西双版纳片断热带雨林的结构、物种组成及其变化的研究

通过对西双版纳地区的６个“龙山”片断热带雨林与同样类型的原始热带雨林的比较研究，探讨了片断热带雨林的群落结构、种类组成、生活型构成、种群结构、植物丰富度及多样性等的变化及其规律。随着热带雨林的片断化，森林边缘效应和人为干扰加剧，热带雨林群落的结构变得不完整，植物丰富度降低。在生活型构成上，附生植物，大、中高位芽植物以及地上芽植物比例减少，藤本植物和小高位芽植物比例明显增高。在种群结构上，受轻、中度干扰的片断雨林，仅含１～２个个体的种类在群落中的相对数量有所增加，乔木种类组成变得不稳定，随着人为干扰的加剧，那些仅有１～２个个体为代表的种类将首先消失。在单位面积种数和物种多样性指数上，情况比较复杂，热带雨林片断化和受到一定干扰可能会增加藤本植物多样性指数，但干扰过度又会减低其多样性指数，附生植物多样性指数则随干扰和隔离时间呈明显下降趋势，但总的说来，片断热带雨林单位面积上的种数远比原始林少得多，随着人为干扰和隔离的加剧，物种多样性指数显著降低。

EFFCTS OF FRAGMENTATION ON THE STRUCTURE,SPECIES COMPOSITION AND DIVERSITY OF TROPICAL RAIN FOREST IN XISHUANGBANNA, YUNNAN

Based on a comparison of fragmented and primary tropical rain forests in Xishuangbanna, the effects of fragmentation on structure, species composition, life form, tree populations, plant abundance and species diversity of the tropical rain forest are analyzed. With increasing fragmentation, edge effects and disturbances, fragments become different from the primary rain forest in various ways. Compared with the primary forest, the fragments were incomplete in community structure, lower in plant abundance and species diversity, and showed a relatively lower percentage of epiphytes and chamaephytes but a conspicuously higher percentage of lianas. In the fragments with slight to inter mediate disturbances, tree populations of only 1 or 2 individuals make an increasing percentage of the total, indicating that the populations of many tree species have become more unstable. In the fragments with serious disturbances, tree species with only 1 or 2 individauls present disappeared first. As the fragments in Xishuangbanna formed and developed under strong human impact, their species diversity shows complicated changes. Liana species diversity increased with a certain extent of disturbances, but decreased when over disturbed. Species diversity decreased in general with increasing disturbance.