关键词: 湑水流域, 植被, 区系地理成分

Abstract: The floristic component of the major vegetation type in Xushui Valley on the southern side of Qinling Mountains is studied in this paper. The result shows: at genus level, the altitude being high, the proportion of tropical elements in community reduces gradually, and its phytocoenology function decreases as well, but the ratio of typical temperate elements in community increases and its phytocoenology function increases as well; at species level, Middle China and East China elements are major flora of vegetation in low elevation sector.A large number of North China elements is centralized on middle altitude mountain sector, and on alpine sector, it's characterised by many Tang-gute elements and the elements endenic to Qinling and there are also some alpino-arctic and Hengduanshan elements. Thus it can be seen that the geographical element of the species and genus has obivous vertical differentiation.

Key words: Xushui Valley, vegetation, floristic component