A study on the flora of Huangshui river valley in Qinghai,China

The Huangshui River valley is situated in eastern Qinghai,China, and between latitude 35°56'-37°38'N and longitude 100°35'- 103°05'E. The area belongs to the transition zone between Qinghai-Ti-betan Plateau and Loess Plateau with altitudes ranging from 1 650 m to 4 395 m. The total area is 16 600 km2. The features of climate are the types with the continent and alpine continent. There are 1 234 species of wild seed plants that belong to 83 families and 400 genera in this region,and respectively have 92. 22% of total families,and of 78. 74% of total genera and of 54. 00% of total species of the Tangute Region from the Qinghai-Tibetan Plateau Subdivision. The floristic characteristics in the area are as foll6ws:①Species are relatively richer in the Tangute Region. ②The North Temperate Zone is superior to numbers of species in this area. The Temperate elements have a percentage of 92. 80%. It shows the clear nature of the temperate zone that is the decisive factor of the floristic characteristics. However,it belongs to the nature of the temperate zone that mainly with the North Temperate elements especially with the typical elements from the warm and cold zone of Europe and Asia continents,and that the type is with warm, cold warm and alpine. Or it can be called the compound floristic characteristics that are from the transition flora in the temperate flora. ③Most of the plants are perennial herbs and poorest of trees. This flora is short of the an- cient type and primitive species,and some endemic elements of China are developed from them relational genera that are wildly distributed indicating the flora is a young and derivative flora. ④The flora was affected by both of the alpine flora from southwest China and the flora of northwest China. As the area of the border of the Qinghai-Tibetan Plateau and the transition flora that far from the hinterland of the Qinghai-Tibetan Plateau,not only the floristic characteristics of plateau and alpine were crippled,but also the elements of plateau and alpine were increased. But it did not change the floristic nature of plateau and alpine.⑤ It is one of representative flora of the transition zone between the Tangute Region and the region of northwest China. ⑥It has only a few of endemic genera and species. By the analysis of this study,it is indisputable that the flora of Huangshui River valley belongs to the Tangute Region from Qinghai-Tibetan Plateau subdivision.