Improved understanding of drought controls on seasonal variation in Mediterranean forest canopy CO₂ and water fluxes through combined in situ measurements and ecosystem modelling
Keenan, Trevor F. (Centre de Recerca Ecològica i d'Aplicacions Forestals)
García, R. (Laboratoire des Sciences du Climat et de l'Environment)
Friend, A. D. (University of Cambridge. Department of Geography)
Zaehle, S. (Laboratoire des Sciences du Climat et de l'Environment)
Gracia, Carles (Centre de Recerca Ecològica i d'Aplicacions Forestals)
Sabaté i Jorba, Santi (Centre de Recerca Ecològica i d'Aplicacions Forestals)

Data:	2009
Resum:	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.
Ajuts:	European Commission 512464
Drets:	Aquest document està subjecte a una llicència d'ús Creative Commons. Es permet la reproducció total o parcial, la distribució, la comunicació pública de l'obra i la creació d'obres derivades, fins i tot amb finalitats comercials, sempre i quan es reconegui l'autoria de l'obra original.
Llengua:	Anglès
Document:	Article ; recerca ; Versió publicada
Matèria:	Drought ; Forest ; Ecosystem ; Mediterranean region
Publicat a:	Biogeosciences, Vol. 6 Issue 8 (Aug. 2009) , p. 1423-1444, ISSN 1726-4189

DOI: 10.5194/bg-6-1423-2009

22 p, 11.0 MB

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Documents de recerca > Documents dels grups de recerca de la UAB > Centres i grups de recerca (producció científica) > Ciències > CREAF (Centre de Recerca Ecològica i d'Aplicacions Forestals)
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