This grant supports a continuation of a long-term study of a tropical rain forest and how it is responding to climate change. The forest is in the Panama Canal on Barro Colorado Island (BCI), a biological reserve managed by the Smithsonian and one of the botanically and ecologically best known tropical forests in the world. The grant is to study germination and survival of seedlings, stages of tree life histories that are most sensitive to climate. Large changes in seasonal and annual rainfall patterns are predicted in the tropics due to increasing atmospheric CO2, which may cause major changes in the tree species composition and turnover rates of tropical forests. Seedlings are early warning systems because of their drought sensitivity. Results of this project should be practically beneficial in forecasting how tropical rain forests will respond to climate change. The study also adds to basic understanding of how tropical rain forests work and why they have so many tree species. The subject research plot, five football fields in size, has twice the tree species found in all of North America north of Mexico. This project will test the hypothesis that seedling fluctuations let more species coexist by giving rare species a competitive edge in years when common species fail to reproduce. Prior support has resulted in the training of many U.S. students in tropical botany and ecology (over 200 undergraduate and graduate trainees since 1980, including 7 Ph.D.'s and 4 Master's students). Students, colleagues, and PIs associated with this project have already published more than 100 papers and 3 books based on data from this project.
