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| Titel |
Can we model observed soil carbon changes from a dense inventory? A case study over England and Wales using three versions of the ORCHIDEE ecosystem model (AR5, AR5-PRIM and O-CN) |
| VerfasserIn |
B. Guenet, F. E. Moyano, N. Vuichard, G. J. D. Kirk, P. H. Bellamy, S. Zaehle, P. Ciais |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1991-959X
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| Digitales Dokument |
URL |
| Erschienen |
In: Geoscientific Model Development ; 6, no. 6 ; Nr. 6, no. 6 (2013-12-19), S.2153-2163 |
| Datensatznummer |
250085026
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| Publikation (Nr.) |
 copernicus.org/gmd-6-2153-2013.pdf |
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| Zusammenfassung |
| A widespread decrease of the topsoil carbon content was observed over
England and Wales during the period 1978–2003 in the National Soil Inventory
(NSI), amounting to a carbon loss of 4.44 Tg yr−1 over 141 550 km2.
Subsequent modelling studies have shown that changes in temperature and
precipitation could only account for a small part of the observed decrease,
and therefore that changes in land use and management and resulting changes
in heterotrophic respiration or net primary productivity were the main
causes. So far, all the models used to reproduce the NSI data have not
accounted for plant–soil interactions and have only been soil carbon models with
carbon inputs forced by data. Here, we use three different versions of a
process-based coupled soil–vegetation model called ORCHIDEE (Organizing Carbon and Hydrology in Dynamic Ecosystems), in order to
separate the effect of trends in soil carbon input from soil carbon
mineralization induced by climate trends over 1978–2003. The first version
of the model (ORCHIDEE-AR5), used for IPCC-AR5 CMIP5 Earth System
simulations, is based on three soil carbon pools defined with first-order
decomposition kinetics, as in the CENTURY model. The second version
(ORCHIDEE-AR5-PRIM) built for this study includes a relationship between
litter carbon and decomposition rates, to reproduce a priming effect on
decomposition. The last version (O-CN) takes into account N-related
processes. Soil carbon decomposition in O-CN is based on CENTURY, but adds N
limitations on litter decomposition. We performed regional gridded
simulations with these three versions of the ORCHIDEE model over England and
Wales. None of the three model versions was able to reproduce the observed
NSI soil carbon trend. This suggests either that climate change is not the
main driver for observed soil carbon losses or that the ORCHIDEE model even
with priming or N effects on decomposition lacks the basic mechanisms to
explain soil carbon change in response to climate, which would raise a
caution flag about the ability of this type of model to project soil carbon
changes in response to future warming. A third possible explanation could be
that the NSI measurements made on the topsoil are not representative of the
total soil carbon losses integrated over the entire soil depth, and thus
cannot be compared with the model output. |
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