In central Amazonian white-water floodplains (várzea), different forest types become established in relation to the flood-level gradient. The formations are characterized by typical patterns of species composition, and their architecture results in different light reflectance patterns, which can be detected by Landsat TM image data. Ground checking comprised a detailed forest inventory of 4 ha, with Digital Elevation Models (DEM) being generated for all sites. The results indicate that, at the average flood level of 3 m, species diversity and architecture of the forests changes, thus justifying the classification into the categories of low várzea (várzea baixa) and high várzea (várzea alta). In a first step to scale up, the study sites were observed by aerial photography. Tree heights, crown sizes, the projected crown area coverage and the gap frequencies provide information, which confirms a remotely sensed classification into three different forest types. The structure of low várzea depends on the successional stage, and species diversity increases with increasing age of the formations. In high várzea, only one successional stage was found and species diversity is higher than in all low-várzea formations. The more complex architecture of the high-várzea forest results in a more diffuse behaviour pattern in pixel distribution, when scanned by TM image data.

The amount and annual net accumulation of above-ground dead woody material were quantified in a tropical deciduous forest in western Mexico. Three plots were located within a small watershed (16 ha) and distributed along a 150-m-elevation gradient (Upper, Middle and Lower plot). Total amount of above-ground dead phytomass (fine + coarse) was 27.2 Mg ha-1. Coarse dead category (branches + logs) made up 70.6% (19.2 Mg ha-1) of the total. The rest comprised the fine fraction, which was lying on the forest floor as surface litter. Of the total coarse dead woody mass, 70.8% was standing, hanging or still attached to live trees (13.6 Mg ha-1). Dead wood net accumulation was 6.6 Mg ha-1 y-1; 58% of this was coarse woody material and the rest comprised the fine litterfall fraction. The amount of standing, hanging/attached dead branches (2-20 cm circumference) varied significantly among plots, with the highest value in the Upper plot. Dead wood net accumulation was similar between the Upper and Middle plots, and significantly higher than the Lower plot. Compared to the intact canopy, the removal of dead mass (hanging/attached dead branches and standing dead logs) caused a significant decrease in throughfall nutrient concentration and nutrient flux by this pathway.

Spatial vegetation utilization of elephants was investigated within mixed woodland savanna along the Chobe River in northern Botswana in the dry season of 1998. Using multiple linear regression, accumulated stem breakage by elephants was predicted by a terrain index, distance to water, stand density, number of trees > 4 m tall, tree height, density of Combretum apiculatum, C. elaeagnoides, C. mossambicense and the density of other (accumulated) tree species. Within mixed woodland at 2–7 km distance from the river fine-grained terrain ruggedness was the most important factor contributing to 55% of observed differences in use by elephants, while distance to water and the density of C. apiculatum contributed an additional 20% and 4%, respectively to the multiple linear regression model. Stem breakage was, on average, almost twice as high in rugged terrain compared with flat terrain at similar distance to water within the same vegetation type. Rugged terrain had 2–3-fold higher proportion of plots with very high Combretum shrub densities. These results suggest that the terrain index may be useful in management, predicting the areas most sensitive to vegetation change in a woodland system with increasing elephant densities.

Lianas of Yasuní National Park and the Huaorani Ethnic Reserve, Ecuador were sampled using 0.2-ha subsamples from 12 1-ha plots. Using surveys and herbarium collections, the total species richness of lianas in the park and reserve is estimated to be close to 500 species. Terra firme habitats are significantly more species rich than floodplain habitats, but density of stems is not significantly different between habitats. The most abundant liana species is Machaerium cuspidatum Kuhlm. & Hoehne (Fabaceae) in both floodplain and terra firme habitats, representing more than 10% of all stems in census plots. Analysis of rarity indicates that none of the liana species encountered on the 12 plots is rare in terms of geographic range, and many species are not rare in terms of population size or habitat specificity. The rank order of abundance, combined with the coefficient of variability in species distribution among plots, is used to identify the 38 species (an oligarchy) that dominate forests in Yasuní.

Amomum villosum Lour. (Zingiberaceae) is an obligate shade plant. Its leaves naturally roll up upon exposure to bright sun. This paper characterizes the effects of its leaf rolling and light on photoinhibition of photosynthesis and thermal dissipation activity under field conditions with sufficient soil moisture. Between the plants from bright and shaded parts of a canopy gap, both maximum photosynthetic rate (mean ≈ 6.5 μmol m-2 s-1) and stomatal conductance (148 vs. 131 mmol m-2 s-1) were not significantly different, but apparent quantum yield (0.021 vs. 0.025) and dark respiration rate (0.49 vs. 0.30 μmol m-2 s-1) were. In the foggy morning, when the incident irradiance was low, photoinhibition had already occurred in plants in the bright part of the canopy gap and also in plants in the shaded part of the gap but to a much lesser degree. Photoinhibition accelerated with increase of incident irradiance and relaxed in the afternoon. Thermal dissipation as indicated by non-photochemical fluorescence quenching (NPQ) increased rapidly in the morning and continued at a high rate in the afternoon. Prevention of leaf rolling resulted in acceleration of photoinhibition. Artificial inhibition of the xanthophyll cycle led to acceleration of both photoinhibition and inactivation of PSII reaction centres, and decrease of NPQ. Photoinhibited leaves in either control or treatment plants recovered overnight. These results show that A. villosum is able effectively to prevent photodamage through the mechanisms of leaf rolling, thermal dissipation and reversible inactivation of PSII reaction centres.

Laboratory and growth-chamber experiments were used to evaluate whether there was evidence for nutrient retention by tropical terrestrial ecosystems being a two-stage process involving first soil adsorption and then plant absorption. Quartz sand with and without Fe and Al oxide coatings were treated with nutrient solution, then subjected to a leaching regime that simulated early wet-season conditions at a tropical location. Nutrient cations applied were rapidly lost in the initial leaches from quartz sand without oxide coatings, but showed a more gradual loss from oxide-coated sand, indicating temporary adsorption by the latter. In a second experiment, oxide-coated sand with and without seedlings of Grevillea robusta (a non-mycorrhizal tree species) were subjected to a similar treatment and leaching losses were compared. The presence of seedlings significantly reduced the losses of all nutrient cations, with the effect being minimal for Na and greatest for K, confirming that plants can gain access to temporarily adsorbed nutrients. More typical tropical soil-vegetation systems are likely to possess properties that magnify both the adsorptive and absorptive processes that have been documented in these experiments, justifying extrapolation of the experimental results to these natural systems. The existence of a two-stage process of nutrient retention provides a plausible explanation for the resistance of most tropical ecosystems to rapid loss of nutrients following events such as fires, which provide acute nutrient loading to the system.

The aim of this work was to analyse the phenological variation of a residual invasive semi-evergreen shrub in Sahelian fallows in Niger. This species, Guiera senegalensis (Combretaceae), has benefited from the elimination of other species thanks to its high resistance to the increasing cutting pressure for cultivation. We sought to identify traits of its life cycle that could contribute to its persistence and widespread dominance under such a disturbance regime. Leafing, flowering and fruiting were monitored on seven fallows differing in topographic location, age, shrub density and degradation state, during two rainy seasons and one dry season. Phenological spectra showed similar timing of the three phenophases of the seven populations. Differences were observed mainly in magnitude of the phases. However, there were both a high intra-fallow variability (64.6% of the whole variability) and a statistically significant inter-fallow variability, despite only 35.4% of the total variability being due to differences between fallows. A statistical classification of the fallows was proposed based on shrub phenological course over the two cycles monitored. This classification corresponds to a gradient of life-cycle achievement primarily linked to the topographic situation of the stations, and then to a combination of other factors. The flexibility of the phenology at the individual, population and metapopulation scales, inherent to its specific semi-evergreenness property, appeared as an essential phenological attribute contributing to successful widespread persistence of G. senegalensis in the study area.

We analysed the selection of tree species consumed by an isolated troop of Mexican howler monkeys (Alouatta palliata mexicana) released in a translocation programme on Agaltepec Island, in Catemaco Lake, Veracruz, Mexico. During November 1989–December 1996, howlers used 36 of the 63 tree species present on the island as food. Selection ratios indicated that six Ficus species (particularly F. pertusa) were among the seven most important food species. Data on time spent feeding showed that the six Ficus species were among the eight most important food species for the monkeys. Howlers spent 64.2% of their feeding time on Ficus products with F. pertusa being consumed significantly more often than foods from other Ficus species. However, monkeys fed on only one third of the 81 adult Ficus trees on the island. No significant differences were found in various food constituents (water, ash, fibre, protein, carbohydrates, lipids) of the six Ficus and two other abundant species in the habitat, whether across species, plant parts (young leaves, mature leaves, fruits), or between seasons (wet, dry). Monkeys consumed Ficus fruits rather the leaves. Fruits showed a much higher energy content per g dry weight than leaves. We also estimated the average daily biomass of leaves and fruits of Ficus spp. consumed by howlers and their energetic contribution to the daily diet of these monkeys. We suggest that some of these tendencies to frugivory reflect the abundance of Ficus trees within the home ranges of the howlers; when few fig trees are present, folivory is the dominant tendency, whereas when many fig trees are present, frugivory is dominant.

Euglossine bees (Hymenoptera: Apidae: Euglossini) are considered keystone species in the neotropics because of their role as pollinators of several plant species, particularly orchids (Dodson et al.1969, Roubik 1992). Pollination by male euglossine bees occurs when they visit flowers to collect fragrances, which may be used for courtship (Eltz et al. 1999) or attraction of other males and females (Peruquetti 2000). Synthetic products that mimic those fragrances have been used frequently in studies of euglossine bee ecology and population structure (Armbruster & McCormick 1990, Powell & Powell 1987, Roubik & Ackerman 1987). The ability of euglossine bees to disperse and find isolated flowers and distant baits (Dressler 1968, Janzen 1971) has led Janzen (1981) and Janzen et al. (1982) to suggest that bees attracted to fragrances come from a wide area that may include different habitats. According to this hypothesis, individuals collected at baiting stations are part of the same pool of bees. However, Armbruster (1993) found significant variation in the number of bees collected at nearby baiting stations, and he considered these differences as demonstration of within-habitat heterogeneity of the euglossine bee community. In Armbruster's model, results of bait collections are strongly affected by the concentration of resources in ‘hot spots’, therefore a sampling station would not necessarily represent the habitat, but only particular microhabitats.

The Amazonian rain forests form one of the largest areas of continuous forest in the world, and they harbour a substantial part of the world's biodiversity (World Conservation Monitoring Centre 1992). The extravagant species richness of Amazonia makes collecting information on species distribution patterns there a formidable challenge. Relatively few studies have been able to provide data that cover both a large enough number of species and wide enough geographical areas to allow relevant biogeographical and ecological generalizations (such studies concerning plants include Balslev 1988, de Oliveira & Daly 1999, Pitman et al. 1999, Prance 1973, ter Steege et al. 2000, Terborgh & Andresen 1998, Tuomisto & Poulsen 1996). The scarcity of field observations is undoubtedly one of the reasons why very different ideas exist about the mechanisms that control plant distributions and patterns of species richness in Amazonia (Balslev 1988, Condit 1996, Gentry 1988, Nelson et al 1990, Pitman et al. 1999, Prance 1973, 1982; ter Steege et al. 2000, Tuomisto et al. 1995).

In 1999, Dalling & Harms simulated 100% above-ground herbivory on seedlings of Gustavia superba, a large-seeded species from Barro Colorado Island, Panama, and showed the remarkable ability for cotyledons to regenerate up to eight new shoots. They used this evidence to propose that cotyledon size (at least in this species)was adaptive in surviving pre- and early post-germination hazards (Dalling & Harms 1999). In this note we describe the first record of multiple resprouting in an Australian tropical plant species. Idiospermum australiense (Diels) S. T. Blake (Calycanthaceae) exhibits characteristics similar (but not identical) to G. superba that support the contention of Dalling & Harms (1999).

Figure 6 was inadvertently printed in black and white instead of full colour. Please see the reprinted page 405 in colour overleaf with 406 backing it. This will enable readers to replace the complete page from part 3 if desired. The publishers would like to apologise to the author and their readers for this error.