• The Luquillo Mountains in northeastern Puerto Rico are geologically
dynamic, with recurrent hurricanes, landslides, and earthquakes.
• Puerto Rico has never been physically connected to continents by land
bridges, which, together with the island’s long distance from North and
South America, contributes to its relatively low numbers of native plant and
animal species for a tropical location and its high rate of endemism.
• The climate is warm, wet, and relatively aseasonal but shows strong gradi-
ents with elevation.
• Soils are deep and highly weathered, with carbon and nutrient concentrations
and standing stocks similar to those in many other tropical forests. Soils
contain much to most of the available nutrients and total carbon, but plant
biomass is a particularly important pool of potassium.
• Nutrient inputs in precipitation are dominated by marine aerosols; these
aerosols and rapid weathering contribute to a substantial export of base
cations in streams.
• Nitrogen budgets are unbalanced at the watershed scale, suggesting that
significant amounts of N fixation are occurring.
• The Luquillo Mountains contain many types of forest, but four are common
and particularly well studied: tabonuco, colorado, palm, and elfin
• Aboveground net primary productivity is high, as it is in many other tropical
sites, and aboveground biomass, productivity, and forest stature decrease
• Large mammalian herbivores and predators are absent; lizards, frogs, snakes,
and a few birds are the top terrestrial predators.
• Stream and river food webs are dominated by freshwater shrimp and fish
species that migrate to the estuary; nonmigratory freshwater crabs are also
important, but aquatic insects are neither diverse nor abundant.
• Leaf litter decomposition is rapid in both the forest and streams, and detrital
pathways provide a major energy source to higher trophic levels.