This study demonstrates that elephant seed-dispersal is vital for Balanites wilsoniana (Zygophyllaceae), a forest canopy tree with no other effective dispersers. Non-dispersed seeds suffered high mortality (84%) and low germination (3%). Elephants were reliable at visiting fruiting trees (46%), ingesting available seeds (55%) and dispersing the fruit crop (26%). Compared with unpassed seeds, seeds passed through an elephant's gut had improved germination (54.9% vs. 2.9%) and reduced time to germination (82 vs. 132 d). Given predation rates under parent trees, elephant gut passage is expected to improve absolute germination by 66%. When this change in germination is divided by germination of unpassed seeds, elephant gut passage is expect to improve relative germination by as much as 4000%. Although post-dispersal predation occurred in dung containing B. wilsoniana seeds, dispersed seedlings were abundant. Compared with seedlings under parent trees, dispersed seedlings had greater survival and height. Dispersed seedlings survived in a diversity of environments, thrived under high-light conditions, and were negligibly affected by post-dispersal density. Although elephants are not essential for B. wilsoniana germination, their actions greatly increase seedling establishment and move a large proportion of seeds. This high degree of effectiveness, together with very low non-dispersed seed survival, provides strong evidence that B. wilsoniana is dependent on elephants for its long-term persistence.

The dependent flora was surveyed on 20 trees at a 1.5-ha site in montane rain forest at 2600 m altitude in western Venezuela. Vascular species were recorded over the whole site and totalled 120 epiphytes, 21 climbers, 3 hemiepiphytes, 5 nomadic vines and 6 mistletoes. Non-vascular species were recorded within 95 sample plots and totalled 22 mosses, 66 liverworts and 46 macrolichens. The angiosperm species were restricted in geographical range to the Neotropics; 22.1% were endemic to Venezuela. Pteridophyte and bryophyte species were largely restricted to the Neotropics but few were endemic. Macrolichen species were mostly pantropical or cosmopolitan; only 9.6% were restricted to the Neotropics and none was endemic. Canonical Correspondence Analysis found the environmental variables most closely correlated with variation in community composition to be height above ground and a horizontal gradient reflecting differences in forest structure. The epiphytic vegetation was classified using Two-way Indicator Species Analysis into a Syrrhopodon gaudichaudii–Elaphoglossum hoffmannii group of lower trunks, an Omphalanthus filiformis–Maxillaria miniata group of intermediate levels and an Usnea–Parmotrema group of upper crowns. Diversity increased with height above ground; non-vascular diversity was greatest in upper crowns whereas vascular diversity was greatest at intermediate levels. Similarity levels were low among sample plots of the same community, whereas between-tree and between-stand similarities were relatively high.

The standing live biomass of papyrus swamps is high compared with most other communities dominated by herbaceous vegetation. For the first time, measurements of below-ground rhizome and root biomass are reported here, in addition to measurements of shoot biomass, for a papyrus swamp located on Lake Naivasha, Kenya. The ratio of rhizome and root to shoot dry weight was 1.38: 1 and the total standing live biomass was 7.8 kg(dry weight) m−2. Detritus, formed from slowly decomposing papyrus, is normally the most important sink for carbon in this ecosystem. The amount of detritus retained by swamps varies but at L. Naivasha it contained almost 20 times the carbon found in living biomass. The net primary production of the swamp was calculated to be 6.28 kg(dry weight) m−2 y−1, which is amongst the highest recorded productivities for natural ecosystems. Model estimates of carbon input into the system from photosynthesis are incorporated into a carbon flow diagram for the swamp and this emphasises the importance of detritus as a sink for carbon in this ecosystem.

Although the floral traits of Parkia conform to the bat-pollination syndrome, many visitors other than bats have been observed at their flowers. Some chiropterophilous plants are also pollinated by other animals; the syndrome is therefore best regarded as a hypothesis for which field observations and pollination experiments are required. The present study aimed, for the first time, to determine the breeding system of the economically important canopy trees, Parkia speciosa and P. timoriana, and to identify their pollinators. Pollination experiments carried out in Trang and Songkhla Provinces, in 28 trees of P. speciosa and four P. timoriana indicated that they are self incompatible. Open pollination resulted in the highest fruit set (average 60–67% of inflorescences per tree) although this was not significantly different from hand-crossed pollination (48–60%). Insect pollination resulted in fruit set in only 12% of P. speciosa inflorescences. Fruit bats, mainly Eonycteris spelaea, visit flowering plants continuously from dusk till after midnight. Nocturnal and diurnal insects (moths and stingless bees respectively) visit capitula, mostly at the nectar zone. Nectarivorous bats are the most effective pollinator for P. speciosa and P. timoriana. The fact that populations of E. spelaea appear to be declining throughout their distribution is therefore a matter of increasing concern.

Frugivorous butterflies were studied in a set of forested islands (0.1 to 1.15 ha) in a reservoir in eastern Venezuela to investigate the effects of fragmentation and the resulting isolation on their abundance, diversity and species composition. While some islands showed reduced abundance and species diversity in comparison to unfragmented (or control) sites, others did not. Isolation status affected both butterfly abundance and diversity. Islands located close to their colonizing sources (0.1–1 km) tended to support similar densities of butterflies but lower numbers of species in comparison to control sites. Far fragments (1–3 km from their colonizing sources) tended to harbour lower butterfly densities in comparison to control sites but undiminished numbers of species. Species composition varied significantly between control sites and islands and amongst control sites, near islands and far islands. Interspecific differences were observed in species' responses to fragmentation. Charaxines, medium-sized satyrines, morphines and brassolines may be vulnerable to extinction after habitat fragmentation while small-sized satyrines may be relatively resistant. Observations during the dry season indicate that butterfly species may exist as mainland-island metapopulations in Lago Guri, in which small habitat fragments require recolonization every year from source populations in large islands and mainland habitat.

Frugivorous birds play an important role in parasitic mistletoe transmission among host species. The foraging behaviour and host selection of Psittacanthus schiedeanus mistletoe fruit-eating birds was studied in cloud forest remnants in Central Veracruz, México. Cedar waxwings, Bombycilla cedrorum, gray silky-flycatchers, Ptilogonys cinereus, and social flycatchers, Myiozetetes similis, eating ripe whole mistletoe fruits and defecating or regurgitating the seeds were observed. That variation in host species selection by frugivorous birds had a direct effect on mistletoe dispersion was hypothesized. To test whether mistletoe host species are visited in proportion to their abundance (total number of trees), or infested-tree abundance (total number of infested trees), or abundance of mistletoes (total number of individual mistletoe plants in each host species), the number of trees, infested trees and individual mistletoe plants were recorded. Tree abundance, infested-tree abundance and mistletoe abundance were different among host species. Frequency of birds' visits to host species varied depending on the tree, infested-tree, or mistletoe abundance. Liquidambar styraciflua was the most abundant host species with the highest number of infested trees and individual mistletoe plants, but Persea americana and Crataegus mexicana host species had the highest number of individual mistletoe plants in each tree. Our data suggest that L. styraciflua was the most selected host species by the three frugivorous birds. Host selection by birds is one behavioural factor in explaining differences in prevalence among host species, and variation in infection levels among individuals of one host species.

RESUMEN. Las aves frugívoras juegan un importante papel en la transmisión de muérdagos parásitos hacia sus árboles hospederos. La conducta de forrajeo y selección de hospedero de aves consumidoras de frutos del muérdago Psittacanthus schiedeanus fueron estudiados en remanentes de bosque mesófilo de montaña del Centro de Veracruz, México. Bombycilla cedrorum, Ptilogonys cinereus and Myiozetetes similis fueron observados consumiendo frutos maduros enteros y defecando o regurgitando las semillas. Hipotetizamos que la variación en la selección de la especie hospedera por las aves frugívoras tiene un efecto directo en la dispersión del muérdago. Para probar si las especies de árboles hospederos son visitadas en proporción a su abundancia (número total de árboles), o la abundancia de hospederos infectados (número de árboles infectados) o la abundancia de muérdagos (número total de plantas individuales de muérdago en una sola especie de árbol); el número de árboles, árboles infestados y plantas de muérdago fueron registradas. La abundancia de árboles, de árboles infestados y de plantas de muérdago fue diferente entre las especies de árboles estudiadas. La frecuencia de visitas de las aves a las especies hospederas varió de acuerdo a la abundancia de árboles, de árboles infestados y de plantas de muérdago. Liquidambar styraciflua fue la especie hospedera más abundante con el mayor número de árboles infestados y abundancia de muérdagos, pero las especies Persea americana y Crataegus mexicana presentaron el mayor número de plantas de múerdago por árbol. Nuestros datos sugieren que L. styraciflua fue la especie hospedera más seleccionada por las aves frugívoras. La selección de hospederos por las aves es uno de los factores conductuales que explican las diferencias en prevalencia entre especies de hospedero, y la variación en los niveles de infestación entre individuos de una de las especies de hospedero.

Kentropyx calcarata (Teiidae) and Mabuya nigropunctata (Scincidae) occur together in lowland tropical forest of the Amazon near the Rio Curuá-Una of Brazil. During the wet season of 1995 these lizards were common at forest edge along narrow roads that transect forest, in treefalls and along streams where sun reaches the ground. Both species are heliothermic, basking to gain heat. Their association with open patches results from high activity temperature requirements in an environment where sun availability is low. Null temperature distributions from forest and treefalls showed that forest does not offer opportunities for heat gain similar to treefalls. Moreover, the large proportion of time spent basking by both species indicates the importance of these patches for thermoregulation. K. calcarata is slightly larger in body length and heavier at a given body length than M. nigropunctata. Both species are active foragers that seek out prey while moving through the habitat, feeding on orthopterans, roaches and spiders. M. nigropunctata also eat significant numbers of insects that occur on vegetation, such as hemipterans. Prey size is larger in K. calcarata and associated with lizard body size. Prey size does not vary with body size in M. nigropunctata and prey are typically relatively small.

Many of the ecological differences between these two lowland forest species appear to be historical: the ecology of K. calcarata is very similar to that of other species of Kentropyx and teiids in general and the ecology of M. nigropunctata is most similar to that of other studied species of south American Mabuya.

Many studies suggest that edaphic variables are major determinants of frog distributions. However, leaf-litter depth and soil characteristics are influenced by distance from streams, so the apparent relationship between edaphic characteristics and species distributions could be an artefact of the dependence of species on free water for reproduction. Therefore, we investigated the effect of edaphic variables on the mesoscale distribution of frog species not dependent on free water for reproduction. We evaluated the effects of soil texture, pH, slope, number of trees and leaf-litter volume on the distribution of nine terrestrially reproducing anuran species in the Reserva Ducke, a 100-km2 terra firme forest preserve in central Amazonia. Diurnal and nocturnal assemblages of anuran species were sampled in 72 plots systematically distributed across the reserve. We sampled the diurnal anuran assemblage by visual encounter in 250 × 1-m plots and the nocturnal assemblage in 250 × 20-m plots using both auditory and visual surveys. The majority of terrestrially breeding anuran species were influenced by topographic and/or edaphic variables, such as slope, soil clay content and pH. However, responses to environmental predictors differed among species. Most species occurred throughout all environmental gradients and relationships with soil characteristics were subtle, indicating that these species occur in the majority of habitats in Reserva Ducke. The results of this study indicate that terrestrially breeding frogs are habitat generalists that show little mesoscale beta diversity associated with habitat variation.

Rainfall and soil moisture availability vary greatly both spatially and temporally. They are prime factors influencing species distribution patterns, diversity and habitat associations in a range of biomes, and limit primary productivity in many natural ecosystems, as well as in forestry and agricultural systems (Hawkins et al. 2003, Kozlowski & Pallardy 1997, Lieth 1975). Projections of drying trends, and increased frequency and intensity of drought events with climate and land-use changes (Hulme & Viner 1998, IPCC 2001) have fuelled an increased interest in the role of drought in determining the structure and function of natural and managed forest systems (Allen & Breshears 1998, Miles et al. 2004). Such projections accentuate the need to assess, understand and predict plant reactions to drought, as well as soil moisture variation at different scales.

Fine roots and their turnover represent a dynamic aspect of below-ground biomass (BGB) and nutrient capital in forest ecosystems, and account for a significant fraction of net primary productivity (NPP) (Cuevas 1995, Vogt et al. 1990). On a weight basis, coarse roots contribute more to total ecosystem biomass than fine roots, but they account for only a small portion of annual root production (Eamus et al. 2002). Despite the fact that fine roots may compose less than 2% of total ecosystem biomass, they may contribute up to 40% of total ecosystem production (Vogt et al. 1990). Therefore, estimates of root production, like estimates of root biomass, should differentiate between coarse- and fine-root production.

The abundance, richness and species composition of frog, reptile, bird and mammal faunas varied along an extensive gradient from 470 to 1406 mm annual rainfall, and between three contrasting soil types (clay, loam and sand) in northern Australia. Patterns varied between and within vertebrate classes. In general, the most fertile soils in the highest rainfall sites supported the greatest species richness and abundance, but this association with fertility broke down at lower rainfall sites. Frogs were richest and most abundant at high rainfall sites, especially on clay soils, presumably because these had greatest water availability. Clay soils supported few reptile species, but these were often at relatively high abundance. High rainfall sites supported the richest reptile faunas. On sand and loam soils, bird species richness varied little along the rainfall gradient, but richness declined very substantially on clay soils. This was probably largely due to the far more marked vegetation structural change on clay soils than on other substrates. Few mammals were reported, and no clear trends were associated with either rainfall gradient or soil texture. Turnover in species composition along the rainfall gradient was gradual and limited on sand and loam soils, but far more marked on clay soils. There were few cases of replacements of ecologically comparable species along the gradient. These patterns reflect the disparate history, fragmentation and landscape positioning of clay soil environments, relative to the far more homogeneous eucalypt-dominated vegetation on sand and loam soils. Although comparable studies are lacking on other continents, patterns revealed here may be idiosyncratic due to the virtual monopolisation by eucalypts of the environment across the very extensive rainfall gradient.

Although the pollination biology of many individual plant species has been investigated in the Oriental region, there have been very few community-level studies. The two most comprehensive of these were in the primary mixed dipterocarp forest of Lambir Hills National Park, Sarawak (4°20′N: Momose et al. 1998, Sakai et al. 1999) and in the warm temperate evergreen broad-leaved forest and cool temperate mixed forest on Yakushima Island (30°N: Yumoto 1987, 1988). Hong Kong (22°17′N) lies midway between these sites, at the northern margin of the tropics, where winter temperatures fall below 10 °C at sea-level for a few days every year and there are occasional frosts above 400 m (Dudgeon & Corlett 1994). Latitudinal effects, however, are compounded in comparisons with other well-studied East Asian sites, by centuries of massive human impact, leaving a degraded landscape of steep, eroded hillsides, covered in fire-maintained grassland, secondary shrublands and, locally, secondary forests (Zhuang & Corlett 1997). This history has left a relatively impoverished fauna but a surprisingly diverse flora, including 400 native tree species (Corlett & Turner 1997). In these circumstances, failures of pollination and dispersal mutualisms might be expected to accelerate the loss of plant species from the landscape (Bond 1994, Kearns & Inouye 1997). Previous studies have shown that most woody vegetation in Hong Kong is dominated by species whose seeds can be dispersed by the commonest avian frugivores, the light-vented and red-whiskered bulbuls (Pycnonotus sinensis (Gmelin) and P. jocosus (Linn.)) and the Japanese white-eye (Zosterops japonicus Swinhoe) (Corlett 1996, 1998), but there is no equivalent information available on pollination biology.

ABSTRACT. Factors contributing to the resistance of gallery forests in savannas to the entry of fire were investigated using field observations and manipulation experiments. Mass of savanna fuels did not decrease close to forest boundaries, and in some instances increased, while savanna fuels adjacent to forests were moister than in the savanna beyond for only 1 d after rainfall. A fuel drying experiment conducted in both forest and savanna microclimates indicated that both fuel type and microclimate contributed to the resistance of forests to fire entry, although the former played a larger role. While savanna fuels in a savanna microclimate became ignitable in c. 1 d after rain, forest fuels in a forest microclimate required 4 wk to achieve ignitability. A further experiment juxtaposing forest fuels to burning savanna indicated that fire entry into forests was faciliated by deep root mats and the presence of a superficial litter layer, both of which become attenuated at the forest/savanna contact. It is concluded that fuels in these forests can reach an ignitable state late in the dry season, but that frequent fire entry is probably precluded by the tendency of savanna fires to occur earlier in the dry season and by discontinuities in fuels at the savanna/forest contact.

RESUMEN. Se investigaron los factores que contribuyen a la resistencia de la entrada del fuego a los bosques en galería de las savanas mediante observaciones de campo y experimentos de manipulación. La masa de los combustibles de la savana no decrecieron cerca de los bordes del bosque; por el contrario, en algunos casos se incrementaron, mientras que los combustibles de la savana cercanos al bosque eran mas húmedos que en la savana restante, solamente por un día despues de un evento de lluvia. Un experimento de secado de combustible, que fue conducido en los microclimas de bosque y de savana, indica que tanto el tipo de combustible como el microclima contribuyen a la resistencia de los bosques a la entrada del fuego, aunque el primer factor tuvo un papel de mayor importancia. Mientras que los combustibles de la savana en el microclima de la savana se volvieron ‘encendibles’ cerca de un día despues de lluvia, los combustibles del bosque dentro del microlima del bosque tomaron cuatro semanas para llegar a dicho estado. Un experimento que sobrepuso combustibles del bosque a la savana ardiente indicó que la entrada del fuego a los bosques se facilitó por la presencia de mantillos orgánicos profundos y de una capa superficial de hojarasca, presencia que se ve atenuada en la zona de contacto bosque/savana. Se concluye que los combustibles en estos bosques pueden alcanzar un estado de ignición tarde en la estación de sequía, pero que la entrada frecuente del fuego es probablemente evitada por la tendencia que tienen los fuegos de savana a presentarse temprano en la estación seca y por las discontinuidades de combustibles en la zona de contacto savana/bosque.

Psittacanthus robustus (Loranthaceae) is a Neotropical mistletoe which grows mainly on species of Vochysiaceae in Brazilian ‘cerrado’ regions. Its parasitizing pattern involves: (a) the height and the aspect of the crown of the host-plants; (b) the presence of sticky substance in the fruits of the parasite; and (c) the feeding behaviour and habitat selection of the dispersal agent, the swallowtanager Tersina viridis viridis. The feeding behaviour of this bird on fruits of P. robustus facilitates seed release and seedling establishment; its foraging habit and habitat selection account for high concentrations of the parasites on their preferred host-plants.

The effect of tree canopy cover on soil properties was studied over three periods: middry season (January), mid-growth period (August) and peak-growth period (October) in three 1 ha plots in savanna of north-west Nigeria. The objective was to find out whether tree canopies change the nutrient status of the soil under them relative to adjacent grasslands. Soils under tree canopies were found to have significantly higher levels of organic matter, calcium, magnesium, potassium, total exchangeable bases, cation exchange capacity and pH than those in open grasslands. Nitrogen and phosphorus were slightly higher in soils under tree canopies than those in the open grasslands. Trees 7 m and above had more influence on soil properties than smaller trees. Differences in soil properties among the study plots were due to differences in their soil texture. Seasonal trends were observed in organic matter, carbon: nitrogen ratio, cation exchange capacity, phosphorus, calcium, sodium, total exchangeable cations and percentage base saturation.

A study of the benthic leaf litter community of the Tarumazinho, a central Amazonian stream (03° S, 60° W) is presented. This small tributary of the Rio Negro is of the blackwater type with a very low nutrient content. The sampling stations were towards the mouth of the tributary where it flowed through annually inundated forest and the work was carried out during the low water season. Previous studies concluded that these acid waters were of very low productivity and held impoverished faunas. However, this study showed that leaf litter banks held a diverse aquatic community of unexpectedly high biomass. This was because the banks supplied food and shelter and were available during the low water period when other habitats had dried out. The macrofauna was dominated by fish and shrimps. From an examination of gut contents a food web was produced. Primary consumers were found to take mainly detritus and fungi and it was concluded that allochthonous inputs were the main source of energy and nutrients. No feeding specialists were found and all the predators took prey from more than one trophic level.

The natural 15N abundance method for estimating symbiotic biological N2-fixation was tested on legume trees from two rain forests on contrasting soils (oxisols and spodosols) in French Guiana. When possible, the significance of N2-fixing species in the plant community was evaluated in terms of density, biomass and contribution of N2-fixation to the building up of the total nitrogen mass in the leaves. Of the two sites, the rain forest on spodosols was the less favourable for application of the δ15N method: the available soil nitrogen was isotopically similar to fixed-N2. Hence, the results showed that a reliable estimate of N2-fixation could not be obtained. A substantial contribution of fixed-N2 to the nitrogen nutrition of legumes was found on oxisols, with an average value of 54 % Ndfa (Nitrogen derived from the atmosphere). The contribution of the N2-fixing legumes to the biomass of the stand was estimated to be 2 t ha−1 for the leaf biomass and 136 t ha−1 for the total above-ground plant biomass. With 7.5 % of trees in the stand able to fix N2 (462 out of 6156), N2-fixation was estimated to be 7 kg ha−1 y−1. These results are the first use of the δ15N method to estimate nitrogen input by N2-fixing legumes to a natural rain forest. The inter-site variability observed in the δ15N of the non-fixing plants suggested different nitrogen-cycling processes in the two soils. The δ15N of the non-N2-fixing plants could be related to the soil nitrogen availability and be used as an indicator of efficient or non-efficient nitrogen-cycling rain forests. The spatial variability of the δ15N in the plant-available soil nitrogen pool and the nitrogen balance in tropical rain forests are discussed.

Litterfall in primary and secondary forests (‘capoeira’) in eastern Brazilian Amazonia was measured fortnightly from August 1979 to October 1980. The nutrient contents of the litter (N, P, K, Ca and Mg) were determined.

Litterfall differed between the two forest types (primary forest − 8.04 t ha−1 yr−1; secondary forest − 5.04 t ha−1 yr−1). The value obtained for primary forest was similar to those reported elsewhere in Brazil (mean = 8 t ha−1 yr−1) and from other regions of S. America (mean = 7.20 t ha−1 yr−1).

Prediction of net primary production from litterfall at the primary forest site gave rise to values of 14.47 and 26.53 t ha−1 yr−1. Estimates of net primary production in ‘capoeira’ ranged from 9.07 to 16.63 t ha−1 yr−1.

Seasonality of litterfall was more marked in ‘capoeira’ than primary forest but in both cases was less pronounced than elsewhere in Brazil.

Nutrient concentrations were highest in ‘capoeira’ litter, a finding which accords with results from other tropical sites; nevertheless input of nutrients per unit area of forest floor was greatest in the primary forest.

Small-scale spatial association of the distribution for 55 abundant tree species with two environmental factors (humus depth and surface microtopography) was examined in two 1-ha plots of a heath (kerangas) forest in Central Kalimantan, Indonesia. More than 80% of the 55 species showed a significant habitat preference in humus depth and/or relative elevation in at least one plot. In particular, ten species occurring in both plots showed a consistent significant preference for humus depth or relative elevation in the two plots. Using randomization tests, however, only five species significantly associated with humus depth and no species with relative elevation. These results suggest that edaphic and topographic factors, especially humus depth, contribute to determining local spatial distribution and floristic composition of abundant tree species in the forest.