9407581 Clark Lowland tropical rain forests contain a substantial part of the planet's above-ground carbon and are the richest terrestrial habitats in plant and animal species. In spite of their global importance and rapid rates of tropical deforestation, surprisingly little is known about the basic ecology of the largest organisms in these forests, the canopy trees. This project will extend the longest running investigation on annually-measured growth, mortality, and tree microenvironment for tropical rain forest trees. The study is located in one of the world's most active centers for tropical rain forest research, the La Selva Biological Station in Costa Rica. Results from the first 11 years of study have led to new insights into the ecology of tropical rain forest trees. Multiple regeneration patterns are apparent. The great dynamism of these forests causes high rates of physical damage to young trees. The vast majority of young trees occupy very dark microenvironments, frequently passing years with no growth. Small increases in light, as cause by the fall of a nearby canopy tree, have important effects on saplings' performance and survival. Substantial differences in annual growth occur concurrently across species, indicating the pervasive impact of short-term climatic variation on the productivity of the forest as a whole. Data from this project are providing a unique understanding of the ecology of canopy trees in tropical rain forest.
