澜沧江下游/湄公河上游片断热带雨林物种多样性动态

 在澜沧江下游/湄公河上游的滇南西双版纳地区，通过样方法比较了热带雨林的连片与3个小片断的物种多样性变化趋势。与连续森林比较，片断热带雨林的植物物种丰富度和物种多样性指数都比较低，而且有相当低比例的大高位芽、中高位芽和附生等生活型植物，而藤本、小高位芽和矮高位芽等生活型植物的比例则较高；泛热带、热带亚洲至热带非洲的区系成分比例较高，而当地成分则减少；群落的上层树木比下层树木更加稳定。同样，动物的物种多样性指数和均衡度在片断热带雨林中都较低，与其密切相关的是片断热带雨林的环境质量，而不是片断的大小。此外，也探讨了片断热带雨林物种变化与森林小气候的关系，阐明了由凉湿向干暖转化的“林内效应”是其物种变化的重要原因之一。

SPECIES DIVERSITY DYNAMICS OF FRAGMENTED TROPICAL RAINFORESTS IN THE LOWER-LANCANG/UPPER-MEKONG RIVER BASIN

Three fragments of tropical rainforest in Xishuangbanna, southern Yunnan and within the Lower-Lancang/Upper-Mekong River basin, were sampled to investigate species diversity patterns based on comparisons with a contiguous tropical rainforest. Compared with the contiguous forest, the fragments were lower in plant abundance, species diversity indicies, a lower percentage of mega-phaenerophytes, meso-phaenerophytes, chamaephytes and epiphytes, but had a higher percentage of liana, micro-phaenerophytes and mini-phaenerophytes. The floristic composition was also different in the fragments with a greater percentage of pan-tropical and tropical Asia to tropical Africa elements increased, whereas the percentage of regional or local elements decreased. Meanwhile, tree species in the upper canopy layer were more stable than that in the lower layers of the fragmented forest. The animal species diversity and evenness were higher in the contiguous forest than in the fragmented forests, which apparently were due to better habitat size and quality. The relationship between changes in the microclimate of the forest fragments and species changes were also considered. The interior forest of the fragmented forests transformed from a wet-cool to dry-warm microclimate, called the internal effect, and was found to be an important mechanisms accounted for observed species changes.