Abstract: Based on data from 50 quadrates, species diversity of plant communities in Baihua mountains were discussed, and measurements of species diversity of quadrates along DCA axis 1 gradient and altitudinal gradient was also carried out. The results showed that: Richness index varied as follows: in forest communities it showed herb layer > shrub layer > tree layer, in shrub communities showed herb layer > shrub layer and Vitex negundo var. heterophylla community showed shrub layer > herb layer. Shannon-Wiener index of the most forest communities showed herb layer > shrub layer > tree layer but Populus davidiana＋Larix principis-rupprechtii community showed shrub layer > herb layer > tree layer, and that of shrub communities showed herb layer > shrub layer but Vitex negundo var. heterophylla community showed shrub layer > herb layer. Evenness index of shrub communities showed shrub layer> herb layer, in forest communities it showed tree layer > shrub layer> herb layer Quercus liaotungensis and Populus davidiana＋Larix principis-rupprechtii community showed shrub layer > tree layer > herb layer. The specie diversity of quadrates along both DCA axis 1 and altitudinal gradient significantly peaked at the intermediate elevations, but there were some differences: the fitted curves of both richness and evenness with altitudinal gradient were more significant than that fitted with DCA axis 1, while that of diversity showed the opposite trend.

Key words: Baihua Mountain, plant community, species diversity, DCA, atitudinal gradient