西双版纳石灰岩山地森林蕨类区系的初步研究

A PRELIMINARY STUDY ON THE PTERIDOFLORA IN XISHUANGBANNA LIMESTONE FOREST

西双版纳位于云南南部，与老挝及缅甸接壤。根据调查，现已知西双版纳石灰岩山地森林中蕨类区系有蕨类植物１２７种（包括变种），隶属于２４个科，５４个属。在该蕨类区系中，最大的科分别是水龙骨科、凤尾蕨科、铁角蕨科、铁线蕨科及三叉蕨科；最大的属分别为凤尾蕨属、铁角蕨属、铁线蕨属、石韦属及毛蕨属。该地蕨类区系具有东南亚热带的性质，其分布区类型的组成是：热带分布或主产热带的科占总科数的７０％以上；热带分布的属占总属数的８０％以上，而在热带分布的属中，有３３．３％的属为热带亚洲分布属。在其种的区系成分上，它们虽与我国相近纬度的广东、广西石灰岩山地区有一定的联系，但根据地区植物区系成分相似性的关系式得出：本地石灰岩山蕨类植物种类与广东、广西两地石灰岩山地区相似性系数均仅为０．３２，且种类大多是产于我国西南、华南或热带亚洲东南亚热带的成分，没有特有的科、属或种。

Xishuangbanna is situated in the southern part of Yunnan Province and is contiguous to Loas and Burma. Accoding to the investigation and grasped data, up to now, 24 families, 52 genera and 127 species (include varieties) of Pteridophytes have been recorded in Xishuangbanna limestone forest. In which,the largest families and genera are Polypodiaceae,Pteridaceae,Aspleniaceae, Adiantaceae,Aspidiaceae and Pteris,Asplenium. Adiantum,Pyrrosia,Cyclosorus. Acording to the results of floristic analysis.this Pteridoflora has the tropical character of SE Asia. In the floristic composition of this forest the families of tropics and mainly tropics distribution make up 70% of the total families;the genera of tropics distribution make up 80% of the total,and the genera of tropics Asia make up 33. 3% of the total. Though the Pteridoflora in Xishuangbanna limestone hills have certain relationship with those of Guangdong and Guangxi,the coefficient of similarity is only 0. 32 on species;and many Pteridoflora components are occured in southwestern China,southern China or SE Asia of tropical Asia. There are no endemic families,genera and species in limestone hills of Xishuangbanna.