古田山中亚热带常绿阔叶林群落物种多样性的空间变异特征

古田山常绿阔叶林的群落组成、结构及其维持机制已有许多研究, 但该地区亚热带常绿阔叶林生物多样性空间变异特征还缺乏认识。本文以古田山24 ha大样地(划分为24个1 ha小样地)为基础, 具体分析了α多样性和β多样性在1 ha尺度上的空间变异特征。结果表明: (1)群落第一、二优势物种在各小样地之间变化不大, 但第三优势种变化较大; (2) α多样性变化中, 样地间木本植物个体数量变异最大, 物种丰富度其次, Pielou均匀度指数变异性最小; (3)物种丰富度与植株个体数量、Pielou均匀度指数没有显著的相关性, 与Shannon-Wiener指数呈显著正相关; Shannon-Wiener指数与Pielou均匀度指数呈显著正相关; (4)相邻样地间物种替代速率空间变异较大, 与物种丰富度的空间变化格局有明显差异。这些结果说明尺度对认识群落结构、探讨群落维持机制有重要作用; 由于森林群落是多尺度生态过程作用的结果, 大尺度样地可能有利于更好地揭示森林群落维持机制。

Spatial variations in species diversity of mid-subtropical evergreen broad-leaved forest community in Gutianshan National Nature Reserve

Many studies have examined the patterns and mechanisms underlying the structure of mid-subtropical forest community, but spatial variation in species diversity has rarely been investigated. We examined spatial variations in α- and β-diversity among and between 24 subplots of 1-ha each within the 24 ha forest dynamics plot in Gutianshan National Nature Reserve. We found that (1) the top two dominant species were the same for almost all the subplots, but the third dominants differed greatly; (2) α-diversity varied greatly among subplots: total number of individuals showed the largest differences, followed by species richness, Shannon-Wiener index, and Pielou evenness index; (3) species richness showed no correlation with total abundance and Pielou evenness index but was positively correlated with Shannon-Wiener index, which was positively correlated with Pielou evenness; (4) there was high species turnover between neighboring subplots, but these patterns were not consistent with the spatial variation in species richness. Our results highlight the importance of spatial scales for assessing community structure and mechanisms of community assembly. Since forest communities are influenced by ecological processes at multiple scales, large-scale plots may be better than small-scale plots to explore multiple mechanisms of community assembly.