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| Titel |
Assessing the ability of three land ecosystem models to simulate gross carbon uptake of forests from boreal to Mediterranean climate in Europe |
| VerfasserIn |
M. Jung, G. Maire, S. Zaehle, S. Luyssaert, M. Vetter, G. Churkina, P. Ciais, N. Viovy, M. Reichstein |
| 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 ; 4, no. 4 ; Nr. 4, no. 4 (2007-08-14), S.647-656 |
| Datensatznummer |
250001859
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| Publikation (Nr.) |
 copernicus.org/bg-4-647-2007.pdf |
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| Zusammenfassung |
Three terrestrial biosphere models (LPJ, Orchidee, Biome-BGC) were evaluated
with respect to their ability to simulate large-scale climate related trends
in gross primary production (GPP) across European forests. Simulated GPP and
leaf area index (LAI) were compared with GPP estimates based on flux
separated eddy covariance measurements of net ecosystem exchange and LAI
measurements along a temperature gradient ranging from the boreal to the
Mediterranean region. The three models capture qualitatively the pattern
suggested by the site data: an increase in GPP from boreal to temperate and
a subsequent decline from temperate to Mediterranean climates. The models
consistently predict higher GPP for boreal and lower GPP for Mediterranean
forests. Based on a decomposition of GPP into absorbed photosynthetic active
radiation (APAR) and radiation use efficiency (RUE), the overestimation of
GPP for the boreal coniferous forests appears to be primarily related to too
high simulated LAI - and thus light absorption (APAR) – rather than too
high radiation use efficiency. We cannot attribute the tendency of the
models to underestimate GPP in the water limited region to model structural
deficiencies with confidence. A likely dry bias of the input meteorological
data in southern Europe may create this pattern.
On average, the models compare similarly well to the site GPP data (RMSE of
~30% or 420 gC/m2/yr) but differences are apparent for different
ecosystem types. In terms of absolute values, we find the agreement between
site based GPP estimates and simulations acceptable when we consider
uncertainties about the accuracy in model drivers, a potential
representation bias of the eddy covariance sites, and uncertainties related
to the method of deriving GPP from eddy covariance measurements data.
Continental to global data-model comparison studies should be fostered in
the future since they are necessary to identify consistent model bias along
environmental gradients. |
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