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| Titel |
The relative importance of decomposition and transport mechanisms in accounting for soil organic carbon profiles |
| VerfasserIn |
B. Guenet, T. Eglin, N. Vasilyeva, P. Peylin, P. Ciais, C. Chenu |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 10, no. 4 ; Nr. 10, no. 4 (2013-04-10), S.2379-2392 |
| Datensatznummer |
250018191
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| Publikation (Nr.) |
 copernicus.org/bg-10-2379-2013.pdf |
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| Zusammenfassung |
| Soil is the major terrestrial reservoir of carbon and a substantial part of
this carbon is stored in deep layers, typically deeper than 50 cm below the
surface. Several studies underlined the quantitative importance of this deep
soil organic carbon (SOC) pool and models are needed to better understand
this stock and its evolution under climate and land-uses changes. In this
study, we tested and compared three simple theoretical models of vertical
transport for SOC against SOC profiles measurements from a long-term bare
fallow experiment carried out by the Central-Chernozem State Natural
Biosphere Reserve in the Kursk Region of Russia. The transport schemes
tested are diffusion, advection and both diffusion and advection. They are
coupled to three different formulations of soil carbon decomposition
kinetics. The first formulation is a first order kinetics widely used in
global SOC decomposition models; the second one, so-called "priming"
model, links SOC decomposition rate to the amount of fresh organic matter,
representing the substrate interactions. The last one is also a first order
kinetics, but SOC is split into two pools. Field data are from a set of
three bare fallow plots where soil received no input during the past 20, 26
and 58 yr, respectively. Parameters of the models were optimised using a
Bayesian method. The best results are obtained when SOC decomposition is
assumed to be controlled by fresh organic matter (i.e., the priming model).
In comparison to the first-order kinetic model, the priming model reduces
the overestimation in the deep layers. We also observed that the transport
scheme that improved the fit with the data depended on the soil carbon
mineralisation formulation chosen. When soil carbon decomposition was
modelled to depend on the fresh organic matter amount, the transport
mechanism which improved best the fit to the SOC profile data was the model
representing both advection and diffusion. Interestingly, the older the bare
fallow is, the lesser the need for diffusion is, suggesting that stabilised
carbon may not be transported within the profile by the same mechanisms than
more labile carbon. |
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