Benítez-Joubert, R. J., Institute for Tropical Ecosystems Studies, University of Puerto Rico Río Piedras Campus, Puerto Rico. firstname.lastname@example.org Ortiz-Zayas, J. R., Institute for Tropical Ecosystems Studies, University of Puerto Rico Río Piedras Campus, Puerto Rico. email@example.com DO ANTROPOGENIC ACTIVITIES AFFECT THE DISSOLVED ORGANIC CARBON IN STRATIFIES ESTUARIES? Around the world, but especially in underdeveloped countries, anthropogenic activities have been affecting and changing many estuarine processes like ecosystem productivity, sequestration of nutrients and the production and processing of dissolved organic carbon (DOC). In this research we studied the effect of the wastewater treatment effluent from a secondary treatment plant on the quality and quantity of DOC, in two stratified estuaries draining part of the Luquillo Mountains in Puerto Rico. Burgos, S. Institute for Tropical Ecosystem Studies, University of Puerto Rico, Río Piedras, Puerto Rico, firstname.lastname@example.org Ramirez, A. Institute for Tropical Ecosystem Studies, Institute for Tropical Ecosystem Studies, University of Puerto Rico, Río Piedras, Puerto Rico, email@example.com THE EFFECT OF LAND USE ON EUKARYOTE DIVERSITY IN STREAM BENTHIC BIOFILMS Changes in stream ecosystem biodiversity can result from watershed disturbances related to land use. Disturbance is known to eliminate sensitive species from biofilm communities and increase dominance of disturbance-resistant groups in impacted sites. Understanding how land use alters benthic biofilm composition is important to understand how streams respond to land use changes. In this study, 15 tropical streams were analyzed in term of their physicochemical parameters and biofilm composition along a land use gradient. Streams formed a clear gradient in conductivity, but were not clearly related to land use as originally expected. Biofilms biodiversity was analyzed for eukaryotes using molecular techniques (e.g. TRFLP) and ranged from 50 to 205 species. Biodiversity vary greatly among streams and was not related to land use. Overall, we found high variability among streams in biofilm diversity suggesting that factors at the watershed level (e.g., land use) are not the main factors controlling them. Cáceres-Charneco, R.I., Institute for Tropical Ecosystem Studies, University of Puerto Rico, Río Piedras, Puerto Rico, firstname.lastname@example.org Ortiz-Zayas, J.R., Institute for Tropical Ecosystem Studies, University of Puerto Rico, Río Piedras, Puerto Rico, email@example.com Blanco, J.F., Instituto de Biología, Facultad de Ciencias Exactas y Naturales, Universidad de Antioquia, Antioquia, Colombia, firstname.lastname@example.org ECOHYDROLOGY OF AN EPHEMRAL TROPICAL POND AND BREEDING HABITAT FOR THE PUERTO RICAN CRESTED TOAD (PELTOPHRYNE LEMUR) Peltophryne lemur, is the endemic toad of Puerto Rico. It was declared a threatened species in 1987 but after more than 20 years of research and conservation efforts the species is now considered stable. Peltophryne lemur is the first amphibian to be part of the Species Survival Program formed by the Association of Zoos and Aquariums. Currently, the only natural breeding habitat is the Tamarindo pond, an ephemeral coastal lagoon located in the Guánica Biosphere Reserve, southwest Puerto Rico. This study was conducted to document habitat conditions after reproduction events and during the growth and development of P. lemur tadpoles. After the heavy rains in August 2008, the Tamarindo pond was divided into five study sites to account for spatial variability within the pond. The pond’s physico-chemistry was studied for a period of three months. Three reproductive events were observed during the 2008’s rainy season: one in August and two in September. A tropical depression increased water levels to a meter deep in the deepest part of the pond and reduced salinity from 5 to 1 ppt. Water temperature ranged from 24 to 37 ° C. Dissolved oxygen and pH were very variable during the study period. During this period, tadpole densities ranged from 100 to 2,000 individuals. This study has provided important information for the conservation efforts of the Puerto Rican Crested Toad. Covich, Alan P., University of Georgia, Athens, Georgia, USA. email@example.com Crowl, Todd A., Utah State University, Logan, Utah, USA. firstname.lastname@example.org CUMULATIVE EFFECTS OF PULSED DISTURBANCES AND DROUGHT ON HEADWATER STREAM COMMUNITIES. Long-term data document impacts of both hurricanes and droughts on stream food webs in the Luquillo Mountains. Headwater streams above steep waterfalls are critically important habitats for a wide range of invertebrate species, especially freshwater shrimps that dominate detrital processing of leaf litter. Their roles in ecosystem processes are significant because of their resiliency and ability to adapt to frequent high-flows. Intense wind and rainfall alter riparian vegetation and result in pulsed inputs of leaf litter and wood that increase abundance of decapod detritivores and their rates of leaf-litter processing. Populations of leaf-litter shredders (freshwater shrimp, Xiphocaris elongata) and filter feeders (other shrimps, Atya lanipes) respond rapidly to pulsed-flow events. These positive species interactions are altered during infrequent droughts. Prolonged drought disrupts and fragments migratory routes along stream channels and reduces depths of pool habitats. Droughts also reduce populations of Xiphocaris as a result of increased predation by larger shrimp, Macrobrachium carcinus. Predator encounter rates increase following crowding of Xiphocaris in shallower pools and following loss of chemical communication (predatory avoidance signals) used by Xiphocaris to reduce exposure to Macrobrachium. The sustainability of these species and their headwater habitats remains a major research challenge in a changing climate. Cusack, D. F., University of California – Berkeley, Berkeley, CA, IN USA, email@example.com. Silver, W. L., University of California – Berkeley, Berkeley, CA, IN USA, firstname.lastname@example.org McDowell, W. H., University of New Hampshire, Durham, NH, IN USA, email@example.com Torn, M. S., Lawrence Berkeley Laboratory, Berkeley, CA, IN USA, firstname.lastname@example.org NITROGEN ADDITIONS ALTER CARBON CYCLING DYNAMICS AND INCREASE SOIL CARBON CONTENT IN TWO HUMID TROPICAL FORESTS Nitrogen (N) deposition is known to impact carbon (C) dynamics in temperate ecosystems, but less is know about the effects of added N in tropical forests, where N is not generally limiting to plant growth. We examined changes in soil C dynamics with N fertilization in two tropical forest types in Puerto Rico. We hypothesized that increased N would accelerate losses of C from labile pools, while increasing stabilization of C in mineral soils, reflecting changes in microbial activity and abiotic soil properties. We measured bulk soil C, C fractions, C:N, and 13C NMR as measures of C content and chemistry in fertilized and control plots. Fluxes of dissolved organic C (DOC) and soil respiration were measured in the field and in a laboratory incubation. After 3.5 years of N fertilization, plots with added N had higher C content (42.3 ± 6.8 and 40.7 ± 4.7 g/cm2, lower and upper respectively) than control plots (34.2 ± 5.9 and 34.3 ± 1.3 g/cm2) at 0 – 10 cm depth. We measured higher DOC production in the top 10 cm of fertilized soils for both forest types, and lower DOC fluxes at 40 cm, indicating increased movement of C into soils from the litter layer. Field measurements indicated significant suppression of soil respiration in fertilized plots for both forest types, corresponding with declines in fine root biomass in both forests. In the laboratory incubation, losses of soil C via heterotrophic respiration also declined with fertilization for both forests. Analysis of soil C fractions showed a decrease in labile (“light”) C pools, while the C content of mineral- associated C increased. Together, these results indicate that the increased stabilization of soil C with N deposition has the potential to outweigh increased losses of labile C in some soils, such that N deposition has the potential to increase C content in highly weathered, clayey tropical soils. Dane, L. J., University of California, Berkeley, Berkeley, CA USA, email@example.com. Herman, D.J., University of California, Berkeley, Berkeley, CA USA, firstname.lastname@example.org. Bird, J.A., Queens College, City University of New York, Flushing, NY USA, email@example.com. Firestone, M. K., University of California, Berkeley, Berkeley, CA USA, firstname.lastname@example.org. IMPACT OF SOIL MICROBIAL COMMUNITY CHARACTERISTICS ON THE STABILIZATION OF SOIL CARBON. Microbial communities are critical controllers of the conversion of plant detritus to humic materials and/or CO2. Since microbial communities can differ in body chemistry and metabolic capacities across ecosystems, we hypothesize that soil microbial community composition influences rates and products of humification. This study uses 13C-labeled microbial (whole killed) cells to delineate control of C partitioning between CO2 and humic materials. Our field incubation follows the fate of 13C-labeled cells in soils from the Luquillo forest and a CA temperate conifer forest. Soil 13C substrate groups were reciprocally applied to each soil to compare the effect of the microbial metabolic capacity in two very different forests. We are tracking the fate of 13C microbial litter for 3 years by measuring total recovery, utilization by indigenous microbial communities and their biomarker components, and ultimately humification products (soil organic matter fractionation). A laboratory incubation also follows the flow of C from the 13C-labeled bodies as it is partitioned into CO2 or humified C in soils from the Luquillo LTER, a CA temperate conifer forest, and a CA coastal redwood forest. To understand the role of climate as it controls microbial community function and carbon cycling, each soil type has been incubated under native vs. non-native climatic regimes in a full factorial design. Carbon flow is being followed over 1 year by analyzing 13C in total carbon, microbial biomass, DOC, CO2, and humification products. Engman, A., Institute for Tropical Ecosystem Studies, University of Puerto Rico at Rio Piedras, Puerto Rico, email@example.com Ramírez, A., Institute for Tropical Ecosystem Studies, University of Puerto Rico at Rio Piedras, Puerto Rico, firstname.lastname@example.org THE EFFECTS OF DISCHARGE ON LEAF DECOMPOSITION RATES IN A TROPICAL URBAN STREAM. The effect of discharge on the rate of Cecropia schreberiana leaf decomposition was evaluated in the Río Piedras at El Señorial, a sub-watershed with 41% urban to suburban land use. In this experiment an experimental and a control group of leaf packs was placed at four locations in a single reach of the stream. In experimental groups leaf packs were placed inside PVC tubes oriented perpendicular to the main current of the stream while the control group was made up of leaf packets inside tubes made of plastic mesh fencing and were also oriented perpendicular to the main direction of flow. This arrangement minimized the shearing force of flowing water and associated scouring by sediment transport in the experimental group while allowing these physical forces to act on the control group. After six weeks the average dry mass remaining in the control groups was slightly less than that of the experimental groups. This difference was observed throughout the rest of the experiment but was never statistically significant. Overall, the rates of decomposition measured in this experiment are slower than previous studies which have been carried out in less impacted streams of Puerto Rico. Heavy sediment deposition was observed after high flow disturbances throughout the experiment and may have blocked leaves from being physically decomposed. Discharge may increase leaf decomposition rates in the Río Piedras but this effect could be reduced by heavy sediment deposition. Figueroa-Nieves, D., University of New Hampshire, New Hampshire, USA, email@example.com McDowell, W. H., University of New Hampshire, New Hampshire, USA, firstname.lastname@example.org Ortiz-Zayas, J. R., University of Puerto Rico at Rio Piedras, Puerto Rico, email@example.com Martínez, G., University of Puerto Rico at Mayagüez Campus, Puerto Rico, firstname.lastname@example.org CONTRIBUTION OF SEWAGE EFFLUENTS TO NUTRIENTS, DISCHARGE, AND DOC IN STREAMS IN PUERTO RICO Waste water treatment plants (WWTP) in Puerto Rico continuously discharge their effluents to streams, changing downstream chemistry and posing a risk to riverine and estuarine organisms. Impacts on receiving waters will vary depending on the nutrient load and hydrologic contribution made by WWTP effluents. Effluent discharges are regulated based on organic load contributed to receiving waters, and thus largely refractory organic matter should be found in WWTP effluents. Some reduction in nutrient loads occurs with secondary and tertiary treatment, but the extent of this nutrient reduction is not well known. Similarly, the extent to which these WWTP contribute to stream base flow is also unknown. Four WWTP were sampled during 2007-2008 at three stations: upstream from the sewage effluent, at the WWTP effluent, and downstream from the effluent. Water samples were collected at these stations to analyze the effluent contribution to stream phosphate, nitrate, ammonium and river DOC concentrations. At the upstream and effluent station, the daily export from these nutrients was calculated by the product of concentration and stream flow and summed to obtain the downstream daily export. Analysis of the biodegradability of organic matter (BOD) and the specific UV absorbance (SUVA) were conducted to observe any contribution from the sewage effluent to the quality of organic matter in the stream. Nitrate, phosphate, ammonium and DOC effluent concentrations highly increased background concentrations changing downstream water chemistry in these streams. The biological oxygen demand was higher in the effluent and SUVA values were lower in the effluent indicating that sewage effluents are contributing labile organic matter to the stream changing the type of organic matter in downstream communities. Sewage effluents contributed a substantial amount of the daily downstream export of the nitrate and phosphate in all the streams sampled. Forero-Montaña, J., University of Puerto Rico at Rio Piedras, Puerto Rico, email@example.com Zimmerman, J. K., University of Puerto Rico, Puerto Rico at Rio Piedras, firstname.lastname@example.org Thompson, J. University of Puerto Rico, Puerto Rico at Rio Piedras, email@example.com POPULATION STRUCTURE AND GROWTH RATES OF THREE DIOECIOUS TREE SPECIES IN A SUB-TROPICAL WET FOREST IN PUERTO RICO Dioecious plants frequently exhibit male biased sex ratios and sexual differences in life history traits such as reproductive patterns and growth, which can be related to greater costs of reproduction borne by females because the resources required per seed are greater than per pollen grain. In this study, we recorded the sexual expression of all the potentially reproductive individuals of two dioecious trees, Cecropia schreberiana and Dacryodes excelsa in the Luquillo Forest Dynamics Plot (LFDP). The cumulative sex ratio of C. schreberiana was not significantly different, while D. excelsa exhibited a female-biased sex ratio. Cecropia schreberiana did not exhibit sexual differences in size distributions or growth rates, which suggested that reproductive maturation and longevity are similar for both sexes in this species. In contrast, D. excelsa, males were larger than females and this difference in size may be explained because males grew slightly faster than females. Thus, sexual differences in growth and size in D. excelsa are consistent with higher costs of reproduction in females than in males, although this did not result in a male-biased sex ratio, as expected. Gupta, A.K., SUNY College of Environmental Science and Forestry, New York, USA. firstname.lastname@example.org Murphy, D.J., SUNY College of Environmental Science and Forestry, New York, USA. email@example.com Hall, C.A.S., SUNY College of Environmental Science and Forestey, New York, USA. firstname.lastname@example.org A PREMLIMINARY ANALYSIS OF THE ECONOMIC EFFICIENCY OF THE CARIBBEAN Economic efficiency is thought to increase upon entering into the free-market. We have made an attempt to scientifically observe this for 20 Caribbean nations. We define economic efficiency as unit GDP over unit energy consumption and used that statistic to see if countries are producing more GDP per unit energy over the period of 1980 to 2006. We then added the potential energy gain from solar radiation for each country to see how much energy can be harnessed from the sun to offset fossil fuels. Overall, we found that the Caribbean is becoming less efficient. We also found that natural capital contributes very little to GDP when compared to fossil fuels. The energy consumption of virtually all 20 countries consists of around 90% fossil fuels, and in some cases 100%. This percentage is on average higher than that for most other regions. Given this downward trend in economic efficiency and declining supplies of fossil fuels, we conclude that the future growth of Caribbean economies is at risk. Herrera-Montes, A., University of Puerto Rico-Río Piedras, email@example.com Brokaw, N., Institute for Tropical Ecosystem Studies, University of Puerto Rico-Río Piedras, firstname.lastname@example.org CONSERVATION VALUE OF TROPICAL SECONDARY FOREST: A HERPETOFAUNA PERSPECTIVE In some areas of the tropics forests are recovering on abandoned cattle pastures. These secondary forests may be important habitats for conserving biodiversity, but we know little about their species composition over the long term. We studied herpetofauna community changes during 40 years of succession forest on abandoned pastures in Puerto Rico. Twelve sites selected in a submontane area (100 to 250 masl) represented four forest recovery stages: pasture, young (1-5 years after abandonment), intermediate (10-20 years), and advanced (40 years). Among these stages we analyzed the relationship of forest structure, microclimate, and herpetofauna community structure. During succession total forest height increased, new strata of vegetation appeared in the understory, and the forest gained more heterogeneity and complexity. Microclimatic changes were associated with changes in the physiognomy and structure of the vegetation and they were more dramatic in forest < 20 years since abandonment. During one year we observed 7,991 individuals of thirteen reptile species and six anuran species. Sixty percent of the observations were of reptiles. Herpetofauna richness was similar among stages, but the species dominance changed through succession. In pastures, herpetofaunal species associated with herbs dominated. With forest recovery, species associated with shrubs and arboreal vegetation became more important. Our study showed that herpetofauna community structure changes are associated with changes in habitat structure during forest succession on abandoned pastures in Puerto Rico. Forest >20 years comes to resemble mature forest in some structural characteristics important to herpetofauna and can provide habitat for a forest herpetofauna in disturbed areas. Liptzin, D., University of California-Berkeley, Berkeley, CA, USA, email@example.com Silver, W.L., University of California-Berkeley, Berkeley, CA, USA, firstname.lastname@example.org TEMPORAL AND SPATIAL PATTERNS IN SOIL OXYGEN AVAILABILITY: IMPLICATIONS FOR BIOGEOCHEMICAL CYCLING Soil redox plays a key role in regulating the biogeochemical transformations of carbon (C) and nutrients. Upland humid tropical forest soils experience fluctuating redox conditions because abundant rainfall limits oxygen (O2) diffusion through finely textured soils and high biological activity enhances O2 consumption. At two sites along an elevation gradient we measured bulk soil carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O), and O2 concentrations in buried chambers over several months and then harvested the chamber soils for iron (Fe) and phosphorus (P) analyses. On average, O2 concentrations were significantly higher in the upper elevation cloud forest (3%) compared to the lower elevation Tabonuco forest (8%). Soil O2 was dynamic, especially in the Tabonuco forest, where concentrations changed by as much as 10% in a single day. At this site there was a periodicity in O2 concentrations at two-week intervals, coherent with the periodicity in precipitation. There were significant correlations among the all soil gases. Soil O2 was positively associated with N2O and negatively associated with CO2 and CH4. Reduced Fe concentrations differed by an order of magnitude between sites and were negatively related to O2 concentrations. Phosphorus concentrations differed between sites, but there were not relationships between Fe and P concentrations within sites. Our results suggest that soil redox is highly dynamic in space and time in humid tropical forests, which affected patterns of C, N, and P cycling. Further, changes in the timing of precipitation may significantly alter the redox environment and nutrient cycles in these forests. Marcano Rivas A.S, University of Puerto Rico, Rio Piedras, Puerto Rico. Bianca_rodriguezpr@hotmail.com Ortiz-Zayas, J. R., University of Puerto Rico at Rio Piedras, Puerto Rico, email@example.com BIODEGRADABILITY OF DISSOLVED ORGANIC CARBON IN THREE DIFFERENT WATERSHEDS Dissolved organic carbon (DOC) is considered the most important source of energy of river ecosystems, including tropical rivers. The quality of the organic matter that is imported to the river is determined by autochthonous means of the river, but also by anthropogenic activity near the watershed of the streams. It is hypothesized that the source can also affect the quality or biodegradability of the DOC. This research pretends to investigate the quantity and quality of DOC along an altitudinal and land use gradients in a tropical setting. We predict that rivers located in the upper forested regions of the watersheds will have more labile DOC, which diminish through the altitudinal gradient. Because headwater sections are closer to the source of production of organic matter, presumably forest litterfall, the DOC present in the water will be more labile. The study sites of the investigation are located in Northeastern Puerto Rico: Río Mameyes, Río Canóvanas, and Río Piedras watersheds. Each watershed differs in terms of land use and human influences. In August 2007, we conducted a synoptic sampling and analyzed samples for TOC, DOC, POC, SUVA, and BOD5. In March 2008, a second sampling was carry out and we analyzed samples for BOD5, TOC, DOC, and SUVA. In April 2009 a third sampling was conducted and analyses for BOD5 were performed. Analyses for DOC, TOC and SUVA are going to be performed. A land use analysis was done to determine the sources of the organic matter in the watersheds and how it affects the quality of the DOC. Preliminary BOD5 data collected so far suggest that BOD5 increases downstream in all three watersheds. This paper will present the results for the other parameters. We expect that this research could increase our understanding on the effects of land use change on the carbon cycle of tropical rivers. Martínez-Rivera, N., Institute for Tropical Ecosystem Studies, University of Puerto Rico at Rio Piedras, Puerto Rico, firstname.lastname@example.org Ramírez, A., Institute for Tropical Ecosystem Studies, University of Puerto Rico at Rio Piedras, Puerto Rico, email@example.com DO MACROCONSUMERS PLAY A ROLE IN LEAF LITTER BREAKDOWN IN TROPICAL URBAN STREAMS? Allochthonous detritus represent a major resource for aquatic food webs. In forested streams, leaf litter breakdown is an ecosystem process that involves the participation of different biotic (e.g. fishes, invertebrates, microbes) and abiotic (e.g., flow, temperature) components. Urbanization decreases aquatic biodiversity and in urban streams abiotic factors may play a large role controlling leaf breakdown. However, urban streams in Puerto Rico that lack large dams still maintain their natural macroconsumer (i.e., fish and shrimp) fauna. Given this characteristic we designed an experiment to determine whether macroconsumers play a role in controlling leaf breakdown in urban streams in Puerto Rico. Leak packs were secured inside 1 cm mesh cages, open cages work as controls and closed cages as macroconsumer exclusion. Leaf packs were collected at 0, 4, 7, 14, 21, 28, 42, 56, 70 and 84 days. Overall, we found no significant differences between treatments in breakdown rates and percent mass remaining. Although native macroconsumers are still abundant in this tropical, they do no play a major role in processing leaf litter. Results are in general agreement with previous studies of non-urban streams, suggesting that abiotic factor might be the driving factors in lowland Puerto Rican streams. Martínez-Rivera, N., Institute for Tropical Ecosystem Studies, University of Puerto Rico at Rio Piedras, Puerto Rico, firstname.lastname@example.org Martinó-Cardona, D. M., Institute for Tropical Ecosystem Studies, University of Puerto Rico at Rio Piedras, Puerto Rico, email@example.com Ramírez, A., Institute for Tropical Ecosystem Studies, University of Puerto Rico at Rio Piedras, Puerto Rico, firstname.lastname@example.org FISH HEALTH IN A TROPICAL URBAN WATERSHED Urban land use impacts streams by altering their hydrology and geomorphology resulting in reductions in biodiversity. Riparian deforestation, sewage discharges, and increased nutrient loading are some of the factors driving ecological degradation. The fish community reflects these impacts. In this study, we evaluated fish health in an urban watershed in Puerto Rico, which is characterized by having a migratory native fish fauna that closely connects them with the ocean. The objective was to evaluate fish community health and condition in the Rio Piedras basin. We sampled fish in ten streams reaches and recorded external abnormalities (deformities, lesions and ulcers, tumors) and parasite infections. Native fishes did not present morphological damages. In contrast, exotic fishes showed external abnormalities, like tumors in anal fins. The migratory behavior of native fishes and the constant recruitment of juveniles from estuaries provide native fishes with a strategy to potentially reduce the negative impacts of urbanization on their populations. Alternatively, native fishes could be tolerant to the impacts of urbanization. Overall, our study indicates that native fishes are healthy suggesting a large potential for management and restoration of urban river ecosystems in Puerto Rico. Martínez-Rivera, N., Institute for Tropical Ecosystem Studies, University of Puerto Rico at Rio Piedras, Puerto Rico, email@example.com Ramírez, A., Institute for Tropical Ecosystem Studies, University of Puerto Rico at Rio Piedras, Puerto Rico, firstname.lastname@example.org URBAN STREAM WATER TEMPERATURE AND ITS IMPACT ON MICROBIAL ACTIVITY IN TROPICAL STREAMS, PUERTO RICO Urbanization has many negative impacts on stream ecosystems. Among them, increases in water temperature are important as can influence rates of ecosystem processes. We studied the degree of water warming created by urban areas in Puerto Rico and its effects on microbial respiration rates. We expected to find warmer water temperature in urban than in forested watersheds, and a positive relation between water temperature and microbial respiration on leaf litter. Using USGS data, we found that urban streams in the Río Piedras watershed, located in the San Juan metropolitan area, had water temperature 2-3 degrees warmer than similar streams in non-urban watersheds. Water temperature in urban streams ranged from 24-29 °C while non-urban ranged from 22-25 °C. Microbial respiration response to temperature was assessed in the laboratory, incubating leaves and measuring dissolved oxygen at different temperatures ranging from 23-38 °C. Microbial respiration increased with water temperature until a threshold is reached at about 32 °C. Overall, our study shows that microbial respiration is strongly influenced by water temperature and that urbanization has a strong potential to accelerate ecosystem processes in streams. Murphy, D.J.R., 302 Illick Hall, SUNY- College of Environmental Science and Forestry, Syracuse, NY, 13210, Phone: (315) 412–4619, Fax: (315) 470-6934, Email: email@example.com ELECTRICITY DEMAND AND THE URBAN HEAT ISLAND IN SAN JUAN PUERTO RICO Warm temperatures affect electricity demand by requiring greater cooling from electric appliances, such as air conditioners, refrigerators, and fans, and perennially warm temperatures in tropical cities like San Juan, Puerto Rico, increase the influence of temperature on electricity demand even further. In addition, recent research shows the existence of a pronounced Urban Heat Island in San Juan, which may increase further the impact of temperature on electricity demand within urban environments. The goals of this research are twofold: 1) to estimate the long and short-run elasticities of electricity demand in Puerto Rico using cointegration and error correction techniques, and 2) to apply the results from number 1 to estimate the increased demand for electricity by urban residents, in both energy and dollars units, caused by the UHI. Preliminary results show that price elasticity of electricity demand is -0.24, the income elasticity is 0.66, and the temperature elasticity is 2.92. The long-run effects of both price and income are roughly 15 and 5 times, respectively, less in magnitude than the effect of temperature. This means that a long-run increase of 1% in annual cooling degree-days (proxy variable for temperature) will yield nearly a 3% increase in electricity consumption. Lastly, when I applied these results to the current UHI, I found that the UHI is costing up to 36 dollars per electricity bill per year for San Juan residents, and aggregated across the population, the UHI is potentially costing between 2.9 and 9 million dollars per year in additional electricity costs. Murphy, D.J.R., 301 Illick Hall, SUNY- College of Environmental Science and Forestry, Syracuse, NY, 13210, Phone: (315) 412–4619, Fax: (315) 470-6934, Email: firstname.lastname@example.org Hall, M., 301 Illick Hall, SUNY- College of Environmental Science and Forestry, Syracuse, NY, 13210 Hall, C., 301 Illick Hall, SUNY- College of Environmental Science and Forestry, Syracuse, NY, 13210 Heisler, G., U.S. Forest Service, 5 Moon Library, SUNY-ESF, Syracuse, NY, 13210 Stehman, S., 301 Illick Hall, SUNY- College of Environmental Science and Forestry, Syracuse, NY, 13210 Anselmi-Molina, C., Physics Building, Marine Science Department, University of Puerto Rico Mayagüez, Puerto Rico, 00681-9000 THE RELATION BETWEEN LAND-COVER AND THE URBAN HEAT ISLAND IN NORTHEASTERN PUERTO RICO Population movements, growth and industrialization are causing rapid urbanization throughout the tropics, which can result in elevated temperatures within urban areas when compared to surrounding rural areas, a phenomenon known as the Urban Heat Island (UHI). One such example is the city of San Juan, Puerto Rico. Our objective in this study is to quantify the UHI created by the San Juan Metropolitan Area over space and time using temperature data collected by mobile and fixed-station measurements. We used the fixed-station measurements to examine the relation between average temperature at a given location and the density of remotely-sensed vegetation located upwind. We then regressed temperatures against regional up-wind land-cover to predict future temperature with projected urbanization. We used the mobile-station measurements to test the hypothesis that temperatures decreased with distance from city center. Our data from the fixed-stations show the existence of a nocturnal UHI, with average nighttime urban-rural temperature differences (ΔTU-R) of up to 3.02°C. Urban-rural temperature differences had negligible seasonal differences. Comparisons of diurnal temperature trends at urban, grassland, and forested sites indicate that canopy cover reduced daytime warming. Temperature was predicted best (r2 = 0.94) by vegetation in upwind easterly directions, especially that within 180 meters of the sensor. Results from the mobile measurements show that the UHI has reached the base of the Luquillo Mountains. Predictions of future development and temperatures suggest that if the present pattern of development continues, over 140 km2 of land that showed no signs of UHI in 2000 will have an average annual UHI between +0.4°C and +1.55°C by 2050. Furthermore, more than 130 km2 of land area with a current UHI between +0.4°C and +1.4°C in 2000 will have an average UHI greater than +1.55°C by 2050. Pérez-Jiménez, J.R., Universidad del Turabo, Gurabo, PR, email@example.com. Cantrell, S. A., Universidad del Turabo, Gurabo, PR, firstname.lastname@example.org. BACTERIAL GUILDS AT LUQUILLO LTER: A METAGENOMIC APPROACH The Luquillo Mts. have four microclimatic zones along the elevation gradient. These zones are characterized by climate and vegetation, defining four forest types along the gradient: Tabonuco, Palo Colorado, Palma de Sierra and Elfin. Other forest types are found at lower elevation such as the dry coastal forest found at Las Cabezas de San Juan. The documentation for bacterial guilds has been limited in the Luquillo Mts. The objective of this study has been to elucidate the richness and endemicity of sulphate- reducing bacteria (SRB) and crenarchaeota along the elevation gradient. SRB are predominant in anoxic environments such as mangroves and microbial mats. Crenarchaeota were initially described as thermal extremophiles with frequent records on mesophitic environments. A 10 cm soil core was taken at each forest type and divided in 0-5 cm and 5-10 cm. Total genomic DNA was extracted from archive soil samples taken in June and December 2005. The dissimilatory sulphite reductase (dsrAB) and 16s rDNA genes were amplified using specific primers for each group. Amplicons were enzimatically digested for TRFLP analyses (community) and/or clone for sequencing. Both bacterial groups were found in soils along the elevation gradient. Higher abundance was obtained during June and at 5-10 cm. Distinctive phylogenetic cluster (endemic groups) emerged from clone libraries. Each forest type seems to harbor a unique community. Diversity changes according to season and depth. Our results suggest that changes in the microbial community might be driven by climate and vegetation. Prather, C. M., University of Notre Dame, Notre Dame, IN USA, email@example.com. Belovsky, G. E., University of Notre Dame, Notre Dame, IN, firstname.lastname@example.org. UNEXPECTED EFFECTS OF INVERTEBRATE CONSUMERS IN THE UNDERSTORY OF A RAINFOREST. In temperate systems, invertebrate consumers have known impacts to ecosystem processes, but in tropical ecology, it is assumed that only plant and microbes affect these processes. This study investigated what impacts common folivores (walking sticks) and detritivores (litter snails) have on decomposition, nutrient cycling and primary productivity in the understory of the Luquillo rainforest. To test these effects, we started an enclosure experiment with consumers both present and absent in 2005. We measured leaf decomposition rates with litterbags, and quantified microbial communities using TRFLP. Soil, plant and litter nutrients were measured yearly. We measured plant characteristics yearly until 2008, when plants were harvested. Multiple regressions were used to determine plant biomass at each earlier time period. While detritivore presence did not affect decomposition, folivore presence reduced leaf decomposition rates, and the richness and relative abundance of bacteria. Since this herbivore prefers consuming faster, more nutritious decomposing foliage, we hypothesize that less of this foliage falls as litter, while more slowly decomposing litter becomes more abundant. This alters the composition of litter bacteria, in turn reducing rates of leaf decomposition. Also, contrary to my expectations, folivores did not affect plant production or total soil nitrogen, while detritivores decreased the total aboveground biomass and total soil nitrogen. We hypothesize that the long-lived, relatively large detritivores sequester nutrients necessary for plant growth. This study shows that invertebrate consumers do affect tropical ecosystem processes, but indirectly. The findings suggest invertebrate consumers should be considered in studies investigating the flow of nutrients in rainforests. Rifkin, S., University of Puerto Rico, Institute for Tropical Ecosystem Studies, email@example.com ABUNDANCE AND POLLINATION VECTORS OF TREE SPECIES IN THE LUQUILLO FOREST DYNAMICS PLOT The Luquillo Forest Dynamics Plot contains several species that are represented by only a few individuals, whereas other species are more common. The abundance and spatial distribution of individuals of tree species may be associated with pollination vector, as pollinating organisms display a wide range of flight distances and flower visitation behavior. The association between pollination vector and spatial distribution of individuals of a tree species has implications for tree species diversity as well as conservation. A forest of widely spaced conspecifics is one with high tree diversity, and is also more prone to reproductive failure. This study will focus upon various tree species of the Luquillo Forest Dynamics Plot, and will examine how pollination strategy relates to abundance and spatial distribution of individuals. Rivera-Figueroa, F. R., Universidad del Turabo, Gurabo, PR, Frivera@suagm.edu. Cantrell, S. A., Universidad del Turabo, Gurabo, PR, firstname.lastname@example.org. THE EFFECT OF A NATURAL DISTURBANCE IN THE MICROBIAL COMMUNITY’S FATTY ACID PROFILES IN THE LUQUILLO EXPERIMENTAL FOREST. Natural disturbances such as hurricanes can open the forest canopy and produced large pulses of litter fall and woody debris. Microorganisms play an important role in the forest’s restoration through their detritus dynamics. Our objective was to determine how the canopy openings and debris pulses affect the soil microbial community structure and composition in the forest. The canopy trimming experiment at the Luquillo Experimental Forest (LEF) simulates some aspects (canopy openness and biomass redistribution) of hurricane disturbances. Soil samples and leaf litter were gathered from three blocks each with four treatment plots in Tabonuco Forest at the LEF. Biochemical analysis approaches such as Ester Linked Fatty Acid Methyl Ester (EL-FAME) were used to determine microbial community shifts in the forest floor. Principal Component Analysis (PCA) suggested that the soil microbial community structure changed significantly after the treatments were applied, but no differences were observed on leaf litter samples. In soil, Fatty acid such as 18:2w6 which is a fungal marker, were proportionally more abundant in non-trimmed than trimmed plots. The fungal to bacteria ratios followed the same pattern. Bacterial markers were more abundant in soil than in leaf litter. The fatty acids cy19 and 10 ME18:0 (Gram negative and Actinomyces respectively) decreased considerably in the litter fraction while the 18:2w6 increased. The changes in microclimate (openness) and structure (redistribution of biomass) created by disturbances such as hurricanes and silvicultural operations may alter the soil microbial community structure and dynamics but significant changes were not detected but control in leaf litter layer. Rodríguez Cardona, B., University of Puerto Rico, Rio Piedras, Puerto Rico. Bianca_rodriguezpr@hotmail.com Ortiz-Zayas, J. R., University of Puerto Rico at Rio Piedras, Puerto Rico, email@example.com BIODEGRADABILITY OF DISSOLVED ORGANIC CARBON IN THE RIO PIEDRAS WATERSHED, PUERTO RICO Urbanization strongly impacts stream ecosystems and little information is known about how it affects DOC in rivers and how consequently it affects tropical rivers. The importance of DOC is that it is the basis of the food chain in many rivers. This project focuses on changes in DOC biodegradability along a tropical urban river in Puerto Rico. The Rio Piedras runs through the heart of the San Juan Metropolitan Area, making it susceptible to human impacts. The headwaters are less urbanized therefore surrounded by riparian forests whereas downstream, urbanization increases and riparian vegetation decreases. Water samples were collected at five sites along the river during the months of June 2008, and November and January 2009. Samples were incubated at 20 ºC and analyzed for BOD. To measure the organic carbon (Particulate + Dissolved Organic Matter) quality, the biodegradability constant (k) was computed for each sample using the Thomas graphing method. The biodegradability constant (k) of DOC seems to increase from upstream (0.336d-1, SD=0.159) to downstream (0.480, SD=0.202).After concluding a t-test these differences proved to be significant (p<0.05). This demonstrates that human impacts (e.g. waste water discharges) cause increases in the biodegradability of DOC downstream. Schoepfer, V.A., University of New Hampshire, New Hampshire, USA, firstname.lastname@example.org McDowell, W.H., University of New Hampshire, New Hampshire, USA, email@example.com LEAF LEACHING AS A SOURCE OF CARBON AND NUTRIENTS IN TROPICAL STREAMS Leaf leaching is a potentially important source of nutrients and carbon in tropical streams. This study examined variability among species and condition (fresh vs. senesced) in the leaching of DOC, NH4, NO3, PO4, and other major anions and cations from leaves of nine common riparian tree species in the Luquillo Experimental Forest in Puerto Rico. Uniform leaf disks were leached in deionized water for one, three, and seven days and the carbon and nutrient content of the resulting leachate was determined. Senesced leaves lost more mass at a faster rate than fresh leaves, due to the decline in leaf integrity. In general, species released more mass as time progressed, despite condition, as integrity was further degraded. DOC was most consistently abundant in leachate regardless of species, condition, or time leached. Dacryodes excelsa was also leached in stream water for six weeks to observe the entire leaching and respiration process. Leachate DOC values increased through the first week, remained constant until the third week, and microbial respiration dominated after the fourth week, reducing DOC values. Tropical leaves, especially senesced, have the potential to lose a great deal of their mass and nutrients upon initial immersion into the stream, with increased influence over time. This suggests that the composition of the riparian vegetation can directly influence changes to the stream; and excess leaf inputs, which often occur during hurricanes, have the potential to highly impact stream biogeochemistry. Walker, L.R., University of Nevada Las Vegas, Las Vegas, Nevada, USA, firstname.lastname@example.org Landau, F.H., University of Nevada Las Vegas, Las Vegas, Nevada, USA, email@example.com Velázquez, E., Department of Ecology, University of Alcalá, Alcalá de Henares, Spain, firstname.lastname@example.org Shiels, A.B., Department of Botany, University of Hawaii, Honolulu, Hawaii, USA, email@example.com Sparrow, A., Department of Natural Resources and Environmental Science, University of Nevada Reno, Reno, Nevada, USA, firstname.lastname@example.org SUCCESSIONAL IMPLICATIONS OF PIONEER SPECIES REMOVALS ON PUERTO RICAN LANDSLIDES In each of three different experiments on recent landslides in a Puerto Rican tropical forest, we removed one type of pioneer: early successional woody plants, thicket-forming scrambling ferns or tree ferns. After seven years, we harvested aboveground biomass. Removal of woody pioneers promoted dense growth and higher species richness of herbaceous, understory plants on some landslides but did not promote late successional woody plants. These results suggest that in the long term, pioneer woody plants might indirectly facilitate establishment of late successional woody plants by suppressing the herbaceous understory. Removal of scrambling ferns facilitated the establishment of early successional woody plants and also increased species richness and cover of forbs, grasses, lycophytes and fine litter. Removal of tree ferns had little effect on plant communities and none of the removal treatments substantially altered soil conditions. High spatial and temporal heterogeneity within and among landslides was demonstrated by markedly different species composition or biomass and highly variable rates of species change across landslides. Understory plants such as scrambling ferns, forbs, grasses and lycophytes appear to have a critical impact on initial plant community assembly with possible long-term implications for forest succession. However, generalizations about plant guilds must be tempered by site-specific variability and the diverse set of potential successional trajectories that reflect the remarkably high spatial heterogeneity of landslides. Wheeler, K., Utah State University, Utah, USA, email@example.com Crowl, T.A., Utah State University, Utah, USA, firstname.lastname@example.org SPATIAL SUBSIDIES ALONG A NEOTROPICAL STREAM-RIPARIAN CORRIDOR: THE ROLE OF EMERGENT AQUATIC INSECT PREY FLUXES Although material flows between stream and riparian ecosystems were long assumed to be unidirectional, dominated by fluxes from terrestrial to aquatic systems (Power et al. 2004), more recent studies have demonstrated the importance of stream-derived subsidies, arriving via emergent aquatic insects, to riparian consumers and communities (see Baxter et al. 2005 for a review). In comparison to temperate systems, aquatic insect emergence in tropical streams shows little seasonality (Corbet 1964; Masteller 1993) and may represent an important energy source for riparian consumers. However, the extent to which tropical consumers rely on stream-derived subsidies is largely unknown (but see Sanzone 2001), and there are no published studies related to the indirect effects associated with these types of aseasonal material fluxes. Consequently, we will examine the role of stream-derived subsidies in watersheds draining the Luquillo Experimental Forest (LEF), where the spatiotemporal variability associated with stream-derived subsidies, the incorporation of stream-derived materials by riparian consumers, the indirect effects of such materials on adjacent and non-adjacent trophic levels, and the factors regulating export of the prey resource from streams can be assessed. Specific hypotheses to be tested include: (1) the indirect effects of stream-derived subsidies on local prey resources are predicted to be negative given the aseasonal resource flow of emergent aquatic insects to riparian consumers; (2) the indirect effects of stream-derived subsidies on higher trophic level predators are predicted to be positive, though the strength of the effect is likely to attenuate with each successive trophic level; and (3) spatial heterogeneity in the export of stream-derived subsidies along a longitudinal stream profile exists largely as a result of variable population densities of grazing freshwater shrimp. Wood, T.E., email@example.com, University of California-Berkeley, Department of Environmental Science, Policy and Management, 137 Mulford #3114, Berkeley, CA 94209, United StatesAU: Silver, W.L., firstname.lastname@example.org, University of California-Berkeley, Department of Environmental Science, Policy and Management, 137 Mulford #3114, Berkeley, CA 94209, United States : Lugo, A.E., email@example.com, International Institute of Tropical Forestry, USDA Forest Service, PO Box 2500, Rio Piedras, PR 00928, United States IMPACT OF AN EXPERIMENTAL DROUGHT ON TRACE GAS EMISSIONS FROM SOILS OF A HUMID TROPICAL FOREST, PUERTO RICOAB: Tropical forest soils are a globally important source of carbon dioxide (CO2), nitrous oxide (N2O), and methane (CH4) to the atmosphere. The production and emission of these greenhouse gases is tightly coupled with the amount and distribution of rainfall and associated redox dynamics. Current models predict increasing frequency and severity of drought in many humid tropical regions. These climate changes are likely to feedback on soil moisture availability in humid tropical forests, and consequently on the magnitude and temporal pattern of trace gas efflux from these systems. In this study, we created an experimental drought in a humid tropical forest in Puerto Rico by excluding three months of wet season throughfall. We paired five 1.24 m2 translucent roofs with five control plots of equal size in each of three forest types in the Bisley watershed (Palm, Ridge and Slope; 30 plots total). We measured weekly changes in CO2 and bi-weekly changes in N2O and CH4 in response to the manipulation for each of the 30 plots. We additionally measured the physical and chemical changes associated with throughfall exclusion, including soil nutrient availability, pH and soil temperature. CO2 emissions decreased significantly in response to soil drying in all forest types. The decrease in CO2 efflux was most pronounced in the sloped sites, followed by the Ridge and the Palm forest sites (32%, 30%, 15%, respectively). The response of CO2 to declining soil moisture was linear in both the Palm and Ridge sites, and non-linear in the Slope site. Surprisingly, CO2 fluxes remained suppressed in both the Ridge and Slope sites several weeks after the exclusion shelters were removed, while the Palm forest demonstrated a very rapid recovery. The effect of throughfall exclusion on CH4 and N2O emissions varied by forest type. The Palm forest became a strong sink for CH4, and went from a source to a sink of N2O. In contrast, CH4 and N2O did not respond to soil drying in either the Slope or the Ridge sites. Overall, the reduction in trace gas emissions from tropical forest soils in response to drought has significant implications for global carbon and nitrogen cycling if climatic change continues to follow current trends. Yang, W.H., University of California, Berkeley, CA, firstname.lastname@example.org Silver, W.L., University of California, Berkeley, CA, email@example.com Weber, K.A., University of Nebraska, Lincoln, NE, firstname.lastname@example.org FEAMMOX: A NOVEL PATHWAY FOR AMMONIUM OXIDATION AND NITROGEN LOSS FROM TERRESTRIAL ECOSYSTEMS. We report on a novel pathway in the terrestrial nitrogen cycle that couples anaerobic ammonium oxidation with iron(III) reduction. The pathway, called Feammox, results in the production of dinitrogen (N2) gas or nitrite (NO2-), which can subsequently be reduced to nitrous oxide (N2O), N2, or ammonium (NH4+) via dissimilatory NO2- reduction. First, we tested for anaerobic NH4+ oxidation by adding equimolar 15NH4+ and 14 NO2- to Fe-rich tropical forest soils. Both anammox and Feammox could change the 15- 14 N2 mole fraction whereas only Feammox could change the 15-15N2 mole fraction. We then tested for NO2- production via Feammox by adding NH4+ only or NH4+ with Fe(III) in stoichiometric equivalency to pre-incubated anaerobic slurries. Lastly, we tested for N2 production via Feammox by adding 15NH4+ only or 15NH4+ with Fe(III) in stoichiometric equivalency and measured changes in 15N2. In the first experiment, we measured considerable 15-15N2 production and no 15-14N2 production during the 96 h incubation, indicating that Feammox occurred. In the following experiments, addition of both NH4+ and Fe(III) resulted in higher aqueous NO2- concentrations and 15-15N2 mole fractions relative to addition of NH4+ alone. Using mass balance calculations we determined that in the third experiment, over 20% of the added 15NH4+ was lost as N2 via Feammox. Our results suggest that Feammox occurs in these upland soils and has the potential to produce significant N2 and NO2-.