An individual-based forest dynamics model (ZELIG) is parameterized for a tropical forest in the western plains of Venezuela using data from six 0.25-ha permanent plots with 34 years of growth records. The forest is located in the "Bosque Universitario 'El Caimital'", classified as a dry with transition to moist tropical forest sensu Holdridge. To simplify model parameterization, instead of using the large number (64) of species present in the plots, the tree species were grouped according to three intervals of tree height (<15 m, 15-30 m, >30 m), and three types of shade tolerance (tolerant, mid-tolerant, intolerant). These criteria reflect, respectively, the capacity to create canopy gaps upon death and to regenerate in such gaps, hence they are related to tree mortality and establishment characteristics. Only six species groups were deemed important since in this forest most large-trees species are mid-tolerant, and small-trees species are rarely mid-tolerant. The model parameters for these six groups were then estimated in the same manner as if they were species. Simulation runs were conducted starting from bare soil and for 240 years, which is the estimated age of the Caimital forest stands, assuming no intervention or timber extraction. The resulting simulated diameter distribution was then compared to the field data to further calibrate model parameters. A good fit was finally achieved, for aggregated plot values as well as plot composition, with some variants that may be attributed to the selective timber extraction which occurred in Caimital four decades ago and for which no data was available. This article contributes a realistic parameterization of an individual-based model for a tropical forest based on the strategy of grouping tree species according to mortality and regeneration characteristics.
Key words: tropical forest, forest dynamics, species groups, simulation model, Venezuela, ZELIG.