IMIS

The assemblage of submodels considered necessary for a stand growth model is presented. This assemblage contains several submodels which in themselves form a stand water-use model but have an important influence on the growth model either because their outputs are needed as inputs to some of the growth submodels, or because of feedback between the growth and water relations submodels. For example, output from the soil and plant water relations submodels is required as input to the submodels concerned with leaf phenology, stomatal conductance, photosynthesis, nutrient status and fine root growth.

A tree water relations model is presented. This model predicts wtaer flow, water content and water potential at points in the tree between the soil and the atmosphere, both where these variables can be measured in the tree with current techniques, and where they cannot because the techniques are inadequate. The model takes storage into account and predicts realistic reductions in the diurnal amplitude of these variables, as wel as phase shifts, in the tree at ground level, as compared with the values in the canopy.