A Floristic Study of Flora of Seed Plants of the Chaqia-Gonghe Basin 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 2 800 m to 5 305 m in altitude, the total area is about 38 300 km2. 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.