Most studies of tropical rain forests have intentionally been conducted on relatively homogeneous sites. However, sudden changes in forest composition, structure, and dynamics can occur with abrupt changes in soils in lowland tropical forests. The importance of such changes and local soil-type heterogeneity for the maintenance of tree species diversity in tropical forests is unknown. A spectacular example is Lambir National Park, Sarawak. This forest, undisturbed by humans, is perhaps the most species- rich tropical forest in Southeast Asia. Establishment of a permanent 50 ha plot is proposed, to straddle a major soil discontinuity at Lambir in order to compare and contrast tree population patterns, and eventually demography and forest dynamics across the soil ecotone. The "source-sink" hypothesis, namely that rare species in the forest on one soil type are sustained by immigration from abundant populations on the other soil type will be also tested initially through comparison of population structure on contrasting soils of species occurring across this ecotone. These tests are important for understanding the specialist vs. generalists strategies of tropical tree species in relation to soils, for the maintenance of rare species in tropical forests, and for the conservation of tropical forest biodiversity. This project is co-sponsored by the Sarawak Forest Department, and by the plant ecology laboratory of Osaka City University. The project will train a new generation of resident and U.S. experts in one of the world's richest floras.
