Luquillo Forest Dynamics Plot Research Articles

Height–diameter allometry for a dominant palm to improve understanding of carbon and forest dynamics in forests of Puerto Rico

AbstractTropical forests play a major role in the global carbon cycle but their diversity and structural complexity challenge our ability to accurately estimate carbon stocks and dynamics. Palms, in particular, are prominent components of many tropical forests that have unique anatomical, physiological, and allometric differences from dicot trees, which impede accurate estimates of their aboveground biomass (AGB) and population dynamics. We focused on improving height estimates and, ultimately, AGB estimates for a highly abundant palm in Puerto Rico, Prestoea acuminata. Based on field measurements of 1003 individuals, we found a strong relationship between stem height and diameter. We also found some evidence that height–diameter allometry of P. acuminata is mediated by various sources of environmental heterogeneity including slope and neighborhood crowding. We then examined variability in AGB estimates derived from three models developed to estimate palm AGB. Finally, we applied our novel height:diameter allometric model to hindcast dynamics of P. acuminata in the Luquillo Forest Dynamics Plot during a 27‐year period (1989–2016) of post‐hurricane recovery. Overall, our study provides improved estimates of AGB in wet forests of Puerto Rico and will facilitate novel insights to the dynamics of palms in tropical forests.Abstract in Spanish is available with online material.

Demographic trade-offs and functional shifts in a hurricane-impacted tropical forest.

Understanding shifts in the demographic and functional composition of forests after major natural disturbances has become increasingly relevant given the accelerating rates of climate change and elevated frequency of natural disturbances. Although plant demographic strategies are often described across a slow-fast continuum, severe and frequent disturbance events influencing demographic processes may alter the demographic trade-offs and the functional composition of forests. We examined demographic trade-offs and the shifts in functional traits in a hurricane-disturbed forest using long-term data from the Luquillo Forest Dynamics Plot (LFPD) in Puerto Rico. We analysed information on growth, survival, seed rain and seedling recruitment for 30 woody species in the LFDP. In addition, we compiled data on leaf, seed and wood functional traits that capture the main ecological strategies for plants. We used this information to identify the main axes of demographic variation for this forest community and evaluate shifts in community-weighted means for traits from 2000 to 2016. The previously identified growth-survival trade-off was not observed. Instead, we identified a fecundity-growth trade-off and an axis representing seedling-to-adult survival. Both axes formed dimensions independent of resprouting ability. Also, changes in tree species composition during the post-hurricane period reflected a directional shift from seedling and tree communities dominated by acquisitive towards conservative leaf economics traits and large seed mass. Wood specific gravity, however, did not show significant directional changes over time. Our study demonstrates that tree demographic strategies coping with frequent storms and hurricane disturbances deviate from strategies typically observed in undisturbed forests, yet the shifts in functional composition still conform to the expected changes from acquisitive to conservative resource-uptake strategies expected over succession. In the face of increased rates of natural and anthropogenic disturbance in tropical regions, our results anticipate shifts in species demographic trade-offs and different functional dimensions.

Forest Structure and Composition Are Critical to Hurricane Mortality

Hurricanes can cause severe damage to tropical forests. To understand the nature of hurricane impacts, we analyze and compare immediate effects from category-4 hurricane María in 2017 and category-3 hurricane Hugo in 1989 at Bisley Experimental Watersheds (BEW) in the Luquillo Experimental Forest, Puerto Rico. We show that hurricane María caused lower mortality than hurricane Hugo, even though hurricane María was a stronger event with higher sustained wind. The lower mortality was due to the combination of lower accumulated cyclone energy at the site and more wind-resistant forest structure and composition at the time of disturbance. We compare our study site with a nearby location that has the same forest type, Luquillo Forest Dynamics Plot (LFDP), and describe the similarities and differences of mortality and impact factors between the two sites during the two events. During hurricane Hugo, LFDP experienced much lower mortality than BEW, even though the accumulated cyclone energy at LFDP was higher. The difference in mortality was due to contrasting forest structure and composition of the two sites. Our results demonstrate that forest structure and composition at the time of the disturbance were more critical to hurricane-induced mortality at the two sites than accumulated cyclone energy.

Tropical forest understorey riparian and upland composition, structure, and function in areas with different past land use

AbstractQuestionsAlthough past land‐use effects on composition and structure are described for many forest types, forested riparian areas have been overlooked. Riparian areas may contain unique species and high species richness, as well as contribute basal leaf‐litter resources for aquatic fauna. We asked: (a) does past land use alter composition in riparian vs upland areas in wet tropical forest; (b) which vegetation life forms characterize riparian zones; and (c) what is the composition and quantity of leaf litter in riparian zones compared to uplands?LocationRiparian and upland locations in tropical wet forest, Luquillo Forest Dynamics Plot (LFDP), Luquillo Experimental Forest, Puerto Rico.MethodsStratified random sampling was conducted in riparian and upland areas of LFDP with high and low past land use. Understorey vegetation life form composition and cover were sampled in plots. Leaf‐litter species composition and components were estimated with collecting baskets placed throughout riparian zones and uplands.ResultsFerns and lianas were more abundant in riparian areas than uplands. Ordination of species composition groups was distinct for riparian and upland areas with different past land use when based on leaf litter, but this ordination pattern was not as clear in plot vegetation.ConclusionCharacterized by greater presence of ferns and lianas, riparian zones had higher species richness values and greater leaf litter biomass. Distinct leaf‐litter species composition within riparian and upland areas may result from a combination of different land‐use histories, various plant types, and environmental conditions. Although riparian areas are proportionally a small component of the forested landscape, they are significant contributors to ecosystem process, terrestrial and aquatic linkages, and plant community composition.

The interaction of land‐use legacies and hurricane disturbance in subtropical wet forest: twenty‐one years of change

AbstractDisturbance shapes plant communities over a wide variety of spatial and temporal scales. How natural and anthropogenic disturbance interact to shape ecological communities is highly variable and begs a greater understanding. We used five censuses spanning the years 1990–2011 from the 16‐ha Luquillo Forest Dynamics Plot (LFDP) in northeast Puerto Rico to investigate the interplay of human land‐use legacies dating to the early 20th century and two recent hurricanes (Hugo, 1989 and Georges, 1998). The LFDP is a landscape mosaic comprised of an area of mature subtropical wet forest and three areas of secondary forest with differing past land‐use intensities. We examined the degree to which hurricane disturbance–effect and subsequent community recovery varied across past land‐use classes. We expected areas with greater intensity of human land use to be more affected by hurricane disturbance therefore exhibiting greater initial damage and longer successional recovery times. Structurally, areas of secondary forest contained smaller trees than old‐growth areas; hurricanes caused widespread recruitment of shrubs and saplings that thinned with time since the first hurricane. Species richness of the plot declined over time, mostly due to the loss of rare species, but also due to the loss of some heliophilic, pioneer species that became abundant after the first hurricane. Species composition differed strongly between areas of secondary and mature forest, and these differences were largely constant over time, except for an increase in compositional differences following the second hurricane. An indicator species analysis attributed this pattern to the longer persistence of pioneer species in areas of greater past land‐use intensity, likely due to the more open canopy in secondary forest. When secondary forest areas of differing past land‐use intensity were considered separately, few species of low community rank were found as indicators. When these areas were combined, more and higher‐ranked species emerged as indicators, creating ecologically meaningful indicator species combinations that better captured the broad‐scale plant community response to past land use. Our findings support the idea that effects of past land use can persist for decades to centuries following land‐use abandonment, illustrating the importance of land‐use legacies in shaping regenerating tropical secondary forests.

Life‐history trade‐offs during the seed‐to‐seedling transition in a subtropical wet forest community

Summary The transition from seed to established seedling (STS) represents a major bottleneck in plant demography with implications for community dynamics and the maintenance of species diversity. The relative strength of seed limitation versus seedling establishment limitation can reveal life‐history trade‐offs that contribute to the maintenance of community diversity. If seed limitation dominates, chance arrival to open sites may play a key role in maintaining diversity. If seedling establishment limitation dominates, however, species relative abundances may depend more on tolerance to environmental and biotic conditions during seedling establishment (i.e. species‐specific regeneration niche). We used three years of seed rain and seedling recruitment data for 19 species of tropical woody plants collected in the Luquillo Forest Dynamics Plot in Puerto Rico to (i) examine a trade‐off between seed and seedling establishment limitation and (ii) quantify the biotic and abiotic factors that mediate the STS transition. We did not find evidence of a life‐history trade‐off in the form of a negative correlation between seed and seedling establishment limitation. However, species varied considerably in the relative levels of seed and seedling establishment limitation they displayed. Seed mass correlated negatively with seedling establishment limitation but not with seed limitation. We found striking differences in STS transition between life‐forms categorized as trees (including two palms) and lianas; lianas exhibited significantly higher STS transition rates than trees. The biotic and abiotic variables most strongly associated with successful STS transition differed between life‐forms. For trees, conspecific seed density and temporal fruiting concentration had negative effects on seedling establishment, while seed mass had a positive effect. A significant interaction between leaf litter input at a plot and seed size suggested that large‐seeded species had higher STS transition probability in plots with more leaf litter biomass. This effect was reversed for small‐seeded species. For lianas, leaf litter had a negative effect on STS transition and temporal fruiting concentration had a positive effect. Synthesis. Our analyses demonstrate the multidimensional axes of regeneration niches and how they can be related to seed size. Long‐term data sets are critical for understanding these relationships because the relevant factors vary along large spatial and temporal scales.

Intervention Analysis of Hurricane Effects on Snail Abundance in a Tropical Forest Using Long-Term Spatiotemporal Data

Large-scale natural disturbances, such as hurricanes, have profound effects on populations, either directly by causing mortality, or indirectly by altering ecological conditions or the quantity, quality, and spatial distribution of resources. In the last 20 years, two major disturbances, Hurricane Hugo in 1989 and Hurricane Georges in 1998, struck the Luquillo Mountains of Puerto Rico, providing an unique opportunity to understand the long-term effects of recurrent disturbances on the abundance of species. Nenia tridens is one of the most abundant and pervasive terrestrial gastropods in the Luquillo Mountains. Estimates of yearly abundance of N. tridens from 40 sites on the Luquillo Forest Dynamics Plot from 1991 to 2007 facilitate the development of a spatiotemporal model with intervention effects on the mean abundance over time in response to each hurricane. Intervention effects characteristically decay over time, similar to those in a time series analysis. Model parameters were estimated in a Bayesian framework. Model comparison and diagnostics suggest that our intervention model provides a plausible description of hurricanes effects on the abundances of N. tridens and may be useful for studying long-term spatiotemporal dynamics from the perspective of disturbance and succession.

Patch dynamics and community metastability of a subtropical forest: compound effects of natural disturbance and human land use

Where large disturbances do not cause landscape-wide mortality and successional change, forested ecosystems should exhibit landscape metastability (landscape equilibrium) at a scale equal to the dominant patch size of disturbance and recovery within the landscape. We investigated this in a 16-ha contiguous plot of subtropical wet forest in Puerto Rico, the Luquillo Forest Dynamics Plot (LFDP), which experienced two major hurricanes during the 15-year study and has a land use history (logging and agriculture 40 or more years hence) that differs in intensity between two areas of the plot. Using he LFDP as our “landscape,” we studied the spatial pattern of community change through time (3–5 year intervals) by calculating community dissimilarity between tree censuses for two size classes of trees (1 to <10 cm DBH and ≥10 cm DBH) in quadrats ranging in size from 0.010–1 ha and for the entire landscape, i.e., plot or land use type. The point at which the decline in community dissimilarity with quadrat size showed maximum curvature identified the dominant patch size (i.e., point of metastability). For canopy trees ≥10 cm dbh, there was no evidence that the community experienced landscape-wide successional changes in either land use type, and we found a consistent patch size of community change around 0.1 ha (range 0.091–0.107). For the understory tree and shrub community (1 to <10 cm dbh) there was some evidence of landscape-wide community changes over time in response to hurricane damage, apparently driven by interactions with the dominant canopy species, whose composition varied with land use intensity, and their species-specific susceptibility to hurricane damage.

Species Composition, Size-Class Structure, and Diversity of the Lienhuachih Forest Dynamics Plot in a Subtropical Evergreen Broad-Leaved Forest in Central Taiwan

The Lienhuachih Forest Dynamics Plot (FDP), measured 500 m by 500 m square, is located in central Taiwan. The collected data, followed a unified method adopted for the worldwide FDP network, were analyzed for floristic composition, size-class structure, and species diversity. In total, the censused trees and shrubs belonged to 144 species in 86 genera and 39 families. The most dominant families were the Fagaceae, Lauraceae, Rubiaceae, Euphorbiaceae, and Melastomataceae. In total, 153268 (6131 ha^(-1)) individuals were recorded, and the total basal area was 34.77 m^2 ha^(-1). Of the 144 species, the most abundant were Randia cochinchinensis and Blastus cochinchinensis. Pasania nantoensis had the highest basal area (8.38%), followed by Engelhardtia roxburghiana (8.12%) and Schefflera octophylla (7.23%). Calculation of the importance value (IV, incorporating relative values of abundance and basal area) showed that R. cochinchinensis, B. cochinchinensis, S. octophylla, Cryptocarya chinensis, and E. roxburghiana were the most dominant species with the highest IV values in the plot. The sum of the 30 top species' IV reached 83.06% of the whole. Although the 1st 2 species were understory and very dominant due to the large number of individuals, certain numbers of rare species however increased the floristic diversity in the plot. Based on the species composition, the forest is characteristic of the Machilus-Castanopsis forest zone of Taiwan, with certain dominant understory species and possessing 2 pioneer species in the major canopy composition. For the size-class structure, 102 (each with total stems ≥ 25) species showed 4 patterns of size-class distribution: L-shaped, inverse J-shaped, fluctuating, and bell-shaped. The former 3 patterns in a total of 98 species, including a great number of small-sized individuals, imply that most current species in this study site can display good recruitment with rich resources of saplings. The woody plant richness of the Lienhuachih FDP is the highest among low-elevation FDPs in Taiwan. Compared to other Center of Ttropical Forest Science forest dynamics plots on islands, Fisher's alpha diversity (ha^(-1)) index of the subtropical Lienhuachih FDP was similar to that of the Luquillo FDP in Puerto Rico but much lower than that of other FDPs in the tropics.

Variation in Susceptibility to Hurricane Damage as a Function of Storm Intensity in Puerto Rican Tree Species

ABSTRACTOne of the most significant challenges in developing a predictive understanding of the long‐term effects of hurricanes on tropical forests is the development of quantitative models of the relationships between variation in storm intensity and the resulting severity of tree damage and mortality. There have been many comparative studies of interspecific variation in resistance of trees to wind damage based on aggregate responses to individual storms. We use a new approach, based on ordinal logistic regression, to fit quantitative models of the susceptibility of a tree species to different levels of damage across an explicit range of hurricane intensity. Our approach simultaneously estimates both the local intensity of the storm within a plot and the susceptibility to storm damage of different tree species within plots. Using the spatial variation of storm intensity embedded in two hurricanes (Hugo in 1989 and Georges in 1998) that struck the 16 ha Luquillo Forest Dynamics Plot in eastern Puerto Rico, we show that variation in susceptibility to storm damage is an important aspect of life history differentiation. Pioneers such as Cecropia schreberiana are highly susceptible to stem damage, while the late successional species Dacryodes excelsa suffered very little stem damage but significant crown damage. There was a surprisingly weak relationship between tree diameter and the susceptibility to damage for most of the 12 species examined. This may be due to the effects of repeated storms and trade winds on the architecture of trees and forest stands in this Puerto Rican subtropical wet forest.

Natural disturbance and human land use as determinants of tropical forest dynamics: results from a forest simulator

Forests are often subject to multiple, compounded disturbances, representing both natural and human‐induced processes. Predicting forest dynamics requires that we consider how these disturbances interact to affect species demography. Here we present results of an individual‐based, spatially explicit forest simulator that we developed to analyze the compounded effects of hurricane disturbance and land use legacies on the dynamics of a subtropical forest. We used data from the 16‐ha Luquillo Forest Dynamics Plot in Puerto Rico, together with a reconstruction of historical wind damage, to parameterize the simulator. We used the model to ask two questions. (1) What are the implications of variation in hurricane frequency and severity for the long‐term dynamics of forest composition, diversity, and structure? Both storm severity and frequency had striking effects on forest dynamics, composition, and structure. The periodicity of disturbance also played an important role, with periods of high hurricane activity fostering the establishment of species that may become rare in the absence of severe storms and quiescent periods allowing these species to reach reproductive size. Species responses to hurricane disturbance could not be predicted from their life history attributes. However, species perceived to be primary forest species exhibited low temporal variation in abundance through the simulations. (2) How do hurricanes and legacies from human land use interact to determine community structure and composition? Our results suggest that, over time, regardless of the storm regime, land use legacies will become less apparent but will lead to a forest community that contains a mixture of secondary and primary forest species formerly dominant in areas of different land use. In the long term, hurricane disturbance generated two communities with slightly greater similarity than those not subject to storms. Thus, the inclusion of hurricane disturbance does not alter the prediction that land use legacies in this tropical forest will diminish over time. Our simulations also highlight the contingent effects of human legacies on subsequent community dynamics, including the response to hurricane disturbance, therefore supporting the notion that compounded disturbances can interact in ways that cannot be predicted by the study of single disturbances. The widespread importance of land use as a large‐scale disturbance makes it imperative that it be addressed as a fundamental ecological process.

Tree species distributions in relation to stream distance in a mid-montane wet forest, Puerto Rico

Riparian zones are dynamic areas adjacent to flowing freshwater that connect aquatic and terrestrial environments. We measured individual tree distances relative to two permanent streams in the Luquillo Forest Dynamics Plot, Puerto Rico, to determine if tree species exhibit distinct affinities for riparian zones in a mid-montane tropical forest. In addition, we also calculated stem density, species richness, and diversity indices in 20 x 20 m randomly selected quadrats at different distances from the streams. We found that no single species in the study site was predominantly associated with riparian zones; however, almost all species were represented by a few stems in close proximity to streams. Multivariate (Fuzzy Set Ordination) ordination of plot species composition in relation to distance to streams indicated that there is greater variation in species composition closer to streams, and less variation in species composition farther from streams. This study suggests that in mid-montane wet forest, riparian zones include all tree species found throughout the forest landscape.

Oeceoclades maculata, an alien tropical orchid in a Caribbean rainforest.

Undisturbed forest habitat can be relatively impenetrable to invasive, non-native species. Orchids are not commonly regarded as invasive, but some species have become invasive and these generally depend on habitat disturbance. One of the most aggressive orchids is Oeceoclades maculata, a terrestrial species with remarkable ecological amplitude. Originally from tropical Africa, it is now widespread in the neotropics. By associating its local distribution with land-use history and habitat characteristics, it was determined whether O. maculata is dependent on habitat disturbance. It was also investigated whether this exotic orchid occupies the same habitat space as two sympatric native species. Six 10 m x 500 m transects were censused in June 2007 on the 16-ha Luquillo Forest Dynamics Plot, located in the Luquillo Mountains, Puerto Rico. The plot had been mapped for historical land use, topography and soil type. Oeceoclades maculata was the most abundant of three orchid species surveyed and was found in all four historical cover classes. In cover class 3 (50-80 % forest cover in 1936), 192 of 343 plants were found at a density of 0.48 plants per 5 x 5 m subplot. Over 93 % of the 1200 subplots surveyed were composed of Zarzal or Cristal soil types, and O. maculata was nearly evenly distributed in both. The orchid was most common on relatively flat terrain. The distribution and abundance of two sympatric orchid species were negatively associated with that of the invasive species. Oeceoclades maculata does penetrate 'old growth' forest but is most abundant in areas with moderate levels of past disturbance. Soil type makes little difference, but slope of terrain can be important. The negative association between O. maculata and native species may reflect differences in habitat requirements or a negative interaction perhaps at the mycorrhizal level.

Cross-Scale Responses of Biodiversity to Hurricane and Anthropogenic Disturbance in a Tropical Forest

In studies of biodiversity, considerations of scale—the spatial or temporal domain to which data provide inference—are important because of the non-arithmetic manner in which species richness increases with area (and total abundance) and because fine-scale mechanisms (for example, recruitment, growth, and mortality of species) can interact with broad scale patterns (for example, habitat patch configuration) to influence dynamics in space and time. The key to understanding these dynamics is to consider patterns of environmental heterogeneity, including patterns produced by natural and anthropogenic disturbance. We studied how spatial variation in three aspects of biodiversity of terrestrial gastropods (species richness, species diversity, and nestedness) on the 16-ha Luquillo Forest Dynamics Plot (LFDP) in a tropical forest of Puerto Rico was affected by disturbance caused by Hurricanes Hugo and Georges, as well as by patterns of historic land use. Hurricane-induced changes in spatial organization of species richness differed from those for species diversity. The gamma components of species richness changed after the hurricanes and were significantly different between Hurricanes Hugo and Georges. Alpha and two beta components of species richness, one related to turnover among sites within areas of similar land use and one related to variation among areas of different land use, varied randomly over time after both hurricanes. In contrast, gamma components of species diversity decreased in indistinguishable manners after both hurricanes, whereas the rates of change in the alpha component of species diversity differed between hurricanes. Beta components of diversity related to turnover among sites declined after both hurricanes in a consistent fashion. Those related to turnover among areas with different historic land uses varied stochastically. The immediate effect of hurricanes was to reduce nestedness of gastropod assemblages. Thereafter, nestedness increased during post-hurricane secondary succession, and did so in the same way, regardless of patterns of historic land use. The rates of change in degree of nestedness during secondary succession were different after each hurricane as a result of differences in the severity and extent of the hurricane-induced damage. Our analyses quantified temporal changes in the spatial organization of biodiversity of gastropod assemblages during forest recovery from hurricane-induced damage in areas that had experienced different patterns of historic human land use, and documented the dependence of biodiversity on spatial scale. We hypothesize that cross-scale interactions, likely those between the local demographics of species at the fine scale and the landscape configuration of patches at the broad scale, play a dominant role in affecting critical transfer processes, such as dispersal, and its interrelationship with aspects of biodiversity. Cross-scale interactions have significant implications for the conservation of biodiversity, as the greatest threats to biodiversity arise from habitat modification and fragmentation associated with disturbance arising from human activities.

Land‐use History Affects the Distribution of the Saprophytic Orchid Wullschlaegelia calcarata in Puerto Rico's Tabonuco Forest1

ABSTRACTHuman activities such as logging and agriculture can severely damage forest ecosystems by changing forest structure, ecosystem function, and biodiversity. These changes may have long‐lasting consequences, which influence forest recovery. We investigated the effect of past human disturbance on the current distribution of an understory, achlorophyllous orchid, Wullschlaegelia calcarata in Puerto Rico's tropical rain forest after 70 yr of recovery. Our study site was the 16‐ha Luquillo Forest Dynamics Plot located in the Luquillo Experimental Forest, which has four areas with differing intensity of land use that have been distinguished from variation in canopy cover seen in aerial photographs taken in 1936. We recorded orchids in six 10‐m‐wide, 500‐m‐long transects across four different areas of land‐use history. We found that the orchid was not present in an area of the plot which had &lt;20 percent canopy cover in 1936, and was most abundant in the area with &gt;80 percent canopy cover, which had been minimally impacted by human activity. Tree species composition varied among land‐use history areas, and our observations suggested that this variation might be influencing the local distribution of W. calcarata. We also measured leaf litter biomass and identified the leaves of litter in areas with and without the orchid. Litter with a high proportion of Buchenavia tetraphylla leaves had more orchids. Even though human disturbance ceased in 1932, land‐use history in the Luquillo Forest still casts a shadow over the distribution of W. calcarata.

Seedling recruitment in a hurricane‐driven tropical forest: light limitation, density‐dependence and the spatial distribution of parent trees

Summary We used inverse modelling to parameterize spatially‐explicit seedling recruitment functions for nine canopy tree species in the Luquillo Forest Dynamics Plot (LFDP), Puerto Rico. We modelled the observed spatial variation in seedling recruitment following Hurricane Georges as a function of the potential number of seedlings at a given location (based on local source trees and the potential contribution of parents from outside of the mapped area) and of light levels and density‐dependent mortality during establishment. We adopted the model comparison paradigm and compared the performance of increasingly complex models against a null model that assumes uniform seedling distribution across the plot. Our data supported a model in which parents must reach a threshold size before any seedling production will occur. Once parents attain that size, the relationship between tree diameter and the number of seedlings produced is fairly flat for the majority of species. These results contradict previous analyses that simply assumed a linear relationship between biomass and seedling production and a uniform size threshold for seedling production across species. The majority of species tested supported models that included at least one of a bath term (contribution from non‐local trees), conspecific density dependence and light availability after the hurricane. Density dependence shifted the mode of the effective dispersal kernel away from potential parent trees and significantly reduced the number of seedlings established near parent trees. Recruitment from non‐local sources accounted for 6–81% of observed seedling recruitment depending upon the tree species. Light availability appeared to divide species into three groups that showed more successful seedling establishment at low (&lt; 5% of full sun), intermediate or high light levels (&gt; 30% full sun). Differences between individual species in the importance of local vs. bath recruitment and the intensity of density dependence suggest the existence of distinct recruitment syndromes that go beyond the traditional focus of tropical tree life histories. Understanding these syndromes will provide valuable insights into the spatial distribution of tropical tree species and the maintenance of tropical forest diversity.

A NEIGHBORHOOD ANALYSIS OF TREE GROWTH AND SURVIVAL IN A HURRICANE‐DRIVEN TROPICAL FOREST

We present a likelihood‐based regression method that was developed to analyze the effects of neighborhood competitive interactions and hurricane damage on tree growth and survival. The purpose of the method is to provide robust parameter estimates for a spatially explicit forest simulator and to gain insight into the processes that drive the patterns of species abundance in tropical forests. We test the method using census data from the 16‐ha Luquillo Forest Dynamics Plot in Puerto Rico and describe effects of the spatial configuration, sizes, and species of neighboring trees on the growth and survival of 12 dominant tree species representing a variety of life history strategies. Variation in size‐dependent growth and mortality suggests a complex relationship between size, growth, and survival under different regimes of light availability. Crowding effects on growth and survival appear to be idiosyncratic to each individual species, and with the exception of pioneers, there is little commonality among species that share similar life histories.We also explain the implications of differential susceptibility to hurricane damage on species' growth and survival and on their ability to respond to damage to neighboring trees. Tree species in the Luquillo Forest Dynamics Plot differ strikingly in both their susceptibility to hurricane disturbance and the nature of their recovery from wind disturbance, through response of both adult plants and juveniles to enhanced resource availability. At the stand level, intense competitive thinning of densely packed saplings that grew after hurricane damage accounted for the majority of post‐hurricane mortality, particularly for shade‐intolerant species. At the individual species level, effects of previous hurricane damage on growth and survival depended primarily on variation in the quantity and quality of hurricane damage sustained by target species and their interaction with life history characteristics of these individual species.Finally, we compare models that make different assumptions about the effects of competing species on tree growth and survival (e.g., equivalence of competitors vs. distinct species‐specific effects). Size effects alone could not account for growth and survival for the majority of target species. Our results also demonstrate that competing species have distinct per capita effects on growth of dominant target species. In contrast, we found moderate support for a model that assumed functional equivalence of competitors on survival.

LAND USE HISTORY, ENVIRONMENT, AND TREE COMPOSITION IN A TROPICAL FOREST

The effects of historical land use on tropical forest must be examined to understand present forest characteristics and to plan conservation strategies. We compared the effects of past land use, topography, soil type, and other environmental variables on tree species composition in a subtropical wet forest in the Luquillo Mountains, Puerto Rico. The study involved stems ≥10 cm diameter measured at 130 cm above the ground, within the 16-ha Luquillo Forest Dynamics Plot (LFDP), and represents the forest at the time Hurricane Hugo struck in 1989. Topography in the plot is rugged, and soils are variable. Historical documents and local residents described past land uses such as clear-felling and selective logging followed by farming, fruit and coffee production, and timber stand improvement in the forest area that now includes the LFDP. These uses ceased 40–60 yr before the study, but their impacts could be differentiated by percent canopy cover seen in aerial photographs from 1936. Using these photographs, we defined four historic cover classes within the LFDP. These ranged from cover class 1, the least tree-covered area in 1936, to cover class 4, with the least intensive historic land use (selective logging and timber stand improvement). In 1989, cover class 1 had the lowest stem density and proportion of large stems, whereas cover class 4 had the highest basal area, species richness, and number of rare and endemic species. Ordination of tree species composition (89 species, 13 167 stems) produced arrays that primarily corresponded to the four cover classes (i.e., historic land uses). The ordination arrays corresponded secondarily to soil characteristics and topography. Natural disturbances (hurricanes, landslides, and local treefalls) affected tree composition, but these effects did not correlate with the major patterns of species distributions on the plot. Thus, it appears that forest development and natural disturbance have not masked the effects of historical land use in this tropical forest, and that past land use was the major influence on the patterns of tree composition in the plot in 1989. The least disturbed stand harbors more rare and endemic species, and such stands should be protected.