Life table studies were conducted on the flowers, pods and seeds of the tree Pithecellobium pallens to assess the extent of damage by the seed predators Stator limbatus and Merobruchus insolitus (Coleoptera: Bruchidae). Brachyacma palpigera (Lepidoptera: Gelechiidae) was also found to feed on the seeds of this tree. Seed predation and herbivore damage destroyed 41% of the seeds. Pods were taken to the laboratory and seed predators within were reared and identified. B. palpigera and M. insolitus were major causes of mortality, whereas damage by S. limbatus was slight. The growth ratio of pods to seeds did not indicate a rapid development of seeds as an evasive strategy against bruchid attack. Experiments showed no successful attack by bruchids on seeds exposed on the ground after dispersal from the tree.

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.

Differences in rainfall between years influenced the proportions of different types of nesting habitats of Caiman crocodilus yacare available near water bodies in a region of intermittent rivers (Campo Dora Ranch). In contrast, rainfall had little effect on the proximity of nesting habitat to water bodies in a region of isolated lakes (Nhumirim Ranch). There was a strong positive correlation between female body size and clutch size Snout-vent lengths of females on Campo Dora Ranch were significantly larger than those from Nhumirim Ranch which probably accounts for the larger mean clutch size than in the region of isolated lakes. Hatchling size was correlated with egg size, but there was no relationship between egg size and female size or egg size and clutch size.

Nothofagus species dominate small patches of rainforest on ultramafic soils in New Caledonia, forming an almost monospecific upper canopy on some sites. These stands are commonly bordered by rainforests of greater floristic and structural complexity, also on ultramafic soils. In two lowland stands, the population size structures of Nothofagus aequilateralis stems greater than 50 cm high had an approximately skewed bell-shaped distribution with a modal size class of 15–25 cm stem diameter, and with no evidence of old trees. This indicates that the establishment of Nothofagus has occurred over a limited time span, without sufficient recent regeneration to allow the future replacement of the existing canopy trees. The factors initiating the major period of regeneration are not certain, but large-scale disturbance is implicated and evidence of past wild-fire on both sites is consistent with this hypothesis. It is unlikely that significant regeneration of Nothofagus will occur as the stands mature and canopy gaps are created by the death of old trees, since saplings of other species already occur at high densities in the understorey and will probably pre-empt the resources made available by canopy gaps. Two other study sites were situated above 900 m asl. At Dzumac, in an apparently older stand dominated by N. codonandra, there is some evidence of recent regeneration, predominantly confined to a single large canopy gap. The population size structure of N. baumanniae on the fourth site, on the summit of Mt Mou, shows a closer approximation to a reverse-J curve. Seedlings, however, are relatively uncommon on this site, and the numerous saplings may be suppressed rather than young.

Analyses of topsoil provided no consistent evidence to suggest that mineral content is controlling the distribution of Nothofagus across vegetation boundaries.

The environmental factors promoting the formation of these monodominant canopies are uncertain, but appear to involve large-scale disturbance by windstorm or fire. The population size structures suggest that the canopies of the two lowland stands, at least, are likely to become more species-rich, with a progressive decline in the frequency of Nothofagus. Therefore, these lowland monodominant forests cannot be regarded as equilibrium communities, irrespective of whether more detailed studies reveal environmental differences across the community boundaries. The status of the two high altitude sites is less certain.

We mapped the occurrence of canopy gaps periodically between 1978 and 1990 in a 1.5 ha study plot within a 70-year-old (in 1978) Neotropical forest on Barro Colorado Island (BCI), Republic of Panama. The total area of the forest under canopy gaps in the plot averaged 4.3% (3.1% to 5.7%, 95% CI). There was high year-to-year variability in the rate of new gap formation. On the basis of repeated observations for four yearly intervals, the annual rate of new gap formation ranged from 0.45% y−1 to 6.5% y−1. Most gaps were small. The mean size of individual gaps originally was 79 m2 (range: 8-604 m2). However, large gaps (≥150 m2) occurred more frequently than expected for a secondary forest on BCI. Gaps closed rapidly the first year after formation but the rate of closure slowed thereafter. Despite the absence of any obvious environmental gradients, gaps were spatially clustered. Even in this relatively small plot, there seemed to be distinct gap-prone and gap-free areas.

Analysis of litterfall, nutrient return and floor mass dynamics was made in mature and recently harvested bamboo savanna sites in a dry tropical region in India. The total annual litterfall was 590 and 267 g m–2 in mature and harvested sites, respectively. Of the total litterfall, 58–77% by weight was contributed by leaf litter. Although litterfall occurred throughout the year, as much as 72–83% of the leaf litterfall was recorded during winter (December–February). Seasonal distribution of total litterfall was: rainy 12–22% of annual, winter 64–65% and summer 13–22%. Nutrient concentrations in bamboo leaf litter were low compared with the other species growing in the same region. Annual nutrient return through litterfall amounted to: 28–49 kg N ha–1, 1.32.9 kg P ha–1, 33–85 kg Ca ha–1, 12–32 kg K ha–1 and 1.4–2.8 kg Na ha–1. While maximum accumulations of fresh litter on the ground occurred in summer, the partly decayed and particulate litter categories peaked in the rainy season. Decaying litter categories showed 1.5–3 times greater nutrient concentrations than the concentrations in fresh leaf litter. Marked immobilization of N and P occurred in decomposing leaf and particulate litter. The mean annual nutrient content of the floor was (kg ha–1): N 29–40, P 1.0–1.9, Ca 13.8–23.9, K 14.6–15.3 and Na 0.85–0.99. The annual turnover in litter layer was: 63–81% for dry mass and 64–90% for different nutrients.

Reproduction by Bolomys lasiurus is strongly seasonal in the Amazonian savanna of Alter do Chāo, Pará, Brazil. No pregnant or lactating females were recorded during the early dry season (July-September). Relative growth rates showed a similar though less consistent pattern. These patterns do not appear to be due to a direct effect of rainfall as high reproduction and growth were recorded during the late dry season (October-November), even though rainfall and the availability of fruits of shrubs were low during that period. It is likely that reinitiation of reproduction during the dry season is due to an increase in the availability of invertebrates and/ or wind-dispersed seeds. Fire at the end of the dry season appears to affect the diet of the rats, causing an increase in the ingestion of invertebrates during the following wet season. However, our data do not indicate that fire affects individual reproductive output or growth.

The most diverse known communities of insectivorous bats in the Palaeotropics and Neotropics are similar in alpha diversity (number of species). However, they show distinct differences with respect to wing morphology and the echolocation behaviour of their component species. In the Palaeotropics, most bat families are clearly separated in wing morphospace. The morphological niche of Rhinolophidae is vacant in the Neotropics, but primitive echolocators using sound primarily for scanning the environment rather than for prey capture are much more frequent there than in the Palaeotropics. In our opinion, a large portion of this difference can be traced to the different evolutionary histories of the respective communities. Bat families of different geographical origin are involved and their foraging styles obviously evolved differently in the Old and New World.

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.