桂西北喀斯特地区不同退化程度植被群落物种组成及多样性特征

世界范围内,很多自然生态系统均在不同程度上受到了损害,喀斯特脆弱生态系统的退化是一个复合过程,喀斯特地区不同退化程度植被群落特征有何差异有待研究。该文采用样方法进行全面的调查,研究了桂西北喀斯特地区5个退化程度植被群落的物种组成、群落结构特征和物种多样性。结果表明:(1)不同退化程度群落物种组成和生活型组成有较大差异,潜在退化群落科属种丰富度最高,沿着退化程度递增的梯度,群落乔木树种逐渐减少至消失,灌木比例呈先增后减的趋势,草本比例逐渐增加。(2)调查到维管束植物218种,隶属于86科168属;以大戟科、楝科、蔷薇科、马鞭草科、禾本科和肾蕨科植物为主;退化过程中,优势种的重要值逐渐降低,其在群落内的支配地位逐渐减弱,伴生种重要值逐渐升高。(3)退化过程中,群落结构趋于简单化,群落木本植物密度、高度和盖度逐渐减少。(4)不同退化程度植被群落乔灌草层物种多样性存在显著性差异,随着退化程度的增加,群落总植被物种丰富度指数、Shannon-Wiener多样性指数、Simpson优势度指数整体呈下降趋势。

Changes in species composition and diversity of vegetation communities along degradation in karst area of Northwest Guangxi

Many natural ecosystems have been suffering from degradation across the world. Karst ecosystems are known for susceptibility and sensitivity to disturbance. So far, little information is available on the characteristics of vegetation communities suffering from different levels of degradation in karst areas. Therefore, we investigated species composition, community structure and species diversity of vegetation communities suffering from different levels of degradation in karst areas. The results were as follows:(1)There were significant differences in species composition and life form composition of communities suffering from different levels of degradation. Numbers of plant families and species were the highest in potential degraded communities. Along degradation, tree species gradually reduced and ultimately disappeared. The proportion of shrubs increased first and then decreased. The proportion of herbal increased gradually along degradation.(2)There was a total of 218 vascular plant species belonging to 86 families and 168 genera, and Euphorbiaceae, Meliaceae, Rosaceae, Verbenaceae, Gramineae, Nephrolepidaceae were the dominant species. Along degradation, the important values of dominant species gradually decreased, and the dominance in the community gradually weakened while the important values of the companion species gradually increased.(3)Community structure tended to simplify along degradation, as density, height and coverage of community decreased.(4)There were significant differences in species diversity indexs of arbor, shrub and herb layers of communities suffering from different levels of degradation. The species richness index, Shannon-Wiener index and Simpson index decreased along degradation.