Abstract:Based on the tree species of forest community in Caohai National Nature Reserve, the forest was divided into four types: Pinus yunnanensis forest, Pinus yunnanensisAlnus cremastogyne forest, Alnus cremastogynePopulus yunnanensis forest, Alnus cremastogynePinus armandii forest. The age structure, survival curve and static life table of the dominant tree species in different communities were analyzed by using the method of space instead of time, and the development trend of the dominant tree species in four communities was predicted by using the time prediction model. The species diversity of the community was analyzed to provide theoretical basis for forest protection and sustainable management in the study area. The results showed that: (1) the diameter structure of dominant tree species of Pinus yunnanensis forests and Pinus yunnanensisAlnus cremastogyne forests showed a partial normal distribution, and the decline trend was obvious, while Alnus cremastogynePopulus yunnanensis forest and Alnus cremastogynePinus armandii forest showed an inverted “J” type, and the decline trend was relatively weak. (2) The analysis of static life table and survival curve showed that different forest communities in the study area were unstable, and the survival curve deviated from Deevey III curve in different degrees. (3) The time series analysis showed that the number of the population increased after the second, fourth and sixth instars in the study area, but the number of middle and young age individuals decreased, and the number of old age individuals increased first and then decreased, the population will inevitably decline. (4) There are 83 species belonging to 70 genera and 35 families, including 29 species belonging to 23 genera and 17 families of shrub layer and 54 species belonging to 48 genera and 21 families of herb layer. The species richness index (S) was herb layer>shrub layer, and the Pielou index (Jsw) was shrub layer > herb layer in three types of forest community, the Alnus cremastogynePinus armandii forest showed the opposite trend, and there were obvious differences in species diversity.