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Characterization of soil organic matter fractions from grassland and cultivated soils via C content and δ13C signature

Authors

  • Frederik Accoe,

    Corresponding author
    1. Department of Applied Analytical and Physical Chemistry, Faculty of Agricultural and Applied Biological Sciences, Ghent University, Belgium
    2. Department of Soil Management and Soil Care, Faculty of Agricultural and Applied Biological Sciences, Ghent University, Belgium
    • Department of Applied Analytical and Physical Chemistry, Faculty of Agricultural and Applied Biological Sciences, Ghent University, Coupure Links 653, 9000 Ghent, Belgium.
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  • Pascal Boeckx,

    1. Department of Applied Analytical and Physical Chemistry, Faculty of Agricultural and Applied Biological Sciences, Ghent University, Belgium
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  • Oswald Van Cleemput,

    1. Department of Applied Analytical and Physical Chemistry, Faculty of Agricultural and Applied Biological Sciences, Ghent University, Belgium
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  • Georges Hofman,

    1. Department of Soil Management and Soil Care, Faculty of Agricultural and Applied Biological Sciences, Ghent University, Belgium
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  • Xu Hui,

    1. Institute of Applied Ecology, Chinese Academy of Science, Shenyang, China
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  • Huang Bin,

    1. Institute of Applied Ecology, Chinese Academy of Science, Shenyang, China
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  • Chen Guanxiong

    1. Institute of Applied Ecology, Chinese Academy of Science, Shenyang, China
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  • Presented at SIMSUG 2002, Belfast, UK.

Abstract

Variations in 13C natural abundance and distribution of total C among five size and density fractions of soil organic matter, water soluble organic C (WSOC) and microbial biomass C (MBC) were investigated in the upper layer (0–20 cm) of a continuous grassland soil (CG, C3 vegetation), a C3-humus soil converted to continuous maize cultivation (CM, C4 vegetation) and a C3-humus soil converted to a rotation of maize cultivation and grassland (R). The amounts of WSOC and MBC were both significantly larger in the CG than in the CM and the R. In the three soils, WSOC was depleted while MBC was enriched in 13C as compared with whole soil C. The relative contributions to the total C content of C stored in the macro-organic matter and in the size fraction 50–150 µm decreased with decreasing total C contents in the order CG > R > CM, while the relative contribution of C associated with the clay- and silt-sized fraction <50 µm increased. This reflects a greater stability and physical protection against microbial degradation associated with soil disruption (tillage) of the clay- and silt-associated organic C, in relation to the organic C in larger size fractions. The size and density fractions from the CG soil showed significant differences in 13C enrichment, indicating different degrees of microbial degradation and stability of soil organic C associated with physically different soil organic matter (SOM) fractions. δ13C analysis of the size and density fractions from CM and R soils reflected a decreasing turnover rate of soil organic C with increasing density among the macro-organic matter fractions and with decreasing particle size. Copyright © 2002 John Wiley & Sons, Ltd.

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