Abstract: Chinese fir (Cunninghamia lanceolata) plantation is one of the main vegetations in the Simian Mountain of Chongqing.Chinese fir is also one of the main species of trees afforesting the area.Based on the data from the survey of a typical Chinese fir plantation in the area,species diversity of the Chinese fir community was analyzed using richness index,Shannon-Wiener index,Simpson index and Pielou evenness index.The existing Chinese fir community in the area can be divided into 2 formation groups (Chinese fir plantation and mixed Chinese fir-broadleaved forest),8 plant formations and 10 associations.Results show that the Chinese fir community is formed of arbor tree,shrubbery and herb layers.In the Chinese fir plantation,the three layers demonstrate a declining trend in richness,diversity and evenness indices,i.e.shrub layer>herb layer>arbor layer,while in Chinese fir mixed wood,the trend in richness index goes as shrub layer>arbor layer>herb layer;and in diversity index as shrub layer>arbor layer>herb layer;and however,the trend in evenness index is rather complicated without any of uniform law.With the rise in altitude the richness index of the Chinese fir community regardless of layers declines as a whole while their diversity indexes increase and display a certain law within a given region,that is,declining with the rising altitude where below 1 180 m,but fluctuating within the range between 1 180 m and 1 351 m,and declining again where above 1 351 m.The change in evenness index with all the layers is rather complicated and has no clear rule.

Key words: Chinese fir community, species diversity, Simian Mountain of Chongqing