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					Benítez-Joubert, R. J., Institute for Tropical Ecosystems Studies, University of Puerto
Rico Río Piedras Campus, Puerto Rico.
Ortiz-Zayas, J. R., Institute for Tropical Ecosystems Studies, University of Puerto Rico
Río Piedras Campus, Puerto Rico.


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,
Ramirez, A. Institute for Tropical Ecosystem Studies, Institute for Tropical Ecosystem
Studies, University of Puerto Rico, Río Piedras, Puerto Rico,


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,
Ortiz-Zayas, J.R., Institute for Tropical Ecosystem Studies, University of Puerto Rico,
Río Piedras, Puerto Rico,
Blanco, J.F., Instituto de Biología, Facultad de Ciencias Exactas y Naturales, Universidad
de Antioquia, Antioquia, Colombia,


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
Covich, Alan P., University of Georgia, Athens, Georgia, USA.
Crowl, Todd A., Utah State University, Logan, Utah, USA.


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,
Silver, W. L., University of California – Berkeley, Berkeley, CA, IN USA,
McDowell, W. H., University of New Hampshire, Durham, NH, IN USA,
Torn, M. S., Lawrence Berkeley Laboratory, Berkeley, CA, IN USA,


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,
Herman, D.J., University of California, Berkeley, Berkeley, CA USA,
Bird, J.A., Queens College, City University of New York, Flushing, NY USA,
Firestone, M. K., University of California, Berkeley, Berkeley, CA USA,


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,
Ramírez, A., Institute for Tropical Ecosystem Studies, University of Puerto Rico at Rio
Piedras, Puerto Rico,


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
Figueroa-Nieves, D., University of New Hampshire, New Hampshire, USA,
McDowell, W. H., University of New Hampshire, New Hampshire, USA,
Ortiz-Zayas, J. R., University of Puerto Rico at Rio Piedras, Puerto Rico,
Martínez, G., University of Puerto Rico at Mayagüez Campus, 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,
Zimmerman, J. K., University of Puerto Rico, Puerto Rico at Rio Piedras,
Thompson, J. University of Puerto Rico, Puerto Rico at Rio Piedras,


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.
Murphy, D.J., SUNY College of Environmental Science and Forestry, New York, USA.
Hall, C.A.S., SUNY College of Environmental Science and Forestey, New York, USA.


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,
Brokaw, N., Institute for Tropical Ecosystem Studies, University of Puerto Rico-Río


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,
Silver, W.L., University of California-Berkeley, Berkeley, CA, USA,


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.
Ortiz-Zayas, J. R., University of Puerto Rico at Rio Piedras, Puerto Rico,


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,
Ramírez, A., Institute for Tropical Ecosystem Studies, University of Puerto Rico at Rio
Piedras, Puerto Rico,


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,
Martinó-Cardona, D. M., Institute for Tropical Ecosystem Studies, University of Puerto
Rico at Rio Piedras, Puerto Rico,
Ramírez, A., Institute for Tropical Ecosystem Studies, University of Puerto Rico at Rio
Piedras, Puerto Rico,


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,
Ramírez, A., Institute for Tropical Ecosystem Studies, University of Puerto Rico at Rio
Piedras, 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:


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:
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


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,
Cantrell, S. A., Universidad del Turabo, Gurabo, PR,


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,
Belovsky, G. E., University of Notre Dame, Notre Dame, IN,


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,


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,
Cantrell, S. A., Universidad del Turabo, Gurabo, PR,


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
Rodríguez Cardona, B., University of Puerto Rico, Rio Piedras, Puerto Rico.
Ortiz-Zayas, J. R., University of Puerto Rico at Rio Piedras, 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,
McDowell, W.H., University of New Hampshire, New Hampshire, USA,


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,
Landau, F.H., University of Nevada Las Vegas, Las Vegas, Nevada, USA,
Velázquez, E., Department of Ecology, University of Alcalá, Alcalá de Henares, Spain,
Shiels, A.B., Department of Botany, University of Hawaii, Honolulu, Hawaii, USA,
Sparrow, A., Department of Natural Resources and Environmental Science, University of
Nevada Reno, Reno, Nevada, USA,


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
Wheeler, K., Utah State University, Utah, USA,
Crowl, T.A., Utah State University, Utah, USA,


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.,, University of California-Berkeley,
Department of Environmental Science, Policy and Management, 137 Mulford #3114,
Berkeley, CA 94209, United StatesAU:
Silver, W.L.,, University of California-Berkeley,
Department of Environmental Science, Policy and Management, 137 Mulford #3114,
Berkeley, CA 94209, United States :
Lugo, A.E.,, International Institute of Tropical Forestry, USDA Forest
Service, PO Box 2500, Rio Piedras, PR 00928, United States


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,
Silver, W.L., University of California, Berkeley, CA,
Weber, K.A., University of Nebraska, Lincoln, NE,


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
   NO2- to Fe-rich tropical forest soils. Both anammox and Feammox could change the 15-
   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-.

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