Species diversity distribution pattern of alpine grassland communities along an altitudinal gradient in the Northern Tibet

A field survey was carried out to describe the species diversity distribution pattern of alpine grassland communities along an altitudinal gradient at the Ritunbu Mountain of Nyainqentanglha Range, Naqu regions in the Northern Tibet. The results of this study showed that aboveground biomass and total coverage of plant communities increased firstly and then decreased as the altitude gradient increased, and peaked at 4 623 m. The species richness index, ShannonWiener index and Pielou evenness index showed a unimodal pattern, and peaking at intermediate levels of altitude.