Vegetative growth, reproductive effort, seedling establishment, and mortality of the bark epiphyte, Dimerandra emarginata (Orchidaceae), were studied over a 3-y period in the moist lowland tropical forest on Barro Colorado Island, Panama. The study included more than 350 individuals growing on 12 branches of five different host tree species. Mortality was highest among small individuals. Most deaths occurred during the dry season and were probably related to drought. Mortality among older individuals, on the other hand, was always related to the instability of the substrate, i.e. flaking bark, breaking branches or falling trees. Vegetative growth was slow. The average increase in size (= height of the most recent, fully developed shoot) was 2.7 cm over 3 y (not considering ‘stemless’ seedlings). This increase was negatively correlated with initial plant size. Growth was highly seasonal, with little variation between years. The reproductive effort increased strongly with plant size. Larger individuals produced fruits more frequently, in larger numbers and of larger size. After reproduction, plants showed reduced vegetative growth in the following year (in 1994). There was no negative effect on future reproduction. Compared to seed production, annual recruitment was very low and showed large year-to-year variation. Fewer than 50% of the seedlings survived the first dry season after germination. After 3 y, their average size was 0.5 cm. The results suggest that slow-growing epiphytes such as D. emarginata can attain considerable age and that their longevity – after an initial vulnerable juvenile stage – is almost exclusively limited by substrate durability.

The dioecious character (sex ratios and stand structures, conspecific neighbour relationships, inflorescence numbers and structure) and reproductive process (phenology, anthesis, flower visitors and fruit production) of a miombo woodland species, Uapaca kirkiana were investigated in natural populations in Malawi. The sex ratio of reproductive individuals ≥ 10 cm diameter at breast height was about 1:1 and departures from this ratio mostly resulted from a higher proportion of the males. Spatially, the sexes were randomly distributed but generally within 10 m of each other with no obvious gender differences in size. Throughout Malawi, male and female reproductive individuals flower synchronously between October–April (with a peak period in February–March). A 6 : 1 male to female inflorescence sex ratio was common. Anthesis in female inflorescences lasts almost twice as long as in male inflorescences and only the latter have any odour. On male trees, inflorescences are in fascicles, whereas on female trees, they are solitary. In both cases, the inflorescences are generally similar in size except for the peduncles of the male inflorescences which are longer than the female's. A range of insects visits U. kirkiana flowers but the most likely pollinators are bees (Apis mellifera), and beetles (Dothera bennigseni, Chelomenes lunata, Alcidodes denticulatus and Mitracamenta sp.). Apart from pollen from the male inflorescences, female flowers do not offer any obvious reward for flower visitors. Pollination studies revealed that assisted pollination did not significantly improve fruit production or seed quality over unpollinated or naturally pollinated inflorescences. Facultative agamospermy (apomixis) is suspected as a phenomenon requiring further attention in U. kirkiana.

Nodulation of Pterocarpus officinalis appears to be widely distributed in the swamp forest of Guadeloupe even under conditions of permanent waterlogging. The large majority of the nodules were found above the water table and as such were located on large aerial buttresses or on root hairs which develop mainly in emerged soil. Further, large trees modify their environment by accumulating litter between the buttresses to the point of ensuring sufficient topographic elevation to keep a volume of soil regularly emerged. Consequently the nodules were concentrated in a small circle (5 m in diameter) around the oldest trees. A few nodules (5%) survived under the water table, provided that healthy root hairs were present, and this kept the rate of nodulation constant over a vertical gradient (0.9 nodule g−1 root DW). The C2H4-evolution rate of P. officinalis, 2.6–5.9 μmol h−1 g−1, appeared to be quite low compared to that of the potted Gliricidia sepium cuttings (19.4 μmol h−1 g−1), but was considerably higher than that of the woody liana Dalbergia monetaria (1.0 μmol h−1 g−1) from the same swamp forest site as P. officinalis. It was concluded that P. officinalis is a N2-fixing tree species under the waterlogged conditions of tropical swamp forests, and was hypothesised that the symbiotic nitrogen fixation on P. officinalis buttresses and root hairs could be considered as an additional adaptation to flooded soil and a contribution to its success in the tropical swamp forests of the Caribbean region.

Information is presented on the phenology, herbivory, phytochemistry and production of the tree species Polylepis quadrijuga. Leaf production was lower during the dry season than during the wet season, when minimum temperatures also occurred. Flower and fruit phenology were also seasonal. Herbivory was significantly higher for leaves expanded during the wet season (20%) than during the dry season (1%), and was also higher for younger leaves. Flavonoids, compounds known as UV-B protectors, were found in high concentration in leaves of P. quadrijuga. There was a significant positive relationship between monthly rainfall, monthly minimum temperatures and flavonoid concentration, but no relationship was found with leaf age. The annual fine litterfall for the Polylepis forest was estimated to be 3.9 t ha−1 y−1, a high value when compared to other paramo and upper montane rain forests in tropical mountains. High production was associated with high leaf nitrogen concentration (3.0–3.5%), high rates of nitrogen retranslocation (80% dry weight), and relatively low leaf longevity (8.4 mo). High production in P. quadrijuga is probably a key factor in explaining the existence of this large woody species in a paramo environment otherwise dominated by bunch grasses, cushion plants and giant rosettes of the genus Espeletia.

Influence of habitat on physiological and structural characteristics was investigated for broad-leaved tropical monocotyledons in the genus Heliconia (Heliconiaceae). Seven species were selected from three different light regimes, enabling an analysis of the extent to which this genus has adapted its photosynthetic strategies and morphological characteristics to different daily photon flux densities (PFD). Predictably, light response curves showed a clear gradient with respect to light saturation and rates of maximum net assimilation (Amax). Heliconia latispatha, an open site species, showed saturation at higher PFD (1400 μmol m−2 s−1) and higher Amax (14–16 μmol m−2 s−1) than H. mathiasiae, a forest edge species (PFD 1000 μmol m−2 s−1; Amax 7.5–8.5 μmol m−2 s−1) and H. irrasa of deep-shade forest understorey (PFD 250 μmol m−2 s−1; Amax 3.5 mol m−2 s−1). Leaf blade areas were largest in open sites, and leaf specific mass was also significantly higher, but leaf support efficiency was highest in understorey species. Species in open sites had thicker leaves with more chlorenchyma, whereas deep-shade species had very thin leaves and low stomatal densities. These rapidly growing herbaceous perennials appear to allocate much of their above-ground biomass to leaf tissues and have a relatively low investment in support tissues. This contrasts with understorey palms, in which leaf form and structural investment has been interpreted as a trade-off between economy and protection against tissue loss from falling branches. Presence of below-ground rhizomes in Heliconia may provide the key to this difference.

An exhaustive floristic inventory was conducted in a 400-ha block of tropical semideciduous forest in the Chiquitanía region of Santa Cruz, Bolivia. A total of 501 species were collected using both quantitative and traditional plant collecting methods. Trees represented the most diverse life form (124 spp), followed by herbs (101 spp), lianas (85), shrubs (66), herbaceous climbers epiphytes (15) and parasites (two). Floristic diversity was greatest for the forest floor community, when compared to either the understorey or canopy tree communities. Quantitative data were obtained for 336 species in 100 plots which contained a series of nested subplots to sample smaller-stature plants. Stem density for trees (dbh≥5 cm) was 914 trees ha−1, with a total density for all life forms estimated to be 135,000 plants ha−1; the total basal area for the forest was estimated to be 27.6 m2 ha−1. Species richness when measured by standard methods was found to be one of the highest for a dry forest region reported for the Neotropics with a mean of 70.8 spp 0.1 ha−1 (dbh ≥ 2.5 cm) and 50 spp ha−1 (dbh ≥ 10 cm). Comparison of life forms and vertical strata showed that the flora on the forest floor was more diverse than all other vertical strata combined. Habitat heterogeneity was studied using ordination procedures based on floristic data and to identify the characteristic species of three plant communities: granite outcrops, valley forest and upland forest. The most abundant tree species in the study area were Acosmium cardenasii, Neea hermaphrodita, Aspidosperma tomentosa and Galipea trifoliata, while the species with the greatest basal area were Anadenanthera colubrina, Acosmium cardenasii, Caesalpinia floribunda, Aspidosperma tomentosa, Piptadenia viridiflora, Chorisia speciosa, Tabebuia impetiginosa, Centrolobium microchaete, and Machaerium scleroxylon. Most canopy and understorey tree species had a population structure characterized by numerous juveniles and relatively few large trees, while emergent species tended to have a size-class distribution with relatively few juvenile individuals. Lianas and canopy trees were predominantly anemochorous, while understorey trees and shrubs were predominantly zoochorous; herbaceous species were largely autochorous, with only fern species relying on wind dispersal (sporochory). A comparison of structural attributes with other dry forest areas in the Neotropics, demonstrates the heterogeneous nature of vegetation types that are commonly assigned to this ecosystem. The Chiquitano dry forest shares many floristic elements with the semideciduous forests of the Andean piedmont of northwestern Argentina, the Misiones region of eastern Paraguay and northeastern Argentina, as well as the Caatinga region of northeastern Brazil.

Geophagy (soil eating) by the forest elephant (Loxodonta africana cyclotis) and other mammal species in the Dzanga National Park, Central African Republic, has led to large treeless licks. The geological and physical properties of these licks were studied and the chemical characteristics and particle sizes of geophagical lick soils were compared with soils from the forest and from licks where evidence of geophagy was absent. Average lick size of 20 licks in the Hokou lick area was 12,900 m2 (SE = 3,400 m2). Licks were situated exclusively in areas of outcropping dolerite intrusions. Physico-chemical analysis of the geophagical lick soil showed significantly higher quantities of sodium, potassium, calcium, magnesium, phosphorus, manganese and clay compared with the other soils. Several samples of the geophagical lick soil had lower nutrient levels than the mean level of forest topsoil, indicating that nutrient supplementation is probably not the only reason for geophagy. The high clay content of the geophagical soil may help absorbing and combating secondary plant compounds. Pronounced geophagy in rainforests may be a sign for poor habitat quality for large mammals living in these ecosystems.

The effects of wet and dry seasons on soil termites within a humid tropical West African forest are examined. Samples were taken monthly, over a 14-mo period, and termite abundances and species richness were estimated. These estimates were compared with the total cumulative rainfall for 30-d, 7-d and 2-d periods before each sampling. For all these time periods abundances and species richness of termites were significantly negatively correlated with rainfall. However, the strongest correlations were generally found with the 2-d period, suggesting that short-term movement of termites up and down the soil profile may be the most important factor in the observed differences, rather than longer term changes in overall abundance or species composition. This conclusion was supported by a detrended correspondence analysis which showed no significant changes in species composition between dry and wet months.

Les effets de saisons sèches ou humides, sur des termites souterrains d'une forêt tropicale humide Ouest-Africaine sont examinés. Les échantillons étaient prélevés mensuellement, sur une période de 14 mois. L'abondance en termites ainsi que leur richesse spécifique sont estimées. Ces estimations sont mises en relation avec un total cumulé des pluies d'une période de 30, 7 et 2 jours avant chaque échantillonage. Pour toutes ces durées, l'abondance et la richesse spécifique sont significativement négativement corrélées avec la pluviométrie. Toutefois, les corrélations les plus fortes sont généralement trouvées avec des pluies des 2 jours précédants, suggérant que les mouvements à court terme des termites au sein du profil du sol, seraient le facteur le plus important des differences observées, plutôt que des changements à long terme de leur abondance ou composition spécifique. Cette conclusion est confortée par une analyse des correspondances, qui ne montrent pas de changements significatifs dans la composition spécifique entre mois secs et pluvieux.

The stomach contents of 683 fishes representing 39 species were examined to determine the diet of fish living in fast-flowing waters (rapids) of the Sinnamary River in French Guiana. Aquatic invertebrates were shown to be an important source of food in the rapids biotopes, in contrast to what has previously been observed for slow-flowing waters. Aquatic insects (e.g., the larval stages of Diptera, Ephemeroptera and Trichoptera) make up 55% of the diet of fish living in rapids. Such prey animals were more common in those biotopes than in slow-flowing waters. Twenty-two species of fish, each represented by at least 10 individuals in all samples, were analyzed for their stomach contents. The spectrum of prey items allowed for an estimation of the similarity of feeding habits. These diets were further compared to those inferred for other rivers of the Amazonian and Guianian regions.