Persistence of soil organic matter in eroding versus depositional landform positions

Soil organic matter (SOM) processes in dynamic landscapes are strongly influenced by soil erosion and sedimentation. We determined the contribution of physical isolation of organic matter (OM) inside aggregates, chemical interaction of OM with soil minerals, and molecular structure of SOM in control...

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Bibliographic Details
Published in:Journal of Geophysical Research: Biogeosciences 2012-06, Vol.117 (G2), p.n/a
Main Authors: Berhe, Asmeret Asefaw, Harden, Jennifer W., Torn, Margaret S., Kleber, Markus, Burton, Sarah D., Harte, John
Format: Article
Language:English
Subjects:
Aggregates
Atmospheric sciences
Biogeography
Carbon
carbon sequestration
Earth sciences
Earth, ocean, space
Ecosystem biology
Environmental factors
Exact sciences and technology
Fractionation
Geobiology
Grasslands
Minerals
Organic matter
Physics
Soil erosion
Soil organic matter
Soil sciences
SOM stabilization mechanisms
Watersheds
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Summary:Soil organic matter (SOM) processes in dynamic landscapes are strongly influenced by soil erosion and sedimentation. We determined the contribution of physical isolation of organic matter (OM) inside aggregates, chemical interaction of OM with soil minerals, and molecular structure of SOM in controlling storage and persistence of SOM in different types of eroding and depositional landform positions. By combining density fractionation with elemental and spectroscopic analyses, we showed that SOM in depositional settings is less transformed and better preserved than SOM in eroding landform positions. However, which environmental factors exert primary control on storage and persistence of SOM depended on the nature of the landform position considered. In an annual grassland watershed, protection of SOM by physical isolation inside aggregates and chemical association of organic matter (complexation) with soil minerals, as assessed by correlation with radiocarbon concentration, were more effective in the poorly drained, lowest‐lying depositional landform positions, compared to well‐drained landform positions in the upper parts of the watershed. Results of this study demonstrated that processes of soil erosion and deposition are important mechanisms of long‐term OM stabilization. Key Points Eroding and depositional landform positions vary in terms of soil carbon storage Mechanisms of SOM stabilization depend on nature of landform position considered Significant fraction of SOM in depositional positions can be easily mineralized
ISSN:0148-0227
2169-8953
2156-2202
2169-8961
DOI:10.1029/2011JG001790