Luquillo Experimental Forest
Located in Puerto Rico, the 11,540 ha (28,516 acres) Luquillo Experimental Forest is the largest tropical forest in the experimental forest and range system and the only experimental forest with the same boundary as the national forest, that is, El Yunque National Forest and the Luquillo are one. It has been studied for over 100 years and is one of the most intensively studied tropical forests in the world. The Luquillo Experimental Forest comprises the largest area of primary forests in Puerto Rico and the most pristine rivers in the island, including several wild and scenic rivers.

History 1876-2017
- 1876: King of Spain Alphonso XII proclaims 10 000 ha (24,710 acres) of forested land in the Luquillo Mountains as a forest reserve.
- 1903: President Theodore Roosevelt establishes the Luquillo Forest Reserve.
- 1956: The forest is designated the Luquillo Experimental Forest to recognize the growing importance of research.
- 1976: The forest is designated as a biosphere reserve by the United Nations.
- 1988: The Long Term Ecological Research (LTER) program begins in collaboration with the University of Puerto Rico.
- 2005: El Toro Wilderness Area is established.
- 2009: The Luquillo Critical Zone Observatory (LCZO) is established within El Yunque.
- 2017: A new management plan for El Yunque National Forest in final revision process.
Climate
Located within the Holdridge Life Zone Classification System, the Luquillo Experimental Forest is a subtropical moist to subtropical rain forest. Along the 1,000-meter elevation gradient (100 to 1,075 m asl), mean annual temperature ranges from 25 to 19 °C and annual rainfall from 2,000 to 5,000 mm. The average annual rainfall for the forest is 3,880 mm. The climate is subtropical maritime andis moderated by steady trade winds, which maintainrelatively constant year-round air temperatures. The annual temperature variation within a climate station is only 3.0 to 3.5 °C. Rainfall intensity varies at all temporal scales from diurnal to decadal. Although all months receive in excess of 100 mm, there is a period of lower rainfall between February and April and peaks of rainfall in September. Storms and hurricanes are climatic events that dramatically change forest conditions. For example, winds normally range from 8 to 18 km/h but exceed 200 km/h during category 5 hurricanes. Rainfall can exceed 400 mm/day during storms and low-pressure systems. Such events trigger numerous landslides. Droughts (< 100 mm/month) recur on decadal scales, but natural fires do not occur.
There are four soil associations representing 19 soil series. The principal orders are Ultisols and Inceptisols, which respectively occupy 50 and 20 percent of the total forest area, and small areas with Inceptisols and other soil types. Dominant soils are deep, highly weathered and leached clays, with low pH and base saturation less than 35 percent at a depth of 1.25 m.
Databases
Numerous data bases are compiled at the Luquillo Experimental Forest, including maps of geology, soils, vegetation, and disturbance history; ten sets of aerial photography (since 1936); air temperature and precipitation (since 1909); solar radiation, windspeed and direction, relative humidity; NADP precipitation (since 1984); as well as chemical composition of precipitation, dryfall,cloudwater, bulk soil, soil solution, throughfall, stemflow, streamwater, plant, animal, and fungal tissue; vegetative composition, above- and below-ground biomass, tree growth/mortality, litterfall, litter decomposition, wood decomposition, mycorrhizal associations, phenology; and population records and biomass of terrestrial and aquatic fauna. Many long-term data records are available on the Luquillo LTER web page. [External Site: Opens in New Window]
Research and Opportunities
Research studies in the Luquillo Experimental Forest range from plantation forestry, reforestation, land rehabilitation, tree growth, and ecosystem structure and function, to wildlife ecology, hydrology, geomorphology, and disturbance and landscape ecology. There are more than 30 cross-site experiments, including:
- LIDET (Long-Term Intersite Decomposition Experiment Team)
- LINX (Lotic Intersite Nitrogen Experiment)
- DONIC (Dissolved Organic Nitrogen Intersite Comparison)
- WW-DECOEX (World Wide Aquatic Leaf Decomposition Experiment)
- Earthworms and soil processes in tropical ecosystems
- Relationship between nutrient inputs and faunal diversity
- Canopy herbivory and soil processes in a temperate and tropical forest
- Global forest dynamics network
- Landscape fragmentation and forest fuel accumulation; effects of fragment size, age, and climate.
The Luquillo Experimental Forest offers opportunities for research in tropical forestry and related fields. Programs such as those of the USDA Forest Service, the National Science Foundation, the USDI Geological Survey, and the University of Puerto Rico are available for research collaboration in all fields of the natural sciences.
Facilities Information
The Sabana Field Research Station
The Sabana Field Research Station is a facility of the USDA Forest Service’s International Institute of Tropical Forestry (Institute), a center for excellence where creativity and accomplishments result in timely products and services that anticipate the needs of society as it mitigates and adapts to environmental change.
Our mission is to develop and disseminate scientifically-based knowledge that contributes to the conservation of forests, wildlife, and watersheds of the American tropics in the context of environmental change. Furthermore, the Institute strives to cultivate an inclusive environment and ensure that all who visit our facilities are provided equal access to opportunities, programs, and services that are available.
The El Verde Field Station

The El Verde Field Station, which has living quarters and laboratory facilities for up to 25 scientists, is maintained by the Institute for Tropical Ecosystem Studies in the Luquillo. The field station provides collections of local plants and animals; a laboratory with light meters, balances, microscopes, pH meters, hoods, etc.; line power backed up by a generator; and gas, air, and vacuum lines. The Biology Department of the University of Puerto Rico (Río Piedras) maintains a second field station in the palo colorado forest of the Luquillo Experimental Forest.
Among the resources available through the Institute are the Bisley Experimental Watersheds, the Sabana Field Research Station, a woodshop, analytical laboratory for soils and vegetation, tropical forestry library with 55,000 documents, 10,000 bound volumes, 100 journal subscriptions, map, film, and slide collections of the entire Oxford forestry collection on microfilm, FAO documents and journal listings from larger libraries (e.g., Oxford, University of Georgia, University of Florida, USDA National Agricultural Library) in microfiche, computerized literature searching facilities, and a research herbarium with more than 95 percent of the 700+ tree species in Puerto Rico. The herbarium is operated by the Botanical Garden of the University of Puerto Rico.
Contact
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Long-term Monitoring and Data
The Bisley Experimental Watersheds (BEW) are three adjacent watersheds managed by the Institute, located in tabonuco forest a few kilometers south of the Sabana Field Research Station.
Within the BEW, a number of long-term ecological, hydrological, and silvicultural research projects have been conducted since the 1980s, carried out by Institute scientists and collaborating researchers from the Luquillo Long-Term Ecological Research Program (LUQ-LTER), the Luquillo Critical Zone Observatory (LCZO), and the U.S. Geological Survey, among others.

Long-term, detailed monitoring of biogeochemistry, climate variables, and stream runoff in Bisley has produced some of the longest environmental records on watershed processes in the Neotropics, and has made significant contributions to the understanding of hydrologic, carbon, nitrogen, and phosphorus cycling in tropical wet forests.
The data from Bisley provide an unequalled opportunity to understand seasonal and inter-annual climatic variability and quantify its relationships with ecosystem processes, including the effects of multiple hurricanes, droughts, plant aboveground stoichiometry, and forest diversity and structure on biogeochemistry and faunal assemblages at the plot and watershed scales. They also contribute to collaborative analysis and research with ecologists from Coweeta Hydrologic Laboratories and other experimental forests and watersheds to support synthesis and large-scale understanding of climate change parameters and stream discharge relationships.
Bisley Facilities

Research facilities include two walk-up canopy towers, climate stations, three stream gages, throughfall and litter collectors, permanent ecological study plots, and areas designated for aquatic research. Forest composition and soil and plant nutrient content are monitored in 83 permanent 10 meter diameter plots on a 40 x 40 meter grid every 5 years.
Canopy throughfall and litterfall are measured weekly. Stream chemistry and coarse particulate export are measured every two weeks in three streams. Shrimp abundances are measured twice yearly in two BEW streams, and algal abundance, ecosystem metabolism, chlorophyll a, and insect abundance are measured biannually in one BEW stream.
Related Publications
- Coral Matos, Amelia Merced, Tamara Heartsill Scalley. 2024. Habitat preferences and distribution of some common bryophytes in a tropical forest at the Luquillo Experimental Forest, Puerto Rico
- Mingjie Shi, Michael Keller, Barbara Bomfim, Lingcheng Li, Charlie Koven, Lara Kueppers, Ryan Knox, Jessica Needham, Shih‐Chieh Kao, Peter E. Thornton, Michele M. Thornton, L. Ruby. Leung. 2024. Functionally Assembled Terrestrial Ecosystem Simulator (FATES) for Hurricane Disturbance and Recovery
- Virginia Hudspeth, Alberto Pastor, Tamara Heartsill Scalley. 2023. High-Light Demanding and Rare Tree Species Define Tropical Riparian Tree Communities
- Alberto C. Cruz-Mendoza, Frank F. Rivera-Milan, Wayne J. Arendt, Laura L. Fidalgo-De Souza, Jessica Ilse, Joseph M. Wunderle Jr. 2023. Effects of Hurricanes Irma and Maria on Abundance and Occupancy of Margarops fuscatus (Pearly-eyed Thrasher) in the Luquillo Experimental Forest, Puerto Rico
- Dingfang Chen, Mei Yu, Grizelle Gonzalez, Qiong Gao. 2023. Altitudinal Pattern of Soil Organic Carbon and Nutrients in a Tropical Forest in Puerto Rico