Currently there are two competing theories that explain tree species dominance, distribution and diversity patterns in tropical forests: the niche-assembly and the neutral theory. The niche-assembly theory states that tree species can co-exist because each species has its own specific niche and thus avoids competition with other tree species. The neutral theory, on the other hand, discards these species specific habitat associations, and states that chance processes, in the form of dispersal limitation, determine tropical tree species co-existence.

Studies carried out so far, provide evidence in favour of both theories. They show that tree species can have specific habitat preferences (supporting the niche-assembly theory), but they also show that the presence of a tree species at a site is often determined by chance (supporting the neutral theory). Apparently there exists a balance between dispersal-assembly and niche-assembly processes. Our aim with this study is to disentangle these effects of environment and chance on tree species dominance, distribution and diversity patterns at different spatial scales, so that we get insight into the relative importance of both processes on local, landscape, regional and Borneo wide spatial scales.

The results of this study will be used to develop scientifically sound conservation strategies for tropical rain forests. Knowledge of the relative importance of dispersal- and niche-assembly theories on tropical tree species dominance, distribution and diversity patterns is important in this respect since both give rather contrasting recommendations on how to conserve tropical forest trees in the most efficient manner.