Luquillo Experimental Forest at the NE Part of Puerto RicoThe overarching goal of the Luquillo LTER program is to determine how changing climate and disturbance regimes, alone or in concert, drive changes in the biota and biogeochemistry.  An enhanced mechanistic understanding of change in natural and human modified landscapes will supply critical information to manage and conserve tropical forest ecosystems globally.  LUQ includes both terrestrial and aquatic studies, from the peaks of the Luquillo Mountains to the coastal ecosystems of San Juan.  It encompasses strong gradients of both climate and land use through a multidisciplinary effort involving population and community ecologists, microbiologists, aquatic ecologists, ecosystem scientists, and social scientists. LUQ is uniquely valuable for its focus on a forested mountainous landscape on a tropical island in the midst of the Caribbean biodiversity hotspot (Reagan & Waide 1996, Brokaw et al. 2012).

LUQ research builds on a long and rich research history. The US Forest Service pioneered research on tropical forest timber management and reforestation in the Luquillo Mountains in the 1940s, including the installation of long-term research plots that eventually led to the establishment of the Luquillo Experimental Forest (LEF) in 1956. In the 1960s, the Atomic Energy Commission-sponsored Rainforest Project provided what was the most detailed understanding to date of forest metabolism, nutrient cycling, energy flows and population dynamics of a tropical forest as context for an experiment to measure the impacts of gamma radiation on tropical forests (Odum & Pigeon 1970). Subsequently, the U.S. Department of Energy continued to support ecosystem research in the LEF until 1988 through the Center for Energy and Environment Research at the University of Puerto Rico (UPR). 

In 1988, the LEF became the only tropical terrestrial site in the Long Term Ecological Research (LTER) Network, with focal research on the effects of long-term climate patterns, intense disturbances (hurricanes and landslides), and forest harvesting on biota and biogeochemical cycling. Currently, the Department of Environmental Science at the University of Puerto Rico-Rio Piedras and the International Institute of Tropical Forestry- IITF (USDA Forest Service) serve as co-leading institutions of the LUQ LTER Program, and are supported by 11 other mainland institutions. Results from the LUQ program have improved our understanding of montane forest ecosystems that provided the foundation for complementary research efforts such as the NSF’s Critical Zone Observatories (CZO) and Urban Long Term Research Areas (ULTRA) programs as well as the USGS’s Water, Energy and Biogeochemical Budgets (WEBB), Center for Tropical Forest Studies (CTFS) that compares tropical forests around the world. The Luquillo LTER continues to use our expanding knowledge of the forests and streams of the Luquillo Mountains to foster a broader understanding of the principles that structure forested montane ecosystems in both temperate and tropical climates.

Research history in the Luquillo Experimental Forest, showing key long-term studies in relation to fundamental components of LUQ activities (horizontal bars). Disturbance and factors which modify the disturbance regime (see Fig. 1) are color-coded gray and measured responses are green. Evolving projects and, since 1988, LTER goals are shown in columns. Information includes the changing conceptual underpinnings of the research programs (blue) as well as administrative history since the 1940s (white at bottom).