Abstract: Biodiversity is the basis for sustainable development of an ecosystem. Exploring the influences of environmental and disturbance factors on species diversity is important for maintaining ecosystem structure and function. Based on the investigation of 160 plots and the occurrence time and severity of natural fires in the Kanas taiga forest in Xinjiang, we analyzed the relationships between species diversity of forest communities and environmental and natural fire disturbance factors, and the relationships between species diversity of herb layer, shrub layer, and tree layer and species diversity ofcommunities by redundancy analysis. The results showed that species diversity in the herb layer was affected mainly by altitude, soil moisture, soil total nitrogen content, soil temperature, and fire severity. Species diversity in shrub layer was mainly affected by altitude, soil moisture, soil conductivity, and soil organic matter content. Tree layer species diversity was affected by altitude, soil moisture, soil organic matter content, soil total nitrogen content, and fire severity. Community species diversity was mainly affected by altitude, soil moisture, soil organic matter content, soil total nitrogen content, and fire severity. Moreover, herb layer and tree layer interacted with each other, and played a determining role in community structure. Species diversity patterns in the Kanas taiga forest were formed by the synthetic action of a variety of environmental factors and natural fires in which elevation played an important role.

Key words: Thuja koraiensis, endangered species, population structure, survival analysis, dyna-mic index.