Variation in Species and Trophic Composition of Insect Communities in Puerto Rico1

Insects are important participants in many ecosystem processes, but the effects of anthropogenic and natural disturbances on insect communities have been poorly studied. To describe how disturbances affect insect communities, we addressed two questions: Do insect communities return to a pre‐hurricane composition? And how do insect communities change during succession? To answer these questions, we studied insect communities in a chronosequence of two abandoned pastures (5 yr and 32 yr) and a mature forest (>80 yr) that were recently disturbed by two hurricanes (Hurricane Hugo, 1989) Hurricane Georges, 1998). Although insect abundance and richness fluctuated during the study, all sites returned to pre‐hurricane (Hurricane Georges) abundance and richness in less than one year. All trophic categories present before Hurricane Georges were present after the hurricane, but richness within categories fluctuated greatly. Insect richness did not increase during succession; the 5 yr site had the highest richness, the >80 yr site had an intermediate richness, and die 32 yr site the lowest. Nevertheless, the species composition of the two forested sites was different in comparison to the 5 yr site. These results suggest that trophic structure varies little in time and space, but the species composition within each trophic category is highly variable.     

Hurricane Disturbance Alters Secondary Forest Recovery in Puerto Rico

Land-use history and large-scale disturbances interact to shape secondary forest structure and composition. How introduced species respond to disturbances such as hurricanes in post-agriculture forest recovery is of particular interest. To examine the effects of hurricane disturbance and previous land use on forest dynamics and composition, we revisited 37 secondary forest stands in former cattle pastures across Puerto Rico representing a range of exposure to the winds of Hurricane Georges in 1998. Stands ranged from 21 to>80 yr since agricultural abandonment and were measured 9 yr posthurricane. Stem density decreased as stands aged, while basal area and species richness tended to increase. Hurricane disturbance exerted contrasting effects on stand structure, contingent on stand age. In older stands, the basal area of large trees fell, shifting to a stand structure characteristic of younger stands, while the basal area of large trees tended to rise in younger stands with increasing hurricane disturbance. These results demonstrate that large-scale natural disturbances can alter the successional trajectory of secondary forest stands recovering from human land use, but stand age, precipitation and soil series were better predictors of changes in stand structure across all study sites. Species composition changed substantially between census intervals, but neither age nor hurricane disturbance consistently predicted species composition change. However, exposure to hurricane winds tended to decrease the abundance of the introduced tree Spathodea campanulata, particularly in smaller size classes. In all sites the abundance of the introduced tree Syzygium jambos showed a declining trend, again most strongly in smaller size classes, suggesting natural thinning through succession.     

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

Abstract 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.     

Hurricane effects on backreef echinoderms of the Caribbean

The impacts of Hurricanes Gilbert (1988) and Hugo (1989) on echinoderm assemblages were assessed in backreef habitats in Jamaica and St. Croix, respectively. One site on each island was censused before the hurricanes. Ophiuroids were monitored at the Jamaican site for three years following Hurricane Gilbert, and ophiuroids and echinoids were monitored at the site on St. Croix for two years following Hurricane Hugo. No hurricane-related changes in ophiuroid abundance were observed at either site. Likewise, there was no evidence that Hurricane Hugo altered echinoid abundance at St. Croix. These negative results correlated with an observed lack of hurricane-generated physical disturbance in the backreef areas, despite 6-m waves that broke on the reef crests at the two sites during the storms. Hurricane impacts on mobile faunas appear to depend directly on physical habitat alterations.     

Land use history, hurricane disturbance, and the fate of introduced species in a subtropical wet forest in Puerto Rico

Tropical forests are suffering from increasing intensities and frequency of disturbances. As a result, non-native species accidentally introduced or intentionally planted for farming, plantations, and ornamental purposes may spread and potentially invade undisturbed native forest. It is not known if these introduced species will become invasive, as a result of recurrent natural disturbances such as hurricanes. Using data from three censuses (spanning 15 years) of a 16-ha subtropical wet forest plot, we investigated the impact of two hurricanes on populations of plant species that were planted in farms and plantations that were then abandoned and from the natural spread of species introduced into Puerto Rico in the past. The populations of four species (Citrus paradis, Mangifera indica, Musa sp., and Simarouba glauca) changed little over time. Six species (Artocarpus altilis, Calophyllum calaba, Genipa americana, Hibiscus pernambucensis, Syzygium jambos, and Swietenia macrophylla) declined between the first two censuses after Hurricane Hugo, then increased again in Census 3 after Hurricane Georges. Spathodea campanulata gradually increased from census to census, while Coffea arabica declined. These introduced species represent only a small part of the forest basal area and few show signs of increasing over time. The number of stems per plant, new recruits, and the growth rates of these introduced species were within the ranges of those for native plant species. The mortality rates over both census intervals were significantly lower for introduced species (<5% year⁻¹) than for native ones (15% year⁻¹). Many new recruits established after Hurricane Hugo (prior to this study) had opened the forest canopy and these high mortality rates reflect their death as the canopy recovered. Only Swietenia macrophylla and Syzygium jambos showed an increase in stem numbers in the closed canopy area of forest that had suffered limited human disturbance in the past. A future increase in frequency of disturbance may enable greater stem numbers of introduced species to establish, while lower-mortality rates compared to native species, may allow them to persist during inter-hurricane intervals. An increase in the population of introduced species, especially for those that grow into large trees, may have an impact on this tropical forest in the future.     

Aboveground Biomass Accumulation in a Tropical Wet Forest in Nicaragua Following a Catastrophic Hurricane Disturbance1

Among their effects on forest structure and carbon dynamics, hurricanes frequently create large‐scale canopy gaps that promote secondary growth. To measure the accumulation of aboveground biomass (AGBM) in a hurricane damaged forest, we established permanent plots 4 mo after the landfall of Hurricane Joan on the Atlantic coast of Nicaragua in October 1988. We quantified AGBM accumulation in these plots by correlating diameter measurements to AGBM values using a published allometric regression equation for tropical wet forests. In the first measurement year following the storm, AGBM in hurricane‐affected plots was quite variable, ranging from 26 to 153 Mg/ha, with a mean of 78 (±15) Mg/ha. AGBM was substantially lower than in two control plots several kilometers outside the hurricane's path (331 ±15 Mg/ha). Biomass accumulation was slow (5.36 ± 0.74 Mg/ha/yr), relative to previous studies of forest regeneration following another hurricane (Hugo) and agricultural activity. We suggest that large‐scale, homogenous canopy damage caused by Hurricane Joan impeded the dispersal and establishment of pioneer trees and led to a secondary forest dominated by late successional species that resprouted and survived the disturbance. With the relatively slow rate of biomass accumulation, any tightening in disturbance interval could reduce the maximum capacity of the living biomass to store carbon.     

Physical Disturbance and Community Structure of Exposed and Protected Reefs: A Case Study from St. John, U.S. Virgin Islands

Major physical disturbances impacted fringing reefs at 4 to12 m depth off the south coast of St. John, at intervals of28, 14 and 12 months over a 6 year period (1985–1991).The most wave exposed habitats were dominated by the hydrocoralMillepora alcicornis and the encrusting gorgonian Erythropodiumcaribaeorum. Both of these species displayed high resistancestability in response to the 1987 bleaching event and to HurricanesGilbert (1988) and Hugo (1989). Although Hurricane Hugo wasranked as the most severe hurricane of the past century, itcaused comparatively little damage to the shallow exposed reef,illustrating that the effects of physical disturbance may notalways conform to a priori predictions based on wave exposure.This counter-intuitive result is explicable when the chronologyof disturbance is considered. For example, the shallow exposedcommunity was more heavily damaged than the protected reef byHurricane Gilbert occurring one year prior to Hurricane Hugo.Sponges and thick mats of E. caribaeorum had accumulated onthe protected reef during a 54 month period of little disturbanceand were vulnerable to disturbance by virtue of their elevationabove the substratum. These organisms were dislodged by extremewater motion generated by Hurricane Hugo. In contrast, the shallowexposed community was still recovering from Hurricane Gilbertwhen Hurricane Hugo struck. Monitored populations of two coralspecies, Agaricia agaricites and Tubastrea coccinea, declinedover the six year period, but recruitment in 1990 partiallycompensated for high mortality caused byHurricane Hugo. Therewere significant increases in the abundance of algal turf onthree out of the four study reefs (4 m exposed and protected,12 m protected) in response to the creation of patch space bythe multiple physical disturbances. This study demonstratesthe need to interpret recent disturbances in light of the historyof past disturbance on the reef.     

Damage and Recovery of Riparian Sierra Palms after Hurricane Georges: Influence of Topography and Biotic Characteristics

Tropical forests are often shaped by disturbance events, especially in regions where hurricanes and other severe storms occur. We studied the effects of Hurricane Georges (September 1998) on the sierra palm ( Prestoea acuminata var. montana ) in the Luquillo Mountains of Puerto Rico. We established riparian transects along two headwater streams that were similar in size and location, but differed in riparian tree species composition and land-use history. Following Hurricane Georges, sierra palms were surveyed periodically for damage and recovery (measured by initial loss and subsequent regrowth of palm leaves), tree height, sun exposure, and production of inflorescences and infructescences. Palm height had the highest association with damage, with most damage occurring to canopy palms. Palm recovery (4 mo and 10 mo post-hurricane) was associated with high tree density, indicating that sun exposure was not limiting. Hurricane Georges likely reduced production of flowers and fruits in sierra palms for at least 10 mo following the storm, although production of new leaves was rapid. Although palms recovered quickly from defoliation after the hurricane, decreased reproduction resulted in reduced availability of fruit for terrestrial and aquatic consumers.     

Effects of large-scale disturbance on metacommunity structure of terrestrial gastropods: temporal trends in nestedness

Distributions of species often exhibit nested structure, such that assemblages at species-poor sites are proper subsets of taxa at more species-rich sites. Traditionally, this has been viewed as a large-scale biogeographic pattern and treated implicitly as static from a temporal perspective. Nonetheless, recent work suggests that nestedness may arise at multiple spatio-temporal scales. A 13-year data set encompassing the effects of two large-scale natural disturbances (hurricanes Hugo and Georges) on terrestrial gastropod assemblages was used to test the hypothesis that changes in species composition resulting from disturbance alter the degree of nestedness exhibited over time at two spatial scales. Gastropod assemblages were least nested immediately following disturbance, and nestedness increased thereafter. Although land-use history influenced the degree of nestedness, trajectories of nestedness following disturbance were similar irrespective of disturbance history or hurricane identity. The effects of hurricanes with respect to nestedness of terrestrial gastropods may be general and predictable, even though species respond to hurricanes in disparate fashions. By damaging some localities within the forest more severely than others, a hurricane dismantles extant patterns of species composition and severs connections among sites, as inhospitable microclimatic conditions limit dispersal of gastropods. As time passes and the forest canopy regenerates, conditions ameliorate, and movement among sites becomes more frequent. Thus, a conclusion based on a single time period may not characterize the study system in general. Consequently, explanations for nested structure that incorporate variability in ecological as well as evolutionary time will improve the applicability and comparability of nested subsets analysis across study systems.     

The Influence of Hurricane Winds on Caribbean Dry Forest Structure and Nutrient Pools1

In 1998, we measured the effects of Hurricane Georges after it passed over long‐term research sites in Puerto Rican dry forest. Our primary objectives were to quantify hurricane effects on forest structure, to compare effects in a large tract of forest versus a series of nearby forest fragments, to evaluate short‐term response to hurricane disturbance in terms of mortality and sprouting, and to assess the ability of hurricanes to maintain forest structure. We sampled damage from 33 plots (1.3 ha) across a 3000‐ha tract of forest as well as in 19 fragments. For stems with 2.5‐cm minimum diameter, 1004 stems/ha (12.4%) suffered structural damage, while 69 percent of the undamaged stems were at least 50 percent defoliated. Basal area lost to structural damage equaled 4.0 m²/ha (22%) in south‐facing native forests. Structural damage and defoliation increased with stem diameter and were more common in certain dry forest species. South‐facing forests and those on ridgetops incurred more damage than north‐facing forests or those comprised primarily of introduced species. Stem mortality was only 2 percent of all stems after 9 mo. Structural damage did not necessarily result in stem mortality. Hurricane‐induced mortality was not associated with stem height or diameter, but was ten times greater than background mortality. Basal sprouting was proportional to the amount of structural damage incurred in a stand. Forest fragments experienced the same patterns of hurricane effects as the reference forest. The low, dense structure of Caribbean dry forest can be maintained by hurricane damage to larger stems and induction of basal sprouting to generate multistemmed trees.     

Factors Affecting Mortality and Resistance to Damage Following Hurricanes in a Rehabilitated Subtropical Moist Forest1

The ability to resist hurricane damage is a property of both individuals and communities, and can have strong effects on the structure and function of many tropical forests. We examined the relative importance of tree size, species, biogeographic origin, local topography, and damage from previous storms in long‐term permanent plots in a rehabilitated subtropical moist forest in Puerto Rico following Hurricane Georges in order to better predict patterns of resistance. Severe damage included uprooted trees, snapped stems, or crowns with greater than 50 percent branch loss. Hurricane induced mortality after 21 mo was 5.2 percent/yr, more than seven times higher than background mortality levels during the nonhurricane periods. Species differed greatly in their mortality and damage patterns, but there was no relationship between damage and wood density or biogeographic origin. Rather, damage for a given species was correlated with mean annual increment, with faster growing species experiencing greater damage, suggesting that growth rate may reflect a variety of life history tradeoffs. Size was also predictive of damage, with larger trees suffering more damage. Trees on ridges and in valleys received greater damage than trees on slopes. A strong relationship was noted between previous hurricane damage and present structural damage, which could not solely be explained by the patterns with size and species. We suggest that resistance of trees to hurricane damage is therefore not only correlated with individual and species characteristics but also with past disturbance history, which suggests that in interpreting the effects of hurricanes on forest structure, individual storms cannot be treated as discrete, independent events.     

Hurricane-induced nitrous oxide fluxes from a wet tropical forest

Hurricane activity is predicted to increase over the mid-Atlantic as global temperatures rise. Nitrous oxide (N₂O), a greenhouse gas with a substantial source from tropical soils, may increase after hurricanes yet this effect has been insufficiently documented. On September 21, 1998, Hurricane Georges crossed Puerto Rico causing extensive defoliation. We used a before–after design to assess the effect of Georges on N₂O emissions, and factors likely influencing N₂O fluxes including soil inorganic nitrogen pools and soil water content in a humid tropical forest at El Verde, Puerto Rico. Emissions of N₂O up to 7 months post-Georges ranged from 5.92 to 4.26 ng cm⁻² h⁻¹ and averaged five times greater than fluxes previously measured at the site. N₂O emissions 27 months after the hurricane remained over two times greater than previously measured fluxes. Soil ammonium pools decreased after Georges and remained low. The first year after the hurricane, nitrate pools increased, but not significantly when compared against a single measurement made before the hurricane. Soil moisture and temperature did not differ significantly in the two sampling periods. These results suggest that hurricanes increase N₂O fluxes in these forests by altering soil N transformations and the relative availabilities of inorganic nitrogen.     

Immediate impact of a hurricane on the structure of a tropical butterfly community

More intense and frequent hurricanes may lead to long‐lasting effects to tropical ecosystems. Here, we describe the immediate impact on the butterfly community of a lowland forest in Belize, following Hurricane Earl. Species richness and abundance increased posthurricane, likely driven by convergence of the organization between the canopy and understory communities.     

Recovery of a tropical rain forest after hurricane damage

More than a year after Hurricane Hugo damaged a Puerto Rican tropical rain forest, recovery of the forest was assessed by observing resprouting of damaged trees in eleven transects which were established before the hurricane in 1989. In each transect, I relocated and identified standing trees and observed if they were resprouting after injury. I found that resprouting was rapid and depended on species. There was no significant relationship between sprouting and diameter classes of trees. This study suggests that resprouting of damaged trees plays major roles in the recovery of the tropical forests which are prone to hurricanes and are in non-equilibrium state.     

Effects of land use history on hurricane damage and recovery in a neotropical forest

Prior land-use history might influence damage and recovery of plant communities from natural disturbance. We examined effects of previous agricultural land use on damage and recovery of plant communities affected by Hurricane Georges. The study was conducted in the karst region of Los Haitises National Park, Dominican Republic. We compared pre- and post-hurricane stem density, basal area and diversity of woody vegetation in sites within the park that had been subject to different land use histories. The type of land uses included a wide range of histories, ranging from abandoned pastures and conucos (mixed plantings) to cacao plantations, intact forests and mogotes (hilltop communities) with no recent history of land use. Previous land use and the amount of basal area present prior to the hurricane determined effects of, and recovery from hurricane disturbance. Systems with high pre-hurricane basal area lost many large trees, whereas the basal area hardly changed in systems without large trees. Thus, basal area decreased at forested sites, mogotes, and cacao plantations and remained comparable to pre-hurricane figures in all other land uses. Shifts in species diversity paralleled to some degree reductions in basal area. Species diversity increased in mogotes and cacao plantations, perhaps as a result of hurricane damage to the forest canopy, which facilitated regeneration of heliophilic species. Finally, regeneration of cacao seedlings in former cacao plantations, and growth of pioneer species in young conucos (mixed plantings) more than doubled post-hurricane stem densities for these two types of land use. Previous agricultural land use left a lasting impression on the structure and composition on plant communities, which persisted even after hurricane damage. This revised version was published online in June 2006 with corrections to the Cover Date.     

Soil functional resistance and stability are linked to different ecosystem properties

The functional resistance and resilience of soils from across the South Island of New Zealand were assessed. Soils were collected from under varying land‐uses (pasture, pine forest, native forest) at each of four different locations (Hokitika, Craigieburn, Eyrewell, Orton Bradley Park). Soil function was measured using carbon utilization profiles (MicroResp technique), and responses to freeze‐thaw disturbance assessed in a multivariate approach. Resistance was defined as the amount of change in functional profiles (multivariate distance) before, and then 10 h after, disturbance. Resilience was defined as the stability in ecosystem function over time (6 sample points spanning 17 days after initial freeze‐thaw disturbance). The functional resistance of soils was not linked to land‐use nor sampling location (permanova P > 0.05) but was negatively correlated with soil Olsen‐P levels (biological‐environmental matching (BIO‐ENV test); ρ = 0.604, P = 0.04). Secondary factors associated with soil organic matter status were associated with functional resistance in soil of low Olsen‐P. This was explicitly tested by repeating the experiment in soils collected from a long‐term P fertilizer management trial; functional resistance remained linked to the underlying P status of the soils (P = 0.002). The functional stability of soil (post‐disturbance) was associated with long‐term rainfall (canonical analysis on principal coordinates – CAP analysis; P = 0.039); soils from high rainfall sites were more stable after disturbance. The results show that variables linked to functional resistance and resilience in soils are different. Furthermore, resilience was not correlated with resistance, or with measures of functional diversity (e.g. evenness of substrate mineralization). Alteration of the P status of soils is likely to impact on the capacity of soils to rapidly respond to disturbance, whereas drivers of climate, such as global warming, may impact soil functional resilience.     

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

One 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.
Abstract in Spanish is available at http://www.blackwell-synergy.com/loi/btp .     

Resistance to wildfire and early regeneration in natural broadleaved forest and pine plantation

The response of an ecosystem to disturbance reflects its stability, which is determined by two components: resistance and resilience. We addressed both components in a study of early post-fire response of natural broadleaved forest (Quercus robur, Ilex aquifolium) and pine plantation (Pinus pinaster, Pinus sylvestris) to a wildfire that burned over 6000 ha in NW Portugal. Fire resistance was assessed from fire severity, tree mortality and sapling persistence. Understory fire resistance was similar between forests: fire severity at the surface level was moderate to low, and sapling persistence was low. At the canopy level, fire severity was generally low in broadleaved forest but heterogeneous in pine forest, and mean tree mortality was significantly higher in pine forest. Forest resilience was assessed by the comparison of the understory composition, species diversity and seedling abundance in unburned and burned plots in each forest type. Unburned broadleaved communities were dominated by perennial herbs (e.g., Arrhenatherum elatius) and woody species (e.g., Hedera hibernica, Erica arborea), all able to regenerate vegetatively. Unburned pine communities presented a higher abundance of shrubs, and most dominant species relied on post-fire seeding, with some species also being able to regenerate vegetatively (e.g., Ulex minor, Daboecia cantabrica). There were no differences in diversity measures in broadleaved forest, but burned communities in pine forest shared less species and were less rich and diverse than unburned communities. Seedling abundance was similar in burned and unburned plots in both forests. The slower reestablishment of understory pine communities is probably explained by the slower recovery rate of dominant species. These findings are ecologically relevant: the higher resistance and resilience of native broadleaved forest implies a higher stability in the maintenance of forest processes and the delivery of ecosystem services.     

The Stability of Invertebrate Communities in Bromeliad Phytotelmata in a Rain Forest Subject to Hurricanes

Communities of invertebrate animals in lower canopy and saxicolous tank bromeliads, originally studied in 1993–1997, were resampled along an elevational gradient in tabonuco, palo colorado, and dwarf or cloud forest in Puerto Rico in 2010. These Puerto Rican montane rain forests were impacted strongly by hurricanes in 1989 and 1998, so the surveys in the 1990s represented 4–8 yr of post‐hurricane recovery, whereas our recent survey represents 12 yr of post‐hurricane recovery. At most elevations, species diversity, both within individual bromeliads and at the forest scale, declined between the 1990s and 2010. This decline in diversity between decades is associated with reductions in bromeliad density as the canopy progressively closed during recovery from hurricane damage. The observed decline in alpha and gamma diversity appears to have involved the loss of rarer species, as might be expected from standard metapopulation theory. By contrast, the most common species were remarkably stable in abundance, composition, and frequency of occurrence over the two decades. In the lowermost tabonuco forest, two endemic bromeliad specialists, restricted to bromeliads for their entire life cycle, were not found on resampling. This study also demonstrates that, at least in Puerto Rico, sets of ten plants from each forest were sufficient to monitor bromeliad invertebrate populations and their diversity over time.     

Cloud Forest Bird Responses to Unusually Severe Storm Damage1

In 1998, storms related to Hurricane Isis caused extensive gaps in the cloud forest of El Triunfo Biosphere Reserve in Chiapas, Mexico, where severe storms are infrequent. We examined how this disturbance affected bird species composition. Species richness and composition were similar both between pre‐ and post‐disturbance forest and between newly created gaps and plots that remained forested after the hurricane. However, differences in response guilds were greater between pre‐ and post‐disturbance plots than between forest plots with gaps after disturbance. Granivorous, omnivorous, and terrestrial species were more abundant before the hurricane, whereas insectivorous, midstory, and generalist foragers were more abundant after the hurricane. In addition, species with high sensitivity to disturbance were more abundant in the pre‐disturbance forest, while low sensitivity species were more abundant after disturbance. In the post‐disturbance forest, insectivorous species were most abundant in gaps and terrestrial‐canopy foragers were most abundant in forest plots. Permanently open areas had significantly lower species richness, but had lowland generalist and second‐growth species not present in the cloud forest. Results suggest that changes in species composition were not limited to the newly created gaps, but also affected the whole forest. The decline of high sensitivity species after disturbance supports the hypothesis that disturbance negatively affects specialists and benefits generalist species. Although there is evidence that natural communities tend to return to pre‐disturbance conditions, changes in community structure could be aggravated if recurrent hurricanes occur before succession takes place.