Ecological Processes in Forest Gap Models — Analysis and Improvement

Abstract

In the last two decades, forest succession models of the JABOWA/FORET type ("gap models") have grown to rather complex models. This makes simulation studies tedious, not the least because of the long simulation times and the inflexibility in experimenting with model modifications. Thus, only little could be learned about the relative importance of the numerous ecological processes built into the models and about their mathematical properties from a systems theoretical viewpoint. Focusing on the FORECE model [2], we first analyze how many simulation runs have to be performed to allow for meaningful calculations of statistical properties of the model output. We then examine the state variable update in the model as a first step toward model simplification. Based on these experiences, we evaluate the relative importance of the ecological processes in the model, and we present a simplified forest gap model encapsulating a minimal set of essential ecological processes to allow for efficient interactive as well as large-scale simulations.