Phytogeography Of Astragalus L. In Qinghai-Xizang Plateau

According to the field investigation and herbarium study in the Herbarium of Beijing Institute of Botany (PE), Northwest A & F University Herbarium (WUK) and the Herbarium of Northwest Plateau Institute of Biology (HWNP) and research on the published literature and other informations, there are 171 species (including varieties) of the Genus Astragauls distribute in Qinghai-Xizang Plateau. With these informations, we completed 51 geographical distribution maps by units of the county and mountains.Based on the combination of distribution maps and the original distribution information, by using Wu Zheng-Yi and Wu Su-gong's System of Chinese Floristic Region, the statistics of counted distributions of these species in the Qinghai-Xizang Plateau was completed. The geographical elements were processed and analyzed. The Geographical element of 6 regions and 13 subregions in the Qinghai-Xizang Plateau were calculated by independent. The species' Floristic elements in endemic of whole Qinghai-Xizang Plateau, Floristic regions and subregions was analyzed. Six plant regions' floristic characteristics in Qinghai-Xizang Plateau are shown.The main results are as follows:1. Genus Astragalus in Qinghai-Xizang plateau have more endemic elements.There are 171 Astragalus species in the entire Qinghai-Xizang plateau, 145 of them are endemic, accounting for 84.8%. In other elements, C. Asiatic element is more important. There are 17 species belong to C. Asiatic desert element, accounting for 10%. Other elements are relatively few.2. Qinghai-Xizang Plateau is one of Astragalus species diversity center.This area has 171 species of Astragalus species, accounting for 41.3% of the total number of China's Astragalus species, which is rapidly since Tertiary uplift of the Qinghai-Xizang Plateau result. A large number of species evolution occurred here forming the modern distribution pattern. It represents the development direction of cold transformation.3. Astragalus species in the Qinghai-Xizang Plateau present obvious geographical substitute. The flora of Qinghai-Xizang Plateau and the surrounding areas have extensive connections. There are some geographical substitution, for the living species in different environments.4. There are 3 mainly dispersal routes of Astragalus spp. from Qinghai-Xizang plateau.A. Hengduan Mountain Region --- Taohe-Minshan Mountain Subregion --- Eurasia Steppe Subkingdom, Central Asiatic Desert Subkingdom, Sino-Japanese Forest SubkingdomB. Tangut Region --- Qilian Mountain Subregion --- Qaidam Basin Subregion --- Central Asiatic Desert SubkingdomC. W. Himalaya Region --- Pamir, Karakorum-Kunlun High Mountain & Plateau Subregion --- Central Asiatic Desert Subkingdom...