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| Titel |
Observed and modelled ecosystem respiration and gross primary production of a grassland in southwestern France |
| VerfasserIn |
C. Albergel, J.-C. Calvet, A.-L. Gibelin, S. Lafont, J.-L. Roujean, C. Berne, O. Traullé, N. Fritz |
| 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 ; 7, no. 5 ; Nr. 7, no. 5 (2010-05-21), S.1657-1668 |
| Datensatznummer |
250004776
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| Publikation (Nr.) |
 copernicus.org/bg-7-1657-2010.pdf |
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| Zusammenfassung |
| In this work, the rich dataset acquired at the SMOSREX experimental
site is used to enhance the A-gs version of the Interactions between
Soil, Biosphere and Atmosphere (ISBA) model. A simple representation
of the soil moisture effect on the ecosystem respiration is
implemented in the ISBA-A-gs model. It results in an improvement of
the modelled CO2 flux over a grassland in southwestern France.
The former temperature-only dependent respiration formulation used
in ISBA-A-gs is not able to model the limitation of the respiration
under dry conditions. In addition to soil moisture and soil
temperature, the only parameter required in this formulation is the
ecosystem respiration parameter Re25. It can be estimated by
means of eddy covariance measurements of turbulent nighttime
CO2 flux (i.e. ecosystem respiration). The resulting
correlation between observed and modelled net ecosystem exchange is
r2=0.63 with a bias of
−2.18 μmol m−2 s−1. It is shown that when
CO2 observations are not available, it is possible to use a
more complex model, able to represent the heterotrophic respiration
and all the components of the autotrophic respiration, to estimate
Re25 with similar results. The modelled ecosystem respiration
estimates are provided by the Carbon Cycle (CC) version of ISBA
(ISBA-CC). ISBA-CC is a version of ISBA able to simulate all the
respiration components, whereas ISBA-A-gs uses a single equation for
ecosystem respiration. ISBA-A-gs is easier to handle and more
convenient than ISBA-CC for the practical use in atmospheric or
hydrological models. Surface water and energy flux observations, as
well as Gross Primary Production (GPP) estimates, are compared with
model outputs. The dependence of GPP to air temperature is
investigated. The observed GPP is less sensitive to temperature than
the modelled GPP. Finally, the simulations of the ISBA-A-gs model
are analysed over a seven year period (2001–2007). Modelled soil
moisture and Leaf Area Index (LAI) are confronted with the observed
surface and root-zone soil moisture content (m3 m−3), and
with LAI estimates derived from surface reflectance measurements. |
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