The Experts below are selected from a list of 99960 Experts worldwide ranked by ideXlab platform
Ingrid Kogelknabner - One of the best experts on this subject based on the ideXlab platform.
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aggregate stability and Physical Protection of soil organic carbon in semi arid steppe soils
European Journal of Soil Science, 2012Co-Authors: Martin Wiesmeier, Agnieszka Reszkowska, Markus Steffens, Angelika Kölbl, Carsten W Mueller, Rainer Horn, Stephan Peth, Ingrid KogelknabnerAbstract:Summary Spatial inaccessibility of soil organic carbon (SOC) for microbial decay within soil aggregates is an important stabilization mechanism. However, little is known about the stability of aggregates in semiarid grasslands and their sensitivity to intensive grazing. In this study, a combined approach using soil chemical and Physical analytical methods was applied to investigate the effect of grazing and grazing exclusion on the amount and stability of soil aggregates and the associated Physical Protection of SOC. Topsoils from continuously grazed (CG) and ungrazed sites where grazing was excluded from 1979 onwards (UG79) were sampled for two steppe types in Inner Mongolia, northern China. All samples were analysed for basic soil properties and separated into free and aggregate-occluded light fractions (fLF, oLF) and mineral-associated fractions. Tensile strength of soil aggregates was measured by crushing tests. Undisturbed as well as artificially compacted samples, where aggregates were destroyed mechanically by compression, were incubated and the mineralization of SOC was measured. For undisturbed samples, the cumulative release of CO2-C was greater for CG compared with UG79 for both steppe types. A considerably greater amount of oLF was found in UG79 than in CG soils, but the stabilities of 10–20-mm aggregates were less for ungrazed sites. Compacted samples showed only a slightly larger carbon release with CG but a considerably enhanced mineralization with UG79. We assume that the continuous trampling of grazing animals together with a smaller input of organic matter leads to the formation of mechanically compacted stable ‘clods’, which do not provide an effective Physical Protection for SOC in the grazed plots. In UG79 sites, a greater input of organic matter acting as binding agents in combination with an exclusion of animal trampling enhances the formation of soil aggregates. Thus, grazing exclusion promotes the Physical Protection of SOC by increasing soil aggregation and is hence a management option to enhance the C sequestration potential of degraded steppe soils.
Randall D. Jackson - One of the best experts on this subject based on the ideXlab platform.
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Separate drivers for microbial carbon mineralization and Physical Protection of carbon
Soil Biology and Biochemistry, 2019Co-Authors: Anna M. Cates, Michael J. Braus, Thea Whitman, Randall D. JacksonAbstract:Abstract While the effects of temperature and moisture on soil microbial activity are relatively well-understood, and it is well-recognized that microbial byproducts are a critical source of soil C, our understanding of how temperature and moisture affect Physical Protection of soil C is lacking. We performed a 6-month incubation of soil and plant litter under varying temperature and moisture. Using 13C-depleted plant litter, we used stable isotope partitioning to trace plant litter C into various aggregate fractions after 30, 50, and 60% of plant C had been respired. In addition, we evaluated microbial biomass C, enzyme activity and bacterial community composition using 16S rRNA genes. While warmer temperatures increased C mineralization rate and enzyme activity and decreased microbial biomass, soil aggregation was enhanced under drier conditions irrespective of temperature. Bacterial community composition shifted over time and with temperature and moisture, and a subset of the bacterial community was associated with the drier conditions that promoted aggregation. These results indicate that Physical Protection of C in aggregates is correlated to changes in moisture regime while microbial C mineralization is more responsive to temperature. Predictions of how management and climate will affect soil C storage should incorporate separate responses to temperature and moisture for aggregate and microbial C pools.
Martin Wiesmeier - One of the best experts on this subject based on the ideXlab platform.
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aggregate stability and Physical Protection of soil organic carbon in semi arid steppe soils
European Journal of Soil Science, 2012Co-Authors: Martin Wiesmeier, Agnieszka Reszkowska, Markus Steffens, Angelika Kölbl, Carsten W Mueller, Rainer Horn, Stephan Peth, Ingrid KogelknabnerAbstract:Summary Spatial inaccessibility of soil organic carbon (SOC) for microbial decay within soil aggregates is an important stabilization mechanism. However, little is known about the stability of aggregates in semiarid grasslands and their sensitivity to intensive grazing. In this study, a combined approach using soil chemical and Physical analytical methods was applied to investigate the effect of grazing and grazing exclusion on the amount and stability of soil aggregates and the associated Physical Protection of SOC. Topsoils from continuously grazed (CG) and ungrazed sites where grazing was excluded from 1979 onwards (UG79) were sampled for two steppe types in Inner Mongolia, northern China. All samples were analysed for basic soil properties and separated into free and aggregate-occluded light fractions (fLF, oLF) and mineral-associated fractions. Tensile strength of soil aggregates was measured by crushing tests. Undisturbed as well as artificially compacted samples, where aggregates were destroyed mechanically by compression, were incubated and the mineralization of SOC was measured. For undisturbed samples, the cumulative release of CO2-C was greater for CG compared with UG79 for both steppe types. A considerably greater amount of oLF was found in UG79 than in CG soils, but the stabilities of 10–20-mm aggregates were less for ungrazed sites. Compacted samples showed only a slightly larger carbon release with CG but a considerably enhanced mineralization with UG79. We assume that the continuous trampling of grazing animals together with a smaller input of organic matter leads to the formation of mechanically compacted stable ‘clods’, which do not provide an effective Physical Protection for SOC in the grazed plots. In UG79 sites, a greater input of organic matter acting as binding agents in combination with an exclusion of animal trampling enhances the formation of soil aggregates. Thus, grazing exclusion promotes the Physical Protection of SOC by increasing soil aggregation and is hence a management option to enhance the C sequestration potential of degraded steppe soils.
Claire Chenu - One of the best experts on this subject based on the ideXlab platform.
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Physical Protection of soil organic matter : a matter of life in soil pores
2015Co-Authors: Claire ChenuAbstract:Physical Protection of soil organic matter : a matter of life in soil pores. 20. ISTRO Conference
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Physical Protection of soil organic matter : scales and questions
2013Co-Authors: Claire ChenuAbstract:Organic matter is stabilized in soils for years to centuries or millennia because of its chemical recalcitrance, stabilization by interaction with the mineral matrix or Physical stabilization. Physical Protection or Physical stabilization of soil organic matter comes from the limited access that microbial decomposers have to organic substrates, water and oxygen in the complex three dimensional architecture of soils. Physical Protection is though to be a major process at temporal scales from decades to centuries. Much work has been performed on this process, usually based on the Physical fractionation of soil aggregates of different sizes and stabilities and of their associated organic matter. Its importance has been demonstrated in soils under various land uses. Here we focus on what we perceive as standing questions regarding this stabilization process: - What are the spatial scalesof Physical Protection? - Which approach should be preferred: the aggregate-based approach or a pore systembased approach? - What is the relative importance of Physical Protection and physico-chemical Protection? Physicochemical Protection results from the adsorption of organic matter to minerals. - How to model Physical Protection? To address these questions we will use results obtained on soils from long term experiments as well as from microcosms experiments.
Anna M. Cates - One of the best experts on this subject based on the ideXlab platform.
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Separate drivers for microbial carbon mineralization and Physical Protection of carbon
Soil Biology and Biochemistry, 2019Co-Authors: Anna M. Cates, Michael J. Braus, Thea Whitman, Randall D. JacksonAbstract:Abstract While the effects of temperature and moisture on soil microbial activity are relatively well-understood, and it is well-recognized that microbial byproducts are a critical source of soil C, our understanding of how temperature and moisture affect Physical Protection of soil C is lacking. We performed a 6-month incubation of soil and plant litter under varying temperature and moisture. Using 13C-depleted plant litter, we used stable isotope partitioning to trace plant litter C into various aggregate fractions after 30, 50, and 60% of plant C had been respired. In addition, we evaluated microbial biomass C, enzyme activity and bacterial community composition using 16S rRNA genes. While warmer temperatures increased C mineralization rate and enzyme activity and decreased microbial biomass, soil aggregation was enhanced under drier conditions irrespective of temperature. Bacterial community composition shifted over time and with temperature and moisture, and a subset of the bacterial community was associated with the drier conditions that promoted aggregation. These results indicate that Physical Protection of C in aggregates is correlated to changes in moisture regime while microbial C mineralization is more responsive to temperature. Predictions of how management and climate will affect soil C storage should incorporate separate responses to temperature and moisture for aggregate and microbial C pools.