Puerto Rico

Urban influences on the nitrogen cycle in Puerto Rico

Ortiz-Zayas, J. R., E. Cuevas, O. L. Mayol-Bracero, L.
Donoso, I. Trebs, D. Figueroa-Nieves, and W. H. Mcdowell.
2006. Urban influences on the nitrogen cycle in Puerto Rico.
Biogeochemistry 79:109–133.

Abstract: 
Anthropogenic actions are altering fluxes of nitrogen (N) in the biosphere at unprecedented rates. Efforts to study these impacts have concentrated in the Northern hemisphere, where experimental data are available. In tropical developing countries, however, experimental studies are lacking. This paper summarizes available data and assesses the impacts of human activities on N fluxes in Puerto Rico, a densely populated Caribbean island that has experienced drastic landscape transformations over the last century associated with rapid socioeconomic changes. N yield calculations conducted in several watersheds of different anthropogenic influences revealed that disturbed watersheds export more N per unit area than undisturbed forested watersheds. Export of N from urban watersheds ranged from 4.8 kg ha)1 year)1 in the Rı´o Bayamo´ n watershed to 32.9 kg ha)1 year)1 in the highly urbanized Rı´o Piedras watershed and 33.3 kg ha)1 year)1 in the rural-agricultural Rı´o Grande de An˜ asco watershed. Along with land use, mean annual runoff explained most of the variance in fluvial N yield. Wastewater generated in the San Juan Metropolitan Area receives primary treatment before it is discharged into the Atlantic Ocean. These discharges are N-rich and export large amounts of N to the ocean at a rate of about 140 kg ha)1 year)1. Data on wet deposition of inorganic N (NHþ4 þ NO 3 ) suggest that rates of atmospheric N deposition are increasing in the pristine forests of Puerto Rico. Stationary and mobile sources of NOx (NO+NO2) and N2O generated in the large urban centers may be responsible for this trend. Comprehensive measurements are required in Puerto Rico to quantitatively characterize the local N cycle. More research is required to assess rates of atmospheric N deposition, N fixation in natural and human-dominated landscapes, N-balance associated with food and feed trade, and denitrification.

Convective rainfall regions in puerto rico

Carter, M.M., 1995. Convective Rainfall Regions in Puerto Rico.
Masters thesis, Florida State University, Tallahassee, 75pp.

Abstract: 
Geographical regions of covariability in hourly precipitation over the island of Puerto Rico are exposed using factor analysis. It is argued that the data are consistent with a common factor model when an orthgonal rotation is applied to the factor loading matrix. The results suggest that Puerto Rico can be divided into six regions, with each region having a similar covariance structure of summer season convective rainfall. The six regions can be grouped into a western area and an eastern area based on contrasting diurnal rainfall signatures. The study is the first step in developing improved forecast guidance for precipitation over the island. It is believed to be one of the first studies attempting geographical regionalization of precipitation on the convective scale.

Development of a Landforms Model for Puerto Rico and its Application for Land Cover Change Analysis

MARTNUZZI, SEBASTIÁN; GOULD, WILLIAM A.; RAMOS GONZÁLEZ, OLGA M.; EDWARDS, BROOK E. 2007. Development of a Landforms Model for Puerto Rico and its Application for Land Cover Change Analysis.. Caribbean Journal of Science, Vol. 43, No. 2, :161-171.

Abstract: 
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 urban areas has typically been associated with low and flat topographies. Forest recovery, on the other hand, has been associated with high elevations and steep slopes. Our study revealed that (1) nearly half of new developments occurred outside the plains, (2) almost all new forests occurred in mountain regions (but not on the steepest slopes), and (3) there are transitional and very dynamic landforms (the side slopes) that experience both important land development and forest recovery. Finally, we present additional examples of the landforms model applications, including vegetation mapping, physiography, and the modeling of vertebrate habitat distributions.

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.

From theory to practice: building more resilient communities in flood-prone areas

López-Marrero T, Tschakert P (2011). ‘From
theory to practice: building more resilient
communities in flood-prone areas’ Environment
and Urbanization 23 (1): in press.

Abstract: 
Enhancing community resilience is key to reducing vulnerability in the face of natural hazards. In this article we discuss the elements that support or undermine community resilience to floods and propose ways of enhancing it. In the study, participatory methods and techniques were used with community members and emergency managers from a flood-prone municipality of Puerto Rico, including conceptual mapping, participatory mapping, and listing and ranking. The findings suggest that enhancing resilience in these communities requires: support for social learning by building on existing knowledge; stressing the importance of developing a diverse set of flood management options; and promoting effective linkages and collaborations between community members and emergency managers to encourage collective flood management. For this to happen, however, mutual distrust, lack of confidence and other obstacles must be overcome.

An integrative approach to study and promote natural hazards adaptive capacity: a case studyof two flood-prone communities in Puerto Rico

LÓPEZ-MARRERO, T. (2010), An integrative approach to study and promote natural hazards adaptive capacity: a case study of two flood-prone communities in Puerto Rico. The Geographical Journal, 176: 150–163. doi: 10.1111/j.1475-4959.2010.00353.x

Abstract: 
capacity to natural hazards of exposed populations. This paper analyses the strategies of adjustment implemented by members of two flood-prone communities in Puerto Rico, and discusses how the adoption of these strategies and other factors could influence future adaptive capacity and vulnerability to floods. Semi-structured interviews with community members from different resource endowment groups were used to elicit the resources behind the process of adjustment along with additional factors that could influence future adaptive capacity, including their perceptions of risks related to floods. The analysis revealed how access to resources – including material, economic and human resources – has facilitated living with floods in these communities; although not everyone has been able to adapt in the same way. Past actions, along with public responses being undertaken in the area (i.e. flood control project and upstream structural modifications) appear to be reducing flood-risk perceptions and promoting a false sense of security among community members, irrespective of resource endowment group. For that reason, developing ways to increase awareness about future flood potential and making clear the need for complementary non-structural strategies is imperative. In short, the research findings emphasise that access to resources and cognitive factors are important determinants of adaptive capacity. Hence, both should be taken into account while developing practical strategies towards increasing adaptive capacity and reducing vulnerability to floods specifically, and to other natural hazards in general.

Putting adaptive capacity into the context of people’s lives: a case study of two flood-prone communities in Puerto Rico

López-Marrero, T. and B. Yarnal (2010). Putting adaptive capacity into the context of people's
lives: a case study of two flood-prone communities in Puerto Rico. Natural Hazards 52:
277-297.

Abstract: 
Recent developments in the vulnerability literature have contested the use of technical solutions as the sole adaptive strategies to reduce natural hazard impact; this literature emphasizes the need to attend to the wider everyday risks to which people are exposed and that aggravate hazard vulnerability. Using a case study of two flood-prone communities in Puerto Rico, this article supports and enhances that literature by placing floods within a wider context of other risks and determining how everyday risks influence people’s perceptions of and capacity to adapt to floods. Participatory methods are used to elicit the everyday risks that concern community members. The analysis reveals that participants perceive floods as one of their risks, but they see them as neither the most important nor most severe risk in their lives. Instead, they find other concerns—health conditions, family well-being, economic factors, and land tenure—more pressing. These competing risks limit adaptive capacity and increase vulnerability to natural hazards. The results suggest that addressing these multiple risks, mainstreaming flood management and adaptation into the wider context of people’s general well being, and increasing risk perception will strengthen adaptive capacity to present and future floods.

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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