The Luquillo LTER, in its tenth year of operation, continues to focus on the goal of integrating studies of the effects of disturbance on the physical environment and the response of the biota to these changes in environmental gradients. The Luquillo program continues to demonstrate high productivity, with over 289 peer-reviewed publications, four books, and five special features in journals resulting from our research. In addition, 17 students have received doctorates and 26 have received Master's degrees for studies associated with the LTER program.

The 31 scientists funded by the Luquillo LTER and 13 independently-funded collaborators continue to share a common research theme and to demonstrate a high degree of interactive inquiry. In addition to our core LTER studies, we have recently initiated investigations on the functional role of biodiversity in our system and the interactions of humans and the Luquillo Ecosystem. Through three grants from NASA we have been able to extend LTER studies of land use and the effect of disturbance on ecosystem processes to other areas in Puerto Rico. All of these initiatives have been aided greatly by a strong group of undergraduate and graduate students.

Physical facilities available to the LTER program will undergo a major expansion in the next few years. With funding from NSF, we will acquire a system for voice and data transmission that will provide e-mail and Internet services to the El Verde Field Station. We will also construct living quarters for 18 researchers at the field site. In addition, the University of Puerto Rico is in the process of purchasing a building near the Luquillo Experimental Forest (LEF) to provide office and housing space for LTER investigators. New offices for the Institute for Tropical Ecosystem Studies are scheduled for completion on the Rio Piedras campus in 2002.

The past year has been marked by major changes in the management of the Luquillo LTER. Robert Waide, the lead principle investigator of the LUQ LTER since its inception in 1988 (along with Ariel Lugo of the USDA Forest Service) , left the University of Puerto Rico to become Executive Director of the LTER Network Office in Albuquerque, New Mexico. Jess Zimmerman (University of Puerto Rico), participant in the LUQ project since 1991 and PI since 1994, has assumed day-to-day direction of the project following Waide=s departure. Waide=s departure motivated the addition of a new member, D. Jean Lodge (USDA Forest Service), to the LUQ Executive Committee (which includes Fred Scatena, USDA Forest Service, in addition to Waide, Lugo, and Zimmerman). Lodge has been involved with the LUQ LTER since 1988, is currently working on the biodiversity of basidiomycete fungi in the LEF and throughout the Greater Antilles. Lodge=s encyclopedic knowledge of fungal systematics and thorough grasp of ecosystem concepts will bring strong direction to the LUQ LTER, particularly as it increases its focus on biodiversity studies. Waide continues on the Executive Committee for the time being to serve as an institutional memory.

During the annual meeting held in June 1998, the investigators of the LUQ LTER discussed and approved three new directions for the research program to be included in the renewal proposal due in January 2000. During this next phase of research we will:

(1) Consider the gradient of environmental conditions, life zones, and disturbance regime along the entire elevational gradient in the Luquillo Mountains. Previous proposals have only considered the lowermost life zone, tabonuco forest. The major foci of research will be (a) the control of species distributions along the elevational gradient with particular reference to the effects of past and future climate change and (b) the importance of human activities, past and present, extending from tabonuco forest into the suburban areas that surround the LEF. 

(2) Study the importance of biodiversity at the site. The LUQ LTER site, because of its tropical nature, is the most diverse site in the LTER network for most groups of plants and animals. The importance of biodiversity will be assessed by narrowly focusing on the litter/soil interface where biodiversity is most easily manipulated but where four important groups (vascular plants [litter], invertebrates, fungi, and bacteria) intimately interact at an important link in the terrestrial nutrient cycle. Similar studies are ongoing or planned for aquatic habitats, which will determine if patterns of material and nutrient processing in the two habitats are generalized.

(3) View the forest in a suburban context. The LEF is an island in a sea of suburbia. The importance of this is currently emphasized in ongoing stream studies which demonstrate a profound impact of dams and water abstraction on migratory shrimp. We will extend our studies of the LEF to the coast along corridors following two or three of the major streams we are currently studying. Human impacts on populations of plants and animals and cycling and transport processes will be investigated along these corridors.

These ideas will be further honed and brought in to line with budgetary and logistical realities at a meeting of a subset of investigators in January.

Research Accomplishments

Research at the Luquillo LTER site is organized around two major questions: (1) What is the distribution of different disturbance types within the LEF and how does the disturbance regime at a given site affect the structure and function of the ecosystem?; and (2) What is the response of the biota to disturbances differing in origin, scale, severity, and frequency and how does this response affect a site=s recovery toward a mature ecosystem? Below we discuss recent progress towards examining these two questions and include concise examples of research results.

1. Disturbance regime and the structure and function of the ecosystem

We originally set out to determine the scale, frequency, severity of disturbance resulting from hurricanes, landslides, treefalls, and tree harvesting. Since the inception of the program, however, human disturbance of all types has been recognized as the most critical disturbance to tabonuco forest. Drought and floods are now recognized as additional important sources of disturbance. Basic studies and models of the structure and function of the Luquillo Ecosystem provide a background for the interpretation of disturbance effects. Some examples to highlight are:

-- David Foster and his colleagues have compiled histories of hurricane impacts for every damaging storm that has struck Puerto Rico since the time of Columbus and have developed meteorological reconstructions on each storm in the 19th and 20th centuries. This information provides the first complete record of gradients of hurricane frequency and intensity in Puerto Rico and will enable researchers in the LUQ LTER to plan landscape to regional analyses of forest ecosystem process and pattern that incorporate wind damage. 

-- The Hurricane Recovery Plot, a 16 ha forest dynamics plot devoted to documenting patterns of hurricane disturbance and recovery (Hurricane Hugo, 1989), is also a long-term study on the human impacts on tropical forests. Approximately one-half of the plot was clear-cut or used for agriculture through the 1930's. The history of human use is now reflected in the distribution of tree species in the plot: Dacryodes excelsa (tabonuco), Manilkara bidentata (ausubo) and other primary species predominate in the least disturbed areas, while the area of human disturbance is dominated by the secondary species, Casearia arborea. Jill Thompson, Nick Brokaw, and Jess Zimmerman have analyzed recent results from the plot that clearly show that the human impacts persist through hurricane disturbance. Ordinations (multivariate analyses) of the community structure of the pre-hurricane tree community and the regenerating saplings measured three years post-hurricane were nearly identical, indicating little effect of the hurricane on human-induced species distributions in the plot.

-- Working on the Hurricane Recovery Plot, Sabine Hohndorf and Jean Lodge studied niche preferences and diversity of wood-inhabiting ascomycetes. Of over 350 species found, only three were host tree specific. However, strong preferences were found for wood of two different diameter classes (<2 and >2 cm). Most interestingly, there appears little species overlap in species composition between areas of the plot with little and severe human disturbance. This suggests that anthropogenic disturbances occurring over 60 years ago affect fungal communities either through direct effects on tree community composition or resulting indirectly from the higher susceptibility of secondary tree species to hurricane damage. This pattern reflects a similar one for functional diversity of soil microbes reported by Willig et al. (1996); patterns of functional diversity differed most greatly between areas of different human land use. Thus, in this plot, patterns of biodiversity or most strongly controlled by the history of human effects and not the pattern of natural disturbance.

-- Research by Catherine Pringle and her student James March on the effects of water abstraction and dams on shrimp mortality and migration in rivers in the LEF has contributed to our conceptual understanding of how streams function by forcing us to address how disturbance is transmitted upstream. The freshwater shrimp of Luquillo=s rivers must complete their life cycle in the sea. Larvae dispersing downstream often end up in the municipal water supply where they are killed. When water levels are low, water abstraction reaches 100% and all larvae hatched during that time are lost from the system. Meanwhile, dams where water abstraction takes place are barriers to upstream migration by maturing adults. While the River Continuum Concept and other stream paradigms emphasize that downstream communities are a function of upstream processes, it is clear that alterations to streams in their lower reaches can produce effects in upstream reaches on levels from genes to ecosystems. 

-- A severe flooding event in the Quebrada Sonadora on March 7, 1998 allowed Joanne Sharpe to determine disturbance effects on rheophytic (inhabiting stream beds) and facultatively rheophytic ferns (those which also inhabit the forest floor). The flood occurred in the seventh year of a long-term study of six fern species. Effects of the flooding included plant mortality, premature leaf loss and rearrangement of habitat. Annualized mortality rates during the flood were 2.5 to over 40 times greater than that during the previous seven years; mortality in two species had never been recorded until the flood. Facultative rheophytes were most susceptible to being dislodged by the increased flow of water. The condition and locations of ferns which appeared to be unaffected by the flooding provide insight into predicting safe sites for long-term establishment of ferns in this dynamic habitat.

-- William McDowell recently completed the Luquillo component of the Lotic Intersite Nitrogen Experiment (LINX). ¹⁵NH₄ was added at tracer levels to a stream in Luquillo between Jan 15 and Feb. 26, 1998. Preliminary data suggest there is a rapid nitrification of NH₄ with approximately 20% of the added ¹⁵NH₄ converted to ¹⁵NO₃ only 70 meters from the point of addition. Epilithic algae, fine benthic organic matter, and suspended particulate organic matter were all highly labeled after only 7 days. Scrapers (juvenile Atya shrimp and Heptageniidae) and filterers (Hydropsyche) were also labeled after 7 days. Thus, epilithon (fine sediments and algae) appear to be the primary link between dissolved N and the invertebrate food web; wood and leaves are of minor importance.

-- Mike Willig and his student Stephen Cox have begun to extend the analysis of the functional diversity of soil microbes from tabonuco forest (Willig et al. 1996) to the gradient of life zones throughout the Luquillo Mountains. A preliminary analysis indicates that both life zone (tabonuco vs. colorado vs. dwarf forest) and topographic position (ridge vs. valley) strongly affect patterns of substrate catabolism.

-- Charles Hall and his student David Marley have recently completed a spatial model of forest productivity in the Luquillo Mountains. The model, TOPOPROD, predicts rates of gross primary productivity by simulating the physiological responses of forest vegetation to environmental gradients of climate and soil moisture. Simulated gross primary productivity ranged from 12 to 69 t carbon/ha/year and compares favorably with the limited empirical data that are available. Comparisons of simulated and empirical gross primary productivity data with empirical net primary productivity data suggest that respiration is higher in the Luquillo Mountains than in other tropical forests.

-- Charles Hall, Hong Wang, and Joe Cornell have developed a spatially-explicit version of the CENTURY model to simulate changes in soil carbon storage and flux as a function of climatic and physical factors. The model showed that total carbon storage, surface microbial carbon, and rates of decomposition are sensitive to changes in elevation. Carbon release due to decomposition ranged from 0.12 - 0.21 t C/ha/mo at low elevations and 0.07 - 0.13 t C/ha/mo at higher elevations.

-- Doug Schaefer and Javier Ososrio have completed measurements of dry deposition in the Luquillo Mountains using marine-derived chloride as a tracer. Their methods distinguish sedimentation from impaction (small particles carried in the wind). Among sites, wet deposition of chloride ranged from 70 to 110 kg/ha/yr and increased with elevation. Sedimentation ranged from 20 to 25 kg/ha/yr. Impaction ranged from 10 to 100 Kg/ha/yr and decreased with elevation. Factors that influence impaction include wind speed, canopy structure, and number of non-rain hours. In the Luquillo Mountains, wind speed increases with elevation, while the other two factors decrease. The decrease in impaction with elevation suggests that canopy structure and wind speed have a greater role than do non-rain hours.

2. Role of the biota in recovery from disturbance

Much effort has been devoted to recording, modeling, and understanding the recovery of tabonuco forest from the disturbance to the forest caused by Hurricane Hugo in September 1989. In the most recent proposal we set out to study certain species we felt held Apivotal@ roles in the recovery from disturbance, including the pioneer tree, Cecropia schreberiana. Understanding recovery from landslide disturbance has also been an important component of LUQ LTER research.

-- Recently analyzed data from the latest census (1995-96) of the Hurricane Recovery Plot (Jill Thompson, Nick Brokaw, and Jess Zimmerman) indicate that Hurricane Hugo did not have a major impact on the community composition of the forest. While 9% of trees died as a result of the hurricane, death was most common in a handful of species and the remaining species showed little impact. Whatever losses occurred were balanced to a degree by recruitment. The major exception was the pioneer tree Cecropia schreberiana which increased nine-fold after the hurricane. We identified C. schreberiana as a pivotal species in the recovery of the forest following hurricanes in our 1994 proposal. Its premier role in the recovery of the plot supports this hypothesis.

-- Ariel Lugo and Jess Zimmerman recently reviewed the knowledge of tropical tree life histories as part of the effort to define the life histories of a subset of tree in tabonuco forest in the context of hurricane disturbance. Their analysis concludes, as others have, that the only clear distinction that can be made in tropical tree life histories is between Apioneers@ and Anonpioneers@. Such proposed groups as Alate secondary@ or Alarge gap@ species cannot be recognized as distinct groups. They also hypothesize that frequent hurricane disturbance will select for species with early ages of reproduction compared to mainland areas without hurricane disturbance.

-- William Pulliam and William Parton have recently implemented a version of the ZELIG model for tabonuco forest. ZELIG is a spatially explicit grid-based forest gap dynamics model, here for the first incorporating the effects of hurricanes. ZELIG simulations produced a mixed species forest dominated by Dacryodes, Manilkara, and Sloanea at the end of 500 years. The addition of simulated hurricanes affected the dominant species only moderately, but substantially increased abundance of many successional species dependent on treefall gaps in the closed canopy forest. Comparisons between ZELIG and CENTURY, a biogeochemical process model, showed similar patterns of LAI over time but substantially less woody biomass in ZELIG than in CENTURY simulations.

-- One of the major effects of a severe hurricane is the deposition of large amounts of woody debris on the forest floor. While much of this woody debris decomposes rapidly, a process which has a large impact on the rest of the ecosystem (Zimmerman et al. 1995), some species decompose rather slowly. Kristina and Dan Vogt have shown that the loss of density after two years in decomposing logs of Dacryodes excelsa (tabonuco) is 22%, not different from estimates used by Zimmerman et al (1995) to model the effects of decomposing woody debris on ecosystem processes. However, the decomposition of Manilkara bidentata (ausubo) is much slower, only a 1.75% loss of density after two years. Thus, ausubo leaves a long-lasting legacy of infrequent severe hurricanes.

-- A conspicuous component of the understory in a forest recovery from hurricane damage are shrubs. Ned Fetcher and Zheng Zheng (a student visiting from Taiwan) showed that whole plant carbon gain in three common species of shrub did not differ significantly. However, the manner in which carbon gain occurred did differ between species. Psychotria berteriana has the tallest stature and thereby received the most light and, as a result, had the highest net assimilation rate of whole leaves (35.1 mmol m^-2 d^-1). Palicourea riparia and Piper glaberescens had net assimilation rates of 19.5 and 15.0 mmol m^-2 d^-1, respectively. Piper had the highest median leaf area (0.18 m²) followed by Psychotria (0.07 m²) and Palicourea (0.05 m²). Leaf respiratioin at night used up 86% of net assimilation from the daytime in Piper and 58% in Palicourea, but only 33% in Psychotria. 

-- Mike Willig and his students report that nine years after Hurricane Hugo, all common snail species have returned to densities similar to those before the hurricane. However, the density of the walking stick Lamponius portoricensis has not recovered to pre-hurricane levels. The density of his normally abundant species was severely reduced by the hurricane and has only recently begun to demonstrate a slight post-hurricane increase in numbers. Because L. portoricensis is an important herbivore on some shrub species when present at high densities, patterns of herbivory may be quite different now than during pre-hurricane times.

-- Lawrence Walker and his coworkers have recently initiated long-term experiments on the recovery of vegetation in landslides. These experiments are based on over 10 years of records of landslide recovery throughout the LEF. The experiments consist of removals of suspected pivotal species in landslide succession. Ferns in the Gleicheniaceade were removed because they often form dense thickets that inhibit the establishment of tree seedlings but which may have a long-term facilitative effect through the effects of the ferns on nitrogen availability. Tree ferns are also aggressive colonizers of landslides that may outcompete other species through their dense shade and rapid nutrient uptake or facilitative the establishment more shade tolerant secondary species. Finally, a suite of common woody colonists on landslides were removed to examine their importance in site stabilization, shading, and other potentially facilitative effects. Preliminary results indicate that revegetation of the removal plots is remarkably variable, even among replicate plots within a landslide. The only consistent pattern has been that grasses are the early dominants in both types of fern removals.

-- Xiaoming Zou and his collaborators have studied earthworm communities in landslides and adjacent forested sites. They have found that the endogenic worm Pontoscolex corethrurus occurred in both upper (slide) and lower (depositional) landslides zones as well as in nearby forested areas. The anecic earthworm Amynthas rodericensis occurred only in forested sites. Earthworm density and biomass correlated positively with leaf litter, the light-carbon fraction in soils and total bacteria, indicating that earthworms were an important component of soil development in landslide scars.

-- Alan Covich, Todd Crowl, and their students have studied the interactive effects of two freshwater shrimp on processing of Cecropia leaves. Each species alone only serves to complete one portion of the processing of leaves: Xiphocaris shreds leaves in to fine particles on which Atya can then filter feed. In the absence of Xiphocaris, Atya abandon filter feeding and forage on epihyton on rocks. In the absence of Atya, the processing of leaves is incomplete. While this is a simple system, the project demonstrates that species have unique functional roles and indicates the importance of biodiversity for ecosystem function.

Information Management

The original goals of the Luquillo LTER information management efforts were to identify candidate data sets and develop accompanying documentation. To date we have catalogued 97 LTER data sets, the majority of which are appropriately documented. An Ad Hoc Information Management Committee has conducting a case-by-case review of metadata to confirm that each data set is adequately described. This review was conducted earlier this year and each investigator whose metadata were incomplete has been contacted. In addition to the LTER data sets, we have identified and archived 99 other data sets from the Luquillo Experimental Forest that are relevant to our LTER work. Many of these data sets were orphaned after previous funding sources disappeared. Our information management staff routinely enter onto magnetic media 14 data sets for LTER investigators and manipulate another 18 data sets to make then easily available to our scientists.

At present, 36 of our data sets are available on the internet. Web forms are available to enter publications and abstracts to the LUQ LTER bibliography and forms are under construction to enter metadata. We plan to add selected data sets to our home page during the next three years. Our goal is to have all commonly requested data sets available by the end of the present funding cycle. At the same time, we will continue to add data sets to our catalogue and to maintain the level and quality of services that we offer to our investigators.

Outreach Activities

Four REU students worked at El Verde Field Station this past summer. Melissa Cintron and Ramon del Moral worked with Bob Waide on his annual bird census and completed projects on radio tracking pigeons and other dispersers of fruits of the sierra palm. Heather Cooley is conducting projects with Whendee Silver on patterns of forest productivity in the LEF and Marcy Okada is conducting projects on shrimp populations dynamics under the supervision of Alan Covich.

For the past two years, the University of Puerto Rico has provide funds for interns at the field station. This past summer Katia Aviles and Sigredo Corraliza worked on projects with Doug Scheafer on land use effects on soil characteristics and water chemistry. Sheila Soles an Ariel Rivera worked with Elvia Melendez conducting projects on frugivory and herbivory on Heliconia plants. Osvaldo Cruz and Edna Francisco conducted experiments on earthworm competition under the direction of Xiaoming Zou. Mariely Morales, Jose Fumero, and Eleinid Espinso also worked at the station on projects involving outcrossing in Begonia plants, and the flowering phenology of Heliconia.

Xiaoming Zou and two current and former LUQ students, Alex Sloan and Grizelle Gonzalez, traveled to Taiwan and the People=s Republic of China to visit LTER sites and give presentations on their research. The trip was sponsored by the Division of International Programs and follows a similar visit by Taiwanese students and researchers to U.S. LTER sites last year.

Xiaoming Zou was interviewed by Discovery Magazine about his earthworm work in relation to reforestation programs in Puerto Rico.

Charles Hall and colleagues have developed an interactive computer display to demonstrate results of LTER research at the newly-opened El Portal Visitor Center in the Luquillo Experimental Forest.

Tim Schowalter acts as a resource for secondary schools in Oregon, meeting with teachers, classes and individual students to discuss/explain rain forest ecology and conservation, based largely on data sets from the Luquillo LTER.

Grants Received by Luquillo LTER Investigators

USDA-FS/UPR, ASoil carbon dynamics in riparian and upland areas in subtropical wet forest of Puerto Rico@, $30,000. 1998-1999. Xiaoming Zou. 

NSF, "Earthworm and soil processes in North American ecosystems: a cross-site study", $200,000, 1995-1998. Paul Hendrix, John Blair, and Xiaoming Zou. 

NSF, Match for "Long-Term Ecological Research on the Luquillo Experimental Forest II", Prime Grant DEB-9705814, $4,800 from the University of Nevada-Las Vegas to Lawrence Walker.

NSF, "Improvements to El Verde Field Station", $90,000. 1996-1999. Elvia Melendez and Jess Zimmerman.

NSF-BS&I, "Basidiomycetes of the Greater Antilles, DEB-95-25902, 1996-2000. D. Jean Lodge.

NSF-REU. Supplement awarded to prime LTER grant. 1997. Robert B. Waide. 

NSF-Nat. Res. Council/Forest Service, Grant Post-doctoral award for Dr. Sharon Cantrell 

NSF, ANitrogen uptake, retention and cycling in stream ecosystems: an intersite N-15 tracer experiment@. $103,169. 1996-1999. William H. McDowell.

NASA, "Land Management in the Tropics and its Effects on the Global Environment", $3,800,000. 1994-99. Robert B. Waide, John Thomlinson, Jess K. Zimmerman, Xiaoming Zou, Douglas Schaefer

NASA/EPSCoR, Collaborating investigator on a proposal to establish the Tropical Atmospheric Science Center, $5,000,000. 1994-1999. Robert B. Waide, Douglas Schaefer

NSF, A Minority Research Center for Excellence in Tropical and Caribbean Studies@ $5,000,000. 1993-1998. Robert B. Waide, Jess K. Zimmerman, Xiaoming Zou.

Cross-site and International Activities

Cross-site comparisons and syntheses conducted by scientists associated with the Luquillo LTER program take a variety of forms. Comparisons with single and multiple sites within the LTER Network make up a key part of our overall research program. However, given the location of Puerto Rico and the affinity of its flora and fauna with the tropics, many of our intersite studies are international in nature. Below we list ongoing and completed comparative studies by LTER (or other) site and investigator (Tables 1 and 2). Many of the projects listed below are part of the regionalization effort of the Luquillo LTER.

Table 1. Cross-site studies involving the Luquillo LTER and at least one other LTER site. The other sites involved are in the first column and the Luquillo investigator and a brief description of the research are in the second column.

Table 2. Cross-site studies involving the Luquillo LTER and at least one other non-LTER site. The number of other sites involved is in the first column and the collaborating investigators, the location of the study, and a brief description of the research are in the second column.

Network-level activities

Table 3. Network-level studies involving the Luquillo LTER. The number of other LTER sites involved in each study is in the first column and the local investigator and a brief description of the research are in the second column.

Publications 1997-1998 and in press 

The following list contains publications resulting directly from work performed under the Luquillo LTER or that was supported in a substantial way by the LTER. Authors who are Co-Pi's on the original LTER proposal are shown in bold. Authors who were not participants in LTER 1 but who are Co-Pi's on the renewal are underlined. Authors who were graduate students supported by the Luquillo LTER are indicated with an asterisk (*). The list includes 248 refereed publications and 40 dissertations, theses, or Master's projects.

JOURNAL ARTICLES

Baroni, T.J. and D.J. Lodge. 1998. Basidiomycetes of the Greater Antilles I: new species and new records of Alboleptonia from Puerto Rico and St. John, USVI. Mycologia, in press.

Baroni, T.J., D.J. Lodge, and S.A. Cantrell. 1997. Tropical connections: Sister species ans species in common between the Caribbean and the eastern United States. McIIvainea 13:4-19.

Baroni, T.J., R. Vilgalys, D.J. Lodge & N.V. Legon. 1998. Calocybe in the Caribbean. The Mycologist, In press.

Bayman, P.L., L. Lebron, R.L. Tremblay, and D.J. Lodge. 1997. Variation in endophytic fungi from roots and leaves of Lepanthes (Orchidaceae). New Phytologist 135:143-149.

Bayman, P., P. Angulo-Sandoval, Zoila Baez-Ortiz & D.J. Lodge. 1998. Mycological Research. Distribution and dispersal of Xylaria endophytes in two tree species in Puerto Rico. Mycological Research. In press.

Benstead, J.P., J.G. March*, C.M. Pringle, and F.N. Scatena. (In press) Effects of water abstraction and damming on migratory tropical stream biota: simulation modeling and mitigation strategies. Ecological Applications 00:00-00.

Callaway, R.M. and L.R. Walker. Competition and facilitation: a synthetic approach to interactions in plant communities. Ecology 78:1958-1965.

Clark, K.C., N.M. Nadkarni, D. Schaefer, and H. L. Gholz. In Press. Atmospheric depisition and net retention of ions by the canoyt in a tropical montane forest, Monteverde, Costa Rica. Journal of Tropical Ecology.

Clark, K.C., N.M. Nadkarni, D. Schaefer, and H.L. Gholz. 1998. Cloud water and precipitation chemistry in a tropical montane forest, Monteverde, Costa Rica. Atmospheric Environment 32:1595-1603.

Delaney, M., S. Brown, A.E. Lugo, A. Torres-Lezama, and N. Bello Quintero. The distribution of organic carbon in major components of forests located in five life zones of Venezuela. Journal of Tropical Ecology 13:697-708.

Eklund, T.J*., W.H. McDowell, and C. Pringle. Seasonal patterns in tropical precipitation chemistry: La Selva, Costa Rica. Atmospheric Environment 31:3903-3910.

Foster, D., M. Fluet and E. Boose. 1998. Human or natural disturbance: landscape-scale dynamics of the tropical forests of Puerto Rico. Ecological Applications (In Press).

Frangi, J.L., and A.E. Lugo. A palm floodplain forest five years after Hurricane Hugo. Biotropica, in press.

Gannon, M.R.*, and M.R. Willig. 1997. The effect of lunar illumination on movement and activity of the red fig-eating bat (Stenoderma rufum). Biotropica 29:525-529.

Gonzalez, G. and X. Zou. in press. Plant and litter influences on earthworm abundance and community structure in a tropical wet forest. Biotropica.

Heneghan, L., D.C. Coleman, X. Zou, D.A. Crossley, Jr. and B.L. Haines. in press. Soil microarthropod community structure and litter decomposition rates: an across-site study of tropical and temperate sites. Applied Soil Ecology.

Huhndorf, S.M., & D. J. Lodge. 1998. Niche preferences and diversity in wood-inabiting Pyrenomycetes (Fungi: Ascomycetes) in a wet tropical forest. Tropical Ecology. In press.

Johnson, K.H., K.A. Vogt, H.J. Clark, O.J. Schmitz and D.J. Vogt. 1997. Biodiversity and the productivity and stability of ecosystems. Trends in Ecology and Evolution 11:372-377

Johnson, K.H., K.A. Vogt, O.J. Schmitz, D.J. Vogt, and H.J. Clark. 1997. Letter on Stand up for parasites: a reply to Windsor. Trends in Ecology and Evolution 12:32-33.

Johnson, S.L.*, A.P. Covich, T.A. Crowl, A. Estrada-Pinto, J. Bithorn and W. Wurtsbaugh. 1996. Do seasonality and disturbance influence reproduction in freshwater atyid shrimp in headwater streams, Puerto Rico? Verhandlungen Internationale Vereinigung fur Theoretische und Angewandte Limnologie.

Lodge, D.J. 1997. Factors related to diversity of decomposer fungi in tropical forests. Biodiversity and Conservation 6.

March, J.G.*, J.P. Benstead, C.M. Pringle, and F.N. Scatena (in press) Migratory drift of freshwater shrimps in two tropical streams, Puerto Rico. Freshwater Biology 00:00-00.

McDowell, W.H. Internal nutrient fluxes in a tropical rain forest. Journal of Tropical Ecology (in press).

Myster, R.W. 1997. Seed predation, disease and germination on landslides in Puerto Rico and Costa Rica. Journal of Vegetation Science 8:55-64.

Myster, R.W. and E.M. Everham. in press. Germination cues across the disturbance regime in the Puerto Rican rainforest. Tropical Ecology.

Myster, R.W. and F.O. Sairmento. Microsite seed input on tropandean landslides in Ecuador. Restoration Ecology 6:35-43.

Myster, R.W., J.R. Thomlinson, and M.C. Larsen. 1997. Predicting landslide patch vegetation on spatial gradients using landscape characteristics in Puerto Rico. Landscape Ecology 12:299-307.

Myster, R.W. and L.R. Walker. 1997. Plant successional pathways on Puerto Rican landslides. Journal of Tropical Ecology 13:165-173.

Nakasone, K., H.H. Burdsall, Jr., and D.J. Lodge. 1998. Phanaerochaete flava in Puerto Rico. Mycologia 90:132-135.

Pegler, D.N., D.J. Lodge, and K.K. Nakasone. 1998. Macrocybe gen. nov. (Tricholomataceae, tribus Tricholomatae). Mycologia 90:494-504.

Pringle, C.M. 1997. Expanding scientific research programs to address conservation challenges in freshwater systems, pp. 305-319 in: Pickett, S.T.A., R.S. Ostfeld, M. Shachak, and G.E. Likens (eds.) Enhancing the ecological basis of conservation: Heterogeneity, ecosystem function and biodiversity. Proceedings of the Sixth Cary Conference, Institute of Ecosystem Studies. Chapman and Hall, New York.

Pringle, C.M. 1997. Connections between downstream disturbance, lag times, and biophysical legacies in headwater streams: To what extent are human influences transmitted upstream. Journal of the North American Benthological Society. Special symposium volume, ANew Concepts in Stream Ecology. J. Vaun Macarthur (ed.). Savannah River Ecology Laboratory, Aiken, SC.

Pringle, C. M. 1997. Exploring how disturbance is transmitted upstream: going against the flow. Journal of the North American Benthological Society 16: 425-438.

Pringle, C.M., N.H. Hemphill, W. McDowell, A. Bednarek, and J. March* (in press) Linking communities and ecosystems: Effects of macrobiota on benthic organic matter in tropical streams. Ecology 00:00-00.

Reagan, D.P. The role of amphibians and reptiles in West Indian food webs. Journal of Herpetology (in press).

Reagan, D.P. Animal community considerations in the sustainable management of tropical forests. Tropical Ecology. (In press)

Silver, W.L.* 1997. The potential effects of elevated CO₂ and climate change on tropical forest biogeochemical cycling. Climatic Change (in press).

Silver, W.L., A.E. Lugo, and M. Keller. Soil oxygen availability and biogeochemistry along rainfall and topographic gradients in upland wet tropical forest soils. Biogeochemistry (in press).

Spooner, B., D.J. Lodge, and T Laessoe. A new Sorokina (Leotiales) from Puerto Rico. Kew Bulletin (in press).

Sullivan, N.H., W.B. Bowden, and W.H. McDowell. Short-term disappearance of foliar litter from three tropical tree species before and after hurricane disturbance. Biotropica (in press)

Vogt, K.A., D.J. Vogt and J. Bloomfield*. 1998. Comparison of direct and indirect methods for studying root dynamics of forests. Plant and Soil 200:71-89.

Waide, R.B., J.K. Zimmerman, and F.N. Scatena. 1997. Controls of primary productivity in a montane tropical forest: Lessons from the Luquillo Mountains in Puerto Rico. Ecology (in press).

Waide, R.B., M.R. Willig, G. Mittelbach, C. Steiner, L. Gough, S.I. Dodson, G.P. Juday, and R. Parmenter. 1998. The relationship between primary productivity and species richness. Ann Rev. Ecol. & Syst. (In press)

Willig, M.R., E.A. Sandlin, and M.R. Gannon*. 1998. Structural and taxonomic correlates of habitat selection by a Puerto Rican land snail. Southwestern Naturalist 43:70-79.

Willig, M.R., and S.K. Lyons. 1998. An analytical model of latitudinal gradients of species richness with an empirical test for marsupials and bats in the New World. Oikos, 81:93-98.

Zou, X., and G. Gonzalez. 1997. Changes in earthworm density and community structure during secondary succession in abandoned tropical pastures. Soil Biology and Biogeochemistry 29:627-629.

Zou, X. and M. Bashkin. in press. Soil carbon accretion and earthworm recovery following revegetation in abandoned sugarcane fields. Soil Biology and Biochemistry.

CHAPTERS IN BOOKS

Brokaw, N. V. L., and R. A. Lent. 1997. Vertical structure. In M. L. Hunter, Jr. (ed.). Maintaining Biodiversity in Forest Ecosystems. Cambridge University Press, Cambridge, U.K.

Gannon, M.R.* and M.R. Willig. 1998. Long-term monitoring protocol for bats: Lessons from the Luquillo Experimental Forest. In F. Dallmeier and J. Comiskey, eds. Forest Biodiversity in North, Central, and South America and the Caribbean: Research and Monitoring. Parthenon Press, Washington, DC. (In press).

Groffman, P., E. Holland, D. Myrold, P. Robertson, and X. Zou. in press. Denitrification. In: Standard soil methods for long-term ecological research. G.P. Robertson, D.C. Coleman, P. Sollins, and C. Bledsoe, editors. Oxford University Press, Oxford, UK.

Lugo, A.E., and J. Zimmerman. Ecological life histories of tropical trees with emphasis on disturbance effects. In J. Vozzo, editor Tropical Tree Seed Manual. USDA Forest Service (in press).

Lugo, A.E., and S. Fu. Structure and dynamics of mahogany plantations in Puerto Rico In Figueroa Colon, editor. Biology, Ecology and Management of Mahogany. Springer Verlag (in press).

Miller, R.M., and D.J. Lodge. 1997. Fungal responses to disturbance - Agriculture and Forestry. Pp 65-84 In The Mycota, Vol. V. Environmental and Microbial Relationships. K. Esser, P.A. Lemke and D.T. Wicklow, Eds. Springer Verlag.

Pringle, C. M. 1997. Fragmentation in stream ecosystems, p. 289-90. In:G.K. Meffe and C. R. Carroll (eds.) Principles of conservation biology. Second Edition. Sinauer Associates Inc., Sunderland, MA.

Pringle, C.M. (in press) River conservation in tropical versus temperate regions, pp. xx-xx. In: P. J. Boon and B. Davies (eds.) Global perspectives on river conservation: Sciencie policy and practice. John Wiley and Sons.

Pringle, C.M. and F.N. Scatena. 1997a. Factors affecting aquatic ecosystem deterioration in Latin America and the Caribbean . In U. Hatch and M.E. Swisher, editors. Tropical managed ecosystems: new perspectives on sustainability. Oxford University Press, Oxford, UK. (In press).

Pringle, C.M. and F.N. Scatena. 1997b. Freshwater resource development: Case studies from Puerto Rico and Costa Rica. In U. Hatch and M.E. Swisher, editors. Tropical managed ecosystems: new perspectives on sustainability. Oxford University Press, Oxford, UK. (In press).

Pringle, C.M., F. Scatena, P. Paaby, and M. Nunez. (in press) Conservation of aquatic ecosystems of Latin America and the Caribbean, pp xx-xx. In: P. J. Boon and B. Davies (eds.) Global perspectives on river conservation: Science, policy and practice. John Wiley and Sons.

Vogt, K.A., H. Asbjornsen, A. Ercelawn, F. Montagnini, and M. Valdes. 1997. Ecosystem integration of roots and mycorrizas in plantations. In: S. Nambiar, A. Brown, and C. Cossalter, eds. Management of Soil, Water and Nutrients in Tropical Plantation Forests. ACIAR (in press)

Walker, L.R. In press. Patterns and processes in primary succession. In: L.R. Walker (Ed.). Ecosystems of Disturbed Ground. Elsevier, Amsterdam.

Walker, L.R., and M. Willig. In press. An introduction to terrestrial disturbances. In: L.R. Walker (Ed.). Ecosystems of Disturbed Ground. Elsevier, Amsterdam.

Walker, L.R. and S.D. Smith. 1997. Impacts of invasive plants on community and ecosystem properties. pp. 69-86 in: J.O.Luken and J. Thieret, Assessment and Management of Plant Invasions. Springer-Verlag.

Willig, M. and L.R. Walker. In press. Disturbance in terrestrial ecosystems: Salient themes, synthesis, and future directions. In: L. R. Walker (Ed.). Ecosystems of Disturbed Ground. Elsevier, Amsterdam.

Willig, M.R., and M.A. McGinley. 1998. Animal responses to natural disturbance and roles as patch generating phenomena. Pp., 000-000, in Ecology of Disturbed Ground, Elsevier Science, Amsterdam, The Netherlands (In press).

Willig, M.R., M.F. Secrest,* S.B. Cox*, G.R. Camilo*, J.F. Cary*, J. Alvarez*, and M.R. Gannon*. 1998. Long-term monitoring of snails in the Luquillo Experimental Forest of Puerto Rico: Heterogeneity, scale, disturbance, and recovery. In F. Dallmeier and J Comisky, eds. Forest Biodiversity in North, Central, and South America and the Caribbean: Research and Monitoring. Parthenon Press, Washington, DC. (In press).

Zak, J.C., and M.R. Willig. 1998. Analysis and interpretation of fungal biodiversity patterns. Pp. 000-000, in Measuring and Monitoring Biological Diversity. Standard Methods for Fungi. (M.S. Foster, Ed) Smithsonian Institution Press, Washington, DC (In press).

OTHER PUBLICATIONS

Alvarez, J. 1997. Patterns of abundance, species richness, habitat use, and morphology in tropical terrestrial molluscs: effects of disturbance and elevation. Ph.D. Dissertation. Texas Tech University.

Boose, E.R., K.E. Chamberlin, and D.R. Foster. 1997. Reconstructing historical hurricanes. Pp. 388-389 In: Preprints of the 22nd Conferencie on Hurricanes and Tropical Meteorology. American Meteorological Society. Boston, MA.

Fernandez del Viso, D.S. 1997. Contrasting light environments and response flexibility of trees in the Luquillo Mountains of Puerto Rico. Ph.D. Dissertation. University of Puerto Rico.

Kent, R. 1997. Seedling survival and colonizing vegetation in wetland plots receiving pig wastes in Puerto Rico. M.S. Thesis. University of Florida.

Kharecha P. 1997. Energy evaluation of the effects of human activities on the Luquillo Experimental Forest, Puerto Rico. M.S. Thesis. University of Florida.

O'Connor, Paul J. 1998. Habitat selection in inusular tropical streams: macroinvertebrate reponses to a riparian invasion by non-indigenus bamboo. MS. Thesis, Colorado State University, Ft. Collins, Colorado. 138 pages.

Quinones Orfila, V. 1997. Estimates of leaf area index from physical parameters and remote sensing data over the Luquillo Experimental Forest. M.S. Thesis. University of Puerto Rico.

Reagan, D.P. (with multiple other contributing authors). Sustainable Environmental Management. Society of Environmental Toxicology and Chemistry (SETAC). (In press)

Reed, Angela M. 1998. Scale-dependent influences of riparian processes on the dominant detritivore of a headwater stream in Puerto Rico. MS. Thesis, Colorado State University, Ft. Collins, Colorado. 107 pages.

Vogt, K.A., J. Gordon, J. Wargo, D. Vogt, H. Asbjornsen, P.A. Palmiotto, H. Clark, J. O=Hara, W.S. Keeton, T. Patel-Wey-nand, E. Witten. 1997. Ecosystems: Balancing Science with Management. Springer-Verlag, New York.

Walker, L.R., (editor). In press. Ecosystems of Disturbed Ground. Elsevier, Amsterdam. 850 pp.

Walker, L.R. 1997. A.E. Lugo and C. Lowe (eds.) 1995. Tropical Forests: Management and Ecology. Forest Ecology and Management (Book Review).

Literature Cited

Willig, M.R., D.L. Moorehead, S.B. Cox, and J.C. Zak. 1996. Functional diversity of soil bacteria communities in the tabonuco forest: The interaction of anthropogenic and natural disturbance. Biotropica Special Issue 28:471-483.

Zimmerman, J. K., W. M. Pulliam, D. J. Lodge, V. Quiñones, N. Fetcher, R. B. Waide, S. Guzmán-Grajales*, J. A. Parrotta, C. E. Asbury, and L.. R. Walker. 1995. Nitrogen immobilization by decomposing woody debris and the recovery of tropical wet forest from hurricane damage. Oikos 72:316-322.