Modelling the interactions between water availability and forest succession on a spatial basis

Transpiration is calculated as the minimum of the amount of water a tree can pump up (Hagen-Poiseuille), the potential transpiration (Penman-Monteith) and the available amount of water. The availability of water is a result of the water uptake by trees, precipitation, interception, run-on and run-off and the depth and radius of the root system. The effect of water on vegetation development is simulated by reducing the net primary production (NPP) by a factor that is a ratio of potential and actual transpiration. The model is validated with data sets from temperate forests and an orchard.