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  • 1
    In: Global Change Biology, February 2017, Vol.23(2), pp.933-944
    Description: Accumulating evidence indicates that future rates of atmospheric N deposition have the potential to increase soil C storage by reducing the decay of plant litter and soil organic matter (). Although the microbial mechanism underlying this response is not well understood, a decline in decay could alter the amount, as well as biochemical composition of . Here, we used size‐density fractionation and solid‐state C‐ spectroscopy to explore the extent to which declines in microbial decay in a long‐term (. 20 yrs.) N deposition experiment have altered the biochemical composition of forest floor, bulk mineral soil, as well as free and occluded particulate organic matter. Significant amounts of organic matter have accumulated in occluded particulate organic matter (~20%; ); however, experimental N deposition had not altered the abundance of carboxyl, aryl, alkyl, or O/N‐alkyl C in forest floor, bulk mineral soil, or any soil fraction. These observations suggest that biochemically equivalent organic matter has accumulated in at a greater rate under experimental N deposition, relative to the ambient treatment. Although we do not understand the process by which experimental N deposition has fostered the occlusion of organic matter by mineral soil particles, our results highlight the importance of interactions among the products of microbial decay and the chemical and physical properties of silt and clay particles that occlude organic matter from microbial attack. Because can reside in soils for decades to centuries, organic matter accumulating under future rates of anthropogenic N deposition could remain in soil for long periods of time. If temperate forest soils in the Northern Hemisphere respond like those in our experiment, then unabated deposition of anthropogenic N from the atmosphere has the potential to foster greater soil C storage, especially in fine‐texture forest soils.
    Keywords: 13 C‐ Nmr ; Anthropogenic N Deposition ; Particulate Organic Matter ; Soil C Storage ; Soil Organic Matter
    ISSN: 1354-1013
    E-ISSN: 1365-2486
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  • 2
    In: Global Change Biology, October 2015, Vol.21(10), pp.3836-3845
    Description: Organic carbon () sequestration in degraded semi‐arid environments by improved soil management is assumed to contribute substantially to climate change mitigation. However, information about the soil organic carbon () sequestration potential in steppe soils and their current saturation status remains unknown. In this study, we estimated the storage capacity of semi‐arid grassland soils on the basis of remote, natural steppe fragments in northern China. Based on the maximum saturation of silt and clay particles 〈20 μm, sequestration potentials of degraded steppe soils (grazing land, arable land, eroded areas) were estimated. The analysis of natural grassland soils revealed a strong linear regression between the proportion of the fine fraction and its content, confirming the importance of silt and clay particles for stabilization in steppe soils. This relationship was similar to derived regressions in temperate and tropical soils but on a lower level, probably due to a lower C input and different clay mineralogy. In relation to the estimated storage capacity, degraded steppe soils showed a high saturation of 78–85% despite massive losses due to unsustainable land use. As a result, the potential of degraded grassland soils to sequester additional was generally low. This can be related to a relatively high contribution of labile , which is preferentially lost in the course of soil degradation. Moreover, wind erosion leads to substantial loss of silt and clay particles and consequently results in a direct loss of the ability to stabilize additional . Our findings indicate that the loss in semi‐arid environments induced by intensive land use is largely irreversible. Observed increases after improved land management mainly result in an accumulation of labile prone to land use/climate changes and therefore cannot be regarded as contribution to long‐term sequestration.
    Keywords: Climate Change ; Fine Fraction ; Soil Organic Carbon ; Soil Texture ; Steppe Soils
    ISSN: 1354-1013
    E-ISSN: 1365-2486
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  • 3
    In: Global Change Biology, April 2018, Vol.24(4), pp.1637-1650
    Description: Global change contributes to the retreat of glaciers at unprecedented rates. The deglaciation facilitates biogeochemical processes on glacial deposits with initiating soil formation as an important driver of evolving ecosystems. The underlying mechanisms of soil formation and the association of soil organic matter () with mineral particles remain unclear, although further insights are critical to understand carbon sequestration in soils. We investigated the microspatial arrangement of coatings at intact soil microaggregate structures during various stages of ecosystem development from 15 to 〉700 years after deglaciation in the proglacial environment of the Damma glacier (Switzerland). The functionally important clay‐sized fraction (2.2 g/cm). To quantify how extends across the surface of mineral particles (coverage) and whether coatings are distributed in fragmented or connected patterns (connectivity), we developed an image analysis protocol based on nanoscale secondary ion mass spectrometry (Nano). We classified and mineral areas depending on the O, C, and CN distributions. With increasing time after glacial retreat, the microspatial coverage and connectivity of increased rapidly. The rapid soil formation led to a succession of patchy distributed to more connected coatings on soil microaggregates. The maximum coverage of 55% at 〉700 years suggests direct evidence for sequestration being decoupled from the mineral surface, as it was not completely masked by and retained its functionality as an ion exchange site. The chemical composition of coatings showed a rapid change toward a higher :C ratio already at 75 years after glacial retreat, which was associated with microbial succession patterns reflecting high N assimilation. Our results demonstrate that rapid sequestration drives the microspatial succession of coatings in soils, a process that can stabilize for the long term. The pronounced retreat of glaciers due to climate change leads to the exposure of glacial deposits where initial soil formation starts along with the accrual of soil carbon. Soil organic matter (SOM) coatings at soil microaggregates were investigated in a chronosequence of soils 15 to 〉700 years after glacial retreat at the Damma glacier (Switzerland). Our results show a rapidly increasing coverage of mineral surfaces by SOM up to a maximum of 55% and a development from patchy distributed to more connected SOM coatings. The microspatial patterns of SOM coatings shaped the sequestration of SOM and partially decoupled it from the mineral particle surfaces, which retain their functionality as an ion exchange sites.
    Keywords: Biogeochemical Soil Interfaces ; Glacier Forefield ; Mineral‐Associated Organic Matter ; Nanoscale Secondary Ion Mass Spectrometry ; Organic Coating ; Organo‐Mineral Associations ; Soil Carbon Sequestration ; Spatial Complexity
    ISSN: 1354-1013
    E-ISSN: 1365-2486
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  • 4
    In: Global Change Biology, February 2014, Vol.20(2), pp.653-665
    Description: Sequestration of atmospheric carbon (C) in soils through improved management of forest and agricultural land is considered to have high potential for global mitigation. However, the potential of soils to sequester soil organic carbon () in a stable form, which is limited by the stabilization of against microbial mineralization, is largely unknown. In this study, we estimated the C sequestration potential of soils in southeast Germany by calculating the potential saturation of silt and clay particles according to Hassink [ (1997) 77] on the basis of 516 soil profiles. The determination of the current content of silt and clay fractions for major soil units and land uses allowed an estimation of the C saturation deficit corresponding to the long‐term C sequestration potential. The results showed that cropland soils have a low level of C saturation of around 50% and could store considerable amounts of additional . A relatively high C sequestration potential was also determined for grassland soils. In contrast, forest soils had a low C sequestration potential as they were almost C saturated. A high proportion of sites with a high degree of apparent oversaturation revealed that in acidic, coarse‐textured soils the relation to silt and clay is not suitable to estimate the stable C saturation. A strong correlation of the C saturation deficit with temperature and precipitation allowed a spatial estimation of the C sequestration potential for Bavaria. In total, about 395 Mt CO‐equivalents could theoretically be stored in A horizons of cultivated soils – four times the annual emission of greenhouse gases in Bavaria. Although achieving the entire estimated C storage capacity is unrealistic, improved management of cultivated land could contribute significantly to mitigation. Moreover, increasing stocks have additional benefits with respect to enhanced soil fertility and agricultural productivity.
    Keywords: Agricultural Management ; Climate Change ; Mitigation ; Soil Organic Carbon Stocks ; Soil Fractionation ; Stabilization Of Soil Organic Matter
    ISSN: 1354-1013
    E-ISSN: 1365-2486
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  • 5
    In: Global Change Biology, March 2018, Vol.24(3), pp.987-1000
    Description: Agricultural soils are widely recognized to be capable of carbon sequestration that contributes to mitigating emissions. To better understand soil organic carbon () stock dynamics and its driving and controlling factors corresponding with a period of rapid agronomic evolution from the 1980s to the 2010s in the North China Plain (), we collected data from two region‐wide soil sampling campaigns (in the 1980s and 2010s) and conducted an analysis of the controlling factors using the random forest model. Between the 1980s and 2010s, environmental (i.e. soil salinity/fertility) and societal (i.e. policy/techniques) factors both contributed to adoption of new management practices (i.e. chemical fertilizer application/mechanization). Results of our work indicate that stocks in the croplands increased significantly, which also closely related to soil total nitrogen changes. Samples collected near the surface (0–20 cm) and deeper (20–40 cm) both increased by an average of 9.4 and 5.1 Mg C ha, respectively, which are equivalent to increases of 73% and 56% compared with initial stocks in the 1980s. The annual carbon sequestration amount in surface soils reached 10.9 Tg C year, which contributed an estimated 43% of total carbon sequestration in all of China's cropland on just 27% of its area. Successful desalinization and the subsequent increases in carbon (C) inputs, induced by agricultural projects and policies intended to support crop production (i.e. reconstruction of low yield farmland, and agricultural subsidies), combined with improved cultivation practices (i.e. fertilization and straw return) since the early 1980s were the main drivers for the stock increase. This study suggests that rehabilitation of soils to reduce salinity and increase crop yields have also served as a pathway for substantial soil C sequestration. SOC stocks in the NCP croplands increased significantly; these changes were accompanied by changes in soil total nitrogen (TN). Annual carbon sequestration in surface soils reached 10.9 Tg C yr, which contributed an estimated 43% of total carbon sequestration in all of China’s cropland on just 27% of its area. Successful desalinization and the subsequent increases in carbon (C) inputs, induced by agricultural projects and policies (i.e. agricultural subsidies), combined with improved cultivation practices (i.e. fertilization, and straw return) since the early 1980s were the main drivers for this SOC stock increase.
    Keywords: Agricultural Policies ; Improved Cultivation ; N Stock Change ; Random Forest ; Soil Organic Carbon Stock Change
    ISSN: 1354-1013
    E-ISSN: 1365-2486
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  • 6
    In: Global Change Biology, July 2012, Vol.18(7), pp.2233-2245
    Description: Precise estimations of soil organic carbon () stocks are of decided importance for the detection of C sequestration or emission potential induced by land use changes. For Germany, a comprehensive, land use–specific data set has not yet been compiled. We evaluated a unique data set of 1460 soil profiles in southeast Germany in order to calculate representative stocks to a depth of 1 m for the main land use types. The results showed that grassland soils stored the highest amount of , with a median value of 11.8 kg m, whereas considerably lower stocks of 9.8 and 9.0 kg m were found for forest and cropland soils, respectively. However, the differences between extensively used land (grassland, forest) and cropland were much lower compared with results from other studies in central European countries. The depth distribution of showed that despite low concentrations in A horizons of cropland soils, their stocks were not considerably lower compared with other land uses. This was due to a deepening of the topsoil compared with grassland soils. Higher grassland stocks were caused by an accumulation of in the B horizon which was attributable to a high proportion of C‐rich Gleysols within grassland soils. This demonstrates the relevance of pedogenetic inventories instead of solely land use–based approaches. Our study indicated that cultivation‐induced depletion was probably often overestimated since most studies use fixed depth increments. Moreover, the application of modelled parameters in inventories is questioned because a calculation of stocks using different pedotransfer functions revealed considerably biased results. We recommend stocks be determined by horizon for the entire soil profile in order to estimate the impact of land use changes precisely and to evaluate C sequestration potentials more accurately.
    Keywords: Carbon Sequestration ; Land Use Change ; Pedotransfer Function ; Soil Organic Matter ; Topsoil Deepening
    ISSN: 1354-1013
    E-ISSN: 1365-2486
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  • 7
    In: Global Change Biology, November 2011, Vol.17(11), pp.3405-3417
    Description: Lowland rice paddy soils may accumulate significant amounts of organic matter. Our aim was to investigate the role of prolonged paddy management on the nitrogen () status of the soils, and to elucidate the contribution of bacteria and fungi to long‐term accumulation processes. For this purpose, we sampled a chronosequence of 0–2000 years of rice cropping with adjacent non‐paddy systems in the ay of angzhou, hina. The samples were analyzed for bulk density, total, mineral and microbial (), and amino sugars as markers for microbial residues. The results showed that during the first 100 years of land embankment, both paddy and non‐paddy soils accumulated at a rate of up to 61 and 77 kg ha per annum, reaching steady‐state conditions after 110–172 years, respectively. Final stocks in paddy fields exceeded those of the non‐paddies by a factor of 1.3. The contribution of amino sugars to total increased to a maximum of 34 g  kg  in both land‐use systems, highlighting a significant accumulation of in microbial residues of the surface soils. Correspondingly, the ratio of to microbial residue‐ decreased to a constant value. In the paddy subsoils, we found that bacterial residues particularly contributed to the pool of microbial residue‐. Nevertheless, the absolute contents of amino sugars in paddy subsoils decreased during the last 1700 years of the chronosequence. We conclude that under paddy cultivation, soil microorganisms may accumulate parts of this in their residues despite low overall availability. However, this accumulation is limited to initial stages of paddy soil development and restricted to the surface horizons, thus challenging its sustainability with future land‐use changes.
    Keywords: Amino Sugars ; Cultivation Chronosequence ; Microbial Biomass ; Nitrogen Accumulation ; Paddy Soil
    ISSN: 1354-1013
    E-ISSN: 1365-2486
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  • 8
    In: Global Change Biology, April 2013, Vol.19(4), pp.1107-1113
    Description: More than 50% of the world's population feeds on rice. Soils used for rice production are mostly managed under submerged conditions (paddy soils). This management, which favors carbon sequestration, potentially decouples surface from subsurface carbon cycling. The objective of this study was to elucidate the long‐term rates of carbon accrual in surface and subsurface soil horizons relative to those of soils under nonpaddy management. We assessed changes in total soil organic as well as of inorganic carbon stocks along a 2000‐year chronosequence of soils under paddy and adjacent nonpaddy management in the angtze delta, hina. The initial organic carbon accumulation phase lasts much longer and is more intensive than previously assumed, e.g., by the ntergovernmental anel on limate hange (). Paddy topsoils accumulated 170–178 kg organic carbon ha a in the first 300 years; subsoils lost 29–84 kg organic carbon ha a during this period of time. Subsoil carbon losses were largest during the first 50 years after land embankment and again large beyond 700 years of cultivation, due to inorganic carbonate weathering and the lack of organic carbon replenishment. Carbon losses in subsoils may therefore offset soil carbon gains or losses in the surface soils. We strongly recommend including subsoils into global carbon accounting schemes, particularly for paddy fields.
    Keywords: Carbon Sequestration ; Inorganic Carbon ; Land Use ; Organic Carbon ; Paddy ; Rice Cultivation ; Soils ; Subsoils
    ISSN: 1354-1013
    E-ISSN: 1365-2486
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