Volcán Barva, Costa Rica, has on its northern slope an unbroken sequence of rain forest on volcanic parent materials from near sea level at La Selva Field Station up to its summit at 2906 m. It provides a good area to study forest changes with altitude and their causes. In the present paper we describe the forests as a background for soil and litterfall studies from 1 ha plots at each of the following altitudes: 100 m, 500 m, 1000 m, 1500 m, 2000 m and 2600 m. The canopy heights (with height of the highest emergent in parentheses) ranged from 35–40 m (45 m) at 100 m to 20–23 m (32 m) at 2600 m; basal area was least (22.7 m2) at 100 m and highest (51.2 m2) at 2600 m; the tree (≥10 cm dbh) density ranged from 391 ha–1at 500 m to 617 ha–1 at 2600 m. Most trees were identified and on samples of them we recorded presence of buttresses, lianes, skiophytic climbers, vascular epiphytes and bryophytes; and drew profile diagrams. In the classification of Whitmore (1984) the two lower plots are evergreen lowland rain forests; the other four are lower montane rain forest. Species richness was highest in the plot at 500 m, with at least 135 species of tree, and least at 2600 m, with at least 35 species. The Volcán Barva forest altitudinal sequence is briefly compared with those elsewhere.

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.

Length-mass relationships within an assemblage of tropical snakes are used to describe morphological groups. We report patterns of body size based on length and mass measurements of 603 individual snakes of 27 species captured at La Selva, Costa Rica from March 1982 through August 1984. This assemblage of snakes is composed of at least four morphological groups each of which consists of species with similar habitat preferences. These groups are heavy-bodied terrestrial forms, light-bodied arboreal forms, long-tailed leaf-litter forms, and forms of unextreme relative mass and tail length. This tropical snake assemblage is more diverse in species richness and morphological diversity than a temperate assemblage.

Terrestrial ungulates use different strategies to cope with widespread annual flooding of the Amazon basin. Red brocket deer (Mazama americana) and collared peccary (Tayassu tajacu) retreat to floodplain islands and shift from a frugivorous to a woody browse diet. However, both white-lipped peccary (Tayassu pecari) and lowland tapir (Tapirus terrestris) diets are unaffected by inundations; in the case of white-lipped peccary because they migrate into and out of flooded areas and in the case of lowland tapir because of their semi-aquatic nature. These-strategies of white-lipped peccary and lowland tapir enable them to exploit the greater fruit production of flooded forests more frequently than brocket deer and collared peccary.

We evaluated occurrence and abundance of lianas and woody hemiepiphytes on canopy and emergent tree species in primary tropical wet forest at the La Selva Biological Station, Costa Rica. Two pioneers, Cecropia obtusifolia and C. insignis, lacked both lianas and hemiepiphytes. The seven non-pioneer species differed significantly in their loads of lianas and hemiepiphytes. For all non-pioneer species, two measures of liana and hemiepiphyte loads (the percentage of the crown occupied and the combined basal area of descending hemiepiphyte and liana roots and stems) increased significantly with tree diameter. In all non-pioneer species, most trees ∵ 70 cm diameter (50–97%) were colonized. Lianas occupied more trees and had a smaller mean host diameter than did hemiepiphytes; however, basal area of descending roots or stems was equivalent for the two life forms in occupied trees. We used partial correlations controlling for tree diameter to evaluate the relationship between annual tree diameter growth and loads of hemiepiphytes and lianas for six non-pioneer species. Five of the six species showed a significant negative correlation between loads and diameter growth. Existing published data show that the high incidence of lianas and hemiepiphytes at La Selva is paralleled in most other Neotropical wet forests.

Flooded savannas in south-west Venezuela consist of seasonal, marshy and flooded grassland communities, the distribution of which depends on soil level. Seasonal grasslands are dominated by tuft-forming, rhizomatous C4-grasses (exemplified by Paspalum chaffanjonii in this study), while flooded grasslands are dominated by stoloniferous grasses which develop rooted, floating culms during the rainy season (Leersia hexandra and Hymenachne amplexi-caulis). The interface between these two communities is a marshy grassland dominated by stoloniferous grass species which tolerate flooding to a depth of 10 to 25 cm (Panicum laxum and Leersia hexandra). All perennial grass species in flooded grasslands behave as typical C3 plants, while marshy grasslands are dominated by Panicum laxum, a species with reduced photo-respiration, low RuBP/PEP-carboxylase ratios, and low absolute RuBP-carboxylase activity compared to C3 grasses. It also has lower photosynthetic rates than the other grass species. Hymenachne amplexicaulis appears to be the least drought tolerant from the species selected, in accordance with its distribution in the wettest side of the flooding gradient studied. The other species showed marked reduction in relative water content and pronounced increase in leaf proline content in drought experiments lasting 6 to 30 days. Alcohol dehydrogenase increased markedly in response to anaerobiosis in the root environment in the tuft forming grasses, while the stoloniferous species with ascending culms were least affected by this treatment, probably as a result of better aeration inside the culms and also to the production of adventitious roots in upper nodes. Nitrate reductase activity increased as a result of anaerobiosis in the roots but not in the leaves, of all species except Leersia hexandra. No difference among the species was found in malate accumulation, or the activity of malic enzyme.

Fruit production by Acacia albida (Leguminosae: Mimosoideae) trees in Mana Pools National Park, Zimbabwe, was monitored over eight years. Timing of ripe fruit-fall varied between years, as did fruit production: production of ripe fruits by the same tree varied from 5.4 kg in 1983 to 290.1 kg in 1988. Baboons reduced fruit production by feeding on unripe fruits and the mass eaten each year was negatively correlated with rainfall. Potential fruit production (i.e. production in the absence of baboons) was high when the late wet season was wet or cool and when fruit production in the previous year was low. Late wet season rainfall and temperature probably determined the degree of defoliation by caterpillars: in 1983 and 1987, when the late wet season was hot and dry, the trees were almost completely defoliated. During the late dry season, A. albida fruits were an important component of the diets of waterbuck, eland, elephant, buffalo and kudu; they were seldom eaten by hippopotamus and were ignored by zebra and warthog.

Necrophagous Diptera were sampled in a seasonal tropical mixed forest in Hong Kong from February 1985 to May 1986 using carrion-baited traps. Six families of flies were caught but only Calliphoridae, Muscidae and Sarcophagidae were considered. They made up a total of 14,669 flies of 21 species in the sample. Total species abundance followed Fisher's log-series distribution. The commonest five species were calliphorids, constituting 79.44% of the total combined catch. Temperature was apparently the main factor affecting seasonality of necrophagous Diptera in Hong Kong. Fluctuations in total abundance, species richness and H' followed seasonal changes in weekly mean air temperatures.

The germination of 43 tree species native to the lowland forests of Malaysia was monitored on forest soil in trays placed in closed-canopy forest, an artificial forest gap, and a large clearing. Germination varied significantly among habitats, with only seven species germinating well in all three sites. Seed germination of most species demonstrated clear patterns of shade tolerance or intolerance identical to those long recognized for tree seedlings. Favoured locations for germination were similar to known distributional patterns of adult individuals in mature and secondary forests. Most forest canopy species germinated in the gap, but germination in the large clearing was dramatically reduced or nil; the regeneration of these species in large clearings will be severely retarded even when seeds are present. Canopy-induced inhibition of germination was apparent in several pioneer species; seeds moved from the forest into the gap or clearing germinated rapidly. Results indicate that natural treefall gaps do not inhibit the germination of most species, but do allow pioneer species to germinate, and therefore regenerate. Although germination occurred in all three locations, the level of germination for particular species varied greatly among habitats. We conclude that germination requirements play a very important role in controlling the species composition of regeneration in forest understorey, gap, and large clearing habitats.

A possible mutualistic dispersal system between a large-seeded tree of French Guiana, Vouacapoua americana (Caesalpiniaceae), and caviomorph rodents, Myoprocta exilis and Dasyprocta leporina, is described. Mast fruiting of Vouacapoua at the beginning of the wet season coincides with scatter-hoarding seed dispersal. During the wet season, almost 100% of marked seeds on three sites were removed: nearly 70% were buried and the rest were eaten by mammals. Unburied seeds were attacked by insects and/or lost their ability to germinate. Rodents preferred ungerminated seeds, and had no interest in germinated seeds. Seeds were buried individually near natural objects such as palms, branches, logs, lianas, roots and trees. After predation by rodents, seedling distribution did not differ from seed distribution. Most seeds were transported less than 5 m from the feeding plots but some were carried as far as 22.4 m. Between 40 and 85% of dispersed seeds were retrieved during the following month by rodents and eaten. The disinterest of caviomorph rodents in germinated seeds, because of rapid exhaustion of endosperm reserves, prevents feeding from hoarded Vouacapoua during the long dry season when resources are scarce. Seedlings emerging from forgotten or abandoned cached seeds appear to increase the recruitment of Vouacapoua americana.