甘南林区兰科植物区系的研究

甘南林区兰科植物计有３９属８３种及１变种。区系分析的结果表明：甘南林区兰科植 物的种类丰富，属的地理成分多样，区系整体属于温带性质，并有少数临界分布的热带成分；种 的分布型以温带的东亚成分、尤其是中国一喜马拉雅植物亚区的区系成分为主；中国特有种占很 大比重，其中横断山地区及其邻近地区特有种居首要地位；白龙江下游小区是我国兰科植物在亚 热带北缘种系分化和适应性辐射的结点，可作为东亚两大植物亚区分界线的重要标志之一。

Notes on the orchid flora in the Gannan forest region, Gansu

The orchids occuring in the Gannan forest region, as a natural territory including three forest districts in the Bailong River, the Tao River and the Xia River located in the South of Gansu province, comprise 39 genera and 83 species with 1 variety. The results of floristic analysis indicate that the flora of orchids in this region as one of temperate flora, is characterized by the abundance in genera and species, dominance of terrestrial species, diversity in geographical elements with numerous species of temperate genera as the dominant aspect and a few species of tropical genera in the limit state of its distribution. The species distribution pattern mainly consist of the temperate elements covering the whole Eastern Asian Region, of which especialy in the Sino-Himalayan Subregion, considerable proportion of the species endemic to China, of which the species endemic to the Hengduan Mountain Region and its adjacent regions occupy a dominant position. The four geographical ditricts of the lower reaches of the Bailong River, the upper reaches of the Bailong River, the middle-upper reaches of the Tao River, the middle-upper reaches of the Xia River, differ widely in some floristic features as follows:the abundance, life forms, copmposition and distribution patterns of genera and species. The lower reaches of the Bailong River may be regarded as one of the knots on the northern fringe of subtropics, at which the species differentiation and adaptative radiation of Chinese orchids have been occuring, and as one of significant marks along the demarcation line between the two floristic subregions of the Eastern Asian Region.