Modelling and Simulation of Mixed Natural Forest Dynamics

Abstract

The dynamics of natural forest regeneration and development are strongly dependent on logging and silvicultural treatments and therefore cannot be reliably assessed by average yield rules. It becomes necessary to construct sophisticated dynamic simulation models incorporating detailed descriptions of the real eco-physiological processes taking place in the forest as a result of forest management. To provide reliable growth computations, the FORMIX forest simulator was developed. It incorporates the canopy layer structure of the natural forest, the basic process of gap succession dynamics, several functionally different species groups (emergents, main canopy trees, pioneers) and the energy balance of assimilation, dissimilation, and increment resulting from the different light conditions for the different canopy layers in the different gap-size areas of a forest mosaic. The vertically and horizontally structured FORMIX model produces time-dependent results (average per hectare data) for stem numbers, diameter distributions, basal areas, standing crop and yield, as well as other information relevant for forest management, as a function of logging method and intensity and silvicultural treatment. Economic and ecological computations can be linked to this forest simulation model. The system can be used for experimental investigations of forest policies and their results. The model has been applied in an exploratory investigation to compute the long-term development of (a) virgin forest and (b) logged-over forest in Sabah, using prototypical data. Results are presented in the form of dynamic maps of forest development as well as animated views of the dynamic development of the forest profile. The results obtained agree with empirical data.