The species abundance and population quantity of epiphytic orchids in the limestone monsoon forest of Xishuangbanna was studied based on the fixed－width line transect method. The research results of 3 years showed: 1) the epiphytic orchids in limestone monsoon forest had rich species (34 species in 21 genera) and relatively low species density (0.6~24.9 individual/hm2) ; 2) the fluctuation of spe-cies abundance was swift ( 2 ~6 species) , and the regeneration of individuals was rapid for 3 years ( mortality=0 ~100% , proportion of recruitment =5.5 ~100% ; short－time annual mortality =7 ~100% ) ; 3) the primary factors of the fluctuations in both species abundance and population quantity were human collecting and the deaths caused by physical factor ( including the death of host, the loss of substrate and the direct impacts of strong wind and some wildlife) , which accounted respectively for 43.6% and 36.4% of the dead or lost individuals. The results revealed that only the protection of forest might not be sufficient to ensure the long－tern conservation of the endangered epiphytic orchid species. The suggestions of strengthening the trade control and establishing the regional local protection system were put forward.%运用定宽样线法研究西双版纳石灰山季雨林附生兰科植物种群丰富度及种群数量动态. 3年的监测结果显示:1)石灰山季雨林内附生兰科植物种类丰富(21 属34 种) ,种群密度较低,为(0.6~24.9株. 丛)/hm2;2)种群丰富度年际波动明显(2~6种),种群个体的更新速率快(3年间的个体死亡率为0~100% ,新增率为5.5% ~100% ,年际消亡率为7% ~100% ) ;3)种群个体消亡的主要原因是人为采摘和物理致亡,由人为采摘和物理因素(附主枯死、基质脱落等物理因素及强风、动物等直接作用)导致的个体消亡分别占消亡总数的43.6%和36.4% .研究结果揭示,单凭立地森林植被的保护还不足以确保其内濒危附生兰科植物的长远保护.提出加强贸易管制,完善区域性就地保护体系设置等保护建议.
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