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Sample records for additional soil carbon

  1. Regulation of Soil Microbial Carbon-use Efficiency by Soil Moisture, Substrate Addition, and Incubation Time

    NASA Astrophysics Data System (ADS)

    Stark, J.

    2015-12-01

    Microbial carbon-use efficiency (CUE) is a key variable in biogeochemical cycling that regulates soil C sequestration, greenhouse gas emissions, and retention of inorganic nutrients. Microbial CUE is the fraction of C converted to biomass rather than respired as CO2. Biogeochemical models have been shown to be highly sensitive to variation in CUE; however, we currently have a poor understanding of how CUE responds to environmental variables such as soil moisture and nutrient limitations. We examined the effect of soil moisture and C supply on CUE in soil from a western hemlock / sitka spruce forest in Oregon, USA, using a novel technique which supplies 13C and 15N substrates through the gas phase so that water addition is not necessary. Soil samples (28 g oven-dry equiv. wt) at two water potentials (-0.03 and -3.55 MPa) were exposed to 13C-acetic acid vapor for either 6 or 30 sec to provide two different concentrations of acetate to soil microbial communities. The soils were also injected with small amounts of 15NH3 gas to allow quantification of microbial N assimilation rates and to provide an alternate method of calculating CUE. Rates of 13CO2 respiration were measured continuously during a 48-h incubation using cavity ring-down spectroscopy. Soil samples were extracted at seven time intervals (0, 0.5, 1.5, 4.5, 12, 24, and 48 h) in 0.5 M K2SO4 and analyzed for DO13C, microbial 13C, DO15N, inorganic 15N, and microbial 15N to calculate how gross rates of C and N assimilation and microbial CUE change with incubation time. As expected, microbial C and N assimilation rates and CUE increased with soil moisture and the quantity of acetate added; however, C:N assimilated was higher at lower soil moisture, suggesting that either C-storage compounds were being created, or that fungal communities were responsible for a greater proportion of the assimilation in drier soils. Assimilation rates and CUE also changed with incubation time, demonstrating that estimates of CUE

  2. Turnover of soil carbon pools following addition of switchgrass-derived biochar to four soils

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The amendment of soils with biochar may improve plant growth and sequester carbon, especially in marginal soils not suitable for the majority of commodity production. While biochar can persist in soils, it is not clear whether its persistence is affected by soil type. Moreover, we know little of how...

  3. Soil microbial community structure and nitrogen cycling responses to agroecosystem management and carbon substrate addition

    NASA Astrophysics Data System (ADS)

    Berthrong, S. T.; Buckley, D. H.; Drinkwater, L. E.

    2011-12-01

    Fertilizer application in conventional agriculture leads to N saturation and decoupled soil C and N cycling, whereas organic practices, e.g. complex rotations and legume incorporation, often results in increased SOM and tightly coupled cycles of C and N. These legacy effects of management on soils likely affect microbial community composition and microbial process rates. This project tested if agricultural management practices led to distinct microbial communities and if those communities differed in ability to utilize labile plant carbon substrates and to produce more plant available N. We addressed several specific questions in this project. 1) Do organic and conventional management legacies on similar soils produce distinct soil bacterial and fungal community structures and abundances? 2) How do these microbial community structures change in response to carbon substrate addition? 3) How do the responses of the microbial communities influence N cycling? To address these questions we conducted a laboratory incubation of organically and conventionally managed soils. We added C-13 labelled glucose either in one large dose or several smaller pulses. We extracted genomic DNA from soils before and after incubation for TRFLP community fingerprinting. We measured C in soil pools and respiration and N in soil extracts and leachates. Management led to different compositions of bacteria and fungi driven by distinct components in organic soils. Biomass did not differ across treatments indicating that differences in cycling were due to composition rather than abundance. C substrate addition led to convergence in bacterial communities; however management still strongly influenced the difference in communities. Fungal communities were very distinct between managements and plots with substrate addition not altering this pattern. Organic soils respired 3 times more of the glucose in the first week than conventional soils (1.1% vs 0.4%). Organic soils produced twice as much

  4. Soil carbon sequestration in semi-arid soil through the addition of fuel gas desulfurization gypsum (FGDG)

    NASA Astrophysics Data System (ADS)

    Han, Young-Soo; Tokunaga, Tetsu; Oh, Chamteut

    2014-05-01

    This study investigated a new strategy for increasing carbon retention in slightly alkaline soils through addition of fuel gas desulfurization gypsum (FGDG, CaSO4•2H2O). FGDG is moderately soluble and thus the FGDG amendment may be effective to reduce microbial respiration, to accelerate calcite (CaCO3) precipitation, and to promote soil organic carbon (SOC) complexation on mineral surfaces, but rates of these processes need to be understood. The effects of FGDG addition were tested in laboratory soil columns with and without FGDG-amended layers, and in greenhouse soil columns planted with switchgrass, a biofuel crop. The results of laboratory column experiments demonstrated that additions of FGDG promote soil carbon sequestration through suppressing microbial respiration to the extent of ~200 g per m2 soil per m of supplied water, and promoting calcite precipitation at similar rates. The greenhouse experiments showed that the FGDG treatments did not adversely affect biomass yield (~600 g dry biomass/m2/harvest) at the higher irrigation rate (50 cm/year), but substantially reduced recoverable biomass under the more water-limited conditions (irrigation rate = 20 cm/year). The main achievements of this study are (1) the identification of conditions in which inorganic and organic carbon sequestration is practical in semi-arid and arid soils, (2) development of a method for measuring the total carbon balance in unsaturated soil columns, and (3) the quantification of different pathways for soil carbon sequestration in response to FGDG amendments. These findings provide information for evaluating land use practices for increased soil carbon sequestration under semi-arid region biofuel crop production.

  5. Charcoal addition to soils in NE England: a carbon sink with environmental co-benefits?

    PubMed

    Bell, M J; Worrall, F

    2011-04-01

    Interest in the application of biochar (charcoal produced during the pyrolysis of biomass) to agricultural land is increasing across the world, recognised as a potential way to capture and store atmospheric carbon. Its interest is heightened by its potential co-benefits for soil quality and fertility. The majority of research has however been undertaken in tropical rather than temperate regions. This study assessed the potential for lump-wood charcoal addition (as a substitute for biochar) to soil types which are typically under arable and forest land-use in North East England. The study was undertaken over a 28 week period and found: i) No significant difference in net ecosystem respiration (NER) between soils containing charcoal and those without, other than in week 1 of the trial. ii) A significantly higher dissolved organic carbon (DOC) flux from soils containing large amounts of charcoal than from those untreated, when planted with ryegrass. iii) That when increased respiration or DOC loss did occur, neither was sufficiently large to alter the carbon sink benefits of charcoal application. iv) That charcoal incorporation resulted in a significantly lower nitrate flux in soil leachate from mineral soils. v) That charcoal incorporation caused significant increases in soil pH, from 6.98 to 7.22 on bare arable soils when 87,500 kg charcoal/ha was applied. Consideration of both the carbon sink and environmental benefits observed here suggests that charcoal application to temperate soils typical of North East England should be considered as a method of carbon sequestration. Before large scale land application is encouraged, further large scale trials should be undertaken to confirm the positive results of this research.

  6. Nutrient additions to a tropical rain forest drive substantial soil carbon dioxide losses to the atmosphere

    PubMed Central

    Cleveland, Cory C.; Townsend, Alan R.

    2006-01-01

    Terrestrial biosphere–atmosphere carbon dioxide (CO2) exchange is dominated by tropical forests, where photosynthetic carbon (C) uptake is thought to be phosphorus (P)-limited. In P-poor tropical forests, P may also limit organic matter decomposition and soil C losses. We conducted a field-fertilization experiment to show that P fertilization stimulates soil respiration in a lowland tropical rain forest in Costa Rica. In the early wet season, when soluble organic matter inputs to soil are high, P fertilization drove large increases in soil respiration. Although the P-stimulated increase in soil respiration was largely confined to the dry-to-wet season transition, the seasonal increase was sufficient to drive an 18% annual increase in CO2 efflux from the P-fertilized plots. Nitrogen (N) fertilization caused similar responses, and the net increases in soil respiration in response to the additions of N and P approached annual soil C fluxes in mid-latitude forests. Human activities are altering natural patterns of tropical soil N and P availability by land conversion and enhanced atmospheric deposition. Although our data suggest that the mechanisms driving the observed respiratory responses to increased N and P may be different, the large CO2 losses stimulated by N and P fertilization suggest that knowledge of such patterns and their effects on soil CO2 efflux is critical for understanding the role of tropical forests in a rapidly changing global C cycle. PMID:16793925

  7. Design of a Soil Science practical exercise to understand the soil carbon sequestration after biochar addition

    NASA Astrophysics Data System (ADS)

    Gascó, Gabriel; Cely, Paola; Saa-Requejo, Antonio; Mendez, Ana; Antón, Jose Manuel; Sánchez, Elena; Moratiel, Ruben; Tarquis, Ana M.

    2014-05-01

    The adaptation of the Universities to European Higher Education Area (EHEA) involves changes in the learning system. Students must obtain specific capabilities in the different degrees or masters. For example, in the degree of Agronomy at the Universidad Politécnica de Madrid (UPM, Spain), they must command Soil science, Mathematics or English. Sometimes, There is not a good communication between teachers and it causes that students do not understand the importance of the different subjects of a career. For this reason, teachers of the Soil Science and Mathematics Departments of the UPM designed a common practice to teach to the students the role of soil on the carbon sequestration. The objective of this paper is to explain the followed steps to the design of the practice. Acknowledgement to Universidad Politécnica de Madrid for the Projects in Education Innovation IE12_13-02009 and IE12_13-02012.

  8. Soil carbon sequestration in prairie grasslands increased by chronic nitrogen addition.

    PubMed

    Fornara, Dario A; Tilman, David

    2012-09-01

    Human-induced increases in nitrogen (N) deposition are common across many terrestrial ecosystems worldwide. Greater N availability not only reduces biological diversity, but also affects the biogeochemical coupling of carbon (C) and N cycles in soil ecosystems. Soils are the largest active terrestrial C pool and N deposition effects on soil C sequestration or release could have global importance. Here, we show that 27 years of chronic N additions to prairie grasslands increased C sequestration in mineral soils and that a potential mechanism responsible for this C accrual was an N-induced increase in root mass. Greater soil C sequestration followed a dramatic shift in plant community composition from native-species-rich C4 grasslands to naturalized-species-rich C3 grasslands, which, despite lower soil C gains per unit of N added, still acted as soil C sinks. Since both high plant diversity and elevated N deposition may increase soil C sequestration, but N deposition also decreases plant diversity, more research is needed to address the long-term implications for soil C storage of these two factors. Finally, because exotic C3 grasses often come to dominate N-enriched grasslands, it is important to determine if such N-dependent soil C sequestration occurs across C3 grasslands in other regions worldwide.

  9. Plant interspecific differences in arbuscular mycorrhizal colonization as a result of soil carbon addition.

    PubMed

    Eschen, René; Müller-Schärer, Heinz; Schaffner, Urs

    2013-01-01

    Soil nutrient availability and colonization by arbuscular mycorrhizal fungi are important and potentially interacting factors shaping vegetation composition and succession. We investigated the effect of carbon (C) addition, aimed at reducing soil nutrient availability, on arbuscular mycorrhizal colonization. Seedlings of 27 plant species with different sets of life-history traits (functional group affiliation, life history strategy and nitrophilic status) were grown in pots filled with soil from a nutrient-rich set-aside field and amended with different amounts of C. Mycorrhizal colonization was progressively reduced along the gradient of increasing C addition in 17 out of 27 species, but not in the remaining species. Grasses had lower colonization levels than forbs and legumes and the decline in AM fungal colonization was more pronounced in legumes than in other forbs and grasses. Mycorrhizal colonization did not differ between annual and perennial species, but decreased more rapidly along the gradient of increasing C addition in plants with high Ellenberg N values than in plants with low Ellenberg N values. Soil C addition not only limits plant growth through a reduction in available nutrients, but also reduces mycorrhizal colonization of plant roots. The effect of C addition on mycorrhizal colonization varies among plant functional groups, with legumes experiencing an overproportional reduction in AM fungal colonization along the gradient of increasing C addition. We therefore propose that for a better understanding of vegetation succession on set-aside fields one may consider the interrelationship between plant growth, soil nutrient availability and mycorrhizal colonization of plant roots.

  10. Carbon flux from plants to soil microbes is highly sensitive to nitrogen addition and biochar amendment

    NASA Astrophysics Data System (ADS)

    Kaiser, C.; Solaiman, Z. M.; Kilburn, M. R.; Clode, P. L.; Fuchslueger, L.; Koranda, M.; Murphy, D. V.

    2012-04-01

    The release of carbon through plant roots to the soil has been recognized as a governing factor for soil microbial community composition and decomposition processes, constituting an important control for ecosystem biogeochemical cycles. Moreover, there is increasing awareness that the flux of recently assimilated carbon from plants to the soil may regulate ecosystem response to environmental change, as the rate of the plant-soil carbon transfer will likely be affected by increased plant C assimilation caused by increasing atmospheric CO2 levels. What has received less attention so far is how sensitive the plant-soil C transfer would be to possible regulations coming from belowground, such as soil N addition or microbial community changes resulting from anthropogenic inputs such as biochar amendments. In this study we investigated the size, rate and sensitivity of the transfer of recently assimilated plant C through the root-soil-mycorrhiza-microbial continuum. Wheat plants associated with arbuscular mycorrhizal fungi were grown in split-boxes which were filled either with soil or a soil-biochar mixture. Each split-box consisted of two compartments separated by a membrane which was penetrable for mycorrhizal hyphae but not for roots. Wheat plants were only grown in one compartment while the other compartment served as an extended soil volume which was only accessible by mycorrhizal hyphae associated with the plant roots. After plants were grown for four weeks we used a double-labeling approach with 13C and 15N in order to investigate interactions between C and N flows in the plant-soil-microorganism system. Plants were subjected to an enriched 13CO2 atmosphere for 8 hours during which 15NH4 was added to a subset of split-boxes to either the root-containing or the root-free compartment. Both, 13C and 15N fluxes through the plant-soil continuum were monitored over 24 hours by stable isotope methods (13C phospho-lipid fatty acids by GC-IRMS, 15N/13C in bulk plant

  11. Plant-Soil Relationships of Bromus tectorum L.: Interactions among Labile Carbon Additions, Soil Invasion Status, and Fertilizer.

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Invasion of western North America by the annual exotic grass Bromus tectorum L. (cheatgrass) has been an ecological disaster. High soil bioavailability of nitrogen is a contributing factor in the invasive potential of B. tectorum. Application of labile carbon sources to the soil can immobilize soil ...

  12. Soil respiration characteristics in different land uses and response of soil organic carbon to biochar addition in high-latitude agricultural area.

    PubMed

    Ouyang, Wei; Geng, Xiaojun; Huang, Wejia; Hao, Fanghua; Zhao, Jinbo

    2016-02-01

    The farmland tillage practices changed the soil chemical properties, which also impacted the soil respiration (R s ) process and the soil carbon conservation. Originally, the farmland in northeast China had high soil carbon content, which was decreased in the recent decades due to the tillage practices. To better understand the R s dynamics in different land use types and its relationship with soil carbon loss, soil samples at two layers (0-15 and 15-30 cm) were analyzed for organic carbon (OC), total nitrogen (TN), total phosphorus (TP), total carbon (TC), available nitrogen (AN), available phosphorus (AP), soil particle size distribution, as well as the R s rate. The R s rate of the paddy land was 0.22 (at 0-15 cm) and 3.01 (at 15-30 cm) times of the upland. The average concentrations of OC and clay content in cultivated areas were much lower than in non-cultivated areas. The partial least squares analysis suggested that the TC and TN were significantly related to the R s process in cultivated soils. The upland soil was further used to test soil CO2 emission response at different biochar addition levels during 70-days incubation. The measurement in the limited incubation period demonstrated that the addition of biochar improved the soil C content because it had high concentration of pyrogenic C, which was resistant to mineralization. The analysis showed that biochar addition can promote soil OC by mitigating carbon dioxide (CO2) emission. The biochar addition achieved the best performance for the soil carbon conservation in high-latitude agricultural area due to the originally high carbon content.

  13. Soil respiration characteristics in different land uses and response of soil organic carbon to biochar addition in high-latitude agricultural area.

    PubMed

    Ouyang, Wei; Geng, Xiaojun; Huang, Wejia; Hao, Fanghua; Zhao, Jinbo

    2016-02-01

    The farmland tillage practices changed the soil chemical properties, which also impacted the soil respiration (R s ) process and the soil carbon conservation. Originally, the farmland in northeast China had high soil carbon content, which was decreased in the recent decades due to the tillage practices. To better understand the R s dynamics in different land use types and its relationship with soil carbon loss, soil samples at two layers (0-15 and 15-30 cm) were analyzed for organic carbon (OC), total nitrogen (TN), total phosphorus (TP), total carbon (TC), available nitrogen (AN), available phosphorus (AP), soil particle size distribution, as well as the R s rate. The R s rate of the paddy land was 0.22 (at 0-15 cm) and 3.01 (at 15-30 cm) times of the upland. The average concentrations of OC and clay content in cultivated areas were much lower than in non-cultivated areas. The partial least squares analysis suggested that the TC and TN were significantly related to the R s process in cultivated soils. The upland soil was further used to test soil CO2 emission response at different biochar addition levels during 70-days incubation. The measurement in the limited incubation period demonstrated that the addition of biochar improved the soil C content because it had high concentration of pyrogenic C, which was resistant to mineralization. The analysis showed that biochar addition can promote soil OC by mitigating carbon dioxide (CO2) emission. The biochar addition achieved the best performance for the soil carbon conservation in high-latitude agricultural area due to the originally high carbon content. PMID:26408119

  14. Stabilization and Destabilization of Soil Carbon with Nitrogen Additions in Two Tropical Forests

    NASA Astrophysics Data System (ADS)

    Cusack, D. F.; Silver, W.; Torn, M.; McDowell, W. H.

    2008-12-01

    Nitrogen (N) deposition is known to effect carbon (C) cycling in temperate ecosystems, but less is known about the effects of added N in tropical forests, where N is not generally limiting to plant growth. We examined changes in soil C dynamics with N fertilization in two tropical forest types (lower elevation and montane) in the Luquillo Mountains, Puerto Rico. We hypothesized that increased N would accelerate the decomposition of labile C pools, while decreasing losses of more recalcitrant C compounds. We measured C and C:N in bulk soil C and C fractions (free light, occluded light, and heavy fractions) as measures of C content and chemical properties in fertilized and control plots. To address our hypotheses, we conducted several measures of microbial activity, including extracellular enzyme activities and respiration during a long-term soil incubation. We included measurements of 14C of CO2 respired during the soil incubation to determine whether added N changed the age of respired C. After 3.5 years of N fertilization, plots with added N had higher C content (42.3 ± 6.8 and 40.7 ± 4.7 g/cm2, lower elevation and montane respectively) than control plots (34.2 ± 5.9 and 34.3 ± 1.3 g/cm2) at 0 - 10 cm depth. While the labile fraction of C declined with added N as a proportion of total soil weight, the C concentration of the heavy fraction increased in fertilized plots (2.9 ± 0.3 and 4.0 ± 0.7%) relative to control plots (2.6 ± 0.4 and 2.8 ± 0.5 %), helping explain the increase in bulk soil C content. The soil incubation revealed changes in microbial respiration with added N, and a trend toward higher 14C of CO2 in fertilized plots for the lower elevation forest. Together, these results indicate that rates of C stabilization in the heavy fraction exceeded the increase in respiration of older C with N additions.

  15. Enhancement of carbon sequestration in soil in the temperature grasslands of northern China by addition of nitrogen and phosphorus.

    PubMed

    He, Nianpeng; Yu, Qiang; Wang, Ruomeng; Zhang, Yunhai; Gao, Yang; Yu, Guirui

    2013-01-01

    Increased nitrogen (N) deposition is common worldwide. Questions of where, how, and if reactive N-input influences soil carbon (C) sequestration in terrestrial ecosystems are of great concern. To explore the potential for soil C sequestration in steppe region under N and phosphorus (P) addition, we conducted a field experiment between 2006 and 2012 in the temperate grasslands of northern China. The experiment examined 6 levels of N (0-56 g N m(-2) yr(-1)), 6 levels of P (0-12.4 g P m(-2) yr(-1)), and a control scenario. Our results showed that addition of both N and P enhanced soil total C storage in grasslands due to significant increases of C input from litter and roots. Compared with control plots, soil organic carbon (SOC) in the 0-100 cm soil layer varied quadratically, from 156.8 to 1352.9 g C m(-2) with N addition gradient (R(2) = 0.99, P < 0.001); and logarithmically, from 293.6 to 788.6 g C m(-2) with P addition gradient (R(2) = 0.56, P = 0.087). Soil inorganic carbon (SIC) decreased quadratically with N addition. The net C sequestration on grassland (including plant, roots, SIC, and SOC) increased linearly from -128.6 to 729.0 g C m(-2) under N addition (R(2) = 0.72, P = 0.023); and increased logarithmically, from 248.5 to 698 g C m(-2)under P addition (R(2) = 0.82, P = 0.014). Our study implies that N addition has complex effects on soil carbon dynamics, and future studies of soil C sequestration on grasslands should include evaluations of both SOC and SIC under various scenarios.

  16. Successful implementation of biochar carbon sequestration in European soils requires additional benefits and close collaboration with the bioenergy sector

    NASA Astrophysics Data System (ADS)

    Hauggaard-Nielsen, Henrik; Müller-Stöver, Dorette; Bruun, Esben W.; Petersen, Carsten T.

    2014-05-01

    Biochar soil application has been proposed as a measure to mitigate climate change and on the same time improve soil fertility by increased soil carbon sequestration. However, while on tropical soils the beneficial effects of biochar application on crop growth often become immediately apparent, it has been shown to be more difficult to demonstrate these effects on the more fertile soils in temperate regions. Therefore and because of the lack of carbon credits for farmers, it is necessary to link biochar application to additional benefits, both related to agricultural as well as to bioenergy production. Thermal gasification of biomass is an efficient (95% energy efficiency) and flexible way (able to cope with many different and otherwise difficult-to-handle biomass fuels) to generate bioenergy, while producing a valuable by-product - gasification biochar, containing recalcitrant carbon and essential crop nutrients. The use of the residual char product in agricultural soils will add value to the technology as well as result in additional soil benefits such as providing plant nutrients and improving soil water-holding capacity while reducing leaching risks. From a soil column (30 x 130 cm) experiment with gasification straw biochar amendment to coarse sandy subsoil increased root density of barley at critical depths in the soil profile reducing the mechanical resistance was shown, increasing yields, and the soil's capacity to store plant available water. Incorporation of residuals from a bioenergy technology like gasification show great potentials to reduce subsoil constraints increasing yield potentials on poor soils. Another advantage currently not appropriately utilized is recovery of phosphorus (P). In a recent pot experiments char products originating from low-temperature gasification of various biofuels were evaluated for their suitability as P fertilizers. Wheat straw gasification biochar generally had a low P content but a high P plant availability. To improve

  17. Carbon stabilization and microbial growth in acidic mine soils after addition of different amendments for soil reclamation

    NASA Astrophysics Data System (ADS)

    Zornoza, Raúl; Acosta, Jose; Ángeles Muñoz, María; Martínez-Martínez, Silvia; Faz, Ángel; Bååth, Erland

    2016-04-01

    The extreme soil conditions in metalliferous mine soils have a negative influence on soil biological activity and therefore on soil carbon estabilization. Therefore, amendments are used to increase organic carbon content and activate microbial communities. In order to elucidate some of the factors controlling soil organic carbon stabilization in reclaimed acidic mine soils and its interrelationship with microbial growth and community structure, we performed an incubation experiment with four amendments: pig slurry (PS), pig manure (PM) and biochar (BC), applied with and without marble waste (MW; CaCO3). Results showed that PM and BC (alone or together with MW) contributed to an important increment in recalcitrant organic C, C/N ratio and aggregate stability. Bacterial and fungal growths were highly dependent on pH and labile organic C. PS supported the highest microbial growth; applied alone it stimulated fungal growth, and applied with MW it stimulated bacterial growth. BC promoted the lowest microbial growth, especially for fungi, with no significant increase in fungal biomass. MW+BC increased bacterial growth up to values similar to PM and MW+PM, suggesting that part of the biochar was degraded, at least in short-term mainly by bacteria rather than fungi. PM, MW+PS and MW+PM supported the highest microbial biomass and a similar community structure, related with the presence of high organic C and high pH, with immobilization of metals and increased soil quality. BC contributed to improved soil structure, increased recalcitrant organic C, and decreased metal mobility, with low stimulation of microbial growth.

  18. The effects of fire severity on black carbon additions to forest soils - 10 years post fire

    NASA Astrophysics Data System (ADS)

    Poore, R.; Wessman, C. A.; Buma, B.

    2013-12-01

    Wildfires play an active role in the global carbon cycle. While large amounts of carbon dioxide are released, a small fraction of the biomass consumed by the fire is only partially combusted, yielding soot and charcoal. These products, also called black carbon (BC) make up only 1-5% of the biomass burnt, yet they can have a disproportionate effect on both the atmosphere and fluxes in long-term carbon pools. This project specifically considers the fraction that is sequestered in forest soils. Black carbon is not a specific compound, and exists along a continuum ranging from partially burned biomass to pure carbon or graphite. Increasing aromaticity as the result of partial combustion means charcoal is highly resistant to oxidation. Although debated, most studies indicate a turnover time on the order of 500-1,000 years in warm, wet, aerobic soils. Charcoal may function as a long-term carbon sink, however its overall significance depends on its rate of formation and loss. At the landscape level, fire characteristics are one of the major factors controlling charcoal production. A few studies suggest that charcoal production increases with cooler, less-severe fires. However, there are many factors to tease apart, partly because of a lack of specificity in how fire severity is defined. Within this greater context, our lab has been working on a landscape-level study within Routt National Forest, north of Steamboat Springs, Colorado. In 2002, a large fire swept through a subalpine spruce, fir and lodgepole pine forest. In 2011-2013 we sampled BC pools in 44 plots across a range of fire severities from unburned to severe crown We hypothesized that charcoal stocks will be higher in areas of low severity fire as compared to high severity because of decreased re-combustion of charcoal in the organic soil and increased overall charcoal production due to lower temperatures. In each of our plots we measured charcoal on snags and coarse woody debris, sampled the entire organic

  19. Artificial stimulation of soil amine production by addition of organic carbon and nitrogen transforming enzymes

    NASA Astrophysics Data System (ADS)

    Kieloaho, Antti-Jussi; Parshintsev, Jevgeni; Riekkola, Marja-Liisa; Kulmala, Markku; Pumpanen, Jukka; Heinonsalo, Jussi

    2013-04-01

    The major part of nitrogen (N) in boreal forest soil is in organic form (Soil Organic Nitrogen, SON). One of the main pathways for amine production is the decay of SON in soil. Amino acids react with specific decarboxylase enzymes which transform them to amines. Amino acid turnover time in forest soil is relatively fast (in hours) because amino acids can be used as N and C source by plants and microbes. Therefore, amino acid production by protease enzymes might be the critical step for amine production and release from forest soil. The aim of the study was to artificially introduce enzymes responsible for protein transformation into amino acids (proteases) as well as soil organic matter (SOM) decomposition (laccase and manganese peroxidase) in order to increase SON transformation and amine synthesis. Glucose addition has been shown to induce natural soil protease activity. Bovine serum albumin (BSA) was used as control protein. Treatments were conducted both in Scots pine seedlings containing as well as non-planted microcosms. N transformations were examined, as well as amine concentration in soil. The experiment consisted of eight different treatments; two as controls concerning enzyme addition, four treatments were planted with one year old nursery grown Scots pine (Pinus sylvestris L.) seedlings and four were non-planted. The experiment lasted approximately six months and the treatments with the additions were conducted within one more month. The protease activity was discovered more commonly after the treatment with protease or glucose additions. In planted BSA-control some natural protease activity was found but not in non-planted controls. Different substrate additions did not cause any differences in total N percentage, but the presence of the seedlings diminished soil N% by approximately 20%. In addition, the same effect was clearly seen in dissolved N, NH4+ and NO3-. Plant has exploited the soluble N forms almost entirely from the system, irrespective of

  20. Increased loss of soil-derived carbon in response to litter addition and temperature

    NASA Astrophysics Data System (ADS)

    Creamer, C.; Krull, E. S.; Sanderman, J.; Farrell, M.

    2013-12-01

    In order to predict the response of soil organic matter (SOM) to increasing temperatures, a mechanistic understanding of the interactions between OM quality, OM availability, and microbial community structure and function is needed. We used short-term incubations of 13C enriched (20 atom%) fresh and pre-incubated eucalyptus leaf litter in an Australian woodland soil to determine changes in allocation of C to various OM pools, as dictated by microbial activity, in response to temperature and substrate quality. The quantity and isotopic composition of microbial phospholipid fatty acids (PLFA) and dissolved organic C (DOC) were measured along with the quantity of dissolved inorganic and organic nitrogen at four destructive time points. The quantity and isotopic composition of respired CO2 was measured throughout the incubation. Although the temperature sensitivities of the two litters were similar (despite different chemical compositions), soil-C was significantly more temperature sensitive than litter-C. We also observed negative priming of soil-C in the fresh litter treatment and positive priming of soil-C in the pre-incubated litter treatment relative to the control (no litter addition). The extent of positive priming in the pre-incubated litter treatment also increased significantly with temperature. The quantity of soil-derived DOC was consistent between both litter treatments and the control, confirming that differences in soil-C availability were not controlling the observed differences in soil-C mineralization. In contrast, dissolved N was significantly higher in the pre-incubated litter treatment and increased with temperature, suggesting enhanced SOM decomposition in the pre-incubated litter treatment resulted in greater N cycling, production, or destabilization from SOM. The pre-incubated litter treatment also had greater proportions of PLFA that predominately cycled soil-derived OM (gram-positive bacteria), and increased in response to elevated temperature

  1. Effects of substrate addition on soil respiratory carbon release under long-term warming and clipping in a tallgrass prairie.

    PubMed

    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

  2. Effects of substrate addition on soil respiratory carbon release under long-term warming and clipping in a tallgrass prairie.

    PubMed

    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.

  3. The response of soil organic matter decomposition and carbon cycling to temperature increase and nitrogen addition

    NASA Astrophysics Data System (ADS)

    Choi, I.; Kang, M.; Choi, J.

    2012-12-01

    Global warming caused by greenhouse effects has raised the worldwide air temperature by 1.4~5.8°C from the pre-industrial level. It has been known that the enhanced air temperature leads to increase the rate of soil organic matter decomposition. The enhanced soil organic matter decomposition could increase the emission of GHG (Green House Gas-mostly CO2, CH4) from the terrestrial ecosystem. GHG emission from the decomposition of soil organic matter can be affected by N deposition. N deposition of Asia has significantly grown from 1000mg N m2yr-1 to 2000mg N m2yr-1during the period of 1990s. It is expected that large area of South and East Asia will receive as large as 5000mg N m2yr-1of nitrogen in the future. Therefore, it is interesting to investigate the effects of global change factors, such as elevated temperature and N deposition on GHG emission from the terrestrial ecosystem. Growth chamber experiments were conducted under the enhanced air temperature and N addition (controlled at 10°C(30°C), 20°C(40°C) from ambient air temperature 18°C/23°C(day/night)) and GHG(CH4,CO2)was measured using gas chromatograph. Since combined changes in temperature and N deposition are sensitive to litter quantity and quality, especially C:N ratio of organic material, we select three sites with different C:N ratio (rice paddy, forest, wetland) in the southern part of Han river in Korea. Our results show that, for the case of rice paddy and forest, CO2 flux at 30°C was higher than at 40°C. However, wetland soil produces higher CO2 flux at 40°C than at 30°C. While CH4 flux was not detected at 30°C for all of three soils, only wetland soil produced CH4 flux at 40°C. Every flux under the condition of N addition was higher than that of N limitation. The GHG fluxes clearly related to the temperature, N concentration difference and soil types. Long term laboratory experiments are needed in three different soil types to determine how different soil type affects GHG by

  4. Biofuels from pyrolysis in perspective: trade-offs between energy yields and soil-carbon additions.

    PubMed

    Woolf, Dominic; Lehmann, Johannes; Fisher, Elizabeth M; Angenent, Largus T

    2014-06-01

    Coproduction of biofuels with biochar (the carbon-rich solid formed during biomass pyrolysis) can provide carbon-negative bioenergy if the biochar is sequestered in soil, where it can improve fertility and thus simultaneously address issues of food security, soil degradation, energy production, and climate change. However, increasing biochar production entails a reduction in bioenergy obtainable per unit biomass feedstock. Quantification of this trade-off for specific biochar-biofuel pathways has been hampered by lack of an accurate-yet-simple model for predicting yields, product compositions, and energy balances from biomass slow pyrolysis. An empirical model of biomass slow pyrolysis was developed and applied to several pathways for biochar coproduction with gaseous and liquid biofuels. Here, we show that biochar production reduces liquid biofuel yield by at least 21 GJ Mg(-1) C (biofuel energy sacrificed per unit mass of biochar C), with methanol synthesis giving this lowest energy penalty. For gaseous-biofuel production, the minimum energy penalty for biochar production is 33 GJ Mg(-1) C. These substitution rates correspond to a wide range of Pareto-optimal system configurations, implying considerable latitude to choose pyrolysis conditions to optimize for desired biochar properties or to modulate energy versus biochar yields in response to fluctuating price differentials for the two commodities.

  5. Responses of soil respiration to elevated carbon dioxide and nitrogen addition in young subtropical forest ecosystems in China

    NASA Astrophysics Data System (ADS)

    Deng, Q.; Zhou, G.; Liu, J.; Liu, S.; Duan, H.; Zhang, D.

    2010-01-01

    Global climate change in the real world always exhibits simultaneous changes in multiple factors. Prediction of ecosystem responses to multi-factor global changes in a future world strongly relies on our understanding of their interactions. However, it is still unclear how nitrogen (N) deposition and elevated atmospheric carbon dioxide concentration [CO2] would interactively influence forest floor soil respiration in subtropical China. We assessed the main and interactive effects of elevated [CO2] and N addition on soil respiration by growing tree seedlings in ten large open-top chambers under CO2 (ambient CO2 and 700 μmol mol-1) and nitrogen (ambient and 100 kg N ha-1 yr-1) treatments. Soil respiration, soil temperature and soil moisture were measured for 30 months, as well as above-ground biomass, root biomass and soil organic matter (SOM). Results showed that soil respiration displayed strong seasonal patterns with higher values observed in the wet season (April-September) and lower values in the dry season (October-March) in all treatments. Significant exponential relationships between soil respiration rates and soil temperatures, as well as significant linear relationships between soil respiration rates and soil moistures (below 15%) were found. Both CO2 and N treatments significantly affected soil respiration, and there was significant interaction between elevated [CO2] and N addition (p<0.001, p=0.003, and p=0.006, respectively). We also observed that the stimulatory effect of individual elevated [CO2] (about 29% increased) was maintained throughout the experimental period. The positive effect of N addition was found only in 2006 (8.17% increased), and then had been weakened over time. Their combined effect on soil respiration (about 50% increased) was greater than the impact of either one alone. Mean value of annual soil respiration was 5.32 ± 0.08, 4.54 ± 0.10, 3.56 ± 0.03 and 3.53 ± 0.03 kg CO2 m-2 yr-1 in the chambers exposed to elevated [CO2] and

  6. Seasonality, Rather than Nutrient Addition or Vegetation Types, Influenced Short-Term Temperature Sensitivity of Soil Organic Carbon Decomposition

    PubMed Central

    He, Feng-Peng; Wang, Wei

    2016-01-01

    The response of microbial respiration from soil organic carbon (SOC) decomposition to environmental changes plays a key role in predicting future trends of atmospheric CO2 concentration. However, it remains uncertain whether there is a universal trend in the response of microbial respiration to increased temperature and nutrient addition among different vegetation types. In this study, soils were sampled in spring, summer, autumn and winter from five dominant vegetation types, including pine, larch and birch forest, shrubland, and grassland, in the Saihanba area of northern China. Soil samples from each season were incubated at 1, 10, and 20°C for 5 to 7 days. Nitrogen (N; 0.035 mM as NH4NO3) and phosphorus (P; 0.03 mM as P2O5) were added to soil samples, and the responses of soil microbial respiration to increased temperature and nutrient addition were determined. We found a universal trend that soil microbial respiration increased with increased temperature regardless of sampling season or vegetation type. The temperature sensitivity (indicated by Q10, the increase in respiration rate with a 10°C increase in temperature) of microbial respiration was higher in spring and autumn than in summer and winter, irrespective of vegetation type. The Q10 was significantly positively correlated with microbial biomass and the fungal: bacterial ratio. Microbial respiration (or Q10) did not significantly respond to N or P addition. Our results suggest that short-term nutrient input might not change the SOC decomposition rate or its temperature sensitivity, whereas increased temperature might significantly enhance SOC decomposition in spring and autumn, compared with winter and summer. PMID:27070782

  7. Seasonality, Rather than Nutrient Addition or Vegetation Types, Influenced Short-Term Temperature Sensitivity of Soil Organic Carbon Decomposition.

    PubMed

    Qian, Yu-Qi; He, Feng-Peng; Wang, Wei

    2016-01-01

    The response of microbial respiration from soil organic carbon (SOC) decomposition to environmental changes plays a key role in predicting future trends of atmospheric CO2 concentration. However, it remains uncertain whether there is a universal trend in the response of microbial respiration to increased temperature and nutrient addition among different vegetation types. In this study, soils were sampled in spring, summer, autumn and winter from five dominant vegetation types, including pine, larch and birch forest, shrubland, and grassland, in the Saihanba area of northern China. Soil samples from each season were incubated at 1, 10, and 20°C for 5 to 7 days. Nitrogen (N; 0.035 mM as NH4NO3) and phosphorus (P; 0.03 mM as P2O5) were added to soil samples, and the responses of soil microbial respiration to increased temperature and nutrient addition were determined. We found a universal trend that soil microbial respiration increased with increased temperature regardless of sampling season or vegetation type. The temperature sensitivity (indicated by Q10, the increase in respiration rate with a 10°C increase in temperature) of microbial respiration was higher in spring and autumn than in summer and winter, irrespective of vegetation type. The Q10 was significantly positively correlated with microbial biomass and the fungal: bacterial ratio. Microbial respiration (or Q10) did not significantly respond to N or P addition. Our results suggest that short-term nutrient input might not change the SOC decomposition rate or its temperature sensitivity, whereas increased temperature might significantly enhance SOC decomposition in spring and autumn, compared with winter and summer.

  8. Seasonality, Rather than Nutrient Addition or Vegetation Types, Influenced Short-Term Temperature Sensitivity of Soil Organic Carbon Decomposition.

    PubMed

    Qian, Yu-Qi; He, Feng-Peng; Wang, Wei

    2016-01-01

    The response of microbial respiration from soil organic carbon (SOC) decomposition to environmental changes plays a key role in predicting future trends of atmospheric CO2 concentration. However, it remains uncertain whether there is a universal trend in the response of microbial respiration to increased temperature and nutrient addition among different vegetation types. In this study, soils were sampled in spring, summer, autumn and winter from five dominant vegetation types, including pine, larch and birch forest, shrubland, and grassland, in the Saihanba area of northern China. Soil samples from each season were incubated at 1, 10, and 20°C for 5 to 7 days. Nitrogen (N; 0.035 mM as NH4NO3) and phosphorus (P; 0.03 mM as P2O5) were added to soil samples, and the responses of soil microbial respiration to increased temperature and nutrient addition were determined. We found a universal trend that soil microbial respiration increased with increased temperature regardless of sampling season or vegetation type. The temperature sensitivity (indicated by Q10, the increase in respiration rate with a 10°C increase in temperature) of microbial respiration was higher in spring and autumn than in summer and winter, irrespective of vegetation type. The Q10 was significantly positively correlated with microbial biomass and the fungal: bacterial ratio. Microbial respiration (or Q10) did not significantly respond to N or P addition. Our results suggest that short-term nutrient input might not change the SOC decomposition rate or its temperature sensitivity, whereas increased temperature might significantly enhance SOC decomposition in spring and autumn, compared with winter and summer. PMID:27070782

  9. [Study on degradation of polycyclic aromatic hydrocarbons (PAHs) with different additional carbon sources in aged contaminated soil].

    PubMed

    Yin, Chun-Qin; Jiang, Xin; Wang, Fang; Wang, Cong-Ying

    2012-02-01

    This study was conducted with different additional carbon sources (such as: glucose, DL-malic acid, citrate, urea and ammonium acetate) to elucidate the degradation of polycyclic aromatic hydrocarbons (PAHs) in aged contaminated soil under an indoor simulation experiment. The results showed that the quantity of CO2 emission in different additional carbon sources treatments was obviously much more than that of check treatment in the first week, and the quantity of CO2 emission in DL-malic acid treatment was the largest. The average CO2 production decreased in an order urea > glucose approximately citrate approximately DL-malic acid approximately ammonium acetate > check. Meanwhile, the amount of volatized PAHs in applied carbon sources treatments was significantly less than that in check treatment. The amount of three volatized PAHs decreased in an order phenanthrene > fluoranthene > benzo(b)fluoranthene. Compared with the check treatment, the average degradation rates of the three PAHs were significantly augmented in the supplied carbon sources treatments, in which rates of the three PAHs were much higher in DL-malic acid and urea treatments than those in other treatments. The largest proportion of residual was benzo(b)fluoranthene (from 72% to 81%) among three PAHs compounds, followed by fluoranthene (from 53% to 70% ) and phenanthrene (from 27% to 44%).

  10. Sulfate reduction in sulfuric material after re-flooding: Effectiveness of organic carbon addition and pH increase depends on soil properties.

    PubMed

    Yuan, Chaolei; Fitzpatrick, Rob; Mosley, Luke M; Marschner, Petra

    2015-11-15

    Sulfuric material is formed upon oxidation of sulfidic material; it is extremely acidic, and therefore, an environmental hazard. One option for increasing pH of sulfuric material may be stimulation of bacterial sulfate reduction. We investigated the effects of organic carbon addition and pH increase on sulfate reduction after re-flooding in ten sulfuric materials with four treatments: control, pH increase to 5.5 (+pH), organic carbon addition with 2% w/w finely ground wheat straw (+C), and organic carbon addition and pH increase (+C+pH). After 36 weeks, in five of the ten soils, only treatment +C+pH significantly increased the concentration of reduced inorganic sulfur (RIS) compared to the control and increased the soil pore water pH compared to treatment+pH. In four other soils, pH increase or/and organic carbon addition had no significant effect on RIS concentration compared to the control. The RIS concentration in treatment +C+pH as percentage of the control was negatively correlated with soil clay content and initial nitrate concentration. The results suggest that organic carbon addition and pH increase can stimulate sulfate reduction after re-flooding, but the effectiveness of this treatment depends on soil properties. PMID:26024614

  11. Sulfate reduction in sulfuric material after re-flooding: Effectiveness of organic carbon addition and pH increase depends on soil properties.

    PubMed

    Yuan, Chaolei; Fitzpatrick, Rob; Mosley, Luke M; Marschner, Petra

    2015-11-15

    Sulfuric material is formed upon oxidation of sulfidic material; it is extremely acidic, and therefore, an environmental hazard. One option for increasing pH of sulfuric material may be stimulation of bacterial sulfate reduction. We investigated the effects of organic carbon addition and pH increase on sulfate reduction after re-flooding in ten sulfuric materials with four treatments: control, pH increase to 5.5 (+pH), organic carbon addition with 2% w/w finely ground wheat straw (+C), and organic carbon addition and pH increase (+C+pH). After 36 weeks, in five of the ten soils, only treatment +C+pH significantly increased the concentration of reduced inorganic sulfur (RIS) compared to the control and increased the soil pore water pH compared to treatment+pH. In four other soils, pH increase or/and organic carbon addition had no significant effect on RIS concentration compared to the control. The RIS concentration in treatment +C+pH as percentage of the control was negatively correlated with soil clay content and initial nitrate concentration. The results suggest that organic carbon addition and pH increase can stimulate sulfate reduction after re-flooding, but the effectiveness of this treatment depends on soil properties.

  12. Influence of residue and nitrogen fertilizer additions on carbon mineralization in soils with different texture and cropping histories

    Technology Transfer Automated Retrieval System (TEKTRAN)

    To improve our ability to predict SOC mineralization response to residue and N additions in soils with different inherent and dynamic organic matter properties, a 330-day incubation was conducted using soil sampled from two long-term experiments (clay loam Mollisols in Iowa [IAsoil] and silt loam Ul...

  13. How do Soil Microbial Enzyme Activities Respond to Changes in Temperature, Carbon, and Nutrient Additions across Gradients in Mineralogy and Nutrient Availability?

    NASA Astrophysics Data System (ADS)

    McCleery, T.; Cusack, D. F.; Reed, S.; Wieder, W. R.; Taylor, P.; Cleveland, C. C.; Chadwick, O.; Vitousek, P.

    2013-12-01

    Microbial enzyme activities are the direct agents of organic matter decomposition, and thus play a crucial role in global carbon (C) cycling. Global change factors like warming and nutrient inputs to soils have the potential to alter the activities of these enzymes, with background site conditions likely driving responses. We hypothesized that enzyme activities in sites with high background nutrient and/or carbon availability would be less sensitive to nutrient additions than nutrient-poor sites. We also hypothesized that sites poor in background nutrients and/or carbon would show greater sensitivity to changes in temperature because of a less robust microbial community. To test our hypothesis we used laboratory temperature incubations combined with long- and short-term nutrient additions to assess changes in enzyme activities for 8 common soil enzymes that acquire nitrogen (N), phosphorus (P) and C from organic matter. We collected mineral soils (0-10 cm depth) from 8 Hawaiian sites that provided maximum variation in nutrient availability and background soil C. Soils were sieved, pooled by site, and homogenized prior to a laboratory addition of a simple C (sucrose) plus N and/or P in full factorial design. The 8 soils were also incubated at 7 different temperatures from 4 - 40 degrees C. We found that temperature sensitivities varied significantly among the sites, and that the laboratory fertilizations altered enzyme activities. Across the 8 sites, laboratory sucrose+N additions nearly doubled P-acquisition enzyme activity (p < 0.05), with the strongest effect in a younger forest soil that was naturally low in N. Similarly, laboratory sucrose+N and sucrose+NP additions significantly increased N-acquiring enzyme activity (p < 0.05), with the strongest effect in a drier, nutrient poor and carbon poor soil. Carbon-acquiring enzyme activities were less responsive, but also increased significantly with additions of sucrose+N and sucrose+NP across sites, with the

  14. Fertilizer addition lessens the flux of microbial carbon to higher trophic levels in soil food webs of grassland.

    PubMed

    Lemanski, Kathleen; Scheu, Stefan

    2014-10-01

    Roots and root-derived C compounds are increasingly recognised as important resources for soil animal food webs. We used (13)C-labelled glucose as a model C compound representing root exudates to follow the incorporation of root-derived C into the soil animal food web of a temperate grassland over a period of 52 weeks. We investigated variations in glucose C incorporation with fertilizer addition and sward composition, i.e. variations in plant functional groups. The approach allowed the differentiation of trophic chains based on primary decomposers feeding on litter and phytophagous species feeding on roots (i.e. not incorporating glucose C) from those based on secondary decomposers feeding on microorganisms (thereby assimilating glucose C). Each of the studied soil animal species incorporated glucose C, indicating that the majority of grassland soil animal species rely on microorganisms as food resources with microorganisms being fuelled by root exudates. However, incorporation of glucose C into soil animal species varied markedly with species identity, suggesting that detritivorous microarthropods complement each other in channelling microbial C through soil food webs. Fertilizer addition markedly reduced the concentration of glucose C in most soil animal species as well as the absolute transfer of glucose C into oribatid mites as major secondary decomposers. The results suggest that fertilizer addition shifts the basis of the decomposer food web towards the use of unlabelled resources, presumably roots, i.e. towards a herbivore system, thereby lessening the link between microorganisms and microbial grazers and hampering the propagation of microbial C to higher trophic levels.

  15. Spatial prediction of Soil Organic Carbon contents in croplands, grasslands and forests using environmental covariates and Generalized Additive Models (Southern Belgium)

    NASA Astrophysics Data System (ADS)

    Chartin, Caroline; Stevens, Antoine; van Wesemael, Bas

    2015-04-01

    Providing spatially continuous Soil Organic Carbon data (SOC) is needed to support decisions regarding soil management, and inform the political debate with quantified estimates of the status and change of the soil resource. Digital Soil Mapping techniques are based on relations existing between a soil parameter (measured at different locations in space at a defined period) and relevant covariates (spatially continuous data) that are factors controlling soil formation and explaining the spatial variability of the target variable. This study aimed at apply DSM techniques to recent SOC content measurements (2005-2013) in three different landuses, i.e. cropland, grassland, and forest, in the Walloon region (Southern Belgium). For this purpose, SOC databases of two regional Soil Monitoring Networks (CARBOSOL for croplands and grasslands, and IPRFW for forests) were first harmonized, totalising about 1,220 observations. Median values of SOC content for croplands, grasslands, and forests, are respectively of 12.8, 29.0, and 43.1 g C kg-1. Then, a set of spatial layers were prepared with a resolution of 40 meters and with the same grid topology, containing environmental covariates such as, landuses, Digital Elevation Model and its derivatives, soil texture, C factor, carbon inputs by manure, and climate. Here, in addition to the three classical texture classes (clays, silt, and sand), we tested the use of clays + fine silt content (particles < 20 µm and related to stable carbon fraction) as soil covariate explaining SOC variations. For each of the three land uses (cropland, grassland and forest), a Generalized Additive Model (GAM) was calibrated on two thirds of respective dataset. The remaining samples were assigned to a test set to assess model performance. A backward stepwise procedure was followed to select the relevant environmental covariates using their approximate p-values (the level of significance was set at p < 0.05). Standard errors were estimated for each of

  16. Changes in water, carbon, and nitrogen fluxes with the addition of biochar to soils: lessons learned from laboratory and greenhouse experiments

    NASA Astrophysics Data System (ADS)

    Barnes, R. T.; Gallagher, M. E.; Masiello, C. A.; Liu, Z.; Dugan, B.; Rudgers, J. A.

    2011-12-01

    The addition of biochar to agricultural soils has the potential to provide a number of ecosystem services, ranging from carbon (C) sequestration to increased soil fertility and crop production. It is estimated that 0.5 to 0.9 Pg of C yr-1 can be sequestered through the addition of biochar to soils, significantly increasing the charcoal flux to the biosphere over natural inputs from fire (0.05 to 0.20 Pg C yr-1). There remain large uncertainties about biochar mobility within the environment, making it a challenge to assess the ecosystem residence time of biochar. We conducted laboratory and greenhouse experiments to understand how soil amendment with laboratory-produced biochar changes water, C, and nitrogen (N) fluxes from soils. We used column experiments to assess how biochar amendment to three types of soils (sand, organic, clay-rich) affected hydraulic conductivity and dissolved organic carbon (DOC) and total dissolved nitrogen (TDN) fluxes. Results varied with soil type; biochar significantly decreased the hydraulic conductivity of the sand and organic soils by a factor of 10.6 and 2.7, respectively. While not statistically significant, biochar addition increased the hydraulic conductivity of the clay-rich soil by 50% on average. The addition of biochar significantly increased the DOC fluxes from the C-poor sand and clay soils while it significantly decreased the DOC flux from the organic-rich soil. In contrast, TDN fluxes decreased with biochar additions from all soil types, though the results were not statistically significant from the clay-rich soil. These laboratory experiments suggest that changes in the hydraulic conductivity of soil due to biochar amendments could play a significant role in understanding how biochar additions to agricultural fields will change watershed C and N dynamics. We additionally conducted a 28-day greenhouse experiment with sorghum plants using a three-way factorial treatment (water availability x biochar x mycorrhizae) to

  17. Characteristics of maize biochar with different pyrolysis temperatures and its effects on organic carbon, nitrogen and enzymatic activities after addition to fluvo-aquic soil.

    PubMed

    Wang, Xiubin; Zhou, Wei; Liang, Guoqing; Song, Dali; Zhang, Xiaoya

    2015-12-15

    In this study, the characteristics of maize biochar produced at different pyrolysis temperatures (300, 450 and 600°C) and its effects on organic carbon, nitrogen and enzymatic activities after addition to fluvo-aquic soil were investigated. As pyrolysis temperature increased, ash content, pH, electrical conductivity, surface area, pore volume and aromatic carbon content of biochar increased while yield, ratios of oxygen:carbon and hydrogen: carbon and alkyl carbon content decreased. During incubation, SOC, total N, and ammonium-N contents increased in all biochar-amended treatments compared with the urea treatment; however, soil nitrate-N content first increased and then decreased with increasing pyrolysis temperature of the applied biochar. Extracellular enzyme activities associated with carbon transformation first increased and then decreased with biochars pyrolyzed at 450 and 600°C. Protease activity markedly increased with increased pyrolysis temperatures, whereas pyrolysis temperature had limited effect on soil urease activity. The results indicated that the responses of extracellular enzymes to biochar were dependent on the pyrolysis temperature, the enzyme itself and incubation time as well.

  18. Effects of Straw Return in Deep Soils with Urea Addition on the Soil Organic Carbon Fractions in a Semi-Arid Temperate Cornfield

    PubMed Central

    Li, Jiaqi; Lu, Jia; Fan, Qingfeng; Yu, Na; Zhang, Yuling; Dang, Xiuli; Zhang, Yulong

    2016-01-01

    Returning straw to deep soil layers by using a deep-ditching-ridge-ploughing method is an innovative management practice that improves soil quality by increasing the soil organic carbon (SOC) content. However, the optimum quantity of straw return has not been determined. To solve this practical production problem, the following treatments with different amounts of corn straw were investigated: no straw return, CK; 400 kg ha-1 straw, S400; 800 kg ha-1 straw, S800; 1200 kg ha-1 straw, S1200; and 1600 kg ha-1 straw, S1600. After straw was returned to the soil for two years, the microbial biomass C (MBC), easily oxidized organic C (EOC), dissolved organic C (DOC) and light fraction organic C (LFOC) content were measured at three soil depths (0–10, 10–20, and 20–40 cm). The results showed that the combined application of 800 kg ha-1 straw significantly increased the EOC, MBC, and LFOC contents and was a suitable agricultural practice for this region. Moreover, our results demonstrated that returning straw to deep soil layers was effective for increasing the SOC content. PMID:27123594

  19. Effects of Straw Return in Deep Soils with Urea Addition on the Soil Organic Carbon Fractions in a Semi-Arid Temperate Cornfield.

    PubMed

    Zou, Hongtao; Ye, Xuhong; Li, Jiaqi; Lu, Jia; Fan, Qingfeng; Yu, Na; Zhang, Yuling; Dang, Xiuli; Zhang, Yulong

    2016-01-01

    Returning straw to deep soil layers by using a deep-ditching-ridge-ploughing method is an innovative management practice that improves soil quality by increasing the soil organic carbon (SOC) content. However, the optimum quantity of straw return has not been determined. To solve this practical production problem, the following treatments with different amounts of corn straw were investigated: no straw return, CK; 400 kg ha-1 straw, S400; 800 kg ha-1 straw, S800; 1200 kg ha-1 straw, S1200; and 1600 kg ha-1 straw, S1600. After straw was returned to the soil for two years, the microbial biomass C (MBC), easily oxidized organic C (EOC), dissolved organic C (DOC) and light fraction organic C (LFOC) content were measured at three soil depths (0-10, 10-20, and 20-40 cm). The results showed that the combined application of 800 kg ha-1 straw significantly increased the EOC, MBC, and LFOC contents and was a suitable agricultural practice for this region. Moreover, our results demonstrated that returning straw to deep soil layers was effective for increasing the SOC content. PMID:27123594

  20. Soil carbon dynamics

    NASA Astrophysics Data System (ADS)

    Trumbore, Susan; Barbosa de Camargo, Plínio

    The amount of organic carbon (C) stored in the upper meter of mineral soils in the Amazon Basin (˜40 Pg C) represents ˜3% of the estimated global store of soil carbon. Adding surface detrital C stocks and soil carbon deeper than 1 m can as much as quadruple this estimate. The potential for Amazon soil carbon to respond to changes in land use, climate, or atmospheric composition depends on the form and dynamics of soil carbon. Much (˜30% in the top ˜10 cm but >85% in soils to 1 m depth) of the carbon in mineral soils of the Oxisols and Ultisols that are the predominant soil types in the Amazon Basin is in forms that are strongly stabilized, with mean ages of centuries to thousands of years. Measurable changes in soil C stocks that accompany land use/land cover change occur in the upper meter of soil, although the presence of deep roots in forests systems drives an active C cycle at depths >1 m. Credible estimates of the potential for changes in Amazon soil C stocks with future land use and climate change are much smaller than predictions of aboveground biomass change. Soil organic matter influences fertility and other key soil properties, and thus is important independent of its role in the global C cycle. Most work on C dynamics is limited to upland soils, and more is needed to investigate C dynamics in poorly drained soils. Work is also needed to relate cycles of C with water, N, P, and other elements.

  1. Carbon-based stock feed additives: a research methodology that explores ecologically delivered C biosequestration, alongside live weights, feed use efficiency, soil nutrient retention, and perennial fodder plantations.

    PubMed

    McHenry, Mark P

    2010-01-30

    There is considerable interest in reliable and practical methods to sequester carbon (C) into agricultural soils to both reduce atmospheric greenhouse gas concentrations and improve conventional productivity. This article outlines a research methodology to refine the efficacy and economics of using long-lived C species (biochars) as stock feed additives, produced from farm waste biomass, for ecologically delivered soil biosequestration, while generating renewable bioenergy. This article also draws attention to potential parallel outputs including annual feed use efficiency, fodder species expansion, soil nutrient retention, aquatic habitat protection, and forestry revegetation, using nitrogen-fixing perennial fodder plant species. A methodology to generate parallel results including standing fodder tree C sequestration, optimised production of Acacia spp. biochar, animal growth on high-tannin fodder with biochar feed additives, soil nutrient and stable C fractions, and economics of Acacia spp. bioenergy production. This form of research is contextually dependent on the regional agricultural production system, legislation, and surrounding ecosystem. Therefore, this article suggests the use of a scenario approach to include regionally specific levels of biochar integration with respect to the local prices for C, fossil fuels, meat and livestock, fertilisers, fodder, feed additives, water, renewable energy, revegetation and capital.

  2. Influence of Residue and Nitrogen Fertilizer Additions on Carbon Mineralization in Soils with Different Texture and Cropping Histories

    PubMed Central

    Chen, Xianni; Wang, Xudong; Liebman, Matt; Cavigelli, Michel; Wander, Michelle

    2014-01-01

    To improve our ability to predict SOC mineralization response to residue and N additions in soils with different inherent and dynamic organic matter properties, a 330-day incubation was conducted using samples from two long-term experiments (clay loam Mollisols in Iowa [IAsoil] and silt loam Ultisols in Maryland [MDsoil]) comparing conventional grain systems (Conv) amended with inorganic fertilizers with 3 yr (Med) and longer (Long), more diverse cropping systems amended with manure. A double exponential model was used to estimate the size (Ca, Cs) and decay rates (ka, ks) of active and slow C pools which we compared with total particulate organic matter (POM) and occluded-POM (OPOM). The high-SOC IAsoil containing highly active smectite clays maintained smaller labile pools and higher decay rates than the low-SOC MDsoil containing semi-active kaolinitic clays. Net SOC loss was greater (2.6 g kg−1; 8.6%) from the IAsoil than the MDsoil (0.9 g kg−1, 6.3%); fractions and coefficients suggest losses were principally from IAsoil’s resistant pool. Cropping history did not alter SOC pool size or decay rates in IAsoil where rotation-based differences in OPOM-C were small. In MDsoil, use of diversified rotations and manure increased ka by 32% and ks by 46% compared to Conv; differences mirrored in POM- and OPOM-C contents. Residue addition prompted greater increases in Ca (340% vs 230%) and Cs (38% vs 21%) and decreases in ka (58% vs 9%) in IAsoil than MDsoil. Reduced losses of SOC from residue-amended MDsoil were associated with increased OPOM-C. Nitrogen addition dampened CO2-C release. Clay type and C saturation dominated the IAsoil’s response to external inputs and made labile and stable fractions more vulnerable to decay. Trends in OPOM suggest aggregate protection influences C turnover in the low active MDsoil. Clay charge and OPOM-C contents were better predictors of soil C dynamics than clay or POM-C contents. PMID:25078458

  3. A global analysis of soil acidification caused by nitrogen addition

    NASA Astrophysics Data System (ADS)

    Tian, Dashuan; Niu, Shuli

    2015-02-01

    Nitrogen (N) deposition-induced soil acidification has become a global problem. However, the response patterns of soil acidification to N addition and the underlying mechanisms remain far from clear. Here, we conducted a meta-analysis of 106 studies to reveal global patterns of soil acidification in responses to N addition. We found that N addition significantly reduced soil pH by 0.26 on average globally. However, the responses of soil pH varied with ecosystem types, N addition rate, N fertilization forms, and experimental durations. Soil pH decreased most in grassland, whereas boreal forest was not observed a decrease to N addition in soil acidification. Soil pH decreased linearly with N addition rates. Addition of urea and NH4NO3 contributed more to soil acidification than NH4-form fertilizer. When experimental duration was longer than 20 years, N addition effects on soil acidification diminished. Environmental factors such as initial soil pH, soil carbon and nitrogen content, precipitation, and temperature all influenced the responses of soil pH. Base cations of Ca2+, Mg2+ and K+ were critical important in buffering against N-induced soil acidification at the early stage. However, N addition has shifted global soils into the Al3+ buffering phase. Overall, this study indicates that acidification in global soils is very sensitive to N deposition, which is greatly modified by biotic and abiotic factors. Global soils are now at a buffering transition from base cations (Ca2+, Mg2+ and K+) to non-base cations (Mn2+ and Al3+). This calls our attention to care about the limitation of base cations and the toxic impact of non-base cations for terrestrial ecosystems with N deposition.

  4. Soil warming, carbon-nitrogen interactions, and forest carbon budgets.

    PubMed

    Melillo, Jerry M; Butler, Sarah; Johnson, Jennifer; Mohan, Jacqueline; Steudler, Paul; Lux, Heidi; Burrows, Elizabeth; Bowles, Francis; Smith, Rose; Scott, Lindsay; Vario, Chelsea; Hill, Troy; Burton, Andrew; Zhou, Yu-Mei; Tang, Jim

    2011-06-01

    Soil warming has the potential to alter both soil and plant processes that affect carbon storage in forest ecosystems. We have quantified these effects in a large, long-term (7-y) soil-warming study in a deciduous forest in New England. Soil warming has resulted in carbon losses from the soil and stimulated carbon gains in the woody tissue of trees. The warming-enhanced decay of soil organic matter also released enough additional inorganic nitrogen into the soil solution to support the observed increases in plant carbon storage. Although soil warming has resulted in a cumulative net loss of carbon from a New England forest relative to a control area over the 7-y study, the annual net losses generally decreased over time as plant carbon storage increased. In the seventh year, warming-induced soil carbon losses were almost totally compensated for by plant carbon gains in response to warming. We attribute the plant gains primarily to warming-induced increases in nitrogen availability. This study underscores the importance of incorporating carbon-nitrogen interactions in atmosphere-ocean-land earth system models to accurately simulate land feedbacks to the climate system.

  5. Prediction of soil organic carbon concentration and soil bulk density of mineral soils for soil organic carbon stock estimation

    NASA Astrophysics Data System (ADS)

    Putku, Elsa; Astover, Alar; Ritz, Christian

    2016-04-01

    Soil monitoring networks provide a powerful base for estimating and predicting nation's soil status in many aspects. The datasets of soil monitoring are often hierarchically structured demanding sophisticated data analyzing methods. The National Soil Monitoring of Estonia was based on a hierarchical data sampling scheme as each of the monitoring site was divided into four transects with 10 sampling points on each transect. We hypothesized that the hierarchical structure in Estonian Soil Monitoring network data requires a multi-level mixed model approach to achieve good prediction accuracy of soil properties. We used this database to predict soil bulk density and soil organic carbon concentration of mineral soils in arable land using different statistical methods: median approach, linear regression and mixed model; additionally, random forests for SOC concentration. We compared the prediction results and selected the model with the best prediction accuracy to estimate soil organic carbon stock. The mixed model approach achieved the best prediction accuracy in both soil organic carbon (RMSE 0.22%) and bulk density (RMSE 0.09 g cm-3) prediction. Other considered methods under- or overestimated higher and lower values of soil parameters. Thus, using these predictions we calculated the soil organic carbon stock of mineral arable soils and applied the model to a specific case of Tartu County in Estonia. Average estimated SOC stock of Tartu County is 54.8 t C ha-1 and total topsoil SOC stock 1.8 Tg in humus horizon.

  6. Deep Soil: Quantifying and Modeling Subsurface Carbon

    NASA Astrophysics Data System (ADS)

    James, J. N.; Devine, W.; Harrison, R. B.

    2014-12-01

    Some soil carbon datasets that are spatially rich, such as the USDA Forest Service Inventory and Analysis National Program dataset, sample soil to only 20 cm (8 inches), despite evidence that substantial stores of soil C can be found deeper in the soil profile. The maximum extent of tree rooting is typically many meters deep and provides: direct exchange with the soil solution; redistribution of water from deep horizons toward the surface during times of drought; resources for active microbial communities in deep soil around root channels; and direct carbon inputs through exudates and root turnover. This study examined soil carbon to a depth of 2.5 meters across 22 soils in Pacific Northwest Douglas-fir forests. Excavations at 20 additional sites took place in summer 2014, greatly expanding the spatial coverage and extent of the data set. Forest floor and mineral soil bulk density samples were collected at depths of 0.1, 0.5, 1.0, 1.5, 2.0 and 2.5 meters. Pool estimates from systematic sampling depths shallower than 1.5 m yielded significantly smaller estimates than the total soil stock to 2.5 meters (P<0.01). On average, only 5% of soil C was found in the litter layer, 35% was found below 0.5 meter, and 21% was found below 1.0 meter. Due to the difficulty of excavating and measuring deep soil carbon, a series of nonlinear mixed effect models were fit to the data to predict deep soil carbon stocks given sampling to 1.0 meter. A model using an inverse polynomial function predicted soil carbon to 2.5 meters with -5.6% mean error. The largest errors occurred in Andisols with non-crystalline minerals, which can adsorb large quantities of carbon on mineral surfaces and preserve it from decomposition. An accurate spatial dataset of soil depth to bedrock would be extremely useful to constrain models of the vertical distribution of soil carbon. Efforts to represent carbon in spatial models would benefit from considering the vertical distribution of carbon in soil. Sampling

  7. Dynamics of maize carbon contribution to soil organic carbon in association with soil type and fertility level.

    PubMed

    Pei, Jiubo; Li, Hui; Li, Shuangyi; An, Tingting; Farmer, John; Fu, Shifeng; Wang, Jingkuan

    2015-01-01

    Soil type and fertility level influence straw carbon dynamics in the agroecosystems. However, there is a limited understanding of the dynamic processes of straw-derived and soil-derived carbon and the influence of the addition of straw carbon on soil-derived organic carbon in different soils associated with different fertility levels. In this study, we applied the in-situ carborundum tube method and 13C-labeled maize straw (with and without maize straw) at two cropland (Phaeozem and Luvisol soils) experimental sites in northeast China to quantify the dynamics of maize-derived and soil-derived carbon in soils associated with high and low fertility, and to examine how the addition of maize carbon influences soil-derived organic carbon and the interactions of soil type and fertility level with maize-derived and soil-derived carbon. We found that, on average, the contributions of maize-derived carbon to total organic carbon in maize-soil systems during the experimental period were differentiated among low fertility Luvisol (from 62.82% to 42.90), high fertility Luvisol (from 53.15% to 30.00%), low fertility Phaeozem (from 58.69% to 36.29%) and high fertility Phaeozem (from 41.06% to 16.60%). Furthermore, the addition of maize carbon significantly decreased the remaining soil-derived organic carbon in low and high fertility Luvisols and low fertility Phaeozem before two months. However, the increasing differences in soil-derived organic carbon between both soils with and without maize straw after two months suggested that maize-derived carbon was incorporated into soil-derived organic carbon, thereby potentially offsetting the loss of soil-derived organic carbon. These results suggested that Phaeozem and high fertility level soils would fix more maize carbon over time and thus were more beneficial for protecting soil-derived organic carbon from maize carbon decomposition.

  8. Dynamics of Maize Carbon Contribution to Soil Organic Carbon in Association with Soil Type and Fertility Level

    PubMed Central

    Pei, Jiubo; Li, Hui; Li, Shuangyi; An, Tingting; Farmer, John; Fu, Shifeng; Wang, Jingkuan

    2015-01-01

    Soil type and fertility level influence straw carbon dynamics in the agroecosystems. However, there is a limited understanding of the dynamic processes of straw-derived and soil-derived carbon and the influence of the addition of straw carbon on soil-derived organic carbon in different soils associated with different fertility levels. In this study, we applied the in-situ carborundum tube method and 13C-labeled maize straw (with and without maize straw) at two cropland (Phaeozem and Luvisol soils) experimental sites in northeast China to quantify the dynamics of maize-derived and soil-derived carbon in soils associated with high and low fertility, and to examine how the addition of maize carbon influences soil-derived organic carbon and the interactions of soil type and fertility level with maize-derived and soil-derived carbon. We found that, on average, the contributions of maize-derived carbon to total organic carbon in maize-soil systems during the experimental period were differentiated among low fertility Luvisol (from 62.82% to 42.90), high fertility Luvisol (from 53.15% to 30.00%), low fertility Phaeozem (from 58.69% to 36.29%) and high fertility Phaeozem (from 41.06% to 16.60%). Furthermore, the addition of maize carbon significantly decreased the remaining soil-derived organic carbon in low and high fertility Luvisols and low fertility Phaeozem before two months. However, the increasing differences in soil-derived organic carbon between both soils with and without maize straw after two months suggested that maize-derived carbon was incorporated into soil-derived organic carbon, thereby potentially offsetting the loss of soil-derived organic carbon. These results suggested that Phaeozem and high fertility level soils would fix more maize carbon over time and thus were more beneficial for protecting soil-derived organic carbon from maize carbon decomposition. PMID:25774529

  9. Permafrost soils and carbon cycling

    DOE PAGES

    Ping, C. L.; Jastrow, J. D.; Jorgenson, M. T.; Michaelson, G. J.; Shur, Y. L.

    2015-02-05

    Knowledge of soils in the permafrost region has advanced immensely in recent decades, despite the remoteness and inaccessibility of most of the region and the sampling limitations posed by the severe environment. These efforts significantly increased estimates of the amount of organic carbon stored in permafrost-region soils and improved understanding of how pedogenic processes unique to permafrost environments built enormous organic carbon stocks during the Quaternary. This knowledge has also called attention to the importance of permafrost-affected soils to the global carbon cycle and the potential vulnerability of the region's soil organic carbon (SOC) stocks to changing climatic conditions. Inmore » this review, we briefly introduce the permafrost characteristics, ice structures, and cryopedogenic processes that shape the development of permafrost-affected soils, and discuss their effects on soil structures and on organic matter distributions within the soil profile. We then examine the quantity of organic carbon stored in permafrost-region soils, as well as the characteristics, intrinsic decomposability, and potential vulnerability of this organic carbon to permafrost thaw under a warming climate. Overall, frozen conditions and cryopedogenic processes, such as cryoturbation, have slowed decomposition and enhanced the sequestration of organic carbon in permafrost-affected soils over millennial timescales. Due to the low temperatures, the organic matter in permafrost soils is often less humified than in more temperate soils, making some portion of this stored organic carbon relatively vulnerable to mineralization upon thawing of permafrost.« less

  10. Soil Carbon Sequestration: Perspectives from Australia

    NASA Astrophysics Data System (ADS)

    Sanderman, J.; Macdonald, L.; Baldock, J.

    2011-12-01

    Australia is currently embarking upon an unparalleled program to mitigate greenhouse gas emissions by engaging farmers and landholders to reduce emissions and store carbon in the soil. Currently, the magnitude of a potential soil carbon sink in Australian agricultural soils is largely unknown. The oft repeated rubric that adoption of recommended management practices (RMP) can raise soil carbon levels to 50-66% of pre-clearing levels has lead many to conclude that soil carbon sequestration can offset a large portion of Australia's current greenhouse gas emissions. Is there evidence in Australia (and abroad) to support these sequestration rates? In this presentation, we will present findings from both a retrospective analysis of existing field trial data and preliminary results from a national scale assessment of current soil carbon stocks under different agricultural management practices. A comprehensive review of field-trial data in Australia suggests that most management shifts within a given agricultural system (i.e. tillage, stubble management, fertilizer application, etc...) result in modest relative gains of 0.1 to 0.3 tC ha-1 yr-1. Importantly, whenever time series data was available, we found that the relative improvement in soil carbon stocks under RMPs was due to a reduction in the rate of loss of soil carbon and not in an actual increase in soil carbon. This finding has important repercussions for both how we think about soil carbon sequestration and how we can account for it in an accounting framework. Current research within the National Soil Carbon Research Program looks to assess the potential for agricultural management to influence soil carbon content and its distribution within various measurable carbon pools (particulate, humus, charcoal-like). For example, 200 randomly selected farms have been sampled in two major agricultural regions in South Australia based on a soil-type by rainfall stratification. In addition to measuring carbon content and

  11. Tracing the source of Beijing soil organic carbon: a carbon isotope approach.

    PubMed

    Guo, Qingjun; Strauss, Harald; Chen, Tong-Bin; Zhu, Guangxu; Yang, Jun; Yang, Junxing; Lei, Mei; Zhou, Xiaoyong; Peters, Marc; Xie, Yunfeng; Zhang, Hanzhi; Wei, Rongfei; Wang, Chunyu

    2013-05-01

    Bulk soil organic carbon concentration and isotopic composition characterize its sources and fate, identify the anthropogenic input of organic carbon into the soil, and trace soil carbon turnover. Coal and/or coal combustion products represent the prime anthropogenic input of organic carbon into three soil profiles located in the vicinity of a steel company. Three profiles positioned away from any direct industrial contribution display vertical pattern in soil organic carbon concentration and isotopic composition that resemble more commonly observed downward gradients in soil carbon chemistry and indicate microbial soil carbon turnover. Two additional profiles located outside of the immediate industrial area display vertical carbon isotope profiles between typical of those from industrial and non-industrial areas. Eight soil profiles and their vertical distribution of bulk organic carbon isotopic composition and concentration collected in the Beijing area reveal and distinguish both anthropogenic and natural contributions of carbon to these soils.

  12. Effects of chemical, biological, and physical aging as well as soil addition on the sorption of pyrene to activated carbon and biochar.

    PubMed

    Hale, Sarah E; Hanley, Kelly; Lehmann, Johannes; Zimmerman, Andrewr; Cornelissen, Gerard

    2011-12-15

    In this study, the suitability of biochar and activated carbon (AC) for contaminated soil remediation is investigated by determining the sorption of pyrene to both materials in the presence and absence of soil and before as well as after aging. Biochar and AC were aged either alone or mixed with soil via exposure to (a) nutrients and microorganisms (biological), (b) 60 and 110 °C (chemical), and (c) freeze-thaw cycles (physical). Before and after aging, the pH, elemental composition, cation exchange capacity (CEC), microporous SA, and sorption isotherms of pyrene were quantified. Aging at 110 °C altered the physicochemical properties of all materials to the greatest extent (for example, pH increased by up to three units and CEC by up to 50% for biochar). Logarithmic K(Fr) values ranged from 7.80 to 8.21 (ng kg(-1))(ng L(-1))(-nF) for AC and 5.22 to 6.21 (ng kg(-1))(ng L(-1))(-nF) for biochar after the various aging regimes. Grinding biochar to a smaller particle size did not significantly affect the sorption of d(10) pyrene, implying that sorption processes operate on the subparticle scale. Chemical aging decreased the sorption of pyrene to the greatest extent (up to 1.8 log unit for the biochar+soil). The sorption to AC was affected more by the presence of soil than the sorption to biochar was. Our results suggest that AC and biochar have a high sorption capacity for pyrene that is maintained both in the presence of soil and during harsh aging. Both materials could therefore be considered in contaminated land remediation.

  13. Biochar addition impacts soil microbial community in tropical soils

    NASA Astrophysics Data System (ADS)

    Paz-Ferreiro, Jorge; Fu, Shenglei; Méndez, Ana; Gascó, Gabriel

    2014-05-01

    Studies on the effect of biochar on soil microbial activity and community structure in tropical areas are scarce. In this study we report the effect of several types of biochar (sewage sludge biochar, paper mill waste biochar, miscanthus biochar and pinewood biochar) in the soil microbial community of two tropical soils, an Acrisol and an Oxisol. In addition we study the effect of the presence or absence of earthworms in soil microbial community. Soil microbial community was more strongly affected by biochar than by the presence or absence of macrofauna.

  14. Does unsaturated flow drive soil carbon residence times?

    NASA Astrophysics Data System (ADS)

    Lawrence, C. R.; Mnich, M.; Druhan, J. L.; Schulz, M. S.; Stonestrom, D. A.; Maher, K.; Harden, J. W.

    2015-12-01

    Soil moisture is widely recognized as a driver of many important biogeochemical processes. For example, ecosystem productivity, microbial lifecycles, soil organic matter decomposition, soil secondary mineralogy, the development and persistence of redox gradients, and the export of dissolved carbon are all sensitive to soil-water content and potential. In turn, each of these processes is recognized as an important control on the turnover of soil organic carbon. These dependencies raise a key question: Is the flux of water through unsaturated soils the dominant driver of soil organic carbon turnover across broad spatial scales? To better characterize the importance of soil moisture fluxes, we synthesize data from a number of soil studies to evaluate how total soil carbon storage, carbon residence time, and depth dependent gradients vary in relation to soil hydrologic fluxes. Specifically, we compare soil carbon storage and stability to measured and/or modeled infiltration ([precipitation + condensation] - [evapotranspiration + runoff]) and long-term soil water flux estimates from chloride mass balance, or other techniques. Additionally, we consider the interaction of soil age and hydrology, as the development of secondary mineral horizons during pedogenesis represents a critical threshold in both soil water flux and soil organic carbon turnover. We focus on data from 3 previously descried soil chronosequences, including the Santa Cruz, Mattole, and Merced terraces, which together span a wide range of age and soil moisture conditions. Across these sites, organic carbon accumulates to greater depths in the soils with highest infiltration but the relationship between turnover and soil moisture is not as straightforward. To help interpret these results, we compare field data against simulations of biogeochemical reactions involving soil carbon and the resulting isotopic gradients using the reactive transport model CrunchTope. Overall, this effort provides for an improved

  15. Use of Additives in Bioremediation of Contaminated Groundwater and Soil

    EPA Science Inventory

    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 ...

  16. Clumped isotopes in soil carbonate

    NASA Astrophysics Data System (ADS)

    Quade, J.; Eiler, J. M.; Daeron, M.

    2011-12-01

    We are monitoring soil temperature and measuring clumped isotopes from modern soil carbonate in North and South America, Hawaii, and Tibet. Clumped isotopes from 50-200 cm soil depth show a strong and systematic bias toward formation in the warmest summer months. For example, soil carbonate as these depths exceed local mean annual temperature by 10-15°C in soils from India and Tibet. Clumped isotope temperatures from modern carbonate increase very regularly (r2 = 0.90) with elevation gain from lowland India to Tibet. Here carbonate forms largely in May-June, just prior to the arrival of the soil-cooling monsoon rains. In this regard, clumped isotopes hold great promise as a paleoaltimeter on the plateau. The question is whether these patterns from a monsoonal climate can be generalized (and they probably can't be) to other climate regimes when soil carbonate forms at a different time of year than the pre-monsoon. For example, in winter-dominated rainfall regimes soil carbonate may form as soils dewater in the spring and soil temperature is closer to mean annual temperature. These are open questions. Diurnal temperature information is also archived in the upper 30 cm of soils. Modern carbonate in Tibet appears to form in very late morning through afternoon, when the surface soil is warmest. Shade and aspect also strongly influence measured soil and clumped isotope temperatures. Both variables will have to be controlled for to correctly interpret clumped isotopes from the paleosol record. Clumped isotope values correlate with δ13C values in soil carbonate from shallowly buried (<1 km) paleosols from Nepal and Pakistan. This makes sense since δ13C values in the sub-tropics are determined the fraction of tree (C3) to grass (C4) cover, and soils under tree-covered areas are cooler. Finally, clumped isotopes from carbonates are reset to higher temperatures at burial depths roughly >2-3 km or >50-75°C. This was reproduced from paleosol and lake carbonates from three

  17. Impact of the addition of different plant residues on carbon-nitrogen content and nitrogen mineralization-immobilization turnover in a soil incubated under laboratory conditions

    NASA Astrophysics Data System (ADS)

    Abbasi, M. K.; Tahir, M. M.; Sabir, N.; Khurshid, M.

    2014-10-01

    Application of plant residues as soil amendment may represent a valuable recycling strategy that affects on carbon (C) and nitrogen (N) cycling, soil properties improvement and plant growth promotion. The amount and rate of nutrient release from plant residues depend on their quality characteristics and biochemical composition. A laboratory incubation experiment was conducted for 120 days under controlled conditions (25 °C and 58% water filled pore space (WFPS)) to quantify initial biochemical composition and N mineralization of leguminous and non-leguminous plant residues i.e. the roots, shoots and leaves of Glycine max, Trifolium repens, Zea mays, Poplus euramericana, Rubinia pseudoacacia and Elagnus umbellate incorporated into the soil at the rate of 200 mg residue N kg-1 soil. The diverse plant residues showed wide variation in total N, carbon, lignin, polyphenols and C/N ratio with higher polyphenol content in the leaves and higher lignin content in the roots. The shoot of G. max and the shoot and root of T. repens displayed continuous mineralization by releasing a maximum of 109.8, 74.8 and 72.5 mg N kg-1 and representing a 55, 37 and 36% of added N being released from these resources. The roots of G. max and Z. mays and the shoot of Z. mays showed continuous negative values throughout the incubation showing net immobilization. After an initial immobilization, leaves of P. euramericana, R. pseudoacacia and E. umbellate exhibited net mineralization by releasing a maximum of 31.8, 63.1 and 65.1 mg N kg-1, respectively and representing a 16, 32 and 33% of added N being released. Nitrogen mineralization from all the treatments was positively correlated with the initial residue N contents (r = 0.89; p ≤ 0.01), and negatively correlated with lignin content (r = -0.84; p ≤ 0.01), C/N ratio (r = -0.69; p ≤ 0.05), lignin/N ratio (r = -0.68; p ≤ 0.05), polyphenol/N ratio (r = -0.73; p ≤ 0.05) and ligin + polyphenol/N ratio (r = -0.70; p ≤ 0.05) indicating

  18. Impact of the addition of different plant residues on nitrogen mineralization-immobilization turnover and carbon content of a soil incubated under laboratory conditions

    NASA Astrophysics Data System (ADS)

    Kaleeem Abbasi, M.; Tahir, M. Mahmood; Sabir, N.; Khurshid, M.

    2015-02-01

    Application of plant residues as soil amendment may represent a valuable recycling strategy that affects carbon (C) and nitrogen (N) cycling in soil-plant systems. The amount and rate of nutrient release from plant residues depend on their quality characteristics and biochemical composition. A laboratory incubation experiment was conducted for 120 days under controlled conditions (25 °C and 58% water-filled pore space) to quantify initial biochemical composition and N mineralization of leguminous and non-leguminous plant residues, i.e., the roots, shoots and leaves of Glycine max, Trifolium repens, Zea mays, Populus euramericana, Robinia pseudoacacia and Elaeagnus umbellata, incorporated into the soil at the rate of 200 mg residue N kg-1 soil. The diverse plant residues showed a wide variation in total N, C, lignin, polyphenols and C / N ratio with higher polyphenol content in the leaves and higher lignin content in the roots. The shoot of Glycine max and the shoot and root of Trifolium repens displayed continuous mineralization by releasing a maximum of 109.8, 74.8 and 72.5 mg N kg-1 and representing a 55, 37 and 36% recovery of N that had been released from these added resources. The roots of Glycine max and Zea mays and the shoot of Zea mays showed continuous negative values throughout the incubation. After an initial immobilization, leaves of Populus euramericana, Robinia pseudoacacia and Elaeagnus umbellata exhibited net mineralization by releasing a maximum of 31.8, 63.1 and 65.1 mg N kg-1, respectively, and representing a 16, 32 and 33% N recovery, respectively. Nitrogen mineralization from all the treatments was positively correlated with the initial residue N contents (r = 0.89; p ≤ 0.01) and negatively correlated with lignin content (r = -0.84; p ≤ 0.01), C / N ratio (r = -0.69; p ≤ 0.05), lignin / N ratio (r = -0.68; p ≤ 0.05), polyphenol / N ratio (r = -0.73; p ≤ 0.05) and (lignin + polyphenol) : N ratio (r = -0.70; p ≤ 0.05) indicating a

  19. Changes in the Dissolved Organic Carbon Concentrations of Stream and Soil Water in Response to a Watershed-Scale Calcium Addition and Recovery from Acidification

    NASA Astrophysics Data System (ADS)

    Fuss, C. B.; Driscoll, C. T.; Ard, G. R.

    2014-12-01

    Positive trends in surface water dissolved organic carbon (DOC) concentrations have been observed in recent decades across many, but not all, surface water monitoring sites in eastern North America and northern Europe. The drivers of these trends are not necessarily clear, although declining acidic deposition is often cited as a likely cause for increased DOC mobilization. Here we used long-term records (16-31 years) of monthly streamwater and soil solution chemistry data from two headwater catchments at the Hubbard Brook Experimental Forest (NH, USA) to evaluate DOC trends in response to the recovery from acidification. We compared the concentrations and trends of DOC in Hubbard Brook's Watershed 6 (W6) and Watershed 1 (W1). W6 is the biogeochemical reference watershed and W1 underwent a treatment with calcium silicate in 1999 to mitigate the effects of long-term acid deposition. Streamwater DOC in W6 initially decreased through the 1980s and 1990s, but has leveled over the past 10-15 years, coincident with a period of modest pH increase. In contrast, W1 streamwater DOC concentrations have significantly increased since the calcium treatment which has led to more marked increases in pH. Greater mobilization of DOC in soil solution in W1 appears to be driving the higher streamwater DOC concentrations. We are analyzing these trends spatially within the watersheds and in conjunction with major solute chemistry to further explain the observed changes in DOC.

  20. Fresh carbon input differentially impacts soil carbon decomposition across natural and managed systems.

    PubMed

    Luo, Zhongkui; Wang, Enli; Smith, Chris

    2015-10-01

    The amount of fresh carbon input into soil is experiencing substantial changes under global change. It is unclear what will be the consequences of such input changes on native soil carbon decomposition across ecosystems. By synthesizing data from 143 experimental comparisons, we show that, on average, fresh carbon input stimulates soil carbon decomposition by 14%. The response was lower in forest soils (1%) compared with soils from other ecosystems (> 24%), and higher following inputs of plant residue-like substrates (31%) compared to root exudate-like substrates (9%). The responses decrease with the baseline soil carbon decomposition rate under no additional carbon input, but increase with the fresh carbon input rate. The rates of these changes vary significantly across ecosystems and with the carbon substrates being added. These findings can be applied to provide robust estimates of soil carbon balance across ecosystems under changing aboveground and belowground inputs as consequence of climate and land management changes.

  1. Elevated atmospheric carbon dioxide increases soil carbon

    SciTech Connect

    Norby, Richard J; Jastrow, Julie D; Miller, Michael R; Matamala, Roser; Boutton, Thomas W; Rice, Charles W; Owensby, Clenton E

    2005-01-01

    In a study funded by the U.S. Department of Energy's Office of Science, researchers from Argonne and Oak Ridge National Laboratories and Kansas State and Texas A&M Universities evaluated the collective results of earlier studies by using a statistical procedure called meta-analysis. They found that on average elevated CO2 increased soil carbon by 5.6 percent over a two to nine year period. They also measured comparable increases in soil carbon for Tennessee deciduous forest and Kansas grassland after five to eight years of experimental exposure to elevated CO2.

  2. An invisible soil acidification: Critical role of soil carbonate and its impact on heavy metal bioavailability.

    PubMed

    Wang, Cheng; Li, Wei; Yang, Zhongfang; Chen, Yang; Shao, Wenjing; Ji, Junfeng

    2015-01-01

    It is well known that carbonates inhibit heavy metals transferring from soil to plants, yet the mechanism is poorly understood. Based on the Yangtze River delta area, we investigated bioaccumulation of Ni and Cd in winter wheat as affected by the presence of carbonates in soil. This study aimed to determine the mechanism through which soil carbonates restrict transport and plant uptake of heavy metals in the wheat cropping system. The results indicate that soil carbonates critically influenced heavy metal transfer from soil to plants and presented a tipping point. Wheat grains harvested from carbonates-depleted (due to severe leaching) soils showed Ni and Cd concentrations 2-3 times higher than those of the wheat grains from carbonates-containing soils. Correspondingly, the incidence of Ni or Cd contamination in the wheat grain samples increased by about three times. With the carbonate concentration >1% in soil, uptake and bioaccumulation of Ni and Cd by winter wheat was independent with the soil pH and carbonate content. The findings suggest that soil carbonates play a critical role in heavy metal transfer from soil to plants, implying that monitoring soil carbonate may be necessary in addition to soil pH for the evaluating soil quality and food safety. PMID:26227091

  3. An invisible soil acidification: Critical role of soil carbonate and its impact on heavy metal bioavailability

    NASA Astrophysics Data System (ADS)

    Wang, Cheng; Li, Wei; Yang, Zhongfang; Chen, Yang; Shao, Wenjing; Ji, Junfeng

    2015-07-01

    It is well known that carbonates inhibit heavy metals transferring from soil to plants, yet the mechanism is poorly understood. Based on the Yangtze River delta area, we investigated bioaccumulation of Ni and Cd in winter wheat as affected by the presence of carbonates in soil. This study aimed to determine the mechanism through which soil carbonates restrict transport and plant uptake of heavy metals in the wheat cropping system. The results indicate that soil carbonates critically influenced heavy metal transfer from soil to plants and presented a tipping point. Wheat grains harvested from carbonates-depleted (due to severe leaching) soils showed Ni and Cd concentrations 2-3 times higher than those of the wheat grains from carbonates-containing soils. Correspondingly, the incidence of Ni or Cd contamination in the wheat grain samples increased by about three times. With the carbonate concentration >1% in soil, uptake and bioaccumulation of Ni and Cd by winter wheat was independent with the soil pH and carbonate content. The findings suggest that soil carbonates play a critical role in heavy metal transfer from soil to plants, implying that monitoring soil carbonate may be necessary in addition to soil pH for the evaluating soil quality and food safety.

  4. Mechanisms of Soil Carbon Sequestration

    NASA Astrophysics Data System (ADS)

    Lal, Rattan

    2015-04-01

    Carbon (C) sequestration in soil is one of the several strategies of reducing the net emission of CO2 into the atmosphere. Of the two components, soil organic C (SOC) and soil inorganic C (SIC), SOC is an important control of edaphic properties and processes. In addition to off-setting part of the anthropogenic emissions, enhancing SOC concentration to above the threshold level (~1.5-2.0%) in the root zone has numerous ancillary benefits including food and nutritional security, biodiversity, water quality, among others. Because of its critical importance in human wellbeing and nature conservancy, scientific processes must be sufficiently understood with regards to: i) the potential attainable, and actual sink capacity of SOC and SIC, ii) permanence of the C sequestered its turnover and mean residence time, iii) the amount of biomass C needed (Mg/ha/yr) to maintain and enhance SOC pool, and to create a positive C budget, iv) factors governing the depth distribution of SOC, v) physical, chemical and biological mechanisms affecting the rate of decomposition by biotic and abiotic processes, vi) role of soil aggregation in sequestration and protection of SOC and SIC pool, vii) the importance of root system and its exudates in transfer of biomass-C into the SOC pools, viii) significance of biogenic processes in formation of secondary carbonates, ix) the role of dissolved organic C (DOC) in sequestration of SOC and SIC, and x) importance of weathering of alumino-silicates (e.g., powered olivine) in SIC sequestration. Lack of understanding of these and other basic processes leads to misunderstanding, inconsistencies in interpretation of empirical data, and futile debates. Identification of site-specific management practices is also facilitated by understanding of the basic processes of sequestration of SOC and SIC. Sustainable intensification of agroecosystems -- producing more from less by enhancing the use efficiency and reducing losses of inputs, necessitates thorough

  5. The Fate of Carbon Draining Permafrost Soils is Controlled by Photochemical Reactions in Addition to Microbial Degradation in Arctic Surface Waters

    NASA Astrophysics Data System (ADS)

    Kling, G. W.; Dobkowski, J.; Ward, C. P.; Crump, B. C.; Neilson, B. T.; Cory, R. M.

    2013-12-01

    Perhaps the unknown of greatest potential consequence in determining the arc of climate change in this century is the role of thawing permafrost carbon. Arctic soil temperatures are increasing and large areas of permafrost have thawed, but not all soils will thaw quietly in place. Destabilization from melting ice has caused an increase in thermokarst failures that expose buried C and release dissolved organic C (DOC) to surface waters. We found that this exposure to sunlight and surface conditions increases the reactivity of permafrost C to microbial attack by 40% compared to soil DOC held in the dark. The range of lability to microbes depends on microbial community composition and especially on prior light exposure, implying that sunlight may act as an amplification factor in converting frozen C to gases in the atmosphere. We also found that photochemical degradation accounted for the majority (up to 80%) of the degradation of DOC in the water column of lakes and streams. This was based on concurrent measurements of (1) respiration of DOM to CO2 by bacteria in the dark, (2) O2 consumed in DOM photo-oxidation, (3) CO2 produced by DOM photo-mineralization, and (4) photo-stimulated bacterial respiration. Using in-situ UV light profiles and surveys of ~70 surface waters on the North Slope of Alaska, we found that depth-integrated water column rates of photochemical DOM degradation equaled or exceeded dark bacterial respiration, by up to 7x depending on the mean depth of the water column. The total dark and light processing of DOM in these waters was estimated to be roughly 20% of the DOM exported from major rivers on the North Slope of Alaska to the Arctic Ocean. The dominant degradation pathway was the partial photo-oxidation of DOC, which was at least 2x greater than complete photo-mineralization of DOC to CO2 or than bacterial respiration to CO2. This means that the dominant fate of permafrost C released as DOC is to be partially degraded and transported through

  6. Variable carbon contents of lunar soil 74220

    NASA Technical Reports Server (NTRS)

    Gibson, E. K., Jr.; Moore, C. B.

    1973-01-01

    Total carbon, sulfur, and inorganic gas release studies have been carried out on an additional split of orange soil 74220. The total carbon content was found to be 4 plus or minus 3 ppm C for this sample as compared to an earlier reported value of 100 plus or minus 10 ppm C. Gas release studies on the two splits of 74220 indicate that the carbon may be present as a surface condensate on the sample showing the higher carbon content. The 'surface condensate' evolves CO2 upon heating to temperatures below 400 C.

  7. Mechanisms of soil carbon storage in experimental grasslands

    NASA Astrophysics Data System (ADS)

    Steinbeiss, S.; Temperton, V. M.; Gleixner, G.

    2007-10-01

    We investigated the fate of root and litter derived carbon into soil organic matter and dissolved organic matter in soil profiles, in order to explain unexpected positive effects of plant diversity on carbon storage. A time series of soil and soil solution samples was investigated at the field site of The Jena Experiment. In addition to the main biodiversity experiment with C3 plants, a C4 species (Amaranthus retroflexus L.) naturally labeled with 13C was grown on an extra plot. Changes in organic carbon concentration in soil and soil solution were combined with stable isotope measurements to follow the fate of plant carbon into the soil and soil solution. A split plot design with plant litter removal versus double litter input simulated differences in biomass input. After 2 years, the no litter and double litter treatment, respectively, showed an increase of 381 g C m-2 and 263 g C m-2 to 20 cm depth, while 71 g C m-2 and 393 g C m-2 were lost between 20 and 30 cm depth. The isotopic label in the top 5 cm indicated that 11 and 15% of soil organic carbon were derived from plant material on the no litter and the double litter treatment, respectively. Without litter, this equals the total amount of carbon newly stored in soil, whereas with double litter this corresponds to twice the amount of stored carbon. Our results indicate that litter input resulted in lower carbon storage and larger carbon losses and consequently accelerated turnover of soil organic carbon. Isotopic evidence showed that inherited soil organic carbon was replaced by fresh plant carbon near the soil surface. Our results suggest that primarily carbon released from soil organic matter, not newly introduced plant organic matter, was transported in the soil solution and contributed to the observed carbon storage in deeper horizons.

  8. Environmental Controls of Soil Organic Carbon in Soils Across Amazonia

    NASA Astrophysics Data System (ADS)

    Quesada, Carlos Alberto; Paz, Claudia; Phillips, Oliver; Nonato Araujo Filho, Raimundo; Lloyd, Jon

    2015-04-01

    Amazonian forests store and cycle a significant amount of carbon on its soils and vegetation. Yet, Amazonian forests are now subject to strong environmental pressure from both land use and climate change. Some of the more dramatic model projections for the future of the Amazon predict a major change in precipitation followed by savanization of most currently forested areas, resulting in major carbon losses to the atmosphere. However, how soil carbon stocks will respond to climatic and land use changes depend largely on how soil carbon is stabilized. Amazonian soils are highly diverse, being very variable in their weathering levels and chemical and physical properties, and thus it is important to consider how the different soils of the Basin stabilize and store soil organic carbon (SOC). The wide variation in soil weathering levels present in Amazonia, suggests that soil groups with contrasting pedogenetic development should differ in their predominant mechanism of SOC stabilization. In this study we investigated the edaphic, mineralogical and climatic controls of SOC concentration in 147 pristine forest soils across nine different countries in Amazonia, encompassing 14 different WRB soil groups. Soil samples were collected in 1 ha permanent plots used for forest dynamics studies as part of the RAINFOR project. Only 0-30 cm deep averages are reported here. Soil samples were analyzed for carbon and nitrogen and for their chemical (exchangeable bases, phosphorus, pH) and physical properties, (particle size, bulk density) and mineralogy through standard selective dissolution techniques (Fe and Al oxides) and by semi-quantitative X-Ray diffraction. In Addition, selected soils from each soil group had SOC fractionated by physical and chemical techniques. Our results indicate that different stabilization mechanisms are responsible for SOC stabilization in Amazonian soils with contrasting pedogenetic level. Ferralsols and Acrisols were found to have uniform mineralogy

  9. Soil carbon determination by thermogravimetrics.

    PubMed

    Pallasser, Robert; Minasny, Budiman; McBratney, Alex B

    2013-01-01

    Determination of soil constituents and structure has a vital role in agriculture generally. Methods for the determination of soil carbon have in particular gained greater currency in recent times because of the potential that soils offer in providing offsets for greenhouse gas (CO2-equivalent) emissions. Ideally, soil carbon which can also be quite diverse in its makeup and origin, should be measureable by readily accessible, affordable and reliable means. Loss-on-ignition is still a widely used method being suitably simple and available but may have limitations for soil C monitoring. How can these limitations be better defined and understood where such a method is required to detect relatively small changes during soil-C building? Thermogravimetric (TGA) instrumentation to measure carbonaceous components has become more interesting because of its potential to separate carbon and other components using very precise and variable heating programs. TGA related studies were undertaken to assist our understanding in the quantification of soil carbon when using methods such as loss-on-ignition. Combining instrumentation so that mass changes can be monitored by mass spectrometer ion currents has elucidated otherwise hidden features of thermal methods enabling the interpretation and evaluation of mass-loss patterns. Soil thermogravimetric work has indicated that loss-on-ignition methods are best constrained to temperatures from 200 to 430 °C for reliable determination for soil organic carbon especially where clay content is higher. In the absence of C-specific detection where mass only changes are relied upon, exceeding this temperature incurs increasing contributions from inorganic sources adding to mass losses with diminishing contributions related to organic matter. The smaller amounts of probably more recalcitrant organic matter released at the higher temperatures may represent mineral associated material and/or simply more refractory forms.

  10. [Responses of forest soil carbon pool and carbon cycle to the changes of carbon input].

    PubMed

    Wang, Qing-kui

    2011-04-01

    Litters and plant roots are the main sources of forest soil organic carbon (C). This paper summarized the effects of the changes in C input on the forest soil C pool and C cycle, and analyzed the effects of these changes on the total soil C, microbial biomass C, dissoluble organic C, and soil respiration. Different forests in different regions had inconsistent responses to C input change, and the effects of litter removal or addition and of root exclusion or not differed with tree species and regions. Current researches mainly focused on soil respiration and C pool fractions, and scarce were about the effects of C input change on the changes of soil carbon structure and stability as well as the response mechanisms of soil organisms especially soil fauna, which should be strengthened in the future. PMID:21774335

  11. [Responses of forest soil carbon pool and carbon cycle to the changes of carbon input].

    PubMed

    Wang, Qing-kui

    2011-04-01

    Litters and plant roots are the main sources of forest soil organic carbon (C). This paper summarized the effects of the changes in C input on the forest soil C pool and C cycle, and analyzed the effects of these changes on the total soil C, microbial biomass C, dissoluble organic C, and soil respiration. Different forests in different regions had inconsistent responses to C input change, and the effects of litter removal or addition and of root exclusion or not differed with tree species and regions. Current researches mainly focused on soil respiration and C pool fractions, and scarce were about the effects of C input change on the changes of soil carbon structure and stability as well as the response mechanisms of soil organisms especially soil fauna, which should be strengthened in the future.

  12. Green Carbon, Black Carbon, White Carbon: Simultaneous Differentiation Between Soil Organic Matter, Pyrogenic Carbon and Carbonates Using Thermal Analysis Techniques

    NASA Astrophysics Data System (ADS)

    Plante, A. F.; Peltre, C.; Chan, J.; Baumgartl, T.; Erskine, P.; Apesteguía, M.; Virto, I.

    2014-12-01

    Quantification of soil carbon stocks and fluxes continues to be an important endeavor in assessments of soil quality, and more broadly in assessments of ecosystem functioning. The quantification of soil carbon in alkaline, carbonate-containing soils, such as those found in Mediterranean areas, is complicated by the need to differentiate between organic carbon (OC) and inorganic carbon (IC), which continues to present methodological challenges. Acidification is frequently used to eliminate carbonates prior to soil OC quantification, but when performed in the liquid phase, can promote the dissolution and loss of a portion of the OC. Acid fumigation (AF) is increasingly preferred for carbonate removal, but its effectiveness is difficult to assess using conventional elemental and isotopic analyses. The two-step approach is time, labor and cost intensive, and generates additional uncertainties from the calculations. Quantification of the actively cycling pool of soil organic C (SOC) in many soils is further complicated by the potential presence of more recalcitrant/stable forms such as pyrogenic or black carbon (BC) derived from incomplete combustion of vegetation, or even geogenic carbon such as coal. The wide spectrum of materials currently considered BC makes its quantification challenging. The chemical method using benzene polycarboxylic acids (BPCAs) as markers of condensed aromatic structures indicative of pyrogenic C is highly time, labor and cost intensive, and can generate artifacts. Several research groups are now developing method for the simultaneous identification and quantification of these various forms of soil carbon using thermal analysis techniques such as thermogravimetry, differential scanning calorimetry and evolved gas analysis. The objective of this presentation is to provide a general overview and specific examples of the current progress and technical challenges in this evolving methodology.

  13. Soil organic carbon mining versus priming - controls of soil organic carbon stocks along a management gradient

    NASA Astrophysics Data System (ADS)

    Blanes, M. Carmen; Reinsch, Sabine; Glanville, Helen C.; Jones, Davey L.; Carreira, José A.; Pastrana, David N.; Emmett, Bridget A.

    2015-04-01

    Soil carbon (C), nitrogen (N) and phosphorous (P) are assumed to be connected stoichiometrically and C:N(:P) ratios are frequently used to interpret the soils nutrient status. However, plants are capable of initiating the supply of nutrients by releasing rhizodeposits into the soil, thereby stimulating soil organic matter decomposition mediated by the rhizosphere microbial community. To test the relative importance of the two mechanisms across a fertility gradient in the UK we carried out a laboratory experiment. Intact soil cores from two depths (0-15 cm and 85-100 cm) were incubated and C, N and P were added in all possible combinations resulting in a total of 216 soil cores. Soil respiration was measured (1 h incubation, 10 oC) nine times over a 2 week period. Preliminary results indicate that all soils were C limited at the surface as measured as increased soil CO2 efflux. N additions increased soil respiration only marginally, whereas C+N stimulated microbial activity on the surface, and was even more pronounced in the deeper soil layer. Belowground responses to C+P were small and even smaller for N+P but similar for both soil depths. Our results indicate nutrient controls on soil organic matter turnover differ not only across a management/fertility gradient but also vertically down the soil profile.

  14. Effects of Biochar Amendment on Soil Properties and Soil Carbon Sequestration

    NASA Astrophysics Data System (ADS)

    Zhang, R.; Zhu, S.

    2015-12-01

    Biochar addition to soils potentially affects various soil properties and soil carbon sequestration, and these effects are dependent on biochars derived from different feedstock materials and pyrolysis processes. The objective of this study was to investigate the effects of amendment of different biochars on soil physical and biological properties as well as soil carbon sequestration. Biochars were produced with dairy manure and woodchip at temperatures of 300, 500, and 700°C, respectively. Each biochar was mixed at 5% (w/w) with a forest soil and the mixture was incubated for 180 days, during which soil physical and biological properties, and soil respiration rates were measured. Results showed that the biochar addition significantly enhanced the formation of soil macroaggregates at the early incubation time. The biochar application significantly reduced soil bulk density, increased the amount of soil organic matter, and stimulated microbial activity and soil respiration rates at the early incubation stage. Biochar applications improved water retention capacity, with stronger effects by biochars produced at higher pyrolysis temperatures. At the same suction, the soil with woodchip biochars possessed higher water content than with the dairy manure biochars. Biochar addition significantly affected the soil physical and biological properties, which resulted in different soil carbon mineralization rates and the amount of soil carbon storage.

  15. [Effects of Chinese fir litter on soil organic carbon decomposition and microbial biomass carbon].

    PubMed

    Wang, Xiao-Feng; Wang, Si-Long; Zhang, Wei-Dong

    2013-09-01

    By using 13C stable isotope tracer technique, this paper studied the effects of Chinese fir litter addition on the soil organic carbon (SOC) decomposition, microbial biomass carbon, and dissolved organic carbon in 0-5 cm and 40-45 cm layers. The decomposition rate of SOC in 40-45 cm layer was significantly lower than that in 0-5 cm layer, but the priming effect induced by the Chinese fir litter addition showed an opposite trend. The Chinese fir litter addition increased the soil total microbial biomass carbon and the microbial biomass carbon derived from native soil significantly, but had less effects on the soil dissolved organic carbon. Turning over the subsoil to the surface of the woodland could accelerate the soil carbon loss in Chinese fir plantation due to the priming effect induced by the litters. PMID:24417093

  16. [Effects of Chinese fir litter on soil organic carbon decomposition and microbial biomass carbon].

    PubMed

    Wang, Xiao-Feng; Wang, Si-Long; Zhang, Wei-Dong

    2013-09-01

    By using 13C stable isotope tracer technique, this paper studied the effects of Chinese fir litter addition on the soil organic carbon (SOC) decomposition, microbial biomass carbon, and dissolved organic carbon in 0-5 cm and 40-45 cm layers. The decomposition rate of SOC in 40-45 cm layer was significantly lower than that in 0-5 cm layer, but the priming effect induced by the Chinese fir litter addition showed an opposite trend. The Chinese fir litter addition increased the soil total microbial biomass carbon and the microbial biomass carbon derived from native soil significantly, but had less effects on the soil dissolved organic carbon. Turning over the subsoil to the surface of the woodland could accelerate the soil carbon loss in Chinese fir plantation due to the priming effect induced by the litters.

  17. Carbon Sequestration in Forest Soils

    NASA Astrophysics Data System (ADS)

    Lal, R.

    2006-05-01

    Carbon (C) sequestration in soils and forests is an important strategy of reducing the net increase in atmospheric CO2 concentration by fossil fuel combustion, deforestation, biomass burning, soil cultivation and accelerated erosion. Further, the so-called "missing or fugitive CO2" is also probably being absorbed in a terrestrial sink. Three of the 15 strategies proposed to stabilize atmospheric CO2 concentrations by 2054, with each one to sequester 1 Pg Cyr-1, include: (i) biofuel plantations for bioethanol production, (ii) reforestation, afforestation and establishment of new plantations, and (iii) conversion of plow tillage to no-till farming. Enhancing soil organic carbon (SOC) pool is an important component in each of these three options, but especially so in conversion of degraded/marginal agricultural soils to short rotation woody perennials, and establishment of plantations for biofuel, fiber and timber production. Depending upon the prior SOC loss because of the historic land used and management-induced soil degradation, the rate of soil C sequestration in forest soils may be 0 to 3 Mg C ha-1 yr-1. Tropical forest ecosystems cover 1.8 billion hectares and have a SOC sequestration potential of 200 to 500 Tg C yr-1 over 59 years. However, increasing production of forest biomass may not always increase the SOC pool. Factors limiting the rate of SOC sequestration include C: N ratio, soil availability of N and other essential nutrients, concentration of recalcitrant macro-molecules (e.g., lignin, suberin), soil properties (e.g., clay content and mineralogy, aggregation), soil drainage, and climate (mean annual precipitation and temperature). The SOC pool can be enhanced by adopting recommended methods of forest harvesting and site preparation to minimize the "Covington effect," improving soil drainage, alleviating soil compaction, growing species with a high NPP, and improving soil fertility including the availability of micro-nutrients. Soil fertility

  18. Worldwide organic soil carbon and nitrogen data

    SciTech Connect

    Zinke, P.J.; Stangenberger, A.G.; Post, W.M.; Emanual, W.R.; Olson, J.S.

    1986-09-01

    The objective of the research presented in this package was to identify data that could be used to estimate the size of the soil organic carbon pool under relatively undisturbed soil conditions. A subset of the data can be used to estimate amounts of soil carbon storage at equilibrium with natural soil-forming factors. The magnitude of soil properties so defined is a resulting nonequilibrium values for carbon storage. Variation in these values is due to differences in local and geographic soil-forming factors. Therefore, information is included on location, soil nitrogen content, climate, and vegetation along with carbon density and variation.

  19. Molecular aspects of aromatic C additions to soils: Implications of biochar quality for ecosystem functionality

    EPA Science Inventory

    Solid residues of incomplete combustion (biochar or char) are continuously being added to soils due to natural vegetation fires in many ecosystems. However, new strategies for carbon sequestration in soils are likely to include the active addition of biochar to soils. Since bioc...

  20. RESPONSE OF SOIL MICROBIAL BIOMASS AND COMMUNITY COMPOSITION TO CHRONIC NITROGEN ADDITIONS AT HARVARD FOREST

    EPA Science Inventory

    Soil microbial communities may respond to anthropogenic increases in ecosystem nitrogen (N) availability, and their response may ultimately feedback on ecosystem carbon and N dynamics. We examined the long-term effects of chronic N additions on soil microbes by measuring soil mi...

  1. Permafrost soils and carbon cycling

    DOE PAGES

    Ping, C. L.; Jastrow, J. D.; Jorgenson, M. T.; Michaelson, G. J.; Shur, Y. L.

    2014-10-30

    Knowledge of soils in the permafrost region has advanced immensely in recent decades, despite the remoteness and inaccessibility of most of the region and the sampling limitations posed by the severe environment. These efforts significantly increased estimates of the amount of organic carbon (OC) stored in permafrost-region soils and improved understanding of how pedogenic processes unique to permafrost environments built enormous OC stocks during the Quaternary. This knowledge has also called attention to the importance of permafrost-affected soils to the global C cycle and the potential vulnerability of the region's soil OC stocks to changing climatic conditions. In this review,more » we briefly introduce the permafrost characteristics, ice structures, and cryopedogenic processes that shape the development of permafrost-affected soils and discuss their effects on soil structures and on organic matter distributions within the soil profile. We then examine the quantity of OC stored in permafrost-region soils, as well as the characteristics, intrinsic decomposability, and potential vulnerability of this OC to permafrost thaw under a warming climate.« less

  2. Biogeochemistry: Soil carbon in a beer can

    NASA Astrophysics Data System (ADS)

    Davidson, Eric A.

    2015-10-01

    Decomposition of soil organic matter could be an important positive feedback to climate change. Geochemical properties of soils can help determine what fraction of soil carbon may be protected from climate-induced decomposition.

  3. Effects of soil warming and nitrogen addition on soil respiration in a New Zealand tussock grassland.

    PubMed

    Graham, Scott L; Hunt, John E; Millard, Peter; McSeveny, Tony; Tylianakis, Jason M; Whitehead, David

    2014-01-01

    Soil respiration (RS) represents a large terrestrial source of CO2 to the atmosphere. Global change drivers such as climate warming and nitrogen deposition are expected to alter the terrestrial carbon cycle with likely consequences for RS and its components, autotrophic (RA) and heterotrophic respiration (RH). Here we investigate the impacts of a 3°C soil warming treatment and a 50 kg ha(-1) y(-1) nitrogen addition treatment on RS, RH and their respective seasonal temperature responses in an experimental tussock grassland. Average respiration in untreated soils was 0.96±0.09 μmol m(-2) s(-1) over the course of the experiment. Soil warming and nitrogen addition increased RS by 41% and 12% respectively. These treatment effects were additive under combined warming and nitrogen addition. Warming increased RH by 37% while nitrogen addition had no effect. Warming and nitrogen addition affected the seasonal temperature response of RS by increasing the basal rate of respiration (R10) by 14% and 20% respectively. There was no significant interaction between treatments for R10. The treatments had no impact on activation energy (E0). The seasonal temperature response of RH was not affected by either warming or nitrogen addition. These results suggest that the additional CO2 emissions from New Zealand tussock grassland soils as a result of warming-enhanced RS constitute a potential positive feedback to rising atmospheric CO2 concentration.

  4. Altered soil microbial community at elevated CO2 leads to loss of soil carbon

    PubMed Central

    Carney, Karen M.; Hungate, Bruce A.; Drake, Bert G.; Megonigal, J. Patrick

    2007-01-01

    Increased carbon storage in ecosystems due to elevated CO2 may help stabilize atmospheric CO2 concentrations and slow global warming. Many field studies have found that elevated CO2 leads to higher carbon assimilation by plants, and others suggest that this can lead to higher carbon storage in soils, the largest and most stable terrestrial carbon pool. Here we show that 6 years of experimental CO2 doubling reduced soil carbon in a scrub-oak ecosystem despite higher plant growth, offsetting ≈52% of the additional carbon that had accumulated at elevated CO2 in aboveground and coarse root biomass. The decline in soil carbon was driven by changes in soil microbial composition and activity. Soils exposed to elevated CO2 had higher relative abundances of fungi and higher activities of a soil carbon-degrading enzyme, which led to more rapid rates of soil organic matter degradation than soils exposed to ambient CO2. The isotopic composition of microbial fatty acids confirmed that elevated CO2 increased microbial utilization of soil organic matter. These results show how elevated CO2, by altering soil microbial communities, can cause a potential carbon sink to become a carbon source. PMID:17360374

  5. Soil nitrogen cycling and nitrous oxide flux in a Rocky Mountain Douglas-fir forest - Effects of fertilization, irrigation and carbon addition

    NASA Technical Reports Server (NTRS)

    Matson, Pamela A.; Gower, Stith T.; Volkmann, Carol; Billow, Christine; Grier, Charles C.

    1992-01-01

    Nitrous oxide fluxes and soil nitrogen transformations were measured in experimentally-treated high elevation Douglas-fir forests in northwestern New Mexico, USA. On an annual basis, forests that were fertilized with 200 kg N/ha emitted an average of 0.66 kg/ha of N2O-N, with highest fluxes occurring in July and August when soils were both warm and wet. Control, irrigated, and woodchip treated plots did not differ, and annual average fluxes ranged from 0.03 to 0.23 kg/ha. Annual net nitrogen mineralization and nitrate production were estimated in soil and forest floor using in situ incubations; fertilized soil mineralized 277 kg/ha/y in contrast to 18 kg/ha/y in control plots. Relative recovery of 15NH4-N applied to soil in laboratory incubations was principally in the form of NO3-N in the fertilized soils, while recovery was mostly in microbial biomass-N in the other treatments. Fertilization apparently added nitrogen that exceeded the heterotrophic microbial demand, resulting in higher rates of nitrate production and higher nitrous oxide fluxes. Despite the elevated nitrous oxide emission resulting from fertilization, we estimate that global inputs of nitrogen into forests are not currently contributing significantly to the increasing concentrations of nitrous oxide in the atmosphere.

  6. A disconnect between O horizon and mineral soil carbon - Implications for soil C sequestration

    SciTech Connect

    Garten Jr, Charles T

    2009-01-01

    Changing inputs of carbon to soil is one means of potentially increasing carbon sequestration in soils for the purpose of mitigating projected increases in atmospheric CO{sub 2} concentrations. The effect of manipulations of aboveground carbon input on soil carbon storage was tested in a temperate, deciduous forest in east Tennessee, USA. A 4.5-year experiment included exclusion of aboveground litterfall and supplemental litter additions (three times ambient) in an upland and a valley that differed in soil nitrogen availability. The estimated decomposition rate of the carbon stock in the O horizon was greater in the valley than in the upland due to higher litter quality (i.e., lower C/N ratios). Short-term litter exclusion or addition had no effect on carbon stock in the mineral soil, measured to a depth of 30 cm, or the partitioning of carbon in the mineral soil between particulate- and mineral-associated organic matter. A two-compartment model was used to interpret results from the field experiments. Field data and a sensitivity analysis of the model were consistent with little carbon transfer between the O horizon and the mineral soil. Increasing aboveground carbon input does not appear to be an effective means of promoting carbon sequestration in forest soil at the location of the present study because a disconnect exists in carbon dynamics between O horizon and mineral soil. Factors that directly increase inputs to belowground soil carbon, via roots, or reduce decomposition rates of organic matter are more likely to benefit efforts to increase carbon sequestration in forests where carbon dynamics in the O horizon are uncoupled from the mineral soil.

  7. Carbon sequestration potential of soils in southeast Germany derived from stable soil organic carbon saturation.

    PubMed

    Wiesmeier, Martin; Hübner, Rico; Spörlein, Peter; Geuß, Uwe; Hangen, Edzard; Reischl, Arthur; Schilling, Bernd; von Lützow, Margit; Kögel-Knabner, Ingrid

    2014-02-01

    Sequestration of atmospheric carbon (C) in soils through improved management of forest and agricultural land is considered to have high potential for global CO2 mitigation. However, the potential of soils to sequester soil organic carbon (SOC) in a stable form, which is limited by the stabilization of SOC against microbial mineralization, is largely unknown. In this study, we estimated the C sequestration potential of soils in southeast Germany by calculating the potential SOC saturation of silt and clay particles according to Hassink [Plant and Soil 191 (1997) 77] on the basis of 516 soil profiles. The determination of the current SOC content of silt and clay fractions for major soil units and land uses allowed an estimation of the C saturation deficit corresponding to the long-term C sequestration potential. The results showed that cropland soils have a low level of C saturation of around 50% and could store considerable amounts of additional SOC. A relatively high C sequestration potential was also determined for grassland soils. In contrast, forest soils had a low C sequestration potential as they were almost C saturated. A high proportion of sites with a high degree of apparent oversaturation revealed that in acidic, coarse-textured soils the relation to silt and clay is not suitable to estimate the stable C saturation. A strong correlation of the C saturation deficit with temperature and precipitation allowed a spatial estimation of the C sequestration potential for Bavaria. In total, about 395 Mt CO2 -equivalents could theoretically be stored in A horizons of cultivated soils - four times the annual emission of greenhouse gases in Bavaria. Although achieving the entire estimated C storage capacity is unrealistic, improved management of cultivated land could contribute significantly to CO2 mitigation. Moreover, increasing SOC stocks have additional benefits with respect to enhanced soil fertility and agricultural productivity.

  8. Soil carbon dynamics in cropland and rangeland.

    PubMed

    Lal, R

    2002-01-01

    Most soils in the Midwestern USA have lost 30 to 50% of their original pool, or 25 to 40 Mg C/ha, upon conversion from natural to agricultural ecosystems. About 60 to 70% of the C thus depleted can be resequestered through adoption of recommended soil and crop management practices. These practices include conversion from plow till to no till, frequent use of winter cover crops in the rotation cycle, elimination of summer fallow, integrated nutrient management along with liberal use of biosolids and biological nitrogen fixation, precision farming to minimize losses and enhance fertilizer use efficiency, and use of improved varieties with ability to produce large root biomass with high content of lignin and suberin. The gross rate of soil organic carbon (SOC) sequestration ranges from 500 to 800 kg/ha/year in cold and humid regions and 100 to 300 kg/ha/year in dry and warm regions. The rate of SOC sequestration can be measured with procedures that are cost effective and credible at soil pedon level, landscape level, regional or national scale. In addition to SOC, there is also a large potential to sequester soil inorganic carbon (SIC) in arid and semi-arid regions. Soil C sequestration has numerous ancillary benefits. It is truly a win-win situation: extremely cost-effective, and a bridge to the future until alternative energy options take effect.

  9. Soil nitrogen cycling and nitrous oxide flux in a Rocky Mountain Douglas-fir forest - Effects of fertilization, irrigation and carbon addition

    NASA Technical Reports Server (NTRS)

    Matson, Pamela A.; Gower, Stith T.; Volkmann, Carol; Billow, Christine; Grier, Charles C.

    1992-01-01

    Nitrous oxide fluxes and soil nitrogen transformations were measured in experimentally-treated high elevation Douglas-fir forests in northwestern New Mexico. On an annual basis, forests that were fertilized with 200 kg N/ha emitted an average of 0.66 kg/ha of N2O-N, with highest fluxes occurring in July and August when soils were both warm and wet. Control, irrigated, and woodchip treated plots were not different from each other, and annual average fluxes ranged from 0.03 to 0.23 kg/ha. Fertilized soil mineralized 277 kg/ha per year in contrast to 18 kg/ha per year in control plots. Relative recovery of (N-15)H4-N applied to soil in laboratory incubations was principally in the form of NO3-N in the fertilized soils, while recovery was mostly in microbial biomass-N in the other treatments. Fertilization apparently added nitrogen that exceeded the heterotrophic microbial demand, resulting in higher rates of nitrate production and higher nitrous oxide fluxes. Global inputs of nitrogen into forests are not currently contributing significantly to the increasing concentrations of nitrous oxide in the atmosphere.

  10. Legacy effects of grassland management on soil carbon to depth.

    PubMed

    Ward, Susan E; Smart, Simon M; Quirk, Helen; Tallowin, Jerry R B; Mortimer, Simon R; Shiel, Robert S; Wilby, Andrew; Bardgett, Richard D

    2016-08-01

    The importance of managing land to optimize carbon sequestration for climate change mitigation is widely recognized, with grasslands being identified as having the potential to sequester additional carbon. However, most soil carbon inventories only consider surface soils, and most large-scale surveys group ecosystems into broad habitats without considering management intensity. Consequently, little is known about the quantity of deep soil carbon and its sensitivity to management. From a nationwide survey of grassland soils to 1 m depth, we show that carbon in grassland soils is vulnerable to management and that these management effects can be detected to considerable depth down the soil profile, albeit at decreasing significance with depth. Carbon concentrations in soil decreased as management intensity increased, but greatest soil carbon stocks (accounting for bulk density differences), were at intermediate levels of management. Our study also highlights the considerable amounts of carbon in subsurface soil below 30 cm, which is missed by standard carbon inventories. We estimate grassland soil carbon in Great Britain to be 2097 Tg C to a depth of 1 m, with ~60% of this carbon being below 30 cm. Total stocks of soil carbon (t ha(-1) ) to 1 m depth were 10.7% greater at intermediate relative to intensive management, which equates to 10.1 t ha(-1) in surface soils (0-30 cm), and 13.7 t ha(-1) in soils from 30 to 100 cm depth. Our findings highlight the existence of substantial carbon stocks at depth in grassland soils that are sensitive to management. This is of high relevance globally, given the extent of land cover and large stocks of carbon held in temperate managed grasslands. Our findings have implications for the future management of grasslands for carbon storage and climate mitigation, and for global carbon models which do not currently account for changes in soil carbon to depth with management.

  11. Legacy effects of grassland management on soil carbon to depth.

    PubMed

    Ward, Susan E; Smart, Simon M; Quirk, Helen; Tallowin, Jerry R B; Mortimer, Simon R; Shiel, Robert S; Wilby, Andrew; Bardgett, Richard D

    2016-08-01

    The importance of managing land to optimize carbon sequestration for climate change mitigation is widely recognized, with grasslands being identified as having the potential to sequester additional carbon. However, most soil carbon inventories only consider surface soils, and most large-scale surveys group ecosystems into broad habitats without considering management intensity. Consequently, little is known about the quantity of deep soil carbon and its sensitivity to management. From a nationwide survey of grassland soils to 1 m depth, we show that carbon in grassland soils is vulnerable to management and that these management effects can be detected to considerable depth down the soil profile, albeit at decreasing significance with depth. Carbon concentrations in soil decreased as management intensity increased, but greatest soil carbon stocks (accounting for bulk density differences), were at intermediate levels of management. Our study also highlights the considerable amounts of carbon in subsurface soil below 30 cm, which is missed by standard carbon inventories. We estimate grassland soil carbon in Great Britain to be 2097 Tg C to a depth of 1 m, with ~60% of this carbon being below 30 cm. Total stocks of soil carbon (t ha(-1) ) to 1 m depth were 10.7% greater at intermediate relative to intensive management, which equates to 10.1 t ha(-1) in surface soils (0-30 cm), and 13.7 t ha(-1) in soils from 30 to 100 cm depth. Our findings highlight the existence of substantial carbon stocks at depth in grassland soils that are sensitive to management. This is of high relevance globally, given the extent of land cover and large stocks of carbon held in temperate managed grasslands. Our findings have implications for the future management of grasslands for carbon storage and climate mitigation, and for global carbon models which do not currently account for changes in soil carbon to depth with management. PMID:26854892

  12. Soil warming, carbon–nitrogen interactions, and forest carbon budgets

    PubMed Central

    Melillo, Jerry M.; Butler, Sarah; Johnson, Jennifer; Mohan, Jacqueline; Steudler, Paul; Lux, Heidi; Burrows, Elizabeth; Bowles, Francis; Smith, Rose; Scott, Lindsay; Vario, Chelsea; Hill, Troy; Burton, Andrew; Zhou, Yu-Mei; Tang, Jim

    2011-01-01

    Soil warming has the potential to alter both soil and plant processes that affect carbon storage in forest ecosystems. We have quantified these effects in a large, long-term (7-y) soil-warming study in a deciduous forest in New England. Soil warming has resulted in carbon losses from the soil and stimulated carbon gains in the woody tissue of trees. The warming-enhanced decay of soil organic matter also released enough additional inorganic nitrogen into the soil solution to support the observed increases in plant carbon storage. Although soil warming has resulted in a cumulative net loss of carbon from a New England forest relative to a control area over the 7-y study, the annual net losses generally decreased over time as plant carbon storage increased. In the seventh year, warming-induced soil carbon losses were almost totally compensated for by plant carbon gains in response to warming. We attribute the plant gains primarily to warming-induced increases in nitrogen availability. This study underscores the importance of incorporating carbon–nitrogen interactions in atmosphere–ocean–land earth system models to accurately simulate land feedbacks to the climate system. PMID:21606374

  13. One strategy for estimating the potential soil carbon storage due to CO{sub 2} fertilization

    SciTech Connect

    Harrison, K.G.; Bonani, G.

    1994-06-01

    Soil radiocarbon measurements can be used to estimate soil carbon turnover rates and inventories. A labile component of soil carbon has the potential to respond to perturbations such as CO{sub 2} fertilization, changing climate, and changing land use. Soil carbon has influenced past and present atmospheric CO{sub 2} levels and will influence future levels. A model is used to calculate the amount of additional carbon stored in soil because of CO{sub 2} fertilization.

  14. Accessibility, searchability, transparency and engagement of soil carbon data: The International Soil Carbon Network

    NASA Astrophysics Data System (ADS)

    Harden, Jennifer W.; Hugelius, Gustaf; Koven, Charlie; Sulman, Ben; O'Donnell, Jon; He, Yujie

    2016-04-01

    correlated with bulk density and porosity of the rock/sediment matrix. Thus C storage is most stable at depth, yet is susceptible to changes in tillage, rooting depths, and erosion/sedimentation. Fourth, current ESMs likely overestimate the turnover time of soil organic carbon and subsequently overestimate soil carbon sequestration, thus datasets combined with other soil properties will help constrain the ESM predictions. Last, analysis of soil horizon and carbon data showed that soils with a history of tillage had significantly lower carbon concentrations in both near-surface and deep layers, and that the effect persisted even in reforested areas. In addition to the opportunities for empirical science using a large database, the database has great promise for evaluation of biogeochemical and earth system models. The preservation of individual soil core measurements avoids issues with spatial averaging while facilitating evaluation of advanced model processes such as depth distributions of soil carbon, land use impacts, and spatial heterogeneity.

  15. Limits to soil carbon stability; Deep, ancient soil carbon decomposition stimulated by new labile organic inputs

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Soil carbon (C) pools store about one-third of the total terrestrial organic carbon. Deep soil C pools (below 1 m) are thought to be stable due to their low biodegradability, but little is known about soil microbial processes and carbon dynamics below the soil surface, or how global change might aff...

  16. Plant soil interactions alter carbon cycling in an upland grassland soil.

    PubMed

    Thomson, Bruce C; Ostle, Nick J; McNamara, Niall P; Oakley, Simon; Whiteley, Andrew S; Bailey, Mark J; Griffiths, Robert I

    2013-01-01

    Soil carbon (C) storage is dependent upon the complex dynamics of fresh and native organic matter cycling, which are regulated by plant and soil-microbial activities. A fundamental challenge exists to link microbial biodiversity with plant-soil C cycling processes to elucidate the underlying mechanisms regulating soil carbon. To address this, we contrasted vegetated grassland soils with bare soils, which had been plant-free for 3 years, using stable isotope ((13)C) labeled substrate assays and molecular analyses of bacterial communities. Vegetated soils had higher C and N contents, biomass, and substrate-specific respiration rates. Conversely, following substrate addition unlabeled, native soil C cycling was accelerated in bare soil and retarded in vegetated soil; indicative of differential priming effects. Functional differences were reflected in bacterial biodiversity with Alphaproteobacteria and Acidobacteria dominating vegetated and bare soils, respectively. Significant isotopic enrichment of soil RNA was found after substrate addition and rates varied according to substrate type. However, assimilation was independent of plant presence which, in contrast to large differences in (13)CO2 respiration rates, indicated greater substrate C use efficiency in bare, Acidobacteria-dominated soils. Stable isotope probing (SIP) revealed most community members had utilized substrates with little evidence for competitive outgrowth of sub-populations. Our findings support theories on how plant-mediated soil resource availability affects the turnover of different pools of soil carbon, and we further identify a potential role of soil microbial biodiversity. Specifically we conclude that emerging theories on the life histories of dominant soil taxa can be invoked to explain changes in soil carbon cycling linked to resource availability, and that there is a strong case for considering microbial biodiversity in future studies investigating the turnover of different pools of soil

  17. Plant soil interactions alter carbon cycling in an upland grassland soil

    PubMed Central

    Thomson, Bruce C.; Ostle, Nick J.; McNamara, Niall P.; Oakley, Simon; Whiteley, Andrew S.; Bailey, Mark J.; Griffiths, Robert I.

    2013-01-01

    Soil carbon (C) storage is dependent upon the complex dynamics of fresh and native organic matter cycling, which are regulated by plant and soil-microbial activities. A fundamental challenge exists to link microbial biodiversity with plant-soil C cycling processes to elucidate the underlying mechanisms regulating soil carbon. To address this, we contrasted vegetated grassland soils with bare soils, which had been plant-free for 3 years, using stable isotope (13C) labeled substrate assays and molecular analyses of bacterial communities. Vegetated soils had higher C and N contents, biomass, and substrate-specific respiration rates. Conversely, following substrate addition unlabeled, native soil C cycling was accelerated in bare soil and retarded in vegetated soil; indicative of differential priming effects. Functional differences were reflected in bacterial biodiversity with Alphaproteobacteria and Acidobacteria dominating vegetated and bare soils, respectively. Significant isotopic enrichment of soil RNA was found after substrate addition and rates varied according to substrate type. However, assimilation was independent of plant presence which, in contrast to large differences in 13CO2 respiration rates, indicated greater substrate C use efficiency in bare, Acidobacteria-dominated soils. Stable isotope probing (SIP) revealed most community members had utilized substrates with little evidence for competitive outgrowth of sub-populations. Our findings support theories on how plant-mediated soil resource availability affects the turnover of different pools of soil carbon, and we further identify a potential role of soil microbial biodiversity. Specifically we conclude that emerging theories on the life histories of dominant soil taxa can be invoked to explain changes in soil carbon cycling linked to resource availability, and that there is a strong case for considering microbial biodiversity in future studies investigating the turnover of different pools of soil

  18. Effects of bagasse-charcoal addition to soil on nitrate leaching in calcaric soils

    NASA Astrophysics Data System (ADS)

    Kameyama, K.; Miyamoto, T.; Shinogi, Y.

    2009-12-01

    Nitrate leaching in soils is often an important aspect in agriculture. Nitrate is leached from the root zone, where plants can utilize them, by surplus rainfall because little nitrate is absorbed by soil colloids. Miyako Island (target area) is located in the subtropical zone and comprised of coral limestone with high permeability. Land surface is covered with calcaric dark red soil that is called “Shimajiri-Maji”. Since the soil has low water- and fertilizer-retaining capacity, fertilizer-derived nitrogen easily leaches from the root zone during surplus rainfall and the nitrogen utilization efficiency of crops is relatively low. Biochars, charcoal produced from pyrolysis of biomass, are known to adsorb dissolved nitrate. Sugarcane bagasse is the main biomass resource on the island because agriculture is the main industry on the island and sugarcane is cultivated in approximately 70% of the farmland. However, the adsorption characteristics of bagasse-charcoals for nitrate have not yet been clarified. The objective of this study was to evaluate the dependency of carbonization temperatures on the nitrate adsorption properties of bagasse-charcoals and the effects of bagasse-charcoal addition to the soil on NO3-N transport in the soil for optimal use of bagasse-charcoal as a soil amendment in Miyako Island. Sugarcane bagasse were air-dried and heated in a batch-type carbonization furnace at five different carbonization temperatures (400, 500, 600, 700 and 800°C) with a holding time of 2 h. Nitrate adsorption by soil and bagasse-charcoals at each carbonization temperature was measured by the batch equilibrium technique. NO3-N transport behavior in charcoal-amended soils (rates of charcoal addition: 0, 5 and 10 wt %) was evaluated in the column experiments. The breakthrough curves of NO3-N concentrations in the effluents from the bottom of the columns were analyzed with a convective-dispersion model. The model described one-dimensional transport of a sorbing solute

  19. Ectomycorrhizal fungi slow soil carbon cycling.

    PubMed

    Averill, Colin; Hawkes, Christine V

    2016-08-01

    Respiration of soil organic carbon is one of the largest fluxes of CO2 on earth. Understanding the processes that regulate soil respiration is critical for predicting future climate. Recent work has suggested that soil carbon respiration may be reduced by competition for nitrogen between symbiotic ectomycorrhizal fungi that associate with plant roots and free-living microbial decomposers, which is consistent with increased soil carbon storage in ectomycorrhizal ecosystems globally. However, experimental tests of the mycorrhizal competition hypothesis are lacking. Here we show that ectomycorrhizal roots and hyphae decrease soil carbon respiration rates by up to 67% under field conditions in two separate field exclusion experiments, and this likely occurs via competition for soil nitrogen, an effect larger than 2 °C soil warming. These findings support mycorrhizal competition for nitrogen as an independent driver of soil carbon balance and demonstrate the need to understand microbial community interactions to predict ecosystem feedbacks to global climate. PMID:27335203

  20. Analysis and Modeling of soil hydrology under different soil additives in artificial runoff plots

    NASA Astrophysics Data System (ADS)

    Ruidisch, M.; Arnhold, S.; Kettering, J.; Huwe, B.; Kuzyakov, Y.; Ok, Y.; Tenhunen, J. D.

    2009-12-01

    The impact of monsoon events during June and July in the Korean project region Haean Basin, which is located in the northeastern part of South Korea plays a key role for erosion, leaching and groundwater pollution risk by agrochemicals. Therefore, the project investigates the main hydrological processes in agricultural soils under field and laboratory conditions on different scales (plot, hillslope and catchment). Soil hydrological parameters were analysed depending on different soil additives, which are known for prevention of soil erosion and nutrient loss as well as increasing of water infiltration, aggregate stability and soil fertility. Hence, synthetic water-soluble Polyacrylamides (PAM), Biochar (Black Carbon mixed with organic fertilizer), both PAM and Biochar were applied in runoff plots at three agricultural field sites. Additionally, as control a subplot was set up without any additives. The field sites were selected in areas with similar hillslope gradients and with emphasis on the dominant land management form of dryland farming in Haean, which is characterised by row planting and row covering by foil. Hydrological parameters like satured water conductivity, matrix potential and water content were analysed by infiltration experiments, continuous tensiometer measurements, time domain reflectometry as well as pressure plates to indentify characteristic water retention curves of each horizon. Weather data were observed by three weather stations next to the runoff plots. Measured data also provide the input data for modeling water transport in the unsatured zone in runoff plots with HYDRUS 1D/2D/3D and SWAT (Soil & Water Assessment Tool).

  1. Ecological value of soil carbon management

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Management of soil carbon is critical to the climate change debate, as well as to the long-term productivity and ecosystem resilience of the biosphere. Soil organic carbon is a key ecosystem property that indicates inherent productivity of land, controls soil biological functioning and diversity, r...

  2. Evolution of black carbon properties in soil

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Black carbon deposited in soil from natural or deliberate wildfires and engineered black carbon products (biochar) intentionally added to soil are known to have significant effects on soil biogeochemical processes and in many cases to influence the yield and quality of crops and to enhance the abili...

  3. Erosion of soil organic carbon: implications for carbon sequestration

    USGS Publications Warehouse

    Van Oost, Kristof; Van Hemelryck, Hendrik; Harden, Jennifer W.; McPherson, B.J.; Sundquist, E.T.

    2009-01-01

    Agricultural activities have substantially increased rates of soil erosion and deposition, and these processes have a significant impact on carbon (C) mineralization and burial. Here, we present a synthesis of erosion effects on carbon dynamics and discuss the implications of soil erosion for carbon sequestration strategies. We demonstrate that for a range of data-based parameters from the literature, soil erosion results in increased C storage onto land, an effect that is heterogeneous on the landscape and is variable on various timescales. We argue that the magnitude of the erosion term and soil carbon residence time, both strongly influenced by soil management, largely control the strength of the erosion-induced sink. In order to evaluate fully the effects of soil management strategies that promote carbon sequestration, a full carbon account must be made that considers the impact of erosion-enhanced disequilibrium between carbon inputs and decomposition, including effects on net primary productivity and decomposition rates.

  4. Ecological controls over global soil carbon storage

    SciTech Connect

    Schimel, D.S.

    1995-09-01

    Globally, soil carbon comprises about 2/3 of terrestrial carbon storage. Soil carbon is thus an important reservoir of carbon, but also influences the responses of ecosystems to change by controlling many aspects of nutrient cycling. While broad-scale patterns of soil carbon accumulation can be explained in terms of climatic and biome distributions, many ecological processes also influence the storage and turnover of carbon in soils. I will present a synthesis of information from field studies, model experiments and global data bases on factors controlling the turnover and storage of soil carbon. First, I will review a series of studies showing links between vegetation change (successional and invasions) and soil carbon. Then I will review model analyses of the sensitivity of soil carbon to climatic and ecological changes. Results show that soil carbon storage is broadly sensitive to climate but greatly influenced by the allocation of detritus between resistant (lignaceous and woody) and more labile forms, and that biotic changes that affect allocation, affect soil carbon substantially at regionally and perhaps global scales.

  5. Soil Organic Carbon Input from Urban Turfgrasses

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Turfgrass is a major vegetation type in the urban and suburban environment. Management practices such as species selection, irrigation, and mowing may affect carbon input and storage in these systems. Research was conducted to determine the rate of soil organic carbon (SOC) changes, soil carbon sequ...

  6. Soil Organic Carbon Input from Urban Turfgrasses

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Turfgrass is a major vegetation type in the urban and suburban environment. Management practices such as species selection, irrigation, and mowing may affect carbon (C) input and storage in these systems. Research was conducted to determine the rate of soil organic carbon (SOC) changes, soil carbon ...

  7. Divergent Effects of Nitrogen Addition on Soil Respiration in a Semiarid Grassland

    PubMed Central

    Zhu, Cheng; Ma, Yiping; Wu, Honghui; Sun, Tao; La Pierre, Kimberly J.; Sun, Zewei; Yu, Qiang

    2016-01-01

    Nitrogen (N) deposition has been steadily increasing for decades, with consequences for soil respiration. However, we have a limited understanding of how soil respiration responds to N availability. Here, we investigated the soil respiration responses to low and high levels of N addition (0.4 mol N m−2 yr−1 vs 1.6 mol N m−2 yr−1) over a two-year period in a semiarid Leymus chinensis grassland in Inner Mongolia, China. Our results show that low-level N addition increased soil respiration, plant belowground biomass and soil microbial biomass carbon (MBC), while high-level N additions decreased them. Soil respiration was positively correlated with plant belowground biomass, MBC, soil temperature and soil moisture. Together plant belowground biomass and MBC explained 99.4% of variation in mean soil respiration, with plant belowground biomass explaining 63.4% of the variation and soil MBC explaining the remaining 36%. Finally, the temperature sensitivity of soil respiration was not influenced by N additions. Overall, our results suggest that low levels of N deposition may stimulate soil respiration, but large increases in N availability may decrease soil respiration, and that these responses are driven by the dissimilar responses of both plant belowground biomass and soil MBC. PMID:27629241

  8. Divergent Effects of Nitrogen Addition on Soil Respiration in a Semiarid Grassland.

    PubMed

    Zhu, Cheng; Ma, Yiping; Wu, Honghui; Sun, Tao; La Pierre, Kimberly J; Sun, Zewei; Yu, Qiang

    2016-01-01

    Nitrogen (N) deposition has been steadily increasing for decades, with consequences for soil respiration. However, we have a limited understanding of how soil respiration responds to N availability. Here, we investigated the soil respiration responses to low and high levels of N addition (0.4 mol N m(-2) yr(-1) vs 1.6 mol N m(-2) yr(-1)) over a two-year period in a semiarid Leymus chinensis grassland in Inner Mongolia, China. Our results show that low-level N addition increased soil respiration, plant belowground biomass and soil microbial biomass carbon (MBC), while high-level N additions decreased them. Soil respiration was positively correlated with plant belowground biomass, MBC, soil temperature and soil moisture. Together plant belowground biomass and MBC explained 99.4% of variation in mean soil respiration, with plant belowground biomass explaining 63.4% of the variation and soil MBC explaining the remaining 36%. Finally, the temperature sensitivity of soil respiration was not influenced by N additions. Overall, our results suggest that low levels of N deposition may stimulate soil respiration, but large increases in N availability may decrease soil respiration, and that these responses are driven by the dissimilar responses of both plant belowground biomass and soil MBC. PMID:27629241

  9. Black Carbon - Soil Organic Matter abiotic and biotic interactions

    NASA Astrophysics Data System (ADS)

    Cotrufo, Francesca; Boot, Claudia; Denef, Karolien; Foster, Erika; Haddix, Michelle; Jiang, Xinyu; Soong, Jennifer; Stewart, Catherine

    2014-05-01

    Wildfires, prescribed burns and the use of char as a soil amendment all add large quantities of black carbon to soils, with profound, yet poorly understood, effects on soil biology and chemical-physical structure. We will present results emerging from our black carbon program, which addresses questions concerning: 1) black carbon-soil organic matter interactions, 2) char decomposition and 3) impacts on microbial community structure and activities. Our understanding derives from a complementary set of post-fire black carbon field surveys and laboratory and field experiments with grass and wood char amendments, in which we used molecular (i.e., BPCA, PLFA) and isotopic (i.e., 13C and 15N labelled char) tracers. Overall, emerging results demonstrate that char additions to soil are prone to fast erosion, but a fraction remains that increases water retention and creates a better environment for the microbial community, particularly favoring gram negative bacteria. However, microbial decomposition of black carbon only slowly consumes a small fraction of it, thus char still significantly contributes to soil carbon sequestration. This is especially true in soils with little organic matter, where black carbon additions may even induce negative priming.

  10. Soil organic carbon across scales.

    PubMed

    O'Rourke, Sharon M; Angers, Denis A; Holden, Nicholas M; McBratney, Alex B

    2015-10-01

    Mechanistic understanding of scale effects is important for interpreting the processes that control the global carbon cycle. Greater attention should be given to scale in soil organic carbon (SOC) science so that we can devise better policy to protect/enhance existing SOC stocks and ensure sustainable use of soils. Global issues such as climate change require consideration of SOC stock changes at the global and biosphere scale, but human interaction occurs at the landscape scale, with consequences at the pedon, aggregate and particle scales. This review evaluates our understanding of SOC across all these scales in the context of the processes involved in SOC cycling at each scale and with emphasis on stabilizing SOC. Current synergy between science and policy is explored at each scale to determine how well each is represented in the management of SOC. An outline of how SOC might be integrated into a framework of soil security is examined. We conclude that SOC processes at the biosphere to biome scales are not well understood. Instead, SOC has come to be viewed as a large-scale pool subjects to carbon flux. Better understanding exists for SOC processes operating at the scales of the pedon, aggregate and particle. At the landscape scale, the influence of large- and small-scale processes has the greatest interaction and is exposed to the greatest modification through agricultural management. Policy implemented at regional or national scale tends to focus at the landscape scale without due consideration of the larger scale factors controlling SOC or the impacts of policy for SOC at the smaller SOC scales. What is required is a framework that can be integrated across a continuum of scales to optimize SOC management.

  11. Soil organic carbon across scales.

    PubMed

    O'Rourke, Sharon M; Angers, Denis A; Holden, Nicholas M; McBratney, Alex B

    2015-10-01

    Mechanistic understanding of scale effects is important for interpreting the processes that control the global carbon cycle. Greater attention should be given to scale in soil organic carbon (SOC) science so that we can devise better policy to protect/enhance existing SOC stocks and ensure sustainable use of soils. Global issues such as climate change require consideration of SOC stock changes at the global and biosphere scale, but human interaction occurs at the landscape scale, with consequences at the pedon, aggregate and particle scales. This review evaluates our understanding of SOC across all these scales in the context of the processes involved in SOC cycling at each scale and with emphasis on stabilizing SOC. Current synergy between science and policy is explored at each scale to determine how well each is represented in the management of SOC. An outline of how SOC might be integrated into a framework of soil security is examined. We conclude that SOC processes at the biosphere to biome scales are not well understood. Instead, SOC has come to be viewed as a large-scale pool subjects to carbon flux. Better understanding exists for SOC processes operating at the scales of the pedon, aggregate and particle. At the landscape scale, the influence of large- and small-scale processes has the greatest interaction and is exposed to the greatest modification through agricultural management. Policy implemented at regional or national scale tends to focus at the landscape scale without due consideration of the larger scale factors controlling SOC or the impacts of policy for SOC at the smaller SOC scales. What is required is a framework that can be integrated across a continuum of scales to optimize SOC management. PMID:25918852

  12. Underestimation of boreal soil carbon stocks by mathematical soil carbon models linked to soil nutrient status

    NASA Astrophysics Data System (ADS)

    Ťupek, Boris; Ortiz, Carina A.; Hashimoto, Shoji; Stendahl, Johan; Dahlgren, Jonas; Karltun, Erik; Lehtonen, Aleksi

    2016-08-01

    Inaccurate estimate of the largest terrestrial carbon pool, soil organic carbon (SOC) stock, is the major source of uncertainty in simulating feedback of climate warming on ecosystem-atmosphere carbon dioxide exchange by process-based ecosystem and soil carbon models. Although the models need to simplify complex environmental processes of soil carbon sequestration, in a large mosaic of environments a missing key driver could lead to a modeling bias in predictions of SOC stock change.We aimed to evaluate SOC stock estimates of process-based models (Yasso07, Q, and CENTURY soil sub-model v4) against a massive Swedish forest soil inventory data set (3230 samples) organized by a recursive partitioning method into distinct soil groups with underlying SOC stock development linked to physicochemical conditions.For two-thirds of measurements all models predicted accurate SOC stock levels regardless of the detail of input data, e.g., whether they ignored or included soil properties. However, in fertile sites with high N deposition, high cation exchange capacity, or moderately increased soil water content, Yasso07 and Q models underestimated SOC stocks. In comparison to Yasso07 and Q, accounting for the site-specific soil characteristics (e. g. clay content and topsoil mineral N) by CENTURY improved SOC stock estimates for sites with high clay content, but not for sites with high N deposition.Our analysis suggested that the soils with poorly predicted SOC stocks, as characterized by the high nutrient status and well-sorted parent material, indeed have had other predominant drivers of SOC stabilization lacking in the models, presumably the mycorrhizal organic uptake and organo-mineral stabilization processes. Our results imply that the role of soil nutrient status as regulator of organic matter mineralization has to be re-evaluated, since correct SOC stocks are decisive for predicting future SOC change and soil CO2 efflux.

  13. Dimethyl carbonate production for fuel additives

    SciTech Connect

    Okada, Y.; Kondo, T.; Asaoka, S.

    1996-12-31

    We have taken note of the transesterification reaction as a highly safe process of dimethyl carbonate (DMC) production for fuel additives. The reaction proceeds under the low corrosiveness and in the relatively mild condition. We have aimed to use an inorganic solid catalyst for this process. The inorganic solid catalyst is thermally stable and can be used in the large-scale fixed bed reactors without a catalyst separation unit. Through the transesterification of ethylene carbonate (EG) with methanol, DMC and ethylene glycol (EG) are co-generated as the products. EG is one of the bulk chemicals produced in the large scale plant comparable to one for the fuel additives. The market balance is important in the coproduction process. On the assumption that the amount of the co-production meets the market balance, the coproduction of DMC and EG is commercially viable. If we can control the amount of the EG coproduction in this process, it makes the process more flexible in the commercial production. Accordingly we have proposed a conceptual process scheme to control the amount of the EG coproduction. In this symposium, the inorganic solid catalyst system applying to the transesterification process and the conceptual process scheme how to control the amount of co-product will be discussed.

  14. A method to detect soil carbon degradation during soil erosion

    NASA Astrophysics Data System (ADS)

    Alewell, Christine; Conen, Franz; Schaub, Monika

    2010-05-01

    Soil erosion has been discussed intensively but controversial both as a significant source or a significant sink of atmospheric carbon possibly explaining the gap in the global carbon budget. One of the major points of discussion has been whether or not carbon is degraded and mineralized to CO2 during detachment, transport and deposition of soil material. By combining the caesium-137 (137Cs) approach (quantification of erosion rates) with stable carbon isotope signatures (process indicator of mixing versus degradation of carbon pools) we were able to show that degradation of carbon occurs during soil erosion processes at the investigated mountain grasslands in the central Swiss Alps (Urseren Valley, Canton Uri). Transects from upland (erosion source) to wetland soils (erosion sinks) of sites affected by sheet and land slide erosion were sampled. Analysis of 137Cs yielded an input of 2 and 4.6 tha-1 yr-1 of soil material into the wetlands sites. Assuming no degradation of soil organic carbon during detachment and transport, carbon isotope signature of soil organic carbon in the wetlands could only be explained with an assumed 500-600 and 350-400 years of erosion input into the wetlands Laui and Spissen, respectively. The latter is highly unlikely with alpine peat growth rates indicating that the upper horizons might have an age between 7 and 200 years. While we do not conclude from our data that eroded soil organic carbon is generally degraded during detachment and transport, we propose this method to gain more information on process dynamics during soil erosion from oxic upland to anoxic wetland soils, sediments or water bodies.

  15. A method to detect soil carbon degradation during soil erosion

    NASA Astrophysics Data System (ADS)

    Alewell, C.; Schaub, M.; Conen, F.

    2009-06-01

    Soil erosion has been discussed intensively but controversial both as a significant source or a significant sink of atmospheric carbon possibly explaining the gap in the global carbon budget. One of the major points of discussion has been whether or not carbon is degraded and mineralized to CO2 during detachment, transport and deposition of soil material. By combining the caesium-137 (137Cs) approach (quantification of erosion rates) with stable carbon isotope signatures (process indicator of mixing versus degradation of carbon pools) we were able to show that degradation of carbon occurs during soil erosion processes at the investigated mountain grasslands in the central Swiss Alps (Urseren Valley, Canton Uri). Transects from upland (erosion source) to wetland soils (erosion sinks) of sites affected by sheet and land slide erosion were sampled. Analysis of 137Cs yielded an input of 2 and 2.6 t ha-1 yr-1 of soil material into the wetlands sites. Assuming no degradation of soil organic carbon during detachment and transport, carbon isotope signature of soil organic carbon in the wetlands could only be explained with an assumed 800 and 400 years of erosion input into the wetlands. The latter is highly unlikely with alpine peat growth rates indicating that the upper horizons might have an age between 7 and 200 years. While we do not conclude from our data that eroded soil organic carbon is generally degraded during detachment and transport, we propose this method to gain more information on process dynamics during soil erosion from oxic upland to anoxic wetland soils, sediments or water bodies.

  16. A method to detect soil carbon degradation during soil erosion

    NASA Astrophysics Data System (ADS)

    Alewell, C.; Schaub, M.; Conen, F.

    2009-11-01

    Soil erosion has been discussed intensively but controversial both as a significant source or a significant sink of atmospheric carbon possibly explaining the gap in the global carbon budget. One of the major points of discussion has been whether or not carbon is degraded and mineralized to CO2 during detachment, transport and deposition of soil material. By combining the caesium-137 (137Cs) approach (quantification of erosion rates) with stable carbon isotope signatures (process indicator of mixing versus degradation of carbon pools) we were able to show that degradation of carbon occurs during soil erosion processes at the investigated mountain grasslands in the central Swiss Alps (Urseren Valley, Canton Uri). Transects from upland (erosion source) to wetland soils (erosion sinks) of sites affected by sheet and land slide erosion were sampled. Analysis of 137Cs yielded an input of 2 and 4.6 tha-1 yr-1 of soil material into the wetlands sites. Assuming no degradation of soil organic carbon during detachment and transport, carbon isotope signature of soil organic carbon in the wetlands could only be explained with an assumed 500-600 and 350-400 years of erosion input into the wetlands Laui and Spissen, respectively. The latter is highly unlikely with alpine peat growth rates indicating that the upper horizons might have an age between 7 and 200 years. While we do not conclude from our data that eroded soil organic carbon is generally degraded during detachment and transport, we propose this method to gain more information on process dynamics during soil erosion from oxic upland to anoxic wetland soils, sediments or water bodies.

  17. Soil and soil organic carbon redistribution on the landscape

    NASA Astrophysics Data System (ADS)

    Ritchie, Jerry C.; McCarty, Gregory W.; Venteris, Erik R.; Kaspar, T. C.

    2007-09-01

    Patterns of soil organic carbon (SOC) vary widely across the landscape leading to large uncertainties in the SOC budget especially for agricultural landscapes where water, tillage and wind erosion redistributes soil and SOC across the landscape. It is often assumed that soil erosion results in a loss of SOC from the agricultural ecosystem but recent studies indicate that soil erosion and its subsequent redistribution within fields can stimulate carbon sequestration in agricultural ecosystems. This study investigates the relationship between SOC and soil redistribution patterns on agricultural landscapes. Soil redistribution (erosion and deposition) patterns were estimated in three tilled agricultural fields using the fallout 137Cesium technique. 137Cs and SOC concentrations of upland soils are significantly correlated in our study areas. Upland areas (eroding) have significantly less SOC than soils in deposition areas. SOC decreased as gradient slope increases and soils on concave slopes had higher SOC than soils on convex slopes. These data suggest that soil redistribution patterns and topographic patterns may be used to help understand SOC dynamics on the landscape. Different productivity and oxidation rates of SOC of eroded versus deposited soils also contribute to SOC spatial patterns. However, the strong significant relationships between soil redistribution and SOC concentrations in the upland soil suggest that they are moving along similar physical pathways in these systems. Our study also indicates that geomorphic position is important for understanding soil movement and redistribution patterns within a field or watershed. Such information can help develop or implement management systems to increase SOC in agricultural ecosystems.

  18. Denitrification with carbon addition--kinetic considerations.

    PubMed

    Dold, P; Takács, I; Mokhayeri, Y; Nichols, A; Hinojosa, J; Riffat, R; Bott, C; Bailey, W; Murthy, S

    2008-05-01

    The Blue Plains Advanced Wastewater Treatment Plant (Washington, D.C.) uses methanol as an external carbon source in a postdenitrification process, to achieve low effluent total nitrogen concentrations. This becomes more difficult in winter, at lower mixed liquor temperatures and higher flows, as a consequence of the kinetic behavior of the methanol-utilizing heterotrophs. The paper reports on an experimental batch test study conducted on Blue Plains postdenitrification sludge to investigate (1) the maximum specific growth rate of methanol-utilizing heterotrophs (Mu(METH)); (2) the temperature dependency of the growth rate; and (3) the efficacy of alternate substrates (ethanol, acetate, and sugar). A limited number of tests were conducted on sludge from two other treatment plants with methanol addition. PMID:18605381

  19. Stuffing Carbon Away: Mechanisms of Carbon Sequestration in Soils

    SciTech Connect

    Reimer, P J; Masiello, C A; Southon, J R; Trumbore, S E; Harden, J W; White, A F; Chadwick, O A; Torn, M S

    2003-01-24

    Soils offer the potential to sequester large quantities of carbon from the atmosphere for decades to millennia and so may ameliorate the anthropogenic influence of fossil fuel release. However changes in climate can drastically affect the soil's ability to store carbon through changes mineralogy on time scales of human interest. It is essential to understand the major controls on soil carbon dynamics before we attempt to manage sequestration to control atmospheric CO{sub 2} buildup. Models of the terrestrial carbon cycle often use clay content to parameterize soil carbon turnover. Evidence from volcanic soils suggests that soil mineralogy is a major control on a soil's ability to store carbon, because different types of minerals have widely varying abilities to physically and chemically isolate soil organic matter from decomposition, however volcanic soils represent only a small percentage of the earth's soils. The relationship between precipitation and soil carbon storage is also complex and poorly constrained. Significantly, precipitation changes predicted as a result of atmospheric CO{sub 2} doubling include increased rainfall throughout California. We utilized {sup 14}C, {delta}{sup 13}C, and the total organic carbon, iron, and aluminum contents to address the question of the importance of mineralogy and climate on carbon storage in soils formed on a globally representative parent material. The California coastal terraces, formed over the last 500 thousand years as a result of tectonic uplift and sea level change, provide a natural laboratory to examine the effect of mineralogy and climate on carbon storage. We have focused on two terraces sequences, one near Eureka and one near Santa Cruz. Within each set of terraces only soil mineral development varies; all other variables are constant (rainfall, plant systems, and soil parent material, and land management). Annual precipitation at Eureka is twice that at Santa Cruz, allowing us to examine its role in the

  20. A global predictive model of carbon in mangrove soils

    NASA Astrophysics Data System (ADS)

    Jardine, Sunny L.; Siikamäki, Juha V.

    2014-10-01

    Mangroves are among the most threatened and rapidly vanishing natural environments worldwide. They provide a wide range of ecosystem services and have recently become known for their exceptional capacity to store carbon. Research shows that mangrove conservation may be a low-cost means of reducing CO2 emissions. Accordingly, there is growing interest in developing market mechanisms to credit mangrove conservation projects for associated CO2 emissions reductions. These efforts depend on robust and readily applicable, but currently unavailable, localized estimates of soil carbon. Here, we use over 900 soil carbon measurements, collected in 28 countries by 61 independent studies, to develop a global predictive model for mangrove soil carbon. Using climatological and locational data as predictors, we explore several predictive modeling alternatives, including machine-learning methods. With our predictive model, we construct a global dataset of estimated soil carbon concentrations and stocks on a high-resolution grid (5 arc min). We estimate that the global mangrove soil carbon stock is 5.00 ± 0.94 Pg C (assuming a 1 meter soil depth) and find this stock is highly variable over space. The amount of carbon per hectare in the world’s most carbon-rich mangroves (approximately 703 ± 38 Mg C ha-1) is roughly a 2.6 ± 0.14 times the amount of carbon per hectare in the world’s most carbon-poor mangroves (approximately 272 ± 49 Mg C ha-1). Considerable within country variation in mangrove soil carbon also exists. In Indonesia, the country with the largest mangrove soil carbon stock, we estimate that the most carbon-rich mangroves contain 1.5 ± 0.12 times as much carbon per hectare as the most carbon-poor mangroves. Our results can aid in evaluating benefits from mangrove conservation and designing mangrove conservation policy. Additionally, the results can be used to project changes in mangrove soil carbon stocks based on changing climatological predictors, e.g. to

  1. Effects of nitrogen addition on soil microbes and their implications for soil C emission in the Gurbantunggut Desert, center of the Eurasian Continent.

    PubMed

    Huang, Gang; Cao, Yan Feng; Wang, Bin; Li, Yan

    2015-05-15

    Nitrogen (N) deposition can influence carbon cycling of terrestrial ecosystems. However, a general recognition of how soil microorganisms respond to increasing N deposition is not yet reached. We explored soil microbial responses to two levels of N addition (2.5 and 5 gN m(-2) yr(-1)) in interplant soil and beneath shrubs of Haloxylon ammodendron and their consequences to soil respiration in the Gurbantunggut Desert, northwestern China from 2011 to 2013. Microbial biomass and respiration were significantly higher beneath H. ammodendron than in interplant soil. The responses of microbial biomass carbon (MBC) and microbial respiration (MR) showed opposite responses to N addition in interplant and beneath H. ammodendron. N addition slightly increased MBC and MR in interplant soil and decreased them beneath H. ammodendron, with a significant inhibition only in 2012. N addition had no impacts on the total microbial physiological activity, but N addition decreased the labile carbon substrate utilization beneath H. ammodendron when N addition level was high. Phospholipid fatty acid (PLFA) analysis showed that N addition did not alter the soil microbial community structure as evidenced by the similar ratios of fungal to bacterial PLFAs and gram-negative to gram-positive bacterial PLFAs. Microbial biomass and respiration showed close correlations with soil water content and dissolved carbon, and they were independent of soil inorganic nitrogen across three years. Our study suggests that N addition effects on soil microorganisms and carbon emission are dependent on the respiratory substrates and water availability in the desert ecosystem.

  2. Organic carbon in soil and the global carbon cycle

    SciTech Connect

    Post, W.M. III

    1991-12-31

    Soil organic matter is, simultaneously, the most inert carbon cycle component of terrestrial ecosystems, and the most dynamic component of terrestrail geologic systems placing it in a pivotal position in the biogeochemistry of carbon. The large size and potentially long residence time of the soil organic matter pool make it an important component of the global carbon cycle. Net terrestrial primary production of about 60 Pg C{center_dot}yr{sup {minus}1} is, over a several-year period of time, balanced by an equivalent flux of litter production and subsequent decomposition of detritus and soil organic matter. However, the input rates and decomposition rates for different terrestrial ecosystems vary over several orders of magnitude resulting in widely different amounts and turnover rates of soil organic matter. The amounts of carbon stored in soils and the rates of exchange of soil carbon with the atmosphere depend on many factors related to the chemistry, biology, and physics of soil and soil organic matter. This report discusses work on organic carbon in soil and aspects of the carbon cycle.

  3. Black carbon as a carbon source for young soils in a glacier forefield?

    NASA Astrophysics Data System (ADS)

    Eckmeier, E.; Pichler, B.; Krebs, R.; Mavris, C.; Egli, M.

    2012-04-01

    Most evident changes in Alpine soils today occur in proglacial areas where existing young soils are continuously developing. Due to climate change, additional areas will become ice-free and subject to weathering and new soil formation. The glacier forefields of the European Alps are continuously exposed since the glaciers reached their maximum expansion in the 1850s. In these proglacial areas, initial soils have started to develop so that they may offer, under optimal conditions, a continuous chronosequence from 0 to 150 year-old soils. The buildup of organic carbon (Corg) in soil is an important factor controlling weathering and the formation of soils. Not only autochthonous but also distant (allochthonous) sources may contribute to the accumulation of soil organic carbon in young soils and surfaces of glacier forefields. Black carbon could be an important component in Alpine soils. However, only little is known about black carbon in very young soils that develop in glacier forefields. The aim of our study was to examine whether black carbon as an allochthonous source of soil organic matter can be detected in the initial soils, and to estimate its relative contribution (as a function of time) to total organic carbon. We investigated surface soil samples (topsoils, A or AO horizon) from 35 sites distributed over the whole proglacial area of Morteratsch, where ideal conditions for a soil chronosequence from 0 to 150 years can be found. Along this sequence, bare till sediments to weakly developed soils (Leptosols) can be encountered. Black carbon concentrations were determined in fine-earth using the benzene polycarboxylic acid (BPCA) marker method as described by Brodowski et al. (2005). We found that the proportion of BPCA-C to total Corg was related to the time since the surface was exposed. The youngest soils (younger than 40 years) contained the highest proportion of BPCA-C (up to 120 g BPCA-C/kg Corg). In these soils, however, the Corg concentrations were very

  4. Influence of attrition scrubbing, ultrasonic treatment, and oxidant additions on uranium removal from contaminated soils

    SciTech Connect

    Timpson, M.E.; Elless, M.P.; Francis, C.W.

    1994-06-01

    As part of the Uranium in Soils Integrated Demonstration Project being conducted by the US Department of Energy, bench-scale investigations of selective leaching of uranium from soils at the Fernald Environmental Management Project site in Ohio were conducted at Oak Ridge National Laboratory. Two soils (storage pad soil and incinerator soil), representing the major contaminant sources at the site, were extracted using carbonate- and citric acid-based lixiviants. Physical and chemical processes were used in combination with the two extractants to increase the rate of uranium release from these soils. Attrition scrubbing and ultrasonic dispersion were the two physical processes utilized. Potassium permanganate was used as an oxidizing agent to transform tetravalent uranium to the hexavalent state. Hexavalent uranium is easily complexed in solution by the carbonate radical. Attrition scrubbing increased the rate of uranium release from both soils when compared with rotary shaking. At equivalent extraction times and solids loadings, however, attrition scrubbing proved effective only on the incinerator soil. Ultrasonic treatments on the incinerator soil removed 71% of the uranium contamination in a single extraction. Multiple extractions of the same sample removed up to 90% of the uranium. Additions of potassium permanganate to the carbonate extractant resulted in significant changes in the extractability of uranium from the incinerator soil but had no effect on the storage pad soil.

  5. Soil Phosphorus Stoichiometry Drives Carbon Turnover Along a Soil C Gradient Spanning Mineral and Organic Soils Under Rice Cultivation

    NASA Astrophysics Data System (ADS)

    Hartman, W.; Ye, R.; Horwath, W. R.; Tringe, S. G.

    2014-12-01

    Soil carbon (C) cycling is linked to the availability of nutrients like nitrogen (N) and phosphorus (P). However, the role of soil P in influencing soil C turnover and accumulation is poorly understood, with most models focusing on C:N ratios based on the assumption that terrestrial ecosystems are N limited. To determine the effects of N and P availability on soil C turnover, we compared soil respiration over the course of a growing season in four adjacent rice fields with 5%, 10%, 20% and 25% soil C. In each of these fields, plots were established to test the effect of N additions on plant growth, using control and N addition treatments (80 kg N/ha urea). Although soil P was not manipulated in parallel, prior work has shown soil P concentrations decline markedly with increasing soil C content. Soil CO2 flux was monitored using static chambers at biweekly intervals during the growing season, along with porewater dissolved organic C and ammonium. Soils were collected at the end of the growing season, and tested for total C, N, and P, extractable N and P, pH, base cations and trace metals. Soil DNA was also extracted for 16S rRNA sequencing to profile microbial communities. Soil N additions significantly increased CO2 flux and soil C turnover (seasonal CO2 flux per unit soil C) in 5% and 10% C fields, but not in 20% or 25% C fields. Soil C content was closely related to soil N:P stoichiometry, with N:P ratios of ca. 12, 16, 24, and 56 respectively in the 5, 10, 20 and 25% C fields. Seasonal CO2 fluxes (per m2) were highest in 10% C soils. However, soil C turnover was inversely related to soil C concentrations, with the greatest C turnover at the lowest values of soil C. Soil C turnover showed stronger relationships with soil chemical parameters than seasonal CO2 fluxes alone, and the best predictors of soil C turnover were soil total and extractable N:P ratios, along with extractable P alone. Our results show that soil P availability and stoichiometry influence the

  6. Estimating Regional Changes in Soil Carbon with High Spatial Resolution

    SciTech Connect

    West, Tristram O.; Brandt, Craig C; Marland, Gregg; De La Torre Ugarte, Daniel G; Larson, James; Hellwinckel, Chad M; Wilson, Bradly; Tyler, Donald G; Nelson, Richard G

    2008-01-01

    To manage lands locally for carbon sequestration and for emissions reductions it is useful to have a system that can monitor and predict changes in soil carbon and greenhouse gas emissions with high spatial resolution. We are developing a carbon accounting framework that can estimate carbon dynamics and net emissions associated with changes in land management. One component of this framework integrates field measurements, inventory data, and remote sensing products to estimate changes in soil carbon and to estimate where these changes are likely to occur at a sub-county (30m x 30m) resolution. We applied this framework component to a mid-western region of the US that consists of 679 counties approximately centered around Iowa. We estimate the 1990 baseline soil carbon to a maximum depth of 3m for this region to be 4,117 Tg C. Cumulative soil carbon accumulation of 70.3 Tg C is estimated for this region between 1991-2000, of which 33.8 Tg C is due to changes in tillage intensity. Without accounting for soil carbon loss following changes to more intensive tillage practices, our estimate increases to 45.0 Tg C. This difference indicates that on-site permanence of soil carbon associated with a change to less intensive tillage practices is approximately 75% if no additional economic incentives are provided for soil carbon sequestration practices. This carbon accounting framework offers a method to integrate inventory and remote sensing data on an annual basis and to transparently account for alternating annual trends in land management and associated carbon stocks and fluxes.

  7. Soil erosion and the global carbon budget.

    PubMed

    Lal, R

    2003-07-01

    Soil erosion is the most widespread form of soil degradation. Land area globally affected by erosion is 1094 million ha (Mha) by water erosion, of which 751 Mha is severely affected, and 549 Mha by wind erosion, of which 296 Mha is severely affected. Whereas the effects of erosion on productivity and non-point source pollution are widely recognized, those on the C dynamics and attendant emission of greenhouse gases (GHGs) are not. Despite its global significance, erosion-induced carbon (C) emission into the atmosphere remains misunderstood and an unquantified component of the global carbon budget. Soil erosion is a four-stage process involving detachment, breakdown, transport/redistribution and deposition of sediments. The soil organic carbon (SOC) pool is influenced during all four stages. Being a selective process, erosion preferentially removes the light organic fraction of a low density of <1.8 Mg/m(3). A combination of mineralization and C export by erosion causes a severe depletion of the SOC pool on eroded compared with uneroded or slightly eroded soils. In addition, the SOC redistributed over the landscape or deposited in depressional sites may be prone to mineralization because of breakdown of aggregates leading to exposure of hitherto encapsulated C to microbial processes among other reasons. Depending on the delivery ratio or the fraction of the sediment delivered to the river system, gross erosion by water may be 75 billion Mg, of which 15-20 billion Mg are transported by the rivers into the aquatic ecosystems and eventually into the ocean. The amount of total C displaced by erosion on the earth, assuming a delivery ratio of 10% and SOC content of 2-3%, may be 4.0-6.0 Pg/year. With 20% emission due to mineralization of the displaced C, erosion-induced emission may be 0.8-1.2 Pg C/year on the earth. Thus, soil erosion has a strong impact on the global C cycle and this component must be considered while assessing the global C budget. Adoption of

  8. [Effects of Green Manure Intercropping and Straw Mulching on Winter Rape Rhizosphere Soil Organic Carbon and Soil Respiration].

    PubMed

    Zhou, Quan; Wang, Long-chang; Xiong, Ying; Zhang, Sai; Du, Juan; Zhao, Lin-lu

    2016-03-15

    Under the background of global warming, the farmland soil respiration has become the main way of agricultural carbon emissions. And green manure has great potential to curb greenhouse gas emissions and achieve energy conservation and emissions reduction. However, in purple soil region of Southwest, China, soil respiration under green manure remains unclear, especially in the winter and intercropping. Through the green manure ( Chinese milk vetch) intercropping with rape, therefore, we compared the effects of rape rhizosphere under straw mulching. The soil organic carbon and soil respiration were examined. The results showed, compared with straw mulching, root separation was the major influencing factors of soil organic carbon on rape rhizosphere. Soil organic carbon was significantly decreased by root interaction. In addition, straw mulching promoted while green manure intercropping inhibited the soil respiration. Soil respiration presented the general characteristics of fall-rise-fall due to the strong influence of rape growth period. Therefore, it showed a cubic curve relationship with soil temperature.

  9. [Effects of Green Manure Intercropping and Straw Mulching on Winter Rape Rhizosphere Soil Organic Carbon and Soil Respiration].

    PubMed

    Zhou, Quan; Wang, Long-chang; Xiong, Ying; Zhang, Sai; Du, Juan; Zhao, Lin-lu

    2016-03-15

    Under the background of global warming, the farmland soil respiration has become the main way of agricultural carbon emissions. And green manure has great potential to curb greenhouse gas emissions and achieve energy conservation and emissions reduction. However, in purple soil region of Southwest, China, soil respiration under green manure remains unclear, especially in the winter and intercropping. Through the green manure ( Chinese milk vetch) intercropping with rape, therefore, we compared the effects of rape rhizosphere under straw mulching. The soil organic carbon and soil respiration were examined. The results showed, compared with straw mulching, root separation was the major influencing factors of soil organic carbon on rape rhizosphere. Soil organic carbon was significantly decreased by root interaction. In addition, straw mulching promoted while green manure intercropping inhibited the soil respiration. Soil respiration presented the general characteristics of fall-rise-fall due to the strong influence of rape growth period. Therefore, it showed a cubic curve relationship with soil temperature. PMID:27337908

  10. How does soil management affect carbon losses from soils?

    NASA Astrophysics Data System (ADS)

    Klik, A.; Trümper, G.

    2009-04-01

    Agricultural soils are a major source as well as a sink of organic carbon (OC). Amount and distribution of OC within the soil and within the landscape are driven by land management but also by erosion and deposition processes. At the other hand the type of soil management influences mineralization and atmospheric carbon dioxide losses by soil respiration. In a long-term field experiment the impacts of soil tillage systems on soil erosion processes were investigated. Following treatments were compared: 1) conventional tillage (CT), 2) conservation tillage with cover crop during the winter period (CS), and 3) no-till with cover crop during winter period (NT). The studies were carried out at three sites in the Eastern part of Austria with annual precipitation amounts from 650 to 900 mm. The soil texture ranged from silt loam to loam. Since 2007 soil CO2 emissions are measured with a portable soil respiration system in intervals of about one week, but also in relation to management events. Concurrent soil temperature and soil water content are measured and soil samples are taken for chemical and microbiological analyses. An overall 14-yr. average soil loss between 1.0 t.ha-1.yr-1 for NT and 6.1 t.ha-1.yr-1 for CT resulted in on-site OC losses from 18 to 79 kg ha-1.yr-1. The measurements of the carbon dioxide emissions from the different treatments indicate a high spatial variation even within one plot. Referred to CT plots calculated carbon losses amounted to 65-94% for NT plots while for the different RT plots they ranged between 84 and 128%. Nevertheless site specific considerations have to be taken into account. Preliminary results show that the adaptation of reduced or no-till management strategies has enormous potential in reducing organic carbon losses from agricultural used soils.

  11. Effect of N and P addition on soil organic C potential mineralization in forest soils in South China.

    PubMed

    Ouyang, Xuejun; Zhou, Guoyi; Huang, Zhongliang; Zhou, Cunyu; Li, Jiong; Shi, Junhui; Zhang, Deqiang

    2008-01-01

    Atmospheric nitrogen deposition is at a high level in some forests of South China. The effects of addition of exogenous N and P on soil organic carbon mineralization were studied to address: (1) if the atmospheric N deposition promotes soil C storage through decreasing mineralization; (2) if the soil available P is a limitation to organic carbon mineralization. Soils (0-10 cm) was sampled from monsoon evergreen broad-leaved forest (MEBF), coniferous and broad-leaved mixed forest (CBMF), and Pinus massoniana forest (PMF) in Dinghushan Biosphere Reserve (located in Guangdong Province, China). The soils were incubated at 25 degrees C for 45 weeks, with addition of N (NH4NO3 solution) or P (KH2PO4 solution). CO2-C emission and the inorganic N (NH4(+)-N and NO3(-)-N) of the soils were determined during the incubation. The results showed that CO2-C emission decreased with the N addition. The addition of P led to a short-term sharp increase in CO2 emission after P application, and the responses of CO2-C evolution to P addition in the later period of incubation related to forest types. Strong P inhibition to CO2 emission occurred in both PMF and CBMF soils in the later incubation. The two-pool kinetic model was fitted well to the data for C turnover in this experiment. The model analysis demonstrated that the addition of N and P changed the distribution of soil organic C between the labile and recalcitrant pool, as well as their mineralization rates. In our experiment, soil pH can not completely explain the negative effect of N addition on CO2-C emission. The changes of soil inorganic N during incubation seemed to support the hypothesis that the polymerization of added nitrogen with soil organic compound by abiotic reactions during incubation made the added nitrogen retard the soil organic carbon mineralization. We conclude that atmospheric N deposition contributes to soil C accretion in the three subtropical forest ecosystems, however, the shortage of soil available P in

  12. [Effects of nitrogen addition on red soil microbes in the Cinnamomum camphora plantation].

    PubMed

    Yu, Pei-Yi; Zhu, Fan; Su, Shao-Feng; Wang, Zhi-Yong; Yan, Wen-De

    2013-08-01

    In order to investigate the effects of nitrogen addition on the red soil microbial communities in Cinnamomum camphora plantation, three treatments of nitrogen addition were designated as control (N0: 0 g x m(-2)), low nitrogen (N1: 5 g x m(-2)) and high nitrogen (N2 :15 g x m(-2)). Soil microbial numbers, microbial biomass carbon (C), biomass N and microbial community functional diversity were analyzed using the methods of plate counting, chloroform fumigation and BIOLOG system, respectively. The results showed that the numbers of bacteria in N1 and N2 were significantly higher than the control 1 month after nitrogen addition, but significantly lower than the control 13 months after nitrogen addition, and the number of fungi and actinomycetes were not significantly changed after nitrogen addition. The soil microbial biomass C, N increased with the increase of nitrogen at 1 month, but the soil microbial biomass C increased significantly 13 months after nitrogen addition when compared with 1 month after nitrogen addition. The soil microbial biomass N was lower 13 months after nitrogen addition when compared with 1 month after nitrogen addition, but the difference was not significant (P > 0.05). The variation of the carbon utilization efficiency of soil microbial communities was resulted from the nitrogen addition. The indices of Shannon index, Simpson index and McIntosh index were calculated to show the differences in nitrogen treatments and in times, which turned out to be insignificant.

  13. [Organic carbon and carbon mineralization characteristics in nature forestry soil].

    PubMed

    Yang, Tian; Dai, Wei; An, Xiao-Juan; Pang, Huan; Zou, Jian-Mei; Zhang, Rui

    2014-03-01

    Through field investigation and indoor analysis, the organic carbon content and organic carbon mineralization characteristics of six kinds of natural forest soil were studied, including the pine forests, evergreen broad-leaved forest, deciduous broad-leaved forest, mixed needle leaf and Korean pine and Chinese pine forest. The results showed that the organic carbon content in the forest soil showed trends of gradual decrease with the increase of soil depth; Double exponential equation fitted well with the organic carbon mineralization process in natural forest soil, accurately reflecting the mineralization reaction characteristics of the natural forest soil. Natural forest soil in each layer had the same mineralization reaction trend, but different intensity. Among them, the reaction intensity in the 0-10 cm soil of the Korean pine forest was the highest, and the intensities of mineralization reaction in its lower layers were also significantly higher than those in the same layers of other natural forest soil; comparison of soil mineralization characteristics of the deciduous broad-leaved forest and coniferous and broad-leaved mixed forest found that the differences of litter species had a relatively strong impact on the active organic carbon content in soil, leading to different characteristics of mineralization reaction.

  14. Soil Organic Carbon Loss: An Overlooked Factor in the Carbon Sequestration Potential of Enhanced Mineral Weathering

    NASA Astrophysics Data System (ADS)

    Dietzen, Christiana; Harrison, Robert

    2016-04-01

    Weathering of silicate minerals regulates the global carbon cycle on geologic timescales. Several authors have proposed that applying finely ground silicate minerals to soils, where organic acids would enhance the rate of weathering, could increase carbon uptake and mitigate anthropogenic CO2 emissions. Silicate minerals such as olivine could replace lime, which is commonly used to remediate soil acidification, thereby sequestering CO2 while achieving the same increase in soil pH. However, the effect of adding this material on soil organic matter, the largest terrestrial pool of carbon, has yet to be considered. Microbial biomass and respiration have been observed to increase with decreasing acidity, but it is unclear how long the effect lasts. If the addition of silicate minerals promotes the loss of soil organic carbon through decomposition, it could significantly reduce the efficiency of this process or even create a net carbon source. However, it is possible that this initial flush of microbial activity may be compensated for by additional organic matter inputs to soil pools due to increases in plant productivity under less acidic conditions. This study aimed to examine the effects of olivine amendments on soil CO2 flux. A liming treatment representative of typical agricultural practices was also included for comparison. Samples from two highly acidic soils were split into groups amended with olivine or lime and a control group. These samples were incubated at 22°C and constant soil moisture in jars with airtight septa lids. Gas samples were extracted periodically over the course of 2 months and change in headspace CO2 concentration was determined. The effects of enhanced mineral weathering on soil organic matter have yet to be addressed by those promoting this method of carbon sequestration. This project provides the first data on the potential effects of enhanced mineral weathering in the soil environment on soil organic carbon pools.

  15. Biochar and biological carbon cycling in temperate soils

    NASA Astrophysics Data System (ADS)

    McCormack, S. A.; Vanbergen, A. J.; Bardgett, R. D.; Hopkins, D. W.; Ostle, N.

    2012-04-01

    Production of biochar, the recalcitrant residue formed by pyrolysis of plant matter, is suggested as a means of increasing storage of stable carbon (C) in the soil (1). Biochar has also been shown to act as a soil conditioner, increasing the productivity of certain crops by reducing nutrient leaching and improving soil water-holding capacity. However, the response of soil carbon pools to biochar addition is not yet well understood. Studies have shown that biochar has highly variable effects on microbial C cycling and thus on soil C storage (2,3,4). This discrepancy may be partially explained by the response of soil invertebrates, which occupy higher trophic levels and regulate microbial activity. This research aims to understand the role of soil invertebrates (i.e. Collembola and nematode worms) in biochar-mediated changes to soil C dynamics across a range of plant-soil communities. An open-air, pot-based mesocosm experiment was established in May, 2011 at the Centre for Ecology and Hydrology, Edinburgh. Three treatments were included in a fully-factorial design: biochar (presence [2 % w/w] or absence), soil type (arable sandy, arable sandy loam, grassland sandy loam), and vegetation type (Hordeum vulgare, Lolium perenne, unvegetated). Monitored parameters include: invertebrate and microbial species composition, soil C fluxes (CO2 and trace gas evolution, leachate C content, primary productivity and soil C content), and soil conditions (pH, moisture content and water-holding capacity). Preliminary results indicate that biochar-induced changes to soil invertebrate communities and processes are affected by pre-existing soil characteristics, and that soil texture in particular may be an important determinant of soil response to biochar addition. 1. Lehmann, 2007. A handful of carbon. Nature 447, 143-144. 2. Liang et al., 2010. Black carbon affects the cycling of non-black carbon in soil. Organic Geochemistry 41, 206-213. 3. Van Zwieten et al., 2010. Influence of

  16. Fate of Soil Organic Carbon and Polycyclic Aromatic Hydrocarbons in a Vineyard Soil Treated with Biochar.

    PubMed

    Rombolà, Alessandro G; Meredith, Will; Snape, Colin E; Baronti, Silvia; Genesio, Lorenzo; Vaccari, Francesco Primo; Miglietta, Franco; Fabbri, Daniele

    2015-09-15

    The effect of biochar addition on the levels of black carbon (BC) and polcyclic aromatic hydrocarbons (PAHs) in a vineyard soil in central Italy was investigated within a two year period. Hydropyrolysis (HyPy) was used to determine the contents of BC (BCHyPy) in the amended and control soils, while the hydrocarbon composition of the semi-labile (non-BCHyPy) fraction released by HyPy was determined by gas chromatography-mass spectrometry, together with the solvent-extractable PAHs. The concentrations of these three polycyclic aromatic carbon reservoirs changed and impacted differently the soil organic carbon over the period of the trial. The addition of biochar (33 ton dry biochar ha(-1)) gave rise to a sharp increase in soil organic carbon, which could be accounted for by an increase in BCHyPy. Over time, the concentration of BCHyPy decreased significantly from 36 to 23 mg g(-1) and as a carbon percentage from 79% to 61%. No clear time trends were observed for the non-BCHyPy PAHs varying from 39 to 34 μg g(-1) in treated soils, not significantly different from control soils. However, the concentrations of extractable PAHs increased markedly in the amended soils and decreased with time from 153 to 78 ng g(-1) remaining always higher than those in untreated soil. The extent of the BCHyPy loss was more compatible with physical rather than chemical processes.

  17. Predicting the impact of biochar additions on soil hydraulic properties.

    PubMed

    Lim, T J; Spokas, K A; Feyereisen, G; Novak, J M

    2016-01-01

    Different physical and chemical properties of biochar, which is made out of a variety of biomass materials, can impact water movement through amended soil. The objective of this research was to develop a decision support tool predicting the impact of biochar additions on soil saturated hydraulic conductivity (Ksat). Four different kinds of biochar were added to four different textured soils (coarse sand, fine sand, loam, and clay texture) to assess these effects at the rates of 0%, 1%, 2%, and 5% (w/w). The Ksat of the biochar amended soils were significantly influenced by the rate and type of biochar, as well as the original particle size of soil. The Ksat decreased when biochar was added to coarse and fine sands. Biochar with larger particles sizes (60%; >1 mm) decreased Ksat to a larger degree than the smaller particle size biochar (60%; <1 mm) in the two sandy textured soils. Increasing tortuosity in the biochar amended sandy soil could explain this behavior. On the other hand, for the clay loam 1% and 2% biochar additions universally increased the Ksat with higher biochar amounts providing no further alterations. The developed model utilizes soil texture pedotransfer functions for predicting agricultural soil Ksat as a function of soil texture. The model accurately predicted the direction of the Ksat influence, even though the exact magnitude still requires further refinement. This represents the first step to a unified theory behind the impact of biochar additions on soil saturated conductivity. PMID:26145507

  18. Predicting the impact of biochar additions on soil hydraulic properties.

    PubMed

    Lim, T J; Spokas, K A; Feyereisen, G; Novak, J M

    2016-01-01

    Different physical and chemical properties of biochar, which is made out of a variety of biomass materials, can impact water movement through amended soil. The objective of this research was to develop a decision support tool predicting the impact of biochar additions on soil saturated hydraulic conductivity (Ksat). Four different kinds of biochar were added to four different textured soils (coarse sand, fine sand, loam, and clay texture) to assess these effects at the rates of 0%, 1%, 2%, and 5% (w/w). The Ksat of the biochar amended soils were significantly influenced by the rate and type of biochar, as well as the original particle size of soil. The Ksat decreased when biochar was added to coarse and fine sands. Biochar with larger particles sizes (60%; >1 mm) decreased Ksat to a larger degree than the smaller particle size biochar (60%; <1 mm) in the two sandy textured soils. Increasing tortuosity in the biochar amended sandy soil could explain this behavior. On the other hand, for the clay loam 1% and 2% biochar additions universally increased the Ksat with higher biochar amounts providing no further alterations. The developed model utilizes soil texture pedotransfer functions for predicting agricultural soil Ksat as a function of soil texture. The model accurately predicted the direction of the Ksat influence, even though the exact magnitude still requires further refinement. This represents the first step to a unified theory behind the impact of biochar additions on soil saturated conductivity.

  19. Soil carbon changes for bioenergy crops.

    SciTech Connect

    Andress, D.

    2004-04-22

    Bioenergy crops, which displace fossil fuels when used to produce ethanol, biobased products, and/or electricity, have the potential to further reduce atmospheric carbon levels by building up soil carbon levels, especially when planted on lands where these levels have been reduced by intensive tillage. The purpose of this study is to improve the characterization of the soil carbon (C) sequestration for bioenergy crops (switchgrass, poplars, and willows) in the Greenhouse gases, Regulated Emissions, and Energy Use in Transportation (GREET) model (Wang 1999) by using the latest results reported in the literature and by Oak Ridge National Laboratory (ORNL). Because soil carbon sequestration for bioenergy crops can play a significant role in reducing greenhouse gas (GHG) emissions for cellulosic ethanol, it is important to periodically update the estimates of soil carbon sequestration from bioenergy crops as new and better data become available. We used the three-step process described below to conduct our study.

  20. Soil salinity decreases global soil organic carbon stocks.

    PubMed

    Setia, Raj; Gottschalk, Pia; Smith, Pete; Marschner, Petra; Baldock, Jeff; Setia, Deepika; Smith, Jo

    2013-11-01

    Saline soils cover 3.1% (397 million hectare) of the total land area of the world. The stock of soil organic carbon (SOC) reflects the balance between carbon (C) inputs from plants, and losses through decomposition, leaching and erosion. Soil salinity decreases plant productivity and hence C inputs to the soil, but also microbial activity and therefore SOC decomposition rates. Using a modified Rothamsted Carbon model (RothC) with a newly introduced salinity decomposition rate modifier and a plant input modifier we estimate that, historically, world soils that are currently saline have lost an average of 3.47 tSOC ha(-1) since they became saline. With the extent of saline soils predicted to increase in the future, our modelling suggests that world soils may lose 6.8 Pg SOC due to salinity by the year 2100. Our findings suggest that current models overestimate future global SOC stocks and underestimate net CO2 emissions from the soil-plant system by not taking salinity effects into account. From the perspective of enhancing soil C stocks, however, given the lower SOC decomposition rate in saline soils, salt tolerant plants could be used to sequester C in salt-affected areas.

  1. Sequestration of Soil Carbon as Secondary Carbonates (Invited)

    NASA Astrophysics Data System (ADS)

    Lal, R.

    2013-12-01

    Rattan Lal Carbon Management and Sequestration Center The Ohio State University Columbus, OH 43210 USA Abstract World soils, the major carbon (C) reservoir among the terrestrial pools, contain soil organic C (SOC) and soil inorganic C (SIC). The SIC pool is predominant in soils of arid and semi-arid regions. These regions cover a land area of about 4.9x109 ha. The SIC pool in soils containing calcic and petrocalcic horizons is estimated at about 695-748 Pg (Pg = 1015 g = 1 gigaton) to 1-m depth. There are two types of carbonates. Lithogenic or primary carbonates are formed from weathering of carbonaceous rocks. Pedogenic or secondary carbonates are formed by dissolution of CO2 in the soil air to form carbonic acid and precipitation as carbonates of Ca+2 or Mg+2. It is the availability of Ca+2 or Mg+2 from outside the ecosystem that is essential to sequester atmospheric CO2. Common among outside sources of Ca+2 or Mg+2 are irrigation water, aerial deposition, sea breeze, fertilizers, manure and other amendments. The decomposition of SOC and root respiration may increase the partial pressure of CO2 in the soil air and lead to the formation of HCO_3^- upon dissolution in H20. Precipitation of secondary carbonates may result from decreased partial pressure of CO2 in the sub-soil, increased concentration of Ca+2, Mg+2 and HCO_3^- in soil solution, and decreased soil moisture content by evapotranspiration. Transport of bicarbonates in irrigated soils and subsequent precipitation above the ground water (calcrete), activity of termites and other soil fauna, and management of urban soils lead to formation of secondary carbonates. On a geologic time scale, weathering of silicate minerals and transport of the by-products into the ocean is a geological process of sequestration of atmospheric CO2. Factors affecting formation of secondary carbonates include land use, and soil and crop management including application of biosolids, irrigation and the quality of irrigation water

  2. [Research methods of carbon sequestration by soil aggregates: a review].

    PubMed

    Chen, Xiao-Xia; Liang, Ai-Zhen; Zhang, Xiao-Ping

    2012-07-01

    To increase soil organic carbon content is critical for maintaining soil fertility and agricultural sustainable development and for mitigating increased greenhouse gases and the effects of global climate change. Soil aggregates are the main components of soil, and have significant effects on soil physical and chemical properties. The physical protection of soil organic carbon by soil aggregates is the important mechanism of soil carbon sequestration. This paper reviewed the organic carbon sequestration by soil aggregates, and introduced the classic and current methods in studying the mechanisms of carbon sequestration by soil aggregates. The main problems and further research trends in this study field were also discussed.

  3. Transient Dissolved Organic Carbon Through Soils

    NASA Astrophysics Data System (ADS)

    Mei, Y.; Hornberger, G. M.; Kaplan, L. A.; Newbold, J. D.; Aufdenkampe, A. K.; Tsang, Y.

    2009-12-01

    Dissolved organic carbon (DOC) is an important constituent of soil solution that plays a role in many chemical and biological processes in soils; it is also an important energy source for bacteria in the soil ecosystem. Hydrology has a significant control on the transport and fate of dissolved organic carbon in the soil but mechanisms that affect said transport are not well understood. In particular, dynamic information on DOC transport through forest soils on short time scales (one or two precipitation event) is lacking at present. DOC is a very complex mix of organic compounds. A key to quantifying DOC dynamics is to establish useful approximations for behavior of this complex mixture. Biodegradable dissolved organic carbon (BDOC) is an important part of DOC. It is reported that between 12 and 44% of DOC released from the forest floor can be decomposed in solutions by indigenous microbes. In our study, we considered how DOC, BDOC, and flow interact in soil columns. In-situ soil cores with two different lengths were installed under a mixed deciduous canopy. The effects of artificial rain on DOC and BDOC transport were examined by dripping nano pure water amended with bromide on the top of soil cores and sampling the water collected at the bottom of the cores for DOC and BDOC. We used plug-flow biofilm reactors to measure the BDOC concentration. It is likely that reduced rates of decomposition in dry soils will cause microbial products of DOC to accumulate; hence DOC concentration should be high at the first flush of rain and decline as the event proceeds. The experimental results show the expected pattern, that is, the first samples we collected always had the highest DOC and BDOC concentrations. The concentrations tend to decline through the simulated precipitation event. Application of a second “storm” forty minutes after the cessation of the first application of water resulted in effluent DOC concentration increasing a small amount initially and then

  4. Seasonal Patterns of Soil Respiration and Related Soil Biochemical Properties under Nitrogen Addition in Winter Wheat Field.

    PubMed

    Liang, Guopeng; Houssou, Albert A; Wu, Huijun; Cai, Dianxiong; Wu, Xueping; Gao, Lili; Li, Jing; Wang, Bisheng; Li, Shengping

    2015-01-01

    Understanding the changes of soil respiration under increasing N fertilizer in cropland ecosystems is crucial to accurately predicting global warming. This study explored seasonal variations of soil respiration and its controlling biochemical properties under a gradient of Nitrogen addition during two consecutive winter wheat growing seasons (2013-2015). N was applied at four different levels: 0, 120, 180 and 240 kg N ha(-1) year(-1) (denoted as N0, N12, N18 and N24, respectively). Soil respiration exhibited significant seasonal variation and was significantly affected by soil temperature with Q10 ranging from 2.04 to 2.46 and from 1.49 to 1.53 during 2013-2014 and 2014-2015 winter wheat growing season, respectively. Soil moisture had no significant effect on soil respiration during 2013-2014 winter wheat growing season but showed a significant and negative correlation with soil respiration during 2014-2015 winter wheat growing season. Soil respiration under N24 treatment was significantly higher than N0 treatment. Averaged over the two growing seasons, N12, N18 and N24 significantly increased soil respiration by 13.4, 16.4 and 25.4% compared with N0, respectively. N addition also significantly increased easily extractable glomalin-related soil protein (EEG), soil organic carbon (SOC), total N, ammonium N and nitrate N contents. In addition, soil respiration was significantly and positively correlated with β-glucosidase activity, EEG, SOC, total N, ammonium N and nitrate N contents. The results indicated that high N fertilization improved soil chemical properties, but significantly increased soil respiration. PMID:26629695

  5. Seasonal Patterns of Soil Respiration and Related Soil Biochemical Properties under Nitrogen Addition in Winter Wheat Field.

    PubMed

    Liang, Guopeng; Houssou, Albert A; Wu, Huijun; Cai, Dianxiong; Wu, Xueping; Gao, Lili; Li, Jing; Wang, Bisheng; Li, Shengping

    2015-01-01

    Understanding the changes of soil respiration under increasing N fertilizer in cropland ecosystems is crucial to accurately predicting global warming. This study explored seasonal variations of soil respiration and its controlling biochemical properties under a gradient of Nitrogen addition during two consecutive winter wheat growing seasons (2013-2015). N was applied at four different levels: 0, 120, 180 and 240 kg N ha(-1) year(-1) (denoted as N0, N12, N18 and N24, respectively). Soil respiration exhibited significant seasonal variation and was significantly affected by soil temperature with Q10 ranging from 2.04 to 2.46 and from 1.49 to 1.53 during 2013-2014 and 2014-2015 winter wheat growing season, respectively. Soil moisture had no significant effect on soil respiration during 2013-2014 winter wheat growing season but showed a significant and negative correlation with soil respiration during 2014-2015 winter wheat growing season. Soil respiration under N24 treatment was significantly higher than N0 treatment. Averaged over the two growing seasons, N12, N18 and N24 significantly increased soil respiration by 13.4, 16.4 and 25.4% compared with N0, respectively. N addition also significantly increased easily extractable glomalin-related soil protein (EEG), soil organic carbon (SOC), total N, ammonium N and nitrate N contents. In addition, soil respiration was significantly and positively correlated with β-glucosidase activity, EEG, SOC, total N, ammonium N and nitrate N contents. The results indicated that high N fertilization improved soil chemical properties, but significantly increased soil respiration.

  6. Seasonal Patterns of Soil Respiration and Related Soil Biochemical Properties under Nitrogen Addition in Winter Wheat Field

    PubMed Central

    Liang, Guopeng; Houssou, Albert A.; Wu, Huijun; Cai, Dianxiong; Wu, Xueping; Gao, Lili; Li, Jing; Wang, Bisheng; Li, Shengping

    2015-01-01

    Understanding the changes of soil respiration under increasing N fertilizer in cropland ecosystems is crucial to accurately predicting global warming. This study explored seasonal variations of soil respiration and its controlling biochemical properties under a gradient of Nitrogen addition during two consecutive winter wheat growing seasons (2013–2015). N was applied at four different levels: 0, 120, 180 and 240 kg N ha-1 year-1 (denoted as N0, N12, N18 and N24, respectively). Soil respiration exhibited significant seasonal variation and was significantly affected by soil temperature with Q10 ranging from 2.04 to 2.46 and from 1.49 to 1.53 during 2013–2014 and 2014–2015 winter wheat growing season, respectively. Soil moisture had no significant effect on soil respiration during 2013–2014 winter wheat growing season but showed a significant and negative correlation with soil respiration during 2014–2015 winter wheat growing season. Soil respiration under N24 treatment was significantly higher than N0 treatment. Averaged over the two growing seasons, N12, N18 and N24 significantly increased soil respiration by 13.4, 16.4 and 25.4% compared with N0, respectively. N addition also significantly increased easily extractable glomalin-related soil protein (EEG), soil organic carbon (SOC), total N, ammonium N and nitrate N contents. In addition, soil respiration was significantly and positively correlated with β-glucosidase activity, EEG, SOC, total N, ammonium N and nitrate N contents. The results indicated that high N fertilization improved soil chemical properties, but significantly increased soil respiration. PMID:26629695

  7. Photoautotrophic microorganisms as a carbon source for temperate soil invertebrates.

    PubMed

    Schmidt, Olaf; Dyckmans, Jens; Schrader, Stefan

    2016-01-01

    We tested experimentally if photoautotrophic microorganisms are a carbon source for invertebrates in temperate soils. We exposed forest or arable soils to a (13)CO2-enriched atmosphere and quantified (13)C assimilation by three common animal groups: earthworms (Oligochaeta), springtails (Hexapoda) and slugs (Gastropoda). Endogeic earthworms (Allolobophora chlorotica) and hemiedaphic springtails (Ceratophysella denticulata) were highly (13)C enriched when incubated under light, deriving up to 3.0 and 17.0%, respectively, of their body carbon from the microbial source in 7 days. Earthworms assimilated more (13)C in undisturbed soil than when the microbial material was mixed into the soil, presumably reflecting selective surface grazing. By contrast, neither adult nor newly hatched terrestrial slugs (Deroceras reticulatum) grazed on algal mats. Non-photosynthetic (13)CO2 fixation in the dark was negligible. We conclude from these preliminary laboratory experiments that, in addition to litter and root-derived carbon from vascular plants, photoautotrophic soil surface microorganisms (cyanobacteria, algae) may be an ecologically important carbon input route for temperate soil animals that are traditionally assigned to the decomposer channel in soil food web models and carbon cycling studies.

  8. Photoautotrophic microorganisms as a carbon source for temperate soil invertebrates.

    PubMed

    Schmidt, Olaf; Dyckmans, Jens; Schrader, Stefan

    2016-01-01

    We tested experimentally if photoautotrophic microorganisms are a carbon source for invertebrates in temperate soils. We exposed forest or arable soils to a (13)CO2-enriched atmosphere and quantified (13)C assimilation by three common animal groups: earthworms (Oligochaeta), springtails (Hexapoda) and slugs (Gastropoda). Endogeic earthworms (Allolobophora chlorotica) and hemiedaphic springtails (Ceratophysella denticulata) were highly (13)C enriched when incubated under light, deriving up to 3.0 and 17.0%, respectively, of their body carbon from the microbial source in 7 days. Earthworms assimilated more (13)C in undisturbed soil than when the microbial material was mixed into the soil, presumably reflecting selective surface grazing. By contrast, neither adult nor newly hatched terrestrial slugs (Deroceras reticulatum) grazed on algal mats. Non-photosynthetic (13)CO2 fixation in the dark was negligible. We conclude from these preliminary laboratory experiments that, in addition to litter and root-derived carbon from vascular plants, photoautotrophic soil surface microorganisms (cyanobacteria, algae) may be an ecologically important carbon input route for temperate soil animals that are traditionally assigned to the decomposer channel in soil food web models and carbon cycling studies. PMID:26740559

  9. Evaluating Soil Carbon Sequestration in Central Iowa

    NASA Astrophysics Data System (ADS)

    Doraiswamy, P. C.; Hunt, E. R.; McCarty, G. W.; Daughtry, C. S.; Izaurralde, C.

    2005-12-01

    The potential for reducing atmospheric carbon dioxide (CO2) concentration through landuse and management of agricultural systems is of great interest worldwide. Agricultural soils can be a source of CO2 when not properly managed but can also be a sink for sequestering CO2 through proper soil and crop management. The EPIC-CENTURY biogeochemical model was used to simulate the baseline level of soil carbon from soil survey data and project changes in soil organic carbon (SOC) under different tillage and crop management practices for corn and soybean crops. The study was conducted in central Iowa (50 km x 100 km) to simulate changes in soil carbon over the next 50 years. The simulations were conducted in two phases; initially a 25-year period (1971-1995) was simulated using conventional tillage practices since there was a transition in new management after 1995. In the second 25-year period (1996-2020), four different modeling scenarios were applied namely; conventional tillage, mulch tillage, no-tillage and no-tillage with a rye cover crop over the winter. The model simulation results showed potential gains in soil carbon in the top layers of the soil for conservation tillage. The simulations were made at a spatial resolution of 1.6 km x 1.6 km and mapped for the study area. There was a mean reduction in soil organic carbon of 0.095 T/ha per year over the 25-year period starting with 1996 for the conventional tillage practice. However, for management practices of mulch tillage, no tillage and no tillage with cover crop there was an increase in soil organic carbon of 0.12, 0.202 and 0.263 T/ha respectively over the same 25-year period. These results are in general similar to studies conducted in this region.

  10. Carbon mineralization in surface and subsurface soils in a subtropical mixed forest in central China

    NASA Astrophysics Data System (ADS)

    Liu, F.; Tian, Q.

    2014-12-01

    About a half of soil carbon is stored in subsurface soil horizons, their dynamics have the potential to significantly affect carbon balancing in terrestrial ecosystems. However, the main factors regulating subsurface soil carbon mineralization are poorly understood. As affected by mountain humid monsoon, the subtropical mountains in central China has an annual precipitation of about 2000 mm, which causes strong leaching of ions and nutrition. The objectives of this study were to monitor subsurface soil carbon mineralization and to determine if it is affected by nutrient limitation. We collected soil samples (up to 1 m deep) at three locations in a small watershed with three soil layers (0-10 cm, 10-30 cm, below 30 cm). For the three layers, soil organic carbon (SOC) ranged from 35.8 to 94.4 mg g-1, total nitrogen ranged from 3.51 to 8.03 mg g-1, microbial biomass carbon (MBC) ranged from 170.6 to 718.4 μg g-1 soil. We measured carbon mineralization with the addition of N (100 μg N/g soil), P (50 μg P/g soil), and liable carbon (glucose labeled by 5 atom% 13C, at five levels: control, 10% MBC, 50% MBC, 100% MBC, 200% MBC). The addition of N and P had negligible effects on CO2 production in surface soil layers; in the deepest soil layer, the addition of N and P decreased CO2 production from 4.32 to 3.20 μg C g-1 soil carbon h-1. Glucose addition stimulated both surface and subsurface microbial mineralization of SOC, causing priming effects. With the increase of glucose addition rate from 10% to 200% MBC, the primed mineralization rate increased from 0.19 to 3.20 μg C g-1 soil carbon h-1 (fifth day of glucose addition). The magnitude of priming effect increased from 28% to 120% as soil layers go deep compare to the basal CO2 production (fifth day of 200% MBC glucose addition, basal CO2 production rate for the surface and the deepest soil was 11.17 and 2.88 μg C g-1 soil carbon h-1). These results suggested that the mineralization of subsurface carbon is more

  11. Alaskan Arctic Soils: Relationship between Microbial Carbon Usage and Soil Composition

    NASA Astrophysics Data System (ADS)

    Li, H.; Ziolkowski, L. A.

    2015-12-01

    Carbon stored in Arctic permafrost carbon is sensitive to climate change. Microbes are known to degrade Arctic soil organic carbon (OC) and potentially release vast quantitates of CO2 and CH4. Previously, it has been shown that warming of Arctic soils leads to microbes respiring older carbon. To examine this process, we studied the microbial carbon usage and its relationship to the soil OC composition in active layer soils at five locations along a latitudinal transect on the North Slope of Alaska using the compound specific radiocarbon signatures of the viable microbial community using phospholipid fatty acids (PLFA). Additional geochemical parameters (C/N, 13C, 15N and 14C) of bulk soils were measured. Overall there was a greater change with depth than location. Organic rich surface soils are rich in vegetation and have high PLFA based cell densities, while deeper in the active layer geochemical parameters indicated soil OC was degraded and cell densities decreased. As expected, PLFA indicative of Fungi and Protozoa species dominated in surface soils, methyl-branched PLFAs, indicative of bacterial origin, increased in deeper in the active layer. A group of previously unreported PLFAs, believed to correlate to anaerobic microbes, increased at the transition between the surface and deep microbial communities. Cluster analysis based on individual PLFAs of samples confirmed compositional differences as a function of depth dominated with no site to site differences. Radiocarbon data of soil OC and PLFA show the preferential consumption of younger soil OC by microbes at all sites and older OC being eaten in deep soils. However, in deeper soil, where the C/N ratio suggests lower bioavailability, less soil OC was incorporated into the microbes as indicating by greater differences between bulk and PLFA radiocarbon ages.

  12. Active Layer Soil Carbon and Nutrient Mineralization, Barrow, Alaska, 2012

    DOE Data Explorer

    Stan D. Wullschleger; Holly M. Vander Stel; Colleen Iversen; Victoria L. Sloan; Richard J. Norby; Mallory P. Ladd; Jason K. Keller; Ariane Jong; Joanne Childs; Deanne J. Brice

    2015-10-29

    This data set consists of bulk soil characteristics as well as carbon and nutrient mineralization rates of active layer soils manually collected from the field in August, 2012, frozen, and then thawed and incubated across a range of temperatures in the laboratory for 28 day periods in 2013-2015. The soils were collected from four replicate polygons in each of the four Areas (A, B, C, and D) of Intensive Site 1 at the Next-Generation Ecosystem Experiments (NGEE) Arctic site near Barrow, Alaska. Soil samples were coincident with the established Vegetation Plots that are located in center, edge, and trough microtopography in each polygon. Data included are 1) bulk soil characteristics including carbon, nitrogen, gravimetric water content, bulk density, and pH in 5-cm depth increments and also by soil horizon, 2) carbon, nitrogen, and phosphorus mineralization rates for soil horizons incubated aerobically (and in one case both aerobically and anaerobically) for 28 days at temperatures that included 2, 4, 8, and 12 degrees C. Additional soil and incubation data are forthcoming. They will be available when published as part of another paper that includes additional replicate analyses.

  13. Organic Phosphorus Characterisation in Agricultural Soils by Enzyme Addition Assays

    NASA Astrophysics Data System (ADS)

    Jarosch, Klaus; Frossard, Emmanuel; Bünemann, Else K.

    2013-04-01

    Phosphorus (P) is a non-renewable resource and it is a building block of many molecules indispensable for life. Up to 80 per cent of total soil P can be in organic form. Hydrolysability and thereby availability to plants and microorganisms differ strongly among the multitude of chemical forms of soil organic P. A recent approach to characterise organic P classes is the addition of specific enzymes which hydrolyse organic P to inorganic orthophosphate, making it detectable by colorimetry. Based on the substrate specificity of the added enzymes, conclusions about the hydrolysed forms of organic P can then be made. The aim of this study was to determine the applicability of enzyme addition assays for the characterisation of organic P species in soil:water suspensions of soils with differing properties. To this end, ten different soil samples originating from four continents, with variable pH (in water) values (4.2-8.0), land management (grassland or cropped land) and P fertilization intensity were analysed. Three different enzymes were used (acid phosphatase, nuclease and phytase). Acid phosphatase alone or in combination with nuclease was applied to determine the content of P in simple monoesters (monoester-like P) and P in DNA (DNA-like P), while P hydrolysed from myo-inositol hexakisphosphate (Ins6P-like P) was calculated from P release after incubation with phytase minus P release by acid phosphatase. To reduce sorption of inorganic P on soil particles of the suspension, especially in highly weathered soils, soil specific EDTA additions were determined in extensive pre-tests. The results of these pre-tests showed that recoveries of at least 30 per cent could be achieved in all soils. Thus, detection of even small organic P pools, such as DNA-like P, was possible in all soils if a suitable EDTA concentration was chosen. The enzyme addition assays provided information about the hydrolysable quantities of the different classes of soil organic P compounds as affected

  14. Ecosystem carbon budgeting and soil carbon sequestration in reclaimed mine soil.

    PubMed

    Shrestha, Raj K; Lal, Rattan

    2006-08-01

    Global warming risks from emissions of green house gases (GHGs) by anthropogenic activities, and possible mitigation strategies of terrestrial carbon (C) sequestration have increased the need for the identification of ecosystems with high C sink capacity. Depleted soil organic C (SOC) pools of reclaimed mine soil (RMS) ecosystems can be restored through conversion to an appropriate land use and adoption of recommended management practices (RMPs). The objectives of this paper are to (1) synthesize available information on carbon dioxide (CO2) emissions from coal mining and combustion activities, (2) understand mechanisms of SOC sequestration and its protection, (3) identify factors affecting C sequestration potential in RMSs, (4) review available methods for the estimation of ecosystem C budget (ECB), and (5) identify knowledge gaps to enhance C sink capacity of RMS ecosystems and prioritize research issues. The drastic perturbations of soil by mining activities can accentuate CO2 emission through mineralization, erosion, leaching, changes in soil moisture and temperature regimes, and reduction in biomass returned to the soil. The reclamation of drastically disturbed soils leads to improvement in soil quality and development of soil pedogenic processes accruing the benefit of SOC sequestration and additional income from trading SOC credits. The SOC sequestration potential in RMS depends on amount of biomass production and return to soil, and mechanisms of C protection. The rate of SOC sequestration ranges from 0.1 to 3.1 Mg ha(-1) yr(-1) and 0.7 to 4 Mg ha(-1) yr(-1) in grass and forest RMS ecosystem, respectively. Proper land restoration alone could off-set 16 Tg CO2 in the U.S. annually. However, the factors affecting C sequestration and protection in RMS leading to increase in microbial activity, nutrient availability, soil aggregation, C build up, and soil profile development must be better understood in order to formulate guidelines for development of an

  15. Ecosystem carbon budgeting and soil carbon sequestration in reclaimed mine soil.

    PubMed

    Shrestha, Raj K; Lal, Rattan

    2006-08-01

    Global warming risks from emissions of green house gases (GHGs) by anthropogenic activities, and possible mitigation strategies of terrestrial carbon (C) sequestration have increased the need for the identification of ecosystems with high C sink capacity. Depleted soil organic C (SOC) pools of reclaimed mine soil (RMS) ecosystems can be restored through conversion to an appropriate land use and adoption of recommended management practices (RMPs). The objectives of this paper are to (1) synthesize available information on carbon dioxide (CO2) emissions from coal mining and combustion activities, (2) understand mechanisms of SOC sequestration and its protection, (3) identify factors affecting C sequestration potential in RMSs, (4) review available methods for the estimation of ecosystem C budget (ECB), and (5) identify knowledge gaps to enhance C sink capacity of RMS ecosystems and prioritize research issues. The drastic perturbations of soil by mining activities can accentuate CO2 emission through mineralization, erosion, leaching, changes in soil moisture and temperature regimes, and reduction in biomass returned to the soil. The reclamation of drastically disturbed soils leads to improvement in soil quality and development of soil pedogenic processes accruing the benefit of SOC sequestration and additional income from trading SOC credits. The SOC sequestration potential in RMS depends on amount of biomass production and return to soil, and mechanisms of C protection. The rate of SOC sequestration ranges from 0.1 to 3.1 Mg ha(-1) yr(-1) and 0.7 to 4 Mg ha(-1) yr(-1) in grass and forest RMS ecosystem, respectively. Proper land restoration alone could off-set 16 Tg CO2 in the U.S. annually. However, the factors affecting C sequestration and protection in RMS leading to increase in microbial activity, nutrient availability, soil aggregation, C build up, and soil profile development must be better understood in order to formulate guidelines for development of an

  16. Integrating microbial diversity in soil carbon dynamic models parameters

    NASA Astrophysics Data System (ADS)

    Louis, Benjamin; Menasseri-Aubry, Safya; Leterme, Philippe; Maron, Pierre-Alain; Viaud, Valérie

    2015-04-01

    Faced with the numerous concerns about soil carbon dynamic, a large quantity of carbon dynamic models has been developed during the last century. These models are mainly in the form of deterministic compartment models with carbon fluxes between compartments represented by ordinary differential equations. Nowadays, lots of them consider the microbial biomass as a compartment of the soil organic matter (carbon quantity). But the amount of microbial carbon is rarely used in the differential equations of the models as a limiting factor. Additionally, microbial diversity and community composition are mostly missing, although last advances in soil microbial analytical methods during the two past decades have shown that these characteristics play also a significant role in soil carbon dynamic. As soil microorganisms are essential drivers of soil carbon dynamic, the question about explicitly integrating their role have become a key issue in soil carbon dynamic models development. Some interesting attempts can be found and are dominated by the incorporation of several compartments of different groups of microbial biomass in terms of functional traits and/or biogeochemical compositions to integrate microbial diversity. However, these models are basically heuristic models in the sense that they are used to test hypotheses through simulations. They have rarely been confronted to real data and thus cannot be used to predict realistic situations. The objective of this work was to empirically integrate microbial diversity in a simple model of carbon dynamic through statistical modelling of the model parameters. This work is based on available experimental results coming from a French National Research Agency program called DIMIMOS. Briefly, 13C-labelled wheat residue has been incorporated into soils with different pedological characteristics and land use history. Then, the soils have been incubated during 104 days and labelled and non-labelled CO2 fluxes have been measured at ten

  17. Uncertainty in soil carbon accounting due to unrecognized soil erosion.

    PubMed

    Sanderman, Jonathan; Chappell, Adrian

    2013-01-01

    The movement of soil organic carbon (SOC) during erosion and deposition events represents a major perturbation to the terrestrial carbon cycle. Despite the recognized impact soil redistribution can have on the carbon cycle, few major carbon accounting models currently allow for soil mass flux. Here, we modified a commonly used SOC model to include a soil redistribution term and then applied it to scenarios which explore the implications of unrecognized erosion and deposition for SOC accounting. We show that models that assume a static landscape may be calibrated incorrectly as erosion of SOC is hidden within the decay constants. This implicit inclusion of erosion then limits the predictive capacity of these models when applied to sites with different soil redistribution histories. Decay constants were found to be 15-50% slower when an erosion rate of 15 t soil ha(-1)  yr(-1) was explicitly included in the SOC model calibration. Static models cannot account for SOC change resulting from agricultural management practices focused on reducing erosion rates. Without accounting for soil redistribution, a soil sampling scheme which uses a fixed depth to support model development can create large errors in actual and relative changes in SOC stocks. When modest levels of erosion were ignored, the combined uncertainty in carbon sequestration rates was 0.3-1.0 t CO2  ha(-1)  yr(-1) . This range is similar to expected sequestration rates for many management options aimed at increasing SOC levels. It is evident from these analyses that explicit recognition of soil redistribution is critical to the success of a carbon monitoring or trading scheme which seeks to credit agricultural activities.

  18. A big-microsite framework for soil carbon modeling.

    PubMed

    Davidson, Eric A; Savage, Kathleen E; Finzi, Adrien C

    2014-12-01

    Soil carbon cycling processes potentially play a large role in biotic feedbacks to climate change, but little agreement exists at present on what the core of numerical soil C cycling models should look like. In contrast, most canopy models of photosynthesis and leaf gas exchange share a common 'Farquhaur-model' core structure. Here, we explore why a similar core model structure for heterotrophic soil respiration remains elusive and how a pathway to that goal might be envisioned. The spatial and temporal variation in soil microsite conditions greatly complicates modeling efforts, but we believe it is possible to develop a tractable number of parameterizable equations that are organized into a coherent, modular, numerical model structure. First, we show parallels in insights gleaned from linking Arrhenius and Michaelis-Menten kinetics for both photosynthesis and soil respiration. Additional equations and layers of complexity are then added to simulate substrate supply. For soils, model modules that simulate carbon stabilization processes will be key to estimating the fraction of soil C that is accessible to enzymes. Potential modules for dynamic photosynthate input, wetting-event inputs, freeze-thaw impacts on substrate diffusion, aggregate turnover, soluble-C sorption, gas transport, methane respiration, and microbial dynamics are described for conceptually and numerically linking our understanding of fast-response processes of soil gas exchange with longer-term dynamics of soil carbon and nitrogen stocks.

  19. Pasture Management Strategies for Sequestering Soil Carbon - Final Report

    SciTech Connect

    Franzluebbers, Alan J.

    2006-03-15

    Pasturelands account for 51 of the 212 Mha of privately held grazing land in the USA. Tall fescue is the most important cool-season perennial forage for many beef cattle producers in the humid region of the USA. A fungal endophyte, Neotyphodium coenophialum, infects the majority of tall fescue stands with a mutualistic association. Ergot alkaloids produced by the endophyte have negative impacts on cattle performance. However, there are indications that endophyte infection of tall fescue is a necessary component of productive and persistent pasture ecology. The objectives of this research were to characterize and quantify changes in soil organic carbon and associated soil properties under tall fescue pastures with and without endophyte infection of grass. Pastures with high endophyte infection had greater concentration of soil organic carbon, but lower concentration of biologically active soil carbon than pastures with low endophyte infection. A controlled experiment suggested that endophyte-infected leaf tissue may directly inhibit the activity of soil microorganisms. Carbon forms of soil organic matter were negatively affected and nitrogen forms were positively affected by endophyte addition to soil. The chemical compounds in endophyte-infected tall fescue (ergot alkaloids) that are responsible for animal health disorders were found in soil, suggesting that these chemicals might be persistent in the environment. Future research is needed to determine whether ergot alkaloids or some other chemicals are responsible for increases in soil organic matter. Scientists will be able to use this information to better understand the ecological impacts of animals grazing tall fescue, and possibly to identify and cultivate other similar associations for improving soil organic matter storage. Another experiment suggested that both dry matter production and soil microbial activity could be affected by the endophyte. Sampling of the cumulative effects of 20 years of tall fescue

  20. Predicting the impact of biochar additions on soil hydraulic properties

    NASA Astrophysics Data System (ADS)

    Spokas, Kurt; Lim, Tae Jun; Feyereisen, Gary; Novak, Jeff

    2015-04-01

    Different physical and chemical properties of biochar, which is made out of a variety of biomass materials, can impact water movement through amended soil. The objective of this research was to develop a decision support tool predicting the impact of biochar additions on soil saturated hydraulic conductivity (Ksat). Four different kinds of biochar were added to four different textured soils (coarse sand, fine sand, loam, and clay texture) to assess these effects at the rates of 0, 1, 2, and 5 % (w/w). The Ksat of the biochar amended soils were significantly influenced by the rate and type of biochar, as well as the original particle size of soil. The Ksat decreased when biochar was added to coarse and fine sands. Biochar with larger particles sizes (60%; >1 mm) decreased Ksat to a larger degree than the smaller particle size biochar (60%; <1 mm) in the two sandy textured soils. Increasing tortuosity in the amended sandy soil could explain this behavior. On the other hand, for the clay loam 1% and 2% biochar additions universally increased the Ksat with higher biochar amounts providing no further alterations. The developed model utilizes soil texture pedotransfer functions for predicting agricultural soil Ksat as a function of soil texture. The model accurately predicted the direction of the Ksat influence, even though the exact magnitude still requires further refinement.

  1. NON-DESTRUCTIVE SOIL CARBON ANALYZER.

    SciTech Connect

    Wielopolski, Lucian; Hendrey, G.; Orion, I.; Prior, S.; Rogers, H.; Runion, B.; Torbert, A.

    2004-02-01

    This report describes the feasibility, calibration, and safety considerations of a non-destructive, in situ, quantitative, volumetric soil carbon analytical method based on inelastic neutron scattering (INS). The method can quantify values as low as 0.018 gC/cc, or about 1.2% carbon by weight with high precision under the instrument's configuration and operating conditions reported here. INS is safe and easy to use, residual soil activation declines to background values in under an hour, and no radiological requirements are needed for transporting the instrument. The labor required to obtain soil-carbon data is about 10-fold less than with other methods, and the instrument offers a nearly instantaneous rate of output of carbon-content values. Furthermore, it has the potential to quantify other elements, particularly nitrogen. New instrumentation was developed in response to a research solicitation from the U.S. Department of Energy (DOE LAB 00-09 Carbon Sequestration Research Program) supporting the Terrestrial Carbon Processes (TCP) program of the Office of Science, Biological and Environmental Research (BER). The solicitation called for developing and demonstrating novel techniques for quantitatively measuring changes in soil carbon. The report includes raw data and analyses of a set of proof-of-concept, double-blind studies to evaluate the INS approach in the first phase of developing the instrument. Managing soils so that they sequester massive amounts of carbon was suggested as a means to mitigate the atmospheric buildup of anthropogenic CO{sub 2}. Quantifying changes in the soils' carbon stocks will be essential to evaluating such schemes and documenting their performance. Current methods for quantifying carbon in soil by excavation and core sampling are invasive, slow, labor-intensive and locally destroy the system being observed. Newly emerging technologies, such as Laser Induced Breakdown Spectroscopy and Near-Infrared Spectroscopy, offer soil-carbon

  2. Reassessing carbon sequestration in the North China Plain via addition of nitrogen.

    PubMed

    Dong, Wenxu; Duan, Yongmei; Wang, Yuying; Hu, Chunsheng

    2016-09-01

    Soil inorganic carbon (SIC) exerts a strong influence on the carbon (C) sequestered in response to nitrogen (N) additions in arid and semi-arid ecosystems, but limited information is available on in situ SIC storage and dissolution at the field level. This study determined the soil organic/inorganic carbon storage in the soil profile at 0-100cm depths and the concentration of dissolved inorganic carbon (DIC) in soil leachate in 4N application treatments (0, 200, 400, and 600kgNha(-1)yr(-)(1)) for 15years in the North China Plain. The objectives were to evaluate the effect of nitrogen fertilizer on total amount of carbon sequestration and the uptake of atmospheric CO2 in an agricultural system. Results showed that after 15years of N fertilizer application the SOC contents at depths of 0-100cm significantly increased, whereas the SIC contents significantly decreased at depths of 0-60cm. However, the actual measured loss of carbonate was far higher than the theoretical maximum values of dissolution via protons from nitrification. Furthermore, the amount of HCO3(-) and the HCO3(-)/(Ca(2+)+Mg(2+)) ratio in soil leachate were higher in the N application treatments than no fertilizer input (CK) for the 0-80cm depth. The result suggested that the dissolution of carbonate was mainly enhanced by soil carbonic acid, a process which can absorb soil or atmosphere CO2 and less influenced by protons through the nitrification which would release CO2. To accurately evaluate soil C sequestration under N input scenarios in semi-arid regions, future studies should include both changes in SIC storage as well as the fractions of dissolution with different sources of acids in soil profiles. PMID:27135576

  3. Soil carbon sequestration: Quantifying this ecosystem service

    EPA Science Inventory

    Soils have a crucial role in supplying many goods and services that society depends upon on a daily basis. These include food and fiber production, water cleansing and supply, nutrient cycling, waste isolation and degradation. Soils also provide a significant amount of carbon s...

  4. Coupling soil Carbon Fluxes, Soil Microbes, and High-Resolution Carbon Profiling in Permafrost Transitions

    NASA Astrophysics Data System (ADS)

    Anderson, C.; Stegen, J.; Bond-Lamberty, B. P.; Tfaily, M. M.; Huang, M.; Liu, Y.

    2015-12-01

    Microbial communities play a central role in the functioning of natural ecosystems by heavily influencing biogeochemical cycles. Understanding how shifts in the environment are tied to shifts in biogeochemical rates via changes in microbial communities is particularly relevant in high latitude terrestrial systems underlain by permafrost due to vast carbon stocks currently stored within thawing permafrost. There is limited understanding, however, of the interplay among soil-atmosphere CO2 fluxes, microbial communities, and SOM chemical composition. To address this knowledge gap, we leverage the distinct spatial transitions in permafrost-affected soils at the Caribou Poker Creek Research Watershed, a 104 km2 boreal watershed ~50 km north of Fairbanks, AK. We integrate a variety of data to gain new knowledge of the factors that govern observed patterns in the rates of soil CO2 fluxes associated with permafrost to non-permafrost transition zones. We show that nonlinearities in fluxes are influenced by depth to permafrost, tree stand structure, and soil C composition. Further, using 16S sequencing methods we explore microbial community assembly processes and their connection to CO2 flux across spatial scales, and suggest a path to more mechanistically link microbes to large-scale biogeochemical cycles. Lastly, we use the Community Land Model (CLM) to compare Earth System Model predictions of soil C cycling with empirical measurements. Deviations between CLM predictions and field observations of CO2 flux and soil C stocks will provide insight for how the model may be improved through inclusion of additional biotic (e.g., microbial community composition) and abiotic (e.g., organic carbon composition) features, which will be critical to improve the predictive power of climate models in permafrost-affected regions.

  5. Black Carbon Contribution to Organic Carbon Stocks in Urban Soil.

    PubMed

    Edmondson, Jill L; Stott, Iain; Potter, Jonathan; Lopez-Capel, Elisa; Manning, David A C; Gaston, Kevin J; Leake, Jonathan R

    2015-07-21

    Soil holds 75% of the total organic carbon (TOC) stock in terrestrial ecosystems. This comprises ecosystem-derived organic carbon (OC) and black carbon (BC), a recalcitrant product of the incomplete combustion of fossil fuels and biomass. Urban topsoils are often enriched in BC from historical emissions of soot and have high TOC concentrations, but the contribution of BC to TOC throughout the urban soil profile, at a regional scale is unknown. We sampled 55 urban soil profiles across the North East of England, a region with a history of coal burning and heavy industry. Through combined elemental and thermogravimetic analyses, we found very large total soil OC stocks (31-65 kg m(-2) to 1 m), exceeding typical values reported for UK woodland soils. BC contributed 28-39% of the TOC stocks, up to 23 kg C m(-2) to 1 m, and was affected by soil texture. The proportional contribution of the BC-rich fraction to TOC increased with soil depth, and was enriched in topsoil under trees when compared to grassland. Our findings establish the importance of urban ecosystems in storing large amounts of OC in soils and that these soils also capture a large proportion of BC particulates emitted within urban areas.

  6. Optimization of soil mixing technology through metallic iron addition.

    SciTech Connect

    Moos, L. P.

    1999-01-15

    Enhanced soil mixing is a process used to remove volatile organic compounds (VOCs) from soil. In this process, also known as soil mixing with thermally enhanced soil vapor extraction, or SM/TESVE, a soil mixing apparatus breaks up and mixes a column of soil up to 9 m (30 ft) deep; simultaneously, hot air is blown through the soil. The hot air carries the VOCs to the surface where they are collected and safely disposed of. This technology is cost effective at high VOC concentrations, but it becomes cost prohibitive at low concentrations. Argonne National Laboratory-East conducted a project to evaluate ways of improving the effectiveness of this system. The project investigated the feasibility of integrating the SM/TESVE process with three soil treatment processes--soil vapor extraction, augmented indigenous biodegradation, and zero-valent iron addition. Each of these technologies was considered a polishing treatment designed to remove the contaminants left behind by enhanced soil mixing. The experiment was designed to determine if the overall VOC removal effectiveness and cost-effectiveness of the SM/TESVE process could be improved by integrating this approach with one of the polishing treatment systems.

  7. CQESTR Simulations of soil organic carbon dynamics

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A processed-based carbon (C) model, CQESTR (sequester), was used to predict soil organic carbon (SOC) dynamics and examine the effect of agricultural management practices on SOC accretion in three diverse regions of the USA. The three regions chosen had long-term experiments (LTEs) ranging from 23 t...

  8. Microbial properties explain temporal variation in soil respiration in a grassland subjected to nitrogen addition

    PubMed Central

    Li, Yue; Liu, Yinghui; Wu, Shanmei; Niu, Lei; Tian, Yuqiang

    2015-01-01

    The role of soil microbial variables in shaping the temporal variability of soil respiration has been well acknowledged but is poorly understood, particularly under elevated nitrogen (N) deposition conditions. We measured soil respiration along with soil microbial properties during the early, middle, and late growing seasons in temperate grassland plots that had been treated with N additions of 0, 2, 4, 8, 16, or 32 g N m−2 yr−1 for 10 years. Representing the averages over three observation periods, total (Rs) and heterotrophic (Rh) respiration were highest with 4 g N m−2 yr−1, but autotrophic respiration (Ra) was highest with 8 to 16 g N m−2 yr−1. Also, the responses of Rh and Ra were unsynchronized considering the periods separately. N addition had no significant impact on the temperature sensitivity (Q10) for Rs but inhibited the Q10 for Rh. Significant interactions between observation period and N level occurred in soil respiration components, and the temporal variations in soil respiration components were mostly associated with changes in microbial biomass carbon (MBC) and phospholipid fatty acids (PLFAs). Further observation on soil organic carbon and root biomass is needed to reveal the long-term effect of N deposition on soil C sequestration. PMID:26678303

  9. Microbial properties explain temporal variation in soil respiration in a grassland subjected to nitrogen addition.

    PubMed

    Li, Yue; Liu, Yinghui; Wu, Shanmei; Niu, Lei; Tian, Yuqiang

    2015-12-18

    The role of soil microbial variables in shaping the temporal variability of soil respiration has been well acknowledged but is poorly understood, particularly under elevated nitrogen (N) deposition conditions. We measured soil respiration along with soil microbial properties during the early, middle, and late growing seasons in temperate grassland plots that had been treated with N additions of 0, 2, 4, 8, 16, or 32 g N m(-2) yr(-1) for 10 years. Representing the averages over three observation periods, total (Rs) and heterotrophic (Rh) respiration were highest with 4 g N m(-2) yr(-1), but autotrophic respiration (Ra) was highest with 8 to 16 g N m(-2) yr(-1). Also, the responses of Rh and Ra were unsynchronized considering the periods separately. N addition had no significant impact on the temperature sensitivity (Q10) for Rs but inhibited the Q10 for Rh. Significant interactions between observation period and N level occurred in soil respiration components, and the temporal variations in soil respiration components were mostly associated with changes in microbial biomass carbon (MBC) and phospholipid fatty acids (PLFAs). Further observation on soil organic carbon and root biomass is needed to reveal the long-term effect of N deposition on soil C sequestration.

  10. Microbial properties explain temporal variation in soil respiration in a grassland subjected to nitrogen addition

    NASA Astrophysics Data System (ADS)

    Li, Yue; Liu, Yinghui; Wu, Shanmei; Niu, Lei; Tian, Yuqiang

    2015-12-01

    The role of soil microbial variables in shaping the temporal variability of soil respiration has been well acknowledged but is poorly understood, particularly under elevated nitrogen (N) deposition conditions. We measured soil respiration along with soil microbial properties during the early, middle, and late growing seasons in temperate grassland plots that had been treated with N additions of 0, 2, 4, 8, 16, or 32 g N m-2 yr-1 for 10 years. Representing the averages over three observation periods, total (Rs) and heterotrophic (Rh) respiration were highest with 4 g N m-2 yr-1, but autotrophic respiration (Ra) was highest with 8 to 16 g N m-2 yr-1. Also, the responses of Rh and Ra were unsynchronized considering the periods separately. N addition had no significant impact on the temperature sensitivity (Q10) for Rs but inhibited the Q10 for Rh. Significant interactions between observation period and N level occurred in soil respiration components, and the temporal variations in soil respiration components were mostly associated with changes in microbial biomass carbon (MBC) and phospholipid fatty acids (PLFAs). Further observation on soil organic carbon and root biomass is needed to reveal the long-term effect of N deposition on soil C sequestration.

  11. [Response of mineralization of dissolved organic carbon to soil moisture in paddy and upland soils in hilly red soil region].

    PubMed

    Chen, Xiang-Bi; Wang, Ai-Hua; Hu, Le-Ning; Huang, Yuan; Li, Yang; He, Xun-Yang; Su, Yi-Rong

    2014-03-01

    Typical paddy and upland soils were collected from a hilly subtropical red-soil region. 14C-labeled dissolved organic carbon (14C-DOC) was extracted from the paddy and upland soils incorporated with 14C-labeled straw after a 30-day (d) incubation period under simulated field conditions. A 100-d incubation experiment (25 degrees C) with the addition of 14C-DOC to paddy and upland soils was conducted to monitor the dynamics of 14C-DOC mineralization under different soil moisture conditions [45%, 60%, 75%, 90%, and 105% of the field water holding capacity (WHC)]. The results showed that after 100 days, 28.7%-61.4% of the labeled DOC in the two types of soils was mineralized to CO2. The mineralization rates of DOC in the paddy soils were significantly higher than in the upland soils under all soil moisture conditions, owing to the less complex composition of DOC in the paddy soils. The aerobic condition was beneficial for DOC mineralization in both soils, and the anaerobic condition was beneficial for DOC accumulation. The biodegradability and the proportion of the labile fraction of the added DOC increased with the increase of soil moisture (45% -90% WHC). Within 100 days, the labile DOC fraction accounted for 80.5%-91.1% (paddy soil) and 66.3%-72.4% (upland soil) of the cumulative mineralization of DOC, implying that the biodegradation rate of DOC was controlled by the percentage of labile DOC fraction.

  12. [Effects of gaps on distribution of soil aggregates and organic carbon in Pinus massoniana plantation].

    PubMed

    Song, Xiao-Yan; Zhang, Dan-Ju; Zhang, Jian; Li, Jian-Ping; Deng, Chang-Chun; Deng, Chao

    2014-11-01

    The effects of forest gap size on the distribution of soil aggregates, organic carbon and labile organic carbon were investigated in a 39-year-old Pinus massoniana plantation in Yibin, Sichuan Province. The results showed that the composition of soil aggregates was dominated by particles > 2 mm, which accounted for 51.7%-78.7% of the whole soil samples under different sized forest gaps and beneath P. massoniana plantation. Soil organic carbon content and labile organic carbon content in > 5 mm aggregates were significantly positively correlated with the soil organic carbon and labile organic carbon contents. Furthermore, the amounts of organic carbon and labile organic carbon storage > 5 mm particles were higher than those in other size particles. Therefore, particles > 5 mm of aggregates dominated the soil carbon pool. Compared with those P. massoniana plantations, the contents of organic carbon in aggregates and total topsoil decreased during the formation of forest gaps, whereas the soil organic carbon storage under 1225 m2 gap was higher. In addition, the soil labile organic carbon content under 225 and 400 m2 gaps and the labile organic carbon storage under 225, 400, 900 and 1225 m2 gaps were higher than those the plantations, but were lower than under the other gaps. It was suggested that an appropriate size of forest gap would increase the accumulation of soil organic carbon and labile organic carbon content. The size of forest gap had significant effects on the distribution of soil aggregates, organic carbon and labile organic carbon. The soil sample under 1225 m2 gap had the highest organic carbon content and storage and a better aggregate proportion, and the higher labile organic carbon storage. Therefore, it was suggested that 1225 m2 gap might be an optimal logging gap size.

  13. Carbon additives for electrical double layer capacitor electrodes

    NASA Astrophysics Data System (ADS)

    Weingarth, D.; Cericola, D.; Mornaghini, F. C. F.; Hucke, T.; Kötz, R.

    2014-11-01

    Electrochemical double layer capacitors (EDLCs) are inherently high power devices when compared to rechargeable batteries. While capacitance and energy storage ability are mainly increased by optimizing the electrode active material or the electrolyte, the power capability could be improved by including conductive additives in the electrode formulations. This publication deals with the use of four different carbon additives - two carbon blacks and two graphites - in standard activated carbon based EDLC electrodes. The investigations include: (i) physical characterization of carbon powder mixtures such as surface area, press density, and electrical resistivity measurements, and (ii), electrochemical characterization via impedance spectroscopy and cyclic voltammetry of full cells made with electrodes containing 5 wt.% of carbon additive and compared to cells made with pure activated carbon electrodes in organic electrolyte. Improved cell performance was observed in both impedance and cyclic voltammetry responses. The results are discussed considering the main characteristics of the different carbon additives, and important considerations about electrode structure and processability are drawn.

  14. Climate-change effects on soils: Accelerated weathering, soil carbon and elemental cycling

    SciTech Connect

    Qafoku, Nikolla

    2015-04-01

    Climate change [i.e., high atmospheric carbon dioxide (CO2) concentrations (≥400 ppm); increasing air temperatures (2-4°C or greater); significant and/or abrupt changes in daily, seasonal, and inter-annual temperature; changes in the wet/dry cycles; intensive rainfall and/or heavy storms; extended periods of drought; extreme frost; heat waves and increased fire frequency] is and will significantly affect soil properties and fertility, water resources, food quantity and quality, and environmental quality. Biotic processes that consume atmospheric CO2, and create organic carbon (C) that is either reprocessed to CO2 or stored in soils are the subject of active current investigations, with great concern over the influence of climate change. In addition, abiotic C cycling and its influence on the inorganic C pool in soils is a fundamental global process in which acidic atmospheric CO2 participates in the weathering of carbonate and silicate minerals, ultimately delivering bicarbonate and Ca2+ or other cations that precipitate in the form of carbonates in soils or are transported to the rivers, lakes, and oceans. Soil responses to climate change will be complex, and there are many uncertainties and unresolved issues. The objective of the review is to initiate and further stimulate a discussion about some important and challenging aspects of climate-change effects on soils, such as accelerated weathering of soil minerals and resulting C and elemental fluxes in and out of soils, soil/geo-engineering methods used to increase C sequestration in soils, soil organic matter (SOM) protection, transformation and mineralization, and SOM temperature sensitivity. This review reports recent discoveries, identifies key research needs, and highlights opportunities offered by the climate-change effects on soils.

  15. Shrub Expansion Effects on Soil Carbon Dynamics in the Arctic

    NASA Astrophysics Data System (ADS)

    Holden, S. R.; Mortero, G.; Welker, J. M.; Czimczik, C. I.

    2015-12-01

    Shrubs are increasing in abundance in the Arctic in response to climate warming, but the consequences of shrub expansion for the vast soil carbon (C) stocks in the Arctic are poorly understood. Increases in productivity and associated increases in soil C inputs may augment soil C stocks. Alternatively, labile C exudates from shrub roots may stimulate decomposition of existing soil C and decrease C stocks. We used two complementary approaches to characterize the potential impacts of shrub expansion on soil C dynamics in the Arctic. First, in graminoid and shrub tundra near Toolik Lake, AK we surveyed thaw depth, measured depth profiles of %C, %N, δ13C, and Δ14C, and inventoried soil C stocks to 1 m. We found that the thaw depth was 42% shallower under shrubs compared to graminoid tundra. In addition, mineral soils from shrub tundra had a significantly higher C content than graminoid tundra. Similarly, mineral soils from shrub tundra had lower (depleted) δ13C values compared to graminoid tundra, indicating that this soil has undergone less microbial processing. We also found that C under shrub tundra was on average older, and shrub tundra had significantly higher C stocks to 1 m than graminoid tundra. Second, we conducted a priming experiment with graminoid soil from Toolik Lake, AK. We incubated organic soil, the top 10 cm of mineral soil, and the lower 10 cm of active layer mineral soil with supplemental sucrose at 7°C and 22°C. We found that the addition of labile C did not increase microbial decomposition of existing C in mineral soils. Taken together, our findings suggest that shrub expansion may augment soil C storage in the Arctic because a greater proportion of soil C is frozen in permafrost, soil C under shrubs turns over more slowly, and existing C in mineral soil does not appear to be vulnerable to loss via priming. The observed impacts of shrub expansion on soil C stocks should be incorporated into earth system models that predict the carbon

  16. ESTABLISHING A SOIL CARBON BASELINE FOR CARBON ACCOUNTING THE FORESTED SOILS OF THE UNITED STATES

    EPA Science Inventory

    Soils are an important global reservoir of organic carbon (C). It has been estimated that at 1500 Pg world soils hold approximately three times the amount of C held in vegetation and two times that in the atmosphere. Soils provide a relatively stable reservoir for C. With the int...

  17. Switchgrass cultivars differentially affect soil carbon stabilization

    NASA Astrophysics Data System (ADS)

    Adkins, J.; Jastrow, J. D.; Wullschleger, S. D.; De Graaff, M.

    2012-12-01

    Soil organic carbon (SOC) storage depends on the amount and quality of plant-derived carbon (C) inputs to soil, which is largely regulated by plant roots via the processes of root turnover and exudation. While we know that plant roots mediate SOC stabilization, we do not fully understand which root characteristics specifically promote soil C storage. With this study we asked whether roots with coarse root systems versus roots with finely branched root systems differentially affect soil C stabilization. In order to answer this question, we collected soil cores (4.8 cm diameter, to a depth of 30 cm) from directly over the crown of six switchgrass (Panicum virgatum L.) cultivars that differed in root architecture. Specifically, three cultivars had fibrous root systems (i.e. high specific root length) and three had coarse root systems (i.e. low specific root length). The cultivars (C4 species) were grown in a C3 grassland for four years, allowing us to use isotopic fractionation techniques to assess differences in soil C input and stabilization. The cores were divided into depth increments of 10 cm and the soils were sieved (2mm). Soil from each depth increment was dispersed by shaking for 16 hours in a NaHMP solution to isolate coarse particulate organic matter (C-POM), fine particulate organic matter (F-POM), silt, and clay-sized fractions. Samples of soil fractions across all depths were analyzed for C and N contents as well as δ13C signature. We found that the relative abundance of the different soil fractions and associated δ13C signatures differed significantly among cultivars. These results indicate that switchgrass cultivars can differentially impact soil carbon inputs and stabilization. We hypothesize that these differences may be driven by variability in root architectures.

  18. Nitrogen Addition Altered the Effect of Belowground C Allocation on Soil Respiration in a Subtropical Forest

    PubMed Central

    He, Tongxin; Wang, Qingkui; Wang, Silong; Zhang, Fangyue

    2016-01-01

    The availabilities of carbon (C) and nitrogen (N) in soil play an important role in soil carbon dioxide (CO2) emission. However, the variation in the soil respiration (Rs) and response of microbial community to the combined changes in belowground C and N inputs in forest ecosystems are not yet fully understood. Stem girdling and N addition were performed in this study to evaluate the effects of C supply and N availability on Rs and soil microbial community in a subtropical forest. The trees were girdled on 1 July 2012. Rs was monitored from July 2012 to November 2013, and soil microbial community composition was also examined by phospholipid fatty acids (PLFAs) 1 year after girdling. Results showed that Rs decreased by 40.5% with girdling alone, but N addition only did not change Rs. Interestingly, Rs decreased by 62.7% under the girdling with N addition treatment. The reducing effect of girdling and N addition on Rs differed between dormant and growing seasons. Girdling alone reduced Rs by 33.9% in the dormant season and 54.8% in the growing season compared with the control. By contrast, girdling with N addition decreased Rs by 59.5% in the dormant season and 65.4% in the growing season. Girdling and N addition significantly decreased the total and bacterial PLFAs. Moreover, the effect of N addition was greater than girdling. Both girdling and N addition treatments separated the microbial groups on the basis of the first principal component through principal component analysis compared with control. This indicated that girdling and N addition changed the soil microbial community composition. However, the effect of girdling with N addition treatment separated the microbial groups on the basis of the second principal component compared to N addition treatment, which suggested N addition altered the effect of girdling on soil microbial community composition. These results suggest that the increase in soil N availability by N deposition alters the effect of

  19. Interactions among roots, mycorrhizas and free-living microbial communities differentially impact soil carbon processes

    DOE PAGES

    Moore, Jessica A. M.; Jiang, Jiang; Patterson, Courtney M.; Mayes, Melanie A.; Wang, Gangsheng; Classen, Aimée T.

    2015-10-20

    Plant roots, their associated microbial community and free-living soil microbes interact to regulate the movement of carbon from the soil to the atmosphere, one of the most important and least understood fluxes of terrestrial carbon. Our inadequate understanding of how plant-microbial interactions alter soil carbon decomposition may lead to poor model predictions of terrestrial carbon feedbacks to the atmosphere. Roots, mycorrhizal fungi and free-living soil microbes can alter soil carbon decomposition through exudation of carbon into soil. Exudates of simple carbon compounds can increase microbial activity because microbes are typically carbon limited. When both roots and mycorrhizal fungi are presentmore » in the soil, they may additively increase carbon decomposition. However, when mycorrhizas are isolated from roots, they may limit soil carbon decomposition by competing with free-living decomposers for resources. We manipulated the access of roots and mycorrhizal fungi to soil insitu in a temperate mixed deciduous forest. We added 13C-labelled substrate to trace metabolized carbon in respiration and measured carbon-degrading microbial extracellular enzyme activity and soil carbon pools. We used our data in a mechanistic soil carbon decomposition model to simulate and compare the effects of root and mycorrhizal fungal presence on soil carbon dynamics over longer time periods. Contrary to what we predicted, root and mycorrhizal biomass did not interact to additively increase microbial activity and soil carbon degradation. The metabolism of 13C-labelled starch was highest when root biomass was high and mycorrhizal biomass was low. These results suggest that mycorrhizas may negatively interact with the free-living microbial community to influence soil carbon dynamics, a hypothesis supported by our enzyme results. Our steady-state model simulations suggested that root presence increased mineral-associated and particulate organic carbon pools, while mycorrhizal

  20. Interactions among roots, mycorrhizas and free-living microbial communities differentially impact soil carbon processes

    SciTech Connect

    Moore, Jessica A. M.; Jiang, Jiang; Patterson, Courtney M.; Mayes, Melanie A.; Wang, Gangsheng; Classen, Aimée T.

    2015-10-20

    Plant roots, their associated microbial community and free-living soil microbes interact to regulate the movement of carbon from the soil to the atmosphere, one of the most important and least understood fluxes of terrestrial carbon. Our inadequate understanding of how plant-microbial interactions alter soil carbon decomposition may lead to poor model predictions of terrestrial carbon feedbacks to the atmosphere. Roots, mycorrhizal fungi and free-living soil microbes can alter soil carbon decomposition through exudation of carbon into soil. Exudates of simple carbon compounds can increase microbial activity because microbes are typically carbon limited. When both roots and mycorrhizal fungi are present in the soil, they may additively increase carbon decomposition. However, when mycorrhizas are isolated from roots, they may limit soil carbon decomposition by competing with free-living decomposers for resources. We manipulated the access of roots and mycorrhizal fungi to soil insitu in a temperate mixed deciduous forest. We added 13C-labelled substrate to trace metabolized carbon in respiration and measured carbon-degrading microbial extracellular enzyme activity and soil carbon pools. We used our data in a mechanistic soil carbon decomposition model to simulate and compare the effects of root and mycorrhizal fungal presence on soil carbon dynamics over longer time periods. Contrary to what we predicted, root and mycorrhizal biomass did not interact to additively increase microbial activity and soil carbon degradation. The metabolism of 13C-labelled starch was highest when root biomass was high and mycorrhizal biomass was low. These results suggest that mycorrhizas may negatively interact with the free-living microbial community to influence soil carbon dynamics, a hypothesis supported by our enzyme results. Our steady-state model simulations suggested that root presence increased mineral-associated and particulate organic carbon pools, while

  1. Intercropping enhances soil carbon and nitrogen.

    PubMed

    Cong, Wen-Feng; Hoffland, Ellis; Li, Long; Six, Johan; Sun, Jian-Hao; Bao, Xing-Guo; Zhang, Fu-Suo; Van Der Werf, Wopke

    2015-04-01

    Intercropping, the simultaneous cultivation of multiple crop species in a single field, increases aboveground productivity due to species complementarity. We hypothesized that intercrops may have greater belowground productivity than sole crops, and sequester more soil carbon over time due to greater input of root litter. Here, we demonstrate a divergence in soil organic carbon (C) and nitrogen (N) content over 7 years in a field experiment that compared rotational strip intercrop systems and ordinary crop rotations. Soil organic C content in the top 20 cm was 4% ± 1% greater in intercrops than in sole crops, indicating a difference in C sequestration rate between intercrop and sole crop systems of 184 ± 86 kg C ha(-1) yr(-1). Soil organic N content in the top 20 cm was 11% ± 1% greater in intercrops than in sole crops, indicating a difference in N sequestration rate between intercrop and sole crop systems of 45 ± 10 kg N ha(-1) yr(-1). Total root biomass in intercrops was on average 23% greater than the average root biomass in sole crops, providing a possible mechanism for the observed divergence in soil C sequestration between sole crop and intercrop systems. A lowering of the soil δ(15) N signature suggested that increased biological N fixation and/or reduced gaseous N losses contributed to the increases in soil N in intercrop rotations with faba bean. Increases in soil N in wheat/maize intercrop pointed to contributions from a broader suite of mechanisms for N retention, e.g., complementary N uptake strategies of the intercropped plant species. Our results indicate that soil C sequestration potential of strip intercropping is similar in magnitude to that of currently recommended management practises to conserve organic matter in soil. Intercropping can contribute to multiple agroecosystem services by increased yield, better soil quality and soil C sequestration.

  2. Intercropping enhances soil carbon and nitrogen.

    PubMed

    Cong, Wen-Feng; Hoffland, Ellis; Li, Long; Six, Johan; Sun, Jian-Hao; Bao, Xing-Guo; Zhang, Fu-Suo; Van Der Werf, Wopke

    2015-04-01

    Intercropping, the simultaneous cultivation of multiple crop species in a single field, increases aboveground productivity due to species complementarity. We hypothesized that intercrops may have greater belowground productivity than sole crops, and sequester more soil carbon over time due to greater input of root litter. Here, we demonstrate a divergence in soil organic carbon (C) and nitrogen (N) content over 7 years in a field experiment that compared rotational strip intercrop systems and ordinary crop rotations. Soil organic C content in the top 20 cm was 4% ± 1% greater in intercrops than in sole crops, indicating a difference in C sequestration rate between intercrop and sole crop systems of 184 ± 86 kg C ha(-1) yr(-1). Soil organic N content in the top 20 cm was 11% ± 1% greater in intercrops than in sole crops, indicating a difference in N sequestration rate between intercrop and sole crop systems of 45 ± 10 kg N ha(-1) yr(-1). Total root biomass in intercrops was on average 23% greater than the average root biomass in sole crops, providing a possible mechanism for the observed divergence in soil C sequestration between sole crop and intercrop systems. A lowering of the soil δ(15) N signature suggested that increased biological N fixation and/or reduced gaseous N losses contributed to the increases in soil N in intercrop rotations with faba bean. Increases in soil N in wheat/maize intercrop pointed to contributions from a broader suite of mechanisms for N retention, e.g., complementary N uptake strategies of the intercropped plant species. Our results indicate that soil C sequestration potential of strip intercropping is similar in magnitude to that of currently recommended management practises to conserve organic matter in soil. Intercropping can contribute to multiple agroecosystem services by increased yield, better soil quality and soil C sequestration. PMID:25216023

  3. Interactive effects of litter quality and soil mineralogy on temperate forest soil carbon response to temperature

    NASA Astrophysics Data System (ADS)

    Rasmussen, C.; Horwath, W.; Southard, R.

    2007-12-01

    Temperate forest soil organic carbon (C) represents a significant pool of terrestrial C that may be released to the atmosphere as CO2 with predicted climate change. To address feedbacks between climate change and terrestrial C turnover, we quantified forest soil C response to litter quality and temperature change as a function of soil parent material. We collected soils from three conifer forest-types dominated by ponderosa pine (PP), white fir (WF), and red fir (RF) from each of three parent materials, granite (GR), basalt (BS), and andesite (AN) in the Sierra Nevada of California. AN soils were dominated by short-range-order (SRO) minerals, GR soils by crystalline minerals, and BS soils by a mix of crystalline and SRO minerals. Field soils were incubated in the laboratory at their mean annual soil temperature (MAST), with addition of native 13C-labeled litter. Further, we incubated WF and RF soils at PP MAST with 13C-labeled PP litter; and RF soils at WF MAST with 13C-labeled WF litter to simulate a migration of MAST and vegetation type up-elevation in response to predicted climate warming. Results indicated that total CO2 and percent of CO2 derived from soil C varied significantly across forest-types, following the pattern of GR>BS>AN. Regression analyses indicated significant control of C mineralization and soil C priming by litter quality and SRO minerals. Addition of litter derived water-soluble compounds enabled priming of recalcitrant soil C in soils with high SRO mineral content, whereas water-soluble litter components did little to promote priming of extant soil C in soils of low SRO mineral content. Results further indicated a 10-300% increase in WF and RF forest-type soil C mineralization under climate change conditions that varied substantially between parent materials. Soils derived from andesite exhibited minimal change; whereas granite and basalt derived soils lost large amounts of soil C under climate change conditions. This study corroborates the

  4. Understanding on Soil Inorganic Carbon Transformation in North China

    NASA Astrophysics Data System (ADS)

    Li, Guitong; Yang, Lifang; Zhang, Chenglei; Zhang, Hongjie

    2015-04-01

    experiment concerning soil carbonate transformation under straw return and biochar addition was carried out. It is designed as a long-term field experiment. In the experiment, Ca2+ and Mg2+ in soil solution of different depth and time, in situ soil pH, soil CO2 concentration, and microbial activity will be measured. The main propose of the experiment is to explore the relationship between the transformation of SOC and SIC. Meanwhile, it is one of important field experiment for biochar effects on crop production, soil processes, and environmental impact. These researches were funded by National Natural Science Foundation of China (NNSFC) under projects of 41171211,40771106, and 40303015.

  5. Metal-contaminated soil remediation by means of paper mill sludges addition: chemical and ecotoxicological evaluation.

    PubMed

    Calace, N; Campisi, T; Iacondini, A; Leoni, M; Petronio, B M; Pietroletti, M

    2005-08-01

    Metal pollution of soils is a great environmental problem. The major risks due to metal pollution of soil consist of leaching to groundwater and potential toxicity to plants and/or animals. The objective of this study is to evaluate by means of chemical and ecotoxicological approach the effects of paper mill sludge addition on the mobile metal fraction of polluted metal soils. The study was carried out on acidic soil derived from mining activities and thus polluted with heavy metals, and on two paper mill sludges having different chemical features. The results obtained by leaching experiments showed that the addition of a paper mill sludge, consisting mainly of carbonates, silicates and organic matter, to a heavy-metal polluted soil produces a decrease of available metal forms. The carbonate content seems to play a key role in the chemical stabilisation of metals and consequently in a decrease of toxicity of soil. The leached solutions have a non-toxic effect. The mild remediation by addition of sludge has moreover a lasting effect.

  6. Urban Tree Effects on Soil Organic Carbon

    PubMed Central

    Edmondson, Jill L.; O'Sullivan, Odhran S.; Inger, Richard; Potter, Jonathan; McHugh, Nicola; Gaston, Kevin J.; Leake, Jonathan R.

    2014-01-01

    Urban trees sequester carbon into biomass and provide many ecosystem service benefits aboveground leading to worldwide tree planting schemes. Since soils hold ∼75% of ecosystem organic carbon, understanding the effect of urban trees on soil organic carbon (SOC) and soil properties that underpin belowground ecosystem services is vital. We use an observational study to investigate effects of three important tree genera and mixed-species woodlands on soil properties (to 1 m depth) compared to adjacent urban grasslands. Aboveground biomass and belowground ecosystem service provision by urban trees are found not to be directly coupled. Indeed, SOC enhancement relative to urban grasslands is genus-specific being highest under Fraxinus excelsior and Acer spp., but similar to grasslands under Quercus robur and mixed woodland. Tree cover type does not influence soil bulk density or C∶N ratio, properties which indicate the ability of soils to provide regulating ecosystem services such as nutrient cycling and flood mitigation. The trends observed in this study suggest that genus selection is important to maximise long-term SOC storage under urban trees, but emerging threats from genus-specific pathogens must also be considered. PMID:25003872

  7. Urban tree effects on soil organic carbon.

    PubMed

    Edmondson, Jill L; O'Sullivan, Odhran S; Inger, Richard; Potter, Jonathan; McHugh, Nicola; Gaston, Kevin J; Leake, Jonathan R

    2014-01-01

    Urban trees sequester carbon into biomass and provide many ecosystem service benefits aboveground leading to worldwide tree planting schemes. Since soils hold ∼75% of ecosystem organic carbon, understanding the effect of urban trees on soil organic carbon (SOC) and soil properties that underpin belowground ecosystem services is vital. We use an observational study to investigate effects of three important tree genera and mixed-species woodlands on soil properties (to 1 m depth) compared to adjacent urban grasslands. Aboveground biomass and belowground ecosystem service provision by urban trees are found not to be directly coupled. Indeed, SOC enhancement relative to urban grasslands is genus-specific being highest under Fraxinus excelsior and Acer spp., but similar to grasslands under Quercus robur and mixed woodland. Tree cover type does not influence soil bulk density or C∶N ratio, properties which indicate the ability of soils to provide regulating ecosystem services such as nutrient cycling and flood mitigation. The trends observed in this study suggest that genus selection is important to maximise long-term SOC storage under urban trees, but emerging threats from genus-specific pathogens must also be considered.

  8. Urban tree effects on soil organic carbon.

    PubMed

    Edmondson, Jill L; O'Sullivan, Odhran S; Inger, Richard; Potter, Jonathan; McHugh, Nicola; Gaston, Kevin J; Leake, Jonathan R

    2014-01-01

    Urban trees sequester carbon into biomass and provide many ecosystem service benefits aboveground leading to worldwide tree planting schemes. Since soils hold ∼75% of ecosystem organic carbon, understanding the effect of urban trees on soil organic carbon (SOC) and soil properties that underpin belowground ecosystem services is vital. We use an observational study to investigate effects of three important tree genera and mixed-species woodlands on soil properties (to 1 m depth) compared to adjacent urban grasslands. Aboveground biomass and belowground ecosystem service provision by urban trees are found not to be directly coupled. Indeed, SOC enhancement relative to urban grasslands is genus-specific being highest under Fraxinus excelsior and Acer spp., but similar to grasslands under Quercus robur and mixed woodland. Tree cover type does not influence soil bulk density or C∶N ratio, properties which indicate the ability of soils to provide regulating ecosystem services such as nutrient cycling and flood mitigation. The trends observed in this study suggest that genus selection is important to maximise long-term SOC storage under urban trees, but emerging threats from genus-specific pathogens must also be considered. PMID:25003872

  9. Soil Carbon Transformation in Heterogeneous Landscapes

    NASA Astrophysics Data System (ADS)

    Riveros-Iregui, D.; Liang, L.; Emanuel, R. E.; McGlynn, B. L.; Dore, J. E.; Kaiser, K.; Seybold, E. C.; Covino, T. P.

    2012-12-01

    Understanding critical belowground carbon processes (e.g., soil carbon turnover, root and microbial dynamics, and greenhouse gas generation and flux) requires examination of coupled physical and biological processes. The spatial patterns of first-order controls such as soil water content, soil temperature, substrate, and vegetation cover has been shown to impose spatial and temporal organization of soil CO2 efflux to the atmosphere. We examined the spatial and temporal variability of soil CO2 ([CO2]) and soil CH4 ([CH4]) concentrations and flux, and the stable isotope composition of CO2 (δ13CCO2) across two watersheds of differing topographic complexity and vegetation cover, including both forested and harvested areas. Samples were collected at 5cm, 20cm, and 50cm at multiple sites (6-10) along seven transects in the Tenderfoot Creek Experimental Forest (TCEF), central Montana. Our results show that [CO2] increases with depth while [CH4] decreases with depth in all dry sites, meaning that dry sites simultaneously act as a source for CO2 and a sink for CH4. Wet sites, however, had pronounced differences in their [CO2] and [CH4] profiles, depending on soil water content and water table depth. Isotopically, deep soil layers had systematically more negative δ13CCO2 values, but the difference between shallow and deep δ13CCO2 values varied as a function of landscape position and vegetation cover. Our results suggest that belowground processes and rates of soil carbon transformation vary across the landscape as a function of environmental gradients.

  10. Sensitivity of Arctic Permafrost Carbon in the Mackenzie River Basin: A substrate addition and incubation experiment

    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

  11. Soil carbon sequestration via cover crops- A meta-analysis

    NASA Astrophysics Data System (ADS)

    Poeplau, Christopher; Don, Axel

    2014-05-01

    Agricultural soils are depleted in soil organic carbon (SOC) and have thus a huge potential to sequester SOC. This can primarily be achieved by increasing carbon inputs into the soil. Replacing winter fallows by cover crop cultivation for green manure has many benefits for the soil and forms an additional carbon input. An increase in carbon concentration has been reported in several studies worldwide. However, the effect on SOC stocks, as well as the influence of environmental parameters and management on SOC dynamics is not known. We therefore conducted a meta-analysis to investigate those issues. A total of 33 studies, comprising 47 sites and 147 plots were compiled. A pedotransfer function was used to estimate bulk densities and calculate SOC stocks. SOC stock change was found to be a linear function of time since introduction, with an annual sequestration rate of 0.32 Mg C ha-1 yr-1. Since no saturation was visible in the observations, we used the model RothC to estimate a new steady state level and the resulting total SOC stock change for an artificial "average cropland". The total average SOC stock change with an annual input of 1.87 Mg C ha-1 yr-1 was 16.76 Mg C ha-1 for the average soil depth of 22 cm. We estimated a potential global SOC sequestration of 0.12±0.03 Pg C yr-1, which would compensate for 8 % of the direct annual greenhouse gas emissions from agriculture.

  12. Advances in spectroscopic methods for quantifying soil carbon

    USGS Publications Warehouse

    Reeves, James B.; McCarty, Gregory W.; Calderon, Francisco; Hively, W. Dean

    2012-01-01

    The current gold standard for soil carbon (C) determination is elemental C analysis using dry combustion. However, this method requires expensive consumables, is limited by the number of samples that can be processed (~100/d), and is restricted to the determination of total carbon. With increased interest in soil C sequestration, faster methods of analysis are needed, and there is growing interest in methods based on diffuse reflectance spectroscopy in the visible, near-infrared or mid-infrared spectral ranges. These spectral methods can decrease analytical requirements and speed sample processing, be applied to large landscape areas using remote sensing imagery, and be used to predict multiple analytes simultaneously. However, the methods require localized calibrations to establish the relationship between spectral data and reference analytical data, and also have additional, specific problems. For example, remote sensing is capable of scanning entire watersheds for soil carbon content but is limited to the surface layer of tilled soils and may require difficult and extensive field sampling to obtain proper localized calibration reference values. The objective of this chapter is to discuss the present state of spectroscopic methods for determination of soil carbon.

  13. Long term yields and soil carbon sequestration from Miscanthus

    NASA Astrophysics Data System (ADS)

    Jones, Michael; Zimmerman, Jesko

    2016-04-01

    Perennial rhizomatous grasses such as Miscanthus have been assumed to give sustainable biomass yields over many years but there have been few productivity trials that have tested this assumption. In addition it has been suggested that soil carbon sequestration increases linearly over time. We review field trials of Miscanthus, established on former grassland and tilled land, that have been harvested annually for up to twenty years and in which changes in soil organic matter content have been measured. Yields of Miscanthus follow an establishment phase, a ceiling phase and then a phase of decline. The lengths of these phases are strongly influenced by climate, soils and management but it is likely that Miscanthus plantations can produce commercially acceptable yield beyond 20 years. Net soil carbon sequestration depends on previous land use and is strongly influenced by the soil carbon stocks at the time of planting. Under Miscanthus a large fraction of the accumulated carbon is labile and would be rapidly lost if Miscanthus plantations were reconverted to cropland. Currently it is not possible to derive a reliable default sequestration rate for land use change from cropland to Miscanthus energy crop.

  14. Immobilization of uranium in contaminated soil by natural apatite addition

    SciTech Connect

    Mrdakovic Popic, Jelena; Stojanovic, Mirjana; Milosevic, Sinisa; Iles, Deana; Zildzovic, Snezana

    2007-07-01

    Available in abstract form only. Full text of publication follows: The goal of this study was to evaluate the effectiveness of Serbian natural mineral apatite as soil additive for reducing the migration of uranium from contaminated sediments. In laboratory study we investigated the sorption properties of domestic apatite upon different experimental conditions, such as pH, adsorbent mass, reaction period, concentration of P{sub 2}O{sub 5} in apatite, solid/liquid ratio. In second part of study, we did the quantification of uranium in soil samples, taken from uranium mine site 'Kalna', by sequential extraction method. The same procedure was, also, used for uranium determination in contaminated soil samples after apatite addition, in order to determine the changes in U distribution in soil fraction. The obtained results showed the significant level of immobilization (96.7%) upon certain conditions. Increase of %P{sub 2}O{sub 5} in apatite and process of mechano-chemical activation led to increase of immobilization capacity from 17.50% till 91.64%. The best results for uranium binding were obtained at pH 5.5 and reaction period 60 days (98.04%) The sequential extraction showed the presence of uranium (48.2%) in potentially available soil fractions, but with the apatite addition uranium content in these fractions decreased (30.64%), what is considering environmental aspect significant fact. In situ immobilization of radionuclide using inexpensive sequestering agents, such as apatite, is very adequate for big contaminated areas of soil with low level of contamination. This investigation study on natural apatite from deposit 'Lisina' Serbia was the first one of this type in our country. Key words: apatite, uranium, immobilization, soil, contamination. (authors)

  15. Impacts of biochar (black carbon) additions on the sorption and efficacy of herbicides

    Technology Transfer Automated Retrieval System (TEKTRAN)

    There is renewed interest in the soil application of charcoal (biochar) as a means of increasing carbon sequestration and combating climate change. The land areas that are targeted for biochar applications are agricultural land, due to the potential positive impacts that charcoal additions have on o...

  16. The Importance of Carbon Fiber to Polymer Additive Manufacturing

    SciTech Connect

    Love, Lonnie J; Kunc, Vlastimil; Rios, Orlando; Duty, Chad E; Post, Brian K; Blue, Craig A

    2014-01-01

    Additive manufacturing holds tremendous promise in terms of revolutionizing manufacturing. However, fundamental hurdles limit mass adoption of the technology. First, production rates are extremely low. Second, the physical size of parts is generally small, less than a cubic foot. Third, while there is much excitement about metal additive manufacturing, the major growth area is in polymer additive manufacturing systems. Unfortunately, the mechanical properties of the polymer parts are poor, limiting the potential for direct part replacement. To address this issue, we describe three benefits of blending carbon fiber with polymer additive manufacturing. First, development of carbon fiber reinforced polymers for additive manufacturing achieves specific strengths approaching aerospace quality aluminum. Second, carbon fiber radically changes the behavior of the material during deposition, enabling large scale, out-of-the-oven, high deposition rate manufacturing. Finally, carbon fiber technology and additive manufacturing complement each other. Merging the two manufacturing processes enables the construction of complex components that would not be possible otherwise.

  17. 46 CFR 151.50-40 - Additional requirements for carbon disulfide (carbon bisulfide) and ethyl ether.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 46 Shipping 5 2013-10-01 2013-10-01 false Additional requirements for carbon disulfide (carbon... Special Requirements § 151.50-40 Additional requirements for carbon disulfide (carbon bisulfide) and ethyl... waterways at the loading and unloading points. (f) The special requirements of § 151.50-41 for...

  18. 46 CFR 151.50-40 - Additional requirements for carbon disulfide (carbon bisulfide) and ethyl ether.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 46 Shipping 5 2012-10-01 2012-10-01 false Additional requirements for carbon disulfide (carbon... Special Requirements § 151.50-40 Additional requirements for carbon disulfide (carbon bisulfide) and ethyl... waterways at the loading and unloading points. (f) The special requirements of § 151.50-41 for...

  19. 46 CFR 151.50-40 - Additional requirements for carbon disulfide (carbon bisulfide) and ethyl ether.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 46 Shipping 5 2014-10-01 2014-10-01 false Additional requirements for carbon disulfide (carbon... Special Requirements § 151.50-40 Additional requirements for carbon disulfide (carbon bisulfide) and ethyl... waterways at the loading and unloading points. (f) The special requirements of § 151.50-41 for...

  20. 46 CFR 151.50-40 - Additional requirements for carbon disulfide (carbon bisulfide) and ethyl ether.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 46 Shipping 5 2010-10-01 2010-10-01 false Additional requirements for carbon disulfide (carbon... Special Requirements § 151.50-40 Additional requirements for carbon disulfide (carbon bisulfide) and ethyl... waterways at the loading and unloading points. (f) The special requirements of § 151.50-41 for...

  1. 46 CFR 151.50-40 - Additional requirements for carbon disulfide (carbon bisulfide) and ethyl ether.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 46 Shipping 5 2011-10-01 2011-10-01 false Additional requirements for carbon disulfide (carbon... Special Requirements § 151.50-40 Additional requirements for carbon disulfide (carbon bisulfide) and ethyl... waterways at the loading and unloading points. (f) The special requirements of § 151.50-41 for...

  2. Storing Carbon in Agricultural Soils to Help Head-Off Global Warming and to Combat Desertification

    SciTech Connect

    Rosenberg, Norman J.; Izaurralde, Roberto C.

    2001-12-31

    We know for sure that addition of organic matter to soil increases water-holding capacity, imparts fertility with the addition of nutrients, increases soil aggregation and improves tilth. Depeing on it's type, organic matter contains between 40 and 60% carbon. Using agricultural management practices to increase the amount of organic matter and carbon in soils can be an effective strategy to offset carbon dioxide emissions to the atmosphere as well as to improve the quality of the soil and slow or prevent desertification.

  3. Soil Organic Carbon dynamics in agricultural soils of Veneto Region

    NASA Astrophysics Data System (ADS)

    Bampa, F. B.; Morari, F. M.; Hiederer, R. H.; Toth, G. T.; Giandon, P. G.; Vinci, I. V.; Montanarella, L. M.; Nocita, M.

    2012-04-01

    One of the eight soil threats expressed in the European Commission's Thematic Strategy for Soil Protection (COM (2006)231 final) it's the decline in Soil Organic Matter (SOM). His preservation is recognized as with the objective to ensure that the soils of Europe remain healthy and capable of supporting human activities and ecosystems. One of the key goals of the strategy is to maintain and improve Soil Organic Carbon (SOC) levels. As climate change is identified as a common element in many of the soil threats, the European Commission (EC) intends to assess the actual contribution of the soil protection to climate change mitigation and the effects of climate change on the possible depletion of SOM. A substantial proportion of European land is occupied by agriculture, and consequently plays a crucial role in maintaining natural resources. Organic carbon preservation and sequestration in the EU's agricultural soils could have some potential to mitigate the effects of climate change, particularly linked to preventing certain land use changes and maintaining SOC stocks. The objective of this study is to assess the SOC dynamics in agricultural soils (cropland and grassland) at regional scale, focusing on changes due to land use. A sub-objective would be the evaluation of the most used land management practices and their effect on SOC content. This assessment aims to determine the geographical distribution of the potential GHG mitigation options, focusing on hot spots in the EU, where mitigation actions would be particularly efficient and is linked with the on-going work in the JRC SOIL Action. The pilot area is Veneto Region. The data available are coming from different sources, timing and involve different variables as: soil texture, climate, soil disturbance, managements and nutrients. The first source of data is the LUCAS project (Land Use/Land Cover Area Frame statistical Survey). Started in 2001, the LUCAS project aims to monitor changes in land cover/use and

  4. Soil Carbon Cycling - More than Changes in Soil Organic Carbon Stocks

    NASA Astrophysics Data System (ADS)

    Lorenz, K.

    2015-12-01

    Discussions about soil carbon (C) sequestration generally focus on changes in soil organic carbon (SOC) stocks. Global SOC mass in the top 1 m was estimated at about 1325 Pg C, and at about 3000 Pg C when deeper soil layers were included. However, both inorganically and organically bound carbon forms are found in soil but estimates on global soil inorganic carbon (SIC) mass are even more uncertain than those for SOC. Globally, about 947 Pg SIC may be stored in the top 1 m, and especially in arid and semi-arid regions SIC stocks can be many times great than SOC stocks. Both SIC and SOC stocks are vulnerable to management practices, and stocks may be enhanced, for example, by optimizing net primary production (NPP) by fertilization and irrigation (especially optimizing belowground NPP for enhancing SOC stocks), adding organic matter (including black C for enhancing SOC stocks), and reducing soil disturbance. Thus, studies on soil C stocks, fluxes, and vulnerability must look at both SIC and SOC stocks in soil profiles to address large scale soil C cycling.

  5. Carbon stabilization mechanisms in soils in the Andes

    NASA Astrophysics Data System (ADS)

    Jansen, Boris; Cammeraat, Erik

    2015-04-01

    The volcanic ash soils of the Andes contain very large stocks of soil organic matter (SOM) per unit area. Consequently, they constitute significant potential sources or sinks of the greenhouse gas CO2. Climate and/or land use change potentially have a strong effect on these large SOM stocks. To clarify the role of chemical and physical stabilisation mechanisms in volcanic ash soils in the montane tropics, we investigated carbon stocks and stabilization mechanisms in the top- and subsoil along an altitudinal transect in the Ecuadorian Andes. The transect encompassed a sequence of paleosols under forest and grassland (páramo), including a site where vegetation cover changed in the last century. We applied selective extraction techniques, performed X-ray diffraction analyses of the clay fraction and estimated pore size distributions at various depths in the top- and subsoil along the transect. In addition, from several soils the molecular composition of SOM was further characterized with depth in the current soil as well as the entire first and the top of the second paleosol using GC/MS analyses of extractable lipids and Pyrolysis-GC/MS analyses of bulk organic matter. Our results show that organic carbon stocks in the mineral soil under forest a páramo vegetation were roughly twice as large as global averages for volcanic ash soils, regardless of whether the first 30cm, 100cm or 200cm were considered. We found the carbon stabilization mechanisms involved to be: i) direct stabilization of SOM in organo-metallic (Al-OM) complexes; ii) indirect protection of SOM through low soil pH and toxic levels of Al; and iii) physical protection of SOM due to a very high microporosity of the soil (Tonneijck et al., 2010; Jansen et al. 2011). When examining the organic carbon at a molecular level, interestingly we found extensive degradation of lignin in the topsoil while extractable lipids were preferentially preserved in the subsoil (Nierop and Jansen, 2009). Both vegetation

  6. Nitrogen addition regulates soil nematode community composition through ammonium suppression.

    PubMed

    Wei, Cunzheng; Zheng, Huifen; Li, Qi; Lü, Xiaotao; Yu, Qiang; Zhang, Haiyang; Chen, Quansheng; He, Nianpeng; Kardol, Paul; Liang, Wenju; Han, Xingguo

    2012-01-01

    Nitrogen (N) enrichment resulting from anthropogenic activities has greatly changed the composition and functioning of soil communities. Nematodes are one of the most abundant and diverse groups of soil organisms, and they occupy key trophic positions in the soil detritus food web. Nematodes have therefore been proposed as useful indicators for shifts in soil ecosystem functioning under N enrichment. Here, we monitored temporal dynamics of the soil nematode community using a multi-level N addition experiment in an Inner Mongolia grassland. Measurements were made three years after the start of the experiment. We used structural equation modeling (SEM) to explore the mechanisms regulating nematode responses to N enrichment. Across the N enrichment gradient, significant reductions in total nematode abundance, diversity (H' and taxonomic richness), maturity index (MI), and the abundance of root herbivores, fungivores and omnivores-predators were found in August. Root herbivores recovered in September, contributing to the temporal variation of total nematode abundance across the N gradient. Bacterivores showed a hump-shaped relationship with N addition rate, both in August and September. Ammonium concentration was negatively correlated with the abundance of total and herbivorous nematodes in August, but not in September. Ammonium suppression explained 61% of the variation in nematode richness and 43% of the variation in nematode trophic group composition. Ammonium toxicity may occur when herbivorous nematodes feed on root fluid, providing a possible explanation for the negative relationship between herbivorous nematodes and ammonium concentration in August. We found a significantly positive relationship between fungivores and fungal phospholipid fatty acids (PLFA), suggesting bottom-up control of fungivores. No such relationship was found between bacterivorous nematodes and bacterial PLFA. Our findings contribute to the understanding of effects of N enrichment in

  7. 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

  8. Fertilization increases paddy soil organic carbon density*

    PubMed Central

    Wang, Shao-xian; Liang, Xin-qiang; Luo, Qi-xiang; Fan, Fang; Chen, Ying-xu; Li, Zu-zhang; Sun, Huo-xi; Dai, Tian-fang; Wan, Jun-nan; Li, Xiao-jun

    2012-01-01

    Field experiments provide an opportunity to study the effects of fertilization on soil organic carbon (SOC) sequestration. We sampled soils from a long-term (25 years) paddy experiment in subtropical China. The experiment included eight treatments: (1) check, (2) PK, (3) NP, (4) NK, (5) NPK, (6) 7F:3M (N, P, K inorganic fertilizers+30% organic N), (7) 5F:5M (N, P, K inorganic fertilizers+50% organic N), (8) 3F:7M (N, P, K inorganic fertilizers+70% organic N). Fertilization increased SOC content in the plow layers compared to the non-fertilized check treatment. The SOC density in the top 100 cm of soil ranged from 73.12 to 91.36 Mg/ha. The SOC densities of all fertilizer treatments were greater than that of the check. Those treatments that combined inorganic fertilizers and organic amendments had greater SOC densities than those receiving only inorganic fertilizers. The SOC density was closely correlated to the sum of the soil carbon converted from organic amendments and rice residues. Carbon sequestration in paddy soils could be achieved by balanced and combined fertilization. Fertilization combining both inorganic fertilizers and organic amendments is an effective sustainable practice to sequestrate SOC. PMID:22467369

  9. Fertilization increases paddy soil organic carbon density.

    PubMed

    Wang, Shao-xian; Liang, Xin-qiang; Luo, Qi-xiang; Fan, Fang; Chen, Ying-xu; Li, Zu-zhang; Sun, Huo-xi; Dai, Tian-fang; Wan, Jun-nan; Li, Xiao-jun

    2012-04-01

    Field experiments provide an opportunity to study the effects of fertilization on soil organic carbon (SOC) sequestration. We sampled soils from a long-term (25 years) paddy experiment in subtropical China. The experiment included eight treatments: (1) check, (2) PK, (3) NP, (4) NK, (5) NPK, (6) 7F:3M (N, P, K inorganic fertilizers+30% organic N), (7) 5F:5M (N, P, K inorganic fertilizers+50% organic N), (8) 3F:7M (N, P, K inorganic fertilizers+70% organic N). Fertilization increased SOC content in the plow layers compared to the non-fertilized check treatment. The SOC density in the top 100 cm of soil ranged from 73.12 to 91.36 Mg/ha. The SOC densities of all fertilizer treatments were greater than that of the check. Those treatments that combined inorganic fertilizers and organic amendments had greater SOC densities than those receiving only inorganic fertilizers. The SOC density was closely correlated to the sum of the soil carbon converted from organic amendments and rice residues. Carbon sequestration in paddy soils could be achieved by balanced and combined fertilization. Fertilization combining both inorganic fertilizers and organic amendments is an effective sustainable practice to sequestrate SOC.

  10. 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.

  11. Long-term rice cultivation stabilizes soil organic carbon and promotes soil microbial activity in a salt marsh derived soil chronosequence

    PubMed Central

    Wang, Ping; Liu, Yalong; Li, Lianqing; Cheng, Kun; Zheng, Jufeng; Zhang, Xuhui; Zheng, Jinwei; Joseph, Stephen; Pan, Genxing

    2015-01-01

    Soil organic carbon (SOC) sequestration with enhanced stable carbon storage has been widely accepted as a very important ecosystem property. Yet, the link between carbon stability and bio-activity for ecosystem functioning with OC accumulation in field soils has not been characterized. We assessed the changes in microbial activity versus carbon stability along a paddy soil chronosequence shifting from salt marsh in East China. We used mean weight diameter, normalized enzyme activity (NEA) and carbon gain from straw amendment for addressing soil aggregation, microbial biochemical activity and potential C sequestration, respectively. In addition, a response ratio was employed to infer the changes in all analyzed parameters with prolonged rice cultivation. While stable carbon pools varied with total SOC accumulation, soil respiration and both bacterial and fungal diversity were relatively constant in the rice soils. Bacterial abundance and NEA were positively but highly correlated to total SOC accumulation, indicating an enhanced bio-activity with carbon stabilization. This could be linked to an enhancement of particulate organic carbon pool due to physical protection with enhanced soil aggregation in the rice soils under long-term rice cultivation. However, the mechanism underpinning these changes should be explored in future studies in rice soils where dynamic redox conditions exist. PMID:26503629

  12. Long-term rice cultivation stabilizes soil organic carbon and promotes soil microbial activity in a salt marsh derived soil chronosequence.

    PubMed

    Wang, Ping; Liu, Yalong; Li, Lianqing; Cheng, Kun; Zheng, Jufeng; Zhang, Xuhui; Zheng, Jinwei; Joseph, Stephen; Pan, Genxing

    2015-10-27

    Soil organic carbon (SOC) sequestration with enhanced stable carbon storage has been widely accepted as a very important ecosystem property. Yet, the link between carbon stability and bio-activity for ecosystem functioning with OC accumulation in field soils has not been characterized. We assessed the changes in microbial activity versus carbon stability along a paddy soil chronosequence shifting from salt marsh in East China. We used mean weight diameter, normalized enzyme activity (NEA) and carbon gain from straw amendment for addressing soil aggregation, microbial biochemical activity and potential C sequestration, respectively. In addition, a response ratio was employed to infer the changes in all analyzed parameters with prolonged rice cultivation. While stable carbon pools varied with total SOC accumulation, soil respiration and both bacterial and fungal diversity were relatively constant in the rice soils. Bacterial abundance and NEA were positively but highly correlated to total SOC accumulation, indicating an enhanced bio-activity with carbon stabilization. This could be linked to an enhancement of particulate organic carbon pool due to physical protection with enhanced soil aggregation in the rice soils under long-term rice cultivation. However, the mechanism underpinning these changes should be explored in future studies in rice soils where dynamic redox conditions exist.

  13. Long-term rice cultivation stabilizes soil organic carbon and promotes soil microbial activity in a salt marsh derived soil chronosequence.

    PubMed

    Wang, Ping; Liu, Yalong; Li, Lianqing; Cheng, Kun; Zheng, Jufeng; Zhang, Xuhui; Zheng, Jinwei; Joseph, Stephen; Pan, Genxing

    2015-01-01

    Soil organic carbon (SOC) sequestration with enhanced stable carbon storage has been widely accepted as a very important ecosystem property. Yet, the link between carbon stability and bio-activity for ecosystem functioning with OC accumulation in field soils has not been characterized. We assessed the changes in microbial activity versus carbon stability along a paddy soil chronosequence shifting from salt marsh in East China. We used mean weight diameter, normalized enzyme activity (NEA) and carbon gain from straw amendment for addressing soil aggregation, microbial biochemical activity and potential C sequestration, respectively. In addition, a response ratio was employed to infer the changes in all analyzed parameters with prolonged rice cultivation. While stable carbon pools varied with total SOC accumulation, soil respiration and both bacterial and fungal diversity were relatively constant in the rice soils. Bacterial abundance and NEA were positively but highly correlated to total SOC accumulation, indicating an enhanced bio-activity with carbon stabilization. This could be linked to an enhancement of particulate organic carbon pool due to physical protection with enhanced soil aggregation in the rice soils under long-term rice cultivation. However, the mechanism underpinning these changes should be explored in future studies in rice soils where dynamic redox conditions exist. PMID:26503629

  14. Long-term rice cultivation stabilizes soil organic carbon and promotes soil microbial activity in a salt marsh derived soil chronosequence

    NASA Astrophysics Data System (ADS)

    Wang, Ping; Liu, Yalong; Li, Lianqing; Cheng, Kun; Zheng, Jufeng; Zhang, Xuhui; Zheng, Jinwei; Joseph, Stephen; Pan, Genxing

    2015-10-01

    Soil organic carbon (SOC) sequestration with enhanced stable carbon storage has been widely accepted as a very important ecosystem property. Yet, the link between carbon stability and bio-activity for ecosystem functioning with OC accumulation in field soils has not been characterized. We assessed the changes in microbial activity versus carbon stability along a paddy soil chronosequence shifting from salt marsh in East China. We used mean weight diameter, normalized enzyme activity (NEA) and carbon gain from straw amendment for addressing soil aggregation, microbial biochemical activity and potential C sequestration, respectively. In addition, a response ratio was employed to infer the changes in all analyzed parameters with prolonged rice cultivation. While stable carbon pools varied with total SOC accumulation, soil respiration and both bacterial and fungal diversity were relatively constant in the rice soils. Bacterial abundance and NEA were positively but highly correlated to total SOC accumulation, indicating an enhanced bio-activity with carbon stabilization. This could be linked to an enhancement of particulate organic carbon pool due to physical protection with enhanced soil aggregation in the rice soils under long-term rice cultivation. However, the mechanism underpinning these changes should be explored in future studies in rice soils where dynamic redox conditions exist.

  15. Short-Term Responses of Soil Respiration and C-Cycle Enzyme Activities to Additions of Biochar and Urea in a Calcareous Soil.

    PubMed

    Song, Dali; Xi, Xiangyin; Huang, Shaomin; Liang, Guoqing; Sun, Jingwen; Zhou, Wei; Wang, Xiubin

    2016-01-01

    Biochar (BC) addition to soil is a proposed strategy to enhance soil fertility and crop productivity. However, there is limited knowledge regarding responses of soil respiration and C-cycle enzyme activities to BC and nitrogen (N) additions in a calcareous soil. A 56-day incubation experiment was conducted to investigate the combined effects of BC addition rates (0, 0.5, 1.0, 2.5 and 5.0% by mass) and urea (U) application on soil nutrients, soil respiration and C-cycle enzyme activities in a calcareous soil in the North China Plain. Our results showed soil pH values in both U-only and U plus BC treatments significantly decreased within the first 14 days and then stabilized, and CO2emission rate in all U plus BC soils decreased exponentially, while there was no significant difference in the contents of soil total organic carbon (TOC), dissolved organic carbon (DOC), total nitrogen (TN), and C/N ratio in each treatment over time. At each incubation time, soil pH, electrical conductivity (EC), TOC, TN, C/N ratio, DOC and cumulative CO2 emission significantly increased with increasing BC addition rate, while soil potential activities of the four hydrolytic enzymes increased first and then decreased with increasing BC addition rate, with the largest values in the U + 1.0%BC treatment. However, phenol oxidase activity in all U plus BC soils showed a decreasing trend with the increase of BC addition rate. Our results suggest that U plus BC application at a rate of 1% promotes increases in hydrolytic enzymes, does not highly increase C/N and C mineralization, and can improve in soil fertility. PMID:27589265

  16. Short-Term Responses of Soil Respiration and C-Cycle Enzyme Activities to Additions of Biochar and Urea in a Calcareous Soil

    PubMed Central

    Song, Dali; Xi, Xiangyin; Huang, Shaomin; Liang, Guoqing; Sun, Jingwen; Zhou, Wei; Wang, Xiubin

    2016-01-01

    Biochar (BC) addition to soil is a proposed strategy to enhance soil fertility and crop productivity. However, there is limited knowledge regarding responses of soil respiration and C-cycle enzyme activities to BC and nitrogen (N) additions in a calcareous soil. A 56-day incubation experiment was conducted to investigate the combined effects of BC addition rates (0, 0.5, 1.0, 2.5 and 5.0% by mass) and urea (U) application on soil nutrients, soil respiration and C-cycle enzyme activities in a calcareous soil in the North China Plain. Our results showed soil pH values in both U-only and U plus BC treatments significantly decreased within the first 14 days and then stabilized, and CO2emission rate in all U plus BC soils decreased exponentially, while there was no significant difference in the contents of soil total organic carbon (TOC), dissolved organic carbon (DOC), total nitrogen (TN), and C/N ratio in each treatment over time. At each incubation time, soil pH, electrical conductivity (EC), TOC, TN, C/N ratio, DOC and cumulative CO2 emission significantly increased with increasing BC addition rate, while soil potential activities of the four hydrolytic enzymes increased first and then decreased with increasing BC addition rate, with the largest values in the U + 1.0%BC treatment. However, phenol oxidase activity in all U plus BC soils showed a decreasing trend with the increase of BC addition rate. Our results suggest that U plus BC application at a rate of 1% promotes increases in hydrolytic enzymes, does not highly increase C/N and C mineralization, and can improve in soil fertility. PMID:27589265

  17. Short-Term Responses of Soil Respiration and C-Cycle Enzyme Activities to Additions of Biochar and Urea in a Calcareous Soil.

    PubMed

    Song, Dali; Xi, Xiangyin; Huang, Shaomin; Liang, Guoqing; Sun, Jingwen; Zhou, Wei; Wang, Xiubin

    2016-01-01

    Biochar (BC) addition to soil is a proposed strategy to enhance soil fertility and crop productivity. However, there is limited knowledge regarding responses of soil respiration and C-cycle enzyme activities to BC and nitrogen (N) additions in a calcareous soil. A 56-day incubation experiment was conducted to investigate the combined effects of BC addition rates (0, 0.5, 1.0, 2.5 and 5.0% by mass) and urea (U) application on soil nutrients, soil respiration and C-cycle enzyme activities in a calcareous soil in the North China Plain. Our results showed soil pH values in both U-only and U plus BC treatments significantly decreased within the first 14 days and then stabilized, and CO2emission rate in all U plus BC soils decreased exponentially, while there was no significant difference in the contents of soil total organic carbon (TOC), dissolved organic carbon (DOC), total nitrogen (TN), and C/N ratio in each treatment over time. At each incubation time, soil pH, electrical conductivity (EC), TOC, TN, C/N ratio, DOC and cumulative CO2 emission significantly increased with increasing BC addition rate, while soil potential activities of the four hydrolytic enzymes increased first and then decreased with increasing BC addition rate, with the largest values in the U + 1.0%BC treatment. However, phenol oxidase activity in all U plus BC soils showed a decreasing trend with the increase of BC addition rate. Our results suggest that U plus BC application at a rate of 1% promotes increases in hydrolytic enzymes, does not highly increase C/N and C mineralization, and can improve in soil fertility.

  18. In-situ soil carbon analysis using inelastic neutron scattering

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In situ soil carbon analysis using inelastic neutron scattering (INS) is based on the emission of 4.43 MeV gamma rays from carbon nuclei excited by fast neutrons. This in-situ method has excellent potential for easily measuring soil carbon since it does not require soil core sampling and processing ...

  19. Mitigation of Climatic Change by Soil Carbon Sequestration: Issues of Science, Monitoring, and Degraded Lands

    SciTech Connect

    Izaurralde, R Cesar C.; Rosenberg, Norman J.; Lal, Rattan

    2001-12-31

    Farmers, gardeners, and, of course, argonomists know that adding organic matter to soils is a good thing to do. Organic matter increases soil water-holding capacity, imparts fertility with the addition of nutrients, increases soil aggregation, and improves tilth. Depending on its type-humus, manure, stubble, litter-organic matter contains between 40 and 60% carbon.

  20. Mitigation of Climatic Change by Soil Carbon Sequestration: Issues of Science, Monitoring, and Degraded Lands

    SciTech Connect

    Izaurralde, R Cesar C.; Rosenberg, Norman J.; Lal, Rattan

    2001-11-01

    Farmers, gardeners, and, of course, argonomists know that adding organic matter to soils is a good thing to do. Organic matter increases soil water-holding capacity, imparts fertility with the addition of nutrients, increases soil aggregation, and improves tilth. Depending on its type-humus, manure, stubble, litter-organic matter contains between 40 and 60% carbon.

  1. Assessing the soil microbial carbon budget: Probing with salt stress

    NASA Astrophysics Data System (ADS)

    Rath, Kristin; Rousk, Johannes

    2014-05-01

    measures are more sensitive to salinity than catabolic processes. This could be an indication that at higher salt concentrations, the microbial community allocates less carbon towards growth, resulting in reduced carbon use efficiency. We also found that microbial processes show different sensitivities depending on the kind of salt used in the experiment. Currently we are making comparative analyses to determine whether osmotic strength or specific ion concentrations best explain toxicity. In addition we are in the process of investigating if pre-exposed communities from naturally saline soils have developed a higher tolerance to salt.

  2. Effects of water addition on soil arthropods and soil characteristics in a precipitation-limited environment

    NASA Astrophysics Data System (ADS)

    Chikoski, Jennifer M.; Ferguson, Steven H.; Meyer, Lense

    2006-09-01

    We investigated the effect of water addition and season on soil arthropod abundance and soil characteristics (%C, %N, C:N, moisture, pH). The experimental design consisted of 24 groups of five boxes distributed within a small aspen stand in Saskatchewan, Canada. The boxes depressed the soil to create a habitat with suitable microclimate for soil arthropods, and by overturning boxes we counted soil arthropods during weekly surveys from April to September 1999. Soil samples were collected at two-month intervals and water was added once per week to half of the plots. Of the eleven recognizable taxonomic units identified, only mites (Acari) and springtails (Collembola) responded to water addition by increasing abundance, whereas ants decreased in abundance with water addition. During summer, springtail numbers increased with water addition, whereas pH was a stronger determinant of mite abundance. In autumn, springtails were positively correlated with water and negatively correlated with mites, whereas mite abundance was negatively correlated with increasing C:N ratio, positively correlated to water addition, and negatively correlated with springtail abundance. Although both mite and springtail numbers decreased in autumn with a decrease in soil moisture, mites became more abundant than springtails suggesting a predator-prey (mite-springtail) relationship. Water had a significant effect on both springtails and mites in summer and autumn supporting the assertion that prairie soil communities are water limited.

  3. Soil management and carbon calculation methods influence changes in soil carbon estimation

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Throughout the years, many studies have evaluated changes in soil organic carbon (SOC) mass on a fixed-depth (FD) basis without considering changes in soil mass caused by changing in bulk density. In two study sites, we investigated the effect of different management practices on SOC changes calcul...

  4. How do changes in bulk soil organic carbon content affect carbon concentrations in individual soil particle fractions?

    NASA Astrophysics Data System (ADS)

    Yang, X. M.; Drury, C. F.; Reynolds, W. D.; Yang, J. Y.

    2016-06-01

    We test the common assumption that organic carbon (OC) storage occurs on sand-sized soil particles only after the OC storage capacity on silt- and clay-sized particles is saturated. Soil samples from a Brookston clay loam in Southwestern Ontario were analysed for the OC concentrations in bulk soil, and on the clay (<2 μm), silt (2-53 μm) and sand (53-2000 μm) particle size fractions. The OC concentrations in bulk soil ranged from 4.7 to 70.8 g C kg-1 soil. The OC concentrations on all three particle size fractions were significantly related to the OC concentration of bulk soil. However, OC concentration increased slowly toward an apparent maximum on silt and clay, but this maximum was far greater than the maximum predicted by established C sequestration models. In addition, significant increases in OC associated with sand occurred when the bulk soil OC concentration exceeded 30 g C kg-1, but this increase occurred when the OC concentration on silt + clay was still far below the predicted storage capacity for silt and clay fractions. Since the OC concentrations in all fractions of Brookston clay loam soil continued to increase with increasing C (bulk soil OC content) input, we concluded that the concept of OC storage capacity requires further investigation.

  5. How do changes in bulk soil organic carbon content affect carbon concentrations in individual soil particle fractions?

    PubMed

    Yang, X M; Drury, C F; Reynolds, W D; Yang, J Y

    2016-01-01

    We test the common assumption that organic carbon (OC) storage occurs on sand-sized soil particles only after the OC storage capacity on silt- and clay-sized particles is saturated. Soil samples from a Brookston clay loam in Southwestern Ontario were analysed for the OC concentrations in bulk soil, and on the clay (<2 μm), silt (2-53 μm) and sand (53-2000 μm) particle size fractions. The OC concentrations in bulk soil ranged from 4.7 to 70.8 g C kg(-1) soil. The OC concentrations on all three particle size fractions were significantly related to the OC concentration of bulk soil. However, OC concentration increased slowly toward an apparent maximum on silt and clay, but this maximum was far greater than the maximum predicted by established C sequestration models. In addition, significant increases in OC associated with sand occurred when the bulk soil OC concentration exceeded 30 g C kg(-1), but this increase occurred when the OC concentration on silt + clay was still far below the predicted storage capacity for silt and clay fractions. Since the OC concentrations in all fractions of Brookston clay loam soil continued to increase with increasing C (bulk soil OC content) input, we concluded that the concept of OC storage capacity requires further investigation.

  6. How do changes in bulk soil organic carbon content affect carbon concentrations in individual soil particle fractions?

    PubMed Central

    Yang, X. M.; Drury, C. F.; Reynolds, W. D.; Yang, J. Y.

    2016-01-01

    We test the common assumption that organic carbon (OC) storage occurs on sand-sized soil particles only after the OC storage capacity on silt- and clay-sized particles is saturated. Soil samples from a Brookston clay loam in Southwestern Ontario were analysed for the OC concentrations in bulk soil, and on the clay (<2 μm), silt (2–53 μm) and sand (53–2000 μm) particle size fractions. The OC concentrations in bulk soil ranged from 4.7 to 70.8 g C kg−1 soil. The OC concentrations on all three particle size fractions were significantly related to the OC concentration of bulk soil. However, OC concentration increased slowly toward an apparent maximum on silt and clay, but this maximum was far greater than the maximum predicted by established C sequestration models. In addition, significant increases in OC associated with sand occurred when the bulk soil OC concentration exceeded 30 g C kg−1, but this increase occurred when the OC concentration on silt + clay was still far below the predicted storage capacity for silt and clay fractions. Since the OC concentrations in all fractions of Brookston clay loam soil continued to increase with increasing C (bulk soil OC content) input, we concluded that the concept of OC storage capacity requires further investigation. PMID:27251365

  7. How do changes in bulk soil organic carbon content affect carbon concentrations in individual soil particle fractions?

    PubMed

    Yang, X M; Drury, C F; Reynolds, W D; Yang, J Y

    2016-01-01

    We test the common assumption that organic carbon (OC) storage occurs on sand-sized soil particles only after the OC storage capacity on silt- and clay-sized particles is saturated. Soil samples from a Brookston clay loam in Southwestern Ontario were analysed for the OC concentrations in bulk soil, and on the clay (<2 μm), silt (2-53 μm) and sand (53-2000 μm) particle size fractions. The OC concentrations in bulk soil ranged from 4.7 to 70.8 g C kg(-1) soil. The OC concentrations on all three particle size fractions were significantly related to the OC concentration of bulk soil. However, OC concentration increased slowly toward an apparent maximum on silt and clay, but this maximum was far greater than the maximum predicted by established C sequestration models. In addition, significant increases in OC associated with sand occurred when the bulk soil OC concentration exceeded 30 g C kg(-1), but this increase occurred when the OC concentration on silt + clay was still far below the predicted storage capacity for silt and clay fractions. Since the OC concentrations in all fractions of Brookston clay loam soil continued to increase with increasing C (bulk soil OC content) input, we concluded that the concept of OC storage capacity requires further investigation. PMID:27251365

  8. Evaluation of Different Soil Carbon Determination Methods

    SciTech Connect

    Chatterjee, Dr Amitava; Lal, Dr R; Wielopolski, Dr L; Martin, Madhavi Z; Ebinger, Dr Michael H

    2009-01-01

    Determining soil carbon (C) with high precision is an essential requisite for the success of the terrestrial C sequestration program. The informed choice of management practices for different terrestrial ecosystems rests upon accurately measuring the potential for C sequestration. Numerous methods are available for assessing soil C. Chemical analysis of field-collected samples using a dry combustion method is regarded as the standard method. However, conventional sampling of soil and their subsequent chemical analysis is expensive and time consuming. Furthermore, these methods are not sufficiently sensitive to identify small changes over time in response to alterations inmanagement practices or changes in land use. Presently, several different in situ analytic methods are being developed purportedly offering increased accuracy, precision and cost-effectiveness over traditional ex situ methods. We consider that, at this stage, a comparative discussion of different soil C determination methods will improve the understanding needed to develop a standard protocol.

  9. Austrian Carbon Calculator (ACC) - modelling soil carbon dynamics in Austrian soils

    NASA Astrophysics Data System (ADS)

    Sedy, Katrin; Freudenschuss, Alexandra; Zethner, Gehard; Spiegel, Heide; Franko, Uwe; Gründling, Ralf; Xaver Hölzl, Franz; Preinstorfer, Claudia; Haslmayr, Hans Peter; Formayer, Herbert

    2014-05-01

    Austrian Carbon Calculator (ACC) - modelling soil carbon dynamics in Austrian soils. The project funded by the Klima- und Energiefonds, Austrian Climate Research Programme, 4th call Authors: Katrin Sedy, Alexandra Freudenschuss, Gerhard Zethner (Environment Agency Austria), Heide Spiegel (Austrian Agency for Health and Food Safety), Uwe Franko, Ralf Gründling (Helmholtz Centre for Environmental Research) Climate change will affect plant productivity due to weather extremes. However, adverse effects could be diminished and satisfying production levels may be maintained with proper soil conditions. To sustain and optimize the potential of agricultural land for plant productivity it will be necessary to focus on preserving and increasing soil organic carbon (SOC). Carbon sequestration in agricultural soils is strongly influenced by management practice. The present management is affected by management practices that tend to speed up carbon loss. Crop rotation, soil cultivation and the management of crop residues are very important measures to influence carbon dynamics and soil fertility. For the future it will be crucial to focus on practical measures to optimize SOC and to improve soil structure. To predict SOC turnover the existing humus balance model the application of the "Carbon Candy Balance" was verified by results from Austrian long term field experiments and field data of selected farms. Thus the main aim of the project is to generate a carbon balancing tool box that can be applied in different agricultural production regions to assess humus dynamics due to agricultural management practices. The toolbox will allow the selection of specific regional input parameters for calculating the C-balance at field level. However farmers or other interested user can also apply their own field data to receive the result of C-dynamics under certain management practises within the next 100 years. At regional level the impact of predefined changes in agricultural management

  10. Effects of biochar addition to soil on nitrogen fluxes in a winter wheat lysimeter experiment

    NASA Astrophysics Data System (ADS)

    Hüppi, Roman; Leifeld, Jens; Neftel, Albrecht; Conen, Franz; Six, Johan

    2014-05-01

    Biochar is a carbon-rich, porous residue from pyrolysis of biomass that potentially increases crop yields by reducing losses of nitrogen from soils and/or enhancing the uptake of applied fertiliser by the crops. Previous research is scarce about biochar's ability to increase wheat yields in temperate soils or how it changes nitrogen dynamics in the field. In a lysimeter system with two different soils (sandy/silt loam) nitrogen fluxes were traced by isotopic 15N enriched fertiliser to identify changes in nitrous oxide emissions, leaching and plant uptake after biochar addition. 20t/ha woodchip-waste biochar (pH=13) was applied to these soils in four lysimeters per soil type; the same number of lysimeters served as a control. The soils were cropped with winter wheat during the season 2012/2013. 170 kg-N/ha ammonium nitrate fertiliser with 10% 15N was applied in 3 events during the growing season and 15N concentrations where measured at different points in time in plant, soil, leachate and emitted nitrous oxide. After one year the lysimeter system showed no difference between biochar and control treatment in grain- and straw yield or nitrogen uptake. However biochar did reduce nitrous oxide emissions in the silt loam and losses of nitrate leaching in sandy loam. This study indicates potential reduction of nitrogen loss from cropland soil by biochar application but could not confirm increased yields in an intensive wheat production system.

  11. Distribution of calcium carbonate in desert soils: A model

    SciTech Connect

    Mayer, L.; McFadden, L.D.; Harden, J.W.

    1988-04-01

    A model that describes the distribution of calcium carbonate in desert soils as a function of dust flux, time, climate, and other soil-forming factors shows which factors most strongly influence the accumulation of carbonate and can be used to evaluate carbonate-based soil age estimates or paleoclimatic reconstructions. Models for late Holocene soils have produced carbonate distributions that are very similar to those of well-dated soils in New Mexico and southern California. These results suggest that (1) present climate is a fair representation of late Holocene climate, (2) carbonate dust flux can be approximated by its Holocene rate, and (3) changes in climate and/or dust flux at the end of the Pleistocene effected profound and complex changes in soil carbonate distributions. Both higher carbonate dust flux and greater effective precipitation are required during the latest Pleistocene-early Holocene to explain carbonate distributions in latest Pleistocene soils. 21 refs., 4 figs., 1 tab.

  12. Recent advances in modeling depth distribution of soil carbon storage

    NASA Astrophysics Data System (ADS)

    Mishra, U.; Shu, S.

    2015-12-01

    Depth distribution of soil carbon storage determines the sensitivity of soil carbon to environmental change. We present different approaches that have been used to represent the vertical heterogeneity of soil carbon both in mapping and modeling studies. In digital soil mapping, many studies applied exponential decay functions in soils where carbon concentration has been observed to decline with depth. Recent studies used various forms of spline functions to better represent the vertical distribution of soil carbon along with soil horizons. These studies fitted mathematical functions that described the observations and then interpolated the model coefficients using soil-forming factors and used maps of model coefficients with depth to predict the SOC storage at desired depth intervals. In general, the prediction accuracy decreased with depth and the challenge remains to find appropriate soil-forming factors that determine/explain subsurface soil variation. Models such as Century, RothC, and Terrestrial Ecosystem Model use the exponential depth distribution functions of soil carbon in their model structures. In CLM 4.5 the soil profile is partitioned into 10 layers down to 3.8 m depth and the carbon input from plant roots is assumed to decrease following an exponential function. Not accounting for soil horizons in representing biogeochemistry and the assumption of globally uniform soil depth remain major sources of uncertainty in these models. In this presentation, we will discuss the merits and demerits of using various profile depth distribution functions to represent the vertical heterogeneity of soil carbon storage.

  13. Microbial Diversity Indexes Can Explain Soil Carbon Dynamics as a Function of Carbon Source

    PubMed Central

    Maron, Pierre-Alain; Menasseri-Aubry, Safya; Sarr, Amadou; Lévêque, Jean; Mathieu, Olivier; Jolivet, Claudy; Leterme, Philippe; Viaud, Valérie

    2016-01-01

    Mathematical models do not explicitly represent the influence of soil microbial diversity on soil organic carbon (SOC) dynamics despite recent evidence of relationships between them. The objective of the present study was to statistically investigate relationships between bacterial and fungal diversity indexes (richness, evenness, Shannon index, inverse Simpson index) and decomposition of different pools of soil organic carbon by measuring dynamics of CO2 emissions under controlled conditions. To this end, 20 soils from two different land uses (cropland and grassland) were incubated with or without incorporation of 13C-labelled wheat-straw residue. 13C-labelling allowed us to study residue mineralisation, basal respiration and the priming effect independently. An innovative data-mining approach was applied, based on generalized additive models and a predictive criterion. Results showed that microbial diversity indexes can be good covariates to integrate in SOC dynamics models, depending on the C source and the processes considered (native soil organic carbon vs. fresh wheat residue). Specifically, microbial diversity indexes were good candidates to help explain mineralisation of native soil organic carbon, while priming effect processes seemed to be explained much more by microbial composition, and no microbial diversity indexes were found associated with residue mineralisation. Investigation of relationships between diversity and mineralisation showed that higher diversity, as measured by the microbial diversity indexes, seemed to be related to decreased CO2 emissions in the control soil. We suggest that this relationship can be explained by an increase in carbon yield assimilation as microbial diversity increases. Thus, the parameter for carbon yield assimilation in mathematical models could be calculated as a function of microbial diversity indexes. Nonetheless, given limitations of the methods used, these observations should be considered with caution and

  14. Microbial Diversity Indexes Can Explain Soil Carbon Dynamics as a Function of Carbon Source.

    PubMed

    Louis, Benjamin P; Maron, Pierre-Alain; Menasseri-Aubry, Safya; Sarr, Amadou; Lévêque, Jean; Mathieu, Olivier; Jolivet, Claudy; Leterme, Philippe; Viaud, Valérie

    2016-01-01

    Mathematical models do not explicitly represent the influence of soil microbial diversity on soil organic carbon (SOC) dynamics despite recent evidence of relationships between them. The objective of the present study was to statistically investigate relationships between bacterial and fungal diversity indexes (richness, evenness, Shannon index, inverse Simpson index) and decomposition of different pools of soil organic carbon by measuring dynamics of CO2 emissions under controlled conditions. To this end, 20 soils from two different land uses (cropland and grassland) were incubated with or without incorporation of 13C-labelled wheat-straw residue. 13C-labelling allowed us to study residue mineralisation, basal respiration and the priming effect independently. An innovative data-mining approach was applied, based on generalized additive models and a predictive criterion. Results showed that microbial diversity indexes can be good covariates to integrate in SOC dynamics models, depending on the C source and the processes considered (native soil organic carbon vs. fresh wheat residue). Specifically, microbial diversity indexes were good candidates to help explain mineralisation of native soil organic carbon, while priming effect processes seemed to be explained much more by microbial composition, and no microbial diversity indexes were found associated with residue mineralisation. Investigation of relationships between diversity and mineralisation showed that higher diversity, as measured by the microbial diversity indexes, seemed to be related to decreased CO2 emissions in the control soil. We suggest that this relationship can be explained by an increase in carbon yield assimilation as microbial diversity increases. Thus, the parameter for carbon yield assimilation in mathematical models could be calculated as a function of microbial diversity indexes. Nonetheless, given limitations of the methods used, these observations should be considered with caution and

  15. Microbial Diversity Indexes Can Explain Soil Carbon Dynamics as a Function of Carbon Source.

    PubMed

    Louis, Benjamin P; Maron, Pierre-Alain; Menasseri-Aubry, Safya; Sarr, Amadou; Lévêque, Jean; Mathieu, Olivier; Jolivet, Claudy; Leterme, Philippe; Viaud, Valérie

    2016-01-01

    Mathematical models do not explicitly represent the influence of soil microbial diversity on soil organic carbon (SOC) dynamics despite recent evidence of relationships between them. The objective of the present study was to statistically investigate relationships between bacterial and fungal diversity indexes (richness, evenness, Shannon index, inverse Simpson index) and decomposition of different pools of soil organic carbon by measuring dynamics of CO2 emissions under controlled conditions. To this end, 20 soils from two different land uses (cropland and grassland) were incubated with or without incorporation of 13C-labelled wheat-straw residue. 13C-labelling allowed us to study residue mineralisation, basal respiration and the priming effect independently. An innovative data-mining approach was applied, based on generalized additive models and a predictive criterion. Results showed that microbial diversity indexes can be good covariates to integrate in SOC dynamics models, depending on the C source and the processes considered (native soil organic carbon vs. fresh wheat residue). Specifically, microbial diversity indexes were good candidates to help explain mineralisation of native soil organic carbon, while priming effect processes seemed to be explained much more by microbial composition, and no microbial diversity indexes were found associated with residue mineralisation. Investigation of relationships between diversity and mineralisation showed that higher diversity, as measured by the microbial diversity indexes, seemed to be related to decreased CO2 emissions in the control soil. We suggest that this relationship can be explained by an increase in carbon yield assimilation as microbial diversity increases. Thus, the parameter for carbon yield assimilation in mathematical models could be calculated as a function of microbial diversity indexes. Nonetheless, given limitations of the methods used, these observations should be considered with caution and

  16. Changes in microbial community characteristics and soil organic matter with nitrogen additions in two tropical forests

    SciTech Connect

    Cusack, Daniela F.; Silver, Whendee; Torn, Margaret S.; Burton, Sarah D.; Firestone, Mary

    2011-03-01

    Microbial communities and their associated enzyme activities affect the amount and chemical quality of carbon (C) in soils. Increasing nitrogen (N) deposition, particularly in N-rich tropical forests, is likely to change the composition and behavior of microbial communities and feed back on ecosystem structure and function. This study presents a novel assessment of mechanistic links between microbial responses to N deposition and shifts in soil organic matter (SOM) quality and quantity. We used phospholipid fatty acid (PLFA) analysis and microbial enzyme assays in soils to assess microbial community responses to long-term N additions in two distinct tropical rain forests. We used soil density fractionation and 13C nuclear magnetic resonance (NMR) spectroscopy to measure related changes in SOM pool sizes and chemical quality. Microbial biomass increased in response to N fertilization in both tropical forests and corresponded to declines in pools of low-density SOM. The chemical quality of this soil C pool reflected ecosystem-specific changes in microbial community composition. In the lower-elevation forest, there was an increase in gram-negative bacteria PLFA biomass, and there were significant losses of labile C chemical groups (O-alkyls). In contrast, the upper-elevation tropical forest had an increase in fungal PLFAs with N additions and declines in C groups associated with increased soil C storage (alkyls). The dynamics of microbial enzymatic activities with N addition provided a functional link between changes in microbial community structure and SOM chemistry. Ecosystem-specific changes in microbial community composition are likely to have far-reaching effects on soil carbon storage and cycling. This study indicates that microbial communities in N-rich tropical forests can be sensitive to added N, but we can expect significant variability in how ecosystem structure and function respond to N deposition among tropical forest types.

  17. Changes in microbial community characteristics and soil organic matter with nitrogen additions in two tropical forests.

    PubMed

    Cusack, Daniela F; Silver, Whendee L; Torn, Margaret S; Burton, Sarah D; Firestone, Mary K

    2011-03-01

    Microbial communities and their associated enzyme activities affect the amount and chemical quality of carbon (C) in soils. Increasing nitrogen (N) deposition, particularly in N-rich tropical forests, is likely to change the composition and behavior of microbial communities and feed back on ecosystem structure and function. This study presents a novel assessment of mechanistic links between microbial responses to N deposition and shifts in soil organic matter (SOM) quality and quantity. We used phospholipid fatty acid (PLFA) analysis and microbial enzyme assays in soils to assess microbial community responses to long-term N additions in two distinct tropical rain forests. We used soil density fractionation and 13C nuclear magnetic resonance (NMR) spectroscopy to measure related changes in SOM pool sizes and chemical quality. Microbial biomass increased in response to N fertilization in both tropical forests and corresponded to declines in pools of low-density SOM. The chemical quality of this soil C pool reflected ecosystem-specific changes in microbial community composition. In the lower-elevation forest, there was an increase in gram-negative bacteria PLFA biomass, and there were significant losses of labile C chemical groups (O-alkyls). In contrast, the upper-elevation tropical forest had an increase in fungal PLFAs with N additions and declines in C groups associated with increased soil C storage (alkyls). The dynamics of microbial enzymatic activities with N addition provided a functional link between changes in microbial community structure and SOM chemistry. Ecosystem-specific changes in microbial community composition are likely to have far-reaching effects on soil carbon storage and cycling. This study indicates that microbial communities in N-rich tropical forests can be sensitive to added N, but we can expect significant variability in how ecosystem structure and function respond to N deposition among tropical forest types.

  18. Changes in microbial community characteristics and soil organic matter with nitrogen additions in two tropical forests.

    PubMed

    Cusack, Daniela F; Silver, Whendee L; Torn, Margaret S; Burton, Sarah D; Firestone, Mary K

    2011-03-01

    Microbial communities and their associated enzyme activities affect the amount and chemical quality of carbon (C) in soils. Increasing nitrogen (N) deposition, particularly in N-rich tropical forests, is likely to change the composition and behavior of microbial communities and feed back on ecosystem structure and function. This study presents a novel assessment of mechanistic links between microbial responses to N deposition and shifts in soil organic matter (SOM) quality and quantity. We used phospholipid fatty acid (PLFA) analysis and microbial enzyme assays in soils to assess microbial community responses to long-term N additions in two distinct tropical rain forests. We used soil density fractionation and 13C nuclear magnetic resonance (NMR) spectroscopy to measure related changes in SOM pool sizes and chemical quality. Microbial biomass increased in response to N fertilization in both tropical forests and corresponded to declines in pools of low-density SOM. The chemical quality of this soil C pool reflected ecosystem-specific changes in microbial community composition. In the lower-elevation forest, there was an increase in gram-negative bacteria PLFA biomass, and there were significant losses of labile C chemical groups (O-alkyls). In contrast, the upper-elevation tropical forest had an increase in fungal PLFAs with N additions and declines in C groups associated with increased soil C storage (alkyls). The dynamics of microbial enzymatic activities with N addition provided a functional link between changes in microbial community structure and SOM chemistry. Ecosystem-specific changes in microbial community composition are likely to have far-reaching effects on soil carbon storage and cycling. This study indicates that microbial communities in N-rich tropical forests can be sensitive to added N, but we can expect significant variability in how ecosystem structure and function respond to N deposition among tropical forest types. PMID:21608471

  19. Soil microbial responses to nitrogen addition in arid ecosystems

    SciTech Connect

    Sinsabaugh, Robert L.; Belnap, Jayne; Rudgers, Jennifer; Kuske, Cheryl R.; Martinez, Noelle; Sandquist, Darren

    2015-08-14

    The N cycle of arid ecosystems is influenced by low soil organic matter, high soil pH, and extremes in water potential and temperature that lead to open canopies and development of biological soil crusts (biocrusts). We investigated the effects of N amendment on soil microbial dynamics in a Larrea tridentata-Ambrosia dumosa shrubland site in southern Nevada USA. Sites were fertilized with a NO3-NH4 mix at 0, 7, and 15 kg N ha-1 y-1 from March 2012 to March 2013. In March 2013, biocrust (0–0.5 cm) and bulk soils (0–10 cm) were collected beneath Ambrosia canopies and in the interspaces between plants. Biomass responses were assessed as bacterial and fungal SSU rRNA gene copy number and chlorophyll a concentration. Metabolic responses were measured by five ecoenzyme activities and rates of N transformation. With most measures, nutrient availability, microbial biomass, and process rates were greater in soils beneath the shrub canopy compared to the interspace between plants, and greater in the surface biocrust horizon compared to the deeper 10 cm soil profile. Most measures responded positively to experimental N addition. Effect sizes were generally greater for bulk soil than biocrust. Results were incorporated into a meta-analysis of arid ecosystem responses to N amendment that included data from 14 other studies. Effect sizes were calculated for biomass and metabolic responses. Regressions of effect sizes, calculated for biomass, and metabolic responses, showed similar trends in relation to N application rate and N load (rate × duration). The critical points separating positive from negative treatment effects were 88 kg ha-1 y-1 and 159 kg ha-1, respectively, for biomass, and 70 kg ha-1 y-1 and 114 kg ha-1, respectively, for metabolism. These critical values are comparable to those for microbial biomass, decomposition rates and respiration

  20. Soil microbial responses to nitrogen addition in arid ecosystems

    DOE PAGES

    Sinsabaugh, Robert L.; Belnap, Jayne; Rudgers, Jennifer; Kuske, Cheryl R.; Martinez, Noelle; Sandquist, Darren

    2015-08-14

    The N cycle of arid ecosystems is influenced by low soil organic matter, high soil pH, and extremes in water potential and temperature that lead to open canopies and development of biological soil crusts (biocrusts). We investigated the effects of N amendment on soil microbial dynamics in a Larrea tridentata-Ambrosia dumosa shrubland site in southern Nevada USA. Sites were fertilized with a NO3-NH4 mix at 0, 7, and 15 kg N ha-1 y-1 from March 2012 to March 2013. In March 2013, biocrust (0–0.5 cm) and bulk soils (0–10 cm) were collected beneath Ambrosia canopies and in the interspaces betweenmore » plants. Biomass responses were assessed as bacterial and fungal SSU rRNA gene copy number and chlorophyll a concentration. Metabolic responses were measured by five ecoenzyme activities and rates of N transformation. With most measures, nutrient availability, microbial biomass, and process rates were greater in soils beneath the shrub canopy compared to the interspace between plants, and greater in the surface biocrust horizon compared to the deeper 10 cm soil profile. Most measures responded positively to experimental N addition. Effect sizes were generally greater for bulk soil than biocrust. Results were incorporated into a meta-analysis of arid ecosystem responses to N amendment that included data from 14 other studies. Effect sizes were calculated for biomass and metabolic responses. Regressions of effect sizes, calculated for biomass, and metabolic responses, showed similar trends in relation to N application rate and N load (rate × duration). The critical points separating positive from negative treatment effects were 88 kg ha-1 y-1 and 159 kg ha-1, respectively, for biomass, and 70 kg ha-1 y-1 and 114 kg ha-1, respectively, for metabolism. These critical values are comparable to those for microbial biomass, decomposition rates and respiration reported in broader meta-analyses of N amendment effects in mesic ecosystems. The large effect sizes at low N

  1. Soil microbial responses to nitrogen addition in arid ecosystems.

    PubMed

    Sinsabaugh, Robert L; Belnap, Jayne; Rudgers, Jennifer; Kuske, Cheryl R; Martinez, Noelle; Sandquist, Darren

    2015-01-01

    The N cycle of arid ecosystems is influenced by low soil organic matter, high soil pH, and extremes in water potential and temperature that lead to open canopies and development of biological soil crusts (biocrusts). We investigated the effects of N amendment on soil microbial dynamics in a Larrea tridentata-Ambrosia dumosa shrubland site in southern Nevada USA. Sites were fertilized with a NO3-NH4 mix at 0, 7, and 15 kg N ha(-1) y(-1) from March 2012 to March 2013. In March 2013, biocrust (0-0.5 cm) and bulk soils (0-10 cm) were collected beneath Ambrosia canopies and in the interspaces between plants. Biomass responses were assessed as bacterial and fungal SSU rRNA gene copy number and chlorophyll a concentration. Metabolic responses were measured by five ecoenzyme activities and rates of N transformation. By most measures, nutrient availability, microbial biomass, and process rates were greater in soils beneath the shrub canopy compared to the interspace between plants, and greater in the surface biocrust horizon compared to the deeper 10 cm soil profile. Most measures responded positively to experimental N addition. Effect sizes were generally greater for bulk soil than biocrust. Results were incorporated into a meta-analysis of arid ecosystem responses to N amendment that included data from 14 other studies. Effect sizes were calculated for biomass and metabolic responses. Regressions of effect sizes, calculated for biomass, and metabolic responses, showed similar trends in relation to N application rate and N load (rate × duration). The critical points separating positive from negative treatment effects were 88 kg ha(-1) y(-1) and 159 kg ha(-1), respectively, for biomass, and 70 kg ha(-1) y(-1) and 114 kg ha(-1), respectively, for metabolism. These critical values are comparable to those for microbial biomass, decomposition rates and respiration reported in broader meta-analyses of N amendment effects in mesic ecosystems. However, large effect sizes at low N

  2. Soil microbial responses to nitrogen addition in arid ecosystems

    PubMed Central

    Sinsabaugh, Robert L.; Belnap, Jayne; Rudgers, Jennifer; Kuske, Cheryl R.; Martinez, Noelle; Sandquist, Darren

    2015-01-01

    The N cycle of arid ecosystems is influenced by low soil organic matter, high soil pH, and extremes in water potential and temperature that lead to open canopies and development of biological soil crusts (biocrusts). We investigated the effects of N amendment on soil microbial dynamics in a Larrea tridentata-Ambrosia dumosa shrubland site in southern Nevada USA. Sites were fertilized with a NO3-NH4 mix at 0, 7, and 15 kg N ha-1 y-1 from March 2012 to March 2013. In March 2013, biocrust (0–0.5 cm) and bulk soils (0–10 cm) were collected beneath Ambrosia canopies and in the interspaces between plants. Biomass responses were assessed as bacterial and fungal SSU rRNA gene copy number and chlorophyll a concentration. Metabolic responses were measured by five ecoenzyme activities and rates of N transformation. By most measures, nutrient availability, microbial biomass, and process rates were greater in soils beneath the shrub canopy compared to the interspace between plants, and greater in the surface biocrust horizon compared to the deeper 10 cm soil profile. Most measures responded positively to experimental N addition. Effect sizes were generally greater for bulk soil than biocrust. Results were incorporated into a meta-analysis of arid ecosystem responses to N amendment that included data from 14 other studies. Effect sizes were calculated for biomass and metabolic responses. Regressions of effect sizes, calculated for biomass, and metabolic responses, showed similar trends in relation to N application rate and N load (rate × duration). The critical points separating positive from negative treatment effects were 88 kg ha-1 y-1 and 159 kg ha-1, respectively, for biomass, and 70 kg ha-1 y-1 and 114 kg ha-1, respectively, for metabolism. These critical values are comparable to those for microbial biomass, decomposition rates and respiration reported in broader meta-analyses of N amendment effects in mesic ecosystems. However, large effect sizes at low N addition

  3. Remediation of metal polluted soils by phytorremediation combined with biochar addition

    NASA Astrophysics Data System (ADS)

    Méndez, Ana; Paz-Ferreiro, Jorge; Gómez-Limón, Dulce; César Arranz, Julio; Saa, Antonio; Gascó, Gabriel

    2016-04-01

    The main objective of this work is to optimize and quantify the treatment of metal polluted soils through phytoremediation techniques combined with the addition of biochar. Biochar is a carbon rich material obtained by thermal treatment of biomass in inert atmosphere. In recent years, it has been attracted considerable interest due to their positive effect after soil addition. The use of biochar also seems appropriate for the treatment of metal-contaminated soils decreasing their mobility. Biochar properties highly depend on the raw material composition and manufacturing conditions. This paper is based on the use of manure wastes, rich in nutrients and therefore interesting raw materials for biochar production, especially when combined with phytoremediation techniques since the biochar act as conditioner and slow release fertilizer. We are very grateful to Ministerio de Economia y Competitividad (Spain) for financial support under Project CGL2014-58322-R.

  4. Assessment of methods for organic and inorganic carbon quantification in carbonate-containing Mediterranean soils

    NASA Astrophysics Data System (ADS)

    Apesteguia, Marcos; Virto, Iñigo; Plante, Alain

    2014-05-01

    Quantification of soil organic matter (SOM) stocks and fluxes continues to be an important endeavor in assessments of soil quality, and more broadly in assessments of ecosystem functioning. The quantification of SOM in alkaline, carbonate-containing soils, such as those found in Mediterranean areas, is complicated by the need to differentiate between organic carbon (OC) and inorganic carbon (IC), which continues to present methodological challenges. Acidification is frequently used to eliminate carbonates prior to soil OC quantification, but when performed in the liquid phase, can promote the dissolution and loss of a portion of the OC. Acid fumigation (AF) is increasingly preferred for carbonate removal, but its effectiveness is difficult to assess using conventional elemental and isotopic analyses. In addition, the potential effects of AF on SOM are not well characterized. The objective of the current study was to apply a multi-method approach to determine the efficacy of carbonate removal by AF and its effects on the residual SOM. We selected a set of 24 surface agricultural soils representing a large range of textures, SOM contents and presumed carbonate contents. For each soil, OC was determined using wet combustion (Walkley-Black) and IC was determined using the calcimeter method. Samples were then subjected to elemental (total C) and isotopic (δ13C) analyses by dry combustion using a Costech autoanalyzer coupled to a Thermo Finnigan Delta Plus isotope ratio mass spectrometer (IRMS) before and after AF. IC was equated to total C determined after fumigation, and OC was estimated as the different in total C before and after AF. Samples were also subjected to ramped oxidation using a Netzsch STA109 PC Luxx thermal analyzer coupled to a LICOR 820A infrared gas analyzer (IRGA). Quantification of OC was performed using evolved gas analysis of CO2 (CO2-EGA) in the exothermic region 200-500° C associated with organic matter combustion. IC was quantified by CO2-EGA

  5. Colluvial soils as a carbon pool in different soil regions

    NASA Astrophysics Data System (ADS)

    Zádorová, Tereza; Penížek, Vít; Žížala, Daniel

    2014-05-01

    Distribution and storage of soil organic matter are controlled by various environmental factors. In areas influenced by soil erosion, the soil organic carbon (SOC) pattern is characterized by both its removal in some parts and its storage in other parts of the landscape. Colluvial soils formed by accumulation of soil sediments represent such a carbon pool. SOC stock in colluvial soils was determined and related to terrain attributes on three agricultural plots (from 7 to 30 hectares) with different soil and geologic (Cambisol, Luvisol and Chernozem) character. The analysis was also focused on differences in SOC distribution in topsoil and subsoil. The study was based on a detailed network of soil borings and deep cores. SOC content was determined in each 25 cm in entire A horizon up to the depth of 5 m. SOC density determined in each point using SOC concentration, bulk density and A horizon thickness was statistically related to various terrain attributes derived from a detailed digital elevation model. Grid of SOC density was obtained by interpolating point measurements using the terrain attributes as accessory variables; the total SOC stock was then calculated by summing the grid cells. In Chernozem and Luvisol regions, SOC stock is strongly related to the terrain character when topographic wetness index and plan curvature were the most significantly related to the distribution of SOC density. In Cambisol region, low relationship between SOC distribution and terrain attributes was observed. Thickness of A horizon is variable in the three plots: its depth reaches up to 5 meters in Chernozem region while in Luvisol and Cambisol the maximum observed thickness was 1 meter. SOC density averages from the three plots are 7.63 kg.m-2 (Cambisol), 12.06 kg.m-2 (Luvisol) and 32.28 kg.m-2 (Chernozem). SOC stock in the topsoil (0-30 cm) represents 54.5 % in Cambisol region, 43.6 % in Luvisol region and only 19.3 % in Chernozem region from the total SOC stock. This finding

  6. Microbes residing in young organic rich Alaskan soils contain older carbon than those residing in old mineral high Arctic soils

    NASA Astrophysics Data System (ADS)

    Ziolkowski, L. A.; Slater, G. F.; Onstott, T. C.; Whyte, L.; Townsend-Small, A.

    2013-12-01

    in Alaskan soil than that of the Canadian high Arctic soil, indicating that Alaskan microbes were interacting with the bulk organic carbon pool and Canadian high Arctic soil microbes were disconnected from the bulk organic carbon pool. Additionally, dissimilarities in the n-alkane distributions suggest vastly different carbon sources to these different soils. Collectively, these results suggest that (a) these Arctic soils contain a comparable abundance of microbes, (b) the organic carbon being accumulated in the Alaskan soil is likely from recent biomass, (c) mineral soil accumulation in the Canadian high Arctic is likely due to erosional inputs of ancient carbon and (d) the carbon stocks in Alaskan soils are more bioavailable to the microbes than those in mineral soils of the Canadian high Arctic. Incubation studies that incorporate gas fluxes and proteomics may tease apart if the observed differences in bioavailability are a function of temperature, substrate availability or some other variable.

  7. 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.

  8. Modelling the effect of agricultural management practices on soil organic carbon stocks: does soil erosion matter?

    NASA Astrophysics Data System (ADS)

    Nadeu, Elisabet; Van Wesemael, Bas; Van Oost, Kristof

    2014-05-01

    Over the last decades, an increasing number of studies have been conducted to assess the effect of soil management practices on soil organic carbon (SOC) stocks. At regional scales, biogeochemical models such as CENTURY or Roth-C have been commonly applied. These models simulate SOC dynamics at the profile level (point basis) over long temporal scales but do not consider the continuous lateral transfer of sediment that takes place along geomorphic toposequences. As a consequence, the impact of soil redistribution on carbon fluxes is very seldom taken into account when evaluating changes in SOC stocks due to agricultural management practices on the short and long-term. To address this gap, we assessed the role of soil erosion by water and tillage on SOC stocks under different agricultural management practices in the Walloon region of Belgium. The SPEROS-C model was run for a 100-year period combining three typical crop rotations (using winter wheat, winter barley, sugar beet and maize) with three tillage scenarios (conventional tillage, reduced tillage and reduced tillage in combination with additional crop residues). The results showed that including soil erosion by water in the simulations led to a general decrease in SOC stocks relative to a baseline scenario (where no erosion took place). The SOC lost from these arable soils was mainly exported to adjacent sites and to the river system by lateral fluxes, with magnitudes differing between crop rotations and in all cases lower under conservation tillage practices than under conventional tillage. Although tillage erosion plays an important role in carbon redistribution within fields, lateral fluxes induced by water erosion led to a higher spatial and in-depth heterogeneity of SOC stocks with potential effects on the soil water holding capacity and crop yields. This indicates that studies assessing the effect of agricultural management practices on SOC stocks and other soil properties over the landscape should

  9. Anthropogenic nitrogen deposition enhances carbon sequestration in boreal soils.

    PubMed

    Maaroufi, Nadia I; Nordin, Annika; Hasselquist, Niles J; Bach, Lisbet H; Palmqvist, Kristin; Gundale, Michael J

    2015-08-01

    It is proposed that carbon (C) sequestration in response to reactive nitrogen (Nr ) deposition in boreal forests accounts for a large portion of the terrestrial sink for anthropogenic CO2 emissions. While studies have helped clarify the magnitude by which Nr deposition enhances C sequestration by forest vegetation, there remains a paucity of long-term experimental studies evaluating how soil C pools respond. We conducted a long-term experiment, maintained since 1996, consisting of three N addition levels (0, 12.5, and 50 kg N ha(-1) yr(-1) ) in the boreal zone of northern Sweden to understand how atmospheric Nr deposition affects soil C accumulation, soil microbial communities, and soil respiration. We hypothesized that soil C sequestration will increase, and soil microbial biomass and soil respiration will decrease, with disproportionately large changes expected compared to low levels of N addition. Our data showed that the low N addition treatment caused a non-significant increase in the organic horizon C pool of ~15% and a significant increase of ~30% in response to the high N treatment relative to the control. The relationship between C sequestration and N addition in the organic horizon was linear, with a slope of 10 kg C kg(-1) N. We also found a concomitant decrease in total microbial and fungal biomasses and a ~11% reduction in soil respiration in response to the high N treatment. Our data complement previous data from the same study system describing aboveground C sequestration, indicating a total ecosystem sequestration rate of 26 kg C kg(-1) N. These estimates are far lower than suggested by some previous modeling studies, and thus will help improve and validate current modeling efforts aimed at separating the effect of multiple global change factors on the C balance of the boreal region.

  10. Anthropogenic nitrogen deposition enhances carbon sequestration in boreal soils.

    PubMed

    Maaroufi, Nadia I; Nordin, Annika; Hasselquist, Niles J; Bach, Lisbet H; Palmqvist, Kristin; Gundale, Michael J

    2015-08-01

    It is proposed that carbon (C) sequestration in response to reactive nitrogen (Nr ) deposition in boreal forests accounts for a large portion of the terrestrial sink for anthropogenic CO2 emissions. While studies have helped clarify the magnitude by which Nr deposition enhances C sequestration by forest vegetation, there remains a paucity of long-term experimental studies evaluating how soil C pools respond. We conducted a long-term experiment, maintained since 1996, consisting of three N addition levels (0, 12.5, and 50 kg N ha(-1) yr(-1) ) in the boreal zone of northern Sweden to understand how atmospheric Nr deposition affects soil C accumulation, soil microbial communities, and soil respiration. We hypothesized that soil C sequestration will increase, and soil microbial biomass and soil respiration will decrease, with disproportionately large changes expected compared to low levels of N addition. Our data showed that the low N addition treatment caused a non-significant increase in the organic horizon C pool of ~15% and a significant increase of ~30% in response to the high N treatment relative to the control. The relationship between C sequestration and N addition in the organic horizon was linear, with a slope of 10 kg C kg(-1) N. We also found a concomitant decrease in total microbial and fungal biomasses and a ~11% reduction in soil respiration in response to the high N treatment. Our data complement previous data from the same study system describing aboveground C sequestration, indicating a total ecosystem sequestration rate of 26 kg C kg(-1) N. These estimates are far lower than suggested by some previous modeling studies, and thus will help improve and validate current modeling efforts aimed at separating the effect of multiple global change factors on the C balance of the boreal region. PMID:25711504

  11. Soil Organic Carbon Degradation, Barrow, 2013-2014

    DOE Data Explorer

    Gu, Baohua; Yang, Ziming

    2015-03-30

    This dataset provides information about soil organic carbon decomposition in Barrow soil incubation studies. The soil cores were collected from low-center polygon (Area A) and were incubated in the laboratory at different temperatures for up to 60 days. Transformations of soil organic carbon were characterized by UV and FT-IR, and small organic acids in water-soluble carbons were quantified by ion chromatography during the incubation

  12. Existing Soil Carbon Models Do Not Apply to Forested Wetlands.

    SciTech Connect

    Trettin, C C; Song, B; Jurgensen, M F; Li, C

    2001-09-14

    Evaluation of 12 widely used soil carbon models to determine applicability to wetland ecosystems. For any land area that includes wetlands, none of the individual models would produce reasonable simulations based on soil processes. Study presents a wetland soil carbon model framework based on desired attributes, the DNDC model and components of the CENTURY and WMEM models. Proposed synthesis would be appropriate when considering soil carbon dynamics at multiple spatial scales and where the land area considered includes both wetland and upland ecosystems.

  13. [Effects of different fertilizer application on soil active organic carbon].

    PubMed

    Zhang, Rui; Zhang, Gui-Long; Ji, Yan-Yan; Li, Gang; Chang, Hong; Yang, Dian-Lin

    2013-01-01

    The variation characteristics of the content and components of soil active organic carbon under different fertilizer application were investigated in samples of calcareous fluvo-aquic soil from a field experiment growing winter wheat and summer maize in rotation in the North China Plain. The results showed that RF (recommended fertilization), CF (conventional fertilization) and NPK (mineral fertilizer alone) significantly increased the content of soil dissolved organic carbon and easily oxidized organic carbon by 24.92-38.63 mg x kg(-1) and 0.94-0.58 mg x kg(-1) respectively compared to CK (unfertilized control). The soil dissolved organic carbon content under OM (organic manure) increased greater than those under NPK and single fertilization, soil easily oxidized organic carbon content under OM and NPK increased greater than that under single chemical fertilization. OM and NPK showed no significant role in promoting the soil microbial biomass carbon, but combined application of OM and NPK significantly increased the soil microbial biomass carbon content by 36.06% and 20.69%, respectively. Soil easily oxidized organic carbon, dissolved organic carbon and microbial biomass carbon accounted for 8.41% - 14.83%, 0.47% - 0.70% and 0.89% - 1.20% of the total organic carbon (TOC), respectively. According to the results, the fertilizer application significantly increased the proportion of soil dissolved organic carbon and easily oxidized organic carbon, but there was no significant difference in the increasing extent of dissolved organic carbon. The RF and CF increased the proportion of soil easily oxidized organic carbon greater than OM or NPK, and significantly increased the proportion of microbial biomass carbon. OM or RF had no significant effect on the proportion of microbial biomass carbon. Therefore, in the field experiment, appropriate application of organic manure and chemical fertilizers played an important role for the increase of soil active organic carbon

  14. [Effects of different fertilizer application on soil active organic carbon].

    PubMed

    Zhang, Rui; Zhang, Gui-Long; Ji, Yan-Yan; Li, Gang; Chang, Hong; Yang, Dian-Lin

    2013-01-01

    The variation characteristics of the content and components of soil active organic carbon under different fertilizer application were investigated in samples of calcareous fluvo-aquic soil from a field experiment growing winter wheat and summer maize in rotation in the North China Plain. The results showed that RF (recommended fertilization), CF (conventional fertilization) and NPK (mineral fertilizer alone) significantly increased the content of soil dissolved organic carbon and easily oxidized organic carbon by 24.92-38.63 mg x kg(-1) and 0.94-0.58 mg x kg(-1) respectively compared to CK (unfertilized control). The soil dissolved organic carbon content under OM (organic manure) increased greater than those under NPK and single fertilization, soil easily oxidized organic carbon content under OM and NPK increased greater than that under single chemical fertilization. OM and NPK showed no significant role in promoting the soil microbial biomass carbon, but combined application of OM and NPK significantly increased the soil microbial biomass carbon content by 36.06% and 20.69%, respectively. Soil easily oxidized organic carbon, dissolved organic carbon and microbial biomass carbon accounted for 8.41% - 14.83%, 0.47% - 0.70% and 0.89% - 1.20% of the total organic carbon (TOC), respectively. According to the results, the fertilizer application significantly increased the proportion of soil dissolved organic carbon and easily oxidized organic carbon, but there was no significant difference in the increasing extent of dissolved organic carbon. The RF and CF increased the proportion of soil easily oxidized organic carbon greater than OM or NPK, and significantly increased the proportion of microbial biomass carbon. OM or RF had no significant effect on the proportion of microbial biomass carbon. Therefore, in the field experiment, appropriate application of organic manure and chemical fertilizers played an important role for the increase of soil active organic carbon

  15. Estimating the soil organic carbon content for European NUTS2 regions based on LUCAS data collection.

    PubMed

    Panagos, Panos; Ballabio, Cristiano; Yigini, Yusuf; Dunbar, Martha B

    2013-01-01

    Under the European Union Thematic Strategy for Soil Protection, the European Commission Directorate-General for the Environment and the European Environmental Agency (EEA) identified a decline in soil organic carbon and soil losses by erosion as priorities for the collection of policy relevant soil data at European scale. Moreover, the estimation of soil organic carbon content is of crucial importance for soil protection and for climate change mitigation strategies. Soil organic carbon is one of the attributes of the recently developed LUCAS soil database. The request for data on soil organic carbon and other soil attributes arose from an on-going debate about efforts to establish harmonized datasets for all EU countries with data on soil threats in order to support modeling activities and display variations in these soil conditions across Europe. In 2009, the European Commission's Joint Research Centre conducted the LUCAS soil survey, sampling ca. 20,000 points across 23 EU member states. This article describes the results obtained from analyzing the soil organic carbon data in the LUCAS soil database. The collected data were compared with the modeled European topsoil organic carbon content data developed at the JRC. The best fitted comparison was performed at NUTS2 level and showed underestimation of modeled data in southern Europe and overestimation in the new central eastern member states. There is a good correlation in certain regions for countries such as the United Kingdom, Slovenia, Italy, Ireland, and France. Here we assess the feasibility of producing comparable estimates of the soil organic carbon content at NUTS2 regional level for the European Union (EU27) and draw a comparison with existing modeled data. In addition to the data analysis, we suggest how the modeled data can be improved in future updates with better calibration of the model. PMID:23178783

  16. Estimating the soil organic carbon content for European NUTS2 regions based on LUCAS data collection.

    PubMed

    Panagos, Panos; Ballabio, Cristiano; Yigini, Yusuf; Dunbar, Martha B

    2013-01-01

    Under the European Union Thematic Strategy for Soil Protection, the European Commission Directorate-General for the Environment and the European Environmental Agency (EEA) identified a decline in soil organic carbon and soil losses by erosion as priorities for the collection of policy relevant soil data at European scale. Moreover, the estimation of soil organic carbon content is of crucial importance for soil protection and for climate change mitigation strategies. Soil organic carbon is one of the attributes of the recently developed LUCAS soil database. The request for data on soil organic carbon and other soil attributes arose from an on-going debate about efforts to establish harmonized datasets for all EU countries with data on soil threats in order to support modeling activities and display variations in these soil conditions across Europe. In 2009, the European Commission's Joint Research Centre conducted the LUCAS soil survey, sampling ca. 20,000 points across 23 EU member states. This article describes the results obtained from analyzing the soil organic carbon data in the LUCAS soil database. The collected data were compared with the modeled European topsoil organic carbon content data developed at the JRC. The best fitted comparison was performed at NUTS2 level and showed underestimation of modeled data in southern Europe and overestimation in the new central eastern member states. There is a good correlation in certain regions for countries such as the United Kingdom, Slovenia, Italy, Ireland, and France. Here we assess the feasibility of producing comparable estimates of the soil organic carbon content at NUTS2 regional level for the European Union (EU27) and draw a comparison with existing modeled data. In addition to the data analysis, we suggest how the modeled data can be improved in future updates with better calibration of the model.

  17. Stimulation of terrestrial ecosystem carbon storage by nitrogen addition: a meta-analysis

    NASA Astrophysics Data System (ADS)

    Yue, Kai; Peng, Yan; Peng, Changhui; Yang, Wanqin; Peng, Xin; Wu, Fuzhong

    2016-01-01

    Elevated nitrogen (N) deposition alters the terrestrial carbon (C) cycle, which is likely to feed back to further climate change. However, how the overall terrestrial ecosystem C pools and fluxes respond to N addition remains unclear. By synthesizing data from multiple terrestrial ecosystems, we quantified the response of C pools and fluxes to experimental N addition using a comprehensive meta-analysis method. Our results showed that N addition significantly stimulated soil total C storage by 5.82% ([2.47%, 9.27%], 95% CI, the same below) and increased the C contents of the above- and below-ground parts of plants by 25.65% [11.07%, 42.12%] and 15.93% [6.80%, 25.85%], respectively. Furthermore, N addition significantly increased aboveground net primary production by 52.38% [40.58%, 65.19%] and litterfall by 14.67% [9.24%, 20.38%] at a global scale. However, the C influx from the plant litter to the soil through litter decomposition and the efflux from the soil due to microbial respiration and soil respiration showed insignificant responses to N addition. Overall, our meta-analysis suggested that N addition will increase soil C storage and plant C in both above- and below-ground parts, indicating that terrestrial ecosystems might act to strengthen as a C sink under increasing N deposition.

  18. Stimulation of terrestrial ecosystem carbon storage by nitrogen addition: a meta-analysis

    PubMed Central

    Yue, Kai; Peng, Yan; Peng, Changhui; Yang, Wanqin; Peng, Xin; Wu, Fuzhong

    2016-01-01

    Elevated nitrogen (N) deposition alters the terrestrial carbon (C) cycle, which is likely to feed back to further climate change. However, how the overall terrestrial ecosystem C pools and fluxes respond to N addition remains unclear. By synthesizing data from multiple terrestrial ecosystems, we quantified the response of C pools and fluxes to experimental N addition using a comprehensive meta-analysis method. Our results showed that N addition significantly stimulated soil total C storage by 5.82% ([2.47%, 9.27%], 95% CI, the same below) and increased the C contents of the above- and below-ground parts of plants by 25.65% [11.07%, 42.12%] and 15.93% [6.80%, 25.85%], respectively. Furthermore, N addition significantly increased aboveground net primary production by 52.38% [40.58%, 65.19%] and litterfall by 14.67% [9.24%, 20.38%] at a global scale. However, the C influx from the plant litter to the soil through litter decomposition and the efflux from the soil due to microbial respiration and soil respiration showed insignificant responses to N addition. Overall, our meta-analysis suggested that N addition will increase soil C storage and plant C in both above- and below-ground parts, indicating that terrestrial ecosystems might act to strengthen as a C sink under increasing N deposition. PMID:26813078

  19. Soil carbon sequestration and biochar as negative emission technologies.

    PubMed

    Smith, Pete

    2016-03-01

    Despite 20 years of effort to curb emissions, greenhouse gas (GHG) emissions grew faster during the 2000s than in the 1990s, which presents a major challenge for meeting the international goal of limiting warming to <2 °C relative to the preindustrial era. Most recent scenarios from integrated assessment models require large-scale deployment of negative emissions technologies (NETs) to reach the 2 °C target. A recent analysis of NETs, including direct air capture, enhanced weathering, bioenergy with carbon capture and storage and afforestation/deforestation, showed that all NETs have significant limits to implementation, including economic cost, energy requirements, land use, and water use. In this paper, I assess the potential for negative emissions from soil carbon sequestration and biochar addition to land, and also the potential global impacts on land use, water, nutrients, albedo, energy and cost. Results indicate that soil carbon sequestration and biochar have useful negative emission potential (each 0.7 GtCeq. yr(-1) ) and that they potentially have lower impact on land, water use, nutrients, albedo, energy requirement and cost, so have fewer disadvantages than many NETs. Limitations of soil carbon sequestration as a NET centre around issues of sink saturation and reversibility. Biochar could be implemented in combination with bioenergy with carbon capture and storage. Current integrated assessment models do not represent soil carbon sequestration or biochar. Given the negative emission potential of SCS and biochar and their potential advantages compared to other NETs, efforts should be made to include these options within IAMs, so that their potential can be explored further in comparison with other NETs for climate stabilization.

  20. Soil carbon sequestration and biochar as negative emission technologies.

    PubMed

    Smith, Pete

    2016-03-01

    Despite 20 years of effort to curb emissions, greenhouse gas (GHG) emissions grew faster during the 2000s than in the 1990s, which presents a major challenge for meeting the international goal of limiting warming to <2 °C relative to the preindustrial era. Most recent scenarios from integrated assessment models require large-scale deployment of negative emissions technologies (NETs) to reach the 2 °C target. A recent analysis of NETs, including direct air capture, enhanced weathering, bioenergy with carbon capture and storage and afforestation/deforestation, showed that all NETs have significant limits to implementation, including economic cost, energy requirements, land use, and water use. In this paper, I assess the potential for negative emissions from soil carbon sequestration and biochar addition to land, and also the potential global impacts on land use, water, nutrients, albedo, energy and cost. Results indicate that soil carbon sequestration and biochar have useful negative emission potential (each 0.7 GtCeq. yr(-1) ) and that they potentially have lower impact on land, water use, nutrients, albedo, energy requirement and cost, so have fewer disadvantages than many NETs. Limitations of soil carbon sequestration as a NET centre around issues of sink saturation and reversibility. Biochar could be implemented in combination with bioenergy with carbon capture and storage. Current integrated assessment models do not represent soil carbon sequestration or biochar. Given the negative emission potential of SCS and biochar and their potential advantages compared to other NETs, efforts should be made to include these options within IAMs, so that their potential can be explored further in comparison with other NETs for climate stabilization. PMID:26732128

  1. Carbon and nitrogen mineralization in vineyard acid soils amended with a bentonitic winery waste

    NASA Astrophysics Data System (ADS)

    Fernández-Calviño, David; Rodríguez-Salgado, Isabel; Pérez-Rodríguez, Paula; Díaz-Raviña, Montserrat; Nóvoa-Muñoz, Juan Carlos; Arias-Estévez, Manuel

    2015-04-01

    Carbon mineralization and nitrogen ammonification processes were determined in different vineyard soils. The measurements were performed in samples non-amended and amended with different bentonitic winery waste concentrations. Carbon mineralization was measured as CO2 released by the soil under laboratory conditions, whereas NH4+ was determined after its extraction with KCl 2M. The time evolution of both, carbon mineralization and nitrogen ammonification, was followed during 42 days. The released CO2 was low in the analyzed vineyard soils, and hence the metabolic activity in these soils was low. The addition of the bentonitic winery waste to the studied soils increased highly the carbon mineralization (2-5 fold), showing that the organic matter added together the bentonitic waste to the soil have low stability. In both cases, amended and non-amended samples, the maximum carbon mineralization was measured during the first days (2-4 days), decreasing as the incubation time increased. The NH4+ results showed an important effect of bentonitic winery waste on the ammonification behavior in the studied soils. In the non-amended samples the ammonification was no detected in none of the soils, whereas in the amended soils important NH4+ concentrations were detected. In these cases, the ammonification was fast, reaching the maximum values of NH4 between 7 and 14 days after the bentonitic waste additions. Also, the percentages of ammonification respect to the total nitrogen in the soil were high, showing that the nitrogen provided by the bentonitic waste to the soil is non-stable. The fast carbon mineralization found in the soils amended with bentonitic winery wastes shows low possibilities of the use of this waste for the increasing the organic carbon pools in the soil.On the other hand, the use of this waste as N-fertilizer can be possible. However, due its fast ammonification, the waste should be added to the soils during active plant growth periods.

  2. Effects of Nitrogen and Phosphorus Additions on Carbon Cycling of Tropical Mountain Rainforests in Hainan, China

    NASA Astrophysics Data System (ADS)

    Lai, J.

    2015-12-01

    Nitrogen (N) and Phosphorus (P) deposition is projected to increase significantly in tropical regions in the coming decades, which has changed and will change the structure and function of ecosystems, and affects on ecosystem Carbon (C) cycle. As an important part in global C cycle, how the C cycle of tropical rainforests will be influenced by the N and P deposition should be focused on. This study simulated N and P deposition in a primary and secondary forest of tropical mountain rainforest in Jianfengling, Hainan, China, during five-year field experiment to evaluate the effects of N and P deposition on C cycling processes and relate characteristics. Six levels of N and P treatments were treated: Control, Low-N, Medium-N, High-N, P and N+P. The relative growth rates (RGR) of tree layer in treatment plots were different from that in control plots after years of N and P addition. Simulated N and P deposition also increased ANPP in primary forest. N and P addition changed the growth of trees by altering soil nutrient and microbial activities. N and P addition increased soil organic carbon (SOC) and total N (TN) content, and significantly increased soil total P (TP) content, not changing soil pH. During the whole process of N and P addition, as net nitrification rate and net N mineralization rate were promoted by N and P addition, and effective N content (nitrate) of soil increased in the plot treated with N treatments compared to the control treatment. The microbial P content was increased by N and P addition, and microbial N was not changed. The increasing N deposition may enhance soil nutrient and stimulate growth of trees, which will lead to an increase of the C sequestration.

  3. "Hot background" of the mobile inelastic neutron scattering system for soil carbon analysis.

    PubMed

    Kavetskiy, Aleksandr; Yakubova, Galina; Prior, Stephen A; Torbert, H Allen

    2016-01-01

    The problem of gamma spectrum peak identification arises when conducting soil carbon analysis using the inelastic neutron scattering (INS) system. Some spectral peaks could be associated with radioisotopes appearing due to neutron activation of both the measurement system and soil samples. The investigation of "hot background" gamma spectra from the construction materials, whole measurement system, and soil samples over time showed that activation of (28)Al isotope can contribute noticeable additions to the soil neutron stimulated gamma spectra. PMID:26595773

  4. Soil carbon distribution and site characteristics in hyper-arid soils of the Atacama Desert: A site with Mars-like soils

    NASA Astrophysics Data System (ADS)

    Valdivia-Silva, Julio E.; Navarro-González, Rafael; Fletcher, Lauren; Perez-Montaño, Saúl; Condori-Apaza, Reneé; Mckay, Christopher P.

    2012-07-01

    The soil carbon content and its relation to site characteristics are important in evaluating current local, regional, and global soil C storage and projecting future variations in response to climate change. In this study we analyzed the concentration of organic and inorganic carbon and their relationship with in situ climatic and geological characteristics in 485 samples of surface soil and 17 pits from the hyper-arid area and 51 samples with 2 pits from the arid-semiarid region from the Atacama Desert located in Peru and Chile. The soil organic carbon (SOC) in hyperarid soils ranged from 1.8 to 50.9 μg C per g of soil for the 0-0.1 m profile and from 1.8 to 125.2 μg C per g of soil for the 0-1 m profile. The analysis of climatic (temperature and precipitation), elevation, and some geologic characteristics (landforms) associated with hyper-arid soils explained partially the SOC variability. On the other hand, soil inorganic carbon (SIC) contents, in the form of carbonates, ranged from 200 to 1500 μg C per g of soil for the 0-0.1 m profile and from 200 to 3000 μg C per g of soil for the 0-1.0 m profile in the driest area. The largest accumulations of organic and inorganic carbon were found near to arid-semiarid areas. In addition, the elemental carbon concentrations show that the presence of other forms of inorganic carbon (e.g. graphite, etc.) was negligible in these hyperarid soils. Overall, the top 1 m soil layer of hyperarid lands contains ˜11.6 Tg of organic carbon and 344.6 Tg of carbonate carbon. The total stored carbon was 30.8-fold the organic carbon alone. To our knowledge, this is the first study evaluating the total budget carbon on the surface and shallow subsurface on ˜160,000 km2 of hyperarid soils.

  5. Soil-carbon response to warming dependent on microbial physiology

    NASA Astrophysics Data System (ADS)

    Allison, Steven D.; Wallenstein, Matthew D.; Bradford, Mark A.

    2010-05-01

    Most ecosystem models predict that climate warming will stimulate microbial decomposition of soil carbon, producing a positive feedback to rising global temperatures. Although field experiments document an initial increase in the loss of CO2 from soils in response to warming, in line with these predictions, the carbon dioxide loss from soils tends to decline to control levels within a few years. This attenuation response could result from changes in microbial physiological properties with increasing temperature, such as a decline in the fraction of assimilated carbon that is allocated to growth, termed carbon-use efficiency. Here we explore these mechanisms using a microbial-enzyme model to simulate the responses of soil carbon to warming by 5∘C. 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 the 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.

  6. Soil Water Cycling Links to Carbon Content between Ecosystems in the Colorado Front Range

    NASA Astrophysics Data System (ADS)

    Powell, K. M.; Anderson, D. E.; Stannard, D. I.; Mladinich, C. S.; Thienelt, T. S.; Blanken, P.

    2011-12-01

    Near surface soil-water content is crucial to the sustainability of an ecosystem. Additionally, the feedbacks between soil water and soil carbon improve the ability to predict carbon sequestration rates. Organic-carbon content in surface soils influences soil texture and, subsequently, water holding capacity. Preliminary research for two growing seasons (2010 and 2011) compares soil water, temperature, heat flux, and evapotranspiration (ET) with soil organic carbon content at several sites in the Colorado Front Range. Continuous measurements of precipitation, soil moisture and temperature, and energy fluxes were conducted from eddy covariance flux towers at three sites around metropolitan Denver: one urban site and two adjacent sites, a montane forest (Flying J Ranch Open Space), and a native tallgrass prairie (Rocky Flats National Wildlife Refuge (NWR)). Irrigation data were obtained for the Denver urban site and added to its precipitation to obtain total water inputs. Soil samples (0-5cm) were collected at each tower site and analyzed for bulk density, volumetric water content, and organic carbon content. Soil water inputs and losses (as ET) were analyzed for each site and compared to soil organic carbon content. Rocky Flats NWR soils contained the highest organic carbon content (20-30 percent), while the urban site and Flying J Ranch soils contained between 10-15 percent. Comparing grassland sites, the urban soil received 5 times higher water input (600mm, more than half from irrigation) in 2010 than those of Rocky Flats. Despite less water input, the Rocky Flats site developed more soil organic carbon, possibly due to large amounts of grassland biomass mineralization and moderate soil moisture conditions through the season. The Denver urban site demonstrated less soil moisture variability in response to surface-water inputs from precipitation compared to soils at the native grassland and montane sites, perhaps limiting the conditions under which soil carbon

  7. Cycling of beryllium and carbon through hillslope soils in Iowa

    USGS Publications Warehouse

    Harden, J.W.; Fries, T.L.; Pavich, M.J.

    2002-01-01

    Isotopes of Be and C were used to reconstruct loess accumulation, hillslope evolution, and agricultural modification in soils of western Iowa. While both elements are derived from additions by the atmosphere (via plants in the case of carbon), the differences in element cycling allow erosional and depositional processes to be separated from biochemical processing. Based on 10Be, loess accumulation likely occurred simultaneously with hillslope degradation. Rates of loess accumulation declined five-fold between early stages (late Pleistocene and early Holocene) and later stages (late Holocene) of accumulation, but the absolute timing of accumulation requires independent dating methods. Based on 14C measurements, plant inputs and decomposition are significant near the surface, but below 1-1.5 m carbon inputs are minimal and decomposition is nearly arrested. The amount of carbon below 1.5 m is constant (0.1%) and is composed of soil organic matter that was buried by loess. Agricultural modification results in a dramatic redistribution of 10Be through soil erosion and deposition. By contrast, the redistribution of soil organic matter is masked by the rapid cycling of C through the topsoil as it continually decomposes and is replaced by plant inputs.

  8. Stabilization of carbon in composts and biochars in relation to carbon sequestration and soil fertility.

    PubMed

    Bolan, N S; Kunhikrishnan, A; Choppala, G K; Thangarajan, R; Chung, J W

    2012-05-01

    There have been increasing interests in the conversion of organic residues into biochars in order to reduce the rate of decomposition, thereby enhancing carbon (C) sequestration in soils. However energy is required to initiate the pyrolysis process during biochar production which can also lead to the release of greenhouse gasses. Alternative methods can be used to stabilize C in composts and other organic residues without impacting their quality. The objectives of this study include: (i) to compare the rate of decomposition among various organic amendments and (ii) to examine the effect of clay materials on the stabilization of C in organic amendments. The decomposition of a number of organic amendments (composts and biochars) was examined by monitoring the release of carbon-dioxide using respiration experiments. The results indicated that the rate of decomposition as measured by half life (t(1/2)) varied between the organic amendments and was higher in sandy soil than in clay soil. The half life value ranged from 139 days in the sandy soil and 187 days in the clay soil for poultry manure compost to 9989 days for green waste biochar. Addition of clay materials to compost decreased the rate of decomposition, thereby increasing the stabilization of C. The half life value for poultry manure compost increased from 139 days to 620, 806 and 474 days with the addition of goethite, gibbsite and allophane, respectively. The increase in the stabilization of C with the addition of clay materials may be attributed to the immobilization of C, thereby preventing it from microbial decomposition. Stabilization of C in compost using clay materials did not impact negatively the value of composts in improving soil quality as measured by potentially mineralizable nitrogen and microbial biomass carbon in soil.

  9. Stabilization of carbon in composts and biochars in relation to carbon sequestration and soil fertility.

    PubMed

    Bolan, N S; Kunhikrishnan, A; Choppala, G K; Thangarajan, R; Chung, J W

    2012-05-01

    There have been increasing interests in the conversion of organic residues into biochars in order to reduce the rate of decomposition, thereby enhancing carbon (C) sequestration in soils. However energy is required to initiate the pyrolysis process during biochar production which can also lead to the release of greenhouse gasses. Alternative methods can be used to stabilize C in composts and other organic residues without impacting their quality. The objectives of this study include: (i) to compare the rate of decomposition among various organic amendments and (ii) to examine the effect of clay materials on the stabilization of C in organic amendments. The decomposition of a number of organic amendments (composts and biochars) was examined by monitoring the release of carbon-dioxide using respiration experiments. The results indicated that the rate of decomposition as measured by half life (t(1/2)) varied between the organic amendments and was higher in sandy soil than in clay soil. The half life value ranged from 139 days in the sandy soil and 187 days in the clay soil for poultry manure compost to 9989 days for green waste biochar. Addition of clay materials to compost decreased the rate of decomposition, thereby increasing the stabilization of C. The half life value for poultry manure compost increased from 139 days to 620, 806 and 474 days with the addition of goethite, gibbsite and allophane, respectively. The increase in the stabilization of C with the addition of clay materials may be attributed to the immobilization of C, thereby preventing it from microbial decomposition. Stabilization of C in compost using clay materials did not impact negatively the value of composts in improving soil quality as measured by potentially mineralizable nitrogen and microbial biomass carbon in soil. PMID:22444054

  10. Uncertainty of upland soil carbon sink estimate for Finland

    NASA Astrophysics Data System (ADS)

    Lehtonen, Aleksi; Heikkinen, Juha

    2016-04-01

    Changes in the soil carbon stock of Finnish upland soils were quantified using forest inventory data, forest statistics, biomass models, litter turnover rates, and the Yasso07 soil model. Uncertainty in the estimated stock changes was assessed by combining model and sampling errors associated with the various data sources into variance-covariance matrices that allowed computationally efficient error propagation in the context of Yasso07 simulations. In sensitivity analysis, we found that the uncertainty increased drastically as a result of adding random year-to-year variation to the litter input. Such variation is smoothed out when using periodic inventory data with constant biomass models and turnover rates. Model errors (biomass, litter, understorey vegetation) and the systematic error of total drain had a marginal effect on the uncertainty regarding soil carbon stock change. Most of the uncertainty appears to be related to uncaptured annual variation in litter amounts. This is due to fact that variation in the slopes of litter input trends dictates the uncertainty of soil carbon stock change. If we assume that there is annual variation only in foliage and fine root litter rates and that this variation is less than 10% from year to year, then we can claim that Finnish upland forest soils have accumulated carbon during the first Kyoto period (2008-2012). The results of the study underline superiority of permanent sample plots compared to temporary ones, when soil model litter input trends have been estimated from forest inventory data. In addition, we also found that the use of IPCC guidelines leads to underestimation of the uncertainty of soil carbon stock change. This underestimation of the error results from the guidance to remove inter-annual variation from the model inputs, here illustrated with constant litter life spans. Model assumptions and model input estimation should be evaluated critically, when GHG-inventory results are used for policy planning

  11. Comparative study on carbon accumulation in soils under managed and unmanaged forests in Central Balkan Mountains

    NASA Astrophysics Data System (ADS)

    Naydenova, Lora; Zhiyanski, Miglena; Leifeld, Jens

    2014-05-01

    Each soil has a carbon storage capacity, which depends on many factors including type of soil, vegetation, precipitation and temperature. The aim of this work is to compare the carbon accumulation in forest floor layers and mineral soil horizons under managed and unmanaged spruce and beech forest ecosystems developed on Cambisols in Central Balkan Mountains, Bulgaria. We have investigated two managed and two unmanaged forests - pure stands of European beech (Fagus sylvatica L.) and Norway spruce (Picea abies Karst.). In each experimental site one representative soil profile was prepared with additional 4 sampling profiles for more precise determination of spatial variability of soil characteristic at site level. The forest floor was sampled in 3 repetitions per site, by a plastic frame (25:25 cm). The textural composition of soil, bulk density, coarse fraction content, pH, carbon and nitrogen content were analysed for forest floor layers and soil at different soil depths (0-10 cm, 10-20 cm, 20-30 cm and 30-50 cm). Both European beech and Norway spruce stands had higher accumulation of organic matter in the forest floor and the Ah horizon under unmanaged conditions. When managed, carbon contents tended to be higher in deeper horizons of the mineral soil, probably due to differences in microclimate after cutting. However, the variability in carbon storage was higher in managed sites which may reflect a higher degree of disturbance. Further work will analyse the soil carbon dynamics using radiocarbon as a tracer.

  12. [Vertical distribution of soil active carbon and soil organic carbon storage under different forest types in the Qinling Mountains].

    PubMed

    Wang, Di; Geng, Zeng-Chao; She, Diao; He, Wen-Xiang; Hou, Lin

    2014-06-01

    Adopting field investigation and indoor analysis methods, the distribution patterns of soil active carbon and soil carbon storage in the soil profiles of Quercus aliena var. acuteserrata (Matoutan Forest, I), Pinus tabuliformis (II), Pinus armandii (III), pine-oak mixed forest (IV), Picea asperata (V), and Quercus aliena var. acuteserrata (Xinjiashan Forest, VI) of Qinling Mountains were studied in August 2013. The results showed that soil organic carbon (SOC), microbial biomass carbon (MBC), dissolved organic carbon (DOC), and easily oxidizable carbon (EOC) decreased with the increase of soil depth along the different forest soil profiles. The SOC and DOC contents of different depths along the soil profiles of P. asperata and pine-oak mixed forest were higher than in the other studied forest soils, and the order of the mean SOC and DOC along the different soil profiles was V > IV > I > II > III > VI. The contents of soil MBC of the different forest soil profiles were 71.25-710.05 mg x kg(-1), with a content sequence of I > V > N > III > II > VI. The content of EOC along the whole soil profile of pine-oak mixed forest had a largest decline, and the order of the mean EOC was IV > V> I > II > III > VI. The sequence of soil organic carbon storage of the 0-60 cm soil layer was V > I >IV > III > VI > II. The MBC, DOC and EOC contents of the different forest soils were significanty correlated to each other. There was significant positive correlation among soil active carbon and TOC, TN. Meanwhile, there was no significant correlation between soil active carbon and other soil basic physicochemical properties.

  13. Carbon Dynamics in Vegetation and Soils

    NASA Technical Reports Server (NTRS)

    Trumbore, Susan; Chambers, Jeffrey Q.; Camargo, Plinio; Martinelli, Luiz; Santos, Joaquim

    2005-01-01

    The overall goals of CD-08 team in Phase I were to quantify the contributions of different components of the carbon cycle to overall ecosystem carbon balance in Amazonian tropical forests and to undertake process studies at a number of sites along the eastern LBA transect to understand how and why these fluxes vary with site, season, and year. We divided this work into a number of specific tasks: (1) determining the average rate (and variability) of tree growth over the past 3 decades; (2) determining age demographics of tree populations, using radiocarbon to determine tree age; (3) assessing the rate of production and decomposition of dead wood debris; (4) determining turnover rates for organic matter in soils and the mean age of C respired from soil using radiocarbon measurements; and (5) comparing our results with models and constructing models to predict the potential of tropical forests to function as sources or sinks of C. This report summarizes the considerable progress made towards our original goals, which have led to increased understanding of the potential for central Amazon forests to act as sources or sinks of carbon with altered productivity. The overall picture of tropical forest C dynamics emerging from our Phase I studies suggests that the fraction of gross primary production allocated to growth in these forests is only 25-30%, as opposed to the 50% assumed by many ecosystem models. Consequent slow tree growth rates mean greater mean tree age for a given diameter, as reflected in our measurements and models of tree age. Radiocarbon measurements in leaf and root litter suggest that carbon stays in living tree biomass for several years up to a decade before being added to soils, where decomposition is rapid. The time lags predicted from 14C, when coupled with climate variation on similar time scales, can lead to significant interannual variation in net ecosystem C exchange.

  14. Microbial carbon recycling: an underestimated process controlling soil carbon dynamics

    NASA Astrophysics Data System (ADS)

    Basler, A.; Dippold, M.; Helfrich, M.; Dyckmans, J.

    2015-07-01

    The mean residence times (MRT) of different compound classes of soil organic matter (SOM) do not match their inherent recalcitrance to decomposition. One reason for this is the stabilisation within the soil matrix, but recycling, i.e. the reuse of "old" organic material to form new biomass may also play a role as it uncouples the residence times of organic matter from the lifetime of discrete molecules in soil. We analysed soil sugar dynamics in a natural 30 years old labelling experiment after a~wheat-maize vegetation change to determine the extent of recycling and stabilisation in plant and microbial derived sugars: while plant derived sugars are only affected by stabilisation processes, microbial sugars may be subject to both, stabilisation and recycling. To disentangle the dynamics of soil sugars, we separated different density fractions (free particulate organic matter (fPOM), light occluded particulate organic matter (≤1.6 g cm-3; oPOM1.6), dense occluded particulate organic matter (≤2 g cm-3; oPOM2) and mineral-associated organic matter (>2 g cm-3; Mineral)) of a~silty loam under long term wheat and maize cultivation. The isotopic signature of sugars was measured by high pressure liquid chromatography coupled to isotope ratio mass spectrometry (HPLC/IRMS), after hydrolysis with 4 M Trifluoroacetic acid (TFA). While apparent mean residence times (MRT) of sugars were comparable to total organic carbon in the bulk soil and mineral fraction, the apparent MRT of sugars in the oPOM fractions were considerably lower than those of the total carbon of these fractions. This indicates that oPOM formation was fuelled by microbial activity feeding on new plant input. In the bulk soil, mean residence times of the mainly plant derived xylose (xyl) were significantly lower than those of mainly microbial derived sugars like galactose (gal), rhamnose (rha), fucose (fuc), indicating that recycling of organic matter is an important factor regulating organic matter dynamics

  15. Calculating carbon mass balance from unsaturated soil columns treated with CaSO₄₋minerals: test of soil carbon sequestration.

    PubMed

    Han, Young-Soo; Tokunaga, Tetsu K

    2014-12-01

    Renewed interest in managing C balance in soils is motivated by increasing atmospheric concentrations of CO2 and consequent climate change. Here, experiments were conducted in soil columns to determine C mass balances with and without addition of CaSO4-minerals (anhydrite and gypsum), which were hypothesized to promote soil organic carbon (SOC) retention and soil inorganic carbon (SIC) precipitation as calcite under slightly alkaline conditions. Changes in C contents in three phases (gas, liquid and solid) were measured in unsaturated soil columns tested for one year and comprehensive C mass balances were determined. The tested soil columns had no C inputs, and only C utilization by microbial activity and C transformations were assumed in the C chemistry. The measurements showed that changes in C inventories occurred through two processes, SOC loss and SIC gain. However, the measured SOC losses in the treated columns were lower than their corresponding control columns, indicating that the amendments promoted SOC retention. The SOC losses resulted mostly from microbial respiration and loss of CO2 to the atmosphere rather than from chemical leaching. Microbial oxidation of SOC appears to have been suppressed by increased Ca(2+) and SO4(2)(-) from dissolution of CaSO4 minerals. For the conditions tested, SIC accumulation per m(2) soil area under CaSO4-treatment ranged from 130 to 260 g C m(-1) infiltrated water (20-120 g C m(-1) infiltrated water as net C benefit). These results demonstrate the potential for increasing C sequestration in slightly alkaline soils via CaSO4-treatment.

  16. Benchmarking the inelastic neutron scattering soil carbon method

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The herein described inelastic neutron scattering (INS) method of measuring soil carbon was based on a new procedure for extracting the net carbon signal (NCS) from the measured gamma spectra and determination of the average carbon weight percent (AvgCw%) in the upper soil layer (~8 cm). The NCS ext...

  17. The responses of soil respiration to nitrogen addition in a temperate grassland in northern China.

    PubMed

    Luo, Qinpu; Gong, Jirui; Zhai, Zhanwei; Pan, Yan; Liu, Min; Xu, Sha; Wang, Yihui; Yang, Lili; Baoyin, Taoge-Tao

    2016-11-01

    Anthropogenic activities have increased nitrogen (N) inputs to grassland ecosystems. Knowledge of the impact of soil N availability on soil respiration (RS) is critical to understand soil carbon balances and their responses to global climate change. A 2-year field experiment was conducted to evaluate the response of RS to soil mineral N in a temperate grassland in northern China. RS, abiotic and biotic factors, and N mineralization were measured in the grassland, at rates of N addition ranging from 0 to 25gNm(-2)yr(-1). Annual and dormant-season RS ranged from 241.34 to 283.64g C m(-2) and from 61.34 to 83.84g C m(-2) respectively. High N application significantly increased RS, possibly due to increased root biomass and increased microbial biomass. High N treatment significantly increased soil NO3-N and inorganic N content compared with the control. The ratio of NO3-N to NH4-N and the N mineralization rate were significantly positively correlated with RS, but NH4-N was not correlated or negatively correlated with RS during the growing season. The temperature sensitivity of RS (Q10) was not significantly affected by N levels, and ranged from 1.90 to 2.20, but decreased marginally significantly at high N. RS outside the growing season is an important component of annual RS, accounting for 25.0 to 29.6% of the total. High N application indirectly stimulated RS by increasing soil NO3-N and net nitrification, thereby eliminating soil N limitations, promoting ecosystem productivity, and increasing soil CO2 efflux. Our results show the importance of distinguishing between NO3-N and NH4-N, as their impact on soil CO2 efflux differed.

  18. The responses of soil respiration to nitrogen addition in a temperate grassland in northern China.

    PubMed

    Luo, Qinpu; Gong, Jirui; Zhai, Zhanwei; Pan, Yan; Liu, Min; Xu, Sha; Wang, Yihui; Yang, Lili; Baoyin, Taoge-Tao

    2016-11-01

    Anthropogenic activities have increased nitrogen (N) inputs to grassland ecosystems. Knowledge of the impact of soil N availability on soil respiration (RS) is critical to understand soil carbon balances and their responses to global climate change. A 2-year field experiment was conducted to evaluate the response of RS to soil mineral N in a temperate grassland in northern China. RS, abiotic and biotic factors, and N mineralization were measured in the grassland, at rates of N addition ranging from 0 to 25gNm(-2)yr(-1). Annual and dormant-season RS ranged from 241.34 to 283.64g C m(-2) and from 61.34 to 83.84g C m(-2) respectively. High N application significantly increased RS, possibly due to increased root biomass and increased microbial biomass. High N treatment significantly increased soil NO3-N and inorganic N content compared with the control. The ratio of NO3-N to NH4-N and the N mineralization rate were significantly positively correlated with RS, but NH4-N was not correlated or negatively correlated with RS during the growing season. The temperature sensitivity of RS (Q10) was not significantly affected by N levels, and ranged from 1.90 to 2.20, but decreased marginally significantly at high N. RS outside the growing season is an important component of annual RS, accounting for 25.0 to 29.6% of the total. High N application indirectly stimulated RS by increasing soil NO3-N and net nitrification, thereby eliminating soil N limitations, promoting ecosystem productivity, and increasing soil CO2 efflux. Our results show the importance of distinguishing between NO3-N and NH4-N, as their impact on soil CO2 efflux differed. PMID:27396319

  19. Changes in soil carbon, nitrogen, and phosphorus due to land-use changes in Brazil

    NASA Astrophysics Data System (ADS)

    Groppo, J. D.; Lins, S. R. M.; Camargo, P. B.; Assad, E. D.; Pinto, H. S.; Martins, S. C.; Salgado, P. R.; Evangelista, B.; Vasconcellos, E.; Sano, E. E.; Pavão, E.; Luna, R.; Martinelli, L. A.

    2015-08-01

    In this paper, soil carbon, nitrogen and phosphorus concentrations and stocks were investigated in agricultural and natural areas in 17 plot-level paired sites and in a regional survey encompassing more than 100 pasture soils In the paired sites, elemental soil concentrations and stocks were determined in native vegetation (forests and savannas), pastures and crop-livestock systems (CPSs). Nutrient stocks were calculated for the soil depth intervals 0-10, 0-30, and 0-60 cm for the paired sites and 0-10, and 0-30 cm for the pasture regional survey by sum stocks obtained in each sampling intervals (0-5, 5-10, 10-20, 20-30, 30-40, 40-60 cm). Overall, there were significant differences in soil element concentrations and ratios between different land uses, especially in the surface soil layers. Carbon and nitrogen contents were lower, while phosphorus contents were higher in the pasture and CPS soils than in native vegetation soils. Additionally, soil stoichiometry has changed with changes in land use. The soil C : N ratio was lower in the native vegetation than in the pasture and CPS soils, and the carbon and nitrogen to available phosphorus ratio (PME) decreased from the native vegetation to the pasture to the CPS soils. In the plot-level paired sites, the soil nitrogen stocks were lower in all depth intervals in pasture and in the CPS soils when compared with the native vegetation soils. On the other hand, the soil phosphorus stocks were higher in all depth intervals in agricultural soils when compared with the native vegetation soils. For the regional pasture survey, soil nitrogen and phosphorus stocks were lower in all soil intervals in pasture soils than in native vegetation soils. The nitrogen loss with cultivation observed here is in line with other studies and it seems to be a combination of decreasing organic matter inputs, in cases where crops replaced native forests, with an increase in soil organic matter decomposition that leads to a decrease in the long

  20. Soil Organic Carbon and Below Ground Biomass: Development of New GLOBE Special Measurements

    NASA Technical Reports Server (NTRS)

    Levine, Elissa; Haskett, Jonathan

    1999-01-01

    A scientific consensus is building that changes in the atmospheric concentrations of radiatively active gases are changing the climate (IPCC, 1990). One of these gases CO2 has been increasing in concentration due to additions from anthropogenic sources that are primarily industrial and land use related. The soil contains a very large pool of carbon, estimated at 1550 Gt (Lal 1995) which is larger than the atmospheric and biosphere pools of carbon combined (Greenland, 1995). The flux between the soil and the atmosphere is very large, 60 Pg C/yr (Lal 1997), and is especially important because the soil can act as either a source or a sink for carbon. On any given landscape, as much as 50% of the biomass that provides the major source of carbon can be below ground. In addition, the movement of carbon in and out of the soil is mediated by the living organisms. At present, there is no widespread sampling of soil biomass in any consistent or coordinated manner. Current large scale estimates of soil carbon are limited by the number and widely dispersed nature of the data points available. A measurement of the amount of carbon in the soil would supplement existing carbon data bases as well as provide a benchmark that can be used to determine whether the soil is storing carbon or releasing it to the atmosphere. Information on the below ground biomass would be a valuable addition to our understanding of net primary productivity and standing biomass. The addition of these as special measurements within GLOBE would be unique in terms of areal extent and continuity, and make a real contribution to scientific understanding of carbon dynamics.

  1. Addition of a clay subsoil to a sandy top soil alters CO2 release and the interactions in residue mixtures.

    PubMed

    Shi, Andong; Marschner, Petra

    2013-11-01

    Addition of clay-rich subsoils to sandy top soils is an agricultural management option to increase water and nutrient retention and may also increase organic carbon sequestration by decreasing the decomposition rates. An incubation experiment was carried out in a loamy sand top soil mixed with a clay-rich subsoil (84% clay) at 0, 10 and 30% (w/w) amended with finely ground mature shoot residues of two native perennial grasses and annual barley individually or in 1:1 mixtures of two residues. Extractable C, microbial biomass C, available N and soil pH were analysed at days 0, 3, 14 and 28. Cumulative respiration after 28 days was highest with barley residue and lowest with Wallaby grass at all clay soil addition rates; 30% clay soil addition reduced cumulative respiration, especially with barley alone. In the mixture of native grasses and barley, the measured respiration was lower than expected at a clay soil addition rate of 10%. A synergistic effect (higher than expected cumulative respiration) was only found in mixture of Kangaroo grass and barley at a clay soil addition rate of 30%. Clay soil addition also decreased extractable C, available N and soil pH. The temporal change in microbial biomass C and available N in residue mixtures differed among clay addition rates. In the mixture of Wallaby grass and Kangaroo grass, microbial biomass C (MBC) decreased from day 0 to day 28 at clay soil addition rates of 0 and 10%, whereas at 30% clay MBC increased from day 0 to day 3 and then decreased. Our study shows that addition of a clay-rich subsoil to a loamy sand soil can increase C sequestration by reducing CO2 release and extractable C which are further modulated by the type of residues present individually or as mixtures.

  2. Soil physical and hydrological properties as affected by long-term addition of various organic amendments

    NASA Astrophysics Data System (ADS)

    Eden, Marie; Völkel, Jörg; Mercier, Vincent; Labat, Christophe; Houot, Sabine

    2014-05-01

    The use of organic residues as soil amendments in agriculture not only reduces the amount of waste needing to be disposed of; it may also lead to improvements in soil properties, including physical and hydrological ones. The present study examines a long-term experiment called "Qualiagro", run jointly by INRA and Veolia Environment in Feucherolles, France (near Paris). It was initiated in 1998 on a loess-derived silt loam (787 g/kg silt, 152 g/kg clay) and includes ten treatments: four types of organic amendments and a control (CNT) each at two levels of mineral nitrogen (N) addition: minimal (Nmin) and optimal (Nopt). The amendments include three types of compost and farmyard manure (FYM), which were applied every other year at a rate of ca. 4 t carbon ha-1. The composts include municipal solid waste compost (MSW), co-compost of green wastes and sewage sludge (GWS), and biowaste compost (BIO). The plots are arranged in a randomized block design and have a size of 450 m²; each treatment is replicated four times (total of 40 plots). Ca. 15 years after the start of the experiment soil organic carbon (OC) had continuously increased in the amended plots, while it remained stable or decreased in the control plots. This compost- or manure-induced increase in OC plays a key role, affecting numerous dependant soil properties like bulk density, porosity and water retention. The water holding capacity (WHC) of a soil is of particular interest to farmers in terms of water supply for plants, but also indicates soil quality and functionality. Addition of OC may affect WHC in different ways: carbon-induced aggregation may increase larger-pore volume and hence WHC at the wet end while increased surface areas may lead to an increased retention of water at the dry end. Consequently it is difficult to predict (e.g. with pedotransfer functions) the impact on the amount of water available for plants (PAW), which was experimentally determined for the soils, along with the entire range

  3. Do microbes destabilise old soil organic matter after fresh substrate addition?

    NASA Astrophysics Data System (ADS)

    Derrien, Delphine; Plain, Caroline; Courty, Pierre-Emmanuel; Gelhaye, Louisette; Moerdijk-Poortvliet, Tanja; Thomas, Fabien; Versini, Antoine; Zeller, Bernd; Koutika, Lydie-Stella; Boschker, Eric; Epron, Daniel

    2014-05-01

    The input of fresh organic matter to soil may stimulate microbial activity and alter soil carbon storage by enhancing mineralization of native soil organic carbon (SOC). Assessing the age of sequestered SOC utilised by stimulated microbes is a major challenge as the destabilisation of old SOC would be much more damageable for the overall carbon budget than the mobilization of recent SOC. Here, we investigated the microbial populations sequentially activated after the addition of a labile substrate. We questioned wether they have distinct metabolic potential and we characterised the age of the native SOC they mineralised. We used C3-C4 soils from Congolese Eucalyptus plantations that were previously under savannah: old (C4) and recent (C3) SOC exhibited different delta 13C. Soils were amended with glucose and incubated for one week. To partition respiration sources, the delta 13C of CO2 was continuously recorded using a tuneable diode laser spectrometer (TDLS). To characterise active microbial populations, this was combined with phospholipids fatty acids (PLFA) analyses and potential metabolic activities measurements after two and seven days of incubation. A peak of glucose mineralization occurred after 17 hours of incubation. After the peak of glucose consumption, over-mineralization of native SOC occurred for some days, first affecting the recent C3 SOC, and later the old C4 SOC. Before this peak, some decomposer populations with a strong feeding preference for recent SOC were triggered by glucose addition. They were likely responsible for glucose consumption but also for the subsequent enhanced mineralization of recent C3 SOC. They were then out-competed by slower communities preferentially utilising the old C4 SOC and displaying a high potential for degrading P- and N- containing substrates. As nitrogen enrichment of old soil organic matter is a general feature, we postulated that nitrogen exhaustion in the poor soil solution was responsible for the succession

  4. 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.

  5. The impact of hazelnuts in land-use changes on soil carbon and in situ soil respiration dynamics.

    PubMed

    Oral, HasanVolkan; Guney, Mert; Kucuker, Mehmet Ali; Onay, Turgut T; Copty, Nadim K; Mater, Baris; Yenigun, Orhan

    2013-11-15

    Our study assessed the impact of hazelnuts (Coryllus avellena L.) in land-use conversion from forest (F) to agricultural land (AL) on various attributes of soil respiration dynamics, such as soil elemental carbon (C%) content, microbial respiration, bulk density, soil pH, electrical conductivity, and seasonal variations. We developed soil C% models to compare soil C% between F and AL soils. Four field trips were conducted in the winter and summer of 2008 and the spring and fall of 2009 in the Karasu region of Turkey. During each trip, 42 sites were visited F (n = 21) and AL (n = 21). Our results showed that hazelnuts plantations in AL could reduce elemental C% by 27% (winter 2008), 16% (summer 2008), 41% (spring 2009), and 22% (fall 2009) in the four seasons studied when compared to F soils. In situ soil respiration was also reduced by 31% (spring 2008), 67% (fall 2008), 88% (spring 2009), and 79% (fall 2009) in AL soils over F soils. The percent of organic matter of AL soils was declined by 36% (winter 2008), 23% (summer 2008), 34% (spring 2009), and 26% (fall 2009) in comparison to F soils. Significant reductions in the correlation between C%-percent clay and C%-electrical conductivity were also recorded for AL soils over F soils. Furthermore, AL soils showed higher bulk density (7.4% and 7%) when compared to F soils. We also found that in situ soil respiration had significant seasonal correlations (p < 0.05) with soil pH (0.537), soil temperature, and percent clay (-0.486) in F soils (summer 2008, spring 2009). Additionally, we found that seasonal variations of four sampling seasons had a moderate impact on in situ respiration and that the differences were statistically significant, except for the winter-summer and spring-fall seasonal pairs. Linear regression C models showed significant differences for F and AL soils.

  6. Effects of Nutrient Enrichment on Microbial Communities and Carbon Cycling in Wetland Soils

    NASA Astrophysics Data System (ADS)

    Hartman, W.; Neubauer, S. C.; Richardson, C. J.

    2013-12-01

    Soil microbial communities are responsible for catalyzing biogeochemical transformations underlying critical wetland functions, including cycling of carbon (C) and nutrients, and emissions of greenhouse gasses (GHG). Alteration of nutrient availability in wetland soils may commonly occur as the result of anthropogenic impacts including runoff from human land uses in uplands, alteration of hydrology, and atmospheric deposition. However, the impacts of altered nutrient availability on microbial communities and carbon cycling in wetland soils are poorly understood. To assess these impacts, soil microbial communities and carbon cycling were determined in replicate experimental nutrient addition plots (control, +N, +P, +NP) across several wetland types, including pocosin peat bogs (NC), freshwater tidal marshes (GA), and tidal salt marshes (SC). Microbial communities were determined by pyrosequencing (Roche 454) extracted soil DNA, targeting both bacteria (16S rDNA) and fungi (LSU) at a depth of ca. 1000 sequences per plot. Wetland carbon cycling was evaluated using static chambers to determine soil GHG fluxes, and plant inclusion chambers were used to determine ecosystem C cycling. Soil bacterial communities responded to nutrient addition treatments in freshwater and tidal marshes, while fungal communities did not respond to treatments in any of our sites. We also compared microbial communities to continuous biogeochemical variables in soil, and found that bacterial community composition was correlated only with the content and availability of soil phosphorus, while fungi responded to phosphorus stoichiometry and soil pH. Surprisingly, we did not find a significant effect of our nutrient addition treatments on most metrics of carbon cycling. However, we did find that several metrics of soil carbon cycling appeared much more related to soil phosphorus than to nitrogen or soil carbon pools. Finally, while overall microbial community composition was weakly correlated with

  7. Stability of organic carbon in deep soil layers controlled by fresh carbon supply.

    PubMed

    Fontaine, Sébastien; Barot, Sébastien; Barré, Pierre; Bdioui, Nadia; Mary, Bruno; Rumpel, Cornelia

    2007-11-01

    The world's soils store more carbon than is present in biomass and in the atmosphere. Little is known, however, about the factors controlling the stability of soil organic carbon stocks and the response of the soil carbon pool to climate change remains uncertain. We investigated the stability of carbon in deep soil layers in one soil profile by combining physical and chemical characterization of organic carbon, soil incubations and radiocarbon dating. Here we show that the supply of fresh plant-derived carbon to the subsoil (0.6-0.8 m depth) stimulated the microbial mineralization of 2,567 +/- 226-year-old carbon. Our results support the previously suggested idea that in the absence of fresh organic carbon, an essential source of energy for soil microbes, the stability of organic carbon in deep soil layers is maintained. We propose that a lack of supply of fresh carbon may prevent the decomposition of the organic carbon pool in deep soil layers in response to future changes in temperature. Any change in land use and agricultural practice that increases the distribution of fresh carbon along the soil profile could however stimulate the loss of ancient buried carbon.

  8. Plant functional traits and soil carbon sequestration in contrasting biomes.

    PubMed

    De Deyn, Gerlinde B; Cornelissen, Johannes H C; Bardgett, Richard D

    2008-05-01

    Plant functional traits control a variety of terrestrial ecosystem processes, including soil carbon storage which is a key component of the global carbon cycle. Plant traits regulate net soil carbon storage by controlling carbon assimilation, its transfer and storage in belowground biomass, and its release from soil through respiration, fire and leaching. However, our mechanistic understanding of these processes is incomplete. Here, we present a mechanistic framework, based on the plant traits that drive soil carbon inputs and outputs, for understanding how alteration of vegetation composition will affect soil carbon sequestration under global changes. First, we show direct and indirect plant trait effects on soil carbon input and output through autotrophs and heterotrophs, and through modification of abiotic conditions, which need to be considered to determine the local carbon sequestration potential. Second, we explore how the composition of key plant traits and soil biota related to carbon input, release and storage prevail in different biomes across the globe, and address the biome-specific mechanisms by which plant trait composition may impact on soil carbon sequestration. We propose that a trait-based approach will help to develop strategies to preserve and promote carbon sequestration.

  9. Phosphorus applications improved the soil microbial responses under nitrogen additions in Chinese fir plantations of subtropical China

    NASA Astrophysics Data System (ADS)

    Zhang, Xinyu; Li, Dandan; Yang, Yang; Tang, Yuqian; Wang, Huimin; Chen, Fusheng; Sun, Xiaomin

    2016-04-01

    Nitrogen (N) deposition and low soil phosphorus (P) content aggravate the P limitation in subtropical forest soils. However, the responses of soil microbial communities, enzyme kinetics, and N cycling genes to P additions in subtropical plantations are still not clear. The hypothesis that P application can alleviate the limitation and improve the soil microbial properties was tested by long term field experiment in the Chinese fir plantations in subtropical China. Thirty 20m×20m plots were established in November 2011 and six different treatments were randomly distributed with five replicates. The treatments are control (CK, no N and P application), low N addition (N1: 50 kg N ha-1 yr-1), high N addition (N2: 100 kg N ha-1 yr-1), P addition (P: 50 kg P ha-1 yr-1), low N and P addition (N1P: 50 kg N ha-1 yr-1 and 50 kg P ha-1 yr-1) and high N and P addition (N2P: 100 kg N ha-1 yr-1 and 50 kg P ha-1 yr-1). A suite of responses of soil microorganism across four years (2012-2015) during three seasons (spring, summer and autumn) were measured. Following 4 years of N amendments, fertilized soils were more acidic and had lower soil microbial biomass carbon contents than CK. However, P alleviated the soil acidification and increased the soil microbial biomass carbon contents. Increases in microbial PLFA biomarkers and exoenzyme kinetics in N fertilized plots were observed in the initial year (2013) but reduced since then (2014 and 2015). Whereas P amendments increased the soil PLFA biomarkers and exoenzyme kinetics through the four years except that the acid phosphatase activities declined after 3 years applications. P applications enhanced the soil N cycling by increases the abundances of nitrifiers (ammonia-oxidizing archea) and denitrifiers (nos Z, norG, and nirK). The bacterial and fungal residue carbons (calculated by amino sugar indicators) were higher under NP fertilizations than the other treatments. Our results suggest that P application could improve the soil

  10. Influences of winery-distillery waste compost stability and soil type on soil carbon dynamics in amended soils.

    PubMed

    Bustamante, M A; Said-Pullicino, D; Paredes, C; Cecilia, J A; Moral, R

    2010-10-01

    The application of organic materials to replenish soil organic matter and improve soil structure and fertility has become a common agronomic practice. This research deals with the effects of soil amendment with winery and distillery waste composts on organic carbon (C) mineralisation in two arable soils. A sandy-loam and clay-loam soil were treated and incubated with a number organic materials obtained from the co-composting of different proportions of grape stalk, grape marc, exhausted grape marc and vinasse, with sewage sludge or animal manure. Moreover, the effect of compost stability on C mineralisation dynamics was studied by applying organic materials from different stages of the composting process. The results obtained showed that the addition of exogenous organic matter stimulated microbial growth, enhanced soil respiration and increased water-extractable C contents in both soils, particularly in the days immediately following amendment. The initial composition of the different organic materials used, especially for the mature samples, and the texture of the receiving soil did not influence significantly the C mineralisation final values, with around 11-20% of the added organic C being mineralised over the first 140 days. However, the contribution of organic amendment to the labile organic C pool, maximum rates of soil respiration, as well as the extent of initial disturbance of the soil microbiota were all found to be related to the degree of organic matter stability. Moreover, irrespective of the type and stability of the organic amendment, the mineralogical composition of the receiving soil was found to significantly influence its resilience in such systems.

  11. Influences of winery-distillery waste compost stability and soil type on soil carbon dynamics in amended soils.

    PubMed

    Bustamante, M A; Said-Pullicino, D; Paredes, C; Cecilia, J A; Moral, R

    2010-10-01

    The application of organic materials to replenish soil organic matter and improve soil structure and fertility has become a common agronomic practice. This research deals with the effects of soil amendment with winery and distillery waste composts on organic carbon (C) mineralisation in two arable soils. A sandy-loam and clay-loam soil were treated and incubated with a number organic materials obtained from the co-composting of different proportions of grape stalk, grape marc, exhausted grape marc and vinasse, with sewage sludge or animal manure. Moreover, the effect of compost stability on C mineralisation dynamics was studied by applying organic materials from different stages of the composting process. The results obtained showed that the addition of exogenous organic matter stimulated microbial growth, enhanced soil respiration and increased water-extractable C contents in both soils, particularly in the days immediately following amendment. The initial composition of the different organic materials used, especially for the mature samples, and the texture of the receiving soil did not influence significantly the C mineralisation final values, with around 11-20% of the added organic C being mineralised over the first 140 days. However, the contribution of organic amendment to the labile organic C pool, maximum rates of soil respiration, as well as the extent of initial disturbance of the soil microbiota were all found to be related to the degree of organic matter stability. Moreover, irrespective of the type and stability of the organic amendment, the mineralogical composition of the receiving soil was found to significantly influence its resilience in such systems. PMID:20382012

  12. Transition metal-catalyzed process for addition of amines to carbon-carbon double bonds

    DOEpatents

    Hartwig, John F.; Kawatsura, Motoi; Loeber, Oliver

    2002-01-01

    The present invention is directed to a process for addition of amines to carbon-carbon double bonds in a substrate, comprising: reacting an amine with a compound containing at least one carbon-carbon double bond in the presence a transition metal catalyst under reaction conditions effective to form a product having a covalent bond between the amine and a carbon atom of the former carbon-carbon double bond. The transition metal catalyst comprises a Group 8 metal and a ligand containing one or more 2-electron donor atoms. The present invention is also directed to enantioselective reactions of amine compounds with compounds containing carbon-carbon double bonds, and a calorimetric assay to evaluate potential catalysts in these reactions.

  13. Use of commercial soil amendments in initial soils (II) - Impact on soil respiratory and carbon isotopic characteristics

    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.

  14. [Organic carbon decomposition rate in different soil types].

    PubMed

    Yin, Yun-Feng; Cai, Zu-Cong

    2007-10-01

    With incubation experiment, this paper studied the decomposition rate of organic carbon in black soil, fluvo-aquic soil, and red soil. It was shown that these three soil types had significantly different decomposition rate constant of organic carbon (P < 0.05 ), with the corresponding value being 2.2 x 10(-4) x d(-1), 6.0 x 10(-4) x d(-1), and 3.4 x 10(-4) x d(-1), respectively. The decomposition rate constant had a significant correlation with soil pH, which was increased greatly when the soil pH was < 5.5 or > 8.0, and a significant negative correlation with the contents of soil clay and silt, indicating that soil clay and silt content was one of the dominant factors affecting the decomposition rate of organic carbon in these soil types.

  15. Soil organic carbon assessments in cropping systems using isotopic techniques

    NASA Astrophysics Data System (ADS)

    Martín De Dios Herrero, Juan; Cruz Colazo, Juan; Guzman, María Laura; Saenz, Claudio; Sager, Ricardo; Sakadevan, Karuppan

    2016-04-01

    Introduction of improved farming practices are important to address the challenges of agricultural production, food security, climate change and resource use efficiency. The integration of livestock with crops provides many benefits including: (1) resource conservation, (2) ecosystem services, (3) soil quality improvements, and (4) risk reduction through diversification of enterprises. Integrated crop livestock systems (ICLS) with the combination of no-tillage and pastures are useful practices to enhance soil organic carbon (SOC) compared with continuous cropping systems (CCS). In this study, the SOC and its fractions in two cropping systems namely (1) ICLS, and (2) CCS were evaluated in Southern Santa Fe Province in Argentina, and the use of delta carbon-13 technique and soil physical fractionation were evaluated to identify sources of SOC in these systems. Two farms inside the same soil cartographic unit and landscape position in the region were compared. The ICLS farm produces lucerne (Medicago sativa Merrill) and oat (Avena sativa L.) grazed by cattle alternatively with grain summer crops sequence of soybean (Glicine max L.) and corn (Zea mays L.), and the farm under continuous cropping system (CCS) produces soybean and corn in a continuous sequence. The soil in the area is predominantly a Typic Hapludoll. Soil samples from 0-5 and 0-20 cm depths (n=4) after the harvest of grain crops were collected in each system and analyzed for total organic carbon (SOC, 0-2000 μm), particulate organic carbon (POC, 50-100 μm) and mineral organic carbon (MOC, <50 μm). Delta carbon-13 was determined by isotopic ratio mass spectrometry. In addition, a site with natural vegetation (reference site, REF) was also sampled for delta carbon-13 determination. ANOVA and Tukey statistical analysis were carried out for all data. The SOC was higher in ICLS than in CCS at both depths (20.8 vs 17.7 g kg-1 for 0-5 cm and 16.1 vs 12.7 g kg-1 at 0-20 cm, respectively, P<0.05). MOC was

  16. Potential effect of No-till management on carbon in the agricultural soils of the former Soviet Union

    SciTech Connect

    Gaston, G.G.; Kolchugina, T.; Vinson, T.S.

    1993-01-01

    Agricultural soils act as both a source and a sink for atmospheric carbon. Since the onset of cultivation, the 211.5 million ha of agricultural soils in the former Soviet Union (FSU) have lost 10.2 Gt of carbon. No-till management represents a promising option to increase the amount of carbon sequestered in the agricultural soil of the FSU. No-till management reduces erosion and sequesters additional carbon in the soil by lowering the soil temperature and raising soil moisture. To determine the carbon sequestered under no-till management, a data base containing precultivation estimates of soil carbon for the seven major classes of soil found in the agricultural areas of the FSU was used to establish an equilibrium carbon content for each soil. Other published data provided a method to quantify the change in soil carbon brought about by converting to no-till management. Soils suitable for no-till management were analyzed and estimates of changes in carbon storage were made. No-till management is not suitable in areas where crop production is limited by cold, wet soils. (Copyright (c) 1993 Elsevier Science Publishers B.V.)

  17. Effects of nitrogen additions on above- and belowground carbon dynamics in two tropical forests

    SciTech Connect

    Cusack, D.; Silver, W.L.; Torn, M.S.; McDowell, W.H.

    2011-04-15

    Anthropogenic nitrogen (N) deposition is increasing rapidly in tropical regions, adding N to ecosystems that often have high background N availability. Tropical forests play an important role in the global carbon (C) cycle, yet the effects of N deposition on C cycling in these ecosystems are poorly understood. We used a field N-fertilization experiment in lower and upper elevation tropical rain forests in Puerto Rico to explore the responses of above- and belowground C pools to N addition. As expected, tree stem growth and litterfall productivity did not respond to N fertilization in either of these Nrich forests, indicating a lack of N limitation to net primary productivity (NPP). In contrast, soil C concentrations increased significantly with N fertilization in both forests, leading to larger C stocks in fertilized plots. However, different soil C pools responded to N fertilization differently. Labile (low density) soil C fractions and live fine roots declined with fertilization, while mineral-associated soil C increased in both forests. Decreased soil CO2 fluxes in fertilized plots were correlated with smaller labile soil C pools in the lower elevation forest (R2 = 0.65, p\\0.05), and with lower live fine root biomass in the upper elevation forest (R2 = 0.90, p\\0.05). Our results indicate that soil C storage is sensitive to N deposition in tropical forests, even where plant productivity is not N-limited. The mineral-associated soil C pool has the potential to respond relatively quickly to N additions, and can drive increases in bulk soil C stocks in tropical forests.

  18. [Roles of soil dissolved organic carbon in carbon cycling of terrestrial ecosystems: a review].

    PubMed

    Li, Ling; Qiu, Shao-Jun; Liu, Jing-Tao; Liu, Qing; Lu, Zhao-Hua

    2012-05-01

    Soil dissolved organic carbon (DOC) is an active fraction of soil organic carbon pool, playing an important role in the carbon cycling of terrestrial ecosystems. In view of the importance of the carbon cycling, this paper summarized the roles of soil DOC in the soil carbon sequestration and greenhouse gases emission, and in considering of our present ecological and environmental problems such as soil acidification and climate warming, discussed the effects of soil properties, environmental factors, and human activities on the soil DOC as well as the response mechanisms of the DOC. This review could be helpful to the further understanding of the importance of soil DOC in the carbon cycling of terrestrial ecosystems and the reduction of greenhouse gases emission.

  19. Quantification of soil organic carbon sequestration potential in cropland: a model approach.

    PubMed

    Qin, ZhangCai; Huang, Yao

    2010-07-01

    Agroecosystems have a critical role in the terrestrial carbon cycling process. Soil organic carbon (SOC) in cropland is of great importance for mitigating atmospheric carbon dioxide increases and for global food security. With an understanding of soil carbon saturation, we analyzed the datasets from 95 global long-term agricultural experiments distributed across a vast area spanning wide ranges of temperate, subtropical and tropical climates. We then developed a statistical model for estimating SOC sequestration potential in cropland. The model is driven by air temperature, precipitation, soil clay content and pH, and explains 58% of the variation in the observed soil carbon saturation (n=76). Model validation using independent data observed in China yielded a correlation coefficient R (2) of 0.74 (n=19, P<0.001). Model sensitivity analysis suggested that soils with high clay content and low pH in the cold, humid regions possess a larger carbon sequestration potential than other soils. As a case study, we estimated the SOC sequestration potential by applying the model in Henan Province. Model estimations suggested that carbon (C) density at the saturation state would reach an average of 32 t C ha(-1) in the top 0-20 cm soil depth. Using SOC density in the 1990s as a reference, cropland soils in Henan Province are expected to sequester an additional 100 Tg C in the future.

  20. Non-destructive measurement of carbonic anhydrase activity and the oxygen isotope composition of soil water

    NASA Astrophysics Data System (ADS)

    Jones, Sam; Sauze, Joana; Ogée, Jérôme; Wohl, Steven; Bosc, Alexandre; Wingate, Lisa

    2016-04-01

    oxygen isotope composition of ambient CO2. This non-destructive approach was tested through laboratory incubations of air-dried soils that were re-wetted with water of known isotopic composition. Performance was assessed by comparing estimates of the soil water oxygen isotope composition derived from open chamber flux measurements with those measured in the irrigation water and soil water extracted following incubations. The influence of soil pH and bovine carbonic anhydrase additions on these estimates was also investigated. Coherent values were found between the soil water composition estimates obtained from the dual steady state approach and those measured for irrigation waters. Estimates of carbonic anhydrase activity made using this approach also reflected well artificial increases to the concentration of carbonic anhydrase and indicated that this activity was sensitive to soil pH.

  1. Aggregate formation and soil carbon sequestration by earthworms at the ORNL FACE experiment

    NASA Astrophysics Data System (ADS)

    Sanchez-de Leon, Y.; Gonzalez-Meler, M. A.; Lugo-Perez, J.; Wise, D. H.; Jastrow, J. D.

    2012-12-01

    Earthworms have an important role in soil carbon sequestration, but their contribution to carbon sequestration in soils exposed to elevated atmospheric CO2 concentrations has been largely overlooked. Previous studies at the Oak Ridge National Laboratory Free Air CO2 Experiment (ORNL FACE) site showed that the formation of soil aggregates is a key mechanism for soil carbon sequestration. We did a microcosm experiment to quantify earthworm-mediated aggregate formation and compare between two earthworm species with different feeding habits (endogeic vs. epi-edogeic). In addition, we wanted to identify the carbon source (soil, leaf litter or root litter) within aggregates formed by earthworms. We used 13C-depleted soil and 15N-enriched sweetgum (Liquidambar styraciflua) leaf and root litter collected from the ORNL FACE site to assess soil aggregate formation of the native, endogeic earthworm Diplocardia sp. and European, epi-endogeic earthworm Lumbricus rubellus. Both earthworm species are present at the ORNL FACE site. We crushed, sieved (< 250 μm) soil and prepared four treatments: (I) soil only; (II) soil and plant material; (III) soil, plant material and Diplocardia sp.; (IV) soil, plant material and L. rubellus. All treatments were at 30% water content and temperature was maintained at 20°C. The incubation period lasted 26 days. We measured aggregate size distribution, total aggregate carbon content and 13C and 15N to elucidate aggregate carbon source. Newly formed soil macroaggregates (> 250 μm) were higher in treatments with earthworms (III and IV) than in treatments without earthworms (I and II) (p = 0.02). Within macroaggregates, most of the carbon was soil-derived. Leaf and root-derived carbon was found in treatment IV only. Our results suggest that earthworms at the ORNL FACE site directly contribute to the formation of soil aggregates, thus contributing to soil carbon sequestration. Carbon source within macroaggregates correspond with earthworm feeding

  2. Soil Organic Matter Stability and Soil Carbon Storage with Changes in Land Use Intensity in Uganda

    NASA Astrophysics Data System (ADS)

    Tiemann, L. K.; Grandy, S.; Hartter, J.

    2014-12-01

    As the foundation of soil fertility, soil organic matter (SOM) formation and break-down is a critical factor of agroecosystem sustainability. In tropical systems where soils are quickly weathered, the link between SOM and soil fertility is particularly strong; however, the mechanisms controlling the stabilization and destabilization of SOM are not well characterized in tropical soils. In western Uganda, we collected soil samples under different levels of land use intensity including maize fields, banana plantations and inside an un-cultivated native tropical forest, Kibale National Park (KNP). To better understand the link between land use intensity and SOM stability we measured total soil C and N, and respiration rates during a 369 d soil incubation. In addition, we separated soils into particle size fractions, and mineral adsorbed SOM in the silt (2-50 μm ) and clay (< 2 μm) fractions was dissociated, purified and chemically characterized via pyrolysis-GC/MS. Cultivated soil C and N have declined by 22 and 48%, respectively, in comparison to uncultivated KNP soils. Incubation data indicate that over the last decade, relatively accessible and labile soil organic carbon (SOC) pools have been depleted by 55-59% in cultivated soils. As a result of this depletion, the chemical composition of SOM has been altered such that clay and silt associated SOM differed significantly between agricultural fields and KNP. In particular, nitrogen containing compounds were in lower abundance in agricultural compared to KNP soils. This suggests that N depletion due to agriculture has advanced to pools of mineral associated organic N that are typically protected from break-down. In areas where land use intensity is relatively greater, increases in polysaccharides and lipids in maize fields compared to KNP indicate increases in microbial residues and decomposition by-products as microbes mine SOM for organic N. Chemical characterization of post-incubation SOM will help us better

  3. Enhancing soil sorption capacity of an agricultural soil by addition of three different organic wastes.

    PubMed

    Rojas, Raquel; Morillo, José; Usero, José; Delgado-Moreno, Laura; Gan, Jay

    2013-08-01

    This study evaluated the ability of three unmodified organic residues (composted sewage sludge, RO1; chicken manure, RO2; and a residue from olive oil production called 'orujillo', RO3) and a soil to sorb six pesticides (atrazine, lindane, alachlor, chlorpyrifos, chlorfenvinphos and endosulfan sulfate) and thereby explored the potential environmental value of these organic residues for mitigating pesticide pollution in agricultural production and removing contaminants from wastewater. Pesticide determination was carried out using gas chromatography coupled with mass spectrometry. Adsorption data were analyzed by the Langmuir and Freundlich adsorption approaches. Experimental results showed that the Freundlich isotherm model best described the adsorption process and that Kf values increased with an increase in organic matter (OM) content of the amended soil. The order of adsorption of pesticides on soils was: chlorpyrifos≥endosulfan sulfate>chlorfenvinphos≥lindane>alachlor≥atrazine. The sorption was greater for the most hydrophobic compounds and lower for the most polar ones, as corroborated by a negative correlation between Kf values and solubility. Sorption increased with an increase in organic matter. Sorption capacity was positively correlated with the organic carbon (OC) content. The organic amendment showing the maximum sorption capacity was RO3 in all cases, except for chlorfenvinphos, in which it was RO2. The order of adsorption capacity of the amendments depended on the pesticide and the organic dosage. In the case of the 10% amendment the order was RO3>RO2>RO1>soil, except for chlorfenvinphos, in which it was RO2>RO3>RO1>soil, and atrazine, where RO2 and RO3 amendments had the same effect on the soil sorption capacity (RO2≥RO3>RO1>soil).

  4. Effect of activated carbon on microbial bioavailability of phenanthrene in soils

    SciTech Connect

    Yang, Y.; Hunter, W.; Tao, S.; Crowley, D.; Gan, J.

    2009-11-15

    Bioavailability is a governing factor that controls the rate of biological degradation of hydrophobic organic contaminants in soil. Among the solid phases that can adsorb hydrophobic organic contaminants in soil, black carbon (BC) exerts a particularly significant effect on phase distribution. However, knowledge on the effect of BC on the microbial availability of polycyclic aromatic hydrocarbons in soil is still limited. In the present study, the effect of a coal-derived activated carbon on the bioavailability of phenanthrene (PHE) during its degradation by Mycobacterium vanbaalenii PYR-1 was measured in three soils. The freely dissolved concentration of PHE was concurrently determined in soil solutions using disposable polydimethylsiloxane fibers. The results showed that PHE mineralization was significantly inhibited after addition of activated carbon in all test soils. After 216 h, only 5.20, 5.83, and 6.85% of PHE was degraded in the 0.5% BC-amended soils initially containing organic carbon at 0.23, 2.1, and 7.1%, respectively. Significant correlation was found between PHE degradability and freely dissolved concentration, suggesting that BC affected PHE bioavailability by decreasing chemical activity. The effect of activated carbon in the amended soils was attributed to its enhancement of soil surface areas and pore volumes. Results from the present study clearly highlighted the importance of BC for influencing the microbial availability of polycyclic aromatic hydrocarbons in soils.

  5. Decadally cycling soil carbon is more sensitive to warming than faster-cycling soil carbon.

    PubMed

    Lin, Junjie; Zhu, Biao; Cheng, Weixin

    2015-12-01

    The response of soil organic carbon (SOC) pools to globally rising surface temperature crucially determines the feedback between climate change and the global carbon cycle. However, there is a lack of studies investigating the temperature sensitivity of decomposition for decadally cycling SOC which is the main component of total soil carbon stock and the most relevant to global change. We tackled this issue using two decadally (13) C-labeled soils and a much improved measuring system in a long-term incubation experiment. Results indicated that the temperature sensitivity of decomposition for decadally cycling SOC (>23 years in one soil and >55 years in the other soil) was significantly greater than that for faster-cycling SOC (<23 or 55 years) or for the entire SOC stock. Moreover, decadally cycling SOC contributed substantially (35-59%) to the total CO2 loss during the 360-day incubation. Overall, these results indicate that the decomposition of decadally cycling SOC is highly sensitive to temperature change, which will likely make this large SOC stock vulnerable to loss by global warming in the 21st century and beyond.

  6. Decadally cycling soil carbon is more sensitive to warming than faster-cycling soil carbon.

    PubMed

    Lin, Junjie; Zhu, Biao; Cheng, Weixin

    2015-12-01

    The response of soil organic carbon (SOC) pools to globally rising surface temperature crucially determines the feedback between climate change and the global carbon cycle. However, there is a lack of studies investigating the temperature sensitivity of decomposition for decadally cycling SOC which is the main component of total soil carbon stock and the most relevant to global change. We tackled this issue using two decadally (13) C-labeled soils and a much improved measuring system in a long-term incubation experiment. Results indicated that the temperature sensitivity of decomposition for decadally cycling SOC (>23 years in one soil and >55 years in the other soil) was significantly greater than that for faster-cycling SOC (<23 or 55 years) or for the entire SOC stock. Moreover, decadally cycling SOC contributed substantially (35-59%) to the total CO2 loss during the 360-day incubation. Overall, these results indicate that the decomposition of decadally cycling SOC is highly sensitive to temperature change, which will likely make this large SOC stock vulnerable to loss by global warming in the 21st century and beyond. PMID:26301625

  7. Simulating soil carbon accumulation in an upland black spruce ecosystem of interior Alaska: implications for permafrost carbon dynamics to climate change

    NASA Astrophysics Data System (ADS)

    Wang, X.; Yokozawa, M.; Toda, M.; Kushida, K.

    2015-12-01

    Boreal terrestrial ecosystems act as a huge reservoir of organic carbon, most of which is mainly stored in both active-layer soils and permafrost. Recently, many observational studies have revealed that ongoing climate warming has promoted changes in fire regime, which stimulates the permafrost thaw in the boreal area. Consequently, the decomposition rate of the organic and mineral soils will increase and a large amount of CO2 will be released into the atmosphere. The sustained CO2­ release from the soils may create a positive feedback in relation to carbon cycling between the atmosphere and boreal terrestrial ecosystems. However, there still remains substantial uncertainty for evaluating the mechanisms of the carbon cycle feedbacks over centuries. In the present study, we examined the effect of warming and fire episodes on soil carbon dynamics in an upland black spruce ecosystem in interior Alaska, by using a Physical and Biogeochemical Soil Dynamics Model (PB-SDM) which can simulate the feedback cycle of soil organic carbon accumulation with soil thermal and hydrological dynamics. The result indicates that soil carbon accumulation in the organic layer was strongly dominated by increased temperature. In addition, fire events by which a great number of soil layers burned contributed to decrease in soil carbon accumulation largely in the organic layer. On the other hand, remarkably increased temperature conditions (around 9.6℃ by 3000) controlled soil carbon accumulation in the mineral layer and changes in soil decomposition rate accompanying with the shift from frozen to thawed conditions with warming accelerated soil carbon decomposition. It is suggested that future climate warming would result in drastic decrease in the soil carbon stock, largely from the organic layer, whereas the vulnerability of deeper soil carbon to future warming is closely connected to permafrost degradation due to wildfire disturbance.

  8. Artificial Warming and Rain Addition Increase Phenol Oxidase Activity in Arctic Soils

    NASA Astrophysics Data System (ADS)

    Kang, H.; Seo, J.; Jang, I.; Lee, Y. K.

    2014-12-01

    Artic tundra is one of the largest carbon stocks, of which amount is estimated up to 1,600 Pg. Global climate change models predict surface temperature rise and higher precipitation during summer in Arctic regions, raising concerns about faster decomposition of organic carbon and consequent releases of CO2, CH4 and DOC. Microorganisms are directly involved in decomposition process by releasing various extracellular enzymes. In particular, phenol oxidase was noted to play a key role because it is related to dynamics of highly recalcitrant carbon, which often represents a rate-limiting step of overall decomposition. In this study, we monitored phenol oxidase activity, hydrolases (β-glucosidase, cellobiohydrolase, N-acetylglucosaminidase and aminopeptidase), microbial abundance (qPCR) and chemical properties (δ13C and δ15N signatures) of tundra soils exposed to artificial warming and rain addition, by employing a passive chamber method in Cambridge Bay, Canada. Warming and rain addition combinedly increased phenol oxidase activity while no such changes were discernible for other hydrolases. Stable isotope signature indicates that warming induced water stress to the ecosystem and that nitrogen availability may be enhanced, which is partially responsible for the changes in enzyme activities. A short-term warming (2 years) may not accelerate mineralization of easily decomposable carbon, but may affect phenol oxidase which has the longer-term influence on recalcitrant carbon.

  9. Limited transport of functionalized multi-walled carbon nanotubes in two natural soils

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Column experiments were conducted in undisturbed and in repacked soil columns at water contents close to saturation (85–96%) to investigate the transport and retention of functionalized 14C-labeled multi-walled carbon nanotubes (MWCNT) in two natural soils. Additionally, a field lysimeter experiment...

  10. How relevant is chemical recalcitrance for predicting climatic effects on mineral soil carbon stocks?

    NASA Astrophysics Data System (ADS)

    Hopkins, F. M.; Torn, M. S.; Trumbore, S.

    2011-12-01

    and mineral soils were initially stimulated by warming, but diminished in time for the organic soils, and not for mineral soils. These data suggest different long term decomposition controls on mineral soil carbon, which may be more temperature sensitive than those acting on litter carbon over the long term. In addition, the 14C signature of respiration suggests an increase in loss of older carbon with warming in mineral soils, but not in organic soils. The absence of change in Δ14C respired by organic soils suggests that the change in mineral soils is likely due to a factor other than recalcitrance. While the effects of warming on chemically recalcitrant carbon may play a role in the short term response, it is not likely contributing to the long term stimulation of fluxes from mineral soils. Ultimately, to predict the response of carbon stocks to warming, we need a more detailed understanding of the processes controlling soil carbon stabilization in mineral soils. While chemical recalcitrance may play a limited role, we need to acknowledge and account for other stabilization pathways.

  11. Australian climate-carbon cycle feedback reduced by soil black carbon

    NASA Astrophysics Data System (ADS)

    Lehmann, Johannes; Skjemstad, Jan; Sohi, Saran; Carter, John; Barson, Michele; Falloon, Pete; Coleman, Kevin; Woodbury, Peter; Krull, Evelyn

    2008-12-01

    Annual emissions of carbon dioxide from soil organic carbon are an order of magnitude greater than all anthropogenic carbon dioxide emissions taken together. Global warming is likely to increase the decomposition of soil organic carbon, and thus the release of carbon dioxide from soils, creating a positive feedback. Current models of global climate change that recognize this soil carbon feedback are inaccurate if a larger fraction of soil organic carbon than postulated has a very slow decomposition rate. Here we show that by including realistic stocks of black carbon in prediction models, carbon dioxide emissions are reduced by 18.3 and 24.4% in two Australian savannah regions in response to a warming of 3∘C over 100 years. This reduction in temperature sensitivity, and thus the magnitude of the positive feedback, results from the long mean residence time of black carbon, which we estimate to be approximately 1,300 and 2,600 years, respectively. The inclusion of black carbon in climate models is likely to require spatially explicit information about its distribution, given that the black carbon content of soils ranged from 0 to 82% of soil organic carbon in a continental-scale analysis of Australia. We conclude that accurate information about the distribution of black carbon in soils is important for projections of future climate change.

  12. Analysis on Soil Seed Bank Diversity Characteristics and Its Relation with Soil Physical and Chemical Properties after Substrate Addition

    PubMed Central

    He, Mengxuan; Lv, Lingyue; Li, Hongyuan; Meng, Weiqing; Zhao, Na

    2016-01-01

    Aims Considered as an essential measure in the application of soil seed bank (SSB) projects, the mixing of substrate and surface soil can effectively improve soil condition. This research is aimed at exploring the diversity characteristics of SSBs and the relationships between SSBs and soil properties. Methods Canonical correspondence analysis (CCA) was adopted to describe the ordination of SSBs on soil properties’ gradients; multiple linear regressions were adopted to analyze the relationship between average growth height and soil properties, density and soil properties. Results Experimental groups of mixed substrate (the mixture of organic and inorganic substrates) had high diversity indexes, especially the Shannon-Wiener Index compared with those of single substrate. Meanwhile, a higher number of species and increased density were also noted in those of mixed substrate. The best test group, No.16, had the highest diversity indexes with a Shannon-Wiener of 1.898, Simpson of 0.633 and Pielou of 0.717, and also showed the highest density of 14000 germinants /m2 and 21 species. In addition, an improvement of the soil’s chemical and physical properties was noted when the substrates were mixed. The mixed substrate of turfy soil and perlite could effectively enhance the soil moisture content, whilst a mixed substrate of rice husk carbon and vermiculite could improve the content of available potassium (AK) and phosphorus (AP) and strengthen soil fertility. The germinated plants also reflected obvious regularities of ordination on soil factor gradients. Three distinct cluster groups were presented, of which the first cluster was distributed in an area with a relatively higher content of AK and AP; the second cluster was distributed at places with relatively higher soil moisture content; and the third cluster of plants didn’t show any obvious relationship with soil physical and chemical properties. Through CCA analysis, AK and AP were considered the most important

  13. Soil organic carbon of European forest soils: current stock and projections under climate change conditions

    NASA Astrophysics Data System (ADS)

    Caddeo, Antonio; Marras, Serena; Spano, Donatella; Sirca, Costantino

    2016-04-01

    Soil organic carbon (SOC) represents the largest terrestrial carbon pool, and it is subjected to climate change impacts. In Europe, a limited number of studies makes a wide-scale comparison of SOC stock and changes under climate change conditions, and most of them are related to agricultural soils. In this work, the SOC stock of the forested areas of Europe (obtained from the CORINE 2006 Land Use Map) was assessed at 1 km resolution using the agro-ecosystem SOC model CENTURY. The results of the model were compared with independent observational datasets (i.e. LUCAS Topsoil Survey Database). In addition, climate simulations (RCPs 4.5 and 8.5) using the CMCC (Euro-Mediterranean Centre on Climate Change) and the CORDEX dataset were used to estimate the SOC changes of these areas under climate change conditions.

  14. Modelling carbon in permafrost soils from preindustrial to the future

    NASA Astrophysics Data System (ADS)

    Kleinen, T.; Brovkin, V.

    2015-12-01

    The carbon release from thawing permafrost soils constitutes one of the large uncertainties in the carbon cycle under future climate change. Analysing the problem further, this uncertainty results from an uncertainty about the total amount of C that is stored in frozen soils, combined with an uncertainty about the areas where soils might thaw under a particular climate change scenario, as well as an uncertainty about the decomposition product since some of the decomposed C might result the release of CH4 as well as CO2. We use the land surface model JSBACH, part of the Max Planck Institute Earth System Model MPI-ESM, to quantify the release of soil carbon from thawing permafrost soils. We have extended the soil carbon model YASSO by introducing carbon storages in frozen soils, with increasing fractions of C being available to decomposition as permafrost thaws. In order to quantify the amount of carbon released as CH4, as opposed to CO2, we have also implemented a TOPMODEL-based wetland scheme, as well as anaerobic C decomposition and methane transport. We initialise the soil C pools for the preindustrial climate state from the Northern Circumpolar Soil Carbon Database to insure initial C pool sizes close to measurements. We then determine changes in soil C storage in transient model experiments following historical and future climate changes under RCP 8.5. Based on these experiments, we quantify the greenhouse gas release from permafrost C decomposition, determining both CH4 and CO2 emissions.

  15. Soil Carbon Storage in Christmas Tree Farms: Maximizing Ecosystem Management and Sustainability for Carbon Sequestration

    NASA Astrophysics Data System (ADS)

    Chapman, S. K.; Shaw, R.; Langley, A.

    2008-12-01

    Management of agroecosystems for the purpose of manipulating soil carbon stocks could be a viable approach for countering rising atmospheric carbon dioxide concentrations, while maximizing sustainability of the agroforestry industry. We investigated the carbon storage potential of Christmas tree farms in the southern Appalachian mountains as a potential model for the impacts of land management on soil carbon. We quantified soil carbon stocks across a gradient of cultivation duration and herbicide management. We compared soil carbon in farms to that in adjacent pastures and native forests that represent a control group to account for variability in other soil-forming factors. We partitioned tree farm soil carbon into fractions delineated by stability, an important determinant of long-term sequestration potential. Soil carbon stocks in the intermediate pool are significantly greater in the tree farms under cultivation for longer periods of time than in the younger tree farms. This pool can be quite large, yet has the ability to repond to biological environmental changes on the centennial time scale. Pasture soil carbon was significantly greater than both forest and tree farm soil carbon, which were not different from each other. These data can help inform land management and soil carbon sequestration strategies.

  16. Managing uncertainty in soil carbon feedbacks to climate change

    NASA Astrophysics Data System (ADS)

    Bradford, Mark A.; Wieder, William R.; Bonan, Gordon B.; Fierer, Noah; Raymond, Peter A.; Crowther, Thomas W.

    2016-08-01

    Planetary warming may be exacerbated if it accelerates loss of soil carbon to the atmosphere. This carbon-cycle-climate feedback is included in climate projections. Yet, despite ancillary data supporting a positive feedback, there is limited evidence for soil carbon loss under warming. The low confidence engendered in feedback projections is reduced further by the common representation in models of an outdated knowledge of soil carbon turnover. 'Model-knowledge integration' -- representing in models an advanced understanding of soil carbon stabilization -- is the first step to build confidence. This will inform experiments that further increase confidence by resolving competing mechanisms that most influence projected soil-carbon stocks. Improving feedback projections is an imperative for establishing greenhouse gas emission targets that limit climate change.

  17. Linking soil functions to carbon fluxes and stocks

    NASA Astrophysics Data System (ADS)

    Olesen, Jørgen E.

    2014-05-01

    Farming practices causing declining returns and inputs of carbon (C) to soils pose threats to sustainable soil functioning by reducing availability of organic matter for soil microbial activities and by affecting soil structure, and soil C stocks that contribute to regulating greenhouse gas emissions. Declines in soil C also affect availability and storage capacity of a range of essential plant nutrients thus affecting needs for external inputs. Soil degradation is considered a serious problem in Europe and a large part of the degradation is caused by agricultural activity with intensive cultivation in arable and mixed farming system contributing to several soil threats. About 45% of European soils are estimated to have low SOM content, principally in southern Europe, but also in areas of France, UK and Germany. The European SOC stocks follow a clear north to south gradient with cooler temperatures favouring higher stocks. However, SOC stocks strongly depend on soil and land management, and there is thus a potential to both increase and lose SOC, although the potential to increase SOC strongly depends on incentives and structures for implementing improved management. Understanding the role of soil C may be better conceptualised by using a soil C flow and stocks concept to assess the impact of C management on crop productivity, soil organic C stocks and other ecosystem services. This concept distinguishes C flows and stocks, which may be hypothesized to have distinctly different effects on biological, chemical and physical soil functions. By separating the roles of carbon flows from the role of carbon stocks, it may become possible to better identify critical levels not only of soil carbon stocks, but also critical levels of carbon inputs, which directly relate to needs for crop and soil management measures. Such critical soil carbon stocks may be linked to soil mineralogy through complexed organic carbon on clay and silt surfaces. Critical levels of soil carbon

  18. Biochar for soil fertility and natural carbon sequestration

    USGS Publications Warehouse

    Rostad, C.E.; Rutherford, D.W.

    2011-01-01

    Biochar is charcoal (similar to chars generated by forest fires) that is made for incorporation into soils to increase soil fertility while providing natural carbon sequestration. The incorporation of biochar into soils can preserve and enrich soils and also slow the rate at which climate change is affecting our planet. Studies on biochar, such as those cited by this report, are applicable to both fire science and soil science.

  19. Elevated carbon dioxide does not offset loss of soil carbon from a corn-soybean agroecosystem.

    SciTech Connect

    Moran, K. K.; Jastrow, J. D.; Biosciences Division

    2010-04-01

    The potential for storing additional C in U.S. Corn Belt soils - to offset rising atmospheric [CO{sub 2}] - is large. Long-term cultivation has depleted substantial soil organic matter (SOM) stocks that once existed in the region's native ecosystems. In central Illinois, free-air CO{sub 2} enrichment technology was used to investigate the effects of elevated [CO{sub 2}] on SOM pools in a conservation tilled corn-soybean rotation. After 5 and 6 y of CO{sub 2} enrichment, we investigated the distribution of C and N among soil fractions with varying ability to protect SOM from rapid decomposition. None of the isolated C or N pools, or bulk-soil C or N, was affected by CO{sub 2} treatment. However, the site has lost soil C and N, largely from unprotected pools, regardless of CO{sub 2} treatment since the experiment began. These findings suggest management practices have affected soil C and N stocks and dynamics more than the increased inputs from CO{sub 2}-stimulated photosynthesis. Soil carbon from microaggregate-protected and unprotected fractions decreased in a conservation tilled corn-soybean rotation despite increases in primary production from exposure to atmospheric CO{sub 2} enrichment.

  20. Soil carbon distribution in Alaska in relation to soil-forming factors

    USGS Publications Warehouse

    Johnson, K.D.; Harden, J.; McGuire, A.D.; Bliss, N.B.; Bockheim, J.G.; Clark, M.; Nettleton-Hollingsworth, T.; Jorgenson, M.T.; Kane, E.S.; Mack, M.; O'Donnell, J.; Ping, C.-L.; Schuur, E.A.G.; Turetsky, M.R.; Valentine, D.W.

    2011-01-01

    The direction and magnitude of soil organic carbon (SOC) changes in response to climate change remain unclear and depend on the spatial distribution of SOC across landscapes. Uncertainties regarding the fate of SOC are greater in high-latitude systems where data are sparse and the soils are affected by sub-zero temperatures. To address these issues in Alaska, a first-order assessment of data gaps and spatial distributions of SOC was conducted from a recently compiled soil carbon database. Temperature and landform type were the dominant controls on SOC distribution for selected ecoregions. Mean SOC pools (to a depth of 1-m) varied by three, seven and ten-fold across ecoregion, landform, and ecosystem types, respectively. Climate interactions with landform type and SOC were greatest in the uplands. For upland SOC there was a six-fold non-linear increase in SOC with latitude (i.e., temperature) where SOC was lowest in the Intermontane Boreal compared to the Arctic Tundra and Coastal Rainforest. Additionally, in upland systems mineral SOC pools decreased as climate became more continental, suggesting that the lower productivity, higher decomposition rates and fire activity, common in continental climates, interacted to reduce mineral SOC. For lowland systems, in contrast, these interactions and their impacts on SOC were muted or absent making SOC in these environments more comparable across latitudes. Thus, the magnitudes of SOC change across temperature gradients were non-uniform and depended on landform type. Additional factors that appeared to be related to SOC distribution within ecoregions included stand age, aspect, and permafrost presence or absence in black spruce stands. Overall, these results indicate the influence of major interactions between temperature-controlled decomposition and topography on SOC in high-latitude systems. However, there remains a need for more SOC data from wetlands and boreal-region permafrost soils, especially at depths > 1 m in order

  1. 12 years of intensive management increases soil carbon stocks in Loblolly pine and Sweetgum stands

    NASA Astrophysics Data System (ADS)

    Sanchez, F. G.; Samuelson, L.; Johnsen, K.

    2009-12-01

    fractions based on management intensity. Additionally, there was no difference between soil carbon fractions based on tree species. These observations suggest that although external inputs (i.e., moisture, carbon and nutrients) increase soil carbon stocks, they do not alter soil carbon stabilization mechanisms at these sites.

  2. Modeling Soil Organic Carbon Turnover in Four Temperate Forests Based on Radiocarbon Measurements of Heterotrophic Respiration and Soil Organic Carbon

    NASA Astrophysics Data System (ADS)

    Ahrens, B.; Borken, W.; Muhr, J.; Schrumpf, M.; Savage, K. E.; Wutzler, T.; Trumbore, S.; Reichstein, M.

    2011-12-01

    Soils of temperate forests store significant amounts of soil organic matter and are considered to be net sinks of atmospheric CO2. Soil organic carbon (SOC) dynamics have been studied using the Δ14C signature of bulk SOC or different SOC fractions as observational constraints in SOC models. Further, the Δ14C signature of CO2 evolved during the incubation of soil and roots has been widely used together with Δ14C of total soil respiration to partition soil respiration into heterotrophic respiration (Rh) and root respiration. However, these data have rarely been used together as observational constraints to determine SOC turnover times. Here, we present a multiple constraints approach, where we used SOC stock and its Δ14C signature, and heterotrophic respiration and its Δ14C signature to estimate SOC turnover times of a simple serial two-pool model via Bayesian optimization. We used data from four temperate forest ecosystems in Germany and the USA with different disturbance and management histories from selective logging to afforestation in the late 19th and early 20th century. The Δ14C signature of the atmosphere with its prominent bomb peak was used as a proxy for the Δ14C signature of aboveground and belowground litterfall. The Δ14C signature of litterfall was lagged behind the atmospheric signal to account for the period between photosynthetic fixation of carbon and its addition to SOC pools. We showed that the combined use of Δ14C measurements of Rh and SOC stocks helped to better constrain turnover times of the fast pool (primarily by Δ14C of Rh) and the slow pool (primarily by Δ14C of SOC). In particular, by introducing two additional parameters that describe the deviation from steady state of the fast and slow cycling pool for both SOC and SO14C, we were able to demonstrate that we cannot maintain the often used steady-state assumption of SOC models in general. Furthermore, a new transport version of our model, including SOC transport via

  3. Soil organic matter and land use change: the effect of soil carbon saturation

    NASA Astrophysics Data System (ADS)

    Six, J. W.; Carrington, E. M.

    2011-12-01

    Land management affects soil organic carbon (SOC) storage through the balance between inputs and outputs, the structural and functional complexity of plant and microbial communities, alterations to microbial processes and activity, and changes to edaphic soil conditions. An ultimate determinant on the rate of accumulation and total C storage potential of a soil, however, is its inherent capacity to protect organic matter within the soil matrix, i.e. soil C saturation. As a soil approaches its soil C saturation level, i.e. finite aggregate and mineral protective capacity, limits the C sequestration potential of a soil. For this reason, the preexisting amount and distribution of soil C in protected soil C pools, in addition to the soil's capacity for stabilization, must be considered when predicting effects of land management change on SOC stocks. Evidence points to the amount, type, and location of silt and clay-sized particles, as well as the soil's inherent potential for aggregate formation, as the main controlling factors of soil C saturation. The innate biochemistry of uncomplexed soil organic matter does not appear to affect soil C saturation, nor does it interact with protective mechanisms at high SOC loadings. This confirms that C saturation level cannot be modified though management of C input quality. Land use induced changes to a soil's physical matrix, such as preferential erosion of smaller particles or soil compaction, could, however, have irreversible threshold effects on a soil's potential for organic matter stabilization. Experiments in agricultural and grassland systems have determined saturating responses of soils and functional soil fractions (i.e. chemical-protection by associations with silt and clay, physical-protection by occlusion in aggregates, and a combination of physical and chemical protection in aggregated silt and clay) to equilibrium C inputs, or C input proxies, such as CO2 or total SOC. Estimates of C saturation parameters for

  4. Simultaneous inhibition of carbon and nitrogen mineralization in a forest soil by simulated acid precipitation

    SciTech Connect

    Klein, T.M.; Novick, N.J.; Kreitinger, J.P.; Alexander, M.

    1984-06-01

    One method to simulate the long-term exposure of soil to acid rain involves the addition of single doses of concentrated acid. The inhibition of carbon mineralization accompanied by a stimulation of nitrogen mineralization may result from this severe, unnatural treatment. The present study was designed to determine whether the inhibition of carbon mineralization and the accompanying enhanced nitrogen mineralization would occur when soils are treated with more dilute acid for long periods of time, as takes place in nature.

  5. Removal of dissolved organic carbon and nitrogen during simulated soil aquifer treatment.

    PubMed

    Essandoh, H M K; Tizaoui, C; Mohamed, M H A

    2013-07-01

    Soil aquifer treatment was simulated in 1 m laboratory soil columns containing silica sand under saturated and unsaturated soil conditions to examine the effect of travel length through the unsaturated zone on the removal of wastewater organic matter, the effect of soil type on dissolved organic carbon removal and also the type of microorganisms involved in the removal process. Dissolved organic carbon removal and nitrification did enhance when the wastewater travelled a longer length through the unsaturated zone. A similar consortium of microorganisms was found to exist in both saturated and unsaturated columns. Microbial concentrations however were lowest in the soil column containing silt and clay in addition to silica sand. The presence of silt and clay was detrimental to DOC removal efficiency under saturated soil conditions due to their negative effect on the hydraulic performance of the soil column and microbial growth.

  6. Carbon Mineralizability Determines Interactive Effects on Mineralization of Pyrogenic Organic Matter and Soil Organic Carbon

    SciTech Connect

    Whitman, Thea L.; Zhu, Zihua; Lehmann, Johannes C.

    2014-10-31

    Soil organic carbon (SOC) is a critical and active pool in the global C cycle, and the addition of pyrogenic organic matter (PyOM) has been shown to change SOC cycling, increasing or decreasing mineralization rates (often referred to as priming). We adjusted the amount of easily mineralizable C in the soil, through 1-day and 6-month pre-incubations, and in PyOM made from maple wood at 350°C, through extraction. We investigated the impact of these adjustments on C mineralization interactions, excluding pH and nutrient effects and minimizing physical effects. We found short-term increases (+20-30%) in SOC mineralization with PyOM additions in the soil pre-incubated for 6 months. Over the longer term, both the 6-month and 1-day pre-incubated soils experienced net ~10% decreases in SOC mineralization with PyOM additions. This was possibly due to stabilization of SOC on PyOM surfaces, suggested by nanoscale secondary ion mass spectrometry. Additionally, the duration of pre-incubation affected priming interactions, indicating that there may be no optimal pre-incubation time for SOC mineralization studies. We show conclusively that relative mineralizability of SOC in relation to PyOM-24 C is an important determinant of the effect of PyOM additions on SOC mineralization.

  7. Carbon mineralizability determines interactive effects on mineralization of pyrogenic organic matter and soil organic carbon.

    PubMed

    Whitman, Thea; Zhu, Zihua; Lehmann, Johannes

    2014-12-01

    Soil organic carbon (SOC) is a critical and active pool in the global C cycle, and the addition of pyrogenic organic matter (PyOM) has been shown to change SOC cycling, increasing or decreasing mineralization rates (often referred to as priming). We adjusted the amount of easily mineralizable C in the soil, through 1-day and 6-month preincubations, and in PyOM made from maple wood at 350 °C, through extraction. We investigated the impact of these adjustments on C mineralization interactions, excluding pH and nutrient effects and minimizing physical effects. We found short-term increases (+20-30%) in SOC mineralization with PyOM additions in the soil preincubated for 6 months. Over the longer term, both the 6-month and 1-day preincubated soils experienced net ∼10% decreases in SOC mineralization with PyOM additions. Additionally, the duration of preincubation affected interactions, indicating that there may be no optimal preincubation time for SOC mineralization studies. We show conclusively that mineralizability of SOC in relation to PyOM-C is an important determinant of the effect of PyOM additions on SOC mineralization. PMID:25361379

  8. Reduced plant uptake of pesticides with biochar additions to soil.

    PubMed

    Yu, Xiang-Yang; Ying, Guang-Guo; Kookana, Rai S

    2009-07-01

    We investigated the effectiveness of two types of biochars in reducing the bioavailability of two soil-applied insecticides (chlorpyrifos and carbofuran) to Spring onion (Allium cepa). The biochars prepared from the pyrolysis of Eucalyptus spp. wood chips at 450 and 850 degrees C (BC850) were thoroughly mixed into the soil to achieve 0%, 0.1%, 0.5% and 1% by soil weight. A spring onion crop was grown for 5 wk in the biochar-amended soils spiked with 50 mgkg(-1) of each pesticide. The loss of both pesticides due to degradation and or sequestration in soils decreased significantly with increasing amounts of biochars in soil. Over 35 d, 86-88% of the pesticides were lost from the control soil, whereas it was only 51% of carbofuran and 44% of chlorpyrifos from the soil amended with 1.0% BC850. Despite greater persistence of the pesticide residues in biochar-amended soils, the plant uptake of pesticides decreased markedly with increasing biochar content of the soil. With 1% of BC850 soil amendment, the total plant residues for chlorpyrifos and carbofuran decreased to 10% and 25% of that in the control treatment, respectively. The BC850 was particularly effective in reducing phytoavailability of both pesticides from soil, due to its high affinity for and ability to sequester pesticide residues.

  9. Soil quality changes after topsoil addition to eroded land

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Soil-landscape rehabilitation within eroded fields can be accomplished by moving topsoil from depositional to eroded landscape positions. The purpose is to improve soil quality and productivity of the upper root zone in eroded areas of the field. Changes in soil quality may be estimated through chan...

  10. Reduced plant uptake of pesticides with biochar additions to soil.

    PubMed

    Yu, Xiang-Yang; Ying, Guang-Guo; Kookana, Rai S

    2009-07-01

    We investigated the effectiveness of two types of biochars in reducing the bioavailability of two soil-applied insecticides (chlorpyrifos and carbofuran) to Spring onion (Allium cepa). The biochars prepared from the pyrolysis of Eucalyptus spp. wood chips at 450 and 850 degrees C (BC850) were thoroughly mixed into the soil to achieve 0%, 0.1%, 0.5% and 1% by soil weight. A spring onion crop was grown for 5 wk in the biochar-amended soils spiked with 50 mgkg(-1) of each pesticide. The loss of both pesticides due to degradation and or sequestration in soils decreased significantly with increasing amounts of biochars in soil. Over 35 d, 86-88% of the pesticides were lost from the control soil, whereas it was only 51% of carbofuran and 44% of chlorpyrifos from the soil amended with 1.0% BC850. Despite greater persistence of the pesticide residues in biochar-amended soils, the plant uptake of pesticides decreased markedly with increasing biochar content of the soil. With 1% of BC850 soil amendment, the total plant residues for chlorpyrifos and carbofuran decreased to 10% and 25% of that in the control treatment, respectively. The BC850 was particularly effective in reducing phytoavailability of both pesticides from soil, due to its high affinity for and ability to sequester pesticide residues. PMID:19419749

  11. [Soil greenhouse gases emission from an Acacia crassicarpa plantation under effects of understory removal and Cassia alata addition].

    PubMed

    Li, Hai-Fang; Zhang, Xing-Feng

    2010-03-01

    Forest soil is one of the main sources of greenhouse gases CO2, CH4, and N2O. By using static chamber and GS technique, this paper measured in situ the CO2, CH4, and N2O fluxes of Acacia crassicarpa plantation in Heshan Hilly Land Interdisciplinary Experimental Station under Chinese Academy of Sciences (CAS), and studied the soil CO2, CH4 and N2O emissions from the plantation under effects of understory removal and Cassia alata addition. The CO2 flux of the plantation maintained at a higher level during rainy season but decreased obviously in dry season, while the CH4 and N2O fluxes varied widely from September to November, with the peaks in October. Under the effects of understory removal and C. alata addition, the soil in the plantation could be a sink or a source of CH4, but consistently a source of CO2 and N2O. Understory removal enhanced the soil CO2 emission (P < 0.05 ), C. alata addition increased the soil CH4 emission (P < 0.05), while both understory removal and C. alata addition increased the soil N2O emission (P < 0.05). Surface soil temperature, moisture content, NO3(-) -N concentration, and microbial biomass carbon were the main factors affecting the soil CO2, CH4 and N2O emissions.

  12. Spatial variability of soil carbon in forested and cultivated sites: implications for change detection.

    PubMed

    Conant, Richard T; Smith, Gordon R; Paustian, Keith

    2003-01-01

    The potential to sequester atmospheric carbon in agricultural and forest soils to offset greenhouse gas emissions has generated interest in measuring changes in soil carbon resulting from changes in land management. However, inherent spatial variability of soil carbon limits the precision of measurement of changes in soil carbon and hence, the ability to detect changes. We analyzed variability of soil carbon by intensively sampling sites under different land management as a step toward developing efficient soil sampling designs. Sites were tilled cropland and a mixed deciduous forest in Tennessee, and old-growth and second-growth coniferous forest in western Washington, USA. Six soil cores within each of three microplots were taken as an initial sample and an additional six cores were taken to simulate resampling. Soil C variability was greater in Washington than in Tennessee, and greater in less disturbed than in more disturbed sites. Using this protocol, our data suggest that differences on the order of 2.0 Mg C ha(-1) could be detected by collection and analysis of cores from at least five (tilled) or two (forest) microplots in Tennessee. More spatial variability in the forested sites in Washington increased the minimum detectable difference, but these systems, consisting of low C content sandy soil with irregularly distributed pockets of organic C in buried logs, are likely to rank among the most spatially heterogeneous of systems. Our results clearly indicate that consistent intramicroplot differences at all sites will enable detection of much more modest changes if the same microplots are resampled.

  13. Factors driving carbon mineralization priming effect in a soil amended with different types of biochar

    NASA Astrophysics Data System (ADS)

    Cely, P.; Tarquis, A. M.; Paz-Ferreiro, J.; Méndez, A.; Gascó, G.

    2014-03-01

    The effect of biochar on soil carbon mineralization priming effect depends on the characteristics of the raw materials, production method and pyrolysis conditions. The goal of the present study is to evaluate the impact of three different types of biochar on soil CO2 emissions and in different physicochemical properties. For this purpose, a sandy-loam soil was amended with the three biochars (BI, BII and BIII) at a rate of 8 wt % and soil CO2 emissions were measured for 45 days. BI is produced from a mixed wood sieving's from wood chip production, BII from a mixture of paper sludge and wheat husks and BIII from sewage sludge. Cumulative CO2 emissions of biochars, soil and amended soil were well fit to a simple first-order kinetic model with correlation coefficients (r2) greater than 0.97. Results shown a negative priming effect in the soil after addition of BI and a positive priming effect in the case of soil amended with BII and BIII. These results can be related with different biochar properties such as ash content, volatile matter, fixed carbon, organic carbon oxidised with dichromate, soluble carbon and metal and phenolic substances content in addition to surface biochar properties. Three biochars increased the values of soil field capacity and wilting point, while effects over pH and cation exchange capacity were not observed.

  14. Labile soil carbon inputs mediate the soil microbial community composition and plant residue decomposition rates

    SciTech Connect

    De Graaff, Marie-Anne; Classen, Aimee T; Castro Gonzalez, Hector F; Schadt, Christopher Warren

    2010-01-01

    Root carbon (C) inputs may regulate decomposition rates in soil, and in this study we ask: how do labile C inputs regulate decomposition of plant residues, and soil microbial communities? In a 14 d laboratory incubation, we added C compounds often found in root exudates in seven different concentrations (0, 0.7, 1.4, 3.6, 7.2, 14.4 and 21.7 mg C g{sup -1} soil) to soils amended with and without {sup 13}C-labeled plant residue. We measured CO{sub 2} respiration and shifts in relative fungal and bacterial rRNA gene copy numbers using quantitative polymerase chain reaction (qPCR). Increased labile C input enhanced total C respiration, but only addition of C at low concentrations (0.7 mg C g{sup -1}) stimulated plant residue decomposition (+2%). Intermediate concentrations (1.4, 3.6 mg C g{sup -1}) had no impact on plant residue decomposition, while greater concentrations of C (> 7.2 mg C g{sup -1}) reduced decomposition (-50%). Concurrently, high exudate concentrations (> 3.6 mg C g{sup -1}) increased fungal and bacterial gene copy numbers, whereas low exudate concentrations (< 3.6 mg C g{sup -1}) increased metabolic activity rather than gene copy numbers. These results underscore that labile soil C inputs can regulate decomposition of more recalcitrant soil C by controlling the activity and relative abundance of fungi and bacteria.

  15. Effects of environmental and biotic factors on carbon isotopic fractionation during decomposition of soil organic matter

    PubMed Central

    Wang, Guoan; Jia, Yufu; Li, Wei

    2015-01-01

    Decomposition of soil organic matter (SOM) plays an important role in the global carbon cycle because the CO2 emitted from soil respiration is an important source of atmospheric CO2. Carbon isotopic fractionation occurs during SOM decomposition, which leads to 12C to enrich in the released CO2 while 13C to enrich in the residual SOM. Understanding the isotope fractionation has been demonstrated to be helpful for studying the global carbon cycle. Soil and litter samples were collected from soil profiles at 27 different sites located along a vertical transect from 1200 to 4500 m above sea level (a.s.l.) in the south-eastern side of the Tibetan Plateau. Their carbon isotope ratios, C and N concentrations were measured. In addition, fiber and lignin in litter samples were also analyzed. Carbon isotope fractionation factor (α) during SOM decomposition was estimated indirectly as the slope of the relationship between carbon isotope ratios of SOM and soil C concentrations. This study shows that litter quality and soil water play a significant role in isotope fractionation during SOM decomposition, and the carbon isotope fractionation factor, α, increases with litter quality and soil water content. However, we found that temperature had no significant impact on the α variance. PMID:26056012

  16. Effects of environmental and biotic factors on carbon isotopic fractionation during decomposition of soil organic matter.

    PubMed

    Wang, Guoan; Jia, Yufu; Li, Wei

    2015-06-09

    Decomposition of soil organic matter (SOM) plays an important role in the global carbon cycle because the CO2 emitted from soil respiration is an important source of atmospheric CO2. Carbon isotopic fractionation occurs during SOM decomposition, which leads to (12)C to enrich in the released CO2 while (13)C to enrich in the residual SOM. Understanding the isotope fractionation has been demonstrated to be helpful for studying the global carbon cycle. Soil and litter samples were collected from soil profiles at 27 different sites located along a vertical transect from 1200 to 4500 m above sea level (a.s.l.) in the south-eastern side of the Tibetan Plateau. Their carbon isotope ratios, C and N concentrations were measured. In addition, fiber and lignin in litter samples were also analyzed. Carbon isotope fractionation factor (α) during SOM decomposition was estimated indirectly as the slope of the relationship between carbon isotope ratios of SOM and soil C concentrations. This study shows that litter quality and soil water play a significant role in isotope fractionation during SOM decomposition, and the carbon isotope fractionation factor, α, increases with litter quality and soil water content. However, we found that temperature had no significant impact on the α variance.

  17. Effects of environmental and biotic factors on carbon isotopic fractionation during decomposition of soil organic matter.

    PubMed

    Wang, Guoan; Jia, Yufu; Li, Wei

    2015-01-01

    Decomposition of soil organic matter (SOM) plays an important role in the global carbon cycle because the CO2 emitted from soil respiration is an important source of atmospheric CO2. Carbon isotopic fractionation occurs during SOM decomposition, which leads to (12)C to enrich in the released CO2 while (13)C to enrich in the residual SOM. Understanding the isotope fractionation has been demonstrated to be helpful for studying the global carbon cycle. Soil and litter samples were collected from soil profiles at 27 different sites located along a vertical transect from 1200 to 4500 m above sea level (a.s.l.) in the south-eastern side of the Tibetan Plateau. Their carbon isotope ratios, C and N concentrations were measured. In addition, fiber and lignin in litter samples were also analyzed. Carbon isotope fractionation factor (α) during SOM decomposition was estimated indirectly as the slope of the relationship between carbon isotope ratios of SOM and soil C concentrations. This study shows that litter quality and soil water play a significant role in isotope fractionation during SOM decomposition, and the carbon isotope fractionation factor, α, increases with litter quality and soil water content. However, we found that temperature had no significant impact on the α variance. PMID:26056012

  18. Potential for Carbon Sequestration using Organic Amendments on Rangeland Soils

    NASA Astrophysics Data System (ADS)

    Ryals, R.; Silver, W. L.

    2009-12-01

    Managed rangelands represent a geographically large land-use footprint and thus have considerable potential to sequester carbon (C) in soil through changes in management practices. Organic amendments are frequently added to agricultural and rangeland soils in an effort to improve fertility and yield, yet little is known about their impact on greenhouse gas dynamics and soil biogeochemical dynamics, especially in rangeland soils. This research aims to explore the effects of organic amendments on soil chemical and physical properties, plant inputs, and soil C and N dynamics in managed rangeland ecosystems. Our research uses field manipulations at two Mediterranean grassland ecosystems replicated within and across bioclimatic zones: the Sierra Foothills Research and Extension Center (SFREC) in Browns Valley, CA and the Nicasio Native Grass Ranch in Nicasio, CA. Both sites are dominated by annual grasses and are moderately grazed by cattle. Three replicate blocks at each site contain 60m x 25m treatment plots (organic amendments and control) with 5m buffer strips. Organic amendments were applied at a level of 14 MgC/ha (equivalent to a 1.27cm surface dressing) at the beginning of the wet season (December 2008). During the wet season (October through June), carbon dioxide (CO2) flux was measured weekly using a LI-8100, while fluxes of methane (CH4) and nitrous oxide (N2O) were measured biweekly using static flux chambers. During the dry season (June through September), fluxes were measured biweekly and monthly, respectively. Soil organic C (SOC) and nitrogen (N) were measured prior to treatment and seven months following treatment at 0-10, 10-30, 30-50, and 50-100 cm depths. Soil moisture and temperature were measured continuously. Changes in oxidative and hydrolytic extracellular enzyme activities are also being explored. After the first year of management, both sites responded similarly to treatments in both trend and magnitude. For example, at SFREC, total soil

  19. [Effects of nitrogen and carbon addition and arbuscular mycorrhiza on alien invasive plant Ambrosia artemisiifolia].

    PubMed

    Huang, Dong; Sang, Wei-guo; Zhu, Li; Song, Ying-ying; Wang, Jin-ping

    2010-12-01

    A greenhouse control experiment was conducted to explore the effects of nitrogen and carbon addition and arbuscular mycorrhiza (AM) on the growth of alien invasive plant Ambrosia artemisiifolia (common ragweed). Nitrogen addition had no significant effects on the morphological indices, biomass and its allocation, and absolute growth rate of A. artemisiifolia, but increased the nitrogen content in the aboveground and underground parts of the plant significantly. Carbon addition increased the content of soil available nitrogen. In this case, the biomass allocation in root system for nutrient (nitrogen) absorption promoted, resulting in a remarkable decrease of branch number, total leaf area, specific leaf area (SLA), and leaf mass ratio. As a result, the total biomass decreased significantly. The symbiosis of A. artemisiifolia and AM fungi had great influence on the common ragweed's soil nitrogen acclimation, which enhanced its resource-capture by the increase of SLA, and this effect was more significant when the soil nitrogen content was low. AM fungi played an important role in the growth of A. artemisiifolia in low-nitrogen environment.

  20. [Effects of nitrogen addition on soil physico-chemical properties and enzyme activities in desertified steppe].

    PubMed

    Su, Jie-Qiong; Li, Xin-Rong; Bao, Jing-Ting

    2014-03-01

    To investigate the impacts of nitrogen (N) enrichment on soil physico-chemical property and soil enzyme activities in desert ecosystems, a field experiment by adding N at 0, 1.75, 3.5, 7, or 14 g N x m(-2) a(-1) was conducted in a temperate desert steppe in the southeastern fringe of the Tengger Desert. The results showed that N addition led to accumulations of total N, NO(3-)-N, NH(4+)-N, and available N in the upper soil (0-10 cm) and subsoil (10-20 cm), however, reductions in soil pH were observed, causing soil acidification to some extent. N addition pronouncedly inhibited soil enzyme activities, which were different among N addition levels, soil depths, and years, respectively. Soil enzyme activities were significantly correlated with the soil N level, soil pH, and soil moisture content, respectively.

  1. Accelerated soil carbon turnover under tree plantations limits soil carbon storage

    PubMed Central

    Chen, Guangshui; Yang, Yusheng; Yang, Zhijie; Xie, Jinsheng; Guo, Jianfen; Gao, Ren; Yin, Yunfeng; Robinson, David

    2016-01-01

    The replacement of native forests by tree plantations is increasingly common globally, especially in tropical and subtropical areas. Improving our understanding of the long-term effects of this replacement on soil organic carbon (SOC) remains paramount for effectively managing ecosystems to mitigate anthropogenic carbon emissions. Meta-analyses imply that native forest replacement usually reduces SOC stocks and may switch the forest from a net sink to a net source of atmospheric carbon. Using a long-term chronosequence during which areas of subtropical native forest were replaced by Chinese fir, we show by direct measurement that plantations have significantly accelerated SOC turnover compared with native forest, an effect that has persisted for almost a century. The immediate stimulation of SOC decomposition was caused by warmer soil before the closure of the plantation’s canopy. Long-term reductions in SOC mean residence times were coupled to litter inputs. Faster SOC decomposition was associated with lower soil microbial carbon use efficiency, which was due to smaller litter inputs and reduced nutrient availabilities. Our results indicate a previously unelucidated control on long-term SOC dynamics in native forests and demonstrate a potential constraint on climate mitigation when such forests are replaced by plantations. PMID:26805949

  2. Impacts of woodchip biochar additions on greenhouse gas production and sorption/degradation of two herbicides in a Minnesota soil.

    PubMed

    Spokas, K A; Koskinen, W C; Baker, J M; Reicosky, D C

    2009-10-01

    A potential abatement to increasing levels of carbon dioxide (CO(2)) in the atmosphere is the use of pyrolysis to convert vegetative biomass into a more stable form of carbon (biochar) that could then be applied to the soil. However, the impacts of pyrolysis biochar on the soil system need to be assessed before initiating large scale biochar applications to agricultural fields. We compared CO(2) respiration, nitrous oxide (N(2)O) production, methane (CH(4)) oxidation and herbicide retention and transformation through laboratory incubations at field capacity in a Minnesota soil (Waukegan silt loam) with and without added biochar. CO(2) originating from the biochar needs to be subtracted from the soil-biochar combination in order to elucidate the impact of biochar on soil respiration. After this correction, biochar amendments reduced CO(2) production for all amendment levels tested (2, 5, 10, 20, 40 and 60% w/w; corresponding to 24-720 tha(-1) field application rates). In addition, biochar additions suppressed N(2)O production at all levels. However, these reductions were only significant at biochar amendment levels >20% w/w. Biochar additions also significantly suppressed ambient CH(4) oxidation at all levels compared to unamended soil. The addition of biochar (5% w/w) to soil increased the sorption of atrazine and acetochlor compared to non-amended soils, resulting in decreased dissipation rates of these herbicides. The recalcitrance of the biochar suggests that it could be a viable carbon sequestration strategy, and might provide substantial net greenhouse gas benefits if the reductions in N(2)O production are lasting.

  3. Isotopic studies of Yucca Mountain soil fluids and carbonate pedogenesis

    SciTech Connect

    McConnaughey, T.A.; Whelan, J.F.; Wickland, K.P.; Moscati, R.J.

    1994-12-31

    Secondary carbonates occurring within the soils, faults, and subsurface fractures of Yucca Mountain contain some of the best available records of paleoclimate and palehydrology for the potential radioactive waste repository site. This article discusses conceptual and analytical advances being made with regard to the interpretation of stable isotope data from pedogenic carbonates, specifically related to the {sup 13}C content of soil CO{sub 2}, CaCO{sub 3}, precipitation mechanisms, and isotopic fractionations between parent fluids and precipitating carbonates. The {sup 13}C content of soil carbon dioxide from Yucca Mountain and vicinity shows most of the usual patterns expected in such contexts: Decreasing {sup 13}C content with depth decreasing {sup 13}C with altitude and reduced {sup 13}C during spring. These patterns exist within the domain of a noisy data set; soil and vegetational heterogeneities, weather, and other factors apparently contribute to isotopic variability in the system. Several soil calcification mechanisms appear to be important, involving characteristic physical and chemical environments and isotopic fractionations. When CO{sub 2} loss from thin soil solutions is an important driving factor, carbonates may contain excess heavy isotopes, compared to equilibrium precipitation with soil fluids. When root calcification serves as a proton generator for plant absorption of soil nutrients, heavy isotope deficiencies are likely. Successive cycles of dissolution and reprecipitation mix and redistribute pedogenic carbonates, and tend to isotopically homogenize and equilibrate pedogenic carbonates with soil fluids.

  4. Topsoil organic carbon content of Europe, a new map based on a generalised additive model

    NASA Astrophysics Data System (ADS)

    de Brogniez, Delphine; Ballabio, Cristiano; Stevens, Antoine; Jones, Robert J. A.; Montanarella, Luca; van Wesemael, Bas

    2014-05-01

    There is an increasing demand for up-to-date spatially continuous organic carbon (OC) data for global environment and climatic modeling. Whilst the current map of topsoil organic carbon content for Europe (Jones et al., 2005) was produced by applying expert-knowledge based pedo-transfer rules on large soil mapping units, the aim of this study was to replace it by applying digital soil mapping techniques on the first European harmonised geo-referenced topsoil (0-20 cm) database, which arises from the LUCAS (land use/cover area frame statistical survey) survey. A generalized additive model (GAM) was calibrated on 85% of the dataset (ca. 17 000 soil samples) and a backward stepwise approach selected slope, land cover, temperature, net primary productivity, latitude and longitude as environmental covariates (500 m resolution). The validation of the model (applied on 15% of the dataset), gave an R2 of 0.27. We observed that most organic soils were under-predicted by the model and that soils of Scandinavia were also poorly predicted. The model showed an RMSE of 42 g kg-1 for mineral soils and of 287 g kg-1 for organic soils. The map of predicted OC content showed the lowest values in Mediterranean countries and in croplands across Europe, whereas highest OC content were predicted in wetlands, woodlands and in mountainous areas. The map of standard error of the OC model predictions showed high values in northern latitudes, wetlands, moors and heathlands, whereas low uncertainty was mostly found in croplands. A comparison of our results with the map of Jones et al. (2005) showed a general agreement on the prediction of mineral soils' OC content, most probably because the models use some common covariates, namely land cover and temperature. Our model however failed to predict values of OC content greater than 200 g kg-1, which we explain by the imposed unimodal distribution of our model, whose mean is tilted towards the majority of soils, which are mineral. Finally, average

  5. The uncertainty of modeled soil carbon stock change for Finland

    NASA Astrophysics Data System (ADS)

    Lehtonen, Aleksi; Heikkinen, Juha

    2013-04-01

    Countries should report soil carbon stock changes of forests for Kyoto Protocol. Under Kyoto Protocol one can omit reporting of a carbon pool by verifying that the pool is not a source of carbon, which is especially tempting for the soil pool. However, verifying that soils of a nation are not a source of carbon in given year seems to be nearly impossible. The Yasso07 model was parametrized against various decomposition data using MCMC method. Soil carbon change in Finland between 1972 and 2011 were simulated with Yasso07 model using litter input data derived from the National Forest Inventory (NFI) and fellings time series. The uncertainties of biomass models, litter turnoverrates, NFI sampling and Yasso07 model were propagated with Monte Carlo simulations. Due to biomass estimation methods, uncertainties of various litter input sources (e.g. living trees, natural mortality and fellings) correlate strongly between each other. We show how original covariance matrices can be analytically combined and the amount of simulated components reduce greatly. While doing simulations we found that proper handling correlations may be even more essential than accurate estimates of standard errors. As a preliminary results, from the analysis we found that both Southern- and Northern Finland were soil carbon sinks, coefficient of variations (CV) varying 10%-25% when model was driven with long term constant weather data. When we applied annual weather data, soils were both sinks and sources of carbon and CVs varied from 10%-90%. This implies that the success of soil carbon sink verification depends on the weather data applied with models. Due to this fact IPCC should provide clear guidance for the weather data applied with soil carbon models and also for soil carbon sink verification. In the UNFCCC reporting carbon sinks of forest biomass have been typically averaged for five years - similar period for soil model weather data would be logical.

  6. Responses of soil enzyme activity and microbial community compositions to nitrogen addition in bulk and microaggregate soil in the temperate steppe of Inner Mongolia

    NASA Astrophysics Data System (ADS)

    Shi, Yao; Sheng, Lianxi; Wang, Zhongqiang; Zhang, Xinyu; He, Nianpeng; Yu, Qiang

    2016-10-01

    In order to explore the responses of soil enzyme activities and microbial community compositions to long-term nitrogen (N) addition in both bulk soil and microaggregate of chestnut soil, we conducted a 7-year urea addition experiment with N treatments at 6 levels (0, 56, 112, 224, 392 and 560 kg N ha-1 yr-1) in a temperate steppe of Inner Mongolia in China. Soil properties and the activities of four enzymes involved in carbon (C), nitrogen (N) and phosphorus (P) cycling were measured in both bulk soil and microaggregate, and phospholipid fatty acids (PLFAs) were measured in bulk soil. The results indicated that: 1) in bulk soil, N addition significantly decreased β-1,4-glucosidase (BG) and leucine aminopeptidase (LAP) activities at the treatment amounts of 224, 392 and 560 kg N ha-1 yr-1, and obviously suppressed β-1,4-N-acetylglucosaminidase (NAG) activity at the treatment amount of 560 kg N ha-1 yr-1. N addition enhanced total PLFAs (totPLFAs) and bacterial PLFAs (bacPLFAs) at the treatment amounts of 392 and 560 kg N ha-1 yr-1, respectively, but fungal PLFAs showed no response to N addition. The activities of BG, NAG and LAP were positively correlated with soil pH, but negatively correlated with the concentration of NH 4 + -N; 2) in microaggregate (53-250 μm), the activities of BG, NAG and AP showed no response to increased addition of N, but the significantly decreased LAP activity was observed at the treatment amount of 392 kg N ha-1 yr-1. These results suggested that enzyme activities were more sensitive to N addition than PLFA biomarkers in soil, and LAP activity in microaggregate may be a good indicator for evaluating N cycle response to long-term N addition.

  7. Effects of Biochar Addition on CO2 and N2O Emissions following Fertilizer Application to a Cultivated Grassland Soil.

    PubMed

    Chen, Jingjing; Kim, Hyunjin; Yoo, Gayoung

    2015-01-01

    Carbon (C) sequestration potential of biochar should be considered together with emission of greenhouse gases when applied to soils. In this study, we investigated CO2 and N2O emissions following the application of rice husk biochars to cultivated grassland soils and related gas emissions tos oil C and nitrogen (N) dynamics. Treatments included biochar addition (CHAR, NO CHAR) and amendment (COMPOST, UREA, NO FERT). The biochar application rate was 0.3% by weight. The temporal pattern of CO2 emissions differed according to biochar addition and amendments. CO2 emissions from the COMPOST soils were significantly higher than those from the UREA and NO FERT soils and less CO2 emission was observed when biochar and compost were applied together during the summer. Overall N2O emission was significantly influenced by the interaction between biochar and amendments. In UREA soil, biochar addition increased N2O emission by 49% compared to the control, while in the COMPOST and NO FERT soils, biochar did not have an effect on N2O emission. Two possible mechanisms were proposed to explain the higher N2O emissions upon biochar addition to UREA soil than other soils. Labile C in the biochar may have stimulated microbial N mineralization in the C-limited soil used in our study, resulting in an increase in N2O emission. Biochar may also have provided the soil with the ability to retain mineral N, leading to increased N2O emission. The overall results imply that biochar addition can increase C sequestration when applied together with compost, and might stimulate N2O emission when applied to soil amended with urea.

  8. Effects of Biochar Addition on CO2 and N2O Emissions following Fertilizer Application to a Cultivated Grassland Soil

    PubMed Central

    Chen, Jingjing; Kim, Hyunjin; Yoo, Gayoung

    2015-01-01

    Carbon (C) sequestration potential of biochar should be considered together with emission of greenhouse gases when applied to soils. In this study, we investigated CO2 and N2O emissions following the application of rice husk biochars to cultivated grassland soils and related gas emissions tos oil C and nitrogen (N) dynamics. Treatments included biochar addition (CHAR, NO CHAR) and amendment (COMPOST, UREA, NO FERT). The biochar application rate was 0.3% by weight. The temporal pattern of CO2 emissions differed according to biochar addition and amendments. CO2 emissions from the COMPOST soils were significantly higher than those from the UREA and NO FERT soils and less CO2 emission was observed when biochar and compost were applied together during the summer. Overall N2O emission was significantly influenced by the interaction between biochar and amendments. In UREA soil, biochar addition increased N2O emission by 49% compared to the control, while in the COMPOST and NO FERT soils, biochar did not have an effect on N2O emission. Two possible mechanisms were proposed to explain the higher N2O emissions upon biochar addition to UREA soil than other soils. Labile C in the biochar may have stimulated microbial N mineralization in the C-limited soil used in our study, resulting in an increase in N2O emission. Biochar may also have provided the soil with the ability to retain mineral N, leading to increased N2O emission. The overall results imply that biochar addition can increase C sequestration when applied together with compost, and might stimulate N2O emission when applied to soil amended with urea. PMID:26020941

  9. Effects of Biochar Addition on CO2 and N2O Emissions following Fertilizer Application to a Cultivated Grassland Soil.

    PubMed

    Chen, Jingjing; Kim, Hyunjin; Yoo, Gayoung

    2015-01-01

    Carbon (C) sequestration potential of biochar should be considered together with emission of greenhouse gases when applied to soils. In this study, we investigated CO2 and N2O emissions following the application of rice husk biochars to cultivated grassland soils and related gas emissions tos oil C and nitrogen (N) dynamics. Treatments included biochar addition (CHAR, NO CHAR) and amendment (COMPOST, UREA, NO FERT). The biochar application rate was 0.3% by weight. The temporal pattern of CO2 emissions differed according to biochar addition and amendments. CO2 emissions from the COMPOST soils were significantly higher than those from the UREA and NO FERT soils and less CO2 emission was observed when biochar and compost were applied together during the summer. Overall N2O emission was significantly influenced by the interaction between biochar and amendments. In UREA soil, biochar addition increased N2O emission by 49% compared to the control, while in the COMPOST and NO FERT soils, biochar did not have an effect on N2O emission. Two possible mechanisms were proposed to explain the higher N2O emissions upon biochar addition to UREA soil than other soils. Labile C in the biochar may have stimulated microbial N mineralization in the C-limited soil used in our study, resulting in an increase in N2O emission. Biochar may also have provided the soil with the ability to retain mineral N, leading to increased N2O emission. The overall results imply that biochar addition can increase C sequestration when applied together with compost, and might stimulate N2O emission when applied to soil amended with urea. PMID:26020941

  10. Microbial removal of atmospheric carbon tetrachloride in bulk aerobic soils.

    PubMed

    Mendoza, Y; Goodwin, K D; Happell, J D

    2011-09-01

    Atmospheric concentrations of carbon tetrachloride (CCl(4)) were removed by bulk aerobic soils from tropical, subtropical, and boreal environments. Removal was observed in all tested soil types, indicating that the process was widespread. The flux measured in field chamber experiments was 0.24 ± 0.10 nmol CCl(4) (m(2) day)(-1) (average ± standard deviation [SD]; n = 282). Removal of CCl(4) and removal of methane (CH(4)) were compared to explore whether the two processes were linked. Removal of both gases was halted in laboratory samples that were autoclaved, dry heated, or incubated in the presence of mercuric chloride (HgCl(2)). In marl soils, treatment with antibiotics such as tetracycline and streptomycin caused partial inhibition of CCl(4) (50%) and CH(4) (76%) removal, but removal was not affected in soils treated with nystatin or myxothiazol. These data indicated that bacteria contributed to the soil removal of CCl(4) and that microeukaryotes may not have played a significant role. Amendments of methanol, acetate, and succinate to soil samples enhanced CCl(4) removal by 59%, 293%, and 72%, respectively. Additions of a variety of inhibitors and substrates indicated that nitrification, methanogenesis, or biological reduction of nitrate, nitrous oxide, or sulfate (e.g., occurring in possible anoxic microzones) did not play a significant role in the removal of CCl(4). Methyl fluoride inhibited removal of CH(4) but not CCl(4), indicating that CH(4) and CCl(4) removals were not directly linked. Furthermore, CCl(4) removal was not affected in soils amended with copper sulfate or methane, supporting the results with MeF and suggesting that the observed CCl(4) removal was not significantly mediated by methanotrophs.

  11. Effects of Vegetation Removal and Soil Disturbance on Soil Organic and Inorganic Carbon Dynamics in California Desert Ecosystems

    NASA Astrophysics Data System (ADS)

    Swanson, A. C.; Allen, E. B.; Allen, M. F.; Hernandez, R. R.

    2015-12-01

    Solar energy developments are projected to be deployed over desert wildland areas with deep soil inorganic carbon (SIC) deposits, which often involves elimination of deep-rooted vegetation. This land cover change may systemically alter SIC pools since respired CO2 is the carbon (C) source during SIC formation. We sought to understand how removal of creosote bush scrub affects soil C pools. We hypothesized that vegetation is important for maintaining SIC and soil organic C (SOC) pools and that disturbance to the vegetation and soil will change CO2 flux with increased losses from SIC. Soils were collected from sites that had intact creosote bush scrub habitat adjacent to disturbed, bare areas where the native vegetation had been previously removed. Samples were taken from beneath shrub canopies and interspaces in intact areas, and from random points in the disturbed area. Soils were analyzed for SIC, SOC, microbial and labile C, and δ13C. Soils were also incubated to determine the potential CO2 flux from disturbed and undisturbed soils along with the sources of CO2. Three replicates per soil underwent a control and water addition treatment and flux and δ13C of CO2 were measured continuously. Control replicates yielded no significant CO2 flux. CO2 flux from watered soils was higher beneath shrub canopy (18.57µmol g soil-1 day-1±1.86) than the interspace soils (0.86 µmol g soil-1 day-1±0.17). Soils collected from bare areas had an intermediate flux (5.41 µmol g soil-1 day-1±2.68 and 3.68 µmol g soil-1 day-1±0.85, respectively) lying between shrub canopy and interspace soils. There was no significant difference between the δ13C values of CO2 from shrub canopy and interspace soils, both of which had a very low δ13C values (-22.60‰±0.64 and -23.88‰±0.89, respectively), resembling that of organic C. However, the isotopic values of CO2 from disturbed soils were significantly higher (-16.68‰±1.36 and -15.22‰±2.12, respectively) suggesting that these

  12. Soil organic carbon enrichment of dust emissions: Magnitude, mechanisms and its implications for the carbon cycle

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Soil erosion is an important component of the global carbon cycle. However, little attention has been given to the role of aeolian processes in influencing soil organic carbon (SOC) flux and the release of greenhouse gasses, such as carbon-dioxide (CO2), to the atmosphere. Understanding the magnitu...

  13. Forest soil carbon is threatened by intensive biomass harvesting

    NASA Astrophysics Data System (ADS)

    Achat, David L.; Fortin, Mathieu; Landmann, Guy; Ringeval, Bruno; Augusto, Laurent

    2015-11-01

    Forests play a key role in the carbon cycle as they store huge quantities of organic carbon, most of which is stored in soils, with a smaller part being held in vegetation. While the carbon storage capacity of forests is influenced by forestry, the long-term impacts of forest managers’ decisions on soil organic carbon (SOC) remain unclear. Using a meta-analysis approach, we showed that conventional biomass harvests preserved the SOC of forests, unlike intensive harvests where logging residues were harvested to produce fuelwood. Conventional harvests caused a decrease in carbon storage in the forest floor, but when the whole soil profile was taken into account, we found that this loss in the forest floor was compensated by an accumulation of SOC in deeper soil layers. Conversely, we found that intensive harvests led to SOC losses in all layers of forest soils. We assessed the potential impact of intensive harvests on the carbon budget, focusing on managed European forests. Estimated carbon losses from forest soils suggested that intensive biomass harvests could constitute an important source of carbon transfer from forests to the atmosphere (142-497 Tg-C), partly neutralizing the role of a carbon sink played by forest soils.

  14. Forest soil carbon is threatened by intensive biomass harvesting.

    PubMed

    Achat, David L; Fortin, Mathieu; Landmann, Guy; Ringeval, Bruno; Augusto, Laurent

    2015-01-01

    Forests play a key role in the carbon cycle as they store huge quantities of organic carbon, most of which is stored in soils, with a smaller part being held in vegetation. While the carbon storage capacity of forests is influenced by forestry, the long-term impacts of forest managers' decisions on soil organic carbon (SOC) remain unclear. Using a meta-analysis approach, we showed that conventional biomass harvests preserved the SOC of forests, unlike intensive harvests where logging residues were harvested to produce fuelwood. Conventional harvests caused a decrease in carbon storage in the forest floor, but when the whole soil profile was taken into account, we found that this loss in the forest floor was compensated by an accumulation of SOC in deeper soil layers. Conversely, we found that intensive harvests led to SOC losses in all layers of forest soils. We assessed the potential impact of intensive harvests on the carbon budget, focusing on managed European forests. Estimated carbon losses from forest soils suggested that intensive biomass harvests could constitute an important source of carbon transfer from forests to the atmosphere (142-497 Tg-C), partly neutralizing the role of a carbon sink played by forest soils. PMID:26530409

  15. Forest soil carbon is threatened by intensive biomass harvesting

    PubMed Central

    Achat, David L.; Fortin, Mathieu; Landmann, Guy; Ringeval, Bruno; Augusto, Laurent

    2015-01-01

    Forests play a key role in the carbon cycle as they store huge quantities of organic carbon, most of which is stored in soils, with a smaller part being held in vegetation. While the carbon storage capacity of forests is influenced by forestry, the long-term impacts of forest managers’ decisions on soil organic carbon (SOC) remain unclear. Using a meta-analysis approach, we showed that conventional biomass harvests preserved the SOC of forests, unlike intensive harvests where logging residues were harvested to produce fuelwood. Conventional harvests caused a decrease in carbon storage in the forest floor, but when the whole soil profile was taken into account, we found that this loss in the forest floor was compensated by an accumulation of SOC in deeper soil layers. Conversely, we found that intensive harvests led to SOC losses in all layers of forest soils. We assessed the potential impact of intensive harvests on the carbon budget, focusing on managed European forests. Estimated carbon losses from forest soils suggested that intensive biomass harvests could constitute an important source of carbon transfer from forests to the atmosphere (142–497 Tg-C), partly neutralizing the role of a carbon sink played by forest soils. PMID:26530409

  16. Carbon Accumulation and Microbial Community Structure in Reclaimed Mine Soils

    NASA Astrophysics Data System (ADS)

    Pfiffner, S. M.; Palumbo, A. V.; Tarver, J. D.; Fisher, S.; Cantu, J.; Brandt, C. C.

    2002-12-01

    microbial biomass and percent carbon and percent nitrogen for the Walls Farm and Jenkins Farm samples was 0.72 and 0.84, respectively. In addition, the PLFA profile was explored for certain PLFA ratios that are indications of physiological or toxic stress. One sample from the Walls Farm showed high stress values for both the cyclopropyl to monoenic ratio and the trans to cis ratio, indicated that there were nutrient limitations and potentially toxic or inhibitory conditions present. In samples from a site with sawdust and two levels of biosolids added, the microbial biomass was not correlated with percent carbon. The microbial biomass was highest in the sawdust treatments, followed by the high and then low biomass treatments. The community structure was similar for the control and low biosolid plots. The high biosolid plot had elevated levels of terminally branched saturates and branched monoenoics (indicative of gram positive prokaryotes and actinomycetes) and reduced levels of polyunsaturates.. ANN was used to more fully assess the relationship between changes in microbial community structure and changes in soil geochemistry.

  17. Addition of organic amendments contributes to C sequestration in trace element contaminated soils.

    NASA Astrophysics Data System (ADS)

    del Mar Montiel Rozas, María; Panettier, Marco; Madejón Rodríguez, Paula; Madejón Rodríguez, Engracia

    2015-04-01

    Nowadays, the study of global C cycle and the different natural sinks of C have become especially important in a climate change context. Fluxes of C have been modified by anthropogenic activities and, presently, the global objective is the decrease of net CO2 emission. For this purpose, many studies are being conducted at local level for evaluate different C sequestration strategies. These techniques must be, in addition to safe in the long term, environmentally friendly. Restoration of contaminated and degraded areas is considered as a strategy for SOC sequestration. Our study has been carried out in the Guadiamar Green Corridor (Seville, Spain) affected by the Aznalcóllar mining accident. This accident occurred 16 years ago, due to the failure of the tailing dam which contained 4-5 million m3 of toxic tailings (slurry and acid water).The affected soils had a layer of toxic sludge containing heavy metals as As, Cd, Cu, Pb and Zn. Restoration techniques began to be applied just after the accident, including the removal of the toxic sludge and a variable layer of topsoil (10-30 cm) from the surface. In a second phase, in a specific area (experimental area) of the Green Corridor the addition of organic amendments (Biosolid compost (BC) and Leonardite (LE), a low grade coal rich in humic acids) was carried out to increase pH, organic matter and fertility in a soil which lost its richest layer during the clean-up operation. In our experimental area, half of the plots (A) received amendments for four years (2002, 2003, 2006 and 2007) whereas the other half (B) received amendments only for two years (2002-2003). To compare, plots without amendments were also established. Net balance of C was carried out using values of Water Soluble Carbon (WSC) and Total Organic Carbon (TOC) for three years (2012, 2013 and 2015). To eliminate artificial changes carried out in the plots, amendment addition and withdrawal of biomass were taken into account to calculate balance of kg TOC

  18. Does North Appalachian Agriculture Contribute to Soil Carbon Sequestration

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Agricultural systems are important for world ecosystems. They can be managed to moderate CO2 emissions. World soils can be both a sink and source of atmospheric CO2, but it is a slow process. Data from long-term soil management experiments are needed to assess soil carbon (C) sink capacity through a...

  19. Microbial Contribution to Organic Carbon Sequestration in Mineral Soil

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Soil productivity and sustainability are dependent on soil organic matter (SOM). Our understanding on how organic inputs to soil from microbial processes become converted to SOM is still limited. This study aims to understand how microbes affect carbon (C) sequestration and the formation of recalcit...

  20. CRADA Carbon Sequestration in Soils and Commercial Products

    SciTech Connect

    Jacobs, G.K.

    2002-01-31

    ORNL, through The Consortium for Research on Enhancing Carbon Sequestration in Terrestrial Ecosystems (CSiTE), collaborated with The Village Botanica, Inc. (VB) on a project investigating carbon sequestration in soils and commercial products from a new sustainable crop developed from perennial Hibiscus spp. Over 500 pre-treated samples were analyzed for soil carbon content. ORNL helped design a sampling scheme for soils during the planting phase of the project. Samples were collected and prepared by VB and analyzed for carbon content by ORNL. The project did not progress to a Phase II proposal because VB declined to prepare the required proposal.

  1. Timing the carbon cycle: how far does the soil erosion benefit stretch ?

    NASA Astrophysics Data System (ADS)

    Wang, Z.; Govers, G.; Van Oost, K.; Merckx, R.

    2012-04-01

    Several papers have now convincingly shown that, on the short term, the intensification of soil erosion due to human activities does not lead to a massive emission of soil organic carbon. Rather, agricultural soil erosion may be responsible for a relatively small carbon sink. This conclusion is mainly based on the fact that a large fraction of the eroded carbon is dynamically replaced by additional soil carbon uptake at eroding sites and the behaviour of the carbon stores created by deposition. Over decadal time periods a large amount of the deposited carbon is indeed retained within the soil reservoir, thereby leading to net extra carbon storage. It is still unclear, however, how stable such stores are over longer time spans. We therefore sampled both active and historical colluvial depositional stores in different landscape settings in the Loess Belt of central Belgium. We determined the total amount of carbon stored as well as the variation in its stable isotope composition and a limited number of samples were subjected to incubation runs. The age of the deposits was determined as accurately as possible by measuring total phosphorous as well as 137Cs analysis as well as by interpreting historical maps and aerial photographs. We used our data to calibrate and validate a simple soil carbon model using two carbon pools only. While the values of the calibration parameters that we obtained for our different sites varied, the results with respect to the lifespan of a soil carbon store created by deposition were consistent. Model simulations show that, under realistic conditions, depositional carbon stores reach equilibrium after 300-1500 years, depending on the deposition rate. At this stage, 20 to 50 % of the deposited soil organic carbon is still present in the colluvium. When accounting for the effects of soil erosion on the global carbon cycle it is therefore important to consider the dynamics of depositional stores over longer time spans. Our analysis shows that

  2. Timing the Carbon Cycle: how far does the Soil Erosion Benefit Stretch ?

    NASA Astrophysics Data System (ADS)

    Govers, G.; Wang, Z.; Van Oost, K.; Merckx, R.

    2011-12-01

    Several papers have now convincingly shown that, on the short term, the intensification of soil erosion due to human activities does not lead to a massive emission of soil organic carbon. Rather, agricultural soil erosion may be responsible for a relatively small carbon sink. This conclusion is mainly based on the fact that a large fraction of the eroded carbon is dynamically replaced by additional soil carbon uptake at eroding sites and the behaviour of the carbon stores created by deposition. Over decadal time periods a large amount of the deposited carbon is indeed retained within the soil reservoir, thereby leading to net extra carbon storage. It is still unclear, however, how stable such stores are over longer time spans. We therefore sampled both active and historical colluvial depositional stores in different landscape settings in the Loess Belt of central Belgium. We determined the total amount of carbon stored as well as the variation in its stable isotope composition and a limited number of samples were subjected to incubation runs. The age of the deposits was determined as accurately as possible by measuring total phosphorous as well as 137Cs analysis as well as by interpreting historical maps and aerial photographs. We used our data to calibrate and validate a simple soil carbon model using two carbon pools only. While the values of the calibration parameters that we obtained for our different sites varied, the results with respect to the lifespan of a soil carbon store created by deposition were consistent. Model simulations show that, under realistic conditions, depositional carbon stores reach equilibrium after 300-1500 years, depending on the deposition rate. At this stage, 20 to 50 % of the deposited soil organic carbon is still present in the colluvium. When accounting for the effects of soil erosion on the global carbon cycle it is therefore important to consider the dynamics of depositional stores over longer time spans. Our analysis shows that

  3. Effects of amendment of different biochars on soil physical and biological properties related to carbon mineralization

    NASA Astrophysics Data System (ADS)

    Zhang, Renduo; Zhu, Shuzhi; Ouyang, Lei

    2014-05-01

    Biochar addition to soils potentially affects various soil properties, and these effects are dependent on biochars derived from different feedstock materials and pyrolysis processes. The objective of this study was to investigate the effects of amendment of different biochars on soil physical and biological properties. Biochars were produced with dairy manure and woodchip at temperatures of 300, 500, and 700°C, respectively. Each biochar was mixed at 5% (w/w) with a forest soil and the mixture was incubated for 180 days, during which soil physical and biological properties, and soil respiration rates were measured. Results showed that the biochar addition significantly enhanced the formation of soil macroaggregates at the early incubation time. The biochar application significantly reduced soil bulk density, increased the amount of soil organic matter, and stimulated microbial activity and soil respiration rates at the early incubation stage. Biochar applications improved water retention capacity, with stronger effects by biochars produced at higher pyrolysis temperatures. At the same suction, the soil with woodchip biochars possessed higher water content than with the dairy manure biochars. Biochar addition significantly affected the soil physical and biological properties, which resulted in different soil carbon mineralization rates.

  4. Effect of biochar or activated carbon amendment on the volatilisation and biodegradation of organic soil pollutants

    NASA Astrophysics Data System (ADS)

    Werner, David; Meynet, Paola; Bushnaf, Khaled

    2013-04-01

    Biochar or activated carbon added to contaminated soil may temporarily reduce the volatilisation of organic pollutants by enhanced sorption. The long-term effect of sorbent amendments on the fate of volatile petroleum hydrocarbon mixtures (VPHs) will depend on the responses of the soil bacterial community members, especially those which may utilize VPHs as carbon substrates. We investigated the volatilisation and biodegradation of VPHs emanating from NAPL sources and migrating through one meter long columns containing unsaturated sandy soil with and without 2% biochar or activated carbon amendment. After 420 days, VPH volatilisation from AC amended soil was less than 10 percent of the cumulative VPH volatilisation flux from unamended soil. The cumulative CO2 volatilisation flux increased more slowly in AC amended soil, but was comparable to the untreated soil after 420 days. This indicated that the pollution attenuation over a 1 meter distance was improved by the AC amendment. Biochar was a weaker VPH sorbent than AC and had a lesser effect on the cumulative VPH and CO2 fluxes. We also investgated the predominant bacterial community responses in sandy soil to biochar and/or VPH addition with a factorially designed batch study, and by analyzing preserved soil samples. Biochar addition alone had only weak effects on soil bacterial communities, while VPH addition was a strong community structure shaping factor. The bacterial community effects of biochar-enhanced VPH sorption were moderated by the limited biomass carrying capacity of the sandy soil investigated which contained only low amounts of inorganic nitrogen. Several Pseudomonas spp., including Pseudomonas putida strains, became dominant in VPH polluted soil with and without biochar. The ability of these versatile VPH degraders to effectively regulate their metabolic pathways according to substrate availabilities may additionally have moderated bacterial community structure responses to the presence of biochar

  5. Black carbon contributes to organic matter in young soils in the Morteratsch proglacial area (Switzerland)

    NASA Astrophysics Data System (ADS)

    Eckmeier, E.; Mavris, C.; Krebs, R.; Pichler, B.; Egli, M.

    2012-10-01

    Most glacier forefields of the European Alps are progressively exposed since the glaciers reached their maximum expansion in the 1850s. Global warming and climate changes additionally promote the exposure of sediments in previously glaciated areas. In these proglacial areas, initial soils have started to develop so that they may offer a continuous chronosequence from 0 to 150 yr-old soils. The build-up of organic matter is an important factor of soil formation, and not only autochthonous but also distant sources might contribute to its accumulation in young soils and surfaces of glacier forefields. Only little is known about black carbon in soils that develop in glacier forefields, although charred organic matter could be an important component of organic carbon in Alpine soils. The aim of our study was to examine whether black carbon is present in the initial soils of a proglacial area, and to estimate its relative contribution to soil organic matter. We investigated soil samples from 35 sites distributed over the whole proglacial area of Morteratsch, covering a chronosequence from 0 to 150 yr. BC concentrations were determined in fine-earth using the benzene polycarboxylic acid (BPCA) marker method. We found that the proportion of BC to total Corg was related to the time since the surface was exposed. Soils on surfaces exposed less than 40 yr ago contained the highest proportion of BC. The absolute concentrations of BC in fine-earth were generally low but increased in soils that had been exposed for more than 40 yr. Charred organic matter occurred in the whole area, and it was a main component of soil organic matter in young soils, where total Corg concentrations were very low. Specific initial microbial communities consequently may profit from this additional C source during the first years of soil evolution and potentially promote soil development in its early stage.

  6. Carbon amendment and soil depth affect the distribution and abundance of denitrifiers in agricultural soils.

    PubMed

    Barrett, M; Khalil, M I; Jahangir, M M R; Lee, C; Cardenas, L M; Collins, G; Richards, K G; O'Flaherty, V

    2016-04-01

    The nitrite reductase (nirS and nirK) and nitrous oxide reductase-encoding (nosZ) genes of denitrifying populations present in an agricultural grassland soil were quantified using real-time polymerase chain reaction (PCR) assays. Samples from three separate pedological depths at the chosen site were investigated: horizon A (0-10 cm), horizon B (45-55 cm), and horizon C (120-130 cm). The effect of carbon addition (treatment 1, control; treatment 2, glucose-C; treatment 3, dissolved organic carbon (DOC)) on denitrifier gene abundance and N2O and N2 fluxes was determined. In general, denitrifier abundance correlated well with flux measurements; nirS was positively correlated with N2O, and nosZ was positively correlated with N2 (P < 0.03). Denitrifier gene copy concentrations per gram of soil (GCC) varied in response to carbon type amendment (P < 0.01). Denitrifier GCCs were high (ca. 10(7)) and the bac:nirK, bac:nirS, bac:nir (T) , and bac:nosZ ratios were low (ca. 10(-1)/10) in horizon A in all three respective treatments. Glucose-C amendment favored partial denitrification, resulting in higher nir abundance and higher N2O fluxes compared to the control. DOC amendment, by contrast, resulted in relatively higher nosZ abundance and N2 emissions, thus favoring complete denitrification. We also noted soil depth directly affected bacterial, archaeal, and denitrifier abundance, possibly due to changes in soil carbon availability with depth.

  7. Soil microbial responses to forest floor litter manipulation and nitrogen addition in a mixed-wood forest of northern China

    PubMed Central

    Sun, Xiao-Lu; Zhao, Jing; You, Ye-Ming; Jianxin Sun, Osbert

    2016-01-01

    Changes in litterfall dynamics and soil properties due to anthropogenic or natural perturbations have important implications to soil carbon (C) and nutrient cycling via microbial pathway. Here we determine soil microbial responses to contrasting types of litter inputs (leaf vs. fine woody litter) and nitrogen (N) deposition by conducting a multi-year litter manipulation and N addition experiment in a mixed-wood forest. We found significantly higher soil organic C, total N, microbial biomass C (MBC) and N (MBN), microbial activity (MR), and activities of four soil extracellular enzymes, including β-glucosidase (BG), N-acetyl-β-glucosaminidase (NAG), phenol oxidase (PO), and peroxidase (PER), as well as greater total bacteria biomass and relative abundance of gram-negative bacteria (G-) community, in top soils of plots with presence of leaf litter than of those without litter or with presence of only fine woody litter. No apparent additive or interactive effects of N addition were observed in this study. The occurrence of more labile leaf litter stimulated G-, which may facilitate microbial community growth and soil C stabilization as inferred by findings in literature. A continued treatment with contrasting types of litter inputs is likely to result in divergence in soil microbial community structure and function. PMID:26762490

  8. Restoration of species-rich grasslands on ex-arable land: seed addition outweighs soil fertility reduction

    SciTech Connect

    Kardol, Paul

    2008-01-01

    A common practice in biodiversity conservation is restoration of former species-rich grassland on ex-arable land. Major constraints for grassland restoration are high soil fertility and limited dispersal ability of plant species to target sites. Usually, studies focus on soil fertility or on methods to introduce plant seeds. However, the question is whether soil fertility reduction is always necessary for getting plant species established on target sites. In a three-year field experiment with ex-arable soil with intensive farming history, we tested single and combined effects of soil fertility reduction and sowing mid-successional plant species on plant community development and soil biological properties. A controlled microcosm study was performed to test short-term effects of soil fertility reduction measures on biomass production of mid-successional species. Soil fertility was manipulated by adding carbon (wood or straw) to incorporate plant-available nutrients into organic matter, or by removing nutrients through top soil removal (TSR). The sown species established successfully and their establishment was independent of carbon amendments. TSR reduced plant biomass, and effectively suppressed arable weeds, however, created a desert-like environment, inhibiting the effectiveness of sowing mid-successional plant species. Adding straw or wood resulted in short-term reduction of plant biomass, suggesting a temporal decrease in plant-available nutrients by microbial immobilisation. Straw and wood addition had little effects on soil biological properties, whereas TSR profoundly reduced numbers of bacteria, fungal biomass and nematode abundance. In conclusion, in ex-arable soils, on a short term sowing is more effective for grassland restoration than strategies aiming at soil fertility reduction.

  9. Effect of almond shell biochar addition on the hydro-physical properties of an arable Central Valley soil

    NASA Astrophysics Data System (ADS)

    Lopez, V.; Ghezzehei, T. A.

    2014-12-01

    Biochar is composed of any carbonaceous matter pyrolyzed under low oxygen exposure. Its use as a soil amendment to address soil infertility has been accelerated by studies reporting positive effects of enhanced nutrient retention, cation exchange capacity, microbial activity, and vegetative growth over time. Biochar has also been considered as a carbon sequestration method because of its reported environmental persistence. While the aforementioned effects are positive benefits of biochar's use, its impact on soil physical properties and water flow are equally important in maintaining soil fertility. This study aims to show how soil physical and hydraulic properties change over time with biochar addition. To address these aims, we conducted a 9 week microcosm incubation experiment with local arable loamy sand soils amended with biochar. Biochar was created from locally collected almond shells and differs by pyrolysis temperatures (350°C, 700°C) and size (<250 μm, 1-2mm). Additionally, biochar was applied to soil at a low (10 t/ha) or high (60 t/ha) rates. Changes in soil water flow properties were analyzed by infiltration or pressure cell experiments immediately after creating our soil-biochar mixtures. These experiments were repeated during and after the incubation period to observe if and how flow is altered over time. Following incubation and hydraulic experiments, a water drop penetration time (WDPT) test was conducted to observe any alterations in surface hydrophobicity. Changes in soil physical properties were analyzed by determining content of water stable aggregates remaining after wet sieving. This series of experiments is expected to provide a greater understanding on the impact biochar addition on soil physical and hydraulic properties. Furthermore, it provides insight into whether or not converting local agricultural waste into biochar for soil use will be beneficial, especially in agricultural systems undergoing climate stress.

  10. Biofuel intercropping effects on soil carbon and microbial activity.

    PubMed

    Strickland, Michael S; Leggett, Zakiya H; Sucre, Eric B; Bradford, Mark A

    2015-01-01

    Biofuels will help meet rising demands for energy and, ideally, limit climate change associated with carbon losses from the biosphere to atmosphere. Biofuel management must therefore maximize energy production and maintain ecosystem carbon stocks. Increasingly, there is interest in intercropping biofuels with other crops, partly because biofuel production on arable land might reduce availability and increase the price of food. One intercropping approach involves growing biofuel grasses in forest plantations. Grasses differ from trees in both their organic inputs to soils and microbial associations. These differences are associated with losses of soil carbon when grasses become abundant in forests. We investigated how intercropping switchgrass (Panicum virgalum), a major candidate for cellulosic biomass production, in loblolly pine (Pinus taeda) plantations affects soil carbon, nitrogen, and microbial dynamics. Our design involved four treatments: two pine management regimes where harvest residues (i.e., biomass) were left in place or removed, and two switchgrass regimes where the grass was grown with pine under the same two biomass scenarios (left or removed). Soil variables were measured in four 1-ha replicate plots in the first and second year following switchgrass planting. Under switchgrass intercropping, pools of mineralizable and particulate organic matter carbon were 42% and 33% lower, respectively. These declines translated into a 21% decrease in total soil carbon in the upper 15 cm of the soil profile, during early stand development. The switchgrass effect, however, was isolated to the interbed region where switchgrass is planted. In these regions, switchgrass-induced reductions in soil carbon pools with 29%, 43%, and 24% declines in mineralizable, particulate, and total soil carbon, respectively. Our results support the idea that grass inputs to forests can prime the activity of soil organic carbon degrading microbes, leading to net reductions in stocks

  11. Compost addition reduces porosity and chlordecone transfer in soil microstructure.

    PubMed

    Woignier, Thierry; Clostre, Florence; Fernandes, Paula; Rangon, Luc; Soler, Alain; Lesueur-Jannoyer, Magalie

    2016-01-01

    Chlordecone, an organochlorine insecticide, pollutes soils and contaminates crops and water resources and is biomagnified by food chains. As chlordecone is partly trapped in the soil, one possible alternative to decontamination may be to increase its containment in the soil, thereby reducing its diffusion into the environment. Containing the pesticide in the soil could be achieved by adding compost because the pollutant has an affinity for organic matter. We hypothesized that adding compost would also change soil porosity, as well as transport and containment of the pesticide. We measured the pore features and studied the nanoscale structure to assess the effect of adding compost on soil microstructure. We simulated changes in the transport properties (hydraulic conductivity and diffusion) associated with changes in porosity. During compost incubation, the clay microstructure collapsed due to capillary stresses. Simulated data showed that the hydraulic conductivity and diffusion coefficient were reduced by 95 and 70% in the clay microstructure, respectively. Reduced transport properties affected pesticide mobility and thus helped reduce its transfer from the soil to water and to the crop. We propose that the containment effect is due not only to the high affinity of chlordecone for soil organic matter but also to a trapping mechanism in the soil porosity.

  12. Compost addition reduces porosity and chlordecone transfer in soil microstructure.

    PubMed

    Woignier, Thierry; Clostre, Florence; Fernandes, Paula; Rangon, Luc; Soler, Alain; Lesueur-Jannoyer, Magalie

    2016-01-01

    Chlordecone, an organochlorine insecticide, pollutes soils and contaminates crops and water resources and is biomagnified by food chains. As chlordecone is partly trapped in the soil, one possible alternative to decontamination may be to increase its containment in the soil, thereby reducing its diffusion into the environment. Containing the pesticide in the soil could be achieved by adding compost because the pollutant has an affinity for organic matter. We hypothesized that adding compost would also change soil porosity, as well as transport and containment of the pesticide. We measured the pore features and studied the nanoscale structure to assess the effect of adding compost on soil microstructure. We simulated changes in the transport properties (hydraulic conductivity and diffusion) associated with changes in porosity. During compost incubation, the clay microstructure collapsed due to capillary stresses. Simulated data showed that the hydraulic conductivity and diffusion coefficient were reduced by 95 and 70% in the clay microstructure, respectively. Reduced transport properties affected pesticide mobility and thus helped reduce its transfer from the soil to water and to the crop. We propose that the containment effect is due not only to the high affinity of chlordecone for soil organic matter but also to a trapping mechanism in the soil porosity. PMID:26250815

  13. Total organic carbon in aggregates as a soil recovery indicator

    NASA Astrophysics Data System (ADS)

    Luciene Maltoni, Katia; Rodrigues Cassiolato, Ana Maria; Amorim Faria, Glaucia; Dubbin, William

    2015-04-01

    The soil aggregation promotes physical protection of organic matter, preservation of which is crucial to improve soil structure, fertility and ensure the agro-ecosystems sustainability. The no-tillage cultivation system has been considered as one of the strategies to increase total soil organic carbono (TOC) contents and soil aggregation, both are closely related and influenced by soil management systems. The aim of this study was to evaluate the distribution of soil aggregates and the total organic carbon inside aggregates, with regard to soil recovery, under 3 different soil management systems, i.e. 10 and 20 years of no-tillage cultivation as compared with soil under natural vegetation (Cerrado). Undisturbed soils (0-5; 5-10; and 10-20 cm depth) were collected from Brazil, Central Region. The soils, Oxisols from Cerrado, were collected from a field under Natural Vegetation-Cerrado (NV), and from fields that were under conventional tillage since 1970s, and 10 and 20 years ago were changed to no-tillage cultivation system (NT-10; NT-20 respectively). The undisturbed samples were sieved (4mm) and the aggregates retained were further fractionated by wet sieving through five sieves (2000, 1000, 500, 250, and 50 μm) with the aggregates distribution expressed as percentage retained by each sieve. The TOC was determined, for each aggregate size, by combustion (Thermo-Finnigan). A predominance of aggregates >2000 μm was observed under NV treatment (92, 91, 82 %), NT-10 (64, 73, 61 %), and NT-20 (71, 79, 63 %) for all three depths (0-5; 5-10; 10-20 cm). In addition greater quantities of aggregates in sizes 1000, 500, 250 and 50 μm under NT-10 and NT-20 treatments, explain the lower aggregate stability under these treatments compared to the soil under NV. The organic C concentration for NV in aggregates >2000 μm was 24,4; 14,2; 8,7 mg/g for each depth (0-5; 5-10; 10-20 cm, respectively), higher than in aggregates sized 250-50 μm (7,2; 5,5; 4,4 mg/g) for all depths

  14. Carbon fiber enhanced bioelectricity generation in soil microbial fuel cells.

    PubMed

    Li, Xiaojing; Wang, Xin; Zhao, Qian; Wan, Lili; Li, Yongtao; Zhou, Qixing

    2016-11-15

    The soil microbial fuel cell (MFC) is a promising biotechnology for the bioelectricity recovery as well as the remediation of organics contaminated soil. However, the electricity production and the remediation efficiency of soil MFC are seriously limited by the tremendous internal resistance of soil. Conductive carbon fiber was mixed with petroleum hydrocarbons contaminated soil and significantly enhanced the performance of soil MFC. The maximum current density, the maximum power density and the accumulated charge output of MFC mixed carbon fiber (MC) were 10, 22 and 16 times as high as those of closed circuit control due to the carbon fiber productively assisted the anode to collect the electron. The internal resistance of MC reduced by 58%, 83% of which owed to the charge transfer resistance, resulting in a high efficiency of electron transfer from soil to anode. The degradation rates of total petroleum hydrocarbons enhanced by 100% and 329% compared to closed and opened circuit controls without the carbon fiber respectively. The effective range of remediation and the bioelectricity recovery was extended from 6 to 20cm with the same area of air-cathode. The mixed carbon fiber apparently enhanced the bioelectricity generation and the remediation efficiency of soil MFC by means of promoting the electron transfer rate from soil to anode. The use of conductively functional materials (e.g. carbon fiber) is very meaningful for the remediation and bioelectricity recovery in the bioelectrochemical remediation. PMID:27162144

  15. Carbon fiber enhanced bioelectricity generation in soil microbial fuel cells.

    PubMed

    Li, Xiaojing; Wang, Xin; Zhao, Qian; Wan, Lili; Li, Yongtao; Zhou, Qixing

    2016-11-15

    The soil microbial fuel cell (MFC) is a promising biotechnology for the bioelectricity recovery as well as the remediation of organics contaminated soil. However, the electricity production and the remediation efficiency of soil MFC are seriously limited by the tremendous internal resistance of soil. Conductive carbon fiber was mixed with petroleum hydrocarbons contaminated soil and significantly enhanced the performance of soil MFC. The maximum current density, the maximum power density and the accumulated charge output of MFC mixed carbon fiber (MC) were 10, 22 and 16 times as high as those of closed circuit control due to the carbon fiber productively assisted the anode to collect the electron. The internal resistance of MC reduced by 58%, 83% of which owed to the charge transfer resistance, resulting in a high efficiency of electron transfer from soil to anode. The degradation rates of total petroleum hydrocarbons enhanced by 100% and 329% compared to closed and opened circuit controls without the carbon fiber respectively. The effective range of remediation and the bioelectricity recovery was extended from 6 to 20cm with the same area of air-cathode. The mixed carbon fiber apparently enhanced the bioelectricity generation and the remediation efficiency of soil MFC by means of promoting the electron transfer rate from soil to anode. The use of conductively functional materials (e.g. carbon fiber) is very meaningful for the remediation and bioelectricity recovery in the bioelectrochemical remediation.

  16. Factors controlling carbon metabolism and humification in different soil agroecosystems.

    PubMed

    Doni, S; Macci, C; Peruzzi, E; Ceccanti, B; Masciandaro, G

    2014-01-01

    The aim of this study was to describe the processes that control humic carbon sequestration in soil. Three experimental sites differing in terms of management system and climate were selected: (i) Abanilla-Spain, soil treated with municipal solid wastes in Mediterranean semiarid climate; (ii) Puch-Germany, soil under intensive tillage and conventional agriculture in continental climate; and (iii) Alberese-Italy, soil under organic and conventional agriculture in Mediterranean subarid climate. The chemical-structural and biochemical soil properties at the initial sampling time and one year later were evaluated. The soils under organic (Alberese, soil cultivated with Triticum durum Desf.) and nonintensive management practices (Puch, soil cultivated with Triticum aestivum L. and Avena sativa L.) showed higher enzymatically active humic carbon, total organic carbon, humification index (B/E(3)s), and metabolic potential (dehydrogenase activity/water soluble carbon) if compared with conventional agriculture and plough-based tillage, respectively. In Abanilla, the application of municipal solid wastes stimulated the specific β-glucosidase activity (extracellular β-glucosidase activity/extractable humic carbon) and promoted the increase of humic substances with respect to untreated soil. The evolution of the chemical and biochemical status of the soils along a climatic gradient suggested that the adoption of certain management practices could be very promising in increasing SOC sequestration potential.

  17. Factors Controlling Carbon Metabolism and Humification in Different Soil Agroecosystems

    PubMed Central

    Doni, S.; Macci, C.; Peruzzi, E.; Ceccanti, B.; Masciandaro, G.

    2014-01-01

    The aim of this study was to describe the processes that control humic carbon sequestration in soil. Three experimental sites differing in terms of management system and climate were selected: (i) Abanilla-Spain, soil treated with municipal solid wastes in Mediterranean semiarid climate; (ii) Puch-Germany, soil under intensive tillage and conventional agriculture in continental climate; and (iii) Alberese-Italy, soil under organic and conventional agriculture in Mediterranean subarid climate. The chemical-structural and biochemical soil properties at the initial sampling time and one year later were evaluated. The soils under organic (Alberese, soil cultivated with Triticum durum Desf.) and nonintensive management practices (Puch, soil cultivated with Triticum aestivum L. and Avena sativa L.) showed higher enzymatically active humic carbon, total organic carbon, humification index (B/E3s), and metabolic potential (dehydrogenase activity/water soluble carbon) if compared with conventional agriculture and plough-based tillage, respectively. In Abanilla, the application of municipal solid wastes stimulated the specific β-glucosidase activity (extracellular β-glucosidase activity/extractable humic carbon) and promoted the increase of humic substances with respect to untreated soil. The evolution of the chemical and biochemical status of the soils along a climatic gradient suggested that the adoption of certain management practices could be very promising in increasing SOC sequestration potential. PMID:25614887

  18. Unambiguous evidence of old soil carbon in grass biosilica particles

    NASA Astrophysics Data System (ADS)

    Reyerson, Paul E.; Alexandre, Anne; Harutyunyan, Araks; Corbineau, Remi; Martinez De La Torre, Hector A.; Badeck, Franz; Cattivelli, Luigi; Santos, Guaciara M.

    2016-03-01

    Plant biosilica particles (phytoliths) contain small amounts of carbon called phytC. Based on the assumptions that phytC is of photosynthetic origin and a closed system, claims were recently made that phytoliths from several agriculturally important monocotyledonous species play a significant role in atmospheric CO2 sequestration. However, anomalous phytC radiocarbon (14C) dates suggested contributions from a non-photosynthetic source to phytC. Here we address this non-photosynthetic source hypothesis using comparative isotopic measurements (14C and δ13C) of phytC, plant tissues, atmospheric CO2, and soil organic matter. State-of-the-art methods assured phytolith purity, while sequential stepwise-combustion revealed complex chemical-thermal decomposability properties of phytC. Although photosynthesis is the main source of carbon in plant tissue, it was found that phytC is partially derived from soil carbon that can be several thousand years old. The fact that phytC is not uniquely constituted of photosynthetic C limits the usefulness of phytC either as a dating tool or as a significant sink of atmospheric CO2. It additionally calls for further experiments to investigate how SOM-derived C is accessible to roots and accumulates in plant biosilica, for a better understanding of the mechanistic processes underlying the silicon biomineralization process in higher plants.

  19. Weathering controls on mechanisms of carbon storage in grassland soils

    USGS Publications Warehouse

    Masiello, C.A.; Chadwick, O.A.; Southon, J.; Torn, M.S.; Harden, J.W.

    2004-01-01

    On a sequence of soils developed under similar vegetation, temperature, and precipitation conditions, but with variations in mineralogical properties, we use organic carbon and 14C inventories to examine mineral protection of soil organic carbon. In these soils, 14C data indicate that the creation of slow-cycling carbon can be modeled as occurring through reaction of organic ligands with Al3+ and Fe3+ cations in the upper horizons, followed by sorption to amorphous inorganic Al compounds at depth. Only one of these processes, the chelation Al3+ and Fe3+ by organic ligands, is linked to large carbon stocks. Organic ligands stabilized by this process traverse the soil column as dissolved organic carbon (both from surface horizons and root exudates). At our moist grassland site, this chelation and transport process is very strongly correlated with the storage and long-term stabilization of soil organic carbon. Our 14C results show that the mechanisms of organic carbon transport and storage at this site follow a classic model previously believed to only be significant in a single soil order (Spodosols), and closely related to the presence of forests. The presence of this process in the grassland Alfisol, Inceptisol, and Mollisol soils of this chronosequence suggests that this process is a more significant control on organic carbon storage than previously thought. Copyright 2004 by the American Geophysical Union.

  20. Weathering controls on mechanisms of carbon storage in grassland soils

    SciTech Connect

    Masiello, C.A.; Chadwick, O.A.; Southon, J.; Torn, M.S.; Harden, J.W.

    2004-09-01

    On a sequence of soils developed under similar vegetation, temperature, and precipitation conditions, but with variations in mineralogical properties, we use organic carbon and 14C inventories to examine mineral protection of soil organic carbon. In these soils, 14C data indicate that the creation of slow-cycling carbon can be modeled as occurring through reaction of organic ligands with Al3+ and Fe3+ cations in the upper horizons, followed by sorption to amorphous inorganic Al compounds at depth. Only one of these processes, the chelation of Al3+ and Fe3+ by organic ligands, is linked to large carbon stocks. Organic ligands stabilized by this process traverse the soil column as dissolved organic carbon (both from surface horizons and root exudates). At our moist grassland site, this chelation and transport process is very strongly correlated with the storage and long-term stabilization of soil organic carbon. Our 14C results show that the mechanisms of organic carbon transport and storage at this site follow a classic model previously believed to only be significant in a single soil order (Spodosols), and closely related to the presence of forests. The presence of this process in the grassland Alfisol, Inceptisol, and Mollisol soils of this chronosequence suggests that this process is a more significant control on organic carbon storage than previously thought.

  1. Soil aggregate stability as affected by clay mineralogy and polyacrylamide addition

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The addition of polyacrylamide (PAM) to soil leads to stabilization of existing aggregates and improved bonding between, and aggregation of adjacent soil particles However, the dependence of PAM efficacy as an aggregate stabilizing agent on soil-clay mineralogy has not been studied. Sixteen soil sam...

  2. Biochar soil amendment for waste-stream diversion, nutrient holding capacity, and carbon sequestration in two contrasting soils

    NASA Astrophysics Data System (ADS)

    Deem, L. M.; Crow, S. E.; Deenik, J. L.; Penton, C. R.; Yanagida, J.

    2013-12-01

    Biochar is organic matter that has been pyrolized under low oxygen conditions for use as a soil amendment. Currently biochar is viewed as a way to improve soil quality (e.g., increased nutrient and water holding capacity) and increase in soil carbon (C) sequestration. The use of biochar in soil is not new, yet little is known about the underlying mechanisms that control the interactions between biochar and soil following amendment. In the past, the effects of biochar addition on crop yields, soil properties and greenhouse gas (GHG) fluxes in both in-situ and controlled experiments have produced inconsistent results. These discrepancies may be uncovered in part by chemical and physical characterization of the biochar prior to amendment and identification of soil- and biochar-specific interactions. Furthermore, a more holistic consideration of the system may demonstrate the virtues of biochar amendment beyond the typical considerations of yield and gas flux. We expect that as the differences between the physical and chemical properties of the biochar and the soil increase, the impact on the soil quality metrics will also increase. For this study, we used a waste product (i.e., anaerobic digester sludge) biochar with 81.5% C, pH of 10.44, pH-independent charge for anion exchange capacity (AEC) and a pH-dependent charge for cation exchange capacity (CEC), 4.14% moisture content and 25.75 cmol¬c /kg exchangeable base cations. This biochar was incorporated into both a low and a high fertility Hawaiian field soil to quantitate biochar effects on crop yield, soil pH, CEC, AEC, hot and cold water extractable C and nitrogen, bulk density, phosphorus, soil microbial ecology, and GHG flux in varying soil conditions. Compared to the higher fertility soil, we hypothesized that the low fertility soil would demonstrate a greater increase in soil quality, including higher pH, CEC and water holding capacity. Two crop management practices were included with each soil: traditional

  3. Extraction of pesticides from contaminated soil using supercritical carbon dioxide

    SciTech Connect

    Hunter, G.B.

    1991-12-31

    The demand for processes to clean up contaminated soils without generating additional contaminants, such as hazardous solvents, is increasing. One approach to minimizing this problem is to use supercritical fluids like light hydrocarbons and CO{sub 2} to extract contaminants from soils. Gases exhibit unique properties under supercritical conditions. They retain the ability to diffuse through the interstitial spaces of solid materials, plus they have the solvating power of liquids. Some examples of extractions using SCFs are caffeine from coffee, cholesterol from eggs, drugs from plants, and nicotine from tobacco. Supercritical CO{sub 2} is an attractive, alternative extraction medium for removal of pesticides from soils. Carbon dioxide is readily available, relatively inexpensive, and if recycled, nonpolluting. Contaminants may be easily recovered by evaporating the CO{sub 2} into an expansion vessel. Supercritical fluid extraction technology is discussed and results are given for the extraction of atrazine, bentazon, alachlor, and permethrin from contaminated soil prepared in the laboratory. Initial studies show >95% removal for these pesticides.

  4. Extraction of pesticides from contaminated soil using supercritical carbon dioxide

    SciTech Connect

    Hunter, G.B.

    1991-01-01

    The demand for processes to clean up contaminated soils without generating additional contaminants, such as hazardous solvents, is increasing. One approach to minimizing this problem is to use supercritical fluids like light hydrocarbons and CO[sub 2] to extract contaminants from soils. Gases exhibit unique properties under supercritical conditions. They retain the ability to diffuse through the interstitial spaces of solid materials, plus they have the solvating power of liquids. Some examples of extractions using SCFs are caffeine from coffee, cholesterol from eggs, drugs from plants, and nicotine from tobacco. Supercritical CO[sub 2] is an attractive, alternative extraction medium for removal of pesticides from soils. Carbon dioxide is readily available, relatively inexpensive, and if recycled, nonpolluting. Contaminants may be easily recovered by evaporating the CO[sub 2] into an expansion vessel. Supercritical fluid extraction technology is discussed and results are given for the extraction of atrazine, bentazon, alachlor, and permethrin from contaminated soil prepared in the laboratory. Initial studies show >95% removal for these pesticides.

  5. Surficial gains and subsoil losses of soil carbon and nitrogen during secondary forest development.

    PubMed

    Mobley, Megan L; Lajtha, Kate; Kramer, Marc G; Bacon, Allan R; Heine, Paul R; Richter, Daniel Deb

    2015-02-01

    Reforestation of formerly cultivated land is widely understood to accumulate above- and belowground detrital organic matter pools, including soil organic matter. However, during 40 years of study of reforestation in the subtropical southeastern USA, repeated observations of above- and belowground carbon documented that significant gains in soil organic matter (SOM) in surface soils (0-7.5 cm) were offset by significant SOM losses in subsoils (35-60 cm). Here, we extended the observation period in this long-term experiment by an additional decade, and used soil fractionation and stable isotopes and radioisotopes to explore changes in soil organic carbon and soil nitrogen that accompanied nearly 50 years of loblolly pine secondary forest development. We observed that accumulations of mineral soil C and N from 0 to 7.5 cm were almost entirely due to accumulations of light-fraction SOM. Meanwhile, losses of soil C and N from mineral soils at 35 to 60 cm were from SOM associated with silt and clay-sized particles. Isotopic signatures showed relatively large accumulations of forest-derived carbon in surface soils, and little to no accumulation of forest-derived carbon in subsoils. We argue that the land use change from old field to secondary forest drove biogeochemical and hydrological changes throughout the soil profile that enhanced microbial activity and SOM decomposition in subsoils. However, when the pine stands aged and began to transition to mixed pines and hardwoods, demands on soil organic matter for nutrients to support aboveground growth eased due to pine mortality, and subsoil organic matter levels stabilized. This study emphasizes the importance of long-term experiments and deep measurements when characterizing soil C and N responses to land use change and the remarkable paucity of such long-term soil data deeper than 30 cm. PMID:25155991

  6. Surficial gains and subsoil losses of soil carbon and nitrogen during secondary forest development.

    PubMed

    Mobley, Megan L; Lajtha, Kate; Kramer, Marc G; Bacon, Allan R; Heine, Paul R; Richter, Daniel Deb

    2015-02-01

    Reforestation of formerly cultivated land is widely understood to accumulate above- and belowground detrital organic matter pools, including soil organic matter. However, during 40 years of study of reforestation in the subtropical southeastern USA, repeated observations of above- and belowground carbon documented that significant gains in soil organic matter (SOM) in surface soils (0-7.5 cm) were offset by significant SOM losses in subsoils (35-60 cm). Here, we extended the observation period in this long-term experiment by an additional decade, and used soil fractionation and stable isotopes and radioisotopes to explore changes in soil organic carbon and soil nitrogen that accompanied nearly 50 years of loblolly pine secondary forest development. We observed that accumulations of mineral soil C and N from 0 to 7.5 cm were almost entirely due to accumulations of light-fraction SOM. Meanwhile, losses of soil C and N from mineral soils at 35 to 60 cm were from SOM associated with silt and clay-sized particles. Isotopic signatures showed relatively large accumulations of forest-derived carbon in surface soils, and little to no accumulation of forest-derived carbon in subsoils. We argue that the land use change from old field to secondary forest drove biogeochemical and hydrological changes throughout the soil profile that enhanced microbial activity and SOM decomposition in subsoils. However, when the pine stands aged and began to transition to mixed pines and hardwoods, demands on soil organic matter for nutrients to support aboveground growth eased due to pine mortality, and subsoil organic matter levels stabilized. This study emphasizes the importance of long-term experiments and deep measurements when characterizing soil C and N responses to land use change and the remarkable paucity of such long-term soil data deeper than 30 cm.

  7. Mineral protection of soil carbon counteracted by root exudates

    NASA Astrophysics Data System (ADS)

    Keiluweit, Marco; Bougoure, Jeremy J.; Nico, Peter S.; Pett-Ridge, Jennifer; Weber, Peter K.; Kleber, Markus

    2015-06-01

    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. 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. 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.

  8. [Effects of water levels and the additions of different nitrogen forms on soil net nitrogen transformation rate and N2O emission in subtropical forest soils].

    PubMed

    Ma, Fen; Ma, Hong-liang; Qiu, Hong; Yang, Hong-yu

    2015-02-01

    An incubation experiment was conducted to investigate the effects of the additions of different nitrogen forms on nitrogen transformation in red soils of subtropical forest under soil moisture conditions with 40%, 70% and 110% of water holding capacity (WHC). The results showed that soil net mineralization and ammonification rates were maximum at 70% WHC and minimum at 40% WHC. Compared with the control, the addition of NO(3-)-N decreased the soil net mineralization and ammonification rates by 56.1% and 43.0% under 70% WHC condition, and decreased by 68.2% and 19.0% under 110% WHC, respectively. However, the proportion of ammonification to mineralization increased at 70% and 110% WHC, which suggested that nitrate addition inhibited the nitrification. With addition of NO(3-)-N at 110% WHC, the net nitrification rate was lowest while N20 emission was highest with the concomitant decrease of nitrate content, indicating that N2O emission was largely derived from denitrification. However, at 40% WHC and 70% WHC, the maximum N20 flux was found at the early stage of incubation. Even with addition of NH(4+)-N and NO(3-)-N, N2O flux did not change much at the latter stage of incubation, indicating that autotrophic nitrification was dominant for N20 production at the early stage of incubation. Under 40% WHC condition, soluble organic carbon increased more and it increased largely with NH(4+)-N addition, which meant NH(4+)-N addition could enhance the mineralization of soil organic matter. Under 40% and 110% WHC conditions, the addition of NH(4+)-N increased significantly the soil soluble organic nitrogen (SON) by 73.6% and 176.6% compared with the control, respectively. A significant increase of 78.7% for SON was only found at 40% WHC under addition of NO(3-)-N compared with the control. These results showed that high soil moisture condition and addition of NH(4+)-N were of benefit to SON formation.

  9. Effects of added organic matter and water on soil carbon sequestration in an arid region.

    PubMed

    Lai, Liming; Li, Yufei; Tian, Yuan; Jiang, Lianhe; Zhao, Xuechun; Zhu, Linhai; Chen, Xi; Gao, Yong; Wang, Shaoming; Zheng, Yuanrun; Rimmington, Glyn M

    2013-01-01

    It is generally predicted that global warming will stimulate primary production and lead to more carbon (C) inputs to soil. However, many studies have found that soil C does not necessarily increase with increased plant litter input. Precipitation has increased in arid central Asia, and is predicted to increase more, so we tested the effects of adding fresh organic matter (FOM) and water on soil C sequestration in an arid region in northwest China. The results suggested that added FOM quickly decomposed and had minor effects on the soil organic carbon (SOC) pool to a depth of 30 cm. Both FOM and water addition had significant effects on the soil microbial biomass. The soil microbial biomass increased with added FOM, reached a maximum, and then declined as the FOM decomposed. The FOM had a more significant stimulating effect on microbial biomass with water addition. Under the soil moisture ranges used in this experiment (21.0%-29.7%), FOM input was more important than water addition in the soil C mineralization process. We concluded that short-term FOM input into the belowground soil and water addition do not affect the SOC pool in shrubland in an arid region.

  10. Effects of Added Organic Matter and Water on Soil Carbon Sequestration in an Arid Region

    PubMed Central

    Tian, Yuan; Jiang, Lianhe; Zhao, Xuechun; Zhu, Linhai; Chen, Xi; Gao, Yong; Wang, Shaoming; Zheng, Yuanrun; Rimmington, Glyn M.

    2013-01-01

    It is generally predicted that global warming will stimulate primary production and lead to more carbon (C) inputs to soil. However, many studies have found that soil C does not necessarily increase with increased plant litter input. Precipitation has increased in arid central Asia, and is predicted to increase more, so we tested the effects of adding fresh organic matter (FOM) and water on soil C sequestration in an arid region in northwest China. The results suggested that added FOM quickly decomposed and had minor effects on the soil organic carbon (SOC) pool to a depth of 30 cm. Both FOM and water addition had significant effects on the soil microbial biomass. The soil microbial biomass increased with added FOM, reached a maximum, and then declined as the FOM decomposed. The FOM had a more significant stimulating effect on microbial biomass with water addition. Under the soil moisture ranges used in this experiment (21.0%–29.7%), FOM input was more important than water addition in the soil C mineralization process. We concluded that short-term FOM input into the belowground soil and water addition do not affect the SOC pool in shrubland in an arid region. PMID:23875022

  11. Short and mid-term effects of different biochar additions on soil GHG fluxes

    NASA Astrophysics Data System (ADS)

    Maier, Regine; Soja, Gerhard; Friesl-Hanl, Wolfgang; Dunst, Gerald; Kitzler, Barbara

    2015-04-01

    The application of biochar (BC) to soils may have a positive influence on physico-chemical soil properties and the mitigation of greenhouse gas (GHG) emissions. Furthermore, biochar contributes to a long-term soil carbon sequestration. The aim of this study is to explore short and mid-term effects (one day up to six months) of different BC-compost applications on soil GHG emissions, particularly CO2, CH4, N2O and NOx. In addition, compounds of the nitrogen cycle like NH4+, NO3- and the microbial biomass nitrogen (Nmic) were measured. For this purpose a field experiment in Kaindorf (Styria/Austria, gleyic Cambisol, loamy, 376 m.a.s.l.) with 16 plots and four different treatments was conducted. K = no BC-compost mixture but fertilized (NH4SO4) corresponding to T3 in 2013; T1 = 1 % BC-compost mixture, no addition of N in 2013 and 2014; T2 = 0.5 % BC-compost mixture, + 175 kg N ha-1 in 2013 and 2014; T3 = 1% BC-compost mixture, + 350 kg N ha-1 in 2013. Nitrogen was added as (NH4)2SO4 directly to the freshly produced biochar before mixing it with compost. Greenhouse gas fluxes (CO2, CH4, N2O) were measured monthly from closed chambers in the field over a period of six months, starting 30 days before BC application and ended shortly before harvesting in September. For the analysis of nitric oxide (NO) fluxes intact soil cylinders were taken from each plot and incubated at the laboratory at ambient air temperature. Mineral N contents were measured by the extraction with KCl-solution and the microbial biomass with chloroform-fumigation extraction (CFE). Biochar application to our agricultural soil showed no reduction potential of NO emissions, but N2O fluxes were significantly lower at T1 and T3 compared to treatment K. Gaseous N fluxes of the pure BC-compost mixture and the additional N fertilization with (NH4)2SO4 led to enormous gaseous N losses in form of N2O and NO. However, after application to the soil, fluxes were only higher for a short time period. We suggest

  12. Black carbon contributes to organic matter in young soils in the Morteratsch proglacial area (Switzerland)

    NASA Astrophysics Data System (ADS)

    Eckmeier, E.; Mavris, C.; Krebs, R.; Pichler, B.; Egli, M.

    2013-03-01

    Most glacier forefields of the European Alps are being progressively exposed since the glaciers reached their maximum expansion in the 1850s. Global warming and climate changes additionally promote the exposure of sediments in previously glaciated areas. In these proglacial areas, initial soils have started to develop so that they may offer a continuous chronosequence from 0 to 150-yr-old soils. The build-up of organic matter is an important factor of soil formation, and not only autochthonous but also distant sources might contribute to its accumulation in young soils and surfaces of glacier forefields. Only little is known about black carbon in soils that develop in glacier forefields, although charred organic matter could be an important component of organic carbon in Alpine soils. The aim of our study was to examine whether black carbon (BC) is present in the initial soils of a proglacial area, and to estimate its relative contribution to soil organic matter. We investigated soil samples from 35 sites distributed over the whole proglacial area of Morteratsch (Upper Engadine, Switzerland), covering a chronosequence from 0 to 150 yr. BC concentrations were determined in fine earth using the benzene polycarboxylic acid (BPCA) marker method. We found that charred organic matter occurred in the whole area, and that it was a main compound of soil organic matter in the youngest soils, where total Corg concentrations were very low. The absolute concentrations of BC in fine earth were generally low but increased in soils that had been exposed for more than 40 yr. Specific initial microbial communities may profit from this additional C source during the first years of soil evolution and potentially promote soil development in its early stage.

  13. Carbon leaching from tropical peat soils and consequences for carbon balances

    NASA Astrophysics Data System (ADS)

    Rixen, Tim; Baum, Antje; Wit, Francisca; Samiaji, Joko

    2016-07-01

    Drainage and deforestation turned Southeast (SE) Asian peat soils into a globally important CO2 source, because both processes accelerate peat decomposition. Carbon losses through soil leaching have so far not been quantified and the underlying processes have hardly been studied. In this study, we use results derived from nine expeditions to six Sumatran rivers and a mixing model to determine leaching processes in tropical peat soils, which are heavily disturbed by drainage and deforestation. Here we show that a reduced evapotranspiration and the resulting increased freshwater discharge in addition to the supply of labile leaf litter produced by re-growing secondary forests increase leaching of carbon by ~200%. Enhanced freshwater fluxes and leaching of labile leaf litter from secondary vegetation appear to contribute 38% and 62% to the total increase, respectively. Decomposition of leached labile DOC can lead to hypoxic conditions in rivers draining disturbed peatlands. Leaching of the more refractory DOC from peat is an irrecoverable loss of soil that threatens the stability of peat-fringed coasts in SE Asia.

  14. Big Data for Big Questions: Global Soil Change and the National Soil Carbon Network

    NASA Astrophysics Data System (ADS)

    Nave, L. E.; Swanston, C.

    2010-12-01

    studies, the mean recovery time for forest floor C was 128 yr. In a broader context, these results demonstrate that combining database work with quantitative synthesis (such as meta-analysis) allows scientists to detect large-scale patterns that are obscured by variation within individual studies. And, in addition to improving analytical capacity for addressing large questions, large databases are useful for identifying data gaps in global soil change research. In light of these benefits, now is an opportune time to advance the study of global soil change by networking and sharing data with the National Soil Carbon Network. The NSCN seeks participants in an effort to compile databases, answer big-picture, predictive questions about soil C vulnerability, and identify and fill data gaps and research needs. The NSCN seeks to be a facilitator that links existing resources rather than reinvents them, and offers opportunities for a variety of activities, including sharing sites, data, archives, and lab infrastructure. The NSCN is fundamentally collaborative, and operates under the assumption that our shared scientific interest in global soil change will be best advanced if we work together rather than in isolation.

  15. Carbon sequestration in soil by in situ catalyzed photo-oxidative polymerization of soil organic matter.

    PubMed

    Piccolo, Alessandro; Spaccini, Riccardo; Nebbioso, Antonio; Mazzei, Pierluigi

    2011-08-01

    Here we describe an innovative mechanism for carbon sequestration in soil by in situ photopolymerization of soil organic matter under biomimetic catalysis. Three different Mediterranean soils were added with a synthetic water-soluble iron-porphyrin, irradiated by solar light, and subjected first to 5 days incubation and, then, 15, and 30 wetting and drying (w/d) cycles. The in situ catalyst-assisted photopolymerization of soil organic carbon (SOC) increased water stability of soil aggregates both after 5 days incubation and 15 w/d cycles, but not after 30 w/d cycles. Particle-size distribution of all treated soils confirmed the induced soil physical improvement, by showing a concomitant lower yield of the clay-sized fraction and larger yields of either coarse sand- or fine sand-size fractions, depending on soil texture, though only after 5 days incubation. The gain in soil physical quality was reflected by the shift of OC content from small to large soil aggregates, thereby suggesting that photopolymerization stabilized OC by both chemical and physical processes. A further evidence of the carbon sequestration capacity of the photocatalytic treatment was provided by the significant reduction of CO(2) respired by all soils after both incubation and w/d cycles. Our findings suggest that "green" catalytic technologies may potentially be the bases for future practices to increase soil carbon stabilization and mitigate CO(2) emissions from arable soils.

  16. Windthrows increase soil carbon stocks in a Central Amazon forest

    NASA Astrophysics Data System (ADS)

    dos Santos, L. T.; Magnabosco Marra, D.; Trumbore, S.; Camargo, P. B.; Chambers, J. Q.; Negrón-Juárez, R. I.; Lima, A. J. N.; Ribeiro, G. H. P. M.; dos Santos, J.; Higuchi, N.

    2015-12-01

    Windthrows change forest structure and species composition in Central Amazon forests. However, the effects of widespread tree mortality associated with wind-disturbances on soil properties have not yet been described. In this study, we investigated short-term effects (seven years after disturbance) of a windthrow event on soil carbon stocks and concentrations in a Central Amazon terra firme forest. The soil carbon stock (averaged over a 0-30 cm depth profile) in disturbed plots (61.4 ± 4.18 Mg ha-1, mean ± standard error) was marginally higher (p = 0.009) than that from undisturbed plots (47.7 ± 6.95 Mg ha-1). The soil organic carbon concentration in disturbed plots (2.0 ± 0.08 %) was significantly higher (p < 0.001) than that from undisturbed plots (1.36 ± 0.12 %). Moreover, soil carbon stocks were positively correlated with soil clay content (r = 0.575 and p = 0.019) and with tree mortality intensity (r = 0.493 and p = 0.045). Our results indicate that large inputs of plant litter associated with large windthrow events cause a short-term increase in soil carbon content, and the degree of increase is related to soil clay content and tree mortality intensity. Higher nutrient availability in soils from large canopy gaps created by wind disturbance may increase vegetation resilience and favor forest recovery.

  17. Soil carbon stock and soil characteristics at Tasik Chini Forest Reserve, Pahang, Malaysia

    NASA Astrophysics Data System (ADS)

    Nur Aqlili Riana, R.; Sahibin A., R.

    2015-09-01

    This study was carried out to determine soil carbon stock and soil characteristic at Tasik Chini Forest Reserve (TCFR), Pahang. A total of 10 (20 m x 25 m) permanent sampling plot was selected randomly within the area of TCFR. Soil samples were taken from all subplots using dutch auger based on soil depth of 0-20cm, 20-40cm, 40-60cm. Soil parameters determined were size distribution, soil water content, bulk density, organic matter, organic carbon content, pH and electrical conductivity. All parameters were determined following their respective standard methods. Results obtained showed that the soil in TCFR was dominated by clay texture (40%), followed by sandy clay loam (30%), loam (20%). Silty clay, clay loam and sandy loam constitutes about 10% of the soil texture. Range of mean percentage of organic matter and bulk density are from 2.42±0.06% to 11.64±0.39% and 1.01 to 1.04 (gcm-ł), respectively. Soil pH are relatively very acidic and mean of electrical conductivity is low. Soil carbon content ranged from 0.83±0.03 to 1.87±0.41%. All soil parameter showed a decreasing trend with depth except electrical conductivity. ANOVA test of mean percentage of organic matter, soil water content, soil pH and electrical conductivity showed a significant difference between plot (p<0.05). However there are no significant difference of mean bulk density between plots (p>0.05). There are no significant difference in mean percentage of soil water content, organic matter and bulk density between three different depth (p>0.05). There were a significant difference on percentage of soil carbon organic between plots and depth. The mean of soil organic carbon stock in soil to a depth of 60 cm calculated was 35.50 t/ha.

  18. Role of carbonates in soil organic matter stabilization in agricultural Mediterranean soils

    NASA Astrophysics Data System (ADS)

    Apesteguía, Marcos; Virto, Iñigo; Plante, Alain

    2016-04-01

    Carbonated soils are present in many semiarid areas, where lithogenic and secondary carbonates are important constituents of the soil mineral matrix. The presence of CaCO3 in calcareous soils has been described as an organic matter stabilization agent mainly due to chemical stabilization mechanisms. In two recent studies in the north of Spain the importance of CaCO3 on soil physical characteristics was highlighted, as they were observed to be acting as macroaggregates stabilization agents. A third study was carried out on the same experimental site, with the hypothesis that the observed differences in aggregation may favor organic matter stabilization in carbonate-containing soils. With that aim we studied the soil physical characteristics (water retention and porosity) and the bioavailability of soil organic matter (SOM) in the two contrasting soils in that site, one Typic Calcixerept (CALC) and one Calcic Haploxerept (DECALC). Bioavailability was evaluated trough the measurement of mineralization rates in a 30 days soil incubations. Intact and disaggregated samples were incubated to evaluate the effect of physical protection on SOM bioavailability in whole soil and macroaggregates 2-5 mm samples. Therefore, four fractions of each soil were studied: intact whole soil < 5 mm (I-WS), disaggregated whole soil (D-WS), intact macroaggregates 2-5 mm (I-Magg), and disaggregated macroaggregates (D-Magg). Soil organic carbon content was greater in CALC and had smaller mineralization rates during incubation, indicating a smaller organic matter bioavailability for microbial decomposition. However, the greater increment of mineralization observed in DECALC after disaggregation, together with the scarce differences observed in physical characteristics among both soils, indicate that physical protection was not responsible of greater SOM stability in CALC soil. New hypotheses are needed to explain the observed better protection of organic matter in carbonate-rich Mediterranean

  19. Permafrost carbon-climate feedback is sensitive to deep soil carbon decomposability but not deep soil nitrogen dynamics.

    PubMed

    Koven, Charles D; Lawrence, David M; Riley, William J

    2015-03-24

    Permafrost soils contain enormous amounts of organic carbon whose stability is contingent on remaining frozen. With future warming, these soils may release carbon to the atmosphere and act as a positive feedback to climate change. Significant uncertainty remains on the postthaw carbon dynamics of permafrost-affected ecosystems, in particular since most of the carbon resides at depth where decomposition dynamics may differ from surface soils, and since nitrogen mineralized by decomposition may enhance plant growth. Here we show, using a carbon-nitrogen model that includes permafrost processes forced in an unmitigated warming scenario, that the future carbon balance of the permafrost region is highly sensitive to the decomposability of deeper carbon, with the net balance ranging from 21 Pg C to 164 Pg C losses by 2300. Increased soil nitrogen mineralization reduces nutrient limitations, but the impact of deep nitrogen on the carbon budget is small due to enhanced nitrogen availability from warming surface soils and seasonal asynchrony between deeper nitrogen availability and plant nitrogen demands. Although nitrogen dynamics are highly uncertain, the future carbon balance of this region is projected to hinge more on the rate and extent of permafrost thaw and soil decomposition than on enhanced nitrogen availability for vegetation growth resulting from permafrost thaw. PMID:25775603

  20. Permafrost carbon-climate feedback is sensitive to deep soil carbon decomposability but not deep soil nitrogen dynamics

    NASA Astrophysics Data System (ADS)

    Koven, Charles D.; Lawrence, David M.; Riley, William J.

    2015-03-01

    Permafrost soils contain enormous amounts of organic carbon whose stability is contingent on remaining frozen. With future warming, these soils may release carbon to the atmosphere and act as a positive feedback to climate change. Significant uncertainty remains on the postthaw carbon dynamics of permafrost-affected ecosystems, in particular since most of the carbon resides at depth where decomposition dynamics may differ from surface soils, and since nitrogen mineralized by decomposition may enhance plant growth. Here we show, using a carbon-nitrogen model that includes permafrost processes forced in an unmitigated warming scenario, that the future carbon balance of the permafrost region is highly sensitive to the decomposability of deeper carbon, with the net balance ranging from 21 Pg C to 164 Pg C losses by 2300. Increased soil nitrogen mineralization reduces nutrient limitations, but the impact of deep nitrogen on the carbon budget is small due to enhanced nitrogen availability from warming surface soils and seasonal asynchrony between deeper nitrogen availability and plant nitrogen demands. Although nitrogen dynamics are highly uncertain, the future carbon balance of this region is projected to hinge more on the rate and extent of permafrost thaw and soil decomposition than on enhanced nitrogen availability for vegetation growth resulting from permafrost thaw.

  1. Soil moisture effects on the carbon isotopic composition of soil respiration

    EPA Science Inventory

    The carbon isotopic composition ( 13C) of recently assimilated plant carbon is known to depend on water-stress, caused either by low soil moisture or by low atmospheric humidity. Air humidity has also been shown to correlate with the 13C of soil respiration, which suggests indir...

  2. When bulk density methods matter: Implications for estimating soil organic carbon pools in rocky soils

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Resolving uncertainty in the carbon cycle is paramount to refining climate predictions. Soil organic carbon (SOC) is a major component of terrestrial C pools, and accuracy of SOC estimates are only as good as the measurements and assumptions used to obtain them. Dryland soils account for a substanti...

  3. Spatial distribution of soil organic carbon stocks in France

    NASA Astrophysics Data System (ADS)

    Martin, M. P.; Wattenbach, M.; Smith, P.; Meersmans, J.; Jolivet, C.; Boulonne, L.; Arrouays, D.

    2010-11-01

    Soil organic carbon plays a major role in the global carbon budget, and can act as a source or a sink of atmospheric carbon, whereby it can influence the course of climate change. Changes in soil organic soil stocks (SOCS) are now taken into account in international negotiations regarding climate change. Consequently, developing sampling schemes and models for estimating the spatial distribution of SOCS is a priority. The French soil monitoring network has been established on a 16 km × 16 km grid and the first sampling campaign has recently been completed, providing circa 2200 measurements of stocks of soil organic carbon, obtained through an in situ composite sampling, uniformly distributed over the French territory. We calibrated a boosted regression tree model on the observed stocks, modelling SOCS as a function of other variables such as climatic parameters, vegetation net primary productivity, soil properties and land use. The calibrated model was evaluated through cross-validation and eventually used for estimating SOCS for the whole of metropolitan France. Two other models were calibrated on forest and agricultural soils separately, in order to assess more precisely the influence of pedo-climatic variables on soil organic carbon for such soils. The boosted regression tree model showed good predictive ability, and enabled quantification of relationships between SOCS and pedo-climatic variables (plus their interactions) over the French territory. These relationship strongly depended on the land use, and more specifically differed between forest soils and cultivated soil. The total estimate of SOCS in France was 3.260 ± 0.872 PgC for the first 30 cm. It was compared to another estimate, based on the previously published European soil organic carbon and bulk density maps, of 5.303 PgC. We demonstrate that the present estimate might better represent the actual SOCS distributions of France, and consequently that the previously published approach at the European

  4. A Radiocarbon Database for Improving Understanding of Global Soil Carbon Dynamics: Part I

    NASA Astrophysics Data System (ADS)

    Torn, M. S.; Trumbore, S.; Smith, L. J.; Nave, L. E.; Sierra, C. A.; Harden, J. W.; Agarwal, D.; van Ingen, C.; Radiocarbon Database Workshop 2011

    2011-12-01

    Soils play a large role in the global carbon cycle, but soil carbon stocks and dynamics remain highly uncertain. Radiocarbon (14C) observations from soils and soil respiration provide one of the only ways to infer terrestrial carbon turnover times or to test ecosystem carbon models. Although a wealth of such observations exists, they are scattered in small data sets held by individual researchers, and have not been compiled in a form easy to use for multi-site analysis, global assessments, or model testing. Here we introduce a new, global radiocarbon database that will synthesize datasets from multiple contributors to facilitate research on three broad questions: (1) What are current patterns of soil carbon dynamics, and what factors influence these patterns? (2) What is the sequestration capacity of different soils? (3) What are likely impacts of global change on the soil resource? (4) How well do models represent important carbon cycle processes, and how can they be improved? In addition to assembling data in a common format for analyses, this database will offer query capabilities and the ability to combine data with gridded global products, such as temporally resolved temperature and precipitation, NPP and GPP, and a climate-based decomposition index. Some of the near-term synthesis goals include analyzing depth profiles of 14C for across gradients in ecosystem state factors (climate, organisms, relief, parent material, time, and human influence) and soil orders; mapping surface-soil 14C values on soil temperature and moisture; and comparing soil carbon turnover times to NPP and soil carbon stocks. We are currently incorporating data from 18 contributors and six continents, with 14C measurements from soils representing nine soil orders, plant and microbial tissues, and respiration fluxes. Our intention is to grow the database and make it available to a wide community of scientists. For example, observations for different disturbance, experimental treatment, or

  5. Chemistry of organic carbon in soil with relationship to the global carbon cycle

    SciTech Connect

    Post, W.M. III

    1988-01-01

    Various ecosystem disturbances alter the balances between production of organic matter and its decomposition and therefore change the amount of carbon in soil. The most severe perturbation is conversion of natural vegetation to cultivated crops. Conversion of natural vegetation to cultivated crops results in a lowered input of slowly decomposing material which causes a reduction in overall carbon levels. Disruption of soil matrix structure by cultivation leads to lowered physical protection of organic matter resulting in an increased net mineralization rate of soil carbon. Climate change is another perturbation that affects the amount and composition of plant production, litter inputs, and decomposition regimes but does not affect soil structure directly. Nevertheless, large changes in soil carbon storage are probable with anticipated CO2 induced climate change, particularly in northern latitudes where anticipated climate change will be greatest (MacCracken and Luther 1985) and large amounts of soil organic matter are found. It is impossible, given the current state of knowledge of soil organic matter processes and transformations to develop detailed process models of soil carbon dynamics. Largely phenomenological models appear to be developing into predictive tools for understanding the role of soil organic matter in the global carbon cycle. In particular, these models will be useful in quantifying soil carbon changes due to human land-use and to anticipated global climate and vegetation changes. 47 refs., 7 figs., 2 tabs.

  6. [Characteristics of soil microbial biomass carbon and soil water soluble organic carbon in the process of natural restoration of Karst forest].

    PubMed

    Huang, Zong-Sheng; Fu, Yu-Hong; Yu, Li-Fei

    2012-10-01

    By the method of taking space instead of time, an incubation test was conducted to study the characteristics of soil microbial biomass carbon and water soluble organic carbon in the process of natural restoration of Karst forest in Maolan Nature Reserve, Guizhou Province of Southwest China. The soil microbial biomass carbon content and soil basal respiration decreased with increasing soil depth but increased with the process of the natural restoration, soil microbial quotient increased with increasing soil depth and with the process of restoration, and soil water soluble organic carbon content decreased with increasing soil depth. In the process of the natural restoration, surface soil water soluble organic carbon content increased, while sublayer soil water soluble organic carbon content decreased after an initial increase. The ratio of soil water soluble organic carbon to total soil organic carbon increased with increasing soil depth but decreased with the process of restoration. Soil quality increased with the process of restoration. Also, the quality and quantity of soil organic carbon increased with the process of restoration, in which, soil microbial biomass carbon content had the greatest change, while soil water soluble organic carbon content had less change. PMID:23359931

  7. [Characteristics of soil microbial biomass carbon and soil water soluble organic carbon in the process of natural restoration of Karst forest].

    PubMed

    Huang, Zong-Sheng; Fu, Yu-Hong; Yu, Li-Fei

    2012-10-01

    By the method of taking space instead of time, an incubation test w