Distributional regularity of species diversity in plant community at different latitudes in subtropics

There are abundant vegetation resources in the subtropical climate zone in China. It is very meaningful to explore the species diversity distribution of typical plant communities with the changes of latitude and altitude. In this paper, four typical plant communities in the national nature reserves of Maoershan, Nanling and Dinghu Mountain were selected from the subtropical area according to the latitude from high to low. Four 1 hm~2 sample sites were set up, investigated and monitored by the national standard methods. In sample area, all species with the individuals of diameter at breast height being greater than 1 cm were used to analyze their species-individual curve, and diameter at breast height(DBH) size-class distribution structure of the dominant species. We also compared and analyzed α and β diversity index of the four communities. The results showed that:(1) the difference in altitude played a key role in the distribution of individual to species, and the number of individuals varied more obviously with altitude. The frequency of single individual species from south to north decreased gradually. The contribution of single individual species to species diversity of community was more significant in low altitude areas.(2) The α diversity in Nanling sample and Dinghu mountain sample was significantly different, although they are located in the similar altitude. Due to the different stages of succession and being greatly disturbed by human activities, the species diversity of Dinghu Mountain sample was lower than that in Nanling area with higher latitude. Comparing two sample plots of Maoershan at the same latitude and different elevations, the Hongjun Ting plot in middle latitude had a higher diversity than the Bajiao Tian plot in high altitude.(3) Due to the difference of habitat, the species composition of the four communities was obviously different. Both latitude and altitude affected the β diversity of the community. The greater the latitude difference between communities, the greater the species difference was existed. The effect of altitude on the β diversity of samples at the same latitude was also significant. In communities with similar elevations and different latitudes, the difference of species composition was also significant.