Treesearch

Ornithologists have hypothesized that some tropical forest birds avoid snake predation by nesting in isolated trees that do not have vines and canopy contact with neighbouring trees. Here we review two complementary studies that support this hypothesis by demonstrating (1) that an abundance of vines and an interlocking canopy characterized Jamaican Black-billed Parrot Amazona agilis nest-trees that failed due to chick loss, presumably to snakes, and (2) that such trees were used preferentially by an arboreal snake congeneric to the snake implicated in the parrot losses. Evidence strongly...

The semi-diurnal tidal regime (
2 m) in the Paria Gulf on the Atlantic coast of Venezuela, and the flat landscape of the region, allow the penetration for tens of km of marine waters into the rivers draining the northeastern coastal plain of the country. The levels of salinity, tidal flooding, and sedimentation decrease perpendicularly from the river channel toward the back swamps. The vegetation varies sequentially from fringe mangroves along the river margins, to back swamps containing forests dominated by Pterocarpus officinalis, herbaceous communities of Lagenocarpus guianensis, and...

We studied gas exchange, leaf dimensions, litter production, leaf and litterfall chemistry, nutrient flux to the forest floor, retranslocation rates, and nutrient use efficiency of mangroves in Jobos Bay, Puerto Rico. The fringe forest had a salinity gradient from the ocean (35‰) to a salt flat (100‰) and a basin (about 80‰). Red (Rhizophora mangle), white (Laguncularia racemosa), and black (Avicennia germinans) mangroves were zoned along this gradient. Photosynthetic rates, stomatal conductance, leaf area and weight, leaf specific area, and nutrient use efficiency decreased with increasing...

The vertical extent of waveforms collected by the Geoscience Laser Altimeter System (onboard ICESat - the Ice, Cloud, and land Elevation Satellite) increases as a function of terrain slope and footprint size (the area on the ground that is illuminated by the laser). Over sloped terrain, returns from both canopy and ground surfaces can occur at the same elevation. As a result, the height of the waveform (waveform extent) is insufficient to make estimates of tree height on sloped terrain, and algorithms are needed that are capable of retrieving information about terrain slope from the...

Microsatellites were used to evaluate the mating system of the remaining trees in a logged population of Swietenia macrophylla, a highly valuable and threatened hardwood species, in the Brazilian Amazon. A total of 25 open pollinated progeny arrays of 16 individuals, with their mother trees, were genotyped using eight highly polymorphic microsatellite loci. Genotypic data analysis from the progeny arrays showed that 373 out of the 400 seedlings (93.25%) were unambiguously the result of outcrossed matings and that the remaining 6.75% had genotypes consistent with self-fertilisation....

Comprehensive analysis of land morphology is essential to supporting a wide range environmental studies. We developed a landforms model that identifies eleven landform units for Puerto Rico based on parameters of land position and slope. The model is capable of extracting operational information in a simple way and is adaptable to different environments and objectives. The implementation of the landforms model for land cover change analysis represents an advanced step towards understanding the expansion of urban areas and forest cover in Puerto Rico between 1977 and 1994. Expansion of...

Primary tropical forests are renowned for their high biodiversity and carbon storage, and considerable research has documented both species and carbon losses with deforestation and agricultural land uses. Economic drivers are now leading to the abandonment of agricultural lands, and the area in secondary forests is increasing. We know little about how long it takes for these ecosystems to achieve the structural and compositional characteristics of primary forests. In this study, we examine changes in plant species composition and aboveground biomass during eight decades of tropical...

Temperate headwater streams with closed canopies rely on inputs of terrestrially derived organic matter to provide the major energy basis for their food webs. Microbial colonization, or conditioning, makes leaf litter more nutritional and palatable to stream detritivores, but few studies have investigated the relative importance of litter source to macroshredders in tropical streams. We determined the source (terrestrial, aquatic, or aerial), quantity, and species composition of allochthonous inputs into the Quebrada Prieta, a tropical headwater stream in Puerto Rico, as a first step...

Three groups of Native Americans, the Ciboneys, Arawaks, and Caribs, reached the Virgin Islands in pre-Columbian times. Since their discovery by Columbus in 1493, the Virgin Islands have been held or governed by Spain, Britain, the Netherlands, France, the Knights of Malta, Denmark, and the United States. They have also been held or used by groups ranging from estate owners and trading companies to pirates and squatters. European settlement of St. Croix, which began about 1625, resulted in the gradual replacement of that island's native forest with agricultural estates. Estate Thomas, on...