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  • 11
    Language: English
    In: Plant and Soil, 2011, Vol.340(1), pp.7-24
    Description: Spatial prediction of soil organic matter is a global challenge and of particular importance for regions with intensive land use and where availability of soil data is limited. This study evaluated a Digital Soil Mapping (DSM) approach to model the spatial distribution of stocks of soil organic carbon (SOC), total carbon (C tot ), total nitrogen (N tot ) and total sulphur (S tot ) for a data-sparse, semi-arid catchment in Inner Mongolia, Northern China. Random Forest (RF) was used as a new modeling tool for soil properties and Classification and Regression Trees (CART) as an additional method for the analysis of variable importance. At 120 locations soil profiles to 1 m depth were analyzed for soil texture, SOC, C tot , N tot , S tot , bulk density (BD) and pH. On the basis of a digital elevation model, the catchment was divided into pixels of 90 m × 90 m and for each cell, predictor variables were determined: land use unit, Reference Soil Group (RSG), geological unit and 12 topography-related variables. Prediction maps showed that the highest amounts of SOC, C tot , N tot and S tot stocks are stored under marshland, steppes and mountain meadows. River-like structures of very high elemental stocks in valleys within the steppes are partly responsible for the high amounts of SOC for grasslands (81–84% of total catchment stocks). Analysis of variable importance showed that land use, RSG and geology are the most important variables influencing SOC storage. Prediction accuracy of the RF modeling and the generated maps was acceptable and explained variances of 42 to 62% and 66 to 75%, respectively. A decline of up to 70% in elemental stocks was calculated after conversion of steppe to arable land confirming the risk of rapid soil degradation if steppes are cultivated. Thus their suitability for agricultural use is limited.
    Keywords: Classification and Regression Trees (CART) ; Soil organic carbon (SOC) ; China ; Grassland
    ISSN: 0032-079X
    E-ISSN: 1573-5036
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  • 12
    Language: English
    In: Soil Biology and Biochemistry, 2010, Vol.42, pp.379-382
    Keywords: Environmental Sciences ; Agriculture ; Environmental Sciences ; Chemistry
    ISSN: 0038-0717
    E-ISSN: 1879-3428
    Source: Hyper Article en Ligne (CCSd)
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  • 13
    In: Nature, 2011, Vol.478(7367), p.49
    Description: Globally, soil organic matter (SOM) contains more than three times as much carbon as either the atmosphere or terrestrial vegetation. Yet it remains largely unknown why some SOM persists for millennia whereas other SOM decomposes readily—and this limits our ability to predict how soils will respond to climate change. Recent analytical and experimental advances have demonstrated that molecular structure alone does not control SOM stability: in fact, environmental and biological controls predominate. Here we propose ways to include this understanding in a new generation of experiments and soil carbon models, thereby improving predictions of the SOM response to global warming. Journal Article.
    Keywords: Environmental Sciences Geosciences;
    ISSN: 0028-0836
    E-ISSN: 14764687
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  • 14
    Language: English
    In: Science of the Total Environment, 01 July 2018, Vol.628-629, pp.906-918
    Description: We compared synchrotron-based C near-edge X-ray absorption fine structure (NEXAFS) and CPMAS C nuclear magnetic resonance (NMR) spectroscopy with respect to their precision and accuracy to quantify different organic carbon (OC) species in defined mixtures of soil organic matter source compounds. We also used both methods to quantify different OC species in organic surface horizons of a Histic Leptosol as well as in mineral topsoil and subsoil horizons of two soils with different parent material, stage of pedogenesis, and OC content (Cambisol: 15–30 OC mg g , Podzol: 0.9–7 OC mg g ). CPMAS C NMR spectroscopy was more accurate and precise (mean recovery of different C functional groups 96–103%) than C NEXAFS spectroscopy (mean recovery 92–113%). For organic surface and topsoil samples, NMR spectroscopy consistently yielded larger O-alkyl C percentages and smaller alkyl C percentages than C NEXAFS spectroscopy. For the Cambisol subsoil samples both methods performed well and showed similar C speciation results. NEXAFS spectroscopy yielded excellent spectra with a high signal-to-noise ratio also for OC-poor Podzol subsoil samples, whereas this was not the case for CPMAS C NMR spectroscopy even after sample treatment with HF. Our results confirm the analytical power of CPMAS C NMR spectroscopy for a reliable quantitative OC speciation in soils with 〉10 mg OC g . Moreover, they highlight the potential of synchrotron-based C NEXAFS spectroscopy as fast, non-invasive method to semi-quantify different C functional groups in soils with low C content (0.9–10 mg g ).
    Keywords: Direct Non-Invasive Soc Speciation ; Method Comparison ; Soil Organic Matter ; C Functional Groups ; Organic Surface Soil ; Mineral Soil ; Environmental Sciences ; Biology ; Public Health
    ISSN: 0048-9697
    E-ISSN: 1879-1026
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  • 15
    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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  • 16
    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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  • 17
    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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  • 18
    Language: English
    In: Soil Biology and Biochemistry, December 2014, Vol.79, pp.57-67
    Description: The study of interactions between minerals, organic matter (OM) and microorganisms is essential for the understanding of soil functions such as OM turnover. Here, we present an interdisciplinary approach using artificial soils to study the establishment of the microbial community and the formation of macro-aggregates as a function of the mineral composition by using artificial soils. The defined composition of a model system enables to directly relate the development of microbial communities and soil structure to the presence of specific constituents. Five different artificial soil compositions were produced with two types of clay minerals (illite, montmorillonite), metal oxides (ferrihydrite, boehmite) and charcoal incubated with sterile manure and a microbial community derived from a natural soil. We used the artificial soils to analyse the response of these model soil systems to additional sterile manure supply (after 562 days). The artificial soils were subjected to a prolonged incubation period of more than two years (842 days) in order to take temporally dynamic processes into account. In our model systems with varying mineralogy, we expected a changing microbial community composition and an effect on macro-aggregation after OM addition, as the input of fresh substrate will re-activate the artificial soils. The abundance and structure of 16S rRNA gene and internal transcribed spacer (ITS) fragments amplified from total community DNA were studied by quantitative real-time PCR (qPCR) and denaturing gradient gel electrophoresis (DGGE), respectively. The formation of macro-aggregates (〉2 mm), the total organic carbon (OC) and nitrogen (N) contents, the OC and N contents in particle size fractions and the CO respiration were determined. The second manure input resulted in higher CO respiration rates, 16S rRNA gene and ITS copy numbers, indicating a stronger response of the microbial community in the matured soil-like system. The type of clay minerals was identified as the most important factor determining the composition of the bacterial communities established. The additional OM and longer incubation time led to a re-formation of macro-aggregates which was significantly higher when montmorillonite was present. Thus, the type of clay mineral was decisive for both microbial community composition as well as macro-aggregation, whereas the addition of other components had a minor effect. Even though different bacterial communities were established depending on the artificial soil composition, the amount and quality of the OM did not show significant differences supporting the concept of functional redundancy.
    Keywords: Dgge ; Illite ; Montmorillonite ; Decomposition ; Respiration ; Soil Formation ; 16s Rrna Gene ; Its Fragment ; Agriculture ; Chemistry
    ISSN: 0038-0717
    E-ISSN: 1879-3428
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  • 19
    Language: English
    In: Soil Biology and Biochemistry, February 2014, Vol.69, pp.168-178
    Description: The stabilization of soil organic matter (SOM) is triggered by three main mechanisms: (i) low bioavailability due to aggregation, (ii) recalcitrance due to the chemical structure, and (iii) association of the SOM with mineral surfaces. In the present study we used particle size SOM fractions (sand, silt and clay), derived from the Ah soil horizon from a Norway spruce forest in Southern Germany, to study the effects of different stabilization mechanisms on the bioavailability of soil organic carbon (SOC) in a one year incubation experiment. The respired CO was hourly recorded, additionally CO was analysed 20 times and CO three times during the incubation experiment. To better differentiate between particulate OM (POM) and mineral associated OM (MIN), the incubated fractions and bulk soil were separated according to density (1.8 g cm ) after the incubation experiment. C-CPMAS NMR spectroscopy was used to study the chemical composition of the incubated samples. We demonstrate a clear increase in SOM bioavailability due to aggregate disruption, as the calculated theoretical CO evolution of the SOM fractions recombined by calculation was 43.8% higher in relation to the intact bulk soil. The incubated sand fraction, dominated by POM rich in O/N-alkyl C, showed a prolonged bioavailability of SOC moieties with mean residence times (MRT) of 78 years. Interestingly, the silt fraction, dominated by highly aliphatic, more recalcitrant POM, showed low mineralization rates and slow MRT's (192 years) close to values for the clay fraction (171 years), which contained a large amount of mineral-associated SOM. The recorded CO signatures showed a high depletion in C during the initial stage of the incubation, but an enrichment of the respired CO of up to 3.4‰ relative to the incubated SOM was observed over longer time periods (after 3 and 4 days for bulk soil and sand, respectively, and after 14 days for silt and clay). Therefore, we found no evidence for a C enrichment of SOM as driven by metabolic isotopic fractionation during microbial SOM mineralization, but an indication of a change in the isotopic composition of the C-source over time.
    Keywords: 13co2 ; 14co2 ; Laboratory Incubation ; Heterotrophic Respiration ; 13c-Cpmas NMR Spectroscopy ; Particle Size Fractionation ; Density Fractionation ; Mean Residence Time ; Microbial Biomass ; Agriculture ; Chemistry
    ISSN: 0038-0717
    E-ISSN: 1879-3428
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  • 20
    Language: English
    In: Plant and Soil, 2014, Vol.381(1), pp.95-110
    Description: Background and aims Differences in chemical composition of root compounds and root systems among tree species may affect organic matter (OM) distribution, source and composition in forest soils. The objective of this study was to elucidate the contribution of species specific cutin and suberin biomarkers as proxies for shoot- and root-derived organic carbon (OC) to soil OM at different depths with increasing distance to the stems of four different tree species. Methods The contribution of cutin- and suberin-derived lipids to OM in a Cutanic Alisol was analyzed with increasing soil depth and distance to the stems of Fagus sylvatica L., Picea abies (L.) Karst., Quercus robur L. and Pseudotsuga menziesii (Mirb.) Franco. Cutin and suberin monomers of plants and soils were analyzed by alkaline hydrolysis and subsequent gas chromatography-mass spectrometry. Results The amount and distribution of suberin-derived lipids in soil clearly reflected the specific root system of the different tree species. The amount of cutin-derived lipids decreased strongly with soil depth, indicating that the input of leaf/needle material is restricted to the topsoil. In contrast to the suberin-derived lipids, the spatial pattern of cutin monomer contribution to soil OM did not depend on tree species. Conclusions Our results document the importance of tree species as a main factor controlling the composition and distribution of OM in forest soils. They reveal the impact of tree species on root-derived OM distribution and the necessity to distinguish among different zones when studying soil OM storage in forests. Keywords Biomarkers * Cutin * Suberin * Depth profile * Subsoil
    Keywords: Biomarkers ; Cutin ; Suberin ; Depth profile ; Subsoil
    ISSN: 0032-079X
    E-ISSN: 1573-5036
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