Abstract: Based on field investigation and related literatures, the geographical distribution patterns of zonal plant community species diversity in West Yunnan of China were approached. The results showed that the species density had a dec reasing trend from south to north and from east to west, and decreased with incr easing altitude. On community scale, the species density was higher in southern part but relatively lower in northern part, being consistent to the spatial vari ation of mean annual air temperature and mean annual precipitation. To some exte nts, mean annual temperature might play a much stronger role. The change rate of species density was much higher along altitudinal gradient than along longitude and latitude gradients, possibly due to the greater change rate of mean annual air temperature at altitudinal gradient. There was an obvious difference in the distribution patterns of the species diversity between community-scale and regi onal-scale. On community scale, species diversity could be controlled by the en ergy level in the environment; while on regional scale, this diversity was possi bly related to the heterogeneity of habitats. Scale effect played a key role in the geographic distribution patterns of species diversity.

Key words: Nitric oxide, Water stress, Poplar, Chlorophyll fluorescence parameter, Protection