Ecophysiology of tropical dry evergreen forest, Thailand: measured and modelled stomatal conductance of Hopea ferrea, a dominant canopy emergent.

Published online
19 May 1997
Content type
Journal article
Journal title
Journal of Applied Ecology

Pitman, J. I.

Publication language


The diurnal variation in leaf stomatal conductance of 3 canopy emergent trees (Hopea ferrea) was measured on 13 days over a 6-wk period (August-September 1988) during the wet season in tropical dry evergreen dipterocarp forest, Sakaerat, Thailand, along with micrometeorological variables. Measured maximum stomatal conductances (g) were 510-343 mmol m-2 s-1. Diurnal variations of g were primarily controlled by incident radiation and soil water potential for the range of temperatures observed. During the measuring period, mean soil water potential (ψs) varied between -0.1 and -2.9 MPa. A multiplicative model was used to estimate the stomatal conductance from measurements of solar radiation (I), temperature (T), vapour pressure deficit (D) and soil water potential (ψs). Non-linear optimization of the g functions for I, T, D and ψs of the pooled normalized tree data set explained 84% of the variance, with I and ψs exerting the greatest effect on g. Optimization of the g functions for the individual tree data sets gave r2 values of 0.8-0.9. The optimized value of ψs that reduces g by 50% was found to be -1.2 (±0.07) MPa. The optimized response to D was small and negative. 5. The model can be used to predict the effects of changes in I, T, D and ψs on the g of tropical dry forests.

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