Abstract
The majority of tree species in tropical rain forests are rare on a local scale. A major problemin ecology is to investigate how these species can persist at such low local density. A related probleminvolves the demographic factors preventing any of the more common species from achieving dominancein the forest such as happens in the temperate zone. To investigate this topic tree populations in threecontrasting mixed dipterocarp forests in Sarawak have been measured at five-year intervals to gain information on rates of tree growth, recruitment and survival. The strengths and weaknesses of our methodology are contrasted with alternative experimental designs to highlight the best approaches for investigations of biodiversity. We have compared the demographic patterns of rare, occasional and commonspecies by combining species into abundance classes. For locally common species we have been able toevaluate population stability using regression analysis of changes in population size over four successiveintervals of five years. Using such approaches, long-term demographic studies can suggest the degree oftemporal stability of rainforest communities and give practical suggestions for preserving tree species innature reserves. These studies are also being used to provide baseline data for comparison with selec-tively logged forests and to assist in effective forest management planning. Such efforts are importantbecause logging and agricultural activities are currently having a major impact on Sarawak’s forests.
