U.S.-Mexico Collaborative Studies on Determinants of Distribution in Piper Species from a Tropical Rain Forest

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This award will support Professor Christopher B. Field of Carnegie Institute of Washington and Professor Robert W. Pearcy of the University of California at Davis in a research collaboration with Professor Carlos Vasquez-Yanes of the Universidad Nacional Autonoma de Mexico (UNAM). The researchers intend to carry out experiments on 2 important but poorly understood aspects of the ecology of rainforest plants in the plant genus Piper, growing in the "Los Tuxtlas" biological preserve, in Veracruz, Mexico. The experiments are multi-species comparisons utilizing Piper species native to habitats of contrasting light availability. One group of experiments focuses on the physiological ecology of plants at the young seedling stage, a stage characterized by high mortality, but about which little is known. On plants less than a few months old and less than 10 cm tall, they intend to study the functional determinants of growth rate, including biomass allocation, mineral nutrition, photosynthesis, and tissue construction costs. The other group of experiments explores photosynthesis and transpiration in fluctuating light. Variation in the efficiency of utilizing fluctuating light is known to have important consequences for carbon balance for several species. The utilization of fluctuating light has not been studied in a system where other functional determinants of growth are as well understood as in the genus Piper. The proposed research will continue to develop the genus Piper as a model system for understanding the mechanisms controlling the distributions of tropical rainforest plants. Much of the infrastructure for the collaboration is already established, as a result of long-standing formal and informal interactions among the principal investigators in both countries. The emphasis on a widely studied model system should yield high returns because many questions in ecology can be answered only through the integration of information concerning multiple aspects of an organism's biology.