The high species richness of tropical forests has long been recognized, yet there remains substantial uncertainty regarding the actual number of tropical tree species. Using a pantropical tree inventory database from closed canopy forests, consisting of 657,630 trees belonging to 11,371 species, we use a fitted value of Fisher's alpha and an approximate pantropical stem total to estimate the minimum number of tropical forest tree species to fall between ∼ 40,000 and ∼ 53,000, i.e., at the high end of previous estimates. Contrary to common assumption, the Indo-Pacific region was found to be as species-rich as the Neotropics, with both regions having a minimum of ∼ 19,000-25,000 tree species. Continental Africa is relatively depauperate with a minimum of ∼ 4,500-6,000 tree species. Very few species are shared among the African, American, and the Indo-Pacific regions. We provide a methodological framework for estimating species richness in trees that may help refine species richness estimates of tree-dependent taxa.

A recent increase in published studies of lianas has been paralleled by a proliferation of protocols for censusing lianas. This article seeks to increase uniformity in liana inventories by providing specific recommendations for the determination of which taxa to include, the location of diameter measurement points on individual stems, the setting of minimum stem diameter cutoffs, the treatment of multiple‐stemmed and rooted clonal groups, and the measurement of noncylindrical stems. Use of more uniform liana censusing protocols may facilitate comparison of independently collected data sets and further our understanding of global patterns in liana abundance, diversity, biomass, and dynamics.

We test the hypotheses proposed by Gentry and Schnitzer that liana density and basal area in tropical forests vary negatively with mean annual precipitation (MAP) and positively with seasonality. Previous studies correlating liana abundance with these climatic variables have produced conflicting results, warranting a new analysis of drivers of liana abundance based on a different dataset. We compiled a pan-tropical dataset containing 28,953 lianas (Z2.5 cm diam.) from studies conducted at 13 Neotropical and 11 Paleotropical dry to wet lowland tropical forests. The ranges in MAP and dry season length (DSL) (number of months with mean rainfall o 100 mm) represented by these datasets were 860-7250 mm/yr and 0-7 mo, respectively. Pan-tropically, liana density and basal area decreased significantly with increasing annual rainfall and increased with increasing DSL, supporting the hypotheses of Gentry and Schnitzer. Our results suggest that much of the variation in liana density and basal area in the tropics can be accounted for by the relatively simple metrics of MAP and DSL.Abstract in Spanish is available at

Summary1. Comparative analyses of diversity variation among and between regions allow testing of alternative explanatory models and ideas. Here, we explore the relationships between the tree α -diversity of small rain forest plots in Africa and in Amazonia and climatic

Aim Tropical rain forests are often regarded as pristine and undisturbed by humans. In Central Africa, community‐wide disturbances by natural causes are rare and therefore current theory predicts that natural gap phase dynamics structure tree species composition and diversity. However, the dominant tree species in many African forests recruit poorly, despite the presence of gaps. To explain this, we studied the disturbance history of a species‐rich and structurally complex rain forest. Location Lowland rain forest in Southern Cameroon. Methods We identified the recruitment conditions of trees in different diameter classes in 16 ha of species‐rich and structurally complex ‘old growth’ rain forest. For the identification of recruitment preference we used independent data on the species composition along a disturbance gradient, ranging from shifting cultivation fields (representing large‐scale disturbance), to canopy gaps and old growth forest. Results In nine of sixteen 1‐ha forest plots the older trees preferred shifting cultivation fields for recruitment while younger trees preferred gaps and closed forest conditions. This indicates that these nine sites once experienced large‐scale disturbances. Three lines of evidence suggest that historical agricultural use is the most likely disturbance factor: (1) size of disturbed and undisturbed patches, (2) distribution of charcoal and (3) historical accounts of human population densities. Main conclusions Present‐day tree species composition of a structurally complex and species‐rich Central African rain forest still echoes historical disturbances, most probably caused by human land use between three to four centuries ago. Human impact on African rain forest is therefore, contrary to common belief, an issue not of the last decades only. Insights in historical use will help to get a more balanced view of the ‘pristine rain forest’, acknowledging that the dualism between ‘old growth’ and ‘secondary’ forest may be less clear than previously thought.

No abstract

Abstract. The occurrence and abundance of 12 canopy tree species from the moist tropical forests of West Africa have been studied in relation to a climatic gradient. We focused on environmental factors related to water availability: annual amount of rainfall, the length of the dry season, and cumulative water deficit. Species occurrence and abundance data are used for 39 forest sites in Liberia and southwest Côte d'Ivoire. Species responses are modelled using a set of five increasingly complex models, ranging from a no‐trend model to a skewed bell‐shaped response curve. The study species show different distribution patterns. Most of them suggest a close relationship to climatic conditions. Fitting of species occurrence data to each of the three climatic factors results in most cases in simple models. In only one out of 36 cases a bell‐shaped response curve is needed to describe the data. Four of the 12 species show no response to the climatic factors when only occurrence is evaluated. When abundance data are used, in 33 of the 36 cases significant response models are found. In general these are much more complex than in the cases of species occurrence data: in 10 of the 36 cases a bell‐shaped response model is found to describe the data best. This is in contrast with the widespread belief that species response curves are bell‐shaped: within the forest zone in the area studied this is not generally the case. The importance of the three climatic factors for the distribution of the species is evaluated: for four species mean annual rainfall is the most important variable, for four species the length of the dry period, and for one species cumulative water deficit. Consequently, the assumption that mean annual rainfall is the most important factor determining tree species distribution in West African forests is not correct. Species response models to climatic factors show where species have their geographical optima. Implications for forest management are briefly discussed.

The abundance of lianas (woody vines) and the detrimental impact that they have on tropical rain forest trees is widely recognized. Lianas are particularly abundant in disturbed areas of the forest, such as logging gaps, and pre-harvest liana cutting has been widely recommended throughout the tropics to reduce the impact of lianas during and following tree harvest. The effectiveness of forest-wide liana cutting, however, is currently unresolved, particularly for reducing liana abundance in logging gaps. Furthermore, our understanding of the dynamics and rate of liana colonization in gaps is limited. We tested: (1) the speed at which lianas recruit into logging gaps and their dynamics afterwards; and (2) whether pre-harvest liana cutting actually reduces the abundance of lianas in post-harvest logging gaps. To test hypothesis 1, we compared liana recruitment in new, 1 and 6-yearold logging gaps. For hypothesis 2, we compared liana abundance and tree infestation by lianas in 1-year-old logging gaps in which all lianas had been cut 9 months prior to tree felling vs. 1-year old logging gaps in which lianas were not cut. Lianas recruited heavily into logging gaps within 1 year, mostly by means of stem sprouts, and many of these new stems were apparently able to persist for longer than 6 years. Lianas were significantly more abundant in the root/bole zone of gaps than in the canopy zone, mostly due to the vigorous regeneration of stem sprouts. Canopy openness was highest in gaps one year after logging, possibly due to the smothering effect of the lianas on developing trees. Although liana abundance increased significantly over the 6-year gap chronosequence, direct liana infestation of trees remained the same. Pre-logging liana cutting, however, significantly reduced the number of lianas and also the number of liana-infested trees in logging gaps. Consequently, liana cutting appears to be an effective method to reduce the abundance of lianas and thus minimize their detrimental effects on regenerating trees in logging gaps. #