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Keith Paustian - One of the best experts on this subject based on the ideXlab platform.
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grassland management impacts on Soil Carbon stocks a new synthesis
Ecological Applications, 2017Co-Authors: Carlos Eduardo Pellegrino Cerri, Richard T. Conant, Brooke B Osborne, Keith PaustianAbstract:Grassland ecosystems cover a large portion of Earths’ surface and contain substantial amounts of Soil organic Carbon. Previous work has established that these Soil Carbon stocks are sensitive to management and land use changes: grazing, species composition, and mineral nutrient availability can lead to losses or gains of Soil Carbon. Because of the large annual Carbon fluxes into and out of grassland systems, there has been growing interest in how changes in management might shift the net balance of these flows, stemming losses from degrading grasslands or managing systems to increase Soil Carbon stocks (i.e., Carbon sequestration). A synthesis published in 2001 assembled data from hundreds of studies to document Soil Carbon responses to changes in management. Here we present a new synthesis that has integrated data from the hundreds of studies published after our previous work. These new data largely confirm our earlier conclusions: improved grazing management, fertilization, sowing legumes and improved grass species, irrigation, and conversion from cultivation all tend to lead to increased Soil C, at rates ranging from 0.105 to more than 1 Mg C·ha−1·yr−1. The new data include assessment of three new management practices: fire, silvopastoralism, and reclamation, although these studies are limited in number. The main area in which the new data are contrary to our previous synthesis is in conversion from native vegetation to grassland, where we find that across the studies the average rate of Soil Carbon stock change is low and not significant. The data in this synthesis confirm that improving grassland management practices and conversion from cropland to grassland improve Soil Carbon stocks.
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Soil: Carbon Sequestration in Agricultural Systems
Encyclopedia of Agriculture and Food Systems, 2014Co-Authors: Keith PaustianAbstract:Soil Carbon sequestration can contribute to greenhouse gas (GHG) mitigation by removing CO 2 from the atmosphere and at the same time improving Soil health and sustainability. This article outlines the basic principles and controlling mechanisms involved in Soil Carbon sequestration and reviews how improved agricultural practices impact Soil Carbon stocks, based on data from long-term field experiments and other sources. It concludes with a section outlining challenges and opportunities for implementation of GHG mitigation strategies involving Soil Carbon sequestration, summarizing key science and policy-related issues.
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Monitoring Soil Carbon will prepare growers for a Carbon trading system
California Agriculture, 2013Co-Authors: Emma C. Suddick, Keith Paustian, Moffatt K. Ngugi, Johan SixAbstract:California growers could reap financial benefits from the low-Carbon economy and cap-and-trade system envisioned by the state's AB 32 law, which seeks to lower greenhouse gas emissions statewide. Growers could gain Carbon credits by reducing greenhouse gas emissions and sequestering Carbon through reduced tillage and increased biomass residue incorporation. First, however, baseline stocks of Soil Carbon need to be assessed for various cropping systems and management practices. We designed and set up a pilot Soil Carbon and land-use monitoring network at several perennial cropping systems in Northern California. We compared Soil Carbon content in two vineyards and two orchards (walnut and almond), looking at conventional and conservation management practices, as well as in native grassland and oak woodland. We then calculated baseline estimates of the total Carbon in almond, wine grape and walnut acreages statewide. The organic walnut orchard had the highest total Soil Carbon, and no-till vineyards had 27% more Carbon in the surface Soil than tilled vineyards. We estimated wine grape vineyards are storing significantly more Soil Carbon per acre than almond and walnut orchards. The data can be used to provide accurate information about Soil Carbon stocks in perennial cropping systems for a future Carbon trading system.
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Partitioning Soil Carbon responses to warming: Model-derived guidance for data interpretation
Soil Biology and Biochemistry, 2010Co-Authors: Richard T. Conant, Michelle L. Haddix, Keith PaustianAbstract:Abstract Parallel incubation at different temperatures combined with 13 CO 2 efflux has been used to distinguish the temperature sensitivity of labile Soil Carbon (young Soil Carbon derived from newly-introduced vegetation) from that of resistant Soil Carbon (old, native vegetation-derived Soil Carbon). But we believe that this approach to assessing relative temperature sensitivities is confounded by differential rates of depletion of labile and resistant Soil Carbon at different temperatures. Here we employ a simple decomposition model to demonstrate potential pitfalls in interpreting 13 CO 2 efflux data that inevitably, and potentially erroneously, lead to the conclusion that decomposition of resistant Soil Carbon pools is more temperature sensitive than labile pools. We conclude by offering a new approach for interpreting these data that eliminates this potential bias.
Mark A. Bradford - One of the best experts on this subject based on the ideXlab platform.
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Temperature sensitivity of Soil Carbon
Ecosystem Consequences of Soil Warming, 2019Co-Authors: Jianwu Tang, Mark A. Bradford, Joanna C. Carey, Thomas W. Crowther, Megan B. Machmuller, Jacqueline E. Mohan, Katherine E. O. Todd-brownAbstract:Abstract Soils contain more than twice as much Carbon as either the atmosphere or terrestrial vegetation. Soil respiration is one of the largest terrestrial fluxes in Earth's Carbon-climate cycle. While Soil warming frequently enhances rates of Carbon efflux and respiration, the sensitivity of Soil Carbon stocks and Soil respiration to temperature is an emerging area of research. This chapter reviews work on the importance of temperature sensitivity of Soil Carbon, Soil respiration, Soil microbes, enzymes, mycorrhiza, and plant roots. The current models on Soil Carbon and Soil respiration are summarized in this chapter. We then recommend new research areas to further our understanding of Soil Carbon in response to warming across the globe.
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Managing uncertainty in Soil Carbon feedbacks to climate change
Nature Climate Change, 2016Co-Authors: Mark A. Bradford, William R. Wieder, Gordon B. Bonan, Noah Fierer, Peter A. Raymond, Thomas W. CrowtherAbstract:Climate change may accelerate decomposition of Soil Carbon leading to a reinforcing cycle of further warming and Soil Carbon loss. This Review considers the uncertainties and modelling challenges involved in projecting Soil responses to warming.
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Biofuel intercropping effects on Soil Carbon and microbial activity.
Ecological Applications, 2015Co-Authors: Michael S. Strickland, Zakiya H. Leggett, Eric B. Sucre, Mark A. BradfordAbstract:Biofuels will help meet rising demands for energy and, ideally, limit climate change associated with Carbon losses from the biosphere to atmosphere. Biofuel management must therefore maximize energy production and maintain ecosystem Carbon stocks. Increasingly, there is interest in intercropping biofuels with other crops, partly because biofuel production on arable land might reduce availability and increase the price of food. One intercropping approach involves growing biofuel grasses in forest plantations. Grasses differ from trees in both their organic inputs to Soils and microbial associations. These differences are associated with losses of Soil Carbon when grasses become abundant in forests. We investigated how intercropping switchgrass (Panicum virgalum), a major candidate for cellulosic biomass production, in loblolly pine (Pinus taeda) plantations affects Soil Carbon, nitrogen, and microbial dynamics. Our design involved four treatments: two pine management regimes where harvest residues (i.e., biomass) were left in place or removed, and two switchgrass regimes where the grass was grown with pine under the same two biomass scenarios (left or removed). Soil variables were measured in four 1-ha replicate plots in the first and second year following switchgrass planting. Under switchgrass intercropping, pools of mineralizable and particulate organic matter Carbon were 42% and 33% lower, respectively. These declines translated into a 21% decrease in total Soil Carbon in the upper 15 cm of the Soil profile, during early stand development. The switchgrass effect, however, was isolated to the interbed region where switchgrass is planted. In these regions, switchgrass-induced reductions in Soil Carbon pools with 29%, 43%, and 24% declines in mineralizable, particulate, and total Soil Carbon, respectively. Our results support the idea that grass inputs to forests can prime the activity of Soil organic Carbon degrading microbes, leading to net reductions in stocks of Soil Carbon. Active microbial biomass, however, is higher under switchgrass, and this microbial biomass is a dominant precursor of Soil Carbon formation. Future studies need to investigate Soil Carbon dynamics throughout the lifetime of intercropping rotations to evaluate whether increases in microbial biomass can offset initial declines in Soil Carbon, and hence, maintain ecosystem Carbon stocks.
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Soil Carbon response to warming dependent on microbial physiology
Nature Geoscience, 2010Co-Authors: Steven D Allison, Matthew D Wallenstein, Mark A. BradfordAbstract:The loss of Carbon dioxide from Soils increases initially under climate warming, but tends to decline to control levels within a few years. Simulations of the Soil-Carbon response to warming with a microbial-enzyme model show that a decline in both microbial biomass and the production of degrading enzymes can explain this attenuation response. Most ecosystem models predict that climate warming will stimulate microbial decomposition of Soil Carbon, producing a positive feedback to rising global temperatures1,2. Although field experiments document an initial increase in the loss of CO2 from Soils in response to warming, in line with these predictions, the Carbon dioxide loss from Soils tends to decline to control levels within a few years3,4,5. This attenuation response could result from changes in microbial physiological properties with increasing temperature, such as a decline in the fraction of assimilated Carbon that is allocated to growth, termed Carbon-use efficiency6. Here we explore these mechanisms using a microbial-enzyme model to simulate the responses of Soil Carbon to warming by 5 ∘C. We find that declines in microbial biomass and degradative enzymes can explain the observed attenuation of Soil-Carbon emissions in response to warming. Specifically, reduced Carbon-use efficiency limits the biomass of microbial decomposers and mitigates the loss of Soil Carbon. However, microbial adaptation or a change in microbial communities could lead to an upward adjustment of the efficiency of Carbon use, counteracting the decline in microbial biomass and accelerating Soil-Carbon loss. We conclude that the Soil-Carbon response to climate warming depends on the efficiency of Soil microbes in using Carbon.
Thomas W. Crowther - One of the best experts on this subject based on the ideXlab platform.
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Sensitivity of global Soil Carbon stocks to combined nutrient enrichment
Ecology Letters, 2019Co-Authors: Thomas W. Crowther, Charlotte E. Riggs, Eric M. Lind, Elizabeth T. Borer, Eric W. Seabloom, Sarah E. Hobbie, Jasper Wubs, Peter B. Adler, Jennifer Firn, Laureano A. GherardiAbstract:Soil stores approximately twice as much Carbon as the atmosphere and fluctuations in the size of the Soil Carbon pool directly influence climate conditions. We used the Nutrient Network global change experiment to examine how anthropogenic nutrient enrichment might influence grassland Soil Carbon storage at a global scale. In isolation, enrichment of nitrogen and phosphorous had minimal impacts on Soil Carbon storage. However, when these nutrients were added in combination with potassium and micronutrients, Soil Carbon stocks changed considerably, with an average increase of 0.04 KgCm−2 year−1 (standard deviation 0.18 KgCm−2 year−1). These effects did not correlate with changes in primary productivity, suggesting that Soil Carbon decomposition may have been restricted. Although nutrient enrichment caused Soil Carbon gains most dry, sandy regions, considerable absolute losses of Soil Carbon may occur in high‐latitude regions that store the majority of the world's Soil Carbon. These mechanistic insights into the sensitivity of grassland Carbon stocks to nutrient enrichment can facilitate biochemical modelling efforts to project Carbon cycling under future climate scenarios.
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Temperature sensitivity of Soil Carbon
Ecosystem Consequences of Soil Warming, 2019Co-Authors: Jianwu Tang, Mark A. Bradford, Joanna C. Carey, Thomas W. Crowther, Megan B. Machmuller, Jacqueline E. Mohan, Katherine E. O. Todd-brownAbstract:Abstract Soils contain more than twice as much Carbon as either the atmosphere or terrestrial vegetation. Soil respiration is one of the largest terrestrial fluxes in Earth's Carbon-climate cycle. While Soil warming frequently enhances rates of Carbon efflux and respiration, the sensitivity of Soil Carbon stocks and Soil respiration to temperature is an emerging area of research. This chapter reviews work on the importance of temperature sensitivity of Soil Carbon, Soil respiration, Soil microbes, enzymes, mycorrhiza, and plant roots. The current models on Soil Carbon and Soil respiration are summarized in this chapter. We then recommend new research areas to further our understanding of Soil Carbon in response to warming across the globe.
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quantifying global Soil Carbon losses in response to warming
Nature, 2016Co-Authors: Thomas W. Crowther, Joanna C. Carey, Megan B. Machmuller, William R. Wieder, Katherine E O Toddbrown, Clara W Rowe, Basten L Snoek, Shibo Fang, Guangsheng ZhouAbstract:The majority of the Earth's terrestrial Carbon is stored in the Soil. If anthropogenic warming stimulates the loss of this Carbon to the atmosphere, it could drive further planetary warming. Despite evidence that warming enhances Carbon fluxes to and from the Soil, the net global balance between these responses remains uncertain. Here we present a comprehensive analysis of warming-induced changes in Soil Carbon stocks by assembling data from 49 field experiments located across North America, Europe and Asia. We find that the effects of warming are contingent on the size of the initial Soil Carbon stock, with considerable losses occurring in high-latitude areas. By extrapolating this empirical relationship to the global scale, we provide estimates of Soil Carbon sensitivity to warming that may help to constrain Earth system model projections. Our empirical relationship suggests that global Soil Carbon stocks in the upper Soil horizons will fall by 30 ± 30 petagrams of Carbon to 203 ± 161 petagrams of Carbon under one degree of warming, depending on the rate at which the effects of warming are realized. Under the conservative assumption that the response of Soil Carbon to warming occurs within a year, a business-as-usual climate scenario would drive the loss of 55 ± 50 petagrams of Carbon from the upper Soil horizons by 2050. This value is around 12-17 per cent of the expected anthropogenic emissions over this period. Despite the considerable uncertainty in our estimates, the direction of the global Soil Carbon response is consistent across all scenarios. This provides strong empirical support for the idea that rising temperatures will stimulate the net loss of Soil Carbon to the atmosphere, driving a positive land Carbon-climate feedback that could accelerate climate change.
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Managing uncertainty in Soil Carbon feedbacks to climate change
Nature Climate Change, 2016Co-Authors: Mark A. Bradford, William R. Wieder, Gordon B. Bonan, Noah Fierer, Peter A. Raymond, Thomas W. CrowtherAbstract:Climate change may accelerate decomposition of Soil Carbon leading to a reinforcing cycle of further warming and Soil Carbon loss. This Review considers the uncertainties and modelling challenges involved in projecting Soil responses to warming.
William R. Wieder - One of the best experts on this subject based on the ideXlab platform.
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quantifying global Soil Carbon losses in response to warming
Nature, 2016Co-Authors: Thomas W. Crowther, Joanna C. Carey, Megan B. Machmuller, William R. Wieder, Katherine E O Toddbrown, Clara W Rowe, Basten L Snoek, Shibo Fang, Guangsheng ZhouAbstract:The majority of the Earth's terrestrial Carbon is stored in the Soil. If anthropogenic warming stimulates the loss of this Carbon to the atmosphere, it could drive further planetary warming. Despite evidence that warming enhances Carbon fluxes to and from the Soil, the net global balance between these responses remains uncertain. Here we present a comprehensive analysis of warming-induced changes in Soil Carbon stocks by assembling data from 49 field experiments located across North America, Europe and Asia. We find that the effects of warming are contingent on the size of the initial Soil Carbon stock, with considerable losses occurring in high-latitude areas. By extrapolating this empirical relationship to the global scale, we provide estimates of Soil Carbon sensitivity to warming that may help to constrain Earth system model projections. Our empirical relationship suggests that global Soil Carbon stocks in the upper Soil horizons will fall by 30 ± 30 petagrams of Carbon to 203 ± 161 petagrams of Carbon under one degree of warming, depending on the rate at which the effects of warming are realized. Under the conservative assumption that the response of Soil Carbon to warming occurs within a year, a business-as-usual climate scenario would drive the loss of 55 ± 50 petagrams of Carbon from the upper Soil horizons by 2050. This value is around 12-17 per cent of the expected anthropogenic emissions over this period. Despite the considerable uncertainty in our estimates, the direction of the global Soil Carbon response is consistent across all scenarios. This provides strong empirical support for the idea that rising temperatures will stimulate the net loss of Soil Carbon to the atmosphere, driving a positive land Carbon-climate feedback that could accelerate climate change.
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Managing uncertainty in Soil Carbon feedbacks to climate change
Nature Climate Change, 2016Co-Authors: Mark A. Bradford, William R. Wieder, Gordon B. Bonan, Noah Fierer, Peter A. Raymond, Thomas W. CrowtherAbstract:Climate change may accelerate decomposition of Soil Carbon leading to a reinforcing cycle of further warming and Soil Carbon loss. This Review considers the uncertainties and modelling challenges involved in projecting Soil responses to warming.
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Global Soil Carbon projections are improved by modelling microbial processes
Nature Climate Change, 2013Co-Authors: William R. Wieder, Gordon B. Bonan, Steven D AllisonAbstract:Earth system models (ESMs) generally have crude representations of the responses of Soil Carbon responses to changing climate. Now an ESM that explicitly represents microbial Soil Carbon cycling mechanisms is able to simulate Carbon pools that closely match observations. Projections from this model produce a much wider range of Soil Carbon responses to climate change over the twenty-first century than conventional ESMs.
Richard T. Conant - One of the best experts on this subject based on the ideXlab platform.
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grassland management impacts on Soil Carbon stocks a new synthesis
Ecological Applications, 2017Co-Authors: Carlos Eduardo Pellegrino Cerri, Richard T. Conant, Brooke B Osborne, Keith PaustianAbstract:Grassland ecosystems cover a large portion of Earths’ surface and contain substantial amounts of Soil organic Carbon. Previous work has established that these Soil Carbon stocks are sensitive to management and land use changes: grazing, species composition, and mineral nutrient availability can lead to losses or gains of Soil Carbon. Because of the large annual Carbon fluxes into and out of grassland systems, there has been growing interest in how changes in management might shift the net balance of these flows, stemming losses from degrading grasslands or managing systems to increase Soil Carbon stocks (i.e., Carbon sequestration). A synthesis published in 2001 assembled data from hundreds of studies to document Soil Carbon responses to changes in management. Here we present a new synthesis that has integrated data from the hundreds of studies published after our previous work. These new data largely confirm our earlier conclusions: improved grazing management, fertilization, sowing legumes and improved grass species, irrigation, and conversion from cultivation all tend to lead to increased Soil C, at rates ranging from 0.105 to more than 1 Mg C·ha−1·yr−1. The new data include assessment of three new management practices: fire, silvopastoralism, and reclamation, although these studies are limited in number. The main area in which the new data are contrary to our previous synthesis is in conversion from native vegetation to grassland, where we find that across the studies the average rate of Soil Carbon stock change is low and not significant. The data in this synthesis confirm that improving grassland management practices and conversion from cropland to grassland improve Soil Carbon stocks.
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Partitioning Soil Carbon responses to warming: Model-derived guidance for data interpretation
Soil Biology and Biochemistry, 2010Co-Authors: Richard T. Conant, Michelle L. Haddix, Keith PaustianAbstract:Abstract Parallel incubation at different temperatures combined with 13 CO 2 efflux has been used to distinguish the temperature sensitivity of labile Soil Carbon (young Soil Carbon derived from newly-introduced vegetation) from that of resistant Soil Carbon (old, native vegetation-derived Soil Carbon). But we believe that this approach to assessing relative temperature sensitivities is confounded by differential rates of depletion of labile and resistant Soil Carbon at different temperatures. Here we employ a simple decomposition model to demonstrate potential pitfalls in interpreting 13 CO 2 efflux data that inevitably, and potentially erroneously, lead to the conclusion that decomposition of resistant Soil Carbon pools is more temperature sensitive than labile pools. We conclude by offering a new approach for interpreting these data that eliminates this potential bias.
