A severe outbreak of Lepidoptera followed the 1997–98 El Niño Southern Oscillation event, during which the climate in central Panama was unusually dry. The outbreak involved the larvae of at least 12 species of Lepidoptera and occurred at a seasonally dry, deciduous forest site, where extensive background data were available regarding climate, tree species and non-outbreak herbivory levels. Most Lepidoptera were associated with only one or two larval host plant species belonging to the same family, and the majority were monophagous during this study. During the outbreak, caterpillar densities for the major outbreak species averaged 1.6 larvae per young leaf and 0.18 larvae per leaf for leaves of all ages. For canopy trees and lianas, the mean level of leaf damage was 13.8%, ranging from 1–100%. Seven out of 20 tree species sustained most of the damage, with 21–37% of the leaf area consumed. Relative to non-outbreak years, damage levels increased by more than 250% during the outbreak. Single-species outbreaks were observed in other areas with a similar drought, but wetter forests in central Panama did not experience outbreaks during this period. Historically, fewer outbreaks have been reported from tropical forests than from temperate forests, however, similar El Niño-related outbreaks have occurred recently in several other locations throughout the tropics.

Dominance of primary rain forests by the ectomycorrhizal, leguminous canopy tree Dicymbe corymbosa (Caesalpiniaceae) was investigated in the Pakaraima Mountains of western Guyana. In five 1-ha forest inventory plots in the Upper Ireng and Upper Potaro River drainages basal areas of D. corymbosa ranged from 38.4-52.8 m2 ha-1 (63-85% of total) among all trees ≥10 cm diameter at breast height (dbh), values in the upper range for tropical moist forests worldwide. The high basal areas for D. corymbosa were due to the prevalence of large (>150 cm dbh), multi-stemmed individuals. Stem densities in Dicymbe plots ranged from 276-433 ha-1, with D. corymbosa contributing 24.6-59.8%. In three 1-ha mixed forest plots adjacent to the Dicymbe plots, D. corymbosa was absent. In the mixed forests, stem densities were higher (480-585 ha-1), basal areas were lower (36.7-39.8 m2 ha-1), species diversity was higher, and canopy tree species were more equitably distributed than in the Dicymbe plots. Tree community composition was not qualitatively different between Dicymbe and mixed forests. In the Dicymbe plots, mean sapling and seedling densities of D. corymbosa were significantly higher than most other canopy species, indicating persistent monodominance. Edaphic variation did not account for variation in forest composition. Life history traits are discussed which may contribute to clumping in D. corymbosa, including coppicing and mast-fruiting, and the potential role of litter-trapping physiognomy and ectomycorrhiza-mediated nutrient dynamics in promoting monodominance is noted.

Relations between soil nutrient availability, the occurrence of root symbioses and tree species composition in tropical Africa are discussed in the light of new evidence. Transects from humid areas at the equator towards the deserts can be summarized as follows:

High availability of nitrogen, low availability of phosphorus, low pH and aluminium toxicity probably restrict the competitiveness of nitrogen-fixing species in the forests on highly weathered and leached soils in humid west and central Africa. Ectomycorrhizal species attain dominance in species-poor forests on the soils poorest in phosphorus, while species with vesicular-arbuscular (VA) mycorrhiza form diverse forests on more fertile soils. Nitrogen-fixing species, which mostly are VA mycorrhizal, are more common in woodlands, where nitrogen is lost in grass fires, than in forests, which have a more closed nitrogen cycle. Low availability of phosphorus, however, limits the growth of nitrogen-fixing species in moist savannas. Ectomycorrhizal species are dominant, possibly because of a competitive advantage conferred by the large storage capacity of the fungal mantles under conditions of discontinuous nutrient supply. Nitrogen-fixing species become more abundant towards drier areas with an increase in soil phosphorus and a decline in soil nitrogen. These conditions culminate at the desert fringe, where nitrogen-fixing species reach their most conspicuous development.

It is concluded that soil nutrient availability and root symbioses interact and strongly affect the composition of vegetation communities.

The central Ituri Forest of Zaïre is characterized by monodominant stands of Gilbert-iodendron dewevrei (mbau forest) within a matrix of mixed forest where Julbernardia seretii is subdominant. Both species produce supra-annual, synchronous (mast) seed crops. The relationship of mast seed production to monodominance for the two tree species was evaluated by investigating: (1) the relationship between seed density and seed survival, (2) the relative impact of mammal versus insect seed predators in high and low seed density areas, and (3) post-germination survival in the understorey. For the latter, tagged seedlings were monitored over 10 years and both species were censused in different understorey size classes. Percentage seed survival was significantly greater for Julbernardia (but not for Gilbertiodendron) in areas of high conspecific seed density. Generalist fruit- and seed-eating mammals were the principal predators on seeds of both species when removed to areas without seed-fall. In mast areas high seed densities appeared to satiate mammalian seed predators but not the specialized beetle seed predators that were the major cause of seed destruction. Gilbertiodendron seedlings survived longer in the forest understorey than did seedlings of Julbernardia. Furthermore, Gilbertiodendron made up a greater proportion of the larger subcanopy size classes in monodominant forest than did Julbernardia in mixed forests. These results suggest that, irrespective of mortality to seeds, the ability to persist in the understorey may confer on Gilbertiodendron a greater probability of reaching and dominating the canopy.

Carollia perspicillata and Sturnira lilium are two species of abundant and widely distributed phyllostomid bats. Both are frugivorous and frequently found coexisting in the same areas. A study on feeding habits and morphology of C. perspicillata and S. lilium was conducted at Serra do Japi, Sấo Paulo, south-eastern Brazil, investigating the mechanisms associated with their coexistence. The two species are fairly similar in morphology and feeding habits. Analysis of faeces produced by captured bats revealed that there is a significant difference in diet between the two species. C. perspicillata tends to specialize in fruits of the genus Piper and S. lilium specializes in Solarium fruits. The fruiting periods of the four species of Piper eaten by bats at the study site are successive, with little overlap and high productivity. The species of Solarium have long and overlapping fruiting periods, with very low productivity. Piper and Solarium provide food resources almost all year, allowing the food specialization that may be an important mechanism of resource partitioning between C. perspicillata and S. lilium.

In tropical West Africa, distribution patterns of forest islands in savannas are influenced by fires which occur regularly in the grass stratum. Along continuous forest–savanna transects in the Comoé National Park, the change in the amount and composition of non-woody phytomass was investigated from savanna to forest interior. This was correlated with the cover of vegetation strata above, soil depth, and the occurrence of seasonal surface fires. Phytomass mainly consisted of leaf litter in the forests (about 400 g m−2 at the end of the rainy season, and about 600 g m−2 at the end of the dry season) and of grasses in the savanna (about 900 g m−2). Low grass biomass appeared to be primarily the result of suppression by competing woody species and not of shallow soil. The occurrence of early dry-season fires seemed to be determined mainly by the amount of grass biomass as fuel because fires occurred in almost all savanna plots while forest sites remained unaffected. However, late dry-season fires will encounter higher amounts of leaf litter raising fire probability in forests. Due to the importance of the amount of combustible phytomass, fire probability and intensity might increase with annual precipitation in both savanna and forest.

In this study four species of the genus Shorea section Doom were investigated. All occur together as canopy trees in the Sinaraja rainforest of south-west Sri Lanka. Partitioning of the regeneration niche can be one explanation for the co-existence of ecologically similar canopy tree species within a forest. Seedlings were planted in plots located in five zones that represent a range of forest groundstorey microenvironments found adjacent to and across canopy openings of three sites – valley, midslope, ridgetop. Experiments were designed to monitor survíval and growth of planted seedlings for two years. At the end of two years percentage survival was calculated, height increment recorded and destructive samples taken to measure dry mass gain of root, stem and leaves. Comparisons were made of establishment and growth performance of seedlings planted in the different plots and sites. Results demonstrated clear differences in survival and growth among species. These differences appeared related to availability of soil moisture and groundstorey radiation regimes. Disturbance patterns that determine species co-existence are suggested.

Plants potentially compete for seed dispersal. Selection may favour temporally segregated fruiting phenologies to minimize this competition and also to maintain resident populations of dispersal agents. Alternatively, selection may favour temporally aggregated fruiting phenologies when the effectiveness of seed dispersal agents varies seasonally or when large, synchronous fruit displays enhance dispersal. These evolutionary scenarios assume that plants share seed dispersal agents. This assumption and temporal overlap in fruiting phenologies were evaluated for the Miconia and Psychotria of central Panama. These two genera accounted for 18 and 27%, respectively, of 1096 fleshy fruits found in regurgitation or faecal samples taken from 2054 birds of 103 species netted in the forest understorey. Two species of manakins accounted for 62% (123/200) of all Miconia fruit taken. Three species of manakins and three species of migratory thrushes accounted for 97% (282/292) of all Psychotria fruits taken. There is a high potential for intrageneric competition for seed dispersal for both plant genera. Null model analyses showed that the fruiting phenologies of Miconia (14 species) are segregated in time, while fruiting of Psychotria (21 species) is highly aggregated. The Miconia were found in up to 24% of the diet samples for the two manakin species, suggesting that Miconia may be a critical resource for both species. The Psychotria fruited when the diversity of understorey fruits was greatest, suggesting a high potential for both intra- and extrageneric competition. The abundance and nomadism of the six bird species that consumed most Psychotria fruit peaked when the Psychotria fruited, supporting the enhancement hypothesis.

The movement and habitat utilization patterns were studied in an Asian elephant population during 1981–83 within a 1130 km2 area in southern India (11° 30′ N to 12° 0′ N and 76° 50′ E to 77° 15′ E). The study area encompasses a diversity of vegetation types from dry thorn forest (250–400 m) through deciduous forest (400–1400 m) to stunted evergreen shola forest and grassland (1400–1800 m).

Home range sizes of some identified elephants were between 105 and 320 km2. Based on the dry season distribution, five different elephant clans, each consisting of between 50 and 200 individuals and having overlapping home ranges, could be defined within the study area. Seasonal habitat preferences were related to the availability of water and the palatability of food plants. During the dry months (January-April) elephants congregated at high densities of up to five individuals km-2 in river valleys where browse plants had a much higher protein content than the coarse tall grasses on hill slopes. With the onset of rains of the first wet season (May-August) they dispersed over a wider area at lower densities, largely into the tall grass forests, to feed on the fresh grasses, which then had a high protein value. During the second wet season (September-December), when the tall grasses became fibrous, they moved into lower elevation short grass open forests.

The normal movement pattern could be upset during years of adverse environmental conditions. However, the movement pattern of elephants in this region has not basically changed for over a century, as inferred from descriptions recorded during the nineteenth century.

In comparison with the Neotropical big cats, jaguar (Panthera onca L.) and puma (Felis concolor L.), medium and small felids are poorly studied. Furthermore, studying wild felids in forest habitats is extremely difficult using direct methods given that most species are principally nocturnal and secretive (Gittleman 1996). Indirect methods are therefore particularly important, e.g. radio-telemetry (Emmons 1987, 1988; Konecny 1989, Ludlow & Sunquist 1987) or camera trapping (Maffei et al. 2002, Trolle & Kéry 2003). Using systematic camera trap surveys, we compare the population density of ocelots (Felis pardalis L.) across five Bolivian dry-forest sites with different habitat types and/or annual rainfall regimes (Table 1). We hypothesize that ocelot densities will decline as rainfall declines. In addition, we estimate the population of ocelots in the 34 400-km2 Kaa-Iya del Gran Chaco National Park. Finally, we describe and evaluate additional ecological information provided by camera trapping: activity patterns relative to seasonality and moon phase, sex ratios, ranging patterns and relative abundance compared with sympatric felids.

Two stands of mature evergreen wet forest in Mauritius (Mascarene Islands) were sampled for floristic composition to assess the extent of invasion by weedy exotic phanerogams (Brise Fer, 550 m alt.; Bon Courage, 200–260 m alt.). All individuals ≥ 2.5 cm dbh were recor ded in 50×2 m transects totalling 0.1 ha at each site, and 2×2 m seedling plots totalling 40 m were also sampled at each site. Both forests showed a high degree of invasion. Although exotics constituted only 5% of woody species ≥ 2.5 cm dbh at Brise Fer and 14.5% at Bon Courage, they comprised 34.8% and 20.8% of the individuals, respectively. Seedling plots at both sites were dominated by exotics, which comprised 20.6% of the species and 97.4% of the individuals at Brise Fer, and 22.2% of the species and 73.9% of the individuals at Bon Courage. Comparisons are made with Macabé forest, sampled nearly 50 years ago. These data suggest that unless steps are taken to check the spread of exotics, floristic composition at these sites will shift towards total invasion and degradation as has occurred elsewhere on Mauritius.

For analysing field data as well as for modelling purposes it is useful to classify tree species into a few functional types. In this paper a new aggregation of tree species of the dipterocarp rain forests in Sabah (Borneo), Malaysia, is developed. The aggregation is based on the two criteria successional status and potential maximum height. Three classes of successional status (early, mid and late successional species) and five classes of potential maximum heights (≥ 5 m, 5–15, 15–25, 25–36, > 36 m) lead to a combination of 15 functional types. The criteria of the developed classification are chosen to suit for applications with process-based models, such as FORMIX3 and FORMIND, which are based on photosynthesis production as the main process determining tree growth. The concept is universal and can easily be applied to other areas. With this new method of grouping a more realistic parametrization of process-based rain forest growth models seems to be possible.

We examined the effects of the 1997–98 El Niño drought on nine rain forests of Mount Kinabalu, Borneo, at four altitudes (700, 1700, 2700 and 3100 m) on contrasting geological substrata (ultrabasic versus non-ultrabasic). Measurements of rainfall and atmospheric aridity indicated that the departure from normal conditions during the drought became greater with increasing altitude. During 1997–99 (drought period) compared to 1995–97 (pre-drought period), median growth rates of stem diameter of trees decreased for both smaller (4.8–10 cm) and larger (≥ 10 cm) diameter classes in the six upland forests (≥ 2700 m on ultrabasic substrata and ≥ 1700 m on non-ultrabasic substrata), but for neither diameter class in the other forests. The majority of species decreased or did not change growth rates during 1997–99, whereas some did increase. Tree mortality increased during 1997–99, at the larger diameter class in the two lowland forests (700 m) on both substrata, and at least at the smaller diameter class in the four upland forests (≥ 1700 m) on non-ultrabasic substrata. In two of these upland forests, mortality was restricted to particular understorey species. Mortality did not significantly increase in the three upland forests (≥ 1700 m) on ultrabasic substrata; this suggests that the adaptation to nutrient-poor soils might have provided the resistance to drought.

The arthropod fauna inhabiting 90 individuals of three different species of epiphyte was investigated in the moist lowland forest of the Barro Colorado National Monument in Panama. In total, 3694 arthropods belonging to 89 morphospecies and 19 orders were collected. While arthropod abundance was primarily a function of host plant biomass irrespective of epiphyte species, there were pronounced differences in species richness, species composition and guild structure of the arthropod faunas of the three epiphyte species. Although all study plants were growing in close proximity on the same host tree species, there was remarkably little overlap in the species assemblages across epiphyte taxa. The inhabitant species also differed dramatically in their ecological functions, as feeding guild and hunting guild analyses indicated. The influence of plant size, structure and impounded leaf litter on arthropod diversity is discussed. We conclude that epiphytes are microhabitats for a diverse and numerous fauna, and that different species of epiphytes foster both taxonomically and ecologically very distinct arthropod assemblages.

An attempt was made to evaluate the consequences of applying a strict definition (Brokaw 1982a) to the delimitation of forest gaps in the field. The northernmost Neotropical rain forest, at Los Tuxtlas, Mexico, was searched for young (1–2 years old) single-event gaps that would meet the criteria of the definition. In 60 ha of rain forest, only 12 such gaps containing pioneer species could be found. Thirty-three pioneer species (shrubs and trees) were used as indicator species for gap conditions. Gap size, measured as projected canopy opening (sensu Brokaw 1982a), underestimated from 44 to 515% the size of the area colonized by pioneer species. On average the size of the colonized area was 3.4 times larger than the size of the projected canopy opening. The majority of the pioneer species showed a relative preference for gap borders, an area generally not included in the projected canopy opening. Pioneer plant abundance and density, and species richness and density, did not differ significantly between gap centres and gap borders. Floristical variation was not related to gap size or location in the gap. These findings can be explained if gap environment (to which pioneer plants respond) is seen as the result of many interacting factors, of which size of the canopy opening is only one. It is concluded that the definition for delimiting gaps in the field as proposed by Brokaw (1982a) cannot be regarded a generally applicable definition, and that its value as a comparative standard is doubtful.

Throughfall volume and interception of bulk precipitation events were measured during individual rain events of differing magnitudes in a primary wet tropical forest at La Selva Biological Station, Costa Rica. The relationship between canopy structure and throughfall were examined to identify key sources of spatial variation. Geostatistical analyses were also used to examine the spatial variation in throughfall, spatial autocorrelation and to determine minimum distances for independence of collectors. Throughfall volume was collected from 56 ground-based (funnel-style) collectors. Throughfall was collected for 26 separate precipitation events during July and August 1998. Per cent cover, distance to nearest tree, distance to nearest leaf were also estimated for each collection point. A weak relationship was found with per cent cover (r2 = 0.11). No relationship was found between throughfall and distance to the nearest leaf above the collector. Estimated interception was 1.88 mm (r2 = 0.94) with increased variance as bulk precipitation increased. A range distance of 45 m was estimated from variograms, strongly suggesting that large tree canopies and gaps are the source of much of the spatial variance in throughfall volume. Interception was reduced by 19% if only spatially independent collectors were used.

Vegetative regeneration is an important component of forest recovery after disturbance. This study focused on the role of resprouting, both as root suckers and above-ground sprouts in comparison to seed regeneration (plants 30–130 cm tall), under different disturbance regimes, pattern with successional age and importance in mature forest. Differently aged forest fallows, a fire-degraded stand (Paraguay), differently aged logged stands (Venezuela) and mature forest in both sites were selected. In Paraguay, the percentage of resprouts declined from 76% in the young forest fallows (2–5-y old) to 48 and 14%, respectively, in the older forest fallows (10 and 15-y old) and mature forest. In Venezuela, by contrast, the proportion of resprouts from the youngest logged stand (5-y old) to the oldest logged stand (19-y old) and mature forest slightly increased from 10 to 16% and 17%, respectively. Root suckers were more common than above-ground sprouts in any of the sampled stands. In forest fallows, 38% of all species possessed both modes of regeneration, while 20 and 18%, respectively, were either found with above-ground sprouts or root suckers. In the fire-degraded stand, most resprouting species were observed with root suckers (28%), whereas species represented with either above-ground sprouts or both modes of vegetative regeneration were less common (7 and 14%, respectively). In logged stands, species reproducing by both means of vegetative regeneration were more frequent (20%) than the other groups (14 and 8%, respectively). In the mature stands in Paraguay and Venezuela, 42 and 14% of the species, respectively, were found with either or both modes of vegetative regeneration. In both sites, significant differences in the ability to resprout between growth forms were found. Of 301 resprouting individuals in Paraguay, 114 were found to be uncut stems, of these 108 produced root suckers andsix above-ground sprouts.

ABSTRACT. The spatial heterogeneity of element fluxes was quantified by measuring litterfall, throughfall and litter decomposition for 1 y in 30 randomly located sampling areas in a lowland dipterocarp rain forest. The idea tested was that turnover of elements is more variable than turnover of dry matter in a forest with extremely high tree species diversity. In spite of the low fertility of the soil (an ultisol), total litter production (leaves, trash, and wood <2 cm in diameter) was high (1105 g m−2 y−1) with inputs to the forest floor of carbon, nitrogen, phosphorus, calcium, magnesium, potassium, manganese and iron of 550, 15.3, 0.47, 6.26, 2.49, 4.75, 0.95 and 0.14 g m−2 y−1 respectively. Throughfall was 81% of the annual rainfall and transferred 22.2, 1.37, 0.14, 1.07, 0.67, 0.39, 7.92, <0.06, and <0.06 g m−2 y−1 of organic carbon, nitrogen (all forms), phosphorus, sulphur, calcium, magnesium, potassium, manganese and iron, respectively. Average turnover rates of nutrients in litter were highest for potassium and decreased in the sequence calcium, magnesium, carbon, nitrogen and phosphorus. Concentrations of phosphorus, nitrogen and potassium in litterfall, litter mass and topsoil were closely correlated with each other. Concentrations of calcium and manganese were positively correlated with each other and with elevation. Variations in leaf chemistry and total litterfall caused the spatial heterogeneity of element input to the forest floor to have a coefficient of variation of 30 — 70%, depending on the element. Due to the strong positive correlation between element fluxes and pools, the spatial variability of turnover rates (CV c. 20%) was lower than that of element input. Turnover rates for K varied by a factor of 4, and for Ca by a factor of 2.8 when the different sites were compared. The results strongly suggest that the most important factor determining spatial heterogeneity of organic matter and element dynamics on the forest floor is the site-specific amount of leaf fall, rather than spatially variable decomposition rates.

This study describes forest succession following slash-and-burn agriculture in central Amazonia, based on four chronosequences (22 sites) of 2- to 25-y-old secondary regrowth and mature forest. Biomass accumulated in the form of a saturation curve: 25 y of regrowth restored half of the mature-forest biomass, 75% would be restored after an estimated 175 y. Biomass accumulation was accompanied by a rapid decrease in woody plant density and an increase of the positive skew of plant size distribution. Liana biomass share declined from 5.0% in young to 1.9% in old regrowth, and 1.3% in mature forest, whereas the share of palms was low (0.5%) in young regrowth and high in old regrowth (1.8%) and mature forest (2.2%). 25-y-old regrowth was similar with mature forest in respect to woody plant density and growth-form composition, but both the plant size distribution and the number of stems per plant differed strongly from mature forest. A moderate increase in land use had only minor effects on biomass accumulation, but profoundly changed structural characteristics of regrowth, pointing to a high vulnerability to degradation. Thus, the sustainability of slash-and-burn in central Amazonia may be lower than the rapid initial biomass accumulation would make it seem.

Patterns of species composition in a neotropical termite assemblage were studied in relation to early effects of forest fragmentation as well as other sources of environmental and spatial heterogeneity. Termite diversity surveys were carried out at three mainland forest sites, and 10 islands of varying size, in an area of lowland tropical forest that had been flooded 4 y earlier, during the creation of the Petit Saut hydroelectric project in French Guiana. The ‘ghost forest’ of dead emergent trees in the flooded zone was also studied for its influence on island termite assemblages. Results suggested that the effects of forest fragmentation upon the total assemblage, and upon soil-feeders in particular, were subordinate to the influence of forest understorey palm density, and the closely associated gradients of soil humus depth and soil pH. Moreover, gradients for these three variables were uncorrelated with forest fragmentation and probably reflected spatial environmental heterogeneity pre-dating inundation events. Nevertheless, factors associated with forest fragmentation appeared to have had a significant effect on changes in termite species composition across the study site, primarily in structuring the wood- and leaf-litter-feeder assemblage. Effects upon the latter were not apparently a result of influx of species from the ghost forest. Purely spatial variation also influenced β-diversity changes in species composition across the site. In conclusion, the effects of forest fragmentation upon termites appear to have been relatively mild compared with other faunal groups, 4 y after flooding. Nevertheless, we predict that the effects of fragmentation on termite assemblages will ultimately be negative. This study also points to the importance of Amazonian understorey palms in structuring a tropical forest termite assemblage.