Abstract: The Dipterocarp forest occuring in the south of Mengia County, Xishuangbanna, is a forest type of tropical rain forest from the northern margin of tropical zone of SE Asia. This for-est, covering about 800 hm2, is estimated to consist of 642 species of vascular plant belonging to 355 genera and 122 families, of which seed plants share 622 species of 340 genera of 109 families and ferns shares the others. In this forest, Rubiaceae with 54 species is the largest family in size and other families are arranged in sequance as following: Lauraceae(35 species), Euphorbiaceae(28), Annonaceae (28), Moraceae (25), Orchidaceae (23), Meliaceae (22), Vitaceae (15), Apocynaceae (13) and Fagaceae (12) etc.. Dipterocarpaceae, Guttiferae, Icacinaceae and Myristicaeae etc., though containing a few species separately, show higher importance value in-dex in this forest community.

Key words: Xishuangban

摘要： 西版纳勐腊县补蚌的龙脑香林是一种东南亚龙脑香林的热带北缘类型。该群落计约800公顷，经调查有维管束植物642种，隶属于122个科，355个属，其中，种子植物占109科340属及622种、亚种和变种。种子植物的分布区类型组成是：热带或主产热带的科占总科数的78.9％；热带分布属占总属数的94.l％； 热带分布种超过总种数的90％。热带分布属中有42.3％为热带亚洲分布属，而热带分布种中有73.3％为热带亚洲分布及变型的种类。在热带亚洲分布及其变型的种类中，又具体以印度-马来西亚分布居首位，占总种数的28.9％。分布区类型组成表明西双版纳龙脑香林植物区系是热带性质的植物区系，属于热带亚洲区系的一部分，并以印度-马来西亚分布为其核心成分。由于特殊的地理位置，西双版纳地区是许多典型热带植物的分布北界，同时又是几种热带成分的交汇地带，这又使该龙脑香林植物区系带有热带边缘性质和几种地理成分交汇带的特点。

关键词: 西双版纳, 龙脑香林, 植物区系