Luquillo LTER - History

The Luquillo Experimental Forest (LEF) Long-Term Ecological Research Program began in 1988 with the goal of integrating studies of disturbance regime and forest structure and dynamics with a landscape perspective. Two central research questions addressed 1) the relative importance of different disturbance types within the four tropical rain forest life zones of the LEF and 2) the importance of the biota in restoring ecosystem productivity after disturbance. The long-term monitoring program initiated as part of the Luquillo LTER was critical to the evaluation of immediate and subsequent effects of Hurricane Hugo, which struck Puerto Rico in 1989. The occurrence of a hurricane soon after the initiation of the LTER program provides an opportunity to study the long-term dynamics of a tropical forest as it recovers from a major disturbance. Emphasis on the impacts of hurricanes and human disturbances on ecosystem dynamics of the LEF continued in LTER 2. Further attention was directed at deciphering interactions among the biota and their impact on critical ecosystem variables that determine responses to natural disturbances. New initiatives expanded the comprehensive analysis of disturbance and ecosystem response to include elevations up to the summit of the Luquillo Mountains. In the LTER 3 proposal, we combined long-term measurements, field experiments, simulation modeling, and cross-site comparisons to address five questions: (1) How do climatic factors, litter quality, and detritivore diversity regulate decomposition of detrital pulses? (2) How do terrestrial and aquatic food webs differ in response to detrital pulses? (3) What is the effect of disturbance frequency on nutrient cycling, plant community composition, and the accumulation of soil organic matter? (4) To what degree is the export of carbon and nutrients from watersheds a result of soil characteristics that are affected by detrital dynamics? (5) How do elevationally related changes in climate impact plant and detritivore communities, and how do these feed back on the quantity and quality of litter inputs and decomposition? Through our focus on disturbance and detrital dynamics, we build on existing strengths in integrating community and ecosystem ecology and the research opportunities provided by infrequent, large-scale disturbance, high diversity, and pronounced elevational gradients in the LEF. Our research is being conducted in two spatial contexts. In mid-elevation tabonuco forest, we will continue long-term measurements of ecosystem response to hurricanes, landslides, and anthropogenic disturbance. Long-term measurements of hydrological and nutrient fluxes in watersheds will relate soil characteristics to stream nutrient and organic matter losses and provide information to gauge the effects of future disturbances. Simulation models of key population, community, biogeochemical, and landscape processes provide null-model predictions to inform these new observations and experiments.


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