As the most species-rich communities on earth, tropical rain forests are a particular challenge to theories of species coexistence. Although many hypotheses have been advanced, the mechanisms responsible for coexistence in diverse forests have not yet been clarified. The over- arching goal of this research is to evaluate evidence for mechanisms of coexistence in rain forest trees, with focus on the adult and seedling stages. The seedling stage may be critical in the maintenance of diversity, and direct evidence of dynamic processes, including density dependence, can be gathered relatively quickly at the seedling stage, even for long-lived trees. Major fruit-masting events occur in Bornean rain forests only once every 6-7 years, on average. A major mast is about to occur, as evidenced by mass flowering of many tree taxa at the study site over the last few months. Thus, the specific objectives of this research are to (1) establish the recruitment, survival and growth rates of seedlings resulting from the mast, and test for the effects of adult conspecific density on seedling recruitment a nd growth, and (2) test for density dependence among seedlings in growth and mortality, using observational and experimental studies on a range of spatial scales. This research will provide a vital understanding of dynamics in tropical rain forests, with the added benefit of capturing data during a year with unusually abundant seed production. In addition, this research will expand our global understand of factors that maintain high species richness in tropical forests.
