Community structure and stability of Pinus kwangtungensis forest in Hainan Province

Pinus kwangtungensis forest, Tropical coniferous forest, is mainly distributed in high altitude regions in Hainan Province, including the Yinggeling Mountains and middle part of Wuzhishan Mountains, and the Jiaxi Mountains in the southwestern part, and the first two regions are most typical. To explore the community structure and stability of P. kwangtungensis forest, we established four plots, three from the Yinggeling Mountains and one from the Jiaxi Mountains, 14,400 square meters totally. We conducted a comparative study in terms of the species composition, age structure and community stability. We found that 1) There is no significant differences in the composition of P. kwangtungensis in the two natural reserves, but the species composition in the high altitude and low altitude is significantly different, indicating that altitude mainly leads to the difference in the species composition; besides, due to the difference of latitude, the species composition of P. kwangtungensis in Hainan and Guangdong, Guangxi were different, and most of them in Hainan belong to the families of tropic distribution and pan tropic distribution while most of them in Guangdong and Guangxi belong to the families of subtropics distribution, which shows the difference of species composition in horizontal distribution between the two areas; 2) P. kwangtungensis population is facing several problems, including seriously aging, difficulty of seedling regeneration, and large age-class dominance. P. kwangtungensis population decline, and plot 1 and 2 have the most obvious declining, which are probably replaced by the broad leaved increasing population; 3) The stability analysis showed that P. kwangtungensis in the Jiaxi Mountains has higher stability than that in the Yinggeling Mountains. As for stability, the three plots from the Yinggeling Mountains can be sorted: plot 1 > plot 3 > plot 2. The stability index of the four plots is away from the stable point “20/80”. We concluded that P. kwangtungensishe forests in Hainan were unstable, resulted from the biological characteristics of dominant species and the environment.