decomposition rate increased: Topics by Science.gov

Sample records for decomposition rate increased

Mixing effects on litter decomposition rates in a young tree diversity experiment

NASA Astrophysics Data System (ADS)

Setiawan, Nuri Nurlaila; Vanhellemont, Margot; De Schrijver, An; Schelfhout, Stephanie; Baeten, Lander; Verheyen, Kris

2016-01-01

Litter decomposition is an essential process for biogeochemical cycling and for the formation of new soil organic matter. Mixing litter from different tree species has been reported to increase litter decomposition rates through synergistic effects. We assessed the decomposition rates of leaf litter from five tree species in a recently established tree diversity experiment on a post-agriculture site in Belgium. We used 20 different leaf litter compositions with diversity levels ranging from 1 up to 4 species. Litter mass loss in litterbags was assessed 10, 20, 25, 35, and 60 weeks after installation in the field. We found that litter decomposition rates were higher for high-quality litters, i.e., with high nitrogen content and low lignin content. The decomposition rates of mixed litter were more affected by the identity of the litter species within the mixture than by the diversity of the litter per se, but the variability in litter decomposition rates decreased as the litter diversity increased. Among the 15 different mixed litter compositions in our study, only three litter combinations showed synergistic effects. Our study suggests that admixing tree species with high-quality litter in post-agricultural plantations helps in increasing the mixture's early-stage litter decomposition rate.
More of the same? In situ leaf and root decomposition rates do not vary between 80 native and nonnative deciduous forest species.

PubMed

Jo, Insu; Fridley, Jason D; Frank, Douglas A

2016-01-01

Invaders often have greater rates of production and produce more labile litter than natives. The increased litter quantity and quality of invaders should increase nutrient cycling through faster litter decomposition. However, the limited number of invasive species that have been included in decomposition studies has hindered the ability to generalize their impacts on decomposition rates. Further, previous decomposition studies have neglected roots. We measured litter traits and decomposition rates of leaves for 42 native and 36 nonnative woody species, and those of fine roots for 23 native and 25 nonnative species that occur in temperate deciduous forests throughout the Eastern USA. Among the leaf and root traits that differed between native and invasive species, only leaf nitrogen was significantly associated with decomposition rate. However, native and nonnative species did not differ systematically in leaf and root decomposition rates. We found that among the parameters measured, litter decomposer activity was driven by litter chemical quality rather than tissue density and structure. Our results indicate that litter decomposition rate per se is not a pathway by which forest woody invasive species affect North American temperate forest soil carbon and nutrient processes. © 2015 The Authors. New Phytologist © 2015 New Phytologist Trust.
Shrub encroachment in Arctic tundra: Betula nana effects on above- and belowground litter decomposition.

PubMed

McLaren, Jennie R; Buckeridge, Kate M; van de Weg, Martine J; Shaver, Gaius R; Schimel, Joshua P; Gough, Laura

2017-05-01

Rapid arctic vegetation change as a result of global warming includes an increase in the cover and biomass of deciduous shrubs. Increases in shrub abundance will result in a proportional increase of shrub litter in the litter community, potentially affecting carbon turnover rates in arctic ecosystems. We investigated the effects of leaf and root litter of a deciduous shrub, Betula nana, on decomposition, by examining species-specific decomposition patterns, as well as effects of Betula litter on the decomposition of other species. We conducted a 2-yr decomposition experiment in moist acidic tundra in northern Alaska, where we decomposed three tundra species (Vaccinium vitis-idaea, Rhododendron palustre, and Eriophorum vaginatum) alone and in combination with Betula litter. Decomposition patterns for leaf and root litter were determined using three different measures of decomposition (mass loss, respiration, extracellular enzyme activity). We report faster decomposition of Betula leaf litter compared to other species, with support for species differences coming from all three measures of decomposition. Mixing effects were less consistent among the measures, with negative mixing effects shown only for mass loss. In contrast, there were few species differences or mixing effects for root decomposition. Overall, we attribute longer-term litter mass loss patterns to patterns created by early decomposition processes in the first winter. We note numerous differences for species patterns between leaf and root decomposition, indicating that conclusions from leaf litter experiments should not be extrapolated to below-ground decomposition. The high decomposition rates of Betula leaf litter aboveground, and relatively similar decomposition rates of multiple species below, suggest a potential for increases in turnover in the fast-decomposing carbon pool of leaves and fine roots as the dominance of deciduous shrubs in the Arctic increases, but this outcome may be tempered by negative litter mixing effects during the early stages of encroachment. © 2017 by the Ecological Society of America.
Direct and Indirect Effects of UV-B Exposure on Litter Decomposition: A Meta-Analysis

PubMed Central

Song, Xinzhang; Peng, Changhui; Jiang, Hong; Zhu, Qiuan; Wang, Weifeng

2013-01-01

Ultraviolet-B (UV-B) exposure in the course of litter decomposition may have a direct effect on decomposition rates via changing states of photodegradation or decomposer constitution in litter while UV-B exposure during growth periods may alter chemical compositions and physical properties of plants. Consequently, these changes will indirectly affect subsequent litter decomposition processes in soil. Although studies are available on both the positive and negative effects (including no observable effects) of UV-B exposure on litter decomposition, a comprehensive analysis leading to an adequate understanding remains unresolved. Using data from 93 studies across six biomes, this introductory meta-analysis found that elevated UV-B directly increased litter decomposition rates by 7% and indirectly by 12% while attenuated UV-B directly decreased litter decomposition rates by 23% and indirectly increased litter decomposition rates by 7%. However, neither positive nor negative effects were statistically significant. Woody plant litter decomposition seemed more sensitive to UV-B than herbaceous plant litter except under conditions of indirect effects of elevated UV-B. Furthermore, levels of UV-B intensity significantly affected litter decomposition response to UV-B (P<0.05). UV-B effects on litter decomposition were to a large degree compounded by climatic factors (e.g., MAP and MAT) (P<0.05) and litter chemistry (e.g., lignin content) (P<0.01). Results suggest these factors likely have a bearing on masking the important role of UV-B on litter decomposition. No significant differences in UV-B effects on litter decomposition were found between study types (field experiment vs. laboratory incubation), litter forms (leaf vs. needle), and decay duration. Indirect effects of elevated UV-B on litter decomposition significantly increased with decay duration (P<0.001). Additionally, relatively small changes in UV-B exposure intensity (30%) had significant direct effects on litter decomposition (P<0.05). The intent of this meta-analysis was to improve our understanding of the overall effects of UV-B on litter decomposition. PMID:23818993
The trait contribution to wood decomposition rates of 15 Neotropical tree species.

PubMed

van Geffen, Koert G; Poorter, Lourens; Sass-Klaassen, Ute; van Logtestijn, Richard S P; Cornelissen, Johannes H C

2010-12-01

The decomposition of dead wood is a critical uncertainty in models of the global carbon cycle. Despite this, relatively few studies have focused on dead wood decomposition, with a strong bias to higher latitudes. Especially the effect of interspecific variation in species traits on differences in wood decomposition rates remains unknown. In order to fill these gaps, we applied a novel method to study long-term wood decomposition of 15 tree species in a Bolivian semi-evergreen tropical moist forest. We hypothesized that interspecific differences in species traits are important drivers of variation in wood decomposition rates. Wood decomposition rates (fractional mass loss) varied between 0.01 and 0.31 yr(-1). We measured 10 different chemical, anatomical, and morphological traits for all species. The species' average traits were useful predictors of wood decomposition rates, particularly the average diameter (dbh) of the tree species (R2 = 0.41). Lignin concentration further increased the proportion of explained inter-specific variation in wood decomposition (both negative relations, cumulative R2 = 0.55), although it did not significantly explain variation in wood decomposition rates if considered alone. When dbh values of the actual dead trees sampled for decomposition rate determination were used as a predictor variable, the final model (including dead tree dbh and lignin concentration) explained even more variation in wood decomposition rates (R2 = 0.71), underlining the importance of dbh in wood decomposition. Other traits, including wood density, wood anatomical traits, macronutrient concentrations, and the amount of phenolic extractives could not significantly explain the variation in wood decomposition rates. The surprising results of this multi-species study, in which for the first time a large set of traits is explicitly linked to wood decomposition rates, merits further testing in other forest ecosystems.
Thermal decomposition of high-nitrogen energetic compounds: TAGzT and GUzT

NASA Astrophysics Data System (ADS)

Hayden, Heather F.

The U.S. Navy is exploring high-nitrogen compounds as burning-rate additives to meet the growing demands of future high-performance gun systems. Two high-nitrogen compounds investigated as potential burning-rate additives are bis(triaminoguanidinium) 5,5-azobitetrazolate (TAGzT) and bis(guanidinium) 5,5'-azobitetrazolate (GUzT). Small-scale tests showed that formulations containing TAGzT exhibit significant increases in the burning rates of RDX-based gun propellants. However, when GUzT, a similarly structured molecule was incorporated into the formulation, there was essentially no effect on the burning rate of the propellant. Through the use of simultaneous thermogravimetric modulated beam mass spectrometry (STMBMS) and Fourier-Transform ion cyclotron resonance (FTICR) mass spectrometry methods, an investigation of the underlying chemical and physical processes that control the thermal decomposition behavior of TAGzT and GUzT alone and in the presence of RDX, was conducted. The objective was to determine why GUzT is not as good a burning-rate enhancer in RDX-based gun propellants as compared to TAGzT. The results show that TAGzT is an effective burning-rate modifier in the presence of RDX because the decomposition of TAGzT alters the initial stages of the decomposition of RDX. Hydrazine, formed in the decomposition of TAGzT, reacts faster with RDX than RDX can decompose itself. The reactions occur at temperatures below the melting point of RDX and thus the TAGzT decomposition products react with RDX in the gas phase. Although there is no hydrazine formed in the decomposition of GUzT, amines formed in the decomposition of GUzT react with aldehydes, formed in the decomposition of RDX, resulting in an increased reaction rate of RDX in the presence of GUzT. However, GUzT is not an effective burning-rate modifier because its decomposition does not alter the initial gas-phase decomposition of RDX. The decomposition of GUzT occurs at temperatures above the melting point of RDX. Therefore, the decomposition of GUzT affects reactions that are dominant in the liquid phase of RDX. Although GUzT is not an effective burning-rate modifier, features of its decomposition where the reaction between amines formed in the decomposition of GUzT react with the aldehydes, formed in the decomposition of RDX, may have implications from an insensitive-munitions perspective.
Climatic effects on decomposing litter and substrate chemistry along climatological gradients.

NASA Astrophysics Data System (ADS)

Berg, B.

2009-04-01

Climatic effects on decomposing litter and substrate chemistry along climatological gradients. B. Berg, Dipartimento Biologia Strutturale e Funzionale, Complesso Universitario, Monte San Angelo, via Cintia, I-80126 Napoli, Italy and Department of Forest Ecology, P.O. Box 27, University of Helsinki, FIN-00014, Helsinki, Finland. Studies of several processes, using climatic gradients do provide new information as compared with studies at e.g. a single site. Decomposition of plant litter in such gradients give response in decomposition rates to natural climate conditions. Thus Scots pine needle litter incubated in a climate gradient with annual average temperature (AVGT) ranging from -0.5 to 6.8oC had a highly significant increase in initial mass-loss rate with R2 = 0.591 (p<0.001) and a 5o increase in temperature doubled the mass-loss rate. As a contrast - needle litter of Norway spruce incubated in the same transect had no significant response to climate and for initial litter a 5o increase increased mass-loss rate c. 6%. For more decomposed Scots pine litter we could see that the effect of temperature on mass-loss rate gradually decreased until it disappeared. Long-term decomposition studies revealed differences in litter decomposition patterns along a gradient, even for the same type of litter. This could be followed by using an asymptotic function that gave, (i) a measure a maximum level of decomposition, (ii) the initial decomposition rate. Over a gradient the calculated maximum level of decomposition decreased with increasing AVGT. Other gradient studies revealed an effect of AVGT on litter chemical composition. Pine needle litter from stands under different climate conditions had nutrient concentrations related to AVGT. Thus N, P, K, and S were positively related to AVGT and Mn negatively, all of them significantly. This information may be used to explain the changing pattern in decomposition over the gradient.
Technical Note: Linking climate change and downed woody debris decomposition across forests of the eastern United States

USGS Publications Warehouse

Russell, Matthew B.; Woodall, Christopher W.; D'Amato, Anthony W.; Fraver, Shawn; Bradford, John B.

2014-01-01

Forest ecosystems play a critical role in mitigating greenhouse gas emissions. Forest carbon (C) is stored through photosynthesis and released via decomposition and combustion. Relative to C fixation in biomass, much less is known about C depletion through decomposition of woody debris, particularly under a changing climate. It is assumed that the increased temperatures and longer growing seasons associated with projected climate change will increase the decomposition rates (i.e., more rapid C cycling) of downed woody debris (DWD); however, the magnitude of this increase has not been previously addressed. Using DWD measurements collected from a national forest inventory of the eastern United States, we show that the residence time of DWD may decrease (i.e., more rapid decomposition) by as much as 13% over the next 200 years, depending on various future climate change scenarios and forest types. Although existing dynamic global vegetation models account for the decomposition process, they typically do not include the effect of a changing climate on DWD decomposition rates. We expect that an increased understanding of decomposition rates, as presented in this current work, will be needed to adequately quantify the fate of woody detritus in future forests. Furthermore, we hope these results will lead to improved models that incorporate climate change scenarios for depicting future dead wood dynamics in addition to a traditional emphasis on live-tree demographics.
Moisture drives surface decomposition in thawing tundra

NASA Astrophysics Data System (ADS)

Hicks Pries, Caitlin E.; Schuur, E. A. G.; Vogel, Jason G.; Natali, Susan M.

2013-07-01

Permafrost thaw can affect decomposition rates by changing environmental conditions and litter quality. As permafrost thaws, soils warm and thermokarst (ground subsidence) features form, causing some areas to become wetter while other areas become drier. We used a common substrate to measure how permafrost thaw affects decomposition rates in the surface soil in a natural permafrost thaw gradient and a warming experiment in Healy, Alaska. Permafrost thaw also changes plant community composition. We decomposed 12 plant litters in a common garden to test how changing plant litter inputs would affect decomposition. We combined species' tissue-specific decomposition rates with species and tissue-level estimates of aboveground net primary productivity to calculate community-weighted decomposition constants at both the thaw gradient and warming experiment. Moisture, specifically growing season precipitation and water table depth, was the most significant driver of decomposition. At the gradient, an increase in growing season precipitation from 200 to 300 mm increased mass loss of the common substrate by 100%. At the warming experiment, a decrease in the depth to the water table from 30 to 15 cm increased mass loss by 100%. At the gradient, community-weighted decomposition was 21% faster in extensive than in minimal thaw, but was similar when moss production was included. Overall, the effect of climate change and permafrost thaw on surface soil decomposition are driven more by precipitation and soil environment than by changes to plant communities. Increasing soil moisture is thereby another mechanism by which permafrost thaw can become a positive feedback to climate change.
Long-term amelioration of acidity accelerates decomposition in headwater streams.

PubMed

Jenkins, Gareth B; Woodward, Guy; Hildrew, Alan G

2013-04-01

The secondary production of culturally acidified streams is low, with a few species of generalist detritivores dominating invertebrate assemblages, while decomposition processes are impaired. In a series of lowland headwater streams in southern England, we measured the rate of cellulolytic decomposition and compared it with values measured three decades ago, when anthropogenic acidification was at its peak. We hypothesized that, if acidity has indeed ameliorated, the rate of decomposition will have accelerated, thus potentially supporting greater secondary production and the longer food chains that have been observed in some well-studied recovering freshwater systems. We used cellulose Shirley test cloth as a standardized bioassay to measure the rate of cellulolytic decomposition, via loss in tensile strength, for 31 streams in the Ashdown Forest over 7 days in summer 2011 and 49 days in winter 2012. We compared this with data from an otherwise identical study conducted in 1978 and 1979. In a secondary study, we determined whether decomposition followed a linear or logarithmic decay and, as Shirley cloth is no longer available, we tested an alternative in the form of readily available calico. Overall mean pH had increased markedly over the 32 years between the studies (from 6.0 to 6.7). In both the previous and contemporary studies, the relationship between decomposition and pH was strongest in winter, when pH reaches a seasonal minimum. As in the late 1970s, there was no relationship in 2011/2012 between pH and decay rate in summer. As postulated, decomposition in winter was significantly faster in 2011/2012 than in 1978/1979, with an average increase in decay rate of 18.1%. Recovery from acidification, due to decreased acidifying emissions and deposition, has led to an increase in the rate of cellulolytic decomposition. This response in a critical ecosystem process offers a potential explanation of one aspect of the limited biological recovery that has been observed so far, an increase in larger bodied predators including fish, which in turn leads to an increase in the length of food chains. © 2012 Blackwell Publishing Ltd.
Decomposition rate of Rhizopora stylosa litter in Tanjung Rejo Village, Deli Serdang Regency, North Sumatera Province

NASA Astrophysics Data System (ADS)

Rambey, R.; Delvian; Sianturi, S. D.

2018-02-01

Research on the decomposition rate of Rhizopora stylosa litter in Tanjung Rejo village, Deli Serdang Regency, North Sumatera Province was conducted from September 2016 to May 2017. The objectives of this research were (1) to measure the decomposition rate of Rhizophora stylosa litter and (2) to determine the type of functional fungi in decomposition of litter. R. stylosa litter decomposition is characterized by a reduction in litter weight per observation period. Decomposition rate tended to increase every week, which was from 0.238 in the seventh day and reached 0.302 on the fiftysixthth day. The decomposition rate of R. stylosa litter of leaf was high with the value of k per day > 0,01 caused by macrobentos and fungi, and also the decomposition of R. stylosa litter conducted in the pond area which is classified far from the coast. Therefore, to enable the high population of fungi which affect the decomposition rate of the litter. The types of fungi decomposers were: Aspergillus sp.-1, Aspergillus sp.-2, Aspergillus sp.-3, Rhizophus sp.-1., Rhizophus sp.-2, Penicillium sp., Syncephalastrum sp. and Fusarium sp.
Termites promote resistance of decomposition to spatiotemporal variability in rainfall.

PubMed

Veldhuis, Michiel P; Laso, Francisco J; Olff, Han; Berg, Matty P

2017-02-01

The ecological impact of rapid environmental change will depend on the resistance of key ecosystems processes, which may be promoted by species that exert strong control over local environmental conditions. Recent theoretical work suggests that macrodetritivores increase the resistance of African savanna ecosystems to changing climatic conditions, but experimental evidence is lacking. We examined the effect of large fungus-growing termites and other non-fungus-growing macrodetritivores on decomposition rates empirically with strong spatiotemporal variability in rainfall and temperature. Non-fungus-growing larger macrodetritivores (earthworms, woodlice, millipedes) promoted decomposition rates relative to microbes and small soil fauna (+34%) but both groups reduced their activities with decreasing rainfall. However, fungus-growing termites increased decomposition rates strongest (+123%) under the most water-limited conditions, making overall decomposition rates mostly independent from rainfall. We conclude that fungus-growing termites are of special importance in decoupling decomposition rates from spatiotemporal variability in rainfall due to the buffered environment they create within their extended phenotype (mounds), that allows decomposition to continue when abiotic conditions outside are less favorable. This points at a wider class of possibly important ecological processes, where soil-plant-animal interactions decouple ecosystem processes from large-scale climatic gradients. This may strongly alter predictions from current climate change models. © 2016 by the Ecological Society of America.
A density functional theory study of the decomposition mechanism of nitroglycerin.

PubMed

Pei, Liguan; Dong, Kehai; Tang, Yanhui; Zhang, Bo; Yu, Chang; Li, Wenzuo

2017-08-21

The detailed decomposition mechanism of nitroglycerin (NG) in the gas phase was studied by examining reaction pathways using density functional theory (DFT) and canonical variational transition state theory combined with a small-curvature tunneling correction (CVT/SCT). The mechanism of NG autocatalytic decomposition was investigated at the B3LYP/6-31G(d,p) level of theory. Five possible decomposition pathways involving NG were identified and the rate constants for the pathways at temperatures ranging from 200 to 1000 K were calculated using CVT/SCT. There was found to be a lower energy barrier to the β-H abstraction reaction than to the α-H abstraction reaction during the initial step in the autocatalytic decomposition of NG. The decomposition pathways for CHOCOCHONO 2 (a product obtained following the abstraction of three H atoms from NG by NO 2 ) include O-NO 2 cleavage or isomer production, meaning that the autocatalytic decomposition of NG has two reaction pathways, both of which are exothermic. The rate constants for these two reaction pathways are greater than the rate constants for the three pathways corresponding to unimolecular NG decomposition. The overall process of NG decomposition can be divided into two stages based on the NO 2 concentration, which affects the decomposition products and reactions. In the first stage, the reaction pathway corresponding to O-NO 2 cleavage is the main pathway, but the rates of the two autocatalytic decomposition pathways increase with increasing NO 2 concentration. However, when a threshold NO 2 concentration is reached, the NG decomposition process enters its second stage, with the two pathways for NG autocatalytic decomposition becoming the main and secondary reaction pathways.
Inundation, vegetation, and sediment effects on litter decomposition in Pacific Coast tidal marshes

USGS Publications Warehouse

Janousek, Christopher; Buffington, Kevin J.; Guntenspergen, Glenn R.; Thorne, Karen M.; Dugger, Bruce D.; Takekawa, John Y.

2017-01-01

The cycling and sequestration of carbon are important ecosystem functions of estuarine wetlands that may be affected by climate change. We conducted experiments across a latitudinal and climate gradient of tidal marshes in the northeast Pacific to evaluate the effects of climate- and vegetation-related factors on litter decomposition. We manipulated tidal exposure and litter type in experimental mesocosms at two sites and used variation across marsh landscapes at seven sites to test for relationships between decomposition and marsh elevation, soil temperature, vegetation composition, litter quality, and sediment organic content. A greater than tenfold increase in manipulated tidal inundation resulted in small increases in decomposition of roots and rhizomes of two species, but no significant change in decay rates of shoots of three other species. In contrast, across the latitudinal gradient, decomposition rates of Salicornia pacifica litter were greater in high marsh than in low marsh. Rates were not correlated with sediment temperature or organic content, but were associated with plant assemblage structure including above-ground cover, species composition, and species richness. Decomposition rates also varied by litter type; at two sites in the Pacific Northwest, the grasses Deschampsia cespitosa and Distichlis spicata decomposed more slowly than the forb S. pacifica. Our data suggest that elevation gradients and vegetation structure in tidal marshes both affect rates of litter decay, potentially leading to complex spatial patterns in sediment carbon dynamics. Climate change may thus have direct effects on rates of decomposition through increased inundation from sea-level rise and indirect effects through changing plant community composition.
Technical Note: Linking climate change and downed woody debris decomposition across forests of the eastern United States

NASA Astrophysics Data System (ADS)

Russell, M. B.; Woodall, C. W.; D'Amato, A. W.; Fraver, S.; Bradford, J. B.

2014-06-01

Forest ecosystems play a critical role in mitigating greenhouse gas emissions. Long-term forest carbon (C) storage is determined by the balance between C fixation into biomass through photosynthesis and C release via decomposition and combustion. Relative to C fixation in biomass, much less is known about C depletion through decomposition of woody debris, particularly under a changing climate. It is assumed that the increased temperatures and longer growing seasons associated with projected climate change will increase the decomposition rates (i.e., more rapid C cycling) of downed woody debris (DWD); however, the magnitude of this increase has not been previously addressed. Using DWD measurements collected from a national forest inventory of the eastern United States, we show that the residence time of DWD may decrease (i.e., more rapid decomposition) by as much as 13% over the next 200 years depending on various future climate change scenarios and forest types. Although existing dynamic global vegetation models account for the decomposition process, they typically do not include the effect of a changing climate on DWD decomposition rates. We expect that an increased understanding of decomposition rates, as presented in this current work, will be needed to adequately quantify the fate of woody detritus in future forests. Furthermore, we hope these results will lead to improved models that incorporate climate change scenarios for depicting future dead wood dynamics, in addition to a traditional emphasis on live tree demographics.
Basic dye decomposition kinetics in a photocatalytic slurry reactor.

PubMed

Wu, Chun-Hsing; Chang, Hung-Wei; Chern, Jia-Ming

2006-09-01

Wastewater effluent from textile plants using various dyes is one of the major water pollutants to the environment. Traditional chemical, physical and biological processes for treating textile dye wastewaters have disadvantages such as high cost, energy waste and generating secondary pollution during the treatment process. The photocatalytic process using TiO2 semiconductor particles under UV light illumination has been shown to be potentially advantageous and applicable in the treatment of wastewater pollutants. In this study, the dye decomposition kinetics by nano-size TiO2 suspension at natural solution pH was experimentally studied by varying the agitation speed (50-200 rpm), TiO2 suspension concentration (0.25-1.71 g/L), initial dye concentration (10-50 ppm), temperature (10-50 degrees C), and UV power intensity (0-96 W). The experimental results show the agitation speed, varying from 50 to 200 rpm, has a slight influence on the dye decomposition rate and the pH history; the dye decomposition rate increases with the TiO2 suspension concentration up to 0.98 g/L, then decrease with increasing TiO2 suspension concentration; the initial dye decomposition rate increases with the initial dye concentration up to a certain value depending upon the temperature, then decreases with increasing initial dye concentration; the dye decomposition rate increases with the UV power intensity up to 64 W to reach a plateau. Kinetic models have been developed to fit the experimental kinetic data well.
Permafrost Thaw, Soil Moisture and Plant Community Change Alter Organic Matter Decomposition in Alaskan Tundra

NASA Astrophysics Data System (ADS)

Natali, S.; Mauritz, M.; Pegoraro, E.; Schuur, E.

2015-12-01

Climate warming in arctic tundra has been associated with increased plant productivity and a shift in plant community composition, specifically an increase in shrub cover, which can impact soil organic matter through changes in the size and composition of the leaf litter pool. Shifts in litter quantity and quality will in turn interact with changes in the soil environment as the climate continues to warm. We examined the effects of permafrost thaw, soil moisture changes, and plant community composition on leaf litter decomposition in an upland tundra ecosystem in Interior Alaska. We present warming and drying effects on decomposition rates of graminoid-dominated and shrub-dominated leaf litter mixtures over three years (2 cm depth), and annual decomposition of a common cellulose substrate (0-10 cm and 10-20 cm) over five years at a permafrost thaw and soil drying experiment. We expected that warming and drying would increase decomposition, and that decomposition would be greater in the shrub litter than in the graminoid litter mix. Decomposition of Betula nana, the dominant shrub, was 50% greater in the shrub-dominated litter mix compared to the graminoid-dominated litter. Surprisingly, there was no significant difference in total litter mass loss between graminoid and shrub litter mixtures, despite significant differences in decomposition rates of the dominant plant species when decomposed alone and in community mixtures. Drying decreased decomposition of B. nana and of the shrub community litter overall, but after two years there was no detected warming effect on shrub-community decomposition. In contrast to leaf litter decomposition, both warming and drying increased decomposition of the common substrate. Warming caused an almost twofold increase in cellulose decomposition in surface soil (0-10cm), and drying caused a twofold increase in cellulose decomposition from deeper organic layer soils (10-20cm). These results demonstrate the importance of interactions among temperature, moisture and vegetation changes on organic matter decomposition, and the potential for increased plant productivity and vegetation changes to alter the size and composition of the soil organic matter pool.
Reactivity continuum modeling of leaf, root, and wood decomposition across biomes

NASA Astrophysics Data System (ADS)

Koehler, Birgit; Tranvik, Lars J.

2015-07-01

Large carbon dioxide amounts are released to the atmosphere during organic matter decomposition. Yet the large-scale and long-term regulation of this critical process in global carbon cycling by litter chemistry and climate remains poorly understood. We used reactivity continuum (RC) modeling to analyze the decadal data set of the "Long-term Intersite Decomposition Experiment," in which fine litter and wood decomposition was studied in eight biome types (224 time series). In 32 and 46% of all sites the litter content of the acid-unhydrolyzable residue (AUR, formerly referred to as lignin) and the AUR/nitrogen ratio, respectively, retarded initial decomposition rates. This initial rate-retarding effect generally disappeared within the first year of decomposition, and rate-stimulating effects of nutrients and a rate-retarding effect of the carbon/nitrogen ratio became more prevalent. For needles and leaves/grasses, the influence of climate on decomposition decreased over time. For fine roots, the climatic influence was initially smaller but increased toward later-stage decomposition. The climate decomposition index was the strongest climatic predictor of decomposition. The similar variability in initial decomposition rates across litter categories as across biome types suggested that future changes in decomposition may be dominated by warming-induced changes in plant community composition. In general, the RC model parameters successfully predicted independent decomposition data for the different litter-biome combinations (196 time series). We argue that parameterization of large-scale decomposition models with RC model parameters, as opposed to the currently common discrete multiexponential models, could significantly improve their mechanistic foundation and predictive accuracy across climate zones and litter categories.
Effects of magnesium-based hydrogen storage materials on the thermal decomposition, burning rate, and explosive heat of ammonium perchlorate-based composite solid propellant.

PubMed

Liu, Leili; Li, Jie; Zhang, Lingyao; Tian, Siyu

2018-01-15

MgH 2 , Mg 2 NiH 4 , and Mg 2 CuH 3 were prepared, and their structure and hydrogen storage properties were determined through X-ray photoelectron spectroscopy and thermal analyzer. The effects of MgH 2 , Mg 2 NiH 4 , and Mg 2 CuH 3 on the thermal decomposition, burning rate, and explosive heat of ammonium perchlorate-based composite solid propellant were subsequently studied. Results indicated that MgH 2 , Mg 2 NiH 4 , and Mg 2 CuH 3 can decrease the thermal decomposition peak temperature and increase the total released heat of decomposition. These compounds can improve the effect of thermal decomposition of the propellant. The burning rates of the propellant increased using Mg-based hydrogen storage materials as promoter. The burning rates of the propellant also increased using MgH 2 instead of Al in the propellant, but its explosive heat was not enlarged. Nonetheless, the combustion heat of MgH 2 was higher than that of Al. A possible mechanism was thus proposed. Copyright © 2017. Published by Elsevier B.V.
The rate of synthesis and decomposition of tissue proteins in hypokinesia and increased muscular activity

NASA Technical Reports Server (NTRS)

Fedorov, I. V.; Chernyy, A. V.; Fedorov, A. I.

1978-01-01

During hypokinesia and physical loading (swimming) of rats, the radioactivity of skeletal muscle, liver, kidney, heart, and blood proteins was determined after administration of radioactive amino acids. Tissue protein synthesis decreased during hypokinesia, and decomposition increased. Both synthesis and decomposition increased during physical loading, but anabolic processes predominated in the total tissue balance. The weights of the animals decreased in hypokinesia and increased during increased muscle activity.

Eutrophication triggers contrasting multilevel feedbacks on litter accumulation and decomposition in fens.

PubMed

Emsens, W-J; Aggenbach, C J S; Grootjans, A P; Nfor, E E; Schoelynck, J; Struyf, E; van Diggelen, R

2016-10-01

Eutrophication is a major threat for the persistence of nutrient-poor fens, as multilevel feedbacks on decomposition rates could trigger carbon loss and increase nutrient cycling. Here, we experimentally investigate the effects of macronutrient (NPK) enrichment on litter quality of six species of sedge (Carex sp.), which we relate to litter decomposition rates in a nutrient-poor and nutrient-rich environment. Our research focused on four levels: we examined how eutrophication alters (1) fresh litter production ("productivity shift"), (2) litter stoichiometry within the same species ("intraspecific shift"), (3) overall litter stoichiometry of the vegetation under the prediction that low-competitive species are outcompeted by fast-growing competitors ("interspecific shift"), and (4) litter decomposition rates due to an altered external environment (e.g., shifts in microbial activity; "exogenous shift"). Eutrophication triggered a strong increase in fresh litter production. Moreover, individuals of the same species produced litter with lower C:N and C:P ratios, higher K contents, and lower lignin, Ca and Mg contents (intraspecific shift), which increased litter decomposability. In addition, species typical for eutrophic conditions produced more easily degradable litter than did species typical for nutrient-poor conditions (interspecific shift). However, the effects of nutrient loading of the external environment (exogenous shift) were contradictory. Here, interactions between litter type and ambient nutrient level indicate that the (exogenous) effects of eutrophication on litter decomposition rates are strongly dependent of litter quality. Moreover, parameters of litter quality only correlated with decomposition rates for litter incubated in nutrient-poor environments, but not in eutrophic environments. This suggests that rates of litter decomposition can be uncoupled from litter stoichiometry under eutrophic conditions. In conclusion, our results show that eutrophication affects litter accumulation and -decomposition at multiple levels, in which stimulatory and inhibitory effects interact. The cumulative effect of these interactions ultimately determine whether peatlands remain sinks or become sources of carbon under eutrophic conditions. © 2016 by the Ecological Society of America.
Effects of Litter Manipulation on Litter Decomposition in a Successional Gradients of Tropical Forests in Southern China

PubMed Central

Chen, Hao; Gurmesa, Geshere A.; Liu, Lei; Zhang, Tao; Fu, Shenglei; Liu, Zhanfeng; Dong, Shaofeng; Ma, Chuan; Mo, Jiangming

2014-01-01

Global changes such as increasing CO2, rising temperature, and land-use change are likely to drive shifts in litter inputs to forest floors, but the effects of such changes on litter decomposition remain largely unknown. We initiated a litter manipulation experiment to test the response of litter decomposition to litter removal/addition in three successional forests in southern China, namely masson pine forest (MPF), mixed coniferous and broadleaved forest (MF) and monsoon evergreen broadleaved forest (MEBF). Results showed that litter removal decreased litter decomposition rates by 27%, 10% and 8% and litter addition increased litter decomposition rates by 55%, 36% and 14% in MEBF, MF and MPF, respectively. The magnitudes of changes in litter decomposition were more significant in MEBF forest and less significant in MF, but not significant in MPF. Our results suggest that change in litter quantity can affect litter decomposition, and this impact may become stronger with forest succession in tropical forest ecosystem. PMID:24901698
FURFURAL YIELD AND DECOMPOSITION IN SODIUM 2,4DIMETHYLBENZENESULFONATE--SULFURIC ACID--WATER SOLUTIONS.

DTIC Science & Technology

Batch-type microreactors (about 1/40 milliliter of reactants) were used to measure furfural yields from acidified xylose solutions containing sodium...It was found that presence of the salt did not affect the quantity of furfural produced, but greatly increased the rate of formation. The regular...increase in rate of furfural formation was directly related to the increase in the rate xylose decomposition, and furfural yields for all salt and acid
Effect of dissolved organic carbon quality on microbial decomposition and nitrification rates in stream sediments

USGS Publications Warehouse

Strauss, E.A.; Lamberti, G.A.

2002-01-01

1. Microbial decomposition of dissolved organic carbon (DOC) contributes to overall stream metabolism and can influence many processes in the nitrogen cycle, including nitrification. Little is known, however, about the relative decomposition rates of different DOC sources and their subsequent effect on nitrification. 2. In this study, labile fraction and overall microbial decomposition of DOC were measured for leaf leachates from 18 temperate forest tree species. Between 61 and 82% (mean, 75%) of the DOC was metabolized in 24 days. Significant differences among leachates were found for labile fraction rates (P < 0.0001) but not for overall rates (P = 0.088). 3. Nitrification rates in stream sediments were determined after addition of 10 mg C L-1 of each leachate. Nitrification rates ranged from below detection to 0.49 ??g N mL sediment-1 day-1 and were significantly correlated with two independent measures of leachate DOC quality, overall microbial decomposition rate (r = -0.594, P = 0.0093) and specific ultraviolet absorbance (r = 0.469, P = 0.0497). Both correlations suggest that nitrification rates were lower in the presence of higher quality carbon. 4. Nitrification rates in sediments also were measured after additions of four leachates and glucose at three carbon concentrations (10, 30, and 50 mg C L-1). For all carbon sources, nitrification rates decreased as carbon concentration increased. Glucose and white pine leachate most strongly depressed nitrification. Glucose likely increased the metabolism of heterotrophic bacteria, which then out-competed nitrifying bacteria for NH4+. White pine leachate probably increased heterotrophic metabolism and directly inhibited nitrification by allelopathy.
Nutrient-enhanced decomposition of plant biomass in a freshwater wetland

USGS Publications Warehouse

Bodker, James E.; Turner, Robert Eugene; Tweel, Andrew; Schulz, Christopher; Swarzenski, Christopher M.

2015-01-01

We studied soil decomposition in a Panicum hemitomon (Schultes)-dominated freshwater marsh located in southeastern Louisiana that was unambiguously changed by secondarily-treated municipal wastewater effluent. We used four approaches to evaluate how belowground biomass decomposition rates vary under different nutrient regimes in this marsh. The results of laboratory experiments demonstrated how nutrient enrichment enhanced the loss of soil or plant organic matter by 50%, and increased gas production. An experiment demonstrated that nitrogen, not phosphorus, limited decomposition. Cellulose decomposition at the field site was higher in the flowfield of the introduced secondarily treated sewage water, and the quality of the substrate (% N or % P) was directly related to the decomposition rates. We therefore rejected the null hypothesis that nutrient enrichment had no effect on the decomposition rates of these organic soils. In response to nutrient enrichment, plants respond through biomechanical or structural adaptations that alter the labile characteristics of plant tissue. These adaptations eventually change litter type and quality (where the marsh survives) as the % N content of plant tissue rises and is followed by even higher decomposition rates of the litter produced, creating a positive feedback loop. Marsh fragmentation will increase as a result. The assumptions and conditions underlying the use of unconstrained wastewater flow within natural wetlands, rather than controlled treatment within the confines of constructed wetlands, are revealed in the loss of previously sequestered carbon, habitat, public use, and other societal benefits.
Temperature sensitivity and enzymatic mechanisms of soil organic matter decomposition along an altitudinal gradient on Mount Kilimanjaro

NASA Astrophysics Data System (ADS)

Blagodatskaya, Evgenia; Blagodatsky, Sergey; Khomyakov, Nikita; Myachina, Olga; Kuzyakov, Yakov

2016-02-01

Short-term acceleration of soil organic matter decomposition by increasing temperature conflicts with the thermal adaptation observed in long-term studies. Here we used the altitudinal gradient on Mt. Kilimanjaro to demonstrate the mechanisms of thermal adaptation of extra- and intracellular enzymes that hydrolyze cellulose, chitin and phytate and oxidize monomers (14C-glucose) in warm- and cold-climate soils. We revealed that no response of decomposition rate to temperature occurs because of a cancelling effect consisting in an increase in half-saturation constants (Km), which counteracts the increase in maximal reaction rates (Vmax with temperature). We used the parameters of enzyme kinetics to predict thresholds of substrate concentration (Scrit) below which decomposition rates will be insensitive to global warming. Increasing values of Scrit, and hence stronger canceling effects with increasing altitude on Mt. Kilimanjaro, explained the thermal adaptation of polymer decomposition. The reduction of the temperature sensitivity of Vmax along the altitudinal gradient contributed to thermal adaptation of both polymer and monomer degradation. Extrapolating the altitudinal gradient to the large-scale latitudinal gradient, these results show that the soils of cold climates with stronger and more frequent temperature variation are less sensitive to global warming than soils adapted to high temperatures.
Can visible light impact litter decomposition under pollution of ZnO nanoparticles?

PubMed

Du, Jingjing; Zhang, Yuyan; Liu, Lina; Qv, Mingxiang; Lv, Yanna; Yin, Yifei; Zhou, Yinfei; Cui, Minghui; Zhu, Yanfeng; Zhang, Hongzhong

2017-11-01

ZnO nanoparticles is one of the most used materials in a wide range including antibacterial coating, electronic device, and personal care products. With the development of nanotechnology, ecotoxicology of ZnO nanoparticles has been received increasing attention. To assess the phototoxicity of ZnO nanoparticles in aquatic ecosystem, microcosm experiments were conducted on Populus nigra L. leaf litter decomposition under combined effect of ZnO nanoparticles and visible light radiation. Litter decomposition rate, pH value, extracellular enzyme activity, as well as the relative contributions of fungal community to litter decomposition were studied. Results showed that long-term exposure to ZnO nanoparticles and visible light led to a significant decrease in litter decomposition rate (0.26 m -1 vs 0.45 m -1 ), and visible light would increase the inhibitory effect (0.24 m -1 ), which caused significant decrease in pH value of litter cultures, fungal sporulation rate, as well as most extracellular enzyme activities. The phototoxicity of ZnO nanoparticles also showed impacts on fungal community composition, especially on the genus of Varicosporium, whose abundance was significantly and positively related to decomposition rate. In conclusion, our study provides the evidence for negatively effects of ZnO NPs photocatalysis on ecological process of litter decomposition and highlights the contribution of visible light radiation to nanoparticles toxicity in freshwater ecosystems. Copyright © 2017 Elsevier Ltd. All rights reserved.
Composition of riparian litter input regulates organic matter decomposition: Implications for headwater stream functioning in a managed forest landscape.

PubMed

Lidman, Johan; Jonsson, Micael; Burrows, Ryan M; Bundschuh, Mirco; Sponseller, Ryan A

2017-02-01

Although the importance of stream condition for leaf litter decomposition has been extensively studied, little is known about how processing rates change in response to altered riparian vegetation community composition. We investigated patterns of plant litter input and decomposition across 20 boreal headwater streams that varied in proportions of riparian deciduous and coniferous trees. We measured a suite of in-stream physical and chemical characteristics, as well as the amount and type of litter inputs from riparian vegetation, and related these to decomposition rates of native (alder, birch, and spruce) and introduced (lodgepole pine) litter species incubated in coarse- and fine-mesh bags. Total litter inputs ranged more than fivefold among sites and increased with the proportion of deciduous vegetation in the riparian zone. In line with differences in initial litter quality, mean decomposition rate was highest for alder, followed by birch, spruce, and lodgepole pine (12, 55, and 68% lower rates, respectively). Further, these rates were greater in coarse-mesh bags that allow colonization by macroinvertebrates. Variance in decomposition rate among sites for different species was best explained by different sets of environmental conditions, but litter-input composition (i.e., quality) was overall highly important. On average, native litter decomposed faster in sites with higher-quality litter input and (with the exception of spruce) higher concentrations of dissolved nutrients and open canopies. By contrast, lodgepole pine decomposed more rapidly in sites receiving lower-quality litter inputs. Birch litter decomposition rate in coarse-mesh bags was best predicted by the same environmental variables as in fine-mesh bags, with additional positive influences of macroinvertebrate species richness. Hence, to facilitate energy turnover in boreal headwaters, forest management with focus on conifer production should aim at increasing the presence of native deciduous trees along streams, as they promote conditions that favor higher decomposition rates of terrestrial plant litter.
[Effects of tree species fine root decomposition on soil active organic carbon].

PubMed

Liu, Yan; Wang, Si-Long; Wang, Xiao-Wei; Yu, Xiao-Jun; Yang, Yue-Jun

2007-03-01

With incubation test, this paper studied the effects of fine root decomposition of Alnus cremastogyne, Cunninghamia lanceolata and Michelia macclurei on the content of soil active organic carbon at 9 degrees C , 14 degrees C , 24 degrees C and 28 degrees C. The results showed that the decomposition rate of fine root differed significantly with test tree species, which was decreased in the order of M. macclurei > A. cremastogyne > C. lanceolata. The decomposition rate was increased with increasing temperature, but declined with prolonged incubation time. Fine root source, incubation temperature, and incubation time all affected the contents of soil microbial biomass carbon and water-soluble organic carbon. The decomposition of fine root increased soil microbial biomass carbon and water-soluble organic carbon significantly, and the effect decreased in the order of M. macclurei > A. cremastogyne > C. lanceolata. Higher contents of soil microbial biomass carbon and water-soluble organic carbon were observed at medium temperature and middle incubation stage. Fine root decomposition had less effect on the content of soil readily oxidized organic carbon.
New monitoring by thermogravimetry for radiation degradation of EVA

NASA Astrophysics Data System (ADS)

Boguski, J.; Przybytniak, G.; Łyczko, K.

2014-07-01

The radiation ageing of ethylene vinyl-acetate copolymer (EVA) as the jacket of cable applied in nuclear power plant was carried out by gamma rays irradiation, and the degradation was monitored by a thermo-gravimetric analysis (TGA). The EVA decomposition rate in air by the isothermal at 400 °C decreased with increase of dose and also with decrease of the dose rate. The behavior of EVA jacket of cable indicated that the decomposition rate at 400 °C was reduced with increase of oxidation. The elongation at break by tensile test for the radiation aged EVA was closely related to the decomposition rate at 400 °C; therefore, the TGA might be applied for a diagnostic technique of the cable degradation.
Effects of fire frequency on litter decomposition as mediated by changes to litter chemistry and soil environmental conditions.

PubMed

Ficken, Cari D; Wright, Justin P

2017-01-01

Litter quality and soil environmental conditions are well-studied drivers influencing decomposition rates, but the role played by disturbance legacy, such as fire history, in mediating these drivers is not well understood. Fire history may impact decomposition directly, through changes in soil conditions that impact microbial function, or indirectly, through shifts in plant community composition and litter chemistry. Here, we compared early-stage decomposition rates across longleaf pine forest blocks managed with varying fire frequencies (annual burns, triennial burns, fire-suppression). Using a reciprocal transplant design, we examined how litter chemistry and soil characteristics independently and jointly influenced litter decomposition. We found that both litter chemistry and soil environmental conditions influenced decomposition rates, but only the former was affected by historical fire frequency. Litter from annually burned sites had higher nitrogen content than litter from triennially burned and fire suppression sites, but this was correlated with only a modest increase in decomposition rates. Soil environmental conditions had a larger impact on decomposition than litter chemistry. Across the landscape, decomposition differed more along soil moisture gradients than across fire management regimes. These findings suggest that fire frequency has a limited effect on litter decomposition in this ecosystem, and encourage extending current decomposition frameworks into disturbed systems. However, litter from different species lost different masses due to fire, suggesting that fire may impact decomposition through the preferential combustion of some litter types. Overall, our findings also emphasize the important role of spatial variability in soil environmental conditions, which may be tied to fire frequency across large spatial scales, in driving decomposition rates in this system.
Effects of fire frequency on litter decomposition as mediated by changes to litter chemistry and soil environmental conditions

PubMed Central

Wright, Justin P.

2017-01-01

Litter quality and soil environmental conditions are well-studied drivers influencing decomposition rates, but the role played by disturbance legacy, such as fire history, in mediating these drivers is not well understood. Fire history may impact decomposition directly, through changes in soil conditions that impact microbial function, or indirectly, through shifts in plant community composition and litter chemistry. Here, we compared early-stage decomposition rates across longleaf pine forest blocks managed with varying fire frequencies (annual burns, triennial burns, fire-suppression). Using a reciprocal transplant design, we examined how litter chemistry and soil characteristics independently and jointly influenced litter decomposition. We found that both litter chemistry and soil environmental conditions influenced decomposition rates, but only the former was affected by historical fire frequency. Litter from annually burned sites had higher nitrogen content than litter from triennially burned and fire suppression sites, but this was correlated with only a modest increase in decomposition rates. Soil environmental conditions had a larger impact on decomposition than litter chemistry. Across the landscape, decomposition differed more along soil moisture gradients than across fire management regimes. These findings suggest that fire frequency has a limited effect on litter decomposition in this ecosystem, and encourage extending current decomposition frameworks into disturbed systems. However, litter from different species lost different masses due to fire, suggesting that fire may impact decomposition through the preferential combustion of some litter types. Overall, our findings also emphasize the important role of spatial variability in soil environmental conditions, which may be tied to fire frequency across large spatial scales, in driving decomposition rates in this system. PMID:29023560
Thermal Decomposition Behaviors and Burning Characteristics of AN/Nitramine-Based Composite Propellant

NASA Astrophysics Data System (ADS)

Naya, Tomoki; Kohga, Makoto

2015-04-01

Ammonium nitrate (AN) has attracted much attention due to its clean burning nature as an oxidizer. However, an AN-based composite propellant has the disadvantages of low burning rate and poor ignitability. In this study, we added nitramine of cyclotrimethylene trinitramine (RDX) or cyclotetramethylene tetranitramine (HMX) as a high-energy material to AN propellants to overcome these disadvantages. The thermal decomposition and burning rate characteristics of the prepared propellants were examined as the ratio of AN and nitramine was varied. In the thermal decomposition process, AN/RDX propellants showed unique mass loss peaks in the lower temperature range that were not observed for AN or RDX propellants alone. AN and RDX decomposed continuously as an almost single oxidizer in the AN/RDX propellant. In contrast, AN/HMX propellants exhibited thermal decomposition characteristics similar to those of AN and HMX, which decomposed almost separately in the thermal decomposition of the AN/HMX propellant. The ignitability was improved and the burning rate increased by the addition of nitramine for both AN/RDX and AN/HMX propellants. The increased burning rates of AN/RDX propellants were greater than those of AN/HMX. The difference in the thermal decomposition and burning characteristics was caused by the interaction between AN and RDX.
Parametric studies of diethyl phosphoramidate photocatalytic decomposition over TiO2.

PubMed

Sun, Bo; Vorontsov, Alexander V; Smirniotis, Panagiotis G

2011-02-28

The present study is focused on influences of parameters including pH, temperature, TiO(2) catalyst concentration, and reactant concentration on the rate of photocatalytic diethyl phosphoramidate (DEPA) decomposition with Hombikat UV 100 (HK) and Degussa P25 (P25) TiO(2). Total mineralization of DEPA is observed. Two regimes of pH, namely in acid and near-neutral environments were found where maximum total carbon (TC) decomposition was observed. The electrostatic effects on adsorption over the TiO(2) surface explain the above phenomena. The maximum rate is observed for P25 at DEPA concentration 1.3 mM whereas the rate grows continuously with DEPA concentration rise for HK. The temperature dependence of TC decomposition rate in the range of 15-63°C with both HK and P25 follows the Arrhenius equation. The activation energy for total carbon decomposition with HK and P25 are 29.5±1.0 and 24.3±3.1 kJ/mol, respectively. The decomposition rate of DEPA is larger over P25 than over HK. The rate over P25 increases faster than that with HK for each unit of the titania added when the TiO(2) concentration is less than 375 mg/l. The higher light absorption and particles aggregation of P25 are responsible for the decrease of reaction rate we observed at catalyst concentration above a certain level. In contrast, the rate over HK increases monotonically with the concentration of the photocatalyst used. Copyright © 2010 Elsevier B.V. All rights reserved.
DOE Office of Scientific and Technical Information (OSTI.GOV)

Glascoe, E A; Zaug, J M; Burnham, A K

The effect of pressure on the thermal decomposition rate of the energetic material HMX was studied. HMX was precompressed in a diamond anvil cell (DAC) and heated at various rates. The parent species population was monitored as a function of time and temperature using Fourier transform infrared (FTIR) spectroscopy. Decomposition rates were determined by fitting the fraction reacted to the extended-Prout-Tompkins nucleation-growth model and the Friedman isoconversional method. The results of these experiments and analysis indicate that pressure accelerates the decomposition at low to moderate pressures (i.e. between ambient pressure and 1 GPa) and decelerates the decomposition at higher pressures.more » The decomposition acceleration is attributed to pressure enhanced autocatalysis whereas the deceleration at high pressures is attributed pressure inhibiting bond homolysis step(s), which would result in an increase in volume. These results indicate that both {beta} and {delta} phase HMX are sensitive to pressure in the thermally induced decomposition kinetics.« less
Thermal Decomposition Mechanism of CL-20 at Different Temperatures by ReaxFF Reactive Molecular Dynamics Simulations.

PubMed

Wang, Fuping; Chen, Lang; Geng, Deshen; Wu, Junying; Lu, Jianying; Wang, Chen

2018-04-26

Hexanitrohexaazaisowurtzitane (CL-20) has a high detonation velocity and pressure, but its sensitivity is also high, which somewhat limits its applications. Therefore, it is important to understand the mechanism and characteristics of thermal decomposition of CL-20. In this study, a ε-CL-20 supercell was constructed and ReaxFF-lg reactive molecular dynamics simulations were performed to investigate thermal decomposition of ε-CL-20 at various temperatures (2000, 2500, 2750, 3000, 3250, and 3500 K). The mechanism of thermal decomposition of CL-20 was analyzed from the aspects of potential energy evolution, the primary reactions, and the intermediate and final product species. The effect of temperature on thermal decomposition of CL-20 is also discussed. The initial reaction path of thermal decomposition of CL-20 is N-NO 2 cleavage to form NO 2 , followed by C-N cleavage, leading to the destruction of the cage structure. A small number of clusters appear in the early reactions and disappear at the end of the reactions. The initial reaction path of CL-20 decomposition is the same at different temperatures. However, as the temperature increases, the decomposition rate of CL-20 increases and the cage structure is destroyed earlier. The temperature greatly affects the rate constants of H 2 O and N 2 , but it has little effect on the rate constants of CO 2 and H 2 .
Pressure-dependent decomposition kinetics of the energetic material HMX up to 3.6 GPa.

PubMed

Glascoe, Elizabeth A; Zaug, Joseph M; Burnham, Alan K

2009-12-03

The effect of pressure on the global thermal decomposition rate of the energetic material HMX was studied. HMX was precompressed in a diamond anvil cell (DAC) and heated at various rates. The parent species population was monitored as a function of time and temperature using Fourier transform infrared (FTIR) spectroscopy. Global decomposition rates were determined by fitting the fraction reacted to the extended-Prout-Tompkins nucleation-growth model and the Friedman isoconversional method. The results of these experiments and analysis indicate that pressure accelerates the decomposition at low-to-moderate pressures (i.e., between ambient pressure and 0.1 GPa) and decelerates the decomposition at higher pressures. The decomposition acceleration is attributed to pressure-enhanced autocatalysis, whereas the deceleration at high pressures is attributed to pressure-inhibiting bond homolysis step(s), which would result in an increase in volume. These results indicate that both the beta- and delta-polymorphs of HMX are sensitive to pressure in the thermally induced decomposition kinetics.
Changes in Root Decomposition Rates Across Soil Depths

NASA Astrophysics Data System (ADS)

Hicks Pries, C.; Porras, R. C.; Castanha, C.; Torn, M. S.

2016-12-01

Over half of global soil organic carbon (SOC) is stored in subsurface soils (>30 cm). Turnover times of soil organic carbon (SOC) increases with depth as evidenced by radiocarbon ages of 1,000 to more than 10,000 years in many deep soil horizons but the reasons for this increase are unclear. Many factors that potentially control SOC decomposition change with depth such as increased protection of SOC in aggregates or organo-mineral complexes and increased spatial heterogeneity of SOC "hotspots" like roots, which limit the accessibility of SOC to microbes. Lower concentrations of organic matter at depth may inhibit microbial activity due to energy limitation, and the microbial community itself changes with depth. To investigate how SOC decomposition differs with depth, we inserted a 13C-labeled fine root substrate into three depths (15, 50, and 90 cm) in a coniferous forest Alfisol and measured the root carbon remaining in particulate (>2 mm), bulk (< 2mm), free light, and mineral soil fractions over 2.5 years. We also characterized how the microbial community and SOC changed with depth. Initial rates of decomposition were unaffected by soil depth—50% of root carbon was lost from all depths within the first year. However, after 2.5 years, decomposition rates were affected by soil depth with only 15% of the root carbon remaining at 15 cm while 35% remained at 90 cm. Microbial communities, based on phospholipid fatty acid analysis, changed with depth—fungal biomarkers decreased whereas actinomycetes biomarkers increased. However, the preferences of different microbial groups for the 13C-labeled root carbon were consistent with depth. In contrast, the amount of mineral-associated SOC did not change with depth. Thus, decreased decomposition rates in this deep soil are not due to mineral associations limiting SOC availability, but may instead be due to changes in microbial communities, particularly in the microbes needed to carry out the later stages of root decomposition.
Effect of body mass and clothing on decomposition of pig carcasses.

PubMed

Matuszewski, Szymon; Konwerski, Szymon; Frątczak, Katarzyna; Szafałowicz, Michał

2014-11-01

Carcass mass and carcass clothing are factors of potential high forensic importance. In casework, corpses differ in mass and kind or extent of clothing; hence, a question arises whether methods for post-mortem interval estimation should take these differences into account. Unfortunately, effects of carcass mass and clothing on specific processes in decomposition and related entomological phenomena are unclear. In this article, simultaneous effects of these factors are analysed. The experiment followed a complete factorial block design with four levels of carcass mass (small carcasses 5-15 kg, medium carcasses 15.1-30 kg, medium/large carcasses 35-50 kg, large carcasses 55-70 kg) and two levels of carcass clothing (clothed and unclothed). Pig carcasses (N = 24) were grouped into three blocks, which were separated in time. Generally, carcass mass revealed significant and frequently large effects in almost all analyses, whereas carcass clothing had only minor influence on some phenomena related to the advanced decay. Carcass mass differently affected particular gross processes in decomposition. Putrefaction was more efficient in larger carcasses, which manifested itself through earlier onset and longer duration of bloating. On the other hand, active decay was less efficient in these carcasses, with relatively low average rate, resulting in slower mass loss and later onset of advanced decay. The average rate of active decay showed a significant, logarithmic increase with an increase in carcass mass, but only in these carcasses on which active decay was driven solely by larval blowflies. If a blowfly-driven active decay was followed by active decay driven by larval Necrodes littoralis (Coleoptera: Silphidae), which was regularly found in medium/large and large carcasses, the average rate showed only a slight and insignificant increase with an increase in carcass mass. These results indicate that lower efficiency of active decay in larger carcasses is a consequence of a multi-guild and competition-related pattern of this process. Pattern of mass loss in large and medium/large carcasses was not sigmoidal, but rather exponential. The overall rate of decomposition was strongly, but not linearly, related to carcass mass. In a range of low mass decomposition rate increased with an increase in mass, then at about 30 kg, there was a distinct decrease in rate, and again at about 50 kg, the rate slightly increased. Until about 100 accumulated degree-days larger carcasses gained higher total body scores than smaller carcasses. Afterwards, the pattern was reversed; moreover, differences between classes of carcasses enlarged with the progress of decomposition. In conclusion, current results demonstrate that cadaver mass is a factor of key importance for decomposition, and as such, it should be taken into account by decomposition-related methods for post-mortem interval estimation.
In situ chemical oxidation of contaminated groundwater by persulfate: decomposition by Fe(III)- and Mn(IV)-containing oxides and aquifer materials.

PubMed

Liu, Haizhou; Bruton, Thomas A; Doyle, Fiona M; Sedlak, David L

2014-09-02

Persulfate (S2O8(2-)) is being used increasingly for in situ chemical oxidation (ISCO) of organic contaminants in groundwater, despite an incomplete understanding of the mechanism through which it is converted into reactive species. In particular, the decomposition of persulfate by naturally occurring mineral surfaces has not been studied in detail. To gain insight into the reaction rates and mechanism of persulfate decomposition in the subsurface, and to identify possible approaches for improving its efficacy, the decomposition of persulfate was investigated in the presence of pure metal oxides, clays, and representative aquifer solids collected from field sites in the presence and absence of benzene. Under conditions typical of groundwater, Fe(III)- and Mn(IV)-oxides catalytically converted persulfate into sulfate radical (SO4(•-)) and hydroxyl radical (HO(•)) over time scales of several weeks at rates that were 2-20 times faster than those observed in metal-free systems. Amorphous ferrihydrite was the most reactive iron mineral with respect to persulfate decomposition, with reaction rates proportional to solid mass and surface area. As a result of radical chain reactions, the rate of persulfate decomposition increased by as much as 100 times when benzene concentrations exceeded 0.1 mM. Due to its relatively slow rate of decomposition in the subsurface, it can be advantageous to inject persulfate into groundwater, allowing it to migrate to zones of low hydraulic conductivity where clays, metal oxides, and contaminants will accelerate its conversion into reactive oxidants.

In Situ Chemical Oxidation of Contaminated Groundwater by Persulfate: Decomposition by Fe(III)- and Mn(IV)-Containing Oxides and Aquifer Materials

PubMed Central

2015-01-01

Persulfate (S2O82–) is being used increasingly for in situ chemical oxidation (ISCO) of organic contaminants in groundwater, despite an incomplete understanding of the mechanism through which it is converted into reactive species. In particular, the decomposition of persulfate by naturally occurring mineral surfaces has not been studied in detail. To gain insight into the reaction rates and mechanism of persulfate decomposition in the subsurface, and to identify possible approaches for improving its efficacy, the decomposition of persulfate was investigated in the presence of pure metal oxides, clays, and representative aquifer solids collected from field sites in the presence and absence of benzene. Under conditions typical of groundwater, Fe(III)- and Mn(IV)-oxides catalytically converted persulfate into sulfate radical (SO4•–) and hydroxyl radical (HO•) over time scales of several weeks at rates that were 2–20 times faster than those observed in metal-free systems. Amorphous ferrihydrite was the most reactive iron mineral with respect to persulfate decomposition, with reaction rates proportional to solid mass and surface area. As a result of radical chain reactions, the rate of persulfate decomposition increased by as much as 100 times when benzene concentrations exceeded 0.1 mM. Due to its relatively slow rate of decomposition in the subsurface, it can be advantageous to inject persulfate into groundwater, allowing it to migrate to zones of low hydraulic conductivity where clays, metal oxides, and contaminants will accelerate its conversion into reactive oxidants. PMID:25133603
Functional and Structural Succession of Soil Microbial Communities below Decomposing Human Cadavers

PubMed Central

Cobaugh, Kelly L.; Schaeffer, Sean M.; DeBruyn, Jennifer M.

2015-01-01

The ecological succession of microbes during cadaver decomposition has garnered interest in both basic and applied research contexts (e.g. community assembly and dynamics; forensic indicator of time since death). Yet current understanding of microbial ecology during decomposition is almost entirely based on plant litter. We know very little about microbes recycling carcass-derived organic matter despite the unique decomposition processes. Our objective was to quantify the taxonomic and functional succession of microbial populations in soils below decomposing cadavers, testing the hypotheses that a) periods of increased activity during decomposition are associated with particular taxa; and b) human-associated taxa are introduced to soils, but do not persist outside their host. We collected soils from beneath four cadavers throughout decomposition, and analyzed soil chemistry, microbial activity and bacterial community structure. As expected, decomposition resulted in pulses of soil C and nutrients (particularly ammonia) and stimulated microbial activity. There was no change in total bacterial abundances, however we observed distinct changes in both function and community composition. During active decay (7 - 12 days postmortem), respiration and biomass production rates were high: the community was dominated by Proteobacteria (increased from 15.0 to 26.1% relative abundance) and Firmicutes (increased from 1.0 to 29.0%), with reduced Acidobacteria abundances (decreased from 30.4 to 9.8%). Once decay rates slowed (10 - 23 d postmortem), respiration was elevated, but biomass production rates dropped dramatically; this community with low growth efficiency was dominated by Firmicutes (increased to 50.9%) and other anaerobic taxa. Human-associated bacteria, including the obligately anaerobic Bacteroides, were detected at high concentrations in soil throughout decomposition, up to 198 d postmortem. Our results revealed the pattern of functional and compositional succession in soil microbial communities during decomposition of human-derived organic matter, provided insight into decomposition processes, and identified putative predictor populations for time since death estimation. PMID:26067226
ADVANCED OXIDATION: OXALATE DECOMPOSITION TESTING WITH OZONE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ketusky, E.; Subramanian, K.

At the Savannah River Site (SRS), oxalic acid is currently considered the preferred agent for chemically cleaning the large underground Liquid Radioactive Waste Tanks. It is applied only in the final stages of emptying a tank when generally less than 5,000 kg of waste solids remain, and slurrying based removal methods are no-longer effective. The use of oxalic acid is preferred because of its combined dissolution and chelating properties, as well as the fact that corrosion to the carbon steel tank walls can be controlled. Although oxalic acid is the preferred agent, there are significant potential downstream impacts. Impacts include:more » (1) Degraded evaporator operation; (2) Resultant oxalate precipitates taking away critically needed operating volume; and (3) Eventual creation of significant volumes of additional feed to salt processing. As an alternative to dealing with the downstream impacts, oxalate decomposition using variations of ozone based Advanced Oxidation Process (AOP) were investigated. In general AOPs use ozone or peroxide and a catalyst to create hydroxyl radicals. Hydroxyl radicals have among the highest oxidation potentials, and are commonly used to decompose organics. Although oxalate is considered among the most difficult organic to decompose, the ability of hydroxyl radicals to decompose oxalate is considered to be well demonstrated. In addition, as AOPs are considered to be 'green' their use enables any net chemical additions to the waste to be minimized. In order to test the ability to decompose the oxalate and determine the decomposition rates, a test rig was designed, where 10 vol% ozone would be educted into a spent oxalic acid decomposition loop, with the loop maintained at 70 C and recirculated at 40L/min. Each of the spent oxalic acid streams would be created from three oxalic acid strikes of an F-area simulant (i.e., Purex = high Fe/Al concentration) and H-area simulant (i.e., H area modified Purex = high Al/Fe concentration) after nearing dissolution equilibrium, and then decomposed to {le} 100 Parts per Million (ppm) oxalate. Since AOP technology largely originated on using ultraviolet (UV) light as a primary catalyst, decomposition of the spent oxalic acid, well exposed to a medium pressure mercury vapor light was considered the benchmark. However, with multi-valent metals already contained in the feed, and maintenance of the UV light a concern; testing was conducted to evaluate the impact from removing the UV light. Using current AOP terminology, the test without the UV light would likely be considered an ozone based, dark, ferrioxalate type, decomposition process. Specifically, as part of the testing, the impacts from the following were investigated: (1) Importance of the UV light on the decomposition rates when decomposing 1 wt% spent oxalic acid; (2) Impact of increasing the oxalic acid strength from 1 to 2.5 wt% on the decomposition rates; and (3) For F-area testing, the advantage of increasing the spent oxalic acid flowrate from 40 L/min (liters/minute) to 50 L/min during decomposition of the 2.5 wt% spent oxalic acid. The results showed that removal of the UV light (from 1 wt% testing) slowed the decomposition rates in both the F & H testing. Specifically, for F-Area Strike 1, the time increased from about 6 hours to 8 hours. In H-Area, the impact was not as significant, with the time required for Strike 1 to be decomposed to less than 100 ppm increasing slightly, from 5.4 to 6.4 hours. For the spent 2.5 wt% oxalic acid decomposition tests (all) without the UV light, the F-area decompositions required approx. 10 to 13 hours, while the corresponding required H-Area decompositions times ranged from 10 to 21 hours. For the 2.5 wt% F-Area sludge, the increased availability of iron likely caused the increased decomposition rates compared to the 1 wt% oxalic acid based tests. In addition, for the F-testing, increasing the recirculation flow rates from 40 liter/minute to 50 liter/minute resulted in an increased decomposition rate, suggesting a better use of ozone.« less
Challenges of including nitrogen effects on decomposition in earth system models

NASA Astrophysics Data System (ADS)

Hobbie, S. E.

2011-12-01

Despite the importance of litter decomposition for ecosystem fertility and carbon balance, key uncertainties remain about how this fundamental process is affected by nitrogen (N) availability. Nevertheless, resolving such uncertainties is critical for mechanistic inclusion of such processes in earth system models, towards predicting the ecosystem consequences of increased anthropogenic reactive N. Towards that end, we have conducted a series of experiments examining nitrogen effects on litter decomposition. We found that both substrate N and externally supplied N (regardless of form) accelerated the initial decomposition rate. Faster initial decomposition rates were linked to the higher activity of carbohydrate-degrading enzymes associated with externally supplied N and the greater relative abundances of Gram negative and Gram positive bacteria associated with green leaves and externally supplied organic N (assessed using phospholipid fatty acid analysis, PLFA). By contrast, later in decomposition, externally supplied N slowed decomposition, increasing the fraction of slowly decomposing litter and reducing lignin-degrading enzyme activity and relative abundances of Gram negative and Gram positive bacteria. Our results suggest that elevated atmospheric N deposition may have contrasting effects on the dynamics of different soil carbon pools, decreasing mean residence times of active fractions comprising very fresh litter, while increasing those of more slowly decomposing fractions including more processed litter. Incorporating these contrasting effects of N on decomposition processes into models is complicated by lingering uncertainties about how these effects generalize across ecosystems and substrates.
Study on Kinetic Mechanism of Bastnaesite Concentrates Decomposition Using Calcium Hydroxide

NASA Astrophysics Data System (ADS)

Cen, Peng; Wu, Wenyuan; Bian, Xue

2018-06-01

The thermal decomposition of bastnaesite concentrates using calcium hydroxide was studied. Calcium hydroxide can effectively inhibit the emission of fluorine during roasting by transforming it to calcium fluoride. The decomposition rate increased with increasing reaction temperature and amount of calcium hydroxide. The decomposition kinetics were investigated. The decomposition reaction was determined to be a heterogeneous gas-solid reaction, and it followed an unreacted shrinking core model. By means of the integrated rate equation method, the reaction was proven to be kinetically first order. Different reaction models were fit to the experimental data to determine the reaction control process. The chemical reaction at the phase interface controlled the reaction rate in the temperatures ranging from 673 K to 773 K (400 °C to 500 °C) with an apparent activation energy of 82.044 kJ·mol-1. From 773 K to 973 K (500 °C to 700 °C), diffusion through the solid product's layer became the determining step, with a lower activation energy of 15.841 kJ·mol-1.
Viscosity effects on the thermal decomposition of bis(perfluoro-2-N-propoxypropionyl) peroxide in dense carbon dioxide and fluorinated solvents.

PubMed

Bunyard, W C; Kadla, J F; DeYoung, J; DeSimone, J M

2001-08-01

The thermal decomposition of the free-radical initiator bis(perfluoro-2-N-propoxyprionyl) peroxide (BPPP) was studied in dense carbon dioxide and a series of fluorinated solvents. For the fluorinated solvents, the observed first-order decomposition rate constants, k(obs), increased with decreasing solvent viscosity, suggesting a single-bond decomposition mechanism. The k(obs) values are comparatively larger in dense carbon dioxide and similar to the "zero-viscosity" rate constants extrapolated from the decomposition kinetics in the fluorinated solvents. The decomposition activation parameters demonstrate a compensation behavior of the activation enthalpy with the activation entropy upon change in solvent viscosity. Comparison of the change in activation parameter values upon change in solvent viscosity for BPPP with two additional initiators, acetyl peroxide (AP) and trifluoroacetyl peroxide (TFAP), further suggests that carbon dioxide exerts a very minimal influence on the decomposition mechanism of these initiators through solvent-cage effects.
Leaf litter decomposition rates increase with rising mean annual temperature in Hawaiian tropical montane wet forests

PubMed Central

Bothwell, Lori D.; Giardina, Christian P.; Litton, Creighton M.

2014-01-01

Decomposing litter in forest ecosystems supplies nutrients to plants, carbon to heterotrophic soil microorganisms and is a large source of CO2 to the atmosphere. Despite its essential role in carbon and nutrient cycling, the temperature sensitivity of leaf litter decay in tropical forest ecosystems remains poorly resolved, especially in tropical montane wet forests where the warming trend may be amplified compared to tropical wet forests at lower elevations. We quantified leaf litter decomposition rates along a highly constrained 5.2 °C mean annual temperature (MAT) gradient in tropical montane wet forests on the Island of Hawaii. Dominant vegetation, substrate type and age, soil moisture, and disturbance history are all nearly constant across this gradient, allowing us to isolate the effect of rising MAT on leaf litter decomposition and nutrient release. Leaf litter decomposition rates were a positive linear function of MAT, causing the residence time of leaf litter on the forest floor to decline by ∼31 days for each 1 °C increase in MAT. Our estimate of the Q10 temperature coefficient for leaf litter decomposition was 2.17, within the commonly reported range for heterotrophic organic matter decomposition (1.5–2.5) across a broad range of ecosystems. The percentage of leaf litter nitrogen (N) remaining after six months declined linearly with increasing MAT from ∼88% of initial N at the coolest site to ∼74% at the warmest site. The lack of net N immobilization during all three litter collection periods at all MAT plots indicates that N was not limiting to leaf litter decomposition, regardless of temperature. These results suggest that leaf litter decay in tropical montane wet forests may be more sensitive to rising MAT than in tropical lowland wet forests, and that increased rates of N release from decomposing litter could delay or prevent progressive N limitation to net primary productivity with climate warming. PMID:25493213
Warming and Nitrogen Addition Increase Litter Decomposition in a Temperate Meadow Ecosystem

PubMed Central

Gong, Shiwei; Guo, Rui; Zhang, Tao; Guo, Jixun

2015-01-01

Background Litter decomposition greatly influences soil structure, nutrient content and carbon sequestration, but how litter decomposition is affected by climate change is still not well understood. Methodology/Principal Findings A field experiment with increased temperature and nitrogen (N) addition was established in April 2007 to examine the effects of experimental warming, N addition and their interaction on litter decomposition in a temperate meadow steppe in northeastern China. Warming, N addition and warming plus N addition reduced the residual mass of L. chinensis litter by 3.78%, 7.51% and 4.53%, respectively, in 2008 and 2009, and by 4.73%, 24.08% and 16.1%, respectively, in 2010. Warming, N addition and warming plus N addition had no effect on the decomposition of P. communis litter in 2008 or 2009, but reduced the residual litter mass by 5.58%, 15.53% and 5.17%, respectively, in 2010. Warming and N addition reduced the cellulose percentage of L. chinensis and P. communis, specifically in 2010. The lignin percentage of L. chinensis and P. communis was reduced by warming but increased by N addition. The C, N and P contents of L. chinensis and P. communis litter increased with time. Warming and N addition reduced the C content and C:N ratios of L. chinensisand P. communis litter, but increased the N and P contents. Significant interactive effects of warming and N addition on litter decomposition were observed (P<0.01). Conclusion/Significance The litter decomposition rate was highly correlated with soil temperature, soil water content and litter quality. Warming and N addition significantly impacted the litter decomposition rate in the Songnen meadow ecosystem, and the effects of warming and N addition on litter decomposition were also influenced by the quality of litter. These results highlight how climate change could alter grassland ecosystem carbon, nitrogen and phosphorus contents in soil by influencing litter decomposition. PMID:25774776
Large herbivores affect forest ecosystem functions by altering the structure of dung beetle communities

NASA Astrophysics Data System (ADS)

Iida, Taichi; Soga, Masashi; Koike, Shinsuke

2018-04-01

Dramatic increases in populations of large mammalian herbivores have become a major ecological issue, particularly in the northern hemisphere, due to their substantial impacts on both animal and plant communities through processes such as grazing, browsing, and trampling. However, little is known about the consequences of these population explosions on ecosystem functions. Here, we experimentally investigated how the population density of sika deer (Cervus nippon) in temperate deciduous forest areas in Japan affected the decomposition of mammal dung by dung beetles, which is a key process in forest ecosystems. We measured a range of environmental variables (e.g., vegetation cover, soil hardness) and the dung decomposition rate, measured as the amount of deer dung decomposed during one week, and sampled dung beetles at 16 study sites with three different deer densities (high/intermediate/low). We then used structural equation modeling to investigate the relationships between deer density, environmental variables, the biomass of dung beetles (classified into small or large species), and the dung decomposition rate. We found that the biomass of small species increased with increasing deer density, whereas that of large species was not related to deer density. Furthermore, the dung decomposition rate was positively related to the biomass of small species but unrelated to that of large species. Overall, our results showed that an increase in deer density affects the decomposition rate of mammal dung by changing the structure of dung beetle communities (i.e., increasing the number of small dung beetles). Such an understanding of how increases in large herbivore populations affect ecosystem functions is important for accurately evaluating the ecological consequences of their overabundance and ultimately managing their populations appropriately.
Theoretical studies of the decomposition mechanisms of 1,2,4-butanetriol trinitrate.

PubMed

Pei, Liguan; Dong, Kehai; Tang, Yanhui; Zhang, Bo; Yu, Chang; Li, Wenzuo

2017-12-06

Density functional theory (DFT) and canonical variational transition-state theory combined with a small-curvature tunneling correction (CVT/SCT) were used to explore the decomposition mechanisms of 1,2,4-butanetriol trinitrate (BTTN) in detail. The results showed that the γ-H abstraction reaction is the initial pathway for autocatalytic BTTN decomposition. The three possible hydrogen atom abstraction reactions are all exothermic. The rate constants for autocatalytic BTTN decomposition are 3 to 10 40 times greater than the rate constants for the two unimolecular decomposition reactions (O-NO 2 cleavage and HONO elimination). The process of BTTN decomposition can be divided into two stages according to whether the NO 2 concentration is above a threshold value. HONO elimination is the main reaction channel during the first stage because autocatalytic decomposition requires NO 2 and the concentration of NO 2 is initially low. As the reaction proceeds, the concentration of NO 2 gradually increases; when it exceeds the threshold value, the second stage begins, with autocatalytic decomposition becoming the main reaction channel.
Climate Induced Changes in Global-Scale Litter Decomposition and Long-term Relationships with Net Primary Productivity

NASA Astrophysics Data System (ADS)

Silver, W. L.; Smith, W. K.; Parton, W. J.; Wieder, W. R.; DelGrosso, S.

2016-12-01

Surface litter decomposition represents the largest annual carbon (C) flux to the atmosphere from terrestrial ecosystems (Esser et al. 1982). Using broad-scale long-term datasets we show that litter decomposition rates are largely predicted by a climate-decomposition index (CDI) at a global scale, and use CDI to estimate patterns in litter decomposition over the 110 years from 1901-2011. There were rapid changes in CDI over the last 30 y of the record amounting to a 4.3% increase globally. Boreal forests (+13.9%), tundra (+12.2%), savannas (+5.3%), and temperate (+2.4%) and tropical (+2.1%) forests all experienced accelerated decomposition. During the same period, most biomes experienced corresponding increases in a primary production index (PPI) estimated from an ensemble of long-term, observation-based productivity indices. The percent increase in PPI was only half that of decomposition globally. Tropical forests and savannas showed no increase in PPI to offset greater decomposition rates. Temperature-limited ecosystems (i.e., tundra, boreal, and temperate forests) showed the greatest differences between CDI and PPI, highlighting potentially large decoupling of C fluxes in these biomes. Precipitation and actual evapotranspiration were the best climate predictors of CDI at a global scale, while PPI varied consistently with actual evapotranspiration. As expected, temperature was the best predictor of PPI across temperature limited ecosystems. Our results show that climate change could be leading to a decoupling of C uptake and losses, potentially resulting in lower C storage in northern latitudes, temperate and tropical forests, and savannas.
The Spatial Variability of Organic Matter and Decomposition Processes at the Marsh Scale

NASA Astrophysics Data System (ADS)

Yousefi Lalimi, Fateme; Silvestri, Sonia; D'Alpaos, Andrea; Roner, Marcella; Marani, Marco

2017-04-01

Coastal salt marshes sequester carbon as they respond to the local Rate of Relative Sea Level Rise (RRSLR) and their accretion rate is governed by inorganic soil deposition, organic soil production, and soil organic matter (SOM) decomposition. It is generally recognized that SOM plays a central role in marsh vertical dynamics, but while existing limited observations and modelling results suggest that SOME varies widely at the marsh scale, we lack systematic observations aimed at understanding how SOM production is modulated spatially as a result of biomass productivity and decomposition rate. Marsh topography and distance to the creek can affect biomass and SOM production, while a higher topographic elevation increases drainage, evapotranspiration, aeration, thereby likely inducing higher SOM decomposition rates. Data collected in salt marshes in the northern Venice Lagoon (Italy) show that, even though plant productivity decreases in the lower areas of a marsh located farther away from channel edges, the relative contribution of organic soil production to the overall vertical soil accretion tends to remain constant as the distance from the channel increases. These observations suggest that the competing effects between biomass production and aeration/decomposition determine a contribution of organic soil to total accretion which remains approximately constant with distance from the creek, in spite of the declining plant productivity. Here we test this hypothesis using new observations of SOM and decomposition rates from marshes in North Carolina. The objective is to fill the gap in our understanding of the spatial distribution, at the marsh scale, of the organic and inorganic contributions to marsh accretion in response to RRSLR.
Influence of sodium carbonate on decomposition of formic acid by pulsed discharge plasma inside bubble in water

NASA Astrophysics Data System (ADS)

Iwabuchi, Masashi; Takahashi, Katsuyuki; Takaki, Koichi; Satta, Naoya

2016-07-01

The influence of sodium carbonate on the decomposition of formic acid by discharge inside bubbles in water was investigated experimentally. Oxygen or argon gases were injected into the water through a vertically positioned glass tube, in which the high-voltage wire electrode was placed to generate plasmas at low applied voltage. The concentration of formic acid was determined by ion chromatography. In the case of sodium carbonate additive, the pH increased owing to the decomposition of the formic acid. In the case of oxygen injection, the percentage of conversion of formic acid increased with increasing pH because the reaction rate of ozone with formic acid increased with increasing pH. In the case of argon injection, the percentage of conversion was not affected by the pH owing to the high rate loss of hydroxyl radicals.
Measurement of the energy dependence of X-ray-induced decomposition of potassium chlorate.

PubMed

Pravica, Michael; Bai, Ligang; Sneed, Daniel; Park, Changyong

2013-03-21

We report the first measurements of the X-ray induced decomposition of KClO3 as a function of energy in two experiments. KClO3 was pressurized to 3.5 GPa and irradiated with monochromatic synchrotron X-rays ranging in energy from 15 to 35 keV in 5 keV increments. A systematic increase in the decomposition rate as the energy was decreased was observed, which agrees with the 1/E(3) trend for the photoelectric process, except at the lowest energy studied. A second experiment was performed to access lower energies (10 and 12 keV) using a beryllium gasket; suggesting an apparent resonance near 15 keV or 0.83 Ǻ maximizing the chemical decomposition rate. A third experiment was performed using KIO3 to ascertain the anionic dependence of the decomposition rate, which was observed to be far slower than in KClO3, suggesting that the O-O distance is the critical factor in chemical reactions. These results will be important for more efficiently initiating chemical decomposition in materials using selected X-ray wavelengths that maximize decomposition to aid useful hard X-ray-induced chemistry and contribute understanding of the mechanism of X-ray-induced decomposition of the chlorates.
Study on the Effect of cellulolytic strain MYB3 for Corn Stover Fermentation

NASA Astrophysics Data System (ADS)

Yan, Han; Bai, Bing; Cheng, Xiao-Xiao; Li, Guang-Chun; Huang, Shi-Chen; Piao, Chun-Xiang

2018-03-01

The effects of corn stover fermentation with the Bacillus megaterium MYB3 was studied in this paper. The results showed that the decomposition rates of cellulose and hemicellulose were 49.6%, 43.46% after 20 days respectively, after fermentation, pH was changed to 5.68, and adjusted to corn stover initial pH 3 to achieve the purpose of sterilization. The decomposition rate was significantly increased by adding corn flour. After adjusting fermentation composes with the ratio of the corn stove to corn flour was 15 : 1, the decomposition rate of cellulose would be 52.37% for 10 days.
Kinetic Studies of the Thermal Decomposition of 2-Chloroethylphosphonic Acid in Aqueous Solution

PubMed Central

Biddle, Eric; Kerfoot, Douglas G. S.; Kho, Yioe Hwa; Russell, Kenneth E.

1976-01-01

The decomposition of 2-chloroethylphosphonic acid in aqueous solution has been studied at pH values from 6 to 9 and at temperatures in the 30 to 55 C range. The rate of decomposition is estimated from the rate of formation of ethylene. The rate is proportional to the concentration of the phosphonate dianion and is independent of the hydroxyl ion concentration. The rate constant at 40 C is 1.9 × 10−4 sec−1 and the activation energy is 29.8 kcal mol−1. The rate of reaction is not affected significantly by the presence of potassium iodide or urea (substances which increase the rate of leaf abscission in trees sprayed by 2-chloroethylphosphonic acid). The rate decreases slightly in the presence of low concentrations of magnesium and calcium ions. PMID:16659748
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. Copyright © 2012 Elsevier B.V. All rights reserved.
Temperature and soil organic matter decomposition rates - synthesis of current knowledge and a way forward

Treesearch

Richard T. Conant; Michael Ryan; Goran I. Agren; Hannah E. Birge; Eric A. Davidson; Peter E. Eliasson; Sarah E. Evans; Serita D. Frey; Christian P. Giardina; Francesca M. Hopkins; Riitta Hyvonen; Miko U. F . Kirschbaum; Jocelyn M. Lavallee; Jens Leifeld; William J. Parton; Jessica Megan Steinweg; Matthew D. Wallenstein; J . A. Martin Wetterstedt; Mark A. Bradford

2011-01-01

The response of soil organic matter (OM) decomposition to increasing temperature is a critical aspect of ecosystem responses to global change. The impacts of climate warming on decomposition dynamics have not been resolved due to apparently contradictory results from field and lab experiments, most of which has focused on labile carbon with short turnover times. But...
Potential macro-detritivore range expansion into the subarctic stimulates litter decomposition: a new positive feedback mechanism to climate change?

PubMed

van Geffen, Koert G; Berg, Matty P; Aerts, Rien

2011-12-01

As a result of low decomposition rates, high-latitude ecosystems store large amounts of carbon. Litter decomposition in these ecosystems is constrained by harsh abiotic conditions, but also by the absence of macro-detritivores. We have studied the potential effects of their climate change-driven northward range expansion on the decomposition of two contrasting subarctic litter types. Litter of Alnus incana and Betula pubescens was incubated in microcosms together with monocultures and all possible combinations of three functionally different macro-detritivores (the earthworm Lumbricus rubellus, isopod Oniscus asellus, and millipede Julus scandinavius). Our results show that these macro-detritivores stimulated decomposition, especially of the high-quality A. incana litter and that the macro-detritivores tested differed in their decomposition-stimulating effects, with earthworms having the largest influence. Decomposition processes increased with increasing number of macro-detritivore species, and positive net diveristy effects occurred in several macro-detritivore treatments. However, after correction for macro-detritivore biomass, all interspecific differences in macro-detritivore effects, as well as the positive effects of species number on subarctic litter decomposition disappeared. The net diversity effects also appeared to be driven by variation in biomass, with a possible exception of net diversity effects in mass loss. Based on these results, we conclude that the expected climate change-induced range expansion of macro-detritivores into subarctic regions is likely to result in accelerated decomposition rates. Our results also indicate that the magnitude of macro-detritivore effects on subarctic decomposition will mainly depend on macro-detritivore biomass, rather than on macro-detritivore species number or identity.
Role of litter decomposition sensitivity to water content in non-additive litter mixture effect: theoretical demonstration and validation with a peatland litter experiment

NASA Astrophysics Data System (ADS)

Gogo, Sébastien; Leroy, Fabien; Zoccatelli, Renata; Bernard-Jannin, Léonard; Laggoun-Défarge, Fatima

2017-04-01

In this work, we showed theoretically that differences in litter water content, evaporation rate and reaction rate sensitivity to water content can give account of non-additive litter mixture effect. More specifically two litters with the same dependence to litter water content and contrasted water content, and 2 litters with contrasted decomposition sensitivity to litter water content can exert synergistic mixture effect on decomposition when the 2 litters interact. In these situations, water can flow from the wettest to the driest litter, changing the whole reaction rate without changing the whole litter water content. The reaction rate increase of the litter receiving the water was relatively more important than the reaction rate decrease of the litter supplying the water. These theoretical considerations were validated with experimental data. Sphagnum rubellum and Molinia caerulea decompose faster in measured mixture than expected from the rates obtained in monoculture incubation. Sphagnum rubellum litter can contain more water, which evaporates at a slower rate than Molinia caerulea. It is thus proposed that water flowed from Sphagnum rubellum litter to the Molinia caerulea litter, with a substantial increase of the decomposition of the latter. The physical and biochemical litter characteristics towards water explains a fraction of the synergistic effect of mixing the 2 litters, which suggests that other factors intervene in this effect, such as the carbon substrate.

Climate change effects on macrofaunal litter decomposition: the interplay of temperature, body masses and stoichiometry.

PubMed

Ott, David; Rall, Björn C; Brose, Ulrich

2012-11-05

Macrofauna invertebrates of forest floors provide important functions in the decomposition process of soil organic matter, which is affected by the nutrient stoichiometry of the leaf litter. Climate change effects on forest ecosystems include warming and decreasing litter quality (e.g. higher C : nutrient ratios) induced by higher atmospheric CO(2) concentrations. While litter-bag experiments unravelled separate effects, a mechanistic understanding of how interactions between temperature and litter stoichiometry are driving decomposition rates is lacking. In a laboratory experiment, we filled this void by quantifying decomposer consumption rates analogous to predator-prey functional responses that include the mechanistic parameters handling time and attack rate. Systematically, we varied the body masses of isopods, the environmental temperature and the resource between poor (hornbeam) and good quality (ash). We found that attack rates increased and handling times decreased (i) with body masses and (ii) temperature. Interestingly, these relationships interacted with litter quality: small isopods possibly avoided the poorer resource, whereas large isopods exhibited increased, compensatory feeding of the poorer resource, which may be explained by their higher metabolic demands. The combination of metabolic theory and ecological stoichiometry provided critically important mechanistic insights into how warming and varying litter quality may modify macrofaunal decomposition rates.
Stream ecosystem integrity is impaired by logging and shifting agriculture in a global megadiversity center (Sarawak, Borneo).

PubMed

Jinggut, Tajang; Yule, Catherine M; Boyero, Luz

2012-10-15

In common with most of Borneo, the Bakun region of Sarawak is currently subject to heavy deforestation mainly due to logging and, to a lesser extent, traditional slash-and-burn farming practices. This has the potential to affect stream ecosystems, which are integrators of environmental change in the surrounding terrestrial landscape. This study evaluated the effects of both types of deforestation by using functional and structural indicators (leaf litter decomposition rates and associated detritivores or 'shredders', respectively) to compare a fundamental ecosystem process, leaf litter decomposition, within logged, farmed and pristine streams. Slash-and-burn agricultural practices increased the overall rate of decomposition despite a decrease in shredder species richness (but not shredder abundance) due to increased microbial decomposition. In contrast, decomposition by microbes and invertebrates was slowed down in the logged streams, where shredders were less abundant and less species rich. This study suggests that shredder communities are less affected by traditional agricultural farming practices, while modern mechanized deforestation has an adverse effect on both shredder communities and leaf breakdown. Copyright © 2012 Elsevier B.V. All rights reserved.
Effects of water flow regulation on ecosystem functioning in a Mediterranean river network assessed by wood decomposition.

PubMed

Abril, Meritxell; Muñoz, Isabel; Casas-Ruiz, Joan P; Gómez-Gener, Lluís; Barceló, Milagros; Oliva, Francesc; Menéndez, Margarita

2015-06-01

Mediterranean rivers are extensively modified by flow regulation practises along their courses. An important part of the river impoundment in this area is related to the presence of small dams constructed mainly for water abstraction purposes. These projects drastically modified the ecosystem morphology, transforming lotic into lentic reaches and increasing their alternation along the river. Hydro-morphologial differences between these reaches indicate that flow regulation can trigger important changes in the ecosystem functioning. Decomposition of organic matter is an integrative process and this complexity makes it a good indicator of changes in the ecosystem. The aim of this study was to assess the effect caused by flow regulation on ecosystem functioning at the river network scale, using wood decomposition as a functional indicator. We studied the mass loss from wood sticks during three months in different lotic and lentic reaches located along a Mediterranean river basin, in both winter and summer. Additionally, we identified the environmental factors affecting decomposition rates along the river orders. The results revealed differences in decomposition rates between sites in both seasons that were principally related to the differences between stream orders. The rates were mainly related to temperature, nutrient concentrations (NO2(-), NO3(2-)) and water residence time. High-order streams with higher temperature and nutrient concentrations exhibited higher decomposition rates compared with low-order streams. The effect of the flow regulation on the decomposition rates only appeared to be significant in high orders, especially in winter, when the hydrological characteristics of lotic and lentic habitats widely varied. Lotic reaches with lower water residence time exhibited greater decomposition rates compared with lentic reaches probably due to more physical abrasion and differences in the microbial assemblages. Overall, our study revealed that in high orders the reduction of flow caused by flow regulation affects the wood decomposition indicating changes in ecosystem functioning. Copyright © 2015 Elsevier B.V. All rights reserved.
Relationship of host recurrence in fungi to rates of tropical leaf decomposition

Treesearch

Mirna E. Santanaa; JeanD. Lodgeb; Patricia Lebowc

2004-01-01

Here we explore the significance of fungal diversity on ecosystem processes by testing whether microfungal âpreferencesâ for (i.e., host recurrence) different tropical leaf species increases the rate of decomposition. We used pairwise combinations of girradiated litter of five tree species with cultures of two dominant microfungi derived from each plant in a microcosm...
Relationship of host recurrence in fungi to rates of tropical leaf decomposition

Treesearch

Mirna E. Santana; D. Jean Lodge; Patricia Lebow

2005-01-01

Here we explore the significance of fungal diversity on ecosystem processes by testing whether microfungal âpreferencesâ for (i.e., host recurrence) different tropical leaf species increases the rate of decomposition. We used pairwise combinations of [gamma]-irradiated litter of five tree species with cultures of two dominant microfungi derived from each plant in a...
ENHANCED CHEMICAL CLEANING: EFFECTIVENESS OF THE UV LAMP TO DECOMPOSE OXALATES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ketusky, E.; Huff, T.; Sudduth, C.

2010-01-19

Enhanced Chemical Cleaning is a new process scheduled to begin cleaning Savannah River Site High Level Waste Tanks in 2012. It is an improvement over the current chemical cleaning method, in that it minimizes downstream impacts on the High Level Waste System. It is based on a state of the art scale removal process used on the secondary side of nuclear power plants, with modifications to accommodate the unique constraints created by the tanks. Both Enhanced Chemical Cleaning and the scale removal process are founded on dissolving metal oxides/hydroxides using oxalic acid, with subsequent oxalate decomposition via hydroxylation using ozonemore » or peroxide, and UV light as a catalyst. A divergence Enhanced Chemical Cleaning has from nuclear power scale removal is the significantly increased solids concentration during oxalate decomposition. These solids can limit the ability of the UV light to create hydroxyl radicals, either by limiting the ability of the light to penetrate through the solution, or by increasing the fouling rate on the UV light. Both will decrease the overall catalytic effectiveness, thereby decreasing the concentration of formed hydroxyl radicals. The hydroxyl radicals are the driving force behind the oxalate decomposition. To understand the impact of increased solids, testing was performed using a medium pressure UV light inside an ozone supplied Oxalate Decomposition Reactor. Using a dissolved metal sludge simulant with an initial oxalate concentration greater than 12,000 ppm, and an initial pH of about 2.0, the spent acid solution was recirculated through the reactor, while the UV light was allowed to foul. For the first few hours, the oxalate decomposition rate was about 1,300 ppm/hour. After about 3 hours, enough time for the UV lamp to foul, the oxalate decomposition rate decreased to about 500 ppm/hour. The decomposition rate then remained roughly constant for the next 16 hours. Overall, testing showed that the oxalate destruction rate decreased by about 2.8. Results from very similartests with similar chemistry suggest that the impact should be about 10. Based on the limited reaction pathwayfor the creation of hydroxyl radicals with iron, ozone, and no UV, the discrepancy suggests that initially, at 'time zero' the UV light failed to perform up to expectations. It is therefore concluded that regardless of the fouling rate, either the increased solids concentration is impacting the initial penetrability (i.e. to many solids), or the light is not adequately sized/configured to have the appropriate flux.« less
A global experiment suggests climate warming will not accelerate litter decomposition in streams but might reduce carbon sequestration.

PubMed

Boyero, Luz; Pearson, Richard G; Gessner, Mark O; Barmuta, Leon A; Ferreira, Verónica; Graça, Manuel A S; Dudgeon, David; Boulton, Andrew J; Callisto, Marcos; Chauvet, Eric; Helson, Julie E; Bruder, Andreas; Albariño, Ricardo J; Yule, Catherine M; Arunachalam, Muthukumarasamy; Davies, Judy N; Figueroa, Ricardo; Flecker, Alexander S; Ramírez, Alonso; Death, Russell G; Iwata, Tomoya; Mathooko, Jude M; Mathuriau, Catherine; Gonçalves, José F; Moretti, Marcelo S; Jinggut, Tajang; Lamothe, Sylvain; M'Erimba, Charles; Ratnarajah, Lavenia; Schindler, Markus H; Castela, José; Buria, Leonardo M; Cornejo, Aydeé; Villanueva, Verónica D; West, Derek C

2011-03-01

The decomposition of plant litter is one of the most important ecosystem processes in the biosphere and is particularly sensitive to climate warming. Aquatic ecosystems are well suited to studying warming effects on decomposition because the otherwise confounding influence of moisture is constant. By using a latitudinal temperature gradient in an unprecedented global experiment in streams, we found that climate warming will likely hasten microbial litter decomposition and produce an equivalent decline in detritivore-mediated decomposition rates. As a result, overall decomposition rates should remain unchanged. Nevertheless, the process would be profoundly altered, because the shift in importance from detritivores to microbes in warm climates would likely increase CO(2) production and decrease the generation and sequestration of recalcitrant organic particles. In view of recent estimates showing that inland waters are a significant component of the global carbon cycle, this implies consequences for global biogeochemistry and a possible positive climate feedback. © 2011 Blackwell Publishing Ltd/CNRS.
Management intensity alters decomposition via biological pathways

USGS Publications Warehouse

Wickings, Kyle; Grandy, A. Stuart; Reed, Sasha; Cleveland, Cory

2011-01-01

Current conceptual models predict that changes in plant litter chemistry during decomposition are primarily regulated by both initial litter chemistry and the stage-or extent-of mass loss. Far less is known about how variations in decomposer community structure (e.g., resulting from different ecosystem management types) could influence litter chemistry during decomposition. Given the recent agricultural intensification occurring globally and the importance of litter chemistry in regulating soil organic matter storage, our objectives were to determine the potential effects of agricultural management on plant litter chemistry and decomposition rates, and to investigate possible links between ecosystem management, litter chemistry and decomposition, and decomposer community composition and activity. We measured decomposition rates, changes in litter chemistry, extracellular enzyme activity, microarthropod communities, and bacterial versus fungal relative abundance in replicated conventional-till, no-till, and old field agricultural sites for both corn and grass litter. After one growing season, litter decomposition under conventional-till was 20% greater than in old field communities. However, decomposition rates in no-till were not significantly different from those in old field or conventional-till sites. After decomposition, grass residue in both conventional- and no-till systems was enriched in total polysaccharides relative to initial litter, while grass litter decomposed in old fields was enriched in nitrogen-bearing compounds and lipids. These differences corresponded with differences in decomposer communities, which also exhibited strong responses to both litter and management type. Overall, our results indicate that agricultural intensification can increase litter decomposition rates, alter decomposer communities, and influence litter chemistry in ways that could have important and long-term effects on soil organic matter dynamics. We suggest that future efforts to more accurately predict soil carbon dynamics under different management regimes may need to explicitly consider how changes in litter chemistry during decomposition are influenced by the specific metabolic capabilities of the extant decomposer communities.
Effects of experimental throughfall reduction and soil warming on fine root biomass and its decomposition in a warm temperate oak forest.

PubMed

Liu, Yanchun; Liu, Shirong; Wan, Shiqiang; Wang, Jingxin; Wang, Hui; Liu, Kuan

2017-01-01

Fine root dynamics play a critical role in regulating carbon (C) cycling in terrestrial ecosystems. Examining responses of fine root biomass and its decomposition to altered precipitation pattern and climate warming is crucial to understand terrestrial C dynamics and its feedback to climate change. Fine root biomass and its decomposition rate were investigated in a warm temperate oak forest through a field manipulation experiment with throughfall reduction and soil warming conducted. Throughfall reduction significantly interacted with soil warming in affecting fine root biomass and its decomposition. Throughfall reduction substantially increased fine root biomass and its decomposition in unheated plots, but negative effects occurred in warmed plots. Soil warming significantly enhanced fine root biomass and its decomposition under ambient precipitation, but the opposite effects exhibited under throughfall reduction. Different responses in fine root biomass among different treatments could be largely attributed to soil total nitrogen (N), while fine root decomposition rate was more depended on microbial biomass C and N. Our observations indicate that decreased precipitation may offset the positive effect of soil warming on fine root biomass and decomposition. Copyright © 2016 Elsevier B.V. All rights reserved.
Quantitative and qualitative measures of decomposition: is there a link?

Treesearch

Robert J. Eaton; Felipe G. Sanchez

2009-01-01

Decomposition rates of loblolly pine coarse woody debris (CWD) were determined by mass loss and wood density changes for trees that differed in source of mortality (natural, girdle-poison, and felling). Specifically, three treatments were examined: (1) control (CON): natural mortality; (2) CD: 5-fold increase in CWD compared with the CON; and (3) CS: 12-fold increase...
The impact of climate change on ecosystem carbon dynamics at the Scandinavian mountain birch forest-tundra heath ecotone.

PubMed

Sjögersten, Sofie; Wookey, Philip A

2009-02-01

Changes in temperature and moisture resulting from climate change are likely to strongly modify the ecosystem carbon sequestration capacity in high-latitude areas, both through vegetation shifts and via direct warming effects on photosynthesis and decomposition. This paper offers a synthesis of research addressing the potential impacts of climate warming on soil processes and carbon fluxes at the forest-tundra ecotone in Scandinavia. Our results demonstrated higher rates of organic matter decomposition in mountain birch forest than in tundra heath soils, with markedly shallower organic matter horizons in the forest. Field and laboratory experiments suggest that increased temperatures are likely to increase CO2 efflux from both tundra and forest soil providing moisture availability does not become limiting for the decomposition process. Furthermore, colonization of tundra heath by mountain birch forest would increase rates of decomposition, and thus CO2 emissions, from the tundra heath soils, which currently store substantial amounts of potentially labile carbon. Mesic soils underlying both forest and tundra heath are currently weak sinks of atmospheric methane, but the strength of this sink could be increased with climate warming and/or drying.
The processing of aluminum gasarites via thermal decomposition of interstitial hydrides

NASA Astrophysics Data System (ADS)

Licavoli, Joseph J.

Gasarite structures are a unique type of metallic foam containing tubular pores. The original methods for their production limited them to laboratory study despite appealing foam properties. Thermal decomposition processing of gasarites holds the potential to increase the application of gasarite foams in engineering design by removing several barriers to their industrial scale production. The following study characterized thermal decomposition gasarite processing both experimentally and theoretically. It was found that significant variation was inherent to this process therefore several modifications were necessary to produce gasarites using this method. Conventional means to increase porosity and enhance pore morphology were studied. Pore morphology was determined to be more easily replicated if pores were stabilized by alumina additions and powders were dispersed evenly. In order to better characterize processing, high temperature and high ramp rate thermal decomposition data were gathered. It was found that the high ramp rate thermal decomposition behavior of several hydrides was more rapid than hydride kinetics at low ramp rates. This data was then used to estimate the contribution of several pore formation mechanisms to the development of pore structure. It was found that gas-metal eutectic growth can only be a viable pore formation mode if non-equilibrium conditions persist. Bubble capture cannot be a dominant pore growth mode due to high bubble terminal velocities. Direct gas evolution appears to be the most likely pore formation mode due to high gas evolution rate from the decomposing particulate and microstructural pore growth trends. The overall process was evaluated for its economic viability. It was found that thermal decomposition has potential for industrialization, but further refinements are necessary in order for the process to be viable.
Assessing the effect of different treatments on decomposition rate of dairy manure.

PubMed

Khalil, Tariq M; Higgins, Stewart S; Ndegwa, Pius M; Frear, Craig S; Stöckle, Claudio O

2016-11-01

Confined animal feeding operations (CAFOs) contribute to greenhouse gas emission, but the magnitude of these emissions as a function of operation size, infrastructure, and manure management are difficult to assess. Modeling is a viable option to estimate gaseous emission and nutrient flows from CAFOs. These models use a decomposition rate constant for carbon mineralization. However, this constant is usually determined assuming a homogenous mix of manure, ignoring the effects of emerging manure treatments. The aim of this study was to measure and compare the decomposition rate constants of dairy manure in single and three-pool decomposition models, and to develop an empirical model based on chemical composition of manure for prediction of a decomposition rate constant. Decomposition rate constants of manure before and after an anaerobic digester (AD), following coarse fiber separation, and fine solids removal were determined under anaerobic conditions for single and three-pool decomposition models. The decomposition rates of treated manure effluents differed significantly from untreated manure for both single and three-pool decomposition models. In the single-pool decomposition model, AD effluent containing only suspended solids had a relatively high decomposition rate of 0.060 d(-1), while liquid with coarse fiber and fine solids removed had the lowest rate of 0.013 d(-1). In the three-pool decomposition model, fast and slow decomposition rate constants (0.25 d(-1) and 0.016 d(-1) respectively) of untreated AD influent were also significantly different from treated manure fractions. A regression model to predict the decomposition rate of treated dairy manure fitted well (R(2) = 0.83) to observed data. Copyright © 2016 Elsevier Ltd. All rights reserved.
Decomposition Behavior of Curcumin during Solar Irradiation when Contact with Inorganic Particles

NASA Astrophysics Data System (ADS)

Nandiyanto, A. B. D.; Wiryani, A. S.; Rusli, A.; Purnamasari, A.; Abdullah, A. G.; Riza, L. S.

2017-03-01

Curcumin is one of materials which have been widely used in medicine, Asian cuisine, and traditional cosmetic. Therefore, understanding the stability of curcumin has been widely studied. The purpose of this study was to investigate the stability of curcumin solution against solar irradiation when making contact with inorganic material. As a model for the inorganic material, titanium dioxide (TiO2) was used. In the experimental method, the curcumin solution was irradiated using a solar irradiation. To confirm the stability of curcumin when contact with inorganic material, we added TiO2 micro particles with different concentrations. The results showed that the concentration of curcumin decreased during solar irradiation. The less concentration of curcumin affected the more decomposition rate obtained. The decomposition rate was increased greatly when TiO2 was added, in which the more TiO2 concentration added allowed the faster decomposition rate. Based on the result, we conclude that the curcumin is relatively stable as long as using higher concentration of curcumin and is no inorganic material existed. Then, the decomposition can be minimized by avoiding contact with inorganic material.
Factors controlling the abiotic photo-degradation of monomethylmercury in surface waters

NASA Astrophysics Data System (ADS)

Black, Frank J.; Poulin, Brett A.; Flegal, A. Russell

2012-05-01

Photo-decomposition is among the most important mechanisms responsible for degrading monomethylmercury (MMHg) in aquatic systems, but this process is not fully understood. We investigated the relative importance of different factors in controlling the rate of MMHg photo-decomposition in surface waters in experiments using DOM isolated from natural waters. We found no evidence of net abiotic production of MMHg in any dark or light exposed treatments. The average (mean ± s.d.) MMHg photo-decomposition rate constant for all light exposed samples using DOM concentrated from three coastal wetlands was 0.0099 ± 0.0020 E-1m2 (range of 0.006-0.015 E-1m2) when expressed in photon flux from 330-700 nm. This was roughly 3-fold higher than the average MMHg photo-decomposition rate constant in coastal seawater of 0.0032 ± 0.0010 E-1m2. MMHg photo-degradation was highly wavelength dependent. The ratio of MMHg photo-decomposition rate constants, with respect to photon flux, was 400:37:1 for UVB:UVA:PAR. However, when integrated across the entire water column over which MMHg photo-demethylation occurs, PAR was responsible for photo-degrading more MMHg than UVB and UVA combined in the three wetland sites because of the more rapid attenuation of UV light with depth. MMHg half-lives in the wetlands were calculated for the upper 250 cm where photo-degradation occurred, and ranged from 7.6 to 20 days under typical summer sunlight conditions at 37°N. Rates of MMHg photo-decomposition decreased with increasing salinity, and were 27% higher at a salinity of 5 than those at a salinity of 25. This difference could not be accounted for by changes in the complexation of MMHg by DOM and chloride. Differences in MMHg photo-degradation rate constants of up to 18% were measured between treatments using DOM concentrated from three different wetlands. Surprisingly, increasing DOM concentration from 1.5 to 11.3 mg OC L-1 had only a small (6%) effect on MMHg photo-decomposition, which was much smaller than the 34% decrease predicted due to the attenuation of light at the higher DOM levels. This suggests that DOM plays an important role in MMHg photo-decomposition apart from mediating light levels and MMHg complexation. Experiments employing various scavengers implied that singlet oxygen and hydroxyl radicals were not involved in the photo-degradation of MMHg in the natural waters used. Varying concentrations of Fe, Cu, and Mn had only small (⩽11%) effects on rates of MMHg photo-decomposition, and relatively high rates were measured in high purity water with no trace metals or DOM. These results demonstrate that MMHg photo-decomposition can occur via pathways not involving Fe, the photo-Fenton reaction, nitrate photolysis, or thiol complexation. Taken with previous studies, multiple reaction pathways appear to exist, and their importance varies as a function of water chemistry and light wavelength.
Effects of Increased Summer Precipitation and Nitrogen Addition on Root Decomposition in a Temperate Desert

PubMed Central

Zhao, Hongmei; Huang, Gang; Li, Yan; Ma, Jian; Sheng, Jiandong; Jia, Hongtao; Li, Congjuan

2015-01-01

Background Climate change scenarios that include precipitation shifts and nitrogen (N) deposition are impacting carbon (C) budgets in arid ecosystems. Roots constitute an important part of the C cycle, but it is still unclear which factors control root mass loss and nutrient release in arid lands. Methodology/Principal Findings Litterbags were used to investigate the decomposition rate and nutrient dynamics in root litter with water and N-addition treatments in the Gurbantunggut Desert in China. Water and N addition had no significant effect on root mass loss and the N and phosphorus content of litter residue. The loss of root litter and nutrient releases were strongly controlled by the initial lignin content and the lignin:N ratio, as evidenced by the negative correlations between decomposition rate and litter lignin content and the lignin:N ratio. Fine roots of Seriphidium santolinum (with higher initial lignin content) had a slower decomposition rate in comparison to coarse roots. Conclusion/Significance Results from this study indicate that small and temporary changes in rainfall and N deposition do not affect root decomposition patterns in the Gurbantunggut Desert. Root decomposition rates were significantly different between species, and also between fine and coarse roots, and were determined by carbon components, especially lignin content, suggesting that root litter quality may be the primary driver of belowground carbon turnover. PMID:26544050
The role of soil drainage class in carbon dioxide exchange and decomposition in boreal black spruce (Picea mariana) forest stands

USGS Publications Warehouse

Wickland, K.P.; Neff, J.C.; Harden, J.W.

2010-01-01

Black spruce (Picea mariana (Mill.) B.S.P.) forest stands range from well drained to poorly drained, typically contain large amounts of soil organic carbon (SOC), and are often underlain by permafrost. To better understand the role of soil drainage class in carbon dioxide (CO2) exchange and decomposition, we measured soil respiration and net CO2 fluxes, litter decomposition and litterfall rates, and SOC stocks above permafrost in three Alaska black spruce forest stands characterized as well drained (WD), moderately drained (MD), and poorly drained (PD). Soil respiration and net CO2 fluxes were not significantly different among sites, although the relation between soil respiration rate and temperature varied with site (Qw: WD > MD > PD). Annual estimated soil respiration, litter decomposition, and groundcover photosynthesis were greatest at PD. These results suggest that soil temperature and moisture conditions in shallow organic horizon soils at PD were more favorable for decomposition compared with the better drained sites. SOC stocks, however, increase from WD to MD to PD such that surface decomposition and C storage are diametric. Greater groundcover vegetation productivity, protection of deep SOC by permafrost and anoxic conditions, and differences in fire return interval and (or) severity at PD counteract the relatively high near-surface decomposition rates, resulting in high net C accumulation.
Dissolved organic matter release in overlying water and bacterial community shifts in biofilm during the decomposition of Myriophyllum verticillatum.

PubMed

Zhang, Lisha; Zhang, Songhe; Lv, Xiaoyang; Qiu, Zheng; Zhang, Ziqiu; Yan, Liying

2018-08-15

This study investigated the alterations in biomass, nutrients and dissolved organic matter concentration in overlying water and determined the bacterial 16S rRNA gene in biofilms attached to plant residual during the decomposition of Myriophyllum verticillatum. The 55-day decomposition experimental results show that plant decay process can be well described by the exponential model, with the average decomposition rate of 0.037d -1 . Total organic carbon, total nitrogen, and organic nitrogen concentrations increased significantly in overlying water during decomposition compared to control within 35d. Results from excitation emission matrix-parallel factor analysis showed humic acid-like and tyrosine acid-like substances might originate from plant degradation processes. Tyrosine acid-like substances had an obvious correlation to organic nitrogen and total nitrogen (p<0.01). Decomposition rates were positively related to pH, total organic carbon, oxidation-reduction potential and dissolved oxygen but negatively related to temperature in overlying water. Microbe densities attached to plant residues increased with decomposition process. The most dominant phylum was Bacteroidetes (>46%) at 7d, Chlorobi (20%-44%) or Proteobacteria (25%-34%) at 21d and Chlorobi (>40%) at 55d. In microbes attached to plant residues, sugar- and polysaccharides-degrading genus including Bacteroides, Blvii28, Fibrobacter, and Treponema dominated at 7d while Chlorobaculum, Rhodobacter, Methanobacterium, Thiobaca, Methanospirillum and Methanosarcina at 21d and 55d. These results gain the insight into the dissolved organic matter release and bacterial community shifts during submerged macrophytes decomposition. Copyright © 2018 Elsevier B.V. All rights reserved.
Critical oxide cluster size on Si(111)

NASA Astrophysics Data System (ADS)

Shklyaev, A. A.; Aono, M.; Suzuki, T.

1999-03-01

The initial stage of oxide growth and subsequent oxide decomposition on Si(111)-7×7 at temperatures between 350 and 720°C are studied with the optical second harmonic generation for O 2 pressures ( Pox) between 5×10 -9 and 4×10 -6 Torr. The obtained pressure dependencies of the initial oxide growth rate ( Rgr) and the subsequent oxide decomposition rate are associated with the cluster-forming nature of the oxidation process. For the model of oxide cluster nucleation and growth, a scaling relationship is derived among the critical oxide cluster size, i, and the experimentally measurable values of Rgr and Pox. The critical oxide cluster size, i, thus obtained from the kinetic data increases with temperature. This correlates with an increase of desorption channels and their rates in that the competition between growth and decomposition requires more stable oxide clusters, i.e. clusters with a larger critical size, for oxide to grow at higher temperatures. The increase of i with decreasing Pox is related with a decrease of Rgr: a decreased Rgr requires critical clusters with a longer lifetime, i.e. clusters with a larger size.
Reaction behaviors of decomposition of monocrotophos in aqueous solution by UV and UV/O processes.

PubMed

Ku, Y; Wang, W; Shen, Y S

2000-02-01

The decomposition of monocrotophos (cis-3-dimethoxyphosphinyloxy-N-methyl-crotonamide) in aqueous solution by UV and UV/O(3) processes was studied. The experiments were carried out under various solution pH values to investigate the decomposition efficiencies of the reactant and organic intermediates in order to determine the completeness of decomposition. The photolytic decomposition rate of monocrotophos was increased with increasing solution pH because the solution pH affects the distribution and light absorbance of monocrotophos species. The combination of O(3) with UV light apparently promoted the decomposition and mineralization of monocrotophos in aqueous solution. For the UV/O(3) process, the breakage of the >C=C< bond of monocrotophos by ozone molecules was found to occur first, followed by mineralization by hydroxyl radicals to generate CO(3)(2-), PO4(3-), and NO(3)(-) anions in sequence. The quasi-global kinetics based on a simplified consecutive-parallel reaction scheme was developed to describe the temporal behavior of monocrotophos decomposition in aqueous solution by the UV/O(3) process.

Decomposition of recalcitrant carbon under experimental warming in boreal forest

PubMed Central

Allison, Steven D.; Treseder, Kathleen K.

2017-01-01

Over the long term, soil carbon (C) storage is partly determined by decomposition rate of carbon that is slow to decompose (i.e., recalcitrant C). According to thermodynamic theory, decomposition rates of recalcitrant C might differ from those of non-recalcitrant C in their sensitivities to global warming. We decomposed leaf litter in a warming experiment in Alaskan boreal forest, and measured mass loss of recalcitrant C (lignin) vs. non-recalcitrant C (cellulose, hemicellulose, and sugars) throughout 16 months. We found that these C fractions responded differently to warming. Specifically, after one year of decomposition, the ratio of recalcitrant C to non-recalcitrant C remaining in litter declined in the warmed plots compared to control. Consistent with this pattern, potential activities of enzymes targeting recalcitrant C increased with warming, relative to those targeting non-recalcitrant C. Even so, mass loss of individual C fractions showed that non-recalcitrant C is preferentially decomposed under control conditions whereas recalcitrant C losses remain unchanged between control and warmed plots. Moreover, overall mass loss was greater under control conditions. Our results imply that direct warming effects, as well as indirect warming effects (e.g. drying), may serve to maintain decomposition rates of recalcitrant C compared to non-recalcitrant C despite negative effects on overall decomposition. PMID:28622366
Do traits of invasive species influence decomposition and soil respiration of disturbed ecosystems?

NASA Astrophysics Data System (ADS)

Wells, A. J.; Balster, N. J.

2009-12-01

Large-scale landscape disturbances typically alter the terrestrial carbon cycle leading to shifts in pools of soil carbon. Restoration of disturbed landscapes with prairie vegetation has thus been practiced with the intent of increasing carbon accrual in soils. However, since disturbed soils are prone to invasion by non-native invasive species, many ecological restorations have resulted in unexpected outcomes, which may be explained by differences in plant traits such as tissue quality and biomass allocation. Typically, the tissue of invasive species has lower C:N ratios relative to native species, and consequently, faster decomposition rates, which potentially can alter the balance in soil carbon. The primary objective of this research was to compare the effects of native prairie species versus non-native invasive species on the carbon cycling within a novel environment: a recently dewatered basin in southwestern Wisconsin following dam removal. We hypothesized that a higher invasive to native species ratio would result in faster litter decomposition and a higher rate of soil respiration. To test this hypothesis, we seeded newly exposed sediments with native prairie seeds in 2005, annually collected aboveground plant biomass (by species per plot), calculated decomposition rate of native and invasive litter (underneath both canopy types), and measured soil respiration during the growing season of 2009. After four years of seeding, the aboveground biomass of the native vegetation has increased significantly (p < 0.01) from 14.4 to 351 g m-2 while invasive species biomass has decreased from 459 to 296 g m-2. Senesced tissue from mixed native species had a higher C:N ratio, 27:1 (43% C: 1.6% N), than tissue from mixed invasive species, 24:1 (35% C: 1.5% N). However, after 7 months, we found that the rate of decomposition depended on both litter type and plant canopy type (p < 0.01); invasive plant tissue had a slightly faster decomposition rate than the native litter and this rate was elevated under invasive species. Mean soil respiration rates ranged from 4.1 to 7.7 µmol C m-2 s-1. Our preliminary results suggest that respiration increases exponentially with soil temperature, as soil temperature explained 20% of the variation in soil respiration. However, the vegetation type did not have a significant effect on the respiration rate. Our results suggest that vegetation traits may be influencing the cycling of carbon at this site, but that spatial variation in abiotic conditions above and belowground appear to control decomposition and soil respiration at a local scale. Moreover, the ecophysiological interactions measured here may have practical implications on the restoration of disturbed ecosystems and the manner in which invasive species are viewed relative to the accrual soil carbon.
Comparison of decomposition rates between autopsied and non-autopsied human remains.

PubMed

Bates, Lennon N; Wescott, Daniel J

2016-04-01

Penetrating trauma has been cited as a significant factor in the rate of decomposition. Therefore, penetrating trauma may have an effect on estimations of time-since-death in medicolegal investigations and on research examining decomposition rates and processes when autopsied human bodies are used. The goal of this study was to determine if there are differences in the rate of decomposition between autopsied and non-autopsied human remains in the same environment. The purpose is to shed light on how large incisions, such as those from a thorocoabdominal autopsy, effect time-since-death estimations and research on the rate of decomposition that use both autopsied and non-autopsied human remains. In this study, 59 non-autopsied and 24 autopsied bodies were studied. The number of accumulated degree days required to reach each decomposition stage was then compared between autopsied and non-autopsied remains. Additionally, both types of bodies were examined for seasonal differences in decomposition rates. As temperature affects the rate of decomposition, this study also compared the internal body temperatures of autopsied and non-autopsied remains to see if differences between the two may be leading to differential decomposition. For this portion of this study, eight non-autopsied and five autopsied bodies were investigated. Internal temperature was collected once a day for two weeks. The results showed that differences in the decomposition rate between autopsied and non-autopsied remains was not statistically significant, though the average ADD needed to reach each stage of decomposition was slightly lower for autopsied bodies than non-autopsied bodies. There was also no significant difference between autopsied and non-autopsied bodies in the rate of decomposition by season or in internal temperature. Therefore, this study suggests that it is unnecessary to separate autopsied and non-autopsied remains when studying gross stages of human decomposition in Central Texas and that penetrating trauma may not be a significant factor in the overall rate of decomposition. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.
The effect of body size on the rate of decomposition in a temperate region of South Africa.

PubMed

Sutherland, A; Myburgh, J; Steyn, M; Becker, P J

2013-09-10

Forensic anthropologists rely on the state of decomposition of a body to estimate the post-mortem-interval (PMI) which provides information about the natural events and environmental forces that could have affected the remains after death. Various factors are known to influence the rate of decomposition, among them temperature, rainfall and exposure of the body. However, conflicting reports appear in the literature on the effect of body size on the rate of decay. The aim of this project was to compare decomposition rates of large pigs (Sus scrofa; 60-90 kg), with that of small pigs (<35 kg), to assess the influence of body size on decomposition rates. For the decomposition rates of small pigs, 15 piglets were assessed three times per week over a period of three months during spring and early summer. Data collection was conducted until complete skeletonization occurred. Stages of decomposition were scored according to separate categories for each anatomical region, and the point values for each region were added to determine the total body score (TBS), which represents the overall stage of decomposition for each pig. For the large pigs, data of 15 pigs were used. Scatter plots illustrating the relationships between TBS and PMI as well as TBS and accumulated degree days (ADD) were used to assess the pattern of decomposition and to compare decomposition rates between small and large pigs. Results indicated that rapid decomposition occurs during the early stages of decomposition for both samples. Large pigs showed a plateau phase in the course of advanced stages of decomposition, during which decomposition was minimal. A similar, but much shorter plateau was reached by small pigs of >20 kg at a PMI of 20-25 days, after which decomposition commenced swiftly. This was in contrast to the small pigs of <20 kg, which showed no plateau phase and their decomposition rates were swift throughout the duration of the study. Overall, small pigs decomposed 2.82 times faster than large pigs, indicating that body size does have an effect on the rate of decomposition. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.
Forest composition modifies litter dynamics and decomposition in regenerating tropical dry forest.

PubMed

Schilling, Erik M; Waring, Bonnie G; Schilling, Jonathan S; Powers, Jennifer S

2016-09-01

We investigated how forest composition, litter quality, and rainfall interact to affect leaf litter decomposition across three successional tropical dry forests in Costa Rica. We monitored litter stocks and bulk litter turnover in 18 plots that exhibit substantial variation in soil characteristics, tree community structure, fungal communities (including forests dominated by ecto- or arbuscular mycorrhizal host trees), and forest age. Simultaneously, we decomposed three standard litter substrates over a 6-month period spanning an unusually intense drought. Decay rates of standard substrates depended on the interaction between litter identity and forest type. Decomposition rates were correlated with tree and soil fungal community composition as well as soil fertility, but these relationships differed among litter types. In low fertility soils dominated by ectomycorrhizal oak trees, bulk litter turnover rates were low, regardless of soil moisture. By contrast, in higher fertility soils that supported mostly arbuscular mycorrhizal trees, bulk litter decay rates were strongly dependent on seasonal water availability. Both measures of decomposition increased with forest age, as did the frequency of termite-mediated wood decay. Taken together, our results demonstrate that soils and forest age exert strong control over decomposition dynamics in these tropical dry forests, either directly through effects on microclimate and nutrients, or indirectly by affecting tree and microbial community composition and traits, such as litter quality.
DFT study of hydrogen production from formic acid decomposition on Pd-Au alloy nanoclusters

NASA Astrophysics Data System (ADS)

Liu, D.; Gao, Z. Y.; Wang, X. C.; Zeng, J.; Li, Y. M.

2017-12-01

Recently, it has been reported that the hydrogen production rate of formic acid decomposition can be significantly increased using Pd-Au binary alloy nano-catalysts [Wang et al. J. Mater. Chem. A 1 (2013) 12721-12725]. To explain the reaction mechanism of this alloy catalysis method, formic acid decomposition reactions on pure Pd and Pd-Au alloy nanoclusters are studied via density functional theory simulations. The simulation results indicate that the addition of inert element Au would not influence formic acid decomposition on Pd surface sites of Pd-Au alloy nanoclusters. On the other hand, the existence of Au surface sites brings relative weak hydrogen atom adsorption. On Pd-Au alloy nanoclusters, the dissociated hydrogen atoms from formic acid are easier to combine as hydrogen molecules than that on pure Pd clusters. Via the synergetic effect between Pd and Au, both formic acid decomposition and hydrogen production are events with large probability, which eventually results in high hydrogen production rate.
Path analyses of the influence of substrate composition on nematode numbers and on decomposition of stranded seaweed at an Antarctic coast

NASA Astrophysics Data System (ADS)

Alkemade, R.; Van Rijswijk, P.

Large amounts of seaweed are deposited along the coast of Admiralty Bay, King George Island, Antarctica. The stranded seaweed partly decomposes on the beach and supports populations of meiofauna species, mostly nematodes. The factors determining the number of nematodes found in the seaweed packages were studied. Seaweed/sediment samples were collected from different locations, along the coast near Arctowski station, covering gradients of salinity, elevation and proximity of Penguin rookeries. On the same locations decomposition rate was determined by means of permeable containers with seaweed material. Models, including the relations between location, seaweed and sediment characteristics, number of nematodes and decomposition rates, were postulated and verified using path analysis. The most plausible and significant models are presented. The number of nematodes was directly correlated with the height of the location, the carbon-to-nitrogen ratio, and the salinity of the sample. Nematode numbers were apparently indirectly dependent on sediment composition and water content. We hypothesize that the different influences of melt water and tidal water, which affect both salinity and water content of the deposits, are important phenomena underlying these results. Analysis of the relation between decomposition rate and abiotic, location-related characteristics showed that decomposition rate was dependent on the water content of the stranded seaweed and sediment composition. Decomposition rates were high on locations where water content of the deposits was high. There the running water from melt water run-off or from the surf probably increased weight losses of seaweed.
Increased site fertility and litter decomposition rate in high-pollution sites in the San Bernardino Mountains

Treesearch

Mark E. Fenn

1991-01-01

Some possible factors causing enhanced litter decomposition in high-pollution sites in the San Bernardino Mountains of southern California were investigated. Nitrogen concentration of soil, as well as foliage and litter of ponderosa pine (Pinus ponderosa Laws.) and Jeffrey pine (Pinus jeffreyi Grev. & Balf.) were greater in...
Dynamics of Potassium Release and Adsorption on Rice Straw Residue

PubMed Central

Li, Jifu; Lu, Jianwei; Li, Xiaokun; Ren, Tao; Cong, Rihuan; Zhou, Li

2014-01-01

Straw application can not only increase crop yields, improve soil structure and enrich soil fertility, but can also enhance water and nutrient retention. The aim of this study was to ascertain the relationships between straw decomposition and the release-adsorption processes of K+. This study increases the understanding of the roles played by agricultural crop residues in the soil environment, informs more effective straw recycling and provides a method for reducing potassium loss. The influence of straw decomposition on the K+ release rate in paddy soil under flooded condition was studied using incubation experiments, which indicated the decomposition process of rice straw could be divided into two main stages: (a) a rapid decomposition stage from 0 to 60 d and (b) a slow decomposition stage from 60 to 110 d. However, the characteristics of the straw potassium release were different from those of the overall straw decomposition, as 90% of total K was released by the third day of the study. The batches of the K sorption experiments showed that crop residues could adsorb K+ from the ambient environment, which was subject to decomposition periods and extra K+ concentration. In addition, a number of materials or binding sites were observed on straw residues using IR analysis, indicating possible coupling sites for K+ ions. The aqueous solution experiments indicated that raw straw could absorb water at 3.88 g g−1, and this rate rose to its maximum 15 d after incubation. All of the experiments demonstrated that crop residues could absorb large amount of aqueous solution to preserve K+ indirectly during the initial decomposition period. These crop residues could also directly adsorb K+ via physical and chemical adsorption in the later period, allowing part of this K+ to be absorbed by plants for the next growing season. PMID:24587364
Dynamics of potassium release and adsorption on rice straw residue.

PubMed

Li, Jifu; Lu, Jianwei; Li, Xiaokun; Ren, Tao; Cong, Rihuan; Zhou, Li

2014-01-01

Straw application can not only increase crop yields, improve soil structure and enrich soil fertility, but can also enhance water and nutrient retention. The aim of this study was to ascertain the relationships between straw decomposition and the release-adsorption processes of K(+). This study increases the understanding of the roles played by agricultural crop residues in the soil environment, informs more effective straw recycling and provides a method for reducing potassium loss. The influence of straw decomposition on the K(+) release rate in paddy soil under flooded condition was studied using incubation experiments, which indicated the decomposition process of rice straw could be divided into two main stages: (a) a rapid decomposition stage from 0 to 60 d and (b) a slow decomposition stage from 60 to 110 d. However, the characteristics of the straw potassium release were different from those of the overall straw decomposition, as 90% of total K was released by the third day of the study. The batches of the K sorption experiments showed that crop residues could adsorb K(+) from the ambient environment, which was subject to decomposition periods and extra K(+) concentration. In addition, a number of materials or binding sites were observed on straw residues using IR analysis, indicating possible coupling sites for K(+) ions. The aqueous solution experiments indicated that raw straw could absorb water at 3.88 g g(-1), and this rate rose to its maximum 15 d after incubation. All of the experiments demonstrated that crop residues could absorb large amount of aqueous solution to preserve K(+) indirectly during the initial decomposition period. These crop residues could also directly adsorb K(+) via physical and chemical adsorption in the later period, allowing part of this K(+) to be absorbed by plants for the next growing season.
Interrelationships among shrub encroachment, land management, and litter decomposition in a semidesert grassland.

PubMed

Throop, Heather L; Archer, Steven R

2007-09-01

Encroachment of woody plants into grasslands, and subsequent brush management, are among the most prominent changes to occur in arid and semiarid systems over the past century. Despite the resulting widespread changes in landcover, substantial uncertainty about the biogeochemical impacts of woody proliferation and brush management exists. We explored the role of shrub encroachment and brush management on leaf litter decomposition in a semidesert grassland where velvet mesquite (Prosopis velutina) abundance has increased over the past 100 years. This change in physiognomy may affect decomposition directly, through altered litter quality or quantity, and indirectly through altered canopy structure. To assess the direct and indirect impacts of shrubs on decomposition, we quantified changes in mass, nitrogen, and carbon in litterbags deployed under mesquite canopies and in intercanopy zones. Litterbags contained foliage from mesquite and Lehmann lovegrass (Eragrostis lehmanniana), a widespread, nonnative grass in southern Arizona. To explore short- and long-term influences of brush management on the initial stages of decomposition, litterbags were deployed at sites where mesquite canopies were removed three weeks, 45 years, or 70 years prior to study initiation. Mesquite litter decomposed more rapidly than lovegrass, but negative indirect influences of mesquite canopies counteracted positive direct effects. Decomposition was positively correlated with soil infiltration into litterbags, which varied with microsite placement, and was lowest under canopies. Low under-canopy decomposition was ostensibly due to decreased soil movement associated with high under-canopy herbaceous biomass. Decomposition rates where canopies were removed three weeks prior to study initiation were comparable to those beneath intact canopies, suggesting that decomposition was driven by mesquite legacy effects on herbaceous cover-soil movement linkages. Decomposition rates where shrubs were removed 45 and 70 years prior to study initiation were comparable to intercanopy rates, suggesting that legacy effects persist less than 45 years. Accurate decomposition modeling has proved challenging in arid and semiarid systems but is critical to understanding biogeochemical responses to woody encroachment and brush management. Predicting brush-management effects on decomposition will require information on shrub-grass interactions and herbaceous biomass influences on soil movement at decadal timescales. Inclusion of microsite factors controlling soil accumulation on litter would improve the predictive capability of decomposition models.
Nitrogen Deposition Reduces Decomposition Rates Through Shifts in Microbial Community Composition and Function

NASA Astrophysics Data System (ADS)

Waldrop, M.; Zak, D.; Sinsabaugh, R.

2002-12-01

Atmospheric nitrogen (N) deposition may alter soil biological activity in northern hardwood forests by repressing phenol oxidase enzyme activity and altering microbial community composition, thereby slowing decomposition and increasing the export of phenolic compounds. We tested this hypothesis by adding 13C-labelled cellobiose, vanillin, and catechol to control and N fertilized soils (30 and 80 kg ha-1) collected from three forests; two dominated by Acer Saccharum and one dominated by Quercus Alba and Quercus Velutina. While N deposition increased total microbial respiration, it decreased soil oxidative enzyme activities, resulting in slower degradation rates of all compounds, and larger DOC pools. This effect was larger in the oak forest, where fungi dominate C-cycling processes. DNA and 13C-phospolipid analyses showed that N addition altered the fungal community and reduced the activity of fungal and bacterial populations in soil, potentially explaining reduced soil enzyme activities and incomplete decomposition.
Influence of ultrasonication on anaerobic bioconversion of sludge.

PubMed

Mao, Taohong; Show, Kuan-Yeow

2007-04-01

The influence of ultrasonication on hydrolysis, acidogenesis, and methanogenesis in anaerobic decomposition of sludge was investigated. The sonicated sludge exhibited prehydrolysis and preacidogenesis effects in the anaerobic decomposition process. First-order hydrolysis rates increased from 0.0384 day(-1) in the control digester to 0.0672 day(-1) in the digester fed, with sludge sonicated at 0.52 W/mL. The sonication appeared to be ineffective in relation to acidogenesis reaction rates, but it provided a better buffering capacity to diminish the adverse effect of acidification. Digesters fed with sonicated sludge demonstrated enhanced methanogenesis over the control unit. Determination by coenzyme F420 verified that sonication is able to promote the growth of methanogenic biomass and facilitate a positive methanogenic microbial development in suppressing the initial methanogenesis limitation. The results suggest that ultrasonication could enhance anaerobic decomposition of sludge, resulting in an accelerated bioconversion, improved organics degradation, improved biogas production, and increased methane content.
Can the biomass-ratio hypothesis predict mixed-species litter decomposition along a climatic gradient?

PubMed Central

Tardif, Antoine; Shipley, Bill; Bloor, Juliette M. G.; Soussana, Jean-François

2014-01-01

Background and Aims The biomass-ratio hypothesis states that ecosystem properties are driven by the characteristics of dominant species in the community. In this study, the hypothesis was operationalized as community-weighted means (CWMs) of monoculture values and tested for predicting the decomposition of multispecies litter mixtures along an abiotic gradient in the field. Methods Decomposition rates (mg g−1 d−1) of litter from four herb species were measured using litter-bed experiments with the same soil at three sites in central France along a correlated climatic gradient of temperature and precipitation. All possible combinations from one to four species mixtures were tested over 28 weeks of incubation. Observed mixture decomposition rates were compared with those predicted by the biomass-ratio hypothesis. Variability of the prediction errors was compared with the species richness of the mixtures, across sites, and within sites over time. Key Results Both positive and negative prediction errors occurred. Despite this, the biomass-ratio hypothesis was true as an average claim for all sites (r = 0·91) and for each site separately, except for the climatically intermediate site, which showed mainly synergistic deviations. Variability decreased with increasing species richness and in less favourable climatic conditions for decomposition. Conclusions Community-weighted mean values provided good predictions of mixed-species litter decomposition, converging to the predicted values with increasing species richness and in climates less favourable to decomposition. Under a context of climate change, abiotic variability would be important to take into account when predicting ecosystem processes. PMID:24482152
Effect of petroleum on decomposition of shrub-grass litters in soil in Northern Shaanxi of China.

PubMed

Zhang, Xiaoxi; Liu, Zengwen; Yu, Qi; Luc, Nhu Trung; Bing, Yuanhao; Zhu, Bochao; Wang, Wenxuan

2015-07-01

The impacts of petroleum contamination on the litter decomposition of shrub-grass land would directly influence nutrient cycling, and the stability and function of ecosystem. Ten common shrub and grass species from Yujiaping oil deposits were studied. Litters from these species were placed into litterbags and buried in petroleum-contaminated soil with 3 levels of contamination (slight, moderate and serious pollution with petroleum concentrations of 15, 30 and 45 g/kg, respectively). A decomposition experiment was then conducted in the lab to investigate the impacts of petroleum contamination on litter decomposition rates. Slight pollution did not inhibit the decomposition of any litters and significantly promoted the litter decomposition of Hippophae rhamnoides, Caragana korshinskii, Amorpha fruticosa, Ziziphus jujuba var. spinosa, Periploca sepium, Medicago sativa and Bothriochloa ischaemum. Moderate pollution significantly inhibited litter decomposition of M. sativa, Coronilla varia, Artemisia vestita and Trrifolium repens and significantly promoted the litter decomposition of C. korshinskii, Z. jujuba var. spinosa and P. sepium. Serious pollution significantly inhibited the litter decomposition of H. rhamnoides, A. fruticosa, B. ischaemum and A. vestita and significantly promoted the litter decomposition of Z. jujuba var. spinosa, P. sepium and M. sativa. In addition, the impacts of petroleum contamination did not exhibit a uniform increase or decrease as petroleum concentration increased. Inhibitory effects of petroleum on litter decomposition may hinder the substance cycling and result in the degradation of plant communities in contaminated areas. Copyright © 2015. Published by Elsevier B.V.
Photodegradation Pathways in Arid Ecosystems

NASA Astrophysics Data System (ADS)

King, J. Y.; Lin, Y.; Adair, E. C.; Brandt, L.; Carbone, M. S.

2013-12-01

Recent interest in improving our understanding of decomposition patterns in arid and semi-arid ecosystems and under potentially drier future conditions has led to a flurry of research related to abiotic degradation processes. Oxidation of organic matter by solar radiation (photodegradation) is one abiotic degradation process that contributes significantly to litter decomposition rates. Our meta-analysis results show that increasing solar radiation exposure corresponds to an average increase of 23% in litter mass loss rate with large variation among studies associated primarily with environmental and litter chemistry characteristics. Laboratory studies demonstrate that photodegradation results in CO2 emissions. Indirect estimates suggest that photodegradation could account for as much as 60% of ecosystem CO2 emissions from dry ecosystems, but these CO2 fluxes have not been measured in intact ecosystems. The current data suggest that photodegradation is important, not only for understanding decomposition patterns, but also for modeling organic matter turnover and ecosystem C cycling. However, the mechanisms by which photodegradation operates, along with their environmental and litter chemistry controls, are still poorly understood. Photodegradation can directly influence decomposition rates and ecosystem CO2 flux via photochemical mineralization. It can also indirectly influence biotic decomposition rates by facilitating microbial degradation through breakdown of more recalcitrant compounds into simpler substrates or by suppressing microbial activity directly. All of these pathways influence the decomposition process, but the relative importance of each is uncertain. Furthermore, a specific suite of controls regulates each of these pathways (e.g., environmental conditions such as temperature and relative humidity; physical environment such as canopy architecture and contact with soil; and litter chemistry characteristics such as lignin and cellulose content), and these controls have not yet been identified or quantified. To advance our understanding of photodegradation and its role in decomposition and in ecosystem C cycling, we must characterize its mechanisms and their associated controls and incorporate this understanding into biogeochemical models. Our objective is to summarize the current state of understanding of photodegradation and discuss some paths forward to address remaining critical gaps in knowledge about its mechanisms and influence on ecosystem C balance.
Litter quality versus soil microbial community controls over decomposition: a quantitative analysis

USGS Publications Warehouse

Cleveland, Cory C.; Reed, Sasha C.; Keller, Adrienne B.; Nemergut, Diana R.; O'Neill, Sean P.; Ostertag, Rebecca; Vitousek, Peter M.

2014-01-01

The possible effects of soil microbial community structure on organic matter decomposition rates have been widely acknowledged, but are poorly understood. Understanding these relationships is complicated by the fact that microbial community structure and function are likely to both affect and be affected by organic matter quality and chemistry, thus it is difficult to draw mechanistic conclusions from field studies. We conducted a reciprocal soil inoculum × litter transplant laboratory incubation experiment using samples collected from a set of sites that have similar climate and plant species composition but vary significantly in bacterial community structure and litter quality. The results showed that litter quality explained the majority of variation in decomposition rates under controlled laboratory conditions: over the course of the 162-day incubation, litter quality explained nearly two-thirds (64 %) of variation in decomposition rates, and a smaller proportion (25 %) was explained by variation in the inoculum type. In addition, the relative importance of inoculum type on soil respiration increased over the course of the experiment, and was significantly higher in microcosms with lower litter quality relative to those with higher quality litter. We also used molecular phylogenetics to examine the relationships between bacterial community composition and soil respiration in samples through time. Pyrosequencing revealed that bacterial community composition explained 32 % of the variation in respiration rates. However, equal portions (i.e., 16 %) of the variation in bacterial community composition were explained by inoculum type and litter quality, reflecting the importance of both the meta-community and the environment in bacterial assembly. Taken together, these results indicate that the effects of changing microbial community composition on decomposition are likely to be smaller than the potential effects of climate change and/or litter quality changes in response to increasing atmospheric CO2 concentrations or atmospheric nutrient deposition.
A molecular dynamics study of model SI clathrate hydrates: the effect of guest size and guest-water interaction on decomposition kinetics.

PubMed

Das, Subhadip; Baghel, Vikesh Singh; Roy, Sudip; Kumar, Rajnish

2015-04-14

One of the options suggested for methane recovery from natural gas hydrates is molecular replacement of methane by suitable guests like CO2 and N2. This approach has been found to be feasible through many experimental and molecular dynamics simulation studies. However, the long term stability of the resultant hydrate needs to be evaluated; the decomposition rate of these hydrates is expected to depend on the interaction between these guest and water molecules. In this work, molecular dynamics simulation has been performed to illustrate the effect of guest molecules with different sizes and interaction strengths with water on structure I (SI) hydrate decomposition and hence the stability. The van der Waals interaction between water of hydrate cages and guest molecules is defined by Lennard Jones potential parameters. A wide range of parameter spaces has been scanned by changing the guest molecules in the SI hydrate, which acts as a model gas for occupying the small and large cages of the SI hydrate. All atomistic simulation results show that the stability of the hydrate is sensitive to the size and interaction of the guest molecules with hydrate water. The increase in the interaction of guest molecules with water stabilizes the hydrate, which in turn shows a slower rate of hydrate decomposition. Similarly guest molecules with a reasonably small (similar to Helium) or large size increase the decomposition rate. The results were also analyzed by calculating the structural order parameter to understand the dynamics of crystal structure and correlated with the release rate of guest molecules from the solid hydrate phase. The results have been explained based on the calculation of potential energies felt by guest molecules in amorphous water, hydrate bulk and hydrate-water interface regions.
Traits drive global wood decomposition rates more than climate.

PubMed

Hu, Zhenhong; Michaletz, Sean T; Johnson, Daniel J; McDowell, Nate G; Huang, Zhiqun; Zhou, Xuhui; Xu, Chonggang

2018-06-14

Wood decomposition is a major component of the global carbon cycle. Decomposition rates vary across climate gradients, which is thought to reflect the effects of temperature and moisture on the metabolic kinetics of decomposers. However, decomposition rates also vary with wood traits, which may reflect the influence of stoichiometry on decomposer metabolism as well as geometry relating the surface areas that decomposers colonize with the volumes they consume. In this paper, we combined metabolic and geometric scaling theories to formalize hypotheses regarding the drivers of wood decomposition rates, and assessed these hypotheses using a global compilation of data on climate, wood traits, and wood decomposition rates. Our results are consistent with predictions from both metabolic and geometric scaling theories. Approximately half of the global variation in decomposition rates was explained by wood traits (nitrogen content and diameter), while only a fifth was explained by climate variables (air temperature, precipitation, and relative humidity). These results indicate that global variation in wood decomposition rates is best explained by stoichiometric and geometric wood traits. Our findings suggest that inclusion of wood traits in global carbon cycle models can improve predictions of carbon fluxes from wood decomposition. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.
Highly reduced mass loss rates and increased litter layer in radioactively contaminated areas.

PubMed

Mousseau, Timothy A; Milinevsky, Gennadi; Kenney-Hunt, Jane; Møller, Anders Pape

2014-05-01

The effects of radioactive contamination from Chernobyl on decomposition of plant material still remain unknown. We predicted that decomposition rate would be reduced in the most contaminated sites due to an absence or reduced densities of soil invertebrates. If microorganisms were the main agents responsible for decomposition, exclusion of large soil invertebrates should not affect decomposition. In September 2007 we deposited 572 bags with uncontaminated dry leaf litter from four species of trees in the leaf litter layer at 20 forest sites around Chernobyl that varied in background radiation by more than a factor 2,600. Approximately one quarter of these bags were made of a fine mesh that prevented access to litter by soil invertebrates. These bags were retrieved in June 2008, dried and weighed to estimate litter mass loss. Litter mass loss was 40% lower in the most contaminated sites relative to sites with a normal background radiation level for Ukraine. Similar reductions in litter mass loss were estimated for individual litter bags, litter bags at different sites, and differences between litter bags at pairs of neighboring sites differing in level of radioactive contamination. Litter mass loss was slightly greater in the presence of large soil invertebrates than in their absence. The thickness of the forest floor increased with the level of radiation and decreased with proportional loss of mass from all litter bags. These findings suggest that radioactive contamination has reduced the rate of litter mass loss, increased accumulation of litter, and affected growth conditions for plants.

Prediction of the Maximum Temperature for Life Based on the Stability of Metabolites to Decomposition in Water

PubMed Central

Bains, William; Xiao, Yao; Yu, Changyong

2015-01-01

The components of life must survive in a cell long enough to perform their function in that cell. Because the rate of attack by water increases with temperature, we can, in principle, predict a maximum temperature above which an active terrestrial metabolism cannot function by analysis of the decomposition rates of the components of life, and comparison of those rates with the metabolites’ minimum metabolic half-lives. The present study is a first step in this direction, providing an analytical framework and method, and analyzing the stability of 63 small molecule metabolites based on literature data. Assuming that attack by water follows a first order rate equation, we extracted decomposition rate constants from literature data and estimated their statistical reliability. The resulting rate equations were then used to give a measure of confidence in the half-life of the metabolite concerned at different temperatures. There is little reliable data on metabolite decomposition or hydrolysis rates in the literature, the data is mostly confined to a small number of classes of chemicals, and the data available are sometimes mutually contradictory because of varying reaction conditions. However, a preliminary analysis suggests that terrestrial biochemistry is limited to environments below ~150–180 °C. We comment briefly on why pressure is likely to have a small effect on this. PMID:25821932
Enhanced precipitation promotes decomposition and soil C stabilization in semiarid ecosystems, but seasonal timing of wetting matters

USGS Publications Warehouse

Campos, Xochi; Germino, Matthew; de Graaff, Marie-Anne

2017-01-01

AimsChanging precipitation regimes in semiarid ecosystems will affect the balance of soil carbon (C) input and release, but the net effect on soil C storage is unclear. We asked how changes in the amount and timing of precipitation affect litter decomposition, and soil C stabilization in semiarid ecosystems.MethodsThe study took place at a long-term (18 years) ecohydrology experiment located in Idaho. Precipitation treatments consisted of a doubling of annual precipitation (+200 mm) added either in the cold-dormant season or in the growing season. Experimental plots were planted with big sagebrush (Artemisia tridentata), or with crested wheatgrass (Agropyron cristatum). We quantified decomposition of sagebrush leaf litter, and we assessed organic soil C (SOC) in aggregates, and silt and clay fractions.ResultsWe found that: (1) increased precipitation applied in the growing season consistently enhanced decomposition rates relative to the ambient treatment, and (2) precipitation applied in the dormant season enhanced soil C stabilization.ConclusionsThese data indicate that prolonged increases in precipitation can promote soil C storage in semiarid ecosystems, but only if these increases happen at times of the year when conditions allow for precipitation to promote plant C inputs rates to soil.
The interactive effects of fire and diversity on short-term responses of ecosystem processes in experimental mediterranean grasslands.

PubMed

Dimitrakopoulos, Panayiotis G; Siamantziouras, Akis-Stavros D; Galanidis, Alexandros; Mprezetou, Irene; Troumbis, Andreas Y

2006-06-01

We conducted a field experiment using constructed communities to test whether species richness contributed to the maintenance of ecosystem processes under fire disturbance. We studied the effects of diversity components (i.e., species richness and species composition) upon productivity, structural traits of vegetation, decomposition rates, and soil nutrients between burnt and unburnt experimental Mediterranean grassland communities. Our results demonstrated that fire and species richness had interactive effects on aboveground biomass production and canopy structure components. Fire increased biomass production of the highest-richness communities. The effects of fire on aboveground biomass production at different levels of species richness were derived from changes in both vertical and horizontal canopy structure of the communities. The most species-rich communities appeared to be more resistant to fire in relation to species-poor ones, due to both compositional and richness effects. Interactive effects of fire and species richness were not important for belowground processes. Decomposition rates increased with species richness, related in part to increased levels of canopy structure traits. Fire increased soil nutrients and long-term decomposition rate. Our results provide evidence that composition within richness levels had often larger effects on the stability of aboveground ecosystem processes in the face of fire disturbance than species richness per se.
Insight into litter decomposition driven by nutrient demands of symbiosis system through the hypha bridge of arbuscular mycorrhizal fungi.

PubMed

Kong, Xiangshi; Jia, Yanyan; Song, Fuqiang; Tian, Kai; Lin, Hong; Bei, Zhanlin; Jia, Xiuqin; Yao, Bei; Guo, Peng; Tian, Xingjun

2018-02-01

Arbuscular mycorrhizal fungi (AMF) play an important role in litter decomposition. This study investigated how soil nutrient level affected the process. Results showed that AMF colonization had no significant effect on litter decomposition under normal soil nutrient conditions. However, litter decomposition was accelerated significantly under lower nutrient conditions. Soil microbial biomass in decomposition system was significantly increased. Especially, in moderate lower nutrient treatment (condition of half-normal soil nutrient), litters exhibited the highest decomposition rate, AMF hypha revealed the greatest density, and enzymes (especially nitrate reductase) showed the highest activities as well. Meanwhile, the immobilization of nitrogen (N) in the decomposing litter remarkably decreased. Our results suggested that the roles AMF played in ecosystem were largely affected by soil nutrient levels. At normal soil nutrient level, AMF exhibited limited effects in promoting decomposition. When soil nutrient level decreased, the promoting effect of AMF on litter decomposition began to appear, especially on N mobilization. However, under extremely low nutrient conditions, AMF showed less influence on decomposition and may even compete with decomposer microorganisms for nutrients.
PROCESS FOR CONTROLLING ANIMAL GROWTH RATE

DOEpatents

Visek, W.J.

1962-04-10

A method of injecting growing animals with the enzyme urease subcutaneously in increasing dosages is described; this generates within the blood anti-urease which enters the intestinal tract and inhibits the enzymatic decomposition of urea by urease in that location. Ammonia, one of the decomposition products, is thereby kept from diffusing through the intestinal walls into the blood, and this greatly reduces the energy requirements of the liver for removing the ammonia, thereby increasing the feeding efficiency of the animals. (AEC)
[Decomposition dynamics of leaf litter in logging residue of a secondary Castanopsis carlesii plantation and its chemical composition changes].

PubMed

Ren, Wei-ling; Guo, Jian-fen; Wu, Bo-bo; Wan, Jing-juan; Ji, Shu-rong; Liu, Xiao-fei

2015-04-01

A field experiment was conducted to understand the decomposition rates and chemical composition changes of leaf litter in logging residues of a 35-year-old secondary Castanopsis carlesii plantation over a period of one year. Mass loss rate of leaf litter showed an exponential decrease with time from May 2012 to April 2013, with a total 80% loss of initial dry mass. Net potassium (K) release was observed during this period, with only 5% of initial K remained. Nitrogen ( N) featured a pattern of accumulation at the early stage and release later, while phosphorus (P) exhibited a sequence of release, accumulation, and release. The remaining of N and P were 19% and 16% of their initial mass, respectively. The release rate was highest for K and the lowest for N. Decomposition of lignin indicated a trend of release-accumulation-release from May 2012 to October 2012, with no further significant change from November 2012 to the end of the experiment. The concentration of cellulose nearly unchanged during the experiment. The N/P rate increased with decomposition, ranging from 18.6 to 21.1. The lignin/N rate fluctuated greatly at the early stage and then almost stabilized thereafter.
Plant traits and decomposition: are the relationships for roots comparable to those for leaves?

PubMed Central

Birouste, Marine; Kazakou, Elena; Blanchard, Alain; Roumet, Catherine

2012-01-01

Background and Aims Fine root decomposition is an important determinant of nutrient and carbon cycling in grasslands; however, little is known about the factors controlling root decomposition among species. Our aim was to investigate whether interspecific variation in the potential decomposition rate of fine roots could be accounted for by root chemical and morphological traits, life history and taxonomic affiliation. We also investigated the co-ordinated variation in root and leaf traits and potential decomposition rates. Methods We analysed potential decomposition rates and the chemical and morphological traits of fine roots on 18 Mediterranean herbaceous species grown in controlled conditions. The results were compared with those obtained for leaves in a previous study conducted on similar species. Key Results Differences in the potential decomposition rates of fine roots between species were accounted for by root chemical composition, but not by morphological traits. The root potential decomposition rate varied with taxonomy, but not with life history. Poaceae, with high cellulose concentration and low concentrations of soluble compounds and phosphorus, decomposed more slowly than Asteraceae and Fabaceae. Patterns of root traits, including decomposition rate, mirrored those of leaf traits, resulting in a similar species clustering. Conclusions The highly co-ordinated variation of roots and leaves in terms of traits and potential decomposition rate suggests that changes in the functional composition of communities in response to anthropogenic changes will strongly affect biogeochemical cycles at the ecosystem level. PMID:22143881
Long-Term Simulated Atmospheric Nitrogen Deposition Alters ...

EPA Pesticide Factsheets

Atmospheric nitrogen deposition has been suggested to increase forest carbon sequestration across much of the Northern Hemisphere; slower organic matter decomposition could contribute to this increase. At four sugar maple (Acer saccharum)-dominated northern hardwood forests, we previously observed that 10 years of chronic simulated nitrogen deposition (30 kg N ha-1 yr-1) increased soil organic carbon. Over three years at these sites, we investigated the effects of nitrogen additions on decomposition of two substrates with documented differences in biochemistry: leaf litter (more labile) and fine roots (more recalcitrant). Further, we combined decomposition rates with annual leaf and fine root litter production to estimate how nitrogen additions altered the accumulation of soil organic matter. Nitrogen additions marginally stimulated early-stage decomposition of leaf litter, a substrate with little acid-insoluble material (e.g., lignin). In contrast, nitrogen additions inhibited the late stage decomposition of fine roots, a substrate with high amount of acid insoluble material and a change consistent with observed decreases in lignin-degrading enzyme activities with nitrogen additions at these sites. At the ecosystem scale, the slower fine root decomposition led to additional root mass retention (g m-2), which explained 5, 48, and 52 % of previously-documented soil carbon accumulation due to nitrogen additions. Our results demonstrated that nitrogen deposition ha
Increasing shrub abundance and N addition in Arctic tundra affect leaf and root litter decomposition differently

NASA Astrophysics Data System (ADS)

McLaren, J.; van de Weg, M. J.; Shaver, G. R.; Gough, L.

2013-12-01

Changes in global climate have resulted in a ';greening' of the Arctic as the abundance of deciduous shrub species increases. Consequently, not only the living plant community, but also the litter composition changes, which in turn can affect carbon turnover patterns in the Arctic. We examined effects of changing litter composition (both root and leaf litter) on decomposition rates with a litter bag study, and specifically focused on the impact of deciduous shrub Betula nana litter on litter decomposition from two evergreen shrubs (Ledum palustre, and Vaccinium vitis-idaea) and one graminoid (Eriophorum vaginatum) species. Additionally, we investigated how decomposition was affected by nutrient availability by placing the litterbags in an ambient and a fertilized moist acidic tundra environment. Measurements were carried out seasonally over 2 years (after snow melt, mid-growing season, end growing season). We measured litter mass loss over time, as well as the respiration rates (standardized for temperature and moisture) and temperature sensitivity of litter respiration at the time of harvesting the litter bags. For leaves, Betula litter decomposed faster than the other three species, with Eriophorum leaves decomposing the slowest. This pattern was observed for both mass loss and litter respiration rates, although the differences in respiration became smaller over time. Surprisingly, combining Betula with any other species resulted in slower overall weight loss rates than would be predicted based on monoculture weight loss rates. This contrasted with litter respiration at the time of sampling, which showed a positive mixing effect of adding Betula leaf liter to the other species. Apparently, during the first winter months (September - May) Betula litter decomposition is negatively affected by mixing the species and this legacy can still be observed in the total mass loss results later in the year. For root litter there were fewer effects of species identity on root decomposition rates; only Ledum roots decomposed slower than the other three species and the overall root litter respiration rates increased with the duration of the experiment (in contrast to leaf liter respiration). A fertilized environment had no effect on overall weight loss of the leaf or root litter within the time of our study, but leaf and root litter respiration rates were significantly larger at the end of the study in the fertilized tundra.The temperature sensitivity of leaf respiration was significantly lower for leaf litter respiration than root liter respiration after fist snow melt, but this difference disappeared throughout the first growing season and neither was influenced by species composition or fertilization with N+P. Overall, our results suggest that as arctic vegetation shifts towards shrub-dominated tundra, both species composition and seasonally dependent processes will determine effects of changing vegetation types on carbon turnover in arctic ecosystems.
Decomposition of soil organic matter from boreal black spruce forest: environmental and chemical controls

Treesearch

Kimberly P. Wickland; Jason C. Neff

2007-01-01

Black spruce forests are a dominant covertype in the boreal forest region, and they inhabit landscapes that span a wide range of hydrologic and thermal conditions. These forests often have large stores of soil organic carbon. Recent increases in temperature at northern latitudes may be stimulating decomposition rates of this soil carbon. It is unclear, however, how...
Enhanced decomposition of stable soil organic carbon and microbial catabolic potentials by long-term field warming

DOE PAGES

Feng, Wenting; Liang, Junyi; Hale, Lauren E.; ...

2017-06-09

Quantifying soil organic carbon (SOC) decomposition under warming is critical to predict carbon–climate feedbacks. According to the substrate regulating principle, SOC decomposition would decrease as labile SOC declines under field warming, but observations of SOC decomposition under warming do not always support this prediction. This discrepancy could result from varying changes in SOC components and soil microbial communities under warming. This study aimed to determine the decomposition of SOC components with different turnover times after subjected to long-term field warming and/or root exclusion to limit C input, and to test whether SOC decomposition is driven by substrate lability under warming.more » Taking advantage of a 12-year field warming experiment in a prairie, we assessed the decomposition of SOC components by incubating soils from control and warmed plots, with and without root exclusion for 3 years. We assayed SOC decomposition from these incubations by combining inverse modeling and microbial functional genes during decomposition with a metagenomic technique (GeoChip). The decomposition of SOC components with turnover times of years and decades, which contributed to 95% of total cumulative CO 2 respiration, was greater in soils from warmed plots. But the decomposition of labile SOC was similar in warmed plots compared to the control. The diversity of C-degradation microbial genes generally declined with time during the incubation in all treatments, suggesting shifts of microbial functional groups as substrate composition was changing. Compared to the control, soils from warmed plots showed significant increase in the signal intensities of microbial genes involved in degrading complex organic compounds, implying enhanced potential abilities of microbial catabolism. These are likely responsible for accelerated decomposition of SOC components with slow turnover rates. Overall, the shifted microbial community induced by long-term warming accelerates the decomposition of SOC components with slow turnover rates and thus amplify the positive feedback to climate change.« less
Enhanced decomposition of stable soil organic carbon and microbial catabolic potentials by long-term field warming

DOE Office of Scientific and Technical Information (OSTI.GOV)

Feng, Wenting; Liang, Junyi; Hale, Lauren E.

Quantifying soil organic carbon (SOC) decomposition under warming is critical to predict carbon–climate feedbacks. According to the substrate regulating principle, SOC decomposition would decrease as labile SOC declines under field warming, but observations of SOC decomposition under warming do not always support this prediction. This discrepancy could result from varying changes in SOC components and soil microbial communities under warming. This study aimed to determine the decomposition of SOC components with different turnover times after subjected to long-term field warming and/or root exclusion to limit C input, and to test whether SOC decomposition is driven by substrate lability under warming.more » Taking advantage of a 12-year field warming experiment in a prairie, we assessed the decomposition of SOC components by incubating soils from control and warmed plots, with and without root exclusion for 3 years. We assayed SOC decomposition from these incubations by combining inverse modeling and microbial functional genes during decomposition with a metagenomic technique (GeoChip). The decomposition of SOC components with turnover times of years and decades, which contributed to 95% of total cumulative CO 2 respiration, was greater in soils from warmed plots. But the decomposition of labile SOC was similar in warmed plots compared to the control. The diversity of C-degradation microbial genes generally declined with time during the incubation in all treatments, suggesting shifts of microbial functional groups as substrate composition was changing. Compared to the control, soils from warmed plots showed significant increase in the signal intensities of microbial genes involved in degrading complex organic compounds, implying enhanced potential abilities of microbial catabolism. These are likely responsible for accelerated decomposition of SOC components with slow turnover rates. Overall, the shifted microbial community induced by long-term warming accelerates the decomposition of SOC components with slow turnover rates and thus amplify the positive feedback to climate change.« less
Enhanced decomposition of stable soil organic carbon and microbial catabolic potentials by long-term field warming.

PubMed

Feng, Wenting; Liang, Junyi; Hale, Lauren E; Jung, Chang Gyo; Chen, Ji; Zhou, Jizhong; Xu, Minggang; Yuan, Mengting; Wu, Liyou; Bracho, Rosvel; Pegoraro, Elaine; Schuur, Edward A G; Luo, Yiqi

2017-11-01

Quantifying soil organic carbon (SOC) decomposition under warming is critical to predict carbon-climate feedbacks. According to the substrate regulating principle, SOC decomposition would decrease as labile SOC declines under field warming, but observations of SOC decomposition under warming do not always support this prediction. This discrepancy could result from varying changes in SOC components and soil microbial communities under warming. This study aimed to determine the decomposition of SOC components with different turnover times after subjected to long-term field warming and/or root exclusion to limit C input, and to test whether SOC decomposition is driven by substrate lability under warming. Taking advantage of a 12-year field warming experiment in a prairie, we assessed the decomposition of SOC components by incubating soils from control and warmed plots, with and without root exclusion for 3 years. We assayed SOC decomposition from these incubations by combining inverse modeling and microbial functional genes during decomposition with a metagenomic technique (GeoChip). The decomposition of SOC components with turnover times of years and decades, which contributed to 95% of total cumulative CO 2 respiration, was greater in soils from warmed plots. But the decomposition of labile SOC was similar in warmed plots compared to the control. The diversity of C-degradation microbial genes generally declined with time during the incubation in all treatments, suggesting shifts of microbial functional groups as substrate composition was changing. Compared to the control, soils from warmed plots showed significant increase in the signal intensities of microbial genes involved in degrading complex organic compounds, implying enhanced potential abilities of microbial catabolism. These are likely responsible for accelerated decomposition of SOC components with slow turnover rates. Overall, the shifted microbial community induced by long-term warming accelerates the decomposition of SOC components with slow turnover rates and thus amplify the positive feedback to climate change. © 2017 John Wiley & Sons Ltd.
Effects of defects on thermal decomposition of HMX via ReaxFF molecular dynamics simulations.

PubMed

Zhou, Ting-Ting; Huang, Feng-Lei

2011-01-20

Effects of molecular vacancies on the decomposition mechanisms and reaction dynamics of condensed-phase β-HMX at various temperatures were studied using ReaxFF molecular dynamics simulations. Results show that three primary initial decomposition mechanisms, namely, N-NO(2) bond dissociation, HONO elimination, and concerted ring fission, exist at both high and lower temperatures. The contribution of the three mechanisms to the initial decomposition of HMX is influenced by molecular vacancies, and the effects vary with temperature. At high temperature (2500 K), molecular vacancies remarkably promote N-N bond cleavage and concerted ring breaking but hinder HONO formation. N-N bond dissociation and HONO elimination are two primary competing reaction mechanisms, and the former is dominant in the initial decomposition. Concerted ring breaking of condensed-phase HMX is not favored at high temperature. At lower temperature (1500 K), the most preferential initial decomposition pathway is N-N bond dissociation followed by the formation of NO(3) (O migration), although all three mechanisms are promoted by molecular vacancies. The promotion effect on concerted ring breaking is considerable at lower temperature. Products resulting from concerted ring breaking appear in the defective system but not in the perfect crystal. The mechanism of HONO elimination is less important at lower temperature. We also estimated the reaction rate constant and activation barriers of initial decomposition with different vacancy concentrations. Molecular vacancies accelerate the decomposition of condensed-phase HMX by increasing the reaction rate constant and reducing activation barriers.
[Relationships between decomposition rate of leaf litter and initial quality across the alpine timberline ecotone in Western Sichuan, China].

PubMed

Yang, Lin; Deng, Chang-chun; Chen Ya-mei; He, Run-lian; Zhang, Jian; Liu, Yang

2015-12-01

The relationships between litter decomposition rate and their initial quality of 14 representative plants in the alpine forest ecotone of western Sichuan were investigated in this paper. The decomposition rate k of the litter ranged from 0.16 to 1.70. Woody leaf litter and moss litter decomposed much slower, and shrubby litter decomposed a little faster. Then, herbaceous litters decomposed fastest among all plant forms. There were significant linear regression relationships between the litter decomposition rate and the N content, lignin content, phenolics content, C/N, C/P and lignin/N. Lignin/N and hemicellulose content could explain 78.4% variation of the litter decomposition rate (k) by path analysis. The lignin/N could explain 69.5% variation of k alone, and the direct path coefficient of lignin/N on k was -0.913. Principal component analysis (PCA) showed that the contribution rate of the first sort axis to k and the decomposition time (t) reached 99.2%. Significant positive correlations existed between lignin/N, lignin content, C/N, C/P and the first sort axis, and the closest relationship existed between lignin/N and the first sort axis (r = 0.923). Lignin/N was the key quality factor affecting plant litter decomposition rate across the alpine timberline ecotone, with the higher the initial lignin/N, the lower the decomposition rate of leaf litter.
Feeding rates of Balloniscus sellowii (Crustacea, Isopoda, Oniscidea): the effect of leaf litter decomposition and its relation to the phenolic and flavonoid content

PubMed Central

Wood, Camila Timm; Schlindwein, Carolina Casco Duarte; Soares, Geraldo Luiz Gonçalves; Araujo, Paula Beatriz

2012-01-01

Abstract The goal of this study was to compare the feeding rates of Balloniscus sellowii on leaves of different decomposition stages according to their phenolic and flavonoid content. Leaves from the visually most abundant plants were offered to isopods collected from the same source site. Schinus terebinthifolius,the plant species consumed at the highest rate, was used to verify feeding rates at different decomposition stages. Green leaves were left to decompose for one, two, or three months, and then were offered to isopods. The total phenolic and flavonoid contents were determined for all decomposition stages. Consumption and egestion rates increased throughout decomposition, were highest for two-month-old leaves, and decreased again in the third month. The assimilation rate was highest for green leaves. The mode time of passage through the gut was two hours for all treatments. Ingestion of leaves occurred after two or three days for green leaves, and on the same day for one-, two- and three-month-old leaves. The speed of passage of leaves with different decomposition stages through the gut does not differ significantly when animals are fed continuously. However, it is possible that the amount retained in the gut during starvation differs depending on food quality. The digestibility value was corrected using a second food source to empty the gut of previously ingested food, so that all of the food from the experiment was egested. The digestibility value was highest for green leaves, whereas it was approximately 20% for all other stages. This was expected given that digestibility declines during decomposition as the metabolite content of the leaves decreases. The phenolic content was highest in the green leaves and lowest in three-month-old leaves. The flavonoid content was highest in green leaves and lowest after two months of decomposition. Animals ingested more phenolics when consumption was highest. The estimated amount of ingested flavonoids followed the same trend as assimilation rate. Flavonoids accounted for a large portion of total phenolics, and the estimated amount of flavonoids consumed was similar for one-, two- and three-month-old leaves. Our results suggest that the high phenolic and flavonoid concentrations in green leaves are feeding deterrents. Isopods may discriminate among concentrations of flavonoids and modify their consumption rates to maintain their intake of flavonoids when ingesting leaves with lower flavonoid content. PMID:22536111
Functionally dissimilar neighbors accelerate litter decomposition in two grass species.

PubMed

Barbe, Lou; Jung, Vincent; Prinzing, Andreas; Bittebiere, Anne-Kristel; Butenschoen, Olaf; Mony, Cendrine

2017-05-01

Plant litter decomposition is a key regulator of nutrient recycling. In a given environment, decomposition of litter from a focal species depends on its litter quality and on the efficiency of local decomposers. Both may be strongly modified by functional traits of neighboring species, but the consequences for decomposition of litter from the focal species remain unknown. We tested whether decomposition of a focal plant's litter is influenced by the functional-trait dissimilarity to the neighboring plants. We cultivated two grass species (Brachypodium pinnatum and Elytrigia repens) in experimental mesocosms with functionally similar and dissimilar neighborhoods, and reciprocally transplanted litter. For both species, litter quality increased in functionally dissimilar neighborhoods, partly as a result of changes in functional traits involved in plant-plant interactions. Furthermore, functional dissimilarity increased overall decomposer efficiency in one species, probably via complementarity effects. Our results suggest a novel mechanism of biodiversity effects on ecosystem functioning in grasslands: interspecific functional diversity within plant communities can enhance intraspecific contributions to litter decomposition. Thus, plant species might better perform in diverse communities by benefiting from higher remineralization rates of their own litter. © 2017 The Authors. New Phytologist © 2017 New Phytologist Trust.
Interactive effects of wildfire and permafrost on microbial communities and soil processes in an Alaskan black spruce forest

USGS Publications Warehouse

Waldrop, M.P.; Harden, J.W.

2008-01-01

Boreal forests contain significant quantities of soil carbon that may be oxidized to CO2 given future increases in climate warming and wildfire behavior. At the ecosystem scale, decomposition and heterotrophic respiration are strongly controlled by temperature and moisture, but we questioned whether changes in microbial biomass, activity, or community structure induced by fire might also affect these processes. We particularly wanted to understand whether postfire reductions in microbial biomass could affect rates of decomposition. Additionally, we compared the short-term effects of wildfire to the long-term effects of climate warming and permafrost decline. We compared soil microbial communities between control and recently burned soils that were located in areas with and without permafrost near Delta Junction, AK. In addition to soil physical variables, we quantified changes in microbial biomass, fungal biomass, fungal community composition, and C cycling processes (phenol oxidase enzyme activity, lignin decomposition, and microbial respiration). Five years following fire, organic surface horizons had lower microbial biomass, fungal biomass, and dissolved organic carbon (DOC) concentrations compared with control soils. Reductions in soil fungi were associated with reductions in phenol oxidase activity and lignin decomposition. Effects of wildfire on microbial biomass and activity in the mineral soil were minor. Microbial community composition was affected by wildfire, but the effect was greater in nonpermafrost soils. Although the presence of permafrost increased soil moisture contents, effects on microbial biomass and activity were limited to mineral soils that showed lower fungal biomass but higher activity compared with soils without permafrost. Fungal abundance and moisture were strong predictors of phenol oxidase enzyme activity in soil. Phenol oxidase enzyme activity, in turn, was linearly related to both 13C lignin decomposition and microbial respiration in incubation studies. Taken together, these results indicate that reductions in fungal biomass in postfire soils and lower soil moisture in nonpermafrost soils reduced the potential of soil heterotrophs to decompose soil carbon. Although in the field increased rates of microbial respiration can be observed in postfire soils due to warmer soil conditions, reductions in fungal biomass and activity may limit rates of decomposition. ?? 2008 The Authors Journal compilation ?? 2008 Blackwell Publishing.
Interacting Microbe and Litter Quality Controls on Litter Decomposition: A Modeling Analysis

PubMed Central

Moorhead, Daryl; Lashermes, Gwenaëlle; Recous, Sylvie; Bertrand, Isabelle

2014-01-01

The decomposition of plant litter in soil is a dynamic process during which substrate chemistry and microbial controls interact. We more clearly quantify these controls with a revised version of the Guild-based Decomposition Model (GDM) in which we used a reverse Michaelis-Menten approach to simulate short-term (112 days) decomposition of roots from four genotypes of Zea mays that differed primarily in lignin chemistry. A co-metabolic relationship between the degradation of lignin and holocellulose (cellulose+hemicellulose) fractions of litter showed that the reduction in decay rate with increasing lignin concentration (LCI) was related to the level of arabinan substitutions in arabinoxylan chains (i.e., arabinan to xylan or A∶X ratio) and the extent to which hemicellulose chains are cross-linked with lignin in plant cell walls. This pattern was consistent between genotypes and during progressive decomposition within each genotype. Moreover, decay rates were controlled by these cross-linkages from the start of decomposition. We also discovered it necessary to divide the Van Soest soluble (labile) fraction of litter C into two pools: one that rapidly decomposed and a second that was more persistent. Simulated microbial production was consistent with recent studies suggesting that more rapidly decomposing materials can generate greater amounts of potentially recalcitrant microbial products despite the rapid loss of litter mass. Sensitivity analyses failed to identify any model parameter that consistently explained a large proportion of model variation, suggesting that feedback controls between litter quality and microbial activity in the reverse Michaelis-Menten approach resulted in stable model behavior. Model extrapolations to an independent set of data, derived from the decomposition of 12 different genotypes of maize roots, averaged within <3% of observed respiration rates and total CO2 efflux over 112 days. PMID:25264895
Rates of Litter Decomposition and Soil Respiration in Relation to Soil Temperature and Water in Different-Aged Pinus massoniana Forests in the Three Gorges Reservoir Area, China

PubMed Central

Zeng, Lixiong; Huang, Zhilin; Lei, Jingpin; Zhou, Benzhi; Li, Maihe

2014-01-01

To better understand the soil carbon dynamics and cycling in terrestrial ecosystems in response to environmental changes, we studied soil respiration, litter decomposition, and their relations to soil temperature and soil water content for 18-months (Aug. 2010–Jan. 2012) in three different-aged Pinus massoniana forests in the Three Gorges Reservoir Area, China. Across the experimental period, the mean total soil respiration and litter respiration were 1.94 and 0.81, 2.00 and 0.60, 2.19 and 0.71 µmol CO2 m−2 s−1, and the litter dry mass remaining was 57.6%, 56.2% and 61.3% in the 20-, 30-, and 46-year-old forests, respectively. We found that the temporal variations of soil respiration and litter decomposition rates can be well explained by soil temperature at 5 cm depth. Both the total soil respiration and litter respiration were significantly positively correlated with the litter decomposition rates. The mean contribution of the litter respiration to the total soil respiration was 31.0%–45.9% for the three different-aged forests. The present study found that the total soil respiration was not significantly affected by forest age when P. masonniana stands exceed a certain age (e.g. >20 years old), but it increased significantly with increased soil temperature. Hence, forest management strategies need to protect the understory vegetation to limit soil warming, in order to reduce the CO2 emission under the currently rapid global warming. The contribution of litter decomposition to the total soil respiration varies across spatial and temporal scales. This indicates the need for separate consideration of soil and litter respiration when assessing the climate impacts on forest carbon cycling. PMID:25004164

Effects of temperature on decomposition of a potential nuisance species: the submerged aquatic macrophyte Egeria najas Planchon (Hydrocharitaceae).

PubMed

Carvalho, P; Thomaz, S M; Bini, L M

2005-02-01

Decomposition of aquatic plants is influenced by several biotic and abiotic factors. Among them, temperature plays an important role. Despite the increasing number of studies describing the effects of temperature on the decomposition of aquatic macrophytes, little attention has been given to the decay of submerged macrophytes. In this paper, we assessed the effect of temperature on weight loss and chemical composition of detritus of the submerged aquatic macrophyte Egeria najas Planchon (Hydrocharitaceae). Fresh plant material was maintained at 17 degrees C and 27 degrees C, in the dark, in incubation chambers. The overall decay process was best described by a linear model, with rates of 0.014 day(-1) (R2= 94%) and 0.045 day(-1) (R2= 96%) obtained at 17 degrees C and 27 degrees C, respectively. The analysis of covariance (ANCOVA) indicated a significant difference between the decomposition rates at the two temperatures. The rapid breakdown of E. najas detritus, indicated by the decay coefficient, may be explained by its low content of resistant compounds such as cellulose and lignin. The variables analyzed in this study (pH, electrical conductivity, dissolved oxygen in the water and organic matter, total nitrogen and total phosphorus concentration in detritus) showed accentuated responses at 27 degrees C. It is likely that the higher temperature increased microbial activity and, therefore, oxygen consumption in the water, consequently affecting the pH and the rate of ion and nutrient liberation into the aquatic ecosystem. Due to the rapid decomposition of E. najas at high temperatures, a small exportation is expected of this species from its stands to distant regions in tropical reservoirs, where it is considered a potential nuisance species.
Short-term standard litter decomposition across three different ecosystems in middle taiga zone of West Siberia

NASA Astrophysics Data System (ADS)

Filippova, Nina V.; Glagolev, Mikhail V.

2018-03-01

The method of standard litter (tea) decomposition was implemented to compare decomposition rate constants (k) between different peatland ecosystems and coniferous forests in the middle taiga zone of West Siberia (near Khanty-Mansiysk). The standard protocol of TeaComposition initiative was used to make the data usable for comparisons among different sites and zonobiomes worldwide. This article sums up the results of short-term decomposition (3 months) on the local scale. The values of decomposition rate constants differed significantly between three ecosystem types: it was higher in forest compared to bogs, and treed bogs had lower decomposition constant compared to Sphagnum lawns. In general, the decomposition rate constants were close to ones reported earlier for similar climatic conditions and habitats.
Does tree species richness attenuate the effect of experimental irrigation and drought on decomposition rate in young plantation forests?

NASA Astrophysics Data System (ADS)

Masudur Rahman, Md; Verheyen, Kris; Castagneyrol, Bastien; Jactel, Hervé; Carnol, Monique

2017-04-01

Expected changes in precipitation in Europe due to climate change are likely to affect soil organic matter (OM) transformation. In forests, increasing tree species diversity might modulate the effect of changed precipitation. We evaluated the effect of tree species richness on the decomposition and stabilization rate in combination with reduced precipitation (FORBIO, Belgium) and irrigation treatment (ORPHEE, southern France) in young (6-8 yr.) experimental plantations. The species richness were one to four in FORBIO and one to five in ORPHEE. Twenty four rainout shelters of 3 m × 3 m were built around oak and beech trees in FORBIO plantation to impose a reduced precipitation treatment, whereas four of the eight blocks (175 m×100 m) in ORPHEE plantation was subjected to irrigation treatment. These treatments resulted in about 4% less soil moisture in FORBIO and about 7% higher soil moisture in ORPHEE compared to control. Commercially available green and rooibos tea bags were buried in the soil at 5-7 cm depth to measure two decomposition indices, known as 'tea bag index' (TBI). These TBI are (i) decomposition rate (k) and (ii) stabilization rate (S). The results showed no species richness effect on TBI indices in both reduced precipitation and irrigation treatment. In FORBIO, reduced precipitation resulted in decreased k and increased S compared to control around the beech trees only. In ORPHEE, both k and S were higher in the irrigation treatment compared to control. Overall, TBI indices were higher in FORBIO than ORPHEE and this might be explained by the sandy soils and poor nutrient content at the ORPHEE site. These results suggest that OM decomposition rate may be slower in drier condition and OM stabilization rate may be slower or faster in drier condition, depending on the site quality. The absence of tree species effects on OM transformation indicates that tree species richness would not be able to modulate the effects of changed precipitation patterns in young plantations. We conclude that in young afforestations, soil moisture has more influence on OM transformation than tree species richness.
Decomposition rates and termite assemblage composition in semiarid Africa

USGS Publications Warehouse

Schuurman, G.

2005-01-01

Outside of the humid tropics, abiotic factors are generally considered the dominant regulators of decomposition, and biotic influences are frequently not considered in predicting decomposition rates. In this study, I examined the effect of termite assemblage composition and abundance on decomposition of wood litter of an indigenous species (Croton megalobotrys) in five terrestrial habitats of the highly seasonal semiarid Okavango Delta region of northern Botswana, to determine whether natural variation in decomposer community composition and abundance influences decomposition rates. 1 conducted the study in two areas, Xudum and Santawani, with the Xudum study preceding the Santawani study. I assessed termite assemblage composition and abundance using a grid of survey baits (rolls of toilet paper) placed on the soil surface and checked 2-4 times/month. I placed a billet (a section of wood litter) next to each survey bait and measured decomposition in a plot by averaging the mass loss of its billets. Decomposition rates varied up to sixfold among plots within the same habitat and locality, despite the fact that these plots experienced the same climate. In addition, billets decomposed significantly faster during the cooler and drier Santawani study, contradicting climate-based predictions. Because termite incidence was generally higher in Santawani plots, termite abundance initially seemed a likely determinant of decomposition in this system. However, no significant effect of termite incidence on billet mass loss rates was observed among the Xudum plots, where decomposition rates remained low even though termite incidence varied considerably. Considering the incidences of fungus-growing termites and non-fungus-growing termites separately resolves this apparent contradiction: in both Santawani and Xudum, only fungus-growing termites play a significant role in decomposition. This result is mirrored in an analysis of the full data set of combined Xudum and Santawani data. The determination that natural variation in the abundance of a single taxonomic group of soil fauna, a termite subfamily, determines almost all observed variation in decomposition rates supports the emerging view that biotic influences may be important in many biomes and that consideration of decomposer community composition and abundance may be critical for accurate prediction of decomposition rates. ?? 2005 by the Ecological Society of America.
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. Copyright © 2012 Elsevier B.V. All rights reserved.
Unusual behavior in the reactivity of 5-substituted-1H-tetrazoles in a resistively heated microreactor

PubMed Central

Gutmann, Bernhard; Glasnov, Toma N; Razzaq, Tahseen; Goessler, Walter; Roberge, Dominique M

2011-01-01

Summary The decomposition of 5-benzhydryl-1H-tetrazole in an N-methyl-2-pyrrolidone/acetic acid/water mixture was investigated under a variety of high-temperature reaction conditions. Employing a sealed Pyrex glass vial and batch microwave conditions at 240 °C, the tetrazole is comparatively stable and complete decomposition to diphenylmethane requires more than 8 h. Similar kinetic data were obtained in conductively heated flow devices with either stainless steel or Hastelloy coils in the same temperature region. In contrast, in a flow instrument that utilizes direct electric resistance heating of the reactor coil, tetrazole decomposition was dramatically accelerated with rate constants increased by two orders of magnitude. When 5-benzhydryl-1H-tetrazole was exposed to 220 °C in this type of flow reactor, decomposition to diphenylmethane was complete within 10 min. The mechanism and kinetic parameters of tetrazole decomposition under a variety of reaction conditions were investigated. A number of possible explanations for these highly unusual rate accelerations are presented. In addition, general aspects of reactor degradation, corrosion and contamination effects of importance to continuous flow chemistry are discussed. PMID:21647324
Seasonal variation in standardized litter decomposition and effects of elevation and land use at Mount Kilimanjaro

NASA Astrophysics Data System (ADS)

Becker, Joscha; Kuzyakov, Yakov

2017-04-01

Decomposition is one of most important ecological steps in organic matter and nutrient cycles, but studies and reliable data from tropical regions in Africa are still scarce. At the global scale, litter decomposition and recycling is controlled by climatic factors and land-use intensity. These factors can be linked to specific ecosystem characteristics along the unique elevation gradient of Mt. Kilimanjaro. Our objectives were to assess the effects of climatic conditions (i.e. elevation) and land-use intensity on C turnover and stabilization and investigated the seasonal variations. Tea-bag Index (see www.teatime4science.org) was used to measure decomposition of a standardized litter substrate by microorganisms and mesofauna <0.25 mm. Nine pairs of litterbags were exposed in eleven ecosystems for 90 days during the short-rainy (October-December), warm-dry (December-March), long-rainy (March-July) and cold-dry season (July-September) respectively. Decomposition rates increased from k=0.007 in savanna, up to a maximum of k=0.022 in cloud forest (i.e. mid elevation). The increase was followed by a decrease of 50% in (sub-) alpine ecosystems. Stabilization factors decreased from savanna (S=0.33) to coffee plantations or cloud forest (S=0.11) respectively and strongly increased again to a maximum of S=0.41 in the alpine helichrysum ecosystem. During all seasons, we found the highest decomposition rates at mid elevation. However, during both warm seasons the peak is shifted upslope. Savanna experienced the strongest seasonal variation, with 23 times higher S-values in dry- compared to rainy season. Mean annual k-values increased for about 30% with increasing land-use intensity. C stabilization in Mt. Kilimanjaro ecosystems is strongly dependent on seasonal moisture limitation (lower slope) and perennial temperature limitation (alpine zone). Ecosystems at mid elevation (around 1920 & 2120m) represent the interception zone of optimal moisture and temperature conditions. High input and fast turnover drive the C sequestration in these ecosystems, while restrains on decomposition control the C turnover in lower and higher elevation zones. Land-use intensification decreases stabilization from new C inputs in transition zones from savanna to maize monocultures and from traditional homegardens to large-scale coffee plantations.
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
Phosphorus availability modulates the toxic effect of silver on aquatic fungi and leaf litter decomposition.

PubMed

Funck, J Arce; Clivot, H; Felten, V; Rousselle, P; Guérold, F; Danger, M

2013-11-15

The functioning of forested headwater streams is intimately linked to the decomposition of leaf litter by decomposers, mainly aquatic hyphomycetes, which enables the transfer of allochthonous carbon to higher trophic levels. Evaluation of this process is being increasingly used as an indicator of ecosystem health and ecological integrity. Yet, even though the individual impacts of contaminants and nutrient availability on decomposition have been well studied, the understanding of their combined effects remains limited. In the current study, we investigated whether the toxic effects of a reemerging contaminant, silver (Ag), on leaf litter decomposition could be partly overcome in situations where microorganisms were benefitting from high phosphorus (P) availability, the latter being a key chemical element that often limits detritus decomposition. We also investigated whether these interactive effects were mediated by changes in the structure of the aquatic hyphomycete community. To verify these hypotheses, leaf litter decomposition by a consortium of ten aquatic hyphomycete species was followed in a microcosm experiment combining five Ag contamination levels and three P concentrations. Indirect effects of Ag and P on the consumption of leaf litter by the detritivorous crustacean, Gammarus fossarum, were also evaluated. Ag significantly reduced decomposition but only at the highest concentration tested, independently of P level. By contrast, P and Ag interactively affected fungal biomass. Both P level and Ag concentrations shaped microbial communities without significantly affecting the overall species richness. Finally, the levels of P and Ag interacted significantly on G. fossarum feeding rates, high [Ag] reducing litter consumption and low P availability tending to intensify the feeding rate. Given the high level of contaminant needed to impair the decomposition process, it is unlikely that a direct effect of Ag on leaf litter decomposition could be observed in situ. However, subtle Ag effects in relation to nutrient levels in ecosystems could be expected. In particular, owing to higher consumption of low P leaf litter, shredding invertebrates could increase the ingestion of contaminated resources, which could, in turn, represent an important threat to headwater stream ecosystems. Copyright © 2013 Elsevier B.V. All rights reserved.
[Effects of simulated acid rain on decomposition of soil organic carbon and crop straw].

PubMed

Zhu, Xue-Zhu; Huang, Yao; Yang, Xin-Zhong

2009-02-01

To evaluate the effects of acid rain on the organic carbon decomposition in different acidity soils, a 40-day incubation test was conducted with the paddy soils of pH 5.48, 6.70 and 8.18. The soils were amended with 0 and 15 g x kg(-1) of rice straw, adjusted to the moisture content of 400 g x kg(-1) air-dried soil by using simulated rain of pH 6.0, 4.5, and 3.0, and incubated at 20 degrees C. The results showed that straw, acid rain, and soil co-affected the CO2 emission from soil system. The amendment of straw increased the soil CO2 emission rate significantly. Acid rain had no significant effects on soil organic carbon decomposition, but significantly affected the straw decomposition in soil. When treated with pH 3.0 acid rain, the amount of decomposed straw over 40-day incubation in acid (pH 5.48) and alkaline (pH 8.18) soils was 8% higher, while that in neutral soil (pH 6.70) was 15% lower, compared to the treatment of pH 6.0 rain. In the treatment of pH 3.0 acid rain, the decomposition rate of soil organic C in acid (pH 5.48) soil was 43% and 50% (P < 0.05) higher than that in neutral (pH 6.70) and alkaline (pH 8.18) soils, while the decomposition rate of straw in neutral soil was 17% and 16% (P < 0.05) lower than that in acid and alkaline soils, respectively.
Modeling the Spray Forming of H13 Steel Tooling

NASA Astrophysics Data System (ADS)

Lin, Yaojun; McHugh, Kevin M.; Zhou, Yizhang; Lavernia, Enrique J.

2007-07-01

On the basis of a numerical model, the temperature and liquid fraction of spray-formed H13 tool steel are calculated as a function of time. Results show that a preheated substrate at the appropriate temperature can lead to very low porosity by increasing the liquid fraction in the deposited steel. The calculated cooling rate can lead to a microstructure consisting of martensite, lower bainite, retained austenite, and proeutectoid carbides in as-spray-formed material. In the temperature range between the solidus and liquidus temperatures, the calculated temperature of the spray-formed material increases with increasing substrate preheat temperature, resulting in a very low porosity by increasing the liquid fraction of the deposited steel. In the temperature region where austenite decomposition occurs, the substrate preheat temperature has a negligible influence on the cooling rate of the spray-formed material. On the basis of the calculated results, it is possible to generate sufficient liquid fraction during spray forming by using a high growth rate of the deposit without preheating the substrate, and the growth rate of the deposit has almost no influence on the cooling rate in the temperature region of austenite decomposition.
Biomass is the main driver of changes in ecosystem process rates during tropical forest succession.

PubMed

Lohbeck, Madelon; Poorter, Lourens; Martínez-Ramos, Miguel; Bongers, Frans

2015-05-01

Over half of the world's forests are disturbed, and the rate at which ecosystem processes recover after disturbance is important for the services these forests can provide. We analyze the drivers' underlying changes in rates of key ecosystem processes (biomass productivity, litter productivity, actual litter decomposition, and potential litter decomposition) during secondary succession after shifting cultivation in wet tropical forest of Mexico. We test the importance of three alternative drivers of ecosystem processes: vegetation biomass (vegetation quantity hypothesis), community-weighted trait mean (mass ratio hypothesis), and functional diversity (niche complementarity hypothesis) using structural equation modeling. This allows us to infer the relative importance of different mechanisms underlying ecosystem process recovery. Ecosystem process rates changed during succession, and the strongest driver was aboveground biomass for each of the processes. Productivity of aboveground stem biomass and leaf litter as well as actual litter decomposition increased with initial standing vegetation biomass, whereas potential litter decomposition decreased with standing biomass. Additionally, biomass productivity was positively affected by community-weighted mean of specific leaf area, and potential decomposition was positively affected by functional divergence, and negatively by community-weighted mean of leaf dry matter content. Our empirical results show that functional diversity and community-weighted means are of secondary importance for explaining changes in ecosystem process rates during tropical forest succession. Instead, simply, the amount of vegetation in a site is the major driver of changes, perhaps because there is a steep biomass buildup during succession that overrides more subtle effects of community functional properties on ecosystem processes. We recommend future studies in the field of biodiversity and ecosystem functioning to separate the effects of vegetation quality (community-weighted mean trait values and functional diversity) from those of vegetation quantity (biomass) on ecosystem processes and services.
Determination of Kinetic Parameters for the Thermal Decomposition of Parthenium hysterophorus

NASA Astrophysics Data System (ADS)

Dhaundiyal, Alok; Singh, Suraj B.; Hanon, Muammel M.; Rawat, Rekha

2018-02-01

A kinetic study of pyrolysis process of Parthenium hysterophorous is carried out by using thermogravimetric analysis (TGA) equipment. The present study investigates the thermal degradation and determination of the kinetic parameters such as activation E and the frequency factor A using model-free methods given by Flynn Wall and Ozawa (FWO), Kissinger-Akahira-Sonuse (KAS) and Kissinger, and model-fitting (Coats Redfern). The results derived from thermal decomposition process demarcate decomposition of Parthenium hysterophorous among the three main stages, such as dehydration, active and passive pyrolysis. It is shown through DTG thermograms that the increase in the heating rate caused temperature peaks at maximum weight loss rate to shift towards higher temperature regime. The results are compared with Coats Redfern (Integral method) and experimental results have shown that values of kinetic parameters obtained from model-free methods are in good agreement. Whereas the results obtained through Coats Redfern model at different heating rates are not promising, however, the diffusion models provided the good fitting with the experimental data.
Interactive effects of fire, soil climate, and moss on CO2 fluxes in black spruce ecosystems of interior Alaska

USGS Publications Warehouse

O'Donnell, J. A.; Turetsky, M.R.; Harden, J.W.; Manies, K.L.; Pruett, L.E.; Shetler, G.; Neff, J.C.

2009-01-01

Fire is an important control on the carbon (C) balance of the boreal forest region. Here, we present findings from two complementary studies that examine how fire modifies soil organic matter properties, and how these modifications influence rates of decomposition and C exchange in black spruce (Picea mariana) ecosystems of interior Alaska. First, we used laboratory incubations to explore soil temperature, moisture, and vegetation effects on CO2 and DOC production rates in burned and unburned soils from three study regions in interior Alaska. Second, at one of the study regions used in the incubation experiments, we conducted intensive field measurements of net ecosystem exchange (NEE) and ecosystem respiration (ER) across an unreplicated factorial design of burning (2 year post-fire versus unburned sites) and drainage class (upland forest versus peatland sites). Our laboratory study showed that burning reduced the sensitivity of decomposition to increased temperature, most likely by inducing moisture or substrate quality limitations on decomposition rates. Burning also reduced the decomposability of Sphagnum-derived organic matter, increased the hydrophobicity of feather moss-derived organic matter, and increased the ratio of dissolved organic carbon (DOC) to total dissolved nitrogen (TDN) in both the upland and peatland sites. At the ecosystem scale, our field measurements indicate that the surface organic soil was generally wetter in burned than in unburned sites, whereas soil temperature was not different between the burned and unburned sites. Analysis of variance results showed that ER varied with soil drainage class but not by burn status, averaging 0.9 ?? 0.1 and 1.4 ?? 0.1 g C m-2d-1 in the upland and peatland sites, respectively. However, a more complex general linear model showed that ER was controlled by an interaction between soil temperature, moisture, and burn status, and in general was less variable over time in the burned than in the unburned sites. Together, findings from these studies across different spatial scales suggest that although fire can create some soil climate conditions more conducive to rapid decomposition, rates of C release from soils may be constrained following fire by changes in moisture and/or substrate quality that impede rates of decomposition. ?? 2008 Springer Science+Business Media, LLC.
Interactive effects of fire, soil climate, and moss on CO2 fluxes in black spruce ecosystems of interior Alaska

USGS Publications Warehouse

O'Donnell, Jonathan A.; Turetsky, Merritt R.; Harden, Jennifer W.; Manies, Kristen L.; Pruett, L.E.; Shetler, Gordon; Neff, Jason C.

2009-01-01

Fire is an important control on the carbon (C) balance of the boreal forest region. Here, we present findings from two complementary studies that examine how fire modifies soil organic matter properties, and how these modifications influence rates of decomposition and C exchange in black spruce (Picea mariana) ecosystems of interior Alaska. First, we used laboratory incubations to explore soil temperature, moisture, and vegetation effects on CO2 and DOC production rates in burned and unburned soils from three study regions in interior Alaska. Second, at one of the study regions used in the incubation experiments, we conducted intensive field measurements of net ecosystem exchange (NEE) and ecosystem respiration (ER) across an unreplicated factorial design of burning (2 year post-fire versus unburned sites) and drainage class (upland forest versus peatland sites). Our laboratory study showed that burning reduced the sensitivity of decomposition to increased temperature, most likely by inducing moisture or substrate quality limitations on decomposition rates. Burning also reduced the decomposability of Sphagnum-derived organic matter, increased the hydrophobicity of feather moss-derived organic matter, and increased the ratio of dissolved organic carbon (DOC) to total dissolved nitrogen (TDN) in both the upland and peatland sites. At the ecosystem scale, our field measurements indicate that the surface organic soil was generally wetter in burned than in unburned sites, whereas soil temperature was not different between the burned and unburned sites. Analysis of variance results showed that ER varied with soil drainage class but not by burn status, averaging 0.9 ± 0.1 and 1.4 ± 0.1 g C m−2 d−1 in the upland and peatland sites, respectively. However, a more complex general linear model showed that ER was controlled by an interaction between soil temperature, moisture, and burn status, and in general was less variable over time in the burned than in the unburned sites. Together, findings from these studies across different spatial scales suggest that although fire can create some soil climate conditions more conducive to rapid decomposition, rates of C release from soils may be constrained following fire by changes in moisture and/or substrate quality that impede rates of decomposition.
Effect of water level drawdown on decomposition in boreal peatlands

NASA Astrophysics Data System (ADS)

Straková, Petra; Penttilä, Timo; Laiho, Raija

2010-05-01

Plant litter production and decomposition are key processes in element cycling in most ecosystems. In peatlands, there has been a long-term imbalance between litter production and decay caused by high water levels (WL) and consequent anoxia. This has resulted in peatlands being a significant sink of carbon (C) from the atmosphere. However, peatlands are experiencing both "natural" (global climate change) and anthropogenic (ditching) changes that threaten their ability to retain this ecosystem identity and function. Many of these alterations can be traced back to WL drawdown, which can cause increased aeration, higher acidity, falling temperatures, and a greater probability of drought. Such changes are also associated with an increasing decomposition rate, and therefore a greater amount of C released back to the atmosphere. Yet studies about how the overall C balance of peatlands will be affected have come up with conflicting conclusions, demonstrating that the C store could increase, decrease, or remain static. A factor that has been largely overlooked is the change in litter type composition following persistent WL drawdown. It is the aim of our study, then, to help to resolve this issue. We studied the effects of short-term (ca. 4 years) and long-term (ca. 40 years) persistent WL drawdown on the decomposition of numerous types of above-ground and below-ground plant litters at three boreal peatland sites: bog, oligotrophic fen and mesotrophic fen. We thus believe that enough permutations have been created to obtain a good assessment of how each factor, site nutrient level, WL regime, and litter type composition, influences decomposition. We used the litter bag method to measure the decomposition rates: placed measured amounts of plant litter, or cellulose strips as a control, into closed mesh bags, and installed the bags in the natural environment for decomposition for each litter type for varying amounts of time. Following litter bag recovery, the litter was cleaned of excess debris and analyzed for changes in mass, enzyme activity, mesofauna presence, and microbial community composition, among other things. The experiment has a run-time of ten years, the results from the first two years are presented in the poster.
Moisture controls decomposition rate in thawing tundra

Treesearch

C.E. Hicks-Pries; E.A.G. Schuur; S.M. Natali; J.G. Vogel

2013-01-01

Permafrost thaw can affect decomposition rates by changing environmental conditions and litter quality. As permafrost thaws, soils warm and thermokarst (ground subsidence) features form, causing some areas to become wetter while other areas become drier. We used a common substrate to measure how permafrost thaw affects decomposition rates in the surface soil in a...
Comparison of the Decomposition VOC Profile during Winter and Summer in a Moist, Mid-Latitude (Cfb) Climate

PubMed Central

Forbes, Shari L.; Perrault, Katelynn A.; Stefanuto, Pierre-Hugues; Nizio, Katie D.; Focant, Jean-François

2014-01-01

The investigation of volatile organic compounds (VOCs) associated with decomposition is an emerging field in forensic taphonomy due to their importance in locating human remains using biological detectors such as insects and canines. A consistent decomposition VOC profile has not yet been elucidated due to the intrinsic impact of the environment on the decomposition process in different climatic zones. The study of decomposition VOCs has typically occurred during the warmer months to enable chemical profiling of all decomposition stages. The present study investigated the decomposition VOC profile in air during both warmer and cooler months in a moist, mid-latitude (Cfb) climate as decomposition occurs year-round in this environment. Pig carcasses (Sus scrofa domesticus L.) were placed on a soil surface to decompose naturally and their VOC profile was monitored during the winter and summer months. Corresponding control sites were also monitored to determine the natural VOC profile of the surrounding soil and vegetation. VOC samples were collected onto sorbent tubes and analyzed using comprehensive two-dimensional gas chromatography – time-of-flight mass spectrometry (GC×GC-TOFMS). The summer months were characterized by higher temperatures and solar radiation, greater rainfall accumulation, and comparable humidity when compared to the winter months. The rate of decomposition was faster and the number and abundance of VOCs was proportionally higher in summer. However, a similar trend was observed in winter and summer demonstrating a rapid increase in VOC abundance during active decay with a second increase in abundance occurring later in the decomposition process. Sulfur-containing compounds, alcohols and ketones represented the most abundant classes of compounds in both seasons, although almost all 10 compound classes identified contributed to discriminating the stages of decomposition throughout both seasons. The advantages of GC×GC-TOFMS were demonstrated for detecting and identifying trace levels of VOCs, particularly ethers, which are rarely reported as decomposition VOCs. PMID:25412504
Comparison of the decomposition VOC profile during winter and summer in a moist, mid-latitude (Cfb) climate.

PubMed

Forbes, Shari L; Perrault, Katelynn A; Stefanuto, Pierre-Hugues; Nizio, Katie D; Focant, Jean-François

2014-01-01

The investigation of volatile organic compounds (VOCs) associated with decomposition is an emerging field in forensic taphonomy due to their importance in locating human remains using biological detectors such as insects and canines. A consistent decomposition VOC profile has not yet been elucidated due to the intrinsic impact of the environment on the decomposition process in different climatic zones. The study of decomposition VOCs has typically occurred during the warmer months to enable chemical profiling of all decomposition stages. The present study investigated the decomposition VOC profile in air during both warmer and cooler months in a moist, mid-latitude (Cfb) climate as decomposition occurs year-round in this environment. Pig carcasses (Sus scrofa domesticus L.) were placed on a soil surface to decompose naturally and their VOC profile was monitored during the winter and summer months. Corresponding control sites were also monitored to determine the natural VOC profile of the surrounding soil and vegetation. VOC samples were collected onto sorbent tubes and analyzed using comprehensive two-dimensional gas chromatography--time-of-flight mass spectrometry (GC × GC-TOFMS). The summer months were characterized by higher temperatures and solar radiation, greater rainfall accumulation, and comparable humidity when compared to the winter months. The rate of decomposition was faster and the number and abundance of VOCs was proportionally higher in summer. However, a similar trend was observed in winter and summer demonstrating a rapid increase in VOC abundance during active decay with a second increase in abundance occurring later in the decomposition process. Sulfur-containing compounds, alcohols and ketones represented the most abundant classes of compounds in both seasons, although almost all 10 compound classes identified contributed to discriminating the stages of decomposition throughout both seasons. The advantages of GC × GC-TOFMS were demonstrated for detecting and identifying trace levels of VOCs, particularly ethers, which are rarely reported as decomposition VOCs.
High temperature phase decomposition in Ti{sub x}Zr{sub y}Al{sub z}N

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lind, Hans; Pilemalm, Robert; Rogström, Lina

2014-12-15

Through a combination of theoretical and experimental observations we study the high temperature decomposition behavior of c-(Ti{sub x}Zr{sub y}Al{sub z}N) alloys. We show that for most concentrations the high formation energy of (ZrAl)N causes a strong tendency for spinodal decomposition between ZrN and AlN while other decompositions tendencies are suppressed. In addition we observe that entropic effects due to configurational disorder favor a formation of a stable Zr-rich (TiZr)N phase with increasing temperature. Our calculations also predict that at high temperatures a Zr rich (TiZrAl)N disordered phase should become more resistant against the spinodal decomposition despite its high and positivemore » formation energy due to the specific topology of the free energy surface at the relevant concentrations. Our experimental observations confirm this prediction by showing strong tendency towards decomposition in a Zr-poor sample while a Zr-rich alloy shows a greatly reduced decomposition rate, which is mostly attributable to binodal decomposition processes. This result highlights the importance of considering the second derivative of the free energy, in addition to its absolute value in predicting decomposition trends of thermodynamically unstable alloys.« less

Crowdsourcing data on decomposition with the help of schools - Tea4Science

NASA Astrophysics Data System (ADS)

Lehtinen, Taru; Dingemans, Bas J. J.; Keuskamp, Joost A.; Hefting, Mariet M.; Sarneel, Judith M.

2015-04-01

Decay of organic material, decomposition, is a critical process for life on earth. Through decomposition, food becomes available for plants and soil organisms that they use in their growth and maintenance. When plant material decomposes, it loses weight and releases the greenhouse gas carbon dioxide (CO2) into the atmosphere. Commercial nylon teabags containing plant material can provide vital information on the global carbon cycle, if we study their decomposition in soils. Terrestrial soils contain three times more carbon than the atmosphere and therefore changes in the balance of soil carbon storage and release can significantly amplify or attenuate global warming. Many factors affecting the global carbon cycle are already known and archived; however, an index for decomposition rate is still missing. It would be a great improvement if we could measure decomposition (rate and degree) globally instead of estimating it from small scale experiments and lab incubations. We developed a cost-effective and standardised method to investigate decomposition rate and carbon stabilisation; by using commercially available teabags as standardised test-kits for simplified litter bag experiments. In order to make it easy for schools to take part through crowdsourcing (i.e. volunteer-assisted data collection by means of Internet applications), a lesson plan has been written to teachers. The so acquired Tea Bag Index (TBI) provides process-driven information on soil functions at local, regional and global scales essential for future climate modelling; and it is sensitive enough to discriminate data between different ecosystems and soil types. The lesson plan will enable students to understand the concept of decomposition and its relevance for soil fertility and our climate. TBI requires only little means and knowledge, making data collection by crowdsourcing possible. Successful results have already been attained by scout groups in Austria. Engaging schools classes as co-researchers would enlarge the crowdsourcing potential of the TBI. Subsequently, it will increase awareness of soils and provide essential development in including soils more frequently into the natural sciences and environmental classes at schools. The numerous data points collected will allow for a great leap forward in mapping decomposition, as well as understanding and modelling the global carbon cycle.
Factors influencing leaf litter decomposition: An intersite decomposition experiment across China

USGS Publications Warehouse

Zhou, G.; Guan, L.; Wei, X.; Tang, X.; Liu, S.; Liu, J.; Zhang, Dongxiao; Yan, J.

2008-01-01

The Long-Term Intersite Decomposition Experiment in China (hereafter referred to as LTIDE-China) was established in 2002 to study how substrate quality and macroclimate factors affect leaf litter decomposition. The LTIDE-China includes a wide variety of natural and managed ecosystems, consisting of 12 forest types (eight regional broadleaf forests, three needle-leaf plantations and one broadleaf plantation) at eight locations across China. Samples of mixed leaf litter from the south subtropical evergreen broadleaf forest in Dinghushan (referred to as the DHS sample) were translocated to all 12 forest types. The leaf litter from each of other 11 forest types was placed in its original forest to enable comparison of decomposition rates of DHS and local litters. The experiment lasted for 30 months, involving collection of litterbags from each site every 3 months. Our results show that annual decomposition rate-constants, as represented by regression fitted k-values, ranged from 0.169 to 1.454/year. Climatic factors control the decomposition rate, in which mean annual temperature and annual actual evapotranspiration are dominant and mean annual precipitation is subordinate. Initial C/N and N/P ratios were demonstrated to be important factors of regulating litter decomposition rate. Decomposition process may apparently be divided into two phases controlled by different factors. In our study, 0.75 years is believed to be the dividing line of the two phases. The fact that decomposition rates of DHS litters were slower than those of local litters may have been resulted from the acclimation of local decomposer communities to extraneous substrate. ?? 2008 Springer Science+Business Media B.V.
Climate and litter quality differently modulate the effects of soil fauna on litter decomposition across biomes

PubMed Central

García-Palacios, Pablo; Maestre, Fernando T.; Kattge, Jens; Wall, Diana H.

2015-01-01

Climate and litter quality have been identified as major drivers of litter decomposition at large spatial scales. However, the role played by soil fauna remains largely unknown, despite its importance for litter fragmentation and microbial activity. We synthesized litterbag studies to quantify the effect sizes of soil fauna on litter decomposition rates at the global and biome scales, and to assess how climate, litter quality and soil fauna interact to determine such rates. Soil fauna consistently enhanced litter decomposition at both global and biome scales (average increment ~27%). However, climate and litter quality differently modulated the effects of soil fauna on decomposition rates between biomes, from climate-driven biomes to those where climate effects were mediated by changes in litter quality. Our results advocate for the inclusion of biome-specific soil fauna effects on litter decomposition as a mean to reduce the unexplained variation in large-scale decomposition models. PMID:23763716
Decomposition Rate and Pattern in Hanging Pigs.

PubMed

Lynch-Aird, Jeanne; Moffatt, Colin; Simmons, Tal

2015-09-01

Accurate prediction of the postmortem interval requires an understanding of the decomposition process and the factors acting upon it. A controlled experiment, over 60 days at an outdoor site in the northwest of England, used 20 freshly killed pigs (Sus scrofa) as human analogues to study decomposition rate and pattern. Ten pigs were hung off the ground and ten placed on the surface. Observed differences in the decomposition pattern required a new decomposition scoring scale to be produced for the hanging pigs to enable comparisons with the surface pigs. The difference in the rate of decomposition between hanging and surface pigs was statistically significant (p=0.001). Hanging pigs reached advanced decomposition stages sooner, but lagged behind during the early stages. This delay is believed to result from lower variety and quantity of insects, due to restricted beetle access to the aerial carcass, and/or writhing maggots falling from the carcass. © 2015 American Academy of Forensic Sciences.
Soil C and N availability determine the priming effect: microbial N mining and stoichiometric decomposition theories.

PubMed

Chen, Ruirui; Senbayram, Mehmet; Blagodatsky, Sergey; Myachina, Olga; Dittert, Klaus; Lin, Xiangui; Blagodatskaya, Evgenia; Kuzyakov, Yakov

2014-07-01

The increasing input of anthropogenically derived nitrogen (N) to ecosystems raises a crucial question: how does available N modify the decomposer community and thus affects the mineralization of soil organic matter (SOM). Moreover, N input modifies the priming effect (PE), that is, the effect of fresh organics on the microbial decomposition of SOM. We studied the interactive effects of C and N on SOM mineralization (by natural (13) C labelling adding C4 -sucrose or C4 -maize straw to C3 -soil) in relation to microbial growth kinetics and to the activities of five hydrolytic enzymes. This encompasses the groups of parameters governing two mechanisms of priming effects - microbial N mining and stoichiometric decomposition theories. In sole C treatments, positive PE was accompanied by a decrease in specific microbial growth rates, confirming a greater contribution of K-strategists to the decomposition of native SOM. Sucrose addition with N significantly accelerated mineralization of native SOM, whereas mineral N added with plant residues accelerated decomposition of plant residues. This supports the microbial mining theory in terms of N limitation. Sucrose addition with N was accompanied by accelerated microbial growth, increased activities of β-glucosidase and cellobiohydrolase, and decreased activities of xylanase and leucine amino peptidase. This indicated an increased contribution of r-strategists to the PE and to decomposition of cellulose but the decreased hemicellulolytic and proteolytic activities. Thus, the acceleration of the C cycle was primed by exogenous organic C and was controlled by N. This confirms the stoichiometric decomposition theory. Both K- and r-strategists were beneficial for priming effects, with an increasing contribution of K-selected species under N limitation. Thus, the priming phenomenon described in 'microbial N mining' theory can be ascribed to K-strategists. In contrast, 'stoichiometric decomposition' theory, that is, accelerated OM mineralization due to balanced microbial growth, is explained by domination of r-strategists. © 2013 John Wiley & Sons Ltd.
Soil C and N availability determine the priming effect: microbial N mining and stoichiometric decomposition theories

NASA Astrophysics Data System (ADS)

Chen, Ruirui; Senbayram, Mehmet; Blagodatsky, Sergey; Dittert, Klaus; Lin, Xiangui; Blagodatskaya, Evgenia; Kuzyakov, Yakov

2014-05-01

The increasing input of anthropogenically derived nitrogen (N) to ecosystems raises a crucial question: how does available N modify the decomposer community and thus affects the mineralization of soil organic matter (SOM). Moreover, N input modifies the priming effect (PE), that is, the effect of fresh organics on the microbial decomposition of SOM. We studied the interactive effects of C and N on SOM mineralization (by natural 13C labelling adding C4-sucrose or C4-maize straw to C3-soil) in relation to microbial growth kinetics and to the activities of five hydrolytic enzymes. This encompasses the groups of parameters governing two mechanisms of priming effects - microbial N mining and stoichiometric decomposition theories. In sole C treatments, positive PE was accompanied by a decrease in specific microbial growth rates, confirming a greater contribution of K-strategists to the decomposition of native SOM. Sucrose addition with N significantly accelerated mineralization of native SOM, whereas mineral N added with plant residues accelerated decomposition of plant residues. This supports the microbial mining theory in terms of N limitation. Sucrose addition with N was accompanied by accelerated microbial growth, increased activities of β-glucosidase and cellobiohydrolase, and decreased activities of xylanase and leucine amino peptidase. This indicated an increased contribution of r-strategists to the PE and to decomposition of cellulose but the decreased hemicellulolytic and proteolytic activities. Thus, the acceleration of the C cycle was primed by exogenous organic C and was controlled by N. This confirms the stoichiometric decomposition theory. Both K- and r-strategists were beneficial for priming effects, with an increasing contribution of K-selected species under N limitation. Thus, the priming phenomenon described in 'microbial N mining' theory can be ascribed to K-strategists. In contrast, 'stoichiometric decomposition' theory, that is, accelerated OM mineralization due to balanced microbial growth, is explained by domination of r-strategists.
A test of the hierarchical model of litter decomposition.

PubMed

Bradford, Mark A; Veen, G F Ciska; Bonis, Anne; Bradford, Ella M; Classen, Aimee T; Cornelissen, J Hans C; Crowther, Thomas W; De Long, Jonathan R; Freschet, Gregoire T; Kardol, Paul; Manrubia-Freixa, Marta; Maynard, Daniel S; Newman, Gregory S; Logtestijn, Richard S P; Viketoft, Maria; Wardle, David A; Wieder, William R; Wood, Stephen A; van der Putten, Wim H

2017-12-01

Our basic understanding of plant litter decomposition informs the assumptions underlying widely applied soil biogeochemical models, including those embedded in Earth system models. Confidence in projected carbon cycle-climate feedbacks therefore depends on accurate knowledge about the controls regulating the rate at which plant biomass is decomposed into products such as CO 2 . Here we test underlying assumptions of the dominant conceptual model of litter decomposition. The model posits that a primary control on the rate of decomposition at regional to global scales is climate (temperature and moisture), with the controlling effects of decomposers negligible at such broad spatial scales. Using a regional-scale litter decomposition experiment at six sites spanning from northern Sweden to southern France-and capturing both within and among site variation in putative controls-we find that contrary to predictions from the hierarchical model, decomposer (microbial) biomass strongly regulates decomposition at regional scales. Furthermore, the size of the microbial biomass dictates the absolute change in decomposition rates with changing climate variables. Our findings suggest the need for revision of the hierarchical model, with decomposers acting as both local- and broad-scale controls on litter decomposition rates, necessitating their explicit consideration in global biogeochemical models.
Dry-season ultraviolet radiation primes litter for wet season decomposition in a Mediterranean grassland

NASA Astrophysics Data System (ADS)

Baker, N. R.; Allison, S. D.

2013-12-01

Traditional decomposition models developed in mesic ecosystems often consistently underestimate rates of decomposition in more arid ecosystems such as deserts and Mediterranean grasslands. Photodegradation of plant litter by ultraviolet radiation (UV) is hypothesized to be one of the mechanisms accounting for the greater-than-expected rates of decomposition observed in these ecosystems. Putatively, photodegradation preferentially degrades complex aromatic compounds in litter such as lignin, whose decomposition is considered a rate-limiting step in the microbial decomposition of plant litter. This study tested the effects of attenuated ultraviolet radiation on the decomposition of two litter types over the course of a year in a Southern California Mediterranean grassland. The two types of litter differed primarily in lignin content to test for a differential effect of UV on high-lignin versus low-lignin litter. Rates of litter mass loss, changes in litter chemistry, and changes in microbial activity and microbial biomass were observed, and assays of extracellular enzymes were conducted at 5 points through the year, beginning during the dry season and continuing until the end of the following dry season. Litter exposed to attenuated ultraviolet radiation during the dry season had lower rates of mass loss than litter exposed to ambient radiation (6.1% vs. 8.6%, respectively, p < 0.04). Extracellular enzyme activities were significantly affected by UV attenuation, as low lignin samples exposed to attenuated UV displayed elevated cellulase enzyme activity potential during the wet season, while high lignin samples displayed decreased oxidative enzyme activity potential during the wet season. For example, potential activity of the cellulase cellobiohydrolase in low-lignin, ambient UV samples was 5286 μmol/hr*g during the wet season, compared to 7969 μmol/hr*g in attenuated UV samples (p < 0.003). Conversely, potential activity of the oxidative enzyme peroxidase in high-lignin, ambient UV samples was 85.9 μmol/hr*g during the wet season, compared to 44.1 μmol/hr*g in attenuated UV samples (p < 0.028). This increased potential cellulase activity under attenuated UV may indicate that dry season photodegradation primes low-lignin litter for wet season decomposition, reducing the selective pressure for microbial decomposers to invest in costly extracellular enzyme production. Similarly, the reduced potential oxidative enzyme activity in high-lignin samples exposed to attenuated UV may indicate that photodegradation is necessary to facilitate the breakdown of more complex compounds such as lignin by microbial decomposers. We conclude that while abiotic factors such as photodegradation can have a significant effect on the mechanisms of plant matter decomposition in semiarid ecosystems, these effects are not only restricted to the dry season and may also facilitate wet season decomposition.
Interspecific variations in mangrove leaf litter decomposition are related to labile nitrogenous compounds

NASA Astrophysics Data System (ADS)

Nordhaus, Inga; Salewski, Tabea; Jennerjahn, Tim C.

2017-06-01

Mangrove leaves form a large pool of carbon, nitrogen and energy that is a major driver of element cycles and detrital food webs inside mangrove forests as well as in adjacent coastal waters. However, there are large gaps in knowledge on the transformation pathways and ultimate fate of leaf nitrogen. Therefore, the main objective of this study was to determine the amount and composition of nitrogenous organic matter and possible species-specific differences during the decomposition of mangrove leaf litter. For that purpose a three month decomposition experiment with litterbags was conducted using leaves of Aegiceras corniculatum, Avicennia alba, Ceriops decandra, Rhizophora apiculata, and Sonneratia caseolaris in the mangrove forest of the Segara Anakan Lagoon, Java, Indonesia. Detrital leaves were analyzed for bulk carbon and total nitrogen (N), stable carbon and nitrogen isotope composition (δ13C, δ15N), total hydrolyzable amino acids (THAA) and total hydrolyzable hexosamines (THHA). Decomposition rates (k d-1) were highest and tM50 values (when 50% of the original mass had been degraded) lowest in S. caseolaris (k = 0.0382 d-1; tM50 = 18 days), followed by A. alba, C. decandra, A. corniculatum, and R. apiculata (k = 0.0098 d-1; tM50 = 71 days). The biochemical composition of detrital leaves differed significantly among species and over time. S. caseolaris and A. alba had higher concentrations of N, THAA and THHA and a lower C/N ratio than the other three species. For most of the species concentrations of N, THAA and THHA increased during decomposition. The hexosamine galactosamine, indicative of bacterial cell walls, was first found in leaves after 5-7 days of decomposition and increased afterwards. Our findings suggest an increasing, but species-specific varying, portion of labile nitrogenous OM and total N in decomposing leaves over time that is partly related to the activity of leaf-colonizing bacteria. Despite a higher relative nitrogen content in the remaining litter of the fast decomposing S. caseolaris and A. alba as compared to the other three species, the total loss of nitrogen was even higher because of the much higher mass loss after three months of decomposition. It is inferred that the amount of labile nitrogenous organic matter plays a major role in determining the rate of decomposition of leaf litter in mangroves.
Catalytic decomposition of hydrogen peroxide and 4-chlorophenol in the presence of modified activated carbons.

PubMed

Huang, Hsu-Hui; Lu, Ming-Chun; Chen, Jong-Nan; Lee, Cheng-Te

2003-06-01

The objective of this research was to examine the heterogeneous catalytic decomposition of H(2)O(2) and 4-chlorophenol (4-CP) in the presence of activated carbons modified with chemical pretreatments. The decomposition of H(2)O(2) was suppressed significantly by the change of surface properties including the decreased pH(pzc) modified with oxidizing agent and the reduced active sites occupied by the adsorption of 4-CP. The apparent reaction rate of H(2)O(2) decomposition was dominated by the intrinsic reaction rates on the surface of activated carbon rather than the mass transfer rate of H(2)O(2) to the solid surface. By the detection of chloride ion in suspension, the reduction of 4-CP was not only attributed to the advanced adsorption but also the degradation of 4-CP. The catalytic activity toward 4-CP for the activated carbon followed the inverse sequence of the activity toward H(2)O(2), suggesting that acidic surface functional group could retard the H(2)O(2) loss and reduce the effect of surface scavenging resulting in the increase of the 4-CP degradation efficiency. Few effective radicals were expected to react with 4-CP for the strong effect of surface scavenging, which could explain why the degradation rate of 4-CP observed in this study was so slow and the dechlorination efficiency was independent of the 4-CP concentration in aqueous phase. Results show that the combination of H(2)O(2) and granular activated carbon (GAC) did increase the total removal of 4-CP than that by single GAC adsorption.
Chemical manipulation of soil biota in a fescue meadow

DOE Office of Scientific and Technical Information (OSTI.GOV)

Malone, C. R.; Reichle, D. E.

Formalin, phorate, and sodium chlorate were used in field enclosures to create artificial habitats in a fescue meadow containing (1) reduced number of earthworms, (2) reduced numbers of earthworms and soil arthropods, and (3) reduction of total soil fauna and rate of microbial decomposition. Under these conditions, confined fescue litter initially decomposed more rapidly where arthropods or earthworms were suppressed than in controls with full complements of soil animals. After one year, reduction in numbers of soil animals had no net effect on litter decomposition, with faunal activity apparently having been compensated for by increased microbial activity. Where animals andmore » microbial activity were reduced, rate of litter loss was depressed initially but recovered after 10 months as the effects of chemical suppression of microbial populations subsided. Contrary to the effects on annual loss of litter, elimination of all or portions of the soil fauna depressed rates of loss of confined and buried roots, reflecting the role of animals in fragmenting roots before their decomposition by microorganisms. Habitat manipulations had pronounced effects on the mobility of 134Cs, and loss of the radionuclide from labelled litter was retarded despite an accelerated rate of decomposition. This effect apparently was associated with proliferation of microorganisms on litter and microbial immobilization of the radionuclide. Immobilization of 134Cs occurred following chemical perturbations, but only after an initial period of rapid loss resulting from increased microbial activity. Distribution of 134Cs in soil beneath tagged litter bags reflected the role of animals in element redistribution within soil. Finally, restricted vertical mobility of the nuclide occurred except where chemical application killed vegetation within the experimental enclosures.« less
N2-fixing red alder indirectly accelerates ecosystem nitrogen cycling

USGS Publications Warehouse

Perakis, Steven S.; Matkins, Joselin J.; Hibbs, David E.

2012-01-01

Symbiotic N2-fixing tree species can accelerate ecosystem N dynamics through decomposition via direct pathways by producing readily decomposed leaf litter and increasing N supply to decomposers, as well as via indirect pathways by increasing tissue and detrital N in non-fixing vegetation. To evaluate the relative importance of these pathways, we compared three-year decomposition and N dynamics of N2-fixing red alder leaf litter (2.34 %N) to both low-N (0.68 %N) and high-N (1.21 %N) litter of non-fixing Douglas-fir, and decomposed each litter source in four forests dominated by either red alder or Douglas-fir. We also used experimental N fertilization of decomposition plots to assess elevated N availability as a potential mechanism of N2-fixer effects on litter mass loss and N dynamics. Direct effects of N2-fixing red alder on decomposition occurred primarily as faster N release from red alder than Douglas-fir litter, but direct increases in N supply to decomposers via fertilization did not stimulate decomposition of any litter. Fixed N indirectly influenced detrital dynamics by increasing Douglas-fir tissue and litter N concentrations, which accelerated litter N release without accelerating mass loss. By increasing soil N, tissue N, and the rate of N release from litter of non-fixers, we conclude that N2-fixing vegetation can indirectly foster plant-soil feedbacks that contribute to the persistence of elevated N availability in terrestrial ecosystems.
Plant Diversity Impacts Decomposition and Herbivory via Changes in Aboveground Arthropods

PubMed Central

Ebeling, Anne; Meyer, Sebastian T.; Abbas, Maike; Eisenhauer, Nico; Hillebrand, Helmut; Lange, Markus; Scherber, Christoph; Vogel, Anja; Weigelt, Alexandra; Weisser, Wolfgang W.

2014-01-01

Loss of plant diversity influences essential ecosystem processes as aboveground productivity, and can have cascading effects on the arthropod communities in adjacent trophic levels. However, few studies have examined how those changes in arthropod communities can have additional impacts on ecosystem processes caused by them (e.g. pollination, bioturbation, predation, decomposition, herbivory). Therefore, including arthropod effects in predictions of the impact of plant diversity loss on such ecosystem processes is an important but little studied piece of information. In a grassland biodiversity experiment, we addressed this gap by assessing aboveground decomposer and herbivore communities and linking their abundance and diversity to rates of decomposition and herbivory. Path analyses showed that increasing plant diversity led to higher abundance and diversity of decomposing arthropods through higher plant biomass. Higher species richness of decomposers, in turn, enhanced decomposition. Similarly, species-rich plant communities hosted a higher abundance and diversity of herbivores through elevated plant biomass and C:N ratio, leading to higher herbivory rates. Integrating trophic interactions into the study of biodiversity effects is required to understand the multiple pathways by which biodiversity affects ecosystem functioning. PMID:25226237
Linkages between grazing history and herbivore exclusion on decomposition rates in mineral soils of subalpine grasslands

Treesearch

Alan G. Haynes; Martin Schutz; Nina Buchmann; Deborah S. Page-Dumroese; Matt D. Busse; Anita C. Risch

2014-01-01

Herbivore-driven changes to soil properties can influence the decomposition rate of organic material and therefore soil carbon cycling within grassland ecosystems. We investigated how aboveground foraging mammalian and invertebrate herbivores affect mineral soil decomposition rates and associated soil properties in two subalpine vegetation types (shortgrass and tall-...
Understanding litter decomposition in semiarid ecosystems: linking leaf traits, UV exposure and rainfall variability

PubMed Central

Gaxiola, Aurora; Armesto, Juan J.

2015-01-01

Differences in litter quality, microbial activity or abiotic conditions cannot fully account for the variability in decomposition rates observed in semiarid ecosystems. Here we tested the role of variation in litter quality, water supply, and UV radiation as drivers of litter decomposition in arid lands. And show that carry-over effects of litter photodegradation during dry periods can regulate decomposition during subsequent wet periods. We present data from a two-phase experiment, where we first exposed litter from a drought-deciduous and an evergreen shrub to natural UV levels during five, rainless summer months and, subsequently, in the laboratory, we assessed the carry-over effects of photodegradation on biomass loss under different irrigation treatments representing the observed range of local rainfall variation among years (15–240 mm). Photodegradation of litter in the field produced average carbon losses of 12%, but deciduous Proustia pungens lost >25%, while evergreen Porlieria chilensis less than 5%. Natural exposure to UV significantly reduced carbon-to-nitrogen and lignin:N ratios in Proustia litter but not in Porlieria. During the subsequent wet phase, remaining litter biomass was lower in Proustia than in Porlieria. Indeed UV exposure increased litter decomposition of Proustia under low and medium rainfall treatments, whereas no carry-over effects were detected under high rainfall treatment. Consequently, for deciduous Proustia carry-over effects of UV exposure were negligible under high irrigation. Litter decomposition of the evergreen Porlieria depended solely on levels of rainfall that promote microbial decomposers. Our two-phase experiment revealed that both the carry-over effects of photodegradation and litter quality, modulated by inter-annual variability in rainfall, can explain the marked differences in decomposition rates and the frequent decoupling between rainfall and litter decomposition observed in semiarid ecosystems. PMID:25852705
Understanding litter decomposition in semiarid ecosystems: linking leaf traits, UV exposure and rainfall variability.

PubMed

Gaxiola, Aurora; Armesto, Juan J

2015-01-01

Differences in litter quality, microbial activity or abiotic conditions cannot fully account for the variability in decomposition rates observed in semiarid ecosystems. Here we tested the role of variation in litter quality, water supply, and UV radiation as drivers of litter decomposition in arid lands. And show that carry-over effects of litter photodegradation during dry periods can regulate decomposition during subsequent wet periods. We present data from a two-phase experiment, where we first exposed litter from a drought-deciduous and an evergreen shrub to natural UV levels during five, rainless summer months and, subsequently, in the laboratory, we assessed the carry-over effects of photodegradation on biomass loss under different irrigation treatments representing the observed range of local rainfall variation among years (15-240 mm). Photodegradation of litter in the field produced average carbon losses of 12%, but deciduous Proustia pungens lost >25%, while evergreen Porlieria chilensis less than 5%. Natural exposure to UV significantly reduced carbon-to-nitrogen and lignin:N ratios in Proustia litter but not in Porlieria. During the subsequent wet phase, remaining litter biomass was lower in Proustia than in Porlieria. Indeed UV exposure increased litter decomposition of Proustia under low and medium rainfall treatments, whereas no carry-over effects were detected under high rainfall treatment. Consequently, for deciduous Proustia carry-over effects of UV exposure were negligible under high irrigation. Litter decomposition of the evergreen Porlieria depended solely on levels of rainfall that promote microbial decomposers. Our two-phase experiment revealed that both the carry-over effects of photodegradation and litter quality, modulated by inter-annual variability in rainfall, can explain the marked differences in decomposition rates and the frequent decoupling between rainfall and litter decomposition observed in semiarid ecosystems.
Effect of oxidized leachate on degradation of lignin by sulfate-reducing bacteria.

PubMed

Kim, Jong-Ho; Kim, Moonil; Bae, Wooken

2009-08-01

Municipal solid waste materials (MSWs) in landfills need a long period of stabilization because lignin compounds in MSWs and leachate are not readily biodegraded, but inhibit methanogenic metabolism. Recirculation of leachate into the landfill offers the potential advantage of increasing the rate of decomposition of organic matter. However, the degradation of lignin by leachate recirculation alone is quite difficult. Several recent studies have demonstrated that sulfate-reducing bacteria (SRB) were able to degrade lignin compounds. In this study, batch tests were conducted to investigate the impacts of SRB enrichment on lignin decomposition rates as well as the decomposition of other biodegradable organics. Further, the effects of nitrite and nitrate on lignin degradation rates were also studied. A 16S rRNA assay showed that the SRB used herein, which were obtained by enriching solid waste collected from a closed MSW landfill, were Thaurea sp. and Desulfovibrio sp. Lignin was found to be biodegraded by the SRB and the rate of lignin removal per unit of waste volatile suspended solid was 2.9 mg lignin g(-1) VSS day(- 1). It was found that the initial degradation rate increased under higher initial lignin concentrations. However, the degradation rate during days 6-19 became slower than that during the initial 9 days because lignin consisted of complexly bonded aromatic compounds that were not readily biodegradable. Adding other organics such as lactate seemed to improve the rate and amount of lignin degradation, probably due to the increase in SRB associated with consumption of the additional organics. The lignin removal percentage decreased with increases in oxidized nitrogen (nitrite or nitrate) concentrations, indicating that oxidized nitrogen could inhibit SRB activity. Conclusively, the study verified the existence of SRB in the landfill and showed that the SRB could be activated for the degradation of lignin by the recirculation of the leachate, which is consistent with other studies showing that leachate recirculation could shorten the stabilization period of the landfill.
Kinetics and Efficiency of H2O2 Activation by Iron-Containing Minerals and Aquifer Materials

PubMed Central

Pham, Anh Le-Tuan; Doyle, Fiona M.; Sedlak, David L.

2014-01-01

To gain insight into factors that control H2O2 persistence and ˙OH yield in H2O2-based in situ chemical oxidation systems, the decomposition of H2O2 and transformation of phenol were investigated in the presence of iron-containing minerals and aquifer materials. Under conditions expected during remediation of soil and groundwater, the stoichiometric efficiency, defined as the amount of phenol transformed per mole of H2O2 decomposed, varied from 0.005 to 0.28%. Among the iron-containing minerals, iron oxides were 2 to 10 times less efficient in transforming phenol than iron-containing clays and synthetic iron-containing catalysts. In both iron-containing mineral and aquifer materials systems, the stoichiometric efficiency was inversely correlated with the rate of H2O2 decomposition. In aquifer materials systems, the stoichiometric efficiency was also inversely correlated with the Mn content, consistent with the fact that the decomposition of H2O2 on manganese oxides does not produce ˙OH. Removal of iron and manganese oxide coatings from the surface of aquifer materials by extraction with citrate-bicarbonate-dithionite slowed the rate of H2O2 decomposition on aquifer materials and increased the stoichiometric efficiency. In addition, the presence of 2 mM of dissolved SiO2 slowed the rate of H2O2 decomposition on aquifer materials by over 80% without affecting the stoichiometric efficiency. PMID:23047055
Kinetics and efficiency of H2O2 activation by iron-containing minerals and aquifer materials.

PubMed

Pham, Anh Le-Tuan; Doyle, Fiona M; Sedlak, David L

2012-12-01

To gain insight into factors that control H(2)O(2) persistence and ·OH yield in H(2)O(2)-based in situ chemical oxidation systems, the decomposition of H(2)O(2) and transformation of phenol were investigated in the presence of iron-containing minerals and aquifer materials. Under conditions expected during remediation of soil and groundwater, the stoichiometric efficiency, defined as the amount of phenol transformed per mole of H(2)O(2) decomposed, varied from 0.005 to 0.28%. Among the iron-containing minerals, iron oxides were 2-10 times less efficient in transforming phenol than iron-containing clays and synthetic iron-containing catalysts. In both iron-containing mineral and aquifer materials systems, the stoichiometric efficiency was inversely correlated with the rate of H(2)O(2) decomposition. In aquifer materials systems, the stoichiometric efficiency was also inversely correlated with the Mn content, consistent with the fact that the decomposition of H(2)O(2) on manganese oxides does not produce ·OH. Removal of iron and manganese oxide coatings from the surface of aquifer materials by extraction with citrate-bicarbonate-dithionite slowed the rate of H(2)O(2) decomposition on aquifer materials and increased the stoichiometric efficiency. In addition, the presence of 2 mM of dissolved SiO(2) slowed the rate of H(2)O(2) decomposition on aquifer materials by over 80% without affecting the stoichiometric efficiency. Copyright © 2012 Elsevier Ltd. All rights reserved.
Kinetics of gas phase formic acid decomposition on platinum single crystal and polycrystalline surfaces

NASA Astrophysics Data System (ADS)

Detwiler, Michael D.; Milligan, Cory A.; Zemlyanov, Dmitry Y.; Delgass, W. Nicholas; Ribeiro, Fabio H.

2016-06-01

Formic acid dehydrogenation turnover rates (TORs) were measured on Pt(111), Pt(100), and polycrystalline Pt foil surfaces at a total pressure of 800 Torr between 413 and 513 K in a batch reactor connected to an ultra-high vacuum (UHV) system. The TORs, apparent activation energies, and reaction orders are not sensitive to the structure of the Pt surface, within the precision of the measurements. CO introduced into the batch reactor depressed the formic acid dehydrogenation TOR and increased the reaction's apparent activation energies on Pt(111) and Pt(100), consistent with behavior predicted by the Temkin equation. Two reaction mechanisms were explored which explain the formic acid decomposition mechanism on Pt, both of which include dissociative adsorption of formic acid, rate limiting formate decomposition, and quasi-equilibrated hydrogen recombination and CO adsorption. No evidence was found that catalytic supports used in previous studies altered the reaction kinetics or mechanism.

Contrasting effects of plant species traits and moisture on the decomposition of multiple litter fractions.

PubMed

Riggs, Charlotte E; Hobbie, Sarah E; Cavender-Bares, Jeannine; Savage, Jessica A; Wei, Xiaojing

2015-10-01

Environmental variation in moisture directly influences plant litter decomposition through effects on microbial activity, and indirectly via plant species traits. Whether the effects of moisture and plant species traits are mutually reinforcing or counteracting during decomposition are unknown. To disentangle the effects of moisture from the effects of species traits that vary with moisture, we decomposed leaf litter from 12 plant species in the willow family (Salicaceae) with different native habitat moisture preferences in paired mesic and wetland plots. We fit litter mass loss data to an exponential decomposition model and estimated the decay rate of the rapidly cycling litter fraction and size of the remaining fraction that decays at a rate approaching zero. Litter traits that covaried with moisture in the species' native habitat significantly influenced the decomposition rate of the rapidly cycling litter fraction, but moisture in the decomposition environment did not. In contrast, for the slowly cycling litter fraction, litter traits that did not covary with moisture in the species' native habitat and moisture in the decomposition environment were significant. Overall, the effects of moisture and plant species traits on litter decomposition were somewhat reinforcing along a hydrologic gradient that spanned mesic upland to wetland (but not permanently surface-saturated) plots. In this system, plant trait and moisture effects may lead to greater in situ decomposition rates of wetland species compared to upland species; however, plant traits that do not covary with moisture will also influence decomposition of the slowest cycling litter fraction.
Decomposition of standing litter in arid grasslands: Interactions between sunlight, non-rainfall moisture, microbes, and plant traits

NASA Astrophysics Data System (ADS)

Logan, J. R. V.; Jacobson, P. J.; Jacobson, K. M.; Evans, S.

2017-12-01

Although arid lands make up 40% of the Earth's land surface, we still lack a strong understanding of carbon cycling and plant decomposition in these systems. One reason for this is that field studies typically only focus on decomposition at or below the ground surface even though standing dead litter (material that has not yet fallen to the ground) accounts for more than 50% of total necromass in many of these systems. While recent work has begun to recognize the important and unique aspects of standing litter decomposition, few studies have investigated specific mechanisms controlling rates of mass loss. We hypothesized that initial photodegradation of the outer plant cuticle of standing litter is an important determinant of litter decomposition because this process increases moisture absorption and subsequent opportunities for biological decomposition. Our preliminary results offer support for this hypothesis. We found that standing grass stems with their cuticles artificially removed had greater water absorbance and more than 400% greater mass loss over a 6-month period relative to controls with intact cuticles. Additionally, spectroscopic measurements of cuticle integrity showed damage to the litter surface after a period of extended photodegradation, allowing increased moisture uptake during simulated fog/dew events. These findings are especially important in the context of recent work by us and others showing that non-rainfall moisture (fog, dew, and water vapor) plays a much larger role in arid land decomposition than previously thought. Improving our understanding of the mechanisms driving decomposition of standing litter will enable us to develop a more predictive understanding of carbon storage in arid lands.
Influence of Different Forest System Management Practices on Leaf Litter Decomposition Rates, Nutrient Dynamics and the Activity of Ligninolytic Enzymes: A Case Study from Central European Forests

PubMed Central

Schulz, Elke; Schloter, Michael; Buscot, François; Hofrichter, Martin; Krüger, Dirk

2014-01-01

Leaf litter decomposition is the key ecological process that determines the sustainability of managed forest ecosystems, however very few studies hitherto have investigated this process with respect to silvicultural management practices. The aims of the present study were to investigate the effects of forest management practices on leaf litter decomposition rates, nutrient dynamics (C, N, Mg, K, Ca, P) and the activity of ligninolytic enzymes. We approached these questions using a 473 day long litterbag experiment. We found that age-class beech and spruce forests (high forest management intensity) had significantly higher decomposition rates and nutrient release (most nutrients) than unmanaged deciduous forest reserves (P<0.05). The site with near-to-nature forest management (low forest management intensity) exhibited no significant differences in litter decomposition rate, C release, lignin decomposition, and C/N, lignin/N and ligninolytic enzyme patterns compared to the unmanaged deciduous forest reserves, but most nutrient dynamics examined in this study were significantly faster under such near-to-nature forest management practices. Analyzing the activities of ligninolytic enzymes provided evidence that different forest system management practices affect litter decomposition by changing microbial enzyme activities, at least over the investigated time frame of 473 days (laccase, P<0.0001; manganese peroxidase (MnP), P = 0.0260). Our results also indicate that lignin decomposition is the rate limiting step in leaf litter decomposition and that MnP is one of the key oxidative enzymes of litter degradation. We demonstrate here that forest system management practices can significantly affect important ecological processes and services such as decomposition and nutrient cycling. PMID:24699676
Influence of different forest system management practices on leaf litter decomposition rates, nutrient dynamics and the activity of ligninolytic enzymes: a case study from central European forests.

PubMed

Purahong, Witoon; Kapturska, Danuta; Pecyna, Marek J; Schulz, Elke; Schloter, Michael; Buscot, François; Hofrichter, Martin; Krüger, Dirk

2014-01-01

Leaf litter decomposition is the key ecological process that determines the sustainability of managed forest ecosystems, however very few studies hitherto have investigated this process with respect to silvicultural management practices. The aims of the present study were to investigate the effects of forest management practices on leaf litter decomposition rates, nutrient dynamics (C, N, Mg, K, Ca, P) and the activity of ligninolytic enzymes. We approached these questions using a 473 day long litterbag experiment. We found that age-class beech and spruce forests (high forest management intensity) had significantly higher decomposition rates and nutrient release (most nutrients) than unmanaged deciduous forest reserves (P<0.05). The site with near-to-nature forest management (low forest management intensity) exhibited no significant differences in litter decomposition rate, C release, lignin decomposition, and C/N, lignin/N and ligninolytic enzyme patterns compared to the unmanaged deciduous forest reserves, but most nutrient dynamics examined in this study were significantly faster under such near-to-nature forest management practices. Analyzing the activities of ligninolytic enzymes provided evidence that different forest system management practices affect litter decomposition by changing microbial enzyme activities, at least over the investigated time frame of 473 days (laccase, P<0.0001; manganese peroxidase (MnP), P = 0.0260). Our results also indicate that lignin decomposition is the rate limiting step in leaf litter decomposition and that MnP is one of the key oxidative enzymes of litter degradation. We demonstrate here that forest system management practices can significantly affect important ecological processes and services such as decomposition and nutrient cycling.
Legume presence reduces the decomposition rate of non-legume roots, role of plant traits?

NASA Astrophysics Data System (ADS)

De Deyn, Gerlinde B.; Saar, Sirgi; Barel, Janna; Semchenko, Marina

2016-04-01

Plant litter traits are known to play an important role in the rate of litter decomposition and mineralization, both for aboveground and belowground litter. However also the biotic and abiotic environment in which the litter decomposes plays a significant role in the rate of decomposition. The presence of living plants may accelerate litter decomposition rates via a priming effects. The size of this effect is expected to be related to the traits of the litter. In this study we focus on root litter, given that roots and their link to ecosystem processes have received relatively little attention in trait-based research. To test the effect of a growing legume plant on root decomposition and the role of root traits in this we used dead roots of 7 different grassland species (comprising grasses, a forb and legumes), determined their C, N, P content and quantified litter mass loss after eight weeks of incubation in soil with and without white clover. We expected faster root decomposition with white clover, especially for root litter with low N content. In contrast we found slower decomposition of grass and forb roots which were poor in N (negative priming) in presence of white clover, while decomposition rates of legume roots were not affected by the presence of white clover. Overall we found that root decomposition can be slowed down in the presence of a living plant and that this effect depends on the traits of the decomposing roots, with a pronounced reduction in root litter poor in N and P, but not in the relatively nutrient-rich legume root litters. The negative priming effect of legume plants on non-legume litter decomposition may have resulted from preferential substrate utilisation by soil microbes.
The Effect of Clothing on the Rate of Decomposition and Diptera Colonization on Sus scrofa Carcasses.

PubMed

Card, Allison; Cross, Peter; Moffatt, Colin; Simmons, Tal

2015-07-01

Twenty Sus scrofa carcasses were used to study the effect the presence of clothing had on decomposition rate and colonization locations of Diptera species; 10 unclothed control carcasses were compared to 10 clothed experimental carcasses over 58 days. Data collection occurred at regular accumulated degree day intervals; the level of decomposition as Total Body Score (TBSsurf ), pattern of decomposition, and Diptera present was documented. Results indicated a statistically significant difference in the rate of decomposition, (t427 = 2.59, p = 0.010), with unclothed carcasses decomposing faster than clothed carcasses. However, the overall decomposition rates from each carcass group are too similar to separate when applying a 95% CI, which means that, although statistically significant, from a practical forensic point of view they are not sufficiently dissimilar as to warrant the application of different formulae to estimate the postmortem interval. Further results demonstrated clothing provided blow flies with additional colonization locations. © 2015 American Academy of Forensic Sciences.
Spider foraging strategy affects trophic cascades under natural and drought conditions.

PubMed

Liu, Shengjie; Chen, Jin; Gan, Wenjin; Schaefer, Douglas; Gan, Jianmin; Yang, Xiaodong

2015-07-23

Spiders can cause trophic cascades affecting litter decomposition rates. However, it remains unclear how spiders with different foraging strategies influence faunal communities, or present cascading effects on decomposition. Furthermore, increased dry periods predicted in future climates will likely have important consequences for trophic interactions in detritus-based food webs. We investigated independent and interactive effects of spider predation and drought on litter decomposition in a tropical forest floor. We manipulated densities of dominant spiders with actively hunting or sit-and-wait foraging strategies in microcosms which mimicked the tropical-forest floor. We found a positive trophic cascade on litter decomposition was triggered by actively hunting spiders under ambient rainfall, but sit-and-wait spiders did not cause this. The drought treatment reversed the effect of actively hunting spiders on litter decomposition. Under drought conditions, we observed negative trophic cascade effects on litter decomposition in all three spider treatments. Thus, reduced rainfall can alter predator-induced indirect effects on lower trophic levels and ecosystem processes, and is an example of how such changes may alter trophic cascades in detritus-based webs of tropical forests.
Spider foraging strategy affects trophic cascades under natural and drought conditions

PubMed Central

Liu, Shengjie; Chen, Jin; Gan, Wenjin; Schaefer, Douglas; Gan, Jianmin; Yang, Xiaodong

2015-01-01

Spiders can cause trophic cascades affecting litter decomposition rates. However, it remains unclear how spiders with different foraging strategies influence faunal communities, or present cascading effects on decomposition. Furthermore, increased dry periods predicted in future climates will likely have important consequences for trophic interactions in detritus-based food webs. We investigated independent and interactive effects of spider predation and drought on litter decomposition in a tropical forest floor. We manipulated densities of dominant spiders with actively hunting or sit-and-wait foraging strategies in microcosms which mimicked the tropical-forest floor. We found a positive trophic cascade on litter decomposition was triggered by actively hunting spiders under ambient rainfall, but sit-and-wait spiders did not cause this. The drought treatment reversed the effect of actively hunting spiders on litter decomposition. Under drought conditions, we observed negative trophic cascade effects on litter decomposition in all three spider treatments. Thus, reduced rainfall can alter predator-induced indirect effects on lower trophic levels and ecosystem processes, and is an example of how such changes may alter trophic cascades in detritus-based webs of tropical forests. PMID:26202370
The Utility of Decomposition and Associated Microbial Parameters to Assess Changes in Stream Ecosystems due to Eutrophication

NASA Astrophysics Data System (ADS)

Gulis, V.; Ferreira, V. J.; Graca, M. A.

2005-05-01

Traditional approaches to assess stream ecosystem health rely on structural parameters, e.g. a variety of biotic indices. The goal of the Europe-wide RivFunction project is to develop methodology that uses functional parameters (e.g. plant litter decomposition) to this end. Here we report on decomposition experiments carried out in Portugal in five pairs of streams that differed in dissolved inorganic nutrients. On average, decomposition rates of alder and oak leaves were 2.8 and 1.4 times higher in high nutrient streams in coarse and fine mesh bags, respectively, than in corresponding reference streams. Breakdown rate correlated better with stream water SRP concentration rather than TIN. Fungal biomass and sporulation rates of aquatic hyphomycetes associated with decomposing leaves were stimulated by higher nutrient levels. Both fungal parameters measured at very early stages of decomposition (e.g. days 7-13) correlated well with overall decomposition rates. Eutrophication had no significant effect on shredder abundances in leaf bags but species richness was higher in disturbed streams. Decomposition is a key functional parameter in streams integrating many other variables and can be useful in assessing stream ecosystem health. We also argue that because decomposition is often controlled by fungal activity, microbial parameters can also be useful in bioassessment.
Root traits predict decomposition across a landscape-scale grazing experiment

PubMed Central

Smith, Stuart W; Woodin, Sarah J; Pakeman, Robin J; Johnson, David; van der Wal, René

2014-01-01

Root litter is the dominant soil carbon and nutrient input in many ecosystems, yet few studies have considered how root decomposition is regulated at the landscape scale and how this is mediated by land-use management practices. Large herbivores can potentially influence below-ground decomposition through changes in soil microclimate (temperature and moisture) and changes in plant species composition (root traits). To investigate such herbivore-induced changes, we quantified annual root decomposition of upland grassland species in situ across a landscape-scale livestock grazing experiment, in a common-garden experiment and in laboratory microcosms evaluating the influence of key root traits on decomposition. Livestock grazing increased soil temperatures, but this did not affect root decomposition. Grazing had no effect on soil moisture, but wetter soils retarded root decomposition. Species-specific decomposition rates were similar across all grazing treatments, and species differences were maintained in the common-garden experiment, suggesting an overriding importance of litter type. Supporting this, in microcosms, roots with lower specific root area (m2 g−1) or those with higher phosphorus concentrations decomposed faster. Our results suggest that large herbivores alter below-ground carbon and nitrogen dynamics more through their effects on plant species composition and associated root traits than through effects on the soil microclimate. PMID:24841886
Carbon dioxide emissions from the electricity sector in major countries: a decomposition analysis.

PubMed

Li, Xiangzheng; Liao, Hua; Du, Yun-Fei; Wang, Ce; Wang, Jin-Wei; Liu, Yanan

2018-03-01

The electric power sector is one of the primary sources of CO 2 emissions. Analyzing the influential factors that result in CO 2 emissions from the power sector would provide valuable information to reduce the world's CO 2 emissions. Herein, we applied the Divisia decomposition method to analyze the influential factors for CO 2 emissions from the power sector from 11 countries, which account for 67% of the world's emissions from 1990 to 2013. We decompose the influential factors for CO 2 emissions into seven areas: the emission coefficient, energy intensity, the share of electricity generation, the share of thermal power generation, electricity intensity, economic activity, and population. The decomposition analysis results show that economic activity, population, and the emission coefficient have positive roles in increasing CO 2 emissions, and their contribution rates are 119, 23.9, and 0.5%, respectively. Energy intensity, electricity intensity, the share of electricity generation, and the share of thermal power generation curb CO 2 emissions and their contribution rates are 17.2, 15.7, 7.7, and 2.8%, respectively. Through decomposition analysis for each country, economic activity and population are the major factors responsible for increasing CO 2 emissions from the power sector. However, the other factors from developed countries can offset the growth in CO 2 emissions due to economic activities.
Rate of hexabromocyclododecane decomposition and production of brominated polycyclic aromatic hydrocarbons during combustion in a pilot-scale incinerator.

PubMed

Miyake, Yuichi; Tokumura, Masahiro; Wang, Qi; Amagai, Takashi; Horii, Yuichi

2017-11-01

Here, we examined the incineration of extruded polystyrene containing hexabromocyclododecane (HBCD) in a pilot-scale incinerator under various combustion temperatures (800-950°C) and flue gas residence times (2-8sec). Rates of HBCD decomposition ranged from 99.996% (800°C, 2sec) to 99.9999% (950°C, 8sec); the decomposition of HBCD, except during the initial stage of combustion (flue gas residence time<2sec), followed a pseudo-first-order kinetics model. An Arrhenius plot revealed that the activation energy and frequency factor of the decomposition of HBCD by combustion were 14.2kJ/mol and 1.69sec -1 , respectively. During combustion, 11 brominated polycyclic aromatic hydrocarbons (BrPAHs) were detected as unintentional by-products. Of the 11 BrPAHs detected, 2-bromoanthracene and 1-bromopyrene were detected at the highest concentrations. The mutagenic and carcinogenic BrPAHs 1,5-dibromoanthracene and 1-bromopyrene were most frequently detected in the flue gases analyzed. The total concentration of BrPAHs exponentially increased (range, 87.8-2,040,000ng/m 3 ) with increasing flue gas residence time. Results from a qualitative analysis using gas chromatography/high-resolution mass spectrometry suggest that bromofluorene and bromopyrene (or fluoranthene) congeners were also produced during the combustion. Copyright © 2017. Published by Elsevier B.V.
Increased nitrogen availability counteracts climatic change feedback from increased temperature on boreal forest soil organic matter degradation

NASA Astrophysics Data System (ADS)

Erhagen, Bjorn; Nilsson, Mats; Oquist, Mats; Ilstedt, Ulrik; Sparrman, Tobias; Schleucher, Jurgen

2014-05-01

Over the last century, the greenhouse gas concentrations in the atmosphere have increased dramatically, greatly exceeding pre-industrial levels that had prevailed for the preceding 420 000 years. At the same time the annual anthropogenic contribution to the global terrestrial nitrogen cycle has increased and currently exceeds natural inputs. Both temperature and nitrogen levels have profound effects on the global carbon cycle including the rate of organic matter decomposition, which is the most important biogeochemical process that returns CO2 to the atmosphere. Here we show for the first time that increasing the availability of nitrogen not only directly affects the rate of organic matter decomposition but also significantly affects its temperature dependence. We incubated litter and soil organic matter from a long-term (40 years) nitrogen fertilization experiment in a boreal Scots pine (Pinus silvestris L.) forest at different temperatures and determined the temperature dependence of the decomposition of the sample's organic matter in each case. Nitrogen fertilization did not affect the temperature sensitivity (Q10) of the decomposition of fresh plant litter but strongly reduced that for humus soil organic matter. The Q10 response of the 0-3 cm soil layer decreased from 2.5±0.35 to an average of 1.9±0.21 over all nitrogen treatments, and from 2.2±0.19 to 1.6±0.16 in response to the most intense nitrogen fertilization treatment in the 4-7 cm soil layer. Long-term nitrogen additions also significantly affected the organic chemical composition (as determined by 13C CP-MAS NMR spectroscopy) of the soil organic matter. These changes in chemical composition contributed significantly (p<0.05) to the reduced Q10 response. These new insights into the relationship between nitrogen availability and the temperature sensitivity of organic matter decomposition will be important for understanding and predicting how increases in global temperature and rising anthropogenic nitrogen inputs will affect the global carbon cycle and the associated climatic feedback processes.
Climate and litter quality differently modulate the effects of soil fauna on litter decomposition across biomes.

PubMed

García-Palacios, Pablo; Maestre, Fernando T; Kattge, Jens; Wall, Diana H

2013-08-01

Climate and litter quality have been identified as major drivers of litter decomposition at large spatial scales. However, the role played by soil fauna remains largely unknown, despite its importance for litter fragmentation and microbial activity. We synthesised litterbag studies to quantify the effect sizes of soil fauna on litter decomposition rates at the global and biome scales, and to assess how climate, litter quality and soil fauna interact to determine such rates. Soil fauna consistently enhanced litter decomposition at both global and biome scales (average increment ~ 37%). [corrected]. However, climate and litter quality differently modulated the effects of soil fauna on decomposition rates between biomes, from climate-driven biomes to those where climate effects were mediated by changes in litter quality. Our results advocate for the inclusion of biome-specific soil fauna effects on litter decomposition as a mean to reduce the unexplained variation in large-scale decomposition models. © 2013 John Wiley & Sons Ltd/CNRS.
Plants mediate soil organic matter decomposition in response to sea level rise.

PubMed

Mueller, Peter; Jensen, Kai; Megonigal, James Patrick

2016-01-01

Tidal marshes have a large capacity for producing and storing organic matter, making their role in the global carbon budget disproportionate to land area. Most of the organic matter stored in these systems is in soils where it contributes 2-5 times more to surface accretion than an equal mass of minerals. Soil organic matter (SOM) sequestration is the primary process by which tidal marshes become perched high in the tidal frame, decreasing their vulnerability to accelerated relative sea level rise (RSLR). Plant growth responses to RSLR are well understood and represented in century-scale forecast models of soil surface elevation change. We understand far less about the response of SOM decomposition to accelerated RSLR. Here we quantified the effects of flooding depth and duration on SOM decomposition by exposing planted and unplanted field-based mesocosms to experimentally manipulated relative sea level over two consecutive growing seasons. SOM decomposition was quantified as CO2 efflux, with plant- and SOM-derived CO2 separated via δ(13) CO2 . Despite the dominant paradigm that decomposition rates are inversely related to flooding, SOM decomposition in the absence of plants was not sensitive to flooding depth and duration. The presence of plants had a dramatic effect on SOM decomposition, increasing SOM-derived CO2 flux by up to 267% and 125% (in 2012 and 2013, respectively) compared to unplanted controls in the two growing seasons. Furthermore, plant stimulation of SOM decomposition was strongly and positively related to plant biomass and in particular aboveground biomass. We conclude that SOM decomposition rates are not directly driven by relative sea level and its effect on oxygen diffusion through soil, but indirectly by plant responses to relative sea level. If this result applies more generally to tidal wetlands, it has important implications for models of SOM accumulation and surface elevation change in response to accelerated RSLR. © 2015 John Wiley & Sons Ltd.
Elevated tropospheric CO2 and O3 may not alter initial wood decomposition rate or wood-decaying fungal community composition of Northern hardwoods

Treesearch

Emmanuel Ebanyenle; Andrew J. Burton; Andrew J. Storer; Dana L. Richter; Jessie A. Glaeser

2016-01-01

We examined the effects of elevated CO2 and/or O3 on the wood-decaying basidiomycete fungal community and wood decomposition rates at the Aspen Free-Air CO2 and O3 Enrichment (Aspen FACE) project. Mass loss rates were determined after one year of log decomposition on the soil...
[Contribution of soil fauna to litter decomposition of Abies faxoniana and Rhododendron lapponicum across an alpine timberline ecotone in Western Sichuan, China.

PubMed

Wang, Li Feng; He, Run Lian; Yang, Lin; Chen, Ya Mei; Liu, Yang; Zhang, Jian

2016-11-18

Soil fauna is an important biological factor in regulation litter decomposition. In order to quantify the contributions of soil fauna to the mass losses of litter of two dominant species fir (Abies faxoniana) and rhododendron (Rhododendron lapponicum) in the alpine timberline ecotone (coniferous forest-timberline-alpine meadow) of western Sichuan, China, a field litterbag experiment was conducted from May 2013 to November 2014. Samples of air-dried leaf litter were placed in nylon litterbags of two different mesh sizes, i.e. 3.00 mm (with the soil animals) and 0.04 mm (excluded the soil animals). The results showed that the decomposition rate of A. faxoniana (k: 0.209-0.243) was higher than that of R. lapponicum (k: 0.173-0.189) across the timberline ecotone. Soil fauna had significant contributions to litter decomposition of two species, the contributions of soil fauna to mass loss showed a decreasing trend with increasing altitude. From the coniferous forest to the alpine meadow, the mass losses caused by soil fauna for the fir litter accounted for 15.2%, 13.2% and 9.8%, respectively and that for the rhododendron litter accounted for 20.1%, 17.5% and 12.4%, respectively. Meanwhile, the daily average contributions caused by soil fauna for the fir and rhododendron litter decomposition accounted for 0.17%, 0.13%, 0.12% and 0.26%, 0.25%, 0.23%, respectively. Relatively, soil fauna had more influence on alpine rhododendron decomposition. Two-way ANOVA showed that species, altitude and their interaction had significant impact on the litter mass loss and decomposition rate caused by soil fauna. The daily average contribution caused by soil fauna for the fir and rhododendron litter decomposition accounted for 0.25% and 0.44% in the first growing season, then 0.10% and 0.19% in the second growing season, both were higher than that of snow-covered season (0.07% and 0.12%). Regression analysis showed that the environmental factors (daily average temperature, freezing and thawing cycles and snow thickness) explained 42.7% and 50.9% in the mass loss as well as 43.2% and 55.6% in the contribution rate of fir and rhododendron litter decomposition. These results suggest that soil fauna contributes strongly to litter decomposition in the alpine ecosystem, and it is of great significance to thorough understanding and recognizing material cycle through the role of soil fauna in the litter decomposition.
Aridity and decomposition processes in complex landscapes

NASA Astrophysics Data System (ADS)

Ossola, Alessandro; Nyman, Petter

2015-04-01

Decomposition of organic matter is a key biogeochemical process contributing to nutrient cycles, carbon fluxes and soil development. The activity of decomposers depends on microclimate, with temperature and rainfall being major drivers. In complex terrain the fine-scale variation in microclimate (and hence water availability) as a result of slope orientation is caused by differences in incoming radiation and surface temperature. Aridity, measured as the long-term balance between net radiation and rainfall, is a metric that can be used to represent variations in water availability within the landscape. Since aridity metrics can be obtained at fine spatial scales, they could theoretically be used to investigate how decomposition processes vary across complex landscapes. In this study, four research sites were selected in tall open sclerophyll forest along a aridity gradient (Budyko dryness index ranging from 1.56 -2.22) where microclimate, litter moisture and soil moisture were monitored continuously for one year. Litter bags were packed to estimate decomposition rates (k) using leaves of a tree species not present in the study area (Eucalyptus globulus) in order to avoid home-field advantage effects. Litter mass loss was measured to assess the activity of macro-decomposers (6mm litter bag mesh size), meso-decomposers (1 mm mesh), microbes above-ground (0.2 mm mesh) and microbes below-ground (2 cm depth, 0.2 mm mesh). Four replicates for each set of bags were installed at each site and bags were collected at 1, 2, 4, 7 and 12 months since installation. We first tested whether differences in microclimate due to slope orientation have significant effects on decomposition processes. Then the dryness index was related to decomposition rates to evaluate if small-scale variation in decomposition can be predicted using readily available information on rainfall and radiation. Decomposition rates (k), calculated fitting single pool negative exponential models, generally decreased with increasing aridity with k going from 0.0025 day-1 on equatorial (dry) facing slopes to 0.0040 day-1 on polar (wet) facing slopes. However, differences in temperature as a result of morning vs afternoon sun on east and west aspects, respectively, (not captured in the aridity metric) resulted in poor prediction of decomposition for the sites located in the intermediate aridity range. Overall the results highlight that relatively small differences in microclimate due to slope orientation can have large effects on decomposition. Future research will aim to refine the aridity metric to better resolve small scale variation in surface temperature which is important when up-scaling decomposition processes to landscapes.
pH controls over methanogenesis and iron reduction along soil depth profile in Arctic tundra

NASA Astrophysics Data System (ADS)

Zheng, J.; Gu, B.; Wullschleger, S. D.; Graham, D. E.

2017-12-01

Increasing soil temperature in the Arctic is expected to accelerate rates of soil organic matter decomposition. However, the magnitude of this impact is uncertain due to the many physical, chemical, and biological processes that control the decomposition pathways. Varying soil redox conditions present a key control over pathways of organic matter decomposition by diverting the flow of reductants among different electron accepting processes and further driving acid-base reactions that alter soil pH. In this study we investigated the pH controls over anaerobic carbon mineralization, methanogenesis, Fe(III) reduction and the interplay between these processes across a range of pH and redox conditions. pH manipulation experiments were conducted by incubating soils representing organic, mineral, cryoturbated transitional layers and permafrost. In the experiments we sought to understand (1) if methanogenesis or Fe(III) reduction had similar pH optima; (2) if this pH response also occurs at `upstream' fermentation process; and (3) if pH alters organo-mineral association or organic matter sorption and desorption and its availability for microbial degradation. Our preliminary results suggest that the common bell-shaped pH response curve provides a good fit for both Fe(III) reduction and methanogenesis, with optimum pH at 6.0-7.0. Exceptions to this were found in transitional layer where methanogenesis rates positively correlated with increasing pH, with maximum rates measured at pH 8.5. It is likely that the transitional layer harbors distinct groups of methanogens that prefer a high pH. Variations in the optimum pH of Fe(III) reduction and methanogenesis may play a significant role in regulating organic matter decomposition pathways and thus greenhouse gas production in thawing soils. These results support biogeochemical modeling efforts to accurately simulate organic matter decomposition under changing redox and pH conditions.
Molecular dynamics simulations of methane hydrate decomposition.

PubMed

Myshakin, Evgeniy M; Jiang, Hao; Warzinski, Robert P; Jordan, Kenneth D

2009-03-12

Molecular dynamics simulations have been carried out to study decomposition of methane hydrate at different cage occupancies. The decomposition rate is found to depend sensitively on the hydration number. The rate of the destruction of the cages displays Arrhenius behavior, consistent with an activated mechanism. During the simulations, reversible formation of partial water cages around methane molecules in the liquid was observed at the interface at temperatures above the computed hydrate decomposition temperature.

Effects of Nitrogen Addition on Litter Decomposition and CO2 Release: Considering Changes in Litter Quantity

PubMed Central

Li, Hui-Chao; Hu, Ya-Lin; Mao, Rong; Zhao, Qiong; Zeng, De-Hui

2015-01-01

This study aims to evaluate the impacts of changes in litter quantity under simulated N deposition on litter decomposition, CO2 release, and soil C loss potential in a larch plantation in Northeast China. We conducted a laboratory incubation experiment using soil and litter collected from control and N addition (100 kg ha−1 year−1 for 10 years) plots. Different quantities of litter (0, 1, 2 and 4 g) were placed on 150 g soils collected from the same plots and incubated in microcosms for 270 days. We found that increased litter input strongly stimulated litter decomposition rate and CO2 release in both control and N fertilization microcosms, though reduced soil microbial biomass C (MBC) and dissolved inorganic N (DIN) concentration. Carbon input (C loss from litter decomposition) and carbon output (the cumulative C loss due to respiration) elevated with increasing litter input in both control and N fertilization microcosms. However, soil C loss potentials (C output–C input) reduced by 62% in control microcosms and 111% in N fertilization microcosms when litter addition increased from 1 g to 4 g, respectively. Our results indicated that increased litter input had a potential to suppress soil organic C loss especially for N addition plots. PMID:26657180
An Apparatus for High-Pressure Thermogravimetry.

DTIC Science & Technology

sulfate pentahydrate to show relatively unchanged decomposition rates with increased pressure. (Author)...Thermograms are presented to show typical operation and performance of the apparatus, using aniline to demonstrate retardation of evaporation and copper
Differential Decomposition Among Pig, Rabbit, and Human Remains.

PubMed

Dautartas, Angela; Kenyhercz, Michael W; Vidoli, Giovanna M; Meadows Jantz, Lee; Mundorff, Amy; Steadman, Dawnie Wolfe

2018-03-30

While nonhuman animal remains are often utilized in forensic research to develop methods to estimate the postmortem interval, systematic studies that directly validate animals as proxies for human decomposition are lacking. The current project compared decomposition rates among pigs, rabbits, and humans at the University of Tennessee's Anthropology Research Facility across three seasonal trials that spanned nearly 2 years. The Total Body Score (TBS) method was applied to quantify decomposition changes and calculate the postmortem interval (PMI) in accumulated degree days (ADD). Decomposition trajectories were analyzed by comparing the estimated and actual ADD for each seasonal trial and by fuzzy cluster analysis. The cluster analysis demonstrated that the rabbits formed one group while pigs and humans, although more similar to each other than either to rabbits, still showed important differences in decomposition patterns. The decomposition trends show that neither nonhuman model captured the pattern, rate, and variability of human decomposition. © 2018 American Academy of Forensic Sciences.
BASE-CATALYZED DESTRUCTION OF PCBS-NEW DONORS, NEW TRANSFER AGENTS/CATALYSTS

EPA Science Inventory

The use of hydrogen transfer agents and catalysts to improve the base-catalyzed decomposition of polychlorinated biphenyls (PCBs) was investigated. The reaction proceeded only in the presence of base, but the rate of PCB disappearance increased with increasing amount of hydrogen ...
Decomposition patterns of buried remains at different intervals in the Central Highveld region of South Africa.

PubMed

Marais-Werner, A; Myburgh, J; Meyer, A; Nienaber, W C; Steyn, M

2017-07-01

Burial of remains is an important factor when one attempts to establish the post-mortem interval as it reduces, and in extreme cases, excludes oviposition by Diptera species. This in turn leads to modification of the decomposition process. The aim of this study was to record decomposition patterns of buried remains using a pig model. The pattern of decomposition was evaluated at different intervals and recorded according to existing guidelines. In order to contribute to our knowledge on decomposition in different settings, a quantifiable approach was followed. Results indicated that early stages of decomposition occurred rapidly for buried remains within 7-33 days. Between 14 and 33 days, buried pigs displayed common features associated with the early to middle stages of decomposition, such as discoloration and bloating. From 33 to 90 days advanced decomposition manifested on the remains, and pigs then reached a stage of advanced decomposition where little change was observed in the next ±90-183 days after interment. Throughout this study, total body scores remained higher for surface remains. Overall, buried pigs followed a similar pattern of decomposition to those of surface remains, although at a much slower rate when compared with similar post-mortem intervals in surface remains. In this study, the decomposition patterns and rates of buried remains were mostly influenced by limited insect activity and adipocere formation which reduces the rate of decay in a conducive environment (i.e. burial in soil).
Decadal changes in peat carbon accrual rates in bogs in Northern Minnesota

NASA Astrophysics Data System (ADS)

Fissore, C.; Nater, E. A.; McFarlane, K. J.

2017-12-01

Throughout the Holocene, peatland ecosystems have accumulated substantial amounts of carbon (C) and currently store about one third of all soil organic carbon (SOC) worldwide. Large uncertainty still persists on whether peatland ecosystems located in northern latitudes will continue to act as C sinks, or if the effects of global warming will have greater effects on decomposition processes than on net ecosystem production. We investigated decadal C accrual rates of the top 25 cm of peats in three Sphagnum-rich peatlands located in Northern Minnesota (two ombrotrophic bogs and one fen). We used radiocarbon analysis of Sphagnum cellulose and model fitting to determine peat ages, and peat FTIR spectroscopy to determine humification indices and relative decomposition of peat samples with depth. We had the scope to detect whether recent warming has had an effect on peat decomposition and C accumulation rates. Modeled C accumulation rates in the three peatlands during the past five decades ranged between 78 and 107 g C m-2 yr-1 in the top 25 cm analyzed in this study, values that are higher than the 22 to 29 g C m-2 yr-1 obtained for long-term (millennial) accumulations for the entire bog profiles. Peat IR spectra and C:N ratios confirm low levels of decomposition across the bog sites, especially in the uppermost parts of the peat. The fen site showed very limited decomposition across the entire sampled profile. Higher rates of C accumulation, combined with low decomposition rates close to the surface provide a good estimate of net primary productivity. As substrate decomposition progresses over time, net rates of accumulation decrease. Peat decomposition was more pronounced in the lower depths of the sampled cores in the two ombrotrophic bogs than in the fen, likely an effect of larger temporal variation in water table depth in the bogs than in the fen. Some of the variation in C accumulation and decomposition observed in our bogs and fen suggests that future C accumulation rates will also largely depend on the effect of warming on hydrology, rather than temperature alone.
Physico-chemical protection, rather than biochemical composition, governs the responses of soil organic carbon decomposition to nitrogen addition in a temperate agroecosystem.

PubMed

Tan, Wenbing; Wang, Guoan; Huang, Caihong; Gao, Rutai; Xi, Beidou; Zhu, Biao

2017-11-15

The heterogeneous responses of soil organic carbon (SOC) decomposition in different soil fractions to nitrogen (N) addition remain elusive. In this study, turnover rates of SOC in different aggregate fractions were quantified based on changes in δ 13 C following the conversion of C 3 to C 4 vegetation in a temperate agroecosystem. The turnover of both total organic matter and specific organic compound classes within each aggregate fraction was inhibited by N addition. Moreover, the intensity of inhibition increases with decreasing aggregate size and increasing N addition level, but does not vary among chemical compound classes within each aggregate fraction. Overall, the response of SOC decomposition to N addition is dependent on the physico-chemical protection of SOC by aggregates and minerals, rather than the biochemical composition of organic substrates. The results of this study could help to understand the fate of SOC in the context of increasing N deposition. Copyright © 2017 Elsevier B.V. All rights reserved.
Effects of biopretreatment of corn stover with white-rot fungus on low-temperature pyrolysis products.

PubMed

Yang, Xuewei; Ma, Fuying; Yu, Hongbo; Zhang, Xiaoyu; Chen, Shulin

2011-02-01

The thermal decomposition of biopretreated corn stover during the low temperature has been studied by using the Py-GC/MS analysis and thermogravimetric analysis with the distributed activation energy model (DAEM). Results showed that biopretreatment with white-rot fungus Echinodontium taxodii 2538 can improve the low-temperature pyrolysis of biomass, by increasing the pyrolysis products of cellulose, hemicellulose (furfural and sucrose increased up to 4.68-fold and 2.94-fold respectively) and lignin (biophenyl and 3,7,11,15-tetramethyl-2-hexadecen-1-ol increased 2.45-fold and 4.22-fold, respectively). Calculated by DAEM method, it showed that biopretreatment can decrease the activation energy during the low temperature range, accelerate the reaction rate and start the thermal decomposition with lower temperature. ATR-FTIR results showed that the deconstruction of lignin and the decomposition of the main linkages between hemicellulose and lignin could contribute to the improvement of the pyrolysis at low temperature. Copyright © 2010 Elsevier Ltd. All rights reserved.
Coupling experimental data and a prototype model to probe the physical and chemical processes of 2,4-dinitroimidazole solid-phase thermal decomposition

DOE Office of Scientific and Technical Information (OSTI.GOV)

Behrens, R.; Minier, L.; Bulusu, S.

1998-12-31

The time-dependent, solid-phase thermal decomposition behavior of 2,4-dinitroimidazole (2,4-DNI) has been measured utilizing simultaneous thermogravimetric modulated beam mass spectrometry (STMBMS) methods. The decomposition products consist of gaseous and non-volatile polymeric products. The temporal behavior of the gas formation rates of the identified products indicate that the overall thermal decomposition process is complex. In isothermal experiments with 2,4-DNI in the solid phase, four distinguishing features are observed: (1) elevated rates of gas formation are observed during the early stages of the decomposition, which appear to be correlated to the presence of exogenous water in the sample; (2) this is followed bymore » a period of relatively constant rates of gas formation; (3) next, the rates of gas formation accelerate, characteristic of an autocatalytic reaction; (4) finally, the 2,4-DNI is depleted and gaseous decomposition products continue to evolve at a decreasing rate. A physicochemical and mathematical model of the decomposition of 2,4-DNI has been developed and applied to the experimental results. The first generation of this model is described in this paper. Differences between the first generation of the model and the experimental data collected under different conditions suggest refinements for the next generation of the model.« less
Experimental and modeling study on decomposition kinetics of methane hydrates in different media.

PubMed

Liang, Minyan; Chen, Guangjin; Sun, Changyu; Yan, Lijun; Liu, Jiang; Ma, Qinglan

2005-10-13

The decomposition kinetic behaviors of methane hydrates formed in 5 cm3 porous wet activated carbon were studied experimentally in a closed system in the temperature range of 275.8-264.4 K. The decomposition rates of methane hydrates formed from 5 cm3 of pure free water and an aqueous solution of 650 g x m(-3) sodium dodecyl sulfate (SDS) were also measured for comparison. The decomposition rates of methane hydrates in seven different cases were compared. The results showed that the methane hydrates dissociate more rapidly in porous activated carbon than in free systems. A mathematical model was developed for describing the decomposition kinetic behavior of methane hydrates below ice point based on an ice-shielding mechanism in which a porous ice layer was assumed to be formed during the decomposition of hydrate, and the diffusion of methane molecules through it was assumed to be one of the control steps. The parameters of the model were determined by correlating the decomposition rate data, and the activation energies were further determined with respect to three different media. The model was found to well describe the decomposition kinetic behavior of methane hydrate in different media.
The potential phototoxicity of nano-scale ZnO induced by visible light on freshwater ecosystems.

PubMed

Du, Jingjing; Qv, Mingxiang; Zhang, Yuyan; Yin, Xiaoyun; Wan, Ning; Zhang, Baozhong; Zhang, Hongzhong

2018-06-06

With the development of nanotechnology, nanomaterials have been widely applied in anti-bacterial coating, electronic device, and personal care products. NanoZnO is one of the most used materials and its ecotoxicity has been extensively studied. To explore the potential phototoxicity of nanoZnO induced by visible light, we conducted a long-term experiment on litter decomposition of Typha angustifolia leaves with assessment of fungal multifaceted natures. After 158 d exposure, the decomposition rate of leaf litter was decreased by nanoZnO but no additional effect by visible light. However, visible light enhanced the inhibitory effect of nanoZnO on fungal sporulation rate due to light-induced dissolution of nanoZnO. On the contrary, enzymes such as β-glucosidase, cellobiohydrolase, and leucine-aminopeptidase were significantly increased by the interaction of nanoZnO and visible light, which led to high efficiency of leaf carbon decomposition. Furthermore, different treatments and exposure time separated fungal community associated with litter decomposition. Therefore, the study provided the evidence of the contribution of visible light to nanoparticle phototoxicity at the ecosystem level. Copyright © 2018 Elsevier Ltd. All rights reserved.
Mass loss and chemical structures of wheat and maize straws in response to ultraviolet-B radiation and soil contact.

PubMed

Zhou, Guixiang; Zhang, Jiabao; Mao, Jingdong; Zhang, Congzhi; Chen, Lin; Xin, Xiuli; Zhao, Bingzi

2015-10-01

The role of photodegradation, an abiotic process, has been largely overlooked during straw decomposition in mesic ecosystems. We investigated the mass loss and chemical structures of straw decomposition in response to elevated UV-B radiation with or without soil contact over a 12-month litterbag experiment. Wheat and maize straw samples with and without soil contact were exposed to three radiation levels: a no-sunlight control, ambient solar UV-B, and artificially elevated UV-B radiation. A block control with soil contact was not included. Compared with the no-sunlight control, UV-B radiation increased the mass loss by 14-19% and the ambient radiation by 9-16% for wheat and maize straws without soil contact after 12 months. Elevated UV-B exposure decreased the decomposition rates of both wheat and maize straws when in contact with soil. Light exposure resulted in decreased O-alkyl carbons and increased alkyl carbons for both the wheat and maize straws compared with no-sunlight control. The difference in soil contact may influence the contribution of photodegradation to the overall straw decomposition process. These results indicate that we must take into account the effects of photodegradation when explaining the mechanisms of straw decomposition in mesic ecosystems.
Mass loss and chemical structures of wheat and maize straws in response to ultraviolet-B radiation and soil contact

PubMed Central

Zhou, Guixiang; Zhang, Jiabao; Mao, Jingdong; Zhang, Congzhi; Chen, Lin; Xin, Xiuli; Zhao, Bingzi

2015-01-01

The role of photodegradation, an abiotic process, has been largely overlooked during straw decomposition in mesic ecosystems. We investigated the mass loss and chemical structures of straw decomposition in response to elevated UV-B radiation with or without soil contact over a 12-month litterbag experiment. Wheat and maize straw samples with and without soil contact were exposed to three radiation levels: a no-sunlight control, ambient solar UV-B, and artificially elevated UV-B radiation. A block control with soil contact was not included. Compared with the no-sunlight control, UV-B radiation increased the mass loss by 14–19% and the ambient radiation by 9–16% for wheat and maize straws without soil contact after 12 months. Elevated UV-B exposure decreased the decomposition rates of both wheat and maize straws when in contact with soil. Light exposure resulted in decreased O-alkyl carbons and increased alkyl carbons for both the wheat and maize straws compared with no-sunlight control. The difference in soil contact may influence the contribution of photodegradation to the overall straw decomposition process. These results indicate that we must take into account the effects of photodegradation when explaining the mechanisms of straw decomposition in mesic ecosystems. PMID:26423726
Thermal explosion analysis of methyl ethyl ketone peroxide by non-isothermal and isothermal calorimetric applications.

PubMed

Chi, Jen-Hao; Wu, Sheng-Hung; Shu, Chi-Min

2009-11-15

In the past, process incidents attributed to organic peroxides (OPs) that involved near misses, over-pressures, runaway reactions, and thermal explosions occurred because of poor training, human error, incorrect kinetic assumptions, insufficient change management, and inadequate chemical knowledge in the manufacturing process. Calorimetric applications were employed broadly to test organic peroxides on a small-scale because of their thermal hazards, such as exothermic behavior and self-accelerating decomposition in the laboratory. In essence, methyl ethyl ketone peroxide (MEKPO) is highly reactive and exothermically unstable. In recent years, it has undergone many thermal explosions and runaway reaction incidents in the manufacturing process. Differential scanning calorimetry (DSC), vent sizing package 2 (VSP2), and thermal activity monitor (TAM) were employed to analyze thermokinetic parameters and safety index. The intent of the analyses was to facilitate the use of various auto-alarm equipments to detect over-pressure, over-temperature, and hazardous materials leaks for a wide spectrum of operations. Results indicated that MEKPO decomposition is detected at low temperatures (30-40 degrees C), and the rate of decomposition was shown to exponentially increase with temperature and pressure. Determining time to maximum rate (TMR), self-accelerating decomposition temperature (SADT), maximum temperature (T(max)), exothermic onset temperature (T(0)), and heat of decomposition (DeltaH(d)) was essential for identifying early-stage runaway reactions effectively for industries.
Relationship between the Decomposition Process of Coarse Woody Debris and Fungal Community Structure as Detected by High-Throughput Sequencing in a Deciduous Broad-Leaved Forest in Japan

PubMed Central

Yamashita, Satoshi; Masuya, Hayato; Abe, Shin; Masaki, Takashi; Okabe, Kimiko

2015-01-01

We examined the relationship between the community structure of wood-decaying fungi, detected by high-throughput sequencing, and the decomposition rate using 13 years of data from a forest dynamics plot. For molecular analysis and wood density measurements, drill dust samples were collected from logs and stumps of Fagus and Quercus in the plot. Regression using a negative exponential model between wood density and time since death revealed that the decomposition rate of Fagus was greater than that of Quercus. The residual between the expected value obtained from the regression curve and the observed wood density was used as a decomposition rate index. Principal component analysis showed that the fungal community compositions of both Fagus and Quercus changed with time since death. Principal component analysis axis scores were used as an index of fungal community composition. A structural equation model for each wood genus was used to assess the effect of fungal community structure traits on the decomposition rate and how the fungal community structure was determined by the traits of coarse woody debris. Results of the structural equation model suggested that the decomposition rate of Fagus was affected by two fungal community composition components: one that was affected by time since death and another that was not affected by the traits of coarse woody debris. In contrast, the decomposition rate of Quercus was not affected by coarse woody debris traits or fungal community structure. These findings suggest that, in the case of Fagus coarse woody debris, the fungal community structure is related to the decomposition process of its host substrate. Because fungal community structure is affected partly by the decay stage and wood density of its substrate, these factors influence each other. Further research on interactive effects is needed to improve our understanding of the relationship between fungal community structure and the woody debris decomposition process. PMID:26110605
Enhanced decomposition offsets enhanced productivity and soil carbon accumulation in coastal wetlands responding to climate change

USGS Publications Warehouse

Kirwan, M.L.; Blum, L.K.

2011-01-01

Coastal wetlands are responsible for about half of all carbon burial in oceans, and their persistence as a valuable ecosystem depends largely on the ability to accumulate organic material at rates equivalent to relative sea level rise. Recent work suggests that elevated CO2 and temperature warming will increase organic matter productivity and the ability of marshes to survive sea level rise. However, we find that organic decomposition rates increase by about 12% per degree of warming. Our measured temperature sensitivity is similar to studies from terrestrial systems, twice as high as the response of salt marsh productivity to temperature warming, and roughly equivalent to the productivity response associated with elevated CO2 in C3 marsh plants. Therefore, enhanced CO2 and warmer temperatures may actually make marshes less resilient to sea level rise, and tend to promote a release of soil carbon. Simple projections indicate that elevated temperatures will increase rates of sea level rise more than any acceleration in organic matter accumulation, suggesting the possibility of a positive feedback between climate, sea level rise, and carbon emissions in coastal environments.
Drought and detritivores determine leaf litter decomposition in calcareous streams of the Ebro catchment (Spain).

PubMed

Monroy, Silvia; Menéndez, Margarita; Basaguren, Ana; Pérez, Javier; Elosegi, Arturo; Pozo, Jesús

2016-12-15

Drought, an important environmental factor affecting the functioning of stream ecosystems, is likely to become more prevalent in the Mediterranean region as a consequence of climate change and enhanced water demand. Drought can have profound impacts on leaf litter decomposition, a key ecosystem process in headwater streams, but there is still limited information on its effects at the regional scale. We measured leaf litter decomposition across a gradient of aridity in the Ebro River basin. We deployed coarse- and fine-mesh bags with alder and oak leaves in 11 Mediterranean calcareous streams spanning a range of over 400km, and determined changes in discharge, water quality, leaf-associated macroinvertebrates, leaf quality and decomposition rates. The study streams were subject to different degrees of drought, specific discharge (Ls -1 km -2 ) ranging from 0.62 to 9.99. One of the streams dried out during the experiment, another one reached residual flow, whereas the rest registered uninterrupted flow but with different degrees of flow variability. Decomposition rates differed among sites, being lowest in the 2 most water-stressed sites, but showed no general correlation with specific discharge. Microbial decomposition rates were not correlated with final nutrient content of litter nor to fungal biomass. Total decomposition rate of alder was positively correlated to the density and biomass of shredders; that of oak was not. Shredder density in alder bags showed a positive relationship with specific discharge during the decomposition experiment. Overall, the results point to a complex pattern of litter decomposition at the regional scale, as drought affects decomposition directly by emersion of bags and indirectly by affecting the functional composition and density of detritivores. Copyright Â© 2016 The Authors. Published by Elsevier B.V. All rights reserved.
RECONSTRUCTION AND ANALYSIS OF HISTORICAL CHANGES IN CARBON STORAGE IN ARCTIC TUNDRA

EPA Science Inventory

Surface air temperature in arctic regions has increased since pre-industrial times, raising concerns that warmer and possibly drier conditions have increased soil decomposition rates, thereby stimulating the release to the atmosphere of the large stores of carbon (C) in arctic so...
High heating rate decomposition dynamics of copper oxide by nanocalorimetry-coupled time-of-flight mass spectrometry

NASA Astrophysics Data System (ADS)

Yi, Feng; DeLisio, Jeffery B.; Nguyen, Nam; Zachariah, Michael R.; LaVan, David A.

2017-12-01

The thermodynamics and evolved gases were measured during the rapid decomposition of copper oxide (CuO) thin film at rates exceeding 100,000 K/s. CuO decomposes to release oxygen when heated and serves as an oxidizer in reactive composites and chemical looping combustion. Other instruments have shown either one or two decomposition steps during heating. We have confirmed that CuO decomposes by two steps at both slower and higher heating rates. The decomposition path influences the reaction course in reactive Al/CuO/Al composites, and full understanding is important in designing reactive mixtures and other new reactive materials.
Hot and sour in the deep ocean

NASA Astrophysics Data System (ADS)

Sabine, Christopher L.

2017-12-01

Stable layering in the ocean limits the rate that human-derived carbon dioxide can acidify the deep ocean. Now observations show that ocean warming, however, can enhance deep-ocean acidification through increased organic matter decomposition.

Chronic impacts of TiO2 nanoparticles on Populus nigra L. leaf decomposition in freshwater ecosystem.

PubMed

Du, Jingjing; Zhang, Yuyan; Guo, Wei; Li, Ningyun; Gao, Chaoshuai; Cui, Minghui; Lin, Zhongdian; Wei, Mingbao; Zhang, Hongzhong

2018-05-15

Titanium dioxide (TiO 2 ) nanoparticles have been applied in diverse commercial products, which could lead to toxic effects on aquatic microbes and would inhibit some important ecosystem processes. The study aimed to investigate the chronic impacts of TiO 2 nanoparticles with different concentrations (5, 50, and 500 mg L -1 ) on Populus nigra L. leaf decomposition in the freshwater ecosystem. After 50 d of decomposing, a significant decrease in decomposition rates was observed with higher concentrations of TiO 2 nanoparticles. During the period of litter decomposition, exposure of TiO 2 nanoparticles led to decreases in extracellular enzyme activities, which was caused by the reduction of microbial especially fungal biomass. In addition, the diversity and composition of the fungal community associated with litter decomposition were strongly affected by the concentrations of TiO 2 nanoparticles. The diversity and composition of the fungal community associated with litter decomposition was strongly affected. The abundance of Tricladium chaetocladium decreased with the increasing concentrations of TiO 2 nanoparticles, indicating the little contribution of the species to the litter decomposition. In conclusion, this study provided the evidence for the chronic exposure effects of TiO 2 nanoparticles on the litter decomposition and further the functions of freshwater ecosystems. Copyright © 2018 Elsevier B.V. All rights reserved.
A comparison between decomposition rates of buried and surface remains in a temperate region of South Africa.

PubMed

Marais-Werner, Anátulie; Myburgh, J; Becker, P J; Steyn, M

2018-01-01

Several studies have been conducted on decomposition patterns and rates of surface remains; however, much less are known about this process for buried remains. Understanding the process of decomposition in buried remains is extremely important and aids in criminal investigations, especially when attempting to estimate the post mortem interval (PMI). The aim of this study was to compare the rates of decomposition between buried and surface remains. For this purpose, 25 pigs (Sus scrofa; 45-80 kg) were buried and excavated at different post mortem intervals (7, 14, 33, 92, and 183 days). The observed total body scores were then compared to those of surface remains decomposing at the same location. Stages of decomposition were scored according to separate categories for different anatomical regions based on standardised methods. Variation in the degree of decomposition was considerable especially with the buried 7-day interval pigs that displayed different degrees of discolouration in the lower abdomen and trunk. At 14 and 33 days, buried pigs displayed features commonly associated with the early stages of decomposition, but with less variation. A state of advanced decomposition was reached where little change was observed in the next ±90-183 days after interment. Although the patterns of decomposition for buried and surface remains were very similar, the rates differed considerably. Based on the observations made in this study, guidelines for the estimation of PMI are proposed. This pertains to buried remains found at a depth of approximately 0.75 m in the Central Highveld of South Africa.
Tropical herbivorous phasmids, but not litter snails, alter decomposition rates by modifying litter bacteria

Treesearch

Chelse M. Prather; Gary E. Belovsky; Sharon A. Cantrell; Grizelle González

2018-01-01

Consumers can alter decomposition rates through both feces and selective feeding in many ecosystems, but these combined effects have seldom been examined in tropical ecosystems. Members of the detrital food web (litter-feeders or microbivores) should presumably have greater effects on decomposition than herbivores, members of the green food web. Using litterbag...
Effects of Residue Management on Decomposition in Irrigated Rice Fields Are Not Related to Changes in the Decomposer Community.

PubMed

Schmidt, Anja; John, Katharina; Arida, Gertrudo; Auge, Harald; Brandl, Roland; Horgan, Finbarr G; Hotes, Stefan; Marquez, Leonardo; Radermacher, Nico; Settele, Josef; Wolters, Volkmar; Schädler, Martin

2015-01-01

Decomposers provide an essential ecosystem service that contributes to sustainable production in rice ecosystems by driving the release of nutrients from organic crop residues. During a single rice crop cycle we examined the effects of four different crop residue management practices (rice straw or ash of burned straw scattered on the soil surface or incorporated into the soil) on rice straw decomposition and on the abundance of aquatic and soil-dwelling invertebrates. Mass loss of rice straw in litterbags of two different mesh sizes that either prevented or allowed access of meso- and macro-invertebrates was used as a proxy for decomposition rates. Invertebrates significantly increased total loss of litter mass by up to 30%. Initially, the contribution of invertebrates to decomposition was significantly smaller in plots with rice straw scattered on the soil surface; however, this effect disappeared later in the season. We found no significant responses in microbial decomposition rates to management practices. The abundance of aquatic fauna was higher in fields with rice straw amendment, whereas the abundance of soil fauna fluctuated considerably. There was a clear separation between the overall invertebrate community structure in response to the ash and straw treatments. However, we found no correlation between litter mass loss and abundances of various lineages of invertebrates. Our results indicate that invertebrates can contribute to soil fertility in irrigated paddy fields by decomposing rice straw, and that their abundance as well as efficiency in decomposition may be promoted by crop residue management practices.
Effects of Residue Management on Decomposition in Irrigated Rice Fields Are Not Related to Changes in the Decomposer Community

PubMed Central

Schmidt, Anja; John, Katharina; Arida, Gertrudo; Auge, Harald; Brandl, Roland; Horgan, Finbarr G.; Hotes, Stefan; Marquez, Leonardo; Radermacher, Nico; Settele, Josef; Wolters, Volkmar; Schädler, Martin

2015-01-01

Decomposers provide an essential ecosystem service that contributes to sustainable production in rice ecosystems by driving the release of nutrients from organic crop residues. During a single rice crop cycle we examined the effects of four different crop residue management practices (rice straw or ash of burned straw scattered on the soil surface or incorporated into the soil) on rice straw decomposition and on the abundance of aquatic and soil-dwelling invertebrates. Mass loss of rice straw in litterbags of two different mesh sizes that either prevented or allowed access of meso- and macro-invertebrates was used as a proxy for decomposition rates. Invertebrates significantly increased total loss of litter mass by up to 30%. Initially, the contribution of invertebrates to decomposition was significantly smaller in plots with rice straw scattered on the soil surface; however, this effect disappeared later in the season. We found no significant responses in microbial decomposition rates to management practices. The abundance of aquatic fauna was higher in fields with rice straw amendment, whereas the abundance of soil fauna fluctuated considerably. There was a clear separation between the overall invertebrate community structure in response to the ash and straw treatments. However, we found no correlation between litter mass loss and abundances of various lineages of invertebrates. Our results indicate that invertebrates can contribute to soil fertility in irrigated paddy fields by decomposing rice straw, and that their abundance as well as efficiency in decomposition may be promoted by crop residue management practices. PMID:26225556
Influence of growth conditions on subsequent submonolayer oxide decomposition on Si(111)

NASA Astrophysics Data System (ADS)

Shklyaev, A. A.; Aono, Masakazu; Suzuki, Takanori

1996-10-01

The decomposition kinetics of oxide with a coverage between 0.1 and 0.5 ML, grown by oxidation of the Si(111)-7×7 surface at temperatures between 550 and 800 °C for oxygen pressures (Pox) between 3×10-8 and 2×10-6 Torr, is investigated with optical second-harmonic generation. Through the analysis of the pressure dependence of the initial oxide-growth rate, we separate the conditions for a slow oxide growth at Pox near Ptr(T) and for a rapid oxide growth at Pox>3Ptr(T), where Ptr(T) is the transition pressure to Si-etching regime without oxide growth. For the rapidly grown oxide, the oxide decomposition rate decreases with increasing oxide coverage, whereas the activation energy of about 3 eV does not change significantly. While in the case when the oxide is desorbed at the same temperature as are used for oxide growth, the oxide decomposition is described by an apparent activation energy of 1.5 eV. For the slowly grown oxide of 0.1 ML coverage, the oxide desorption kinetics shows a rapid decomposition stage followed by a slow stage. For the slowly grown oxide of 0.3 ML coverage, the slow stage with a large activation energy of 4.1 eV becomes dominant in the latter part of decomposition. The dependence of the desorption kinetics on the oxide-growth conditions described here could be a reason for the scattering of the kinetic parameters in the literature for O2 interaction with silicon at elevated temperatures.
Species and tissue type regulate long-term decomposition of brackish marsh plants grown under elevated CO2 conditions

NASA Astrophysics Data System (ADS)

Jones, Joshua A.; Cherry, Julia A.; McKee, Karen L.

2016-02-01

Organic matter accumulation, the net effect of plant production and decomposition, contributes to vertical soil accretion in coastal wetlands, thereby playing a key role in whether they keep pace with sea-level rise. Any factor that affects decomposition may affect wetland accretion, including atmospheric CO2 concentrations. Higher CO2 can influence decomposition rates by altering plant tissue chemistry or by causing shifts in plant species composition or biomass partitioning. A combined greenhouse-field experiment examined how elevated CO2 affected plant tissue chemistry and subsequent decomposition of above- and belowground tissues of two common brackish marsh species, Schoenoplectus americanus (C3) and Spartina patens (C4). Both species were grown in monoculture and in mixture under ambient (350-385 μL L-1) or elevated (ambient + 300 μL L-1) atmospheric CO2 conditions, with all other growth conditions held constant, for one growing season. Above- and belowground tissues produced under these treatments were decomposed under ambient field conditions in a brackish marsh in the Mississippi River Delta, USA. Elevated CO2 significantly reduced nitrogen content of S. americanus, but not sufficiently to affect subsequent decomposition. Instead, long-term decomposition (percent mass remaining after 280 d) was controlled by species composition and tissue type. Shoots of S. patens had more mass remaining (41 ± 2%) than those of S. americanus (12 ± 2%). Belowground material decomposed more slowly than that placed aboveground (62 ± 1% vs. 23 ± 3% mass remaining), but rates belowground did not differ between species. Increases in atmospheric CO2 concentration will likely have a greater effect on overall decomposition in this brackish marsh community through shifts in species dominance or biomass allocation than through effects on tissue chemistry. Consequent changes in organic matter accumulation may alter marsh capacity to accommodate sea-level rise through vertical accretion.
Species and tissue type regulate long-term decomposition of brackish marsh plants grown under elevated CO2 conditions

USGS Publications Warehouse

Jones, Joshua A; Cherry, Julia A; Mckee, Karen L.

2016-01-01

Organic matter accumulation, the net effect of plant production and decomposition, contributes to vertical soil accretion in coastal wetlands, thereby playing a key role in whether they keep pace with sea-level rise. Any factor that affects decomposition may affect wetland accretion, including atmospheric CO2 concentrations. Higher CO2 can influence decomposition rates by altering plant tissue chemistry or by causing shifts in plant species composition or biomass partitioning. A combined greenhouse-field experiment examined how elevated CO2 affected plant tissue chemistry and subsequent decomposition of above- and belowground tissues of two common brackish marsh species, Schoenoplectus americanus (C3) and Spartina patens (C4). Both species were grown in monoculture and in mixture under ambient (350-385 μL L-1) or elevated (ambient + 300 μL L-1) atmospheric CO2 conditions, with all other growth conditions held constant, for one growing season. Above- and belowground tissues produced under these treatments were decomposed under ambient field conditions in a brackish marsh in the Mississippi River Delta, USA. Elevated CO2 significantly reduced nitrogen content of S. americanus, but not sufficiently to affect subsequent decomposition. Instead, long-term decomposition (percent mass remaining after 280 d) was controlled by species composition and tissue type. Shoots of S. patens had more mass remaining (41 ± 2%) than those of S. americanus (12 ± 2 %). Belowground material decomposed more slowly than that placed aboveground (62 ± 1% vs. 23 ± 3% mass remaining), but rates belowground did not differ between species. Increases in atmospheric CO2concentration will likely have a greater effect on overall decomposition in this brackish marsh community through shifts in species dominance or biomass allocation than through effects on tissue chemistry. Consequent changes in organic matter accumulation may alter marsh capacity to accommodate sea-level rise through vertical accretion.
Decomposition dynamics of mixed litter in a seasonally flooded forest near the Orinoco river

NASA Astrophysics Data System (ADS)

Bastianoni, Alessia; Chacón, Noemí; Méndez, Carlos L.; Flores, Saúl

2015-04-01

We evaluated the decomposition of a litter mixture in the seasonally flooded forest of a tributary of the Orinoco river. This mixture was prepared using three litter species, based on the litter fall rate observed over a complete hydro-period (2012-2013). The mixture loading ratio was 0.46 of Pouteria orinocoensis (Sapotaceae), 0.38 of Alibertia latifolia (Rubiaceae) and 0.16 of Acosmium nitens (Fabaceae). The initial chemical composition of each single litter species was also determined. Litterbags (20 × 20 cm, 2 mm opening) containing either each single species or the mixture, were deployed on the flooded forest soil and sampled after 30, 240, 270, 300 and 330 days. There were differences in initial total N and P concentrations, with A. nitens (AN) showing the highest nutrient concentrations (%NAN = 1.86 ± 0.19; %PAN = 0.058 ± 0.008) and P. orinocoensis (PO) and A. latifolia (AL) the lowest (%NPO = 0.92 ± 0.06; %NAL = 1.04 ± 0.04; %PPO = 0.029 ± 0.005; %PAL = 0.032 ± 0.001). Litter from AN showed the greatest mass loss (55%) and fastest decomposition rate (k = 0.00185 ± 0.00028) while litter from AL and the mixture showed the smallest mass loss (24% and 27% respectively) and the slowest decomposition rate (kAL = 0.00078 ± 0.00012 and kMIX = 0.00077 ± 0.00006). Decomposition rates were significantly and positively correlated with initial N (r = 0.556, p < 0.05) and P concentrations (r = 0.482, p < 0.05). Nevertheless, there were no significant differences between the expected decomposition rate and the observed decomposition rate of the mixture (additive response). To test the nature of the additivity, an enhancement factor (f) on decomposition rates for each single species was calculated. The species with the highest and smallest value of f were AN and AL, respectively. The fact that two out of the three species had values significantly different from 1, suggests that the additivity detected in our mixture was a consequence of the counterbalancing of the positive and negative effects of each species over the decomposition of the litter mixture.
Development of rate expressions for the thermal decomposition of RDX

DOE Office of Scientific and Technical Information (OSTI.GOV)

Erickson, K.L.; Behrens, R. Jr.; Bulusu, S.

Decomposition and combustion of energetic materials involve processes in both condensed and gas phases. Development of reliable models for design, performance, stability, and hazard analyses requires detailed understanding of the mechanisms for both the initial condensed phase decomposition of the energetic material and the subsequent reaction of the decomposition species to form the ultimate reaction products. Those mechanisms must be described in terms of constitutive rate expressions that can be incorporated into mathematical models. The thermal decomposition of RDX has been studied by Behrens and Bulusu using Simultaneous Thermogravimetric Modulated Beam Mass Spectrometry (STMBMS). Their work provides a basis formore » developing some of the constitutive rate expressions that are needed in models for design, performance, stability and hazard analyses involving RDX. Behrens and Bulusu have identified four primary reaction pathways that control the liquid-phase decomposition of RDX at temperatures between 200 and 215{degrees}C, and one that controls solid-phase decomposition at temperatures below 200{degrees}C. Two of the liquid-phase pathways appear to be first order in RDX. Arrhenius parameters for the first-order rate constants were evaluated from data reported by Behrens and Bulusu. Reaction rates extrapolated to temperatures between 370 and 450{degrees}C are in good agreement with global reaction rates observed by Trott et al. using high-speed photography and laser-heated thin-film samples. Furthermore, the STMBMS results of Behrens and Bulusu appear to be consistent with condensed-phase infrared results reported by Trott et al. and Erickson et al.« less
Development of rate expressions for the thermal decomposition of RDX

DOE Office of Scientific and Technical Information (OSTI.GOV)

Erickson, K.L.; Behrens, R. Jr.; Bulusu, S.

Decomposition and combustion of energetic materials involve processes in both condensed and gas phases. Development of reliable models for design, performance, stability, and hazard analyses requires detailed understanding of the mechanisms for both the initial condensed phase decomposition of the energetic material and the subsequent reaction of the decomposition species to form the ultimate reaction products. Those mechanisms must be described in terms of constitutive rate expressions that can be incorporated into mathematical models. The thermal decomposition of RDX has been studied by Behrens and Bulusu using Simultaneous Thermogravimetric Modulated Beam Mass Spectrometry (STMBMS). Their work provides a basis formore » developing some of the constitutive rate expressions that are needed in models for design, performance, stability and hazard analyses involving RDX. Behrens and Bulusu have identified four primary reaction pathways that control the liquid-phase decomposition of RDX at temperatures between 200 and 215[degrees]C, and one that controls solid-phase decomposition at temperatures below 200[degrees]C. Two of the liquid-phase pathways appear to be first order in RDX. Arrhenius parameters for the first-order rate constants were evaluated from data reported by Behrens and Bulusu. Reaction rates extrapolated to temperatures between 370 and 450[degrees]C are in good agreement with global reaction rates observed by Trott et al. using high-speed photography and laser-heated thin-film samples. Furthermore, the STMBMS results of Behrens and Bulusu appear to be consistent with condensed-phase infrared results reported by Trott et al. and Erickson et al.« less
Short-term Dynamics of Photopriming Increase Carbon Loss During Litter Decomposition

NASA Astrophysics Data System (ADS)

Lin, Y.; King, J. Y.; Karlen, S. D.; Ralph, J.

2017-12-01

Solar radiation plays a key role in carbon (C) cycling by increasing the decomposition rates of plant litter through photodegradation. This process is particularly important in drylands where solar radiation is high and microbial activity may be limited by water availability. One mechanism of photodegradation may be the facilitation of microbial decomposition of litter by altering litter chemistry and consequently degradability, termed photopriming. However, it remains unclear to what extent photopriming contributes to litter decomposition. We evaluated photopriming by ultraviolet (UV) radiation through two laboratory experiments. In one experiment, we found that four months of UV exposure increased mass loss by 3-4% compared to dark treatment in two of three litter species commonly found in California oak savanna; however, UV exposure did not alter litter degradability as measured by microbial respiration in an incubation study. UV exposure had limited effects on lignin and other cell wall structures, but one month of microbial decomposition in the dark significantly reduced lignin β-aryl ether inter-unit linkages and acetylated xylans, which interestingly was the same pattern seen in litter exposed to UV radiation under field conditions and may account for the significant effects of UV exposure on litter mass loss observed in situ. These results indicate that microbial decomposition, not abiotic photodegradation, was ultimately responsible for changes in litter chemistry observed in the field. In a separate experiment, litter of a common grass was incubated for 128 days under either alternating UV radiation and dark conditions at two-day intervals or continuous darkness. During the second half of the experiment, alternating UV exposure increased CO2 production by 35% compared to continuous darkness, suggesting that UV exposure induces subtle but important changes in litter chemistry that facilitate microbial decomposition on a temporal scale of days. Together the results point to microbial facilitation as the primary mechanism of photodegradation and suggest that photopriming is governed by short-term dynamics at the litter-microbe interface. The C cycling associated with these short-term dynamics may be especially sensitive to anticipated increases in drought conditions in drylands.
Prediction of in situ root decomposition rates in an interspecific context from chemical and morphological traits

PubMed Central

Aulen, Maurice; Shipley, Bill; Bradley, Robert

2012-01-01

Background and Aims We quantitatively relate in situ root decomposition rates of a wide range of trees and herbs used in agroforestry to root chemical and morphological traits in order to better describe carbon fluxes from roots to the soil carbon pool across a diverse group of plant species. Methods In situ root decomposition rates were measured over an entire year by an intact core method on ten tree and seven herb species typical of agroforestry systems and were quantified using decay constants (k values) from Olson's single exponential model. Decay constants were related to root chemical (total carbon, nitrogen, soluble carbon, cellulose, hemicellulose, lignin) and morphological (specific root length, specific root length) traits. Traits were measured for both absorbing and non-absorbing roots. Key Results From 61 to 77 % of the variation in the different root traits and 63 % of that in root decomposition rates was interspecific. N was positively correlated, but total carbon and lignin were negatively correlated with k values. Initial root traits accounted for 75 % of the variation in interspecific decomposition rates using partial least squares regressions; partial slopes attributed to each trait were consistent with functional ecology expectations. Conclusions Easily measured initial root traits can be used to predict rates of root decomposition in soils in an interspecific context. PMID:22003237
Spatial Variability in Decomposition of Organic Carbon Along a Meandering River Floodplain

NASA Astrophysics Data System (ADS)

Sutfin, N. A.; Rowland, J. C.; Tfaily, M. M.; Bingol, A. K.; Washton, N.

2017-12-01

Rivers are an important component of the terrestrial carbon cycle and floodplains can provide significant storage of organic carbon. Quantification of long-term storage, however, requires determination of the residence time of sediment and the decomposition rate of organic carbon in floodplains. We use fourier transform ion cyclotron resonance (FTICR) mass spectrometry to examine the organic carbon compounds present in sediment within three floodplain settings: point bars, cutbanks, and abandoned channels. We define decomposition of organic carbon in floodplain sediment as the ratio between the number of protein versus lignin, which serve as proxies for microbial-derived and terrestrial-derived organic carbon, respectively. Samples were collected at 0-5 cm, 5-15cm, and 15-30 cm depth along four transects that span a longitudinal valley distance of 8 km on the East River near Crested Butte, CO. Although no significant trends in decomposition ratio exist longitudinally between the fours transects, floodplain settings exhibit significant differences. At shallow depths (0-5 cm), there are no significant differences among settings, with the exception of gravel portions of point bars below bankfull flow, where the highest decomposition is present. Conversely, cutbanks contain significantly lower decomposition ratios compared with point bars, gravel bars, and abandoned channels when considering all depth intervals. Pointbars exhibit significantly greater protein vs. lignin at the surface compared to greater depth. Higher decomposition ratios along abandoned channels and point bars suggest that frequent wetting and drying periods, abundant oxygen, and continuous downstream movement and decomposition of organic matter occurs within the channel. Lower decomposition ratios and consistent trends with depth along cutbanks, suggest that these stable surfaces serve as organic carbon reservoirs that could become an increased source of carbon to the channel with increasing bank erosion. Detailed differences of organic carbon compounds in sediments of cutbanks, point bars, and abandoned channel will be examined in September 2017 using nuclear magnetic resonance (NMR).
Soil organic matter decomposition follows plant productivity response to sea-level rise

NASA Astrophysics Data System (ADS)

Mueller, Peter; Jensen, Kai; Megonigal, James Patrick

2015-04-01

The accumulation of soil organic matter (SOM) is an important mechanism for many tidal wetlands to keep pace with sea-level rise. SOM accumulation is governed by the rates of production and decomposition of organic matter. While plant productivity responses to sea-level rise are well understood, far less is known about the response of SOM decomposition to accelerated sea-level rise. Here we quantified the effects of sea-level rise on SOM decomposition by exposing planted and unplanted tidal marsh monoliths to experimentally manipulated flood duration. The study was performed in a field-based mesocosm facility at the Smithsonian Global Change Research Wetland, a micro tidal brackish marsh in Maryland, US. SOM decomposition was quantified as CO2 efflux, with plant- and SOM-derived CO2 separated using a stable carbon isotope approach. Despite the dogma that decomposition rates are inversely related to flooding, SOM mineralization was not sensitive to varying flood duration over a 35 cm range in surface elevation in unplanted mesocoms. In the presence of plants, decomposition rates were strongly and positively related to aboveground biomass (p≤0.01, R2≥0.59). We conclude that rates of soil carbon loss through decomposition are driven by plant responses to sea level in this intensively studied tidal marsh. If our result applies more generally to tidal wetlands, it has important implications for modeling carbon sequestration and marsh accretion in response to accelerated sea-level rise.
Effect of liposomes on the rate of alkaline hydrolysis of indomethacin and acemetacin.

PubMed

Matos, C; Chaimovich, H; Lima, J L; Cuccovia, I M; Reis, S

2001-03-01

The anti-inflammatory, analgesic, and antipyretic drugs indomethacin (INDO) and acemetacin (ACE), extensively used for the treatment of diseases of degenerative or inflammatory character, exhibit marked gastric irritant action, have low water solubility at neutral pH, and decompose in alkali. Alternative formulations are being investigated to obtain products with lower toxicity and higher stability. Here we examine the effect of liposome charge on the rate of alkaline decomposition of INDO and ACE using micelles as reference. Binding of ACE and INDO to zwitterionic hexadecylphosphocholine (HDPC) micelles and phosphatidylcholine (PC) liposomes was analyzed using a two-phase separation model to quantify the effect of these aggregates on the rate of alkaline degradation. The substrate association constants to HDPC micelles were 1335 and 2192 M(-1) for INDO and ACE, respectively, whereas the corresponding values for PC vesicles were 612 and 3050 M(-1). The difference was attributed to the additional hydrophobicity of ACE. The inhibitory effect of HDPC micelles and PC vesicles was quantified by calculating the ratio between the rate constants in water (k(w)) and in the aggregate (k(m)). The values of the k(w)/k(m) ratios for INDO and ACE in HDPC micelles were, respectively, 80 and 42, and in PC liposomes these ratios were 21 and 3.7, respectively. Positively charged micelles of hexadecyltrimethylammonium chloride (CTAC) and vesicles containing varying proportions of dioctadecyldimethylammonium chloride (DODAC) and PC increase the rate of INDO and ACE alkaline decomposition. Vesicle effects were very sensitive to the DODAC/PC ratio, with rates increasing with the proportion of DODAC. The data were analyzed quantitatively using a pseudophase model with explicit consideration of ion exchange. The calculated second-order rate constants in micelles and vesicles were lower than that in water. The charge density in the liposome necessary to increase the entrapment efficiency and decrease drug decomposition can be modulated, by judicious choice of pH and ionic strength. These manipulations can lead to more stable formulation with increased efficiency in drug entrapment and controlled effects on drug stability.
Local geology determines responses of stream producers and fungal decomposers to nutrient enrichment: A field experiment.

PubMed

Mykrä, Heikki; Sarremejane, Romain; Laamanen, Tiina; Karjalainen, Satu Maaria; Markkola, Annamari; Lehtinen, Sirkku; Lehosmaa, Kaisa; Muotka, Timo

2018-04-16

We examined how short-term (19 days) nutrient enrichment influences stream fungal and diatom communities, and rates of leaf decomposition and algal biomass accrual. We conducted a field experiment using slow-releasing nutrient pellets to increase nitrate (NO 3 -N) and phosphate (PO 4 -P) concentrations in a riffle section of six naturally acidic (naturally low pH due to catchment geology) and six circumneutral streams. Nutrient enrichment increased microbial decomposition rate on average by 14%, but the effect was significant only in naturally acidic streams. Nutrient enrichment also decreased richness and increased compositional variability of fungal communities in naturally acidic streams. Algal biomass increased in both stream types, but algal growth was overall very low. Diatom richness increased in response to nutrient addition by, but only in circumneutral streams. Our results suggest that primary producers and decomposers are differentially affected by nutrient enrichment and that their responses to excess nutrients are context dependent, with a potentially stronger response of detrital processes and fungal communities in naturally acidic streams than in less selective environments.
Chemistry and long-term decomposition of roots of Douglas-fir grown under elevated atmospheric carbon dioxide and warming conditions.

PubMed

Chen, H; Rygiewicz, P T; Johnson, M G; Harmon, M E; Tian, H; Tang, J W

2008-01-01

Elevated atmospheric CO(2) concentrations and warming may affect the quality of litters of forest plants and their subsequent decomposition in ecosystems, thereby potentially affecting the global carbon cycle. However, few data on root tissues are available to test this feedback to the atmosphere. In this study, we used fine (diameter < or = 2 mm) and small (2-10 mm) roots of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) seedlings that were grown for 4 yr in a 2 x 2 factorial experiment: ambient or elevated (+ 180 ppm) atmospheric CO(2) concentrations, and ambient or elevated (+3.8 degrees C) atmospheric temperature. Exposure to elevated CO(2) significantly increased water-soluble extractives concentration (%WSE), but had little effect on the concentration of N, cellulose, and lignin of roots. Elevated temperature had no effect on substrate quality except for increasing %WSE and decreasing the %lignin content of fine roots. No significant interaction was found between CO(2) and temperature treatments on substrate quality, except for %WSE of the fine roots. Short-term (< or = 9 mo) root decomposition in the field indicated that the roots from the ambient CO(2) and ambient temperature treatment had the slowest rate. However, over a longer period of incubation (9-36 mo) the influence of initial substrate quality on root decomposition diminished. Instead, the location of the field incubation sites exhibited significant control on decomposition. Roots at the warmer, low elevation site decomposed significantly faster than the ones at the cooler, high elevation site. This study indicates that short-term decomposition and long-term responses are not similar. It also suggests that increasing atmospheric CO(2) had little effect on the carbon storage of Douglas-fir old-growth forests of the Pacific Northwest.
Microbial decomposition is highly sensitive to leaf litter emersion in a permanent temperate stream.

PubMed

Mora-Gómez, Juanita; Duarte, Sofia; Cássio, Fernanda; Pascoal, Cláudia; Romaní, Anna M

2018-04-15

Drought frequency and intensity in some temperate regions are forecasted to increase under the ongoing global change, which might expose permanent streams to intermittence and have severe repercussions on stream communities and ecosystem processes. In this study, we investigated the effect of drought duration on microbial decomposition of Populus nigra leaf litter in a temperate permanent stream (Oliveira, NW Portugal). Specifically, we measured the response of the structural (assemblage composition, bacterial and fungal biomass) and functional (leaf litter decomposition, extracellular enzyme activities (EEA), and fungal sporulation) parameters of fungal and bacterial communities on leaf litter exposed to emersion during different time periods (7, 14 and 21d). Emersion time affected microbial assemblages and litter decomposition, but the response differed among variables. Leaf decomposition rates and the activity of β-glucosidase, cellobiohydrolase and phosphatase were gradually reduced with increasing emersion time, while β-xylosidase reduction was similar when emersion last for 7 or more days, and the phenol oxidase reduction was similar at 14 and 21days of leaf emersion. Microbial biomass and fungal sporulation were reduced after 21days of emersion. The structure of microbial assemblages was affected by the duration of the emersion period. The shifts in fungal assemblages were correlated with a decreased microbial capacity to degrade lignin and hemicellulose in leaf litter exposed to emersion. Additionally, some resilience was observed in leaf litter mass loss, bacterial biomass, some enzyme activities and structure of fungal assemblages. Our study shows that drought can strongly alter structural and functional aspects of microbial decomposers. Therefore, the exposure of leaf litter to increasing emersion periods in temperate streams is expected to affect decomposer communities and overall decomposition of plant material by decelerating carbon cycling in streams. Copyright © 2017 Elsevier B.V. All rights reserved.
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.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Whitford, W.G.; Elkins, N.Z.; Parker, L.W.

In laboratory microcosms of coal mine spoil amended with bark and wood chips, the activity of termites increased organic matter and increased total nitrogen. Termite survival was reduced in microcosms with spoil and paper or straw amendments. Field studies evaluating the efficacy of organic amendments in developing a soil biota showed that decomposition rates of wood chip-bark amended spoil were the same as unmined soil and that decomposition rates were lower than all other mulch-spoil combinations. Wood and bark amended-spoil had the highest density and diversity of soil fauna. Top dressing spoils with borrow soil did not improve any ofmore » the soil biological parameters measured. Based on these data it was recommended that reclamation procedures be changed to eliminate borrow soil top-dressing and that wood removed from mined areas be returned to the contoured spoil as wood chip amendment in addition to straw mulch.« less
Surface fuel litterfall and decomposition in the northern Rocky Mountains, U.S.A.

Treesearch

Robert E. Keane

2008-01-01

Surface fuel deposition and decomposition rates are important to fire management and research because they can define the longevity of fuel treatments in time and space and they can be used to design, build, test, and validate complex fire and ecosystem models useful in evaluating management alternatives. We determined rates of surface fuel litterfall and decomposition...
Decomposition of carbon dioxide by recombining hydrogen plasma with ultralow electron temperature

NASA Astrophysics Data System (ADS)

Yamazaki, Masahiro; Nishiyama, Shusuke; Sasaki, Koichi

2018-06-01

We examined the rate coefficient for the decomposition of CO2 in low-pressure recombining hydrogen plasmas with electron temperatures between 0.15 and 0.45 eV, where the electron-impact dissociation was negligible. By using this ultralow-temperature plasma, we clearly observed decomposition processes via vibrational excited states. The rate coefficient of the overall reaction, CO2 + e → products, was 1.5 × 10‑17 m3/s in the ultralow-temperature plasma, which was 10 times larger than the decomposition rate coefficient of 2 × 10‑18 m3/s in an ionizing plasma with an electron temperature of 4 eV.
Plant litter decomposition and nutrient release in peatlands

NASA Astrophysics Data System (ADS)

Bragazza, Luca; Buttler, Alexandre; Siegenthaler, Andy; Mitchell, Edward A. D.

Decomposition of plant litter is a crucial process in controlling the carbon balance of peatlands. Indeed, as long as the rate of litter decomposition remains lower than the rate of above- and belowground litter production, a net accumulation of peat and, thus, carbon will take place. In addition, decomposition controls the release of important nutrients such as nitrogen, phosphorus, and potassium, the availability of which affects the structure and the functioning of plant communities. This chapter describes the role of the main drivers in affecting mass loss and nutrient release from recently deposited plant litter. In particular, the rate of mass loss of Sphagnum litter and vascular plant litter is reviewed in relation to regional climatic conditions, aerobic/anaerobic conditions, and litter chemistry. The rate of nutrient release is discussed in relation to the rate of mass loss and associated litter chemistry by means of a specific case study.
Nonequilibrium adiabatic molecular dynamics simulations of methane clathrate hydrate decomposition

NASA Astrophysics Data System (ADS)

Alavi, Saman; Ripmeester, J. A.

2010-04-01

Nonequilibrium, constant energy, constant volume (NVE) molecular dynamics simulations are used to study the decomposition of methane clathrate hydrate in contact with water. Under adiabatic conditions, the rate of methane clathrate decomposition is affected by heat and mass transfer arising from the breakup of the clathrate hydrate framework and release of the methane gas at the solid-liquid interface and diffusion of methane through water. We observe that temperature gradients are established between the clathrate and solution phases as a result of the endothermic clathrate decomposition process and this factor must be considered when modeling the decomposition process. Additionally we observe that clathrate decomposition does not occur gradually with breakup of individual cages, but rather in a concerted fashion with rows of structure I cages parallel to the interface decomposing simultaneously. Due to the concerted breakup of layers of the hydrate, large amounts of methane gas are released near the surface which can form bubbles that will greatly affect the rate of mass transfer near the surface of the clathrate phase. The effects of these phenomena on the rate of methane hydrate decomposition are determined and implications on hydrate dissociation in natural methane hydrate reservoirs are discussed.
Nonequilibrium adiabatic molecular dynamics simulations of methane clathrate hydrate decomposition.

PubMed

Alavi, Saman; Ripmeester, J A

2010-04-14

Nonequilibrium, constant energy, constant volume (NVE) molecular dynamics simulations are used to study the decomposition of methane clathrate hydrate in contact with water. Under adiabatic conditions, the rate of methane clathrate decomposition is affected by heat and mass transfer arising from the breakup of the clathrate hydrate framework and release of the methane gas at the solid-liquid interface and diffusion of methane through water. We observe that temperature gradients are established between the clathrate and solution phases as a result of the endothermic clathrate decomposition process and this factor must be considered when modeling the decomposition process. Additionally we observe that clathrate decomposition does not occur gradually with breakup of individual cages, but rather in a concerted fashion with rows of structure I cages parallel to the interface decomposing simultaneously. Due to the concerted breakup of layers of the hydrate, large amounts of methane gas are released near the surface which can form bubbles that will greatly affect the rate of mass transfer near the surface of the clathrate phase. The effects of these phenomena on the rate of methane hydrate decomposition are determined and implications on hydrate dissociation in natural methane hydrate reservoirs are discussed.
The influence of preburial insect access on the decomposition rate.

PubMed

Bachmann, Jutta; Simmons, Tal

2010-07-01

This study compared total body score (TBS) in buried remains (35 cm depth) with and without insect access prior to burial. Sixty rabbit carcasses were exhumed at 50 accumulated degree day (ADD) intervals. Weight loss, TBS, intra-abdominal decomposition, carcass/soil interface temperature, and below-carcass soil pH were recorded and analyzed. Results showed significant differences (p < 0.001) in decomposition rates between carcasses with and without insect access prior to burial. An approximately 30% enhanced decomposition rate with insects was observed. TBS was the most valid tool in postmortem interval (PMI) estimation. All other variables showed only weak relationships to decomposition stages, adding little value to PMI estimation. Although progress in estimating the PMI for surface remains has been made, no previous studies have accomplished this for buried remains. This study builds a framework to which further comparable studies can contribute, to produce predictive models for PMI estimation in buried human remains.
Edge effects on moisture reduce wood decomposition rate in a temperate forest.

PubMed

Crockatt, Martha E; Bebber, Daniel P

2015-02-01

Forests around the world are increasingly fragmented, and edge effects on forest microclimates have the potential to affect ecosystem functions such as carbon and nutrient cycling. Edges tend to be drier and warmer due to the effects of insolation, wind, and evapotranspiration and these gradients can penetrate hundreds of metres into the forest. Litter decomposition is a key component of the carbon cycle, which is largely controlled by saprotrophic fungi that respond to variation in temperature and moisture. However, the impact of forest fragmentation on litter decay is poorly understood. Here, we investigate edge effects on the decay of wood in a temperate forest using an experimental approach, whereby mass loss in wood blocks placed along 100 m transects from the forest edge to core was monitored over 2 years. Decomposition rate increased with distance from the edge, and was correlated with increasing humidity and moisture content of the decaying wood, such that the decay constant at 100 m was nearly twice that at the edge. Mean air temperature decreased slightly with distance from the edge. The variation in decay constant due to edge effects was larger than that expected from any reasonable estimates of climatic variation, based on a published regional model. We modelled the influence of edge effects on the decay constant at the landscape scale using functions for forest area within different distances from edge across the UK. We found that taking edge effects into account would decrease the decay rate by nearly one quarter, compared with estimates that assumed no edge effect. © 2014 John Wiley & Sons Ltd.
Formation and loss of humic substances during decomposition in a pine forest floor

USGS Publications Warehouse

Qualls, R.G.; Takiyama, A.; Wershaw, R. L.

2003-01-01

Since twice as much C is sequestered in soils as is contained in the atmosphere, the factors controlling the decomposition rate of soil C are important to the assessment of the effects of climatic change. The formation of chemically resistant humic substances might be an important process controlling recycling of CO2 to the atmosphere. Our objectives were to measure the rate of formation and loss of humic substances during 13 yr of litter decomposition. We placed nets on the floor of a white pine (Pinus strobus) forest to separate each annual layer of litter for 13 yr and measured humic substance concentration using NaOH extraction followed by chromatographic fractionation. The humic acid fraction increased from 2.1% of the C in litterfall to 15.7% after 1 yr. On a grams per square meter (g m-2) basis the humic substance fraction increased during the first year and then declined, with a half decay time (t1/2) of 5.1 yr, which was significantly slower than the bulk litter (t1/2 = 3.9 yr). The carboxylic C concentration estimated from 13C nuclear magnetic resonance (NMR) increased in the litter over time, though total mass of carboxylic acid C in the forest floor also declined over the 13-yr period (t1/2 = 4.6 yr). While humic substances in the forest floor decomposed at a somewhat slower rate than bulk litter during Years 1 to 13, they decomposed much faster than has been calculated from 14C dating of the refractory fraction of organic matter in the mineral soil.
Effect of simulated acid rain on the litter decomposition of Quercus acutissima and Pinus massoniana in forest soil microcosms and the relationship with soil enzyme activities.

PubMed

Wang, Congyan; Guo, Peng; Han, Guomin; Feng, Xiaoguang; Zhang, Peng; Tian, Xingjun

2010-06-01

With the continuing increase in human activities, ecologists are increasingly interested in understanding the effects of acid rain on litter decomposition. Two dominant litters were chosen from Zijin Mountain in China: Quercus acutissima from a broad-leaved forest and Pinus massoniana from a coniferous forest. The litters were incubated in microcosms and treated with simulated acid rain (gradient pH levels). During a six-month incubation, changes in chemical composition (i.e., lignin, total carbohydrate, and nitrogen), litter mass losses, soil pH values, and activities of degradative enzymes were determined. Results showed that litter mass losses were depressed after exposure to acid rain and the effects of acid rain on the litter decomposition rates of needles were higher than on those of leaves. Results also revealed that simulated acid rain restrained the activities of cellulase, invertase, nitrate reductase, acid phosphatase, alkaline phosphatase, polyphenol oxidase, and urease, while it enhanced the activities of catalase in most cases during the six-month decomposition process. Catalase and polyphenol oxidase were primarily responsible for litter decomposition in the broad-leaved forest, while invertase, nitrate reductase, and urease were primarily responsible for litter decomposition in the coniferous forest. The results suggest acid rain-restrained litter decomposition may be due to the depressed enzymatic activities. According to the results of this study, soil carbon in subtropical forests would accumulate as a long-term consequence of continued acid rain. This may presumably alter the balance of ecosystem carbon flux, nutrient cycling, and humus formation, which may, in turn, have multiple effects on forest ecosystems. Copyright (c) 2010 Elsevier B.V. All rights reserved.
[Release and supplement of carbon, nitrogen and phosphorus from jellyfish (Nemopilema nomurai) decomposition in seawater].

PubMed

Qu, Chang-feng; Song, Jin-ming; Li, Ning; Li, Xue-gang; Yuan, Hua-mao; Duan, Li-qin

2016-01-01

Abstract: Jellyfish bloom has been increasing in Chinese seas and decomposition after jellyfish bloom has great influences on marine ecological environment. We conducted the incubation of Nemopilema nomurai decomposing to evaluate its effect on carbon, nitrogen and phosphorus recycling of water column by simulated experiments. The results showed that the processes of jellyfish decomposing represented a fast release of biogenic elements, and the release of carbon, nitrogen and phosphorus reached the maximum at the beginning of jellyfish decomposing. The release of biogenic elements from jellyfish decomposition was dominated by dissolved matter, which had a much higher level than particulate matter. The highest net release rates of dissolved organic carbon and particulate organic carbon reached (103.77 ± 12.60) and (1.52 ± 0.37) mg · kg⁻¹ · h⁻¹, respectively. The dissolved nitrogen was dominated by NH₄⁺-N during the whole incubation time, accounting for 69.6%-91.6% of total dissolved nitrogen, whereas the dissolved phosphorus was dominated by dissolved organic phosphorus during the initial stage of decomposition, being 63.9%-86.7% of total dissolved phosphorus and dominated by PO₄³⁻-P during the late stage of decomposition, being 50.4%-60.2%. On the contrary, the particulate nitrogen was mainly in particulate organic nitrogen, accounting for (88.6 ± 6.9) % of total particulate nitrogen, whereas the particulate phosphorus was mainly in particulate. inorganic phosphorus, accounting for (73.9 ±10.5) % of total particulate phosphorus. In addition, jellyfish decomposition decreased the C/N and increased the N/P of water column. These indicated that jellyfish decomposition could result in relative high carbon and nitrogen loads.
Analysis of the Sensitivity of K-Type Molecular Sieve-Deposited MWNTs for the Detection of SF6 Decomposition Gases under Partial Discharge

PubMed Central

Zhang, Xiaoxing; Li, Xin; Luo, Chenchen; Dong, Xingchen; Zhou, Lei

2015-01-01

Sulfur hexafluoride (SF6) is widely utilized in gas-insulated switchgear (GIS). However, part of SF6 decomposes into different components under partial discharge (PD) conditions. Previous research has shown that the gas responses of intrinsic and 4 Å-type molecular sieve-deposited multi-wall carbon nanotubes (MWNTs) to SOF2 and SO2F2, two important decomposition components of SF6, are not obvious. In this study, a K-type molecular sieve-deposited MWNTs sensor was developed. Its gas response characteristics and the influence of the mixture ratios of gases on the gas-sensing properties were studied. The results showed that, for sensors with gas mixture ratios of 5:1, 10:1, and 20:1, the resistance change rate increased by nearly 13.0% after SOF2 adsorption, almost 10 times that of MWNTs sensors, while the sensors’ resistance change rate with a mixture ratio of 10:1 reached 17.3% after SO2F2 adsorption, nearly nine times that of intrinsic MWNT sensors. Besides, a good linear relationship was observed between concentration of decomposition components and the resistance change rate of sensors. PMID:26569245
Analysis of the Sensitivity of K-Type Molecular Sieve-Deposited MWNTs for the Detection of SF₆ Decomposition Gases under Partial Discharge.

PubMed

Zhang, Xiaoxing; Li, Xin; Luo, Chenchen; Dong, Xingchen; Zhou, Lei

2015-11-11

Sulfur hexafluoride (SF6) is widely utilized in gas-insulated switchgear (GIS). However, part of SF6 decomposes into different components under partial discharge (PD) conditions. Previous research has shown that the gas responses of intrinsic and 4 Å-type molecular sieve-deposited multi-wall carbon nanotubes (MWNTs) to SOF2 and SO2F2, two important decomposition components of SF6, are not obvious. In this study, a K-type molecular sieve-deposited MWNTs sensor was developed. Its gas response characteristics and the influence of the mixture ratios of gases on the gas-sensing properties were studied. The results showed that, for sensors with gas mixture ratios of 5:1, 10:1, and 20:1, the resistance change rate increased by nearly 13.0% after SOF2 adsorption, almost 10 times that of MWNTs sensors, while the sensors' resistance change rate with a mixture ratio of 10:1 reached 17.3% after SO2F2 adsorption, nearly nine times that of intrinsic MWNT sensors. Besides, a good linear relationship was observed between concentration of decomposition components and the resistance change rate of sensors.
Decomposition rate comparisons between frequently burned and unburned areas of uneven-aged loblolly pine stands in southeastern Arkansas

Treesearch

Miclele Renschin; Hal O. Leichty; Michael G. Shelton

2001-01-01

Although fire has been used extensively over long periods of time in loblolly pine (Pinis taeda L.) ecosystems, little is known concerning the effects of frequent fire use on nutrient cycling and decomposition. To better understand the long-term effects of fire on these processes, foliar litter decomposition rates were quantified in a study...
Elevated CO(2) and nitrogen effects on a dominant N(2)- fixing shrub

NASA Astrophysics Data System (ADS)

Wallace, Alison Marie

The responses of N2-fixing species to global change are likely to be an important component in predicting the existence and direction of feedbacks between carbon and nitrogen cycles, as both are radically changing at an unprecedented pace. Increased carbon storage may be more likely in ecosystems not limited by available nitrogen, such as those with abundant N2-fixing species. If elevated CO2 affects growth and N2-fixation of dominant N2-fixers, then non-fixers in the system may experience indirect effects through changes in competitive interactions and nitrogen availability. The goal of this research was to investigate these effects on the growth, competitive ability, leaf and litter chemistry, and litter decomposition of Lupinus arboreus, a N2-fixing evergreen shrub, and to test the central hypothesis that an increase in growth and competitive ability would occur at low nitrogen and high CO2. In a growth chamber experiment, three CO2 levels, 350, 500, and 650 ppm were crossed with two nitrogen levels. Lupins were grown alone or in competition with an introduced annual grass, Bromus diandrus. Contrary to findings from previous studies of positive growth and competition responses by N2-fixers, Lupinus seedlings demonstrated no significant responses to CO2. Nitrogen was far more important than CO2 in affecting relative competitive ability. Nitrogen, alkaloids, and C:N ratios in fresh foliage did not change with CO2 or nitrogen. Carbon and biomass increased slightly in lupins at 500 ppm only, suggesting an early but limited growth response. Nitrogen did decrease in lupin litter at elevated CO2, but there were no effects on litter decomposition rates in the field. Simulations by the CENTURY surface litter decomposition model predicted the litter decomposition rates of field-grown litter nearly perfectly, and predicted the general direction but underestimated the rate of litter from the greenhouse grown at different CO2 levels. Very low or high nitrogen decreased growth and competitive ability of lupin seedlings in an additional greenhouse experiment. Slight increases of nitrogen in the field did not affect lupin aboveground biomass. In conclusion, it is unlikely that Lupinus abundance or rate of its nitrogen inputs will be affected by elevated CO2 and/or changes in nitrogen availability.
Study on US/O3 mechanism in p-chlorophenol decomposition

PubMed Central

Xu, Xian-wen; Xu, Xin-hua; Shi, Hui-xiang; Wang, Da-hui

2005-01-01

Study on the effects of sonolysis, ozonolysis and US/O3 system on the decomposition of p-chlorophenol in aqueous solutions indicated that in the cases of US/O3 system, individual ozonolysis and sonolysis, the decomposition rate of p-chlorophenol reached 78.78%, 56.20%, 2.79% after a 16-min reaction while its CODcr (chemical oxygen demand) removal rate was 97.02%, 62.17%, 3.67% after a 120-min reaction. The decomposition reaction of p-chlorophenol follows pseudo-first-order kinetics. The enhancement factors of p-chlorophenol and its CODcr under US/O3 system reached 63% and 237% respectively. The main intermediates during the decomposition include catechol, hydroquinone, p-benzoquinone, phenol, fumaric acid, maleic acid, oxalic acid and formic acid. The decomposition mechanism of p-chlorophenol was also discussed. PMID:15909343
Effect of pressure on rate of burning /decomposition with flame/ of liquid hydrazine.

NASA Technical Reports Server (NTRS)

Antoine, A. C.

1966-01-01

Liquid hydrazine decomposition process to determine what chemical or physical changes may be occurring that cause breaks in burning rate/ pressure curves, measuring flame temperature and light emission
Evaluation of factors affecting soil carbon sequestration services of stormwater wet retention ponds in varying climate zones.

PubMed

Merriman, L S; Moore, T L C; Wang, J W; Osmond, D L; Al-Rubaei, A M; Smolek, A P; Blecken, G T; Viklander, M; Hunt, W F

2017-04-01

The carbon sequestration services of stormwater wet retention ponds were investigated in four different climates: U.S., Northern Sweden, Southern Sweden, and Singapore, representing a range of annual mean temperatures, growing season lengths and rainfall depths: geographic factors that were not statistically compared, but have great effect on carbon (C) accumulation. A chronosequence was used to estimate C accumulations rates; C accumulation and decomposition rates were not directly measured. C accumulated significantly over time in vegetated shallow water areas (0-30cm) in the USA (78.4gCm -2 yr -1 ), in vegetated temporary inundation zones in Sweden (75.8gCm -2 yr -1 ), and in all ponds in Singapore (135gCm -2 yr -1 ). Vegetative production appeared to exert a stronger influence on relative C accumulation rates than decomposition. Comparing among the four climatic zones, the effects of increasing rainfall and growing season lengths (vegetative production) outweighed the effects of higher temperature on decomposition rates. Littoral vegetation was a significant source to the soil C pool relative to C sources draining from watersheds. Establishment of vegetation in the shallow water zones of retention ponds is vital to providing a C source to the soil. Thus, the width of littoral shelves containing this vegetation along the perimeter may be increased if C sequestration is a design goal. This assessment establishes that stormwater wet retention ponds can sequester C across different climate zones with generally annual rainfall and lengths of growing season being important general factors for C accumulation. Copyright © 2017 Elsevier B.V. All rights reserved.
Shock wave and modeling study of the thermal decomposition reactions of pentafluoroethane and 2-H-heptafluoropropane.

PubMed

Cobos, C J; Sölter, L; Tellbach, E; Troe, J

2014-06-07

The thermal decomposition reactions of CF3CF2H and CF3CFHCF3 have been studied in shock waves by monitoring the appearance of CF2 radicals. Temperatures in the range 1400-2000 K and Ar bath gas concentrations in the range (2-10) × 10(-5) mol cm(-3) were employed. It is shown that the reactions are initiated by C-C bond fission and not by HF elimination. Differing conclusions in the literature about the primary decomposition products, such as deduced from experiments at very low pressures, are attributed to unimolecular falloff effects. By increasing the initial reactant concentrations in Ar from 60 to 1000 ppm, a retardation of CF2 formation was observed while the final CF2 yields remained close to two CF2 per C2F5H or three CF2 per C3F7H decomposed. This is explained by secondary bimolecular reactions which lead to comparably stable transient species like CF3H, releasing CF2 at a slower rate. Quantum-chemical calculations and kinetic modeling help to identify the reaction pathways and provide estimates of rate constants for a series of primary and secondary reactions in the decomposition mechanism.
Hydrogen Peroxide - Material Compatibility Studied by Microcalorimetry

NASA Technical Reports Server (NTRS)

Homung, Steven D.; Davis, Dennis D.; Baker, David; Popp, Christopher G.

2003-01-01

Environmental and toxicity concerns with current hypergolic propellants have led to a renewed interest in propellant grade hydrogen peroxide (HP) for propellant applications. Storability and stability has always been an issue with HP. Contamination or contact of HP with metallic surfaces may cause decomposition, which can result in the evolution of heat and gas leading to increased pressure or thermal hazards. The NASA Johnson Space Center White Sands Test Facility has developed a technique to monitor the decompositions of hydrogen peroxide at temperatures ranging from 25 to 60 C. Using isothermal microcalorimetry we have measured decomposition rates at the picomole/s/g level showing the catalytic effects of materials of construction. In this paper we will present the results of testing with Class 1 and 2 materials in 90 percent hydrogen peroxide.

Litter decomposition patterns and dynamics across biomes: Initial results from the global TeaComposition initiative

NASA Astrophysics Data System (ADS)

Djukic, Ika; Kappel Schmidt, Inger; Steenberg Larsen, Klaus; Beier, Claus

2017-04-01

Litter decomposition represents one of the largest fluxes in the global terrestrial carbon cycle and a number of large-scale decomposition experiments have been conducted focusing on this fundamental soil process. However, previous studies were most often based on site-specific litters and methodologies. The contrasting litter and soil types used and the general lack of common protocols still poses a major challenge as it adds major uncertainty to meta-analyses across different experiments and sites. In the TeaComposition initiative, we aim to investigate the potential litter decomposition by using standardized substrates (tea) for comparison of temporal litter decomposition rates across different ecosystems worldwide. To this end, Lipton tea bags (Rooibos and Green Tea) has been buried in the H-A or Ah horizon and incubated over the period of 36 months within 400 sites covering diverse ecosystems in 9 zonobiomes. We measured initial litter chemistry and litter mass loss 3 months after the start of decomposition and linked the decomposition rates to site and climatic conditions as well as to the existing decompositions rates of the local litter. We will present and discuss the outcomes of this study. Acknowledgment: We are thankful to colleagues from more than 300 sites who were participating in the implementation of this initiative and who are not mentioned individually as co-authors yet.
Separating and Recycling Plastic, Glass, and Gallium from Waste Solar Cell Modules by Nitrogen Pyrolysis and Vacuum Decomposition.

PubMed

Zhang, Lingen; Xu, Zhenming

2016-09-06

Many countries have gained benefits through the solar cells industry due to its high efficiency and nonpolluting power generation associated with solar energy. Accordingly, the market of solar cell modules is expanding rapidly in recent decade. However, how to environmentally friendly and effectively recycle waste solar cell modules is seldom concerned. Based on nitrogen pyrolysis and vacuum decomposition, this work can successfully recycle useful organic components, glass, and gallium from solar cell modules. The results were summarized as follows: (i) nitrogen pyrolysis process can effectively decompose plastic. Organic conversion rate approached 100% in the condition of 773 K, 30 min, and 0.5 L/min N2 flow rate. But, it should be noted that pyrolysis temperature should not exceed 773 K, and harmful products would be increased with the increasing of temperature, such as benzene and its derivatives by GC-MS measurement; (ii) separation principle, products analysis, and optimization of vacuum decomposition were discussed. Gallium can be well recycled under temperature of 1123 K, system pressure of 1 Pa and reaction time of 40 min. This technology is quite significant in accordance with the "Reduce, Reuse, and Recycle Principle" for solid waste, and provides an opportunity for sustainable development of photovoltaic industry.
The Effect of Body Mass on Outdoor Adult Human Decomposition.

PubMed

Roberts, Lindsey G; Spencer, Jessica R; Dabbs, Gretchen R

2017-09-01

Forensic taphonomy explores factors impacting human decomposition. This study investigated the effect of body mass on the rate and pattern of adult human decomposition. Nine males and three females aged 49-95 years ranging in mass from 73 to 159 kg who were donated to the Complex for Forensic Anthropology Research between December 2012 and September 2015 were included in this study. Kelvin accumulated degree days (KADD) were used to assess the thermal energy required for subjects to reach several total body score (TBS) thresholds: early decomposition (TBS ≥6.0), TBS ≥12.5, advanced decomposition (TBS ≥19.0), TBS ≥23.0, and skeletonization (TBS ≥27.0). Results indicate no significant correlation between body mass and KADD at any TBS threshold. Body mass accounted for up to 24.0% of variation in decomposition rate depending on stage, and minor differences in decomposition pattern were observed. Body mass likely has a minimal impact on postmortem interval estimation. © 2017 American Academy of Forensic Sciences.
Testing the Use of Pigs as Human Proxies in Decomposition Studies.

PubMed

Connor, Melissa; Baigent, Christiane; Hansen, Eriek S

2017-12-28

Pigs are a common human analogue in taphonomic study, yet data comparing the trajectory of decomposition between the two groups are lacking. This study compared decomposition rate and gross tissue change in 17 pigs and 22 human remains placed in the Forensic Investigation Research Station in western Colorado between 2012 and 2015. Accumulated degree days (ADD) were used to assess the number of thermal units required to reach a given total body score (TBS) (1) which was used as the measure of decomposition. A comparison of slopes in linear mixed effects model indicated that decomposition rates significantly differed between human donors and pig remains χ 2 (1) = 5.662, p = 0.017. Neither the pig nor the human trajectory compared well to the TBS model. Thus, (i) pigs are not an adequate proxy for human decomposition studies, and (ii) in the semiarid environment of western Colorado, there is a need to develop a regional decomposition model. © 2017 American Academy of Forensic Sciences.
Climate fails to predict wood decomposition at regional scales

NASA Astrophysics Data System (ADS)

Bradford, Mark A.; Warren, Robert J., II; Baldrian, Petr; Crowther, Thomas W.; Maynard, Daniel S.; Oldfield, Emily E.; Wieder, William R.; Wood, Stephen A.; King, Joshua R.

2014-07-01

Decomposition of organic matter strongly influences ecosystem carbon storage. In Earth-system models, climate is a predominant control on the decomposition rates of organic matter. This assumption is based on the mean response of decomposition to climate, yet there is a growing appreciation in other areas of global change science that projections based on mean responses can be irrelevant and misleading. We test whether climate controls on the decomposition rate of dead wood--a carbon stock estimated to represent 73 +/- 6 Pg carbon globally--are sensitive to the spatial scale from which they are inferred. We show that the common assumption that climate is a predominant control on decomposition is supported only when local-scale variation is aggregated into mean values. Disaggregated data instead reveal that local-scale factors explain 73% of the variation in wood decomposition, and climate only 28%. Further, the temperature sensitivity of decomposition estimated from local versus mean analyses is 1.3-times greater. Fundamental issues with mean correlations were highlighted decades ago, yet mean climate-decomposition relationships are used to generate simulations that inform management and adaptation under environmental change. Our results suggest that to predict accurately how decomposition will respond to climate change, models must account for local-scale factors that control regional dynamics.
Enhanced decomposition offsets enhanced productivity and soil carbon accumulation in coastal wetlands responding to climate change

USGS Publications Warehouse

Kirwan, M.L.; Blum, L.K.

2011-01-01

Coastal wetlands are responsible for about half of all carbon burial in oceans, and their persistence as a valuable ecosystem depends largely on the ability to accumulate organic material at rates equivalent to relative sea level rise. Recent work suggests that elevated CO2 and temperature warming will increase organic matter productivity and the ability of marshes to survive sea level rise. However, we find that organic decomposition rates increase by about 12% per degree of warming. Our measured temperature sensitivity is similar to studies from terrestrial systems, twice as high as the response of salt marsh productivity to temperature warming, and roughly equivalent to the productivity response associated with elevated CO2 in C3 marsh plants. Therefore, enhanced CO2 and warmer temperatures may actually make marshes less resilient to sea level rise, and tend to promote a release of soil carbon. Simple projections indicate that elevated temperatures will increase rates of sea level rise more than any acceleration in organic matter accumulation, suggesting the possibility of a positive feedback between climate, sea level rise, and carbon emissions in coastal environments. ?? 2011 Author(s).
[Effects of simulated nitrogen deposition on lignin and cellulose degradation of foliar litter in natural evergreen broad-leaved forest in Rainy Area of Western China.

PubMed

2016-05-01

In order to detect the effects of simulated nitrogen deposition on litter decomposition and degradation of lignin and cellulose, a one-year field experiment of simulated nitrogen deposition has been conducted using litter bag method from November 2013 to November 2014 in an evergreen broad-leaved forest, Rainy Area of West China. Four levels of nitrogen deposition were set, i.e., control (0 g N·m -2 ·a -1 ), low (5 g N·m -2 ·a -1 ), medium (15 g N·m -2 ·a -1 ) and high (30 g N·m -2 ·a -1 ) nitrogen deposition. The results indicated that foliar litter decomposed faster in summer, obviously faster than in the other seasons. N deposition significantly inhibited the decomposition of foliar litter in this evergreen broad-leaved forest. As N deposition increased, the inhibition effect was enhanced. The time of 95% mass loss (T 95% ) of foliar litter due to simulated N deposition was increased by 0.53-1.88 years compared with T 95% of control (4.81 years). N deposition significantly inhibited the degradation of lignin and cellulose. The mass remaining after one year of decomposition of lignin and cellulose in the medium and high nitrogen deposition treatments were significantly higher than that in the control. There was a significant positive linear relationship among mass remaining rate and lignin and cellulose remaining rates. The inhibiting effects of inorga-nic N on degradation of lignin and cellulose explained the inhibitory effect of N on foliar litter decomposition.
Long-term litter decomposition controlled by manganese redox cycling

PubMed Central

Keiluweit, Marco; Nico, Peter; Harmon, Mark E.; Mao, Jingdong; Pett-Ridge, Jennifer; Kleber, Markus

2015-01-01

Litter decomposition is a keystone ecosystem process impacting nutrient cycling and productivity, soil properties, and the terrestrial carbon (C) balance, but the factors regulating decomposition rate are still poorly understood. Traditional models assume that the rate is controlled by litter quality, relying on parameters such as lignin content as predictors. However, a strong correlation has been observed between the manganese (Mn) content of litter and decomposition rates across a variety of forest ecosystems. Here, we show that long-term litter decomposition in forest ecosystems is tightly coupled to Mn redox cycling. Over 7 years of litter decomposition, microbial transformation of litter was paralleled by variations in Mn oxidation state and concentration. A detailed chemical imaging analysis of the litter revealed that fungi recruit and redistribute unreactive Mn2+ provided by fresh plant litter to produce oxidative Mn3+ species at sites of active decay, with Mn eventually accumulating as insoluble Mn3+/4+ oxides. Formation of reactive Mn3+ species coincided with the generation of aromatic oxidation products, providing direct proof of the previously posited role of Mn3+-based oxidizers in the breakdown of litter. Our results suggest that the litter-decomposing machinery at our coniferous forest site depends on the ability of plants and microbes to supply, accumulate, and regenerate short-lived Mn3+ species in the litter layer. This observation indicates that biogeochemical constraints on bioavailability, mobility, and reactivity of Mn in the plant–soil system may have a profound impact on litter decomposition rates. PMID:26372954
Long-term litter decomposition controlled by manganese redox cycling.

PubMed

Keiluweit, Marco; Nico, Peter; Harmon, Mark E; Mao, Jingdong; Pett-Ridge, Jennifer; Kleber, Markus

2015-09-22

Litter decomposition is a keystone ecosystem process impacting nutrient cycling and productivity, soil properties, and the terrestrial carbon (C) balance, but the factors regulating decomposition rate are still poorly understood. Traditional models assume that the rate is controlled by litter quality, relying on parameters such as lignin content as predictors. However, a strong correlation has been observed between the manganese (Mn) content of litter and decomposition rates across a variety of forest ecosystems. Here, we show that long-term litter decomposition in forest ecosystems is tightly coupled to Mn redox cycling. Over 7 years of litter decomposition, microbial transformation of litter was paralleled by variations in Mn oxidation state and concentration. A detailed chemical imaging analysis of the litter revealed that fungi recruit and redistribute unreactive Mn(2+) provided by fresh plant litter to produce oxidative Mn(3+) species at sites of active decay, with Mn eventually accumulating as insoluble Mn(3+/4+) oxides. Formation of reactive Mn(3+) species coincided with the generation of aromatic oxidation products, providing direct proof of the previously posited role of Mn(3+)-based oxidizers in the breakdown of litter. Our results suggest that the litter-decomposing machinery at our coniferous forest site depends on the ability of plants and microbes to supply, accumulate, and regenerate short-lived Mn(3+) species in the litter layer. This observation indicates that biogeochemical constraints on bioavailability, mobility, and reactivity of Mn in the plant-soil system may have a profound impact on litter decomposition rates.
Comparative evaluation of thermal decomposition behavior and thermal stability of powdered ammonium nitrate under different atmosphere conditions.

PubMed

Yang, Man; Chen, Xianfeng; Wang, Yujie; Yuan, Bihe; Niu, Yi; Zhang, Ying; Liao, Ruoyu; Zhang, Zumin

2017-09-05

In order to analyze the thermal decomposition characteristics of ammonium nitrate (AN), its thermal behavior and stability under different conditions are studied, including different atmospheres, heating rates and gas flow rates. The evolved decomposition gases of AN in air and nitrogen are analyzed with a quadrupole mass spectrometer. Thermal stability of AN at different heating rates and gas flow rates are studied by differential scanning calorimetry, thermogravimetric analysis, paired comparison method and safety parameter evaluation. Experimental results show that the major evolved decomposition gases in air are H 2 O, NH 3 , N 2 O, NO, NO 2 and HNO 3 , while in nitrogen, H 2 O, NH 3 , NO and HNO 3 are major components. Compared with nitrogen atmosphere, lower initial and end temperatures, higher heat flux and broader reaction temperature range are obtained in air. Meanwhile, higher air gas flow rate tends to achieve lower reaction temperature and to reduce thermal stability of AN. Self-accelerating decomposition temperature of AN in air is much lower than that in nitrogen. It is considered that thermostability of AN is influenced by atmosphere, heating rate and gas flow rate, thus changes of boundary conditions will influence its thermostability, which is helpful to its safe production, storage, transportation and utilization. Copyright © 2017 Elsevier B.V. All rights reserved.
A potential loss of carbon associated with greater plant growth in the European Arctic

NASA Astrophysics Data System (ADS)

Hartley, Iain P.; Garnett, Mark H.; Sommerkorn, Martin; Hopkins, David W.; Fletcher, Benjamin J.; Sloan, Victoria L.; Phoenix, Gareth K.; Wookey, Philip A.

2012-12-01

Rapid warming is expected to increase plant growth in the Arctic, and result in trees gradually colonizing tundra. Models predict that enhanced carbon (C) storage in plant biomass may help offset atmospheric CO2 increases and reduce rates of climate change. However, in some Arctic ecosystems, high plant productivity is associated with rapid cycling and low storage of soil C (refs , , ); thus, as plant growth increases, soil C may be lost through enhanced decomposition. Here we show that, in northern Sweden, total ecosystem C storage is greater in tundra heath (owing to greater soil C stocks) than in more productive mountain-birch forest. Furthermore, we demonstrate that in the forest, high plant activity during the middle of the growing season stimulates the decomposition of older soil organic matter. Such a response, referred to as positive priming, helps explain the low soil C storage in the forest when compared with the tundra. We suggest that, as more productive forest communities colonize tundra, the decomposition of the large C stocks in tundra soils could be stimulated. Thus, counter-intuitively, increased plant growth in the European Arctic could result in C being released to the atmosphere, accelerating climate change.
The correlation between elongation at break and thermal decomposition of aged EPDM cable polymer

NASA Astrophysics Data System (ADS)

Šarac, T.; Devaux, J.; Quiévy, N.; Gusarov, A.; Konstantinović, M. J.

2017-03-01

The effect of simultaneous thermal and gamma irradiation ageing on the mechanical and physicochemical properties of industrial EPDM was investigated. Accelerated ageing, covering a wide range of dose rates, doses and temperatures, was preformed in stagnant air on EPDM polymer samples extracted from the cables in use in the Belgian nuclear power plants. The mechanical properties, ultimate tensile stress and elongation at break, are found to exhibit the strong dependence on the dose, ageing temperature and dose rate. The thermal decomposition of aged polymer is observed to be the dose dependent when thermogravimetry test is performed under air atmosphere. No dose dependence is observed when thermal decomposition is performed under nitrogen atmosphere. The thermal decomposition rates are found to fully mimic the reduction of elongation at break for all dose rates and ageing temperatures. This effect is argued to be the result of thermal and radiation mediated oxidation degradation process.
Rate of warming affects temperature sensitivity of anaerobic peat decomposition and greenhouse gas production.

PubMed

Sihi, Debjani; Inglett, Patrick W; Gerber, Stefan; Inglett, Kanika S

2018-01-01

Temperature sensitivity of anaerobic carbon mineralization in wetlands remains poorly represented in most climate models and is especially unconstrained for warmer subtropical and tropical systems which account for a large proportion of global methane emissions. Several studies of experimental warming have documented thermal acclimation of soil respiration involving adjustments in microbial physiology or carbon use efficiency (CUE), with an initial decline in CUE with warming followed by a partial recovery in CUE at a later stage. The variable CUE implies that the rate of warming may impact microbial acclimation and the rate of carbon-dioxide (CO 2 ) and methane (CH 4 ) production. Here, we assessed the effects of warming rate on the decomposition of subtropical peats, by applying either a large single-step (10°C within a day) or a slow ramping (0.1°C/day for 100 days) temperature increase. The extent of thermal acclimation was tested by monitoring CO 2 and CH 4 production, CUE, and microbial biomass. Total gaseous C loss, CUE, and MBC were greater in the slow (ramp) warming treatment. However, greater values of CH 4 -C:CO 2 -C ratios lead to a greater global warming potential in the fast (step) warming treatment. The effect of gradual warming on decomposition was more pronounced in recalcitrant and nutrient-limited soils. Stable carbon isotopes of CH 4 and CO 2 further indicated the possibility of different carbon processing pathways under the contrasting warming rates. Different responses in fast vs. slow warming treatment combined with different endpoints may indicate alternate pathways with long-term consequences. Incorporations of experimental results into organic matter decomposition models suggest that parameter uncertainties in CUE and CH 4 -C:CO 2 -C ratios have a larger impact on long-term soil organic carbon and global warming potential than uncertainty in model structure, and shows that particular rates of warming are central to understand the response of wetland soils to global climate change. © 2017 John Wiley & Sons Ltd.
Decomposition Dynamics and Changes in Chemical Composition of Wheat Straw Residue under Anaerobic and Aerobic Conditions

PubMed Central

Gao, Hongjian; Chen, Xi; Wei, Junling; Zhang, Yajie; Zhang, Ligan; Chang, Jiang; Thompson, Michael L.

2016-01-01

Soil aeration is a crucial factor that regulates crop residue decomposition, and the chemical composition of decomposing crop residues may change the forms and availability of soil nutrients, such as N and P. However, to date, differences in the chemical composition of crop straw residues after incorporation into soil and during its decomposition under anaerobic vs. aerobic conditions have not been well documented. The objective of the present study was to assess changes in the C-containing functional groups of wheat straw residue during its decomposition in anaerobic and aerobic environments. A 12-month incubation experiment was carried out to investigate the temporal variations of mass, carbon, and nitrogen loss, as well as changes in the chemical composition of wheat (Triticum aestivum L) straw residues under anaerobic and aerobic conditions by measuring C-containing functional groups using solid state nuclear magnetic resonance (NMR) spectroscopy. The residual mass, carbon content, and nitrogen content of the straw residue sharply declined during the initial 3 months, and then slowly decreased during the last incubation period from 3 to 12 months. The decomposition rate constant (k) for mass loss under aerobic conditions (0.022 d-1) was higher than that under anaerobic conditions (0.014 d-1). The residual mass percentage of cellulose and hemicellulose in the wheat straw gradually declined, whereas that of lignin gradually increased during the entire 12-month incubation period. The NMR spectra of C-containing functional groups in the decomposing straw under both aerobic and anaerobic conditions were similar at the beginning of the incubation as well as at 1 month, 6 months, and 12 months. The main alterations in C-containing functional groups during the decomposition of wheat straw were a decrease in the relative abundances of O-alkyl C and an increase in the relative abundances of alkyl C, aromatic C and COO/N-C = O functional groups. The NMR signals of alkyl C and aromatic C in decomposing wheat straw residues under anaerobic condition were higher than those under aerobic conditions. The higher mass percentages of lignin and the higher signals of aromatic C and alkyl C functional groups in decomposing wheat residues under anaerobic conditions than under aerobic conditions were due to the slower decomposition rates of aryl C and alkyl C in wheat straw residues under anaerobic conditions. PMID:27380023
Can species-specific differences in foliar chemistry influence leaf litter decomposition in grassland species?

NASA Astrophysics Data System (ADS)

Sanaullah, M.; Chabbi, A.; Rumpel, C.

2009-04-01

The influence of litter quality on its rate of decomposition is a crucial aspect of C cycle. In this study we concentrated on grassland ecosystems where leaf litter is one of the major sources of C input. To quantify the contribution of initial leaf chemistry within different plant species, the decomposition of chemically different leaf litter of three grassland species (Lolium perenne, Festuca arundinacea and Dactylis glomerata) was monitored, using the litter bag technique. Litter of different maturity stages i.e. green (fresh leaves) and brown litter (brown leaves were still attached to the plant), were incubated on bare soil surface. Samples were taken at different time intervals (0, 2, 4, 8, 20 and 44 weeks) and were analyzed for mass loss, organic C and N contents and stable isotopic signatures (C and N). Changes in litter chemistry were addressed by determining lignin-derived phenols after CuO oxidation and non-cellulosic polysaccharides after acid hydrolysis followed by gas chromatography. Green litter was chemically different from brown litter due to higher initial N and lower lignin contents. While in grassland species, both L. perenne and D. glomerata were similar in their initial chemical composition compared with F. arundinacea. Green litter showed higher rate of degradation. In green litter, Percent lignin remaining of initial (% OI) followed the similar decomposition pattern as of C remaining indicating lignin as controlling factor in decomposition. Constant Acid-to-Aldehyde ratios of lignin-derived phenols (vanillyl and syringyl) did not suggest any transformation in lignin structures. In green litter, increase in non-cellulosic polysaccharides ratios (C6/C5 and deoxy/C5) proposed microbial-derived sugars, while there was no significant increase in these ratios in brown litter. In conclusion, due to the differences in initial chemical composition (initial N and lignin contents), green litter decomposition was higher than brown litter in all grassland species. Regardless of similarities in initial composition of grassland species, green and brown litter of Lolium perenne decomposed more rapidly compared with other two species. So, Species related differences in initial litter chemistry did not control its degradation.
Decomposition rates of American chestnut (Castanea dentata) wood and implications for coarse woody debris pools

Treesearch

Arjan de Bruijn; Eric J. Gustafson; Daniel M. Kashian; Harmony J. Dalgleish; Brian R. Sturtevant; Douglass F. Jacobs

2014-01-01

Observations of the rapid growth and slow decomposition of American chestnut (Castanea dentata (Marsh.) Borkh.) suggest that its reintroduction could enhance terrestrial carbon (C) sequestration. A suite of decomposition models was fit with decomposition data from coarse woody debris (CWD) sampled in Wisconsin and Virginia, U.S. The optimal (two-...
Predicting the decomposition of Scots pine, Norway spruce, and birch stems in Finland.

PubMed

Mäkinen, Harri; Hynynen, Jari; Siitonen, Juha; Sievänen, Risto

2006-10-01

Models were developed for predicting the decomposition of dead wood for the main tree species in Finland, based on data collected from long-term thinning experiments in southern and central Finland. The decomposition rates were strongly related to the number of years after tree death. In contrast to previous studies, which have used the first-order exponential model, we found that the decomposition rate was not constant. Therefore, the Gompertz and Chapman-Richard's functions were fitted to the data. The slow initial decomposition period was mainly due to the fact that most dead trees remained standing as snags after their death. The initial period was followed by a period of rapid decomposition and, finally, by a period of moderately slow decomposition. Birch stems decomposed more rapidly than Scots pine and Norway spruce stems. Decomposition rates of Norway spruce stems were somewhat lower than those of Scots pine. Because the carbon concentration of decaying boles was relatively stable (about 50%) the rate of carbon loss follows that of mass loss. Models were also developed for the probability that a dead tree remains standing as a snag. During the first years after death, the probability was high. Thereafter, it decreased rapidly, the decrease being faster for birch stems than for Scots pine and Norway spruce stems. Almost all stems had fallen down within 40 years after their death. In Scots pine and Norway spruce, most snags remained hard and belonged to decay class 1. In birch, a higher proportion of snags belonged to the more advanced decay classes. The models provide a framework for predicting dead wood dynamics in managed as well as dense unthinned stands. The models can be incorporated into forest management planning systems, thereby facilitating estimates of carbon dynamics.
Bleaching of cotton fabric with tetraacetylhydrazine as bleach activator for H2O2.

PubMed

Liu, Kai; Zhang, Xuan; Yan, Kelu

2018-05-15

Tetraacetylhydrazine (TH) as bleach activator for H 2 O 2 cotton bleaching was synthesized and characterized by 1 H NMR, 13 C NMR and MS spectra. TH has better solubility than that of TAED. The CIE whiteness index (WI), H 2 O 2 decomposition rate and bursting strength were employed to investigate the performance of H 2 O 2 /TH bleaching system. By addition of TH, WI and H 2 O 2 decomposition rate increased significantly at 70 °C. Bleaching temperature, NaHCO 3 concentration and bleaching time were also discussed in detail and the loss of bursting strength is not clear. By using benzenepentacarboxylic acid (BA) as a fluorescent probe for hydroxyl radical detection, the bleaching process of H 2 O 2 /TH system was investigated. Acetylhydrazine and diacetylhydrazine were also utilized to further confirm the process. In addition, bimolecular decomposition was investigated by using 9,10-dimethylanthracene (DMA) as fluorescent probe of 1 O 2 . Based on these experimental results, the bleaching mechanism of H 2 O 2 /TH system was proposed. Copyright © 2018 Elsevier Ltd. All rights reserved.
Temporal Dynamics of Abiotic and Biotic Factors on Leaf Litter of Three Plant Species in Relation to Decomposition Rate along a Subalpine Elevation Gradient

PubMed Central

Zhu, Jianxiao; Yang, Wanqin; He, Xinhua

2013-01-01

Relationships between abiotic (soil temperature and number of freeze-thaw cycles) or biotic factors (chemical elements, microbial biomass, extracellular enzymes, and decomposer communities in litter) and litter decomposition rates were investigated over two years in subalpine forests close to the Qinghai-Tibet Plateau in China. Litterbags with senescent birch, fir, and spruce leaves were placed on the forest floor at 2,704 m, 3,023 m, 3,298 m, and 3,582 m elevation. Results showed that the decomposition rate positively correlated with soil mean temperature during the plant growing season, and with the number of soil freeze-thaw cycles during the winter. Concentrations of soluble nitrogen (N), phosphorus (P) and potassium (K) had positive effects but C:N and lignin:N ratios had negative effects on the decomposition rate (k), especially during the winter. Meanwhile, microbial biomass carbon (MBC), N (MBN), and P (MBP) were positively correlated with k values during the first growing season. These biotic factors accounted for 60.0% and 56.4% of the variation in decomposition rate during the winter and the growing season in the first year, respectively. Specifically, litter chemistry (C, N, P, K, lignin, C:N and lignin:N ratio) independently explained 29.6% and 13.3%, and the microbe-related factors (MBC, MBN, MBP, bacterial and fungal biomass, sucrase and ACP activity) explained 22.9% and 34.9% during the first winter and the first growing season, respectively. We conclude that frequent freeze-thaw cycles and litter chemical properties determine the winter decomposition while microbe-related factors play more important roles in determining decomposition in the subsequent growing season. PMID:23620803
Plant species traits are the predominant control on litter decomposition rates within biomes worldwide.

PubMed

Cornwell, William K; Cornelissen, Johannes H C; Amatangelo, Kathryn; Dorrepaal, Ellen; Eviner, Valerie T; Godoy, Oscar; Hobbie, Sarah E; Hoorens, Bart; Kurokawa, Hiroko; Pérez-Harguindeguy, Natalia; Quested, Helen M; Santiago, Louis S; Wardle, David A; Wright, Ian J; Aerts, Rien; Allison, Steven D; van Bodegom, Peter; Brovkin, Victor; Chatain, Alex; Callaghan, Terry V; Díaz, Sandra; Garnier, Eric; Gurvich, Diego E; Kazakou, Elena; Klein, Julia A; Read, Jenny; Reich, Peter B; Soudzilovskaia, Nadejda A; Vaieretti, M Victoria; Westoby, Mark

2008-10-01

Worldwide decomposition rates depend both on climate and the legacy of plant functional traits as litter quality. To quantify the degree to which functional differentiation among species affects their litter decomposition rates, we brought together leaf trait and litter mass loss data for 818 species from 66 decomposition experiments on six continents. We show that: (i) the magnitude of species-driven differences is much larger than previously thought and greater than climate-driven variation; (ii) the decomposability of a species' litter is consistently correlated with that species' ecological strategy within different ecosystems globally, representing a new connection between whole plant carbon strategy and biogeochemical cycling. This connection between plant strategies and decomposability is crucial for both understanding vegetation-soil feedbacks, and for improving forecasts of the global carbon cycle.

Decomposition and arthropod succession in Whitehorse, Yukon Territory, Canada.

PubMed

Bygarski, Katherine; LeBlanc, Helene N

2013-03-01

Forensic arthropod succession patterns are known to vary between regions. However, the northern habitats of the globe have been largely left unstudied. Three pig carcasses were studied outdoors in Whitehorse, Yukon Territory. Adult and immature insects were collected for identification and comparison. The dominant Diptera and Coleoptera species at all carcasses were Protophormia terraneovae (R-D) (Fam: Calliphoridae) and Thanatophilus lapponicus (Herbst) (Fam: Silphidae), respectively. Rate of decomposition, patterns of Diptera and Coleoptera succession, and species dominance were shown to differ from previous studies in temperate regions, particularly as P. terraenovae showed complete dominance among blowfly species. Rate of decomposition through the first four stages was generally slow, and the last stage of decomposition was not observed at any carcass due to time constraints. It is concluded that biogeoclimatic range has a significant effect on insect presence and rate of decomposition, making it an important factor to consider when calculating a postmortem interval. © 2012 American Academy of Forensic Sciences.
LANDFILL BIOREACTOR PERFORMANCE, SECOND INTERIM REPORT

EPA Science Inventory

A bioreactor landfill is a landfill that is operated in a manner that is expected to increase the rate and extent of waste decomposition, gas generation, and settlement compared to a traditional landfill. This Second Interim Report was prepared to provide an interpretation of fie...
Decades of Fertilization Increase Greenhouse Gas Emissions at Great Sippewissett Marsh, Cape Cod, USA

EPA Science Inventory

Coastal wetlands’ ecological and biogeochemical characteristics make them important sites of carbon sequestration and nitrogen interception and transformation. In coastal wetlands, decomposition rates are low and productivity is high, making these systems net sinks of carb...
A stoichiometric organic matter decomposition model in a chemostat culture.

PubMed

Kong, Jude D; Salceanu, Paul; Wang, Hao

2018-02-01

Biodegradation, the disintegration of organic matter by microorganism, is essential for the cycling of environmental organic matter. Understanding and predicting the dynamics of this biodegradation have increasingly gained attention from the industries and government regulators. Since changes in environmental organic matter are strenuous to measure, mathematical models are essential in understanding and predicting the dynamics of organic matters. Empirical evidence suggests that grazers' preying activity on microorganism helps to facilitate biodegradation. In this paper, we formulate and investigate a stoichiometry-based organic matter decomposition model in a chemostat culture that incorporates the dynamics of grazers. We determine the criteria for the uniform persistence and extinction of the species and chemicals. Our results show that (1) if at the unique internal steady state, the per capita growth rate of bacteria is greater than the sum of the bacteria's death and dilution rates, then the bacteria will persist uniformly; (2) if in addition to this, (a) the grazers' per capita growth rate is greater than the sum of the dilution rate and grazers' death rate, and (b) the death rate of bacteria is less than some threshold, then the grazers will persist uniformly. These conditions can be achieved simultaneously if there are sufficient resources in the feed bottle. As opposed to the microcosm decomposition models' results, in a chemostat culture, chemicals always persist. Besides the transcritical bifurcation observed in microcosm models, our chemostat model exhibits Hopf bifurcation and Rosenzweig's paradox of enrichment phenomenon. Our sensitivity analysis suggests that the most effective way to facilitate degradation is to decrease the dilution rate.
[Decomposition model of energy-related carbon emissions in tertiary industry for China].

PubMed

Lu, Yuan-Qing; Shi, Jun

2012-07-01

Tertiary industry has been developed in recent years. And it is very important to find the factors influenced the energy-related carbon emissions in tertiary industry. A decomposition model of energy-related carbon emissions for China is set up by adopting logarithmic mean weight Divisia method based on the identity of carbon emissions. The model is adopted to analyze the influence of energy structure, energy efficiency, tertiary industry structure and economic output to energy-related carbon emissions in China from 2000 to 2009. Results show that the contribution rate of economic output and energy structure to energy-related carbon emissions increases year by year. Either is the contribution rate of energy efficiency or the tertiary industry restraining to energy-related carbon emissions. However, the restrain effect is weakening.
Thermal decomposition of hydroxylamine: isoperibolic calorimetric measurements at different conditions.

PubMed

Adamopoulou, Theodora; Papadaki, Maria I; Kounalakis, Manolis; Vazquez-Carreto, Victor; Pineda-Solano, Alba; Wang, Qingsheng; Mannan, M Sam

2013-06-15

Thermal decomposition of hydroxylamine, NH2OH, was responsible for two serious accidents. However, its reactive behavior and the synergy of factors affecting its decomposition are not being understood. In this work, the global enthalpy of hydroxylamine decomposition has been measured in the temperature range of 130-150 °C employing isoperibolic calorimetry. Measurements were performed in a metal reactor, employing 30-80 ml solutions containing 1.4-20 g of pure hydroxylamine (2.8-40 g of the supplied reagent). The measurements showed that increased concentration or temperature, results in higher global enthalpies of reaction per unit mass of reactant. At 150 °C, specific enthalpies as high as 8 kJ per gram of hydroxylamine were measured, although in general they were in the range of 3-5 kJ g(-1). The accurate measurement of the generated heat was proven to be a cumbersome task as (a) it is difficult to identify the end of decomposition, which after a fast initial stage, proceeds very slowly, especially at lower temperatures and (b) the environment of gases affects the reaction rate. Copyright © 2013 Elsevier B.V. All rights reserved.
Thermal decomposition of pyrazole to vinylcarbene + N 2: A first principles/RRKM study

NASA Astrophysics Data System (ADS)

da Silva, Gabriel

2009-05-01

Thermal decomposition of pyrazole, a five-membered nitrogen-containing heterocycle, has been studied using ab initio G3X theory and RRKM rate theory. The decomposition mechanism involves an intramolecular hydrogen shift to 3 H-pyrazole, followed by ring opening to 3-diazo-1-propene and dissociation to vinylcarbene (CH 2CHCH) + N 2. At 1 atm the calculated rate equation k [s -1] = 1.26 × 10 50T-10.699e -41200/T is obtained, which agrees with the results of flash vacuum pyrolysis experiments. The pyrazole decomposition product vinylcarbene is expected to rearrange to propyne, making pyrazole decomposition essentially thermoneutral. It is hypothesized that at high concentrations vinylcarbene could undergo a self-reaction to 1,3- and 1,4-cyclohexadiene.
The carbon cycle and biogeochemical dynamics in lake sediments

USGS Publications Warehouse

Dean, W.E.

1999-01-01

The concentrations of organic carbon (OC) and CaCO3 in lake sediments are often inversely related. This relation occurs in surface sediments from different locations in the same lake, surface sediments from different lakes, and with depth in Holocene sediments. Where data on accumulation rates are available, the relation holds for organic carbon and CaCO3 accumulation rates as well. An increase of several percent OC is accompanied by a decrease of several tens of percent CaCO3 indicating that the inverse relation is not due to simple dilution of one component by another. It appears from core data that once the OC concentration in the sediments becomes greater than about 12%, the CO2 produced by decomposition of that OC and production of organic acids lowers the pH of anoxic pore waters enough to dissolve any CaCO3 that reaches the sediment-water interface. In a lake with a seasonally anoxic hypolimnion, processes in the water column also can produce an inverse relation between OC and CaCO3 over time. If productivity of the lake increases, the rain rate of OC from the epilimnion increases. Biogenic removal of CO2 and accompanying increase in pH also may increase the production of CaCO3. However, the decomposition of organic matter in the hypolimnion will decrease the pH of the hypolimnion causing greater dissolution of CaCO3 and therefore a decrease in the rain rate of CaCO3 to the sediment-water interface.
Let's Break it Down: A Study of Organic Decomposition Rates in Clay Soil

NASA Astrophysics Data System (ADS)

Weiss, E.

2016-12-01

In this experiment I will be testing if temperature affects the organic decomposition rates in clay soil. I will need to be able to clean and weigh each filter paper without disrupting my data damaging or brushing off additional paper material. From there I need to be able to analyze and interpret my data to factor anything else that may affect the decomposition rates in the soil. Soil decomposers include bacteria and fungi. They obtain energy from plant and animal detritus through aerobic decomposition, which is similar to how humans break down sugar. The formula is: C6H12O6 + O2 → CO2 + H2O + energy. Besides oxygen and sugar the organisms need nutrients such as water and sustainable temperatures. Decomposition is important to us because it helps regulate soil structure, moisture, temperature, and provides nutrients to soil organisms. This matters on a global scale since decomposers release a large amount of carbon when breaking down matter, which contributes to greenhouse gasses such as carbon dioxide and methane. These greenhouse gasses affect the earth's climate. People who care about decomposition are farmers and those in agriculture, as well as environmental scientists. Even national parks might care because decomposition may affect park safety, how the park looks, and the amount of plants and wildlife. Things that can affect decomposition are the decomposers in the soil, temperature, and water or moisture. My secondary research also showed that PH and chemical composition of the soil affect the rate of decomposition.Cold or freezing temperatures can help preserve organic material in soil because it freezes the soil and moisture, making it too dense for the organic decomposers to break down the organic matter. Soil also can be preserved by drying out and being stored at 4º Celsius (or 39º Fahrenheit) for 28 days. However, soil can degrade slowly in these conditions because it is not frozen and can be oxidized.
Genotype × Herbivore Effect on Leaf Litter Decomposition in Betula Pendula Saplings: Ecological and Evolutionary Consequences and the Role of Secondary Metabolites

PubMed Central

Silfver, Tarja; Paaso, Ulla; Rasehorn, Mira; Rousi, Matti; Mikola, Juha

2015-01-01

Plant genetic variation and herbivores can both influence ecosystem functioning by affecting the quantity and quality of leaf litter. Few studies have, however, investigated the effects of herbivore load on litter decomposition at plant genotype level. We reduced insect herbivory using an insecticide on one half of field-grown Betula Pendula saplings of 17 genotypes, representing random intrapopulation genetic variation, and allowed insects to naturally colonize the other half. We hypothesized that due to induced herbivore defence, saplings under natural herbivory produce litter of higher concentrations of secondary metabolites (terpenes and soluble phenolics) and have slower litter decomposition rate than saplings under reduced herbivory. We found that leaf damage was 89 and 53% lower in the insecticide treated saplings in the summer and autumn surveys, respectively, which led to 73% higher litter production. Litter decomposition rate was also affected by herbivore load, but the effect varied from positive to negative among genotypes and added up to an insignificant net effect at the population level. In contrast to our hypothesis, concentrations of terpenes and soluble phenolics were higher under reduced than natural herbivory. Those genotypes, whose leaves were most injured by herbivores, produced litter of lowest mass loss, but unlike we expected, the concentrations of terpenes and soluble phenolics were not linked to either leaf damage or litter decomposition. Our results show that (1) the genetic and herbivore effects on B. pendula litter decomposition are not mediated through variation in terpene or soluble phenolic concentrations and suggest that (2) the presumably higher insect herbivore pressure in the future warmer climate will not, at the ecological time scale, affect the mean decomposition rate in genetically diverse B. pendula populations. However, (3) due to the significant genetic variation in the response of decomposition to herbivory, evolutionary changes in mean decomposition rate are possible. PMID:25622034
Rates of forest floor decomposition and nutrient turnover in aspen, pine, and spruce stands on two soils.

Treesearch

D. A. Perala; D.H. Alban

1982-01-01

Compares rates of forest floor decomposition and nutrient turnover in aspen and conifers. These rates were generally most rapid under aspen, slowest under spruce, and more rapid on a loamy fine sand than on a very fine sandy loam. Compares results with literature values.
Intrapopulation Genotypic Variation of Foliar Secondary Chemistry during Leaf Senescence and Litter Decomposition in Silver Birch (Betula pendula)

PubMed Central

Paaso, Ulla; Keski-Saari, Sarita; Keinänen, Markku; Karvinen, Heini; Silfver, Tarja; Rousi, Matti; Mikola, Juha

2017-01-01

Abundant secondary metabolites, such as condensed tannins, and their interpopulation genotypic variation can remain through plant leaf senescence and affect litter decomposition. Whether the intrapopulation genotypic variation of a more diverse assortment of secondary metabolites equally persists through leaf senescence and litter decomposition is not well understood. We analyzed concentrations of intracellular phenolics, epicuticular flavonoid aglycones, epicuticular triterpenoids, condensed tannins, and lignin in green leaves, senescent leaves and partly decomposed litter of silver birch, Betula pendula. Broad-sense heritability (H2) and coefficient of genotypic variation (CVG) were estimated for metabolites in senescent leaves and litter using 19 genotypes selected from a B. pendula population in southern Finland. We found that most of the secondary metabolites remained through senescence and decomposition and that their persistence was related to their chemical properties. Intrapopulation H2 and CVG for intracellular phenolics, epicuticular flavonoid aglycones and condensed tannins were high and remarkably, increased from senescent leaves to decomposed litter. The rank of genotypes in metabolite concentrations was persistent through litter decomposition. Lignin was an exception, however, with a diminishing genotypic variation during decomposition, and the concentrations of lignin and condensed tannins had a negative genotypic correlation in the senescent leaves. Our results show that secondary metabolites and their intrapopulation genotypic variation can for the most part remain through leaf senescence and early decomposition, which is a prerequisite for initial litter quality to predict variation in litter decomposition rates. Persistent genotypic variation also opens an avenue for selection to impact litter decomposition in B. pendula populations through acting on their green foliage secondary chemistry. The negative genotypic correlations and diminishing heritability of lignin concentrations may, however, counteract this process. PMID:28694813
Intrapopulation Genotypic Variation of Foliar Secondary Chemistry during Leaf Senescence and Litter Decomposition in Silver Birch (Betula pendula).

PubMed

Paaso, Ulla; Keski-Saari, Sarita; Keinänen, Markku; Karvinen, Heini; Silfver, Tarja; Rousi, Matti; Mikola, Juha

2017-01-01

Abundant secondary metabolites, such as condensed tannins, and their interpopulation genotypic variation can remain through plant leaf senescence and affect litter decomposition. Whether the intrapopulation genotypic variation of a more diverse assortment of secondary metabolites equally persists through leaf senescence and litter decomposition is not well understood. We analyzed concentrations of intracellular phenolics, epicuticular flavonoid aglycones, epicuticular triterpenoids, condensed tannins, and lignin in green leaves, senescent leaves and partly decomposed litter of silver birch, Betula pendula . Broad-sense heritability ( H 2 ) and coefficient of genotypic variation ( CV G ) were estimated for metabolites in senescent leaves and litter using 19 genotypes selected from a B. pendula population in southern Finland. We found that most of the secondary metabolites remained through senescence and decomposition and that their persistence was related to their chemical properties. Intrapopulation H 2 and CV G for intracellular phenolics, epicuticular flavonoid aglycones and condensed tannins were high and remarkably, increased from senescent leaves to decomposed litter. The rank of genotypes in metabolite concentrations was persistent through litter decomposition. Lignin was an exception, however, with a diminishing genotypic variation during decomposition, and the concentrations of lignin and condensed tannins had a negative genotypic correlation in the senescent leaves. Our results show that secondary metabolites and their intrapopulation genotypic variation can for the most part remain through leaf senescence and early decomposition, which is a prerequisite for initial litter quality to predict variation in litter decomposition rates. Persistent genotypic variation also opens an avenue for selection to impact litter decomposition in B. pendula populations through acting on their green foliage secondary chemistry. The negative genotypic correlations and diminishing heritability of lignin concentrations may, however, counteract this process.
Soil C dynamics under intensive oil palm plantations in poor tropical soils

NASA Astrophysics Data System (ADS)

Guillaume, Thomas; Ruegg, Johanna; Quezada, Juan Carlos; Buttler, Alexandre

2017-04-01

Oil palm cultivation mainly takes place on heavily-weathered tropical soils where nutrients are limiting factors for plant growth and microbial activity. Intensive fertilization and changes of C input by oil palms strongly affects soil C and nutrient dynamics, challenging long-term soil fertility. Oil palm plantations management offers unique opportunities to study soil C and nutrients interactions in field conditions because 1) they can be considered as long-term litter manipulation experiments since all aboveground C inputs are concentrated in frond pile areas and 2) mineral fertilizers are only applied in specific areas, i.e. weeded circle around the tree and interrows, but not in harvest paths. Here, we determined impacts of mineral fertilizer and organic matter input on soil organic carbon dynamics and microbial activity in mature oil palm plantation established on savanna grasslands. Rates of savanna-derived soil organic carbon (SOC) decomposition and oil palm-derived SOC net stabilization were determined using changes in isotopic signature of in C input following a shift from C4 (savanna) to C3 (oil palm) vegetation. Application of mineral fertilizer alone did not affect savanna-derived SOC decomposition or oil palm-derived SOC stabilization rates, but fertilization associated with higher C input lead to an increase of oil palm-derived SOC stabilization rates, with about 50% of topsoil SOC derived from oil palm after 9 years. High carbon and nutrients inputs did not increase microbial biomass but microorganisms were more active per unit of biomass and SOC. In conclusion, soil organic matter decomposition was limited by C rather than nutrients in the studied heavily-weathered soils. Fresh C and nutrient inputs did not lead to priming of old savanna-derived SOC but increased turnover and stabilization of new oil palm-derived SOC.
Tracing nitrogen accumulation in decaying wood and examining its impact on wood decomposition rate

NASA Astrophysics Data System (ADS)

Rinne, Katja T.; Rajala, Tiina; Peltoniemi, Krista; Chen, Janet; Smolander, Aino; Mäkipää, Raisa

2016-04-01

Decomposition of dead wood, which is controlled primarily by fungi is important for ecosystem carbon cycle and has potentially a significant role in nitrogen fixation via diazotrophs. Nitrogen content has been found to increase with advancing wood decay in several studies; however, the importance of this increase to decay rate and the sources of external nitrogen remain unclear. Improved knowledge of the temporal dynamics of wood decomposition rate and nitrogen accumulation in wood as well as the drivers of the two processes would be important for carbon and nitrogen models dealing with ecosystem responses to climate change. To tackle these questions we applied several analytical methods on Norway spruce logs from Lapinjärvi, Finland. We incubated wood samples (density classes from I to V, n=49) in different temperatures (from 8.5oC to 41oC, n=7). After a common seven day pre-incubation period at 14.5oC, the bottles were incubated six days in their designated temperature prior to CO2 flux measurements with GC to determine the decomposition rate. N2 fixation was measured with acetylene reduction assay after further 48 hour incubation. In addition, fungal DNA, (MiSeq Illumina) δ15N and N% composition of wood for samples incubated at 14.5oC were determined. Radiocarbon method was applied to obtain age distribution for the density classes. The asymbiotic N2 fixation rate was clearly dependent on the stage of wood decay and increased from stage I to stage IV but was substantially reduced in stage V. CO2 production was highest in the intermediate decay stage (classes II-IV). Both N2 fixation and CO2 production were highly temperature sensitive having optima in temperature 25oC and 31oC, respectively. We calculated the variation of annual levels of respiration and N2 fixation per hectare for the study site, and used the latter data together with the 14C results to determine the amount of N2 accumulated in wood in time. The proportion of total nitrogen in wood originating from N2 increased from 0.4% (class I) to 22% (V). Despite significant N inputs, N2 fixation explained only 34%-57% of the increase in wood N content of classes III-V. The DNA results indicated that mycorrhizal colonization of wood could only partially explain the remaining increase in N content. However, majority of the samples contained one or more wood decomposing fungal species that have been reported to have the capability to produce rhizomorphs or mycelial cords used for scavenging nutrients from outside sources. Assuming that the remaining increase in N content was due to fungal activity, we modelled the δ15N variation of wood from class I to V and compared the modelled and measured δ15N values (r = 0.95, p<0.05). The increase in wood nitrogen content in time was observed to have a significant, positive impact on the respiration rate (I-IV: r = 0.57, p<0.01).
Seasonal necrophagous insect community assembly during vertebrate carrion decomposition.

PubMed

Benbow, M E; Lewis, A J; Tomberlin, J K; Pechal, J L

2013-03-01

Necrophagous invertebrates have been documented to be a predominant driver of vertebrate carrion decomposition; however, very little is understood about the assembly of these communities both within and among seasons. The objective of this study was to evaluate the seasonal differences in insect taxa composition, richness, and diversity on carrion over decomposition with the intention that such data will be useful for refining error estimates in forensic entomology. Sus scrofa (L.) carcasses (n = 3-6, depending on season) were placed in a forested habitat near Xenia, OH, during spring, summer, autumn, and winter. Taxon richness varied substantially among seasons but was generally lower (1-2 taxa) during early decomposition and increased (3-8 taxa) through intermediate stages of decomposition. Autumn and winter showed the highest richness during late decomposition. Overall, taxon richness was higher during active decay for all seasons. While invertebrate community composition was generally consistent among seasons, the relative abundance of five taxa significantly differed across seasons, demonstrating different source communities for colonization depending on the time of year. There were significantly distinct necrophagous insect communities for each stage of decomposition, and between summer and autumn and summer and winter, but the communities were similar between autumn and winter. Calliphoridae represented significant indicator taxa for summer and autumn but replaced by Coleoptera during winter. Here we demonstrated substantial variability in necrophagous communities and assembly on carrion over decomposition and among seasons. Recognizing this variation has important consequences for forensic entomology and future efforts to provide error rates for estimates of the postmortem interval using arthropod succession data as evidence during criminal investigations.
Climate fails to predict wood decomposition at regional scales

Treesearch

Mark A. Bradford; Robert J. Warren; Petr Baldrian; Thomas W. Crowther; Daniel S. Maynard; Emily E. Oldfield; William R. Wieder; Stephen A. Wood; Joshua R. King

2014-01-01

Decomposition of organic matter strongly influences ecosystem carbon storage1. In Earth-system models, climate is a predominant control on the decomposition rates of organic matter2, 3, 4, 5. This assumption is based on the mean response of decomposition to climate, yet there is a growing appreciation in other areas of global change science that projections based on...
Seasonal Variability May Affect Microbial Decomposers and Leaf Decomposition More Than Warming in Streams.

PubMed

Duarte, Sofia; Cássio, Fernanda; Ferreira, Verónica; Canhoto, Cristina; Pascoal, Cláudia

2016-08-01

Ongoing climate change is expected to affect the diversity and activity of aquatic microbes, which play a key role in plant litter decomposition in forest streams. We used a before-after control-impact (BACI) design to study the effects of warming on a forest stream reach. The stream reach was divided by a longitudinal barrier, and during 1 year (ambient year) both stream halves were at ambient temperature, while in the second year (warmed year) the temperature in one stream half was increased by ca. 3 °C above ambient temperature (experimental half). Fine-mesh bags containing oak (Quercus robur L.) leaves were immersed in both stream halves for up to 60 days in spring and autumn of the ambient and warmed years. We assessed leaf-associated microbial diversity by denaturing gradient gel electrophoresis and identification of fungal conidial morphotypes and microbial activity by quantifying leaf mass loss and productivity of fungi and bacteria. In the ambient year, no differences were found in leaf decomposition rates and microbial productivities either between seasons or stream halves. In the warmed year, phosphorus concentration in the stream water, leaf decomposition rates, and productivity of bacteria were higher in spring than in autumn. They did not differ between stream halves, except for leaf decomposition, which was higher in the experimental half in spring. Fungal and bacterial communities differed between seasons in both years. Seasonal changes in stream water variables had a greater impact on the activity and diversity of microbial decomposers than a warming regime simulating a predicted global warming scenario.
Long-term Priming-induced Changes in Permafrost Soil Organic Matter Decomposition

NASA Astrophysics Data System (ADS)

Pegoraro, E.; Bracho, R. G.; Schuur, E.

2016-12-01

Warming of tundra ecosystems due to climate change is predicted to thaw permafrost and increase plant biomass and litter input to soil. Additional input of easily decomposable carbon can stimulate microbial activity, consequently increasing soil organic matter decomposition rates. This phenomenon, known as the priming effect, can exacerbate the effects of climate change by releasing more CO2 from permafrost soils; however, the extent to which it could decrease soil carbon stocks in the Arctic is unknown. Most priming incubation studies are conducted for a short period of time, making it difficult to assess if priming is a short-term phenomenon, or could persist over the long-term. We incubated permafrost soil from a moist acidic tundra site in Healy, Alaska for 456 days at 15° C. Soil from surface and deep layers were amended with three pulses of uniformly 13C labeled glucose, a fast decomposing substrate, every 152 days. We also quantified the proportion of old carbon respired by measuring 14CO2. Substrate addition resulted in higher respiration rates in glucose amended soils; however, positive priming was only observed in deep layers, where on average 9%, 57%, and 25% more soil-derived C was respired at 45-55, 65-75, and 75-85 cm depth increments for the duration of the experiment. This suggests that microbes in deep layers are limited in energy, and the addition of easily decomposable carbon increases native soil organic matter decomposition.
Effects of nutrient enrichment on the decomposition of wood and associated microbial activity in streams

USGS Publications Warehouse

Gulis, V.; Rosemond, A.D.; Suberkropp, K.; Weyers, H.S.; Benstead, J.P.

2004-01-01

1. We determined the effects of nutrient enrichment on wood decomposition rates and microbial activity during a 3-year study in two headwater streams at Coweeta Hydrologic Laboratory, NC, U.S.A. After a 1-year pretreatment period, one of the streams was continuously enriched with inorganic nutrients (nitrogen and phosphorus) for 2 years while the other stream served as a reference. We determined the effects of enrichment on both wood veneers and sticks, which have similar carbon quality but differ in physical characteristics (e.g. surface area to volume ratios, presence of bark) that potentially affect microbial colonisation and activity. 2. Oak wood veneers (0.5 mm thick) were placed in streams monthly and allowed to decompose for approximately 90 days. Nutrient addition stimulated ash-free dry mass loss and increased mean nitrogen content, fungal biomass and microbial respiration on veneers in the treatment stream compared with the reference. The magnitude of the response to enrichment was great, with mass loss 6.1 times, and per cent N, fungal biomass and microbial respiration approximately four times greater in the treatment versus reference stream. 3. Decomposition rate and nitrogen content of maple sticks (ca. 1-2 cm diameter) also increased; however, the effect was less pronounced than for veneers. Wood response overall was greater than that determined for leaves in a comparable study, supporting the hypothesis that response to enrichment may be greater for lower quality organic matter (high C:N) than for higher quality (low C:N) substrates. 4. Our results show that moderate nutrient enrichment can profoundly affect decomposition rate and microbial activity on wood in streams. Thus, the timing and availability of wood that provides retention, structure, attachment sites and food in stream ecosystems may be affected by nutrient concentrations raised by human activities.

Pulse frequency and soil-litter mixing alter the control of cumulative precipitation over litter decomposition.

PubMed

Joly, François-Xavier; Kurupas, Kelsey L; Throop, Heather L

2017-09-01

Macroclimate has traditionally been considered the predominant driver of litter decomposition. However, in drylands, cumulative monthly or annual precipitation typically fails to predict decomposition. In these systems, the windows of opportunity for decomposer activity may rather depend on the precipitation frequency and local factors affecting litter desiccation, such as soil-litter mixing. We used a full-factorial microcosm experiment to disentangle the relative importance of cumulative precipitation, pulse frequency, and soil-litter mixing on litter decomposition. Decomposition, measured as litter carbon loss, saturated with increasing cumulative precipitation when pulses were large and infrequent, suggesting that litter moisture no longer increased and/or microbial activity was no longer limited by water availability above a certain pulse size. More frequent precipitation pulses led to increased decomposition at high levels of cumulative precipitation. Soil-litter mixing consistently increased decomposition, with greatest relative increase (+194%) under the driest conditions. Collectively, our results highlight the need to consider precipitation at finer temporal scale and incorporate soil-litter mixing as key driver of decomposition in drylands. © 2017 by the Ecological Society of America.
Long-term litter decomposition controlled by manganese redox cycling

DOE PAGES

Keiluweit, Marco; Nico, Peter S.; Harmon, Mark; ...

2015-09-08

Litter decomposition is a keystone ecosystem process impacting nutrient cycling and productivity, soil properties, and the terrestrial carbon (C) balance, but the factors regulating decomposition rate are still poorly understood. Traditional models assume that the rate is controlled by litter quality, relying on parameters such as lignin content as predictors. However, a strong correlation has been observed between the manganese (Mn) content of litter and decomposition rates across a variety of forest ecosystems. Here, we show that long-term litter decomposition in forest ecosystems is tightly coupled to Mn redox cycling. Over 7 years of litter decomposition, microbial transformation of littermore » was paralleled by variations in Mn oxidation state and concentration. A detailed chemical imaging analysis of the litter revealed that fungi recruit and redistribute unreactive Mn 2+ provided by fresh plant litter to produce oxidative Mn 3+ species at sites of active decay, with Mn eventually accumulating as insoluble Mn 3+/4+ oxides. Formation of reactive Mn 3+ species coincided with the generation of aromatic oxidation products, providing direct proof of the previously posited role of Mn 3+-based oxidizers in the breakdown of litter. Our results suggest that the litter-decomposing machinery at our coniferous forest site depends on the ability of plants and microbes to supply, accumulate, and regenerate short-lived Mn 3+ species in the litter layer. As a result, this observation indicates that biogeochemical constraints on bioavailability, mobility, and reactivity of Mn in the plant–soil system may have a profound impact on litter decomposition rates.« less
Sulfur capture under periodically changing oxidizing and reducing conditions in PFBC

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zevenhoven, R.; Yrjas, P.; Hupa, M.

1999-07-01

During in situ sulfur capture with a calcium-based sorbent in fluidized bed combustion (FBC), a temperature optimum is found, at atmospheric pressure, at {approximately}850 C. The repeated decomposition of sulfated limestone during stages where the gas atmosphere surrounding the sorbent particle is not oxidizing but reducing has been identified to explain this maximum. Under pressurized (PFBC) conditions, an additional aspect is the direct conversion of calcium carbonate (CaCO{sub 3}) without the intermediate calcium oxide (CaO) due to the partial pressure of carbon dioxide (CO{sub 2}). In this work it was evaluated how stable calcium sulfate (CaSO{sub 4}) is in amore » gas atmosphere that periodically changes from oxidizing to reducing and vice versa. Atmospheric as well as elevated pressures are considered. CaO or CaCO{sub 3}, and/or calcium sulfide (CaS) are formed during the reducing stage. Using a pressurized thermogravimetric reactor (PTGR) a limestone was periodically sulfated under oxidizing conditions and decomposed under reducing conditions with carbon monoxide (CO), or with CO + H{sub 2} (hydrogen). Experiments at 1 bar and 15 bar were carried out, at temperatures from 850 C to 950 C, at C O and CO + H{sub 2} concentrations up to 4%-vol. The experimental data were modeled using simple first order (parallel) reaction schemes that allowed for sorbent structure changes. This gave rate parameters for the sulfation and the decomposition reactions, and identified the decomposition products. It was found that 1 bar, CO + H{sub 2} gives a higher reduction of CaSO{sub 4} than CO, at the same total concentration. The rate of decomposition increases faster with temperature than the sulfation, explaining the sulfation efficiency maximum mentioned above. At 15 bar, a different picture is seen. The reductive decomposition rate as well as the sulfation rate are slower, with CO as well as CO with small amounts of H{sub 2} as the reducing species. There is a significant effect of the water which is present in the gas at higher concentrations than H{sub 2}. Thermodynamics indicate that this leads to the decomposition of CaS, releasing H{sub 2}S.« less
Decomposition of soil organic matter from boreal black spruce forest: Environmental and chemical controls

USGS Publications Warehouse

Wickland, K.P.; Neff, J.C.

2008-01-01

Black spruce forests are a dominant covertype in the boreal forest region, and they inhabit landscapes that span a wide range of hydrologic and thermal conditions. These forests often have large stores of soil organic carbon. Recent increases in temperature at northern latitudes may be stimulating decomposition rates of this soil carbon. It is unclear, however, how changes in environmental conditions influence decomposition in these systems, and if substrate controls of decomposition vary with hydrologic and thermal regime. We addressed these issues by investigating the effects of temperature, moisture, and organic matter chemical characteristics on decomposition of fibric soil horizons from three black spruce forest sites. The sites varied in drainage and permafrost, and included a "Well Drained" site where permafrost was absent, and "Moderately well Drained" and "Poorly Drained" sites where permafrost was present at about 0.5 m depth. Samples collected from each site were incubated at five different moisture contents (2, 25, 50, 75, and 100% saturation) and two different temperatures (10??C and 20??C) in a full factorial design for two months. Organic matter chemistry was analyzed using pyrolysis gas chromatography-mass spectrometry prior to incubation, and after incubation on soils held at 20??C, 50% saturation. Mean cumulative mineralization, normalized to initial carbon content, ranged from 0.2% to 4.7%, and was dependent on temperature, moisture, and site. The effect of temperature on mineralization was significantly influenced by moisture content, as mineralization was greatest at 20??C and 50-75% saturation. While the relative effects of temperature and moisture were similar for all soils, mineralization rates were significantly greater for samples from the "Well Drained" site compared to the other sites. Variations in the relative abundances of polysaccharide-derivatives and compounds of undetermined source (such as toluene, phenol, 4-methyl phenol, and several unidentifiable compounds) could account for approximately 44% of the variation in mineralization across all sites under ideal temperature and moisture conditions. Based on our results, changes in temperature and moisture likely have similar, additive effects on in situ soil organic matter (SOM) decomposition across a wide range of black spruce forest systems, while variations in SOM chemistry can lead to significant differences in decomposition rates within and among forest sites. ?? 2007 Springer Science+Business Media B.V.
Effect of variable rates of daily sampling of fly larvae on decomposition and carrion insect community assembly: implications for forensic entomology field study protocols.

PubMed

Michaud, Jean-Philippe; Moreau, Gaétan

2013-07-01

Experimental protocols in forensic entomology successional field studies generally involve daily sampling of insects to document temporal changes in species composition on animal carcasses. One challenge with that method has been to adjust the sampling intensity to obtain the best representation of the community present without affecting the said community. To this date, little is known about how such investigator perturbations affect decomposition-related processes. Here, we investigated how different levels of daily sampling of fly eggs and fly larvae affected, over time, carcass decomposition rate and the carrion insect community. Results indicated that a daily sampling of <5% of the egg and larvae volumes present on a carcass, a sampling intensity believed to be consistent with current accepted practices in successional field studies, had little effect overall. Higher sampling intensities, however, slowed down carcass decomposition, affected the abundance of certain carrion insects, and caused an increase in the volume of eggs laid by dipterans. This study suggests that the carrion insect community not only has a limited resilience to recurrent perturbations but that a daily sampling intensity equal to or <5% of the egg and larvae volumes appears adequate to ensure that the system is representative of unsampled conditions. Hence we propose that this threshold be accepted as best practice in future forensic entomology successional field studies.
Litter quality mediated nitrogen effect on plant litter decomposition regardless of soil fauna presence.

PubMed

Zhang, Weidong; Chao, Lin; Yang, Qingpeng; Wang, Qingkui; Fang, Yunting; Wang, Silong

2016-10-01

Nitrogen addition has been shown to affect plant litter decomposition in terrestrial ecosystems. The way that nitrogen deposition impacts the relationship between plant litter decomposition and altered soil nitrogen availability is unclear, however. This study examined 18 co-occurring litter types in a subtropical forest in China in terms of their decomposition (1 yr of exposure in the field) with nitrogen addition treatment (0, 0.4, 1.6, and 4.0 mol·N·m -2 ·yr -1 ) and soil fauna exclusion (litter bags with 0.1 and 2 cm mesh size). Results showed that the plant litter decomposition rate is significantly reduced because of nitrogen addition; the strength of the nitrogen addition effect is closely related to the nitrogen addition levels. Plant litters with diverse quality responded to nitrogen addition differently. When soil fauna was present, the nitrogen addition effect on medium-quality or high-quality plant litter decomposition rate was -26% ± 5% and -29% ± 4%, respectively; these values are significantly higher than that of low-quality plant litter decomposition. The pattern is similar when soil fauna is absent. In general, the plant litter decomposition rate is decreased by soil fauna exclusion; an average inhibition of -17% ± 1.5% was exhibited across nitrogen addition treatment and litter quality groups. However, this effect is weakly related to nitrogen addition treatment and plant litter quality. We conclude that the variations in plant litter quality, nitrogen deposition, and soil fauna are important factors of decomposition and nutrient cycling in a subtropical forest ecosystem. © 2016 by the Ecological Society of America.
Kinetics of electron-induced decomposition of CF2Cl2 coadsorbed with water (ice): A comparison with CCl4

NASA Astrophysics Data System (ADS)

Faradzhev, N. S.; Perry, C. C.; Kusmierek, D. O.; Fairbrother, D. H.; Madey, T. E.

2004-11-01

The kinetics of decomposition and subsequent chemistry of adsorbed CF2Cl2, activated by low-energy electron irradiation, have been examined and compared with CCl4. These molecules have been adsorbed alone and coadsorbed with water ice films of different thicknesses on metal surfaces (Ru; Au) at low temperatures (25 K; 100 K). The studies have been performed with temperature programmed desorption (TPD), reflection absorption infrared spectroscopy (RAIRS), and x-ray photoelectron spectroscopy (XPS). TPD data reveal the efficient decomposition of both halocarbon molecules under electron bombardment, which proceeds via dissociative electron attachment (DEA) of low-energy secondary electrons. The rates of CF2Cl2 and CCl4 dissociation increase in an H2O (D2O) environment (2-3×), but the increase is smaller than that reported in recent literature. The highest initial cross sections for halocarbon decomposition coadsorbed with H2O, using 180 eV incident electrons, are measured (using TPD) to be 1.0±0.2×10-15 cm2 for CF2Cl2 and 2.5±0.2×10-15 cm2 for CCl4. RAIRS and XPS studies confirm the decomposition of halocarbon molecules codeposited with water molecules, and provide insights into the irradiation products. Electron-induced generation of Cl- and F- anions in the halocarbon/water films and production of H3O+, CO2, and intermediate compounds COF2 (for CF2Cl2) and COCl2, C2Cl4 (for CCl4) under electron irradiation have been detected using XPS, TPD, and RAIRS. The products and the decomposition kinetics are similar to those observed in our recent experiments involving x-ray photons as the source of ionizing irradiation.
Influence of nitrogen additions on litter decomposition, nutrient dynamics, and enzymatic activity of two plant species in a peatland in Northeast China.

PubMed

Song, Yanyu; Song, Changchun; Ren, Jiusheng; Tan, Wenwen; Jin, Shaofei; Jiang, Lei

2018-06-01

Nitrogen (N) availability affects litter decomposition and nutrient dynamics, especially in N-limited ecosystems. We investigated the response of litter decomposition to N additions in Eriophorum vaginatum and Vaccinium uliginosum peatlands. These two species dominate peatlands in Northeast China. In 2012, mesh bags containing senesced leaf litter of Eriophorum vaginatum and Vaccinium uliginosum were placed in N addition plots and sprayed monthly for two years with NH 4 NO 3 solution at dose rates of 0, 6, 12, and 24gNm -2 year -1 (CK, N1, N2 and N3, respectively). Mass loss, N and phosphorus (P) content, and enzymatic activity were measured over time as litter decomposed. In the control plots, V. uliginosum litter decomposed faster than E. vaginatum litter. N1, N2, and N3 treatments increased the mass losses of V. uliginosum litter by 6%, 9%, and 4% respectively, when compared with control. No significant influence of N additions was found on the decomposition of E. vaginatum litter. However, N and P content in E. vaginatum litter and V. uliginosum litter significantly increased with N additions. Moreover, N additions significantly promoted invertase and β-glucosidase activity in E. vaginatum and V. uliginosum litter. However, only in V. uliginosum litter was polyphenol oxidase activity significantly enhanced. Our results showed that initial litter quality and polyphenol oxidase activity influence the response of plant litter to N additions in peatland ecosystems. Increased N availability may change peatland soil N and P cycling by enhancing N and P immobilization during litter decomposition. Copyright © 2018 Elsevier B.V. All rights reserved.
The effects of local forearm muscle cooling on motor unit properties.

PubMed

Mallette, Matthew M; Green, Lara A; Gabriel, David A; Cheung, Stephen S

2018-02-01

Muscle cooling impairs maximal force. Using needle electromyography (EMG) to assess motor unit properties during muscle cooling, is limited and equivocal. Therefore, we aimed to determine the impact of local muscle cooling on motor unit firing properties using surface EMG decomposition. Twenty participants (12 M, 8 F) completed maximal, evoked, and trapezoidal contractions during thermoneutral and cold muscle conditions. Forearm muscle temperature was manipulated using 10-min neutral (~ 32 °C) or 20-min cold (~ 3 °C) water baths. Twitches and maximal voluntary contractions were performed prior to, and after, forearm immersion in neutral or cold water. Motor unit properties were assessed during trapezoidal contractions to 50% baseline force using surface EMG decomposition. Impaired contractile properties from muscle cooling were evident in the twitch amplitude, duration, and rate of force development indicating that the muscle was successfully cooled from the cold water bath (all d ≥ 0.5, P < 0.05). Surface EMG decomposition showed muscle cooling increased the number of motor units (d = 0.7, P = 0.01) and motor unit action potential (MUAP) duration (d = 0.6, P < 0.001), but decreased MUAP amplitude (d = 0.2, P = 0.012). Individually, neither motor unit firing rates (d = 0.1, P = 0.843) nor recruitment threshold (d = 0.1, P = 0.746) changed; however, the relationship between the recruitment threshold and motor unit firing rate was steeper (d = 1.0, P < 0.001) and had an increased y-intercept (d = 0.9, P = 0.007) with muscle cooling. Since muscle contractility is impaired with muscle cooling, these findings suggest a compensatory increase in the number of active motor units, and small but coupled changes in motor unit firing rates and recruitment threshold to produce the same force.
Response of an Alpine Tundra in the Southern Rocky Mountains to Climate Change by 2100: Projections of Water, Carbon, and Nitrogen Cycling under RCP 4.5 and RCP 8.5 Scenarios

NASA Astrophysics Data System (ADS)

Dong, Z.; Driscoll, C. T.; Hayhoe, K.; Pourmokhtarian, A.; Stoner, A. M. K.

2016-12-01

Biogeochemical cycling of water, carbon, and nitrogen in alpine tundra ecosystems are closely related to the water and nutrient supply and ecosystem function of watersheds. While studies on the response of alpine tundra to climate change have largely focused on ecosystem structure, research on response of ecosystem function and element cycling are less well established. Using downscaled future climate scenarios under Representative Concentration Pathways (RCP) and revised algorithm of the ecosystem model, PnET-BGC, we investigated water, carbon, and nitrogen cycling of an alpine tundra ecosystem under different projections of future climate change at Saddle site of Niwot Ridge, Colorado. Simulations from this study suggest that future water supply from the alpine tundra was well predicted by the Budyko curve, which contrasts with findings from several previous studies. Although foliar display is projected to decrease due to summer water stress, an extend growing season and increasing atmospheric CO2 concentrations reverse its effects on carbon fixation by allowing longer period of photosynthesis and greater photosynthetic rate per leaf area. As a result of the increasing carbon sequestration, large increases in carbon storage are projected in living and dead biomass. Decomposition of soil organic carbon and mineralization of soil organic nitrogen increase with temperature and soil moisture, but also related to the period of snow cover which likely enhances microbial activity and associated soil decomposition and N immobilization. Future increase in winter precipitation leads to increasing snow water content which increases spring soil moisture and decomposition. Shorter future snow cover period and decreased summer soil moisture caused lower decomposition in both seasons, therefore negligible long-term pattern is projected. Future net N mineralization generally followed the pattern of organic carbon decomposition, but slightly increased because of decreasing winter immobilization due to projected shorter snow cover period. Nitrogen uptake is projected to be higher under radiative forcing scenarios of higher primary production and greater net N mineralization.
Effects of mesh bag enclosure and termites on fine woody debris decomposition in a subtropical forest

Treesearch

Allison M. Stoklosa; Michael D. Ulyshen; Zhaofei Fan; Morgan Varner; Sebastian Seibold; Jorg Muller

2016-01-01

The role of insects in terrestrial decomposition remains poorly resolved, particularly for infrequently studied substrates like small diameter woody debris.Â Uncertainty about how mesh bags used to exclude arthropods may affect decomposition rates continues to impede progress in this area.Â We sought to (1) measure how insects affect the decomposition of small diameter...
Nutrient dynamics and decomposition of riparian Arundinaria gigantea (Walt.)Muhl. leaves in southern Illinois

USDA-ARS?s Scientific Manuscript database

Leaf litter quality and quantity can influence soil nutrient dynamics and stream productivity through decomposition and serving as allochthonous stream inputs. Leaf deposition, nitrogen (N)-resorption efficiency and proficiency, and decomposition rates were analyzed in riparian stands of Arundinaria...
Mineral cycling in soil and litter arthropod food chains. Three-year progress report, February 1, 1984-January 31, 1987

DOE Office of Scientific and Technical Information (OSTI.GOV)

Crossley, D.A. Jr.

1986-08-29

This report summarizes progress in a three-year research project on the influence of soil arthropods (mites, collembolans, insects, millipedes and others) upon decomposition rates and nutrient dynamics in decaying vegetable matter. Research has concentrated on two aspects of elemental dynamics in decomposing organic matter: Effects of arthropods on rates of decomposition and nutrient loss (mineralization of carbon and other elements), and arthropod stimulation of microbial immobilization of nutrient elements during decomposition.
Heterogeneity in leaf litter decomposition in a temporary Mediterranean stream during flow fragmentation.

PubMed

Abril, Meritxell; Muñoz, Isabel; Menéndez, Margarita

2016-05-15

In temporary Mediterranean streams, flow fragmentation during summer droughts originates an ephemeral mosaic of terrestrial and aquatic habitat types. The heterogeneity of habitat types implies a particular ecosystem functioning in temporary streams that is still poorly understood. We assessed the initial phases of leaf litter decomposition in selected habitat types: running waters, isolated pools and moist and dry streambed sediments. We used coarse-mesh litter bags containing Populus nigra leaves to examine decomposition rates, microbial biomass, macroinvertebrate abundance and dissolved organic carbon (DOC) release rates in each habitat type over an 11-day period in late summer. We detected faster decomposition rates in aquatic (running waters and isolated pools) than in terrestrial habitats (moist and dry streambed sediments). Under aquatic conditions, decomposition was characterized by intense leaching and early microbial colonization, which swiftly started to decompose litter. Microbial colonization in isolated pools was primarily dominated by bacteria, whereas in running waters fungal biomass predominated. Under terrestrial conditions, leaves were most often affected by abiotic processes that resulted in small mass losses. We found a substantial decrease in DOC release rates in both aquatic habitats within the first days of the study, whereas DOC release rates remained relatively stable in the moist and dry sediments. This suggests that leaves play different roles as a DOC source during and after flow fragmentation. Overall, our results revealed that leaf decomposition is heterogeneous during flow fragmentation, which has implications related to DOC utilization that should be considered in future regional carbon budgets. Copyright © 2016 Elsevier B.V. All rights reserved.
Iron oxidation stimulates organic matter decomposition in humid tropical forest soils.

PubMed

Hall, Steven J; Silver, Whendee L

2013-09-01

Humid tropical forests have the fastest rates of organic matter decomposition globally, which often coincide with fluctuating oxygen (O2 ) availability in surface soils. Microbial iron (Fe) reduction generates reduced iron [Fe(II)] under anaerobic conditions, which oxidizes to Fe(III) under subsequent aerobic conditions. We demonstrate that Fe (II) oxidation stimulates organic matter decomposition via two mechanisms: (i) organic matter oxidation, likely driven by reactive oxygen species; and (ii) increased dissolved organic carbon (DOC) availability, likely driven by acidification. Phenol oxidative activity increased linearly with Fe(II) concentrations (P < 0.0001, pseudo R(2) = 0.79) in soils sampled within and among five tropical forest sites. A similar pattern occurred in the absence of soil, suggesting an abiotic driver of this reaction. No phenol oxidative activity occurred in soils under anaerobic conditions, implying the importance of oxidants such as O2 or hydrogen peroxide (H2 O2 ) in addition to Fe(II). Reactions between Fe(II) and H2 O2 generate hydroxyl radical, a strong nonselective oxidant of organic compounds. We found increasing consumption of H2 O2 as soil Fe(II) concentrations increased, suggesting that reactive oxygen species produced by Fe(II) oxidation explained variation in phenol oxidative activity among samples. Amending soils with Fe(II) at field concentrations stimulated short-term C mineralization by up to 270%, likely via a second mechanism. Oxidation of Fe(II) drove a decrease in pH and a monotonic increase in DOC; a decline of two pH units doubled DOC, likely stimulating microbial respiration. We obtained similar results by manipulating soil acidity independently of Fe(II), implying that Fe(II) oxidation affected C substrate availability via pH fluctuations, in addition to producing reactive oxygen species. Iron oxidation coupled to organic matter decomposition contributes to rapid rates of C cycling across humid tropical forests in spite of periodic O2 limitation, and may help explain the rapid turnover of complex C molecules in these soils. © 2013 John Wiley & Sons Ltd.
Heterogeneous decomposition of silane in a fixed bed reactor

NASA Technical Reports Server (NTRS)

Iya, S. K.; Flagella, R. N.; Dipaolo, F. S.

1982-01-01

Heterogeneous decomposition of silane in a fluidized bed offers an attractive route for the low-cost production of silicon for photovoltaic application. To obtain design data for a fluid bed silane pyrolysis reactor, deposition experiments were conducted in a small-scale fixed bed apparatus. Data on the decomposition mode, plating rate, and deposition morphology were obtained in the temperature range 600-900 C. Conditions favorable for heterogeneous decomposition with good deposition morphology were identified. The kinetic rate data showed the reaction to be first order with an activation energy of 38.8 kcal/mol, which agrees well with work done by others. The results are promising for the development of an economically attractive fluid bed process.
Inundation Effects on Growth and Decomposition of Two Tidal Marsh Plant Species, Spartina Alterniflora and Typha Angustifolia

EPA Science Inventory

Tidal marshes of southern New England have exhibited substantial changes over the past century: multiple anthropogenic stressors, such as enhanced rates of sea level rise, hydrological modifications, the introduction of invasive species, and increased nutrient loading have result...
Does increasing pressure always accelerate the condensed material decay initiated through bimolecular reactions? A case of the thermal decomposition of TKX-50 at high pressures.

PubMed

Lu, Zhipeng; Zeng, Qun; Xue, Xianggui; Zhang, Zengming; Nie, Fude; Zhang, Chaoyang

2017-08-30

Performances and behaviors under high temperature-high pressure conditions are fundamentals for many materials. We study in the present work the pressure effect on the thermal decomposition of a new energetic ionic salt (EIS), TKX-50, by confining samples in a diamond anvil cell, using Raman spectroscopy measurements and ab initio simulations. As a result, we find a quadratic increase in decomposition temperature (T d ) of TKX-50 with increasing pressure (P) (T d = 6.28P 2 + 12.94P + 493.33, T d and P in K and GPa, respectively, and R 2 = 0.995) and the decomposition under various pressures initiated by an intermolecular H-transfer reaction (a bimolecular reaction). Surprisingly, this finding is contrary to a general observation about the pressure effect on the decomposition of common energetic materials (EMs) composed of neutral molecules: increasing pressure will impede the decomposition if it starts from a bimolecular reaction. Our results also demonstrate that increasing pressure impedes the H-transfer via the enhanced long-range electrostatic repulsion of H +δ H +δ of neighboring NH 3 OH + , with blue shifts of the intermolecular H-bonds. And the subsequent decomposition of the H-transferred intermediates is also suppressed, because the decomposition proceeds from a bimolecular reaction to a unimolecular one, which is generally prevented by compression. These two factors are the basic root for which the decomposition retarded with increasing pressure of TKX-50. Therefore, our finding breaks through the previously proposed concept that, for the condensed materials, increasing pressure will accelerate the thermal decomposition initiated by bimolecular reactions, and reveals a distinct mechanism of the pressure effect on thermal decomposition. That is to say, increasing pressure does not always promote the condensed material decay initiated through bimolecular reactions. Moreover, such a mechanism may be feasible to other EISs due to the similar intermolecular interactions.
Moisture can be the dominant environmental parameter governing cadaver decomposition in soil.

PubMed

Carter, David O; Yellowlees, David; Tibbett, Mark

2010-07-15

Forensic taphonomy involves the use of decomposition to estimate postmortem interval (PMI) or locate clandestine graves. Yet, cadaver decomposition remains poorly understood, particularly following burial in soil. Presently, we do not know how most edaphic and environmental parameters, including soil moisture, influence the breakdown of cadavers following burial and alter the processes that are used to estimate PMI and locate clandestine graves. To address this, we buried juvenile rat (Rattus rattus) cadavers (approximately 18 g wet weight) in three contrasting soils from tropical savanna ecosystems located in Pallarenda (sand), Wambiana (medium clay), or Yabulu (loamy sand), Queensland, Australia. These soils were sieved (2mm), weighed (500 g dry weight), calibrated to a matric potential of -0.01 megapascals (MPa), -0.05 MPa, or -0.3 MPa (wettest to driest) and incubated at 22 degrees C. Measurements of cadaver decomposition included cadaver mass loss, carbon dioxide-carbon (CO(2)-C) evolution, microbial biomass carbon (MBC), protease activity, phosphodiesterase activity, ninhydrin-reactive nitrogen (NRN) and soil pH. Cadaver burial resulted in a significant increase in CO(2)-C evolution, MBC, enzyme activities, NRN and soil pH. Cadaver decomposition in loamy sand and sandy soil was greater at lower matric potentials (wetter soil). However, optimal matric potential for cadaver decomposition in medium clay was exceeded, which resulted in a slower rate of cadaver decomposition in the wettest soil. Slower cadaver decomposition was also observed at high matric potential (-0.3 MPa). Furthermore, wet sandy soil was associated with greater cadaver decomposition than wet fine-textured soil. We conclude that gravesoil moisture content can modify the relationship between temperature and cadaver decomposition and that soil microorganisms can play a significant role in cadaver breakdown. We also conclude that soil NRN is a more reliable indicator of gravesoil than soil pH. (c) 2010 Elsevier Ireland Ltd. All rights reserved.
Investigation of Molecular Structure and Thermal Properties of Thermo-Oxidative Aged SBS in Blends and Their Relations

PubMed Central

Xu, Xiong; Yu, Jianying; Xue, Lihui; Zhang, Canlin; Zha, Yagang; Gu, Yi

2017-01-01

Tri-block copolymer styrene–butadiene (SBS) is extensively applied in bituminous highway construction due to its high elasticity and excellent weather resistance. With the extension of time, tri-block structural SBS automatically degrades into bi-block structural SB- with some terminal oxygen-containing groups under the comprehensive effects of light, heat, oxygen, etc. In this paper, the effects of aging temperature, aging time and oxygen concentration on the molecular structure of thermo-oxidative aged SBS were mainly investigated using Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS), and the correlation between oxygen-containing groups and thermal properties (TG–DTG) was further discussed. The FTIR and XPS results show that rapid decomposition of SBS will occur with increments of aging temperature, aging time and oxygen concentration, and a large number of oxygen-containing groups such as –OH, C=O, –COOH, etc. will be formed during thermo-oxidative aging. In short-term aging, changes in aging temperature and oxygen concentration have a significant impact on the structural damage of SBS. However, in long-term aging, it has no further effect on the molecular structure of SBS or on increasing oxygen concentration. The TG and DTG results indicate that the concentration of substances with low molecular weight gradually increases with the improvement of the degree of aging of the SBS, while the initial decomposition rate increases at the beginning of thermal weightlessness and the decomposition rate slows down in comparison with neat SBS. From the relation between the XPS and TG results, it can be seen that the initial thermal stability of SBS rapidly reduces as the relative concentration of the oxygen-containing groups accumulates around 3%, while the maximum decomposition temperature slowly decreases when the relative concentration of the oxygen-containing groups is more than 3%, due to the difficult damage to strong bonds on the molecular structure of aged SBS. PMID:28773124

Investigation of Molecular Structure and Thermal Properties of Thermo-Oxidative Aged SBS in Blends and Their Relations.

PubMed

Xu, Xiong; Yu, Jianying; Xue, Lihui; Zhang, Canlin; Zha, Yagang; Gu, Yi

2017-07-07

Tri-block copolymer styrene-butadiene (SBS) is extensively applied in bituminous highway construction due to its high elasticity and excellent weather resistance. With the extension of time, tri-block structural SBS automatically degrades into bi-block structural SB- with some terminal oxygen-containing groups under the comprehensive effects of light, heat, oxygen, etc. In this paper, the effects of aging temperature, aging time and oxygen concentration on the molecular structure of thermo-oxidative aged SBS were mainly investigated using Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS), and the correlation between oxygen-containing groups and thermal properties (TG-DTG) was further discussed. The FTIR and XPS results show that rapid decomposition of SBS will occur with increments of aging temperature, aging time and oxygen concentration, and a large number of oxygen-containing groups such as -OH, C=O, -COOH, etc. will be formed during thermo-oxidative aging. In short-term aging, changes in aging temperature and oxygen concentration have a significant impact on the structural damage of SBS. However, in long-term aging, it has no further effect on the molecular structure of SBS or on increasing oxygen concentration. The TG and DTG results indicate that the concentration of substances with low molecular weight gradually increases with the improvement of the degree of aging of the SBS, while the initial decomposition rate increases at the beginning of thermal weightlessness and the decomposition rate slows down in comparison with neat SBS. From the relation between the XPS and TG results, it can be seen that the initial thermal stability of SBS rapidly reduces as the relative concentration of the oxygen-containing groups accumulates around 3%, while the maximum decomposition temperature slowly decreases when the relative concentration of the oxygen-containing groups is more than 3%, due to the difficult damage to strong bonds on the molecular structure of aged SBS.
Organic matter transformation in the peat column at Marcell Experimental Forest: Humification and vertical stratification

NASA Astrophysics Data System (ADS)

Tfaily, Malak M.; Cooper, William T.; Kostka, Joel E.; Chanton, Patrick R.; Schadt, Christopher W.; Hanson, Paul J.; Iversen, Colleen M.; Chanton, Jeffrey P.

2014-04-01

We characterized peat decomposition at the Marcell Experimental Forest (MEF), Minnesota, USA, to a depth of 2 m to ascertain the underlying chemical changes using Fourier transform infrared (FT IR) and 13C nuclear magnetic resonance (NMR) spectroscopy) and related these changes to decomposition proxies C:N ratio, δ13C and δ15N, bulk density, and water content. FT IR determined that peat humification increased rapidly between 30 and 75 cm, indicating a highly reactive intermediate-depth zone consistent with changes in C:N ratio, δ13C and δ15N, bulk density, and water content. Peat decomposition at the MEF, especially in the intermediate-depth zone, is mainly characterized by preferential utilization of O-alkyl-C, carboxyl-C, and other oxygenated functionalities with a concomitant increase in the abundance of alkyl- and nitrogen-containing compounds. Below 75 cm, less change was observed but aromatic functionalities and lignin accumulated with depth. Significant correlations with humification indices, identified by FT IR spectroscopy, were found for C:N ratios. Incubation studies at 22°C revealed the highest methane production rates, greatest CH4:CO2 production ratios, and significant O-alkyl-C utilization within this 30 and 75 cm zone. Oxygen-containing functionalities, especially O-alkyl-C, appear to serve as excellent proxies for soil decomposition rate and should be a sensitive indicator of the response of the solid phase peat to increased temperatures caused by climate change and the field study manipulations that are planned to occur at this site. Radiocarbon signatures of microbial respiration products in deeper pore waters at the MEF resembled the signatures of more modern dissolved organic carbon rather than solid phase peat, indicating that recently photosynthesized organic matter fueled the bulk of subsurface microbial respiration. These results indicate that carbon cycling at depth at the MEF is not isolated from surface processes.
THE INFLUENCE OF DOM CHARACTER ON OZONE DECOMPOSITION RATES AND RCT

EPA Science Inventory

The effects of DOM character on ozonation of natural waters and solutions of DOM isolates were investigated. Batch kinetic investigations measured O3 decomposition rate constants and Rct values. Rct describes the ratio of ?OH concentration to O3 concentration, and thus provides...
Kinetics of the cellular decomposition of supersaturated solid solutions

NASA Astrophysics Data System (ADS)

Ivanov, M. A.; Naumuk, A. Yu.

2014-09-01

A consistent description of the kinetics of the cellular decomposition of supersaturated solid solutions with the development of a spatially periodic structure of lamellar (platelike) type, which consists of alternating phases of precipitates on the basis of the impurity component and depleted initial solid solution, is given. One of the equations, which determines the relationship between the parameters that describe the process of decomposition, has been obtained from a comparison of two approaches in order to determine the rate of change in the free energy of the system. The other kinetic parameters can be described with the use of a variational method, namely, by the maximum velocity of motion of the decomposition boundary at a given temperature. It is shown that the mutual directions of growth of the lamellae of different phases are determined by the minimum value of the interphase surface energy. To determine the parameters of the decomposition, a simple thermodynamic model of states with a parabolic dependence of the free energy on the concentrations has been used. As a result, expressions that describe the decomposition rate, interlamellar distance, and the concentration of impurities in the phase that remain after the decomposition have been derived. This concentration proves to be equal to the half-sum of the initial concentration and the equilibrium concentration corresponding to the decomposition temperature.
Variation in decomposition rates in the fynbos biome, South Africa: the role of plant species and plant stoichiometry.

PubMed

Bengtsson, Jan; Janion, Charlene; Chown, Steven L; Leinaas, Hans Petter

2011-01-01

Previous studies in the fynbos biome of the Western Cape, South Africa, have suggested that biological decomposition rates in the fynbos vegetation type, on poor soils, may be so low that fire is the main factor contributing to litter breakdown and nutrient release. However, the fynbos biome also comprises vegetation types on more fertile soils, such as the renosterveld. The latter is defined by the shrub Elytropappus rhinocerotis, while the shrub Galenia africana may become dominant in overgrazed areas. We examined decomposition of litter of these two species and the geophyte Watsonia borbonica in patches of renosterveld in an agricultural landscape. In particular, we sought to understand how plant species identity affects litter decomposition rates, especially through variation in litter stoichiometry. Decomposition (organic matter mass loss) varied greatly among the species, and was related to litter N and P content. G. africana, with highest nutrient content, lost 65% of its original mass after 180 days, while E. rhinocerotis had lost ca. 30%, and the very nutrient poor W. borbonica <10%. Litter placed under G. africana decomposed slightly faster than when placed under E. rhinocerotis. Over the course of the experiment, G. africana and E. rhinocerotis lost N and P, while W. borbonica showed strong accumulation of these elements. Decomposition rates of G. africana and E. rhinocerotis were substantially higher than those previously reported from fynbos vegetation, and variation among the species investigated was considerable. Our results suggest that fire may not always be the main factor contributing to litter breakdown and nutrient release in the fynbos biome. Thus, biological decomposition has likely been underestimated and, along with small-scale variation in ecosystem processes, would repay further study.
Litter chemistry prevails over litter consumers in mediating effects of past steel industry activities on leaf litter decomposition.

PubMed

Lucisine, Pierre; Lecerf, Antoine; Danger, Michaël; Felten, Vincent; Aran, Delphine; Auclerc, Apolline; Gross, Elisabeth M; Huot, Hermine; Morel, Jean-Louis; Muller, Serge; Nahmani, Johanne; Maunoury-Danger, Florence

2015-12-15

Soil pollution has adverse effects on the performance and life history traits of microorganisms, plants, and animals, yet evidence indicates that even the most polluted sites can support structurally-complex and dynamic ecosystems. The present study aims at determining whether and how litter decomposition, one of the most important soil ecological processes leaf, is affected in a highly trace-metal polluted site. We postulated that past steel mill activities resulting in soil pollution and associated changes in soil characteristics would influence the rate of litter decomposition through two non-exclusive pathways: altered litter chemistry and responses of decomposers to lethal and sub-lethal toxic stress. We carried out a litter-bag experiment using Populus tremula L. leaf litter collected at, and allowed to decompose in, a trace metal polluted site and in three unpolluted sites used as controls. We designed a fully-factorial transplant experimental design to assess effects of litter origin and exposure site on the rate of litter decomposition. We further determined initial litter chemistry, fungal biomass, mesofauna abundance in litter bags, and the soil macrofauna community. Irrespective of the site of litter exposure, litter originating from the polluted site had a two-fold faster decomposition than litter from the unpolluted sites. Litter chemistry, notably the lignin content, seemed most important in explaining the degradation rate of the leaf litter. Abundance of meso and macro-detritivores was higher at the polluted site than at the unpolluted sites. However, litter decomposition proceeded at similar rates in polluted and unpolluted sites. Our results show that trace metal pollution and associated soil and litter changes do not necessarily weaken consumer control on litter decomposition through lethal and sub-lethal toxic stress. Copyright © 2015. Published by Elsevier B.V.
Plants Regulate Soil Organic Matter Decomposition in Response to Sea Level Rise

NASA Astrophysics Data System (ADS)

Megonigal, P.; Mueller, P.; Jensen, K.

2014-12-01

Tidal wetlands have a large capacity for producing and storing organic matter, making their role in the global carbon budget disproportionate to their land area. Most of the organic matter stored in these systems is in soils where it contributes 2-5 times more to surface accretion than an equal mass of minerals. Soil organic matter (SOM) sequestration is the primary process by which tidal wetlands become perched high in the tidal frame, decreasing their vulnerability to accelerated sea level rise. Plant growth responses to sea level rise are well understood and represented in century-scale forecast models of soil surface elevation change. We understand far less about the response of soil organic matter decomposition to rapid sea level rise. Here we quantified the effects of sea level on SOM decomposition rates by exposing planted and unplanted tidal marsh monoliths to experimentally manipulated flood duration. The study was performed in a field-based mesocosm facility at the Smithsonian's Global Change Research Wetland. SOM decomposition rate was quantified as CO2 efflux, with plant- and SOM-derived CO2 separated with a two end-member δ13C-CO2 model. Despite the dogma that decomposition rates are inversely related to flooding, SOM mineralization was not sensitive to flood duration over a 35 cm range in soil surface elevation. However, decomposition rates were strongly and positively related to aboveground biomass (R2≥0.59, p≤0.01). We conclude that soil carbon loss through decomposition is driven by plant responses to sea level in this intensively studied tidal marsh. If this result applies more generally to tidal wetlands, it has important implications for modeling soil organic matter and surface elevation change in response to accelerated sea level rise.
Ab initio investigation of the thermal decomposition of n-butylcyclohexane.

PubMed

Ali, Mohamad Akbar; Dillstrom, V Tyler; Lai, Jason Y W; Violi, Angela

2014-02-13

Environmental and energy security concerns have motivated an increased focus on developing clean, efficient combustors, which increasingly relies on insight into the combustion chemistry of fuels. In particular, naphthenes (cycloalkanes and alkylcycloalkanes) are important chemical components of distillate fuels, such as diesel and jet fuels. As such, there is a growing interest in describing napthene reactivity with kinetic mechanisms. Use of these mechanisms in predictive combustion models aids in the development of combustors. This study focuses on the pyrolysis of n-butylcyclohexane (n-BCH), an important representative of naphthenes in jet fuels. Seven different unimolecular decomposition pathways of C-C bond fission were explored utilizing ab initio/DFT methods. Accurate reaction energies were computed using the high-level quantum composite G3B3 method. Variational transition state theory, Rice-Ramsperger-Kassel-Marcus/master equation simulations provided temperature- and pressure-dependent rate constants. Implementation of these pathways into an existing chemical kinetic mechanism improved the prediction of experimental OH radical and H2O speciation in shock tube oxidation. Simulations of this combustion showed a change in the expected decomposition chemistry of n-BCH, predicting increased production of cyclic alkyl radicals instead of straight-chain alkenes. The most prominent reaction pathway for the decomposition of n-BCH is n-BCH = C3H7 + C7H13. The results of this study provide insight into the combustion of n-BCH and will aid in the future development of naphthene kinetic mechanisms.
Changes in mass and nutrient content of wood during decomposition in a south Florida mangrove forest

USGS Publications Warehouse

Romero, L.M.; Smith, T. J.; Fourqurean, J.W.

2005-01-01

1 Large pools of dead wood in mangrove forests following disturbances such as hurricanes may influence nutrient fluxes. We hypothesized that decomposition of wood of mangroves from Florida, USA (Avicennia germinans, Laguncularia racemosa and Rhizophora mangle), and the consequent nutrient dynamics, would depend on species, location in the forest relative to freshwater and marine influences and whether the wood was standing, lying on the sediment surface or buried. 2 Wood disks (8-10 cm diameter, 1 cm thick) from each species were set to decompose at sites along the Shark River, either buried in the sediment, on the soil surface or in the air (above both the soil surface and high tide elevation). 3 A simple exponential model described the decay of wood in the air, and neither species nor site had any effect on the decay coefficient during the first 13 months of decomposition. 4 Over 28 months of decomposition, buried and surface disks decomposed following a two-component model, with labile and refractory components. Avicennia germinans had the largest labile component (18 ?? 2% of dry weight), while Laguncularia racemosa had the lowest (10 ?? 2%). Labile components decayed at rates of 0.37-23.71% month -1, while refractory components decayed at rates of 0.001-0.033% month-1. Disks decomposing on the soil surface had higher decay rates than buried disks, but both were higher than disks in the air. All species had similar decay rates of the labile and refractory components, but A. germinans exhibited faster overall decay because of a higher proportion of labile components. 5 Nitrogen content generally increased in buried and surface disks, but there was little change in N content of disks in the air over the 2-year study. Between 17% and 68% of total phosphorus in wood leached out during the first 2 months of decomposition, with buried disks having the greater losses, P remaining constant or increasing slightly thereafter. 6 Newly deposited wood from living trees was a short-term source of N for the ecosystem but, by the end of 2 years, had become a net sink. Wood, however, remained a source of P for the ecosystem. 7 As in other forested ecosystems, coarse woody debris can have a significant impact on carbon and nutrient dynamics in mangrove forests. The prevalence of disturbances, such as hurricanes, that can deposit large amounts of wood on the forest floor accentuates the importance of downed wood in these forests. ?? 2005 British Ecological Society.
Sodium fertilization increases termites and enhances decomposition in an Amazonian forest.

PubMed

Kaspari, Michael; Clay, Natalie A; Donoso, David A; Yanoviak, Steven P

2014-04-01

Added Na was used to determine whether litter decomposition and associated fungal biomass and termites are limited by Na availability in a lowland tropical rainforest at Yasuni, Ecuador. This is a partial test of the "sodium ecosystem respiration" (SER) hypothesis that posits Na is critical for consumers but not plants, that Na shortfall is more likely on highly weathered soils inland from oceanic aerosols, and that this shortfall results in decreased decomposer activity. We fertilized 4 x 4 m plots twice a month for a year with quantities of Na comparable to those falling on a coastal tropical rainforest. Decomposition rates of four substrates were consistently higher on +NaCl plots by up to 70% for cellulose, and 78%, 68%, and 29% for three woods of increasing percentage lignin. The density of termite workers averaged 17-fold higher on +NaCl plots; fungal biomass failed to differ. After controlling for temperature and precipitation, which co-limit gross primay productivity (GPP) and ecosystem respiration (ER), these results suggest that Na shortfall is an agent enhancing the storage of coarse woody debris in inland tropical forests.
Decomposition Characteristics of Acetone in a DC Corona Discharge at Atmospheric Pressure

NASA Astrophysics Data System (ADS)

Sakamoto, Takahiro; Satoh, Kohki; Itoh, Hidenori

Decomposition characteristics of acetone in a DC corona discharge generated between a multi-needle and a plane electrodes in nitrogen-oxygen mixtures at atmospheric pressure are investigated mainly by infrared absorption spectroscopy in this work. It is found that CO2, CO, CH4, HCHO, HCOOH and HCN are the by-products of acetone in the corona discharge, and that CO, CH4, HCHO, HCOOH and HCN are intermediate products, which tend to be decomposed in the corona discharge. CO2 is found to be the major and end-product. It is also found that acetone is chiefly inverted to CO2 via CO at high oxygen concentration (20%) and via CO and CH4 at relatively low oxygen concentration (0.2%), in addition to the direct conversion from acetone to CO2. As the oxygen concentration increases, the percentages of carbon atoms contained in deposit on the plane electrode and the wall of the discharge chamber increases. Further, the decomposition process of acetone is deduced from the examination of rate constants for the reactions in the gaseous phase.
Plastic waste sacks alter the rate of decomposition of dismembered bodies within.

PubMed

Scholl, Kassra; Moffatt, Colin

2017-07-01

As a result of criminal activity, human bodies are sometimes dismembered and concealed within sealed, plastic waste sacks. Consequently, due to the inhibited ingress of insects and dismemberment, the rate of decomposition of the body parts within may be different to that of whole, exposed bodies. Correspondingly, once found, an estimation of the postmortem interval may be affected and lead to erroneous inferences. This study set out to determine whether insects were excluded and how rate of decomposition was affected inside such plastic sacks. The limbs, torsos and heads of 24 dismembered pigs were sealed using nylon cable ties within plastic garbage sacks, half of which were of a type claimed to repel insects. Using a body scoring scale to quantify decomposition, the body parts in the sacks were compared to those of ten exposed, whole pig carcasses. Insects were found to have entered both types of plastic sack. There was no difference in rate of decomposition in the two types of sack (F 1,65 = 1.78, p = 0.19), but this was considerably slower than those of whole carcasses (F 1,408 = 1453, p < 0.001), with heads showing the largest differences. As well as a slower decomposition, sacks resulted in formation of some adipocere tissue as a result of high humidity within. Based upon existing methods, postmortem intervals for body parts within sealed sacks would be significantly underestimated.
Effect of fast neutron, gamma-ray and combined radiations on the thermal decomposition of ammonium perchlorate single crystals

NASA Technical Reports Server (NTRS)

Herley, P. J.; Wang, C. S.; Varsi, G.; Levy, P. W.

1974-01-01

The thermal decomposition kinetics have been determined for ammonium perchlorate crystals subjected to a fast neutron irradiation or to a fast neutron irradiation followed by a gamma-ray irradiation. Qualitatively, the radiation induced changes are similar to those obtained in this and in previous studies, with samples exposed only to gamma rays. The induction period is shortened and the rate constants, obtained from an Avrami-Erofeyev kinetic analysis, are modified. The acceleratory period constant increases and the decay period constant decreases. When compared on an equal deposited energy basis, the fast neutron induced changes are appreciably larger than the gamma-ray induced changes. Some, or all, of the fast neutron induced effects might be attributable to the introduction of localized regions of concentrated radiation damage ('spikes') by lattice atom recoils which become thermal decomposition sites when the crystals are heated.
Stronger influence of litter quality on decomposition rates than microbial home field advantage in novel subtropical dry forests

NASA Astrophysics Data System (ADS)

Marin-Spiotta, E.; Atkinson, E. E.

2015-12-01

Litter decomposition is one of the most studied ecosystem processes, given its role in carbon cycling and nutrient availability, yet our knowledge of how decomposition is influenced by novel species assemblages in tropical forests emerging on post-agricultural landscapes is limited. This is especially true in tropical dry forests, which are some of the most fragmented forests worldwide due to human pressures and sensitive to changes in rainfall and fire regimes. Here we tested for the effects of litter quality, site conditions, and microbial "home-field advantage" on decomposition rates in subtropical dry forests in St. Croix, U.S. Virgin Islands. We conducted a 22-month in situ and reciprocal transplant field decomposition experiment of aboveground litter and fine roots in 10-year old sites dominated by an early successional N-fixing tree and 40-year old mixed-species secondary forests. Total annual litterfall mass did not differ between the two forest types, but monthly amounts did, with more litter accumulating in the 40-year old secondary forests during the dry season and in the 10-year old secondary forests during the wet season. Litter chemistry differed between the two forest types and showed divergent patterns over the two-year field incubation. To test for the effects of litter quality on decomposition rates, we compared mass loss rates for aboveground and root litter from each forest decomposed in situ and transplanted to the other forest type. Litter in the 10-year old forests decomposed faster in situ (k= 1.07 ± 0.04) than when it was transplanted (k=0.86 ± 0.04). Litter from the 40-year old forests showed the opposite pattern. In situ root decomposition in both forests occurred at the same rate compared to roots that were transplanted there from the other forest type, suggesting that site conditions were equally important as litter quality. Our results were not consistent with a microbial home-field advantage for litter and root decomposition, that is, microbes were not more efficient at decomposing their own native litter, regardless of chemistry. Rather, decomposition patterns may be largely controlled by litter quality (and the combined effects of litter quality and site conditions specifically for roots) in contrast to the decomposer community in these subtropical dry forests.
Plant resource history effects on contemporary microbial processes

NASA Astrophysics Data System (ADS)

Bradford, Mark

2010-05-01

Background/Questions/Methods Soil microbial communities play a pivotal role in providing ecosystem services, given that they are key drivers of biogeochemical processes such as carbon and nitrogen cycling. As species-rich communities, made-up of populations with short generation times, it is commonly assumed that there is a high degree of functional redundancy within soil communities with respect to broad-physiological processes, such as organic carbon decomposition. This assumption underlies the majority of terrestrial ecosystem models, where relationships between processes and controlling factors are parameterized using statistical relationships generated from measurements across space. However, microbial communities display biogeographic patterns, even at fine scales and it is possible that these patterns extend to influence their function. I first present experiments that combine common garden and reciprocal transplant approaches to test whether microbial communities sourced from distinct habitats across the contiguous United States exhibit functional similarity (i.e. redundancy) or dissimilarity in common environments. The environments are experimental microcosms composed of leaf litters differing markedly in recalcitrance. Following inoculation with the microbial communities, decomposition rates are followed across 300 days. Next, using a similar experimental microcosm design, I present experiments that test whether a common resource history might cause communities, which are initially dissimilar, to converge functionally. Distinct microbial communities are introduced into a fresh litter environment every 100 days for 300 days total. Finally, I present an experiment to test whether functional convergence (either partial or complete) is associated with a reduction in function in alternate environments (essentially a functional ‘trade-off'). In this last experiment decomposition rates are measured for 100 days in alternate environments following 300 days of successive exposure to a single litter type. Results/Conclusions I show in the first experiment that rates of carbon dioxide production from litter decomposition are strongly dependent on the microbial inoculum, with differences in the microbial community alone accounting for substantial (up to 85%) variation in total carbon mineralized. Communities that share a common history with a given foliar litter exhibit higher decomposition rates when compared to communities foreign to that habitat, suggestive of local adaptation. In the second experiment, decomposition rates (measured as cumulative carbon dioxide values per 100-day run) converge partially in the second 100-day run, and cumulative values for all six inocula increase toward the highest values observed in the initial 100-day run. Convergence continues but at a reduced rate in the third 100-day run; yet increases in function appear to asymptote. The increasing similarity in cumulative values between inocula, observed in the successive 100-day runs, is consistent with partial functional convergence of communities exposed to a common environment. In the final experiment, microbial inocula crossed to an alternate environment (e.g. those communities maintained in a grass environment then inoculated into a hardwood litter environment) results in cumulative values in the alternate environments that are approximately half those observed for communities inoculated into the same environment. Collectively, our results suggest that the implicit assumption in ecosystem models (i.e. microbial communities in the same environment are functionally equivalent) is incorrect. The increasing similarity across time in function in common environments of inocula sourced from different resource habitats shows the potential for function to converge. Yet this convergence is only partial and is associated with "apparent' trade-offs in the ability to decompose substrates from the original environments from which the inocula were sourced. To predict accurately how biogeochemical processes will respond to global change may require consideration of the community composition and/or adaptation of microbial communities to past resource environments and the consequences of their (partial) adaptation to new ones.
Sensitivity of decomposition rates of soil organic matter with respect to simultaneous changes in temperature and moisture

NASA Astrophysics Data System (ADS)

Sierra, Carlos A.; Trumbore, Susan E.; Davidson, Eric A.; Vicca, Sara; Janssens, I.

2015-03-01

The sensitivity of soil organic matter decomposition to global environmental change is a topic of prominent relevance for the global carbon cycle. Decomposition depends on multiple factors that are being altered simultaneously as a result of global environmental change; therefore, it is important to study the sensitivity of the rates of soil organic matter decomposition with respect to multiple and interacting drivers. In this manuscript, we present an analysis of the potential response of decomposition rates to simultaneous changes in temperature and moisture. To address this problem, we first present a theoretical framework to study the sensitivity of soil organic matter decomposition when multiple driving factors change simultaneously. We then apply this framework to models and data at different levels of abstraction: (1) to a mechanistic model that addresses the limitation of enzyme activity by simultaneous effects of temperature and soil water content, the latter controlling substrate supply and oxygen concentration for microbial activity; (2) to different mathematical functions used to represent temperature and moisture effects on decomposition in biogeochemical models. To contrast model predictions at these two levels of organization, we compiled different data sets of observed responses in field and laboratory studies. Then we applied our conceptual framework to: (3) observations of heterotrophic respiration at the ecosystem level; (4) laboratory experiments looking at the response of heterotrophic respiration to independent changes in moisture and temperature; and (5) ecosystem-level experiments manipulating soil temperature and water content simultaneously.
Long-term changes in forest floor processes in southern Appalachian forests

Treesearch

Jennifer D. Knoepp; Barbara C. Reynolds; D.A. Crossley; Wayne T. Swank

2005-01-01

Soil nutrient concentrations decreased in an aggrading southern Appalachian forest over a 20-year period. Construction of nutrient budgets showed significant nutrient sequestration aboveground including increased forest floor mass. We hypothesized that the changes in forest floor mass resulted from decreased litter decomposition rates because of decreased litter...
A novel hybrid decomposition-and-ensemble model based on CEEMD and GWO for short-term PM2.5 concentration forecasting

NASA Astrophysics Data System (ADS)

Niu, Mingfei; Wang, Yufang; Sun, Shaolong; Li, Yongwu

2016-06-01

To enhance prediction reliability and accuracy, a hybrid model based on the promising principle of "decomposition and ensemble" and a recently proposed meta-heuristic called grey wolf optimizer (GWO) is introduced for daily PM2.5 concentration forecasting. Compared with existing PM2.5 forecasting methods, this proposed model has improved the prediction accuracy and hit rates of directional prediction. The proposed model involves three main steps, i.e., decomposing the original PM2.5 series into several intrinsic mode functions (IMFs) via complementary ensemble empirical mode decomposition (CEEMD) for simplifying the complex data; individually predicting each IMF with support vector regression (SVR) optimized by GWO; integrating all predicted IMFs for the ensemble result as the final prediction by another SVR optimized by GWO. Seven benchmark models, including single artificial intelligence (AI) models, other decomposition-ensemble models with different decomposition methods and models with the same decomposition-ensemble method but optimized by different algorithms, are considered to verify the superiority of the proposed hybrid model. The empirical study indicates that the proposed hybrid decomposition-ensemble model is remarkably superior to all considered benchmark models for its higher prediction accuracy and hit rates of directional prediction.
Gas Pressure Monitored Iodide-Catalyzed Decomposition Kinetics of H[subscript 2]O[subscript 2]: Initial-Rate and Integrated-Rate Methods in the General Chemistry Lab

ERIC Educational Resources Information Center

Nyasulu, Frazier; Barlag, Rebecca

2010-01-01

The reaction kinetics of the iodide-catalyzed decomposition of [subscript 2]O[subscript 2] using the integrated-rate method is described. The method is based on the measurement of the total gas pressure using a datalogger and pressure sensor. This is a modification of a previously reported experiment based on the initial-rate approach. (Contains 2…
Effects of different tree species on soil organic matter composition, decomposition rates and temperature sensitivities in boreal forest

NASA Astrophysics Data System (ADS)

Segura, Javier; Nilsson, Mats B.; Erhagen, Björn; Sparrman, Tobias; Ilstedt, Ulrik; Schleucher, Jürgen; Öquist, Mats

2017-04-01

High-latitude ecosystems store a large proportion of the global soil organic matter (SOM) and its mineralization constitutes a major carbon flux to the atmosphere. It has been suggested that different tree species can significantly influence organo-chemical composition of SOM, and rate and temperature sensitivity of SOM decomposition. In this study we used surface soil samples (top 5 cm) from a field experiment where five different tree species (Pinus silvestrys L, Picea abies (L.) H. Karst., Larix decidua Mill., Betula pendula Roth, and Pinus contorta Douglas) were planted on a grass meadow in a randomized block design (n=3) ca. 40 years ago. The samples were incubated at 4, 9, 14, and 19 °C at a soil water potential of -25 kPa (previously determined as optimal water content for decomposition). CO2 production rates were measured hourly for 13 days. CO2 production rates were consequently lowest in the control plots and increased in the order Meadow< Contorta < Betula < Larix < Pinus < Picea. The values ranged between 0.03-0.1, 0.06-0.154, 0.1-0.24 and 0.13-0.36 mg CO2 g-1 OM (dw) h-1 at 4, 9, 14 and 19°C respectively. The temperature response of CO2 production corresponded to Q10s of 2.22 (±0.11), 2.22(±0.15), 2.66 (±0.18), 2.09 (±0.33), 2.38 (±0.31) and 2.31 (±0.09) for meadow, contorta, betula, larix, pinus and picea respectively. Only betula resulted in significantly higher Q10s as compared to the control plots, picea, contorta and larix treatments. These differences in tree species effects on SOM decomposition and its temperature sensitivity will be further discussed in relation to the organo-chemical composition of SOM as determined by pyrolysis gas chromatography-mass spectrometry (Py-GC-MS) and nuclear magnetic resonance spectroscopy (NMR) techniques. We conclude that the temperature response of SOM decomposition rates is likely coupled to tree species composition and may have important implications for soil C dynamics. This finding can have important implications for both the understanding of forest ecosystem carbon balances in high latitude ecosystems and also the selection of different tree species in forest management schemes.

Thermal stability and kinetics of decomposition of ammonium nitrate in the presence of pyrite.

PubMed

Gunawan, Richard; Zhang, Dongke

2009-06-15

The interaction between ammonium nitrate based industrial explosives and pyrite-rich minerals in mining operations can lead to the occurrence of spontaneous explosion of the explosives. In an effort to provide a scientific basis for safe applications of industrial explosives in reactive mining grounds containing pyrite, ammonium nitrate decomposition, with and without the presence of pyrite, was studied using a simultaneous Differential Scanning Calorimetry and Thermogravimetric Analyser (DSC-TGA) and a gas-sealed isothermal reactor, respectively. The activation energy and the pre-exponential factor of ammonium nitrate decomposition were determined to be 102.6 kJ mol(-1) and 4.55 x 10(7)s(-1) without the presence of pyrite and 101.8 kJ mol(-1) and 2.57 x 10(9)s(-1) with the presence of pyrite. The kinetics of ammonium nitrate decomposition was then used to calculate the critical temperatures for ammonium nitrate decomposition with and without the presence of pyrite, based on the Frank-Kamenetskii model of thermal explosion. It was shown that the presence of pyrite reduces the temperature for, and accelerates the rate of, decomposition of ammonium nitrate. It was further shown that pyrite can significantly reduce the critical temperature of ammonium nitrate decomposition, causing undesired premature detonation of the explosives. The critical temperature also decreases with increasing diameter of the blast holes charged with the explosive. The concept of using the critical temperature as indication of the thermal stability of the explosives to evaluate the risk of spontaneous explosion was verified in the gas-sealed isothermal reactor experiments.
The impact of sea-level rise on organic matter decay rates in Chesapeake Bay brackish tidal marshes

USGS Publications Warehouse

Kirwanm, M.L.; Langley, J.A.; Guntenspergen, Gleen R.; Megonigal, J.P.

2013-01-01

The balance between organic matter production and decay determines how fast coastal wetlands accumulate soil organic matter. Despite the importance of soil organic matter accumulation rates in influencing marsh elevation and resistance to sea-level rise, relatively little is known about how decomposition rates will respond to sea-level rise. Here, we estimate the sensitivity of decomposition to flooding by measuring rates of decay in 87 bags filled with milled sedge peat, including soil organic matter, roots and rhizomes. Experiments were located in field-based mesocosms along 3 mesohaline tributaries of the Chesapeake Bay. Mesocosm elevations were manipulated to influence the duration of tidal inundation. Although we found no significant influence of inundation on decay rate when bags from all study sites were analyzed together, decay rates at two of the sites increased with greater flooding. These findings suggest that flooding may enhance organic matter decay rates even in water-logged soils, but that the overall influence of flooding is minor. Our experiments suggest that sea-level rise will not accelerate rates of peat accumulation by slowing the rate of soil organic matter decay. Consequently, marshes will require enhanced organic matter productivity or mineral sediment deposition to survive accelerating sea-level rise.
The impact of sea-level rise on organic matter decay rates in Chesapeake Bay brackish tidal marshes

NASA Astrophysics Data System (ADS)

Kirwan, M. L.; Langley, J. A.; Guntenspergen, G. R.; Megonigal, J. P.

2013-03-01

The balance between organic matter production and decay determines how fast coastal wetlands accumulate soil organic matter. Despite the importance of soil organic matter accumulation rates in influencing marsh elevation and resistance to sea-level rise, relatively little is known about how decomposition rates will respond to sea-level rise. Here, we estimate the sensitivity of decomposition to flooding by measuring rates of decay in 87 bags filled with milled sedge peat, including soil organic matter, roots and rhizomes. Experiments were located in field-based mesocosms along 3 mesohaline tributaries of the Chesapeake Bay. Mesocosm elevations were manipulated to influence the duration of tidal inundation. Although we found no significant influence of inundation on decay rate when bags from all study sites were analyzed together, decay rates at two of the sites increased with greater flooding. These findings suggest that flooding may enhance organic matter decay rates even in water-logged soils, but that the overall influence of flooding is minor. Our experiments suggest that sea-level rise will not accelerate rates of peat accumulation by slowing the rate of soil organic matter decay. Consequently, marshes will require enhanced organic matter productivity or mineral sediment deposition to survive accelerating sea-level rise.
The impact of sea-level rise on organic matter decay rates in Chesapeake Bay brackish tidal marshes

NASA Astrophysics Data System (ADS)

Kirwan, M. L.; Langley, J. A.; Guntenspergen, G. R.; Megonigal, J. P.

2012-10-01

The balance between organic matter production and decay determines how fast coastal wetlands accumulate soil organic matter. Despite the importance of soil organic matter accumulation rates in influencing marsh elevation and resistance to sea-level rise, relatively little is known about how decomposition rates will respond to sea-level rise. Here, we estimate the sensitivity of decomposition to flooding by measuring rates of decay in 87 bags filled with milled sedge peat, including soil organic matter, roots and rhizomes. Experiments were located in field-based mesocosms along 3 mesohaline tributaries of the Chesapeake Bay. Mesocosm elevations were manipulated to influence the duration of tidal inundation. Although we found no significant influence of inundation on decay rate when bags from all study sites were analyzed together, decay rates at two of the sites increased with greater flooding. These findings suggest that flooding may enhance organic matter decay rates even in water-logged soils, but that the overall influence of flooding is minor. Our experiments suggest that sea-level rise will not accelerate rates of peat accumulation by slowing the rate of soil organic matter decay. Consequently, marshes will require enhanced organic matter productivity or mineral sediment deposition to survive accelerating sea-level rise.
Optimized FPGA Implementation of Multi-Rate FIR Filters Through Thread Decomposition

NASA Technical Reports Server (NTRS)

Kobayashi, Kayla N.; He, Yutao; Zheng, Jason X.

2011-01-01

Multi-rate finite impulse response (MRFIR) filters are among the essential signal-processing components in spaceborne instruments where finite impulse response filters are often used to minimize nonlinear group delay and finite precision effects. Cascaded (multistage) designs of MRFIR filters are further used for large rate change ratio in order to lower the required throughput, while simultaneously achieving comparable or better performance than single-stage designs. Traditional representation and implementation of MRFIR employ polyphase decomposition of the original filter structure, whose main purpose is to compute only the needed output at the lowest possible sampling rate. In this innovation, an alternative representation and implementation technique called TD-MRFIR (Thread Decomposition MRFIR) is presented. The basic idea is to decompose MRFIR into output computational threads, in contrast to a structural decomposition of the original filter as done in the polyphase decomposition. A naive implementation of a decimation filter consisting of a full FIR followed by a downsampling stage is very inefficient, as most of the computations performed by the FIR state are discarded through downsampling. In fact, only 1/M of the total computations are useful (M being the decimation factor). Polyphase decomposition provides an alternative view of decimation filters, where the downsampling occurs before the FIR stage, and the outputs are viewed as the sum of M sub-filters with length of N/M taps. Although this approach leads to more efficient filter designs, in general the implementation is not straightforward if the numbers of multipliers need to be minimized. In TD-MRFIR, each thread represents an instance of the finite convolution required to produce a single output of the MRFIR. The filter is thus viewed as a finite collection of concurrent threads. Each of the threads completes when a convolution result (filter output value) is computed, and activated when the first input of the convolution becomes available. Thus, the new threads get spawned at exactly the rate of N/M, where N is the total number of taps, and M is the decimation factor. Existing threads retire at the same rate of N/M. The implementation of an MRFIR is thus transformed into a problem to statically schedule the minimum number of multipliers such that all threads can be completed on time. Solving the static scheduling problem is rather straightforward if one examines the Thread Decomposition Diagram, which is a table-like diagram that has rows representing computation threads and columns representing time. The control logic of the MRFIR can be implemented using simple counters. Instead of decomposing MRFIRs into subfilters as suggested by polyphase decomposition, the thread decomposition diagrams transform the problem into a familiar one of static scheduling, which can be easily solved as the input rate is constant.
Decreases in Soil Moisture and Organic Matter Quality Suppress Microbial Decomposition Following a Boreal Forest Fire

DOE Office of Scientific and Technical Information (OSTI.GOV)

Holden, Sandra R.; Berhe, Asmeret A.; Treseder, Kathleen K.

Climate warming is projected to increase the frequency and severity of wildfires in boreal forests, and increased wildfire activity may alter the large soil carbon (C) stocks in boreal forests. Changes in boreal soil C stocks that result from increased wildfire activity will be regulated in part by the response of microbial decomposition to fire, but post-fire changes in microbial decomposition are poorly understood. Here, we investigate the response of microbial decomposition to a boreal forest fire in interior Alaska and test the mechanisms that control post-fire changes in microbial decomposition. We used a reciprocal transplant between a recently burnedmore » boreal forest stand and a late successional boreal forest stand to test how post-fire changes in abiotic conditions, soil organic matter (SOM) composition, and soil microbial communities influence microbial decomposition. We found that SOM decomposing at the burned site lost 30.9% less mass over two years than SOM decomposing at the unburned site, indicating that post-fire changes in abiotic conditions suppress microbial decomposition. Our results suggest that moisture availability is one abiotic factor that constrains microbial decomposition in recently burned forests. In addition, we observed that burned SOM decomposed more slowly than unburned SOM, but the exact nature of SOM changes in the recently burned stand are unclear. Finally, we found no evidence that post-fire changes in soil microbial community composition significantly affect decomposition. Taken together, our study has demonstrated that boreal forest fires can suppress microbial decomposition due to post-fire changes in abiotic factors and the composition of SOM. Models that predict the consequences of increased wildfires for C storage in boreal forests may increase their predictive power by incorporating the observed negative response of microbial decomposition to boreal wildfires.« less
Predicting Large-scale Effects During Cookoff of Plastic-Bonded Explosives (PBX 9501 PBX 9502 and LX-14)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hobbs, Michael L.; Kaneshige, Michael J.; Erikson, William W.

In this study, we have made reasonable cookoff predictions of large-scale explosive systems by using pressure-dependent kinetics determined from small-scale experiments. Scale-up is determined by properly accounting for pressure generated from gaseous decomposition products and the volume that these reactive gases occupy, e.g. trapped within the explosive, the system, or vented. The pressure effect on the decomposition rates has been determined for different explosives by using both vented and sealed experiments at low densities. Low-density explosives are usually permeable to decomposition gases and can be used in both vented and sealed configurations to determine pressure-dependent reaction rates. In contrast, explosivesmore » that are near the theoretical maximum density (TMD) are not as permeable to decomposition gases, and pressure-dependent kinetics are difficult to determine. Ignition in explosives at high densities can be predicted by using pressure-dependent rates determined from the low-density experiments as long as gas volume changes associated with bulk thermal expansion are also considered. In the current work, cookoff of the plastic-bonded explosives PBX 9501 and PBX 9502 is reviewed and new experimental work on LX-14 is presented. Reactive gases are formed inside these heated explosives causing large internal pressures. The pressure is released differently for each of these explosives. For PBX 9501, permeability is increased and internal pressure is relieved as the nitroplasticizer melts and decomposes. Internal pressure in PBX 9502 is relieved as the material is damaged by cracks and spalling. For LX-14, internal pressure is not relieved until the explosive thermally ignites. The current paper is an extension of work presented at the 26th ICDERS symposium [1].« less
ORCHIMIC (v1.0), a microbe-mediated model for soil organic matter decomposition

NASA Astrophysics Data System (ADS)

Huang, Ye; Guenet, Bertrand; Ciais, Philippe; Janssens, Ivan A.; Soong, Jennifer L.; Wang, Yilong; Goll, Daniel; Blagodatskaya, Evgenia; Huang, Yuanyuan

2018-06-01

The role of soil microorganisms in regulating soil organic matter (SOM) decomposition is of primary importance in the carbon cycle, in particular in the context of global change. Modeling soil microbial community dynamics to simulate its impact on soil gaseous carbon (C) emissions and nitrogen (N) mineralization at large spatial scales is a recent research field with the potential to improve predictions of SOM responses to global climate change. In this study we present a SOM model called ORCHIMIC, which utilizes input data that are consistent with those of global vegetation models. ORCHIMIC simulates the decomposition of SOM by explicitly accounting for enzyme production and distinguishing three different microbial functional groups: fresh organic matter (FOM) specialists, SOM specialists, and generalists, while also implicitly accounting for microbes that do not produce extracellular enzymes, i.e., cheaters. ORCHIMIC and two other organic matter decomposition models, CENTURY (based on first-order kinetics and representative of the structure of most current global soil carbon models) and PRIM (with FOM accelerating the decomposition rate of SOM), were calibrated to reproduce the observed respiration fluxes of FOM and SOM from the incubation experiments of Blagodatskaya et al. (2014). Among the three models, ORCHIMIC was the only one that effectively captured both the temporal dynamics of the respiratory fluxes and the magnitude of the priming effect observed during the incubation experiment. ORCHIMIC also effectively reproduced the temporal dynamics of microbial biomass. We then applied different idealized changes to the model input data, i.e., a 5 K stepwise increase of temperature and/or a doubling of plant litter inputs. Under 5 K warming conditions, ORCHIMIC predicted a 0.002 K-1 decrease in the C use efficiency (defined as the ratio of C allocated to microbial growth to the sum of C allocated to growth and respiration) and a 3 % loss of SOC. Under the double litter input scenario, ORCHIMIC predicted a doubling of microbial biomass, while SOC stock increased by less than 1 % due to the priming effect. This limited increase in SOC stock contrasted with the proportional increase in SOC stock as modeled by the conventional SOC decomposition model (CENTURY), which can not reproduce the priming effect. If temperature increased by 5 K and litter input was doubled, ORCHIMIC predicted almost the same loss of SOC as when only temperature was increased. These tests suggest that the responses of SOC stock to warming and increasing input may differ considerably from those simulated by conventional SOC decomposition models when microbial dynamics are included. The next step is to incorporate the ORCHIMIC model into a global vegetation model to perform simulations for representative sites and future scenarios.
Using atmospheric fallout to date organic horizon layers and quantify metal dynamics during decomposition

NASA Astrophysics Data System (ADS)

Kaste, James M.; Bostick, Benjamin C.; Heimsath, Arjun M.; Steinnes, Eiliv; Friedland, Andrew J.

2011-03-01

High concentrations of metals in organic matter can inhibit decomposition and limit nutrient availability in ecosystems, but the long-term fate of metals bound to forest litter is poorly understood. Controlled experiments indicate that during the first few years of litter decay, Al, Fe, Pb, and other metals that form stable complexes with organic matter are naturally enriched by several hundred percent as carbon is oxidized. The transformation of fresh litter to humus takes decades, however, such that current datasets describing the accumulation and release of metals in decomposing organic matter are timescale limited. Here we use atmospheric 210Pb to quantify the fate of metals in canopy-derived litter during burial and decay in coniferous forests in New England and Norway where decomposition rates are slow and physical soil mixing is minimal. We measure 210Pb inventories in the O horizon and mineral soil and calculate a 60-630 year timescale for the production of mobile organo-metallic colloids from the decomposition of fresh forest detritus. This production rate is slowest at our highest elevation (˜1000 m) and highest latitude sites (>63°N) where decomposition rates are expected to be low. We calculate soil layer ages by assuming a constant supply of atmospheric 210Pb and find that they are consistent with the distribution of geochemical tracers from weapons fallout, air pollution, and a direct 207Pb application at one site. By quantifying a gradient of organic matter ages with depth in the O horizon, we describe the accumulation and loss of metals in the soil profile as organic matter transforms from fresh litter to humus. While decomposition experiments predict that Al and Fe concentrations increase during the initial few years of decay, we show here that these metals continue to accumulate in humus for decades, and that enrichment occurs at a rate higher than can be explained by quantitative retention during decomposition alone. Acid extractable Al and Fe concentrations are higher in the humus layer of the O horizon than in the mineral soil immediately beneath this layer: it is therefore unlikely that physical soil mixing introduces significant Al and Fe to humus. This continuous enrichment of Al and Fe over time may best be explained by the recent suggestion that metals are mined from deeper horizons and brought into the O horizon via mycorrhizal plants. In sharp contrast to Al and Fe, we find that Mn concentrations in decomposing litter layers decrease exponentially with age, presumably because of leaching or rapid uptake, which may explain the low levels of acid extractable Mn in the mineral soil. This study quantifies how metals are enriched and lost in decomposing organic matter over a longer timescale than previous studies have been able to characterize. We also put new limits on the rate at which metals in litter become mobile organo-metallic complexes that can migrate to deeper soil horizons or surface waters.
Photodegradation at day, microbial decomposition at night - decomposition in arid lands

NASA Astrophysics Data System (ADS)

Gliksman, Daniel; Gruenzweig, Jose

2014-05-01

Our current knowledge of decomposition in dry seasons and its role in carbon turnover is fragmentary. So far, decomposition during dry seasons was mostly attributed to abiotic mechanisms, mainly photochemical and thermal degradation, while the contribution of microorganisms to the decay process was excluded. We asked whether microbial decomposition occurs during the dry season and explored its interaction with photochemical degradation under Mediterranean climate. We conducted a litter bag experiment with local plant litter and manipulated litter exposure to radiation using radiation filters. We found notable rates of CO2 fluxes from litter which were related to microbial activity mainly during night-time throughout the dry season. This activity was correlated with litter moisture content and high levels of air humidity and dew. Day-time CO2 fluxes were related to solar radiation, and radiation manipulation suggested photodegradation as the underlying mechanism. In addition, a decline in microbial activity was followed by a reduction in photodegradation-related CO2 fluxes. The levels of microbial decomposition and photodegradation in the dry season were likely the factors influencing carbon mineralization during the subsequent wet season. This study showed that microbial decomposition can be a dominant contributor to CO2 emissions and mass loss in the dry season and it suggests a regulating effect of microbial activity on photodegradation. Microbial decomposition is an important contributor to the dry season decomposition and impacts the annual litter turn-over rates in dry regions. Global warming may lead to reduced moisture availability and dew deposition, which may greatly influence not only microbial decomposition of plant litter, but also photodegradation.
Climate history shapes contemporary leaf litter decomposition

Treesearch

Michael S. Strickland; Ashley D. Keiser; Mark A. Bradford

2015-01-01

Litter decomposition is mediated by multiple variables, of which climate is expected to be a dominant factor at global scales. However, like other organisms, traits of decomposers and their communities are shaped not just by the contemporary climate but also their climate history. Whether or not this affects decomposition rates is underexplored. Here we source...
Thermal decomposition characteristics of microwave liquefied rape straw residues using thermogravimetric analysis

Treesearch

Xingyan Huang; Cornelis F. De Hoop; Jiulong Xie; Chung-Yun Hse; Jinqiu Qi; Yuzhu Chen; Feng Li

2017-01-01

The thermal decomposition characteristics of microwave liquefied rape straw residues with respect to liquefaction condition and pyrolysis conversion were investigated using a thermogravimetric (TG) analyzer at the heating rates of 5, 20, 50 Â°C min-1. The hemicellulose decomposition peak was absent at the derivative thermogravimetric analysis (DTG...
Decomposition of Metrosideros polymorpha leaf litter along elevational gradients in Hawaii

Treesearch

Paul G. Scowcroft; Douglas R. Turner; Peter M. Vitousek

2000-01-01

We examined interactions between temperature, soil development, and decomposition on three elevational gradients, the upper and lower ends of each being situated on a common lava flow or ash deposit. We used the reciprocal transplant technique to estimate decomposition rates of Metrosideros polymorpha leaf litter during a three-year period at warm...
Litter decomposition across an air-pollution gradient in the San Bernardino Mountains

Treesearch

Mark E. Fenn; Paul H. Dunn

1989-01-01

Air pollution may affect forest ecosystems by altering nutrient cycling rates. The objective of this study was to compare decomposition rates of L-layer litter of ponderosa pine (Pinus ponderosa Laws.) and Jeffrey pine (Pinus jeffreyi Grev. & Balf,) collected from across an air-pollution gradient in the San Bernardino Mountains...
Fast Sampling Gas Chromatography (GC) System for Speciation in a Shock Tube

DTIC Science & Technology

2016-10-31

capture similar ethylene decomposition rates for temperature-dependent shock experiments. (a) Papers published in peer-reviewed journals (N/A for none...3 GC Sampling System Validation Experiments ............................................................................... 5 Ethylene ...results for cold shock experiments, and both techniques capture similar ethylene decomposition rates for temperature-dependent shock experiments. Problem
Influence of macrophyte decomposition on growth rate and community structure of okefenokee swamp bacterioplankton.

PubMed

Murray, R E; Hodson, R E

1986-02-01

Dissolved substances released during decomposition of the white water lily (Nymphaea odorata) can alter the growth rate of Okefenokee Swamp bacterioplankton. In microcosm experiments dissolved compounds released from senescent Nymphaea leaves caused a transient reduction in the abundance and activity of water column bacterioplankton, followed by a period of intense bacterial growth. Rates of [H]thymidine incorporation and turnover of dissolved d-glucose were depressed by over 85%, 3 h after the addition of Nymphaea leachates to microcosms containing Okefenokee Swamp water. Bacterial activity subsequently recovered; after 20 h [H]thymidine incorporation in leachate-treated microcosms was 10-fold greater than that in control microcosms. The recovery of activity was due to a shift in the composition of the bacterial population toward resistance to the inhibitory compounds present in Nymphaea leachates. Inhibitory compounds released during the decomposition of aquatic macrophytes thus act as selective agents which alter the community structure of the bacterial population with respect to leachate resistance. Soluble compounds derived from macrophyte decomposition influence the rate of bacterial secondary production and the availability of microbial biomass to microconsumers.
Influence of macrophyte decomposition on growth rate and community structure of Okefenokee Swamp bacterioplankton

DOE Office of Scientific and Technical Information (OSTI.GOV)

Murray, R.E.; Hodson, R.E.

1986-02-01

Dissolved substances released during decomposition of the white water lily (Nymphaea odorata) can alter the growth rate of Okefenokee Swamp bacterioplankton. In microcosm experiments dissolved compounds released bacterioplankton, followed by a period of intense bacterial growth. Rates of (/sup 3/H)thymidine incorporation and turnover of dissolved D-glucose were depressed by over 85%, 3 h after the addition of Nymphaea leachates to microcosms containing Okefenokee Swamp water. Bacterial activity subsequently recovered; after 20 h (/sup 3/H)thymidine incorporation in leachate-treated microcosms was 10-fold greater than that in control microcosms. The recovery of activity was due to a shift in the composition of themore » bacterial population toward resistance to the inhibitory compounds present in Nymphaea leachates. Inhibitory compounds released during the decomposition of aquatic macrophytes thus act as selective agents which alter the community structure of the bacterial population with respect to leachate resistance. Soluble compounds derived from macrophyte decomposition influence the rate of bacterial secondary production and the availability of microbial biomass to microconsumers.« less
Litter mixture dominated by leaf litter of the invasive species, Flaveria bidentis, accelerates decomposition and favors nitrogen release.

PubMed

Li, Huiyan; Wei, Zishang; Huangfu, Chaohe; Chen, Xinwei; Yang, Dianlin

2017-01-01

In natural ecosystems, invasive plant litter is often mixed with that of native species, yet few studies have examined the decomposition dynamics of such mixtures, especially across different degrees of invasion. We conducted a 1-year litterbag experiment using leaf litters from the invasive species Flaveria bidentis (L.) and the dominant co-occurring native species, Setaria viridis (L.). Litters were allowed to decompose either separately or together at different ratios in a mothproof screen house. The mass loss of all litter mixtures was non-additive, and the direction and strength of effects varied with species ratio and decomposition stage. During the initial stages of decomposition, all mixtures had a neutral effect on the mass loss; however, at later stages of decomposition, mixtures containing more invasive litter had synergistic effects on mass loss. Importantly, an increase in F. bidentis litter with a lower C:N ratio in mixtures led to greater net release of N over time. These results highlight the importance of trait dissimilarity in determining the decomposition rates of litter mixtures and suggest that F. bidentis could further synchronize N release from litter as an invasion proceeds, potentially creating a positive feedback linked through invasion as the invader outcompetes the natives for nutrients. Our findings also demonstrate the importance of species composition as well as the identity of dominant species when considering how changes in plant community structure influence plant invasion.
Development of Novel Decontamination and Inerting Techniques for Explosives Contaminated Facilities. Phase 1. Identification and Evaluation of Novel Decontamination Concepts. Volume 1

DTIC Science & Technology

1983-07-01

the decomposition reaction (Leider, 1981; Kageyama, 1973; Wolfrom, 1956), 2) Hydrolysis of linkages between glucose units (Urbanski, 1964), 3... dehydration ), 2) Acceleration period (to 50 percent decomposition ), 3) First order reaction rate period. The products of thermal decomposition of...simple mechanism to clean an entire building at once. o Depending on the contaminant, thermal decomposition and or hydrolysis may occur. o May be
Theoretical evidence of the observed kinetic order dependence on temperature during the N(2)O decomposition over Fe-ZSM-5.

PubMed

Guesmi, Hazar; Berthomieu, Dorothee; Bromley, Bryan; Coq, Bernard; Kiwi-Minsker, Lioubov

2010-03-28

The characterization of Fe/ZSM5 zeolite materials, the nature of Fe-sites active in N(2)O direct decomposition, as well as the rate limiting step are still a matter of debate. The mechanism of N(2)O decomposition on the binuclear oxo-hydroxo bridged extraframework iron core site [Fe(II)(mu-O)(mu-OH)Fe(II)](+) inside the ZSM-5 zeolite has been studied by combining theoretical and experimental approaches. The overall calculated path of N(2)O decomposition involves the oxidation of binuclear Fe(II) core sites by N(2)O (atomic alpha-oxygen formation) and the recombination of two surface alpha-oxygen atoms leading to the formation of molecular oxygen. Rate parameters computed using standard statistical mechanics and transition state theory reveal that elementary catalytic steps involved into N(2)O decomposition are strongly dependent on the temperature. This theoretical result was compared to the experimentally observed steady state kinetics of the N(2)O decomposition and temperature-programmed desorption (TPD) experiments. A switch of the reaction order with respect to N(2)O pressure from zero to one occurs at around 800 K suggesting a change of the rate determining step from the alpha-oxygen recombination to alpha-oxygen formation. The TPD results on the molecular oxygen desorption confirmed the mechanism proposed.

Oxidative decomposition of propylene carbonate in lithium ion batteries: a DFT study.

PubMed

Leggesse, Ermias Girma; Lin, Rao Tung; Teng, Tsung-Fan; Chen, Chi-Liang; Jiang, Jyh-Chiang

2013-08-22

This paper reports an in-depth mechanistic study on the oxidative decomposition of propylene carbonate in the presence of lithium salts (LiClO4, LiBF4, LiPF6, and LiAsF6) with the aid of density functional theory calculations at the B3LYP/6-311++G(d,p) level of theory. The solvent effect is accounted for by using the implicit solvation model with density method. Moreover, the rate constants for the decompositions of propylene carbonate have been investigated by using transition-state theory. The shortening of the original carbonyl C-O bond and a lengthening of the adjacent ethereal C-O bonds of propylene carbonate, which occurs as a result of oxidation, leads to the formation of acetone radical and CO2 as a primary oxidative decomposition product. The termination of the primary radical generates polycarbonate, acetone, diketone, 2-(ethan-1-ylium-1-yl)-4-methyl-1,3-dioxolan-4-ylium, and CO2. The thermodynamic and kinetic data show that the major oxidative decomposition products of propylene carbonate are independent of the type of lithium salt. However, the decomposition rate constants of propylene carbonate are highly affected by the lithium salt type. On the basis of the rate constant calculations using transition-state theory, the order of gas volume generation is: [PC-ClO4](-) > [PC-BF4](-) > [PC-AsF6](-) > [PC-PF6](-).
Sensory irritation and incapacitation evoked by thermal decomposition products of polymers and comparisons with known sensory irritants.

PubMed

Barrow, C S; Alarie, Y; Stock, M F

1978-01-01

A decrease in respiratory rate in mice during exposure to irritating airborne chemicals has been utilized as a response parameter to characterize the degree of upper respiratory tract irritation (sensory irritation) to the thermal decomposition products of various polymers. These included polystyrene, polyvinyl chloride, flexible polyurethane foam, polytetrafluorethylene, a fiber glass reinforced polyester resin, and Douglas Fir. Each of the materials was thermally decomposed in a low-mass vertical furnace in an air atmosphere at a programmed heating rate of 20 degrees C/min. Mice, in groups of four, were exposed to graded concentrations of the thermal decomposition products of each of the above materials. Dose-response curves were obtained by utilizing the maximum percent decrease in respiratory rate as the response parameter during each exposure. Comparison of these dose-response curves with other sensory irritants such as chlorine, ammonia, hydrogen chloride, sulfur dioxide, and toluene diisocyanate gave an indication of the sensory irrtation potential of the thermal decomposition products of these various polymers versus that of well-known single airborne chemical irritants. Total stress and incapacitation of the organism during exposure to sensory irritants such as from the thermal decomposition products of synthetic polymers is discussed.
Survey of materials for hydrazine propulsion systems in multicycle extended life applications

NASA Technical Reports Server (NTRS)

Coulbert, C. D.; Yankura, G.

1972-01-01

An assessment is presented of materials compatibility data for hydrazine monopropellant propulsion systems applicable to the Space Shuttle vehicle missions. Materials were evaluated for application over a 10-yr/100-mission operational lifetime with minimum refurbishment. A general materials compatibility rating for a broad range of materials and several propellants based primarily on static liquid propellant immersion testing and an in-depth evaluation of hydrazine decomposition as a function of purity, temperature, material, surface conditions, etc., are presented. The most promising polymeric material candidates for propellant diaphragms and seals appear to have little effect on increasing hydrazine decomposition rates, but the materials themselves do undergo changes in physical properties which can affect their 10-yr performance in multicycle applications. The available data on these physical properties of elastomeric materials as affected by exposure to hydrazine or related environments are presented.
Approaches to understanding the semi-stable phase of litter decomposition

NASA Astrophysics Data System (ADS)

Preston, C. M.; Trofymow, J. A.

2012-12-01

The slowing or even apparent cessation of litter decomposition with time has been widely observed, but causes remain poorly understood. We examine the question in part through data from CIDET (the Canadian Intersite Decomposition Experiment) for 10 foliar litters at one site with MAT 6.7 degrees C. The initial rapid C loss in the first year for some litters is followed by a second phase (1-7y) with decay rates from 0.21-0.79/y, influenced by initial litter chemistry especially the ratio AUR/N (acid-unhydrolyzable residue, negative). By contrast, 10-23% of the initial litter C mass entered the semi-stable decay phase (>7 y) with modeled decay rates of 0.0021-0.0035/y. The slowing and convergence of k values was similar to trends in chemical composition. From 7-12 y, concentrations of Ca, Mg, K, P, Mn and Zn generally declined and became more similar among litters, and total N converged around 20 mg/g. Non-polar and water-soluble extractables and acid solubles continued to decrease slowly and AUR to increase. Solid-state C-13 NMR showed continuing slight declines in O- and di-O-alkyl C and increases in alkyl, methoxyl, aryl and carboxyl C. CIDET and other studies now clearly show that lignin is not selectively preserved, and that AUR is not a measure of foliar lignin as it includes components from condensed tannins and long-chain alkyl C. Interaction with soil minerals strongly enhances soil C stabilization, but what slows decomposition so much in organic horizons? The role of inherent "chemical recalcitrance" or possible formation of new covalent bonds is hotly debated in soil science, but increasingly complex or random molecular structures no doubt present greater challenges to enzymes. A relevant observation from soils and geochemistry is that decomposition results in a decline in individual compounds that can be identified from chemical analysis and a corresponding increase in the "molecularly uncharacterizable component" (MUC). Long-term declines in Ca, Mg, K and Mn concentrations, but continuing increases in Al and Fe may also decrease attractiveness of litter, and P and N availability may be low. Unfortunately, recent advances in understanding the progression of microbial decomposer guilds, and also in modeling have remained largely disconnected from similar advances in organic matter chemistry, especially for the resistant MUC. For example, the emphasis on aryl C and oxidative enzymes for the semi-stable stage ignores its typically high alkyl component and associated hydrophobicity and many "lignin-based" hypotheses fail because AUR does not measure lignin. The past three decades have brought unimaginable advances in SOM chemistry and microbiology, and also in data analysis and ways of networking and collaborating. Substantial new insights into decomposition will require interdisciplinary networks that incorporate application of well-established methods to characterize the changing chemical and physical properties of the substrates.
Shelters of leaf-tying herbivores decompose faster than leaves damaged by free-living insects: Implications for nutrient turnover in polluted habitats.

PubMed

Kozlov, Mikhail V; Zverev, Vitali; Zvereva, Elena L

2016-10-15

Leaf-eating insects can influence decomposition processes by modifying quality of leaf litter, and this impact can be especially pronounced in habitats where leaf-eating insects reach high densities, for example in heavily polluted areas. We hypothesized that the decomposition rate is faster for shelters of leaf-tying larvae than for leaves damaged by free-living insects, in particular due to the accumulation of larval frass within shelters. We exposed litter bags containing samples of three different compositions (shelters built by moth larvae, leaves damaged by free-living insects and intact leaves of mountain birch, Betula pubescens ssp. czerepanovii) for one year at two heavily polluted sites near the nickel-copper smelter at Monchegorsk in north-western Russia and at two unpolluted sites. The decomposition rate of leaves damaged by free-living insects was 91% of that of undamaged leaves, whereas the mass loss of leaves composing shelters did not differ of that of undamaged leaves. These differences between leaves damaged by different guilds of herbivorous insects were uniform across the study sites, although the decomposition rate in polluted sites was reduced to 77% of that in unpolluted sites. Addition of larval frass to undamaged leaves had no effect on the subsequent decomposition rate. Therefore we suggest that damaged leaves tied by shelter-building larvae decompose faster than untied damaged leaves due to a looser physical structure of the litter, which creates favourable conditions for detritivores and soil decomposers. Thus, while leaf damage by insects per se reduces litter quality and its decomposition rate, structuring of litter by leaf-tying insects counterbalances these negative effects. We conclude that leaf-tying larvae, in contrast to free-living defoliators, do not impose negative effects on nutrient turnover rate even at their high densities, which are frequently observed in heavily polluted sites. Copyright © 2016 Elsevier B.V. All rights reserved.
Cigarette Butt Decomposition and Associated Chemical Changes Assessed by 13C CPMAS NMR

PubMed Central

Bonanomi, Giuliano; Incerti, Guido; Cesarano, Gaspare; Gaglione, Salvatore A.; Lanzotti, Virginia

2015-01-01

Cigarette butts (CBs) are the most common type of litter on earth, with an estimated 4.5 trillion discarded annually. Apart from being unsightly, CBs pose a serious threat to living organisms and ecosystem health when discarded in the environment because they are toxic to microbes, insects, fish and mammals. In spite of the CB toxic hazard, no studies have addressed the effects of environmental conditions on CB decomposition rate. In this study we investigate the interactive effects of substrate fertility and N transfer dynamics on CB decomposition rate and carbon quality changes. We carried out an experiment using smoked CBs and wood sticks, used as a slow decomposing standard organic substrate, incubated in both laboratory and field conditions for two years. CB carbon quality changes during decomposition was assessed by 13C CPMAS NMR. Our experiment confirmed the low degradation rate of CBs which, on average, lost only 37.8% of their initial mass after two years of decomposition. Although a net N transfer occurred from soil to CBs, contrary to our hypothesis, mass loss in the medium-term (two years) was unaffected by N availability in the surrounding substrate. The opposite held for wood sticks, in agreement with the model that N-rich substrates promote the decomposition of other N-poor natural organic materials with a high C/N ratio. As regards CB chemical quality, after two years of decomposition 13C NMR spectroscopy highlighted very small changes in C quality that are likely to reflect a limited microbial attack. PMID:25625643
Litterfall dynamics and nutrient decomposition of arid mangroves in the Gulf of California: Their role sustaining ecosystem heterotrophy

NASA Astrophysics Data System (ADS)

Sánchez-Andrés, R.; Sánchez-Carrillo, S.; Alatorre, L. C.; Cirujano, S.; Álvarez-Cobelas, M.

2010-10-01

This study shows results on litterfall dynamics and decay in mangrove stands of Avicennia germinans distributed along a latitudinal gradient (three forest sites) in the Gulf of California, in order to assess whether internal sources could support the observed mangrove ecosystem organic deficit in this arid tropic. Total mean annual litterfall production increased southward (712.6 ± 53.3, 1501.3 ± 145.1 and 1506.2 ± 280.5 g DW m -2 y -1, in the Yaqui, Mayo and Fuerte areas respectively), leaves being the main component of litter in all locations during the entire year, followed by fruits. The wet season (June-September) showed the highest litterfall rates through fruits. The temporal trend of litterfall production was significantly explained through mean air temperature ( R2 = 68%) whilst total annual litter production in the entire region showed a statistically significant relationship with total soil phosphorus, salinity, total nitrogen, organic matter and tree height ( R2 = 0.67). Throughout 117 days of the decomposition experiment, the litter lost 50% of its original dry weight in 5.8 days (average decay rate of 0.032 ± 0.04 g DW d -1) and there were not significant differences in the remaining mass after 6 days. The percentage of both C and P released from the litter correlated significantly with the ratio of tidal inundated days to total experiment days ( R2 = 0.62, p = 0.03 and R2 = 0.67, p = 0.02, respectively); however, the frequency of tidal inundation only showed a significant increase in C release from Avicennia litter after 6 and above 48 days of decomposition. Whereas the total C content of litter bags decreased linearly over the decomposition to (% Total C = 5.52 - 0.46 days, R2 = 0.81, p = 0.0005), N content displayed an irregular pattern with a significant increase of decay between 48 and 76 days from the beginning of the experiment. The pattern for relative P content of litter revealed reductions of up to 99% of the original (%tot- P = -9.77 to 1.004 days, R2 = 0.72, p = 0.01) although most of the P reduction occurred between 17 and 34 days after the experiment started. Soil N and P contents, which exhibited significant differences in the course of the decomposition experiment, appeared to show significant differences between sampling sites, although they were not related to tidal influence, nor by leaf and nutrient leaching. In a global basis, C/ N litter ratios decreased linearly ( C/ N = 32.86 - 0.1006 days, R2 = 0.62, p = 0.02), showing a strong and significant correlation with meteorological variables ( R2 = 0.99, p = 0.01). C/ P ratios of litter increased through an exponential function ( C/ P = 119.35e 0.04day, R2 = 0.89, p < 0.001). Changes in the remaining percentage of litter mass during the experiment were significantly correlated with soil C/ N ratio ( R2 = 0.56, p = 0.03) as well as with the soil C/ P ratio ( R2 = 0.98, p < 0.001). Our results of litter decomposition dynamics in this mangrove support the fact of null net primary productivity of the arid mangrove wetlands: fast litter decomposition compensates the ecosystem organic deficit in order to sustain the mangrove productivity. Litter decomposition plays a key role in the ecosystem metabolism in mangroves of arid tropics.
Kinetics and selectivity of 2-propanol conversion on oxidized anatase TiO{sub 2}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rekoske, J.E.; Barteau, M.A.

1997-01-01

The steady-state kinetics of 2-propanol decomposition on oxidized anatase TiO{sub 2} have been determined at temperatures ranging from 448 to 598 K and 2-propanol partial pressures from 8.9 to 102.7 Torr. The effects of the addition of O{sub 2} and water to the carrier gas were also investigated. The steady-state reaction results primarily in the formation of a dehydration product, propylene, and a dehydrogenation product, acetone, with small amounts of carbon oxides also being observed. Depending on the reaction conditions, the selectivity to either propylene or acetone can range between 5 and 95%. The rate of dehydrogenation increases dramatically withmore » the addition of both O{sub 2} and water, while the dehydration rate is unaffected by their presence. Accordingly, the kinetics of 2-propanol decomposition were investigated using both air and an inert carrier. Using air as the carrier gas, the dehydration and dehydrogenation reactions were determined to be approximately one-half order with respect to 2-propanol partial pressure. The activation energies determined for the two processes are substantially different, 68 kJ mol{sup -1} for dehydrogenation and 130 kJ mol{sup -1} for dehydration, as evidenced by the strong temperature dependence of the decomposition selectivity. Using an inert carrier, the reaction kinetics depend in a complex fashion on the conversion of 2-propanol. The dependence on conversion was found to arise from the influence of water on the dehydrogenation kinetics. The presence of water, whether produced by 2-propanol dehydration or added independently, was found to increase the rate of 2-propanol dehydrogenation. 48 refs., 9 figs., 6 tabs.« less
Decomposition rate and enzymatic activity of composted municipal waste and poultry manure in the soil in a biofuel crops field.

PubMed

Cordovil, Cláudia Marques-Dos-Santos; de Varennes, Amarilis; Pinto, Renata Machado Dos Santos; Alves, Tiago Filipe; Mendes, Pedro; Sampaio, Sílvio César

2017-05-01

Biofuel crops are gaining importance because of the need to replace non-renewable sources. Also, due to the increasing amounts of wastes generated, there is the need to recycle them to the soil, both to fertilize crops and to improve soil physical properties through organic matter increase and microbiological changes in the rhizosphere. We therefore studied the influence of six biofuel crops (elephant grass, giant cane, sugarcane, blue gum, black cottonwood, willow) on the decomposition rate and enzymatic activity of composted municipal solid waste and poultry manure. Organic amendments were incubated in the field (litterbag method), buried near each plant or bare soil. Biomass decrease and dehydrogenase, urease and acid phosphatase level in amendments was monitored over a 180-day period. Soil under the litterbags was analysed for the same enzymatic activity and organic matter fractions (last sampling). After 365 days, a fractionation of organic matter was carried out in both amendments and soil under the litterbags. For compost, willow and sugarcane generally led to the greatest enzymatic activity, at the end of the experiment. For manure, dehydrogenase activity decreased sharply with time, the smallest value near sugarcane, while phosphatase and urease generally presented the highest values, at the beginning or after 90 days' incubation. Clustering showed that plant species could be grouped based on biomass and enzymes measured over time. Plant species influenced the decomposition rate and enzymatic activities of the organic amendments. Overall, mineralization of both amendments was associated with a greater urease activity in soils. Dehydrogenase activity in manure was closely associated with urease activity. © 2016 Society of Chemical Industry. © 2016 Society of Chemical Industry.
The response of soil carbon storage and microbially mediated carbon turnover to simulated climatic disturbance in a northern peatland forest. Revisiting the concept of soil organic matter recalcitrance

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kostka, Joel

The goal of this project was to investigate changes in the structure of dissolved and solid phase organic matter, the production of CO 2 and CH 4, and the composition of decomposer microbial communities in response to the climatic forcing of environmental processes that determine the balance between carbon gas production versus storage and sequestration in peatlands. Cutting-edge analytical chemistry and next generation sequencing of microbial genes were been applied to habitats at the Marcell Experimental Forest (MEF), where the US DOE’s Oak Ridge National Laboratory and the USDA Forest Service are constructing a large-scale ecosystem study entitled, “Spruce andmore » Peatland Responses Under Climatic and Environmental Change”(SPRUCE). Our study represented a comprehensive characterization of the sources, transformation, and decomposition of organic matter in the S1 bog at MEF. Multiple lines of evidence point to distinct, vertical zones of organic matter transformation: 1) the acrotelm consisting of living mosses, root material, and newly formed litter (0-30 cm), 2) the mesotelm, a mid-depth transition zone (30-75 cm) characterized by labile organic C compounds and intense decomposition, and 3) the underlying catotelm (below 75cm) characterized by refractory organic compounds as well as relatively low decomposition rates. These zones are in part defined by physical changes in hydraulic conductivity and water table depth. O-alkyl-C, which represents the carbohydrate fraction in the peat, was shown to be an excellent proxy for soil decomposition rates. The carbon cycle in deep peat was shown to be fueled by modern carbon sources further indicating that hydrology and surface vegetation play a role in belowground carbon cycling. We provide the first metagenomic study of an ombrotrophic peat bog, with novel insights into microbial specialization and functions in this unique terrestrial ecosystem. Vertical structuring of microbial communities closely paralleled the chemical evolution of peat, with large shifts in microbial populations occurring in the biogeochemical hotspot, the mesotelm, where the highest rates of decomposition were detected. Stable isotope geochemistry and potential rates of methane production paralleled vertical changes in methanogen community composition to indicate a predominance of acetoclastic methanogenesis mediated by the Methanosarcinales in the mesotelm, while hydrogen-utilizing methanogens dominated in the deeper catotelm. Evidence pointed to the availability of phosphorus as well as nitrogen limiting the microbially-mediated turnover of organic carbon at MEF. Prior to initiation of the experimental treatments, our study provided key baseline data for the SPRUCE site on the vertical stratification of peat decomposition, key enzymatic pathways, and microbial taxa containing these pathways. The sensitivity of soil carbon turnover to climate change is strongly linked to recalcitrant carbon stocks and the temperature sensitivity of decomposition is thought to increase with increasing molecular complexity of carbon substrates. This project delivered results on how climate change perturbations impact the microbially-mediated turnover of recalcitrant organic matter in peatland forest soils, both under controlled conditions in the laboratory and at the ecosystem-scale in the field. This project revisited the concept of “recalcitrance” in the regulation of soil carbon turnover using a combination of natural abundance radiocarbon and optical spectroscopic measurements on bulk DOM, and high resolution molecular characterization of DOM. The project elucidated how organic matter reactivity and decomposition will respond to climate change in a both a qualitative (organic matter lability) and quantitiative (increased rates) manner. An Aromaticity Index was developed to represent a more direct and accurate parameter for modeling of DOM reactivity in peatlands. The abundance and community composition of soil microorganisms that mediate C cycling were interrogated with depth in the peat, with season, and in manipulated climate enclosures at unprecedented resolution. Therefore this project delivered strategic new insights on the functioning of peatland ecosystems that collectively store approximately one-third of the world's soil carbon. Furthermore, results from the detailed characterization of DOM lability and microbial community structure/ function will be employed to further develop biogeochemical models to include microbial respiration pathways as well as to track carbon flow with a term that incorporates relative reactivity based on aromaticity index. As it stands now, detailed soil organic matter structure and microbial parameters are not included in Earth system models.« less
NMR study of methane + ethane structure I hydrate decomposition.

PubMed

Dec, Steven F; Bowler, Kristen E; Stadterman, Laura L; Koh, Carolyn A; Sloan, E Dendy

2007-05-24

The thermally activated decomposition of methane + ethane structure I hydrate was studied with use of 13C magic-angle spinning (MAS) NMR as a function of composition and temperature. The observed higher decomposition rate of large sI cages initially filled with ethane gas can be described in terms of a model where a distribution of sI unit cells exists such that a particular unit cell contains zero, one, or two methane molecules in the unit cell; this distribution of unit cells is combined to form the observed equilibrium composition. In this model, unit cells with zero methane molecules are the least stable and decompose more rapidly than those populated with one or two methane molecules leading to the observed overall faster decomposition rate of the large cages containing ethane molecules.
Sonochemical Effects on 14 Flavonoids Common in Citrus: Relation to Stability

PubMed Central

Qiao, Liping; Sun, Yujing; Chen, Rongrong; Fu, Yu; Zhang, Wenjuan; Li, Xin; Chen, Jianchu; Shen, Yan; Ye, Xingqian

2014-01-01

The sonochemical effects of ultrasound (US) treatment on 14 flavonoids representing the main flavonoids in citrus fruit were investigated in a standard mixture by stability evaluation of a model system. Degradation products were further tentatively identified by Fourier transform infrared spectroscopy and high-performance liquid chromatography–ultraviolet detection–electrospray ionization tandem mass spectrometry. Thirteen flavonoids (i.e., eriocitrin, narirutin, neohesperidin, quercitrin, eridictyol, didymin, naringenin, luteolin, sinensetin, nobiletin, tangeretin, naringin, and hesperidin) were fairly stable whereas quercetin was degraded significantly by US treatment. The types of solvent and temperature used were important factors that determined the resulting degradation reactions. The degradation rate of quercetin was highest in 80% ethanol aqueous solution and decreased with increasing temperature. Longer US durations caused increases in the extent of quercetin degradation. Liquid height, ultrasonic intensity, pulse length, and duty cycle of US affected degradation rates but did not change the nature of degradation of the flavonoids. Four types of reactions occurred simultaneously for quercetin under US treatment: oxidation, addition, polymerization, and decomposition. Eight degradation products were tentatively identified as dimer, alcohol addition, oxidation, and decomposition products. PMID:24516562
Climate warming and the carbon cycle in the permafrost zone of the former Soviet Union

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kolchugina, T.P.; Vinson, T.S.

1993-01-01

The continuous permafrost zone of the former Soviet Union occupies 5% of the land surface area of the earth and stores a significant amount of carbon. Climate warming could disrupt the balance between carbon (C) accumulation and decomposition processes within the permafrost zone. Increased temperatures may accelerate the rate of organic matter decomposition. At the same time, the productivity of vegetation may increase in response to warming. To assess the future carbon cycle within the permafrost zone under a climate-warming scenario, it is necessary to quantify present carbon pools and fluxes. The present carbon cycle was assessed on the basismore » of an ecosystem/ecoregion approach. Under the present climate, the phytomass carbon pool was estimated at 17.0 Giga tons. The mortmass (coarse woody debris) carbon pool was estimated at 16.1 Giga tons. The soil carbon pool, including peatlands, was 139.4 Giga tons. The present rate of carbon turnover was 1.6 Giga tons/yr. (Copyright (c) 1993 by John Wiley and Sons, Ltd.)« less
Sonochemical effects on 14 flavonoids common in citrus: relation to stability.

PubMed

Qiao, Liping; Sun, Yujing; Chen, Rongrong; Fu, Yu; Zhang, Wenjuan; Li, Xin; Chen, Jianchu; Shen, Yan; Ye, Xingqian

2014-01-01

The sonochemical effects of ultrasound (US) treatment on 14 flavonoids representing the main flavonoids in citrus fruit were investigated in a standard mixture by stability evaluation of a model system. Degradation products were further tentatively identified by Fourier transform infrared spectroscopy and high-performance liquid chromatography-ultraviolet detection-electrospray ionization tandem mass spectrometry. Thirteen flavonoids (i.e., eriocitrin, narirutin, neohesperidin, quercitrin, eridictyol, didymin, naringenin, luteolin, sinensetin, nobiletin, tangeretin, naringin, and hesperidin) were fairly stable whereas quercetin was degraded significantly by US treatment. The types of solvent and temperature used were important factors that determined the resulting degradation reactions. The degradation rate of quercetin was highest in 80% ethanol aqueous solution and decreased with increasing temperature. Longer US durations caused increases in the extent of quercetin degradation. Liquid height, ultrasonic intensity, pulse length, and duty cycle of US affected degradation rates but did not change the nature of degradation of the flavonoids. Four types of reactions occurred simultaneously for quercetin under US treatment: oxidation, addition, polymerization, and decomposition. Eight degradation products were tentatively identified as dimer, alcohol addition, oxidation, and decomposition products.
Biophysical controls on surface fuel litterfall and decomposition in the northern Rocky Mountains, USA

Treesearch

Robert E. Keane

2008-01-01

Litterfall and decomposition rates of the organic matter that comprise forest fuels are important to fire management, because they define fuel treatment longevity and provide parameters to design, test, and validate ecosystem models. This study explores the environmental factors that control litterfall and decomposition in the context of fuel management for several...
Reduced substrate supply limits the temperature response of soil organic carbon decomposition

Treesearch

Cinzia Fissore; Christian P. Giardina; Randall K. Kolka

2013-01-01

Controls on the decomposition rate of soil organic carbon (SOC), especially the more stable fraction of SOC, remain poorly understood, with implications for confidence in efforts to model terrestrial C balance under future climate. We investigated the role of substrate supply in the temperature sensitivity of SOC decomposition in laboratory incubations of coarse-...
Bark coverage and insects influence wood decomposition: direct and indirect effects

Treesearch

Michael D. Ulyshen; Jorg Muller; Sebastian Seibold

2016-01-01

Rates of terrestrial wood decomposition are known to vary widely depending on regional and local climatic conditions, substrate characteristics and the organisms involved but the influence of many factors remain poorly quantified. We sought to determine how bark and insects contribute to decomposition in a southeastern U.S. forest. Open-topped stainless steel pans with...
The effects of substrate supply on the temperature sensitivity of soil carbon decomposition

Treesearch

Cinzia Fissore; Christian P. Giardina; Randall K. Kolka

2013-01-01

Controls on the decomposition rate of soil organic carbon (SOC), especially the more stable fraction of SOC, remain poorly understood, with implications for confidence in efforts to model terrestrial C balance under future climate. We investigated the role of substrate supply in the temperature sensitivity of SOC decomposition in laboratory incubations of coarse-...
Interacting effects of insects and flooding on wood decomposition.

Treesearch

Michael Ulyshen

2014-01-01

Saproxylic arthropods are thought to play an important role in wood decomposition but very few efforts have been made to quantify their contributions to the process and the factors controlling their activities are not well understood. In the current study, mesh exclusion bags were used to quantify how arthropods affect loblolly pine (Pinus taeda L.) decomposition rates...
Decomposition and nutrient release from fresh and dried pine roots under two fertilizer regimes

Treesearch

Kim H. Ludovici; Lance W. Kress

2006-01-01

Root decomposition and nutrient release are typically estimated from dried root tissues; however, it is unlikely that roots dehydrate prior to decomposing. Soil fertility and root diameter may also affect the rate of decomposition. This study monitored mass loss and nutrient concentrations of dried and fresh roots of two size classes (

Boreal soil carbon dynamics under a changing climate: a model inversion approach

Treesearch

Zhaosheng Fan; Jason C. Neff; Jennifer W. Harden; Kimberly P. Wickland

2008-01-01

Several fundamental but important factors controlling the feedback of boreal organic carbon (OC) to climate change were examined using a mechanistic model of soil OC dynamics, including the combined effects of temperature and moisture on the decomposition of OC and the factors controlling carbon quality and decomposition with depth. To estimate decomposition rates and...
Comparing intra- and inter-specific effects on litter decomposition in an old-field ecosystem

DOE Office of Scientific and Technical Information (OSTI.GOV)

Crutsinger, Greg; Sanders, Dr. Nathan James; Classen, Aimee T

2009-09-01

Plant species can differ in the quantity and quality of leaf litter they produce, and many studies have examined whether plant species diversity affects leaf-litter decomposition and nutrient release. A growing number of studies have indicated that intra-specific variation within plant species can also affect key ecosystem processes. However, the relative importance of intra- versus inter-specific variation for the functioning of ecosystems remains poorly known. Here, we investigate the effects of intra-specific variation in a dominant old-field plant species, tall goldenrod (Solidago altissima), and inter-specific variation among goldenrod species on litter quality, decomposition, and nitrogen (N) release. We found thatmore » the nutrient concentration of leaf litter varied among genotypes, which translated into 50% difference in decomposition rates. Variation among other goldenrod species in decomposition rate was more than twice that of genetic variation within S. altissima. Furthermore, by manipulating litterbags to contain 1, 3, 6, or 9 genotypes, we found that S. altissima genotype identity had much stronger effects than did genotypic diversity on leaf-litter quality, decomposition, and N release. Taken together, these results suggest that the order of ecological importance for controlling leaf-litter decomposition and N release dynamics is plant species identitygenotype identity>genotypic diversity.« less
A comparison of carcass decomposition and associated insect succession onto burnt and unburnt pig carcasses.

PubMed

McIntosh, Craig S; Dadour, Ian R; Voss, Sasha C

2017-05-01

The rate of decomposition and insect succession onto decomposing pig carcasses were investigated following burning of carcasses. Ten pig carcasses (40-45 kg) were exposed to insect activity during autumn (March-April) in Western Australia. Five replicates were burnt to a degree described by the Crow-Glassman Scale (CGS) level #2, while five carcasses were left unburnt as controls. Burning carcasses greatly accelerated decomposition in contrast to unburnt carcasses. Physical modifications following burning such as skin discolouration, splitting of abdominal tissue and leathery consolidation of skin eliminated evidence of bloat and altered microambient temperatures associated with carcasses throughout decomposition. Insect species identified on carcasses were consistent between treatment groups; however, a statistically significant difference in insect succession onto remains was evident between treatments (PERMANOVA F (1, 224) = 14.23, p < 0.01) during an 8-day period that corresponds with the wet stage of decomposition. Differences were noted in the arrival time of late colonisers (Coleoptera) and the development of colonising insects between treatment groups. Differences in the duration of decomposition stages and insect assemblages indicate that burning has an effect on both rate of decomposition and insect succession. The findings presented here provide baseline data for entomological casework involving burnt remains criminal investigations.
Solar radiation uncorks the lignin bottleneck on plant litter decomposition in terrestrial ecosystems

NASA Astrophysics Data System (ADS)

Austin, A.; Ballare, C. L.; Méndez, M. S.

2015-12-01

Plant litter decomposition is an essential process in the first stages of carbon and nutrient turnover in terrestrial ecosystems, and together with soil microbial biomass, provide the principal inputs of carbon for the formation of soil organic matter. Photodegradation, the photochemical mineralization of organic matter, has been recently identified as a mechanism for previously unexplained high rates of litter mass loss in low rainfall ecosystems; however, the generality of this process as a control on carbon cycling in terrestrial ecosystems is not known, and the indirect effects of photodegradation on biotic stimulation of carbon turnover have been debated in recent studies. We demonstrate that in a wide range of plant species, previous exposure to solar radiation, and visible light in particular, enhanced subsequent biotic degradation of leaf litter. Moreover, we demonstrate that the mechanism for this enhancement involves increased accessibility for microbial enzymes to plant litter carbohydrates due to a reduction in lignin content. Photodegradation of plant litter reduces the structural and chemical bottleneck imposed by lignin in secondary cell walls. In litter from woody plant species, specific interactions with ultraviolet radiation obscured facilitative effects of solar radiation on biotic decomposition. The generalized positive effect of solar radiation exposure on subsequent microbial activity is mediated by increased accessibility to cell wall polysaccharides, which suggests that photodegradation is quantitatively important in determining rates of mass loss, nutrient release and the carbon balance in a broad range of terrestrial ecosystems.
A highly efficient autothermal microchannel reactor for ammonia decomposition: Analysis of hydrogen production in transient and steady-state regimes

NASA Astrophysics Data System (ADS)

Engelbrecht, Nicolaas; Chiuta, Steven; Bessarabov, Dmitri G.

2018-05-01

The experimental evaluation of an autothermal microchannel reactor for H2 production from NH3 decomposition is described. The reactor design incorporates an autothermal approach, with added NH3 oxidation, for coupled heat supply to the endothermic decomposition reaction. An alternating catalytic plate arrangement is used to accomplish this thermal coupling in a cocurrent flow strategy. Detailed analysis of the transient operating regime associated with reactor start-up and steady-state results is presented. The effects of operating parameters on reactor performance are investigated, specifically, the NH3 decomposition flow rate, NH3 oxidation flow rate, and fuel-oxygen equivalence ratio. Overall, the reactor exhibits rapid response time during start-up; within 60 min, H2 production is approximately 95% of steady-state values. The recommended operating point for steady-state H2 production corresponds to an NH3 decomposition flow rate of 6 NL min-1, NH3 oxidation flow rate of 4 NL min-1, and fuel-oxygen equivalence ratio of 1.4. Under these flows, NH3 conversion of 99.8% and H2 equivalent fuel cell power output of 0.71 kWe is achieved. The reactor shows good heat utilization with a thermal efficiency of 75.9%. An efficient autothermal reactor design is therefore demonstrated, which may be upscaled to a multi-kW H2 production system for commercial implementation.
Decomposition of naphthalene by dc gliding arc gas discharge.

PubMed

Yu, Liang; Li, Xiaodong; Tu, Xin; Wang, Yu; Lu, Shengyong; Yan, Jianhua

2010-01-14

Gliding arc discharge has been proved to be effective in treatment of gas and liquid contaminants. In this study, physical characteristics of dc gliding arc discharge and its application to naphthalene destruction are investigated with different external resistances and carrier gases. The decomposition rate increases with increasing of oxygen concentration and decreases with external resistance. This value can be achieved up to 92.3% at the external resistance of 50 kOmega in the oxygen discharge, while the highest destruction energy efficiency reaches 3.6 g (kW h)(-1) with the external resistance of 93 kOmega. Possible reaction pathways and degradation mechanisms in the plasma with different gases are proposed by qualitative analysis of postdestructed products. In the air and oxygen gliding arc discharges, the naphthalene degradation is mainly governed by reactions with oxygen-derived radicals.
Global trends in peatland methane production

NASA Astrophysics Data System (ADS)

Hoyt, A.; Corbett, J. E.; Gandois, L.; Cobb, A.; Pangala, S. R.; Gauci, V.; Harvey, C. F.

2017-12-01

Peatland methane production rates and fluxes to the atmosphere vary globally. Here we present a systematic comparison of peatland CH4 production across latitudes. We developed and applied an isotope-based mass transport model to characterize rates of methanogenesis and recharge rates across ten ombrotrophic peatlands from around the world. We validated our model against peat incubations and surface fluxes where data was available. We found striking similarities in the DIC and CH4 concentrations and δ13C isotope profiles across northern bogs, despite highly variable precipitation, recharge rates, and peat characteristics. Profiles from northern sites were similar because increased recharge rates were always compensated by increased CH4 production rates. This could represent a feedback mechanism between recharge rates and methanogenesis in northern bogs or could represent a shared dependence of these two properties on the degree of peat decomposition. We also found strong differences between northern and tropical sites, both in the rate of CH4 production, the recharge rate, and in the transport pathways and fluxes to the atmosphere. Our findings have important implications for methane transport and release to the atmosphere. In northern bogs, low flow rates allow CH4 concentrations to build up, and CH4 escapes by surface diffusion, ebullition, and plant-mediated transport. Thus, the majority of CH4 produced escapes through the peat surface. In tropical peatlands, high flow rates suppress CH4 concentrations, which do not build up above the threshold for ebullition. Instead, CH4 leaves the peat by lateral transport and surface fluxes are small. This work provides evidence that peat properties and hydrology are fundamental controls on decomposition, CH4 production, and peat formation across latitudes.
Very high pressure combustion; Reaction propagation rates of nitromethane within a diamond anvil cell

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rice, S.F.; Foltz, M.F.

1991-11-01

This paper reports on the combustion-front propagation rate of nitromethane that has been examined to pressures of 40 GPa. A new and general technique involving pulsed laser ignition of an energetic material within a diamond anvil cell and a method for monitoring the rapid decomposition of nitromethane and other explosives to more stable chemical products is described in detail. Nitromethane is shown to exhibit a flame propagation rate that increases smoothly to 100 m/s at 30 GPa as a function of pressure. Above 30 GPa, the final solid-state combustion products change dramatically and the flame propagation rate begins to decrease.more » The combustion-front propagation rate is analyzed in terms of an existing condensed-phase model that predicts a relationship between the front propagation rate, U, and the pressure derivative of the chemical kinetic activation energy, dE{sub a}/dP, such that a plot of logU{sup 2} vs. P should be linear. The activation energy is analyzed to yield an effective volume of activation, {Delta}V, of {minus}3.4 ml/mol. The chemical kinetic parameters determined from the combustion-front propagation rate analysis of solid high-pressure nitromethane is compared with results from other thermal decomposition studies of this prototypic molecular explosive.« less
A contribution to the knowledge of HMX decomposition and application of results. [at atmospheric pressure

NASA Technical Reports Server (NTRS)

Kraeutle, K. J.

1980-01-01

The decomposition of cyclotramethylenetetranitramine (HMX) in the solid and liquid phase was studied by isothermal and nonisothermal heating at atmospheric pressure. Decomposition rates of solid HMX changed with sample size and gaseous environment. Kinetic parameters were obtained from weight loss measurements in the temperature range 229 C - 269 C. These tests also yielded highly porous solid residues. Qualitative aspects of solid and liquid phase decomposition of HMX with additives were also investigated in isothermal and nonisothermal tests.
Species richness and trophic diversity increase decomposition in a co-evolved food web.

PubMed

Baiser, Benjamin; Ardeshiri, Roxanne S; Ellison, Aaron M

2011-01-01

Ecological communities show great variation in species richness, composition and food web structure across similar and diverse ecosystems. Knowledge of how this biodiversity relates to ecosystem functioning is important for understanding the maintenance of diversity and the potential effects of species losses and gains on ecosystems. While research often focuses on how variation in species richness influences ecosystem processes, assessing species richness in a food web context can provide further insight into the relationship between diversity and ecosystem functioning and elucidate potential mechanisms underpinning this relationship. Here, we assessed how species richness and trophic diversity affect decomposition rates in a complete aquatic food web: the five trophic level web that occurs within water-filled leaves of the northern pitcher plant, Sarracenia purpurea. We identified a trophic cascade in which top-predators--larvae of the pitcher-plant mosquito--indirectly increased bacterial decomposition by preying on bactivorous protozoa. Our data also revealed a facultative relationship in which larvae of the pitcher-plant midge increased bacterial decomposition by shredding detritus. These important interactions occur only in food webs with high trophic diversity, which in turn only occur in food webs with high species richness. We show that species richness and trophic diversity underlie strong linkages between food web structure and dynamics that influence ecosystem functioning. The importance of trophic diversity and species interactions in determining how biodiversity relates to ecosystem functioning suggests that simply focusing on species richness does not give a complete picture as to how ecosystems may change with the loss or gain of species.
Species Richness and Trophic Diversity Increase Decomposition in a Co-Evolved Food Web

PubMed Central

Baiser, Benjamin; Ardeshiri, Roxanne S.; Ellison, Aaron M.

2011-01-01

Ecological communities show great variation in species richness, composition and food web structure across similar and diverse ecosystems. Knowledge of how this biodiversity relates to ecosystem functioning is important for understanding the maintenance of diversity and the potential effects of species losses and gains on ecosystems. While research often focuses on how variation in species richness influences ecosystem processes, assessing species richness in a food web context can provide further insight into the relationship between diversity and ecosystem functioning and elucidate potential mechanisms underpinning this relationship. Here, we assessed how species richness and trophic diversity affect decomposition rates in a complete aquatic food web: the five trophic level web that occurs within water-filled leaves of the northern pitcher plant, Sarracenia purpurea. We identified a trophic cascade in which top-predators — larvae of the pitcher-plant mosquito — indirectly increased bacterial decomposition by preying on bactivorous protozoa. Our data also revealed a facultative relationship in which larvae of the pitcher-plant midge increased bacterial decomposition by shredding detritus. These important interactions occur only in food webs with high trophic diversity, which in turn only occur in food webs with high species richness. We show that species richness and trophic diversity underlie strong linkages between food web structure and dynamics that influence ecosystem functioning. The importance of trophic diversity and species interactions in determining how biodiversity relates to ecosystem functioning suggests that simply focusing on species richness does not give a complete picture as to how ecosystems may change with the loss or gain of species. PMID:21673992
Degradation of Penicillin G by heat activated persulfate in aqueous solution.

PubMed

Norzaee, Samira; Taghavi, Mahmoud; Djahed, Babak; Kord Mostafapour, Ferdos

2018-06-01

We used Heat Activated of Persulfate (HAP) to decompose Penicillin G (PEN G) in aqueous solution. The effect of pH (3-11), temperature (313-353 K), and initial concentration of Sodium Persulfate (SPS) (0.05-0.5 mM) on the decomposition level of PEN G were investigated. The residue of PEN G was determined by spectrophotometry at the wavelength of 290 nm. Also, the Chemical Oxygen Demand (COD) was measured in each experiment. The Total Organic Carbon (TOC) analysis was utilized for surveying the mineralization of PEN G. In addition, based on Arrhenius equation, the activation energy of PEN G decomposition was calculated. The results indicated that the maximum PEN G removal rate was obtained at pH 5 and by increasing the doses of SPS from 0.05 to 0.5 mM, the PEN G decomposition was enhanced. It was found that an increase in temperature is accompanied by an increase in removal efficiency of PEN G. The activation energy of the studied process was determined to be 94.8 kJ mol -1 , suggesting that a moderate activation energy is required for PEN G decomposition. The TOC measurements indicate that the HAP can efficiently mineralize PEN G. Besides, the presence of the scavengers significantly suppressed the HAP process to remove the PEN G. Overall, the results of this study demonstrate that using HAP process can be a suitable method for decomposing of PEN G in aqueous solutions. Copyright © 2018 Elsevier Ltd. All rights reserved.
An efficient computational approach to model statistical correlations in photon counting x-ray detectors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Faby, Sebastian; Maier, Joscha; Sawall, Stefan

2016-07-15

Purpose: To introduce and evaluate an increment matrix approach (IMA) describing the signal statistics of energy-selective photon counting detectors including spatial–spectral correlations between energy bins of neighboring detector pixels. The importance of the occurring correlations for image-based material decomposition is studied. Methods: An IMA describing the counter increase patterns in a photon counting detector is proposed. This IMA has the potential to decrease the number of required random numbers compared to Monte Carlo simulations by pursuing an approach based on convolutions. To validate and demonstrate the IMA, an approximate semirealistic detector model is provided, simulating a photon counting detector inmore » a simplified manner, e.g., by neglecting count rate-dependent effects. In this way, the spatial–spectral correlations on the detector level are obtained and fed into the IMA. The importance of these correlations in reconstructed energy bin images and the corresponding detector performance in image-based material decomposition is evaluated using a statistically optimal decomposition algorithm. Results: The results of IMA together with the semirealistic detector model were compared to other models and measurements using the spectral response and the energy bin sensitivity, finding a good agreement. Correlations between the different reconstructed energy bin images could be observed, and turned out to be of weak nature. These correlations were found to be not relevant in image-based material decomposition. An even simpler simulation procedure based on the energy bin sensitivity was tested instead and yielded similar results for the image-based material decomposition task, as long as the fact that one incident photon can increase multiple counters across neighboring detector pixels is taken into account. Conclusions: The IMA is computationally efficient as it required about 10{sup 2} random numbers per ray incident on a detector pixel instead of an estimated 10{sup 8} random numbers per ray as Monte Carlo approaches would need. The spatial–spectral correlations as described by IMA are not important for the studied image-based material decomposition task. Respecting the absolute photon counts and thus the multiple counter increases by a single x-ray photon, the same material decomposition performance could be obtained with a simpler detector description using the energy bin sensitivity.« less
Comparison of protocols for measuring and calculating postmortem submersion intervals for human analogs in fresh water.

PubMed

Humphreys, Michael K; Panacek, Edward; Green, William; Albers, Elizabeth

2013-03-01

Protocols for determining postmortem submersion interval (PMSI) have long been problematic for forensic investigators due to the wide variety of factors affecting the rate of decomposition of submerged carrion. Likewise, it has been equally problematic for researchers to develop standardized experimental protocols to monitor underwater decomposition without artificially affecting the decomposition rate. This study compares two experimental protocols: (i) underwater in situ evaluation with photographic documentation utilizing the Heaton et al. total aquatic decomposition (TAD) score and (ii) weighing the carrion before and after submersion. Complete forensic necropsies were performed as a control. Perinatal piglets were used as human analogs. The results of this study indicate that in order to objectively measure decomposition over time, the human analog should be examined at depth using the TAD scoring system rather than utilizing a carrion weight evaluation. The acquired TAD score can be used to calculate an approximate PMSI. © 2012 American Academy of Forensic Sciences.
New insights into thermal decomposition of polycyclic aromatic hydrocarbon oxyradicals.

PubMed

Liu, Peng; Lin, He; Yang, Yang; Shao, Can; Gu, Chen; Huang, Zhen

2014-12-04

Thermal decompositions of polycyclic aromatic hydrocarbon (PAH) oxyradicals on various surface sites including five-membered ring, free-edge, zigzag, and armchair have been systematically investigated by using ab initio density functional theory B3LYP/6-311+G(d,p) basis set. The calculation based on Hückel theory indicates that PAHs (3H-cydopenta[a]anthracene oxyradical) with oxyradicals on a five-membered ring site have high chemical reactivity. The rate coefficients of PAH oxyradical decomposition were evaluated by using Rice-Ramsperger-Kassel-Marcus theory and solving the master equations in the temperature range of 1500-2500 K and the pressure range of 0.1-10 atm. The kinetic calculations revealed that the rate coefficients of PAH oxyradical decomposition are temperature-, pressure-, and surface site-dependent, and the oxyradical on a five-membered ring is easier to decompose than that on a six-membered ring. Four-membered rings were found in decomposition of the five-membered ring, and a new reaction channel of PAH evolution involving four-membered rings is recommended.
Pollutant content in marine debris and characterization by thermal decomposition.

PubMed

Iñiguez, M E; Conesa, J A; Fullana, A

2017-04-15

Marine debris (MDs) produces a wide variety of negative environmental, economic, safety, health and cultural impacts. Most marine litter has a very low decomposition rate (plastics), leading to a gradual accumulation in the coastal and marine environment. Characterization of the MDs has been done in terms of their pollutant content: PAHs, ClBzs, ClPhs, BrPhs, PCDD/Fs and PCBs. The results show that MDs is not a very contaminated waste. Also, thermal decomposition of MDs materials has been studied in a thermobalance at different atmospheres and heating rates. Below 400-500K, the atmosphere does not affect the thermal degradation of the mentioned waste. However, at temperatures between 500 and 800K the presence of oxygen accelerates the decomposition. Also, a kinetic model is proposed for the combustion of the MDs, and the decomposition is compared with that of their main constituents, i.e., polyethylene (PE), polystyrene (PS), polypropylene (PP), nylon and polyethylene-terephthalate (PET). Copyright © 2017 Elsevier Ltd. All rights reserved.
The stability of amoxicillin trihydrate and potassium clavulanate combination in aqueous solutions.

PubMed

Jerzsele, Akos; Nagy, Gábor

2009-12-01

The effect of various environmental factors on the stability of aqueous solutions of amoxicillin-clavulanic acid combination in a veterinary water-soluble powder product was investigated. In the swine industry, the combination is administered via the drinking water, where both substances are quickly decomposed depending on several environmental factors. The degradation rate of the substances was determined in solutions of different water hardness levels (German hardness of 2, 6 and 10) and pH values (3.0, 7.0 and 10.0), and in troughs made of different materials (metal or plastic). Increasing the water hardness decreased the stability of both substances, amoxicillin being more stable at each hardness value than clavulanate. Amoxicillin trihydrate proved to be most stable at an acidic pH, while increasing the pH decreased its stability (P < 0.05). Maximum stability of potassium clavulanate was experienced at neutral pH, while its decomposition rate was significantly higher at acidic and alkaline pH values (P < 0.01). The stability of the amoxicillin-clavulanic acid combination depends mainly on the less stable clavulanate, although the effect of metallic ions significantly increased the decomposition rate of amoxicillin, rendering it less stable in metal troughs than clavulanate (P < 0.05). Therefore, the amoxicillin-clavulanic acid combination should be administered to the animals in soft water, at neutral pH and in plastic troughs.
Accelerated decay rates drive soil organic matter persistence and storage in temperate forests via greater mineral stabilization of microbial residues.

NASA Astrophysics Data System (ADS)

Phillips, R.; Craig, M.; Turner, B. L.; Liang, C.

2017-12-01

Climate predicts soil organic matter (SOM) stocks at the global scale, yet controls on SOM stocks at finer spatial scales are still debated. A current hypothesis predicts that carbon (C) and nitrogen (N) storage in soils should be greater when decomposition is slow owing to microbial competition for nutrients or the recalcitrance of organic substrates (hereafter the `slow decay' hypothesis). An alternative hypothesis predicts that soil C and N storage should be greater in soils with rapid decomposition, owing to the accelerated production of microbial residues and their stabilization on soil minerals (hereafter the `stabilization hypothesis'). To test these alternative hypotheses, we quantified soil C and N to 1-m depth in temperate forests across the Eastern and Midwestern US that varied in their biotic, climatic, and edaphic properties. At each site, we sampled (1) soils dominated by arbuscular mycorrhizal (AM) tree species, which typically have fast decay rates and accelerated N cycling, (2) soils dominated by ectomycorrhizal (ECM) tree species, which generally have slow decay rates and slow N cycling, and (3) soils supporting both AM and ECM trees. To the extent that trees and theor associated microbes reflect and reinforce soil conditions, support for the slow decay hypothesis would be greater SOM storage in ECM soils, whereas support for the stabilization hypothesis would be greater SOM storage in AM soils. We found support for both hypotheses, as slow decomposition in ECM soils increased C and N storage in topsoil, whereas fast decomposition in AM soils increased C and N storage in subsoil. However, at all sites we found 57% greater total C and N storage in the entire profile in AM- soils (P < 0.0001), supporting the stabilization hypothesis. Amino sugar biomarkers (an indicator of microbial necromass) and particle size fractionation revealed that the greater SOM storage in AM soils was driven by an accumulation of microbial residues on clay minerals and metal oxides. Taken together, our results indicate that tree species influence soil C and N storage owing to how differences in decay rates affect mineral stabilization of organic matter. Further, our findings indicate that slow decay promotes soil C and N stocks at the soil surface, whereas fast decay promotes greater soil C and N stocks at depth.
Silver-palladium catalysts for the direct synthesis of hydrogen peroxide

NASA Astrophysics Data System (ADS)

Khan, Zainab; Dummer, Nicholas F.; Edwards, Jennifer K.

2017-11-01

A series of bimetallic silver-palladium catalysts supported on titania were prepared by wet impregnation and assessed for the direct synthesis of hydrogen peroxide, and its subsequent side reactions. The addition of silver to a palladium catalyst was found to significantly decrease hydrogen peroxide productivity and hydrogenation, but crucially increase the rate of decomposition. The decomposition product, which is predominantly hydroxyl radicals, can be used to decrease bacterial colonies. The interaction between silver and palladium was characterized using scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy (XPS) and temperature programmed reduction (TPR). The results of the TPR and XPS indicated the formation of a silver-palladium alloy. The optimal 1% Ag-4% Pd/TiO2 bimetallic catalyst was able to produce approximately 200 ppm of H2O2 in 30 min. The findings demonstrate that AgPd/TiO2 catalysts are active for the synthesis of hydrogen peroxide and its subsequent decomposition to reactive oxygen species. The catalysts are promising for use in wastewater treatment as they combine the disinfectant properties of silver, hydrogen peroxide production and subsequent decomposition. This article is part of a discussion meeting issue 'Providing sustainable catalytic solutions for a rapidly changing world'.
Study on Thermal Decomposition Characteristics of Ammonium Nitrate Emulsion Explosive in Different Scales

NASA Astrophysics Data System (ADS)

Wu, Qiujie; Tan, Liu; Xu, Sen; Liu, Dabin; Min, Li

2018-04-01

Numerous accidents of emulsion explosive (EE) are attributed to uncontrolled thermal decomposition of ammonium nitrate emulsion (ANE, the intermediate of EE) and EE in large scale. In order to study the thermal decomposition characteristics of ANE and EE in different scales, a large-scale test of modified vented pipe test (MVPT), and two laboratory-scale tests of differential scanning calorimeter (DSC) and accelerating rate calorimeter (ARC) were applied in the present study. The scale effect and water effect both play an important role in the thermal stability of ANE and EE. The measured decomposition temperatures of ANE and EE in MVPT are 146°C and 144°C, respectively, much lower than those in DSC and ARC. As the size of the same sample in DSC, ARC, and MVPT successively increases, the onset temperatures decrease. In the same test, the measured onset temperature value of ANE is higher than that of EE. The water composition of the sample stabilizes the sample. The large-scale test of MVPT can provide information for the real-life operations. The large-scale operations have more risks, and continuous overheating should be avoided.

Understanding Litter Input Controls on Soil Organic Matter Turnover and Formation are Essential for Improving Carbon-Climate Feedback Predictions for Arctic, Tundra Ecosystems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wallenstein, Matthew

The Arctic region stored vast amounts of carbon (C) in soils over thousands of years because decomposition has been limited by cold, wet conditions. Arctic soils now contain roughly as much C that is contained in all other soils across the globe combined. However, climate warming could unlock this oil C as decomposition accelerates and permafrost thaws. In addition to temperature-driven acceleration of decomposition, several additional processes could either counteract or augment warming-induced SOM losses. For example, increased plant growth under a warmer climate will increase organic matter inputs to soils, which could fuel further soil decomposition by microbes, butmore » will also increase the production of new SOM. Whether Arctic ecosystems store or release carbon in the future depends in part on the balance between these two counteracting processes. By differentiating SOM decomposition and formation and understanding the drivers of these processes, we will better understand how these systems function. We did not find evidence of priming under current conditions, defined as an increase in the decomposition of native SOM stocks. This suggests that decomposition is unlikely to be further accelerated through this mechanism. We did find that decomposition of native SOM did occur when nitrogen was added to these soils, suggesting that nitrogen limits decomposition in these systems. Our results highlight the resilience and extraordinary C storage capacity of these soils, and suggest shrub expansion may partially mitigate C losses from decomposition of old SOM as Arctic soils warm.« less
Stable carbon isotope depth profiles and soil organic carbon dynamics in the lower Mississippi Basin

USGS Publications Warehouse

Wynn, J.G.; Harden, J.W.; Fries, T.L.

2006-01-01

Analysis of depth trends of 13C abundance in soil organic matter and of 13C abundance from soil-respired CO2 provides useful indications of the dynamics of the terrestrial carbon cycle and of paleoecological change. We measured depth trends of 13C abundance from cropland and control pairs of soils in the lower Mississippi Basin, as well as the 13C abundance of soil-respired CO2 produced during approximately 1-year soil incubation, to determine the role of several candidate processes on the 13C depth profile of soil organic matter. Depth profiles of 13C from uncultivated control soils show a strong relationship between the natural logarithm of soil organic carbon concentration and its isotopic composition, consistent with a model Rayleigh distillation of 13C in decomposing soil due to kinetic fractionation during decomposition. Laboratory incubations showed that initially respired CO 2 had a relatively constant 13C content, despite large differences in the 13C content of bulk soil organic matter. Initially respired CO2 was consistently 13C-depleted with respect to bulk soil and became increasingly 13C-depleted during 1-year, consistent with the hypothesis of accumulation of 13C in the products of microbial decomposition, but showing increasing decomposition of 13C-depleted stable organic components during decomposition without input of fresh biomass. We use the difference between 13C / 12C ratios (calculated as ??-values) between respired CO 2 and bulk soil organic carbon as an index of the degree of decomposition of soil, showing trends which are consistent with trends of 14C activity, and with results of a two-pooled kinetic decomposition rate model describing CO2 production data recorded during 1 year of incubation. We also observed inconsistencies with the Rayleigh distillation model in paired cropland soils and reasons for these inconsistencies are discussed. ?? 2005 Elsevier B.V. All rights reserved.
The invasive species Alliaria petiolata (garlic mustard) increases soil nutrient availability in northern hardwood-conifer forests.

PubMed

Rodgers, Vikki L; Wolfe, Benjamin E; Werden, Leland K; Finzi, Adrien C

2008-09-01

The invasion of non-native plants can alter the diversity and activity of soil microorganisms and nutrient cycling within forests. We used field studies to analyze the impact of a successful invasive groundcover, Alliaria petiolata, on fungal diversity, soil nutrient availability, and pH in five northeastern US forests. We also used laboratory and greenhouse experiments to test three mechanisms by which A. petiolata may alter soil processes: (1) the release of volatile, cyanogenic glucosides from plant tissue; (2) the exudation of plant secondary compounds from roots; and (3) the decomposition of litter. Fungal community composition was significantly different between invaded and uninvaded soils at one site. Compared to uninvaded plots, plots invaded by A. petiolata were consistently and significantly higher in N, P, Ca and Mg availability, and soil pH. In the laboratory, the release of volatile compounds from the leaves of A. petiolata did not significantly alter soil N availability. Similarly, in the greenhouse, the colonization of native soils by A. petiolata roots did not alter soil nutrient cycling, implying that the exudation of secondary compounds has little effect on soil processes. In a leaf litter decomposition experiment, however, green rosette leaves of A. petiolata significantly increased the rate of decomposition of native tree species. The accelerated decomposition of leaf litter from native trees in the presence of A. petiolata rosette leaves shows that the death of these high-nutrient-content leaves stimulates decomposition to a greater extent than any negative effect that secondary compounds may have on the activity of the microbes decomposing the native litter. The results presented here, integrated with recent related studies, suggest that this invasive plant may change soil nutrient availability in such a way as to create a positive feedback between site occupancy and continued proliferation.
Differences in SOM decomposition and temperature sensitivity among soil aggregate size classes in a temperate grasslands.

PubMed

Wang, Qing; Wang, Dan; Wen, Xuefa; Yu, Guirui; He, Nianpeng; Wang, Rongfu

2015-01-01

The principle of enzyme kinetics suggests that the temperature sensitivity (Q10) of soil organic matter (SOM) decomposition is inversely related to organic carbon (C) quality, i.e., the C quality-temperature (CQT) hypothesis. We tested this hypothesis by performing laboratory incubation experiments with bulk soil, macroaggregates (MA, 250-2000 μm), microaggregates (MI, 53-250 μm), and mineral fractions (MF, <53 μm) collected from an Inner Mongolian temperate grassland. The results showed that temperature and aggregate size significantly affected on SOM decomposition, with notable interactive effects (P<0.0001). For 2 weeks, the decomposition rates of bulk soil and soil aggregates increased with increasing incubation temperature in the following order: MA>MF>bulk soil >MI(P <0.05). The Q10 values were highest for MA, followed (in decreasing order) by bulk soil, MF, and MI. Similarly, the activation energies (Ea) for MA, bulk soil, MF, and MI were 48.47, 33.26, 27.01, and 23.18 KJ mol-1, respectively. The observed significant negative correlations between Q10 and C quality index in bulk soil and soil aggregates (P<0.05) suggested that the CQT hypothesis is applicable to soil aggregates. Cumulative C emission differed significantly among aggregate size classes (P <0.0001), with the largest values occurring in MA (1101 μg g-1), followed by MF (976 μg g-1) and MI (879 μg g-1). These findings suggest that feedback from SOM decomposition in response to changing temperature is closely associated withsoil aggregation and highlights the complex responses of ecosystem C budgets to future warming scenarios.
Factors controlling bark decomposition and its role in wood decomposition in five tropical tree species

PubMed Central

Dossa, Gbadamassi G. O.; Paudel, Ekananda; Cao, Kunfang; Schaefer, Douglas; Harrison, Rhett D.

2016-01-01

Organic matter decomposition represents a vital ecosystem process by which nutrients are made available for plant uptake and is a major flux in the global carbon cycle. Previous studies have investigated decomposition of different plant parts, but few considered bark decomposition or its role in decomposition of wood. However, bark can comprise a large fraction of tree biomass. We used a common litter-bed approach to investigate factors affecting bark decomposition and its role in wood decomposition for five tree species in a secondary seasonal tropical rain forest in SW China. For bark, we implemented a litter bag experiment over 12 mo, using different mesh sizes to investigate effects of litter meso- and macro-fauna. For wood, we compared the decomposition of branches with and without bark over 24 mo. Bark in coarse mesh bags decomposed 1.11–1.76 times faster than bark in fine mesh bags. For wood decomposition, responses to bark removal were species dependent. Three species with slow wood decomposition rates showed significant negative effects of bark-removal, but there was no significant effect in the other two species. Future research should also separately examine bark and wood decomposition, and consider bark-removal experiments to better understand roles of bark in wood decomposition. PMID:27698461
Factors controlling bark decomposition and its role in wood decomposition in five tropical tree species.

PubMed

Dossa, Gbadamassi G O; Paudel, Ekananda; Cao, Kunfang; Schaefer, Douglas; Harrison, Rhett D

2016-10-04

Organic matter decomposition represents a vital ecosystem process by which nutrients are made available for plant uptake and is a major flux in the global carbon cycle. Previous studies have investigated decomposition of different plant parts, but few considered bark decomposition or its role in decomposition of wood. However, bark can comprise a large fraction of tree biomass. We used a common litter-bed approach to investigate factors affecting bark decomposition and its role in wood decomposition for five tree species in a secondary seasonal tropical rain forest in SW China. For bark, we implemented a litter bag experiment over 12 mo, using different mesh sizes to investigate effects of litter meso- and macro-fauna. For wood, we compared the decomposition of branches with and without bark over 24 mo. Bark in coarse mesh bags decomposed 1.11-1.76 times faster than bark in fine mesh bags. For wood decomposition, responses to bark removal were species dependent. Three species with slow wood decomposition rates showed significant negative effects of bark-removal, but there was no significant effect in the other two species. Future research should also separately examine bark and wood decomposition, and consider bark-removal experiments to better understand roles of bark in wood decomposition.
Impacts Of Long-Term Prescribed Fire On Decomposition And Litter Quality In Uneven-Aged Loblolly Pine Stands

Treesearch

Michele L. Renschin; Hal O. Liechty; Michael G. Shelton

2002-01-01

Abstract - Although fire has long been an important forest management tool in the southern United States, little is known concerning the effects of long-term fire use on nutrient cycling and decomposition. To better understand the effects of fire on these processes, decomposition rates, and foliage litter quality were quantified in a study...
Premelting, Melting, and Degradation Properties of Molten Alkali Nitrates: LiNO3, NaNO3, KNO3, and Binary NaNO3-KNO3

NASA Astrophysics Data System (ADS)

Mohammad, Mehedi Bin; Brooks, Geoffrey Alan; Rhamdhani, Muhammad Akbar

2018-02-01

A simultaneous thermal analyzer (STA) was used to observe the transition and degradation events of LiNO3, NaNO3, KNO3, and binary NaNO3-KNO3 salts for potential use as phase change materials (PCMs) and heat transfer fluid (HTF). Samples were heated from 50 °C to 800 °C at 10 °C/min scanning rate in three atmospheres (argon, air, and oxygen) using an STA to observe decomposition behavior. Thermal stability increased for all salts at high partial pressure of O2 ( P_{{{O}2 }} = 1.0) compared to inert argon ( P_{{{O}2 }} = 0). O2, N2, NO, N2O, and NO2 were main evolved gases during nitrate decomposition. NO and O2 started to evolve at approximately the same temperature after melting, indicating that primary and secondary decomposition reactions were concurrent and overlapping. The solid-solid transition, liquidus and solidus temperatures, heat of transition, heat of melting, and heat of solidification were obtained at various heating-cooling rates (1, 2, 4, 5, 6, 8, 10, and 15 °C/min) using an STA. At all heating-cooling rates, a small gap exists between liquidus and solidus temperatures for all samples due to the salts exhibiting supercooling phenomena. This study showed that the degradation point depends on the blanket atmosphere top of the molten salts and that heating rates have a minor effect on transition events (peaks height, peaks width, and transition enthalpies).
Premelting, Melting, and Degradation Properties of Molten Alkali Nitrates: LiNO3, NaNO3, KNO3, and Binary NaNO3-KNO3

NASA Astrophysics Data System (ADS)

Mohammad, Mehedi Bin; Brooks, Geoffrey Alan; Rhamdhani, Muhammad Akbar

2018-06-01

A simultaneous thermal analyzer (STA) was used to observe the transition and degradation events of LiNO3, NaNO3, KNO3, and binary NaNO3-KNO3 salts for potential use as phase change materials (PCMs) and heat transfer fluid (HTF). Samples were heated from 50 °C to 800 °C at 10 °C/min scanning rate in three atmospheres (argon, air, and oxygen) using an STA to observe decomposition behavior. Thermal stability increased for all salts at high partial pressure of O2 ( P_{{{O}2 }} = 1.0) compared to inert argon ( P_{{{O}2 }} = 0). O2, N2, NO, N2O, and NO2 were main evolved gases during nitrate decomposition. NO and O2 started to evolve at approximately the same temperature after melting, indicating that primary and secondary decomposition reactions were concurrent and overlapping. The solid-solid transition, liquidus and solidus temperatures, heat of transition, heat of melting, and heat of solidification were obtained at various heating-cooling rates (1, 2, 4, 5, 6, 8, 10, and 15 °C/min) using an STA. At all heating-cooling rates, a small gap exists between liquidus and solidus temperatures for all samples due to the salts exhibiting supercooling phenomena. This study showed that the degradation point depends on the blanket atmosphere top of the molten salts and that heating rates have a minor effect on transition events (peaks height, peaks width, and transition enthalpies).
Influence of the kind of peat and the depth of sampling on the biochemical properties of Tagan peatland

NASA Astrophysics Data System (ADS)

Wojciech Szajdak, Lech; Inisheva, Lydia I.

2010-05-01

The upper layer of a peat bog in which organic matter decomposes aerobically much more rapidly than in the underlying, anaerobic catotelm. As litter accumulates at the surface the size of the catotelm increases, because the thickness of the acrotelm is limited to depth at which aerobic respiration can occur. Although the rate of decomposition per unit volume of material is much greater in the acrotelm than in the catotelm, a point is reached at which the difference in volume between the two layers is such that the total rate of decomposition in the catotelm is equal to that in the acrotelm. This limits the thickness to which the bog can grow. Should there be a climate change (e.g. an increase in precipitation) growth can resume. Bogs therefore preserve a record of climatic conditions. Soils samples were taken from four places marked as No 1, 2, 3 and 4 each from two depth 0-25 and 50-75 cm of the peatland Tagan. Peatlands Tagan is located near Tomsk, West Siberia, Russia. Place No 1 in both layers represents grasses peat with the degree of the decomposition ranged from 25 to 35% (pH 6.31-7.95). Point 2 is characterized by wooden and wooden grasses peat with 35% degree of the decomposition (pH 5.16-9.31. There is buckbean peat in the points 3 and 4 (pH 6.4-6.49). However, 1.5 m depth of sapropel is located in point 4. The activity of the following enzymes: xanthine oxidase, phenolic oxidase, peroxidase, urease, nitrate reductase were measured and two forms of organic carbon (total organic carbon and dissolved organic carbon) and two form of iron Fe(II) and Fe(III) were determined in these samples. These enzymes participate in several biochemical pathways in soil connected with redox potential. The concentrations of indole-3-acetic acid, very famous fitohormone were also measured. It was observed in all places of sampling significant increase of the total organic carbon with an increase of the depth. However, the quantity of dissolved organic carbon closely decreased with an increase of the depth, suggesting lower microbiological activity of this level. The increase of the ratios Fe(II)/Fe(III) for place 1 and 2 and 4 and both depth 0-25 were similar (0.56; 0.59 and 0.65) indicating similar redox properties of these levels. Higher contents of F(III) were determined in upper layer than in lower layer of all samples. It indicate higher oxidizing properties upper layer than lower one The activity of nitrate reductase, peroxidase, phenolic axidase and xanthine oxidase agree with the content of two forms of iron in samples from all depth. In all samples was observed the decrease of the activity of urease with an increase of the depth. It suggest higher rate of the degradation process of urea created from the decomposition of peptides in peat. In sample No 1 the concentrations of indole-3-acetic acid very famous phytohormone were similar in both determined levels. However for sample No 2, 3 and 4 the significant decrease of the concentrations of indole-3-acetic acid with and increase of the depth of sampling was observed. Acknowledgements: This work was supported by a grant No. N N305 3204 36 founded by Polish Ministry of Education and by RFFR (No.No. 09-05-00235, 09-05-00395), Minister of Education and Science (No. 02.740.11.0325).
Comparison of litter decomposition in a natural versus coal-slurry pond reclaimed as a wetland

USGS Publications Warehouse

Taylor, J.; Middleton, B.A.

2004-01-01

Decomposition is a key function in reclaimed wetlands, and changes in its rate have ramifications for organic-matter accumulation, nutrient cycling, and production. The purpose of this study was to compare leaf litter decomposition rates in coal-slurry ponds vs. natural wetlands on natural floodplain wetlands in Illinois, USA. The rate of decomposition was slower in the natural wetland vs. the coal pond (k=0.0043??0.0008 vs. 0.0066??0.0011, respectively); the soil of the natural wetland was more acidic than the coal pond in this study (pH=5.3 vs. 7.9, respectively). Similarly, higher organic matter levels were related to lower pH levels, and organic matter levels were seven-times higher in the natural wetland than in the coal pond. The coal slurry pond was five years old at the time of the study, while the natural oxbow wetland was older (more than 550 years). The coal-slurry pond was originally a floodplain wetland (slough); the downstream end was blocked with a stoplog structure and the oxbow filled with slurry. The pattern of decomposition for all species in the coal pond was the same as in the natural pond; Potomogeton nodosus decomposed more quickly than Phragmites australis, and both of these species decomposed more quickly than either Typha latifolia or Cyperus erythrorhizos (k=0.0121??0.0008, 0.0051??0.0006, 0.0024??0.0001, 0-0024??0.0004, respectively). Depending on how open or closed the system is to outside inputs, decomposition rate regulates other functions such as production, nutrient cycling, organic-layer accumulation in the soil, and the timing and nature of delivery of detritus to the food chain. ?? 2004 John Wiley and Sons, Ltd.
Analytical electron microscope study of eight ataxites

NASA Technical Reports Server (NTRS)

Novotny, P. M.; Goldstein, J. I.; Williams, D. B.

1982-01-01

Optical and electron optical (SEM, TEM, AEM) techniques were employed to investigate the fine structure of eight ataxite-iron meteorites. Structural studies indicated that the ataxites can be divided into two groups: a Widmanstaetten decomposition group and a martensite decomposition group. The Widmanstaetten decomposition group has a Type I plessite microstructure and the central taenite regions contain highly dislocated lath martensite. The steep M shaped Ni gradients in the taenite are consistent with the fast cooling rates, of not less than 500 C/my, observed for this group. The martensite decomposition group has a Type III plessite microstructure and contains all the chemical group IVB ataxites. The maximum taenite Ni contents vary from 47.5 to 52.7 wt % and are consistent with slow cooling to low temperatures of not greater than 350 C at cooling rates of not greater than 25 C/my.
Experimental and theoretical study of the sec-C[sub 4]H[sub 9] [r reversible] CH[sub 3] + C[sub 3]H[sub 6] reaction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Knyazev, V.D.; Dubinsky, I.A.; Slagle, I.R.

1994-10-27

The kinetics of the unimolecular decomposition of the sec-C[sub 4]H[sub 9] radical has been studied experimentally in a heated tubular flow reactor coupled to a photoionization mass spectrometer. Rate constants for the decomposition were determined in time-resolved experiments as a function of temperature (598-680 K) and bath gas density (3-18) [times] 10[sup 16] molecules cm[sup [minus]3] in three bath gases: He, Ar, and N[sub 2]. The rate constants are in the falloff region under the conditions of the experiments. The results of earlier studies of the reverse reaction were reanalyzed and used to create a transition state model of themore » reaction. This transition state model was used to obtain values of the microcanonical rate constants, k (E). Falloff behavior was reproduced using master equation modeling with the energy barrier height for decomposition (necessary to calculate k(E)) obtained from optimization of the agreement between experimental and calculated rate constants. The resulting model of the reaction provides the high-pressure limit rate constants for the decomposition reaction and the reverse reaction. 52 refs., 7 figs., 3 tabs.« less
Soil respiration in the cold desert environment of the Colorado Plateau (USA): Abiotic regulators and thresholds

USGS Publications Warehouse

Fernandez, D.P.; Neff, J.C.; Belnap, J.; Reynolds, R.L.

2006-01-01

Decomposition is central to understanding ecosystem carbon exchange and nutrient-release processes. Unlike mesic ecosystems, which have been extensively studied, xeric landscapes have received little attention; as a result, abiotic soil-respiration regulatory processes are poorly understood in xeric environments. To provide a more complete and quantitative understanding about how abiotic factors influence soil respiration in xeric ecosystems, we conducted soil- respiration and decomposition-cloth measurements in the cold desert of southeast Utah. Our study evaluated when and to what extent soil texture, moisture, temperature, organic carbon, and nitrogen influence soil respiration and examined whether the inverse-texture hypothesis applies to decomposition. Within our study site, the effect of texture on moisture, as described by the inverse texture hypothesis, was evident, but its effect on decomposition was not. Our results show temperature and moisture to be the dominant abiotic controls of soil respiration. Specifically, temporal offsets in temperature and moisture conditions appear to have a strong control on soil respiration, with the highest fluxes occurring in spring when temperature and moisture were favorable. These temporal offsets resulted in decomposition rates that were controlled by soil moisture and temperature thresholds. The highest fluxes of CO2 occurred when soil temperature was between 10 and 16??C and volumetric soil moisture was greater than 10%. Decomposition-cloth results, which integrate decomposition processes across several months, support the soil-respiration results and further illustrate the seasonal patterns of high respiration rates during spring and low rates during summer and fall. Results from this study suggest that the parameters used to predict soil respiration in mesic ecosystems likely do not apply in cold-desert environments. ?? Springer 2006.
Soil organic matter-hydrogen peroxide dynamics in the treatment of contaminated soils and groundwater using catalyzed H2O2 propagations (modified Fenton's reagent).

PubMed

Bissey, Lauren L; Smith, Jeffrey L; Watts, Richard J

2006-07-01

The interactions between catalyzed H(2)O(2) propagations (CHP-i.e. modified Fenton's reagent) and soil organic matter (SOM) during the treatment of contaminated soils and groundwater was studied in a well-characterized surface soil. The fate of two fractions of SOM, particulate organic matter (POM) and nonparticulate organic matter (NPOM), during CHP reactions was evaluated using concentrations of hydrogen peroxide from 0.5 to 3M catalyzed by soluble iron (III), an iron (III)-ethylenediamine tetraacetic acid (EDTA) chelate, or naturally-occurring soil minerals. The destruction of total SOM in CHP systems was directly proportional to the hydrogen peroxide dosage, and was significantly greater at pH 3 than at neutral pH; furthermore, SOM destruction occurred predominantly in the NPOM fraction. At pH 3, SOM did not affect hydrogen peroxide decomposition rates or hydroxyl radical activity in CHP reactions. However, at neutral pH, increasing the mass of SOM decreased the hydrogen peroxide decomposition rate and increased the rate of hydroxyl radical generation in CHP systems. These results show that, while CHP reactions destroy some of the organic carbon pools, SOM does not have a significant effect on the CHP treatment of soils and groundwater.
Using a Hands-On Hydrogen Peroxide Decomposition Activity to Teach Catalysis Concepts to K-12 Students

ERIC Educational Resources Information Center

Cybulskis, Viktor J.; Ribeiro, Fabio H.; Gounder, Rajamani

2016-01-01

A versatile and transportable laboratory apparatus was developed for middle and high school (6th-12th grade) students as part of a hands-on outreach activity to estimate catalytic rates of hydrogen peroxide decomposition from oxygen evolution rates measured by using a volumetric displacement method. The apparatus was constructed with inherent…
Holocene carbon stocks and carbon accumulation rates altered in soils undergoing permafrost thaw

Treesearch

Caitlin E. Hicks Pries; Edward A.G. Schuur; K. Grace Crummer

2012-01-01

Permafrost soils are a significant global store of carbon (C) with the potential to become a large C source to the atmosphere. Climate change is causing permafrost to thaw, which can affect primary production and decomposition, therefore affecting ecosystem C balance. We modeled decadal and millennial soil C inputs, decomposition constants, and C accumulation rates by...
Influence of Macrophyte Decomposition on Growth Rate and Community Structure of Okefenokee Swamp Bacterioplankton †

PubMed Central

Murray, Robert E.; Hodson, Robert E.

1986-01-01

Dissolved substances released during decomposition of the white water lily (Nymphaea odorata) can alter the growth rate of Okefenokee Swamp bacterioplankton. In microcosm experiments dissolved compounds released from senescent Nymphaea leaves caused a transient reduction in the abundance and activity of water column bacterioplankton, followed by a period of intense bacterial growth. Rates of [3H]thymidine incorporation and turnover of dissolved d-glucose were depressed by over 85%, 3 h after the addition of Nymphaea leachates to microcosms containing Okefenokee Swamp water. Bacterial activity subsequently recovered; after 20 h [3H]thymidine incorporation in leachate-treated microcosms was 10-fold greater than that in control microcosms. The recovery of activity was due to a shift in the composition of the bacterial population toward resistance to the inhibitory compounds present in Nymphaea leachates. Inhibitory compounds released during the decomposition of aquatic macrophytes thus act as selective agents which alter the community structure of the bacterial population with respect to leachate resistance. Soluble compounds derived from macrophyte decomposition influence the rate of bacterial secondary production and the availability of microbial biomass to microconsumers. Images PMID:16346986
Direct water decomposition on transition metal surfaces: Structural dependence and catalytic screening

DOE PAGES

Tsai, Charlie; Lee, Kyoungjin; Yoo, Jong Suk; ...

2016-02-16

Density functional theory calculations are used to investigate thermal water decomposition over the close-packed (111), stepped (211), and open (100) facets of transition metal surfaces. A descriptor-based approach is used to determine that the (211) facet leads to the highest possible rates. As a result, a range of 96 binary alloys were screened for their potential activity and a rate control analysis was performed to assess how the overall rate could be improved.
Nanostructuring one-dimensional and amorphous lithium peroxide for high round-trip efficiency in lithium-oxygen batteries.

PubMed

Dutta, Arghya; Wong, Raymond A; Park, Woonghyeon; Yamanaka, Keisuke; Ohta, Toshiaki; Jung, Yousung; Byon, Hye Ryung

2018-02-14

The major challenge facing lithium-oxygen batteries is the insulating and bulk lithium peroxide discharge product, which causes sluggish decomposition and increasing overpotential during recharge. Here, we demonstrate an improved round-trip efficiency of ~80% by means of a mesoporous carbon electrode, which directs the growth of one-dimensional and amorphous lithium peroxide. Morphologically, the one-dimensional nanostructures with small volume and high surface show improved charge transport and promote delithiation (lithium ion dissolution) during recharge and thus plays a critical role in the facile decomposition of lithium peroxide. Thermodynamically, density functional calculations reveal that disordered geometric arrangements of the surface atoms in the amorphous structure lead to weaker binding of the key reaction intermediate lithium superoxide, yielding smaller oxygen reduction and evolution overpotentials compared to the crystalline surface. This study suggests a strategy to enhance the decomposition rate of lithium peroxide by exploiting the size and shape of one-dimensional nanostructured lithium peroxide.

Colonization by Chironomidae Larvae in Decomposition Leaves of Eichhornia azurea in a Lentic System in Southeastern Brazil

PubMed Central

da Silveira, Lidimara Souza; Martins, Renato Tavares; da Silveira, Guilherme Augusto; Grazul, Richard Michael; Lobo, Danielle Pinheiro; da Gama Alves, Roberto

2013-01-01

The objective of this study was to analyze the colonization of Chironomidae (Diptera) larvae during the decomposition of Eichhornia azurea (Swartz) Kunth (Commelinales: Pontederiaceae) leaves in a lake in southeastern Brazil in two seasons of the year. The experiment was conducted from September to November 2007 and February to April 2008. In each period, 21 litter bags were used, each containing 10 g of dried leaves. Three bags were removed after 2, 5, 8, 12, 25, 45, and 65 days of colonization. The decomposition rate of the E. azurea leaves was rapid in both seasons, with no significant difference between them. The Chironomidae showed higher density than the other invertebrates. Goeldichironomus, Tonytarsus, and Corynoneura were the most abundant genera of Chironomidae. The invertebrate density increased during the experiment, differing within days but not between seasons. The faunal composition differed between the decomposition phases (initial and final), but did not differ between the seasons (dry and wet). The taxa Ablabesmyia, Caladomyia, Chironomus, Goeldichironomus, and Parachironomus were the most closely related to the final days of the experiment. Litter was the main food item found in the gut contents of the organisms of all the genera analyzed, both at the beginning and end of the decomposition. We believe that the feeding activity combined with the high larval density is an important factor contributing to the rapid decomposition of the E. azurea leaves. In conclusion, the succession process along the detritus chain of E. azurea was more important in structuring the assemblage of Chironomidae larvae than seasonal variations. PMID:23886040
Colonization by Chironomidae larvae in decomposition leaves of Eichhornia azurea in a lentic system in Southeastern Brazil.

PubMed

da Silveira, Lidimara Souza; Martins, Renato Tavares; da Silveira, Guilherme Augusto; Grazul, Richard Michael; Lobo, Danielle Pinheiro; Alves, Roberto da Gama

2013-01-01

The objective of this study was to analyze the colonization of Chironomidae (Diptera) larvae during the decomposition of Eichhornia azurea (Swartz) Kunth (Commelinales: Pontederiaceae) leaves in a lake in southeastern Brazil in two seasons of the year. The experiment was conducted from September to November 2007 and February to April 2008. In each period, 21 litter bags were used, each containing 10 g of dried leaves. Three bags were removed after 2, 5, 8, 12, 25, 45, and 65 days of colonization. The decomposition rate of the E. azurea leaves was rapid in both seasons, with no significant difference between them. The Chironomidae showed higher density than the other invertebrates. Goeldichironomus, Tonytarsus, and Corynoneura were the most abundant genera of Chironomidae. The invertebrate density increased during the experiment, differing within days but not between seasons. The faunal composition differed between the decomposition phases (initial and final), but did not differ between the seasons (dry and wet). The taxa Ablabesmyia, Caladomyia, Chironomus, Goeldichironomus, and Parachironomus were the most closely related to the final days of the experiment. Litter was the main food item found in the gut contents of the organisms of all the genera analyzed, both at the beginning and end of the decomposition. We believe that the feeding activity combined with the high larval density is an important factor contributing to the rapid decomposition of the E. azurea leaves. In conclusion, the succession process along the detritus chain of E. azurea was more important in structuring the assemblage of Chironomidae larvae than seasonal variations.
Decomposition and particle release of a carbon nanotube/epoxy nanocomposite at elevated temperatures

NASA Astrophysics Data System (ADS)

Schlagenhauf, Lukas; Kuo, Yu-Ying; Bahk, Yeon Kyoung; Nüesch, Frank; Wang, Jing

2015-11-01

Carbon nanotubes (CNTs) as fillers in nanocomposites have attracted significant attention, and one of the applications is to use the CNTs as flame retardants. For such nanocomposites, possible release of CNTs at elevated temperatures after decomposition of the polymer matrix poses potential health threats. We investigated the airborne particle release from a decomposing multi-walled carbon nanotube (MWCNT)/epoxy nanocomposite in order to measure a possible release of MWCNTs. An experimental set-up was established that allows decomposing the samples in a furnace by exposure to increasing temperatures at a constant heating rate and under ambient air or nitrogen atmosphere. The particle analysis was performed by aerosol measurement devices and by transmission electron microscopy (TEM) of collected particles. Further, by the application of a thermal denuder, it was also possible to measure non-volatile particles only. Characterization of the tested samples and the decomposition kinetics were determined by the usage of thermogravimetric analysis (TGA). The particle release of different samples was investigated, of a neat epoxy, nanocomposites with 0.1 and 1 wt% MWCNTs, and nanocomposites with functionalized MWCNTs. The results showed that the added MWCNTs had little effect on the decomposition kinetics of the investigated samples, but the weight of the remaining residues after decomposition was influenced significantly. The measurements with decomposition in different atmospheres showed a release of a higher number of particles at temperatures below 300 °C when air was used. Analysis of collected particles by TEM revealed that no detectable amount of MWCNTs was released, but micrometer-sized fibrous particles were collected.
[Effects of brackish water irrigation on soil enzyme activity, soil CO2 flux and organic matter decomposition].

PubMed

Zhang, Qian-qian; Wang, Fei; Liu, Tao; Chu, Gui-xin

2015-09-01

Brackish water irrigation utilization is an important way to alleviate water resource shortage in arid region. A field-plot experiment was set up to study the impact of the salinity level (0.31, 3.0 or 5.0 g · L(-1) NaCl) of irrigated water on activities of soil catalase, invertase, β-glucosidase, cellulase and polyphenoloxidase in drip irrigation condition, and the responses of soil CO2 flux and organic matter decomposition were also determined by soil carbon dioxide flux instrument (LI-8100) and nylon net bag method. The results showed that in contrast with fresh water irrigation treatment (CK), the activities of invertase, β-glucosidase and cellulase in the brackish water (3.0 g · L(-1)) irrigation treatment declined by 31.7%-32.4%, 29.7%-31.6%, 20.8%-24.3%, respectively, while soil polyphenoloxidase activity was obviously enhanced with increasing the salinity level of irrigated water. Compared to CK, polyphenoloxidase activity increased by 2.4% and 20.5%, respectively, in the brackish water and saline water irrigation treatments. Both soil microbial biomass carbon and microbial quotient decreased with increasing the salinity level, whereas, microbial metabolic quotient showed an increasing tendency with increasing the salinity level. Soil CO2 fluxes in the different treatments were in the order of CK (0.31 g · L(-1)) > brackish water irrigation (3.0 g · L(-1)) ≥ saline water irrigation (5.0 g · L(-1)). Moreover, CO2 flux from plastic film mulched soil was always much higher than that from no plastic film mulched soil, regardless the salinity of irrigated water. Compared with CK, soil CO2 fluxes in the saline water and brackish water treatments decreased by 29.8% and 28.2% respectively in the boll opening period. The decomposition of either cotton straw or alfalfa straw in the different treatments was in the sequence of CK (0.31 g · L(-1)) > brackish water irrigation (3.0 g · L(-1)) > saline water treatment (5.0 g · L(-1)). The organic matter decomposition rate in the plastic film mulched soil was significantly higher than that in the no plastic film mulched soil. 125 days after incubation, the recovery rates of cotton straw and alfalfa straw were 39.7% and 46.5% with saline water irrigation, 36.3% and 36.5% with brackish water irrigation, and 30.5% and 35.4% with CK, respectively. In conclusion, brackish water drip irrigation had a significant adverse effect on soil enzyme activities, which decreased soil microbial biomass, soil CO2 flux and soil organic matter decomposition, and subsequently deteriorated the soil biological characteristics in oasis farmland.
Soil Warming: Consequences for Foliar Litter Decay in a Spruce-Fir Forest in Maine, USA

Treesearch

Lindsey E. Rustad; Ivan J. Fernandez

1998-01-01

Increased rates of litter decay due to projected global warming could substantially alter the balance between C assimilation and release in forest soils, with consequent feedbacks to climate change. This study was conducted to investigate the effects of soil warming on the decomposition of red spruce (Picea rubens Sarg.) and red maple (...
Leaf litter decomposition rates increase with rising mean annual temperature in Hawaiian tropical montane wet forests

Treesearch

Lori D. Bothwell; Paul C. Selmants; Christian P. Giardina; Creighton M. Litton

2014-01-01

Decomposing litter in forest ecosystems supplies nutrients to plants, carbon to heterotrophic soil microorganisms and is a large source of CO2 to the atmosphere. Despite its essential role in carbon and nutrient cycling, the temperature sensitivityof leaf litter decay in tropical forest ecosystems remains poorly resolved, especially in tropical...
Influence of endrin on soil microbial populations and their activity.

Treesearch

W.B. Bollen; C.M. Tu

1971-01-01

Endrin applied to soil at rates of more than three times the maximum that might be expected from application of endrin-treated tree seed exerted no appreciable effect on numbers of soil microbes or on ammonification, nitrification, or sulfur oxidation. The decomposition of soil organic matter, as indicated by the production of CO2, was increased...
Enhanced summer warming reduces fungal decomposer diversity and litter mass loss more strongly in dry than in wet tundra.

PubMed

Christiansen, Casper T; Haugwitz, Merian S; Priemé, Anders; Nielsen, Cecilie S; Elberling, Bo; Michelsen, Anders; Grogan, Paul; Blok, Daan

2017-01-01

Many Arctic regions are currently experiencing substantial summer and winter climate changes. Litter decomposition is a fundamental component of ecosystem carbon and nutrient cycles, with fungi being among the primary decomposers. To assess the impacts of seasonal climatic changes on litter fungal communities and their functioning, Betula glandulosa leaf litter was surface-incubated in two adjacent low Arctic sites with contrasting soil moisture regimes: dry shrub heath and wet sedge tundra at Disko Island, Greenland. At both sites, we investigated the impacts of factorial combinations of enhanced summer warming (using open-top chambers; OTCs) and deepened snow (using snow fences) on surface litter mass loss, chemistry and fungal decomposer communities after approximately 1 year. Enhanced summer warming significantly restricted litter mass loss by 32% in the dry and 17% in the wet site. Litter moisture content was significantly reduced by summer warming in the dry, but not in the wet site. Likewise, fungal total abundance and diversity were reduced by OTC warming at the dry site, while comparatively modest warming effects were observed in the wet site. These results suggest that increased evapotranspiration in the OTC plots lowered litter moisture content to the point where fungal decomposition activities became inhibited. In contrast, snow addition enhanced fungal abundance in both sites but did not significantly affect litter mass loss rates. Across sites, control plots only shared 15% of their fungal phylotypes, suggesting strong local controls on fungal decomposer community composition. Nevertheless, fungal community functioning (litter decomposition) was negatively affected by warming in both sites. We conclude that although buried soil organic matter decomposition is widely expected to increase with future summer warming, surface litter decay and nutrient turnover rates in both xeric and relatively moist tundra are likely to be significantly restricted by the evaporative drying associated with warmer air temperatures. © 2016 John Wiley & Sons Ltd.
Disease and age pattern of hospitalisation and associated costs in India: 1995-2014.

PubMed

Kastor, Anshul; Mohanty, Sanjay K

2018-01-24

The prime objective of this study is to examine the trends of disease and age pattern of hospitalisation and associated costs in India during 1995-2014. Present study used nationally representative data on morbidity and healthcare from the 52nd (1995) and 71st (2014) rounds of the National Sample Survey. A total of 120 942 and 65 932 households were surveyed in 1995 and 2014, respectively. Descriptive statistics, logistic regression analyses and decomposition analyses were used in examining the changes in patterns of hospitalisation and associated costs. Hospitalisation rates and costs per hospitalisation (out-of-pocket expenditure) were estimated for selected diseases and in four broad categories: communicable diseases, non-communicable diseases (NCDs), injuries and others. All the costs are presented at 2014 prices in US$. Hospitalisation rate in India has increased from 1661 in 1995 to 3699 in 2014 (per 100 000 population). It has more than doubled across all age groups. Hospitalisation among children was primarily because of communicable diseases, while NCDs were the leading cause of hospitalisation for the 40+ population. Costs per hospitalisation have increased from US$177 in 1995 to US$316 in 2014 (an increase of 79%). Costs per hospitalisation for NCDs in 2014 were US$471 compared with US$175 for communicable diseases. It was highest for cancer inpatients (US$942) followed by heart diseases (US$674). Age is the significant predictor of hospitalisation for all the selected diseases. Decomposition results showed that about three-fifth of the increase in unconditional costs per hospitalisation was due to increase in mean hospital costs, and the other two-fifth was due to increase in hospitalisation rates. There has been more than twofold increase in hospitalisation rates in India during the last two decades, and significantly higher rates were observed among infants and older adults. Increasing hospitalisation rates and costs per hospitalisation are contributing substantially to the rising healthcare costs in India. © Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2018. All rights reserved. No commercial use is permitted unless otherwise expressly granted.
Warming accelerates decomposition of decades-old carbon in forest soils

DOE PAGES

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

2012-06-11

Global climate carbon-cycle models predict acceleration of soil organic carbon losses to the atmosphere with warming, but the size of this feedback is poorly known. The temperature sensitivity of soil carbon decomposition is commonly determined by measuring changes in the rate of carbon dioxide (CO 2) production under controlled laboratory conditions. We added measurements of carbon isotopes in respired CO 2 to constrain the age of carbon substrates contributing to the temperature response of decomposition for surface soils from two temperate forest sites with very different overall rates of carbon cycling. Roughly one-third of the carbon respired at any temperaturemore » was fixed from the atmosphere more than 10 y ago, and the mean age of respired carbon reflected a mixture of substrates of varying ages. Consistent with global ecosystem model predictions, the temperature sensitivity of the carbon fixed more than a decade ago was the same as the temperature sensitivity for carbon fixed less than 10 y ago. However, we also observed an overall increase in the mean age of carbon respired at higher temperatures, even correcting for potential substrate limitation effects. The combination of several age constraints from carbon isotopes showed that warming had a similar effect on respiration of decades-old and younger (<10 y) carbon but a greater effect on decomposition of substrates of intermediate (between 7 and 13 y) age. Our results highlight the vulnerability of soil carbon to warming that is years-to-decades old, which makes up a large fraction of total soil carbon in forest soils globally.« less
Warming accelerates decomposition of decades-old carbon in forest soils.

PubMed

Hopkins, Francesca M; Torn, Margaret S; Trumbore, Susan E

2012-06-26

Global climate carbon-cycle models predict acceleration of soil organic carbon losses to the atmosphere with warming, but the size of this feedback is poorly known. The temperature sensitivity of soil carbon decomposition is commonly determined by measuring changes in the rate of carbon dioxide (CO(2)) production under controlled laboratory conditions. We added measurements of carbon isotopes in respired CO(2) to constrain the age of carbon substrates contributing to the temperature response of decomposition for surface soils from two temperate forest sites with very different overall rates of carbon cycling. Roughly one-third of the carbon respired at any temperature was fixed from the atmosphere more than 10 y ago, and the mean age of respired carbon reflected a mixture of substrates of varying ages. Consistent with global ecosystem model predictions, the temperature sensitivity of the carbon fixed more than a decade ago was the same as the temperature sensitivity for carbon fixed less than 10 y ago. However, we also observed an overall increase in the mean age of carbon respired at higher temperatures, even correcting for potential substrate limitation effects. The combination of several age constraints from carbon isotopes showed that warming had a similar effect on respiration of decades-old and younger (<10 y) carbon but a greater effect on decomposition of substrates of intermediate (between 7 and 13 y) age. Our results highlight the vulnerability of soil carbon to warming that is years-to-decades old, which makes up a large fraction of total soil carbon in forest soils globally.
Influence of storage conditions on the stability of monomeric anthocyanins studied by reversed-phase high-performance liquid chromatography.

PubMed

Morais, Helena; Ramos, Cristina; Forgács, Esther; Cserháti, Tibor; Oliviera, José

2002-04-25

The effect of light, storage time and temperature on the decomposition rate of monomeric anthocyanin pigments extracted from skins of grape (Vitis vinifera var. Red globe) was determined by reversed-phase high-performance liquid chromatography (RP-HPLC). The impact of various storage conditions on the pigment stability was assessed by stepwise regression analysis. RP-HPLC separated well the five anthocyanins identified and proved the presence of other unidentified pigments at lower concentrations. Stepwise regression analysis confirmed that the overall decomposition rate of monomeric anthocyanins, peonidin-3-glucoside and malvidin-3-glucoside significantly depended on the time and temperature of storage, the effect of storage time being the most important. The presence or absence of light exerted a negligible impact on the decomposition rate.
Crowdsourcing Austrian data on decomposition with the help of citizen scientists

NASA Astrophysics Data System (ADS)

Sandén, Taru; Berthold, Helene; Schwarz, Michael; Baumgarten, Andreas; Spiegel, Heide

2017-04-01

Decay of organic material, decomposition, is a critical process for life on earth. Through decomposition, food becomes available for plants and soil organisms that they use in their growth and maintenance. When plant material decomposes, it loses weight and releases the greenhouse gas carbon dioxide (CO2) into the atmosphere. Terrestrial soils contain about three times more carbon than the atmosphere and, therefore, changes in the balance of soil carbon storage and release can significantly amplify or attenuate global warming. Many factors affecting the global carbon cycle are already known and mapped; however, an index for decomposition rate is still missing, even though it is needed for climate modelling. The Tea Bag Index (TBI) measures decomposition in a standardised, achievable, climate-relevant, and time-relevant way by burying commercial nylon tea bags in soils for three months (Keuskamp et al., 2013). In the summer of 2016, TBI (expressed as decomposition rate (k) and stabilisation index (S)) was measured with the help of Austrian citizen scientists at 7-8 cm soil depth in three different land uses (maize croplands, grasslands and forests). In total ca. 2700 tea bags were sent to the citizen scientists of which ca. 50% were returned. The data generated by the citizen scientists will be incorporated into an Austrian as well as a global soil map of decomposition. This map can be used as input to improve climate modelling in the future.
Young Children's Thinking About Decomposition: Early Modeling Entrees to Complex Ideas in Science

NASA Astrophysics Data System (ADS)

Ero-Tolliver, Isi; Lucas, Deborah; Schauble, Leona

2013-10-01

This study was part of a multi-year project on the development of elementary students' modeling approaches to understanding the life sciences. Twenty-three first grade students conducted a series of coordinated observations and investigations on decomposition, a topic that is rarely addressed in the early grades. The instruction included in-class observations of different types of soil and soil profiling, visits to the school's compost bin, structured observations of decaying organic matter of various kinds, study of organisms that live in the soil, and models of environmental conditions that affect rates of decomposition. Both before and after instruction, students completed a written performance assessment that asked them to reason about the process of decomposition. Additional information was gathered through one-on-one interviews with six focus students who represented variability of performance across the class. During instruction, researchers collected video of classroom activity, student science journal entries, and charts and illustrations produced by the teacher. After instruction, the first-grade students showed a more nuanced understanding of the composition and variability of soils, the role of visible organisms in decomposition, and environmental factors that influence rates of decomposition. Through a variety of representational devices, including drawings, narrative records, and physical models, students came to regard decomposition as a process, rather than simply as an end state that does not require explanation.
Using domain decomposition in the multigrid NAS parallel benchmark on the Fujitsu VPP500

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, J.C.H.; Lung, H.; Katsumata, Y.

1995-12-01

In this paper, we demonstrate how domain decomposition can be applied to the multigrid algorithm to convert the code for MPP architectures. We also discuss the performance and scalability of this implementation on the new product line of Fujitsu`s vector parallel computer, VPP500. This computer has Fujitsu`s well-known vector processor as the PE each rated at 1.6 C FLOPS. The high speed crossbar network rated at 800 MB/s provides the inter-PE communication. The results show that the physical domain decomposition is the best way to solve MG problems on VPP500.
Kinetic study of corn straw pyrolysis: comparison of two different three-pseudocomponent models.

PubMed

Li, Zhengqi; Zhao, Wei; Meng, Baihong; Liu, Chunlong; Zhu, Qunyi; Zhao, Guangbo

2008-11-01

With heating rates of 20, 50 and 100 K min(-1), the thermal decomposition of corn straw samples (corn stalks skins, corn stalks cores, corn bracts and corn leaves) were studied using thermogravimetric analysis. The maximum pyrolysis rates increased with the heating rate increasing and the temperature at the peak pyrolysis rate also increased. Assuming the addition of three independent parallel reactions, corresponding to three pseudocomponents linked to the hemicellulose, cellulose and lignin, two different three-pseudocomponent models were used to simulate the corn straw pyrolysis. Model parameters of pyrolysis were given. It was found that the three-pseudocomponent model with n-order kinetics was more accurate than the model with first-order kinetics at most cases. It showed that the model with n-order kinetics was more accurate to describe the pyrolysis of the hemicellulose.
Correlation of foliage and litter chemistry of sugar maple, Acer saccharum, as affected by elevated CO2 and varying N availability, and effects on decomposition

Treesearch

J. S. King; K. S. Pregitzer; D. R. Zak; M. E. Kubiske; W. E. Holmes

2001-01-01

Rising atmospheric carbon dioxide has the potential to alter leaf litter chemistry, potentially affecting decomposition and rates of carbon and nitrogen cycling in forest ecosystems. This study was conducted to determine whether growth under elevated atmospheric CO2 altered the quality and microbial decomposition of leaf litter of a widely...
Wood decomposition following clearcutting at Coweeta Hydrologic Laboratory

Treesearch

Kim G. Mattson; Wayne T. Swank

2014-01-01

Most of the forest on Watershed (WS) 7 was cut and ledt on site to decompose. This Chapter describes the rate and manner of wood decomposition and also quantifies the fluxes from decaying wood to the forest floor on WS 7. In doing so, we make the case that wood and its process of decomposition contributes to ecosystem stability. We also review some of the history of...
Litter Decomposition in Low and High Mortality Northern Red Oak Stands on Extremely Acidic Southwestern Pennsylvania Soils

Treesearch

Michael C. Demchik; William E. Sharpe

2004-01-01

Previous research has shown that decomposition of organic matter is slower in soils with high levels of soil acidity and available aluminum (Al). The objective of this experiment was to determine if differences in decomposition rates of northern red oak leaves occurred between extremely acidic and less acidic sites that also differed in oak mortality. Leaf litter from...
Thermal decomposition of gaseous ammonium nitrate at low pressure: kinetic modeling of product formation and heterogeneous decomposition of nitric acid.

PubMed

Park, J; Lin, M C

2009-12-03

The thermal decomposition of ammonium nitrate, NH(4)NO(3) (AN), in the gas phase has been studied at 423-56 K by pyrolysis/mass spectrometry under low-pressure conditions using a Saalfeld reactor coated with boric acid. The sublimation of NH(4)NO(3) at 423 K was proposed to produce equal amounts of NH(3) and HNO(3), followed by the decomposition reaction of HNO(3), HNO(3) + M --> OH + NO(2) + M (where M = third-body and reactor surface). The absolute yields of N(2), N(2)O, H(2)O, and NH(3), which can be unambiguously measured and quantitatively calibrated under a constant pressure at 5-6.2 torr He are kinetically modeled using the detailed [H,N,O]-mechanism established earlier for the simulation of NH(3)-NO(2) (Park, J.; Lin, M. C. Technologies and Combustion for a Clean Environment. Proc. 4th Int. Conf. 1997, 34-1, 1-5) and ADN decomposition reactions (Park, J.; Chakraborty, D.; Lin, M. C. Proc. Combust. Inst. 1998, 27, 2351-2357). Since the homogeneous decomposition reaction of HNO(3) itself was found to be too slow to account for the consumption of reactants and the formation of products, we also introduced the heterogeneous decomposition of HNO(3) in our kinetic modeling. The heterogeneous decomposition rate of HNO(3), HNO(3) + (B(2)O(3)/SiO(2)) --> OH + NO(2) + (B(2)O(3)/SiO(2)), was determined by varying its rate to match the modeled result to the measured concentrations of NH(3) and H(2)O; the rate could be represented by k(2b) = 7.91 x 10(7) exp(-12 600/T) s(-1), which appears to be consistent with those reported by Johnston and co-workers (Johnston, H. S.; Foering, L.; Tao, Y.-S.; Messerly, G. H. J. Am. Chem. Soc. 1951, 73, 2319-2321) for HNO(3) decomposition on glass reactors at higher temperatures. Notably, the concentration profiles of all species measured could be satisfactorily predicted by the existing [H,N,O]-mechanism with the heterogeneous initiation process.

Thermal Decomposition of Gaseous Ammonium Nitrate at Low Pressure: Kinetic Modeling of Product Formation and Heterogeneous Decomposition of Nitric Acid

NASA Astrophysics Data System (ADS)

Park, J.; Lin, M. C.

2009-10-01

The thermal decomposition of ammonium nitrate, NH4NO3 (AN), in the gas phase has been studied at 423-56 K by pyrolysis/mass spectrometry under low-pressure conditions using a Saalfeld reactor coated with boric acid. The sublimation of NH4NO3 at 423 K was proposed to produce equal amounts of NH3 and HNO3, followed by the decomposition reaction of HNO3, HNO3 + M → OH + NO2 + M (where M = third-body and reactor surface). The absolute yields of N2, N2O, H2O, and NH3, which can be unambiguously measured and quantitatively calibrated under a constant pressure at 5-6.2 torr He are kinetically modeled using the detailed [H,N,O]-mechanism established earlier for the simulation of NH3-NO2 (Park, J.; Lin, M. C. Technologies and Combustion for a Clean Environment. Proc. 4th Int. Conf. 1997, 34-1, 1-5) and ADN decomposition reactions (Park, J.; Chakraborty, D.; Lin, M. C. Proc. Combust. Inst. 1998, 27, 2351-2357). Since the homogeneous decomposition reaction of HNO3 itself was found to be too slow to account for the consumption of reactants and the formation of products, we also introduced the heterogeneous decomposition of HNO3 in our kinetic modeling. The heterogeneous decomposition rate of HNO3, HNO3 + (B2O3/SiO2) → OH + NO2 + (B2O3/SiO2), was determined by varying its rate to match the modeled result to the measured concentrations of NH3 and H2O; the rate could be represented by k2b = 7.91 × 107 exp(-12 600/T) s-1, which appears to be consistent with those reported by Johnston and co-workers (Johnston, H. S.; Foering, L.; Tao, Y.-S.; Messerly, G. H. J. Am. Chem. Soc. 1951, 73, 2319-2321) for HNO3 decomposition on glass reactors at higher temperatures. Notably, the concentration profiles of all species measured could be satisfactorily predicted by the existing [H,N,O]-mechanism with the heterogeneous initiation process.
Scoring of Decomposition: A Proposed Amendment to the Method When Using a Pig Model for Human Studies.

PubMed

Keough, Natalie; Myburgh, Jolandie; Steyn, Maryna

2017-07-01

Decomposition studies often use pigs as proxies for human cadavers. However, differences in decomposition sequences/rates relative to humans have not been scientifically examined. Descriptions of five main decomposition stages (humans) were developed and refined by Galloway and later by Megyesi. However, whether these changes/processes are alike in pigs is unclear. Any differences can have significant effects when pig models are used for human PMI estimation. This study compared human decomposition models to the changes observed in pigs. Twenty pigs (50-90 kg) were decomposed over five months and decompositional features recorded. Total body scores (TBS) were calculated. Significant differences were observed during early decomposition between pigs and humans. An amended scoring system to be used in future studies was developed. Standards for PMI estimation derived from porcine models may not directly apply to humans and may need adjustment. Porcine models, however, remain valuable to study variables influencing decomposition. © 2016 American Academy of Forensic Sciences.
Advanced water remediation from ofloxacin by ionizing radiation

NASA Astrophysics Data System (ADS)

Esposito, Biagio R.; Capobianco, Massimo L.; Martelli, Alessandro; Navacchia, Maria Luisa; Pretali, Luca; Saracino, Michela; Zanelli, Alberto; Emmi, Salvatore S.

2017-12-01

The performances of remediation processes initiated by ionizing radiation on ofloxacin are investigated in ambient conditions. The effectiveness of the decomposition of ofloxacin has been assessed both by γ-rays and electron beam in various aqueous solutions differentiated by the dissolved gases (Air or oxygen saturated) and H2O2. By HPLC it is shown that ofloxacin is removed according to a first order process vs. dose in any system. O2 accelerates the decomposition rate, while H2O2 does not seem to enhance any oxidation effect. The simultaneous oxidative-reductive treatment (no additive) demonstrated to have better mineralizing performances than the fully oxidative one (H2O2 present). Mineralization by γ results to be more efficient than by EB. The Total Organic Carbon decrease was investigated in dependence of dose and of the •OH production rate. The latter parameter was changed over 7 orders of magnitude by controlling dose rate and/or by adding H2O2. A steep increase of acidity remarks the phases of fluorine-carbon bond break.
Study on cross-reactivity to the para group.

PubMed

Picardo, M; Cannistraci, C; Cristaudo, A; De Luca, C; Santucci, B

1990-01-01

In 80 patients, positive to at least one hapten of the para group (para-phenylenediamine, diaminodiphenylmethane, benzocaine, PPD mix), patch tests were carried out with freshly prepared solutions of para-phenylenediamine (PPD) and of 3 selected aromatic compounds related structurally to PPD (para-aminophenol, ortho-aminophenol, hydroquinone). The number of positive reactions correlated with the rate of decomposition of the substances as evaluated by high-pressure liquid chromatography. PPD, which was almost decomposed after 24 h, gave the highest number of positive reactions, followed by ortho-aminophenol and by para-aminophenol, while hydroquinone, which was oxidized to the extent of 35%, did not give any reactions. To evaluate if a different rate of oxidation can modify the patch test response, in the same patients and in 10 normal volunteers, tests were carried out with PPD solutions containing the oxidizing agent silver oxide (0.1%). By this procedure a significant increase in the number of positive responses was observed. The results suggest that the rate of decomposition and therefore the amount of quinone(s) generated, might be the key to eliciting patch test responses to oxidizable aromatic haptens.
Ab initio kinetics of gas phase decomposition reactions.

PubMed

Sharia, Onise; Kuklja, Maija M

2010-12-09

The thermal and kinetic aspects of gas phase decomposition reactions can be extremely complex due to a large number of parameters, a variety of possible intermediates, and an overlap in thermal decomposition traces. The experimental determination of the activation energies is particularly difficult when several possible reaction pathways coexist in the thermal decomposition. Ab initio calculations intended to provide an interpretation of the experiment are often of little help if they produce only the activation barriers and ignore the kinetics of the decomposition process. To overcome this ambiguity, a theoretical study of a complete picture of gas phase thermo-decomposition, including reaction energies, activation barriers, and reaction rates, is illustrated with the example of the β-octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) molecule by means of quantum-chemical calculations. We study three types of major decomposition reactions characteristic of nitramines: the HONO elimination, the NONO rearrangement, and the N-NO(2) homolysis. The reaction rates were determined using the conventional transition state theory for the HONO and NONO decompositions and the variational transition state theory for the N-NO(2) homolysis. Our calculations show that the HMX decomposition process is more complex than it was previously believed to be and is defined by a combination of reactions at any given temperature. At all temperatures, the direct N-NO(2) homolysis prevails with the activation barrier at 38.1 kcal/mol. The nitro-nitrite isomerization and the HONO elimination, with the activation barriers at 46.3 and 39.4 kcal/mol, respectively, are slow reactions at all temperatures. The obtained conclusions provide a consistent interpretation for the reported experimental data.
High-Temperature Adhesives for Thermally Stable Aero-Assist Technologies

NASA Technical Reports Server (NTRS)

Eberts, Kenneth; Ou, Runqing

2013-01-01

Aero-assist technologies are used to control the velocity of exploration vehicles (EVs) when entering Earth or other planetary atmospheres. Since entry of EVs in planetary atmospheres results in significant heating, thermally stable aero-assist technologies are required to avoid the high heating rates while maintaining low mass. Polymer adhesives are used in aero-assist structures because of the need for high flexibility and good bonding between layers of polymer films or fabrics. However, current polymer adhesives cannot withstand temperatures above 400 C. This innovation utilizes nanotechnology capabilities to address this need, leading to the development of high-temperature adhesives that exhibit high thermal conductivity in addition to increased thermal decomposition temperature. Enhanced thermal conductivity will help to dissipate heat quickly and effectively to avoid temperature rising to harmful levels. This, together with increased thermal decomposition temperature, will enable the adhesives to sustain transient high-temperature conditions.
[Edge effects of forest gap in Pinus massoniana plantations on the decomposition of leaf litter recalcitrant components of Cinnamomum camphora and Toona ciliata.

PubMed

Zhang, Yan; Zhang, Dan Ju; Li, Xun; Liu, Hua; Zhang, Ming Jin; Yang, Wan Qin; Zhang, Jian

2016-04-22

The objective of the study was to evaluate the dynamics of recalcitrant components during foliar litter decomposition under edge effects of forest gap in Pinus massoniana plantations in the low hilly land, Sichuan basin. A field litterbag experiment was conducted in seven forest gaps with different sizes (100, 225, 400, 625, 900, 1225, 1600 m 2 ) which were generated by thinning P. massoniana plantations. The degradation rate of four recalcitrant components, i.e., condensed tannins, total phenol, lignin and cellulose in foliar litter of two native species (Cinnamomum camphora and Toona ciliata) at the gap edge and under the closed canopy were measured. The results showed that the degradation rate of recalcitrant components in T. ciliata litter except for cellulose at the gap edge were significantly higher than that under the closed canopy. For C. camphora litter, only the degradation of lignin at the gap edge was higher than that under the closed canopy. After one-year decomposition, four recalcitrant components in two types of foliar litter exhibited an increment of degradation rate, and the degradation rate of condensed tannin was the fastest, followed by total phenol and cellulose, but the lignin degradation rate was the slowest. With the increase of gap size, except for cellulose, the degradation rate ofthe other three recalcitrant components of the T. ciliata at the edge of medium sized gaps (400 and 625 m 2 ) were significantly higher than at the edge of other gaps. However, lignin in the C. camphora litter at the 625 m 2 gap edge showed the greatest degradation rate. Both temperature and litter initial content were significantly correlated with litter recalcitrant component degradation. Our results suggested that medium sized gaps (400-625 m 2 ) had a more significant edge effect on the degradation of litter recalcitrant components in the two native species in P. massoniana plantations, however, the effect also depended on species.
Input of easily available organic C and N stimulates microbial decomposition of soil organic matter in arctic permafrost soil

PubMed Central

Wild, Birgit; Schnecker, Jörg; Alves, Ricardo J. Eloy; Barsukov, Pavel; Bárta, Jiří; Čapek, Petr; Gentsch, Norman; Gittel, Antje; Guggenberger, Georg; Lashchinskiy, Nikolay; Mikutta, Robert; Rusalimova, Olga; Šantrůčková, Hana; Shibistova, Olga; Urich, Tim; Watzka, Margarete; Zrazhevskaya, Galina; Richter, Andreas

2014-01-01

Rising temperatures in the Arctic can affect soil organic matter (SOM) decomposition directly and indirectly, by increasing plant primary production and thus the allocation of plant-derived organic compounds into the soil. Such compounds, for example root exudates or decaying fine roots, are easily available for microorganisms, and can alter the decomposition of older SOM (“priming effect”). We here report on a SOM priming experiment in the active layer of a permafrost soil from the central Siberian Arctic, comparing responses of organic topsoil, mineral subsoil, and cryoturbated subsoil material (i.e., poorly decomposed topsoil material subducted into the subsoil by freeze–thaw processes) to additions of 13C-labeled glucose, cellulose, a mixture of amino acids, and protein (added at levels corresponding to approximately 1% of soil organic carbon). SOM decomposition in the topsoil was barely affected by higher availability of organic compounds, whereas SOM decomposition in both subsoil horizons responded strongly. In the mineral subsoil, SOM decomposition increased by a factor of two to three after any substrate addition (glucose, cellulose, amino acids, protein), suggesting that the microbial decomposer community was limited in energy to break down more complex components of SOM. In the cryoturbated horizon, SOM decomposition increased by a factor of two after addition of amino acids or protein, but was not significantly affected by glucose or cellulose, indicating nitrogen rather than energy limitation. Since the stimulation of SOM decomposition in cryoturbated material was not connected to microbial growth or to a change in microbial community composition, the additional nitrogen was likely invested in the production of extracellular enzymes required for SOM decomposition. Our findings provide a first mechanistic understanding of priming in permafrost soils and suggest that an increase in the availability of organic carbon or nitrogen, e.g., by increased plant productivity, can change the decomposition of SOM stored in deeper layers of permafrost soils, with possible repercussions on the global climate. PMID:25089062
How mycorrhizal plant-soil interactions affect formation and degradation of soil organic matter in boreal forest

NASA Astrophysics Data System (ADS)

Adamczyk, Bartosz; Sietiö, Outi-Maaria; Ahvenainen, Anu; Strakova, Petra; Heinonsalo, Jussi

2017-04-01

Forest soil organic matter (SOM) contains more carbon (C) than all the flora and atmosphere combined and that is why C release as CO2 from SOM may have drastic consequences for climate globally. SOM is enormous C sink which has the potential to become C source (IPCC 2013). To predict long-term soil C storage and climate feedbacks we need profound understanding of dynamics and drivers of SOM decomposition. Ecosystem processes associated with C cycle are constrained by C and N interactions. At the level of ecosystem boreal forest is N-limited, as most of soil N is stored in recalcitrant organic form bound or complexed with soil compounds such as polyphenols. To improve N uptake, also from less available pools, plant species form symbioses with mycorrhizal fungi able to degrade recalcitrant N and sharing it with plants. As a feedback, plants provide to fungal symbiont assimilated C. Climate change through elevated CO2 level led to increases in photosynthesis which enhance the C flow belowground accelerating N uptake by plants also from more recalcitrant N pools. Increased SOM decomposition would possibly result also in increase of CO2 production from soil. Our field experiment was conducted at Hyytiälä forestry field station (SMEAR II, University of Helsinki) located in southern Finland (61°84'N, 24°26'E). In this 3-year long experiment, we discriminated SOM decomposition with different mesh bags filled with humus. These mesh bags allowed for the entrance of mycorrhiza and fine roots (1mm mesh size), or only mycorrhiza (50µm), or both were excluded (1µm). We followed changes in SOM content, N pools and enzymatic activity. The results suggests that plant-mycorrhiza interactions increase recalcitrant pool of organic N in SOM due to root-derived tannins, but mycorrhizal plants have still access to this N. Although mycorrhizal plant-soil interaction seems to strongly affect the formation of recalcitrant SOM, the net decomposition is not hindered by these chemical changes. This study underline that plant-soil feedbacks and especially soil chemistry behind this interaction are decisive factors for estimating changes in SOM decomposition rate.
Root architecture impacts on root decomposition rates in switchgrass

NASA Astrophysics Data System (ADS)

de Graaff, M.; Schadt, C.; Garten, C. T.; Jastrow, J. D.; Phillips, J.; Wullschleger, S. D.

2010-12-01

Roots strongly contribute to soil organic carbon accrual, but the rate of soil carbon input via root litter decomposition is still uncertain. Root systems are built up of roots with a variety of different diameter size classes, ranging from very fine to very coarse roots. Since fine roots have low C:N ratios and coarse roots have high C:N ratios, root systems are heterogeneous in quality, spanning a range of different C:N ratios. Litter decomposition rates are generally well predicted by litter C:N ratios, thus decomposition of roots may be controlled by the relative abundance of fine versus coarse roots. With this study we asked how root architecture (i.e. the relative abundance of fine versus coarse roots) affects the decomposition of roots systems in the biofuels crop switchgrass (Panicum virgatum L.). To understand how root architecture affects root decomposition rates, we collected roots from eight switchgrass cultivars (Alamo, Kanlow, Carthage, Cave-in-Rock, Forestburg, Southlow, Sunburst, Blackwell), grown at FermiLab (IL), by taking 4.8-cm diameter soil cores from on top of the crown and directly next to the crown of individual plants. Roots were carefully excised from the cores by washing and analyzed for root diameter size class distribution using WinRhizo. Subsequently, root systems of each of the plants (4 replicates per cultivar) were separated in 'fine' (0-0.5 mm), 'medium' (0.5-1 mm) and 'coarse' roots (1-2.5 mm), dried, cut into 0.5 cm (medium and coarse roots) and 2 mm pieces (fine roots), and incubated for 90 days. For each of the cultivars we established five root-treatments: 20g of soil was amended with 0.2g of (1) fine roots, (2) medium roots, (3) coarse roots, (4) a 1:1:1 mixture of fine, medium and coarse roots, and (5) a mixture combining fine, medium and coarse roots in realistic proportions. We measured CO2 respiration at days 1, 3, 7, 15, 30, 60 and 90 during the experiment. The 13C signature of the soil was -26‰, and the 13C signature of plants was -12‰, enabling us to differentiate between root-derived C and native SOM-C respiration. We found that the relative abundance of fine, medium and coarse roots were significantly different among cultivars. Root systems of Alamo, Kanlow and Cave-in-Rock were characterized by a large abundance of coarse-, relative to fine roots, whereas Carthage, Forestburg and Blackwell had a large abundance of fine, relative to coarse roots. Fine roots had a 28% lower C:N ratio than medium and coarse roots. These differences led to different root decomposition rates. We conclude that root architecture should be taken into account when predicting root decomposition rates; enhanced understanding of the mechanisms of root decomposition will improve model predictions of C input to soil organic matter.
[A field study of tundra plant litter decomposition rate via mass loss and carbon dioxide emission: the role of biotic and abiotic controls, biotope, season of year, and spatial-temporal scale].

PubMed

Pochikalov, A V; Karelin, D V

2014-01-01

Although many recently published original papers and reviews deal with plant matter decomposition rates and their controls, we are still very short in understanding of these processes in boreal and high latiude plant communities, especially in permafrost areas of our planet. First and foremost, this is holds true for winter period. Here, we present the results of 2-year field observations in south taiga and south shrub tundra ecosystems in European Russia. We pioneered in simultaneous application of two independent methods: classic mass loss estimation by litter-bag technique, and direct measurement of CO2 emission (respiration) of the same litter bags with different types of dead plant matter. Such an approach let us to reconstruct intra-seasonal dynamics of decomposition rates of the main tundra litter fractions with high temporal resolution, to estimate the partial role of different seasons and defragmentation in the process of plant matter decomposition, and to determine its factors under different temporal scale.
A Taphonomic Study Exploring the Differences in Decomposition Rate and Manner between Frozen and Never Frozen Domestic Pigs (Sus scrofa).

PubMed

Roberts, Lindsey G; Dabbs, Gretchen R

2015-05-01

This research examined differences in decomposition rate and manner of domestic pig subjects (Sus scrofa) in never frozen (control) and previously frozen (experimental) research conditions. Eight control and experimental subjects were placed in an identical outdoor research environment. Daily quantitative and qualitative measurements were collected: abdominal circumference, total body score (TBS), temperature, photographs, descriptive decomposition stages, and visual observations. Field necropsies were performed at accumulated degree days (ADD) between 50 and 300 (Celsius). Paired samples t-tests of ADD to TBS >3.0, TBS >9.5, and TBS >16.0 indicate the rate of decomposition of experimental subjects was significantly slower than controls at both TBS >3 and >9.5 (p = 0.003 and p = 0.002, respectively). A suite of qualitative indicators of predecomposition freezing is also reported. The differences between experimental and control subjects suggest previously frozen subjects should not be used in taphonomic research, as results do not accurately reflect the "normal" taphonomic condition. © 2015 American Academy of Forensic Sciences.
Interactions of tissue and fertilizer nitrogen on decomposition dynamics of lignin-rich conifer litter

USGS Publications Warehouse

Perakis, Steven S.; Matkins, Joselin J.; Hibbs, David E.

2012-01-01

High tissue nitrogen (N) accelerates decomposition of high-quality leaf litter in the early phases of mass loss, but the influence of initial tissue N variation on the decomposition of lignin-rich litter is less resolved. Because environmental changes such as atmospheric N deposition and elevated CO2 can alter tissue N levels within species more rapidly than they alter the species composition of ecosystems, it is important to consider how within-species variation in tissue N may shape litter decomposition and associated N dynamics. Douglas-fir (Pseudotsuga menziesii ) is a widespread lignin-rich conifer that dominates forests of high carbon (C) storage across western North America, and displays wide variation in tissue and litter N that reflects landscape variation in soil N. We collected eight unique Douglas-fir litter sources that spanned a two-fold range in initial N concentrations (0.67–1.31%) with a narrow range of lignin (29–35%), and examined relationships between initial litter chemistry, decomposition, and N dynamics in both ambient and N fertilized plots at four sites over 3 yr. High initial litter N slowed decomposition rates in both early (0.67 yr) and late (3 yr) stages in unfertilized plots. Applications of N fertilizer to litters accelerated early-stage decomposition, but slowed late-stage decomposition, and most strongly affected low-N litters, which equalized decomposition rates across litters regardless of initial N concentrations. Decomposition of N-fertilized litters correlated positively with initial litter manganese (Mn) concentrations, with litter Mn variation reflecting faster turnover of canopy foliage in high N sites, producing younger litterfall with high N and low Mn. Although both internal and external N inhibited decomposition at 3 yr, most litters exhibited net N immobilization, with strongest immobilization in low-N litter and in N-fertilized plots. Our observation for lignin-rich litter that high initial N can slow decomposition yet accelerate N release differs from findings where litter quality variation across species promotes coupled C and N release during decomposition. We suggest reevaluation of ecosystem models and projected global change effects to account for a potential decoupling of ecosystem C and N feedbacks through litter decomposition in lignin-rich conifer forests.
Interaction of initial litter quality and thinning intensity on litter decomposition rate, nitrogen accumulation and release in a pine plantation

Treesearch

Xiao Chen; Deborah Page-Dumroese; Ruiheng Lv; Weiwei Wang; Guolei Li; Yong Liu

2014-01-01

Thinning alters litter quality and microclimate under forests. Both of these two changes after thinning induce alterations of litter decomposition rates and nutrient cycling. However, a possible interaction between these two changes remains unclear. We placed two types of litter (LN, low N concentration litter; HN, high N concentration litter) in a Chinese pine (Pinus...
The burden of infectious and cardiovascular diseases in India from 2004 to 2014.

PubMed

Banerjee, Kajori; Dwivedi, Laxmi Kant

2016-01-01

In India, both communicable and non-communicable diseases have been argued to disproportionately affect certain socioeconomic strata of the population. Using the 60th (2004) and 71st (2014) rounds of the National Sample Survey, this study assessed the balance between infectious diseases and cardiovascular diseases (CVD) from 2004 to 2014, as well as changes in the disease burden in various socioeconomic and demographic subpopulations. Prevalence rates, hospitalization rates, case fatality rates, and share of in-patients deaths were estimated to compare the disease burdens at these time points. Logistic regression and multivariate decomposition were used to evaluate changes in disease burden across various socio-demographic and socioeconomic groups. Evidence of stagnation in the infectious disease burden and rapid increase in the CVD burden was observed. Along with the drastic increase in case fatality rate, share of in-patients deaths became more skewed towards CVD from 2004 to 2014. Logistic regression analysis demonstrated a significant shift of the chance of succumbing to CVD from the privileged class, comprising non-Scheduled Castes and Tribes, more highly educated individuals, and households with higher monthly expenditures, towards the underprivileged population. Decomposition indicated that a change in the probability of suffering from CVD among the subcategories of age, social groups, educational status, and monthly household expenditures contributed to the increase in CVD prevalence more than compositional changes of the population from 2004 to 2014. This study provides evidence of the ongoing tendency of CVD to occur in older population segments, and also confirms the theory of diffusion, according to which an increased probability of suffering from CVD has trickled down the socioeconomic gradient.
Contribution of rice straw carbon to CH4 emission from rice paddies using 13C-enriched rice straw

NASA Astrophysics Data System (ADS)

Watanabe, Akira; Yoshida, Mariko; Kimura, Makoto

1998-04-01

It is generally recognized that the application of rice straw (RS) increases CH4 emission from rice paddies. To estimate the contribution of RS carbon to CH4 emission, a pot experiment was conducted using 13C-enriched RS. The percentage contributions of RS carbon to CH4 emission throughout the rice growth period were 10±1, 32±3, and 43±3% for the treatments with RS applied at the rates of 2, 4, and 6 g kg-1 soil, respectively. The increase in the rate of application of RS increased CH4 emission derived from both RS carbon and other carbon sources. The percentage contribution of RS carbon to CH4 emission was larger in the earlier period (maximum 96%) when the decomposition rate of RS was larger. After RS decomposition had slowed, CH4 emission derived from RS carbon decreased. However, the δ13C values of CH4 emitted from the pots with 13C-enriched RS applied at rates of 4 and 6 g kg-1 soil were significantly higher than those from the pots with natural RS until the harvesting stage. An increased atom-13C% of roots of rice plants growing in the pots with 6 g kg-1 of 13C-enriched RS at around the maximum tiller number stage and a decrease during the following 2 months suggested that rice plants assimilated RS carbon once and then released a portion of it. This supply of RS carbon from roots may be one of the sources of CH4 in the late period of rice growth.
Leaf and root litter decomposition is discontinued at high altitude tropical montane rainforests contributing to carbon sequestration.

PubMed

Marian, Franca; Sandmann, Dorothee; Krashevska, Valentyna; Maraun, Mark; Scheu, Stefan

2017-08-01

We investigated how altitude affects the decomposition of leaf and root litter in the Andean tropical montane rainforest of southern Ecuador, that is, through changes in the litter quality between altitudes or other site-specific differences in microenvironmental conditions. Leaf litter from three abundant tree species and roots of different diameter from sites at 1,000, 2,000, and 3,000 m were placed in litterbags and incubated for 6, 12, 24, 36, and 48 months. Environmental conditions at the three altitudes and the sampling time were the main factors driving litter decomposition, while origin, and therefore quality of the litter, was of minor importance. At 2,000 and 3,000 m decomposition of litter declined for 12 months reaching a limit value of ~50% of initial and not decomposing further for about 24 months. After 36 months, decomposition commenced at low rates resulting in an average of 37.9% and 44.4% of initial remaining after 48 months. In contrast, at 1,000 m decomposition continued for 48 months until only 10.9% of the initial litter mass remained. Changes in decomposition rates were paralleled by changes in microorganisms with microbial biomass decreasing after 24 months at 2,000 and 3,000 m, while varying little at 1,000 m. The results show that, irrespective of litter origin (1,000, 2,000, 3,000 m) and type (leaves, roots), unfavorable microenvironmental conditions at high altitudes inhibit decomposition processes resulting in the sequestration of carbon in thick organic layers.
Factors regulating carbon sinks in mangrove ecosystems.

PubMed

Li, Shi-Bo; Chen, Po-Hung; Huang, Jih-Sheng; Hsueh, Mei-Li; Hsieh, Li-Yung; Lee, Chen-Lu; Lin, Hsing-Juh

2018-05-23

Mangroves are recognized as one of the richest carbon storage systems. However, the factors regulating carbon sinks in mangrove ecosystems are still unclear, particularly in the subtropical mangroves. The biomass, production, litterfall, detrital export and decomposition of the dominant mangrove vegetation in subtropical (Kandelia obovata) and tropical (Avicennia marina) Taiwan were quantified from October 2011 to July 2014 to construct the carbon budgets. Despite the different tree species, a principal component analysis revealed the site or environmental conditions had a greater influence than the tree species on the carbon processes. For both species, the net production (NP) rates ranged from 10.86 to 27.64 Mg C ha -1 year -1 and were higher than the global average rate due to the high tree density. While most of the litterfall remained on the ground, a high percentage (72%-91%) of the ground litter decomposed within 1 year and fluxed out of the mangroves. However, human activities might cause a carbon flux into the mangroves and a lower NP rate. The rates of the organic carbon export and soil heterotrophic respiration were greater than the global mean values and those at other locations. Only a small percentage (3%-12%) of the NP was stored in the sediment. The carbon burial rates were much lower than the global average rate due to their faster decomposition, indicating that decomposition played a critical role in determining the burial rate in the sediment. The summation of the organic and inorganic carbon fluxes and soil heterotrophic respiration well exceeded the amount of litter decomposition, indicating an additional source of organic carbon that was unaccounted for by decomposition in the sediment. Sediment-stable isotope analyses further suggest that the trapping of organic matter from upstream rivers or adjacent waters contributed more to the mangrove carbon sinks than the actual production of the mangrove trees. © 2018 John Wiley & Sons Ltd.
Modeling the Response of Soil Organic Matter Decomposition to Warming: Effects of Dynamical Enzyme Productivity and Nuanced Representation of Respiration.

NASA Astrophysics Data System (ADS)

Sihi, D.; Gerber, S.; Inglett, K. S.; Inglett, P.

2014-12-01

Recent development in modeling soil organic carbon (SOC) decomposition includes the explicit incorporation of enzyme and microbial dynamics. A characteristic of these models is a feedback between substrate and consumers which is absent in traditional first order decay models. Second, microbial decomposition models incorporate carbon use efficiency (CUE) as a function of temperature which proved to be critical to prediction of SOC with warming. Our main goal is to explore microbial decomposition models with respect to responses of microbes to enzyme activity, costs to enzyme production, and to incorporation of growth vs. maintenance respiration. In order to simplify the modeling setup we assumed quick adjustment of enzyme activity and depolymerized carbon to microbial and SOC pools. Enzyme activity plays an important role to decomposition if its production is scaled to microbial biomass. In fact if microbes are allowed to optimize enzyme productivity the microbial enzyme model becomes unstable. Thus if the assumption of enzyme productivity is relaxed, other limiting factors must come into play. To stabilize the model, we account for two feedbacks that include cost of enzyme production and diminishing return of depolymerization with increasing enzyme concentration and activity. These feedback mechanisms caused the model to behave in a similar way to traditional, first order decay models. Most importantly, we found, that under warming, the changes in SOC carbon were more severe in enzyme synthesis is costly. In turn, carbon use efficiency (CUE) and its dynamical response to temperature is mainly determined by 1) the rate of turnover of microbes 2) the partitioning of dead microbial matter into different quality pools, and 3) and whether growth, maintenance respiration and microbial death rate have distinct responses to changes in temperature. Abbreviations: p: decay of enzyme, g: coefficient for growth respiration, : fraction of material from microbial turnover that enters the DOC pool, loss of C scaled to microbial mass, half saturation constant.
Temperature sensitivity of microbial respiration of fine root litter in a temperate broad-leaved forest.

PubMed

Makita, Naoki; Kawamura, Ayumi

2015-01-01

The microbial decomposition respiration of plant litter generates a major CO2 efflux from terrestrial ecosystems that plays a critical role in the regulation of carbon cycling on regional and global scales. However, the respiration from root litter decomposition and its sensitivity to temperature changes are unclear in current models of carbon turnover in forest soils. Thus, we examined seasonal changes in the temperature sensitivity and decomposition rates of fine root litter of two diameter classes (0-0.5 and 0.5-2.0 mm) of Quercus serrata and Ilex pedunculosa in a deciduous broad-leaved forest. During the study period, fine root litter of both diameter classes and species decreased approximately exponentially over time. The Q10 values of microbial respiration rates of root litter for the two classes were 1.59-3.31 and 1.28-6.27 for Q. serrata and 1.36-6.31 and 1.65-5.86 for I. pedunculosa. A significant difference in Q10 was observed between the diameter classes, indicating that root diameter represents the initial substrate quality, which may determine the magnitude of Q10 value of microbial respiration. Changes in these Q10 values were related to seasonal soil temperature patterns; the values were higher in winter than in summer. Moreover, seasonal variations in Q10 were larger during the 2-year decomposition period than the 1-year period. These results showed that the Q10 values of fine root litter of 0-0.5 and 0.5-2.0 mm have been shown to increase with lower temperatures and with the higher recalcitrance pool of the decomposed substrate during 2 years of decomposition. Thus, the temperature sensitivity of microbial respiration in root litter showed distinct patterns according to the decay period and season because of the temperature acclimation and adaptation of the microbial decomposer communities in root litter.

Soil ecosystem function under native and exotic plant assemblages as alternative states of successional grasslands

NASA Astrophysics Data System (ADS)

Spirito, Florencia; Yahdjian, Laura; Tognetti, Pedro M.; Chaneton, Enrique J.

2014-01-01

Old fields often become dominated by exotic plants establishing persistent community states. Ecosystem functioning may differ widely between such novel communities and the native-dominated counterparts. We evaluated soil ecosystem attributes in native and exotic (synthetic) grass assemblages established on a newly abandoned field, and in remnants of native grassland in the Inland Pampa, Argentina. We asked whether exotic species alter soil functioning through the quality of the litter they shed or by changing the decomposition environment. Litter decomposition of the exotic dominant Festuca arundinacea in exotic assemblages was faster than that of the native dominant Paspalum quadrifarium in native assemblages and remnant grasslands. Decomposition of a standard litter (Triticum aestivum) was also faster in exotic assemblages than in native assemblages and remnant grasslands. In a common garden, F. arundinacea showed higher decay rates than P. quadrifarium, which reflected the higher N content and lower C:N of the exotic grass litter. Soil respiration rates were higher in the exotic than in the native assemblages and remnant grasslands. Yet there were no significant differences in soil N availability or net N mineralization between exotic and native assemblages. Our results suggest that exotic grass dominance affected ecosystem function by producing a more decomposable leaf litter and by increasing soil decomposer activity. These changes might contribute to the extended dominance of fast-growing exotic grasses during old-field succession. Further, increased organic matter turnover under novel, exotic communities could reduce the carbon storage capacity of the system in the long term.
Priming of native soil organic matter by pyrogenic organic matter

NASA Astrophysics Data System (ADS)

DeCiucies, Silene; Dharmakeerthi, Saman; Whitman, Thea; Woolf, Dominic; Lehmann, Johannes

2015-04-01

Priming, in relation to pyrogenic organic matter (PyOM), describes the change in mineralization rate of non-pyrogenic ("native") soil organic matter (nSOM) due to the addition of PyOM. Priming may be 'positive', in that the addition of pyC increases the mineralization rate of native SOM, or 'negative', in that the mineralization rate of nSOM is decreased. Reasons for increased mineralization may include: (i) co-metabolism: microbial decomposition of labile C-additions increases microbial activity, and facilitates additional decomposition of npSOC by active enzymes; (ii) stimulation: substrate additions result in lifted pH, nutrient, oxygen, or water constraints resulting in increased microbial activity. Decreased mineralization may be a result of: (i) inhibition: the opposite of stimulation whereby constraints are aggravated by substrate addition. Substrate addition may also cause inhibition by interfering with enzymes or signaling compounds; (ii) preferential substrate utilization: labile fraction of PyOM additions are preferentially used up by microbes thus causing a decrease in nSOC decomposition; (iii) sorption: organic compounds are adsorbed onto PyOM surfaces, decreasing their rate of mineralization; (iv) stabilization: formation of organo-mineral associations forms stable SOC pools. We have conducted a suite of experiments to investigate these potential interactions. In a seven year long incubation study, PyOM additions increased total OM mineralization for the first 2.5 years, was equal to control after 6.2 years, and was 3% lower after 7.1 years. Cumulative nSOM mineralization was 23% less with the PyOM additions than without, and over 60% of the added PyOM was present in the labile soil fraction after the 7.1 year incubation. Two additional incubation studies, one with and without plants, showed greater nSOM mineralization in the short term and lower nSOM mineralization over the long term. Increased nSOC mineralization due to the presence of plants was counteracted by PyOM additions. However, repeated additions of crop residues over seven years did not result in lower mineralization of the residue and nSOM. We have also determined that, although there is no optimal duration for pre-incubation of soil before SOC studies, the type of carbon available is crucial in determining the effects of PyOM additions. We will continue to examine the contribution of the different mechanisms by isolating variables such as nutrient addition, soil texture, and mineral availability. We anticipate that sorption on PyOM surfaces are important in nSOM stabilization and will continue to study these effects using highly labeled substrates and nano secondary ion mass spectrometry (nano-SIMS).
Litter dynamics in two Sierran mixed conifer forests. I. Litterfall and decomposition rates

USGS Publications Warehouse

Stohlgren, Thomas J.

1988-01-01

Litterfall was measured for 4 years and leaf litter decomposition rates were studied for 3.6 years in two mixed conifer forest (giant sequoia-fir and fir-pine) in the southern Sierra Nevada of California. The giant sequoia-fir forest (GS site) was dominated by giant sequoia (Sequoiadendron giganteum (Lindl.) Buchh.), white fir (Abies concolor Lindl. & Gord.), and sugar pine (Pinus lambertiana Dougl.). The fir-pine forest (FP site) was dominated by white fir, sugar pine, and incense cedar (Calocedrus decurrens (Torr.) Florin). Litterfall, including large woody debris -1•year-1 compared with 4355 kg•ha-1•year-1 at the FP site (3.4:1). In the GS site, leaf litter decomposition after 3.6 years was slowest for giant sequoia (28.2% mass loss), followed by sugar pine (34.3%) and white fie (45.1%). In the FP site, mass loss was slowest for sugar pine (40.0%), followed by white fir (45.1%), while incense cedar showed the greatest mass loss (56.9%) after 3.6 years. High litterfall rates of large woody debris (i.e., 2.5-15.2 cm diameter) and slow rates of leaf litter decomposition in the giant sequoia-fir forest type may result in higher litter accumulation rates than in the fir-pine type. Leaf litter times to 95% decay for the GS and FP sites were 30 and 27 years, respectively, if the initial 0.7-year period (a short period of rapid mass decay) was ignored in the calculation. A mass balance approach for total litterfall (<15.2 cm diameter) decomposition yielded lower decay constants than did the litterbag study and therefore longer times to 95% decay (57 years for the GS site and 62 years for the FP site).
THERMAL DECOMPOSITION OF PEROXYACETYL NITRATE AND REACTIONS OF ACETYL PEROXY RADICALS WITH NO AND NO2 OVER THE TEMPERATURE RANGE 283-313K

EPA Science Inventory

The thermal decomposition of peroxyacetyl nitrate (PAN) in NO-NO2-air (or N2) mixtures has been studied at 740 torr total pressure over the temperature range 283-313 K. he experimental data obtained yield a rate constant for the thermal decomposition of PAN of k3 = 2.52 x 1016 e-...
Does oxygen exposure time control the extent of organic matter decomposition in peatlands?

NASA Astrophysics Data System (ADS)

Philben, Michael; Kaiser, Karl; Benner, Ronald

2014-05-01

The extent of peat decomposition was investigated in four cores collected along a latitudinal gradient from 56°N to 66°N in the West Siberian Lowland. The acid:aldehyde ratios of lignin phenols were significantly higher in the two northern cores compared with the two southern cores, indicating peats at the northern sites were more highly decomposed. Yields of hydroxyproline, an amino acid found in plant structural glycoproteins, were also significantly higher in northern cores compared with southern cores. Hydroxyproline-rich glycoproteins are not synthesized by microbes and are generally less reactive than bulk plant carbon, so elevated yields indicated that northern cores were more extensively decomposed than the southern cores. The southern cores experienced warmer temperatures, but were less decomposed, indicating that temperature was not the primary control of peat decomposition. The plant community oscillated between Sphagnum and vascular plant dominance in the southern cores, but vegetation type did not appear to affect the extent of decomposition. Oxygen exposure time appeared to be the strongest control of the extent of peat decomposition. The northern cores had lower accumulation rates and drier conditions, so these peats were exposed to oxic conditions for a longer time before burial in the catotelm, where anoxic conditions prevail and rates of decomposition are generally lower by an order of magnitude.
Interactions between soil and tree roots accelerate long-term soil carbon decomposition.

PubMed

Dijkstra, Feike A; Cheng, Weixin

2007-11-01

Decomposition of soil organic carbon (SOC) is the main process governing the release of CO(2) into the atmosphere from terrestrial systems. Although the importance of soil-root interactions for SOC decomposition has increasingly been recognized, their long-term effect on SOC decomposition remains poorly understood. Here we provide experimental evidence for a rhizosphere priming effect, in which interactions between soil and tree roots substantially accelerate SOC decomposition. In a 395-day greenhouse study with Ponderosa pine and Fremont cottonwood trees grown in three different soils, SOC decomposition in the planted treatments was significantly greater (up to 225%) than in soil incubations alone. This rhizosphere priming effect persisted throughout the experiment, until well after initial soil disturbance, and increased with a greater amount of root-derived SOC formed during the experiment. Loss of old SOC was greater than the formation of new C, suggesting that increased C inputs from roots could result in net soil C loss.
Degradation and intermediates of diclofenac as instructive example for decomposition of recalcitrant pharmaceuticals by hydroxyl radicals generated with pulsed corona plasma in water.

PubMed

Banaschik, Robert; Jablonowski, Helena; Bednarski, Patrick J; Kolb, Juergen F

2018-01-15

Seven recalcitrant pharmaceutical residues (diclofenac, 17α-ethinylestradiol, carbamazepine, ibuprofen, trimethoprim, diazepam, diatrizoate) were decomposed by pulsed corona plasma generated directly in water. The detailed degradation pathway was investigated for diclofenac and 21 intermediates could be identified in the degradation cascade. Hydroxyl radicals have been found primarily responsible for decomposition steps. By spin trap enhanced electron paramagnetic resonance spectroscopy (EPR), OH-adducts and superoxide anion radical adducts were detected and could be distinguished applying BMPO as a spin trap. The increase of concentrations of adducts follows qualitatively the increase of hydrogen peroxide concentrations. Hydrogen peroxide is eventually consumed in Fenton-like processes but the concentration is continuously increasing to about 2mM for a plasma treatment of 70min. Degradation of diclofenac is inversely following hydrogen peroxide concentrations. No qualitative differences between byproducts formed during plasma treatment or due to degradation via Fenton-induced processes were observed. Findings on degradation kinetics of diclofenac provide an instructive understanding of decomposition rates for recalcitrant pharmaceuticals with respect to their chemical structure. Accordingly, conclusions can be drawn for further development and a first risk assessment of the method which can also be applied towards other AOPs that rely on the generation of hydroxyl radicals. Copyright © 2017 Elsevier B.V. All rights reserved.
Temperature effect on mineralization of SOM, plant litter and priming: modified by soil type?

NASA Astrophysics Data System (ADS)

Azzaroli Bleken, Marina; Berland Frøseth, Randi

2015-04-01

The purpose of this study was to provide improved temperature response functions to be used in models of soil organic carbon (SOC) and litter mineralization, with focus on the winter period. Our working hypothesis were: 1) decomposition of SOM and plant residue occurs also at temperature close to the freezing point; 2) the effect of temperature on SOC decomposition is stronger in clayey than in sandy soil; 3) decomposition and response to temperature of added plant litter is not affected by soil type. A silty clay loam (27% clay, 3% sand) and a sandy loam (6% clay, 51% sand) with similar weather and cultivation history were pre-incubated at about 15° C for about 4.5 months. Clover leaves labelled with 13C were added to half of the samples, and soil with and without clover was incubated for 142 days at 0, 4, 8.5 or 15 °C. Mineralization of SOC and clover leaves was observed also at 0° C. In the absence of added plant material, SOC decomposition followed a first order reaction which was twice as fast in the sandy soil as in the clay soil. The decomposition rate of clover leaves was also higher in the sandy soil than in the clay soil. However, the influence of temperature on SOC and on clover decomposition was the same in both soils. In presence of plant material, there was a positive priming effect on SOC, which initially correlated with decomposition of plant litter. There was a progressively lower priming effect at higher temperatures, particularly in the sandy soil, that could be understood as substrates exhaustion in a restricted volume of influence around the added clover leaves. We provide parameterised Arrhenius and alternative modifying linear temperature functions together with decay rates at reference temperature, which can be used for predicting decay rates of SOC per se and of the labile pool of clover leaves. We also show the superiority of these functions compared to the use of Q10 as temperature factor. Further, we suggest approaches for modelling the priming effect caused by plant litter. Reference: Frøseth RB, Bleken MA(2015) Effect of low temperature and soil type on the decomposition rate of soil organic carbon and clover leaves, and related priming effect. Soil Biology and Biochemistry 80:156-166.
Decomposition of mixed malodorants in a wire-plate pulse corona reactor.

PubMed

Shi, Y; Ruan, J; Wang, X; Li, W; Tan, T

2005-09-01

Decomposition characteristics of two groups of representative mixed malodorants (1, ethanethiol + hydrogen sulfide; 2, ethanethiol + ammonia) in air were investigated employing a wire-plate pulse corona reactor. A new type of high-voltage pulse generator with a thyratron switch and a Blumlein pulse-forming network (BPFN) was used in our experiments. The experiments were conducted at a gas-flow rate of 13 m3/h. Important parameters, including peak voltage, chemical structures of malodorants, pulse frequency, and initial concentration, which influenced the removal efficiency, were investigated. The results showed that the mixed malodorants could be treated effectively by pulse corona. The removal efficiencies of 200 mg/m3 C2H5SH and 200 mg/m3 H2S for group 1 were 95.6% and 100%, respectively, which were almost equal to those of the two pollutants separately. The energy cost was about 65.1-81.4 J/L, which was 31.5-45.2% lower than for treating pollutants alone. The removal efficiencies of 105 mg/m3 C2HsSH and 40 mg/m3 NH3 for group 2 were 93.1% and almost 100%, and the energy cost was 65.1 J/L, 55.6% lower than that which was treated separately. In the case of two groups of mixed malodorants removal, NOx, 03, SO2, CO2, and CO were all observed. Moreover, some sulfur and white crystal ammonium nitrates were discovered adhering to the corona wires in the removal of groups 1 and 2, respectively. A dynamics model was developed to describe the relation of the removal efficiency with specific energy density and initial concentration. In the case of group 1 removal,the decomposition rate constants decreased as compared to the single treating. As for group 2 removal, the decomposition rate constants increased, especially for NH3. According to the results, the optimization design for the reactor and the matching of high pulse voltage source can be reckoned.
[Litter production and breakdown in swamps dominated by palms (Arecaceae) in northeastern Costa Rica].

PubMed

Myers, Ronald L

2013-09-01

In Raffia (Raphia taedigera) palm-swamps, it is frequent to observe high mounds at the base of the palm clumps. These mounds are formed by the accumulation of litter and organic matter, or might result from upturned roots of wind-thrown trees. The mounds serve as anchorage site for the palms, and could be important for the establishment of woody tree species in the swamp. The formation of these mounds might be explained by the unequal accumulation of organic matter in the wetland, or by differences in decomposition rates between Raffia litter versus the litter produced in adjacent mixed forests. To distinguish between these hypotheses, I compared the spatial distribution of litter in a R. taedigera swamp with the litter distribution on an adjacent slope forest, where litter distribution is expected to be homogeneous. In addition, I compared decomposition rates of major components of fine litter in three different environments: two wetlands dominated by palms (R. taedigera and Manicaria saccifera) and a slope forest that experiences lower inundation effects. On the palm swamp, noticeable concentration of litter was observed near the bases of clumps of palm as opposed to the swamp floor. In the adjacent slope forest, the magnitude of the differences in the distribution of litter is small and there is no accumulation at the base of emergent trees. It was also found that litter production increases during heavy rains and storms that follow dry periods. The swamp environment, independent of the litter, showed significantly lower decomposition rates than the surrounding forest slope. Furthermore, R. taedigera litter decomposes as fast as the slope forest litter. Overall, these results suggest that resistance to decomposition is not a major factor in the formation of mounds at the bases of R. taedigera clumps. Instead, litter accumulation contributes to the formation of the mounds that rise above the surface of the swamp.
Enhanced simulations of CH4 and CO2 production in permafrost-affected soils address soil moisture controls on anaerobic decomposition

NASA Astrophysics Data System (ADS)

Graham, D. E.; Zheng, J.; Moon, J. W.; Painter, S. L.; Thornton, P. E.; Gu, B.; Wullschleger, S. D.

2017-12-01

Rapid warming of Arctic ecosystems exposes soil organic carbon (SOC) to accelerated microbial decomposition, leading to increased emissions of carbon dioxide (CO2) and methane (CH4) that have a positive feedback on global warming. The magnitude, timing, and form of carbon release will depend not only on changes in temperature, but also on biogeochemical and hydrological properties of soils. In this synthesis study, we assessed the decomposability of thawed organic carbon from active layer soils and permafrost from the Barrow Environmental Observatory across different microtopographic positions under anoxic conditions. The main objectives of this study were to (i) examine environmental conditions and soil properties that control anaerobic carbon decomposition and carbon release (as both CO2 and CH4); (ii) develop a common set of parameters to simulate anaerobic CO2 and CH4 production; and (iii) evaluate uncertainties generated from representations of pH and temperature effects in the current model framework. A newly developed anaerobic carbon decomposition framework simulated incubation experiment results across a range of soil water contents. Anaerobic CO2 and CH4 production have different temperature and pH sensitivities, which are not well represented in current biogeochemical models. Distinct dynamics of CH4 production at -2° C suggest methanogen biomass and growth rate limit activity in these near-frozen soils, compared to warmer temperatures. Anaerobic CO2 production is well constrained by the model using data-informed labile carbon pool and fermentation rate initialization to accurately simulate its temperature sensitivity. On the other hand, CH4 production is controlled by water content, methanogenesis biomass, and the presence of alternative electron acceptors, producing a high temperature sensitivity with large uncertainties for methanogenesis. This set of environmental constraints to methanogenesis is likely to undergo drastic changes due to permafrost thawing, and extrapolation of methanogenesis rates into a future warmer climate remains challenging.
Early diagenesis of mangrove leaves in a tropical estuary: Bulk chemical characterization using solid-state 13C NMR and elemental analyses

NASA Astrophysics Data System (ADS)

Benner, Ronald; Hatcher, Patrick G.; Hedges, John I.

1990-07-01

Changes in the chemical composition of mangrove ( Rhizophora mangle) leaves during decomposition in tropical estuarine waters were characterized using solid-state 13C nuclear magnetic resonance (NMR) and elemental (CHNO) analysis. Carbohydrates were the most abundant components of the leaves accounting for about 50 wt% of senescent tissues. Tannins were estimated to account for about 20 wt% of leaf tissues, and lipid components, cutin, and possibly other aliphatic biopolymers in leaf cuticles accounted for about 15 wt%. Carbohydrates were generally less resistant to decomposition than the other constituents and decreased in relative concentration during decomposition. Tannins were of intermediate resistance to decomposition and remained in fairly constant proportion during decomposition. Paraffinic components were very resistant to decomposition and increased in relative concentration as decomposition progressed. Lignin was a minor component of all leaf tissues. Standard methods for the colorimetric determination of tannins (Folin-Dennis reagent) and the gravimetric determination of lignin (Klason lignin) were highly inaccurate when applied to mangrove leaves. The N content of the leaves was particularly dynamic with values ranging from 1.27 wt% in green leaves to 0.65 wt% in senescent yellow leaves attached to trees. During decomposition in the water the N content initially decreased to 0.51 wt% due to leaching, but values steadily increased thereafter to 1.07 wt% in the most degraded leaf samples. The absolute mass of N in the leaves increased during decomposition indicating that N immobilization was occurring as decomposition progressed.
Early diagenesis of mangrove leaves in a tropical estuary: Bulk chemical characterization using solid-state 13C NMR and elemental analyses

USGS Publications Warehouse

Benner, R.; Hatcher, P.G.; Hedges, J.I.

1990-01-01

Changes in the chemical composition of mangrove (Rhizophora mangle) leaves during decomposition in tropical estuarine waters were characterized using solid-state 13C nuclear magnetic resonance (NMR) and elemental (CHNO) analysis. Carbohydrates were the most abundant components of the leaves accounting for about 50 wt% of senescent tissues. Tannins were estimated to account for about 20 wt% of leaf tissues, and lipid components, cutin, and possibly other aliphatic biopolymers in leaf cuticles accounted for about 15 wt%. Carbohydrates were generally less resistant to decomposition than the other constituents and decreased in relative concentration during decomposition. Tannins were of intermediate resistance to decomposition and remained in fairly constant proportion during decomposition. Paraffinic components were very resistant to decomposition and increased in relative concentration as decomposition progressed. Lignin was a minor component of all leaf tissues. Standard methods for the colorimetric determination of tannins (Folin-Dennis reagent) and the gravimetric determination of lignin (Klason lignin) were highly inaccurate when applied to mangrove leaves. The N content of the leaves was particularly dynamic with values ranging from 1.27 wt% in green leaves to 0.65 wt% in senescent yellow leaves attached to trees. During decomposition in the water the N content initially decreased to 0.51 wt% due to leaching, but values steadily increased thereafter to 1.07 wt% in the most degraded leaf samples. The absolute mass of N in the leaves increased during decomposition indicating that N immobilization was occurring as decomposition progressed. ?? 1990.
Fire and nutrient cycling in shortgrass steppe of the southern Great Plains, USA

Treesearch

P.L. Ford; C.S. White

2005-01-01

Fire in semi-arid grasslands releases nutrients bound up in organic matter and accelerates the rate of decomposition in the soil. This research experimentally tested effects of season and frequency of fire on nutrient cycling dynamics in shortgrass steppe. The objective was to identify if fire treatments have the ability to increase potential grassland productivity...
Long-term sensitivity of soil carbon turnover to warming.

PubMed

Knorr, W; Prentice, I C; House, J I; Holland, E A

2005-01-20

The sensitivity of soil carbon to warming is a major uncertainty in projections of carbon dioxide concentration and climate. Experimental studies overwhelmingly indicate increased soil organic carbon (SOC) decomposition at higher temperatures, resulting in increased carbon dioxide emissions from soils. However, recent findings have been cited as evidence against increased soil carbon emissions in a warmer world. In soil warming experiments, the initially increased carbon dioxide efflux returns to pre-warming rates within one to three years, and apparent carbon pool turnover times are insensitive to temperature. It has already been suggested that the apparent lack of temperature dependence could be an artefact due to neglecting the extreme heterogeneity of soil carbon, but no explicit model has yet been presented that can reconcile all the above findings. Here we present a simple three-pool model that partitions SOC into components with different intrinsic turnover rates. Using this model, we show that the results of all the soil-warming experiments are compatible with long-term temperature sensitivity of SOC turnover: they can be explained by rapid depletion of labile SOC combined with the negligible response of non-labile SOC on experimental timescales. Furthermore, we present evidence that non-labile SOC is more sensitive to temperature than labile SOC, implying that the long-term positive feedback of soil decomposition in a warming world may be even stronger than predicted by global models.
Rapid destruction of the rhodamine B using TiO2 photocatalyst in the liquid phase plasma

PubMed Central

2013-01-01

Background Rhodamine B (RhB) is widely used as a colorant in textiles and food stuffs, and is also a well-known water tracer fluorescent. It is harmful to human beings and animals, and causes irritation of the skin, eyes and respiratory tract. The carcinogenicity, reproductive and developmental toxicity, neurotoxicity and chronic toxicity toward humans and animals have been experimentally proven. RhB cannot be effectively removed by biological treatment due to the slow kinetics. Therefore, RhB is chosen as a model pollutant for liquid phase plasma (LPP) treatment in the present investigation. Results This paper presents experimental results for the bleaching of RhB from aqueous solutions in the presence of TiO2 photocatalyst with LPP system. Properties of generated plasma were investigated by optical emission spectroscopy methods. The results of electrical-discharge degradation of RhB showed that the decomposition rate increased with the applied voltage, pulse width, and frequency. The oxygen gas addition to reactant solution increases the degradation rate by active oxygen species. The RhB decomposition rate was shown to increase with the TiO2 particle dosage. Conclusion This work presents the conclusions on the photocatalytic oxidation of RhB, as a function of plasma conditions, oxygen gas bubbling as well as TiO2 particle dosage. We knew that using the liquid phase plasma system with TiO2 photocatalyst at high speed we could remove the organic matter in the water. PMID:24041151
Controllable pneumatic generator based on the catalytic decomposition of hydrogen peroxide

NASA Astrophysics Data System (ADS)

Kim, Kyung-Rok; Kim, Kyung-Soo; Kim, Soohyun

2014-07-01

This paper presents a novel compact and controllable pneumatic generator that uses hydrogen peroxide decomposition. A fuel micro-injector using a piston-pump mechanism is devised and tested to control the chemical decomposition rate. By controlling the injection rate, the feedback controller maintains the pressure of the gas reservoir at a desired pressure level. Thermodynamic analysis and experiments are performed to demonstrate the feasibility of the proposed pneumatic generator. Using a prototype of the pneumatic generator, it takes 6 s to reach 3.5 bars with a reservoir volume of 200 ml at the room temperature, which is sufficiently rapid and effective to maintain the repetitive lifting of a 1 kg mass.
Controllable pneumatic generator based on the catalytic decomposition of hydrogen peroxide.

PubMed

Kim, Kyung-Rok; Kim, Kyung-Soo; Kim, Soohyun

2014-07-01

This paper presents a novel compact and controllable pneumatic generator that uses hydrogen peroxide decomposition. A fuel micro-injector using a piston-pump mechanism is devised and tested to control the chemical decomposition rate. By controlling the injection rate, the feedback controller maintains the pressure of the gas reservoir at a desired pressure level. Thermodynamic analysis and experiments are performed to demonstrate the feasibility of the proposed pneumatic generator. Using a prototype of the pneumatic generator, it takes 6 s to reach 3.5 bars with a reservoir volume of 200 ml at the room temperature, which is sufficiently rapid and effective to maintain the repetitive lifting of a 1 kg mass.
Thermal Decomposition of Energetic Materials. 2. Deuterium Isotope Effects and Isotopic Scrambling in Condensed-Phase Decomposition of Octahydro-1, 3,5,7-Tetranitro-1,3,5,7-Tetrazocine

DTIC Science & Technology

1993-02-01

HMX , 1) and hexahydro- 1,3,5-trinitro-s-triazine decomposition of H MX show that the identity and rates of release ( RDX , 11) are energetic ingredients...quadruple scission pathway Reviews$ of the literature on RDX and HMX have discussed HMX -- 4H2C=N-NO2 (R2) the roles of unimolecular decomposition and...N-NO2 -- CH 2O + NO (R3) lavior otCyclotrimethylene-trinitraminr ( RDX ) and Cycloteiramethylene- tctranitramine ( HMX ). In Fundamentals of Solid
Structural, optical, electron paramagnetic, thermal and dielectric characterization of chalcopyrite.

PubMed

Prameena, B; Anbalagan, G; Gunasekaran, S; Ramkumaar, G R; Gowtham, B

2014-03-25

Chalcopyrite (CuFeS2) a variety of pyrite minerals was investigated through spectroscopic techniques and thermal analysis. The morphology and elemental analysis of the chalcopyrite have been done by high resolution SEM with EDAX. The lattice parameters were from the powder diffraction data (a=5.3003±0.0089 Å, c=10.3679±0.0289 Å; the volume of the unit cell=291.266 Å(3) with space group I42d (122)). The thermal decomposition behavior of chalcopyrite was studied by means of thermogravimetric analysis at three different heating rates 10, 15 and 20 °C/min. The values of effective activation energy (Ea), pre-exponential factor (ln A) for thermal decomposition have been measured at three different heating rates by employing Kissinger, Kim-Park and Flynn-Wall methods. Dielectric studies at different temperatures have also been carried out and it was found that both dielectric constant and dielectric loss decreases with the increase of frequency. Copyright © 2013 Elsevier B.V. All rights reserved.

Soil organic carbon dynamics across a nitrogen deposition gradient: application of the PnET-SOM model to northeastern forest ecosystems

NASA Astrophysics Data System (ADS)

Tonitto, C.; Goodale, C. L.; Ollinger, S. V.; Jenkins, J.

2009-12-01

Anthropogenic forcing of the C and N cycles has caused rapid change in atmospheric CO2 and N deposition, with complex and uncertain effects on forest C and N balance. We developed the PnET-SOM model to enhance the model description of carbon and nitrogen coupling. Here we applied PnET-SOM to study changes to ecosystem carbon storage across a nitrogen deposition gradient. We designed the PnET-SOM model to: 1) represent SOM structured around measurable SOM pools, 2) expand simulated soil horizon complexity beyond the 1-box approach to hydrology and SOM structure used in PnET-CN, 3) model humified and mineral associated SOM using parameters derived from C14 field studies, and 4) couple C and N cycles to allow N-limitation of decomposition and plant growth. We explicitly modeled labile, biochemically recalcitrant (humified SOM), and physically-chemically protected (mineral associated SOM) C pools. These SOM pools are modeled in distinct soil horizons including: a forest floor, a mixed organic horizon, an A horizon, and a B horizon. Slow turnover pools of the A and B horizon constitute a significant proportion of SOC; explicitly modeling a deeper soil profile is important for estimating ecosystem SOC storage. In the latest version of PnET-SOM, we described N mineralization-immobilization in the forest floor based on equations derived in the LIDET synthesis study. Validation of the PnET-SOM model was conducted using 1) long-term water flux and nitrate leaching data from the Hubbard Brook LTER, 2) CO2 respiration observations from the Harvard Forest LTER, and 3) C and N stock and flux observations from the Harvard Forest LTER. In this work, we applied the PnET-SOM model to study the effects of an N deposition gradient on SOC dynamics over a 300 year simulation. We represented the effects of N deposition on litter decomposition by varying the exponential decay parameters of the litter layer based on observations from the Harvard Forest N addition experiment. We derived the change in limit value across the N deposition gradient simulated by applying a polynomial fit to limit values observed in the Harvard Forest N addition experimental plots. In PnET-SOM, changes in SOC dynamics under varying N deposition rates are derived from 1) change in litter decomposition rate, which directly affects OM inputs into soil pools, and 2) altered N availability which limits decomposition of OM throughout the soil profile. In our model application, the coarse woody debris pool decreased with increasing N deposition, while the forest floor pools increased. Relative to SOC pools under current N deposition rates at the Harvard Forest (8 gN/m2), deposition at a rate of 20 gN/m2 over a 300 year simulation resulted in a 3.4% increase in the O horizon humified SOC pool, a 2.3% increase in the A horizon humified SOC pool, a 1.3% increase in the A horizon mineral associated SOC pool, and a 0.14% increase in the B horizon mineral associated SOC pool.
Oil shale combustor model developed by Greek researchers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Not Available

1986-09-01

Work carried out in the Department of Chemical Engineering at the University of Thessaloniki, Thessaloniki, Greece has resulted in a model for the combustion of retorted oil shale in a fluidized bed combustor. The model is generally applicable to any hot-solids retorting process, whereby raw oil shale is retorted by mixing with a hot solids stream (usually combusted spent shale), and then the residual carbon is burned off the spent shale in a fluidized bed. Based on their modelling work, the following conclusions were drawn by the researchers. (1) For the retorted particle size distribution selected (average particle diameter 1600more » microns) complete carbon conversion is feasible at high pressures (2.7 atmosphere) and over the entire temperature range studied (894 to 978 K). (2) Bubble size was found to have an important effect, especially at conditions where reaction rates are high (high temperature and pressure). (3) Carbonate decomposition increases with combustor temperature and residence time. Complete carbon conversion is feasible at high pressures (2.7 atmosphere) with less than 20 percent carbonate decomposition. (4) At the preferred combustor operating conditions (high pressure, low temperature) the main reaction is dolomite decomposition while calcite decomposition is negligible. (5) Recombination of CO/sub 2/ with MgO occurs at low temperatures, high pressures, and long particle residence times.« less
Gap locations influence the release of carbon, nitrogen and phosphorus in two shrub foliar litter in an alpine fir forest

PubMed Central

He, Wei; Wu, Fuzhong; Yang, Wanqin; Zhang, Danju; Xu, Zhenfeng; Tan, Bo; Zhao, Yeyi; Justine, Meta Francis

2016-01-01

Gap formation favors the growth of understory plants and affects the decomposition process of plant debris inside and outside of gaps. Little information is available regarding how bioelement release from shrub litter is affected by gap formation during critical periods. The release of carbon (C), nitrogen (N), and phosphorus (P) in the foliar litter of Fargesia nitida and Salix paraplesia in response to gap locations was determined in an alpine forest of the eastern Qinghai-Tibet Plateau via a 2-year litter decomposition experiment. The daily release rates of C, N, and P increased from the closed canopy to the gap centers during the two winters, the two later growing seasons and the entire 2 years, whereas this trend was reversed during the two early growing seasons. The pairwise ratios among C, N, and P converged as the litter decomposition proceeded. Compared with the closed canopy, the gap centers displayed higher C:P and N:P ratio but a lower C:N ratio as the decomposition proceeded. Alpine forest gaps accelerate the release of C, N, and P in decomposing shrub litter, implying that reduced snow cover resulting from vanishing gaps may inhibit the release of these elements in alpine forests. PMID:26906762
Effects of hydrology on short term plant decomposition and nutrient content in a re-created Everglades wetland

NASA Astrophysics Data System (ADS)

Serna, A.; Richards, J.; Scinto, L.

2012-12-01

The effect of water depth and flow on tissue nutrients and decomposition rates of marsh plant species, and soil chemistry in vegetated plots was measured in the Loxahatchee Impoundment Landscape Assessment (LILA) facility in Boynton Beach, Florida, USA. The LILA facility consists of replicated wetland macrocosms that mimic Everglades ridge-and-slough landscape features. The experiments were conducted in two macrocosms that each had three habitats at different water depths (ridge, shallow slough and deep slough) but differed in flow. Decomposition rates of three common Everglades species, Cladium jamaicense (sawgrass), Eleocharis cellulosa (spikerush), and Nymphaea odorata (white water lily), were measured using litter bags incubated during both a wet and dry condition. Litter bag losses were more pronounced under wet conditions, and decomposition rates were not affected by the hydrologic conditions in this experiment, but rather by litter nutrient content and species. Litter nutrient (TC, TN, TP) concentrations varied over time. Species rich in the limiting nutrient (P) in the ecosystem decomposed faster. Therefore, N. odorata decomposed faster than C. jamaicense and E. cellulosa, confirming the importance of P availability in controlling microbial processes in the Everglades. Planted species had no effect on soil nutrient content over the 3 yrs period of plant growth in these plots. Our results have contributed to defining potential flow targets for restoration in Florida's Everglades by showing that average water velocities of 0.5 cm s-1 may not be sufficient to drive ecosystem changes in decomposition rates for the native species and soil chemistry.
Optimized FPGA Implementation of Multi-Rate FIR Filters Through Thread Decomposition

NASA Technical Reports Server (NTRS)

Zheng, Jason Xin; Nguyen, Kayla; He, Yutao

2010-01-01

Multirate (decimation/interpolation) filters are among the essential signal processing components in spaceborne instruments where Finite Impulse Response (FIR) filters are often used to minimize nonlinear group delay and finite-precision effects. Cascaded (multi-stage) designs of Multi-Rate FIR (MRFIR) filters are further used for large rate change ratio, in order to lower the required throughput while simultaneously achieving comparable or better performance than single-stage designs. Traditional representation and implementation of MRFIR employ polyphase decomposition of the original filter structure, whose main purpose is to compute only the needed output at the lowest possible sampling rate. In this paper, an alternative representation and implementation technique, called TD-MRFIR (Thread Decomposition MRFIR), is presented. The basic idea is to decompose MRFIR into output computational threads, in contrast to a structural decomposition of the original filter as done in the polyphase decomposition. Each thread represents an instance of the finite convolution required to produce a single output of the MRFIR. The filter is thus viewed as a finite collection of concurrent threads. The technical details of TD-MRFIR will be explained, first showing its applicability to the implementation of downsampling, upsampling, and resampling FIR filters, and then describing a general strategy to optimally allocate the number of filter taps. A particular FPGA design of multi-stage TD-MRFIR for the L-band radar of NASA's SMAP (Soil Moisture Active Passive) instrument is demonstrated; and its implementation results in several targeted FPGA devices are summarized in terms of the functional (bit width, fixed-point error) and performance (time closure, resource usage, and power estimation) parameters.
Species associations overwhelm abiotic conditions to dictate the structure and function of wood-decay fungal communities.

PubMed

Maynard, Daniel S; Covey, Kristofer R; Crowther, Thomas W; Sokol, Noah W; Morrison, Eric W; Frey, Serita D; van Diepen, Linda T A; Bradford, Mark A

2018-04-01

Environmental conditions exert strong controls on the activity of saprotrophic microbes, yet abiotic factors often fail to adequately predict wood decomposition rates across broad spatial scales. Given that species interactions can have significant positive and negative effects on wood-decay fungal activity, one possibility is that biotic processes serve as the primary controls on community function, with abiotic controls emerging only after species associations are accounted for. Here we explore this hypothesis in a factorial field warming- and nitrogen-addition experiment by examining relationships among wood decomposition rates, fungal activity, and fungal community structure. We show that functional outcomes and community structure are largely unrelated to abiotic conditions, with microsite and plot-level abiotic variables explaining at most 19% of the total variability in decomposition and fungal activity, and 2% of the variability in richness and evenness. In contrast, taxonomic richness, evenness, and species associations (i.e., co-occurrence patterns) exhibited strong relationships with community function, accounting for 52% of the variation in decomposition rates and 73% in fungal activity. A greater proportion of positive vs. negative species associations in a community was linked to strong declines in decomposition rates and richness. Evenness emerged as a key mediator between richness and function, with highly even communities exhibiting a positive richness-function relationship and uneven communities exhibiting a negative or null response. These results suggest that community-assembly processes and species interactions are important controls on the function of wood-decay fungal communities, ultimately overwhelming substantial differences in abiotic conditions. © 2018 by the Ecological Society of America.
Process-based modeling of silicate mineral weathering responses to increasing atmospheric CO2 and climate change

NASA Astrophysics Data System (ADS)

Banwart, Steven A.; Berg, Astrid; Beerling, David J.

2009-12-01

A mathematical model describes silicate mineral weathering processes in modern soils located in the boreal coniferous region of northern Europe. The process model results demonstrate a stabilizing biological feedback mechanism between atmospheric CO2 levels and silicate weathering rates as is generally postulated for atmospheric evolution. The process model feedback response agrees within a factor of 2 of that calculated by a weathering feedback function of the type generally employed in global geochemical carbon cycle models of the Earth's Phanerozoic CO2 history. Sensitivity analysis of parameter values in the process model provides insight into the key mechanisms that influence the strength of the biological feedback to weathering. First, the process model accounts for the alkalinity released by weathering, whereby its acceleration stabilizes pH at values that are higher than expected. Although the process model yields faster weathering with increasing temperature, because of activation energy effects on mineral dissolution kinetics at warmer temperature, the mineral dissolution rate laws utilized in the process model also result in lower dissolution rates at higher pH values. Hence, as dissolution rates increase under warmer conditions, more alkalinity is released by the weathering reaction, helping maintain higher pH values thus stabilizing the weathering rate. Second, the process model yields a relatively low sensitivity of soil pH to increasing plant productivity. This is due to more rapid decomposition of dissolved organic carbon (DOC) under warmer conditions. Because DOC fluxes strongly influence the soil water proton balance and pH, this increased decomposition rate dampens the feedback between productivity and weathering. The process model is most sensitive to parameters reflecting soil structure; depth, porosity, and water content. This suggests that the role of biota to influence these characteristics of the weathering profile is as important, if not more important, than the role of biota to influence mineral dissolution rates through changes in soil water chemistry. This process-modeling approach to quantify the biological weathering feedback to atmospheric CO2 demonstrates the potential for a far more mechanistic description of weathering feedback in simulations of the global geochemical carbon cycle.
INVASIVE GRASS ALTERS LITTER DECOMPOSITION BY INFLUENCING MACRO-DETRITIVORES

EPA Science Inventory

Nitrogen fertilization experiments have produced results with inconsistent rates of plant litter decomposition, a phenomenon that may be explained if the influence of animal detritivores (macro-detritivores) on litter mass loss is greater than that of microbial decomposers whose ...
Biological decomposition efficiency in different woodland soils.

PubMed

Herlitzius, H

1983-03-01

The decomposition (meaning disappearance) of different leaf types and artificial leaves made from cellulose hydrate foil was studied in three forests - an alluvial forest (Ulmetum), a beech forest on limestone soil (Melico-Fagetum), and a spruce forest in soil overlying limestone bedrock.Fine, medium, and coarse mesh litter bags of special design were used to investigate the roles of abiotic factors, microorganisms, and meso- and macrofauna in effecting decomposition in the three habitats. Additionally, the experimental design was carefully arranged so as to provide information about the effects on decomposition processes of the duration of exposure and the date or moment of exposure. 1. Exposure of litter samples oor 12 months showed: a) Litter enclosed in fine mesh bags decomposed to some 40-44% of the initial amount placed in each of the three forests. Most of this decomposition can be attributed to abiotic factors and microoganisms. b) Litter placed in medium mesh litter bags reduced by ca. 60% in alluvial forest, ca. 50% in beech forest and ca. 44% in spruce forest. c) Litter enclosed in coarse mesh litter bags was reduced by 71% of the initial weights exposed in alluvial and beech forests; in the spruce forest decomposition was no greater than observed with fine and medium mesh litter bags. Clearly, in spruce forest the macrofauna has little or no part to play in effecting decomposition. 2. Sequential month by month exposure of hazel leaves and cellulose hydrate foil in coarse mesh litter bags in all three forests showed that one month of exposure led to only slight material losses, they did occur smallest between March and May, and largest between June and October/November. 3. Coarse mesh litter bags containing either hazel or artificial leaves of cellulose hydrate foil were exposed to natural decomposition processes in December 1977 and subsampled monthly over a period of one year, this series constituted the From-sequence of experiments. Each of the From-sequence samples removed was immediately replaced by a fresh litter bag which was left in place until December 1978, this series constituted the To-sequence of experiments. The results arising from the designated From- and To-sequences showed: a) During the course of one year hazel leaves decomposed completely in alluvial forest, almost completely in beech forest but to only 50% of the initial value in spruce forest. b) Duration of exposure and not the date of exposure is the major controlling influence on decomposition in alluvial forest, a characteristic reflected in the mirror-image courses of the From- and To-sequences curves with respect to the abscissa or time axis. Conversely the date of exposure and not the duration of exposure is the major controlling influence on decomposition in the spruce forest, a characteristic reflected in the mirror-image courses of the From-and To-sequences with respect to the ordinate or axis of percentage decomposition. c) Leaf powder amendment increased the decomposition rate of the hazel and cellulose hydrate leaves in the spruce forest but had no significant effect on their decomposition rate in alluvial and beech forests. It is concluded from this, and other evidence, that litter amendment by leaf fragments of phytophage frass in sites of low biological decomposition activity (eg. spruce) enhances decomposition processes. d) The time course of hazel leaf decomposition in both alluvial and beech forest is sigmoidal. Three s-phases are distinguished and correspond to the activity of microflora/microfauna, mesofauna/macrofauna, and then microflora/microfauna again. In general, the sigmoidal pattern of the curve can be considered valid for all decomposition processes occurring in terrestrial situations. It is contended that no decomposition (=disappearance) curve actually follows an e-type exponential function. A logarithmic linear regression can be constructed from the sigmoid curve data and although this facilitates inter-system comparisons it does not clearly express the dynamics of decomposition. 4. The course of the curve constructed from information about the standard deviations of means derived from the From- and To-sequence data does reflect the dynamics of litter decomposition. The three s-phases can be recognised and by comparing the actual From-sequence deviation curve with a mirror inversion representation of the To-sequence curve it is possible to determine whether decomposition is primarily controlled by the duration of exposure or the date of exposure. As is the case for hazel leaf decomposition in beech forest intermediate conditions can be readily recognised.
Modelling the buried human body environment in upland climes using three contrasting field sites.

PubMed

Wilson, Andrew S; Janaway, Robert C; Holland, Andrew D; Dodson, Hilary I; Baran, Eve; Pollard, A Mark; Tobin, Desmond J

2007-06-14

Despite an increasing literature on the decomposition of human remains, whether buried or exposed, it is important to recognise the role of specific microenvironments which can either trigger or delay the rate of decomposition. Recent casework in Northern England involving buried and partially buried human remains has demonstrated a need for a more detailed understanding of the effect of contrasting site conditions on cadaver decomposition and on the microenvironment created within the grave itself. Pigs (Sus scrofa) were used as body analogues in three inter-related taphonomy experiments to examine differential decomposition of buried human remains. They were buried at three contrasting field sites (pasture, moorland, and deciduous woodland) within a 15 km radius of the University of Bradford, West Yorkshire, UK. Changes to the buried body and the effect of these changes on hair and associated death-scene textile materials were monitored as was the microenvironment of the grave. At recovery, 6, 12 and 24 months post-burial, the extent of soft tissue decomposition was recorded and samples of fat and soil were collected for gas chromatography mass spectrometry (GCMS) analysis. The results of these studies demonstrated that (1) soil conditions at these three burial sites has a marked effect on the condition of the buried body but even within a single site variation can occur; (2) the process of soft tissue decomposition modifies the localised burial microenvironment in terms of microbiological load, pH, moisture and changes in redox status. These observations have widespread application for the investigation of clandestine burial and time since deposition, and in understanding changes within the burial microenvironment that may impact on biomaterials such as hair and other associated death scene materials.
Restoration of Tidal Flow to Impounded Salt Marsh Exerts Mixed Effect on Leaf Litter Decomposition

NASA Astrophysics Data System (ADS)

Henry, B. A.; Schade, J. D.; Foreman, K.

2015-12-01

Salt marsh impoundments (e.g. roads, levees) disconnect marshes from ocean tides, which impairs ecosystem services and often promotes invasive species. Numerous restoration projects now focus on removing impoundments. Leaf litter decomposition is a central process in salt marsh carbon and nutrient cycles, and this study investigated the extent to which marsh restoration alters litter decomposition rates. We considered three environmental factors that can potentially change during restoration: salinity, tidal regime, and dominant plant species. A one-month field experiment (Cape Cod, MA) measured decay of litter bags in impounded, restored, and natural marshes under ambient conditions. A two-week lab experiment measured litter decay in controlled incubations under experimental treatments for salinity (1ppt and 30 ppt), tidal regime (inundated and 12 hr wet-dry cycles), and plant species (native Spartina alterniflora and invasive Phragmites australis). S. alterniflora decomposed faster in situ than P. australis (14±1.0% mass loss versus 0.74±0.69%). Corroborating this difference in decomposition, S. alterniflora supported greater microbial respiration during lab incubation, measured as CO2 flux from leaf litter and biological oxygen demand of water containing leached organic matter (OM). However, nutrient analysis of plant tissue and leached OM show P. australis released more nitrogen than S. alterniflora. Low salinity treatments in both lab and field experiments decayed more rapidly than high salinity treatments, suggesting that salinity inhibited microbial activity. Manipulation of inundation regime did not affect decomposition. These findings suggest the reintroduction of tidal flow to an impounded salt marsh can have mixed effects; recolonization by the native cordgrass could supply labile OM to sediment and slow carbon sequestration, while an increase in salinity might inhibit decomposition and accelerate sequestration.
Quantifying the effect of plant growth on litter decomposition using a novel, triple-isotope label approach

NASA Astrophysics Data System (ADS)

Ernakovich, J. G.; Baldock, J.; Carter, T.; Davis, R. A.; Kalbitz, K.; Sanderman, J.; Farrell, M.

2017-12-01

Microbial degradation of plant detritus is now accepted as a major stabilizing process of organic matter in soils. Most of our understanding of the dynamics of decomposition come from laboratory litter decay studies in the absence of plants, despite the fact that litter decays in the presence of plants in many native and managed systems. There is growing evidence that living plants significantly impact the degradation and stabilization of litter carbon (C) due to changes in the chemical and physical nature of soils in the rhizosphere. For example, mechanistic studies have observed stimulatory effects of root exudates on litter decomposition, and greenhouse studies have shown that living plants accelerate detrital decay. Despite this, we lack a quantitative understanding of the contribution of living plants to litter decomposition and how interactions of these two sources of C build soil organic matter (SOM). We used a novel triple-isotope approach to determine the effect of living plants on litter decomposition and C cycling. In the first stage of the experiment, we grew a temperate grass commonly used for forage, Poa labillardieri, in a continuously-labelled atmosphere of 14CO2 fertilized with K15NO3, such that the grass biomass was uniformly labelled with 14C and 15N. In the second stage, we constructed litter decomposition mescososms with and without a living plant to test for the effect of a growing plant on litter decomposition. The 14C/15N litter was decomposed in a sandy clay loam while a temperate forage grass, Lolium perenne, grew in an atmosphere of enriched 13CO2. The fate of the litter-14C/15N and plant-13C was traced into soil mineral fractions and dissolved organic matter (DOM) over the course of nine weeks using four destructive harvests of the mesocosms. Our preliminary results suggest that living plants play a major role in the degradation of plant litter, as litter decomposition was greater, both in rate and absolute amount, for soil mesocosms with a growing plant. Our observations during the decomposition experiment suggests that plant roots physically disrupted litter to increase decomposition. Isotopic analyses are currently underway, and transformations of litter-14C will be presented. Refining our understanding of in situ litter decay will add to our growing knowledge of the C cycle.
Thermal Decomposition Behavior of Hydroxytyrosol (HT) in Nitrogen Atmosphere Based on TG-FTIR Methods.

PubMed

Tu, Jun-Ling; Yuan, Jiao-Jiao

2018-02-13

The thermal decomposition behavior of olive hydroxytyrosol (HT) was first studied using thermogravimetry (TG). Cracked chemical bond and evolved gas analysis during the thermal decomposition process of HT were also investigated using thermogravimetry coupled with infrared spectroscopy (TG-FTIR). Thermogravimetry-Differential thermogravimetry (TG-DTG) curves revealed that the thermal decomposition of HT began at 262.8 °C and ended at 409.7 °C with a main mass loss. It was demonstrated that a high heating rate (over 20 K·min -1 ) restrained the thermal decomposition of HT, resulting in an obvious thermal hysteresis. Furthermore, a thermal decomposition kinetics investigation of HT indicated that the non-isothermal decomposition mechanism was one-dimensional diffusion (D1), integral form g ( x ) = x ², and differential form f ( x ) = 1/(2 x ). The four combined approaches were employed to calculate the activation energy ( E = 128.50 kJ·mol -1 ) and Arrhenius preexponential factor (ln A = 24.39 min -1 ). In addition, a tentative mechanism of HT thermal decomposition was further developed. The results provide a theoretical reference for the potential thermal stability of HT.
Is it worth hyperaccumulating Ni on non-serpentine soils? Decomposition dynamics of mixed-species litters containing hyperaccumulated Ni across serpentine and non-serpentine environments.

PubMed

Adamidis, George C; Kazakou, Elena; Aloupi, Maria; Dimitrakopoulos, Panayiotis G

2016-06-01

Nickel (Ni)-hyperaccumulating species produce high-Ni litters and may potentially influence important ecosystem processes such as decomposition. Although litters resembling the natural community conditions are essential in order to predict decomposition dynamics, decomposition of mixed-species litters containing hyperaccumulated Ni has never been studied. This study aims to test the effect of different litter mixtures containing hyperaccumulated Ni on decomposition and Ni release across serpentine and non-serpentine soils. Three different litter mixtures were prepared based on the relative abundance of the dominant species in three serpentine soils in the island of Lesbos, Greece where the Ni-hyperaccumulator Alyssum lesbiacum is present. Each litter mixture decomposed on its original serpentine habitat and on an adjacent non-serpentine habitat, in order to investigate whether the decomposition rates differ across the contrasted soils. In order to make comparisons across litter mixtures and to investigate whether additive or non-additive patterns of mass loss occur, a control non-serpentine site was used. Mass loss and Ni release were measured after 90, 180 and 270 d of field exposure. The decomposition rates and Ni release had higher values on serpentine soils after all periods of field exposure. The recorded rapid release of hyperaccumulated Ni is positively related to the initial litter Ni concentration. No differences were found in the decomposition of the three different litter mixtures at the control non-serpentine site, while their patterns of mass loss were additive. Our results: (1) demonstrate the rapid decomposition of litters containing hyperaccumulated Ni on serpentine soils, indicating the presence of metal-tolerant decomposers; and (2) imply the selective decomposition of low-Ni parts of litters by the decomposers on non-serpentine soils. This study provides support for the elemental allelopathy hypothesis of hyperaccumulation, presenting the potential selective advantages acquired by metal-hyperaccumulating plants through litter decomposition on serpentine soils. © The Author 2016. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved. For Permissions, please email: journals.permissions@oup.com.
Demonstration of the Catalytic Decomposition of Hydrogen Peroxide

NASA Astrophysics Data System (ADS)

Conklin, Alfred R., Jr.; Kessinger, Angela

1996-09-01

Catalytic decomposition is demonstrated by placing hydrogen peroxide solutions in a one liter graduated cylinder and adding soap, food coloring, and potassium iodide. Released oxygen is trapped by the soap producing bubbles. The volume of bubbles is proportional to the concentration of hydrogen peroxide. Chloride and bromide do not cause decomposition. Increased reactant temperature increases the volume of bubbles formed.
Nanorods, nanospheres, nanocubes: Synthesis, characterization and catalytic activity of nanoferrites of Mn, Co, Ni, Part-89

DOE Office of Scientific and Technical Information (OSTI.GOV)

Singh, Supriya; Srivastava, Pratibha; Singh, Gurdip, E-mail: gsingh4us@yahoo.com

2013-02-15

Graphical abstract: Prepared nanoferrites were characterized by FE-SEM and bright field TEM micrographs. The catalytic effect of these nanoferrites was evaluated on the thermal decomposition of ammonium perchlorate using TG and TG–DSC techniques. The kinetics of thermal decomposition of AP was evaluated using isothermal TG data by model fitting as well as isoconversional method. Display Omitted Highlights: ► Synthesis of ferrite nanostructures (∼20.0 nm) by wet-chemical method under different synthetic conditions. ► Characterization using XRD, FE-SEM, EDS, TEM, HRTEM and SAED pattern. ► Catalytic activity of ferrite nanostructures on AP thermal decomposition by thermal techniques. ► Burning rate measurements ofmore » CSPs with ferrite nanostructures. ► Kinetics of thermal decomposition of AP + nanoferrites. -- Abstract: In this paper, the nanoferrites of Mn, Co and Ni were synthesized by wet chemical method and characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), energy dispersive, X-ray spectra (EDS), transmission electron microscopy (TEM) and high resolution transmission electron microscopy (HR-TEM). It is catalytic activity were investigated on the thermal decomposition of ammonium perchlorate (AP) and composite solid propellants (CSPs) using thermogravimetry (TG), TG coupled with differential scanning calorimetry (TG–DSC) and ignition delay measurements. Kinetics of thermal decomposition of AP + nanoferrites have also been investigated using isoconversional and model fitting approaches which have been applied to data for isothermal TG decomposition. The burning rate of CSPs was considerably enhanced by these nanoferrites. Addition of nanoferrites to AP led to shifting of the high temperature decomposition peak toward lower temperature. All these studies reveal that ferrite nanorods show the best catalytic activity superior to that of nanospheres and nanocubes.« less
Biochemical Control of Fungal Biomass and Enzyme Production During Native Hawaiian Litter Degradation

NASA Astrophysics Data System (ADS)

Amatangelo, K. L.; Cordova, T. P.; Vitousek, P. M.

2007-12-01

Microbial growth and enzyme production during decomposition is controlled by the availability of carbon substrates, essential elements, and the ratios of these (such as lignin:N). We manipulated carbon:nutrient stoichiometry during decomposition using a natural fertility gradient in Hawaii and litter of varying initial biochemistry. We collected freshly senesced litter of seven biochemically distinct species from three sites offering differing levels of N, P, cations, and 15N , but similar yearly rainfall and temperature patterns. Litter types were decomposed at both the sites they were collected, and at the other site(s) that species was found. Litter was collected at multiple time points, and after one year of decomposition, calculated K constants varied an order of magnitude, from 0.276 to 2.76. Decomposition rates varied significantly with both litter site of origin and deployment, except at the oldest, P-limited site, where litter site of origin was not significantly correlated with decomposition within species. As microbial exocellular enzymes provide the catalyst for the breakdown of organic molecules including phenols, cellulose, and cutin, we assayed polyphenol oxidase, cellobiohydrolase, cutinase, chitinase, and lignin peroxidase to evaluate the breakdown sequence of different litter types. To measure the fungal biomass accumulating during decomposition, we extracted (22E)-Ergosta-5,7,22-trien-3beta- ol (ergosterol) on a subset of samples. The production of particular exocellular enzymes on litter species responded distinctly to origin and decomposition sites: after six months, chitinase and cellobiohydrolase were significantly affected by origin site, whereas polyphenol oxidase activity was controlled by deployment site. We conclude that site characteristics can alter the interaction between litter carbon:nutrient ratios and decomposition rate, mediated through microbial biomass and enzyme production.
Effect of temperature and moisture on the mineralization and humification of leaf litter in a model incubation experiment

NASA Astrophysics Data System (ADS)

Larionova, A. A.; Maltseva, A. N.; Lopes de Gerenyu, V. O.; Kvitkina, A. K.; Bykhovets, S. S.; Zolotareva, B. N.; Kudeyarov, V. N.

2017-04-01

The mineralization and humification of leaf litter collected in a mixed forest of the Prioksko-Terrasny Reserve depending on temperature (2, 12, and 22°C) and moisture (15, 30, 70, 100, and 150% of water holding capacity ( WHC)) has been studied in long-term incubation experiments. Mineralization is the most sensitive to temperature changes at the early stage of decomposition; the Q 10 value at the beginning of the experiment (1.5-2.7) is higher than at the later decomposition stages (0.3-1.3). Carbon losses usually exceed nitrogen losses during decomposition. Intensive nitrogen losses are observed only at the high temperature and moisture of litter (22°C and 100% WHC). Humification determined from the accumulation of humic substances in the end of incubation decreases from 34 to 9% with increasing moisture and temperature. The degree of humification CHA/CFA is maximum (1.14) at 12°C and 15% WHC; therefore, these temperature and moisture conditions are considered optimal for humification. Humification calculated from the limit value of litter mineralization is almost independent of temperature, but it significantly decreases from 70 to 3% with increasing moisture. A possible reason for the difference between the humification values measured by two methods is the conservation of a significant part of hemicelluloses, cellulose, and lignin during the transformation of litter and the formation of a complex of humic substances with plant residues, where HSs fulfill a protectoral role and decrease the decomposition rate of plant biopolymers.
Temperature, oxygen, and vegetation controls on decomposition in a James Bay peatland

NASA Astrophysics Data System (ADS)

Philben, Michael; Holmquist, James; MacDonald, Glen; Duan, Dandan; Kaiser, Karl; Benner, Ronald

2015-06-01

The biochemical composition of a peat core from James Bay Lowland, Canada, was used to assess the extent of peat decomposition and diagenetic alteration. Our goal was to identify environmental controls on peat decomposition, particularly its sensitivity to naturally occurring changes in temperature, oxygen exposure time, and vegetation. All three varied substantially during the last 7000 years, providing a natural experiment for evaluating their effects on decomposition. The bottom 50 cm of the core formed during the Holocene Climatic Optimum (~7000-4000 years B.P.), when mean annual air temperature was likely 1-2°C warmer than present. A reconstruction of the water table level using testate amoebae indicated oxygen exposure time was highest in the subsequent upper portion of the core between 150 and 225 cm depth (from ~2560 to 4210 years B.P.) and the plant community shifted from mostly Sphagnum to vascular plant dominance. Several independent biochemical indices indicated that decomposition was greatest in this interval. Hydrolysable amino acid yields, hydroxyproline yields, and acid:aldehyde ratios of syringyl lignin phenols were higher, while hydrolysable neutral sugar yields and carbon:nitrogen ratios were lower in this zone of both vascular plant vegetation and elevated oxygen exposure time. Thus, peat formed during the Holocene Climatic Optimum did not appear to be more extensively decomposed than peat formed during subsequent cooler periods. Comparison with a core from the West Siberian Lowland, Russia, indicates that oxygen exposure time and vegetation are both important controls on decomposition, while temperature appears to be of secondary importance. The low apparent sensitivity of decomposition to temperature is consistent with recent observations of a positive correlation between peat accumulation rates and mean annual temperature, suggesting that contemporary warming could enhance peatland carbon sequestration, although this could be offset by an increasing contribution of vascular plants to the vegetation.
Early-stage changes in natural (13)C and (15)N abundance and nutrient dynamics during different litter decomposition.

PubMed

Gautam, Mukesh Kumar; Lee, Kwang-Sik; Song, Byeong-Yeol; Lee, Dongho; Bong, Yeon-Sik

2016-05-01

Decomposition, nutrient, and isotopic (δ(13)C and δ(15)N) dynamics during 1 year were studied for leaf and twig litters of Pinus densiflora, Castanea crenata, Erigeron annuus, and Miscanthus sinensis growing on a highly weathered soil with constrained nutrient supply using litterbags in a cool temperate region of South Korea. Decay constant (k/year) ranged from 0.58 to 1.29/year, and mass loss ranged from 22.36 to 58.43 % among litter types. The results demonstrate that mass loss and nutrient dynamics of decomposing litter were influenced by the seasonality of mineralization and immobilization processes. In general, most nutrients exhibited alternate phases of rapid mineralization followed by gradual immobilization, except K, which was released throughout the field incubation. At the end of study, among all the nutrients only N and P showed net immobilization. Mobility of different nutrients from decomposing litter as the percentage of initial litter nutrient concentration was in the order of K > Mg > Ca > N ≈ P. The δ(13)C (0.32-6.70 ‰) and δ(15)N (0.74-3.90 ‰) values of residual litters showed nonlinear increase and decrease, respectively compared to initial isotopic values during decomposition. Litter of different functional types and chemical quality converged toward a conservative nutrient use strategy through mechanisms of slow decomposition and slow nutrient mobilization. Our results indicate that litter quality and season, are the most important regulators of litter decomposition in these forests. The results revealed significant relationships between litter decomposition rates and N, C:N ratio and P, and seasonality (temperature). These results and the convergence of different litters towards conservative nutrient use in these nutrient constrained ecosystems imply optimization of litter management because litter removal can have cascading effects on litter decomposition and nutrient availability in these systems.

Toward a reaction rate model of condensed-phase RDX decomposition under high temperatures

NASA Astrophysics Data System (ADS)

Schweigert, Igor

2014-03-01

Shock ignition of energetic molecular solids is driven by microstructural heterogeneities, at which even moderate stresses can result in sufficiently high temperatures to initiate material decomposition and the release of the chemical energy. Mesoscale modeling of these ``hot spots'' requires a chemical reaction rate model that describes the energy release with a sub-microsecond resolution and under a wide range of temperatures. No such model is available even for well-studied energetic materials such as RDX. In this presentation, I will describe an ongoing effort to develop a reaction rate model of condensed-phase RDX decomposition under high temperatures using first-principles molecular dynamics, transition-state theory, and reaction network analysis. This work was supported by the Naval Research Laboratory, by the Office of Naval Research, and by the DOD High Performance Computing Modernization Program Software Application Institute for Multiscale Reactive Modeling of Insensitive Munitions.
Toward a reaction rate model of condensed-phase RDX decomposition under high temperatures

NASA Astrophysics Data System (ADS)

Schweigert, Igor

2015-06-01

Shock ignition of energetic molecular solids is driven by microstructural heterogeneities, at which even moderate stresses can result in sufficiently high temperatures to initiate material decomposition and chemical energy release. Mesoscale modeling of these ``hot spots'' requires a reaction rate model that describes the energy release with a sub-microsecond resolution and under a wide range of temperatures. No such model is available even for well-studied energetic materials such as RDX. In this presentation, I will describe an ongoing effort to develop a reaction rate model of condensed-phase RDX decomposition under high temperatures using first-principles molecular dynamics, transition-state theory, and reaction network analysis. This work was supported by the Naval Research Laboratory, by the Office of Naval Research, and by the DoD High Performance Computing Modernization Program Software Application Institute for Multiscale Reactive Modeling of Insensitive Munitions.
Microbial plant litter decomposition in aquatic and terrestrial boreal systems along a natural fertility gradient

NASA Astrophysics Data System (ADS)

Soares, A. Margarida P. M.; Kritzberg, Emma S.; Rousk, Johannes

2017-04-01

Plant litter decomposition is a global ecosystem process, with a crucial role in carbon and nutrient cycling. The majority of litter processing occurs in terrestrial systems, but an important fraction also takes place in inland waters. Among environmental factors, pH impacts the litter decomposition through its selective influence on microbial decomposers. Fungal communities are less affected by pH than bacteria, possibly owing to a wider pH tolerance by this group. On the other hand, bacterial pH optima are constrained to a narrower range of pH values. The microbial decomposition of litter is universally nutrient limited; but few comparisons exist between terrestrial and aquatic systems. We investigated the microbial colonisation and decomposition of plant litter along a fertility gradient, which varied in both pH and N availability in both soil and adjacent water. To do this we installed litterbags with birch (Betula pendula) in streams and corresponding soils in adjacent riparian areas in a boreal system, in Krycklan, Sweden. During the four months covering the ice-free growth season we monitored the successional dynamics of fungal (acetate incorporation into ergosterol) and bacterial growth (thymidine incorporation), microbial respiration in leaf litter, and quantitative and qualitative changes in litter over time. We observed that bacterial growth rates were initially higher in litter decomposing in streams than those in soils, but differences between terrestrial and aquatic bacterial production converged towards the end of the experiment. In litter bags installed in soils, bacterial growth was lower at sites with more acidic pH and lower N availability, while aquatic bacteria were relatively unaffected by the fertility level. Fungal growth rates were two-fold higher for litter decomposing in streams than in soils. In aquatic systems, fungal growth was initially lower in low fertility sites, but differences gradually disappeared over the time course. Fungal growth rates measured on litter-bags in soils were relatively stable over time, with unclear links to fertility. Microbial respiration rates were highest in litterbags buried in soils, and only initially negatively affected by pH. There was a large decrease in litter mass loss initially in aquatic systems. Subsequently the rates of loss stabilized to similar values to those in terrestrial systems, to finally be exceeded by the rates of loss in terrestrial systems. In conclusion, initial decomposition of litter appeared to be N-limited in aquatic systems, which was associated with a fungal dominance. In contrast, litter decomposition in terrestrial systems appeared to be lower in acidic sites, which coincided with lower growth rates of bacteria. Litter degradation was initially faster in aquatic systems, but overall mass-loss over the full time course was higher in terrestrial systems.
Tea polyphenols dominate the short-term tea (Camellia sinensis) leaf litter decomposition*

PubMed Central

Fan, Dong-mei; Fan, Kai; Yu, Cui-ping; Lu, Ya-ting; Wang, Xiao-chang

2017-01-01

Polyphenols are one of the most important secondary metabolites, and affect the decomposition of litter and soil organic matter. This study aims to monitor the mass loss rate of tea leaf litter and nutrient release pattern, and investigate the role of tea polyphenols played in this process. High-performance liquid chromatography (HPLC) and classical litter bag method were used to simulate the decomposition process of tea leaf litter and track the changes occurring in major polyphenols over eight months. The release patterns of nitrogen, potassium, calcium, and magnesium were also determined. The decomposition pattern of tea leaf litter could be described by a two-phase decomposition model, and the polyphenol/N ratio effectively regulated the degradation process. Most of the catechins decreased dramatically within two months; gallic acid (GA), catechin gallate (CG), and gallocatechin (GC) were faintly detected, while others were outside the detection limits by the end of the experiment. These results demonstrated that tea polyphenols transformed quickly and catechins had an effect on the individual conversion rate. The nutrient release pattern was different from other plants which might be due to the existence of tea polyphenols. PMID:28124839
Tea polyphenols dominate the short-term tea (Camellia sinensis) leaf litter decomposition.

PubMed

Fan, Dong-Mei; Fan, Kai; Yu, Cui-Ping; Lu, Ya-Ting; Wang, Xiao-Chang

Polyphenols are one of the most important secondary metabolites, and affect the decomposition of litter and soil organic matter. This study aims to monitor the mass loss rate of tea leaf litter and nutrient release pattern, and investigate the role of tea polyphenols played in this process. High-performance liquid chromatography (HPLC) and classical litter bag method were used to simulate the decomposition process of tea leaf litter and track the changes occurring in major polyphenols over eight months. The release patterns of nitrogen, potassium, calcium, and magnesium were also determined. The decomposition pattern of tea leaf litter could be described by a two-phase decomposition model, and the polyphenol/N ratio effectively regulated the degradation process. Most of the catechins decreased dramatically within two months; gallic acid (GA), catechin gallate (CG), and gallocatechin (GC) were faintly detected, while others were outside the detection limits by the end of the experiment. These results demonstrated that tea polyphenols transformed quickly and catechins had an effect on the individual conversion rate. The nutrient release pattern was different from other plants which might be due to the existence of tea polyphenols.
Tropospheric ozone effects on chemical composition and decomposition rate of Quercus ilex L. leaves.

PubMed

Baldantoni, Daniela; Fagnano, Massimo; Alfani, Anna

2011-02-01

We determined the effects of tropospheric ozone on the chemical composition of Quercus ilex L. leaves and their decomposition, with a view to assessing the influence of ozone on nutrient cycling and the sustainability of Mediterranean holm oak forests. Forming one of the most widespread thermophilous vegetation communities in the area, Q. ilex is a dominant and widespread evergreen oak in the Mediterranean, where concentrations of tropospheric ozone are particularly high. The dynamics of carbon, nitrogen, lignin and cellulose concentrations were monitored for six months during the decomposition of leaves from plants subjected to controlled ozone exposure in open-top chambers. Ozone-exposed leaves, compared to unexposed leaves, showed no significant differences in C, N, lignin and cellulose concentrations prior to the incubation in mesocosms. However, during decomposition, leaves from plants exposed to ozone lost C significantly more slowly and showed a higher C/N ratio than unexposed leaves. Ozone exposure significantly slowed down the decomposition rate, indicating a negative effect of tropospheric ozone on nutrient cycling, which may reduce long-term sustainability of the holm oak forest. Copyright Â© 2010 Elsevier B.V. All rights reserved.
Arbuscular mycorrhiza enhance the rate of litter decomposition while inhibiting soil microbial community development

PubMed Central

Gui, Heng; Hyde, Kevin; Xu, Jianchu; Mortimer, Peter

2017-01-01

Although there is a growing amount of evidence that arbuscular mycorrhizal fungi (AMF) influence the decomposition process, the extent of their involvement remains unclear. Therefore, given this knowledge gap, our aim was to test how AMF influence the soil decomposer communities. Dual compartment microcosms, where AMF (Glomus mosseae) were either allowed access (AM+) to or excluded (AM−) from forest soil compartments containing litterbags (leaf litter from Calophyllum polyanthum) were used. The experiment ran for six months, with destructive harvests at 0, 90, 120, 150, and 180 days. For each harvest we measured AMF colonization, soil nutrients, litter mass loss, and microbial biomass (using phospholipid fatty acid analysis (PLFA)). AMF significantly enhanced litter decomposition in the first 5 months, whilst delaying the development of total microbial biomass (represented by total PLFA) from T150 to T180. A significant decline in soil available N was observed through the course of the experiment for both treatments. This study shows that AMF have the capacity to interact with soil microbial communities and inhibit the development of fungal and bacterial groups in the soil at the later stage of the litter decomposition (180 days), whilst enhancing the rates of decomposition. PMID:28176855
Soil microbes shift C-degrading activity along an ambient and experimental nitrogen gradient

NASA Astrophysics Data System (ADS)

Moore, J.; Frey, S. D.

2017-12-01

The balance between soil carbon (C) accumulation and decomposition is determined in large part by the activity and biomass of soil microbes, and yet their sensitivity to global changes remains unresolved. Atmospheric nitrogen (N) deposition has increased 22% (for NH4+) in the last two decades despite initiation of the Clean Air Act. Nitrogen deposition alters ecosystem processes by changing nutrient availability and soil pH, creating physiologically stressful environments that select for stress tolerant microbes. The functional fungal community may switch from domination by species with traits associated with decomposition via oxidative enzymes to traits associated with stress tolerance if global changes push fungal physiological limits. We examined changes in soil microbial activity across seven sites representing a gradient of ambient atmospheric N deposition, and five of these sites also had long-term N addition experiments. We measured changes in abundance of decomposition genes and C mineralization rates as indicators of microbial activity. We expected microbes to be less active with high N deposition, thus decreasing C mineralization rates. We found that C mineralization rates declined with total N deposition (ambient plus experimental additions), and this decline was more sensitive to N deposition where it occurred naturally compared to experimental treatments. Carbon mineralization declined by 3% in experimentally fertilized soils compared to 10% in control soils for every 1 kg/ha/y increase in ambient N deposition. Thus, microbes exposed to ambient levels of N deposition (2 - 12 kg/ha/y) had a stronger response than those exposed to fertilized soils (20 - 50 kg/ha/y). Long-term experimental N-addition seems to have selected for a microbial community that is tolerant of high N deposition. In sum, we provide evidence that soil microbial activity responded to N deposition, and may shift over time to a community capable of tolerating environmental change.
Surfactant process for promoting gas hydrate formation and application of the same

DOEpatents

Rogers, Rudy E.; Zhong, Yu

2002-01-01

This invention relates to a method of storing gas using gas hydrates comprising forming gas hydrates in the presence of a water-surfactant solution that comprises water and surfactant. The addition of minor amounts of surfactant increases the gas hydrate formation rate, increases packing density of the solid hydrate mass and simplifies the formation-storage-decomposition process of gas hydrates. The minor amounts of surfactant also enhance the potential of gas hydrates for industrial storage applications.
Proceedings of International Pyrotechnics Seminar (4th), Held at Steamboat Village, Colorado, 22-26 July 1974

DTIC Science & Technology

1974-06-17

10-1 I1. Burning Rate Modifiers, D.R. Dillehay ............................. 11-1 12. Spectroscopic Analysis of Azide Decomposition Products for use...solid, and Pit that they ignite a short distance from the surface. Further- more, decomposition of sodium nitrate, which produces the gas to blow the...decreasing U the thermal conductivity of the basic binary. Class 2 compounds, con- sisting of nanganese oxides, catalyze the normal decomposition of
Thermogravimetric analysis and kinetic modeling of low-transition-temperature mixtures pretreated oil palm empty fruit bunch for possible maximum yield of pyrolysis oil.

PubMed

Yiin, Chung Loong; Yusup, Suzana; Quitain, Armando T; Uemura, Yoshimitsu; Sasaki, Mitsuru; Kida, Tetsuya

2018-05-01

The impacts of low-transition-temperature mixtures (LTTMs) pretreatment on thermal decomposition and kinetics of empty fruit bunch (EFB) were investigated by thermogravimetric analysis. EFB was pretreated with the LTTMs under different duration of pretreatment which enabled various degrees of alteration to their structure. The TG-DTG curves showed that LTTMs pretreatment on EFB shifted the temperature and rate of decomposition to higher values. The EFB pretreated with sucrose and choline chloride-based LTTMs had attained the highest mass loss of volatile matter (78.69% and 75.71%) after 18 h of pretreatment. For monosodium glutamate-based LTTMs, the 24 h pretreated EFB had achieved the maximum mass loss (76.1%). Based on the Coats-Redfern integral method, the LTTMs pretreatment led to an increase in activation energy of the thermal decomposition of EFB from 80.00 to 82.82-94.80 kJ/mol. The activation energy was mainly affected by the demineralization and alteration in cellulose crystallinity after LTTMs pretreatment. Copyright © 2018 Elsevier Ltd. All rights reserved.
Toluene decomposition performance and NOx by-product formation during a DBD-catalyst process.

PubMed

Guo, Yufang; Liao, Xiaobin; Fu, Mingli; Huang, Haibao; Ye, Daiqi

2015-02-01

Characteristics of toluene decomposition and formation of nitrogen oxide (NOx) by-products were investigated in a dielectric barrier discharge (DBD) reactor with/without catalyst at room temperature and atmospheric pressure. Four kinds of metal oxides, i.e., manganese oxide (MnOx), iron oxide (FeOx), cobalt oxide (CoOx) and copper oxide (CuO), supported on Al2O3/nickel foam, were used as catalysts. It was found that introducing catalysts could improve toluene removal efficiency, promote decomposition of by-product ozone and enhance CO2 selectivity. In addition, NOx was suppressed with the decrease of specific energy density (SED) and the increase of humidity, gas flow rate and toluene concentration, or catalyst introduction. Among the four kinds of catalysts, the CuO catalyst showed the best performance in NOx suppression. The MnOx catalyst exhibited the lowest concentration of O3 and highest CO2 selectivity but the highest concentration of NOx. A possible pathway for NOx production in DBD was discussed. The contributions of oxygen active species and hydroxyl radicals are dominant in NOx suppression. Copyright © 2014. Published by Elsevier B.V.
Direct vs. Microclimate-Driven Effects of Tree Species Diversity on Litter Decomposition in Young Subtropical Forest Stands.

PubMed

Seidelmann, Katrin N; Scherer-Lorenzen, Michael; Niklaus, Pascal A

2016-01-01

Effects of tree species diversity on decomposition can operate via a multitude of mechanism, including alterations of microclimate by the forest canopy. Studying such effects in natural settings is complicated by the fact that topography also affects microclimate and thus decomposition, so that effects of diversity are more difficult to isolate. Here, we quantified decomposition rates of standard litter in young subtropical forest stands, separating effects of canopy tree species richness and topography, and quantifying their direct and micro-climate-mediated components. Our litterbag study was carried out at two experimental sites of a biodiversity-ecosystem functioning field experiment in south-east China (BEF-China). The field sites display strong topographical heterogeneity and were planted with tree communities ranging from monocultures to mixtures of 24 native subtropical tree species. Litter bags filled with senescent leaves of three native tree species were placed from Nov. 2011 to Oct. 2012 on 134 plots along the tree species diversity gradient. Topographic features were measured for all and microclimate in a subset of plots. Stand species richness, topography and microclimate explained important fractions of the variations in litter decomposition rates, with diversity and topographic effects in part mediated by microclimatic changes. Tree stands were 2-3 years old, but nevertheless tree species diversity explained more variation (54.3%) in decomposition than topography (7.7%). Tree species richness slowed litter decomposition, an effect that slightly depended on litter species identity. A large part of the variance in decomposition was explained by tree species composition, with the presence of three tree species playing a significant role. Microclimate explained 31.4% of the variance in decomposition, and was related to lower soil moisture. Within this microclimate effect, species diversity (without composition) explained 8.9% and topography 34.4% of variance. Topography mainly affected diurnal temperature amplitudes by varying incident solar radiation.
Direct vs. Microclimate-Driven Effects of Tree Species Diversity on Litter Decomposition in Young Subtropical Forest Stands

PubMed Central

Seidelmann, Katrin N.; Scherer-Lorenzen, Michael; Niklaus, Pascal A.

2016-01-01

Effects of tree species diversity on decomposition can operate via a multitude of mechanism, including alterations of microclimate by the forest canopy. Studying such effects in natural settings is complicated by the fact that topography also affects microclimate and thus decomposition, so that effects of diversity are more difficult to isolate. Here, we quantified decomposition rates of standard litter in young subtropical forest stands, separating effects of canopy tree species richness and topography, and quantifying their direct and micro-climate-mediated components. Our litterbag study was carried out at two experimental sites of a biodiversity-ecosystem functioning field experiment in south-east China (BEF-China). The field sites display strong topographical heterogeneity and were planted with tree communities ranging from monocultures to mixtures of 24 native subtropical tree species. Litter bags filled with senescent leaves of three native tree species were placed from Nov. 2011 to Oct. 2012 on 134 plots along the tree species diversity gradient. Topographic features were measured for all and microclimate in a subset of plots. Stand species richness, topography and microclimate explained important fractions of the variations in litter decomposition rates, with diversity and topographic effects in part mediated by microclimatic changes. Tree stands were 2–3 years old, but nevertheless tree species diversity explained more variation (54.3%) in decomposition than topography (7.7%). Tree species richness slowed litter decomposition, an effect that slightly depended on litter species identity. A large part of the variance in decomposition was explained by tree species composition, with the presence of three tree species playing a significant role. Microclimate explained 31.4% of the variance in decomposition, and was related to lower soil moisture. Within this microclimate effect, species diversity (without composition) explained 8.9% and topography 34.4% of variance. Topography mainly affected diurnal temperature amplitudes by varying incident solar radiation. PMID:27490180
Physical Properties and Thermal Decomposition of Aqueous Solutions of 2-Amino-2-hydroxymethyl-1, 3-propanediol (AHPD)

NASA Astrophysics Data System (ADS)

Murshid, Ghulam; Shariff, Azmi Mohd; Lau, K. K.; Bustam, Mohammad Azmi; Ahmad, Faizan

2011-10-01

Physical properties such as density, viscosity, refractive index, surface tension, and thermal stability of 2-amino-2-hydroxymethyl-1,3-propanediol (AHPD) were experimentally measured. All the experimental measurements were made over a wide range of temperatures from (298.15 to 333.15) K and AHPD concentrations of (1, 7, 13, 19, and 25) mass%. An overall decrease in all the measured physical properties was observed with increasing temperature. The experimental results are presented as a function of temperature and AHPD mass fraction. All the measured physical properties were correlated as a function of temperature. Thermal decomposition of pure and aqueous solutions of AHPD was investigated using a thermo-gravimetric analyzer (TGA) at a heating rate of 10 K · min-1.
Reactivity of fluoroalkanes in reactions of coordinated molecular decomposition

NASA Astrophysics Data System (ADS)

Pokidova, T. S.; Denisov, E. T.

2017-08-01

Experimental results on the coordinated molecular decomposition of RF fluoroalkanes to olefin and HF are analyzed using the model of intersecting parabolas (IPM). The kinetic parameters are calculated to allow estimates of the activation energy ( E) and rate constant ( k) of these reactions, based on enthalpy and IPM algorithms. Parameters E and k are found for the first time for eight RF decomposition reactions. The factors that affect activation energy E of RF decomposition (the enthalpy of the reaction, the electronegativity of the atoms of reaction centers, and the dipole-dipole interaction of polar groups) are determined. The values of E and k for reverse reactions of addition are estimated.
Theoretical study of gas hydrate decomposition kinetics: model predictions.

PubMed

Windmeier, Christoph; Oellrich, Lothar R

2013-11-27

In order to provide an estimate of intrinsic gas hydrate dissolution and dissociation kinetics, the Consecutive Desorption and Melting Model (CDM) was developed in a previous publication (Windmeier, C.; Oellrich, L. R. J. Phys. Chem. A 2013, 117, 10151-10161). In this work, an extensive summary of required model data is given. Obtained model predictions are discussed with respect to their temperature dependence as well as their significance for technically relevant areas of gas hydrate decomposition. As a result, an expression for determination of the intrinsic gas hydrate decomposition kinetics for various hydrate formers is given together with an estimate for the maximum possible rates of gas hydrate decomposition.
Exploring Patterns of Soil Organic Matter Decomposition with Students through the Global Decomposition Project (GDP) and the Interactive Model of Leaf Decomposition (IMOLD)

NASA Astrophysics Data System (ADS)

Steiner, S. M.; Wood, J. H.

2015-12-01

As decomposition rates are affected by climate change, understanding crucial soil interactions that affect plant growth and decomposition becomes a vital part of contributing to the students' knowledge base. The Global Decomposition Project (GDP) is designed to introduce and educate students about soil organic matter and decomposition through a standardized protocol for collecting, reporting, and sharing data. The Interactive Model of Leaf Decomposition (IMOLD) utilizes animations and modeling to learn about the carbon cycle, leaf anatomy, and the role of microbes in decomposition. Paired together, IMOLD teaches the background information and allows simulation of numerous scenarios, and the GDP is a data collection protocol that allows students to gather usable measurements of decomposition in the field. Our presentation will detail how the GDP protocol works, how to obtain or make the materials needed, and how results will be shared. We will also highlight learning objectives from the three animations of IMOLD, and demonstrate how students can experiment with different climates and litter types using the interactive model to explore a variety of decomposition scenarios. The GDP demonstrates how scientific methods can be extended to educate broader audiences, and data collected by students can provide new insight into global patterns of soil decomposition. Using IMOLD, students will gain a better understanding of carbon cycling in the context of litter decomposition, as well as learn to pose questions they can answer with an authentic computer model. Using the GDP protocols and IMOLD provide a pathway for scientists and educators to interact and reach meaningful education and research goals.
Alkaloids May Not be Responsible for Endophyte Associated Reductions in Tall Fescue Decomposition Rates

USDA-ARS?s Scientific Manuscript database

1. Fungal endophyte - grass symbioses can have dramatic ecological effects, altering individual plant physiology, plant and animal community structure and function, and ecosystem processes such as litter decomposition and nutrient cycling. 2. Within the tall fescue (Schedonorus arundinaceus) - funga...
Phlogopite Decomposition, Water, and Venus

NASA Technical Reports Server (NTRS)

Johnson, N. M.; Fegley, B., Jr.

2005-01-01

Venus is a hot and dry planet with a surface temperature of 660 to 740 K and 30 parts per million by volume (ppmv) water vapor in its lower atmosphere. In contrast Earth has an average surface temperature of 288 K and 1-4% water vapor in its troposphere. The hot and dry conditions on Venus led many to speculate that hydrous minerals on the surface of Venus would not be there today even though they might have formed in a potentially wetter past. Thermodynamic calculations predict that many hydrous minerals are unstable under current Venusian conditions. Thermodynamics predicts whether a particular mineral is stable or not, but we need experimental data on the decomposition rate of hydrous minerals to determine if they survive on Venus today. Previously, we determined the decomposition rate of the amphibole tremolite, and found that it could exist for billions of years at current surface conditions. Here, we present our initial results on the decomposition of phlogopite mica, another common hydrous mineral on Earth.

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