Treesearch

Adult populations of big-leaf mahogany (Swietenia macrophylla) occur in aggregations along seasonal streams in transitional evergreen forests of southeast Pará, Brazil. To test whether variable seedling survival and growth across topography may underlie this observed distribution pattern, we planted nursery-grown seedlings in the forest understory and in artificial gaps at opposite ends of a slope gradient where mahogany occurs (low-ground hydromorphic soils) and does not occur (high-ground dystrophic soils). At both positions seedling survival and growth were significantly greater through...

Contrary to the general trend in the tropics, forests have recovered in Puerto Rico from less than 10% of the landscape in the late 1940s to more than 40% in the present. The recent Puerto Rican history of forest recovery provides the opportunity to study the ecological consequences of economic globalization, reflected in a shift from agriculture to manufacturing and in human migration from rural to urban areas. Forest structure rapidly recovers through secondary succession, reaching mature forest levels of local biodiversity and biomass in approximately 40 years. Despite the rapid...

Tropical stream food webs are thought to be based primarily on terrestrial resources (leaf litter) in small forested headwater streams and algal resources in larger, wider streams. In tropical island streams, the dominant consumers are often omnivorous freshwater shrimps that consume algae, leaf litter, insects, and other shrimps. We used stable isotope analysis to examine (1) the relative importance of terrestrial and algal-based food resources to shrimps and other consumers and determine (2) if the relative importance of these food resources changed along the stream continuum. We...

Spatially explicit climate data contribute to watershed resource management, mapping vegetation type with satellite imagery, mapping present and hypothetical future ecological zones, and predicting species distributions. The regression based Parameter-elevation Regressions on Independent Slopes Model (PRISM) uses spatial data sets, a knowledge base and expert interaction to generate GIS-compatible grids of climate variables. This study applied PRISM to generate maps of mean monthly and annual precipitation and minimum and maximum temperature for the Caribbean islands of Puerto Rico,...

1. Long-term data on rainfall suggests that perennial rainforest streams rarely are subject to drying of riffles or pools in the wet, non-seasonal Caribbean climate of Puerto Rico. Unusually low rainfall in 1994 caused some headwater riffles to dry out completely, resulting in isolated pools, reduced pool volumes and loss of access to microhabitats by benthic invertebrates. 2. From 1992 to 1998, shrimp populations were sampled bimonthly using baited traps in six pools along 1200 m (from 305 to 480 m in altitude) of Quebrada Prieta, a second-order headwater stream in the Luquillo Experimenta...

We conducted a quantitative analysis of adult and juvenile Eleutherodactylus coqui (coquí) habitat preferences in Puerto Rico. The analysis consisted of two surveys: one to quantify potential habitat and another to quantify habitat use. Coquís were found to use most habitats available to them; however, adults and juveniles preferred different plant species, habitat structural components, and heights from the forest floor. Adult and juvenile coquís had opposite associations with many important plant species in the forest (e.g., Prestoea montana and Heliconia carabea) and habitat structural...

We studied changes that occurred between 1980 and 2000 in forest floor biomass (necromass+ biomass of herbaceous plants), nutrient stocks, and plant composition of a Prestoea montana floodplain forest. The forest was located in the Luquillo Mountains of Puerto Rico. Several storms and hurricanes passed near the study site during that period, the most severe being hurricane Hugo in 1989, and Georges in 1998. Hugo opened the canopy and increased the nutrient and biomass stocks of the forest floor. Six years after the passage of Hugo and two years after Georges, the forest floor necromass was...

The combination of human population growth, increased water usage, and limited groundwater resources often leads to extensive damming of rivers and streams on tropical islands. Ecological effects of dams on tropical islands can be dramatic, because the vast majority of native stream faunas (fishes, shrimps, and snails) migrate between freshwater and saltwater during their lives. Dams and associated water withdrawals have been shown to extirpate native faunas from upstream reaches and increase mortality of downstream-drifting larvae. A better understanding of the effects of dams and the...

Rapid Changes in vegetation over short distances, high species diversity, and fragmented landscape challege the implementation of the Forest service's Forest inventory and Analysis (FIA)program on Puerto Rico. Applying the hexagonal FIA grid as used on the continental United States, the Forest service is installing a new forest sampling and monitoring framework that incorporates previous inventory plots and has an expanded scope. however, an adequete description of Puerto Rico's diverse tropical forests requires additional sampling:

This study describes the avifauna of the Tapajos National forest, an area on the east bank of the Tapajos River where controlled resource exploitation occurs. Here we provide a near complete species list for terra firme forest with an incomplete list of species from less comprehensively surveyed habitats such as "varzea" forest.