Mt. Van Wijk et al., Modeling daily gas exchange of a Douglas-fir forest: comparison of three stomatal conductance models with and without a soil water stress function, TREE PHYSL, 20(2), 2000, pp. 115-122
Modeling stomatal conductance is a key element in predicting tree growth an
d water use at the stand scale. We compared three commonly used models of s
tomatal conductance, the Jarvis-Loustau, Ball-Berry and Leuning models, for
their suitability for incorporating soil water stress into their formulati
on, and for their performance in modeling forest ecosystem fluxes. We optim
ized the parameters of each of the three models with sap flow and soil wate
r content data. The optimized Ball-Berry model showed clear relationships w
ith air temperature and soil water content, whereas the optimized Leuning a
nd Jarvis-Loustau models only showed a relationship with soil water content
. We conclude that use of relative humidity instead of vapor pressure defic
it, as in the Ball-Berry model, is not suitable for modeling daily gas exch
ange in Douglas-fir (Pseudotsuga menziesii (Mirb.) France) in the Speulderb
os forest near the village of Garderen, The Netherlands. Based on the calcu
lated responses to soil water content, we linked a model of forest growth,
FORGRO, with a model of soil water, SWIF, to obtain a forest water-balance
model that satisfactorily simulated carbon and water (transpiration) fluxes
and soil water contents in the Douglas-fir forest for 1995.