eddy covariance measurements and total and partitioned soil CO2 efflux. The time lagged analysis showed that Ra was overall best correlated with GPP with a peak at 3 days of delay (r= 0,72, p<0,001) while Rs had a peak in the fraction of variance explained corresponding to 4 days of delay (r=0,66, p=0,001). These findings confirm that CO2 efflux from soil is strongly affected by environmental factors and substrates supplied by photosynthetic activity, but suggest that the effects they exert on autotrophic and heterotrophic fluxes follow different mechanisms and temporal dynamics.
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Bio-ISRU Concepts using microorganisms to release O2 and H2 on Moon and Mars
NASA Astrophysics Data System (ADS)
Slenzka, Klaus; Kempf, Juergen
Since space exploration missions begun, numerous spacecrafts were sent to space for examina-tion of other planets. One limiting factor of the endurance of such missions is the unlasting energy supply to run devices and motors of the space crafts as well as for locally habitats. The high weight and volume of fuels makes embedding of local resources necessary to allow ex-tension to long term missions. Nature demonstrates how to survive in extreme environments. Some more adapted microorganisms like Chlamydomonas reinhardii even release elementary hydrogen from water under special nutrition which might be used to run fuel cells and provide electric energy. The same organism release oxygen by photosysthesis under standard nutrition, the counterpart of hydrogen to operate fuel cells. Planets of interest are covered by potential toxic soil called "Regolith". Lunar regolith is known to be extremely aggressive and inhibit cells grows not only due to its sharp edges. First studies on lunar soil simulant tolerance of Chl.reinhardii have shown promising results. The single cells surround the substrate without any negative influence. A 3-dimensional tissue like matrix was build by the proliferating now adhering micro algae cells and the substrate. The photosynthesis rate was not negatively in-fluenced by the soil. This enables Chl.reinhardii to become a first settler organism of the lunar surface. Maybe a first step of terraforming to allow the growth of higher organisms. Lunar soil regolith consists of several components. Especially in minerals bound oxygen plays an out-standing role for industrial use. Some microorganisms of the proteobacteria type are reducing ferroxides to gain oxygen under anaerobic conditions while they produce electric energy simul-taneously. For a faster electron transfer the Shewanella bacteria built filamentous nanowire-like structures to connect one cell to the other. A bioreactor hosting specific microorganism might be run to provide oxygen to the life support system embedded in a permanent Moon or Mars base. This method demonstrates a low energetic oxygen release, a serious alternative to high the energetic oxygen separation of the ilmenite process, fluorination process, melting hydrol-ysis, vacuum distillation or photo dissociation, respectively. Not only oxygen production of the biological processes should be in focus of space application. Also the metal oxide reducing component of the process might run batteries to provide energy to devices of a Moon or Mars base.
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Carbon mineralization in acidic, xeric forest soils: induction of new activities.
Tate, R L
1985-08-01
Carbon mineralization was examined in Lakehurst and Atsion sands collected from the New Jersey Pinelands and in Pahokee muck from the Everglades Agricultural Area. Objectives were (i) to estimate the carbon mineralization capacities of acidic, xeric Pinelands soils in the absence of exogenously supplied carbon substrate (nonamended carbon mineralization rate) and to compare these activities with those of agriculturally developed pahokee muck, and (ii) to measure the capacity for increased carbon mineralization in the soils after carbon amendment. In most cases, nonamended carbon mineralization rates were greater in samples of the acid- and moisture-stressed Pinelands soils than in Pahokee muck collected from a fallow (bare) field. Carbon amendment resulted in augmented catabolic activity in Pahokee muck samples, suggesting that the microbial community was carbon limited in this soil. With many of the substrates, no stimulation of the catabolic rate was detected after amendment of Pinelands soils. This was documented by the observation that amendment of Pahokee muck with an amino acid mixture, glucose, or acetate resulted in a 3.0-, 3.9-, or 10.5-fold stimulation of catabolic activity, respectively, for the added substrate. In contrast, amendment of the Pinelands soils resulted in increased amino acid and acetate catabolic rates in Lakehurst sand and increased acetate metabolism only in Atsion sand. Other activities were unchanged. The increased glucose respiration rates resulted from stimulation of existing microbial activity rather than from microbial proliferation since no change in the microbial growth rate, as estimated by the rate of incorporation of C-labeled acetate into cell membranes, occurred after glucose amendment of the soils. A stimulation of microbial growth rate was recorded with glucose-amended Lakehurst sand collected from the B horizon.
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Carbon Mineralization in Acidic, Xeric Forest Soils: Induction of New Activities †
Tate, Robert L.
1985-01-01
Carbon mineralization was examined in Lakehurst and Atsion sands collected from the New Jersey Pinelands and in Pahokee muck from the Everglades Agricultural Area. Objectives were (i) to estimate the carbon mineralization capacities of acidic, xeric Pinelands soils in the absence of exogenously supplied carbon substrate (nonamended carbon mineralization rate) and to compare these activities with those of agriculturally developed pahokee muck, and (ii) to measure the capacity for increased carbon mineralization in the soils after carbon amendment. In most cases, nonamended carbon mineralization rates were greater in samples of the acid- and moisture-stressed Pinelands soils than in Pahokee muck collected from a fallow (bare) field. Carbon amendment resulted in augmented catabolic activity in Pahokee muck samples, suggesting that the microbial community was carbon limited in this soil. With many of the substrates, no stimulation of the catabolic rate was detected after amendment of Pinelands soils. This was documented by the observation that amendment of Pahokee muck with an amino acid mixture, glucose, or acetate resulted in a 3.0-, 3.9-, or 10.5-fold stimulation of catabolic activity, respectively, for the added substrate. In contrast, amendment of the Pinelands soils resulted in increased amino acid and acetate catabolic rates in Lakehurst sand and increased acetate metabolism only in Atsion sand. Other activities were unchanged. The increased glucose respiration rates resulted from stimulation of existing microbial activity rather than from microbial proliferation since no change in the microbial growth rate, as estimated by the rate of incorporation of 14C-labeled acetate into cell membranes, occurred after glucose amendment of the soils. A stimulation of microbial growth rate was recorded with glucose-amended Lakehurst sand collected from the B horizon. PMID:16346862
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J.S. Norman; J.E. Barrett
2016-01-01
We sought to investigate the drivers of richness of ammonia-oxidizing bacteria (AOB) and archaea (AOA) in temperate forest soils. We sampled soils across four experimental watersheds in the Coweeta Hydrologic Laboratory, North Carolina USA. These watersheds are geographically close, but vary in soil chemistry due to differences in land use history. While we...
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Gleason, Frank H.; Crawford, John W.; Neuhauser, Sigrid; Henderson, Linda E.; Lilje, Osu
2012-01-01
Zoosporic true fungi have frequently been identified in samples from soil and freshwater ecosystems using baiting and molecular techniques. In fact some species can be components of the dominant groups of microorganisms in particular soil habitats. Yet these microorganisms have not yet been directly observed growing in soil ecosystems. Significant physical characteristics and features of the three-dimensional structures of soils which impact microorganisms at the microscale level are discussed. A thorough knowledge of soil structures is important for studying the distribution of assemblages of these fungi and understanding their ecological roles along spatial and temporal gradients. A number of specific adaptations and resource seeking strategies possibly give these fungi advantages over other groups of microorganisms in soil ecosystems. These include chemotactic zoospores, mechanisms for adhesion to substrates, rhizoids which can penetrate substrates in small spaces, structures which are resistant to environmental extremes, rapid growth rates and simple nutritional requirements. These adaptations are discussed in the context of the characteristics of soils ecosystems. Recent advances in instrumentation have led to the development of new and more precise methods for studying microorganisms in three-dimensional space. New molecular techniques have made identification of microbes possible in environmental samples. PMID:22308003
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Schiefer, Jasmin; Lair, Georg J; Lüthgens, Christopher; Wild, Eva Maria; Steier, Peter; Blum, Winfried E H
2018-07-01
During COP 21 in Paris 2015, several states and organizations agreed on the "4/1000" initiative for food security and climate. This initiative aims to increase world's soil organic carbon (SOC) stocks by 4‰ annually. The influence of soil development status on SOC dynamics is very important but usually not considered in studies. We analyse SOC accumulation under forest, grassland and cropping systems along a soil age gradient (10-17,000years) to show the influence of soil development status on SOC increase. SOC stocks (0-40cm) and accumulation rates along a chronosequence in alluvial soils of the Danube River in the Marchfeld (eastern Austria) were analysed. The analysed Fluvisols and Chernozems have been used as forest, grassland and cropland for decades or hundreds of years. The results showed that there is a fast build-up of OC stocks (0-40cm) in young soils with accumulation of ~1.3tha -1 a -1 OC in the first 100years and ~0.5tha -1 a -1 OC between 100 and 350years almost independent of land use. Chernozems with a sediment deposition age older than 5.000years have an accumulation rate<0.01tOCha -1 a -1 (0-40cm). Radiocarbon dating showed that the topsoil (0-10cm) consists mainly of ">modern" and "modern" carbon indicating a fast carbon cycling. Carbon in subsoil is less exposed to decomposition and OC can be stored at long-time scales in the subsoil ( 14 C age of 3670±35 BP). In view of the '4/1000' initiative, soils with constant carbon input (forest & grassland) fulfil the intended 4‰ growth rate of SOC stocks only in the first 60years of soil development. We proclaim that under the present climate in Central Europe, the increase of SOC stocks in soil is strongly affected by the state of soil development. Copyright © 2018 Elsevier B.V. All rights reserved.
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Canyon Country Ecosystems Research Site
Soil Crust Home Crust 101 Advanced Gallery References CCERS Site Links updated: April 24, 2006 cyanobacteria, algae, lichens and mosses, that stabilize soil against wind and water erosion, enhance water 3400 m, and features a range of climates on both the same and different soil and bedrock substrates
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PESTICIDE MODELS FOR SIMULATING ENVIRONMENTAL TRANSPORT OF SOIL FUMIGANTS
USDA-ARS?s Scientific Manuscript database
Soil fumigants are a special group of pesticides that possess relatively high vapor pressure. Thus a large fraction is in the vapor phase after application in the substrate soil environment. Because of the high vapor pressure, they are also volatile organic compounds with strong potential for air p...
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USDA-ARS?s Scientific Manuscript database
Nitrogen-limited soil microbial activity has important implications for soil carbon storage and nutrient availability, but previous methods for assessing resource limitation have been restricted, due to enrichment criteria (i.e., long incubation periods, high substrate amendments) and/or logistical ...
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Microbial responses to chitin and chitosan in oxic and anoxic agricultural soil slurries
NASA Astrophysics Data System (ADS)
Wieczorek, A. S.; Hetz, S. A.; Kolb, S.
2014-02-01
Chitin is the second most abundant biopolymer in terrestrial ecosystems and is subject to microbial degradation. Chitin can be deacetylated to chitosan or can be hydrolyzed to N,N'-diacetylchitobiose and oligomers of N-acetylglucosamine by aerobic and anaerobic microorganisms. Which pathway of chitin hydrolysis is preferred by soil microbial communities has previously been unknown. Supplementation of chitin stimulated microbial activity under oxic and anoxic conditions in agricultural soil slurries, whereas chitosan had no effect. Thus, the soil microbial community likely was more adapted to chitin as a substrate. In addition, this finding suggested that direct hydrolysis of chitin was preferred to the pathway that starts with deacetylation. Chitin was apparently degraded by aerobic respiration, ammonification, and nitrification to carbon dioxide and nitrate under oxic conditions. When oxygen was absent, fermentation products (acetate, butyrate, propionate, hydrogen, carbon dioxide) and ammonia were detected, suggesting that butyric and propionic acid fermentation were along with ammonification likely responsible for apparent anaerobic chitin degradation. In total, 42 different chiA genotypes were detected of which twenty were novel at an amino acid sequence dissimilarity of >50%. Various chiA genotypes responded to chitin supplementation and affiliated with a novel deep-branching bacterial chiA genotype (anoxic conditions), genotypes of Beta- and Gammaproteobacteria (oxic and anoxic conditions), and Planctomycetes (oxic conditions). Thus, this study provides evidence that detected chitinolytic bacteria were catabolically diverse and occupied different ecological niches with regard to oxygen availability enabling chitin degradation under various redox conditions at the level of the community.
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A real-scale soil phytoremediation.
Macci, Cristina; Doni, Serena; Peruzzi, Eleonora; Bardella, Simone; Filippis, Giorgio; Ceccanti, Brunello; Masciandaro, Grazia
2013-07-01
In the present investigation, a phytoremediation process with a combination of different plant species (Populus nigra (var.italica), Paulownia tomentosa and Cytisus scoparius), and natural growing vegetation has been proposed at real-scale (10.000 m(2)) to bioremediate and functionally recover a soil historically contaminated by heavy metals and hydrocarbons. In the attempts to assess both effectiveness and evolution of the remediation system towards a natural soil ecosystem, besides the pollution parameters, also parameters describing the efficiency of the microbiological components (enzyme activities), were investigated. In 3 years, the total content of hydrocarbons and heavy metals in soil decreased with time (40 % and 20-40 %, respectively), reaching concentrations under the limit of National legislation and making the site suitable for environmental reusing. The reduction in pollutants was probably the reason of the increase in dehydrogenase (indicator of overall microbial activity), β-glucosidase and phosphatase activities, enzymes related to C and P cycles, respectively. However, this trend was obviously due also to the increase of chemical nutrients, acting as substrate of these enzymes. Moreover, a phytotest carried out with Raphanus sativus, showed, after 3 years, a significant increase in percentage of plant growth, confirming a reduction in soil toxicity and an improvement in soil nutritional state. Therefore, this phytoremediation system seems very promising to perform both decontamination and functional recovery of a polluted soil at real-scale level.
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Implications of altered rainfall and exotic plants on soil microbial communities and carbon biomass
NASA Astrophysics Data System (ADS)
Castro, S.; Lipson, D.; Cleland, E. E.
2016-12-01
Climate and exotic plant disturbances are among the most significant threats to Mediterranean-type ecosystems, compromising their renowned biodiversity and role in the global carbon cycle. Predicted shifts in rainfall patterns have become a particular concern, especially when interactions with other stressors and effects on biogeochemical processes remain poorly understood. To understand the impacts of altered rainfall on belowground dynamics as well as the role of inter- and intra-annual variation and plant community composition, we monitored soil microbial communities under native and exotic plant dominated plots with rainfall manipulation treatments in a semi-arid Mediterranean-type ecosystem. We measured microbial biomass, respiration rates, and community structure across treatments and vegetation types. Soil moisture and dissolved organic carbon were also measured to characterize abiotic soil properties. The soil moisture gradient established by the rainfall treatments had a positive correlation with microbial biomass carbon under native- and exotic-dominated plots but had no effect on respiration rates. A significant reduction in microbial biomass under exotic plants was found in 2013 but not in 2014 and 2015. Substrate-induced respiration values were higher in the exotic-dominated plots during the spring seasons, resulting in a significant interaction between plant community type and season. Bacterial communities showed little variation except in the Proteobacteria phyla, which was lower in exotic plants-dominated plots. Dissolved organic carbon was significantly reduced in exotic-dominated plots by approximately 26% based on average values of all plots throughout. Our results illustrate that rainfall quantity and exotic plants can cause changes in microbial biomass, community composition and respiration rates jeopardizing soil carbon storage. They also reinforce the importance of temporal variability and the need for repeated sampling to correctly interpret environmental changes in semi-arid ecosystems. We conclude that to improve predictions of the implications of global stressors on biogeochemical cycles in semi-arid ecosystems, there is a need to incorporate microbial data with the understanding that it is highly dependent on temporal dynamics and plant community.
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Substrate effects on pupation and adult emergence of Hermetia illucens (Diptera: Stratiomyidae).
Holmes, L A; Vanlaerhoven, S L; Tomberlin, J K
2013-04-01
Black soldier flies, Hermetia illucens (L.) (Diptera: Stratiomyidae), are of particular interest for their applications in waste management. Feeding on decaying organic waste, black soldier flies successfully reduce manure in confined animal feeding operations of poultry, swine, and cattle. To optimize waste conversion in confined animal feeding operations and landfill facilities, it is imperative to optimize black soldier fly development. Unfortunately, black soldier flies only convert waste during their larval feeding stages and therefore it is of interest to optimize the nonfeeding stages of development, specifically, the postfeeding and pupal stages. The time spent in these stages is thought to be determined by the pupation substrate encountered by the postfeeding larvae. The objective of this study was to determine the effect different pupation substrates have on postfeeding development time, pupation time, and adult emergence success. Five pupation substrates were compared: wood shavings, potting soil, topsoil, sand, and nothing. Postfeeding larvae took longer to reach pupation in the absence of a pupation substrate, although reaching pupation in the shortest time in potting soil and wood shavings. The time spent in the pupal stage was shortest in the absence of a pupation substrate. However, fewer adults emerged when a pupation substrate was not provided.
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Aboul-Eid, H Z; Noweer, E M A; Ashour, N E; Ameen, Hoda H
2006-01-01
A field trial was conducted in El-Shourouk Farm, El-Beheira governorate, western Nile valley, Egypt to determine the effectiveness of the commercial bio-product Dbx 1003 20% containing the nematode-trapping fungus Dactylaria brochopaga against root-knot nematode Meloidogyne incognita infesting grapevine variety Superior. Its effects on plant growth criteria and yield production were also investigated. The fungus was introduced to soil by either of two ways. First: soil was drenched with spore suspension at the rate of 3 l/tree. Second: 1/2 kg of a vermiculite substrate, as a carrier of spores and mycelia was added around each tree both as single and twice application in autumn and spring. All treatments significantly reduced M. incognita J2 in soil and number of root galls compared with the untreated control. Significant yield increases have been observed with all treatments compared with the untreated control. Spores suspension twice applications gave the highest yield production.
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Ghislain, Thierry; Faure, Pierre; Biache, Coralie; Michels, Raymond
2010-11-15
Reactivity of polycyclic aromatic hydrocarbons (PAHs) in the subsurface is of importance to environmental assessment, as they constitute a highly toxic hazard. Understanding their reactivity in the long term in natural recovering systems is thus a key issue. This article describes an experimental investigation on the air oxidation of fluoranthene (a PAH abundant in natural systems polluted by industrial coal use) at 100°C on different mineral substrates commonly found in soils and sediments (quartz sand, limestone, and clay). Results demonstrate that fluoranthene is readily oxidized in the presence of limestone and clay, leading to the formation of high molecular weight compounds and a carbonaceous residue as end product especially for clay experiments. As demonstrated elsewhere, the experimental conditions used permitted the reproduction of the geochemical pathway of organic matter observed under natural conditions. It is therefore suggested that low-temperature, mineral-catalyzed air oxidation is a mechanism relevant to the stabilization of PAHs in sediments and soils.
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The Role of Iron-Bearing Minerals in NO2 to HONO Conversion on Soil Surfaces.
Kebede, Mulu A; Bish, David L; Losovyj, Yaroslav; Engelhard, Mark H; Raff, Jonathan D
2016-08-16
Nitrous acid (HONO) accumulates in the nocturnal boundary layer where it is an important source of daytime hydroxyl radicals. Although there is clear evidence for the involvement of heterogeneous reactions of NO2 on surfaces as a source of HONO, mechanisms remain poorly understood. We used coated-wall flow tube measurements of NO2 reactivity on environmentally relevant surfaces (Fe (hydr)oxides, clay minerals, and soil from Arizona and the Saharan Desert) and detailed mineralogical characterization of substrates to show that reduction of NO2 by Fe-bearing minerals in soil can be a more important source of HONO than the putative NO2 hydrolysis mechanism. The magnitude of NO2-to-HONO conversion depends on the amount of Fe(2+) present in substrates and soil surface acidity. Studies examining the dependence of HONO flux on substrate pH revealed that HONO is formed at soil pH < 5 from the reaction between NO2 and Fe(2+)(aq) present in thin films of water coating the surface, whereas in the range of pH 5-8 HONO stems from reaction of NO2 with structural iron or surface complexed Fe(2+) followed by protonation of nitrite via surface Fe-OH2(+) groups. Reduction of NO2 on ubiquitous Fe-bearing minerals in soil may explain HONO accumulation in the nocturnal boundary layer and the enhanced [HONO]/[NO2] ratios observed during dust storms in urban areas.
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Predicting the response of soil organic matter microbial decomposition to moisture
NASA Astrophysics Data System (ADS)
Chenu, Claire; Garnier, Patricia; Monga, Olivier; Moyano, Fernando; Pot, Valérie; Nunan, Naoise; Coucheney, Elsa; Otten, Wilfred
2014-05-01
Next to temperature, soil moisture is a main driver of soil C and N transformations in soils, because it affects microbial activity and survival. The moisture sensitivity of soil organic matter decay may be a source of uncertainty of similar magnitude to that of the temperature sensitivity and receives much less attention. The basic concepts and mechanisms relating soil water to microorganisms were identified early (i.e. in steady state conditions : direct effects on microbial physiology, diffusion substrates, nutrients, extracellular enzymes, diffusion of oxygen, movement of microorganisms). However, accounting for how moisture controls soil microbial activity remains essentially empirical and poorly accounts for soil characteristics. Soil microorganisms live in a complex 3-D framework of mineral and organic particles defining pores of various sizes, connections with adjacent pores, and with pore walls of contrasted nature, which result in a variety of microhabitats. The water regime to which microorganisms are exposed can be predicted to depend the size and connectivity of pores in which they are located. Furthermore, the spatial distribution of microorganisms as well as that of organic matter is very heterogeneous, determining the diffusion distances between substrates and decomposers. A new generation of pore scale models of C dynamics in soil may challenge the difficulty of modelling such a complex system. These models are based on an explicit representation of soil structure (i.e. soil particles and voids), microorganisms and organic matter localisation. We tested here the ability of such a model to account for changes in microbial respiration with soil moisture. In the model MOSAIC II, soil pore space is described using a sphere network coming from a geometrical modelling algorithm. MicroCT tomography images were used to implement this representation of soil structure. A biological sub-model describes the hydrolysis of insoluble SOM into dissolved organic matter, its assimilation, respiration and microbial mortality. A recent improvement of the model was the description of the diffusion of soluble organic matter. We tested the model using the results from an experiment where a simple substrate (fructose) was decomposed by bacteria within a simple media (sand). Separate incubations in microcosms were carried out using five different bacterial communities at two different moisture conditions corresponding to water potentials of -0.01 and -0.1 bars. We calibrated the biological parameters using the experimental data obtained at high water content and we tested the model without any parameters change at low water content. Both the experiments and simulations showed a decrease in mineralisation with a decrease of water content, of which pattern depended on the bacterial species and its physiological characteristics. The model was able to correctly simulate the decrease of connectivity between substrate and microorganism due the decrease of water content. The potential and required developments of such models in describing how heterotrophic respiration is affected by micro-scale distribution and processes in soils and in testing scenarios regarding water regimes in a changing climate is discussed.
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Weaker soil carbon-climate feedbacks resulting from microbial and abiotic interactions
NASA Astrophysics Data System (ADS)
Tang, Jinyun; Riley, William J.
2015-01-01
The large uncertainty in soil carbon-climate feedback predictions has been attributed to the incorrect parameterization of decomposition temperature sensitivity (Q10; ref. ) and microbial carbon use efficiency. Empirical experiments have found that these parameters vary spatiotemporally, but such variability is not included in current ecosystem models. Here we use a thermodynamically based decomposition model to test the hypothesis that this observed variability arises from interactions between temperature, microbial biogeochemistry, and mineral surface sorptive reactions. We show that because mineral surfaces interact with substrates, enzymes and microbes, both Q10 and microbial carbon use efficiency are hysteretic (so that neither can be represented by a single static function) and the conventional labile and recalcitrant substrate characterization with static temperature sensitivity is flawed. In a 4-K temperature perturbation experiment, our fully dynamic model predicted more variable but weaker soil carbon-climate feedbacks than did the static Q10 and static carbon use efficiency model when forced with yearly, daily and hourly variable temperatures. These results imply that current Earth system models probably overestimate the response of soil carbon stocks to global warming. Future ecosystem models should therefore consider the dynamic interactions between sorptive mineral surfaces, substrates and microbial processes.
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NASA Astrophysics Data System (ADS)
Charteris, Alice; Michaelides, Katerina; Evershed, Richard
2015-04-01
Organic N concentrations far exceed those of inorganic N in most soils and despite much investigation, the composition and cycling of this complex pool of SOM remains poorly understood. A particular problem has been separating more recalcitrant soil organic N from that actively cycling through the soil system; an important consideration in N cycling studies and for the soil's nutrient supplying capacity. The use of 15N-labelled substrates as stable isotope tracers has contributed much to our understanding of the soil system, but the complexity and heterogeneity of soil organic N prevents thorough compound-specific 15N analyses of organic N compounds and makes it difficult to examine any 15N-labelled organic products in any detail. As a result, a significant proportion of previous work has either simply assumed that since the majority of soil N is organic, all of the 15N retained in the soil is organic N (e.g. Sebilo et al., 2013) or subtracted 15N-labelled inorganic compounds from bulk values (e.g. Pilbeam et al., 1997). While the latter approach is more accurate, these methods only provide an estimate of the bulk 15N value of an extremely complex and non-uniformly labelled organic pool. A more detailed approach has been to use microbial biomass extraction (Brookes et al., 1985) and subsequent N isotopic analysis to determine the 15N value of biomass-N, representing the fraction of 15N assimilated by microbes or the 15N cycling through the 'living' or 'active' portion of soil organic N. However, this extraction method can only generate estimates and some lack of confidence in its validity and reliability remains. Here, we present an alternative technique to obtain a measure of the assimilation of an applied 15N substrate by the soil microbial biomass and an estimate of the newly synthesized soil protein, which is representative of the magnitude of the active soil microbial biomass. The technique uses a stable isotope tracer and compound-specific 15N analysis, but unlike previous works analyses for amino acids (representing organic products) rather than ammonium (NH4+) and nitrate (NO3-). Amino acids are commonly referred to as 'the building blocks of life' as they form the proteins which regulate life's essential biochemical reactions. Proteinaceous matter generally comprises 20-40% of total soil N and is ubiquitous in living organisms, so is a likely 'organic product' of microbial activity/assimilation. Hence, we consider it likely that amino acids represent the major organic nitrogenous products and a reasonable 'proxy' for/measure of the assimilation of an applied 15N substrate by the soil microbial biomass and an estimate of the newly synthesized soil protein. Brookes, P. C. et al. Soil Biol Biochem. 1985, 17, 837-842. Jenkinson, D. S. et al. Soil Biol Biochem. 2004, 36, 5-7. Nannipieri, P. et al. Plant Soil. 1999, 208, 43-56. Pilbeam, C. J. et al. J Agr Sci. 1997, 128, 415-424. Sebilo, M. et al. PNAS. 2013, 110, 18185-18189.
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Ovipositional site selection by Anopheles gambiae: influences of substrate moisture and texture.
Huang, J; Walker, E D; Giroux, P Y; Vulule, J; Miller, J R
2005-12-01
The influence of substrate moisture (hydration) and grain size (texture) on oviposition was quantified in choice tests using Anopheles gambiae sensu stricto Giles (Diptera: Culicidae) laboratory strains and gravid An. gambiae sensu lato from a natural population in Western Kenya. A strong, positive correlation was found between moisture content and the degree of egg-laying, which peaked at saturation with standing water. Soil moisture quantified as surface conductivity, was measured with an electronic leaf-wetness sensor slightly modified from a unit available commercially. Although An. gambiae females were sensitive to measurable differences in substrate moisture, they distributed eggs on both fully hydrated and less hydrated substrates. In contrast, An. gambiae females showed little response to substrate texture: they oviposited with equal frequency on all silica substrates of eight particle size classes, ranging from small pebbles (850 microm diameter) to very fine grains (< 38 microm diameter), when all were moist. Female An. gambiae laid more eggs on dark than white substrates against a light background, but did not discriminate between moist, pulverized black soapstone and moist black Kenyan soil taken from typical An. gambiae larval habitats. We conclude that hydration and visual contrast are critical ovipositional site qualities for An. gambiae, but substrate texture is not.
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Kaur, Jasmeen; Adamchuk, Viacheslav I.; Whalen, Joann K.; Ismail, Ashraf A.
2015-01-01
The eco-toxicological indicators used to evaluate soil quality complement the physico-chemical criteria employed in contaminated site remediation, but their cost, time, sophisticated analytical methods and in-situ inapplicability pose a major challenge to rapidly detect and map the extent of soil contamination. This paper describes a sensor-based approach for measuring potential (substrate-induced) microbial respiration in diesel-contaminated and non-contaminated soil and hence, indirectly evaluates their microbial activity. A simple CO2 sensing system was developed using an inexpensive non-dispersive infrared (NDIR) CO2 sensor and was successfully deployed to differentiate the control and diesel-contaminated soils in terms of CO2 emission after glucose addition. Also, the sensor system distinguished glucose-induced CO2 emission from sterile and control soil samples (p ≤ 0.0001). Significant effects of diesel contamination (p ≤ 0.0001) and soil type (p ≤ 0.0001) on glucose-induced CO2 emission were also found. The developed sensing system can provide in-situ evaluation of soil microbial activity, an indicator of soil quality. The system can be a promising tool for the initial screening of contaminated environmental sites to create high spatial density maps at a relatively low cost. PMID:25730479
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Aloupi, M; Koutrotsios, G; Koulousaris, M; Kalogeropoulos, N
2012-04-01
The objectives of this survey were (1) to assess for the first time the Cd, Cu, Cr, Fe, Mn, Ni, Pb and Zn contents in wild edible mushrooms (Russula delica, Lactarius sanguifluus, Lactarius semisanguifluus, Lactarius deliciosus, Suillus bellinii) from the island of Lesvos, (2) to investigate the metals' variability among the species, as well as in relation to the chemical composition of the underlying soil, comparing mushrooms collected from volcanic and serpentine substrates and (3) to estimate metal intake by the consumption of the mushrooms under consideration. The trace metals in 139 samples were determined by flame or flameless atomic absorption spectroscopy. The median metal concentrations were as follows: Cd: 0.14; Cr: 0.10; Cu: 8.51; Fe: 30.3; Mn: 5.26; Ni: 0.34; Pb: 0.093 and Zn: 64.50, all in mgkg(-1) dry weight. The observed concentrations are among the lowest reported for mushrooms from Europe or Turkey, while Pb and Cd values did not exceed the limits set by the European Union. Significant species- and substrate-related differences in the metal contents were found, but the variability did not follow a uniform pattern for all the metals in all mushroom species. As a general trend, the mushrooms growing in serpentine sites contained higher Cd, Cr and Ni than those from volcanic sites. The calculated bioconcentration factors (BCFs) showed that none of the mushrooms can be regarded as a metal bioaccumulator, although BCF values slightly above unity were found for Zn in the three Lactarius species, and for Cu in R. delica. The studied mushrooms could supply considerable amounts of essential metals such as Zn and Cr. On the other hand, the consumption of R. delica collected from volcanic soils could provide 12% of the Cd daily tolerable intake and as high as 53% when collected from serpentine soils. Nonetheless, our results indicate that the regular consumption of wild edible mushrooms from Lesvos is quite safe for human health. Copyright © 2011 Elsevier Inc. All rights reserved.
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Vertebrate Decomposition Is Accelerated by Soil Microbes
Lauber, Christian L.; Metcalf, Jessica L.; Keepers, Kyle; Ackermann, Gail; Carter, David O.
2014-01-01
Carrion decomposition is an ecologically important natural phenomenon influenced by a complex set of factors, including temperature, moisture, and the activity of microorganisms, invertebrates, and scavengers. The role of soil microbes as decomposers in this process is essential but not well understood and represents a knowledge gap in carrion ecology. To better define the role and sources of microbes in carrion decomposition, lab-reared mice were decomposed on either (i) soil with an intact microbial community or (ii) soil that was sterilized. We characterized the microbial community (16S rRNA gene for bacteria and archaea, and the 18S rRNA gene for fungi and microbial eukaryotes) for three body sites along with the underlying soil (i.e., gravesoils) at time intervals coinciding with visible changes in carrion morphology. Our results indicate that mice placed on soil with intact microbial communities reach advanced stages of decomposition 2 to 3 times faster than those placed on sterile soil. Microbial communities associated with skin and gravesoils of carrion in stages of active and advanced decay were significantly different between soil types (sterile versus untreated), suggesting that substrates on which carrion decompose may partially determine the microbial decomposer community. However, the source of the decomposer community (soil- versus carcass-associated microbes) was not clear in our data set, suggesting that greater sequencing depth needs to be employed to identify the origin of the decomposer communities in carrion decomposition. Overall, our data show that soil microbial communities have a significant impact on the rate at which carrion decomposes and have important implications for understanding carrion ecology. PMID:24907317
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Biodegradation kinetics of BTE-OX and MTBE by a diesel-grown biomass.
Acuna-Askar, K; de la Torre-Torres, M A; Guerrero-Munoz, M J; Garza-Gonzalez, M T; Chavez-Gomez, B; Rodriguez-Sanchez, I P; Barrera-Saldana, H A
2006-01-01
The biodegradation kinetics of BTE-oX and MTBE, mixed all together in the presence of diesel-grown bioaugmented bacterial populations as high as 885 mg/L VSS, was evaluated. The effect of soil in aqueous samples and the effect of Tergitol NP-10 on substrate biodegradation rates were also evaluated. Biodegradation kinetics was evaluated for 54 h, every 6 h. All BTE-oX chemicals followed a first-order two-phase biodegradation kinetic model, whereas MTBE followed a zero-order removal kinetic model in all samples. BTE-oX removal rates were much higher than those of MTBE in all samples. The presence of soil in aqueous samples retarded BTE-oX and MTBE removal rates. The addition of Tergitol NP-10 to aqueous samples containing soil had a positive effect on substrate removal rate in all samples. Substrate percent removals ranged between 64.8-98.9% for benzene, toluene and ethylbenzene. O-xylene and MTBE percent removals ranged between 18.7-40.8% and 7.2-10.3%, respectively.
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Microbial community changes as a possible factor controlling carbon sequestration in subsoil
NASA Astrophysics Data System (ADS)
Strücker, Juliane; Jörgensen, Rainer Georg
2015-04-01
In order to gain more knowledge regarding the microbial community and their influence on carbon sequestration in subsoil two depth profiles with different soil organic carbon (SOC) concentrations were sampled. The SOC concentrations developed naturally due to deposition and erosion. This experiment offers the opportunity to investigate to which extend natural SOC availability or other subsoil specific conditions influence the composition and the functional diversity of the microbial community and in return if there is any evidence how the microbial community composition affects carbon sequestration under these conditions. Soil samples were taken at four different depths on two neighbouring arable sites; one Kolluvisol with high SOC concentrations (8-12 g/kg) throughout the profile and one Luvisol with low SOC concentrations (3-4 g/kg) below 30 cm depth. The multi substrate induced respiration (MSIR) method was used to identify shifts in the functional diversity of the microbial community along the depth profiles. Amino sugars Muramic Acid and Glucosamine were measured as indicators for bacterial and fungal residues and ergosterol was determined as marker for saprotrophic fungi. The results of the discriminant analysis of the respiration values obtained from the 17 substrates used in the MSIR show that the substrate use in subsoil is different from the substrate use in topsoil. The amino sugar analysis and the ratio of ergosterol to microbial biomass C indicate that the fungal dominance of the microbial community decreases with depth. The results from this study support previous findings, which also observed decreasing fungal dominance with depth. Furthermore the MSIR approach shows clearly that not only the composition of the microbial community but also their substrate use changes with depth. Thus, a different microbial community with altered substrate requirements could be an important reason for enhanced carbon sequestration in subsoil. The fact that the MSIR was also able to differentiate between the two sites proves the assumption that resources are an important factor controlling the functional diversity of the microbial community, as abiotic factors are very similar for the two profiles, but the sites show a different depth gradient for SOC.
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Contributions of water supply from the weathered bedrock zone to forest soil quality
James H. Witty; Robert C. Graham; Kenneth R. Hubbert; James A. Doolittle; Jonathan A. Wald
2003-01-01
One measure of forest soil quality is the ability of the soil to support tree growth. In mediterranean-type ecosystems, such as most of California's forests, there is virtually no rainfall during the summer growing season, so trees must rely on water stored within the substrate. Water is the primary limitation to productivity in these forests. Many forest soils in...
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NASA Astrophysics Data System (ADS)
Pérez, Francisco L.
2017-10-01
This study examines biogeomorphic interactions between nurse rocks, slope processes, and 300 kūpaoa (Dubautia menziesii) shrubs in Haleakalā Crater (Maui, Hawai'i). Research objectives were to: assess the association of kūpaoa with substrates upslope and downslope of plants, and proximity to the closest rock uphill; contrast shrub/substrate relationships with site frequency of sediment types; measure surface soil shear-strength and compressibility on 50 paired locations near boulders; and investigate the aggregation characteristics and spatial patterns of kūpaoa in relation to rock and substrate variation. Data analyzed came from three 100-plant surveys at 3 sites: a plant census at 2720-2975 m altitude, and wandering-quarter transects (WQTs) across two areas (2610-2710 m); ground sediment cover was estimated along four phototransects on these sites. Data for the three 100-plant surveys included substrate type-outcrops, blocks, cobbles, pebbles, exposed soil, organic litter-upslope from each plant, and distance to the largest rock upslope. The two surveys examined along WQTs included substrate type found downslope from kūpaoa, plant height, plant diameters across and along the slope, and distance between successively censused plants. Most plants grew downslope of nurse rocks; > 74% were adjacent to blocks or outcrops, and > 17% near cobbles. Plants showed avoidance for finer substrates; only 5.3% and 2.7% grew on/near bare soils and pebbles, respectively. About 92% of kūpaoa were ≤ 10 cm downslope of rocks; > 89% grew ≤ 2 cm away, and 83% in direct contact with a rock. Some seedlings also grew on pukiawe (Leptecophylla tameiameiae) nurse plants. Several stable rock microsites protected plants from disturbance by slope processes causing debris shift. Site sediments were significantly finer than substrates near plants; shrubs grew preferentially adjacent to boulders > 20 cm wide, which were more common near plants than across sites. Soils downslope of 50 boulders-mean 41.3 cm-showed higher shear strength and compressibility than soils along rock sides. These boulder dams stop descending debris, steadily deflecting them toward rock sides, whereas protected soils downslope of blocks are infrequently disturbed and develop into downslope elongated, clast-free fine-earth flags. Kūpaoa were uniformly dispersed across slopes, showing a single-phase mosaic arrangement, without apparent aggregation. Slopes where kūpaoa grows had a relatively uniform distribution of surface sediments; observed kūpaoa patterns may have resulted from the array of microsites generated by surface rocks and sediments, as shrubs simply responded to such spatial structure.
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Soils as records of past and present environments
NASA Astrophysics Data System (ADS)
Sauer, Daniela
2015-04-01
This contribution reflects selected pedological concepts that are helpful for interpreting soil properties related to past and present environments. These concepts are illustrated by examples from various landscapes, and their combination finally leads to some further conclusions. The concept of Targulian and Gerasimova (2009) distinguishes soil system and soil body. Soil system is defined as "open multiphase system functioning in any solid-phase substrate at its interface with the atmosphere, hydrosphere and biota", and soil body as "solid-phase part of a soil system produced by its long-term functioning and composed of a vertical sequence of genetic horizons". Soil system functioning corresponds to the recent environmental factors and includes heat and moisture dynamics, biomass production, biogeochemical cycles, and other processes. In contrast, a soil body is a record of the long-term functioning of a soil system. It thus provides a record not only of the functioning of the soil system under the present environmental conditions but also under past, possibly different, conditions. Hence, Targulian and Goryachkin (2004) called it the "memory" of the landscape. Richter and Yaalon (2012) argued that most soils comprise both, features that developed under the present environmental conditions and features that reflect different conditions that the soils experienced in the past; they concluded that most soils are polygenetic. Although the current functioning of the soil system in the concept of Targulian and Gerasimova (2009) is mainly controlled by the present-day combination of environmental factors, it should be added that past processes also influence the soil system, because past processes changed the soil properties in a way that also the present-day functioning of the soil system is affected by these changes. Earlier, Yaalon (1971) had categorised soil properties according to the time-span required for their adjustment to the actual environment, distinguishing (i) rapidly adjusting soil properties (adjusting within some hundreds of years), (ii) slowly adjusting soil properties (adjusting within some thousands of years), and (iii) persistent soil properties (showing no changes over ten thousands to millions of years). In a polygenetic soil, rapidly adjusting soil properties may already be in equilibrium with the present conditions, whereas slowly adjusting soil properties may still reflect past conditions. Thus, the lower the rate at which a certain soil property in a polygenetic soil adjusts, the larger is the extent to which this property is still determined by earlier environmental conditions. Knowledge on the rates at which soil properties adjust may hence be used to estimate the time at which a significant environmental change took place, based on the degree of overprinting of the different kinds of soil properties adjusting at different rates in a polygenetic soil. References: Richter, D. de B., Yaalon, D.H., 2012. "The changing model of soil" revisited. Soil Sci. Soc. Am. J. 76, 766-778. Targulian, V. O., Goryachkin, S. V., 2004. Soil memory: Types of records, carriers, hierarchy and diversity. Revista Mexicana Ciencias Geol. 21, 1-8. Targulian, V.O., Gerasimova, M., 2009. Soil geography: geography of soil systems and soil bodies. Soil Geography: New Horizons. International Conference, 16-20 November 2009 in Huatulco, Mexico. Book of abstracts, 39. Yaalon, D.H., 1971. Soil forming processes in time and space. In: Yaalon, D.H. (Ed.), Paleopedology-origin, nature and dating of paleosols. Int. Soc. Soil Sci. and Israel Univ. Press, Jerusalem, pp. 29-39.
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USDA-ARS?s Scientific Manuscript database
Biochar application to soils has been suggested to elevate nutrient sorption, improve soil fertility and reduce net greenhouse gas (GHG) emissions. We examined the impact of composting biochar together with a biologically active substrate (i.e., livestock manure-straw mixture). We hypothesized that ...
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Ferrari, Belinda C.; Binnerup, Svend J.; Gillings, Michael
2005-01-01
Traditional microbiological methods of cultivation recover less than 1% of the total bacterial species, and the culturable portion of bacteria is not representative of the total phylogenetic diversity. Classical cultivation strategies are now known to supply excessive nutrients to a system and therefore select for fast-growing bacteria that are capable of colony or biofilm formation. New approaches to the cultivation of bacteria which rely on growth in dilute nutrient media or simulated environments are beginning to address this problem of selection. Here we describe a novel microcultivation method for soil bacteria that mimics natural conditions. Our soil slurry membrane system combines a polycarbonate membrane as a growth support and soil extract as the substrate. The result is abundant growth of uncharacterized bacteria as microcolonies. By combining microcultivation with fluorescent in situ hybridization, previously “unculturable” organisms belonging to cultivated and noncultivated divisions, including candidate division TM7, can be identified by fluorescence microscopy. Successful growth of soil bacteria as microcolonies confirmed that the missing culturable majority may have a growth strategy that is not observed when traditional cultivation indicators are used. PMID:16332866
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Seedling growth and biomass allocation of endemic and threatened shrubs of rupestrian fields
NASA Astrophysics Data System (ADS)
Negreiros, Daniel; Fernandes, G. Wilson; Silveira, Fernando A. O.; Chalub, Clarissa
2009-03-01
The increasing anthropogenic pressure in the rare rupestrian fields in southeastern Brazil has led to the expansion of degraded areas on the extremely nutrient-deficient quartzitic soils. On the other hand, the use of rupestrian field native species in reclamation programmes has been hampered by the lack of studies involving seedling physiological ecology. The present study evaluated biomass allocation and seedling growth rate during early seedling growth of four Fabaceae shrubs: Collaea cipoensis, Calliandra fasciculata, Chamaecrista ramosa, and Mimosa foliolosa. The following hypotheses were tested: (i) species proportionally allocate higher biomass to the roots, presenting a high root/shoot ratio; and (ii) species exhibit low phenotypic variation because they have adapted to poor nutritional environments. A 12-month greenhouse experiment was carried out to evaluate seedling growth and biomass allocation performance in substrates with contrasting levels of soil fertility. The four species studied presented values of root/shoot ratio lower than one in both fertility conditions of the substrate. Growth parameters for Collaea and Calliandra increased with increasing soil fertility, while no differences were observed for Mimosa and Chamaecrista. Although the four species are naturally adapted to low nutritional quality soils, seedling development was not hindered by high fertility substrate conditions. Despite the remarkable differences in fertility between the substrates, the responsiveness in growth and allocation in Chamaecrista and Mimosa was lower than that expected if the species would exhibit high phenotypic variation. The implications for rupestrian field restoration are discussed.
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Nitrogen trace gas fluxes from a semiarid subtropical savanna under woody legume encroachment
NASA Astrophysics Data System (ADS)
Soper, Fiona M.; Boutton, Thomas W.; Groffman, Peter M.; Sparks, Jed P.
2016-05-01
Savanna ecosystems are a major source of nitrogen (N) trace gases that influence air quality and climate. These systems are experiencing widespread encroachment by woody plants, frequently associated with large increases in soil N, with no consensus on implications for trace gas emissions. We investigated the impact of encroachment by N-fixing tree Prosopis glandulosa on total reactive N gas flux (Nt = NO + N2O + NOy + NH3) from south Texas savanna soils over 2 years. Contrary to expectations, upland Prosopis groves did not have greater Nt fluxes than adjacent unencroached grasslands. However, abiotic conditions (temperature, rainfall, and topography) were strong drivers. Emissions from moist, low-lying Prosopis playas were up to 3 times higher than from Prosopis uplands. Though NO dominated emissions, NH3 and NOy (non-NO oxidized N) comprised 12-16% of the total summer N flux (up to 7.9 µg N m-2 h-1). Flux responses to soil wetting were temperature dependent for NO, NH3, and NOy: a 15 mm rainfall event increased flux 3-fold to 22-fold after 24 h in summer but had no effect in winter. Repeated soil wetting reduced N flux responses, indicating substrate depletion as a likely control. Rapid (<1 min) increases in NO emissions following wetting of dry soils suggested that abiotic chemodenitrification contributes to pulse emissions. We conclude that temperature and wetting dynamics, rather than encroachment, are primary drivers of N flux from these upland savannas, with implications for future emission patterns under altered precipitation regimes.
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Menkis, Audrius; Burokienė, Daiva; Gaitnieks, Talis; Uotila, Antti; Johannesson, Hanna; Rosling, Anna; Finlay, Roger D; Stenlid, Jan; Vasaitis, Rimvydas
2012-08-01
The aim of this study was to assess belowground occurrence, persistence and possible impact of the biocontrol agent Phlebiopsis gigantea (Fr.) Jülich on soil fungi. Sampling of soil and roots of Picea abies (L.) H. Karst. was carried out at 12 P. gigantea-treated and five nontreated control sites representing 1- to 60-month-old clear-cuts and thinned forest sites in Finland and Latvia. The 454-sequencing of ITS rRNA from fine roots, humus and mineral soil resulted in 8626 high-quality fungal sequences. Phlebiopsis gigantea represented 1.3% of all fungal sequences and was found in 14 treated and nontreated sites and in all three substrates. In different substrates, the relative abundance of P. gigantea at stump treatment sites either did not differ significantly or was significantly lower than in nontreated controls. No significant correlation was found between the time elapsed since the tree harvesting and/or application of the biocontrol and abundance of P. gigantea in different substrates. In conclusion, the results demonstrate that P. gigantea occasionally occurs belowground in forest ecosystems but that stump treatment with the biocontrol agent has little or no impact on occurrence and persistence of P. gigantea belowground, and consequently no significant impact on soil fungi. © 2012 Federation of European Microbiological Societies. Published by Blackwell Publishing Ltd. All rights reserved.
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NASA Astrophysics Data System (ADS)
Leewis, Mary-Cathrine; Uhlik, Ondrej; Leigh, Mary Beth
2016-02-01
Aerobic mineralization of PCBs, which are toxic and persistent organic pollutants, involves the upper (biphenyl, BP) and lower (benzoate, BZ) degradation pathways. The activity of different members of the soil microbial community in performing one or both pathways, and their synergistic interactions during PCB biodegradation, are not well understood. This study investigates BP and BZ biodegradation and subsequent carbon flow through the microbial community in PCB-contaminated soil. DNA stable isotope probing (SIP) was used to identify the bacterial guilds involved in utilizing 13C-biphenyl (unchlorinated analogue of PCBs) and/or 13C-benzoate (product/intermediate of BP degradation and analogue of chlorobenzoates). By performing SIP with two substrates in parallel, we reveal microbes performing the upper (BP) and/or lower (BZ) degradation pathways, and heterotrophic bacteria involved indirectly in processing carbon derived from these substrates (i.e. through crossfeeding). Substrate mineralization rates and shifts in relative abundance of labeled taxa suggest that BP and BZ biotransformations were performed by microorganisms with different growth strategies: BZ-associated bacteria were fast growing, potentially copiotrophic organisms, while microbes that transform BP were oligotrophic, slower growing, organisms. Our findings provide novel insight into the functional interactions of soil bacteria active in processing biphenyl and related aromatic compounds in soil, revealing how carbon flows through a bacterial community.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Kebede, Mulu A.; Bish, David L.; Losovyj, Yaroslav
Nitrous acid (HONO) accumulates in the nocturnal boundary layer where it is an important source of daytime hydroxyl radicals. Although there is clear evidence for the involvement of heterogeneous reactions of NO2 on surfaces as a source of HONO, mechanisms remain poorly understood. We used coated-wall flow tube measurements of NO2 reactivity on environmentally relevant surfaces [Fe (hydr)oxides, clay minerals, and soil from Arizona and the Saharan Desert] and detailed mineralogical characterization of substrates to show that reduction of NO2 by Fe-bearing minerals in soil can be a more important source of HONO than the putative NO2 hydrolysis mechanism. Themore » magnitude of NO2-to-HONO conversion depends on the amount of Fe2+ present in substrates and soil surface acidity. Studies examining the dependence of HONO flux on substrate pH revealed that HONO is formed at soil pH < 5 from the reaction between NO2 and Fe2+(aq) present in thin films of water coating the surface, whereas in the range of pH 5–8 HONO stems from reaction of NO2 with structural iron or surface complexed Fe2+ followed by protonation of nitrite via surface Fe-OH2+ groups. Reduction of NO2 on ubiquitous Fe-bearing minerals in soil may explain HONO accumulation in the nocturnal boundary layer and the enhanced [HONO]/[NO2] ratios observed during dust storms in urban areas.« less
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ANAEROBIC SOIL DISINFESTATION IN MICROCOSMS OF TWO SANDY SOILS.
Stremińska, M A; Runia, W T; Termorshuizen, A J; Feil, H; Van Der Wurff, A W G
2014-01-01
In recent years, anaerobic soil disinfestation (ASD) has been proposed as an alternative control method of soil-borne plant pathogens. It involves adding a labile carbon source, irrigating the soil to stimulate decomposition of organic material and then covering the soil with air-tight plastic to limit gas exchange. During the ASD process, soil microorganisms switch from aerobic to anaerobic metabolism. As a result, by-products of anaerobic metabolism are released into the soil environment such as various organic acids and gases. These by-products are reported to have a negative effect on survival of soil-borne plant pathogens. However, the efficacy of ASD to reduce soil-borne pathogens in practice may vary significantly. Therefore, we studied the efficacy of the ASD process in two different soils. In addition, it was investigated whether a pre-treatment with an anaerobic bacterial inoculum prior to ASD affected the efficacy of the process. Two sandy soils (dune sand and glacial sand) were inoculated in 2 L soil microcosms. We tested the efficacy of ASD treatment against the potato cyst nematode Globodera pallida. For each soil, three treatments were used: control treatment (no Herbie addition, aerobic incubation), ASD 1 (organic substrate addition, anaerobic incubation) and ASD 2 (organic substrate and anaerobic bacterial inoculum addition, anaerobic incubation). Soil microcosms were incubated in the dark at 20°C for two weeks. We observed that anaerobic soil disinfestation treatments were highly effective against Potato Cyst Nematode (PCN), with pathogen being eradicated totally in all but one ASD treatment (glacial sand ASD2) within two weeks. The relative abundance of Firmicutes (spore-forming bacteria, often fermentative) in total bacteria increased significantly in ASD treated soils. Numbers of these bacteria correlated positively with increased concentrations of acetic and butyric acids in soil water phase in ASD treatments.
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Persisting effects of armored military maneuvers on some soils of the Mojave Desert
Prose, D.V.
1985-01-01
Soil compaction and substrate modification produced during large-scale armored military maneuvers in the early 1940s were examined in 1981 at seven sites in California's eastern Mojave Desert Recording penetrometer measurements show that tracks left by a single pass of an M3 "medium" tank have average soil resistance values that are 50% greater than those of the surrounding untracked soil in the upper 20 cm At one site, measurements made along short segments of track that have been visually eliminated by erosion and deposition processes show a 73% increase in penetrometer resistance over adjacent, undisturbed soils Dirt roadways at three former base camp locations could not be penetrated below 5-10 cm because of extreme compaction Soil bulk density was not as sensitive an indicator of soil compaction as was penetrometer resistance Density values in the upper 10 cm of soil are not significantly different between tank tracks and undisturbed soils at most sites, and roadways at two base camps show an average increase in bulk density of only 12% over adjacent soils. Trench excavations across tank tracks show that physical modifications of the substrate can extend vertically beneath a track to a depth of 25 cm and outward from a track's edge to 50 cm These soil disturbances are probably major factors that encourage accelerated soil erosion throughout the manuever area and also retard or prevent the return of vegetation to pre-disturbance conditions ?? 1985 Springer-Verlag New York Inc.
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NASA Astrophysics Data System (ADS)
Lehmeier, C.; Min, K.; Good, H. J.; Billings, S. A.
2015-12-01
Temperature (T) is a major determinant of microbial decomposition of soil organic matter (SOM). Quantifying T responses of microbial C fluxes is crucial to improve predictions of SOM dynamics and atmospheric CO2 concentrations, but interpretation of experimental data is complicated by many properties inherent to soils. Comparing such data with complementary, reductionist experiments can help to identify basic mechanisms and interpret soil measurements. We quantified T effects on activity levels (i.e., rates of substrate cleavage) of microbial extracellular enzymes β-glucosidase (BGase) and β-N-acetyl glucosaminidase (NAGase), and on rates of CO2 efflux in soil incubations. We compare the results to those derived from purified enzyme assays, and to measurements of microbial respiration rates in continuous-flow chemostat culture in which a population of the soil bacterium Pseudomonas fluorescens was grown on medium with similar C:N ratio as the incubated SOM (10:1). Activity levels of both BGase and NAGase decreased by 80% between 25 and 5 °C. These T responses were higher than predictions from intrinsic (i.e., maximum) T responses in purified assays of BGase (minus 50%) and NAGase (minus 67%). This suggests that factors like physical access to substrate or reduced microbial production of enzymes constrained substrate decomposition rates in the soils relatively more at low than at high T. In chemostats, (mass-)specific bacterial respiration rate at T 14.5 °C was 50% of the rate observed at 26.5 °C; in contrast, CO2 efflux from the soil incubations decreased by only ~25% from 25 to 15 °C. The reason for this discrepancy can be manifold, including changes in microbial community composition, but results from ongoing measurements of microbial biomass in the soil samples will allow a closer comparison of these respiration rate responses. Our efforts highlight the significance of experimenting across scales and complexity for a better understanding of SOM dynamics.
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Muhammad, Akmal; Xu, Jianming; Li, Zhaojun; Wang, Haizhen; Yao, Huaiying
2005-07-01
A study was conducted to evaluate the effects of different concentrations of lead (Pb) and cadmium (Cd) applied as their nitrates on soil microbial biomass carbon (C(mic)) and nitrogen (N(mic)), and substrate utilization pattern of soil microbial communities. The C(mic) and N(mic) contents were determined at 0, 14, 28, 42 and 56 days after heavy metal application (DAA). The results showed a significant decline in the C(mic) for all Pb and Cd amended soils from the start to 28 DAA. From 28 to 56 DAA, C(mic) contents changed non-significantly for all other treatments except for 600 mgkg(-1) Pb and 100 mgkg(-1) Cd in which it declined significantly from 42 to 56 DAA. The N(mic) contents also decreased significantly from start to 28 DAA for all other Pb and Cd treatments except for 200 mgkg(-1) Pb which did not show significant difference from the control. Control and 200 mgkg(-1) Pb had significantly lower soil microbial biomass C:N ratio as compared with other Pb treatments from 14 to 42 DAA, however at 56 DAA, only 1000 mgkg(-1) Pb showed significantly higher C:N ratio compared with other treatments. No significant difference in C:N ratio for all Cd treated soils was seen from start to 28 DAA, however from 42 to 56 DAA, 100 mgkg(-1) Pb showed significantly higher C:N ratio compared with other treatments. On 56 DAA, substrate utilization pattern of soil microbial communities was determined by inoculating Biolog ECO plates. The results indicated that Pb and Cd addition inhibited the functional activity of soil microbial communities as indicated by the intensity of average well color development (AWCD) during 168 h of incubation. Multivariate analysis of sole carbon source utilization pattern demonstrated that higher levels of heavy metal application had significantly affected soil microbial community structure.
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NASA Astrophysics Data System (ADS)
Bowen, G. J.; Abels, H.
2015-12-01
Abrupt changes in the isotope composition of exogenic carbon pools accompany many major episodes of global change in the geologic record. The global expression of this change in substrates that reflect multiple carbon pools provides important evidence that many events reflect persistent, global redistribution of carbon between reduced and oxidized stocks. As the diversity of records documenting any event grows, however, discrepancies in the expression of carbon isotope change among substrates are almost always revealed. These differences in magnitude, pace, and pattern of change can complicate interpretations of global carbon redistribution, but under ideal circumstances can also provide additional information on changes in specific environmental and biogeochemical systems that accompanied the global events. Here we evaluate possible environmental influences on new terrestrial records of the negative carbon isotope excursions (CIEs) associated with multiple hyperthermals of the Early Eocene, which show a common pattern of amplified carbon isotope change in terrestrial paleosol carbonate records relative to that recorded in marine substrates. Scaling relationships between climate and carbon-cycle proxies suggest that that the climatic (temperature) impact of each event scaled proportionally with the magnitude of its marine CIE, likely implying that all events involved release of reduced carbon with a similar isotopic composition. Amplification of the terrestrial CIEs, however, does not scale with event magnitude, being proportionally less for the first, largest event (the PETM). We conduct a sensitivity test of a coupled plant-soil carbon isotope model to identify conditions that could account for the observed CIE scaling. At least two possibilities consistent with independent lines of evidence emerge: first, varying effects of pCO2 change on photosynthetic carbon isotope discrimination under changing background pCO2, and second, contrasting changes in regional hydroclimate during the PETM and subsequent hyperthermals. These mechanisms have very different implications for the reconstruction of environmental conditions, and resolving the correct interpretation will require new, complimentary records of plant and soil conditions associated with the Early Eocene hyperthermals.
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NASA Astrophysics Data System (ADS)
Barkhatov, Yuri; Gubanov, Vladimir; Tikhomirov, Alexander A.; Degermendzhy, Andrey G.
A mathematical model of the "plant community -soil-like substrate -gas exchange with the human" experimental biological life support system (BLSS) has been constructed to predict its functioning and estimate feasibility of controlling it. The mathematical model consists of three compartments -two `phytotron' models (with wheat and radish) and the `mycotron' model (for mushrooms). The following components are included in the model: edible mushrooms (mushroom fruit bodies and mycelium); wheat; radish; straw (processed by mycelium); dead organic matter in the phytotron (separately for the wheat unit and for the radish unit); worms; worms' coprolites; vermicompost used as a soil-like substrate (SLS); bacterial microflora; min-eral nitrogen, phosphorus and iron; products of the system intended for humans (wheat grains, radish roots and mushroom fruit bodies); oxygen and carbon dioxide. Under continuous gas exchange, the mass exchange between the compartments occurs at the harvesting time. The conveyor character of the closed ecosystem functioning has been taken into account -the num-ber of culture age groups can be regulated (in experiments -4 and 8 age groups). The conveyor cycle duration can be regulated as well. The module is designed for the food and gas exchange requirements of 1/30 of a virtually present human. Aim of model analysis is determination of investigation direction in real experimental BLSS. The model allows doing dynamic calcu-lations of closure coefficient based on the main elements taken into account in the model and evaluating all dynamic components of the system under different conditions and modes of its operation, especially under the conditions that can hardly be created experimentally. One of the sustainability conditions can be long-duration functioning of the system under the light-ing that is far from the optimum. The mathematical model of the system can demonstrate variants of its sustainable functioning or ruin under various critical conditions probable for the LSS. An example is loss of part of green plant biomass. Model calculations have been done for different variants of loss of wheat biomass. We estimated the ability of the model to predict the optimal number of age groups in the LSS plant conveyor. This is an essential parameter, because if the number is too low, the total mass of the system components will vary and if it is too high, the system will be too complicated and costly. A high value of this parameter can also be interpreted as approximation to biosphere models. Dynamics of closure coefficient for the nitrogen and carbon loops was investigated for different variants of the BLSS. The system with biological utilization of the wheat straw has the highest closure coefficient, reaching 0.96, and can be used as a prototype of the BLSS of a new generation, with an essentially closed material cycling.
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NASA Astrophysics Data System (ADS)
Bircher, Simone; Richaume, Philippe; Mahmoodi, Ali; Mialon, Arnaud; Fernandez-Moran, Roberto; Wigneron, Jean-Pierre; Demontoux, François; Jonard, François; Weihermüller, Lutz; Andreasen, Mie; Rautiainen, Kimmo; Ikonen, Jaakko; Schwank, Mike; Drusch, Mattias; Kerr, Yann H.
2017-04-01
From the passive L-band microwave radiometer onboard the Soil Moisture and Ocean Salinity (SMOS) space mission global surface soil moisture data is retrieved every 2 - 3 days. Thus far, the empirical L-band Microwave Emission of the Biosphere (L-MEB) radiative transfer model applied in the SMOS soil moisture retrieval algorithm is exclusively calibrated over test sites in dry and temperate climate zones. Furthermore, the included dielectric mixing model relating soil moisture to relative permittivity accounts only for mineral soils. However, soil moisture monitoring over the higher Northern latitudes is crucial since these regions are especially sensitive to climate change. A considerable positive feedback is expected if thawing of these extremely organic soils supports carbon decomposition and release to the atmosphere. Due to differing structural characteristics and thus varying bound water fractions, the relative permittivity of organic material is lower than that of the most mineral soils at a given water content. This assumption was verified by means of L-band relative permittivity laboratory measurements of organic and mineral substrates from various sites in Denmark, Finland, Scotland and Siberia using a resonant cavity. Based on these data, a simple empirical dielectric model for organic soils was derived and implemented in the SMOS Soil Moisture Level 2 Prototype Processor (SML2PP). Unfortunately, the current SMOS retrieved soil moisture product seems to show unrealistically low values compared to in situ soil moisture data collected from organic surface layers in North America, Europe and the Tibetan Plateau so that the impact of the dielectric model for organic soils cannot really be tested. A simplified SMOS processing scheme yielding higher soil moisture levels has recently been proposed and is presently under investigation. Furthermore, recalibration of the model parameters accounting for vegetation and roughness effects that were thus far only evaluated using the default dielectric model for mineral soils is ongoing for the "organic" L-MEB version. Additionally, in order to decide where a soil moisture retrieval using the "organic" dielectric model should be triggered, information on soil organic matter content in the soil surface layer has to be considered in the retrieval algorithm. For this purpose, SoilGrids (www.soilgrids.org) providing soil organic carbon content (SOCC) in g/kg is under study. A SOCC threshold based on the relation between the SoilGrids' SOCC and the presence of organic soil surface layers (relevant to alter the microwave L-band emissions from the land surface) in the SoilGrids' source soil profile information has to be established. In this communication, we present the current status of the above outlined studies with the objective to advance towards an improved soil moisture retrieval for organic-rich soils from SMOS passive microwave L-band observations.
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Gotoh, Keiko
2017-01-01
The detergency of products, mainly textiles, was evaluated using various experimental systems and discussed from the viewpoint of interfacial phenomena. The detergency phenomena observed for geometrically simple model systems were explained in terms of the total potential energy of interaction between the soil and the substrate, which was calculated as the sum of the electrical double layer, Lifshitzvan der Waals, and acid-base interactions using electrokinetic potentials and surface free energy components. Cleaning experiments using artificially soiled fabrics were performed using electro-osmotic flow and ultrasound as mechanical actions for soil removal, and the results were compared with those obtained with mechanical actions commonly used in textile washing. Simultaneous hydrophilization of the substrate and soil by an atmospheric pressure plasma jet remarkably improved the detergency in aqueous solutions. The application of the atmospheric pressure plasma jet to anti-fouling textiles was also proposed.
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Visualization of soil particulate organic matter by means of X-ray CT?
NASA Astrophysics Data System (ADS)
Sleutel, Steven; Van Loo, Denis; Maenhout, Peter; Van Hoorebeke, Luc; Cnudde, Veerle; De Neve, Stefaan
2014-05-01
The role of soil structure in organic matter (OM) stabilization has been primarily investigated through physical fractionation studies operative at the scale of aggregates and smaller organo-mineral particles. By narrowing down soil structure to an arrangement of mineral and organic particles, the majority of studies did not explore the spatial organization of the soil pore network, the actual habitat of microorganisms. The pore structure of soil can have a significant impact on soil processes like OM decomposition by excluding OM from micro-organisms in small pores, by regulating the diffusion of substrates and metabolites and by regulating aeration and presence of moisture. Because of its ability to visualize the 3D architecture of soil non-destructively, X-ray Computed Tomography (CT) is becoming a widespread tool for studying soil pore network structure. However, phase determination of pore space, soil OM, soil mineral matter (MM) and water is often limited even with the latest technological and software advances, allowing high resolution and better quality imaging. Contrast agents commonly used in histology enable enhancement of X-ray attenuation of targeted structures or compounds. Here we report on the first systematic investigation of the use of such X-ray contrast agents for soil research. An evaluation procedure as well as a method to apply the agents to soil samples was developed and applied on reference soil samples. The effectiveness and selectivity of the contrast agents was evaluated for soil organic matter (SOM), MM and water. Several products were found to selectively increase the attenuation of water or SOM. The four agents with the best OM-staining capabilities (Phosphomolybdenic acid (PMA), silver nitrate, lead nitrate and lead acetate) were further tested on an OM-MM mixture. Observed differences in reactivity of the staining agents with MM components were apparent, suggesting that contrasting agents may have to be selected for the specific composition of the soil mineral matrix. Furthermore, techniques such as multiple-energy scanning and K-edge imaging, even in the future perhaps in combination with spectral resolving detectors or spectroscopic techniques can could further enhance the potential benefit from this study of X-ray CT staining agents. The high Z elements of the staining agents have unique and characteristic traits that can be detected or quantified with the abovementioned techniques and methods. We conclude that, given resolution limits and inherent presence of partial volume effects staining, X-ray CT-based localization of discrete SOM particles will be limited to a lower limit of 20-50 µm. Still, the improved 3D visualization of OM and soil pore space opens up possibilities for tailored lab experiments with measures of microbial activity, which could generate new insights in carbon cycling at small scales. In addition, we report on a lab incubation experiment in which CO2 respiration from soil cores was monitored (headspace GC analysis) and an X-ray CT approach yielded soil pore size distributions. We incubated a sandy loam soil (with application of ground grass or sawdust) in 18 small aluminium rings (Ø 1 cm, h 1 cm). Bulk density was adjusted to 1.1 or 1.3 Mg m-3 (compaction) and 6 rings were filled at a coarser Coarse Sand:Fine Sand:Silt+Clay ratio. While compaction induced a strong reduction in the cumulative C mineralization for both grass and sawdust substrates, artificial change to a coarser soil texture only reduced net C mineralization from the added sawdust. There thus appears to be a strong interaction effect between soil pore structure and substrate type on substrate decomposition. Correlation coefficients between the C mineralization rates and volumes of 7 pore size classes (from the X-ray CT data) also showed an increasing positive correlation with increasing pore size. Since any particulate organic matter initially present in the soil was removed prior to the experiment (sieving, ashing the >53µm fraction and recombining with the <53µm fraction), the added OM can be localized by means of X-ray CT. Through on-going image analysis the surrounding porosity of the added grass or sawdust particles is being quantified to further study the interaction between the soil pore structure and substrate decomposition.
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Haack, S.K.; Garchow, H.; Klug, M.J.; Forney, L.J.
1995-01-01
We determined factors that affect responses of bacterial isolates and model bacterial communities to the 95 carbon substrates in Biolog microliter plates. For isolates and communities of three to six bacterial strains, substrate oxidation rates were typically nonlinear and were delayed by dilution of the inoculum. When inoculum density was controlled, patterns of positive and negative responses exhibited by microbial communities to each of the carbon sources were reproducible. Rates and extents of substrate oxidation by the communities were also reproducible but were not simply the sum of those exhibited by community members when tested separately. Replicates of the same model community clustered when analyzed by principal- components analysis (PCA), and model communities with different compositions were clearly separated un the first PCA axis, which accounted for >60% of the dataset variation. PCA discrimination among different model communities depended on the extent to which specific substrates were oxidized. However, the substrates interpreted by PCA to be most significant in distinguishing the communities changed with reading time, reflecting the nonlinearity of substrate oxidation rates. Although whole-community substrate utilization profiles were reproducible signatures for a given community, the extent of oxidation of specific substrates and the numbers or activities of microorganisms using those substrates in a given community were not correlated. Replicate soil samples varied significantly in the rate and extent of oxidation of seven tested substrates, suggesting microscale heterogeneity in composition of the soil microbial community.
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Soil Carbon Decomposition: "Quality control" or logistic challenge?
NASA Astrophysics Data System (ADS)
Kleber, M.
2011-12-01
A long tradition of soil organic matter research has generated the belief that there is "stable" soil organic carbon, thought to be recalcitrant because molecular compounds such as aromatic rings and aliphatic chains are joined to polymeric macromolecules by processes of secondary syntheses. The Carbon-Quality Temperature (CQT) theory posits that such materials should be considered "low quality" substrates, because they would require large Arrhenius activation energies for full conversion to CO2. This, in turn, has generated the notion that recalcitrant organic matter should be more temperature sensitive to elevated temperatures than less complex, more "labile" soil organic matter. Yet the molecular properties of stable carbon are elusive - so far, it has not been possible to parameterize molecular recalcitrance in a context -independent fashion. Classic humic substances and even charcoal are readily broken down when placed in an environment where microorganisms with a suitable catabolic toolbox can resort to a plentiful supply of cometabolites and oxygen. At the same time we find labile substrates such as glucose to survive for decades when enclosed within soil aggregates. What then determines the temperature sensitivity of decomposition? Should the scientific community continue to hunt for some molecular proxy for organic matter quality (such as degree of polymerization, aromaticity, aqueous solubility etc) to predict the fate of soil organic carbon in a changing world? This contribution proposes a fundamentally different approach by treating soils as reaction vessels analogous to an industrial bioreactor. Soils are considered as capable of processing dead plant material in all its molecular variations. Decomposition is seen as constrained by environmental drivers, microbial ecology and community composition, and the physical structure of the soil environment. The hypotheses is put forward that, compared to variations in the logistic status of the soil reactor, molecular variations within the substrate are insignificant for the response of the system to rising temperatures. Three functional soil reactor types are distinguished, each representing a specific process space with unique, rate controlling logistics: a) the litter layer, b) the rhizosphere and c) the subsoil.
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Wei, Hui; Chen, Xiaomei; Xiao, Guoliang; Guenet, Bertrand; Vicca, Sara; Shen, Weijun
2015-12-16
Soil temperature and moisture are widely-recognized controlling factors on heterotrophic soil respiration (Rh), although they often explain only a portion of Rh variability. How other soil physicochemical and microbial properties may contribute to Rh variability has been less studied. We conducted field measurements on Rh half-monthly and associated soil properties monthly for two years in four subtropical forests of southern China to assess influences of carbon availability and microbial properties on Rh. Rh in coniferous forest was significantly lower than that in the other three broadleaf species-dominated forests and exhibited obvious seasonal variations in the four forests (P < 0.05). Temperature was the primary factor influencing the seasonal variability of Rh while moisture was not in these humid subtropical forests. The quantity and decomposability of dissolved organic carbon (DOC) were significantly important to Rh variations, but the effect of DOC content on Rh was confounded with temperature, as revealed by partial mantel test. Microbial biomass carbon (MBC) was significantly related to Rh variations across forests during the warm season (P = 0.043). Our results suggest that DOC and MBC may be important when predicting Rh under some conditions, and highlight the complexity by mutual effects of them with environmental factors on Rh variations.
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NASA Astrophysics Data System (ADS)
Targulian, V. O.; Mergelov, N. S.; Goryachkin, S. V.
2017-02-01
Soils sensu stricto are absent on Mars; most probably, they have never been formed there, because, up to now, we have no evidence of the presence of life, either relict or recent, on this planet. Numerous references to "Martian soils" in scientific literature concern loose substrates rather than Dokuchaev's soils. In this context, surface bodies on Mars can be described using the concept of planetary shells, or exons. Exons can be subdivided into sitons formed via in situ transformation of parent material, transons formed in the course of lateral transportation and deposition of substances, and transsitons formed by the combination of both in situ and lateral processes. Among Martian exons, transons predominate. They represent loose sediments of mainly eolian genesis related to extremely strong winds. Soil-like bodies (soloids) on Mars are represented by sitons and transsitons. These are abiotic formations having the profiles differentiated by the contents of iron oxides, soluble salts, and clay minerals and mainly formed in the presence of liquid water during the paleohumid eras of Mars evolution more than 2.5/3 billion years ago. True deep sitons (Martian weathering mantles) could only be formed under the impact of long-term weathering on stable surfaces during humid eras. Then, they were either buried by later deposited sediments, or eroded. Up to now, such objects have not been discovered on Mars.
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Direct impacts of biochar on N2O production during denitrification by a soil microbial community
NASA Astrophysics Data System (ADS)
Mishra, Akanksha; Harter, Johannes; Hagemann, Nikolas; Kappler, Andreas
2017-04-01
Biochar, i.e. biomass heated under O2 limitation to 350-1000°C (pyrolysis), is suggested as a beneficial soil amendment to mitigate climate change and to maintain and restore the fertility of agro-ecosystems. Its stability enables long-term carbon sequestration and biochar effectively reduces soil-borne N2O emissions. Biochar's ability to reduce N2O emissions is well recognized through field and laboratory experiments as well as meta-analyses. However, the underlying mechanisms remain widely debated. Microbial nitrogen transformations, especially denitrification, the stepwise reduction of nitrate/nitrite via NO and N2O to N2, are considered to be a major source of N2O emissions. Soil microcosm experiments showed lower N2O emissions in the presence of biochar often correlate with a higher abundance and/or activity of N2O reducing bacteria in the presence of biochar. However, it is still unknown whether these shifts in the microbial community and/or activity is cause or effect of reduced N2O production. Biochar has the potential to change the physico-chemical environment towards conditions that favor complete denitrification, i.e. decrease the N2O/(N2O+N2) product ratio. Specifically, biochar can increase soil pH, reduce the availability of nitrate and increase the entrapment of gases, including N2O. These effects are known to decrease the N2O/(N2O+N2) ratio. In addition to the observed effects in the physio-chemical environment, we hypothesized that biochar has a direct impact on the soil microbial community. For instance, it has been shown to provide a suitable habitat to microorganisms, or facilitate electron transfer between microbe and substrates by acting as an electron shuttle or as a temporary acceptor/donor of electrons. To test this hypothesis, our experiment consisted of a microbial community extracted from soil and cultivated under anoxic conditions. It was introduced as an inoculum into three different treatments: biochar, quartz (control with a solid) and a solid-free control in the presence of a well-defined liquid medium. To maintain consistency with respect to geochemical parameters as well as to exclude any indirect effects of biochar, the concentration of substrates (nitrate, acetate) and the pH were kept identical in all three treatments. The biochar used was previously shown to reduce soil-borne N2O emissions. The results showed that biochar promoted nitrate reduction coupled to acetate consumption leading to a faster intermediate accumulation of nitrite compared to the non-biochar treatments. Additionally, N2O intermediately accumulated in the biochar treatment. Gene copy numbers from quantitative polymerase chain reaction combined with optical density measurements suggested that microbes were attached to the biochar surface instead of being suspended in the liquid. This association of microbial cells with biochar's surface might result in expedited consumption of acetate and nitrate. Since similar effects were not observed in the treatment containing quartz, they were concluded to be specific to biochar. These results can be put forth as the first evidence for a direct impact of biochar on microbial denitrification. Overall, our study highlights the need to take a detailed look at biochar's direct effect on the activity of the soil microbial community when designing biochars that target N2O mitigation.
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Probing soil C metabolism in response to temperature: results from experiments and modeling
NASA Astrophysics Data System (ADS)
Dijkstra, P.; Dalder, J.; Blankinship, J.; Selmants, P. C.; Schwartz, E.; Koch, G. W.; Hart, S.; Hungate, B. A.
2010-12-01
C use efficiency (CUE) is one of the least understood aspects of soil C cycling, has a very large effect on soil respiration and C sequestration, and decreases with elevated temperature. CUE is directly related to substrate partitioning over energy production and biosynthesis. The production of energy and metabolic precursors occurs in well-known processes such as glycolysis and Krebs cycle. We have developed a new stable isotope approach using position-specific 13C-labeled metabolic tracers to measure these fundamental metabolic processes in intact soil communities (1). We use this new approach, combined with models of soil metabolic flux patterns, to analyze the response of microbial energy production, biosynthesis, and CUE to temperature. The method consists of adding small but precise amounts of position-specific 13C -labeled metabolic tracers to parallel soil incubations, in this case 1-13C and 2,3-13C pyruvate and 1-13C and U-13C glucose. The measurement of CO2 released from the labeled tracers is used to calculate the C flux rates through various metabolic pathways. A simplified metabolic model consisting of 23 reactions is iteratively solved using results of the metabolic tracer experiments and information on microbial precursor demand under different temperatures. This new method enables direct study of fundamental aspects of microbial energy production, C use efficiency, and soil organic matter formation in response to temperature. (1) Dijkstra P, Blankinship JC, Selmants PC, Hart SC, Koch GW, Schwarz E and Hungate BA. Probing metabolic flux patterns of soil microbial communities using parallel position-specific tracer labeling. Soil Biology and Biochemistry (accepted)
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Textural and isotopic evidence for Ca-Mg carbonate pedogenesis
NASA Astrophysics Data System (ADS)
Diaz-Hernandez, J. L.; Sánchez-Navas, A.; Delgado, A.; Yepes, J.; Garcia-Casco, A.
2018-02-01
Models for evaluating the terrestrial carbon cycle must take into account not only soil organic carbon, represented by a mixture of plant and animal remains, but also soil inorganic carbon, contained in minerals, mainly in calcite and dolomite. Thick soil caliches derived from weathering of mafic and ultramafic rocks must be considered as sinks for carbon storage in soils. The formation of calcite and dolomite from pedogenic alteration of volcanic tephras under an aridic moisture regime is studied in an unusually thick 3-m soil profile on Gran Canaria island (Canary Islands, Spain). The biological activity of the pedogenic environment (soil respiration) releases CO2 incorporated as dissolved inorganic carbon (DIC) in waters. It drives the formation of low-magnesian calcite and calcian dolomite over basaltic substrates, with a δ13C negative signature (-8 to -6‰ vs. V-PDB). Precipitation of authigenic carbonates in the soil is accompanied by the formation of Mg-rich clay minerals and quartz after the weathering of basalts. Mineralogical, textural, compositional, and isotopic variations throughout the soil profile studied indicate that dolomite formed at greater depths and earlier than the calcite. The isotopic signatures of the surficial calcite and deeper dolomite crusts are primary and resulted from the dissolution-precipitation cycles that led to the formation of both types of caliches under different physicochemical conditions. Dolomite formed within a clay-rich matrix through diffusive transport of reactants. It is precipitated from water with more negative δ18O values (-1.5 to -3.5‰ vs. V-SMOW) in the subsoil compared to those of water in equilibrium with surficial calcite. Thus, calcite precipitated after dolomite, and directly from percolating solutions in equilibrium with vadose water enriched in δ18O (-0.5 to +1.5‰) due to the evaporation processes. The accumulation of inorganic carbon reaches 586.1 kg m-2 in the soil studied, which means that the carbon sequestration capacity of mafic rocks must be taken into account for certain terrestrial settings. Dolomite together with calcite should be assessed when quantifying carbon stored in arid-semiarid soils as a result of the natural weathering processes.
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Huang, Jing; Chen, Zhe; Nie, Yuanjun; Wang, Changbiao
2018-01-01
Bio-organic fertilizers (BOFs) combine functional microbes with a suitable substrate and have been shown to effectively suppress soil-borne diseases and promote plant growth. Here, we developed a novel bio-organic fertilizer (BOF) by fermentation of a cow plus chicken manure (M) compost using Fen-liquor Daqu (FLD) as a fermentation starter and compared the compositions of bacterial and fungal communities in the rhizosphere soil of watermelon plants after treatment with different fertilizers. Further, we aimed to explore the mechanisms underlying plant-promoting and disease (Fusarium wilt)-suppressing activities of each rhizosphere microbial community. The microbial communities of soil amended with cow plus chicken manure compost (S+M), soil amended with the BOF (S+BOF), and untreated control soil (S) without plants were analyzed through sequence analysis using the Illumina MiSeq platform. The results showed that a new microbial community was formed in the manure compost after fermentation by the Daqu. Application of the BOF to the soil induced remarkable changes in the rhizosphere microbial communities, with increased bacterial diversity and decreased fungal diversity. Most importantly, S+BOF showed the lowest abundance of Fusarium. Moreover, watermelon quality was higher (P < 0.05) in the S+BOF than in the S+M treatment. Thus, application of the BOF favorably altered the composition of the rhizosphere microbial community, suppressing Fusarium wilt disease and promoting plant quality. PMID:29451918
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Zhao, Jia; Liu, Jiang; Liang, Hong; Huang, Jing; Chen, Zhe; Nie, Yuanjun; Wang, Changbiao; Wang, Yuguo
2018-01-01
Bio-organic fertilizers (BOFs) combine functional microbes with a suitable substrate and have been shown to effectively suppress soil-borne diseases and promote plant growth. Here, we developed a novel bio-organic fertilizer (BOF) by fermentation of a cow plus chicken manure (M) compost using Fen-liquor Daqu (FLD) as a fermentation starter and compared the compositions of bacterial and fungal communities in the rhizosphere soil of watermelon plants after treatment with different fertilizers. Further, we aimed to explore the mechanisms underlying plant-promoting and disease (Fusarium wilt)-suppressing activities of each rhizosphere microbial community. The microbial communities of soil amended with cow plus chicken manure compost (S+M), soil amended with the BOF (S+BOF), and untreated control soil (S) without plants were analyzed through sequence analysis using the Illumina MiSeq platform. The results showed that a new microbial community was formed in the manure compost after fermentation by the Daqu. Application of the BOF to the soil induced remarkable changes in the rhizosphere microbial communities, with increased bacterial diversity and decreased fungal diversity. Most importantly, S+BOF showed the lowest abundance of Fusarium. Moreover, watermelon quality was higher (P < 0.05) in the S+BOF than in the S+M treatment. Thus, application of the BOF favorably altered the composition of the rhizosphere microbial community, suppressing Fusarium wilt disease and promoting plant quality.
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NASA Astrophysics Data System (ADS)
Cammalleri, C.; Anderson, M. C.; Ciraolo, G.; Durso, G.; Kustas, W. P.; La Loggia, G.; Minacapilli, M.
2010-12-01
For open orchard and vineyard canopies containing significant fractions of exposed soil (>50%), typical of Mediterranean agricultural regions, the energy balance of the vegetation elements is strongly influenced by heat exchange with the bare soil/substrate. For these agricultural systems a "two-source" approach, where radiation and turbulent exchange between the soil and canopy elements are explicitly modelled, appears to be the only suitable methodology for reliably assessing energy fluxes. In strongly clumped canopies, the effective wind speed profile inside and below the canopy layer can strongly influence the partitioning of energy fluxes between the soil and vegetation components. To assess the impact of in-canopy wind profile on model flux estimates, an analysis of three different formulations is presented, including algorithms from Goudriaan (1977), Massman (1987) and Lalic et al. (2003). The in-canopy wind profile formulations are applied to the thermal-based two-source energy balance (TSEB) model developed by Norman et al. (1995) and modified by Kustas and Norman (1999). High resolution airborne remote sensing images, collected over an agricultural area located in the western part of Sicily (Italy) comprised primarily of vineyards, olive and citrus orchards, are used to derive all the input parameters needed to apply the TSEB. The images were acquired from June to October 2008 and include a relatively wide range of meteorological and soil moisture conditions. A preliminary sensitivity analysis of the three wind profile algorithms highlights the dependence of wind speed just above the soil/substrate to leaf area index and canopy height over the typical range of canopy properties encountered in these agricultural areas. It is found that differences among the models in wind just above the soil surface are most significant under sparse and medium fractional cover conditions (15-50%). The TSEB model heat flux estimates are compared with micro-meteorological measurements from a small aperture scintillometer and an eddy covariance tower collected over an olive orchard characterized by moderate fractional vegetation cover (≍35%) and relatively tall crop (≍3.5 m). TSEB fluxes for the 7 image acquisition dates generated using both the Massman and Goudriaan in-canopy wind profile formulations give close agreement with measured fluxes, while the Lalic et al. equations yield poor results. The Massman wind profile scheme slightly outperforms that of Goudriaan, but it requires an additional parameter accounting for the roughness sub-layer of the underlying vegetative surface. The analysis also suggests that within-canopy wind profile model discrepancies become important, in terms of impact on modelled sensible heat flux, only for sparse canopies with moderate vegetation coverage.
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Exposure to(ozone 0-3)has been shown to decrease the allocation of carbon to tree roots. Decreased allocation of carbon to roots might disrupt root metabolism and rhizosphere organisms. The effects of soil type and shoot 0, exposure on below-ground respiration and soil microbial ...
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NASA Astrophysics Data System (ADS)
Bateman, Amber; Lewandrowski, Wolfgang; Stevens, Jason; Muñoz-Rojas, Miriam
2016-04-01
Introduction With the limited knowledge available regarding the impact of drought on seedling growth, an understanding of seedling tolerance to arid conditions is crucial for restoration success (James et al., 2013; Muñoz-Rojas et al., 2014). However, restoration in semi-arid areas faces the challenge of re-establishing plant communities on altered soil substrates (Muñoz-Rojas et al., 2015). These substrates are a result of anthropogenic disturbances such as mining which have altered the plant-soil-water dynamics of the ecosystem (Machado et al., 2013). The aim of this study was to assess the impact of mining on the plant-soil-water dynamics of an arid ecosystem of Western Australia (Pilbara region, North Western Australia) and the implications these altered relationships have on seedling growth and their responses to drought. Methods Drought responses of native plant species were assessed through a series of glasshouse experiments. Firstly, 21 species dominant to the Pilbara region were subjected to drought in a topsoil growth media to assess variation in responses (leaf water potential at the time of stomatal closure) across species and identify traits associated with drought tolerance. Secondly, four species ranging in their drought tolerance identified previously, were grown to two leaf stages (second and fourth leaf stage) in three mining substrates (topsoil, a topsoil and waste mix and waste) to assess seedling drought responses to various potential restoration substrates and how that varied with plant development stage. Results and discussion Four morphological traits were found to be significantly associated with drought indicators (leaf mass ratio, stem area, stem length, stem weight), however, these were weak correlations. Waste substrate and its addition to topsoil reduced plant total biomass but did not alter species responses to drought. However, the soil physical properties of the waste reduced water retention and water availability for plant uptake resulting in seedling mortality at less negative soil water potential. Finally, no significant differences in drought tolerance were observed between the two leaf stages across the four species tested. Analysis of plant desiccation curves found the advanced leaf stage to be less tolerant of drought as shown by a decrease in soil water potential at the time of stomatal closure. Species possess a range of morphological traits, some of which are associated with drought tolerance. However, these traits on their own may not be main drivers for drought resilience and other factors play a role, for example soil nutrient availability. Materials tested in this study that may be available to create novel restoration substrates hinder plant growth but not necessarily plant responses to drought. These findings go a long way to defining some of the limitations of seedling growth and the degree of drought tolerance which will assist in the management of post-mining restoration. References James, J.J., Sheley, R.L., Erickson,T., Rollins, K.S., Taylor, M.H., Dixon, K.W. (2013) A systems approach to restoring degraded drylands. Journal of Applied Ecology 50:730-739. Machado, N. A. M., Leite, M. G. P., Figueiredo, M. A., Kozovits, A. R. (2013) Growing Ereman-thus erythropappus in crushed laterite: A promising alternative to topsoil for baux¬ite-mine revegetation. Journal of Environmental Management 129: 149-156. Muñoz-Rojas, M., Erickson, T., Merritt, D., Dixon, K. (2014) Optimising post-mining soil conditions to maximise restoration success in a biodiverse semiarid environment. Geophysical Research. Abstracts Vol. 16, EGU2014-2069-1, EGU General Assembly. Muñoz-Rojas, M., Erickson, T., Merritt, D., Dixon, K. (2015) Applying soil science for restoration of post mining degraded landscapes in semi-arid Australia: challenges and opportunities. Geophysical Research. Abstracts Vol. 17, EGU2015-3967-1, EGU General Assembly.
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Use of soil-like substrate for growing plant to enhance closedness of biological lie support system
NASA Astrophysics Data System (ADS)
Gros, J. B.; Lasseur, C.; Tikhomirov, A. A.; Manuskovsky, N. S.; Kovalev, V. S.; Ushakova, S. A.; Zolotukhin, I. G.; Tirranen, L. S.; Gribovskaya, I. V.
Soil-like substrate (SLS) a potential candidate for use for growing plants in closed biological life support systems (BLSS) was studied. SLS was made by successive transformation of wheat straw by oyster mushrooms and Californian worms. Fertility of SLS of different degree of maturity has been tested. Mature SLS contained 9.5 % of humus acids and 4.9 % of fulvic acids. Wheat, bean and cucumber crops cultivated on mature SLS were comparable to crops obtained on a neutral substrate (expanded clay aggregate). In the wheat-SLS system, net CO2 absorption started on the sixth day after sowing and stopped 5 days prior to harvesting whereas in the wheat-neutral substrate system, net CO2 absorption was registered throughout vegetation. In the SLS, dominant bacteria included the spore-forming bacteria of the Bacillus genus and dominant fungi included the genus Trichoderma. In the hydroponic cultivation on neutral substrate dominant bacteria were of the Pseudomonas genus, while most commonly found fungi were species of the Fusarium genus. Consequence of SLS incorporation in artificial BLSS for increasing the closure degree of internal mass exchange in comparison with a neutral substrate is considered.
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Feng, Guojun; Du, Liangwei; Zeng, Dongqiang
2017-01-01
A diuron-degrading endophyte DP8-1 was isolated from sugarcane root grown in diuron-treated soil in the present study. The endophyte was identified as Neurospora intermedia based on the morphological characteristics and sequence analysis. The fermentation parameters including temperature, pH, inoculation size, carbon source, and initial diuron concentration were also investigated for the optimization of degradation efficiency. The results indicated that strain DP8-1 was capable of degrading up to 99% diuron within 3 days under the optimal degrading condition. The study of degradation spectrum indicated that strain DP8-1 could also degrade and utilize fenuron, monuron, metobromuron, isoproturon, chlorbromuron, linuron, and chlortoluron as substrate for strain growth. On basis of liquid chromatography-mass spectrometry analysis for the products of the degradation of diuron, strain DP8-1 metabolized diuron to produce N-(3,4-dichlorophenyl)-urea and N-(3,4-dichlorophenyl)-N-methylurea through sequential N-dealkylations. In a soil bioaugmentation experiment, the inoculation of strain DP8-1 into diuron-treated soil effectively enhanced the disappearance rate of diuron. PMID:28809955
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Armstrong, Alacia; Valverde, Angel; Ramond, Jean-Baptiste; Makhalanyane, Thulani P.; Jansson, Janet K.; Hopkins, David W.; Aspray, Thomas J.; Seely, Mary; Trindade, Marla I.; Cowan, Don A.
2016-01-01
The temporal dynamics of desert soil microbial communities are poorly understood. Given the implications for ecosystem functioning under a global change scenario, a better understanding of desert microbial community stability is crucial. Here, we sampled soils in the central Namib Desert on sixteen different occasions over a one-year period. Using Illumina-based amplicon sequencing of the 16S rRNA gene, we found that α-diversity (richness) was more variable at a given sampling date (spatial variability) than over the course of one year (temporal variability). Community composition remained essentially unchanged across the first 10 months, indicating that spatial sampling might be more important than temporal sampling when assessing β-diversity patterns in desert soils. However, a major shift in microbial community composition was found following a single precipitation event. This shift in composition was associated with a rapid increase in CO2 respiration and productivity, supporting the view that desert soil microbial communities respond rapidly to re-wetting and that this response may be the result of both taxon-specific selection and changes in the availability or accessibility of organic substrates. Recovery to quasi pre-disturbance community composition was achieved within one month after rainfall. PMID:27680878
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Armstrong, Alacia; Valverde, Angel; Ramond, Jean-Baptiste; Makhalanyane, Thulani P; Jansson, Janet K; Hopkins, David W; Aspray, Thomas J; Seely, Mary; Trindade, Marla I; Cowan, Don A
2016-09-29
The temporal dynamics of desert soil microbial communities are poorly understood. Given the implications for ecosystem functioning under a global change scenario, a better understanding of desert microbial community stability is crucial. Here, we sampled soils in the central Namib Desert on sixteen different occasions over a one-year period. Using Illumina-based amplicon sequencing of the 16S rRNA gene, we found that α-diversity (richness) was more variable at a given sampling date (spatial variability) than over the course of one year (temporal variability). Community composition remained essentially unchanged across the first 10 months, indicating that spatial sampling might be more important than temporal sampling when assessing β-diversity patterns in desert soils. However, a major shift in microbial community composition was found following a single precipitation event. This shift in composition was associated with a rapid increase in CO 2 respiration and productivity, supporting the view that desert soil microbial communities respond rapidly to re-wetting and that this response may be the result of both taxon-specific selection and changes in the availability or accessibility of organic substrates. Recovery to quasi pre-disturbance community composition was achieved within one month after rainfall.
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Zimmer, Jean-Yves; Brostaux, Yves; Haubruge, Eric; Francis, Frédéric
2014-10-15
Some Culicoides species of biting midges (Diptera: Ceratopogonidae) are biological virus vectors worldwide and have indeed been associated with outbreaks of important epizoonoses in recent years, such as bluetongue and Schmallenberg disease in northern Europe. These diseases, which affect domestic and wild ruminants, have caused considerable economic losses. Knowledge of substrates suitable for Culicoides larval development is important, particularly for the main vector temperate species. This study, realized during two years, aimed to highlight the larval development sites of these biting midge species in the immediate surroundings of ten Belgian cattle farms. Moreover, spatial distribution of the coprophilic Culicoides larvae (C. chiopterus and C. dewulfi) within pastures was studied with increasing distance from farms along linear transects (farm-pasture-woodland). A total of 4347 adult specimens belonging to 13 Culicoides species were obtained by incubation of 2131 soil samples belonging to 102 different substrates; 18 of these substrates were suitable for larval development. The Obsoletus complex (formed by two species) was observed in a wide range of substrates, including silage residues, components of a chicken coop, dung adhering to walls inside stables, leftover feed along the feed bunk, a compost pile of sugar beet residues, soil of a livestock trampling area, and decaying wood, while the following served as substrates for the other specimens: C. chiopterus, mainly cow dung; C. dewulfi, cow dung and molehill soil; C. circumscriptus, algae; C. festivipennis, algae and soil in stagnant water; C. nubeculosus, algae and silt specifically from the edge of a pond; C. punctatus, mainly wet soil between silage reserves; C. salinarius, algae; and C. stigma, algae and wet soil between silage reserves. We also recorded significantly higher densities of coprophilic larvae within pastures in cow dung located near forests, which is likely due to the localization of potential hosts; the presence of these larvae within cow dung is, however, uninfluenced by relative distance from farms. A better knowledge of the microhabitats of Culicoides biting midges and their spatial distribution may allow the development of targeted species-specific vector control strategies, and may help to prevent the creation of new larval development sites. Copyright © 2014 Elsevier B.V. All rights reserved.
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NASA Astrophysics Data System (ADS)
Mergelov, N. S.
2014-09-01
The properties and spatial distribution of soils and soil-like bodies in valleys of the coastal Larsemann Hills and Vestfold Hills oases—poorly investigated in terms of the soil areas of East Antarctica—are discussed. In contrast to Dry Valleys—large continental oases of Western Antarctica—the studied territory is characterized by the presence of temporarily waterlogged sites in the valleys. It is argued that the deficit of water rather than the low temperature is the major limiting factor for the development of living organisms and the pedogenesis on loose substrates. The moisture gradients in the surface soil horizons explain the spatial distribution of the different soils and biotic complexes within the studied valleys. Despite the permanent water-logging of the deep suprapermafrost horizons of most of the soils in the valleys, no gley features have been identified in them. The soils of the wet valleys in the Larsemann Hills oasis do not contain carbonates. They have a slightly acid or neutral reaction. The organic carbon and nitrogen contents are mainly controlled by the amount of living and dead biomass rather than by the humic substances proper. The larger part of the biomass is concentrated inside the mineral soil matrix rather than on the soil surface. The stresses caused by surface drying, strong winds, and ultraviolet radiation prevent the development of organisms on the surface of the soil and necessitate the search for shelter within the soil fine earth material (endoedaphic niche) or under the gravelly pavement (hypolithic niche). In the absence of higher plants, humified products of their decomposition, and rainwater that can wash the soil profile and upon the low content of silt and clay particles in the soil material, "classical" soil horizons are not developed. The most distinct (and, often, the only diagnosed) products of pedogenesis in these soils are represented by organomineral films on the surface of mineral particles.
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Influence of biochar on the physical, chemical and retention properties of an amended sandy soil
NASA Astrophysics Data System (ADS)
Baiamonte, Giorgio; De Pasquale, Claudio; Parrino, Francesco; Crescimanno, Giuseppina
2017-04-01
Soil porosity plays an important role in soil-water retention and water availability to crops, potentially affecting both agricultural practices and environmental sustainability. The pore structure controls fluid flow and transport through the soil, as well as the relationship between the properties of individual minerals and plants. Moreover, the anthropogenic pressure on soil properties has produced numerous sites with extensive desertification process close to residential areas. Biochar (biologically derived charcoal) is produced by pyrolysis of biomasses under low oxygen conditions, and it can be applied for recycling organic waste in soils and increase soil fertility, improving soil structure and enhancing soil water storage and soil water movement. Soil application of biochar might have agricultural, environmental and sustainability advantages over the use of organic manures or compost, as it is a porous material with a high inner surface area. The main objectives of the present study were to investigate the possible application of biochar from forest residues, derived from mechanically chipped trunks and large branches of Abies alba M., Larix decidua Mill., Picea excelsa L., Pinus nigra A. and Pinus sylvestris L. pyrolysed at 450 °C for 48h, to improve soil structural and hydraulic properties (achieving a stabilization of soil). Different amount of biochar were added to a desertic sandy soil, and the effect on soil porosity water retention and water available to crops were investigated. The High Energy Moisture Characteristic (HEMC) technique was applied to investigate soil-water retention at high-pressure head levels. The adsorption and desorption isotherms of N2 on external surfaces were also determined in order to investigate micro and macro porosity ratio. Both the described model of studies on adsorption-desorption experiments with the applied isotherms model explain the increasing substrate porosity with a particular attention to the macro and micro porosity, respectively.
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Effect of pattern formation on C and N turnover heterogeneity in initial soils
NASA Astrophysics Data System (ADS)
Schaaf, Wolfgang; Zimmermann, Claudia
2013-04-01
The formation of vegetation patterns and hydrological processes, among others, result in soil heterogeneity in newly exposed land surfaces. We studied the effect of these developling structures on carbon and nitrogen trunover in soils of the artificial catchment Chicken Creek (Schaaf et al. 2011, 2012). Substrates with different physical and geochemical properties in combination with different labelled plant litter materials were studied in a microcosm experiment over a period of 80 weeks. Main objectives of the microcosm experiment were to determine the transformation processes of C and N from litter decomposition within the gaseous, liquid and solid phase, the interaction with mineral surfaces and its role for the establishment of biogeochemical cycles. The microcosm experiments were established in a climate chamber at constant 10 °C. In total, 48 soil columns (diameter: 14.4 cm; height: 30 cm) were filled with two different quaternary substrates (sand and loamy sand) representing the textural variation within the catchment at a bulk density of 1.4-1.5 g cm-3. The columns were automatically irrigated with artificial rainwater four times a day with 6.6 ml each (corresponding to 600 mm yr-1). The gaseous phase in the headspace of the microcosms was analyzed continuously for CO2 and N2O concentrations. C and N transformation processes were studied using 13C and 15N labelled litter of two different plant species occurring at the catchment (Lotus corniculatus, Calamagrostis epigejos) that was incorporated into the microcosm surface. By including litter from species with wide distribution within the catchment and soil substrates representing the main variation types of the sediments used for catchment construction we were able to characterize the general function of these sub-patches within the catchment with respect to litter decomposition, soil solution composition, DOC and nutrient leaching, and impact on the mineral soil phase. The results suggest that initial differences in substrate composition in combination with invading vegetation leads to the development of patterns with different biogeochemical process intensities within the catchment. These patterns are not mere additive effects of substrates plus litter, but reflect differences in element cycling. Schaaf, W., Bens, O., Fischer, A., Gerke, H.H., Gerwin, W., Grünewald, U., Holländer, H.M., Kögel-Knabner, I., Mutz, M., Schloter, M., Schulin, R., Veste, M., Winter, S. & Hüttl, R.F. (2011): Patterns and processes of initial terrestrial ecosystem development. J Plant Nutr Soil Sci, 174, 229-239. Schaaf, W., Elmer, M., Fischer, A., Gerwin, W., Nenov, R., Pretzsch, H., Seifert, S., Winter, S., Zaplata, M. (2012): Monitoring the formation of structures and patterns during initial development of an artificial catchment. Environmental Monitoring and Assessment. doi: 10.1007/s10661-012-2998-x.
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Valorisation of used cooking oil sludge by codigestion with swine manure.
Fierro, J; Martínez, E J; Morán, A; Gómez, X
2014-08-01
The addition of lipid wastes to the digestion of swine manure was studied as a means of increasing biogas production. Lipid waste was obtained from a biodiesel plant where used cooking oil is the feedstock. Digestion of this co-substrate was proposed as a way of valorising residual streams from the process of biodiesel production and to integrate the digestion process into the biorefinery concept. Batch digestion tests were performed at different co-digesting proportions obtaining as a result an increase in biogas production with the increase in the amount of co-substrate added to the mixture. Semi-continuous digestion was studied at a 7% (w/w) mass fraction of total solids. Co-digestion was successful at a hydraulic retention time (HRT) of 50 d but a decrease to 30 d resulted in a decrease in specific gas production and accumulation of volatile and long chain fatty acids. The CH4 yield obtained was 326 ± 46 l/kg VSfeed at an HRT of 50 d, while this value was reduced to 274 ± 43 l/kg VSfeed when evaluated at an HRT of 30 d. However these values were higher than the one obtained under batch conditions (266 ± 40 l/kg VSfeed), thus indicating the need of acclimation to the co-substrate. Despite of operating at low organic loading rate (OLR), measurements from respirometry assays of digestate samples (at an HRT of 50 d) suggested that the effluent could not be directly applied to the soil as fertiliser and might have a negative effect over soil or crops. Copyright © 2014 Elsevier Ltd. All rights reserved.
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NASA Astrophysics Data System (ADS)
Liu, H.; Yu, C. Y.; Manukovsky, N. S.; Kovalev, V. S.; Gurevich, Yu L.; Wang, J.
2008-09-01
The paper presents a conceptual configuration of the lunar base bioregenerative life support system (LBLSS), including soil-like substrate (SLS) for growing plants. SLS makes it possible to combine the processes of plant growth and the utilization of plant waste. Plants are to be grown on SLS on the basis of 20 kg of dry SLS mass or 100 kg of wet SLS mass per square meter. The substrate is to be delivered to the base ready-made as part of the plant growth subsystem. Food for the crew was provided by prestored stock 24% and by plant growing system 76%. Total dry weight of the food is 631 g per day (2800 kcal/day) for one crew member (CM). The list of candidate plants to be grown under lunar BLSS conditions included 14 species: wheat, rice, soybean, peanuts, sweet pepper, carrots, tomatoes, coriander, cole, lettuce, radish, squash, onion and garlic. From the prestored stock the crew consumed canned fish, iodinated salt, sugar, beef sauce and seafood sauce. Our calculations show that to provide one CM with plant food requires the area of 47.5 m 2. The balance of substance is achieved by the removal dehydrated urine 59 g, feces 31 g, food waste 50 g, SLS 134 g, and also waters 86 g from system and introduction food 236 g, liquid potassium soap 4 g and mineral salts 120 g into system daily. To reduce system setup time the first plants could be sowed and germinated to a certain age on the Earth.
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Boron accumulation and toxicity in hybrid poplar (Populus nigra × euramericana).
Rees, Rainer; Robinson, Brett H; Menon, Manoj; Lehmann, Eberhard; Günthardt-Goerg, Madeleine S; Schulin, Rainer
2011-12-15
Poplars accumulate high B concentrations and are thus used for the phytomanagement of B contaminated soils. Here, we performed pot experiments in which Populus nigra × euramericana were grown on a substrate with B concentrations ranging from 13 to 280 mg kg(-1) as H(3)BO(3). Salix viminalis, Brassica juncea, and Lupinus albus were grown under some growing conditions for comparison. Poplar growth was unaffected at soil B treatment levels up to 93 mg kg(-1). Growth was progressively reduced at levels of 168 and 280 mg kg(-1). None of the other species survived at these substrate B levels. At leaf B concentrations <900 mg kg(-1) only <10% of the poplar leaf area showed signs of toxicity. Neutron radiography revealed that chlorotic leaf tissues had B concentrations of 1000-2000 mg kg(-1), while necrotic tissues had >2000 mg kg(-1). Average B concentrations of up to 3500 mg kg(-1) were found in leaves, while spots within leaves had concentrations >7000 mg kg(-1), showing that B accumulation in leaf tissue continued even after the onset of necrosis. The B accumulation ability of P. nigra × euramericana is associated with B hypertolerance in the living tissue and storage of B in dead leaf tissue.
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NASA Astrophysics Data System (ADS)
Hugelius, G.; Ahlström, A.; Canadell, J.; Koven, C. D.; Jackson, R. B.; Luo, Y.
2016-12-01
Soils hold the largest reactive pool of carbon (C) on earth. Global soil organic C stocks (0-200 cm depth plus full peatland depth) are estimated to 2200 Pg C (adapted from Hugelius et al., 2014, Köchy et al., 2015 and Batjes, 2016). Soil C stocks in Earth system models (ESMs) can be generated by running the model over a longer time period until soil C pools are in or near steady-state. Inherent in this concept is the idea that soil C stocks are in (quasi)equilibrium as determined by the balance of net ecosystem input to soil organic matter and its turnover. The rate of turnover is sometimes subdivided into several pools and the rates are affected by various environmental factors. Here we break down the empirically based estimates of global soil C pools into equilibrium-type soils which current (Coupled Model Intercomparison Project, phase 5; CMIP5) generation ESMs are set-up to represent and non-equilibrium type soils which are generally not represented in current ESMs. We define equilibrium soils as those where pedogenesis (and associated soil C formation) is not significantly limited by the environmental factors perennial soil freezing, waterlogging/anoxia or limited unconsolidated soil substrate. This is essentially all permafrost-free mineral soils that are not in a wetland or alpine setting. On the other hand, non-equlibrium soils are defined as permafrost soils, peatlands and alpine soils with a limited fine-soil matrix. Based on geospatial analyses of state-of-the-art datasets on soil C stocks, we estimate that the global soil C pool is divided roughly equally between equilibrium and non-equlibrium type soils. We discuss the ways in which this result affects C cycling in ESMs and projections of soil C sensitivity under a changing climate. ReferencesBatjes N.H. (2016) Geoderma, 269, 61-68, doi: 10.1016/j.geoderma.2016.01.034 Hugelius G. et al. (2014) Biogeosciences, 11, 6573-6593, doi:10.5194/bg-11-6573-2014 Köchy M. et al. (2015) Soil 1, 351-365. DOI: doi:10.5194/soil-1-351-2015
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Bacterial Dispersal Promotes Biodegradation in Heterogeneous Systems Exposed to Osmotic Stress
Worrich, Anja; König, Sara; Banitz, Thomas; Centler, Florian; Frank, Karin; Thullner, Martin; Harms, Hauke; Miltner, Anja; Wick, Lukas Y.; Kästner, Matthias
2016-01-01
Contaminant biodegradation in soils is hampered by the heterogeneous distribution of degrading communities colonizing isolated microenvironments as a result of the soil architecture. Over the last years, soil salinization was recognized as an additional problem especially in arid and semiarid ecosystems as it drastically reduces the activity and motility of bacteria. Here, we studied the importance of different spatial processes for benzoate biodegradation at an environmentally relevant range of osmotic potentials (ΔΨo) using model ecosystems exhibiting a heterogeneous distribution of the soil-borne bacterium Pseudomonas putida KT2440. Three systematically manipulated scenarios allowed us to cover the effects of (i) substrate diffusion, (ii) substrate diffusion and autonomous bacterial dispersal, and (iii) substrate diffusion and autonomous as well as mediated bacterial dispersal along glass fiber networks mimicking fungal hyphae. To quantify the relative importance of the different spatial processes, we compared these heterogeneous scenarios to a reference value obtained for each ΔΨo by means of a quasi-optimal scenario in which degraders were ab initio homogeneously distributed. Substrate diffusion as the sole spatial process was insufficient to counteract the disadvantage due to spatial degrader heterogeneity at ΔΨo ranging from 0 to −1 MPa. In this scenario, only 13.8−21.3% of the quasi-optimal biodegradation performance could be achieved. In the same range of ΔΨo values, substrate diffusion in combination with bacterial dispersal allowed between 68.6 and 36.2% of the performance showing a clear downwards trend with decreasing ΔΨo. At −1.5 MPa, however, this scenario performed worse than the diffusion scenario, possibly as a result of energetic disadvantages associated with flagellum synthesis and emerging requirements to exceed a critical population density to resist osmotic stress. Network-mediated bacterial dispersal kept biodegradation almost consistently high with an average of 70.7 ± 7.8%, regardless of the strength of the osmotic stress. We propose that especially fungal network-mediated bacterial dispersal is a key process to achieve high functionality of heterogeneous microbial ecosystems also at reduced osmotic potentials. Thus, mechanical stress by, for example, soil homogenization should be kept low in order to preserve fungal network integrity. PMID:27536297
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Susceptibility of Permafrost Soil Organic Carbon under Warming Climate
NASA Astrophysics Data System (ADS)
Yang, Z.; Wullschleger, S. D.; Liang, L.; Graham, D. E.; Gu, B.
2015-12-01
Degradation of soil organic carbon (SOC) that has been stored in permafrost is a key concern under warming climate because it could provide a positive feedback. Studies and conceptual models suggest that SOC degradation is largely controlled by the decomposability of SOC, but it is unclear exactly what portions of SOC are susceptible to rapid breakdown and what mechanisms may be involved in SOC degradation. Using a suite of analytical techniques, we examined the dynamic consumption and production of labile SOC compounds, including sugars, alcohols, and small molecular weight organic acids in incubation experiments (up to 240 days at either -2 or 8 °C) with a tundra soil under anoxic conditions, where SOC respiration and iron(III) reduction were monitored. We observe that sugars and alcohols are main components in SOC accounting for initial rapid release of CO2 and CH4 through anaerobic fermentation, whereas the fermentation products such as acetate and formate are subsequently utilized as primary substrates for methanogenesis. Iron(III) reduction is correlated to acetate production and methanogenesis, suggesting its important roles as an electron acceptor in tundra SOC respiration. These observations corroborate strongly with the glucose addition during incubation, in which rapid CO2 and CH4 production is observed concurrently with rapid production and consumption of organics such as acetate. Thus, the biogeochemical processes we document here are pertinent to understanding the accelerated SOC decomposition with temperature and could provide basis for model predicting feedbacks to climate warming in the Arctic.
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Zhang, Naili; Liu, Weixing; Yang, Haijun; Yu, Xingjun; Gutknecht, Jessica L M; Zhang, Zhe; Wan, Shiqiang; Ma, Keping
2013-11-01
A better understanding of soil microbial ecology is critical to gaining an understanding of terrestrial carbon (C) cycle-climate change feedbacks. However, current knowledge limits our ability to predict microbial community dynamics in the face of multiple global change drivers and their implications for respiratory loss of soil carbon. Whether microorganisms will acclimate to climate warming and ameliorate predicted respiratory C losses is still debated. It also remains unclear how precipitation, another important climate change driver, will interact with warming to affect microorganisms and their regulation of respiratory C loss. We explore the dynamics of microorganisms and their contributions to respiratory C loss using a 4-year (2006-2009) field experiment in a semi-arid grassland with increased temperature and precipitation in a full factorial design. We found no response of mass-specific (per unit microbial biomass C) heterotrophic respiration to warming, suggesting that respiratory C loss is directly from microbial growth rather than total physiological respiratory responses to warming. Increased precipitation did stimulate both microbial biomass and mass-specific respiration, both of which make large contributions to respiratory loss of soil carbon. Taken together, these results suggest that, in semi-arid grasslands, soil moisture and related substrate availability may inhibit physiological respiratory responses to warming (where soil moisture was significantly lower), while they are not inhibited under elevated precipitation. Although we found no total physiological response to warming, warming increased bacterial C utilization (measured by BIOLOG EcoPlates) and increased bacterial oxidation of carbohydrates and phenols. Non-metric multidimensional scaling analysis as well as ANOVA testing showed that warming or increased precipitation did not change microbial community structure, which could suggest that microbial communities in semi-arid grasslands are already adapted to fluctuating climatic conditions. In summary, our results support the idea that microbial responses to climate change are multifaceted and, even with no large shifts in community structure, microbial mediation of soil carbon loss could still occur under future climate scenarios.
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Long-term litter manipulation alters soil organic matter turnover in a temperate deciduous forest.
Wang, Jun-Jian; Pisani, Oliva; Lin, Lisa H; Lun, Olivia O Y; Bowden, Richard D; Lajtha, Kate; Simpson, André J; Simpson, Myrna J
2017-12-31
Understanding soil organic matter (OM) biogeochemistry at the molecular-level is essential for assessing potential impacts from management practices and climate change on shifts in soil carbon storage. Biomarker analyses and nuclear magnetic resonance (NMR) spectroscopy were used in an ongoing detrital input and removal treatment experiment in a temperate deciduous forest in Pennsylvania, USA, to examine how above- and below-ground plant inputs control soil OM quantity and quality at the molecular-level. From plant material to surface soils, the free acyclic lipids and cutin, suberin, and lignin biomarkers were preferentially retained over free sugars and free cyclic lipids. After 20years of above-ground litter addition (Double Litter) or exclusion (No Litter) treatments, soil OM composition was relatively more degraded, as revealed by solid-state 13 C NMR spectroscopy. Under Doubled Litter inputs, soil carbon and phospholipid fatty acid (PLFA) concentrations were unchanged, suggesting that the current OM degradation status is a reflection of microbial-mediated degradation that occurred prior to the 20-year sampling campaign. Soil OM degradation was higher in the No Litter treatments, likely due to the decline in fresh, above-ground litter inputs over time. Furthermore, root and root and litter exclusion treatments (No Roots and No Inputs, respectively) both significantly reduced free sugars and PLFAs and increased preservation of suberin-derived compounds. PLFA stress ratios and the low N-acetyl resonances from diffusion edited 1 H NMR also indicate substrate limitations and reduced microbial biomass with these treatments. Overall, we highlight that storage of soil carbon and its biochemical composition do not linearly increase with plant inputs because the microbial processing of soil OM is also likely altered in the studied forest. Copyright © 2017 Elsevier B.V. All rights reserved.
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NASA Astrophysics Data System (ADS)
Song, Yanyu; Song, Changchun; Yang, Guisheng; Miao, Yuqing; Wang, Jiaoyue; Guo, Yuedong
2012-09-01
The extensive reclamation of marshland into cropland has tremendously impacted the ecological environment of the Sanjiang Plain in northeast China. To understand the impacts of marshland reclamation and restoration on soil properties, we investigated the labile organic carbon fractions and the soil enzyme activities in an undisturbed marshland, a cultivated marshland and three marshlands that had been restored for 3, 6 and 12 years. Soil samples collected from the different management systems at a depth of 0-20 cm in July 2009 were analyzed for soil organic carbon (SOC), dissolved organic carbon (DOC), microbial biomass carbon (MBC) and easily degradable organic carbon. In addition, the activities of the invertase, β-glucosidase, urease and acid phosphatase were determined. These enzymes are involved in C, N and P cycling, respectively. Long-term cultivation resulted in decreased SOC, DOC, MBC, microbial quotient and C (invertase, β-glucosidase) and N-transforming (urease) enzyme activities compared with undisturbed marshland. After marshland restoration, the MBC and DOC concentrations and the soil invertase, β-glucosidase and urease activities increased. Soil DOC and MBC concentrations are probably the main factors responsible for the different invertase, β-glucosidase and urease activities. In addition, marshland restoration caused a significant increase in the microbial quotient, which reflects enhanced efficiency of organic substrate use by microbial biomass. Our observations demonstrated that soil quality recovered following marshland restoration. DOC, MBC and invertase, β-glucosidase and urease activities were sensitive for discriminating soil ecosystems under the different types of land use. Thus, these parameters should be considered to be indicators for detecting changes in soil quality and environmental impacts in marshlands.
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Effects of single-walled carbon nanotubes on soil microorganisms
NASA Astrophysics Data System (ADS)
Jin, L.; Chung, H.; Son, Y.
2011-12-01
Single-walled carbon nanotubes (SWCNTs) are novel materials that have the potential to be used in various commercial fields due to their unique physicochemical properties. As a result of commercial development of nanotechnology, SWCNTs may be discharged to the soil environment with unknown consequences. However, there are as yet no data in the scientific literature that demonstrate the effects of SWCNTs on microbial function in soils. Therefore, we aimed to determine the effects of SWCNTs on soil microbial activity through a 2-week incubation study on urban soils supplemented with different concentrations of SWCNTs ranging from 0 to 1000 μg CNT/g soil. Fluorometric test using fluorogenic substrates were employed for the measurement of several enzyme activities in soil samples. More specifically, we determined the changes in the activities of cellobiohydrolase, β-1,4-glucosidase, β-1,4-xylosidase, β-1,4-N-acetylglucosaminidase, L-leucine aminopeptidase and acid phosphatase which play important roles in the carbon, nitrogen, and phosphorus cycles in response to the addition of SWCNTs. We found that microbial enzyme activities decreased as the concentrations of SWCNT added increased. The lowest enzyme activities were observed under 1000 μg CNT/g soil. The overall pattern shows that enzyme activities decreased slightly in the first 2-3 days and increased in the later stage of the incubation. Our results suggest that relatively high concentrations of SWCNTs can inhibit microbial activities, and this may be due to microbial cell membrane damage caused by SWCNTs. However, further study needs to be conducted to determine the mechanism responsible for inhibitory effect of SWCNTs on soil microbial activity. It can be concluded that changes in the activities of extracellular enzymes can indicate the effect of SWCNTs on soil microorganisms and nutrient cycling.
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Plant-soil-microbe interactions regulating soil C storage
NASA Astrophysics Data System (ADS)
Hofmockel, K. S.; Bach, E.; Williams, R.
2016-12-01
Integration across disciplines is required to identify the emergent microbial scale properties that regulate the release or occlusion of plant inputs in soil organic matter. To investigate how micro-scale processes influence soil carbon cycling, we measured microbial community composition and activity within soil aggregates monthly over two growing seasons of a long-term bioenergy field experiment. Using a biologically sensitive sieving technique, soil aggregates were isolated and microbial community activity and composition were measured. This aggregate approach revealed biogeochemical processes regulating C cycling that are not detected using whole soil approaches. Soil aggregation influenced microbe-substrate interactions, where diversified perennial grassland systems supported greater aggregation and reduced severity of aggregate turnover compared to corn systems. Aggregate turnover and concurrent increases in activity resulted in greater microbial biomass and physical protection of soil organic matter in prairie systems, especially fertilized prairies. Fertilized prairie enhanced microbial biomass, enzyme activity, and soil aggregation despite greater root biomass in unfertilized prairie. Independent of ecosystem or sampling date, N-acetyl-glucosaminidase activity and Nitrospirae abundance was greatest in large macroaggregates (>2000 µm), which harbored the highest C:N; cellobiohydrolase activity and Acidobacteria abundance was greatest in microaggregates (<250 µm) which had the lowest C:N. Aggregate fractions differed in microbial community composition (bacteria, archaea, and fungi) and potential enzyme activity, independent of cropping system. Microaggregates harbored significantly greater microbial diversity and richness across all bioenergy cropping systems. Together these results suggest that by mediating access to substrates, soil structure (aggregates) can influence the microbial community composition and extracellular enzyme activity to regulate ecosystem scale decomposition of soil organic matter.
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Wnek, John P; Bien, Walter F; Avery, Harold W
2013-06-01
Diamondback terrapins (Malaclemys terrapin) inhabit estuaries in eastern USA and may tolerate salinity of sea-water for short durations. Many North American estuaries are adversely affected by anthropogenic impacts, such as pollution, dredging and invasion by non-native plants. Many nesting areas have been altered or destroyed, causing terrapins to nest on roadsides and artificial islands made of dredged substrate from bottom sediments. Shading by non-native plants may suppress development and reduce survival of embryos. In Barnegat Bay, New Jersey, USA, there is a mosaic of natural and degraded terrapin nesting habitats. We investigated the effects of dredge soil and shade on the hatching success of diamondback terrapins to determine whether nesting habitat could be increased by using dredged bottom sediments. In year 1, unshaded nests in natural loamy-sand had the highest hatching success (55.2%), while nests in dredge soil produced no hatchlings. In year 2, nests in unshaded loamy-sand had a hatching success of 85.3%, whereas those in dredge soil, aged 1 year, had a hatching success of 59.4%. Dredge soil improved as an incubation substrate after aging 1 year by the washout of salt. Nest temperatures were generally cool and produced mostly male hatchlings. Uncontaminated dredge soil may provide suitable nesting substrates for diamondback terrapins if used after one year, and may be particularly beneficial if used for constructing islands that provide new nesting sites with reduced access of mammalian predators. © 2013 Wiley Publishing Asia Pty Ltd, ISZS and IOZ/CAS.
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NASA Astrophysics Data System (ADS)
Nabel, Moritz; Bueno Piaz Barbosa, Daniela; Horsch, David; Jablonowski, Nicolai David
2014-05-01
The global demand for energy security and the mitigation of climate change are the main drivers pushing energy-plant production in Germany. However, the cultivation of these plants can cause land use conflicts since agricultural soil is mostly used for plant production. A sustainable alternative to the conventional cultivation of food-based energy-crops is the cultivation of special adopted energy-plants on marginal lands. To further increase the sustainability of energy-plant cultivation systems the dependency on synthetic fertilizers needs to be reduced via closed nutrient loops. In the presented study the energy-plant Sida hermaphrodita (Malvaceae) will be used to evaluate the potential to grow this high potential energy-crop on a marginal sandy soil in combination with fertilization via digestate from biogas production. With this dose-response experiment we will further identify an optimum dose, which will be compared to equivalent doses of NPK-fertilizer. Further, lethal doses and deficiency doses will be observed. Two weeks old Sida seedlings were transplanted to 1L pots and fertilized with six doses of digestate (equivalent to a field application of 5, 10, 20, 40, 80, 160t/ha) and three equivalent doses of NPK-fertilizer. Control plants were left untreated. Sida plants will grow for 45 days under greenhouse conditions. We hypothesize that the nutrient status of the marginal soil can be increased and maintained by defined digestate applications, compared to control plants suffering of nutrient deficiency due to the low nutrient status in the marginal substrate. The dose of 40t/ha is expected to give a maximum biomass yield without causing toxicity symptoms. Results shall be used as basis for further experiments on the field scale in a field trial that was set up to investigate sustainable production systems for energy crop production under marginal soil conditions.
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Microbial Enzyme Activity and Carbon Cycling in Grassland Soil Fractions
NASA Astrophysics Data System (ADS)
Allison, S. D.; Jastrow, J. D.
2004-12-01
Extracellular enzymes are necessary to degrade complex organic compounds present in soils. Using physical fractionation procedures, we tested whether old soil carbon is spatially isolated from degradative enzymes across a prairie restoration chronosequence in Illinois, USA. We found that carbon-degrading enzymes were abundant in all soil fractions, including macroaggregates, microaggregates, and the clay fraction, which contains carbon with a mean residence time of ~200 years. The activities of two cellulose-degrading enzymes and a chitin-degrading enzyme were 2-10 times greater in organic matter fractions than in bulk soil, consistent with the rapid turnover of these fractions. Polyphenol oxidase activity was 3 times greater in the clay fraction than in the bulk soil, despite very slow carbon turnover in this fraction. Changes in enzyme activity across the restoration chronosequence were small once adjusted for increases in soil carbon concentration, although polyphenol oxidase activity per unit carbon declined by 50% in native prairie versus cultivated soil. These results are consistent with a `two-pool' model of enzyme and carbon turnover in grassland soils. In light organic matter fractions, enzyme production and carbon turnover both occur rapidly. However, in mineral-dominated fractions, both enzymes and their carbon substrates are immobilized on mineral surfaces, leading to slow turnover. Soil carbon accumulation in the clay fraction and across the prairie restoration chronosequence probably reflects increasing physical isolation of enzymes and substrates on the molecular scale, rather than the micron to millimeter scale.
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Long-term Priming-induced Changes in Permafrost Soil Organic Matter Decomposition
NASA Astrophysics Data System (ADS)
Pegoraro, E.; Bracho, R. G.; Schuur, E.
2016-12-01
Warming of tundra ecosystems due to climate change is predicted to thaw permafrost and increase plant biomass and litter input to soil. Additional input of easily decomposable carbon can stimulate microbial activity, consequently increasing soil organic matter decomposition rates. This phenomenon, known as the priming effect, can exacerbate the effects of climate change by releasing more CO2 from permafrost soils; however, the extent to which it could decrease soil carbon stocks in the Arctic is unknown. Most priming incubation studies are conducted for a short period of time, making it difficult to assess if priming is a short-term phenomenon, or could persist over the long-term. We incubated permafrost soil from a moist acidic tundra site in Healy, Alaska for 456 days at 15° C. Soil from surface and deep layers were amended with three pulses of uniformly 13C labeled glucose, a fast decomposing substrate, every 152 days. We also quantified the proportion of old carbon respired by measuring 14CO2. Substrate addition resulted in higher respiration rates in glucose amended soils; however, positive priming was only observed in deep layers, where on average 9%, 57%, and 25% more soil-derived C was respired at 45-55, 65-75, and 75-85 cm depth increments for the duration of the experiment. This suggests that microbes in deep layers are limited in energy, and the addition of easily decomposable carbon increases native soil organic matter decomposition.
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Wu, Yue; Jiang, Ying; Jiao, Jiaguo; Liu, Manqiang; Hu, Feng; Griffiths, Bryan S; Li, Huixin
2014-02-01
Laccases play an important role in the degradation of soil phenol or phenol-like substance and can be potentially used in soil remediation through immobilization. Iron and aluminum minerals can adsorb extracellular enzymes in soil environment. In the present study, we investigated the adsorptive interaction of laccase, from the white-rot fungus Trametes versicolor, with soil iron and aluminum minerals and characterized the properties of the enzyme after adsorption to minerals. Results showed that both soil iron and aluminum minerals adsorbed great amount of laccase, independent of the mineral specific surface areas. Adsorbed laccases retained 26-64% of the activity of the free enzyme. Compared to the free laccase, all adsorbed laccases showed higher Km values and lower Vmax values, indicating a reduced enzyme-substrate affinity and a lower rate of substrate conversion in reactions catalyzed by the adsorbed laccase. Adsorbed laccases exhibited increased catalytic activities compared to the free laccase at low pH, implying the suitable application of iron and aluminum mineral-adsorbed T. versicolor laccase in soil bioremediation, especially in acid soils. In terms of the thermal profiles, adsorbed laccases showed decreased thermal stability and higher temperature sensitivity relative to the free laccase. Moreover, adsorption improved the resistance of laccase to proteolysis and extended the lifespan of laccase. Our results implied that adsorbed T. versicolor laccase on soil iron and aluminum minerals had promising potential in soil remediation. Crown Copyright © 2013. Published by Elsevier B.V. All rights reserved.
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Bonachela, Juan A; Pringle, Robert M; Sheffer, Efrat; Coverdale, Tyler C; Guyton, Jennifer A; Caylor, Kelly K; Levin, Simon A; Tarnita, Corina E
2015-02-06
Self-organized spatial vegetation patterning is widespread and has been described using models of scale-dependent feedback between plants and water on homogeneous substrates. As rainfall decreases, these models yield a characteristic sequence of patterns with increasingly sparse vegetation, followed by sudden collapse to desert. Thus, the final, spot-like pattern may provide early warning for such catastrophic shifts. In many arid ecosystems, however, termite nests impart substrate heterogeneity by altering soil properties, thereby enhancing plant growth. We show that termite-induced heterogeneity interacts with scale-dependent feedbacks to produce vegetation patterns at different spatial grains. Although the coarse-grained patterning resembles that created by scale-dependent feedback alone, it does not indicate imminent desertification. Rather, mound-field landscapes are more robust to aridity, suggesting that termites may help stabilize ecosystems under global change. Copyright © 2015, American Association for the Advancement of Science.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Yen, T.F.
1985-01-01
Chemical oxidation of lignite by means of hydrogen peroxide - acetic acid was executed. Methanol fractionation of the oxidized product yielded 76.4% methanol solubles, 9.3% methanol insolubles and 11.2% CO/sub 2/. Biodegradation of the methanol fraction by soil bacteria was found to be positive as demonstrated by gel permeation chromatography (GPC). The shift of the average molecular weight throughout biodegradation was estimated to be from 310 g/mole, to 243 g/mole, zero day and four weeks respectively. Biodegradation of lignitic substrates, benzene - methanol fraction (A - 1), aqueous alkaline fraction (A - 2), clean lignite residue (A - 3), rawmore » lignite, and methanol soluble fraction after oxidation, by means of oil - field soil bacteria and Polyporus versicolor ATCC 12679 was attempted. All previous mentioned lignitic substrates yielded positive results for oil-field soil bacteria, while A - 2 fraction and raw lignite yielded positive results for P. versicolor. Unidentified fungi strains, N 1, L 1, and L 2 were also tested on lignitic substrates. Mild growth was observed in these cases.« less
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Williams, C M; Grimes, J L; Mikkelsen, R L
1999-07-01
The purpose of this investigation was to determine the feasibility of utilizing poultry litter as a source of microorganisms, C co-substrate, N, and P to enhance the biodegradation of petroleum compounds in contaminated soil. An initial laboratory-scale study utilized soil contaminated with approximately 3,000 mg/kg (ppm) total petroleum hydrocarbons (TPHC) as diesel fuel. Biotreatment units, each containing 10 L of contaminated soil, were supplemented (0, 1, 10, and 20%, total weight basis) with broiler litter containing 3.65% N and 1.89% P. Petroleum-degrading microorganisms previously enriched from broiler and turkey litter were also inoculated into the litter-treated units. A significant first order rate of TPHC biodegradation was measured for all treatment units containing broiler litter (P < 0.05). Based on these results, a subsequent study was conducted at the site of a commercial facility permitted to treat soil (ex situ) contaminated with hazardous compounds. Soil treatment plots, each containing approximately 1 ton of soil contaminated with approximately 1,200 to 1,600 mg/kg diesel fuel were established. Each plot was replicated four times and the experiment was conducted for 35 d. Treatments were as follows: control, soil only; soil + commercial blend of bioremediation nutrients; soil + commercial fertilizer; soil + poultry litter (1% by volume); soil + poultry litter (10% by volume); soil + pelleted poultry litter (10% by volume). The results showed that the remediation of soil contaminated with petroleum compounds is significantly (P < 0.05) enhanced when supplemented with poultry litter (pelleted or nonpelleted) in concentrations of 10% soil volume. These results demonstrate the potential for a specialized market for the use of poultry litter.
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Variation in pH optima of hydrolytic enzyme activities in tropical rain forest soils.
Turner, Benjamin L
2010-10-01
Extracellular enzymes synthesized by soil microbes play a central role in the biogeochemical cycling of nutrients in the environment. The pH optima of eight hydrolytic enzymes involved in the cycles of carbon, nitrogen, phosphorus, and sulfur, were assessed in a series of tropical forest soils of contrasting pH values from the Republic of Panama. Assays were conducted using 4-methylumbelliferone-linked fluorogenic substrates in modified universal buffer. Optimum pH values differed markedly among enzymes and soils. Enzymes were grouped into three classes based on their pH optima: (i) enzymes with acidic pH optima that were consistent among soils (cellobiohydrolase, β-xylanase, and arylsulfatase), (ii) enzymes with acidic pH optima that varied systematically with soil pH, with the most acidic pH optima in the most acidic soils (α-glucosidase, β-glucosidase, and N-acetyl-β-glucosaminidase), and (iii) enzymes with an optimum pH in either the acid range or the alkaline range depending on soil pH (phosphomonoesterase and phosphodiesterase). The optimum pH values of phosphomonoesterase were consistent among soils, being 4 to 5 for acid phosphomonoesterase and 10 to 11 for alkaline phosphomonoesterase. In contrast, the optimum pH for phosphodiesterase activity varied systematically with soil pH, with the most acidic pH optima (3.0) in the most acidic soils and the most alkaline pH optima (pH 10) in near-neutral soils. Arylsulfatase activity had a very acidic optimum pH in all soils (pH ≤3.0) irrespective of soil pH. The differences in pH optima may be linked to the origins of the enzymes and/or the degree of stabilization on solid surfaces. The results have important implications for the interpretation of hydrolytic enzyme assays using fluorogenic substrates.
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Growth of chitinolytic dune soil beta-subclass Proteobacteria in response to invading fungal hyphae.
De Boer, W; Klein Gunnewiek, P J; Kowalchuk, G A; Van Veen, J A
2001-08-01
It has frequently been reported that chitinolytic soil bacteria, in particular biocontrol strains, can lyse living fungal hyphae, thereby releasing potential growth substrate. However, the conditions used in such assays (high bacterial density, rich media, fragmented hyphae) make it difficult to determine whether mycolytic activity is actually of importance for the growth and survival of chitinolytic bacteria in soils. An unidentified group of beta-subclass Proteobacteria (CbetaPs) was most dominant among the culturable nonfilamentous chitinolytic bacteria isolated from Dutch sand dune soils. Here we demonstrate that the CbetaPs grew at the expense of extending fungal mycelium of three dune soil fungi (Chaetomium globosum, Fusarium culmorum, and Mucor hiemalis) under nutrient-limiting, soil-like conditions. Aggregates of CbetaPs were also often found attached to fungal hyphae. The growth of a control group of dominant nonchitinolytic dune soil bacteria (beta- and gamma-subclass Proteobacteria) was not stimulated in the mycelial zone, indicating that growth-supporting materials were not independently released in appreciable amounts by the extending hyphae. Therefore, mycolytic activities of CbetaPs have apparently been involved in allowing them to grow after exposure to living hyphae. The chitinase inhibitor allosamidin did not, in the case of Mucor, or only partially, in the cases of Chaetomium and Fusarium, repress mycolytic growth of the CbetaPs, indicating that chitinase activity alone could not explain the extent of bacterial proliferation. Chitinolytic Stenotrophomonas-like and Cytophaga-like bacteria, isolated from the same dune soils, were only slightly stimulated by exposure to fungal hyphae.
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Zalman, Cassandra A.; Meade, N.; Chanton, J.; Kostka, J. E.; Bridgham, S. D.; Keller, J. K.
2017-12-01
This study investigated the potential for methylotrophic methanogenesis in three Sphagnum-dominated peatland soils in northern Minnesota. Collected soils were amended with 13C-labeled traditional substrates (acetate and sodium bicarbonate/ H2) and methylated substrates (methanol, monomethylamine (“MMA”), dimethylsulfide (“DMS”)) and monitored for δ13C-CH4, δ 13C-CO2, and net CH4 and CO2 production in laboratory incubations. The peatlands included in the study were (1) the S1 Bog, home to the SPRUCE Experiment and located at the Marcell Experimental Forest (MEF, U.S. Forest Service), (2) Bog Lake Fen, also located at the MEF, and (3) Zim Bog. These sites have been described in detail previously (Medvedeff et al., 2015)
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Forest composition modifies litter dynamics and decomposition in regenerating tropical dry forest.
Schilling, Erik M; Waring, Bonnie G; Schilling, Jonathan S; Powers, Jennifer S
2016-09-01
We investigated how forest composition, litter quality, and rainfall interact to affect leaf litter decomposition across three successional tropical dry forests in Costa Rica. We monitored litter stocks and bulk litter turnover in 18 plots that exhibit substantial variation in soil characteristics, tree community structure, fungal communities (including forests dominated by ecto- or arbuscular mycorrhizal host trees), and forest age. Simultaneously, we decomposed three standard litter substrates over a 6-month period spanning an unusually intense drought. Decay rates of standard substrates depended on the interaction between litter identity and forest type. Decomposition rates were correlated with tree and soil fungal community composition as well as soil fertility, but these relationships differed among litter types. In low fertility soils dominated by ectomycorrhizal oak trees, bulk litter turnover rates were low, regardless of soil moisture. By contrast, in higher fertility soils that supported mostly arbuscular mycorrhizal trees, bulk litter decay rates were strongly dependent on seasonal water availability. Both measures of decomposition increased with forest age, as did the frequency of termite-mediated wood decay. Taken together, our results demonstrate that soils and forest age exert strong control over decomposition dynamics in these tropical dry forests, either directly through effects on microclimate and nutrients, or indirectly by affecting tree and microbial community composition and traits, such as litter quality.
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Czechowski, Paul; White, Duanne; Clarke, Laurence; McKay, Alan; Cooper, Alan; Stevens, Mark I
2016-12-01
The potential impact of environmental change on terrestrial Antarctic ecosystems can be explored by inspecting biodiversity patterns across large-scale gradients. Unfortunately, morphology-based surveys of Antarctic invertebrates are time-consuming and limited by the cryptic nature of many taxa. We used biodiversity information derived from high-throughput sequencing (HTS) to elucidate the relationship between soil properties and invertebrate biodiversity in the Prince Charles Mountains, East Antarctica. Across 136 analysed soil samples collected from Mount Menzies, Mawson Escarpment and Lake Terrasovoje, we found invertebrate distribution in the Prince Charles Mountains significantly influenced by soil salinity and/or sulfur content. Phyla Tardigrada and Arachnida occurred predominantly in low-salinity substrates with abundant nutrients, whereas Bdelloidea (Rotifera) and Chromadorea (Nematoda) were more common in highly saline substrates. A significant correlation between invertebrate occurrence, soil salinity and time since deglaciation indicates that terrain age indirectly influences Antarctic terrestrial biodiversity, with more recently deglaciated areas supporting greater diversity. Our study demonstrates the value of HTS metabarcoding to investigate environmental constraints on inconspicuous soil biodiversity across large spatial scales.
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BioChar Amendments for Improved Plant Microbiome and Crop Health Project
NASA Technical Reports Server (NTRS)
Zeitlin, Nancy; Smith, David; Catechis, John; Khodadad, Christina; Koss, Lawrence; Mejia, Oscar Monje; Spencer, Lashelle
2015-01-01
Plant-based Environmental Control and Life Support Systems (ECLSS) enable human existence beyond Low Earth Orbit (LEO) by providing oxygen, water and food. The root modules are key to success of sustainable plant-based ECLSS. In microgravity, hydroponics is not viable as gases separate from fluids, thus plants are grown in soil substrates, which are bulky and must be maintained for optimal plant growth. Soil substrate selection also impacts ECLSS self-sufficiency. Savings in resupply mass and volume are possible if soil is developed in-situ from regolith found on moons or planets. Biochar, a soil amendment used by ancient civilizations to improve soil fertility that promotes plant health and root zone microbes, can be produced by pyrolysis of plant biomass. The goal is to study the effect of biochar on sequential crop plantings in a single root module. The objectives are: 1) follow changes in root-microbe interactions using metagenomic techniques, 2) measure changes in microbial populations during sequential cropping in a single root module, and 3) examine effect of biochar amendments.
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White, Duanne; Clarke, Laurence; McKay, Alan; Cooper, Alan; Stevens, Mark I.
2016-01-01
The potential impact of environmental change on terrestrial Antarctic ecosystems can be explored by inspecting biodiversity patterns across large-scale gradients. Unfortunately, morphology-based surveys of Antarctic invertebrates are time-consuming and limited by the cryptic nature of many taxa. We used biodiversity information derived from high-throughput sequencing (HTS) to elucidate the relationship between soil properties and invertebrate biodiversity in the Prince Charles Mountains, East Antarctica. Across 136 analysed soil samples collected from Mount Menzies, Mawson Escarpment and Lake Terrasovoje, we found invertebrate distribution in the Prince Charles Mountains significantly influenced by soil salinity and/or sulfur content. Phyla Tardigrada and Arachnida occurred predominantly in low-salinity substrates with abundant nutrients, whereas Bdelloidea (Rotifera) and Chromadorea (Nematoda) were more common in highly saline substrates. A significant correlation between invertebrate occurrence, soil salinity and time since deglaciation indicates that terrain age indirectly influences Antarctic terrestrial biodiversity, with more recently deglaciated areas supporting greater diversity. Our study demonstrates the value of HTS metabarcoding to investigate environmental constraints on inconspicuous soil biodiversity across large spatial scales. PMID:28083092
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Mingo, Felix Sebastian; Diekert, Gabriele; Studenik, Sandra
2016-02-01
The O-demethylation of phenyl methyl ethers under anaerobic conditions is a metabolic feature of acetogens and Desulfitobacterium spp. Desulfitobacteria as well as most acetogens are Gram-positive bacteria with a low GC content and belong to the phylum Firmicutes. The consumption of the phenyl methyl ether syringate was studied in enrichment cultures originating from five different topsoils. Desulfitobacterium spp. were detected in all topsoils via quantitative PCR. Desulfitobacteria could be enriched using the O-demethylation of syringate as a growth-selective process. The enrichment was significantly favoured by an external electron acceptor such as 3-chloro-4-hydroxyphenylacetate or thiosulfate. Upon cultivation in the presence of syringate and thiosulfate, which naturally occur in soil, a maximum number of 16S rRNA gene copies of Desulfitobacterium spp. was reached within the first three subcultivation steps and accounted for 3-10% of the total microbial community depending on the soil type. Afterwards, a loss of Desulfitobacterium gene copies was observed. Community analyses revealed that Proteobacteria, Acidobacteria, Actinobacteria and Bacteroidetes were the main phyla in the initial soil samples. Upon addition of syringate and thiosulfate as growth substrates, these phyla were rapidly outcompeted by Firmicutes, which were under-represented in soil. The main Firmicutes genera identified were Alkalibaculum, Clostridium, Sporobacterium, Sporomusa and Tissierella, which might be responsible for outcompeting the desulfitobacteria. Most of these organisms belong to the acetogens, which have previously been described to demethylate phenyl methyl ethers. The shift of the native community structure to almost exclusively Firmicutes supports the participation of members of this phylum in environmental demethylation processes.
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Miller, Robin L.; Hastings, Lauren; Fujii, Roger
2000-01-01
Subsidence of organic soils in the Sacramento-San Joaquin Delta, California, has increased the potential for levee failure and flooding in the region. Because oxidation of the peat soils is a primary cause of subsidence, reversion of affected lands to wetlands has been proposed as a mitigation tool. To test this hypothesis, three 10 x 10 meter enclosures were built on Twitchell Island in the Delta and managed as different wetland habitats. Emissions of carbon dioxide and methane were measured in situ from October 1995 through December 1997, from the systems that developed under the different water-management treatments. Treatments included a seasonal control (SC) under current island management conditions; reverse flooding (RF), where the land is intentionally flooded from early dry season until midsummer; permanent shallow flooding (F); and a more deeply flooded, open-water (OW) treatment. Hydrologic treatments affected microbial processes, plant community and temperature dynamics which, in turn, affected carbon cycling. Water-management treatments with a period of flooding significantly decreased gaseous carbon emissions compared to the seasonal control. Permanent flooding treatments showed significantly higher methane fluxes than treatments with some period of aerobic conditions. Shallow flooding treatments created conditions that support cattail [Typha species (spp.)] marshes, while deep flooding precluded emergent vegetation. Carbon inputs to the permanent shallow flooding treatment tended to be greater than the measured losses. This suggests that permanent shallow flooding has the greatest potential for managing subsidence of these soils by generating organic substrate more rapidly than is lost through decomposition. Carbon input estimates of plant biomass compared to measurements of gaseous carbon losses indicate the potential for mitigation of subsidence through hydrologic management of the organic soils in the area.
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Use of Additives in Bioremediation of Contaminated Groundwater and Soil
This chapter reviews application of additives used in bioremediation of chlorinated solvents and fuels for groundwater and soil remediation. Soluble carbon substrates are applicable to most site conditions except aquifers with very high or very low groundwater flow. Slow-release ...
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Kang, Yijun; Hao, Yangyang; Shen, Min; Zhao, Qingxin; Li, Qing; Hu, Jian
2016-08-01
Using pig manure (PM) compost as a partial substitute for the conventional chemical fertilizers (CFs) is considered an effective approach in sustainable agricultural systems. This study aimed to analyze the impacts of supplementing CF with organic fertilizers (OFs) manufactured using pig manure as a substrate on the spread of tetracycline resistance genes (TRGs) as well as the community structures and diversities of tetracycline-resistant bacteria (TRB) in bulk and cucumber rhizosphere soils. In this study, three organic fertilizers manufactured using the PM as a substrate, namely fresh PM, common OF, and bio-organic fertilizer (BF), were supplemented with a CF. Composted manures combined with a CF did not significantly increase TRB compared with the CF alone, but PM treatment resulted in the long-term survival of TRB in soil. The use of CF+PM also increased the risk of spreading TRGs in soil. As beneficial microorganisms in BF may function as reservoirs for the spread of antibiotic resistance genes, care should be taken when adding them to the OF matrix. The PM treatment significantly altered the community structures and increased the species diversity of TRB, especially in the rhizosphere soil. BF treatment caused insignificant changes in the community structure of TRB compared with CF treatment, yet it reduced the species diversities of TRB in soil. Thus, the partial use of fresh PM as a substitute for CF could increase the risk of spread of TRGs. Apart from plant growth promotion, BF was a promising fertilizer owing to its potential ability to control TRGs. Copyright © 2016 Elsevier Inc. All rights reserved.
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Effect of several environmental parameters on carbon metabolism in histosols.
Tate, R L
1980-12-01
High specific activity(14)C-labeled glucose, succinate, acetate, salicylate, and amino acids were used to examine carbon metabolism by the microbial community of Pahokee muck (aLithic medisaprist), a drained, cultivated soil of the Florida Everglades. Variations in carbon oxidation were observed from the end of the wet season through the dry season in a fallow (bare) field. Evolution of(14)CO2 varied with the substrate added and time. Calculation of(14)CO2 evolution for each substrate as a proportion of total respiration of the microbial community which was measured by succinate oxidation (relative oxidation) allowed for determination of the proportion of metabolic activity contributed by the oxidation of each carbon source. Except for the May sample when an approximate 30% decline in relative salicylate oxidation activity was observed, the proportion of total catabolic activity contributed by salicylate oxidation and acetate degradation was constant with time. Relative oxidation of glucose and amino acids ranged from 0.12 to 0.52 and 0.10 to 0.23, respectively. At two times during the dry season, the effect of depth of soil and crop on the carbon oxidation was examined. Relative acetate and amino acid oxidation were constant with depth whereas statistically significant variation was observed in glucose and salicylate oxidation. Generally, with the latter substrates, the activity declined with increased soil depth. Greatest effect of crop on these metabolic activities was noted with oxidation of salicylate in soils from a St. Augustinegrass [Stenatophrum secundatum (Walt.) Kuntz] pasture. In these soils, oxidation of salicylate was nearly double that of the fallow field or of soil planted with sugarcane (Saccharum sp.).
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Rivera, Desirée; Mejías, Violeta; Jáuregui, Berta M; Costa-Tenorio, Marga; López-Archilla, Ana Isabel; Peco, Begoña
2014-01-01
The construction of linear transport infrastructure has severe effects on ecosystem functions and properties, and the restoration of the associated roadslopes contributes to reduce its impact. This restoration is usually approached from the perspective of plant cover regeneration, ignoring plant-soil interactions and the consequences for plant growth. The addition of a 30 cm layer of topsoil is a common practice in roadslope restoration projects to increase vegetation recovery. However topsoil is a scarce resource. This study assesses the effects of topsoil spreading and its depth (10 to 30 cm) on two surrogates of microbial activity (β-glucosidase and phosphatase enzymes activity and soil respiration), and on plant cover, plant species richness and floristic composition of embankment vegetation. The study also evaluates the differences in selected physic-chemical properties related to soil fertility between topsoil and the original embankment substrate. Topsoil was found to have higher values of organic matter (11%), nitrogen (44%), assimilable phosphorous (50%) and silt content (54%) than the original embankment substrate. The topsoil spreading treatment increased microbial activity, and its application increased β-glucosidase activity (45%), phosphatase activity (57%) and soil respiration (60%). Depth seemed to affect soil respiration, β-glucosidase and phosphatase activity. Topsoil application also enhanced the species richness of restored embankments in relation to controls. Nevertheless, the depth of the spread topsoil did not significantly affect the resulting plant cover, species richness or floristic composition, suggesting that both depths could have similar effects on short-term recovery of the vegetation cover. A significant implication of these results is that it permits the application of thinner topsoil layers, with major savings in this scarce resource during the subsequent slope restoration work, but the quality of topsoil relative to the original substrate should be previously assessed on a site by site basis.
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Multivariate regulation of soil CO2 and N2 O pulse emissions from agricultural soils.
Liang, Liyin L; Grantz, David A; Jenerette, G Darrel
2016-03-01
Climate and land-use models project increasing occurrence of high temperature and water deficit in both agricultural production systems and terrestrial ecosystems. Episodic soil wetting and subsequent drying may increase the occurrence and magnitude of pulsed biogeochemical activity, affecting carbon (C) and nitrogen (N) cycles and influencing greenhouse gas (GHG) emissions. In this study, we provide the first data to explore the responses of carbon dioxide (CO2 ) and nitrous oxide (N2 O) fluxes to (i) temperature, (ii) soil water content as percent water holding capacity (%WHC), (iii) substrate availability throughout, and (iv) multiple soil drying and rewetting (DW) events. Each of these factors and their interactions exerted effects on GHG emissions over a range of four (CO2 ) and six (N2 O) orders of magnitude. Maximal CO2 and N2 O fluxes were observed in environments combining intermediate %WHC, elevated temperature, and sufficient substrate availability. Amendments of C and N and their interactions significantly affected CO2 and N2 O fluxes and altered their temperature sensitivities (Q10 ) over successive DW cycles. C amendments significantly enhanced CO2 flux, reduced N2 O flux, and decreased the Q10 of both. N amendments had no effect on CO2 flux and increased N2 O flux, while significantly depressing the Q10 for CO2 , and having no effect on the Q10 for N2 O. The dynamics across DW cycles could be attributed to changes in soil microbial communities as the different responses to wetting events in specific group of microorganisms, to the altered substrate availabilities, or to both. The complex interactions among parameters influencing trace gas fluxes should be incorporated into next generation earth system models to improve estimation of GHG emissions. © 2015 John Wiley & Sons Ltd.
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Fritz, J I; Franke-Whittle, I H; Haindl, S; Insam, H; Braun, R
2012-07-01
Vermicompost, the digestion product of organic material by earthworms, has been widely reported to have a more positive effect on plant growth and plant health than conventional compost. A study was conducted to investigate the effects of different vermicompost elutriates (aerated compost teas) on soils and plant growth. The teas were analyzed by chemical, microbiological, and molecular methods accompanied by plant growth tests at laboratory and field scale. The number of microorganisms in the teas increased during the extraction process and was affected by substrate addition. The vermicompost tea found to increase plant growth best under laboratory tests was applied to cereals (wheat and barley) and vegetables (Raphanus sativus, Rucola selvatica, and Pisum sativum) in a field study. The results revealed no effects of tea application on plant yield; however, sensoric tests indicated an improvement in crop quality. The soils from laboratory and field studies were investigated to detect possible microbial or chemical changes. The results indicated that minor changes to the soil microbial community occurred following tea application by foliar spray in both the laboratory-scale and field-scale experiments.
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Diversity and natural functions of antibiotics produced by beneficial and plant pathogenic bacteria.
Raaijmakers, Jos M; Mazzola, Mark
2012-01-01
Soil- and plant-associated environments harbor numerous bacteria that produce antibiotic metabolites with specific or broad-spectrum activities against coexisting microorganisms. The function and ecological importance of antibiotics have long been assumed to yield a survival advantage to the producing bacteria in the highly competitive but resource-limited soil environments through direct suppression. Although specific antibiotics may enhance producer persistence when challenged by competitors or predators in soil habitats, at subinhibitory concentrations antibiotics exhibit a diversity of other roles in the life history of the producing bacteria. Many processes modulated by antibiotics may be inherently critical to the producing bacterium, such as the acquisition of substrates or initiation of developmental changes that will ensure survival under stressful conditions. Antibiotics may also have roles in more complex interactions, including in virulence on host plants or in shaping the outcomes of multitrophic interactions. The innate functions of antibiotics to producing bacteria in their native ecosystem are just beginning to emerge, but current knowledge already reveals a breadth of activities well beyond the historical perspective of antibiotics as weaponry in microbial conflicts.
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Li, Junhui; Lu, Qihong; de Toledo, Renata Alves; Lu, Ying; Shim, Hojae
2015-12-01
An indigenous Pseudomonas sp., isolated from the regional contaminated soil and identified as P. plecoglossicida, was evaluated for its aerobic cometabolic removal of cis-1,2-dichloroethylene (cis-DCE) and trichloroethylene (TCE) using toluene as growth substrate in a laboratory-scale soil slurry. The aerobic simultaneous bioremoval of the cis-DCE/TCE/toluene mixture was studied under different conditions. Results showed that an increase in toluene concentration level from 300 to 900 mg/kg prolonged the lag phase for the bacterial growth, while the bioremoval extent for cis-DCE, TCE, and toluene declined as the initial toluene concentration increased. In addition, the cometabolic bioremoval of cis-DCE and TCE was inhibited by the presence of hydrogen peroxide as the additional oxygen source, while the bioremoval of toluene (900 mg/kg) was enhanced after 9 days of incubation. The subsequent addition of toluene did not improve the cometabolic bioremoval of cis-DCE and TCE. The obtained results would help to enhance the applicability of bioremediation technology to the mixed waste contaminated sites.
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The essential role of coumarin secretion for Fe acquisition from alkaline soil
Clemens, Stephan; Weber, Michael
2016-01-01
ABSTRACT Plant productivity is limited by the scarcity of the essential micronutrient iron particularly in alkaline soils. The root secretion of phenolics has long been recognized as a component of the acidification-reduction strategy to acquire iron (strategy I). However, very little molecular insight into this process was available until recently several research groups independently discovered the important role of coumarins for the growth of Arabidopsis thaliana under Fe-limited conditions. Genome-wide analyses of iron deficiency responses, mutant screening and metabolomics experiments all converged on the finding that the synthesis and root exudation of scopoletin, esculetin and other coumarins is essential for iron uptake from substrates with low iron availability. Here we describe the evidence supporting this conclusion and discuss important questions that now have to be addressed in order to better understand the mechanistic basis of coumarin-dependent iron uptake and its significance within the plant kingdom. PMID:26618918
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Effects of substrate mineralogy on the biodegradability of fuel components
DOE Office of Scientific and Technical Information (OSTI.GOV)
Apitz, S.E.; Meyers-Schulte, K.J.
1996-11-01
Experiments were carried out to determine the effects of mineralogy on the biodegradability of components of a whole fuel by a soil microbial consortium. Samples of quartz sand (Fischer Sea Sand) and illite clay (API 35) were spiked with marine diesel fuel, aged, slurried, and inoculated, and concentrations of fuel components were monitored over time. To help distinguish biotic from abiotic processes, identical samples were poisoned with mercuric chloride and were run in parallel. While there was a chromatographic and biomarker evidence of n-alkane biodegradation in the sand samples, illite samples showed no evidence of biogenic loss of aliphatic components.more » Polycyclic aromatic hydrocarbons, on the other hand, were lost equivalently on both minerals and in both cases were lost to a much greater extent than were total petroleum hydrocarbons (TPHs). These results suggest that under experimental conditions, illite inhibited the bioavailability of some TPH components to the soil microbial consortium.« less
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Microbial control over carbon cycling in soil
Schimel, Joshua P.; Schaeffer, Sean M.
2012-01-01
A major thrust of terrestrial microbial ecology is focused on understanding when and how the composition of the microbial community affects the functioning of biogeochemical processes at the ecosystem scale (meters-to-kilometers and days-to-years). While research has demonstrated these linkages for physiologically and phylogenetically “narrow” processes such as trace gas emissions and nitrification, there is less conclusive evidence that microbial community composition influences the “broad” processes of decomposition and organic matter (OM) turnover in soil. In this paper, we consider how soil microbial community structure influences C cycling. We consider the phylogenetic level at which microbes form meaningful guilds, based on overall life history strategies, and suggest that these are associated with deep evolutionary divergences, while much of the species-level diversity probably reflects functional redundancy. We then consider under what conditions it is possible for differences among microbes to affect process dynamics, and argue that while microbial community structure may be important in the rate of OM breakdown in the rhizosphere and in detritus, it is likely not important in the mineral soil. In mineral soil, physical access to occluded or sorbed substrates is the rate-limiting process. Microbial community influences on OM turnover in mineral soils are based on how organisms allocate the C they take up – not only do the fates of the molecules differ, but they can affect the soil system differently as well. For example, extracellular enzymes and extracellular polysaccharides can be key controls on soil structure and function. How microbes allocate C may also be particularly important for understanding the long-term fate of C in soil – is it sequestered or not? PMID:23055998
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Vida, Carmen; Bonilla, Nuria; de Vicente, Antonio; Cazorla, Francisco M.
2016-01-01
This study focused on the microbial profile present in an agricultural soil that becomes suppressive after the application of composted almond shells (AS) as organic amendments. For this purpose, we analyzed the functions and composition of the complex communities present in an experimental orchard of 40-year-old avocado trees, many of them historically amended with composted almond shells. The role of microbes in the suppression of Rosellinia necatrix, the causative agent of avocado white root rot, was determined after heat-treatment and complementation experiments with different types of soil. Bacterial and fungal profiles obtained from natural soil samples based on the 16S rRNA gene and ITS sequencing revealed slight differences among the amended (AS) and unamended (CT) soils. When the soil was under the influence of composted almond shells as organic amendments, an increase in Proteobacteria and Ascomycota groups was observed, as well as a reduction in Acidobacteria and Mortierellales. Complementary to these findings, functional analysis by GeoChip 4.6 confirmed these subtle differences, mainly present in the relative abundance of genes involved in the carbon cycle. Interestingly, a group of specific probes included in the “soil benefit” category was present only in AS-amended soils, corresponding to specific microorganisms previously described as potential biocontrol agents, such as Pseudomonas spp., Burkholderia spp., or Actinobacteria. Considering the results of both analyses, we determined that AS-amendments to the soil led to an increase in some orders of Gammaproteobacteria, Betaproteobacteria, and Dothideomycetes, as well as a reduction in the abundance of Xylariales fungi (where R. necatrix is allocated). The combination of microbial action and substrate properties of suppressiveness are discussed. PMID:26834725
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Swarzenski, C.M.; Doyle, T.W.; Fry, B.; Hargis, T.G.
2008-01-01
To help evaluate effects of Mississippi River inputs to sustainability of coastal Louisiana ecosystems, we compared porewater and substrate quality of organic-rich Panicum hemitomon freshwater marshes inundated by river water annually for more than 30 years (Penchant basin, PB) or not during the same time (Barataria basin, BB). In the marshes receiving river water the soil environment was more reduced, the organic substrate was more decomposed and accumulated more sulfur. The porewater dissolved ammonium and orthophosphate concentrations were an order of magnitude higher and sulfide and alkalinity concentrations were more than twice as high in PB compared with BB marshes. The pH was higher and dissolved iron concentrations were more than an order of magnitude lower in PB marshes than in BB marshes. The influx of nutrient-rich river water did not enhance end-of-year above-ground standing biomass or vertical accretion rates of the shallow substrate. The differences in porewater chemistry and substrate quality are reasonably linked to the long-term influx of river water through biogeochemical processes and transformations involving alkalinity, nitrate and sulfate. The key factor is the continual replenishment of alkalinity, nitrate and sulfate via overland flow during high river stage each year for several weeks to more than 6 months. This leads to a reducing soil environment, pooling of the phytotoxin sulfide and inorganic nutrients in porewater, and internally generated alkalinity. Organic matter decomposition is enhanced under these conditions and root mats degraded. The more decomposed root mat makes these marshes more susceptible to erosion during infrequent high-energy events (for example hurricanes) and regular low-energy events, such as tides and the passage of weather fronts. Our findings were unexpected and, if generally applicable, suggest that river diversions may not be the beneficial mitigating agent of wetland restoration and conservation that they are anticipated to be. ?? 2008 Springer Science+Business Media B.V.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Allen, C.C.R.; Boyd, D.R.; Hempenstall, F.
The biotransformation of the polycyclic aromatic hydrocarbons (PAHs) naphthalene and phenanthrene was investigated by using two dioxygenase-expressing bacteria, Pseudomonas sp. strain 9816/11 and Sphingomonas yanoikuyae B8/36, under conditions which facilitate mass-transfer limited substrate oxidation. Both of these strains are mutants that accumulate cis-dihydrodiol metabolites under the reaction conditions used. The effects of the nonpolar solvent 2,2,4,4,6,8,8-heptamethylnonane (HMN) and the nonionic surfactant Triton X-100 on the rate of accumulation of these metabolites were determined. HMN increased the rate of accumulation of metabolites for both microorganisms, with both substrates. The enhancement effect was most noticeable with phenanthrene, which has a lower aqueousmore » solubility than naphthalene. Triton X-100 increased the rate of oxidation of the PAHs with strain 9816/11 with the effect being most noticeable when phenanthrene was used as a substrate. However, the surfactant inhibited the biotransformation of both naphthalene and phenanthrene with strain B8/36 under the same conditions. The observation that a nonionic surfactant could have such contrasting effects on PAH oxidation by different bacteria, which are known to be important for the degradation of these compounds in the environment, may explain why previous research on the application of the surfactants to PAH bioremediation has yielded inconclusive results. The surfactant inhibited growth of the wild-type strain S. yanoikuyae B1 on aromatic compounds but did not inhibit B8/36 dioxygenase enzyme activity in vitro.« less
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de Roffignac, Laure; Cattan, Philippe; Mailloux, Julie; Herzog, David; Le Bellec, Fabrice
2008-12-01
After the rinsing of spray equipment, the rinsing water contains polluting products. One way to avoid pollution is to bring the rinsing water over a purification system, a biological bed. The system consists of an impermeable tub filled with a biomix substrate that facilitates biodegradation of pesticides. Usually, straw is one component of the biomix. The objective of this study was to assess the efficiency of an unusual substrate, bagasse, a residue of sugar cane, for the degradation of three pesticides, glyphosate, malathion and lambda-cyhalothrin. Results showed that more than 99% of malathion and glyphosate were degraded in 6 months. In the biological bed, the DT(50) value for malathion was 17 days, for glyphosate 33 days and for lambda-cyhalothrin 43 days. The degradation rate of aminomethylphosphonic acid (AMPA) residues from the degradation of glyphosate was slower than that of the other pesticides (DT(50) 69 days). Finally, the innocuousness of the biomix after 6 months of degradation was confirmed by biological tests. Although the degradation rates of the three pesticides in the present bagasse-based system were similar to those under temperate conditions, the degradation conditions were improved by comparison with those in soil under the given tropical conditions. Further benefits of this system are pesticide confinement, to avoid their dispersion in the environment by liquids or solids, and a lower overall cost. Finally, possibilities for optimising the bagasse-based system (e.g. management of the water content and nature of the biomix) are discussed.
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NASA Astrophysics Data System (ADS)
Teh, Yit Arn; Silver, Whendee L.
2006-03-01
Controls on methanogenesis are often determined from laboratory incubations of soils converted to slurries. Destruction of soil structure during slurry conversion may disrupt syntrophic associations, kill methanogens, and/or alter the microsite distribution of methanogenic activity, suppressing CH4 production. The effects of slurry conversion on methanogenesis were investigated to determine if disruption of aggregate structure impacted methanogenesis, substrate utilization, and C partitioning between methanogenic pathways. Soils were collected from the tropical rain forest life zone of the Luquillo Experimental Forest, Puerto Rico, and exposed to different physical disturbances, including flooding and physical homogenization. Slurry conversion negatively impacted methanogenesis. Rates of CH4 production declined by a factor of 17 after well-aggregated soils were converted to slurries. Significantly more 13C-acetate was recovered in CO2 compared to CH4 after slurry conversion, suggesting that methanogens consumed less acetate after slurry conversion and may have competed less effectively with other anaerobes for acetate. Isotopic data indicate that the relative partitioning of C between aceticlastic and hydrogenotrophic pathways was unchanged after slurry conversion. These data suggest that experiments which destroy soil structure may significantly underestimate methanogenesis and overestimate the potential for other microorganisms to compete with methanogens for organic substrates. Current knowledge of the factors that regulate methanogenesis in soil may be biased by the findings of slurry-based experiments, that do not accurately represent the complex, spatially heterogeneous conditions found in well-aggregated soils.
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Gaylor, Michael O; Harvey, Ellen; Hale, Robert C
2013-12-03
Polybrominated diphenyl ether (PBDE) flame retardants have been used in consumer polymers at up to percent levels. While long viewed as biologically inaccessible therein, PBDEs may become bioaccessible following volatilization or polymer deterioration. PBDEs may then enter soils via polymer fragmentation or following land application of sewage sludge-derived biosolids. Studies of direct PBDE uptake from these materials by soil organisms are scarce. We thus exposed earthworms ( Eisenia fetida ) to artificial soil amended with a Class B anaerobically digested biosolid (ADB), an exceptional quality composted biosolid (CB), PBDE-containing polyurethane foam (PUF) microparticles, and Penta-BDE-spiked artificial soil (SAS). Worms accumulated mg/kg (lipid) ∑Penta-PBDE burdens from all substrates. Biota-soil accumulation factors (BSAFs) for worms exposed to ADB- and CB-amended soils were comparable after 28 d. BSAFs generally decreased with increasing congener KOW and substrate dosage. Biosolids-associated PBDE bioavailability was lower than spiked PBDEs. BSAFs for worms exposed to PUF microparticles ranged from 3.9 to 33.4, with ∑Penta-PBDE tissue burdens reaching 3740 mg/kg lipid. Congener accumulation patterns were similar in worms and polyethylene passive sampling devices immersed in ADB-amended soil coincident with exposed worms. However, passive sampler accumulation factors were lower than BSAFs. Our results demonstrate that PBDEs may accumulate in organisms ingesting soils containing biosolids or waste plastics. Such organisms may then transfer their burdens to predators or translocate them from the site of application/disposal.