西双版纳热带雨林树种多样性的尺度效应

基于西双版纳20hm2森林动态监测样地内直径≥1cm的树种资料,分析了该样地树种香农多样性指数和辛普森多样性指数及其方差和变异系数在7个取样尺度(5m×5m、10m×10m、20m×20m、25m×25m、50m×50m、100m×100m、200m×250m)的变化规律,结果表明:(1)香农指数-面积曲线在尺度100m×100m有一个峰值,而辛普森指数-面积曲线在尺度为20m×20m有一个峰值。(2)香农指数和辛普森指数的方差随尺度的增加而减小,其中香农指数的方差在尺度100m×100m上最小,辛普森指数在尺度20m×20m方差最小,表明香农多样性指数在100m×100m的尺度上所获得的多样性信息比较可靠,而辛普森指数在20m×20m的尺度上所获得信息比较可靠。(3)多样性指数的方差和变异系数远大于随机模型拟合的数值,说明样地内树种不是随机分布。

Scale Effects of Tree Diversity in a Tropical Rain Forest in Xishuangbanna

Based on trees with DBH≥1 cm in a 20 hm2 stem-mapped tropical rain forest in Xishuangbanna,we investigated spatial variations of Shannon and Simpson diversity indices across seven scales(grain sizes)(5 m×5 m,10 m×10 m,20 m×20 m,25 m×25 m,50 m×50 m,100 m×100 m,200 m×250 m).The results showed that:(1)Shannon and Simpson have the largest values at 100 m×100 m and 20 m×20 m,respectively.(2)The spatial variances of Shannon and Simpson indices generally decrease with scale,and with the smallest variances occurring at 100 m×100 m and 20 m×20 m,respectively.So we concluded that the reliable spatial scale for biodiversity estimation of Shannon diversity index is 100 m×100 m,whereas that of Simpson index is 20 m×20 m.(3)The variances of all the diversity indices are larger than those estimated by the random placement model,reflecting that spatial distribution of trees in the study area is more correspondents to habitat heterogeneity than random distribution.