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Aim Successional and soil filtering processes are key drivers of the assembly of tropical tree communities, yet little is known about how they interact. Herein, we determine whether successional pathways depend on soil type, how the soil filtering effect varies during forest succession and whether succession is accompanied by changes in trait composition. Location South-western Central African Republic. Methods We used inventory data on 90 dominant tree species (72% of the stems ≥ 30 cm d.b.h.) in 15,420 plots (each 0.5 ha) distributed over an 8300-km2 mosaic of primary and secondary forests on contrasting clay and sandy soils. We gathered data on six traits: dispersal mode, nitrogen fixation, deciduousness, leaf area, wood density and maximum diameter. After validation with historical information, we used a successional index based on pioneer proportion to assess variations in trait composition, and in α- and β-diversity, in forest succession, and within and between soil types. Results Taxonomic and functional dissimilarities between clay and sandy soils decreased continuously during forest succession. Within soil types, early-successional communities had a low taxonomic but relatively high functional α-diversity. At the landscape scale, β-diversity was higher among earlier successional stages, except in rich soils where taxonomic β-diversity was high throughout the succession. Mean values for all traits, except leaf area, showed marked variations during forest succession in both soil types. Main conclusions The effect of soil type on community composition declines during succession, suggesting that the relative importance of neutral processes is higher in mature forests. Successional pathways were fairly similar in both soil types: disturbances reduced taxonomic diversity locally and enhanced β-diversity between sites, probably because the disturbances varied in type. We also demonstrated how easy-to-collect traits help improve predictions of ecological patterns and deepen our understanding of species assembly processes. [ABSTRACT FROM AUTHOR]

. This paper aims at proposing efficient vegetation sampling strategies. It describes how the estimation of species richness and diversity of moist evergreen forest is affected by (1) sampling design (simple random sampling, random cluster sampling, systematic cluster sampling, stratified cluster sampling); (2) choice of species richness estimators (number of observed species vs. non-parametric estimators) and (3) choice of diversity index (Simpson vs. Shannon). Two sites are studied: a 28-ha area situated in the Western Ghats of India and a 25-ha area located at Pasoh in Peninsular Malaysia. The results show that: (1) whatever the sampling strategy, estimates of species richness depend on sample size in these very diverse forest ecosystems which contain many rare species; (2) Simpson's diversity index reaches a stable value at low sample sizes while Shannon's index is affected more by the addition of rare species with increasing sample size; (3) cluster sampling strategies provide a good compromise between cost and statistical efficiency; (4) 300 - 400 sample trees grouped in small clusters (10-50 individuals) are enough to obtain unbiased and precise estimates of Simpson's index; (5) the local topography of the Western Ghats has a major influence on forest composition, the steep slopes being richer and more diverse than the ridges and gentle slopes; (6) stratified cluster sampling is thus an interesting alternative to systematic cluster sampling. [ABSTRACT FROM AUTHOR]