西双版纳片断热带雨林植物区系成分及变化趋势

本文以西双版纳地区的6个“龙山”片断热带雨林的植物物种多样性编目为基础，通过与同样类型的原始热带雨林的比较，探讨了片断热带雨林植物区系成分的变化。随着热带雨林的片断化，森林边缘效应和人为干扰加剧，阳性先锋植物和藤本植物等的侵入，导致这些先锋植物和藤本植物所属的科属在群落中的种数增多，优势度增大。而一些含喜荫湿的荫生植物、群落顶极树种及附生植物较多的科属则在群落中的种数减小了，优势度下降。在植物属的地理成分构成上，片断热带雨林中全热带分布和热带亚洲—热带非洲分布成分比例相对增高，而热带亚洲成分相对减少。在种的地理成分构成上，片断热带雨林中广域分布种比例相对增高，显示了与属的地理成分类似的变化。这也是森林片断化后，由于边缘效应和林内生境在一定程度上干暖化，喜光的先锋成分增多，而先锋成分大多为一些广域分布属种所致。

Floristic composition and change of rain forest fragments in Xishuangbanna, southern Yunnan

Floristic inventories of six rain forest fragments on Holy Hills of Dai people in Xishuangbanna,southern Yunnan, were made. Change in floristic composition of the fragments was analyzed based on the comparison with the continuous primary rain forest of the region. With fragmentation and growing distur_bances on the rain forest fragments, some plant families, such as Papilionaceae, Rutaceae and Euphorbiaceae,conspicuously increased in relative number of species or species percentage, while some families such as Ochi_daceae, Lauraceae, Annonaceae and Urticaceae, decreased in relative number of species, i. e. their formerdominance faded owing to the invasion of a lot of pioneers and declination or extinction of shande tolerant andclimax species. In composition of geographical elements of the flora of fragments, the elements of pantropicand tropical Asia to tropical Africa distributions increased in percentage at genus level and those of wide distri_bution increased, while those of the usually limited or local distribution decreased at species level.