峨眉山兰科植物的地理分布和区系特点

The Geographical Distribution and Floristic Features of the Orchid Flora in the Mt. Emei in China

 Situated in western part of Sichuan Province, 29°30'N, 103°20'E, the sacred Mt. Emei is one of the well-known large mountains in China. Its summit is about 3100 m ab- ove sea level with a relative height of 2550 m.        The orchid flora in Mt. Emei so far known comprises 47 genera and 109 species, among which 21 are epiphytes, 83 terrestrials and 5 saprophytes (Table 1.)        1.  The vertical distribution of the orchid flora in the mountain. The epiphytic orchids are concentrated in the lower region  below Hongchunping and Wanniansi (1100 m alt.), where there are 20 species, which make over 95% of epiphytic species; the upper limit for the epiphytic orchids is Jiulaodong and Chudian ( 1800 m alt.). The terrestrial orchids also mainly occur at the lower region below Jiulaodong and Chudian (1800 m alt.), where there are 54 species, most of which are found at even lower part of the mountain, below Hongchunping and Wanniansi (1100 m alt.). The tropicas orchids in the mountain, such as Cleisostoma, Vanda, Holcoglossum, Tropiclia, Thunia, Mischobulbum, Ludisia, Anoectochilus, Odontochilus, etc. all grow only at the lower part of the mountain below Hongchunping and Wanniansi (1100 m alt.).        2. The floristic features of the orchid flora in the Mt. Emei.        (1)  The orchid flora in the mountain so far known comprises 47 genera (over 2/3 of the total orchid genera in Sichuan) and 109 species (over 1/3 of the total orchid species in Sichuan). The Mt. Emei is very rich in orchid species, as compared with neighbouring mountains of same magnitude, such as Mt. Shennonjia in western Hubei, Qin Ling in sou- thern Shaanxi, Jinfo Shan in south-eastern Sichuan, and Erlang Shan in western Sichuan.        (2)  The orchids in the mountain are complex in floristic components as indicated below:        1)  Twenty seven species, belonging to 18 genera, are widespread, covering the whole East-Asian region.        2)  Twenty three species, belonging to 15 genera, are the elements of the Sino-Japanese Subregion. Among them 13 species occur only in Japan and eastern China with the mountain ar the westernmost limit, but the other species extend westwards as far as Kangding and ErLang Shan or Baoxing in Sichuan Province.        3)  Forty two species, belonging to 22 genera, are the elements of the Sino-Himala-yan Subregion, with 5 species having their range extending from the Himalayan  region eastwards to Mt. Emei.        4)  Some tropical genera (8 species), belonging to Indo-Malaysian floristic elements, have the mountain as their northern limit of distribution.       The orchid flora of the Mt. Emei contains not only the East-Asian elements, but also some Indo-Malaysian elements, though its composition is mainly of the temperate and subtropical Eastern Asian (Sino-Japanese) ones.        (3)  The orchid flora in the mountain is characterized by geographical vicariation and differentiation.       There are nine species-pairs (belong to genera Calanthe,  Platanthera,  Dendrobium etc.) of the vertical vicarism and six species-pairs (belonging to genera Tropidia, Aneoctochilus, Mischobulbum, Gymnadenia Orchis, etc.) of the horizontal vicarism in the Mt.  Emei.       Remarkable differentiation of orchid flora in the Mt. Emei is shown in the abundance of endemic elements and as clear geographical vicariation.        (4)  There are 8 endemic species and one variety of orchids in the Mt. Emei, more  abundant than in Xizang.      The floristic features of the orchid flora of the Mt. Emei are rich in species, compara tively complex in components, rather prolific in endemic species, and characterized by geographical vicariation and differentiation. The orchid flora in the Mt. Emei mainly consists of the subtropical and temperate East-Asian elements, with a  considerable proportion of tropical elements though.