LTER III: Long-Term Ecological Research on the Luquillo Experimental Forest

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The Luquillo Experimental Forest (LEF) Long-term Ecological Research (LTER) 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 themes were 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 LEF-LTER was critical to the evaluation of the immediate effects of Hurricane Hugo, which struck Puerto Rico in 1989, and the long-term response of the forested ecosystems of the LEF to that severe disturbance. Monitoring of the effects of several less-severe storms and a subsequent hurricane (Hurricane Georges in 1998) has resulted in the LEF-LTER being in the position of the most thoroughly studies forested ecosystem subjected to repeated hurricane disturbance. Important strides also have been made in determining the spatial and temporal patterns of other natural disturbances (landslides, treefalls, floods, and drought). The LEF-LTER also has been instrumental in establishing the predominant importance of human disturbance in molding the structure and functioning of tropical ecosystems. In the LEF, legacies of human disturbance dating from before the 1930's appear in present times as important sources of variation in forest structure and species composition. Human disturbance affects natural disturbance regimes by making particular events more likely to occur (e.g., landslides near roads) or increasing their severity. The long-term experiments and measurements initiated in 1988 will remain the central focus of the LEF-LTER. Emphasis on the impacts of hurricanes and human disturbances on ecosystem dynamics of the LEF will continue. Further attention will be directed at deciphering interactions among the biota and their impact on critical ecosystem variables that determine responses to natural disturbances. New initiatives will expand the comprehensive analysis of disturbance and ecosystem response to include elevations up to the summit of the Luquillo Mountains.