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Drone-based remote sensing is a promising new technology that combines the benefits of ground-based and satellite-derived forest monitoring by collecting fine-scale data over relatively large areas in a cost-effective manner. Here, we explore the potential of the GatorEye drone-lidar system to monitor tropical forest succession by canopy structural attributes including canopy height, spatial heterogeneity, gap fraction, leaf area density (LAD) vertical distribution, canopy Shannon index (an index of LAD), leaf area index (LAI), and understory LAI. We focus on these variables? relationship to aboveground biomass (AGB) stocks and species diversity. In the Caribbean lowlands of northeastern Costa Rica, we analyze nine tropical forests stands (seven secondgrowth and two old-growth). Stands were relatively homogenous in terms of canopy height and spatial heterogeneity, but not in their gap fraction. Neither species density nor tree community Shannon diversity index was significantly correlated with the canopy Shannon index. Canopy height, LAI, and AGB did not show a clear pattern as a function of forest age. However, gap fraction and spatial heterogeneity increased with forest age, whereas understory LAI decreased with forest age. Canopy height was strongly correlated with AGB. The heterogeneous mosaic created by successional forest patches across human-managed tropical landscapes can now be better characterized. Drone-lidar systems offer the opportunity to improve assessment of forest recovery and develop general mechanistic carbon sequestration models that can be rapidly deployed to specific sites, an essential step for monitoring progress within the UN Decade on Ecosystem Restoration. Made available in DSpace on 2020-08-01T11:12:46Z (GMT). No. of bitstreams: 1 27015.pdf: 1386408 bytes, checksum: cce9ebab5fed640e715ad6387e973c5a (MD5) Previous issue date: 2020

Understory plants are an important component of the high plant species diversity characteristic of neotropical rain forests. Herbs, shrubs, understory trees, and saplings of canopy trees occupy a broadly uniform environment of abundant rainfall, low light levels, and high humidity. We asked whether this community at the La Selva Biological Station in the Caribbean lowlands of Costa Rica was structured by environmental filters such as soil origin, topographic position, and understory light availability. We used nested quadrats to assess effects of soil origin (recent alluvium, weathered alluvium, residual volcanic soil) and topographic position (ridges, mid‐slopes and flats) on species composition, density, and diversity and measured six edaphic and understory light parameters. Non‐metric multidimensional scaling ordinations were based on frequency of occurrence in 20 quadrats for 272 species in the shrub size class and 136 species in the small‐tree size class for 17 sites. Three axes were correlated with composite environmental variables produced by principal component analysis representing slope, extractable phosphorus, and light. NMS site positions also reflected soil origin, topographic position, and geographic location. The analyses illustrated a complex community structured by species responses to environmental filters at multiple, interdigitated spatial scales. We suggest that light availability affected by canopy dynamics and dispersal limitation provides additional sources of variation in species distributions, which interact with edaphic patterns in complex ways. Abstract in Spanish is available with online material.

Seeds of many Amaryllidaceae are unorthodox (recalcitrant) and toxic, and cannot survive ingestion, yet are packaged in brightly colored fruits suggestive of zoochory. Seed dispersal and germination of the understory amaryllid, Clivia miniata, were investigated in KwaZulu‐Natal, South Africa. Motion‐activated cameras revealed that samango monkeys (Cercopithecus mitis labiatus) are the primary disperser of C. miniata seeds. They eat the mesocarp and, to a lesser extent, the exocarp, and spit the large (13 mm diameter) seeds whole and cleaned onto the forest floor. Most seeds were dispersed farther than 1 m from the parent. Experimental removal of the fruit pulp had a small positive effect on the rate of seed germination, but did not affect subsequent seedling growth rates. The main advantages of monkey dispersal of Clivia seeds appear to be short‐distance dispersal away from the dense foliage of clumped parent plants and occasional long‐distance dispersal through cheek‐pouching behavior.

Seasonal drought has been shown to greatly influence the distributions and species composition of plants in tropical rain forests. By conducting a series of field, greenhouse, and growth chamber experiments, we examined how Costus villosissimus, a forest edge species, has adapted to drought and differentiated from C. allenii, its closely related species in the understory. We hypothesize that delayed seed germination and high drought tolerance may lead to habitat differentiation and thus reproductive isolation between closely related plant species in the tropics. Abstract in Spanish is available with online material.

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 post-hurricane, likely driven by convergence of the organisation between the canopy and understory communities.

Light availability is an important modulator of seedling growth and plant–herbivore dynamics. Logging increases light levels in forests, potentially altering herbivore–plant interactions that drive seedling establishment. We conducted a transplant experiment to evaluate how logging and herbivory affect seedling growth and survival in three shade-tolerant tree species, at paired canopy gap and understory sites in logged forest and an adjacent unlogged area in central Amazonia (Brazil). Seedlings were either left exposed to naturally occurring insect herbivores or protected from insects by a fine netting structure. We measured the herbivore damage and growth rate of seedlings after 18 mo. In general, logged areas received more light than unlogged sites. Growth and herbivory rates were positively influenced by light, and herbivory was also influenced positively by logging. In gaps, increased growth mitigated foliar damage. Logging resulted in a loss of foliar tissue due to increased herbivory. Herbivory rates were higher in the understory of logged sites than in that of unlogged understory sites, but growth was similar in these areas. Thus, the understory of logged areas provided the least favorable sites for shade-tolerant tree regeneration, due to higher herbivory rates. The effect of logging on biotic interactions can extend beyond the gaps it creates into untouched understory sites. To our knowledge, this is the first time such a pattern has been observed, highlighting the importance of evaluating the impact of logging on biotic interactions.

Worldwide, fungal richness peaks in tropical forest biomes where they are the primary drivers of decomposition. Understanding how environmental and anthropogenic factors influence tropical macrofungal fruiting patterns should provide insight as to how, for example, climate change and deforestation may impact their long-term demographic stability and evolutionary potential. However, in Amazonia no studies have yet to disentangle the effects of substrate, seasonality and forest history on phenology. Here, we quantitate spatial and temporal variation in community structure of fruiting macrofungi in relation to these factors at a long-term forest management research site in central Amazonia: the Biomass and Nutrients of Tropical Rain Forest (BIONTE's). Basidiome surveys of four substrate classes (leaves, soil, branches and trunks) were conducted along 250 m2 transects in primary and secondary (managed) forests, between 2012–13. From the 669 basidiomes collected, 290 taxa were identified of which 44 percent were restricted to primary and 36 percent to secondary forests. Although species-accumulation curves did not asymptote, rarefaction analyses and Fisher's alpha indicate contrasting differences in richness among forests in relation to substrate type. For example, leaf litter basidiome richness was higher in secondary forests, whereas the contrary was observed for soil communities, suggesting that variation in fruiting patterns in relation to disturbance is substrate-dependent possibly due to differences in necromass quality and/or understory micro-climates. Furthermore, secondary forests harbored significantly lower basidiome richness and abundance in dry months, suggesting synergistic impacts of seasonality and management history on fruiting regimes.

Light is considered a non-limiting factor for vascular epiphytes. Nevertheless, an epiphyte's access to light may be limited by phorophyte shading and the spatio-temporal environmental patchiness characteristic of epiphytic habitats. We assessed the extent to which potential light interception in Rodriguezia granadensis, an epiphytic orchid, is determined by individual factors (plant size traits and leaf traits), or environmental heterogeneity (light patchiness) within the crown of the phorophyte, or both. We studied 104 adult plants growing on Psidium guajava trees in two habitats with contrasting canopy cover: a dry tropical forest edge, and isolated trees in a pasture. We recorded the number of leaves and the leaf area, the leaf position angles, and the potential exposure of the leaf surface to direct irradiance (silhouette area of the leaf blade), and the potential irradiance incident on each plant. We found the epiphytes experience a highly heterogeneous light environment in the crowns of P. guajava. Nonetheless, R. granadensis plants displayed a common light interception strategy typical of low-light environments, resembling terrestrial, forest understory plants. Potential exposure of the total leaf surface to direct irradiance correlated positively with plant size and within-plant variation in leaf orientation. In many-leaved individuals, within-plant variation in leaf angles produced complementary leaf positions that enhanced potential light interception. This light interception strategy suggests that, in contrast to current wisdom, enhancing light capture is important for vascular epiphytes in canopies with high spatio-temporal heterogeneity in light environments.

Afromontane landscapes are typically characterized by a mosaic of smallholder farms and the biodiversity impacts of these practices will vary in accordance to local management and landscape context. Here, we assess how tropical butterfly diversity is maintained across an agricultural landscape in the Jimma Highlands of Ethiopia. We used transect surveys to sample understory butterfly communities within degraded natural forest, semi-managed coffee forest (SMCF), exotic timber plantations, open woodland, croplands and pasture. Surveys were conducted in 29 one-hectare plots and repeated five times between January and June 2013. We found that natural forest supports higher butterfly diversity than all agricultural plots (measured with Hill's numbers). SMCF and timber plantations retain relatively high abundance and diversity, but these metrics drop off sharply in open woodland, cropland and pasture. SMCF and timber plantations share the majority of their species with natural forest and support an equivalent abundance of forest-dependent species, with no increase in widespread species. There was some incongruence in the responses of families and sub-families, notably that Lycaenidae are strongly associated with open woodland and pasture. Adult butterflies clearly utilize forested agricultural practices such as SMCF and timber plantations, but species diversity declines steeply with distance from natural forest suggesting that earlier life-stages may depend on host plants and/or microclimatic conditions that are lost under agricultural management. From a management perspective, the protection of natural forest remains a priority for tropical butterfly conservation, but understanding functioning of the wider landscape mosaic is important as SMCF and timber plantations may act as habitat corridors that facilitate movement between forest fragments.

To cope with the limiting light conditions in the rain forest understory, many tropical tree species have evolved large seeds that provide the emerging seedlings with nutritional reserves. Habitat fragmentation might change the adaptive value of seed size by modifying the biotic and physical conditions of the forest understory. We experimentally assessed the potential of fragmentation to alter how seed mass affects seedling survival, vigor, and attack by natural enemies of the tropical tree Nectandra ambigens. Seeds from different mother trees (families) were individually weighed and sown in experimental sites established in continuous forest and in forest fragments. Seedling survival, vigor, and damage by herbivores and pathogens were recorded periodically. While seedlings derived from larger seeds had higher survival rates in both habitats, seedling survival and vigor were significantly greater in forest fragments, and the seedlings also suffered fewer attacks by natural enemies. We found genetic variance for seed mass among families with a heritability value (h2) of 0.66, and we found evidence for selection on seed size. Average seed size differed between dead and living seedlings in three sites. In one fragment, seed size was selectively neutral in relation to survival. Overall, selection for seed size promoted survival and thus appears to affect the distribution of this trait. The maintenance of genetic variance could be related to the stochastic nature of the formation of light gaps. Our results highlight the importance of evaluating the adaptive value of traits susceptible to environmental changes for conservation purposes.

Gene dispersal and clonality are important aspects of plant evolution affecting the spatial genetic structure (SGS) and the long-term survival of species. In the tropics these parameters have mostly been investigated in trees and some herbs, but rarely in climbers which frequently: (1) show clonal growth leading to a patchy distribution pattern similar to that of understory herbs; and (2) flower in the canopy where they may have access to long-distance dispersal like canopy trees. We thus hypothesize for climbers an intermediate genetic structure between herbs and trees. The study aims at assessing breeding system and spatial extent of clonality and gene dispersal in Haumania danckelmaniana (Marantaceae), a common climber in the tropical rain forests from western Central Africa. In eastern Cameroon, 330 ramets were sampled at three spatial scales and genotyped at seven microsatellite loci. Clonality was moderate (clonal extend: 15–25 m, clonal diversity 0.4–0.65) indicating the importance of recruitment from seeds at this locality. The low inbreeding (FIS) suggested predominant outcrossing. The rate of decay of the relatedness between individuals with distance indicated limited gene dispersal distance (σg = 9–50 m, neighborhood sizes Nb = 23–67) in accordance with narrowly gravity dispersed seeds and restricted pollen transfer distance in densely flowering populations. The marked SGS (Sp = 0.011–0.026) was similar to that reported in tropical trees, but might increase with augmented clonality as in many herbs, especially under more severe disturbance regimes.

Tropical rain forest understory insectivorous birds are declining, even in large forest reserves, yet the mechanisms remain unclear. Abundant large mammals can reshape forest structure, which degrades foraging microhabitat. We used six sites in Nicaragua, Costa Rica, and Panama with varying collared peccary (Pecari tajacu) density to test three linked hypotheses: (1) locally declining understory insectivores forage preferentially in liana tangles; (2) vine and liana density, cover, and frequency of dense tangles are lower in the presence of abundant collared peccaries; and consequently (3) abundant collared peccaries are associated with reduced understory insectivorous bird abundance. Three insectivores that declined at La Selva preferentially foraged in liana tangles: Checker-throated Antwren (Epinecrophylla fulviventris), Dot-winged Antwren (Microrhopias quixensis), and Ruddy-tailed Flycatcher (Terenotriccus erythrurus). Vine density, liana cover, liana tangle frequency, and forest cover were lower in the presence of collared peccaries relative to experimental mammal exclosures, with the greatest differences at La Selva Biological Station, Costa Rica. Across sites, five of seven vine and liana measures showed negative, curvilinear relationships with peccary densities. Vine and liana measures peaked at sites with intermediate peccary density, and were low at La Selva. Structural equation models suggest negative indirect effects of the collared peccaries on focal bird densities, mediated by vine and liana density, cover, or tangle frequency. Forest area and rainfall affected both lianas and birds, but collared peccaries also contributed to the reduced abundance of understory insectivores. Indirect effects such as that suggested here may occur even in large, protected forest reserves where large mammal communities are changing. Resumen A pesar de que las aves insectivoras de sotobosque de bosques lluviosos estan disminuyendo en los tropicos, e incluso en grandes reservas forestales, no se conocen los mecanismos causantes. Los grandes mamiferos en abundancia, pueden cambiar la estructura del bosque a traves de efectos troficos y no troficos, degradar microhabitats a traves del forrajeo. Utilizamos seis sitios en Nicaragua, Costa Rica y Panama con densidades diferentes de sainos (Pecari tajacu) para poner a prueba tres hipotesis con efecto en cadena: (1) varias aves insectivoras en disminucion forrajean preferiblemente en maranas de lianas, (2) la densidad de lianas y cobertura, y la frecuencia de maranas densas son mas bajos en la presencia de abundantes sainos, y en consecuencia (3) sainos abundantes se asocian con una reduccion de aves insectivoras de sotobosque. Tres aves insectivoras que disminuyeron en La Selva forrajearon preferiblemente en maranas de lianas: Epinecrophylla fulviventris, Microrhopias quixensis, y Terenotriccus erythrurus. La densidad de los bejucos, la cubierta de lianas, la frecuencia de maranas de lianas, y la cobertura de bosque fueron menores en presencia de sainos en relacion a exclusiones experimentales de mamiferos, con las mayores diferencias en Estacion Biologica La Selva, Costa Rica. En todos los sitios, cinco de las siete variables de bejucos y lianas mostraron relaciones negativas y curvilineas con densidades de sainos. Medidas de los bejucos y lianas fueron mayores en sitios con densidades intermedias de sainos, y estaban baja en La Selva. Los modelos de ecuaciones estructurales sugieren que los sainos tienen efectos indirectos negativos en la abundancia de aves focales, mediadas por la densidad y cubierta de bejucos y lianas o la frecuencia de maranas de lianas. El area del bosque y las lluvias tambien afectan a las lianas y a las aves, pero los sainos tambien contribuyeron a la disminucion de la abundancia de aves insectivoras de sotobosque. Los efectos indirectos documentados aqui pueden ocurrir incluso en grandes reservas forestales protegidas, donde las comunidades de mamiferos grandes estan cambiando.

Primary tropical rain forests are being rapidly perforated with new edges via roads, logging, and pastures, and vast areas of secondary forest accumulate following abandonment of agricultural lands. To determine how insectivorous Amazonian understory birds respond to edges between primary rain forest and three age classes of secondary forest, we radio-tracked two woodcreepers (Glyphorynchus spirurus, N = 17; Xiphorhynchus pardalotus, N = 18) and a terrestrial antthrush (Formicarius colma, N = 19). We modeled species-specific response to distance to forest edge (a continuous variable) based on observations at varying distances from the primary-secondary forest interface. All species avoided 8-14-yr-old secondary forest. Glyphorynchus spirurus and F. colma mostly remained within primary forest 100 m into secondary forest 27-31 yr old. Young Formicarius colma and most G. spirurus showed a unimodal response to 8-14-yr-old secondary forest, with relative activity concentrated just inside primary forest. After land abandonment, G. spirurus was the first to recover to the point where there was no detectable edge response (after 11-14 yr), whereas X. pardalotus was intermediate (15-20 yr), and F. colma last (28-30 yr +). Given the relatively quick recovery by our woodcreeper species, new legislation on protection of secondary forests > 20-yr old in Brazil's Pará state may represent a new opportunity for conservation and management; however, secondary forest must mature to at least 30 yr before the full compliment of rain forest-dependent species can use secondary forest without adverse edge effects. Florestas tropicais primárias têm sido rapidamente perfuradas com novas bordas devido estradas, extração de madeira e criação de gado, gerando vastas áreas de floresta secundária que surgem após o abandono de áreas desflorestadas. Para determinar como aves insetívoras de sub‐bosque da Amazônia Central respondem ao efeito de borda entre floresta primária e três classes etárias de florestas secundárias, nós monitoramos com a ajuda de rádio‐transmissores, dois dendrocolaptídeos (Glyphorynchus spirurus, N = 17; Xiphorhynchus pardalotus, N = 18), e um formicarídeo terrestre (Formicarius colma, N = 19). Nós modelamos respostas espécie‐específicas para a distância até a borda da floresta (variável contínua), baseadas em observações de distâncias variadas na interface entre a floresta primária e secundária. Glyphorynchus spirurus e F. colma permaneceram a maior parte do tempo dentro da floresta primária, < 100 m da borda jovem. Jovens de F. colma raramente adentraram > 100 m da floresta secundária mais velha (27–31 anos). Os jovens de F. colma e a maioria dos G. spirurus mostraram uma resposta unimodal em relação as florestas secundárias jovens, com atividade concentrada apenas dentro da floresta primária. Após o abandono da terra, G. spirurus foi o primeiro a demonstrar não haver mais um efeito detectável da borda (após 11–14 anos), enquanto que X. pardalotus apresentou uma resposta intermediária (15–20 anos), e F. colma a mais longa (28–30 anos +). Diante da recuperação relativamente rápida dos Dendrocolaptídeos, uma nova legislação que proteja florestas secundárias >20 anos no estado brasileiro do Pará pode representar uma nova oportunidade para a conservação e manejo. No entanto, a floresta secundária deve amadurecer por, pelo menos, 30 anos antes que toda a comunidade de espécies dependentes das floresta primária possa usar a floresta secundária sem os efeitos adversos das bordas. Fil: Powell, Luke L.. Instituto Nacional de Pesquisas da Amazônia; Brasil. National Zoological Park. Smithsonian Migratory Bird Center; Estados Unidos. State University of Louisiana; Estados Unidos Fil: Zurita, Gustavo Andres. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Biología Subtropical. Instituto de Biología Subtropical - Nodo Posadas | Universidad Nacional de Misiones. Instituto de Biología Subtropical. Instituto de Biología Subtropical - Nodo Posadas; Argentina Fil: Wolfe, Jared D.. Instituto Nacional de Pesquisas da Amazônia; Brasil. State University of Louisiana; Estados Unidos. United States Department of Agriculture. Forest Service. Redwood Sciences Laboratory; Estados Unidos Fil: Johnson, Erik I.. Instituto Nacional de Pesquisas da Amazônia; Brasil. State University of Louisiana; Estados Unidos. National Audubon Society; Estados Unidos Fil: Stouffer, Phillip C.. State University of Louisiana; Estados Unidos. Instituto Nacional de Pesquisas da Amazônia; Brasil

Gap dynamics theory proposes that treefall gaps provide high light levels needed for regeneration in the understory, and by increasing heterogeneity in the light environment allow light-demanding tree species to persist in the community. Recent studies have demonstrated age-related declines in leaf area index of individual temperate trees, highlighting a mechanism for gradual changes in the forest canopy that may also be an important, but less obvious, driver of forest dynamics. We assessed the prevalence of age-related crown thinning among 12 tropical canopy tree species sampled in lowland forests in Panama and Puerto Rico (total N = 881). Canopy gap fraction of individual canopy tree crowns was positively related to stem diameter at 1.3 m (diameter at breast height) in a pooled analysis, with 10 of 12 species showing a positive trend. Considered individually, a positive correlation between stem diameter and canopy gap fraction was statistically significant in 4 of 12 species, all of which were large-statured canopy to emergent species: Beilschmiedia pendula, Ceiba pentandra, Jacaranda copaia, and Prioria copaifera. Pooled analyses also showed a negative relationship between liana abundance and canopy gap fraction, suggesting that lianas could be partially obscuring age-related crown thinning. We conclude that age-related crown thinning occurs in tropical forests, and could thus influence patterns of tree regeneration and tropical forest community dynamics.

Woody tree species in seasonally dry tropical forests are known to have traits that help them to recover from recurring disturbances such as fire. Two such traits are resprouting and rapid post-fire growth. We compared survival and growth rates of regenerating small-sized individuals (juveniles) of woody tree species after dry season fire (February-March) at eight adjacent pairs of burnt and unburnt transects in a seasonally dry tropical forest in southern India. Juveniles were monitored at 3-mo intervals between August 2009 and August 2010. High juvenile survivorship (>95%) was observed in both burnt and unburnt areas. Growth rates of juveniles, analyzed at the community level as well as for a few species individually (especially fast-growing ones), were distinctly higher in burnt areas compared to unburnt areas after a fire event, particularly during the pre-monsoon season immediately after a fire. Rapid growth by juveniles soon after a fire may be due to lowered competition from other vegetative forms such as grasses, possibly aided by the availability of resources stored belowground. Such an adaptation would allow a juvenile bank to be retained in the understory of a dry forest, from where individuals can grow to a possible fire-tolerant size during favorable conditions.

Negative density dependence contributes to seedling dynamics in forested ecosystems, but the relative importance of this factor for different woody plant life-forms is not well-understood. We used 1 yr of seedling survivorship data for woody seedlings in 17 different plots of lower to mid-montane rain forests on the island of Dominica to examine how seedling height, abiotic factors, and biotic factors such as negative density dependence are related to seedling survival of five different life-forms (canopy, midstory, and understory trees; shrubs; and lianas). Across 64 species, taller seedlings in seedling plots with higher canopy openness, greater seedling density, lower relative abundance of conspecific seedlings, and lower relative abundance of conspecific adults generally had a greater probability of surviving. Height was the strongest predictor of seedling survival for all life-forms except lianas. Greater seedling density was positively related to survival for canopy and midstory trees but negatively related to survival for the other life-forms. For trees, the relative abundance of conspecific seedling and adult neighbors had weak and strong negative effects on survival respectively. Neither shrub nor liana seedling survival was affected by the relative abundance of conspecific neighbors. Thus, negative density dependence is confirmed as an important structuring mechanism for tree seedling communities but does not seem to be important for lianas and shrubs in Dominican rain forests. These results represent the first direct assessment of controls on seedling survival of all woody life-forms – an important step in understanding the dynamics and structure of the entire woody plant community.

Amazonian Dark Earths (ADE) are the result of human modification of the Amazonian landscape since pre-Columbian times. ADE are characterized by increased soil fertility compared to natural soils. In the Amazonian forest, soil fertility influences understory herb and fern species composition. However, little research has been done to evaluate the effect of ADE on the composition of the understory community. We evaluated the effects of ADE and soil in 36 plots (150 m × 4 m) established in a Bolivian moist forest (La Chonta). For each plot, we determined soil nutrients, and the composition, richness, and abundance of terrestrial fern, angiosperm herb, and understory palm species. We found that the presence of ADE created a gradient in soil nutrients and pH that affected the understory species composition especially of ferns and palms. Additionally, the higher nutrient concentration and more neutral soil pH on ADE soils caused a decrease of ferns species richness. We therefore conclude that the current composition of the understory community in this particular Bolivian forest is a reflection of past human modifications of the soil.

Neighboring upland and nutrient-poor seasonally flooded Amazon forests were penetrated by a fire in 2009, providing a natural com-parative experiment of fire damage for these widespread forest types. In upland, only 16 10% ( 2 SEM) of stems and 21 8%of basal area were lost to fire, while seasonally flooded forest lost 59 13% of stems and 57 13% of basal area. Drier understorycontributes to greater flammability. Much of the area occupied by seasonally flooded woody vegetation (>11.5 percent of the Amazonregion) is vulnerable to fire due to high flammability and slow recovery.Abstract in Portuguese is available in the online version of this article. Key words: flammability; forest structure; igapo; litter layer; relative humidity; tropical forest. O VER 11.5 PERCENT OF THE AMAZON BASIN IS OCCUPIED BY SEASON-ALLY INUNDATED WOODY VEGETATION (Melack & Hess 2010).Seasonally flooded Amazon forests are home to a high diversityof trees (Wittmann et al. 2010), endemic invertebrates (Adis et al.2010) and frugivorous fish (Goulding et al. 1988, Correa et al.2007). Although inundated for much of the year, the litter layerof a low open-canopy floodplain forest of the upper Rio Negrocan ignite when relative humidity of the understory drops below65 percent (Uhl et al. 1988).Fire also penetrates closed-canopy floodplain forests of themiddle Rio Negro. Using field inventories and high-resolutionimages Flores et al. (2014) found average tree mortality of 90 per-cent from fires associated with droughts—much higher than themortality or percent of biomass loss reported after a first burn ofupland forests (Barbosa & Fearnside 1999, Cochrane et al. 1999,Barlow & Peres 2004). Amazon forests seasonally flooded bynutrient-poor waters have an aerated root mat and accumulationof leaf litter which together comprise a stock of fine, quick-dryingfuel two to three times larger than in nearby upland forest(Kauffmann et al. 1988, Dos Santos & Nelson 2013).These prior results suggest that flooded forest is less resistantto fire damage than upland forest. However, no experiment has yetbeen performed comparing fire resistance of these two widespreadforest types. The Rio Negro provides few situations to compareflammability; river channels act as fire breaks between the two for-est types and ignition sources differ (e.g., fishermen’s campfires aremore abundant in the floodplain). A report by Nelson (2001) com-pared fire damage between upland and floodplain forests in closeproximity and penetrated by the same fire, but relied only on visualinspection of satellite images and air photography.Here, we use a natural experiment to address the hypothesisthat given equal ignition opportunity and identical recent rainfallhistory, fire will cause greater damage to undisturbed nutrient-poor flooded forest than undisturbed upland forest (H1). Oursecond hypothesis examines cause: The unburned flooded forestunderstory has more prolonged periods of flammability than theunburned upland forest understory (H2).South of the central sector of the Amazon River are exten-sive terraces 15–20 m above the present local high water level.Irion et al. (2010) interpret these as paleo-floodplains depositedduring Pleistocene interglacial periods, such as 110,000 years ago,when the Amazon River was slightly above its present relativelevel. During the final Pleistocene low sea stand the paleo-flood-plains became upland and were weakly incised by erosion, form-ing dense dendritic networks of shallow valleys. Post-Pleistocenesea level rise back-flooded the Amazon main stem and theseshallow incised valleys. Currently, they are seasonally inundatedby a 10 m amplitude annual flood pulse and are colonized bytrees tolerant to periodic inundation. Between the seasonallyflooded valleys, the paleo-floodplain terrace forms flat narrowinterfluves covered by flood intolerant upland tree species.For three reasons, fires on this landscape provide the idealnatural experiment to address H1. First, tree cover is continuousbetween the two forest types, with no intervening open water orerosional scarp to impede passage of fire. Second, the two foresttypes are spatially intercalated because of the dense network ofseasonally flooded valleys, allowing placement of all plots in closeproximity. As a result, sites can have identical pre-burn rainfalland equal ignition opportunity when fires course through the sea-sonally flooded valley forest (Fig. S1). Finally, because ignitionsources for both forest types (swidden fields and pastures) wereabsent over much of the area until recent decades, it is easy tofind forest that has burned only once.

We investigated how deciduousness of overstory tree species influences the community structure and species composition in the understory. The results suggest that deciduous overstory trees have positive effects on light-demanding species, and that the processes underlying such effects may involve reduced competition for light or facilitation through increased water availability. Resumo Nos investigamos como a deciduidade das arvores do dossel influencia a estrutura e a composicao do subosque. Os resultados sugerem que as arvores deciduas tem efeitos positivos sobre especies exigentes em luz, provavelmente pela reducao da competicao por luz ou facilitacao pelo aumento na disponibilidade de agua no solo.

Continually flowering plants bloom continuously throughout the year, as often seen in plants distributed along the roadsides or in the understory layers in Southeast Asia's tropical rain forests. Dillenia suffruticosa (Griff. ex Hook. f. & Thomson) Martelli (Dilleniaceae) is one such continually flowering shrub that flowers during periods of community-wide mass flowering, general flowering (GF), and non-GF. During irregularly occurring GF periods, when species of all forest layers flower synchronously for several months, some pollinators migrate to the canopy layer, where GF promotes the pollination success of participating plants. Continually flowering plants share the available pollinator community with GF plants, and the reproductive success of continually flowering plants may be affected during the GF period. To assess the effects of GF on the reproductive success of a diverse range of continually flowering plants, we examined the differences in pollinator density and reproductive success between GF and non-GF periods in D. suffruticosa at four different research sites. Although the seed set differed among the four research sites, pollinator density and fruit set did not differ between GF and non-GF periods or research sites. Our results suggest that the reproductive success of D. suffruticosa was maintained at an approximately constant level, regardless of the flowering phenology of the canopy layer or other vegetation components.

Amazonian forests harbor a large variety of understory herbs adapted to areas with different hydrological conditions, ranging from well-drained to seasonally flooded forests. The presence versus absence of flooding forms the extremes of a hydrological gradient, with various intermediate conditions, such as seasonal soil waterlogged areas, in between. We investigated the relationship between understory herbs and hydrological conditions in Central Amazonian forests using eighty-eight 250 × 2 m plots distributed along a 600-km transect. Hydrological conditions were determined regionally by precipitation and locally by topographic conditions based on drainage potential, flooding height and soil permeability (sand content). Soil cation concentration was used as a proxy for soil fertility. The floristic dissimilarities among plots were visualized by Nonmetric Multidimensional Scaling, and simple and multiple regressions were used to identify the best predictor of herb species composition. Local drainage potential was more important in determining herb species composition than soil fertility or precipitation at non-flooded and flooded sites. Flooded sites comprised a very distinctive herb species composition even when the flood height was low (0.3 m). We conclude that hydrological conditions are the primary constraint of herb distribution within this flat regional landscape with moderate amounts of soil fertility variation (0.09–2.280 cmol(+)/kg). Hydrological models that consider local water conditions explained the largest part of herb species composition. Therefore, predictions of species distribution based on large-scale climatic variables may underestimate the favorable area for understory herbs if the variation on local hydrological conditions is not considered. Resumo Florestas Amazonicas abrigam uma grande variedade de plantas de sub-bosque adaptadas a diferentes condicoes hidrologicas, que incluem areas bem-drenadas ate areas sazonalmente alagadas. A presenca versus ausencia de alagamentos sao extremos do gradiente hidrologico enquanto algumas areas, como areas encharcadas, sao intermediarias desse gradiente. Nos investigamos a relacao entre plantas herbaceas e condicoes hidrologicas na Amazonia Central em 88 parcelas de 250 × 2 m em um transecto de ca 600 km. Condicoes hidrologicas foram determinadas regionalmente pela precipitacao e localmente pelas condicoes topograficas, dadas pela permeabilidade do solo (teores de areia), potencial de drenagem e profundidade do alagamento. A fertilidade do solo foi medida pela concentracao de cations do solo. As dissimilaridades floristicas entre as parcelas foram visualizada pelo uso de escalonamento multidimensional nao-metrico e regressoes simples e multiplas foram usadas para identificar os melhores preditores da composicao floristica. O potencial de drenagem local foi mais importante como preditor da composicao de ervas do que precipitacao e a fertilidade, tanto em areas alagaveis como nas nao alagaveis. A composicao de ervas em areas alagaveis foi bastante distinta, mesmo com o alagamento superfical (0.3 m). Nos concluimos que condicoes hidrologicas sao limitantes da composicao de ervas em areas com variacao moderada nos valores de fertilidade do solo (0.09–2.280 cmol(+)/kg). Modelos hidrologicos que consideram as condicoes hidrologicas locais explicaram a maior parte da composicao de ervas. Portanto, previsoes sobre a distribuicao de especies considerando apenas dados climaticos podem subestimar areas favoraveis para ervas caso as condicoes hidrologicas locais nao sejam consideradas.

In Amazonia, the assemblages of several taxa differ significantly between upland terra firme and white-water flooded varzea forests, but little is known about the diversity and distribution of bats in these two forest types. We compare the spatio-temporal patterns of bat assemblage composition and structure in adjacent terra firme and varzea forests in the lower Purus River region of central Brazilian Amazonia. Bats were sampled using mist nets at five sites in each forest type during 40 nights (2400 net-hours). We captured 1069 bats representing 42 species and Phyllostomidae bats comprised 99.3 percent of all captures. The bat assemblages in varzea and terra firme forests were significantly different, mainly due to a marked dissimilarity in species composition and in the number of captures during high-water season. In addition, bat assemblages within forest types differed significantly between seasons for both terra firme and varzea. Frugivores dominated the bat assemblages in both forest types. Overall guild structure did not change between varzea and terra firme or between seasons, but frugivore and animalivore abundance increased significantly in varzea forest during the inundation. The difference in assemblage structure observed in the high-water season is probably caused by the annual varzea flooding, which provides an effective barrier to the persistence of many understory bats. We also hypothesize that some bat species may undertake seasonal movements between forest types in response to fruit abundance, and our results further underline the importance of floodplain habitats for the conservation of species in the Amazon.

Concerns have been expressed that research methods and research infrastructure may affect the systems under study, which could lead to biased results. Effects of research activities on seedlings, saplings, and understory plants that are subjected to trampling and injury have been demonstrated. However, as of yet, no effects on epiphytic plants have been reported. In this paper, we demonstrate the impact of research trails on the abundance of an epiphytic tropical bromeliad, Guzmania vittata, at a research site in Peruvian Amazonia. Compared to the interior of the forest, the abundance of this bromeliad is significantly higher along the research trails. While we do not know the exact cause for the increased bromeliad abundance along the trails, we discuss enhanced dispersal of anemochorous seeds as a potential mechanism that generates this impact.

Although differences in canopy openness, herbivory and their interaction may promote species coexistence, how these factors affect pioneer tree species and potentially limit growth, and survival has been poorly studied, particularly in tropical South Asia. We monitored the effect of canopy openness and herbivore damage on seedling survival and growth of 960 individuals of six pioneer tree species: Dillenia triquetra, Macaranga indica, Macaranga peltata, Schumacheria castaneifolia, Trema orientalis, and Wendlandia bicuspidata. Seedlings were placed in four gap-understory positions—center, outer gap edge, inner forest edge, and understory—in four large, natural gaps within the Sinharaja World Heritage Reserve, Sri Lanka. Canopy openness positively affected survival probability beyond the 550-d experiment, while herbivory decreased survival and was highest in understory conditions. The relative order of species survival stayed fairly consistent between gap-understory positions and followed their known shade tolerance rankings. When averaged across all experimental conditions, T. orientalis had the lowest survival probability estimate beyond the 550-d experiment (0.05), but the greatest capacity for growth where it successfully established, while the species with highest averaged survival probability (0.79), D. triquetra, showed the lowest growth. One species, W. bicuspidata, responded positively to herbivory by re-sprouting. Coexistence of D. triquetra, T. orientalis, and W. bicuspidata can be explained by a trade-off among species in survival, growth, and response to herbivory. In addition to variation in canopy light environment, herbivory may be important in determining pioneer species distribution through fine-scale niche partitioning and should be carefully considered in reforestation efforts.

The availability and quality of resources for herbivores in tropical dry forests (TDFs) vary in time and space, affecting herbivore guilds differently across spatial scales (both horizontally and vertically), with consequences to the distribution of leaf damage in these forests. We attempted to elucidate the distribution patterns of herbivorous insect guilds and leaf damage throughout the secondary succession and vertical stratification along the rainy season in a Brazilian TDF. With the advance of the succession, a greater richness and abundance of herbivorous insects were found, resulting in higher leaf damage in intermediate and late stages. This pattern, however, was not observed for the frequency of leaf miners. At a smaller spatial scale, the host tree height positively affected the richness and abundance of insects. The higher leaf damage was found in canopy, which also harbored a greater richness and abundance of chewing herbivores compared to the understory at both the beginning and the end of the rainy season. Although for sap-sucking insects, this was only true at the beginning of the season. We detected a decrease in insect richness and abundance at the end of the rainy season, probably due to a synchronization of insect activity with the availability of young, highly nutritious plant tissues. These results are consistent with other studies that found a general trend of increasing richness and abundance of herbivorous insects and leaf damage throughout the secondary succession (early to late stages) and between vertical strata (understory to canopy), suggesting that forest complexity positively affects herbivores.

One of the main natural disturbances that affects the structure of rain forests is treefalls, frequently resulting in gaps. Tree-fall gaps can bring drastic changes in environmental conditions compared with the undisturbed understory. We investigated the effect of tree-fall gaps on fruit-feeding butterfly (Nymphalidae) species assemblages in an undisturbed lowland rain forest in southeastern Peru. We used fruit-baited traps suspended 2 m above ground in 15 tree-fall gaps ranging in area from 100 to 1000 m2 and in adjacent undisturbed understory. Our data support the hypothesis that tree-fall gap and understory habitats are utilized by different butterfly species assemblages. There were morphological differences between gap and understory species, where the understory species had a larger wing area to thoracic volume. Vegetation structure and composition were important factors affecting the butterfly assemblages. Most of the butterfly species showed an avoidance of vines and a strong association with the presence of trees and shrubs in gaps. There were also differences among gap assemblages that increased with gap size. Some of the species that were associated with gaps have been considered as canopy species. Other gap species in the present study, however, are known to feed on fruits and/or use host plants mainly, or only, occurring in gaps, implicating that the gap assemblage is a mix of canopy species and those unique to gaps. This indicates that, in an undisturbed Amazon forest, tree-fall gaps may contribute to maintain species diversity by creating a mosaic of specific habitats and resources that favors different butterfly assemblages.

Logging in tropical forests may create large canopy openings. These gaps provide suitable conditions for some opportunistic shrubs and herbs to take advantage of the surge in resources and rapidly colonize disturbed sites. This dense plant cover may limit forest regeneration by interfering with tree seedling establishment, growth, and survival by altering the light and nutrients available to seedlings, modifying herbivore behavior, or a number of other factors. In Kibale National Park (Uganda), old logging sites are mainly covered by dense stands of Acanthus pubescens Engl., which appear to inhibit tree regeneration. We wanted to identify the ecological processes underlying this regeneration collapse. To do so, we designed a factorial experiment to evaluate the influences of herbivory and vegetation cover on the growth and survival of tree seedlings. We compared the survival and growth of transplanted tree seedlings in A. pubescens stands and logged forests, in the presence or absence of the understory vegetation layer (logged forest) or vegetation cover (A. pubescens), and with or without herbivory. We found no evidence to support the hypothesis that herbivory is significantly higher under dense A. pubescens cover. Seedling survival was not influenced by the environment. Seedling growth, however, was positively influenced by the removal of A. pubescens, suggesting that changes in resource availability associated with the presence of A. pubescens, may be important for regeneration. Our results suggest that sustained cutting of A. pubescens cover could foster the growth of established seedlings and could lead to tree regeneration and habitat restoration.

We examined long-term responses of an Amazonian bird assemblage to wildfire disturbance, investigating how understory birds reacted to forest regeneration 1, 3, and 10years after a widespread fire event. The bird community was sampled along the Arapiuns and Maro river catchments in central Brazilian Amazonia. Sampling took place in 1998, 2000, and 2008 using mist-nets in eight plots (four burned, four unburned sites). Species richness did not change significantly in unburned sites. In burned sites, however, we found significantly lower richness in 1998, higher richness in 2000, and similar richness in 2008. Multi-dimensional scaling ordination showed consistent differences in bird communities both within burned sites sampled in different sampling years, and between burned and unburned sites in all years. Of the 30 most abundant species, 12 had not recovered 10years after the fires, including habitat specialists such as mixed flocks specialists and ant-followers. Fire-disturbance favored three species (two hummingbirds and a manakin) in the short term only. All other species were either favored throughout the study (seven species of omnivores and small insectivores) or did not show a clear response (eight species). In burned sites, we also found significantly lower abundance of species sensitive to disturbances and habitat specialists over the entire study period. Although the bird community seems to be recovering in terms of richness, the overall community composition and abundance of some species in post-burned and unburned sites remain very different, and have not recovered after 10years of forest regeneration.

Mistletoes rely on birds for seed dispersal, but the presumed importance of mistletoe-specialist frugivores has not been critically examined nor compared with generalist frugivores and opportunistic foragers. The contribution of these three groups was compared directly by quantifying bird visitation to fruiting mistletoe plants ( Oryctanthus occidentalis: Loranthaceae) at Barro Colorado Island, Panama, and by comparing these results with proportions calculated from other empirical studies of mistletoe visitation conducted elsewhere. After more than 100 h of timed watches, 23 bird species were recorded visiting eight heavily infected host trees ( Luehea seemannii: Tiliaceae). Eight of these species visited mistletoe, of which five (all tyrannids) consumed mistletoe fruit. Although two mistletoe specialist frugivores ( Tyrannulus elatus and Zimmerius vilissimus) removed most fruit (73%), more than a quarter was consumed by one generalist frugivore ( Mionectes oleagineus) and two opportunists ( Myiozetetes cayanensis and Myiozetetes similis). Post consumption behaviour varied: the specialists flew from mistletoe to mistletoe, the generalist rested in the subcanopy and understory, and the opportunists spent most time hawking insects and resting high in the canopy. Integrating these data with previous work, the dietary specialization, short gut passage rate and strict habitat preferences of mistletoe specialists suggests that their services relate primarily to intensification and contagious dispersal, while species with broader diets are more likely to visit uninfected trees and establish new infections. The presumed importance of mistletoe-specialist frugivores was not supported and mistletoes are considered to be comparable to many other bird-dispersed plants, relying on both specialist and generalist frugivores, while opportunists may be disproportionately important in long-distance dispersal.

Blackwater floodplain forests of the Rio Negro are susceptible to understory fires. Bird composition was distinct between burned andunburned floodplain forest but not between young (12–18 yr) and old burns (>25 yr), indicating low resilience after fire. Forest regener-ation is slow, with open grassy areas persisting >80 yr.Abstract in Portuguese is available in the online version of this article. Key words: Amazon blackwater forest; birds; fires; point counts. T ROPICAL FOREST FIRES HAVE RECENTLY RECEIVED ATTENTION DUETO THEIR FREQUENCY AND EXTENT (e.g., Cochrane et al. 1999,Nepstad et al. 1999). Humid tropical forests are not adapted tofires and may take many years to recover (Cochrane 2003). Firesdamage soil structure and fragment the landscape (Brotons et al.2004), modify vegetation structure (Cochrane et al. 1999, Barlow& Peres 2004), and impact fauna (Barlow & Peres 2008, Claveiroet al. 2011).Blackwater floodplain forests of the Rio Negro have burnedduring years of very low water level over the past century (Stern-berg 1987, Williams et al. 2005). Understory fires in this regionare a serious problem for four reasons. First, they occur despitehigh rainfall and low human population density (Borges et al.2001, Oliveira et al. 2001). Fishermen’s campfires are the mainignition source. Second, tree mortality from ground fire is veryhigh. For upland forest, Cochrane et al. (1999) found biomassloss of only 9 percent after a first ground fire, increasing to 47and 81 percent after second and third burns. Data are lacking forreburning of blackwater floodplain forest, but all 36 floodplainburn scars examined by Flores et al. (unpublished) had tree mor-tality above 75 percent, suggesting that high mortality occurs aftera single burn. Third, forest regeneration rates are extremely slow.Some open grassy areas are attributed by local informants to for-est fires as long ago as 1925. Finally, even under the optimisticSRB1 emissions scenario of the IPCC, the HADCM3 global cli-mate model shows >1000 mm drop in annual rainfall for themiddle and lower Rio Negro by the 2080s (IntergovernmentalPanel on Climate Change—IPCC 2012).Seasonally flooded woody vegetation comprises 12.1 percentof the Rio Negro basin and 11.5 percent of the entire Amazonbasin (Melack & Hess 2010). Although upland forests havegreater species richness, flooded forests have their often uniqueflora and fauna (Remsen & Parker 1983). In mist-netting studiesin the Jau National Park, 14 percent of the bird species wererestricted to flooded forests (Borges & Carvalhaes 2000).Birds are one of the best-studied animal groups in the Ama-zon (Cohn-Haft et al. 1997). They are good environmental indica-tors, in the light of the cost-benefits of sampling methods andtheir habitat sensitivity (Gardner et al. 2008). After fire distur-bance, some bird species decline in abundance while othersincrease (e.g., Barlow et al. 2002, 2006, Barlow & Peres 2004,2008, Claveiro et al. 2011).Here, we ask what has been the impact of past wildfires onthe bird composition of blackwater floodplain, using both con-ventional and occupancy model methods. We compare post-firerecovery of the bird fauna between older (>25 yr) and morerecent burns (12–18 yr) to give some indication of the resilienceof the ecosystem in the face of fire.The study area is the blackwater floodplain of the lowerCuini River (0°58′ S, 62°56′ W), a tributary of the middle RioNegro. The floodplain has many open areas with sparse standingtrunks of dead trees, evidence of past forest fires (see SupportingInformation). Most of these burned prior to 1985, the year ofthe earliest reliable satellite images. In 2010, the burn scars werehighly variable in their vegetation structure, ranging from opengrassy cover or open with many standing and fallen dead trunksto dense woody secondary vegetation.We chose 44 sampling points in the floodplain, half inunburned forest and half in nearby burned sites (Fig. S1). Toreduce the chances of recording the same bird at two differentsites or of recording upland species, all plots were separated fromeach other and from upland forest by at least 500 m (Barlow &Peres 2004, Sberze et al. 2009). We measured the fraction of for-est area within a radius of 250 m. We weighted this fraction bydistance from the listening point, starting with a weight of 100percent at 0–25 m, dropping to 10 percent at 200–250 m, asbirds more than 200 m away are inaudible to the recorder.We recorded bird vocalizations at high water and the earlystages of receding water, between 27 June and 4 August, 2010.

Global change puts an increasing pressure on tropical forests and their inherent diversity by the risk of longer droughts and drier microclimatic conditions within the forest. How organisms will respond is uncertain, especially for organisms highly depending on their microclimatic environment such as bryophytes. An adequate tolerance to desiccation is important to face these changes, however, little is known for tropical bryophytes. We investigated for the first time the desiccation tolerance of epiphytic bryophytes from contrasting microsites at the tropical lowland forest in French Guiana. Using chlorophyll-fluorescence (Fv/Fm) as an indicator of recovery, we tested: (1) desiccation tolerance for short (3 d) and long (9 d) desiccation events; (2) different desiccation intensities; and (3) recovery by rehydration with water vapor. Species from the canopy were well adapted to desiccation events. Thirteen of 18 species maintained more than 75 percent of their photosynthetic capacity after recovery at the strongest desiccation treatment of 9 d at 43 percent relative humidity (RH). In contrast, species from the understory were sensitive and withstood desiccation only at humid conditions of 75 percent RH and higher. The photosystem of the studied bryophytes was reactivated efficiently in equilibration with water vapor only—a yet neglected phenomenon in bryology. A novel introduced desiccation tolerance index allows global comparison of desiccation tolerances and highlights the sensitivity of understory species. Our results suggest that decreasing humidity caused by climate change and forest degradation could be a concerning threat for understory species.

Drip-tips are a common feature of the leaves of rain forest trees, but their functional significance remains contested. The most widely accepted hypothesis is that drip-tips assist drainage of the lamina thereby aiding drying of the leaf surface and reducing the rate of colonization and abundance of epiphyllic organisms. The drying action of drip-tips may also enhance transpiration and reduce the need for investment in support structures. Furthermore, drip-tips may help prevent splash erosion around the base of the tree. Data from 130 forest Amazonian plots are used to investigate the abundance and distribution of drip-tips and, through regression methods that incorporate spatial autocorrelation, seek to identify associations between the frequency of drip-tips and a range of climatic variables. The average frequency of species and trees with drip-tips across all plots was 32 and 33 percent, respectively. Trees and species with drip-tips were significantly more prevalent in the Central-East Amazon than the other regions. Drip-tips were also associated with tree species that have smaller maximum heights and with trees with smaller trunk diameters. The proportion of species and individuals with drip-tips was more strongly correlated with precipitation of the wettest trimester than with total annual precipitation or length of the dry season. Our results extend and provide support for both existing hypotheses for the functional benefit of possessing a drip-tip. Moreover, the currently unrecognized macrogeographic association between the frequency of drip-tips in trees of the tropical forest understory and areas of heavy precipitation suggests a new function for this trait.

Nonnative ungulates can alter the structure and function of forest ecosystems. Feral pigs in particular pose a substantial threat to native plant communities throughout their global range. Hawaiian forests are exceptionally vulnerable to feral pig activity because native vegetation evolved in the absence of large mammalian herbivores. A common approach for conserving and restoring forests in Hawaii is fencing and removal of feral pigs. The extent of native plant community recovery and nonnative plant invasion following pig removal, however, is largely unknown. Our objective was to quantify changes in native and nonnative understory vegetation over a 16 yr period in adjacent fenced (pig-free) vs. unfenced (pig-present) Hawaiian montane wet forest. Native and nonnative understory vegetation responded strongly to feral pig removal. Density of native woody plants rooted in mineral soil increased sixfold in pig-free sites over 16 yr, whereas establishment was almost exclusively restricted to epiphytes in pig-present sites. Stem density of young tree ferns increased significantly (51.2%) in pig-free, but not pig-present sites. Herbaceous cover decreased over time in pig-present sites (67.9%). In both treatments, number of species remained constant and native woody plant establishment was limited to commonly occurring species. The nonnative invasive shrub, Psidium cattleianum, responded positively to release from pig disturbance with a fivefold increase in density in pig-free sites. These results suggest that while common native understory plants recover within 16 yr of pig removal, control of nonnative plants and outplanting of rarer native species are necessary components of sustainable conservation and restoration efforts in these forests.

Scant information is available on how soil phosphorus (P) availability responds to atmospheric nitrogen (N) deposition, especially in the tropical zones. This study examined the effect of N addition on soil P availability, and compared this effect between forest sites of contrasting land-use history. Effects of N addition on soil properties, litterfall production, P release from decomposing litter, and soil P availability were studied in a disturbed (reforested pine forest with previous understory vegetation and litter harvesting) and a rehabilitated (reforested mixed pine/broadleaf forest with no understory vegetation and litter harvesting) tropical forest in southern China. Experimental N-treatments (above ambient) were the following: Control (no N addition), N50 (50 kg N ha 1 yr 1 ), and N100 (100 kg N ha 1 yr 1 ). Results indicated that N addition significantly decreased soil P availability in the disturbed forest. In the rehabilitated forest, however, soil P availability was significantly increased by N addition. Decreases in soil P availability may be correlated with decreases in rates of P release from decomposing litter in the N-treated plots, whereas the increase in soil P availability was correlated with an increase in litterfall production. Our results suggest that response of soil P availability to N deposition in the reforested tropical forests in southern China may vary greatly with temporal changes in tree species composition and soil nutrient status, caused by different land-use practices.

Cyclones, which change tree communities and alter forest structure, are thought to have had a significant selective pressure on the flora and fauna of Madagascar. Very little information, however, is available on the actual impact of cyclones on Malagasy ecosystems. On 21 January 2009, Cyclone Fanele made landfall on the western coast of Madagascar with sustained winds of 185 km/h. We examined the immediate effects of the cyclone on tropical dry forest structure in the Kirindy Mitea National Park. In July and August 2009, we measured the height, diameter at breast height (dbh), and damage for 1361 trees in nine 25 A— 25 m plots. We found that: (1) over 95 percent of trees experienced some sort of damage, including 8.8 percent mortality; (2) understory and emergent trees experienced significantly higher mortality than canopy trees; and (3) stem density was reduced 9.2±4.5 percent and biomass was reduced 13.4±8.1 percent after the cyclone. Dbh was the best predictor of trunk damage and mortality. This extensive alteration of forest structure will have a substantial short‐ and long‐term impact on the biotic communities of western Madagascar.

The consequences of habitat alteration on the role of understory insectivorous birds as predators of herbivorous insects in tropical forests are poorly understood. To examine whether fragmentation may affect the top–down controls of herbivory, we compared the number of species, individuals, and the community structure of insectivorous birds between fragments and continuous tropical moist forest in Mexico. We also registered insect herbivore abundances and conducted a larvae predation experiment to evaluate the potential role of insectivorous birds as predators of herbivorous insects. We recorded 63 bird species from 22 families, 43 percent of which were insectivorous birds. Species richness, abundance, and diversity of the avian community were higher in continuous forest compared with forest fragments. For insectivorous birds in particular, there was low similarity in avian insectivore communities between forest types, and forest fragments had more heavily dominated communities of avian insectivores. During the dry season, forest fragments presented significantly higher predation rates on artificial caterpillars, and lower abundance of herbivorous Lepidoptera larvae, compared with continuous forest. Furthermore, there was a significant negative correlation between artificial caterpillar predation rate and larval Lepidoptera abundance, with higher rates of predation in sample sites of low Lepidoptera abundance. Hence, the potentially greater light in the dry season combined with a more dominated avian insectivore community in forest fragments may facilitate increased predation by avian insectivores, resulting in a decline in abundance of larval Lepidoptera, with implications for the process of insect-driven herbivory in forest fragments.

Suppression of tree seedlings by the understory is an important ecological filter with implications for tree diversity and dynamics. In a greenhouse competition experiment, we used seedlings of four canopy species from coastal dune forest (Diospyros natalensis, Euclea racemosa, Sideroxylon inerme and Apodytes dimidiata) to examine the relative competitive effects of the dominant understory herb Isoglossa woodii on seedling performance. We manipulated I. woodii density, light and nutrient levels and measured growth responses. Total seedling biomass decreased with density of I. woodii. The magnitude of biomass suppression with competitor density was similar among tree species. Consequently there was no discernable hierarchy of competitive ranking among tree species. The relative growth rate of seedlings decreased at higher densities of I. woodii and increased at higher nutrient levels but was unaffected by variation in light conditions. Aboveground biomass decreased at higher densities of I. woodii and at higher light levels but increased at higher nutrient levels. Size asymmetric competition for light and nutrients may be the major driver of aboveground interactions between tree seedling and I. woodii. While tree species showed no hierarchy of competitive ability their seedlings exhibited equivalent responses to competition from an understory dominant, permitting species coexistence and the maintenance of species diversity.

We investigated the mechanism of coexistence of the rare Amani Sunbird (Hedydipna pallidigastra) and the widespread Collared Sunbird (H. collaris), within Brachystegia woodland in the Arabuko-Sokoke Forest, Kenya. We compared how prey abundance and search strategies affect resource exploitation by the two species. We used foraging theory to direct our measures of feeding activities as influenced by sunbird species, tree species and foraging height. We evaluated invertebrate abundance among tree species at different heights within trees. The Collared Sunbird primarily used the understory, and the Amani Sunbird primarily used the upper-canopy. Overall, the rate of prey attacks per flight of the Amani Sunbird was 2.8 times greater than that of the Collared Sunbird. The Amani Sunbird, however, used increased search and attack rates in the understory compared with the mid- and upper-canopies, but the Collared Sunbird foraged similarly throughout all strata. We hypothesize that the increased foraging rate of the Amani in the understory reflects increased foraging costs due to interference from the Collared Sunbird in that stratum. Furthermore, the Collared Sunbird exploits rich patches by moving frequently from place to place. The Amani Sunbird forages slowly, with reduced travel rates, and with a greater number of prey captures within a patch. Arthropod density did not differ among the vegetative strata, but was higher in Brachystegia spiciformis and Hymenaea verrucosa than in six other tree species. We hypothesize that the Amani Sunbird appears dependent upon continued tall B. spiciformis trees within the canopy of the Arabuko-Sokoke Forest.

Many plant species have the capacity to regenerate asexually by resprouting from stem and leaf fragments. In the pan-tropical shrub genus Piper, this tendency is thought to be higher in shade-tolerant than light-demanding species, and to represent a trade-off with annual seed production. Here we use molecular markers to identify clones in fivePiper species varying in light requirements. We test predictions that (i) asexual recruitment success is highest in shade-tolerant species, and (ii) that consequently, shade-tolerant species are characterized by lower genotypic diversity than light-demanding Piper. We found that two shade-tolerant Piper species recruited asexually more frequently (36‐42% of sampled shoots were of asexual origin) than, two light-demanding and one shade-tolerant species (0‐26%). Furthermore, as predicted, genotypic diversity was negatively correlated with the frequency of asexual recruitment in the population. Nonetheless, genotypic diversity of Piper was high compared with other clonal plants. The proportion of unique genotypes found per population ranged from 0.58 to 1.0 and the genotypic Simpson’s diversity ranged from 0.93 to 1.0 for all five species. Our results suggest that even though asexual reproduction plays an important role in maintaining local populations of Piper in the understory, it does not seem to reduce genotypic diversity to levels that will threaten these species ability to respond to environmental change.

Old field secondary succession of tropical dry forests (TDFs) is poorly understood, particularly regarding the dynamics of seedlings, saplings, and sprouts (regenerative communities). We used chronosequence and dynamic approaches to: (1) document successional trajectories of regenerative communities during the first dozen years of regeneration in abandoned pastures at Chamela, Mexico; (2) test the usefulness of chronosequences to predict the dynamics of regenerative communities along time; and (3) assess the influence of surrounding forest matrix, stand density, and understory light availability (in the rainy season) as driving factors of such dynamics. More than 1000 plants and 95 species of shrubs and trees 10‐100cm tall were monitored between 2004 and 2007 in nine abandoned pastures (0‐12yr since abandonment) and two old-growth forest (OGF) sites; gain and loss rates of plants, species, and plant cover were obtained. Chronosequence predicted a rapid and asymptotic increase of plant density, species density, and plant cover toward the OGF values. Such prediction did not match with dynamic data that showed negative or neutral net community rates of change, independently of fallow age. Recruitment and species gain rates increased with the amount surrounding forest matrix. No other effect of the explored factors was detected. Strong rainfall shortenings could be responsible for the high loss and low gain rates of plants and species recorded in most sites. We highlight the critical role of supra-annual rainfall variability on the dynamics of TDF regenerative communities and the poor predictive value of chronosequences in forest systems subjected to strong environmental temporal variation.

Edge effects along tropical forest–pasture margins are thought to cause a shift toward early successional characteristics of the understory forest vegetation. We tested this idea by sampling vegetation at five forest sites in northeast Costa Rica each of which had edges that were established over 20 yr earlier. Four of these sites had been selectively logged. We sampled woody plants >0.2 and ≤1.3 m height in 54 m2 within 0.2 ha plots at edges (N=14), and at 150 m (N=11) and 300 m from edges (N=9). Composition and diversity did not vary with edge distance. Abundance of tree regeneration, mainly of canopy and emergent species, increased at edges. Abundance of lianas and slow-growing tree species did not differ significantly across the sampling locations. Weighted mean wood density varied little, with a reduction at edges for canopy species. Palms were less abundant at edges, but not less species rich. At edges, these plant assemblages maintain many of the characteristics of forest interior vegetation, though the changes observed may indicate ongoing functional change. Degradation of forest–pasture edges is not a universal feature of tropical forest fragmentation, and forests with high rates of natural turnover might have a high capacity to maintain themselves within forest edges alongside pasture. RESUMEN Son escasos los estudios de los efectos de borde sobre el sotobosque de los bosques humedos tropicales - un conjunto de individuos juveniles de arboles, palmas y lianas, asi como de individuos adultos de especies como palmas enanas -. ?Tienden siempre los bordes de los bosques que limitan con pasturas a adquirir caracteristicas de sucesion temprana, como algunas veces se tiende a generalizar? En cinco bosques del noroeste de Costa Rica que limitan desde hace 20 anos o mas con pasturas - cuatro con extraccion selectiva de madera - se registraron todos los individuos de plantas lenosas con altura > 0.2 m y ≤ 1.3 m, en sub-parcelas de 54 m2 dentro de parcelas de 0.2 ha, en los bordes (n = 14) y a 150 m (n = 11) y 300 m (n = 9) de ellos. La composicion y la diversidad no variaron en funcion a la distancia a los bordes. La abundancia de la regeneracion arborea, principalmente la de las especies emergentes y de dosel, fue mayor en los bordes pero no asi la de las lianas, y la de las especies arboreas de crecimiento lento no disminuyo. La media ponderada de la densidad de la madera de la comunidad vario poco, a pesar de que la de los arboles de dosel fue menor en los bordes. La abundancia de las palmas disminuyo en los bordes, mas no su riqueza especifica. Las covariables relacionadas a la extraccion de madera no afectaron los resultados. Esta vegetacion mantiene en los bordes muchas caracteristicas de la del interior de bosque, aunque las variaciones observadas pueden indicar importantes cambios funcionales en curso. La degradacion de los bordes bosque-pasturas no es un rasgo universal de la fragmentacion del bosque tropical, y los bosques con tasas altas de recambio natural pueden tener una alta capacidad inherente para mantener sus bordes aun ante usos hostiles de la tierra. Palabras clave: bosque humedo tropical, densidad de la madera, fragmentacion del bosque, media ponderada de la comunidad, sotobosque.

Recent studies on the impacts of forest fragmentation on understory insectivorous birds in the Neotropics have highlighted that even narrow linear clearings, such as roads, can affect the movements of this guild of birds. We used playback trials of territorial vocalizations to assess the movements of three understory insectivorous bird species across two unpaved roads bisecting Parque Estadual Carlos Botelho in southeast Brazil, located within one of the largest remaining continuous Atlantic Forests. Movement patterns varied among species. While Chamaeza campanisona never crossed these roads, Pyriglena leucoptera crossed them in almost 100 percent of tests. Although Conopophaga lineata exhibited a significantly lower number of crossings along cleared sites, it was eventually willing to traverse the roads, showing an intermediate pattern. Shaded areas with connected canopy did not improve birds' willingness to cross roads compared with areas where treecrowns were at least 3 m apart. Similarly, birds' willingness to cross an 8-m wide road with limited traffic (six vehicles/wk) was not significantly greater than that of a 12-m wide road with more intense traffic (41 vehicles/d). Our findings suggest that the negative impact of roads on bird movement is an issue that should be addressed by managers of Atlantic Forest conservation units, especially as economic development results in pressure to pave and widen roads. Abstract in Portuguese is available at http://www.blackwell-synergy.com/loi/btp.

Canopy trees are largely responsible for the environmental heterogeneity in the understory of tropical and subtropical species-rich forests, which in turn may influence sapling community dynamics. We tested the effect of the specific identity of four cloud forest canopy trees on total solar radiation, canopy openness, soil moisture, litter depth, and soil temperature, as well as on the structure and dynamics of the sapling community growing beneath their canopies. We observed significant effects of the specific identity of canopy trees on most understory microenvironmental variables. Soil moisture was higher and canopy openness lower beneath Cornus disciflora. In turn, canopy openness and total solar radiation were higher beneath Oreopanax xalapensis, while the lowest soil moisture occurred beneath Quercus laurina. Moreover, Chiranthodendron pentadactylon was the only species having a positive effect on litter depth under its canopy. In spite of these between-species environmental differences, only C. pentadactylon had significant, negative effects on sapling density and species richness, which may be associated to low seed germination and seedling establishment due to an increased litter depth in its vicinity. The relevance of the specific identity of canopy trees for natural regeneration processes and species richness maintenance depends on its potential to differentially affect sapling dynamics through species-specific modifications of microenvironmental conditions. RESUMEN Los arboles del dosel son responsables en gran medida de la heterogeneidad ambiental del sotobosque en bosques tropicales y subtropicales ricos en especies, lo cual a su vez influye en la dinamica de la comunidad de plantulas. Probamos el efecto de la identidad especifica de cuatro especies arboreas del dosel de un bosque nublado sobre la radiacion solar total, la apertura del dosel, la humedad y la temperatura del suelo, y la profundidad del mantillo, asi como sobre la estructura y la dinamica de la comunidad de plantulas, debajo de sus copas. Observamos efectos significativos de la identidad especifica de los arboles del dosel sobre la mayoria de las variables microambientales del sotobosque. La humedad del suelo fue mayor y la apertura del dosel menor debajo de Cornus disciflora. A su vez, la apertura del dosel y la radiacion solar total fueron mayores debajo de Oreopanax xalapensis, mientras que la humedad del suelo mas baja se registro debajo de Quercus ocoteifolia. Ademas, Chiranthodendron pentadactylon fue la unica especie que mostro un efecto positivo sobre la profundidad del mantillo bajo sus copas. A pesar de estas diferencias ambientales entre especies, solo Chiranthodendron pentadactylon tuvo un efecto negativo significativo sobre la densidad de plantulas y la riqueza de especies, lo que puede estar asociado con tasas bajas de germinacion de semillas y de establecimiento de plantulas debidas al incremento de la profundidad del mantillo cerca de los arboles de esta especies. La relevancia de la identidad especifica de los arboles del dosel en el proceso de regeneracion y el mantenimiento de la riqueza de especies dependen del potencial que tienen estos organismos de afectar diferencialmente la comunidad de plantulas a traves de las modificaciones de las condiciones microambientales.

The regeneration of many tropical trees is threatened by forest fragmentation because it produces major physical, biological and ecological changes that limit seed germination and seedling establishment. We analyzed the regenerative potential of an old growth forest tree species—Ampelocera hottlei (Ulmaceae)—in three contrasting habitats located in the Lacandona rain forest, southeastern Mexico: continuous forest, fragments occupied by black howler monkeys (Alouatta pigra) and fragments unoccupied by howlers. We tested if germination of A. hottlei seeds among habitats was affected by understory temperature, light incidence and ingestion by A. pigra. We compared seedling survival and relative growth rate in height (RGRH) for 20 d among habitats and between ingested and control seeds (from mature fruits). Germination was higher in continuous forest than in fragments (occupied or not), with higher germination rates for ingested seeds in fragments. Temperature and light incidence were lower in continuous forest than in fragments. Germination decreased with increasing temperature and light incidence with this relationship being significantly higher for ingested seeds. Seedling survival was higher in continuous forest than in fragments, whereas RGRH did not differ among habitats. In addition, survival and RGRH were higher in seedlings originating from ingested seeds. Overall, our results suggest that the populations of A. hottlei can be limited in fragments where changes in the understory physical environment and the extirpation of A. pigra will likely have deleterious consequences for the regeneration of A. hottlei and possibly for other tree species, ultimately affecting forest composition and structure. Abstract in Spanish is available at http://www.blackwell-synergy.com/loi/btp.

Multispecies agro-forestry is generally lauded for providing ecosystem services, especially in tropical environments. Avian communities contribute to services such as biodiversity and pest management. Characterizing and evaluating avian community composition in similar cropping systems will help optimize management for ecosystem services. We examined the relationship between cropping system vegetation and avian communities in four shaded agro-forestry systems common to the Limprovince of Costa Rica: abandoned and managed systems of cacao, cacao with banana, and banana. During two field seasons, we detected 2605 birds from 106 species and identified 2791 trees and shrubs from 62 morphospecies. We compared vegetation and avian species richness across systems with mixed-effects linear models. Canopy, understory, and groundcover vegetation differed among agro-forestry systems. More ground- and understory-foraging forest species were detected in agro-forestry systems lacking banana, whereas richness of agricultural generalist species was highest in systems with banana. Richness of understory- and ground- foraging species correlated with understory tree species richness and leaf litter. Our results indicate that shaded cacao and banana systems can have similar canopy- foraging species richness that includes both agricultural and woodland generalist species, but that interspersing banana with cacao can adversely influence understory forest bird community composition. Agro-forests with diverse understory vegetation support more understory-foraging bird species that have proven valuable in pest management. Abstract in Spanish is available at http: //www.blackwell-synergy.com/loi/btp.

Habitat complexity is an important factor structuring local faunal assemblages. Many invasive plant species alter vegetation complexity because they are both functionally and structurally different from native flora. This study investigated the effects of an invasive grass (Andropogon gayanus Kunth.), which is invading undisturbed savannas in northern Australia. Although A. gayanus is a similar lifeform to that dominant in the native understory (i.e., a C4 grass), it is structurally different and significantly alters habitat complexity. We, therefore, hypothesized that there would be a substantial effect of the invasive grass on ant, spider, and other invertebrate assemblages. Contrary to our hypothesis, there was no effect of A. gayanus on ant species richness, abundance, or composition, nor were spiders or other invertebrates affected. Instead the change in weather conditions with season was more important in structuring the local invertebrate assemblages. Change in habitat complexity was most pronounced vertically, rather than horizontally at ground level, thus although there was a clear difference in the vertical structure between invaded and noninvaded habitats, the limited invertebrate response to different A. gayanus densities suggests some invertebrates are less sensitive to vertical changes in vegetation structure.

Invasive species interacting with fires pose a relatively unknown, but potentially serious, threat to the tropical forests of Hawaii. Fires may create conditions that facilitate species invasions, but the degree to which this occurs in different tropical plant communities has not been quantified. We documented the survival and establishment of plant species for 2yr following 2003 wildfires in tropical moist and wet forest life zones in Hawaii Volcanoes National Park, Hawaii.Fires were ignited by lava flows and burned across a steep environmental gradient encompassing two previously burned shrub-dominated communities and three Metrosideros polymorpha forest communities. Fires in all community types were stand replacing, where 495 percent of overstory trees were top killed. Over half (457%) of the trees survived via basal sprouting, but sprout growth differed among forest communities. Sprout growth (4250,000cm 3 ) was greatest in the forest community where postfire understory cover was lowest presumably due to thick native Dicranopteris linearis fern litter that remained postfire. In contrast, M. polymorpha sprout growth was much slower (o100,000cm 3 ) in the two forest communities where there was rapid understory recovery of nonnative ferns Nephrolepis multiflora and invasive grasses Paspalum conjugatum. These results suggest that the rapid establishment of an invasive-dominated understory limited recovery of the overstory dominant M. polymorpha. In contrast to the three forest communities, there were few changes in vegetation composition in the shrubland communities. Nonnative species invasions coupled with repeated fires selectively eliminated fire-sensitive species thereby maintaining these communities in dominance of primarily nonnative, fire-resilient, species.