The food habits of four hypogeous Macrotermitinae species were studied using stable carbon isotope analysis in several biotopes of a humid savanna of West Africa (Lamto, Côte d'Ivoire). The proportion of woody and herbaceous material in the diet of the different species was determined by measuring the 13C natural abundance in the fungus comb. The diet varied with season and biotope, especially tree density. The results confirm the flexibility of the food habits of the fungus-growing termites as a consequence of their exosymbiosis with the fungus Termitomyces sp.

The present study showed that the density of germinable seeds in the soil of a humid tropical forest ecosystem at Nelliampathy, in the Western Ghats of Kerala in India, fluctuates sharply at different times of the year. There were more germinable seeds in the soil during the monsoon season. Regeneration was activated after canopy gap formation and thus a decline in the soil seed density in 1-year-old gaps was recorded. However, soil seed density increased with gap age. Differences were found between primary, late secondary and early secondary categories of species with respect to their soil seed bank. There were more seeds of primary species in the soil of natural gaps than in selection felled ones, while the seeds of early secondary shrubs and herbs were more in the soil of selection felled gaps than in natural gaps. The soil seed banks of the primary forest species, being transient, are not an important conservation tool for these species.

The floral biology, breeding system and pollination of Caryocar brasiliense were studied in the cerrado vegetation of Central Brazil. The large, yellowish-cream, brush-like flowers are pollinated mainly by glossophagine bats (Glossophaga soricina and Anoura geoffroyi). Three non-glossophagine bats (Phyllostomus discolor, Vampyrops lineatus and Carollia perspicillata) and two short probosisced hawk moths (Erinyis ello and Pseudosphinx tetrio) may also act as occasional pollinators. Caryocar brasiliense is self-compatible although it sets significantly more fruits when crossed than when selfed. The natural fruit set (fruit/flower ratio) and seed set (seed/ovule ratio) are 3.1% and 1.0% respectively. Most of the fruits and seeds are formed through the action of the flower visitors, despite the fact that about 20% of the non-visited flowers receive self pollen on at least one stigma.

The effect of the red land crab (Gecarcinus lateralis) on leaf litter biomass and nutrient transformation was investigated in a semi-deciduous tropical forest on coastal dunes using access and exclusion plots observed for six months. Crabs were in burrows during drought, but began foraging immediately after rainfall. Crabs accelerated litter disappearance significantly during the wet season at one site located beneath Brosimum alicastrum, but had no effect beneath a nearby Enterolobium cyclocarpum. The difference is tentatively attributed to small leaflet size in the latter species which crabs were unable to handle and consume. At both sites, litter in exdosures had approximately doubled by the end of the ensuing dry season. At the Brosimum site it is attributed to sporadic crab detritivory occurring after dry seasonal rains. At the Enterolobium site it is attributed to preferential retention of litter in the cxclosures during strong dry season winds. The nutrient content of litter exposed to, or protected from, crabs was not significantly different at either site and differences in litter nutrient pools reflected differences in litter biomass. Accelerated nutrient mineralization due to crab detritivory was concentrated early in the wet season before leaching began from the soils, and it is suggested that this altered seasonal pattern of mineralization may reduce the loss of nutrients from the site in percolating water.

Numbers of lianas ≥2 cm gbh were recorded on trees ≥30 cm gbh in two 4 ha plots of dipterocarp forest. Associations between lianas and trees of the 12 commonest families and 16 commonest species were analysed. Liana density was 882 ha-1. Fifty-seven per cent of trees supported lianas and the mean number lianas per tree was 2.1. Lianas were highly aggregated on individual trees in most families; numbers of lianas per tree followed the negative binomial distribution for the Dipterocarpaceae but not Euphorbiaceae. Dipterocarpaceae and Euphorbiaceae differed in susceptibility, with 41 and 64% of their trees respectively supporting lianas. The proportions of trees with lianas (i.e. % trees laden) were correlated between plots at the species, but not the family, level. They were not related to tree girth; differences in proportions between families and species were maintained for trees in the 30–40 cm gbh class. At the species level, proportions of trees with lianas and the mean number of lianas per tree were significantly inversely correlated with mean branch-free bole height of trees in the 30–40 cm gbh class. Increased branch-free bole height and associated branch shedding may therefore decrease the susceptibility of trees to lianas and explain the lower susceptibility in the Dipterocarpaceae than the Euphorbiaceae.

Air and soil temperatures were measured during dry season heading fires in three different physiognomic forms of native vegetation common in Central Brazil: cerrado sensu stricto (dense scrub of shrubs and trees), campo cerrado (open scrub), and campo sujo (open grassland with scattered shrubs). The vegetation was protected from fire for 15 y in some areas, had been burned once every two years, and once each year in other areas. The temperatures were measured with type-k thermocouples and recorded at intervals of 22.5 sees. Air temperature measurements were taken at 1, 60 and 160 cm. Maximum air temperatures ranged from 85°C to 840°C, and the duration above 60°C varied from 20 to 270 seconds. In the soil, negligible temperature increases were recorded below 5 cm depth, whereas at 2 cm maximum soil temperatures varied from 29 to 38°C. Possible influences of fuel load and moisture on the recorded data and on the behaviour of fire in the cerrado ecosystems are discussed.

Soil seed banks from four Mexican lower montane forests were studied. These forests are in the transition zone between neartic and Neotropical floristic regions. Soil seed bank characteristics were biased toward the dominant – temperate or tropical – phytogeographical affinity. The northern site (El Cielo Biosphere Reserve, Tamaulipas) had the lowest seed density, 720 seeds m−2. The eastern (Rancho La Mesa, Veracruz), western (Sierra de Manantlán Biosphere Reserve, Jalisco) and southern (El Triunfo Biosphere Reserve, Chiapas) sites all had much higher seed densities (2291, 2901, and 2341 seeds m−2, respectively). Germinated tropical species seeds were more abundant than temperate species seeds at all four sites, and were higher for southern and intermediate sites when compared with the northern site. On the basis of family, El Cielo appears to be different. The tropical family Melastomataceae was absent from this northern site, whereas it represented >30% of total germinated seeds at the other three sites. Trees were the most abundant life form at the southern site but were particularly poorly represented in the eastern and northern sites. Herbs were very abundant in the eastern, western and northern sites but were poorly represented in the seed bank of the southern site. The four seed banks differ between themselves and resemble seed banks of neither temperate deciduous nor tropical forests. In some ways they are unique, at least with respect to floristic composition, seed density, and life form representation.

The species richness of pimpline ichneumonids was examined using catches from a network of Malaise traps operated throughout Costa Rica. More species were caught at some sites than at reasonably well-collected sites in other countries. When corrected for area, the species richness of ‘Pimplinae’ and Pimplini in Costa Rica as a whole is greater than that for virtually any other region recorded to date. The local richness of both groups appears to be a function of their regional richness. Many of the species found in Costa Rica apparently have large geographic ranges.

Different C4 photosynthesis pathways may influence plant response to shade and/or moisture stress. In the savanna of south-eastern Botswana, seedlings of PCK C4 type grass species were frequently observed to emerge in shaded habitats. The species Digitaria eriantha subsp. pentzii, which shows the NADP-ME pathway, was also found to be associated with the tree canopy. Species emerging in habitats exposed to full sun often showed the NAD-ME C4 pathway. Seedlings or Aristida congesla, Eragrostis rigidior and Tragus berteronianus which normally emerge in full light, showed higher relative growth rates and/or unit leaf rates compared with seedlings of Panicum maximum and Urochloa panicoides which are associated with shaded habitats. Seedlings of the latter species, however, survived low light conditions. Relative growth rate of the seedlings appeared to be negatively related to caryopsis weight. Light response analysis of leaves of Digitaria eriantha subsp. pentzii, grown under low light intensities, showed similar trends in light saturation to those reported for the PCK type in Panicum maximum. Mesophyll rather than stomatal limitations appeared to induce light saturation at higher light intensities in leaves grown under shade conditions.

The reproductive process of two species of Kielmeyera, K. coriacea and K. speciosa, sympatric in savanna areas in central Brazil, has been studied. The trees have similar pollination systems and dispersal mechanisms but distinct phenological behaviours. Fast germination after the beginning of the wet season, early root swelling forming a xylopodium which enables survival during the dry season, and recurrent sprouting from the swollen root system during the first years of development were features of an establishment syndrome common to both species. The seedling survival after establishment was high; after five years 64% of the seedling cohort of K. coriacea was still alive. These seedlings, in natural conditions, remain poorly developed and resprout recurrently from the soil during some years. The recruitment of adult plants seems to occur from this ‘seedling bank’. The reproductive process was higher in K. coriacea during most stages of the reproductive process which may explain the smaller population size and distribution range of K. speciosa. For both species, the reproductive process as a whole was mainly affected by biotic factors in the wet season and not by seasonal drought or periodic fire.