Quantitative characteristics of timberline vegetation on Mt. Shergyla, Tibet

In order to make clear the spatial distribution of timberline vegetation and its ecological adaptability, we quantified the characteristics of the vegetation in the timberline ecotone on Mt. Shergyla in Tibet using multivariate analysis (TWINSPAN classification and DCA ordination) of the importance values of the plant species (herb, shrub and tree layer) in each of the 26 study plots. Results from TWINSPAN showed that along the timberline ecotone in an altitudinal range of 1 000 m, seven vegetation types (associations) were distinguished and the transitional belts between adjacent vegetation types were narrow. Results from DCA were similar to those from TWINSPAN, i.e., each vegetation type had its own ranges and demarcation lines. The first DCA ordination axis stood for altitude, and vegetation types changed with the changing altitude; the second DCA ordination axis represented soil water condition, and it increased with the increasing altitude; the ordination series in the diagonal line indicated the environmental heterogeneity of the habitats on Mt. Shergyla in Tibet.