LTER 5b: Understanding Ecosystem Change in Northeastern Puerto Rico

This long-term research project in Puerto Rico integrates research, educational activities, and outreach to broad audiences through examination of responses of wet tropical forests to disturbances. Development of strategies to manage and conserve tropical forested ecosystems globally depends critically on understanding the mechanisms by which these ecosystems respond to natural and human-induced change. The program will train numerous graduate and undergraduate students, especially members of underrepresented groups, producing a cadre of collaborative, multidisciplinary scientists who can link population, community, and ecosystem approaches to provide a predictive understanding of environmental change. An active schoolyard program develops K-12 curricula in science and mathematics throughout Puerto Rico, including a new 'data jam' workshop in which teachers will use the project's data to investigate basic ecological questions. The program will engage Puerto Rican high school students and teachers in educational programs at the El Verde Field Station. To date, 954 teachers and 1662 students have participated in an interactive teaching website, the Journey to El Yunque. The project collaborates with other large-scale networks including the National Ecological Observatory Network, the Luquillo Critical Zone Observatory, the Cloud Forest Research Coordination Network, and the Forest Global Earth Observatories, strengthening research infrastructure to tackle future challenges. The Luquillo LTER project will, over the coming three years, explore the development of novel ecosystems resulting from the separate and combined effects of increased drought and hurricane frequencies as these disturbances are mediated by land use legacies. Researchers predict that novel ecosystems resulting from these altered disturbances will differ from previous and current ones both structurally and functionally, and will integrate biogeochemistry, productivity, and population and community ecology studies to understand these differences. Two new experiments will be added to ongoing efforts: a stream drought experiment in which stream flow is reduced by manipulation and a forest through-fall reduction experiment in which rainfall is manipulated. The stream experiment will manipulate stream flow to examine the short- and long-term effects of drought on biota and biogeochemical cycling. The through fall exclusion experiment will determine the impact of multiple short-term droughts on soil biogeochemistry as well as on microbes, seedlings, and litter organisms. Results from both manipulations will be incorporated into models to investigate long-term effects and to evaluate the feasibility of future large scale manipulations that are logistically challenging in the forested ecosystems. A novel canopy trimming experiment will continue to simulate hurricanes in order to examine the effects of changes in hurricane frequencies and to separate the effects of canopy openness from deposition of material to the forest floor on forest composition, soil carbon storage, nutrient dynamics, and forest floor community structure. Results will test the hypothesis that increased frequency of intense hurricanes will increase the dominance of shade intolerant species with cascading effects through other biota and biogeochemistry. This integration of observational and experimental approaches is powerful because the effects of these disturbances over long time periods are poorly understood. The potential to gain insight into the mechanisms whereby these disturbance regimes result in future non-analog ecosystems in tropical forests is high and will significantly advance understanding of ecosystem ecology.