西双版纳热带山地雨林群落乔木树种多样性研究

根据块样地资料对西双版纳热带山地雨林树种多样性特征进行了分析.结果表明,在2 500m²的样地上,随着起测胸径递增,各样地乔木个体数和树种丰富度均表现为依次递减;低海拔带上(850～1000 m)的山地雨林(1、2号样地)的各指数值无一定变化规律,较高海拔带上(1200～2000 m)的山地雨林(3～6号样地)的Shannon-Wiener指数和Simpson指数均表现为依次递减,而Pielou均匀度指数则呈依次递增的趋势.较高海拔带上的山地雨林在较小乔木起测胸径(≥2 cm、≥5 cm、≥10 cm)的树种丰富度、多样性和均匀度指数均要明显大于低海拔带上的山地雨林,而两者在较大乔木起测胸径(≥20 cm、≥30 cm、≥50 cm)的各指数值无明显差异.随着取样面积的递增,各样地树种丰富度、多样性和均匀度指数在取样面积递增到2 000m²处均已趋于平缓.

Tree species diversity of tropical montane rain forest in Xishuangbanna, Yunnan

Tropical montane rain forest (TMR), one of the main forest vegetation types in Xishuangbanna of Yunnan Province, occurs horizontally in the north (TMRF I) and vertically in the south (TMRF II). In order to understand its tree species diversity in different zones, six fixed plots (50 m x 50 m) at different sites in Xishuangbanna were established, two (plots 1 and 2) for TMRF I, and four (plots 3, 4, 5 and 6) for TMRF II. Grid method (10 m x 10 m) was used to record all the individuals with DBH greater than 2.0 cm in each plot, and tree species richness and diversity characteristics along DBH class, as well as changing trend of tree species diversity with increasing sampling area were analyzed. The results showed that the tree stem and species richness in the six plots both declined constantly along the DBH class gradient. For the communities of TMRF I (altitude was 850 1000 m), all indices had no clear trend with the gradient, while for the communities of TMRF II (altitude 1 200 - 2000 m), Shannon-Wiener and Simpson indices declined constantly with gradient, but Pielou's evenness index had the opposite trend. In smaller DBH classes (> or =2 cm, > or =5 cm and > or =10 cm), the tree species richness, diversity, and evenness of the communities of TMRF II were obviously higher than those of the communities of TMRF I, but there was no difference between the communities of TMRF I and TMRF II in larger DBH classes (> or = 20.0 cm, > or =30.0 cm and > or =50.0 cm) . With sampling area increased, the tree species richness, Shannon-Wiener index, Simpson index and Pielou's evenness index of the six plots all had the trend to be smooth when the sampling area increased to 2 000 m2.