Daily variation of photosynthetic ecophysiological characteristics of lithophytic shrub dominant species in peak cluster depressions of Nongla, Guangxi

Physiologic characters of Lonicera japonica, Vitex negundo , Alchornea trewioides and Callicarpa nudiflora and some other lithophytic shrub dominant species in NongLa peak cluster depression are measured by LI-6400 and their daily variations of physiologic and ecologic index, such as net photosynthetic rate（Pn）and photosynthetic active radiation, are compared with each other. It indicates that the daily variations of environment factors for lithophytic shrub community in peak cluster depressions are quite complicated, and that different shrub communities have different regulate and control effect to microclimate. The Vitex negundo and Alchornea trewioides communities can better adjust CO2 density in the air. The Vitex negundo community is of the highest average Pn level and averagetramspiration level, but the Alchornea trewioides community is of the highest average water use efficiency level and average apparent quantum efficiency level. The Lonicera japonica and Callicarpa nudiflora communities show obvious “midday depression” in photosynthesis. Plant physiological factors are restricted by environment factors. Environmental factors and plant physiological factors influence photosynthesis together but different factors influence differently in these lithophytic shrub dominant species. At the same time, stepwise regression method is used to establish linear regression equations for net photosynthetic rate and various factors. All of the linear regression equations are statistically significant and predict well.