Tuesday, August 5, 2008
Exhibit Hall CD, Midwest Airlines Center
S.K. Morgan Ernest, Department of Biology, Utah State University, Logan, UT, Ethan P. White, Wildlife Ecology and Conservation, University of Florida, James H. Brown, Department of Biology, University of New Mexico, Albuquerque, NM and Richard Condit, The field museum, Chicago, IL
Background/Question/Methods Understanding how the structure and function of ecosystems change in response to natural and human-caused perturbations is a necessary precondition to predicting impacts of human activities. Many ecological and evolutionary theories are based on the assumption that limiting resources constrain the structure and dynamics of species and community. We use the concept of metabolic-based zero-sum constraints to explain long-term changes in abundance in a well-studied tropical forest community at Barro Colorado Island, Panama that has experienced long-term changes in precipitation patterns.
Results/Conclusions
A framework based on metabolic zero-sum dynamics can explain changes over 25 years in the tropical tree community on Barro Colorado Island, Panama. The average diameter of a tree increased by ~10%, the number of trunks decreased by ~20%, but the total rate of energy flux remained unchanged. The quantitative magnitude of the tradeoff between size and abundance is predicted by metabolic resource limitation: the smaller number of larger individuals uses resources at the same rate as the larger number of smaller individuals before changes in climate altered the size distribution of trees. These results indicate the power of a metabolic zero-sum framework for understanding the structure and dynamics of ecosystems, both at steady state and in response to perturbations caused by changes in climate and other environmental conditions.
