Ecology

HABITAT SEGREGATION OF DENGUE VECTORS ALONG AN URBAN ENVIRONMENTAL GRADIENT

Cox, J, Grillet, ME, Ramos, OM, Ammador, M, et al. Habitat
segregation of dengue vectors along an urban environmental
gradient. Am J Trop Med Hyg 2007; 76:820–826.

Abstract: 
Differential distributions of Aedes aegypti and Ae. mediovittatus (potential inter-epidemic dengue vector) and other mosquitoes colonizing bamboo pots in San Juan, Puerto Rico were studied along an urban-rural gradient. City regions (urban, suburban, and rural) and landscape elements within regions (forest [F], low-density housing [LDH], and high-density housing [HDH]) were identified using satellite imagery. Aedes species extensively overlapped in LDH of urban, suburban, and rural areas. Mosquito species showed their high specificity for landscape elements (96.6% correct classification by discriminant analysis); absence of Ae. mediovittatus in HDH or absence of Ae. aegypti in forests were the main indicator variables. The gradient was explained using a canonical correspondence analysis, which showed the association of Ae. aegypti with HDH in urban areas, Culex quinquefasciatus with LDH in suburbs, and Ae. mediovittatus and other native mosquitoes (Cx. antillummagnorum, Toxorhynchites portoricencis) with less disturbed habitats (forests, LDH).

Factors Influencing Tropical Island Freshwater Fishes: Species, Status, and Management Implications in Puerto Rico

Neal JW, Lilyestrom CG, Kwak TJ (2009) Factors influencing tropical island freshwater fishes: species, status, and management implications in Puerto Rico. Fisheries 37:546-554

Abstract: 
Anthropogenic effects including river regulation, watershed development, contamination, and fish introductions have substantially affected the majority of freshwater habitats in Europe and North America. This pattern of resource development and degradation is widespread in the tropics, and often little is known about the resources before they are lost. This article describes the freshwater resources of Puerto Rico and identifies factors that threaten conservation of native fishes. The fishes found in freshwater habitats of Puerto Rico represent a moderately diverse assemblage composed of 14 orders, 29 families, and 82 species. There are fewer than 10 species of native peripherally-freshwater fish that require a link to marine systems. Introductions of nonindigenous species have greatly expanded fish diversity in freshwater systems, and native estuarine and marine species (18 families) also commonly enter lowland rivers and brackish lagoons. Environmental alterations, including land use and development, stream channelization, pollution, and the impoundment of rivers, combined with nonnative species introductions threaten the health and sustainability of aquatic resources in Puerto Rico. Six principal areas for attention that are important influences on the current and future status of the freshwater fish resources of Puerto Rico are identified and discussed.

Nutrient relations of dwarf Rhizophora mangle L. mangroves on peat in eastern Puerto Rico

Medina E, Cuevas E, Lugo AE (2010) Nutrient relations of
dwarf Rhizophora mangle L. mangroves on peat in eastern
Puerto Rico. Plant Ecol 207:13–24

Abstract: 
Dwarf mangroves on peat substrate growing in eastern Puerto Rico (Los Machos, Ceiba State Forest) were analyzed for element concentration, leaf sap osmolality, and isotopic signatures of C and N in leaves and substrate. Mangrove communities behind the fringe presented poor structural development with maximum height below 1.5 m, lacked a main stem, and produced horizontal stems from which rhizophores developed. This growth form departs from other dwarf mangrove sites in Belize, Panama, and Florida. The dwarf mangroves were not stressed by salinity but by the low P availability reflected in low P concentrations in adult and senescent leaves. Low P availability was associated with reduced remobilization of N and accumulation of K in senescent leaves, contrasting with the behavior of this cation in terrestrial plants. Remobilization of N and P before leaf abscission on a weight basis indicated complete resorption of these nutrients. On an area basis, resorption was complete for P but not for N. Sulfur accumulated markedly with leaf age, reaching values up to 400%, compared with relatively modest accumulation of Na (40%) in the same leaves. This suggests a more effective rejection of Na than sulfate at the root level. Dwarf mangrove leaves had more positive d13C values, which were not related to salinity, but possibly to drought during the dry season due to reduced flooding, and/or reduced hydraulic conductance under P limitation. Negative leaf d15N values were associated with low leaf P concentrations. Comparison with other R. mangle communities showed that P concentration in adult leaves below 13 mmol kg-1 is associated with negative d15N values, whereas leaves with P concentrations above 30 mmol kg-1 in non-polluted environments had positive d15N values.

LONG-TERM PATTERNS IN TROPICAL REFORESTATION: PLANT COMMUNITY COMPOSITION AND ABOVEGROUND BIOMASS ACCUMULATION

MARIN-SPIOTTA, E. ; OSTERTAG, R.; SILVER W. L. 2007. Long-term, patterns in tropical reforestation: plant community composition and aboveground biomass accumulation.. Ecological Applications, 17(3), :828-839.

Abstract: 
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 secondary succession in Puerto Rico, and compare these patterns with primary forests. Using a well-replicated chronosequence approach, we sampled primary forests and secondary forests established 10, 20, 30, 60, and 80 years ago on abandoned pastures. Tree species composition in all secondary forests was different from that of primary forests and could be divided into early (10-, 20-, and 30-year) vs. late (60- and 80-year) successional phases. The highest rates of aboveground biomass accumulation occurred in the first 20 years, with rates of C sequestration peaking at 6.7 6 0.5 Mg Cha1yr1. Reforestation of pastures resulted in an accumulation of 125 Mg C/ha in aboveground standing live biomass over 80 years. The 80 year-old secondary forests had greater biomass than the primary forests, due to the replacement of woody species by palms in the primary forests. Our results show that these new ecosystems have different species composition, but similar species richness, and significant potential for carbon sequestration, compared to remnant primary forests.

The Ecological Life Zones of Puerto Rico and the U.S. Virgin Islands

Ewel, J.J.; Whitmore, J.L. 1973. The Ecological Life Zones of Puerto Rico and the U.S. Virgin Islands. USDA Forest Service, Institute of Tropical Forestry, Research Paper ITF-018.

Abstract: 
Most of the neotropical nations except Mexico and Brazil are mapped according to the Moldridge system of ecological life zones. In order to have comparability with these areas, Puerto Rico and the U.S. Virgin Islands were mapped and a discussion and a description of each life zone were written. The manuscript in English offers water balances, a description of the Holdridge theory of biotemperature, and greater detail in general. The shortened version in Spanish is intended as a field manual to be used with the map. Six life zones are present on these islands and are present also in South and Central America, representing large areas there. Research done on the islands will be directly applicable to those areas and conversely, successful practices done there will be applicable in corresponding life zones on the islands.

Forest conservation and land development in Puerto Rico

Helmer, E.H., 2004. Forest conservation and land development in Puerto Rico.
Landscape Ecol. 19, 29–40.

Abstract: 
In the Caribbean island of Puerto Rico, rapid land-use changes over the past century have included recent land-cover conversion to urban/built-up lands. Observations of this land development adjacent to reserves or replacing dense forest call into question how the changes relate to forests or reserved lands. Using existing maps, this study first summarizes island-wide land-cover change between 1977-78 and 1991-92. Then, using binomial logit modeling, it seeks evidence that simple forest cover attributes, reserve locations, or existing land cover influence land development locations. Finally, this study quantifies land development, reserve protection and forest cover by ecological zone. Results indicate that 1) pasture is more likely to undergo land development than shrubland plus forest with low canopy density, 2) forest condition and conservation status appear unimportant in that development locations neither distinguish between classes of forest canopy development nor relate to forest patch size or reserve proximity, and 3) most land development occurs in the least-protected ecological zones. Outside the boundaries of strictly protected forest and other reserves, accessibility, proximity to existing urban areas, and perhaps desirable natural settings, serve to increase land development. Over the coming century, opportunities to address ecological zone gaps in the island’s forest reserve system could be lost more rapidly in lowland ecological zones, which are relatively unprotected.

Mapping the Forest Type and Land Cover of Puerto Rico, a Component of the Caribbean Biodiversity Hotspot

ELMER,E. H.; RAMOS, O.; LÓPEZ, T. DEL M.; QUIÑONES, M.; DIAZ, W. 2002. Mapping the Forest Type and Land Cover of Puerto Rico, a Component of the Caribbean Biodiversity Hotspot. Caribbean Journal of Science, Vol. 38, No. 3-4, 165-183, .

Abstract: 
The Caribbean is one of the world’s centers of biodiversity and endemism. As in similar regions, many of its islands have complex topography, climate and soils, and ecological zones change over small areas. A segmented, supervised classification approach using Landsat TM imagery enabled us to develop the most detailed island-wide map of Puerto Rico’s extremely complex natural vegetation cover. Many Caribbean forest formations that are not spectrally distinct had distributions approximately separable using climatic zone, geology, elevation, and rainfall. Classification accuracy of 26 land cover and woody vegetation classes was 71 % overall and 83 % after combining forest successional stages within image mapping zones. In 1991-92, Puerto Rico had about 364,000 ha of closed forest, which covered 41.6 % of the main island. Unlike previous island-wide mapping, this map better identifies the spatial distributions of forest formations where certain groups of endemic species occur. Approximately 5 % of Puerto Rico’s forest area is under protection, but the reserve system grossly underrepresents lowland moist, seasonal evergreen forests.

Recovery of a tropical stream after a harvest-related chlorine poisoning event

GREATHOUSE, EFFIE A.; MARCH, JAMES G.; PRINGLE; CATHERINE M. 2005. Recovery of a tropical stream after a harvest-related chlorine poisoning event.. Freshwater Biology 50, :603-615.

Abstract: 
1. Harvest-related poisoning events are common in tropical streams, yet research on stream recovery has largely been limited to temperate streams and generally does not include any measures of ecosystem function, such as leaf breakdown. 2. We assessed recovery of a second-order, high-gradient stream draining the Luquillo Experimental Forest, Puerto Rico, 3 months after a chlorine-bleach poisoning event. The illegal poisoning of freshwater shrimps for harvest caused massive mortality of shrimps and dramatic changes in those ecosystem properties influenced by shrimps. We determined recovery potential using an established recovery index and assessed actual recovery by examining whether the poisoned reach returned to conditions resembling an undisturbed upstream reference reach. 3. Recovery potential was excellent (score ¼ 729 of a possible 729) and can be attributed to nearby sources of organisms for colonisation, the mobility of dominant organisms, unimpaired habitat, rapid flushing and processing of chlorine, and location within a national forest. 4. Actual recovery was substantial. Comparison of the reference reach with the formerly poisoned reach indicated: (1) complete recovery of xiphocaridid and palaemonid shrimp population abundances, shrimp size distributions, leaf breakdown rates, and abundances of oligochaetes and mayflies on leaves, and (2) only small differences in atyid shrimp abundance and community and ecosystem properties influenced by atyid shrimps(standing stocks of epilithic fine inorganic and organic matter, chlorophyll a, and abundances of chironomids and copepods on leaves). 5. There was no detectable pattern between any measured variables and distance downstream from the poisoning. However, shrimp size-distributions indicated that the observed recovery may represent a source-sink dynamic, in which the poisoned reach acts as a sink which depletes adult shrimp populations from surrounding undisturbed habitats. Thus, the rapid recovery observed in this study is consistent with results from other field studies of pulse chlorine disturbances, harvest-related fish poisonings, and recovery of freshwater biotic interactions, but it is unlikely to be sustainable if multiple poisonings deplete adult populations to the extent that juvenile recruitment does not offset adult shrimp mortality.

Do small-scale exclosure/enclosure experiments predict the eVects of large-scale extirpation of freshwater migratory fauna?

Do Small-Scale Exclosure/Enclosure Experiments Predict the Effects of Large-Scale Extirpation of Freshwater Migratory Fauna?
Effie A. Greathouse, Catherine M. Pringle and William H. McDowell
Oecologia
Vol. 149, No. 4 (Oct., 2006), pp. 709-717

Abstract: 
A variety of theoretical and empirical studies indicate that the abilities of small-scale experiments to predict responses to large-scale perturbations vary. Small-scale experiments often do not predict the directions of large-scale responses, and relatively few empirical studies have examined whether small-scale experiments predict the magnitudes of large-scale responses. Here we present an empirical example of small-scale manipulations predicting not only the directions but also the magnitudes of the eVects of whole-catchment, decades-long decimation of migratory freshwater shrimp populations. In streams of Puerto Rico (USA), we used arena sizes of < 2 m2 in 1- to 4-week exclosure/enclosure experiments. EVects of small-scale experiments largely matched those of largescale shrimp loss above dams for a variety of response variables (abiotic and biotic factors including epilithic Wne sediments, algae and organic matter, and invertebrate grazers, detritivores, and predators). The results of our extrapolation contrast with studies of small- versus large-scale perturbations in the temperate zone. Our Wndings are likely explained by: a set of response variables that are more dominated by within-patch processes than exchange processes, an experimental manipulation that encompassed the characteristic scales of response variables, our use of open arenas lacking cage artifacts, and/or our combination of two distinct experimental approaches (exclosures and enclosures). Based on our study design, we suggest that extrapolation across experimental scales can be greatly enhanced by embedding open arenas within large-scale conditions that represent all treatment levels.
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