Nutrient fluxes in stemflow and throughfall were compared among three successional stages of an upper montane rain forest and related to structural characteristics of the stands (stem density, leaf area, epiphyte abundance). An old-growth forest stand, an early successional (10-y-old) forest stand and a mid-successional (40-y-old) forest stand were studied in the Cordillera Talamanca, Costa Rica. All three sites were dominated by Quercus copeyensis with a variable admixture of other tree species. There was no difference in the average stand leaf area index between the old-growth forest and the early successional forest. A significantly higher leaf area was found in the mid-successional forest. There were large differences in litterfall from non-vascular epiphytes (mosses, liverworts and lichens) which reflected differences in epiphyte abundance, with highest values in the old-growth forest. Total nutrient transfer via stemflow and throughfall from the canopy to the soil showed only minor differences among the stands. The stands differed widely in the ratio of nutrient transport via stemflow to the total nutrient flux by water below the canopy. The K flux with stemflow accounted for 5% of the total in the old-growth forest but it accounted for 17% (early successional forest) and 26% (mid-successional forest) in the secondary forests. It is concluded that differences in canopy structure and epiphyte abundance in old-growth and secondary forests resulted in large differences in the partitioning of nutrient transport into stemflow and throughfall components although total nutrient transfers via water reaching the soil were similar.

Seedlings of Pentaclethra macroloba (Willd.) Kuntze, a dominant, shade-tolerant species of tropical moist forest in Costa Rica, were raised under three light conditions to assess their acclimatization and growth responses to irradiance. The light environments used were full sun, partial shade (25% of full sun), and full shade (1% of full sun). To test the effect of a sudden change in light level such as would occur in the event of a treefall gap, the seedlings in the above conditions were switched between environments after two months and grown for an additional 1.5 months. Plants in full sun and partial shade had similar total weight; switching between the two environments had no effect on biomass. Plants switched from full sun and partial shade to full shade had negative growth as a result of negative CO2, flux and leaf abscission. Plants transferred from full shade to full sun had lower growth rates than those switched from full shade to partial shade because of severe leaf damage in full sun. The previous environment significantly affected the response of most growth and size characteristics to the present environment. Maximum photosynthesis changed only 30% in response to light level during growth. However, large changes in other photosynthetic and structural characteristics were found. Leaves developed in full shade had lower respiration, leaf thickness, and stomatal density and higher apparent quantum yield, specific leaf area, and chlorophyll content than leaves from full sun. Osmotic potentials were similar between treatments. Despite only small changes in maximum photosynthesis, acclimatization to extreme shade or sun rendered leaves unsuitable for large changes in environment. Consequently, in the event of a large treefall gap, plants already present in the understory will require a substantial period of adjustment before they respond to the increase in light.

Above-ground biomass (AGB) is increasing in most of the Amazon forests. One hypothesis is that forests are responding to widespread and intense human intervention prior to the European conquest (>500 y ago). In this study we confront this hypothesis with changes in AGB over 6.3 y in a large western Amazonian forest plot (>150 000 shrubs and trees and 1100 species with dbh ≥ 10 mm in 25 ha). We examined AGB flux in different habitats and across diameter classes. The forest lost small stems (4.6%), gained large trees (2.6%), and gained biomass (0.7%). The change in AGB stock was due entirely to this upward shift in size leading to more canopy trees and fewer saplings after just 6 y. Across habitats, the biggest increment in biomass was in the secondary-forest patch (3.4% y−1) which we know was cleared about 27 y ago, whereas mature forest on ridges and valleys had small increases (0.10% and 0.09% y−1, respectively). In both censuses, AGB stocks were >50% higher on the ridge than in the valley while relative growth and mortality were higher in the valley. Mean wood specific gravity (WSG) decreased with increasing diameter class; WSG did not change much between censuses in mature forests and did not contribute to the change in AGB stocks. Our forest increased its standing biomass, but far less than the average reported for other Amazonian forests (i.e. 0.30 vs. 0.98 Mg ha−1 y−1). We find no evidence to support the notion that this forest is recovering from long-past human intervention. Instead of a long-term recovery, we believe the forest changed in response to natural fluctuations of the environment (e.g. changes in precipitation, higher CO2), windstorms or other more recent events. The significant differences in AGB stocks between valley and ridge suggest that the terra firme forests are a mosaic of natural habitats, and that this mosaic is in part responsible for the variation in biomass stocks detected in Amazonian terra firme forests.

Resumen: La biomasa aérea de la mayoría de los bosques amazónicos está incrementando. Una hipótesis es que los bosques están respondiendo a un disturbio humano intenso y ampliamente distribuido, anterior a la llegada de los conquistadores europeos (>500 años atrás). En este estudio se confronta esta hipótesis con los cambios en biomasa encontrados en 6.3 años en una parcela de gran escala de la Amazonia occidental (>150.000 arbustos y árboles con diámetro a la altura del pecho ≥10 mm y 1100 especies en 25 ha). Los resultados se examinan por categorías de diámetro y hábitat. En este período el bosque perdió tallos pequeños (4.6%), ganó árboles grandes (2.6%) y ganó biomasa (0.7%). La ganancia en biomasa fue debida enteramente al incremento de árboles de gran tamaño que significó más árboles de dosel y menos juveniles en apenas 6 años. Entre los hábitats, el mayor incremento en biomasa se encontró en un parche de bosque secundario de colina (3.4%/año), cuya edad es de 27 años, mientras el bosque maduro de las colinas y los valles incrementó escasamente (0.10% y 0.09%/año, respectivamente). Tanto al inicio como al final del estudio, el stock de biomasa fue >50% más grande en la colina que en el valle mientras que el crecimiento y la mortalidad relativa fueron mayores en el valle. La media de la gravedad específica de la madera (GEM) fue menor a mayor clase diamétrica; en el bosque maduro, el cambio en la GEM fue insignificante y no contribuyó al aumento en stocks de biomasa. El bosque incrementó la biomasa aérea pero mucho menos que el promedio reportado para otros bosques amazónicos (i.e. 0.30 vs. 0.98 Mg ha−1/año). No se encontró evidencia que apoye la noción de que el bosque se está recuperando de un disturbio de gran escala ocurrido en el pasado. En su lugar, se cree que el bosque cambió en respuesta a fluctuaciones naturales del ambiente (e.g. cambios en precipitación, mayor concentración de CO2), vendavales u otro tipo de eventos más recientes. La diferencia significativa en los stocks de biomasa encontrada entre el valle y la colina sugiere que la tierra firme es un mosaico de hábitats naturales y que este mosaico podría explicar en parte la variación encontrada en los stocks de biomasa de bosques amazónicos de tierra firme.

Patterns of leaf phenological diversity were documented in nine key tree species of a tropical deciduous forest in the Vindhyan region of India. Monthly leaf counts on 160 tagged twigs on ten individuals of each species were made through two annual cycles. Tree species exhibited a gradient of deciduousness (∼leafless duration), ranging from semi-evergreen species (entire population never becoming leafless) to 7-mo-deciduous species. The semi-evergreen species initiated leaf flush (bud break of vegetative bud) earlier around the spring equinox. In all deciduous tree species synchronous leaf-flush initiation, with low inter-annual variability, occurred during the hot dry summer (May–June, day temperature >40 °C), prior to the onset of the rainy season. Based on the quantification of leafless period, leaf-flush duration, and leaf strategy index (leaf-flush rate/leaf-fall rate, proposed in this study) in different species, four plant functional types were recognized: (a) semi-evergreen, spring flushing, showing leaf exchange, with mean leafless period 8 d, leaf-flush duration 6–7 mo and leaf strategy index <0.5 (Shorea robusta); (b) <2-mo-deciduous, summer flushing, leafless period 3–8 wk, leaf-flush duration 5–6 mo, and leaf strategy index >0.5−<0.7 (Anogeissus latifolia, Diospyros melanoxylon and Hardwickia binata); (c) 2–4-mo-deciduous, summer flushing, leafless period 2–3 mo, leaf-flush duration 4–5 mo, and leaf strategy index >0.8−<1.0 (Acacia catechu, Lagerstroemia parviflora and Terminalia tomentosa); and (d) >4-mo-deciduous, summer flushing, leafless period >4–7 mo, leaf-flush duration 3–4 mo, and leaf strategy index 1.0 (Boswellia serrata and Lannea coromandelica). Conspecific trees showed asynchrony with respect to leaf-flush completion, initiation and completion of leaf-fall, and extent of leafless period. Leaf strategy index (indicating rate of resource use and conservation) was strongly related with the leafless period in different species (r=0.82) and can serve as a useful index in leaf phenological studies and classification of plant functional types.

The potential role of predation as a factor underlying variation in leaf-cutter ant (Atta sp.) densities was investigated on recently isolated land-bridge islands in Lago Guri, Venezuela. A survey of mature Atta colonies revealed a sharp increase in densities on small and medium islands (5.6 and 2.3 colonies ha−1 respectively) compared to large islands (0.72 colonies ha−1) and the mainland (0 nests in 5.5 ha). Incipient colonies showed the reverse trend with higher densities on larger landmasses. Cage experiments were conducted to test the impacts of predation on the survival of incipient and young Atta colonies. Protection by wire-mesh cages increased the survival of both incipient and young colonies at all sites. The survival of unprotected incipient and young colonies was significantly reduced on larger landmasses relative to small islands. These results are consistent with burrow survey data that provided indirect evidence of higher armadillo densities on larger landmasses. Findings suggest that reduced predation is a potentially important factor underlying observed variation in Atta density patterns in the Guri islands.

Reproductive traits of 123 species of rain-forest tree from ultramafic regions of New Caledonia were assessed, mainly from herbarium specimens. Most species had extremely small, simple, pale-coloured flowers that are probably mainly pollinated by small insects, but not including bees. The seeds of most species were considered to be bird dispersed. However, wind is also important for pollination and seed dispersal. The phenological trend was for an increase in the number of species flowering and fruiting around the end of the warm dry season/start of the hot wet season, followed by a decline at the end of the wet season, and lower proportions during the cooler season. Seed size was significantly correlated with fruit size. Other correlations, between flower size and fruit size, and between seed size and seed number, were significant using species as independent observations, but did not hold following phylogenetic correction. Compared with non-dioecious species, dioecious species had significantly larger seeds, and a greater proportion of species with biotic dispersal, abiotic pollination and solitary (female) flowers. The long-term persistence of at least the larger-seeded tree species in New Caledonia is precarious, since the endemic giant pigeon, Ducula goliath, is probably their principal effective disperser, and this species is in decline.

Natural seed deposition patterns and their effects on post-dispersal seed fate are critical in tropical tree recruitment. Previous research showed that the key dispersal agent of the neotropical tree, Virola calophylla, is the spider monkey (Ateles paniscus). Spider monkeys generate a heterogeneous seed deposition pattern because they scatter-disperse seeds diurnally, whereas they clump-disperse seeds at their sleeping sites. The recruitment consequences of this pattern were investigated using manipulative experiments and observations. Scatter-hoarding by spiny rats (Proechimys spp.) caused little rearrangement of the initial seed deposition pattern because they moved seeds only short distances. Seed survival to the seedling stage depended negatively on conspecific seed density and positively on the distance from the nearest adult V. calophylla female. These effects were likely mediated by two important seed predators, spiny rats and beetles (Scolytidae). Furthermore, spider monkeys' seed deposition patterns influenced seed survival. Scatter-dispersed and experimentally dispersed seeds had the highest survival. Conversely, clump-dispersed seeds at sleeping sites, which are far from V. calophylla females, and non-dispersed seeds had equally low survival, suggesting that conspecific density- and distance-dependence acted independently and did not explain all variation in seed survival. Instead, other characteristics of the seed deposition pattern, such as the multi-specific assemblage of seeds at sleeping sites, also affected post-dispersal seed fates.

Resumen: La conexión entre el patrón natural de dispersión de semillas con el destino después de la dispersión es clave para el reclutamiento de árboles tropicales. Mediante experimentos y observaciones se investigó esta conexión utilizando el árbol neotropical Virola calophylla (Myristicaceae). Ateles paniscus (maquisapa), el principal dispersor de sus semillas, genera un patrón de deposición heterogéneo. Durante el día las semillas son depositadas de manera esparcida mientras que en los dormitorios las semillas son depositadas de manera agregada. En este estudio se encontró que los roedores espinosos (Proechimys spp.) almacenaron semillas individuales debajo de la hojarasca, sin embargo estos no alteraron el patrón de dispersión ya que las semillas fueron transportadas distancias cortas y la tasa de predación fue alta. Se encontró que la tasa de sobrevivencia hasta la etapa de plántula tuve una relación negativa con la densidad de las semillas y una relación positiva con la distancia al árbol hembra de V. calophylla mas cercano. Estos efectos sucedieron por medio de roedores espinosos y coleópteros (Scolytidae), predadores importantes de las semillas de V. callophylla. Adicionalemente, el patrón de deposición de los maquisapas influenció la sobrevivencia de las semillas. Tanto las semillas dispersadas por los maquisapas como las dispersadas experimentalmente tuvieron la tasa de sobrevivencia más alta. Por el contrario, tanto las semillas depositadas en los dormitorios, usualmente lejos de hembras de V. calophylla, como las semillas que cayeron debajo del árbol hembra tuvieron bajos niveles de sobrevivencia. Estos reultados sugieren que tanto la densidad como la distancia tuvieron efectos independientes y no explicaron toda la variación observada en la sobrevivencia de semillas. Por el contrario, otras características de la deposición de semillas tales como la riqueza de especies de la comunidad de semillas en los dormitorios también afectaron el destino de las semillas después de dispersadas.

To be able to make accurate estimates of the carbon stocks present in the world's tropical forests, there is a growing need for accurate tree biomass estimations on large spatial scales (Chave et al. 2004, Cummings et al. 2002, Nascimento & Laurance 2004). Wood-specific gravity forms an important component of these biomass estimations (Baker et al. 2004, Magcale-Macandog 2004, Nogueira et al. 2005). Even though Chave et al. (2004) found that the most important source of error in above-ground biomass estimation (AGB) is currently related to the choice of allometric model, Baker et al. (2004) show that for two estimates of AGB in Amazonian forests derived using different allometric equations, stand-level specific wood gravity still explained 45.4% and 29.7% of the total variation in AGB.

Decomposition of litter on the forest floor and of leaves of five species, Celtis zenkeri, Cola lepidota, Desbordesia glaucescens, Ceiba pentandra and Terminalia superba in nylon mesh bags, as well as wood decay were studied in the tropical rainforest at Southern Bakundu Forest Reserve, Cameroon.

The rate of loss of dry matter was fastest in Celtis zenkeri which was significantly different from the other species, while potassium was the most rapidly released element from all species with more than 50% being released in the first two months of the experiment. Nitrogen and phosphorus showed initial increases in bagged leaf litter independent of dry weight losses and while nitrogen was later released phosphorus continued to increase reaching 2–3 times the initial concentration. Decomposition constant (k) of litter on the forest floor was found to be 2.23 whereas the mean decomposition constants of the different species were as follows: Celtis zenkeri 4.18, Cola lepidota 2.18, Desbordesia glaucescens 1.60 and Ceiba pentandra 2.16 for the two experiments.

Termites were found to have a very great influence on the decay of the wood of Terminalia superba with decay due to micro-organisms being negligible.

Three census methods for studying fruiting phenology and fruit production were compared: platform observation, fruit-trap collection and raked-ground survey. The estimation of fresh fruit mass varied greatly with the census method used. Moreover, the fruiting phenology recorded using the fruit-trap collection and raked-ground survey methods showed a delay of one to two months compared with the platform observation method. Any of the three methods can be used for the approximation of annual fruiting phenology, but that of fruit-trap collection is suited to measure the annual fruit production, and that of platform observation offers the best estimation of the quantity of fruit in tree crowns at a given time.

In the Australian wet–dry tropics, temperatures are high year-round but rainfall is concentrated in a 4-mo wet season. Regular nightly surveys in the Fogg Dam Nature Reserve provided data on temporal (monthly, seasonal) variation in biological attributes of three snake species: water pythons (Liasis fuscus, Pythonidae), keelbacks (Tropidonophis mairii, Colubridae) and slatey-grey snakes (Stegonotus cucullatus, Colubridae). Adults of all three taxa were encountered more frequently during the dry season than the wet season, whereas juveniles were more commonly encountered in the wet season. The sex ratio among adult snakes also shifted seasonally, but in different ways in different species. These sex-ratio shifts probably reflect reproductive activity (mate-searching by males, oviposition migrations by females) and were accompanied by increased encounter rates. Feeding rates and body condition of keelbacks (a frog specialist) were highest during the wet season when frogs were most abundant. Rats migrated away from Fogg Dam during the wet season, and most pythons (rat specialists) left this area to follow their prey. The pythons that remained at Fogg Dam exhibited low feeding rates and poor body condition. Slatey-grey snakes (a generalist predator) showed less seasonal variation in feeding rates or body condition. Our data show that tropical seasonality induces strong fluctuations in many attributes of snake populations, and that patterns of response differ both among and within species.

Fruit production by an understorey tree, Miconia centrodesma, was monitored in treefall gaps and under intact canopy in a Costa Rican lowland rain forest. Trees in gaps displayed much less seasonality in fruit production than trees of intact forest sites. For example, ripe fruits were common on gap trees for a six month period (January-June) when few or no trees under intact canopy were in fruit. The frequent and aseasonal fruiting of gap trees demonstrates that they are not constrained by phenological cueing mechanisms; the influence of such cues is overridden by habitat. Trees in gaps also produced larger crops, had more extended fruiting episodes, and fruited more frequently than shaded conspecifics. This level of intraspecific variation in fruiting behaviour suggests that treefall gaps play an important role in determining the reproductive success of M. centrodesma. A substantial proportion of an individual's lifetime seed output may be produced during the brief period it occupies a gap. In addition, the large and continuous supply of fruits produced in gaps by M. centrodesma and other understorey plants, may mean that gaps function as ‘keystone habitats’ by providing resident frugivores with fruit during periods of general fruit scarcity.

A seed-removal experiment was conducted to assess the role of Proechimys semispinosus (Central American spiny rat) as potential predator and disperser of Astrocaryum standleyanum (black palm) seeds. One hundred fresh ripe A. standleyanum fruits were placed in semipermeable cages on each of 14 small islands in Panama, and seed disappearance rates were calculated for each island. Spiny rat density and biomass were determined by live-trapping on each island for 5 consecutive days and 4 nights. Censuses of fruiting trees were conducted on each island to control for effects of food availability on removal of palm fruits. Disappearance rates were related positively to total spiny rat density, density of adult and subadult spiny rats, and spiny rat biomass, but the density of fruiting trees accounted for very little variation. Spiny rats evidently prey heavily on A. standleyanum seeds, based on the high removal rates and on feeding observations of captive individuals. Since spiny rats may scatterhoard A. standleyanum seeds, they may also function as effective seed dispersers if seeds are removed to favourable germination sites unavailable to other seed predators. Results indicate that spiny rats, because of their abundance and wide distribution, may be important but overlooked predators and dispersers of A. standleyanum seeds and of other large-seeded tree species.

Estimates of roosting habitat availability and population size using unbiased sampling regimes are completely lacking for any bat species. The use of conspicuous and accessible roosts in the developing, rolled leaves of Heliconia and Calathea plants by Thyroptera tricolor (Spix's disc-winged bat) provided an ideal opportunity to address this need. To assess roost availability and population size, the number of occupied and unoccupied leaves and bats in known areas in an area of lowland rain forest in north-eastern Costa Rica were quantified in 1998–99. A high density of leaves was available on any given day (mean: 43 leaves ha−1), but the density of roost leaves was low (mean: 2.5 leaves ha−1), corresponding with a low occupancy rate of 5.7 or 12% based on different methods of estimation. Developing leaves were available for 8–16 h in the preferred size range of leaves used by T. tricolor, and a maximum of 28–60 h, depending on the plant species. Using closed-population mark–recapture models, the 5.69-ha study area supported 261 individuals over a 4-mo period in 1998, corresponding to a density of 43 bats ha−1. These results have important implications for the results of studies on bat community structure and rarity, and for the behaviour and ecology of T. tricolor.

We describe forests from three areas of Jamaica, all on White Limestone but with markedly different rainfall regimes. The areas are Hog House Hill in the north-east with lower montane rain forest at c. 450 m altitude with a rainfall of c. 4000 mm yr−1; Broom Hall in the centre of the island with evergreen seasonal forest at c. 670 m altitude and with a rainfall of c. 1600 mm yr−1 and a marked dry season; and Round Hill near the south coast with dry semi-evergreen forest at c. 300 m altitude with an irregularly distributed rainfall of c. 1000 mm yr−1. Species lists were made from c. 180 ha at Hog House Hill, c. 5 ha at Broom Hall and c. 50 ha at Round Hill, and detailed inventories made of five sample sites of c. 1000 m2, two at Hog House Hill, one at Broom Hall and two at Round Hill.

At Hog House Hill we listed 280 vascular plant species, including 118 species of trees and larger shrubs; at Broom Hall 247 and 135; at Round Hill 129 and 81. Species-area and species-individuals curves confirm that Broom Hall was richer in tree species than Hog House Hill. The wetter forests contain high proportions of species endemic to Jamaica: 40% of the total flora at Hog House Hill and 36% at Broom Hall. Canopy height decreased from c. 26–28 m at Hog House Hill to c. 13–24 m at Broom Hall to c. 8–15 m at Round Hill. Predominant leaf size decreased from mesophyll at Hog House Hill to notophyll at Broom Hall to microphyll at Round Hill.

Compared with forests on other Caribbean islands, the Jamaican forests appear to be as species-rich as any, but lower in stature than natural forest in Trinidad and Dominica. Continental Neotropical forests are both more species-rich and taller.

Hurricane Gilbert caused disturbance to Jamaican montane rainforests in 1988. This study provides a detailed characterization of landscape-level changes in light below the canopy of these forests after the hurricane. Hemispherical photographs were taken below the forest canopy at four sites at permanent points 1 m above the ground between 7 and 33 mo after the hurricane. For each photograph photosynthetically active radiation (PAR) was computed. PAR declined exponentially in all sites during the period of measurement. During the first 24 mo after the hurricane, PAR beneath the canopy was significantly greater in sites that had been defoliated during the hurricane than in sites where few trees had been defoliated. By 28 mo after the hurricane there was no significant difference in PAR beneath the canopy among the four sites. By 33 mo after the hurricane canopy recovery was nearly complete and PAR was only slightly higher than measurements made before the hurricane. Our results were compared with studies of changes in light environment resulting from treefall gaps and under deciduous canopies. PAR during the first 18 mo after the hurricane was similar to that recorded in small canopy gaps in other forests. Widespread defoliation caused by hurricanes can thus increase PAR beneath the canopy over large areas and consequently opportunities may arise for widespread recruitment of tree species in response to increased light levels.

An on-going controversy in community ecology involves the debate about the many factors that affect the assembly and composition of a given species assemblage. Theory suggests that community composition is influenced by environmental gradients or biotic processes. This study examines patterns of community composition in two tropical tree frog assemblages of primary and exploited lowland rain-forest sites in the Guiana Shield area of central Guyana, South America and the Upper Guinean rain-forest block of south-western Côte d'Ivoire, West Africa. We tested community composition and species abundance data of two adult tree frog communities collected on 21 standardized transects during a period of 5 y for evidence of spatial correlation in community composition. We applied simple and partial Mantel tests to separate the effects of environmental variables, spatial distance and spatial autocorrelation on community composition. Whenever environmental effects were accounted for, we found significant positive spatial correlation of community composition. All assemblages appeared to be spatially structured, i.e. sites in close proximity had similar species assemblages. However, spatially structured environmental variation (autocorrelation) did not account for the spatial structure of species incidence. Environmental factors did not prove to be significant predictors of species incidence in any of the assemblages analysed, even if we controlled for spatial effects. Observed correlation patterns of species composition were consistent within respective realms and disturbance regimes. Moreover, general correlation patterns were consistent between geographic regions. These results are in contrast to previously published results from a study on leaf-litter anurans and indicate that group-specific differences must not be neglected when analysing patterns of species composition in anurans as they may drastically alter the outcome of the analysis.