热带森林树种多度和丰富度空间分布特征研究

用巴拿马50 hm2森林动态监测样地内直径≥1 cm的树种资料,分析了该样地树种多度(个体数)和丰富度(物种数)及其方差和变异系数在6个取样尺度(5 m×5 m,10 m×10 m,20 m×20 m,25 m×25 m,50 m×50 m,100 m×100 m)的变化规律.结果显示:(1)由于多度的可加性,不同取样尺度在样地内树种多度的变化表现出一致性;随取样尺度的增加,多度方差呈线性增加,而变异系数呈线性减小.(2)丰富度随取样尺度的变化较为复杂,随取样尺度的增加,丰富度方差呈非线性变化,在取样尺度为25 m×25 m时方差最大;变异系数随取样尺度的增加而呈线性减小.研究表明,大尺度的多度值可以由小尺度的多度值通过外推法估计,而丰富度却不能,在生物多样性的保护和管理中不能简单地从一个取样尺度的生物丰富度推测另一个取样尺度丰富度.

Study on the Spatial Distribution of Tree Abudance and Species Richness in a Tropical Forest

Richness and abundance are the two most basic diversity variables.However,their usefulness for measuring biodiversity in large part is relied on their response to scale effect.Based on trees with DBH≥1 cm in a 50 hm2 stem-mapped tropical forest of Panama,we investigated spatial variations of abundance and richness across six 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).The results showed that:(1)Tree abundance shows a linear relationship with scale due to the additive nature.The spatial variances of abundance linearly increase with scales,whereas the coefficient of variation decreases.(2)Richness shows an erratic variation across scale.The spatial variance of richness has a hat shape across scale with the largest variance occurring at 25 m×25 m.The coefficient of variation of richness decreases linearly with scales.The results indicates that abundance of large scale can be estimated though extrapolation from smaller scales,whereas richness can not be estimated.In conclusion,extreme caution should be exercised if one has to use diversity measured at a single scale for the purposes of diversity management and conservation.The non-additive property of richness makes the identification of biodiversity hotspots problematic as a hotspot at one scale can become a coldspot at another scale.