Abstract: To analyze the relationships between plant diversity and community structure of semi-humid evergreen broadleaved forests at different secondary succession stage in the Samachang area of Yunnan Province, some numeral indices were tested, and the results showed that the plant diversity increased gradually with succession, and the species number reached 24 at the latest succession stage. There was a positive linear correlation between plant individual density and species diversity, which could be described by y=506.99x+554.56. A negative correlation was observed between the average height of plant individuals and plant species diversity, and the equation y=-0.3862x+11.406 could describe it well. The crown density and basal area increased in logarithm with plant species diversity, and the two equations y=21.756ln x +11.607 and y=7.4028lnx+9.6198 could describe the relations. No regular patterns were observed for the changes of aboveground biomass and plant individual density with plant species diversity. The relations of plant species with plant individual number could also be described by negative power function. Plant competition was intensified with plant species diversity, and each plant species might take the strategy to conserve its greatest population, and to avoid decreasing to less than its critical population, which led to a high individual density, and might change the structural character of the community.

Key words: Kiwifruit bacterial canker, Bacteriostatic action