Simulation of the growth of a lowland Dipterocarp rain forest with FORMIX3

In this paper a new model for simulation of the growth of tropical rain forest is presented (FORMIX3). The model describes growth, mortality, recruitment of trees and competition between trees. The calculation of tree growth is based on a carbon balance. The carbon gain of a tree depends on the photo production of its leaves, respiration and other losses. Trees compete for light and space. Dying large trees fall down and create gaps in the forest. Based on an extensive field data review, a parametrisation was developed for the simulation of lowland Dipterocarp rain forest at Deramakot, Malaysia. A total of 28 variables describing different aspects of forest structure and growth were compared with field data. The model reproduces most parts of the forest dynamics well. A new concept for sensitivity analysis is presented: 46 model parameter were varied and analysed in respect to their influence on 26 variables describing the forest state. The influence of the different processes on forest structure is complex. Some general trends can be observed: The growth characteristics of the two Dipterocarp species groups strongly influences species composition in the forest, but not general forest structure (biomass, leaf area, production, leaf area, tree size distribution)