Reproductive traits of 123 species of rain-forest tree from ultramafic regions of New Caledonia were assessed, mainly from herbarium specimens. Most species had extremely small, simple, pale-coloured flowers that are probably mainly pollinated by small insects, but not including bees. The seeds of most species were considered to be bird dispersed. However, wind is also important for pollination and seed dispersal. The phenological trend was for an increase in the number of species flowering and fruiting around the end of the warm dry season/start of the hot wet season, followed by a decline at the end of the wet season, and lower proportions during the cooler season. Seed size was significantly correlated with fruit size. Other correlations, between flower size and fruit size, and between seed size and seed number, were significant using species as independent observations, but did not hold following phylogenetic correction. Compared with non-dioecious species, dioecious species had significantly larger seeds, and a greater proportion of species with biotic dispersal, abiotic pollination and solitary (female) flowers. The long-term persistence of at least the larger-seeded tree species in New Caledonia is precarious, since the endemic giant pigeon, Ducula goliath, is probably their principal effective disperser, and this species is in decline.

Neotropical bats occupy a large variety of trophic niches, and represent locally abundant, species-rich communities. As such, they are highly suited as a model group for the study of temporal and spatial dynamics of animal communities. However, despite this important research potential, data on the dynamics and turnover rates of Neotropical bat communities are lacking. We here study both aspects for bats inhabiting two natural forests surrounded by savanna in Bolivia. Over a period of 8 y, both bat communities showed high rates of species turnover. As predicted, species relying on fluctuating food resources were more likely to be absent in particular years, whereas species relying on more predictable food supplies were present in all years.

For many tropical forests a tendency for fruit production to fluctuate seasonally has been established, with pronounced peaks of abundance and periods of fruit scarcity during which a few important resources maintain frugivore communities. However, there is a lack of studies in subtropical forests on community phenology and on the identification of important resources. In this study, community-wide fruit availability and its use by the local frugivore community was investigated in the subtropical coastal dry forest of Oribi Gorge Nature Reserve, South Africa over 13 mo from July 1997 to July 1998. Along 19.5 km of phenology trails, 940 individuals of 96 plant species bearing fleshy fruits were monitored twice per month and fruit-eating animals observed. Although some fruit was available all year round richness of both fruiting species and fruit abundance showed a seasonal pattern with peaks at the end of August to beginning of October (i.e. before the rainy season) and March to May (i.e. after the rainy season). Periods of fruit scarcity were found in July and August (i.e. during the long dry season) and in November and December (i.e. during the rainy season). Fruits of 23 plant species were observed being eaten by 18 species of bird and two of monkey. Highest animal numbers were attracted by Ficus thonningii, a species that fruited asynchronously during most of the year and during periods of fruit scarcity, and provided high overall fruit biomass. The importance of this species as a potential keystone resource for the frugivore community is discussed.

Microhabitat use and habitat-abundance relationships of four freshwater shrimps, Atyopsis moluccensis, Macrobrachium pilimanus, Macrobrachium trompii and Macrobrachium neglectum, were surveyed in tropical streams running through primary and secondary forests in Borneo, East Malaysia. Underwater observations revealed that A. moluccensis preferred relatively high water velocity and a boulder substrate. Macrobrachium pilimanus also preferred high water velocity and a cobble substrate, whereas M. trompii occupied stream margins with slow current and fine substrates (from POM (particulate organic matter) to pebbles). In contrast, M. neglectum was distributed relatively evenly through the stream channel. The abundance of A. moluccensis, M. pilimanus and M. trompii in the stream reaches was best explained by the abundance of boulders, cobbles and POM, respectively, suggesting that the amount of preferred microhabitat is an important factor affecting shrimp abundances in the tropical rain-forest streams. The primary-forest reaches were dominated by coarse substrates, such as cobbles and boulders, while a great proportion of the streambeds in the secondary-forest reaches were covered with sand. Owing probably to such habitat differences, the abundance of both A. moluccensis and M. pilimanus, which preferred coarse substrates, was less in the secondary- than in the primary-forest reaches. These suggested that loss of preferred habitat, namely decreased coarse substrate availability, by sedimentation resulting from riparian deforestation had altered the shrimp assemblage structures.

The effects of defoliation on leaf and propagule production, and leaf chemistry of the mangrove Kandelia candel (L.) Druce were evaluated in a manipulative experiment in Hong Kong. Artificial defoliation of leaf lamina at 50% of the length of midrib resulted in significant reduction in leaf, twig and propagule production, and size of the latter. Through the negative effects on propagule number and size, severe herbivory may influence fitness of the mangrove, and, thus, community structure. In contrast, no apparent adverse effects on growth and production were observable at 25% defoliation. Defoliation also significantly affected leaf chemistry of the trees, particularly those suffering 50% defoliation. Concentrations of soluble tannins and carbohydrates in leaves were significantly lower at 50% defoliation compared with the control. Total nitrogen also decreased significantly with increased per cent defoliation. Plants surviving in stressful habitats, such as mangroves, are probably more affected by loss of leaf biomass than those surviving in favourable environments.

The effect of tillage, clipping, precipitation and temperature on above-ground grass production was investigated in permanent plots at a Zambian savanna site for 5 y (1996^2001) by the harvest method. Mean species richness was 4.6 species m-2 with a total of 15 species at the study site. Mean end-of-season grass phytomass was 464 g m-2 with no statistically significant differences among years in control quadrats. Grass phytomass recovered within two wet seasons after tillage and a similar trend was observed after cessation of a 2-y monthly harvesting regime. However, in experimental quadrats, plot, treatment and year had significant effects on grass production. Previous- and current-season precipitation had no significant effect on end-of-wet-season grass phytomass but phytomass of the previous season explained 27-53% of the variation in end-of-wet-season phytomass. Grass production peaked in the wet season and declined sharply as the dry season progressed. The interaction between precipitation, temperature, harvesting and duration of the dry season explained 81-91% of the variation in daily grass production but the significance of the interactions varied with season and duration of harvesting. Precipitation-use efficiency (PUE) of grasses declined from 2.25 g m-2 mm-1 at the start of the wet season in December to 0.25 g m-2 mm-1 at the end of the season in March. Monthly harvesting for 1 y reduced PUE to less than 25%. The results indicate very complex relationships between above-ground grass production (dependent variable) and climate and land-use (independent) factors that makes the prediction of grass production in central southern African savannas difficult.

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.

Microhabitat use by tadpole species was investigated in streams of montane meadows of the Serra do Cipó, south-eastern Brazil. Microhabitats were classified into 24 types based on water depth, current, aquatic vegetation and substrate type, and quantified in 16 streams. A total of 844 tadpoles from 19 species was recorded, as well as microhabitat types used. Tadpoles, from all species pooled, used microhabitat types in the proportions available in the set of sampled streams. Diversity of microhabitats used was considered as a measure of niche breadth for tadpoles, and microhabitat diversity in streams was interpreted as available niche space. For the most part, species used microhabitats in different proportions, and conspecifics differed in microhabitat use among different streams. Neither niche breadths nor niche overlaps of tadpoles could be related to the number of species occupying streams. Thus not all available niche space may be occupied by tadpole species. More generalist species (those with broader niches) did not generally occupy more streams. Behavioural flexibility of tadpoles in microhabitat use may be a response to the unpredictability of the montane-meadow stream habitat. The role of adult anurans in choosing oviposition sites may also influence the distribution of tadpole species among streams.

The species present, and the frequencies and intensities of termite attack on 600 paper baits exposed at the soil surface were compared over three seasonal exposures and between two savanna sites of contrasting vegetation structure in northern Australia. Eleven species were recorded, with Microcerotermes nervosus and Schedorhinotermes actuosus comprising 43% and 27% of collections respectively. The most commonly sampled species nest underground or build epigeal mounds and are known to feed on sound and decaying wood. Changes in species dominance occurred between seasons and the two forest types. In both vegetation types, the number of species active and the frequency of attack increased with the duration of bait exposure and decreased in the order: transitional > wet > dry. Bait consumption was greater in the site with higher canopy cover, and did not differ significantly between seasons. No direct relationships were noted between rainfall recorded at the sites and species richness, frequency and intensity of attack on baits. We recommend exposure of paper baits for at least 2 mo during the transitional period as the optimal protocol for sampling at the time of greatest activity and diversity of those species within the guild of wood-feeding species regularly attracted to paper baits.

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.

In lowland tropical and temperate forests, nitrogen (N) and phosphorus (P) resorption from senesced leaves may reflect a mechanism of conservation of a limiting nutrient (Edwards & Grubb 1982, Killingbeck 1996, Proctor et al. 1989, Scott et al. 1992, Songwe et al. 1997, Vitousek & Sanford 1986). At the ecosystem level it has important implications for element cycling. The nutrients which are resorbed during leaf senescence are directly available for further plant growth, which makes a species less dependent on current nutrient uptake. Nutrients which are not resorbed, however, will be circulated through litterfall in the longer term (Aerts 1996).

Interest in the colour of fruits eaten by vertebrates has a long history (Ridley 1930, Turcek 1963, van der Pijl 1972). Within a given geographical area, colours of bird-consumed fruits compared with mammal-consumed fruits are fairly consistent (Janson 1983, Wheelwright & Janson 1985, Willson & Whelan 1990), but comparisons among different regions reveal selective pressures of different animal groups (Lord 2002, Willson et al. 1989). One consistent pattern among regions is that fruits with a two-colour display typically are eaten by birds (Wheelwright & Janson 1985, Willson & Thompson 1982, Willson & Whelan 1990). Thus, it is thought that such bicoloured displays are specifically adapted to attract birds and plants with these displays presumably benefit from seed dispersal by birds (Janson 1983, Willson & Whelan 1990).

As part of the programme Écosystèmes et Paléoécosystémes des Forêts Intertropicales (ECOFIT,France),we are engaged in multisite comparative studies of how forests regenerate across ecotones such as those between forests and savannas (Vincens et al. 2000).One such ecotone comprises the forest succession from bare soil that occurs naturally on beach successions along meandering rivers. To gauge the development of foliar layers during succession and quantify changes of efficiency of the vegetation in capturing the available solar energy, we are measuring the Leaf Area Index (LAI) of transects within forests and across their edges.