三峡水库岛屿成岛前的植被特征与物种丰富度

三峡水库蓄水导致原有生境的岛屿化, 本文调查了三峡水库6个即将形成的岛屿蓄水前的植被特征, 并对这些岛屿上各类群落类型的物种丰富度进行了分析。共调查到群落类型28个, 其中草丛12个, 灌丛7个, 森林9个。研究结果表明, 绝大多数岛屿自然植被覆盖率低, 植被退化严重。主要表现为森林比重很小, 群落多样性低, 撂荒地上处于次生演替初始阶段的杂类草草丛占了相当大的比例。6个岛屿的植物种数分别为126、157、175、189、242、254; 其中森林群落的平均物种丰富度指数为42.19, 灌、草丛分别为15.96和17.89。杂类草草丛具有较高的丰富度指数, 而演替到较为稳定的退化草丛物种丰富度指数呈下降趋势。各类灌丛之间物种丰富度指数相差不大。在针阔混交林向阔叶林演替过程中, 物种丰富度指数表现为较大的波动性。由于自然植被被严重破坏, 岛屿上外来入侵种形成了较大的灾害。三峡库区即将形成的这些岛屿具有重要的研究价值, 建议选择一些岛屿建立保护区。

Vegetation and plant species richness on six pre-islands, the Three Gorges Reservoir

We studied the vegetation on six pre-islands (land areas which will become islands as a result of flooding) in the Three Gorges Reservoir with a focus on plant species richness for each community. A total of 28 community types were found on these pre-islands,comprising of 12 hassocks,7 shrubs,and 9 forests. The results showed that natural vegetation was characterized by intense degradation,implied low vegetation cov-erage,restricted distribution of forests,low community diversity and high ratio of ruderal community types. The species richness of wild vascular plants on the six pre-islands was 126,157,175,189,242,and 254,re-spectively. The average species richness was 42.9 for forest,15.96 for shrub,and 17.89 for hassock commu-nities. In all hassock communities,species richness was high in ruderals but was low in typical degraded hassocks. Species richness was generally low in all shrub communities. In the process of secondary succes-sion from conifer-broadleaf forest to broadleaf forest,species richness fluctuated remarkably. Exotic plants significantly impacted the landscape,resulting in degradation of the natural vegetation. These pre-islands are valuable for scientific research,we suggest establishing some nature reserves on them.