PINE INVASIONS IN THE SOUTHERN-HEMISPHERE - MODELING INTERACTIONS BETWEEN ORGANISM, ENVIRONMENT AND DISTURBANCE

Current theories of plant invasion have been criticized for their limi ted heuristic and predictive value. We explore the heuristic and predi ctive potential of a model which explicitly simulates the mechanisms o f plant invasion. The model, a spatially-explicit individual-based sim ulation, is applied to the invasion of pine trees (Pinus spp.; Pinacea e) in three vegetation types in the southern hemisphere. The model sim ulates factors which have been invoked as major determinants of invasi ve success: plant traits, environmental features and disturbance level . Results show that interactions between these determinants of invasiv e success are at least as important as the main effects. The complexit y of invasions has promoted the belief that many factors must be invok ed to explain invasions. This study shows that by incorporating intera ctions and mechanisms into our models we can potentially reduce the nu mber of factors needed to predict plant invasions. The importance of i nteractions, however, means that predictions about invasions must be c ontext-specific. The search for all-encompassing rules for invasions i s therefore futile. The model presented here is of heuristic value sin ce it improves our understanding of invasions, and of management value since it defines the data and models needed for predicting invasions.