The Flora of Datong River Valley in Qinghai,China

The Datong River valley is situated in eastern Qinghai,China,and between latitude 36°45′-38°20′ N and longitude 98°50′-103°00′ E.This area belongs to the transition zone between Qinghai-Tibetan Plateau and Loess Plateau with altitudes ranging from 1 900?m to 5 254?m.The total area is 17 600?km~2.The features of climate are the type with the continent or alpine continent.There are 1 154 species of wild seed plants that belong to 77 families and 368 genera in this region,and it has 85.56% of total family,and of 72.44% of total genera and of 50.50% of total species of the Tangute Region from the Qinghai-Tibetan Plateau Subdivision respectively.The floristic characteristics in the area are as follows:(1) This area is a type locality of many species in the Tangute Region that is well worth protecting,and the species are relatively richer.(2) On the level of genera,the flora belongs to the nature of the temperate zone that mainly with the North Temperate elements,especially dominated with the typical elements from the warm and cold zone of Europe and Asia continents,and also with warm,cold warm and alpine ones.(3) The flora is a young and derivative one,i.e.most of the plants are perennial herbs and poorest on trees,short of the ancient type and primitive species,and some endemic elements of China are developed from their related taxa.(4) Being the area of the border of the Qinghai-Tibetan Plateau and the transition flora that far from the hinterland of the Qinghai-Tibetan Plateau, while the flora was affected by both alpine one of SW China and other one of N China.It keeps the floristic nature of plateau and alpine.(5) It is one of representative floras of the transition zone between the Loess Plateau and Qinghai-Tibetan Plateau of China.By the analysis of this study,it is indisputable that the flora of Datong River valley belongs to the Tangute Region,Qinghai-Tibetan Plateau subdivision.