Articles
COMPARISON OF SEVERAL APPROACHES TO MODELLING STOMATAL CONDUCTANCE IN WELL-WATERED AND DROUGHT-STRESSED ALMOND TREES
Article number
922_37
Pages
285 – 293
Language
English
Abstract
Hourly values of mean stomatal conductance (gs) were derived in a top-down approach from whole-canopy water flux measurements in well-watered (FI) and drought-stressed (DI) almond trees.
Leaf photosynthesis rates (A) were simulated by using the photosynthesis model of Farquhar et al. (1980), previously calibrated and validated for FI and DI almond trees, and coupled to the radiation interception model Rayprun validated for an isolated almond tree.
A complete dataset of physiological and environmental variables was used to parameterize and test eight stomatal conductance models (multiplicative, coupled A-gs and SPA models). Five coupled A-gs models presented a similar degree of performance under non limiting soil moisture conditions.
Two of them (Ball et al., 1987; Jacobs et al., 1996) were selected to test their performance under limiting soil moisture conditions because of their higher simplicity (only two tuning parameters). The Jacobs et al. (1996) model performed slightly better than the Ball et al. (1987) model under soil water deficit conditions.
In order to account for the regulatory effects of soil water deficit on gs, four water stress functions, dependent on soil matric potential, were implemented in the Jacobs et al. (1996) model to be fitted and tested.
All these functions adequately described the changes in gs under contrasting soil water availabilities.
Leaf photosynthesis rates (A) were simulated by using the photosynthesis model of Farquhar et al. (1980), previously calibrated and validated for FI and DI almond trees, and coupled to the radiation interception model Rayprun validated for an isolated almond tree.
A complete dataset of physiological and environmental variables was used to parameterize and test eight stomatal conductance models (multiplicative, coupled A-gs and SPA models). Five coupled A-gs models presented a similar degree of performance under non limiting soil moisture conditions.
Two of them (Ball et al., 1987; Jacobs et al., 1996) were selected to test their performance under limiting soil moisture conditions because of their higher simplicity (only two tuning parameters). The Jacobs et al. (1996) model performed slightly better than the Ball et al. (1987) model under soil water deficit conditions.
In order to account for the regulatory effects of soil water deficit on gs, four water stress functions, dependent on soil matric potential, were implemented in the Jacobs et al. (1996) model to be fitted and tested.
All these functions adequately described the changes in gs under contrasting soil water availabilities.
Authors
G. Egea, A. Verhoef, M.M. González-Real, A. Baille, P.A. Nortes, R. Domingo
Keywords
gas exchange, matric potential, photosynthesis, Prunus dulcis, water stress
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