Both vertebrate- and wind-dispersed seeds moved farther from rain forest into old field than from old field into forest. Vertebrate-dispersed seeds from the rain forest moved farther into the field than wind-dispersed seeds, but seeds of both types moved similar distances from field into forest.

Habitat structure affected seed deposition patterns in the field, where shrubs provided perches for flying vertebrates. Vertebrate-dispersed seed deposition was significantly greater, and deposition of plumed, wind-dispersed seeds was significantly less, under shrubs than in the open. Deposition of vertebrate-dispersed seeds under fruiting shrubs was significantly less than under non-fruiting shrubs.

Cerrado is a species-rich savanna-like vegetation that covers a large area in central Brazil. Soil, and particularly soil fertility, is considered to be the major factor determining the wide and diverse physiognomic-floristic gradients encountered within cerrado vegetation. To describe the vegetational variations within a cerrado in southern Mato Grosso state (15° 21'S, 55° 49'W), a 1 ha transect was located to pass through an interfluvial cerrado and climb a steep talus slope. The vegetational and environmental variations are described by means of field classification, direct gradient analysis and reciprocal averaging ordination. The effects of differences in ground water regime in the interfluvial cerrado and differences in inclination with associated rockiness in the talus cerrado are related to the vegetational variations. As the soils are very similar in texture and in the majority of chemical properties, the role of the above environmental factors was more easily distinguished. In the interfluvial cerrado, the vegetation variations are probably related to the seasonal fluctuation in water table level.

Site data from 291 forest inventory plots in Mixed Dipterocarp Forest in central Sarawak were simplified by factor analysis. The distribution of the 33 commonest canopy tree species was related to site factor scores by ‘t’ tests. There appears to be a degree of edaphic influence on the distribution of many species. Fairly constant soil characteristics related to the lithology of the parent material appear to be more important than ephemerally variable pro perties such as organic matter or exchangeable cations. Magnesium appears to be particularly important, possibly because of an effect on the capacity of mycorrhizal root systems to absorb phosphorus.

Photosynthesis was limited by low-intensity photosynthetically active radiation (PAR) and leaf wetness in a lower montane cloud forest (LMCF) of Cauca, Colombia. Mean PAR intensity remained below the saturation level for leaf-scale net photosynthesis (Pn) throughout the solar day during the wet season and for most of the solar day during the dry season. PAR represented a smaller fraction of total solar radiation (K↓) in LMCF than in lowland rain forest (LRF). In LMCF trees and shrubs, mean PAR-saturated Pn ranged from 4.3–10.6 μmol C m−2 s−1 at 1450 m, and from 3.5–10.2 μmol C m−2 s−1 at 2150 m. Pn was reduced by abaxial wetness in leaves of some trees and shrubs, and eliminated in others. This study indicates that persistent cloudiness and interception of cloud water by leaves limit LMCF productivity.

The floral biology and pollination ecology of durian, Durio zibethinus, were determined in eight semi-wild trees in mixed-fruit orchards in southern Thailand during April-May 2003 and 2005. Flowers open fully at 16h00–16h30 and most androecia drop around 01h00. Anthers dehisce at 19h30–20h00 when the stigmata are already receptive. In a series of pollination experiments, fruit was set in all treatments within 10 d. The greatest pollination success occurred after hand-crossed (76.6%), open (54.4%) and emasculation pollination (53.3%). Consistently, hand-crossed (12.2%), emasculation (8.7%) and open pollination (5.1%) yielded a substantial fruit set 2 mo after the pollination experiments. Very low pollination success in facilitated autogamy suggests that most durian trees are highly self incompatible. No mature fruit was found after insect pollination and automatic autogamy. Fruit bats, especially Eonycteris spelaea, are the major pollinators of this durian although the giant honey bee (Apis dorsata) was the most frequent visitor to the flowers. Bats visited durian flowers at the rate of 26.1 (SD = 20.7) visits per inflorescence per night. Since this semi-wild durian depends on fruit bats as its pollinator, protecting fruit bat populations and their roosts is vital for the production of the durian fruit crop.

Throughfall and soil solution chemistry were studied for 1 y in a tropical montane forest in the Luquillo Mountains of Puerto Rico. Passage of precipitation through the forest canopy resulted in an increase in the concentration and flux of all solutes except H+ and NO3−. Throughfall chemistry showed no strong seasonal patterns, but concentrations of many solutes declined during weeks of high rainfall. Enrichment in throughfall relative to precipitation was similar to values reported recently for several other tropical sites, with the exception of NH4+, which was particularly high at this site. Based on net throughfall deposition of Cl−, dry deposition of marine aerosols appears to be a relatively minor component (c. 15%) of total deposition. In soil solution, no seasonal patterns in concentration were evident and variability was highest for elements with high biological activity (especially N). Concentrations and fluxes of K+ and dissolved organic carbon (DOC) showed the largest declines as throughfall passed through the soil profile; concentrations of most other elements increased or were relatively constant. Declining DOC flux through the soil profile appears to be due to sorption processes similar to those observed in many temperate forests. Concentrations and fluxes of HCO3− and SiO2 increased substantially in soil solution, but never approached those observed in the stream. This suggests that additional weathering must occur as groundwater moves from this ridgetop site to the stream.

Archival rainfall data are used to investigate changes in drought frequency and severity in Sabah and other parts of northern Borneo since the late nineteenth century. Two measures of drought severity are used: drought duration (given by the number of consecutive months with less than 100 mm rain); and drought intensity (indexed by the cumulative rainfall deficit below 100 mm per month of a drought sequence). Within northern Borneo dry periods are very short (>3 months) and infrequent in Sarawak, south-western Sabah, Brunei and central and western Kalimantan; droughts occur seasonally, but are comparatively short in north-western Sabah; droughts are less frequent) but more severe in eastern Sabah and parts of eastern Kalimantan. In coastal Sabah and Brunei, there has been a statistically significant increase in the frequency and severity of droughts since the late 1960s. At Sandakan, two drought-prone epochs in 1877–1915 and 1968–92 (each experiencing five droughts of at least 4 months duration) are identified, separated by a 52-year period that was nearly drought-free. At Sandakan also, the ecologically damaging 1982–3 drought was neither as long or severe as those of 1903 and 1915. Links with El Niño-Southern Oscillation events are found to be not as strong as previous studies have suggested. Possible implications of the spatial and temporal patterns in drought magnitude-frequency for differences in tropical rain forest character within the region are discussed.

Hong Kong has a native angiosperm flora of approximately 1800 species, of which 27% (482 spp.) bear fleshy, presumably vertebrate-dispersed fruits, including 76% of the 337 tree and shrub species and 70% of the 103 climber species. Morphological characteristics were determined for 255 species and nutritional characteristics of the fruit pulp for 153 species. Most fruit species were black (45.1%) or red (24.3%) and 85.9% had a mean diameter <13 mm. Nutritional characteristics varied widely between species with ranges and median values as follows: pulp percentage (range 10.0–99.2%, median 69.2%), water content of pulp (11.1–94.0%, 78%), lipid (0–84.0%, 2.0%), soluble carbohydrate (4–88%, 53%), nitrogen (0.2–3.4%, 0.86%), neutral detergent fibre (1–44%, 14.3%). Fruit development time (50–360 d, 156 d) showed a negative correlation with lipid content, but no significant correlation with fruit or seed size. Principal components analysis of fruit characteristics was dominated by a trend from single-seeded fruits with a thin, lipid-rich pulp layer to multiple-seeded fruits with much, watery, carbohydrate-rich pulp. Birddispersed species cover the full range of fruit characteristics except those too large to swallow and too hard to peck bits from. Mammals (bats, civets and/or macaques) are known or suspected to consume most of the fruits too large for birds as well as many bird fruits but none with high-lipid content. Summer fruits (May—September) were significantly larger and had significantly higher seed size and carbohydrate content than winter fruits (November-March). Winter fruits took more than twice as long to develop as summer fruits.

Bee colonies in lowland forest in Panama were monitored for pollen and nectar harvest, pollen species utilization and nectar quality and quantity per returning forager. Despite sharing most pollen resources and nectar of the same quality with 20 introduced colonies of the African honey bee (Apis mellifera), native stingless bees of 12 species were largely unaffected by its activity. Pollen and nectar harvested by the honey bees were 10–200 times that procured by 17 stingless bee colonies. This discrepancy in total harvest and general lack of competitive effect is explained by a honey bee foraging area over 10 times that of the native bees, and apparent foraging shifts to escape competition with honey bees, thus reduced potential overlap in foraging sites.

Seven cases of direct resource competition for pollen or nectar were documented, out of 31 tests. Rare periods of intensive harvest were diminished by competing African honey bees. Such harvest peaks lasted for only a few hours in 13 days of observation. Despite average duration of 4% foraging time for each species, peaks included as much as 51% total harvest. Calculations based upon colony populations, food stores and flight range show that if African honey bees persist at a density of 1 colony per km2, colonies of some stingless bee species may disappear after 10 years. Their chances of escaping food competition by taxonomic specialization on flowers seem slight.

This study provides a community-level analysis of how regeneration requirement and adult stature are related to tree allometry (diameter, height and crown size) throughout post-seedling ontogeny on Barro Colorado Island, Panama. Comparing 65 species, gap species are taller, have higher diameter growth rates and occupy more low-canopy sites (≤10 m canopy height) than shade species at small diameters (≤10 cm dbh). For trees >10 cm dbh, diameter-height relationships and growth rates no longer differ between gap and shade species, but shade species have larger, particularly deeper, crowns than gap species. Species with tall adult stature have more slender stems with larger crowns compared with treelet and mid-canopy species starting at 5 cm dbh. From 10 to 40 cm dbh, diameter growth rate is also significantly greater for tall species. The consistent allometric differences between functional groups on a community level will, in part, determine vertical and horizontal stand structure.

Treefalls gaps contribute to the habitat heterogeneity of tropical forest floors. Previous studies have shown that these gaps play an important role in plant and bird communities, however less is known about their role in arthropod communities. Using eight Malaise traps we investigated the difference in arthropod abundance of 19 taxonomic groups between gaps and understorey for 21 wk during the rainy season and 8 wk in the dry season on Barro Colorado Island, Panama. More (33.8%) arthropods were collected in gaps during the rainy season and 32.2% more in the understorey during the dry season. To assess the possible factors contributing to these differences we measured light, plant densities and young leaf densities, as indicators of abiotic factors and food resources for insect herbivores. Arthropod abundance was negatively correlated with light in the dry season. Thus, abiotic stress may explain the pattern of abundance in the dry season. While there was no correlation with light in the rainy season, predator abundance was positively correlated with herbivore abundance. The plant and young leaf density data suggest that there is significantly higher food availability for herbivores in gaps. Thus, less stressful abiotic conditions and more food resources may contribute to more herbivores followed by more predators in gaps during the rainy season.

The frugivorous phyllostomid bat Carollia perspicillata is closely associated with specific fruits which are found and picked in flight, then eaten at a feeding roost. Each fruit eaten corresponds to a single flight. An apparatus designed for this study permits the simultancous tracking of 10 bats equipped with double rhythm transmitters (slow rate corresponding to resting position and rapid rate to flying bouts). (1) The number of flights, (2) the percentage time spent flying and (3) the range of activity were recorded for different categories of animals during two periods of fruit production. Heavier males displayed high activity, while other males, non-breeding females and females in early pregnancy displayed a similar pattern of flying behaviour. Full-term pregnant females and lactating females performed almost as many flying bouts as non-reproductive females, but these flights were much shorter. This unexpected feeding strategy can be interpreted as a means of shifting energy to reproductive effort from exploratory behaviour (non-breeding females performed longer flights which combine the survey of environment and the fruit collection). This strategy, based upon the optimization of flying bouts, is in contrast to those of non-flying mammals and probably is only compatible with periods of high food production.

Plots in the Jamaican montane forest were fertilized with nitrogen or with phosphorus to test the hypothesis that growth of trees in this natural forest is limited by the supply of N and P from the soil.

Once a year from 1983 to 1986, urea was added to one plot (at 150 kg N ha−1 y−1) and triple superphosphate was added to another (at 50 kg P ha−1 y−1). In each of these plots and in two control plots, foliage of four common tree species was collected immediately before each fertilizer addition. Trunk growth was measured in 105 individuals.

Foliar N concentrations were not significantly higher in trees fertilized with N compared to control trees. In Dendropanax cf. pendulus and Hedyosmum arborescens fertilization with N resulted in lower P concentrations but only after the third year of fertilization, possibly due to dilution by increased leaf production. Mean trunk diameter growth was significantly higher in the N-fertilized trees than in controls.

Mean foliar P concentrations were higher in Podocarpus urbanii and Clethra occidentalis following fertilization with P, but only after two years of fertilization. Trunk diameter growth was greater in the P fertilized plot.

Thus growth in some Jamaican montane forest trees was limited by the natural supplies of N and of P.

Continuous litterfall measurements were made from 1977 to 1982, at two sites with contrasting topography in a mature tropical deciduous forest in Chamela, Jalisco, on the Pacific Coast of Mexico (19° 30′ N, 105° 03′ W). The climate is strongly seasonal with the annual rainfall (x = 748 mm) concentrated in six months (June to November) and a mean annual temperature of 24.9°C. Results of the five-year study show that at the Valley Site (slope <5°) the mean annual litterfall was 6.58 ±0.15 (SE) Mg ha−1 y−1 composed of 73.3% leaves, 17.1% woody material, 5.6% reproductive remains and 4.0% finely fragmented debris. At the Hill Site (slope 20°–40°) mean annual litterfall was 3.95 ± 0.16 Mg ha−1 y−1, consisting of 68.8% leaves, 17.0% woody material, 9.4% reproductive remains and 4.7% fragmented debris. At the Valley Site the year-to-year variation in total litterfall was not significant. In contrast, at the Hill Site it fluctuated markedly from year to year. Litter production exhibited a pronounced seasonally: at the Hill Site total litterfall peaked near the onset of the dry season; at the Valley Site it occurred two months later, apparently as a result of differences in soil moisture availability between the study sites.

Concentration of CO2, above and below the soil surface and δ13C values of plant tissues, soil litter and organic matter were measured in a caatinga forest of the upper Rio Negro basin in southern Venezuela. CO2, concentrations near the forest floor were consistently higher than in the atmosphere. CO2, gradient in the soil was very steep probably because of the poor aeration in this flood-prone forest. δ13C values of plant tissues showed a clear pattern with lower values in the ground herbaceous plants and under-canopy trees. Tree seedlings showed δ13C values similar to the upper-canopy trees indicating their dependence on reserves carried in the seed from the mother tree. Decomposing litter and soil organic matter also showed δ13C values similar to the upper-canopy trees. It is suggested that lower δ13C values of the shade flora result primarily from the assimilation of CO2, depleted in δ13C originating from soil respiration. Probable effects of low light intensity and physiological factors are discussed.

Geophagy (soil eating) by the forest elephant (Loxodonta africana cyclotis) and other mammal species in the Dzanga National Park, Central African Republic, has led to large treeless licks. The geological and physical properties of these licks were studied and the chemical characteristics and particle sizes of geophagical lick soils were compared with soils from the forest and from licks where evidence of geophagy was absent. Average lick size of 20 licks in the Hokou lick area was 12,900 m2 (SE = 3,400 m2). Licks were situated exclusively in areas of outcropping dolerite intrusions. Physico-chemical analysis of the geophagical lick soil showed significantly higher quantities of sodium, potassium, calcium, magnesium, phosphorus, manganese and clay compared with the other soils. Several samples of the geophagical lick soil had lower nutrient levels than the mean level of forest topsoil, indicating that nutrient supplementation is probably not the only reason for geophagy. The high clay content of the geophagical soil may help absorbing and combating secondary plant compounds. Pronounced geophagy in rainforests may be a sign for poor habitat quality for large mammals living in these ecosystems.

We measured macronutrient concentrations in soils and leaves of trees, shrubs and herbs at 1900, 2400 and 3000 m in an Ecuadorian tropical montane forest. Foliar N, P, S and K concentrations in trees were highest at 1900 m (21.7, 2.2, 1.9 and 10.0 mg g−1). At 2400 and 3000 m, foliar concentrations of N, P, S and K were similar to nutrient concentrations in tropical trees with apparent nutrient deficiency, as presented in literature. Unlike foliar nutrient concentrations, the amounts of plant-available nutrients in mineral soil were not affected by altitude or increased significantly with increasing altitude. High C:N ratios (25:1 at 2400 m and 34:1 at 3000 m) and C:P ratios (605:1 at 2400 m and 620:1 at 3000 m) in the soil organic layer suggested slow mineralization of plant litter and thus, a low availability of N and P at high altitudes. Foliar N:P ratios were significantly higher at 2400 m (11.3:1) than at 3000 m (8.3:1), indicating that at high altitudes, N supply was more critical than P supply. In conclusion, the access of plants to several nutrients, most likely N, P, S and K, decreased markedly with increasing altitude in this tropical montane forest.

The mountain gorilla (Gorilla beringei beringei) lives in two geographically separated populations, Bwindi Impenetrable National Park, Uganda and in three national parks spanning the Virunga mountain region in Rwanda, Democratic Republic of Congo, and Uganda. The altitude, climate and plant composition of these habitats differ. Our goal was to compare the diets of gorillas living in each of these habitats. The nutrients in staple foods and in the diets of individuals in a group of gorillas in Bwindi (N = 12 individuals) and a group in the Virungas (N = 7 individuals) were compared to determine if differences in dietary composition affected concentrations of nutrients in their diets. At both sites gorilla diets consisted primarily of herbaceous leaves, but the diet of Bwindi gorillas contained more tree leaves, fruit, pith and dry wood, and fewer stems. Despite differences in habitat and dietary composition, the nutrient concentrations in both gorilla diets were remarkably similar. On a dry matter basis, the diets and staple foods of Bwindi and Virunga gorillas contained similar concentrations of crude protein (CP), fibre (NDF) and non-structural carbohydrates (TNC). Bwindi gorillas ate diets containing 18% CP, 43% NDF and 19% TNC on a dry-matter basis, while the diets of the Virunga gorillas contained 17% CP, 41% NDF and 18% TNC. Our results demonstrate that gorillas consume diets that differ by plant species and part, but contain similar concentrations of nutrients. This suggests that classifying animals by broad dietary strategy (e.g. frugivory and folivory) does not provide a reliable indicator of the nutritional quality of their diet, and that our previous assumptions about these categories should be re-evaluated.

The suitability of several methods for estimating light conditions in the understorey of tropical forests, and of different sampling schedules was evaluated. Light conditions at 16 understorey sites in a Panamanian lowland forest were continuously measured for 9 mo with quantum sensors and photodiodes. Light conditions at the sites were also assessed indirectly with hemispherical fisheye photographs, plant canopy analysis, 38-mm photographs, 24-mm photographs and a spherical densiometer. Estimates from all indirect methods, except the spherical densiometer, were highly correlated with the direct measurements. Short-term direct light measurements for a day or a week also correlated with long-term light conditions. The indirect measures differed by up to c. 70% from the direct measures relative to single site measurements. Hence, the indirect methods are inadequate where single site light conditions have to be assessed accurately. However, because light conditions encountered in the understorey varied up to 13-fold, the indirect methods were found to be well suited to rank understorey light conditions among a large number of sites. The results from frequent and infrequent sampling schedules differed only slightly, suggesting that taking indirect measures at the beginning and the end of a study offers a reasonable compromise between accuracy and sampling effort.

Patterns of insect herbivore and leaf pathogen attack are described for 25 plant species (10 trees, 10 shrubs and five herbs) at a Brazilian savanna (cerrado) site. Plant and leaf traits were correlated with interspecific variation in attack by herbivores and pathogens in order to account for differences among plant species. Across all species, pathogen damage was 1.5 times higher than insect damage (17.3% vs. 6.8%, respectively). Most insect damage occurred to young leaves while they were expanding (end of the dry season). In contrast, pathogen attack was low on young expanding leaves at the end of the dry season, increased as those leaves matured in the wet season, but continued to increase through the next dry season. Protein-binding capacity was negatively associated with interspecific differences in insect damage to mature leaves. Protein availability and plant height were positive predictors of pathogen attack among plant species, while leaf expansion rate was a significant negative predictor. Interspecific differences in leaf phenology had little effect on the amount of damage caused by either insects or pathogens. However, new leaves produced during the wet season suffered less insect damage than leaves produced during the dry season, the time of greatest leaf production. Timing of young leaf production affected pathogen attack but the season of escape depended on plant species. In contrast, there was no evidence for escape in space as common species were less likely to suffer high pathogen attack than rare species. New and mature leaf toughness, and time for a leaf to reach full expansion all increased from herbs to shrub to trees, while mature leaf nitrogen decreased in that order.