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| Titel |
Improved understanding of drought controls on seasonal variation in Mediterranean forest canopy CO2 and water fluxes through combined in situ measurements and ecosystem modelling |
| VerfasserIn |
T. Keenan, R. García, A. D. Friend, S. Zaehle, C. Gracia, S. Sabate |
| 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 ; 6, no. 8 ; Nr. 6, no. 8 (2009-08-05), S.1423-1444 |
| Datensatznummer |
250003939
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| Publikation (Nr.) |
 copernicus.org/bg-6-1423-2009.pdf |
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| Zusammenfassung |
Water stress is a defining characteristic of Mediterranean ecosystems,
and is likely to become more severe in the coming decades.
Simulation models are key tools for making predictions, but
our current understanding of how soil moisture controls ecosystem
functioning is not sufficient to adequately constrain
parameterisations.
Canopy-scale flux data from four forest ecosystems with
Mediterranean-type climates were used in order to analyse the
physiological controls on carbon and water flues through the
year. Significant non-stomatal limitations on photosynthesis were
detected, along with lesser changes in the conductance-assimilation relationship.
New model parameterisations were derived and implemented in
two contrasting modelling approaches.
The effectiveness of two models, one a dynamic global vegetation model ("ORCHIDEE"), and the
other a forest growth model particularly developed for Mediterranean
simulations ("GOTILWA+"), was assessed and modelled
canopy responses to seasonal changes in soil moisture were analysed
in comparison with in situ flux measurements.
In contrast to commonly held assumptions, we find that changing the ratio of
conductance to assimilation under natural,
seasonally-developing, soil moisture stress is not sufficient to reproduce
forest canopy CO2 and water fluxes. However, accurate
predictions of both CO2 and water fluxes under all soil moisture
levels encountered in the field are obtained if photosynthetic capacity is
assumed to vary with soil moisture. This new parameterisation has
important consequences for simulated responses of carbon and water
fluxes to seasonal soil moisture stress, and should greatly improve our
ability to anticipate future impacts of climate changes on the
functioning of ecosystems in Mediterranean-type climates. |
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