Abstract:

It may be made such ecological analysis for flora formation, the correlation between plant species the distribution patterns in ecological series and 2 and 3 dimensional ordinations of subalpine forest vegetations in western Sichuan as follows:

(1) The flora of subalpine forest in this region has been formed by three process--the convergence of external flora components; the vertical differentiation during the orogenic movement; the internal differentiation within the mountain region accompanying with ecological isolation in south-western China.

(2) As result of a plexus or semi-matrix diagram of species based on correlation analysis for 6 major subalpine forest associations in western Sichuan, the shrub and herb species could be divided clearly into 2 close linkage natural groups-the sciohydrophytic one in higher elevation and the semixerophytic one in lower elevation, and a losse mesophytic group. The mosses could be divided into a close semixerophytic and a close thermophytic group in lower elevation, and a losse scio-hydrophytic group in higher elevation.

(3) Plant species distributing along ecological series are in 4 patterns: 1. narrow in elevation in synusia form on the whole; 2. narrow in elevation in scattered form on the whole; 3. broad in elevation, but narrow distribut in elevation only in synusia form; 4. broad in elevation. The last one has less indicative significance.

( 4) In 2 and 3 dimensional ordination, the samples of 6 major forest associations may be plotted according to the axes related to the elevation, moisture and soil fertility gradients in ordination fields. The positions on each axis and distance values between associations can quantitatively reflect the difference between associations.