西双版纳石灰岩森林的植物区系地理研究

^A PHYTOGEOGRAPHICAL RESEARCH ON THE FOREST FLORA OF LIMESTONE HILLSIN XISHUANGBANNA

西双版纳石灰岩森林植物区系经调查有维管束植物１５３科，６４０属，１３９４种及变种，其中，种子植物占１２９科５５８属１２６９种及变种。种子植物的分布区类型组成是热带和主产热带的科占总科数的７１．３％；热带分布属占总属数的９０．１％；热带分布种超过总种数的９０％。热带分布属中又以热带亚洲分布属最多，占总数的３５．３％；热带分布种中则以热带亚洲分布及其变型的种类占总种数的６４．５％为特点。这表明该石灰岩森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。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，同时又是几种地理成分的交汇地带，这又使该石灰岩区系带有明显热带边缘性质和多种地理成分交汇的特点。

The forest flora of limestone hills in Xishuangbanna, Yunnan, is estimated to consist of 1394 vascular plant species belonging to 640 genera and 153 families, of which seed plants share 1269 species of 558 genera, 129 families, and ferns share the others. In the forest flora, Ochidaceae with 86 species, is the largest family in size; Rubiaceae with 68 species is the second; and other families are arranged in sequance as following: Euphorbiaceae (58 species), Papilionaceae (55),Moraceae (48), Vitaceae (38), Acanthaceae (36), Rutaceae (35), Asclepiadaceae (35), Urticaceae (35), Lauraceae (35), Apocynaceae (33), Anonaceae (30), and Meliaceae (30) etc. The statistics of distributional Patterns of taxa shows that the families, genera and species of tropical distribution take up 71. 3%, 90. 1% and more than 90% of the sum total of the flora separately. Furthermore, the genera of tropical Asian distribution take up 35.3% of total genera; the genera of pantropics 21. 1%; the ones of old world tropics 13.8%; the ones of tropical Asia to tropical Australia 9.0%. and the ones of tropical Asia to tropical Africa 7.9% etc.. The specise of tropical Asian distribution and its varieties take up 64.5%, the ones of S China and its varieties take up 24.2% and the ones of tropical Asia to tropical Australia 3.2% etc.. Therefore, the forest flora is explicitly of tropics in nature and as a Part of tropical Asian flora. Occured at the montane habitats of northern margin of tropical Asia, the forest flora also shows conspicuous characters of marginal tropics.Xishuangbanna is geographically a transional area from strict tropics to subtropics where the floristic element of Indo-Malesia from south, the one of india or S Himalayas from west and the one of S China from northeast and the one of Indochina from southeast mingle each other. So the flora is endowed with the characteristics of floristic confluence.