Studies On The Pleurocarpous Mosses Of Bailongjiang River Basin Of Gansu, China

At present, 506 species of bryophytes in 185 genera and 56 families are recognized of Gansu province. Among them, 432 species, 155 genera and 38 family of mosses have been reported.Bailongjiang River is situated in the south of Gansu Province, locating in the convergence zone of the Qinghai-Tibet Plateau, Loess Plateau and Qinba Mountains(32°21′~35°50N ; 101°40′~105°20′E).The basin covers the area of 31,800 km2, and is known as one of the first-order branches of Jialingjiang River . The highest elevation is 4920m, and its bottom is only 550m.The climate of the upper reaches is temperate-humid, and that of the middle warm-humid, while that of the lower reaches subtropical-humid.Based on the investigation, collection and study of pleurocarpous mosses from the Bailongjiang River Basin, 226 species of pleurocarpous mosses in 91 genera and 25 families (including 8 varieties and 4 subspecies)are recognized .From Bailongjiang basin not only the species of pleurocarpous mosses are very abundant, but the distribution type is diverse obviously. In the bryoflora of Bailongjiang basin, Temperate taxa are dominant, and East Asia element are exist.According to Prof. Wu Zheng-Yi's opinion, the bryoflora of Bailongjiang basin have been divided into 13 areal types. North Temperate type ( 27.88% ) are the most important one and the East-Asiatic type ( 22.12% ) are also abundant; then the Endemic to China type ( 20.35% ) are the third one. In the East-Asiatic species, Sino-Japan type(11.50%)is more than Sino-Himalaya type(4.42%).Comparison between the pleurocarpous mosses of Bailongjiang River and those of the other regions. The relationships of the bryoflora between those of Bailongjiang River , Mt.Qinling , Shennongjia, Mt. Hengduan are very close. These bryofloras represent not only the transitional characteristic between North and South China, but also Sino-Japanese type and Sino-Himalayan one.