Abstract:

With the ecologically important value of plants in plots as an index, vegetation characteristics in the semi-arid valley region of Lasa were analyzed with TWINSPAN and DCA multivariate analysiss methods, and quantity classification and sorting of the plots and species were carried on separately. The sampling surveys basically included all cover types in the region, and we obtained 35 sample plots. TWINSPAN analysis results indicated that: 1) the 1 350 m altitude scope was divided into 4 groups of vegetation types, 7 vegetation types; 14 formations, and 16 associations in the semi-arid valley region. In this region, several characteristics, such as diverse vegetation, distinct vertical band spectrum, and narrow intermediate belt and so on, displayed; 2) The result of DCA ordination was consistent with TWINSPAN classification, and each community type had its own scope and boundary; 3) The vegetation existed obvious minute belt along with change of the elevation in the semi-arid valley region. The first sorting axis of DCA reflected the altitude gradient of the plant community in the environment and the second reflected the water status. From bottom to top, the moisture content of the soil increased gradually; 4) The various communities order of rank synthesis of the DCA diagonal line reflected the vegetation communitys environmental heterogeneity, which provided a theory basis for the local vegetations zonality vegetation restoration.

Key words: vegetation, important value, TWINSPAN classification, DCA ordination, semi-arid valley region of Lasa