Floristic Geography Of The Taizi Mountains In Gansu Province

The seed plants from the Taizi Mountains, as an independent floristic unit, were investigated and counted in view of taxonomy and floristic geography. On the basis of the modern geographic distribution patterns of all species, genera and family in this region, the geographic distribution types at the three toxonomic levels were identified and taken into statistical analysis. By three methods of Principle Component Analysis (PCA), clustering analysis and similarity analysis, the flora of Taizi Mountains were compared with 11 adjacent regions to identify the relationships of floristic similarity among them. Also issue on the basic features, floristic properties and the principal origin of the floristic components in the Taizi Mountains were discussed. The results were showed as follows: 1. The flora of the Taizi Mountains was consisted of 827 species of vascular plants, belonging to 94 families and 352 genera. The angiosperm occupied a dominant position, and Salicaceae, Ranunculaceae, Rosaceae, Leguminosae, Compositae and Gramineae were the dominant families. 2. The temperate properties of the flora were obvious and the geographic elements were complicated. The temperate element occupied absolutely dominant position. The dominant families and dominant genera belonged to temperate elements. 3. As the relative young geology age, the time of speciation was shorter and the differentiation later in Taizi Mountains. So the flora elements were younger. The species analysis showed that the distribution pattern of the region was the adaptable radiation from Southwest to Northeast as the major way, which was originated from Southwest regions and the Northeast border district of Qinghai—Xizang plateau. 4. The Taizi Mountains was the intersection of Southwest element, North China element, Sino-Himalayas sub form and Sino—Japanese sub form, and the region was short of endemic species, which showed the features of transitional flora in Taizi Mountains. 5. The flora of Taizi Mountains had the closest relationship with the adjunctive flora of the Lianhua Mountains, the Qilian Mountains, the Maxian Mountains and the Tao River Basin; The relationship between the flora of Taizi Mountains and the one of Taibai Mountains, Xiaolong Mountains, the middle—upper reaches of Bailong River took the second place; The relationship between the flora of Taizi Mountains and the Hengduan Mountains, Baishui River and Helan Mountains was the farest. 6. The region should be divided into the vegetation area of Hengduan Mountains and sub district of Northwest of Sichuan, Southwest of Gansu and Southeast of Qinghai, which was the boundary line of floristic district of the Hengduan Mountains, North China and subdistrict of the Loess plateau. 7. There was the diversity of vegetation form in the Taizi Mountains. The communities of secondary forest in Taizi Mountains were divided into 5 vegetation forms, 22 formation-types and 45 formations.