Characteristics on the flora of seed plants from Maqu in the eastern margin of Qinghai鄄Tibet Plateau,western China.

Maqu lies in the northeast of Qinghai-Tibet Plateau and southwest of Gansu Province. It is the area where more floras are convergent, and the floral composition is complex. It connects nearby floristic areas extensively. The seed plants from Maqu were investigated and counted in view of taxonomy and floristic geography. On the basis of modern geographic distribution patterns of all species, genera and family in this region, the geographic distribution types were identified and taken into statistical analysis. By the method of principle component analysis (PCA), the flora of Maqu were compared with 12 adjacent regions to identify the relationships of floristic similarity among them. The results were showed as follows: the flora of Maqu consisted of 83 families , 353 genera and 936 species of seed plants. The resource plants are rich. The seed plants of Maqu are complex geographical components, mainly consisting of temperate distribution ( including 272 temperate genera and 428 temperate species, accounting for 89.18% of all the genera and 46.37% of all the species), typical north temperate in nature. Most plants of the flora are perennial herbs and poorest on trees, short of the ancient type and primitive species, and some endemic elements of China are few. Because of the relative young geology age, the time of speciation is shorter and the differentiation is later in Maqu. Maqu is the intersection of southwest element, north China element and the Tangute Region, showing the features of transitional flora.