A Floristic Study of Flora of Seed Plants of the Chaqia-GongheBasin and Its Contiguous Zone in Qinghai,China

The Chaqia-Gonghe Basin and its contiguous zone is situated in eastern Qinghai of China, between latitude 34°45′- 37°00′N and longitude 98°45′- 101°30′E . Ranging from 2 800m to 5 305 m in altitude, the total area is about 38 300km2 . Its climate is continental or plateau-continental one . There are 854 species of native seed plants belonging to 59 families and 277 genera there , which occupied 37. 37% of the total species, 54 . 53% of the total genera and 65. 56% of the total families in Qinghai respectively . The floristic characteristics of the native seed plants are as follows : ( 1) Number of species and woody ones there are poor . (2) At generic level, the flora is temperate in nature, dominated by north temperate elements especially the typical elements from the warm and cold zone of Eurasia , but also with some elements of warm, cold warm and alpine ones . (3 ) The area is a margin of distribution for many species or genera especially for tropical ones, and thus , the flora of the area is clearly marginal in nature . (4) Floristic-geographically , it is a converged and transitional region for the Qinghai-Tibetan Plateau Alpine Flora , Loess Plateau Warm Flora , as well as East Asia Alpine Desert Flora. (5 ) It is a part of the Tangute Flora . (6 ) It is a key area to divide the subregions in the flora of Qinghai on the Tangute Area .