© 2000 Heron Publishing—Victoria, Canada
Modeling daily gas exchange of a Douglas-fir forest: comparison of three stomatal conductance models with and without a soil
water stress function
M. T. Van Wijk (1), S. C. Dekker (1), W. Bouten (1), F. C. Bosveld (2), W. Kohsiek (2), K. Kramer (3) and G. M. J. Mohren (3)
1. Department of Physical Geography and Soil Science, Universiteit van Amsterdam, Nieuwe Prinsengracht 130, 1018 VZ Amsterdam,
The Netherlands / 2. Royal Meteorological Institute of the Netherlands (KNMI), P.O. Box 201, 3730 AE De Bilt, The Netherlands / 3. Institute of Forestry and Nature Research, IBN-DLO, P.O. Box 23, 6700 AA Wageningen, The Netherlands / Received December 21, 1998
Summary
Modeling stomatal conductance is a key element in predicting tree growth and water use at the stand scale. We compared three
commonly used models of stomatal conductance, the Jarvis-Loustau, Ball-Berry and Leuning models, for their suitability for
incorporating soil water stress into their formulation, and for their performance in modeling forest ecosystem fluxes. We
optimized the parameters of each of the three models with sap flow and soil water content data. The optimized Ball-Berry model
showed clear relationships with air temperature and soil water content, whereas the optimized Leuning and Jarvis-Loustau models
only showed a relationship with soil water content. We conclude that use of relative humidity instead of vapor pressure deficit,
as in the Ball-Berry model, is not suitable for modeling daily gas exchange in Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) in the Speulderbos forest near the village of Garderen, The Netherlands. Based on the calculated 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.
Keywords:
carbon fluxes, Pseudotsuga menziesii, simulation models, soil water content, transpiration.
