三峡水库岛屿成岛前的植被特征与物种丰富度

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

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。

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 coverage,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,respectively. The average species richness was 42.9 for forest,15.96 for shrub,and 17.89 for hassock communities. 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 succession 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.