Treesearch

Nutrient inputs into tank bromeliads were studied in relation to growth and productivity, and the abundance, diversity and biomass of their animal inhabitants, in three forest types along an elevational gradient. Concentrations of phosphorus, potassium and calcium in canopy-derived debris, and nitrogen and phosphorus in phytotelm water, declined with increasing elevation. Dwarf forest bromeliads contained the smallest amounts of debris/plant and lowest concentrations of nutrients in plant tissue. Their leaf turnover rate and productivity were highest and, because of high plant density,...

Partners in Flight (PIF) is a coalition of federal, state, and local government agencies; nongovernmental organizations (NGOs); philanthropic foundations; and industry that is working to conserve the birds of the Western Hemisphere. PIF was launched in 1990 in response to growing concerns about declines in the populations of many landbirds, and to spearhead the conservation of birds not covered by existing initiatives, such as the North America Waterfowl Management Plan. The initial focus of PIF was on Neotropical migrants (species that breed in North America north of the tropics and...

Nitrous oxide (N2O) and nitric oxide (NO) are important atmospheric trace gases participating in the regulation of global climate and environment. Predictive models on the emissions of N2O and NO emissions from soil into the atmosphere are required. We modified the CENTURY model (Soil Sci. Soc. Am. J., 51 (1987) 1173) to simulate the emissions of N2O and NO from tropical primary forests in the Atlantic Zone of Costa Rica at a monthly time step. Combined fluxes of N2O and NO were simulated as a function of gross N mineralization and water-filled pore space (WFPS). The coefficients for...

The introduction of bamboo to montane rain forests of the Luquillo Mountains, Puerto Rico in the 1930s and 1940s has led to present-day bamboo monocultures in numerous riparian areas. When a non-native species invades a riparian ecosystem, in-stream detritivores can be affected. Bamboo dynamics expected to in¯uence stream communities in the Luquillo Experimental Forest (LEF) were examined. Based on current distributions, bamboo has spread downstream at a rate of 8 m y-1. Mean growth rate of bamboo culms was 15.3 cm d-1. Leaf fall from bamboo stands exceeded that of native mixed-species...

Grasses and ferns characterized the recovery of elfin woodland for the first 18 years after a December 1968 airplane crash. From 1986 to 1998, ferns and woody dicots were prominent and the total aboveground dry weight biomass increased from 775 to 2210 g/m2. Woody dicots increased 3.5 times, palms 1.3 times, and ferns 4.4 times above their 1986 levels. Grasses and herbs decreased by nearly 10 %. Recovery was patchy, with some areas dominated by trees ³4 m in height and others by grasses and scattered ferns. Puerto Rican endemic trees are playing a critical role in the recovery of the elfin...

We used a humid tropical elevation gradient to examine the relationships among climate, edaphic conditions, belowground carbon storage, and soil respiration rates. We also compared open and closed canopy sites to increase the range of microclimate conditions sampled along the gradient, and determine the effects of canopy openings on C and P storage, and C dynamics. Total soil C, the light C fraction, and all of the component fractions of the P pool were significantly related to soil moisture, and all but total soil C were also significantly related to temperature. Both labile and recalcitra...

Seedling and sapling dynamics in a Puerto Rican rain forest were compared between forest understory and soil pits created by the uprooting of 27 trees during Hurricane Hugo. Soil N and P, organic matter, and soil moisture were lower and bulk densities were higher in the disturbed mineral soils of the pits than in undisturbed forest soils ten months after the hurricane. No differences in N and P levels were found in pit or forest soils under two trees with N-fixing symbionts (Inga laurina and Ormosia krugii) compared to soils under a tree species without N-fixing symbionts (Casearia...

Two species of tropicbirds (Phaethontidae) live in the Western North Atlantic. The Whitetailed Tropicbird of the region is an endemic race, Phaethon lepturus catesbyi, with approximately 5000 pairs. This is half the estimate made less than two decades ago. The Red-billed Tropicbird, P. aethereus, has approximately 2000 pairs regionally and fewer than 8000 pairs globally. Neither species has been considered to be of conservation concern. We suggest that the Atlantic populations of Phaethon lepturus and the global population of Phaethon aethereus be considered for appropriate conservation...

Soil texture plays a key role in belowground C storage in forest ecosystems and strongly influences nutrient availability and retention, particularly in highly weathered soils. We used field data and the Century ecosystem model to explore the role of soil texture in belowground C storage, nutrient pool sizes, and N fluxes in highly weathered soils in an Amazonian forest ecosystem. Our field results showed that sandy soils stored approximately 113 Mg C ha-1 to a 1-m depth versus 101 Mg C ha-1 in clay soils. Coarse root C represented a large and significant ecosystem C pool, amounting to 62%...

Migratory freshwater shrimps represent important links between the headwaters and estuaries of many tropical rivers. These species exhibit amphidromous life cycles in which larvae are released by females in upper reaches of rivers; first stage (i.e., newly hatched) larvae drift passively to coastal environments where they develop and metamorphose into postlarvae that subsequently migrate back upstream to adult (freshwater) habitat. Recent studies in rivers draining northeastern Puerto Rico and Costa Rica’s Caribbean slope have been the first to document migratory drift of first stage...