Many species of termite (Isoptera) build their nests inside mounds because a mound has direct and positive feedback effects on the termite colonies through the maintenance of humidity and protection of the population from enemies, e.g. ants (Jouquet et al. 2006, Korb 2003, Noirot & Darlington 2000). Soil manipulation by termites (Isoptera) for mound construction is of particular interest for many researchers in terms of pedogenesis of the tropics (Lavelle et al. 1992, Lobry de Bruyn & Conacher 1990). The termites select soil particles according to ecological requirements such as water availability (Jouquet et al. 2002, 2007) and improve soil structural stability by means of application of clay particles and saliva/excreta (Fall et al. 2001, Jouquet et al. 2004). The nest-building activity of the termites inevitably causes regional translocation of soils (Bagine 1984, Holt & Lepage 2000) and distinctive patches in local ecosystems, which contributes to ecological diversity (Lavelle et al. 1992). This is the reason why termites are regarded as an ecological engineer (Jouquet et al. 2006). Soil-particle selection by the termites, however, has not been fully explored in relation to diverse ecologies and landscapes in Africa.

Swamp forest covers c. 2600 ha of coastal wetlands in Guadeloupe. An inventory of all vascular plants was conducted together with a characterization of the main abiotic descriptors within seventeen 10-m × 40-m plots, systematically sampled throughout the forest. Girth at breast height (GBH) was measured for all trees ≥10 cm GBH. Four forest types were discriminated according to pH, clay content and redox potential of the soils. Among the 107 species recorded, lianas and epiphytes were as much represented as tree species (28%). However, no epiphytes were encountered at the canopy level where Pterocarpus officinalis (Papilionaceae) was the evenly dominant tree. Local hummock-hollow topography was responsible for an aggregated distribution of P. officinalis. This species exhibits several adaptative traits which may explain its dominance over all of the lowland swamp forests subjected to permanent waterlogging in the hurricane-prone Caribbean islands.

Climate change may increase the intensity of hurricanes (Emanuel 1987, 2003), and thus the size of disturbance in tropical forests. As a consequence, disturbance-specialist plants, such as lianas, may increase in abundance there (Phillips & Gentry 1994). Putz (1984) hypothesized that lianas create larger treefall gaps by connecting trees together and pulling down multiple trees during storms. This positive-feedback cycle may increase the prevalence of lianas in disturbed tropical forests (Schnitzer & Bongers 2002, Schnitzer & Carson 2001). Alternatively, Putz (1984) proposed that lianas tie and stabilize canopies together, resulting in less disturbance. Forest age may determine the role of lianas during disturbance because liana abundance and composition vary through secondary succession (De Walt et al. 2000, Schnitzer et al. 2000). To test the two hypotheses of Putz (1984), we evaluated the effect of liana cutting between forests of different successional ages on tree damage by hurricane Wilma.

We investigated the relative influences of vegetation cover, invertebrate biomass as an index of food availability and the short-term effects of fires on the spatial variation in densities of the rodent Bolomys lasiurus in an Amazonian savanna. Densities were evaluated in 31 plots of 4 ha distributed over an area of approximately 10×10 km. The cover of the tall grass (Trachypogon plumosus), short grass (Paspalum carinatum), shrubs and the extent of fire did not explain the variance in densities of Bolomys lasiurus. Food availability alone explained about 53% of the variance in B. lasiurus densities, and there was no significant relationship between insect abundance and vegetation structure. Fires had little short-term impact on the density of Bolomys lasiurus in the area we studied. As the species appears to respond principally to food availability, habitat suitability models based on easily recorded vegetation-structure variables, or the frequency of disturbance by fire, may not be effective in predicting the distribution of the species within savannas.

Total ecosystem carbon storage has frequently been found to increase with woody encroachment in savannas. However the loss of grass roots associated with woody encroachment can lead to a decrease in below-ground carbon storage which is not compensated for by an increase in above-ground carbon. To investigate how the extent of total woody cover affected ecosystem carbon, soil and above-ground carbon storage along eight thicket–savanna and five forest–grassland boundaries were measured. To investigate whether changes in soil carbon concentrations were related to the percentage of C4 (grass) roots to total roots and root quantity and quality, we measured fine-root biomass, root C : N ratios, root N, and % C4 roots at three different depths across thicket patches of different ages (n = 189). Forests contained significantly more carbon than adjacent grasslands in both above-ground carbon (mean difference 12.1 kg m−2) and in the top 100 cm of the soil (mean difference 4.54 kg m−2). Thickets contained significantly more above-ground carbon than adjacent savannas (3.33 kg m−2) but no significant differences in soil carbon were evident. Total fine-root biomass appeared to be more important than root quality (root C : N) in determining soil carbon concentrations during the encroachment process (i.e. in thicket of different ages). Similarly for thickets, the % C4 roots had no significant effect on soil carbon concentrations. In conclusion, thicket invading into open savanna vegetation did not lead to significant gains in ecosystem carbon at this study site. Significant gains were only evident in mature forest, suggesting that the process may take place very slowly.

At Lamto, little is known about animal community responses to habitat variability resulting from fires and the mosaic pattern of the vegetation in general and in particular about that of termites which play key roles in this ecosystem. With a standardized method, data were collected on termites from four habitats differing in their vegetation cover and fire-history: annually burned savanna, savanna woodland, forest island and gallery forest. A range of environmental variables was measured and correlated with species abundances. The number of termite species collected in the savanna woodland was very close to that found in the gallery forest while the forest island was the richest habitat. The species richness of the savanna woodland and forest island seemed partly due to their heterogeneous and transitional vegetation structures and variable food resources. With regard to the fire-history of habitats, Connell's intermediate disturbance hypothesis offers an explanation for differences in the patterns of habitat-specific species richness. Variation in species abundances was significantly correlated with only two environmental variables (soil pH and woody plant species richness). The pH appeared as the most influential factor for fungus-growers while tree invasion in the savanna strongly reduces the abundance of grass-feeding species (e.g. Trinervitermes geminatus). Although not significantly correlated with species abundances, soil carbon showed a positive correlation with the dominant soil-feeder Basidentitermes potens. As for wood-feeders, they were not strongly correlated with woody plant species richness; this fact might be linked to their use for other sources of nourishment. Overall, it appears that habitat variability in the Lamto reserve contributes to the maintenance of different subsets of the termite community.

Fire history was reconstructed from fire-scarred individuals of the endemic pine (Pinus occidentalis) along climatic gradients in the Cordillera Central, Dominican Republic. We analysed variation in fire frequency by climate, elevation and aspect (windward and leeward of the central massif). A high correspondence between known fires and fire-scar chronologies indicates that the primary rings of this species are annual. Evidence was found for 41 fire years since 1727 A.D.; 28 were landscape-scale fires, nine of which were exceptionally large and linked to El Niño-triggered droughts. Mean fire return interval (FRI; the mean of individual samples) and mean fire interval (MFI; the composite mean of a group of samples) were used to estimate the upper and lower range in fire frequency. Mean FRI of the entire study area was 31.5 y (±24.9 y SD) and MFI for landscape-scale fires was 5.6 y (±4.1 y SD). The fire regime varied significantly with elevation and aspect. Mean FRI was 42.1 y (±27.6 y SD) and MFI was 9.8 y (±16.7 y SD) on moister windward zones, and mean FRI was 16.7 y (±7.8 y SD) and MFI 4.2 y (±1.9 y SD) in drier leeward zones. On windward slopes, high-elevation mean FRI (26.4 y) was significantly shorter than at middle (44.5 y) and low elevations (58.4 y). On leeward slopes, mean FRI did not vary significantly with elevation. The strong windward elevational patterning of the fire regime is driven by the trade wind inversion which traps moist air below 2000–2300 m. Such elevational patterns may be characteristic of montane fire regimes throughout the tropical trade wind belt.

Edge effects encompass biotic and abiotic changes resulting from the interaction between two different habitat types (Murcia 1995). Edge habitats are ecologically distinct from patch interiors, and understanding how ecological patterns change near edges is important in understanding landscape-level dynamics such as the impacts of fragmentation (Ries et al. 2004). Abiotic conditions at the forest edge, such as increased wind and solar radiation, increased fluctuations in temperature, and decreased humidity, may affect forest-adapted organisms (Harper et al. 2005, Murcia 1995). So, edges may affect lizards and amphibians due to their physiological needs (Lehtinen et al. 2003, Vallan 2000). Anurans are considered sensitive to environmental changes due to their permeable skin, shell-less eggs and use of land as well as freshwater habitats (Vallan 2000). Changes in vegetation structure and microclimate are likely to be the predominant factor affecting amphibian abundances across edges (Jellinek et al. 2004, Marsh & Pearman 1997, Schaepfer & Gavin 2001, Urbina-Cardona et al. 2006).

Four structural types of cerrado vegetation were examined to test the following hypotheses: (1) there are predictable changes in woody plant density, species richness and life-history strategies from one structural type to another; and (2) plant species composition in the less-rich structural types represent particular and impoverished subsets of those found in the richer ones. The study was conducted at Fazenda Palmares (5°33′S, 42°37′W) Piauí State, Brazil. A 47% decrease in woody plant density between cerradão (forest) and the least-dense type of cerrado sensu stricto (scrub) was associated with a 40% decrease in species richness. The percentage of lower-layer species was reduced by 29% in the least dense type of cerrado sensu stricto compared to cerradão. The proportion of species that flower and fruit during the rainy season was also reduced by one third. Species were not distributed as impoverished subsets along the cerradão–cerrado sensu stricto gradient. It is argued that the reduction in woody plant density and richness is partly due to factors limiting the occurrence of species with particular life-history strategies. The species composition of structural types is affected by the ‘mass effect’ and also by surrounding biotas, which provide species that colonize particular types of cerrado vegetation. Both these processes reduce the likelihood that the species composition in the poorer structural types are simple subsets of those present in the richer types.

The germinable seed bank of the colonizing weed Eupatorium odoratum was studied at the University of Ghana's Agricultural Research Station, near Kade. Five sites representing different successional stages were selected: a closed-canopy forest; intermittent-canopy forest; secondary forest; agricultural land; and a burnt forest. Twenty-five soil samples (each 500 cm3; 10×10×5 cm) were taken at random in each site, to be used for germination experiments. The secondary forest site had significantly more seeds of Eupatorium odoratum (8428 seeds per m2) than any of the other four sites. In this site Eupatorium odoratum constituted 81% of the total seed bank and had significantly more rapid germination of seeds than any other species. The results indicate that the existence of a soil seed bank may depend on: (1) time allowed for seed accumulation; (2) habitat accessibility to dispersing seeds; (3) the type of disturbance that occurs in an area; (4) dispersal capabilities of colonizing species; and (5) the history of the species′ distribution in the area.

An assessment of carnivore species richness and food habits was carried out in a 100 km2 area of dry tropical forest in Huai Kha Khaeng Wildlife Sanctuary, Thailand. Twenty-one carnivore species of five families were found to be feeding on at least 34 mammal species, as well as birds, lizards, snakes, crabs, fish, insects, and fruits. Forty-four percent of the prey identified in faeces of larger carnivores, primarily leopards, consisted of barking deer, Muntiacus muntjak. Sambar deer, macaques, wild boar, porcupine, and hog badger were important secondary prey items. In faeces from small carnivores (< 10kg), murid rodents accounted for 33% of identified food items. The two most frequently encountered mammalian prey species were the yellow rajah rat, Maxomys surifer, and the bay bamboo rat, Cannomys badius. Non-mammal prey accounted for 21.3%, and fruit seeds for 12.4%, of all food items found in small carnivore faeces.

With the aim of characterizing tree growth patterns, this paper re-examines the growth data of 100 selected trees belonging to 24 species that were recorded monthly in a 0.2-ha plot of a wet evergreen forest in the Western Ghats of India during the period 1980–82 using dendrometer bands. The mean growth profile, combining all of the selected trees, showed: (a) a significantly lower annual growth rate during the second year of survey which seemed to be negatively related to monsoon precipitation; (b) significant intra-annual growth variation clearly related to the regular alternation between a period of heavy rain and a quite long dry season of the monsoon climatic regime. Analysis of the variability of the individual smoothed growth profiles representing the 2-y trend of the growth data showed that: (a) the mean growth rate depended on a combination of an intrinsic endogenous variable (the structural class grouping species according to their maximum size), a tree size variable (tree diameter at breast height, dbh) and a neighbourhood variable (the number of taller neighbours in a 10-m radius); (b) the sudden change in growth rate from one year to the other was not predictable using these variables. The amplitude of the seasonal variations, investigated from the detrended growth profiles, appeared to be dependent on a combination of tree dbh and the number of taller neighbours in a 10-m radius. A co-inertia analysis of the smoothed and the detrended growth profiles indicated that the trees with fast growth also exhibited high seasonal variation. It is suggested that fast growing trees are those with favourable crown positions, which are consequently subject to high transpiration rates due to radiation and wind exposure.

Natural forests are composed of a heterogeneous mixture of plant architectures that change temporally and spatially. In addition, variation in ridges, tree falls, natural clearing, logs and animal or man-made paths results in a topographic complexity which is likely to have a profound effect on the movements of animals within the forest.

Effects of seed passage through digestive tracts of principal animal dispersers (bats and birds) on seed germination were investigated for two columnar cactus species, Stenocereus griseus and Subpilocereus repandus. In general, seeds ingested showed more rapid germination times and higher overall germination rates than untreated seeds. The bat Glossophaga longirostris, and the birds Mimus gilvus and Tachyphonus rufus seem to be the most efficient cacti dispersers in terms of quality of treatment. The increment of germination speed and particularly the decrease of imbibition time, could favour the probability of germination in dry areas such as arid and semi-arid environments.

Understanding the causes of savanna–forest dynamics is vital as small but widespread changes in the extent of tropical forests can have major impacts on global climate, biodiversity and human well-being. Comparison of aerial photographs for 50 rain-forest patches in Kakadu National Park had previously revealed a landscape-wide monotonic expansion of rain-forest boundaries between 1964 and 2004. Here floristic, structural, environmental and disturbance attributes of the changes were investigated by sampling 588 plots across 30 rain-forest patches. Areas that had changed from savanna to rain forest were associated with a significantly higher abundance of rain-forest trees and less grasses, relative to stable savanna areas. Ordination analyses showed that overall floristic composition was not significantly different between newly established rain forest and longer established rain forest. Generalized linear models also indicated that contemporary levels of disturbance (fire and feral animal impact) and environmental variables (slope and soil texture) were poor predictors of historical vegetation change. We concluded that (1) the rain-forest boundaries are highly dynamic at the decadal scale; (2) rain-forest expansion is consistent with having been driven by global environmental change phenomena such as increases in rainfall and atmospheric CO2; and (3) expansion will continue if current climatic trends and management conditions persist.

Decomposition was studied in a reciprocal litter transplant experiment to examine the effects of forest type, litter quality and their interaction on leaf decomposition in four tropical forests in south-east Brazil. Litterbags were used to measure decomposition of leaves of one tree species from each forest type: Calophyllum brasiliense from restinga forest; Guapira opposita from Atlantic forest; Esenbeckia leiocarpa from semi-deciduous forest; and Copaifera langsdorffii from cerradão. Decomposition rates in rain forests (Atlantic and restinga) were twice as fast as those in seasonal forests (semi-deciduous and cerradão), suggesting that intensity and distribution of precipitation are important predictors of decomposition rates at regional scales. Decomposition rates varied by species, in the following order: E. leiocarpa > C. langsdorffii > G. opposita > C. brasiliense. However, there was no correlation between decomposition rates and chemical litter quality parameters: C:N, C:P, lignin concentration and lignin:N. The interaction between forest type and litter quality was positive mainly because C. langsdorffii decomposed faster than expected in its native forest. This is a potential indication of a decomposer's adaptation to specific substrates in a tropical forest. These findings suggest that besides climate, interactions between decomposers and plants might play an essential role in decomposition processes and it must be better understood.

Survival of Afrotropical primary forests depends not only on habitat protection but also on the protection of animal species such as frugivorous primates, recognized as the most important seed dispersers for many plants. Here we investigate seed-dispersal services by the bonobo (Pan paniscus) in an evergreen lowland tropical rain forest of the Congo Basin. In the long-term research site of LuiKotale, we investigated food habits and seed processing based on 22 mo of behavioural observation, seed trial experiment and long-term daily GPS tracking of a habituated ape community. Bonobos were mainly frugivores (66% of all feeding sessions), spending about 3.5 h d−1 swallowing seeds that were transported for an average of 24 h in the gut. On average, an individual bonobo dispersed 172 kg y−1 of seeds (or 220000 seeds y−1) of more than 91 plant species by endozoochory over an average distance of 1.2 km from the parent tree. Passed seeds germinated more rapidly, more successfully and had greater post-dispersal survival than unpassed seeds. Bonobo-dispersed plants accounted for 40% of tree species and 65% of individual trees in the study site (12 1-ha plots census). Since bonobos show little functional overlap with other frugivores, the loss of their seed-dispersal services is likely to affect forest structure and dynamics. Our results justify description of the threatened bonobo as a gardener of the Congo forest.

Rates of litterfall over a period of 3 y at one undisturbed site and two sites disturbed by selective harvesting are reported for a tropical rain forest area in North Queensland, Australia. Litterfall over a period of 18 months is also reported for a further undisturbed site in the same area. No significant differences were found in annual litterfall between the sites, with annual litterfall rates ranging from 5.0 to 6.0 t ha−1 y−1. These rates are considerably lower than those reported for other rain forest areas in Australia, and are within the lower ranges recorded for other tropical rain forests. Litterfall was found to be strongly seasonal at all sites with the maximum falls occurring from the end of the dry season to the end of the wet season. The between year variability of the sites was quite low, with the ratio of maximum to minimum production ranging from 1.05 to 1.20. The average percentages of leaves, wood and reproductive material in litterfall were similar at each site. Leaves were the dominant component of litterfall with the average proportion of the total litterfall ranging from 72% to 76% over the study period at each of the four sites. At certain times, however, the fall of wood and reproductive material was quite significant, comprising as much as 71% and 34% of litterfall respectively. A strong negative correlation was found between the fall of leaves and wood at all sites.