Abstract: To explore the evolvement pattern of grasslands in humid Tibetan Plateau region and its responses to ongoing climate change, we selected the alpine grasslands with different altitudes along the sunny slope of Yajiageng mountain in the eastern Tibetan Plateau, and studied the variation in smallscale characteristics of grassland communities along the elevation gradient, and analyzed the effects of climate and soil variables on community characteristics. Our results showed that aboveground biomass decreased significantly with  the altitude increasing, while the underground biomass and the rootshoot ratios of community increased significantly. Community diversity indexes showed significant change between lower altitude sites, but did not change significantly between higher altitude sites. Overall community diversity and evenness increased with
 the altitude increasing. The variation in community characteristics of different altitudes was mainly controlled by climatic factors, and the temperature played a leading role. The interpretation of the variance from soil factors could be ignored.  Community diversity indexes showed negative correlations with aboveground biomass along the elevation gradient, which supports root competition hypothesis and light competition hypothesis.

Key words: functional diversity, Jianfengling tropical montane rain forest, species abundance weighted, functional traits, forest canopy