The trait gradient analysis as a hot topic in ecological research provides an improved approach to explain community assembly and ecosystem structure and functions.Twenty-four dominant species in Yanhe Basin were investigated by recording their heights in their communities.The heights were then decomposed into α and β components to characterize the variations of plant heights within and among communities.The results show that the height variations of the dominant species were owing more to the interactions between species within the community than to the influences of the environment.The herbage communities had higher α than β values,similar to the whole basin,implying a dominant influence from the interaction among species.While in shrub and tree community,the β value was generally higher than α value,suggesting stronger impacts from the environment gradient changes.The findings of this study are of great significance to understand the role of environmental factors and biological interactions in the formation of plant communities,providing bases for revealing changes of vegetation patterns and guides for vegetation restoration.