This study is the first to compare bird communities across different sites within the same large continuous neotropical primary forest area. The objectives were to document bird distribution patterns, the spatial variability of specific abundances and the between-site turnover in species compositions. I censused 268 forest-interior species, 39 raptors and 135 natural-gap species in 20 widely spaced, c. 2000-ha sites in the interior of French Guiana, divided into three main zones. At least 59% of species had a very low abundance index and/or rate of occurrence among sites and only 1% were widespread dominants. Beta diversity was an important determinant of regional species richness. There was an average 29% species turnover between sites and 7% between regions, as well as a lack of nested-subset structure among communities and a random occurrence of pairs of similar congeners. At the country scale, only one species had a truly restricted geographical range, independent of habitat availability, but at a local scale, many species had uneven distributional gaps (36% present at < 50% of sites with suitable habitat). Among sites, abundance or incidence variability had no definite pattern. Frequency of occurrence in suitable patches decreased with increasing natural fragmentation of habitats. There were significant relationships between habitat selection and abundance or frequency of occurrence but not with diet or body size. Few species exhibited consistent geographical trends along the north-south gradient of decreasing rainfall. Guianan endemics tended to be widespread within the country. Several seasonal movements and inter-annual population fluctuations were documented. Rarity had different forms, but no general ecological correlates. Nearly half of rare species were associated with various types of forest gaps or edges, and were consequently more abundant outside the forest zone, i.e. in grasslands or clearings. Local occurrences and abundances seem to be the result of highly species-specific factors, and hence any general determinant of community structure may be obscured by specific reactions in such species-rich, heterogeneous and complex tropical rain-forest communities.

Distribution patterns of vascular plants with diameter at breast height (dbh) ≥ 2.5 cm were studied on the basis of compositional data from 30 small plots located in a rain-forest area in Colombian Amazonia. The research questions were: How are distribution patterns of species in relation to local abundance in plots? Do understorey species (defined as species with individuals that never attained dbh ≥ 10 cm anywhere) show better correlations with soils and environment than canopy species (defined as species with individuals that attained dbh ≥ 10 cm)? Are patterns found in the entire range of landscape units comparable to those found in well-drained uplands alone? Species that occurred in more than one plot showed higher local abundances. This pattern was consistent among environmental generalists and specialists. Locally rare species (with only one individual in a plot) occurred mostly in well-drained uplands. Considering all landscape units, Mantel tests showed substantial correlations between environmental data (soil chemical data, drainage and flooding) and species composition. Canopy species were only slightly less correlated with environmental data than understorey species. Elimination of the spatial component in the data did not reduce these correlations. In well-drained uplands, understorey species were better correlated with soils than canopy species. Here, however, the spatial configuration of the plots became more important in explaining species patterns.

A study of nutrient movement through rainfall, throughfall and stemflow, as well as epiphytic bryophyte (moss and liverwort) biomass and its effect on nutrient composition of stemflow, was conducted for 2 y in subtropical montane moist forest (Lithocarpus–Castanopsis association) at Xujiaba, Ailao Mountain National Nature Reserve, Yunnan, south-west China. Base cation and fluxes were increased in throughfall, while NH4+-N and NO3--N were reduced relative to precipitation. Annual throughfall inputs of N, P, Ca and S were mainly from precipitation, while most K and two-thirds of Mg throughfall input was due to canopy leaching. Input of Na in the precipitation and throughfall was low in this forest. Net flux (throughfall flux minus bulk precipitation) and deposition ratios (ratio of throughfall flux to bulk precipitation flux) were in the low part of the range reported for other tropical montane rain forests. The throughfall data for this forest reveal generally low cycling rates for mineral elements. Abundant epiphytic bryophytes on bole bark affected the chemical composition of stemflow by selective uptake or release of elements. Relative to trees without epiphytic bryophytes, the annual amounts of total N, NH4+-N, Mg, Na and SO42--S were enhanced, while NO3--N, K, P and Ca were depleted in stemflow. Contributions of N from nitrogen-fixing organisms are likely to be constrained by low temperatures.

In the Australian wet–dry tropics, temperatures are high year-round but rainfall is concentrated in a 4-mo wet season. Regular nightly surveys in the Fogg Dam Nature Reserve provided data on temporal (monthly, seasonal) variation in biological attributes of three snake species: water pythons (Liasis fuscus, Pythonidae), keelbacks (Tropidonophis mairii, Colubridae) and slatey-grey snakes (Stegonotus cucullatus, Colubridae). Adults of all three taxa were encountered more frequently during the dry season than the wet season, whereas juveniles were more commonly encountered in the wet season. The sex ratio among adult snakes also shifted seasonally, but in different ways in different species. These sex-ratio shifts probably reflect reproductive activity (mate-searching by males, oviposition migrations by females) and were accompanied by increased encounter rates. Feeding rates and body condition of keelbacks (a frog specialist) were highest during the wet season when frogs were most abundant. Rats migrated away from Fogg Dam during the wet season, and most pythons (rat specialists) left this area to follow their prey. The pythons that remained at Fogg Dam exhibited low feeding rates and poor body condition. Slatey-grey snakes (a generalist predator) showed less seasonal variation in feeding rates or body condition. Our data show that tropical seasonality induces strong fluctuations in many attributes of snake populations, and that patterns of response differ both among and within species.

In tropical forests, severe droughts caused by El Niño events may strongly influence the water relations of tree seedlings and thereby increase their mortality. Data on known-aged seedlings of three common shade-tolerant canopy tree species (Trichilia tuberculata, Tetragastris panamensis and Quararibea asterolepis) in a Panamanian moist forest are presented. Seedling survival during a severe El Niño dry season (1997-98) was compared with prior long-term survival data, and levels of drought stress were assessed by measuring plant water potentials and gas exchange characteristics. Contrary to prediction, dry-season seedling survival was not dramatically reduced in any species compared with that expected in ‘normal’ years. In Trichilia and Quararibea, pre-dawn water potentials averaged −2 MPa and midday water potentials about −3 MPa. Stomatal conductances were very low, averaging 26 mmol m-2 s-1 for Tetragastris and 11–13 mmol m-2 s-1 for Trichilia and Quararibea. Photosynthetic rates also were very low but consistently positive, averaging 0.8–1.1 μmol m-2 s-1. The findings suggest that, once established, seedlings of common tree species in this semi-deciduous forest may be tolerant of drought events.

To study the impact of the annual long-term flooding (flood-pulse) on seasonal tree development in Amazonian floodplains, the phenology and growth in stem diameter of various tree species with different leaf-change patterns were observed over a period of 2 y. The trees of the functional ecotypes, evergreen, brevi-deciduous, deciduous and stem-succulent showed a periodic behaviour mainly triggered by the flood-pulse. Trees have high increment during the terrestrial phase. Flooding causes a shedding of some or all leaves leading to a cambial dormancy of about 2 mo and the formation of an annual ring. Studies carried out in tropical dry forests verify a strong relationship between the phenological development and the water status of the trees, strongly affected by seasonal drought. The comparison of the phenology and the diameter growth of the corresponding ecotypes in floodplain forest and a semi-deciduous forest in Venezuela shows a displacement of at least 2 mo in the periodicity, except for stem-succulent tree species. For stem-succulent trees it remains unclear which factors influence phenology and stem diameter growth.

Damage caused by elephants was monitored in two woodland stands of Zakouma National Park (Chad) between February and March 1998. The Acacia seyal savanna was more severely damaged (29.8% of trees damaged of which 13.2% severely) than the Combretaceae savanna (26.5% of trees damaged of which only 4.2% severely). Nearly all severely damaged trees showed resprouts (respectively 86.8% and 88.5% in Combretaceae and A. seyal savannas). Both low damage rate and low mortality rate indicate that no serious ‘elephant problem’ occurred in Zakouma National Park. Elephants selected trees to damage according to species and height. Such selection also occurred for severe damage in A. seyal savanna, but only height affected severity of damage in Combretaceae savanna. In both savannas, the plots close to a water point were the most frequently damaged. In Combretaceae savanna, the distribution of damaged trees was clumped. On the other hand, spatial auto-correlation was not significant for the severity or the frequency of damage in A. seyal savanna. Neither tree density nor diversity of woody species affected the spatial patterns of damage or severe damage.

The fact that certain climatic variables are similar in high-latitude temperate zones and at high-altitude sites in the tropics, has led to assumptions about ecologically equivalent situations. The altitudinal differences between two data sets obtained in forests in temperate Denmark at sea level and in tropical Ecuador at 3000–3350 m above sea level provided a comparison suitable for examining whether high-altitude Andean forests are temperate or tropical from the standpoint of avian richness, abundance and trophic organization. Sampling methods at the two locations were similar. The Ecuadorian high-altitude sites were found to be significantly more species-rich than Danish temperate sites at all spatial scales studied (from point census to 10 km2). Additionally, species–area curves from the two countries displayed positive correlations, as expected, but with different rates of increase. The high-altitude Andean curve demonstrated a higher rate of increase causing the two curves to separate widely as more area was added. This means that when increasing areas are considered, proportionately more species squeeze into the Ecuadorian high-altitude forest landscape than do into the temperate Danish forest landscape. Corresponding to the data on richness, bird abundance was significantly higher at the Ecuadorian sites than at the Danish ones. The analysis of rank–abundance plots from Denmark and Ecuador throws light on the organization of bird species and abundance. The majority of communities in both countries fitted both the log-series and the log-normal models, making statistical distinction impossible. However, a visual inspection of the rank-ordered abundance distributions demonstrated that the Danish communities, in contrast to the Ecuadorian ones, had dominant species with relatively higher abundance, had more species with intermediate abundance, and had fewer species ‘rare by abundance’. Some major food resources (especially fruit and nectar) exploited in high-altitude sites of Ecuador were not reliably available in temperate Denmark leading also to differences in the distribution of bird species within six major trophic categories. In conclusion, the ecological characteristics of birds of the high Andes apparently are similar to those of the tropical and tropical lower montane sites (increased richness and abundance, similar organization of richness and abundance, similar additional trophic categories, similar clutch sizes), and not to those of the high- and low-latitude temperate sites.

Because of its position on the northern margin of the tropics (22° 17′N) and the southern coast of a huge continent, Hong Kong has a climate in which both temperature and rainfall are highly seasonal. Although summer temperatures are equatorial, the January mean is only 15.8 °C,and the absolute minimum recorded at sea level is 0 °C (Dudgeon & Corlett 1994). As a result, all aspects of the ecology of Hong Kong show seasonal changes. The most dramatic changes occur in the bird fauna, with the majority of species migratory (Carey et al. 2001). The winter fruiting peak in secondary shrublands and the forest understorey coincides with the arrival of partially frugivorous migrant robins and thrushes (Corlett 1993). However, while resident insectivore-frugivores consume almost entirely fruit during this period (Corlett 1998), all the winter visitors continue to eat insects and some (e.g. Phylloscopus warblers) are entirely insectivorous. The study of insect seasonality reported here formed part of a 30-mo study of the seasonality of a forest bird community in Hong Kong (Kwok & Corlett 1999, 2000). Plant names follow Corlett et al. (2000).