How many tree species are in the Himalayan treelines and how are they distributed?

Increase in endemism with elevation is a common feature in Himalayas because of increased isolation of higher areas like treelines. To protect species of treeline, we at least need to record their numbers and distribution. We estimated that the total number of tree species in Himalayan treeline is 58, and they belong to 14 genera and 8 families. It is impressive, given that globally alpine treeline species richness is unlikely to be considerably higher than 100. While estimating the species number, we confronted uncertainties in some cases concerning synonyms of species, weak demarcation between species and incorrect identification. Because of a high species differentiation in the Hengduan Mountains and Western Sichuan Province in Tibet, the eastern part of the Himalayan arc (88 degrees E and more) has much higher species richness than the western part (less than 88 degrees E), despite similar number of genera. These areas of high species differentiation accounted for nearly half of the total species. The dominant genera in terms of geographical distribution areJuniperus, Abies, Rhododendron, andBetula. Among the families, Pinaceae, Cupressaceae, Ericaceae, Betulaceae, and Rosaceae were prominent. Because of global climatic change, species shifts are predicted to occur along an altitudinal gradient (representing temperature gradient) as well as along the 31o longitudinal range, representing a moisture gradient. The Himalayan treelines are relatively species-rich, largely because of variations in precipitation, topography, continentality, and cultural factors, among others along the east-to-west arc. There is a need to undertake additional taxonomic studies, using tools such as molecular techniques to provide solution to confusion relating to incorrect identification of some species.