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| Titel |
Seasonal leaf dynamics for tropical evergreen forests in a process-based global ecosystem model |
| VerfasserIn |
M. Weirdt, H. Verbeeck, F. Maignan, P. Peylin, B. Poulter, D. Bonal, P. Ciais, K. Steppe |
| 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 ; 5, no. 5 ; Nr. 5, no. 5 (2012-09-06), S.1091-1108 |
| Datensatznummer |
250002843
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| Publikation (Nr.) |
 copernicus.org/gmd-5-1091-2012.pdf |
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| Zusammenfassung |
| The influence of seasonal phenology on canopy photosynthesis in tropical
evergreen forests remains poorly understood, and its representation in global
ecosystem models is highly simplified, typically with no seasonal variation
of canopy leaf properties taken into account. Including seasonal variation
in leaf age and photosynthetic capacity could improve the correspondence of
global vegetation model outputs with the wet–dry season CO2 patterns
measured at flux tower sites in these forests. We introduced a leaf
litterfall dynamics scheme in the global terrestrial ecosystem model
ORCHIDEE based on seasonal variations in net primary production (NPP),
resulting in higher leaf turnover in periods of high productivity. The
modifications in the leaf litterfall scheme induce seasonal variation in
leaf age distribution and photosynthetic capacity. We evaluated the results
of the modification against seasonal patterns of three long-term in-situ
leaf litterfall datasets of evergreen tropical forests in Panama, French
Guiana and Brazil. In addition, we evaluated the impact of the model
improvements on simulated latent heat (LE) and gross primary productivity
(GPP) fluxes for the flux tower sites Guyaflux (French Guiana) and
Tapajós (km 67, Brazil). The results show that the introduced seasonal
leaf litterfall corresponds well with field inventory leaf litter data and
times with its seasonality. Although the simulated litterfall improved
substantially by the model modifications, the impact on the modelled fluxes
remained limited. The seasonal pattern of GPP improved clearly for the
Guyaflux site, but no significant improvement was obtained for the
Tapajós site. The seasonal pattern of the modelled latent heat fluxes
was hardly changed and remained consistent with the observed fluxes. We
conclude that we introduced a realistic and generic litterfall dynamics
scheme, but that other processes need to be improved in the model to achieve
better simulations of GPP seasonal patterns for tropical evergreen forests. |
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