Please use this identifier to cite or link to this item: http://hdl.handle.net/2445/65360
Title: Improved understanding of drought controls on seasonal variation in Mediterranean forest canopy CO2 and water fluxes through combined in situ measurements and ecosystem modelling
Author: Keenan, T.
Garcia, R.
Friend, A.D.
Zaehle, S.
Gracia, Carles
Sabaté i Jorba, Santi
Keywords: Ecologia forestal
Ecologia fluvial
Boscos
Gestió dels ecosistemes
Forest ecology
Stream ecology
Forests
Ecosystem management
Issue Date: 5-Aug-2009
Publisher: European Geosciences Union
Abstract: 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.
Note: Reproducció del document publicat a: http://dx.doi.org/10.5194/bg-6-1423-2009
It is part of: Biogeosciences, 2009, vol. 6, p. 1423-1444
Related resource: http://dx.doi.org/10.5194/bg-6-1423-2009
URI: http://hdl.handle.net/2445/65360
ISSN: 1726-4170
Appears in Collections:Articles publicats en revistes (Biologia Evolutiva, Ecologia i Ciències Ambientals)

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