A phylogenetic classification of the world’s tropical forests

Knowledge about the biogeographic affinities of the world’s tropical forests helps to better understand regional differences in forest structure, diversity, composition and dynamics. Such understanding will enable anticipation of region specific responses to global environmental change. Modern phylogenies, in combination with broad coverage of species inventory data, now allow for global biogeographic analyses that take species evolutionary distance into account. Here we present the first classification of the world’s tropical forests based on their phylogenetic similarity. We identify five principal floristic regions and their floristic relationships: (1) Indo-Pacific, (2) Subtropical, (3) African, (4) American, and (5) Dry forests. Our results do not support the traditional Neo- versus Palaeo-tropical forest division, but instead separate the combined American and African forests from their Indo-Pacific counterparts. We also find indications for the existence of a global dry forest region, with representatives in America, Africa, Madagascar and India. Additionally, a northern hemisphere Subtropical forest region was identified with representatives in Asia and America, providing support for a link between Asian and American northern hemisphere forests

An estimate of the number of tropical tree species

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

Phylogenetic classification of the world's tropical forests

Knowledge about the biogeographic affinities of the world’s tropical forests helps to better understand regional differences in forest structure, diversity, composition, and dynamics. Such understanding will enable anticipation of region-specific responses to global environmental change. Modern phylogenies, in combination with broad coverage of species inventory data, now allow for global biogeographic analyses that take species evolutionary distance into account. Here we present a classification of the world’s tropical forests based on their phylogenetic similarity. We identify five principal floristic regions and their floristic relationships: (i) Indo-Pacific, (ii) Subtropical, (iii) African, (iv) American, and (v) Dry forests. Our results do not support the traditional neo- versus paleotropical forest division but instead separate the combined American and African forests from their Indo-Pacific counterparts. We also find indications for the existence of a global dry forest region, with representatives in America, Africa, Madagascar, and India. Additionally, a northern-hemisphere Subtropical forest region was identified with representatives in Asia and America, providing support for a link between Asian and American northern-hemisphere forests.</p

Influence of grazing intensity on swamp plant communities in the tropical montane wetland ecosystems, Nilgiris, Southern India

Livestock grazing is a major anthropogenic impact influencing both grasslands and wetlands of the world which often results in the alteration of the structure, diversity and functioning of the plant communities. Here, we seek to understand how grazing intensity influences swamp vegetation, with an emphasis on their diversity, structure and function. Six swamps were selected, two each in high, moderate and low intensity grazing sites, from the tropical montane swamps of the Upper Nilgiri Mountains, southern India. We recorded a total of 78 species belonging to 63 genera and 31 families. Our results showed that species richness, abundance and species composition differed significantly across grazing treatments. Moreover, mean vegetation cover and mean height differed significantly across grazing treatments, indicating that grazing significantly affected the vegetation structure and growth of swamp plant communities. Species compositional patterns showed that moderately grazed plant communities were significantly different from low and high grazing sites. In summary, grazing intensity influenced swamp species richness, abundance, and swamp plant communities. Specifically, high grazing pressure reduced vegetation cover causing changes in swamp community structure leading to the gradual conversion of the swamp habitat into grasslands

Selective logging intensity alters the population stand structure of Cullenia-Mesua-Palaquium dominated tropical wet evergreen forest of the Western Ghats, South India

The present study was conducted in a population structure of selectively logged tropical wet evergreen forest, Cullenia-Mesua-Palaquium (CMP) forest series in the tropical wet evergreen forests of the Nelliampathy Hills, Western Ghats. The study was aimed to focus on how selectively logged treatment influences the density and basal area of CMP forest series stand structure. We sampled the number of individual trees (≥ 1 cm dbh, diameter at breast height) of CMP at 30 sites (20 × 50 m quadrat size), covering an area of 30.8 hectare (ha) in total. A total of 5936 tree individuals sampled had a mean density of 246 ha-1 and basal area of 20.73 metre square (m2) ha-1 from an area of 0.1 to 2.5 ha. Tree density per hectare and basal area differed significantly among plots with different logging treatments. Tree density and basal area were significantly lower in highly logged plots as compared to moderately logged and unlogged plots. The density of smaller trees was significantly higher in moderately logged plots. We suggest that heavy logging treatments might be a serious threat to the CMP forest series and may possibly alter its population structure and that the moderately logged treatments showed positive impacts on CMP stand structure and regeneration