Treesearch

This greenhouse study examines the effects of Pontoscolex corethrurus on the growth of Cecropia scheberiana in forest and pasture soils. Four treatments (0, 2, 20 worms and 0 worms + urea fertilizer) were applied to the soils to test if earthworms affect nitrogen availability, and consequently the growth of C. scheberiana. We recorded the number of seedlings, leaves, and height of plants, and measured NH4+ and NO3- concentrations in water leachates during a six month period. The growth of C. scheberiana and nitrogen concentration in leachates differed between pasture and forest soils....

Plant communities may impose strong control on soil fauna properties. We examined the abundance and distribution pattern of earthworms in two contrasting plant communities within a tropical wet forest in Puerto Rico. The Dacryodes community occurs in well-drained soils and is dominated by Dacryodes excels, Manilkara bidentata, Guarea guidonea, and Sloanea berteriana. The Heliconia community occurs in poorly-drained soils and is dominated by Heliconia caribaea and Prestoa montana. Earthworm biomass and density in Dacryodes community were twice those in the Heliconia community. Earthworm...

Plant communities differ in species composition and litter input. To examine the influence of plant species on the abundance and community structure of soil fauna, we sampled earthworms in areas close to and away from the bases of Dacryodes excelsa and Heliconia caribaea, two distinct plant communities within a tropical wet forest in Puerto Rico. We also carried out a litter manipulation experiment to examine the short-term responses of earthworms to litter removal and litter addition treatments. We found that: ( I ) the density and biomass of both soil-feeding endogeic and litrer-feeding...

Aim Our main goals were to develop a map of the life zones for the conterminous United States, based on the Holdridge Life Zone system, as a tool for ecosystem mapping, and to compare the map of Holdridge life zones with other global vegetation classification and mapping efforts. Location The area of interest is the forty-eight contiguous states of the United States. Methods We wrote a PERL program for determining life zones from climatic data and linked it to the image processing workbench (IPW). The inputs were annual precipitation (Pann), biotemperature (Tbio), sea-level biotemperature...

Recent surveys of tropical forest water use suggest that rainfall interception by the canopy is largest in wet maritime locations. To investigate the underlying processes at one such location—the Luquillo Experimental Forest in eastern Puerto Rico—66 days of detailed throughfall and above-canopy climatic data were collected in 1996 and analysed using the Rutter and Gash models of rainfall interception. Throughfall occurred on 80% of the days distributed over 80 rainfall events. Measured interception loss was 50% of gross precipitation. When Penman–Monteith based estimates for the wet...

Tree growth, biomass productivity, litterfall mass and nutrient content, changes in soil chemical properties and understory forest succession were evaluated over a 8.5-year period in single- and mixed-species (50 : 50) plantations of two N2-®xing species, Casuarina equisetifolia and Leucaena leucocephala, and a non-®xing species, Eucalyptus robusta. At the optimal harvest age for maximum biomass production (4 years), total aboveground biomass ranged from 63 Mg haÿ1 in the Eucalyptus monoculture to 124 Mg haÿ1 in the Casuarina/Leucaena mixture, and was generally greater in the mixed-species...

Residentsa nd wintering Nearctic migrantsw ere sampledb y point countsi n 40 smallt o medium-sized(0 .07-8.65 ha) shadec offeep lantationsw ith an overstoryo f Inga vera in the Cordillera Central, Dominican Republic. The purpose of the study was to determine the relative importance of plantation area, isolation, and habitat structure to avian distribution and abundance. Variation in abundance was unrelated to plantation area for all migrant species (n = 7), whereas the local abundance of four of ten resident species increased significantlyw ith area. Elevationw ast he only variablet hat...

While herbaceous species and vines constitute a minor portion of the biomass in tropical closed forest ecosystems, they account for a substantial portion of the diversity of these ecosystems and become more conspicuous after natural disturbances. This study describes the changes in abundance and diversity of the herbs and vines during 5 years following Hurricane Hugo at the Bisley Experimental Watersheds, Puerto Rico. The cover of herbs, ferns, and vine species was sampled within a 5-m2 area in 25 randomly chosen circular permanent plots within the 13 ha of these watersheds. Sampling was...

The 178-hectarea(ha) northeastern tip of Puerto Rico, Which is known locally as "Las Cabezas de San Juan Nature Reserve", is managed by the Puerto Rican Conservation Trust to protect the area's scenic beauty and to provide enviromental education and research opportunities to the island's resident and visitors

Fruit availability on 25 plant species, consumed or potentially consumed by the Puerto Rican Parrot (Amazona vittata), was studied to document the seasonal and annual variation in fruit production in the Luquillo Mountains. In the 33 months before Hurricane Hugo, an annual cycle in the number of species with ripe fruit was evident, with a peak in October-February and a trough during June-July. About half the plant species showed this annual fruiting cycle. Irregular noncyclic fruiting was found in the other half, and varied among species in annual duration. Fruit production reached its...