Infestation rates by palm bruchid beetles (Bruchidae: Pachymerini) on Attalea palm seeds are so high that most endocarps remaining near parent trees contain larvae rather than endosperm a few months after the peak fruiting season. Vertebrates feeding on palm endocarp contents may therefore be feeding on animal rather than plant matter, and the timing of use of endocarps may be influenced by the presence of larvae rather than by background fruit availability. On Maracá Island Ecological Reserve, Roraima State, Brazil, white-lipped peccaries (Tayassu pecari), agoutis (Dasyprocta leporina) and squirrels (Sciurus igniventris) all fed on bruchid beetle larvae from Attalea maripa palm endocarps. Squirrels fed on both larvae and endosperm year-round in all habitat types; agoutis fed on both larvae and seeds only at times and at sites where alternate foods were not available; and white-lipped peccaries fed almost exclusively on bruchid larvae in high-palm-density habitats. Differences in timing and location of endocarp use by these species may provide an index of mammal community dynamics in neotropical forests.

Diurnal and nocturnal censuses were conducted on animal visitors at a single strangler Ficus aff. cotinifolia (H.B.K.) tree during the entire period of ripe fruit availability. Fruit fall to the ground was measured with fruit traps, and chemical analyses were conducted on the figs. Fourteen species of birds, four species of nonvolant mammals and two species of bats consumed the figs. Of the total number of ripe figs accounted for during the sampling period (N= 1.9 X 105), 42% fell to the ground, 45% were removed by mammals and 13% by birds. Frugivores such as the howling monkey Alouatta palliata, the cacomistle Bassariscus sumichrasti, the keel-billed toucan Ramphastos sulphuratus and fruit-eating bats removed the largest amounts of figs from the tree and deposited seeds of 13 plant species other than figs below the tree crown.

Vertebrate seed dispersers could impact the evolution of seed size or alter the pattern of seedling recruitment if they responded differently to seeds of varying size (Jordano 1995). For example, models of seed caching by birds and mammals predict that seeds of higher nutritive value should be placed farther from parent trees and in lower densities than lower quality seeds (Clarkson et al. 1986, Stapanian & Smith 1978, Tamura et al. 1999). Comparisons of seed removal rates among tropical tree species in South-East Asia (Blate et al. 1998) and Australia (Osunkoya 1994) failed to show a relationship between seed size and removal rate, although the probability that a seed was scatterhoarded by agoutis (Dasyprocta punctata) in a neotropical rain forest increased with interspecific seed size (Forget et al. 1998).

During the course of a population study of small mammals in a Brazilian coastal shrubland we calculated the movements between successive captures, the residence time, the indices of aggregation and the kinds of movements of the five most common species of small mammal. A capture-mark-recapture study was undertaken over two years, quarterly. Philander opossum, Akodon cursor and Proechimys iheringi presented low mobility, with a high proportion of restricted movements, long residence time and larger coefficients of aggregation. Didelphis aurita and Metachirus nudicaudatus presented higher mobility and exploratory movements, short residence time and small coefficients of aggregation. The species with lower mobility had permanent populations within our sampling grid, while the species with higher mobility used areas outside the grid, presenting no local populations but occupying portions of regional metapopulations.

Large seasonal variation in the rate of change in girth of tropical rain-forest tree species has been described, but its origin is still under debate. We tested whether this variation might be related to variation in atmospheric relative humidity through its influence on bark water content and thickness. Variation in trunk circumference of 182 adult trees was measured about twice a month in an undisturbed tropical rain forest over 18 mo using dendrometers. Furthermore, a laboratory experiment was conducted to test the direct influence of relative air humidity on bark water content and thickness. In the field, most trees displayed highly positive rates of change in girth at the onset of the wet season, while a quarter of the trees displayed negative changes during long dry seasons, whatever their total annual growth. This variation was correlated with environmental conditions, particularly with atmospheric relative humidity. Trees with high bark water content and thickness displayed a stronger decrease in girth during the dry season. In the chamber experiment, desiccation induced a decrease in the diameter of the trunk sections in tandem with a decrease in bark water content. As a result, seasonal variation in the rate of change in girth of tropical rain-forest trees reflects variation in trunk biophysical properties, through the influence of relative humidity on bark properties, but not directly variation in secondary growth.

Discrete humus layers are common on podzols under temperate coniferous and tropical heath forests, and patchy layers also occur under some temperate broadleaved forests on non-podzolic soils. We used multiple data sets to test the reported association of humus with oligotrophic but non-podzolic soils under non-heath dipterocarp forest at Lambir, Sarawak. We examined the distribution, morphology and nutrient dynamics of necromass on soils derived from sandstone and shale. Concentrations of the main mineral nutrients were lower in fresh litter on the very oligotrophic sandstone soils than on shale. The rates of litterfall were similar, so that annual litterfall fluxes of all nutrients were lower on sandstone. The lower nutrient concentrations and fluxes in the litter on sandstone resulted in slower decomposition, longer residence times and larger standing crops of forest-floor necromass, with lower concentrations of nutrients. The necromass on sandstone sequestered significantly more N, K and Mg but less Ca and Mn than on shale, with no significant difference for P. The variations in necromass nutrient dynamics were associated with morphological differences. There were mats of densely rooted humus under the litter on sandstone, whereas litter lay directly over the mineral topsoil on shale. Spatial associations with soil nutrients were weak for necromass thickness, but clear for humus. The proportions of nutrients in the litterfall and necromass reflected the stoichiometric profiles of the soils. We attribute the differences in necromass nutrient dynamics and their association with soil reserve nutrients to lower rates of nutrient replenishment from the weathering of sandstone than from shale. Necromass characteristics are robust field indicators of multivariate edaphic differences in these and other tropical forests on Acrisols/Ultisols derived from Tertiary clastic sediments.

Conversion of tropical evergreen forests to crops or pastures results in significant depletions of terrestrial carbon (C) pools. Root biomass and root C pools were quantified in tropical evergreen primary forest, and in secondary forests and pastures of different ages, in the Los Tuxtlas Region, Veracruz, Mexico. Total root biomass to 1-m depth ranged from 19 to 27 Mg ha-1 in primary forest, from 5.5 to 22.5 Mg ha-1 in secondary forests (8-, 20- and 30-y-old), and from 3.1 to 5.4 Mg ha-1 in pastures (12-, 20- and 28-y-old). Large roots (> 20 mm in diameter) were largely absent below 40 cm depth in secondary forests and pastures. Roots in the 0–40 cm soil depth represented 60–76% of the total root biomass in primary forest, 77–93% in secondary forests, and 89–96% in pastures. Root biomass comprised 4.7–6.2% of the total biomass in primary forests and between 6.8–8.5% in secondary forests. These low values, the relatively high concentration of roots in the top 40 cm of soil, and the shallow depth at which large roots occurred in secondary forests suggest forest susceptibility to natural disturbances. Root C pools ranged from 7.9 to 11.6 Mg ha-1 in primary forests, from 2.1 to 9.6 Mg ha-1 in secondary forests and from 1.0 to 1.9 Mg ha-1 in pastures. The estimated total ecosystem C pool in primary forest was 415 Mg ha-1, it ranged from 187-246 Mg ha-1 in secondary forests, and was 179 Mg ha-1 in pastures. Tropical forest conversion to pasture decreased the root C pool by nearly 80% and represented a 94% loss of C in ecosystem biomass. Absolute losses of root C were nevertheless small when compared with the above-ground C loss. Carbon distribution among ecosystem biomass components is key to adequately understanding the consequences of land-use/cover change on C dynamics in tropical regions.

Tropical montane rain forest is widely considered to be a highly threatened hotspot of global diversity (Brummitt & Nic Lughadha 2003), and one of the least understood humid tropical forest ecosystems in terms of nutrient cycling (Bruijnzeel & Proctor 1995). There is, therefore, an urgent need to improve our understanding of nutrient cycling processes in this ecosystem, including the absorption of nutrients (mainly N and P) from senescing leaves, which may be a key component of adaptive mechanisms that conserve limiting nutrients (Killingbeck 1996). Nutrients which are not resorbed, however, will be circulated through litterfall in the longer term (Aerts 1996). The degree of nutrient resorption affects litter quality, which consequently affects decomposition rates and soil nutrient availability (Aerts & Chapin 2000). The importance of resorption in nutrient conservation has led to general hypotheses that species adapted to nutrient-poor environments have high resorption efficiencies (Richardson et al. 2005), and that low leaf nutrient concentrations are associated with high resorption efficiencies within species (Aerts 1996, Kobe et al. 2005). Nutrient resorption has also been shown not to differ greatly between growth forms (e.g. shrubs, grasses, forbs and trees) (Aerts 1996). However, its relative importance among plant functional groups is still highly controversial (Richardson et al. 2005).

Animal-pollinated angiosperm plants that replenish removed nectar invest energy that can entail a reproductive cost. Here we investigated whether or not seed production is affected by replenishing nectar in hummingbird-pollinated Tillandsia multicaulis and T. deppeana (Bromeliaceae) in a montane cloud forest in eastern Mexico. These epiphytic plants respond strongly and positively to repeated nectar removal. The female reproductive cost was assessed in manually, cross-pollinated flowers with or without repeated nectar removal. Seed production from experimental flowers was then contrasted with those naturally exposed to pollination and nectar removal. Tillandsia deppeana set the same number of seeds of the same size regardless of whether or not it had to replenish nectar. Seeds were slightly smaller if the result of natural open pollination than from copious hand crossing. In contrast, T. multicaulis set about half as many seeds when it had to replenish than when it did not, indicating a substantial cost to replenishment. There was no difference in seed number of T. multicaulis between open and hand-augmented pollination. The contrasting results for plants that respond strongly and positively to repeated nectar removal suggest that the female reproductive costs of nectar replenishment can range from costly to beneficial, depending on the conditions of the plants and on the species.

In a subtropical montane forest of north-western Argentina (27°S, 1000 m elevation), we analysed the effect of crown illumination, trunk diameter, foliar phenology and tree species identity as determinants of liana–host tree associations, as well as the spatial pattern of liana abundance in a 6-ha permanent plot. We recorded 2346 liana individuals ≥ 2 cm and 2320 trees ≥ 10 cm dbh. Sixty-five per cent of the trees hosted at least one liana stem. Large and well-lit trees were more likely to support lianas and supported more liana abundance than small and shaded trees. Yet, when trees were standardized by their size (liana basal area/tree basal area ratio), lianas were more abundant in smaller and less-exposed trees. Foliar phenology and tree species identity showed no association with the frequency of liana colonization and their abundance. Overall, tree features played a minor or even neutral role in structuring the liana community within this forest. Instead, lianas showed a positive autocorrelation at spatial scales up to 40 m. This suggests that lianas might be mostly structured by light-and dispersal-related factors such as those involving canopy access or canopy disturbances, with a negligible effect of host species identity and foliar phenology.

Elephant populations have declined greatly in the rain forests of Upper Guinea (Africa, west of the Dahomey Gap). Elephants have a number of well-known influences on vegetation, both detrimental and beneficial to trees. They are dispersers of a large number of woody forest species, giving rise to concerns that without elephants the plant diversity of Upper Guinean forest plant communities will not be maintained. This prospect was examined with respect to four sources of inventory and research data from Ghana, covering nearly all (more than 2000) species of forest plant. Evidence supporting the hypothesis that plant populations are collapsing without elephants is conspicuously absent in these datasets, although Balanites wilsoniana is likely to suffer dramatically on a centennial scale in the absence of forest elephants. A few other species are likely to decline, although at an even slower rate. In the context of other processes current in these forests, loss of elephants is an insignificant concern for plant biodiversity. Elephant damage of forests can be very significant in Africa, but loss of this influence is more than compensated for by human disturbance. Elephants have played a significant part in the shaping of West African rain forest vegetation. However, it is the conservation of elephants that should be of primary concern. Tree populations should be managed to promote them, rather than vice versa.

In this paper, we report on range use patterns of birds in relation to tropical forest fragmentation. Between 2003 and 2005, three understorey passerine species were radio-tracked in five locations of a fragmented and in two locations of a contiguous forest landscape on the Atlantic Plateau of São Paulo in south-eastern Brazil. Standardized ten-day home ranges of 55 individuals were used to determine influences of landscape pattern, season, species, sex and age. In addition, total observed home ranges of 76 individuals were reported as minimum measures of spatial requirements of the species. Further, seasonal home ranges of recaptured individuals were compared to examine site fidelity. Chiroxiphia caudata, but not Pyriglena leucoptera or Sclerurus scansor, used home ranges more than twice as large in the fragmented versus contiguous forest. Home range sizes of C. caudata differed in relation to sex, age, breeding status and season. Seasonal home ranges greatly overlapped in both C. caudata and in S. scansor. Our results suggest that one response by some forest bird species to habitat fragmentation entails enlarging their home ranges to include several habitat fragments, whereas more habitat-sensitive species remain restricted to larger forest patches.

The feeding behaviour of free-ranging black-handed tamarins, Saguinus midas niger, was monitored over 6 mo in a forest fragment in eastern Amazonia. The tamarins' diet included arthropods and plant exudates, but was predominantly frugivorous (87.5% of feeding records, 18 plant species) in all months. The seeds of at least six species were ingested whole and defecated intact. Ingested seeds were relatively large, but those with diameter > 1 cm or length > 2 cm were discarded. Seeds took 2–4 h to pass through the digestive tract, and more than half (50.6%) were dispersed to a habitat different from that in which they were ingested. A fifth (19.3%) of all seeds were dispersed from primary to secondary forest, indicating that S. m. niger may play an important rôle in forest regeneration, a rôle that will become increasingly important in the fragmented landscape of eastern Amazonia.

The effect of fluctuations in temperature and moisture supply on hard seeds of nine tropical coastal sand dune legumes, including herbs (Schrankia atiadrivalvis, Macropiilium atropurpureum and Canavalia rosea), and shrubs (Acacia farncsiana, A. macracantha, Mimosa chaetocarpa, Indigoftra sujjruticosa, Crolalaria incana and Chamaecrista chamaecrutoides), has been studied under laboratory and field conditions. Using a fluctuating temperature gradient bar seeds buried in sand were exposed to various amplitudes of diurnal temperature fluctuation over an extended period of time and seed germinability was examined at intervals. Germination percentage increased considerably in most species as a consequence of treatment with marked effects occurring at temperature fluctuations greater than 20°C and becoming detectable after 45 days. In several species the effect of applying wetting and drying cycles was to lower the amplitude of temperature fluctuation necessary to soften the seeds. Species can be grouped into physiological groups on the basis of differences in seed response to temperature fluctuations. It is suggested that these differences may help to explain the mechanisms distinguishing the different colonization patterns observed in tropical sand dune systems.

Over the last few decades a rapid and extensive conversion of tropical forests to agricultural land has taken place resulting in mosaics of fragmented forest patches, pastures and farmland. While the effects of forest fragmentation on biodiversity have been intensively studied within the remaining forests, relatively little is known about the biodiversity in tropical farmland (Daily et al. 2001, Pimentel et al. 1992). Frugivorous birds are an important group of species in tropical farmland ecosystems. Frugivorous birds are significant seed dispersers and can play a prominent role in transporting seeds into disturbed areas and setting the stage for the regeneration of these systems. Isolated fleshy-fruited trees in agricultural landscapes have been shown to attract birds, leading to an increased seed rain and seedling establishment under their canopies (Carrière et al. 2002, Duncan & Chapman 1999, Guevara et al. 1986, 2004; Slocum & Horvitz 2000).

To evaluate N limitation on above-ground net primary production in a tropical lower montane rain forest, an N fertilization experiment was conducted for 2 y. The study site is located at 1200–1300 m asl in the Fortuna forest reserve in western Panama and has a mature, mixed-species stand growing on an Andisol soil. Control and N-fertilized (125 kg urea-N ha−1 y−1) treatments were represented by four replicate plots (each 40 × 40 m, separated by at least 40 m). Stem diameter growth was analysed by diameter at breast height classes and also for the three most abundant species. The three species did not respond to N addition. The response of stem growth and above-ground woody biomass production to N fertilization varied among dbh classes. Stem growth of trees of 10–30 cm dbh increased only in the first year of N addition while trees of 30–50 cm dbh responded in the second year of N addition, which may be due to differences in light conditions between years. Trees >50 cm dbh did not respond during 2 years of N addition. As a result, the overall stem growth and above-ground woody biomass production were not affected by N fertilization. Annual total fine litterfall increased in the first year of N fertilization, while annual leaf litterfall increased in both years of N addition. Above-ground net primary production, of which total fine litterfall constituted 68%, also increased only in the first year of N addition. The magnitude and timing of response of stem diameter growth and litterfall suggest that these aspects of above-ground productivity are not uniformly limited by N availability.

We used stable isotope analysis (15N/14N) to characterize the trophic relationships of consumer communities of an aquatic food web (a permanent pond) and the adjacent terrestrial food web (secondary dry dipterocarp forest) from a seasonal tropical field site in north-eastern Thailand. In general, isotopic signatures of aquatic vertebrates were higher (δ15N range = 4.51–9.90‰) than those of invertebrates (δ15N range = 1.10–6.00‰). High 15N signatures identified water snakes and swamp eels as top predators in the pond food web. In the terrestrial food web 15N signatures of saprophagous litter invertebrates (diplopods, earthworms), termites, ants and beetle larvae were lower than in those of predatory invertebrates (scolopendrids, scorpions, whip spiders). Predatory terrestrial frogs and caecilians had lower 15N signatures than snakes, indicating that snakes are among the top predators in the terrestrial web. Based on the distribution of isotopic signatures, we estimated five trophic levels for both the aquatic and terrestrial food web. The food chains of a seasonal tropical site studied were rather short, which implies similarities to the structure of temperate food webs.

The soil of remnant primary rainforest on granite in Singapore is very acidic (pH mostly 3.5–4.2 at 0–10 cm) and has unusually low total concentrations of nitrogen and phosphorus, but the mean concentrations of N and P in the living leaves and freshly fallen leaves of the more shade-tolerant species are within the ranges found for other lowland forests on infertile oxisols and ultisols. The concentration of Ca in freshly fallen leaves is very low. The soil under secondary forest (bselukar) on sandstone dominated by Adinandra dumosa (Theaceae) was degraded during use for agriculture. It has the same pH range but even lower values of total N and P. The mean concentrations of N, P, K, Ca and Mg in the living leaves are slightly higher than in leaves of the more shade-tolerant trees of primary forest, but lower than in the leaves of the species which require canopy gaps for establishment or early onward growth. The few species sampled in both primary forest and belukar show no consistent trend in foliar concentrations. The degraded soil has selected species with inherently lower foliar concentrations.

Seed dispersal into fragmented tropical landscapes limits the rate and character of ecological succession between forest remnants. In a novel experiment in recovery of dispersal between forest remnants, 120 1-m2 seed traps were placed in fenced plots in active pasture 90–250 m from forest, and in nearby primary and secondary forests. Total seed rain from December 2006 to January 2008 included 69 135 seeds of 57 woody species. High richness of seed rain of early-successional trees occurred in all habitats, but seed rain of late-successional woody plants was much lower into pastures and secondary forest than into old-growth forest. Non-metric ordination analysis further demonstrated high movement of late-successional species within and between forest and secondary forest, but little movement of species of either forest type to pastures. Most species were dispersed by animals, but most seeds were dispersed by wind. A pattern of seed rain biased strongly towards wind-dispersed species creates a template for regeneration quite unlike that in nearby forest.

The distribution of the forest tree Pisonia grandis (Nyctaginaceae) coincides with seabird colonies on small tropical islands. Its seeds are enclosed in a calyx exuding extremely sticky resin which adheres strongly to feathers. Birds are obviously seed-dispersal vectors, but the multi-seeded infructescences frequently entangle birds, often fatally. On Cousin Island, Seychelles, I investigated the production, germination, survival, and tolerance to seawater of Pisonia seeds, and the occurrence of entanglement with birds. Fresh seeds had high germination success (62–87% in experimental trays), but seedling survival in Cousin's forests was low (0.1% of 6020 seeds survived as seedlings after 2–8 mo). Some seeds tolerated 30 min daily immersions in seawater (8–15% germination after 14–28 d treatment), but not continuous immersion in seawater (reduced germination after 5 d and none after 12 d). Inter-island dispersal is likely via living unencumbered seabirds carrying a few seeds, but not on floating carcasses. Seeds attached to carcasses did not have improved germination or survival. Intra-island propagation is almost entirely vegetative, with negligible local seed dispersal. Pisonia plants therefore do not benefit from fatal entanglements. The extreme stickiness of the seeds evidently evolved to resist removal by seabirds and so facilitate long-distance dispersal. The mortality of some potential vectors is an unfortunate consequence, but has little impact on the large populations of tree- and ground-nesting seabirds which nest in or under these trees.