FORSUM, a forest succession model of the JABOWA/FORET-type has been developed to explore the relationships between long-term forest succession and biogenic (e.g., browsing) and anthropogenic factors. FORSUM combines long-term (decades to centuries) and short-term (minutes to hours) processes. lt calculates soil water movement and root water uptake by the plants by calculating the water flow through a one-dimensional, non homogeneous soil profile on a daily basis. Different management options are implemented in the model. Model testing included plausibility tests (e.g., modelling efficiency, model performance) and sensitivity analyses of factors intrinsic or extrinsic to species and stands, respectively.
Assuming the validation criterions to be sufficient FORSUM was applied to different forest ecosystems in Switzerland and Germany to evaluate its use as a 'predictive' tool for forest succession dynamics or climate impact risk assessment.