Treesearch

Diadromous faunas dominate most tropical coastal streams and rivers, but the factors controlling their distribution are not well understood. Our study documents abiotic variables controlling the distribution and abundance of the diadromous snail Neritina virginea (Gastropoda:Neritidae) in the Caribbean island of Puerto Rico. An intensive survey of N. virginea density and shell size, and channel substrate, velocity, and depth was conducted at microhabitat, habitat, and reach scales of a coastal plain reach of the Río Mameyes between August and December 2000. In addition, the inland extent...

We used a fluorescence technique to mark and re-count the invasive earthworm, Pontoscolex corethrurus from PVC tubes established in a forest and a recently abandoned pasture in Puerto Rico to test the effects of the labeling treatment on earthworm population survival over time. A fluorescent marker was injected into the earthworms in the middle third section of the body, between inside and outside walls. Five labeled juveniles and two unlabeled adults of P. corethrurus were incubated in the PVC tubes under field conditions and retrieved after 2, 4, 8, and 16 weeks (labeled population; four...

Extreme events (hurricanes, floods, and droughts) can influence upstream migration of macroinvertebrates and wash out benthic communities, thereby locally altering food webs and species interactions. We sampled palaemonid river shrimp (Macrobrachium spp.), dominant consumers in headwaters of the Luquillo Mountains of northeastern Puerto Rico, to determine their distributions along an elevational gradient (274–456 m asl) during a series of disturbances (Hurricane Hugo in 1989, a drought in 1994, and Hurricane Georges in 1998) that occurred over a 15-y period (1988
2002).We measured shrimp...

Populations of some native earthworm species are decreasing or disappearing due to human activities like habitat disturbance and introduction of exotic earthworms. Habitat disturbance can cause changes in soil physical structure and nutrient cycling, which may reduce native earthworm populations prior to the invasion of exotic earthworms. Our purpose was 1) to investigate habitat disturbance as a key process in the decline or extirpation of native earthworms, and 2) to measure the ability of native earthworms to re-colonize disturbed areas. We hypothesized that habitat disturbance will...

Wet tropical forests play a critical role in global ecosystem carbon (C) cycle, but C allocation and the response of different C pools to nutrient addition in these forests remain poorly understood. We measured soil organic carbon (SOC), litterfall, root biomass, microbial biomass and soil physical and chemical properties in a wet tropical forest from May 1996 to July 1997 following a 7-year continuous fertilization. We found that although there was no significant difference in total SOC in the top 0–10cm of the soils between the fertilization plots (5.42
0.18 kgm2) and the control...

Post-logging seedling regeneration density by big-leaf mahogany (Swietenia macrophylla), a nonpioneer light-demanding timber species, is generally reported to be low to nonexistent. To investigate factors limiting seedling density following logging within the study region, we quantified seed production rates, germinability, dispersal patterns, and seed fates on the forest floor through germination and the first seedling growing season in southeastern Amazonia, Brazil. Fruit production rates were low by three logged and one unlogged populations compared to reports from other regions....

Question: What are the composition, conservation status, and structural and environmental characteristics of eight mature tropical forest plant communities that occur along an elevational gradient. Location: Northeastern Puerto Rico. Methods: We quantified the species composition, diversity, conservation status, and ecological attributes of eight mature tropical forest plant communities in replicated plots located to sample representative components of important forest types occurring along an elevational gradient. A suite of environmental and vegetation characteristics were sampled at...

We examined whether a tropical stream in Puerto Rico matched predictions of the river continuum concept (RCC) for macroinvertebrate functional feeding groups (FFGs). Sampling sites for macroinvertebrates, basal resources, and fishes ranged from headwaters to within 2.5 km of the fourth-order estuary. In a comparison with a model temperate system in which RCC predictions generally held, we used catchment area as a measure of stream size to examine truncated RCC predictions (i.e., cut off to correspond to the largest stream size sampled in Puerto Rico). Despite dominance of generalist...

The Luquillo Mountains of northeastern Puerto Rico harbours important fractions of tropical montane cloud forests. Although it is well known that the frequent occurrence of dense fog is a common climatic characteristic of cloud forests around the world, it is poorly understood how fog processes shape and influence these ecosystems. Our study focuses on the physical characteristics of fog and quantifies the fogwater input to elfin cloud forest using direct eddy covariance net flux measurements during a 43-day period in 2002.We used an ultrasonic anemometer–thermometer in combination with a...

The most conspicuous biological invasions in terrestrial ecosystems have been by exotic plants, insects and vertebrates. Invasions by exotic earthworms, although not as well studied, may be increasing with global commerce in agriculture, waste management and bioremediation. A number of cases has documented where invasive earthworms have caused significant changes in soil profiles, nutrient and organic matter dynamics, other soil organisms or plant communities. Most of these cases are in areas that have been disturbed (e.g., agricultural systems) or were previously devoid of earthworms...