A Nutrient Limitation Trap for Recovering Tropical Forests?
David Medvigy, Associate Professor
Department of Biological Sciences, University of Notre Dame
Thursday, August 24 11:00 a.m. – noon
Room F119 Building 4500N
Many tropical forests are recovering from past land use. It is unclear to what extent this recovery may be attenuated by nutrient limitation. This seminar will discuss how mechanistic, numerical models can be used to generate hypotheses about nutrient limitation in tropical forests. A Costa Rican dry forest site where a nutrient addition experiment is underway was used as a first case study. This site was modeled using a coupled terrestrial biosphere model that included ED2 (vegetation dynamics), MEND (biogeochemistry), and N-COM (plant-microbe competition for nutrients). Here, the MEND-component of the model was extended to include nitrogen (N) and phosphorus (P) cycles. Simulations indicated that this forest can be limited by both N and P. In both observations and simulations, nutrient addition resulted in increased fine root biomass. Additional simulations illustrated mechanisms and conditions for plants to escape nutrient limitation. Finally, using a Panamanian moist forest as a second case study, I describe a special role for symbiotic dinitrogen-fixation. A carbon-nitrogen feedback mechanism is developed, in which N-fixing trees can provide the N needed for the ecosystem to maintain high carbon accumulation rates following disturbance.
“I seek to understand the structure, composition, and functioning of terrestrial ecosystems. My specific interests are linked together by the idea of “scaling”, or the discovery of relationships between small-scale spatiotemporal ecosystem variability and large-scale ecosystem properties. The context of my research is that of environmental change: how do changes in climate or other exogenous forcings affect terrestrial ecosystems? My approach is to develop state-of-the-science numerical models that are capable of predicting ecosystem responses to environmental change.”
About the CCSI Seminar Series
This seminar is part of the series in Nutrient Cycling. As part of its strategic plan, CCSI is seeking to advance our knowledge of key nutrient cycles by better understanding the nitrogen/nutrients limit plant productivity, how to enhance global carbon sinks, and the development of an ecological forecasting system. How does understanding key nutrient cycles improve climate prediction?