LTREB: A Long-Term Investigation of the Interplay of Biotic vs. Abiotic Factors in a Chilean Semiarid Community

Northern Illinois University, Dekalb IL

Investigators

Abstract

The goal of this study is to continue, and to refocus, a long-term, large-scale experiment that investigates the importance of predation, competition and herbivory in a Chilean semi-arid community. Existing results show that the most dramatic effect on vegetation is this area has been in response to increased rainfall associated with a recent El Nino-Southern Oscillation (ENSO) event, rather than to herbivory or predation. This finding suggests the hypothesis that bottom-up effects structure this community during dry years, while biotic interactions (top-down regulation) become more important as animal numbers increase in response to increased productivity associated with rainfall. The specific purpose of this study is to continue our long-term experiment to confirm this suspected pattern of events, and to extend our observations to lizards, birds, and insects. This experiment promises, over the long-term, to provide an instructive example of how direct and indirect effects diverge through a community, and how their importance shifts as the physical environment changes. In addition to addressing basic ecological questions, this study provides important baseline data for understanding ecosystem change in the heavily desertified north-central Chilean semi-arid zone. It continues to be a valuable training ground for Chilean and American students and contributes directly to the development of science in both countries.