PATTERNS OF BIODIVERSITY ALONG THE VERTICAL VEGETATION SPECTRUM Of THE EAST ASPECT OF GONGGA MOUNTAIN
贡嘎山东坡植被垂直带谱的物种多样性格局分析

This paper explores the structural properties and altitudinal patterns of plant biodiversity on the east aspect of Mt. Gongga through analysis of transect and plot data. Analyses of altitudinal variations in species richness and species area relationships, the altitudinal patterns of the structural components of species diversity counting on their areal types and lifeforms were completed. Detrended Correspondence Analysis (DCA) and Canonical Correspondence Analysis (CCA) were applied to detect relationships among 17 measured environmental indices, as well as the effects of environmental factors on the spatial patterns of 27 structural indices of biodiversity and 67 sampling plots. These analyses also permitted the quantitative partitioning of contributions of the environmental factors acting at different scales. While the study detected a generally decreasing gradient of plant species diversity with elevation locally opposite patterns were also found. These abnormalities were notable between the valley arid shrub and meadow zone and the evergreen broad leaved forest zone and between the alpine shrub and alpine meadow zones. Ten groups of geographical components (the areal types of species) showed a range of vertical pattern with richness: a vertical comparison of species richness among 9 ecological components (lifeforms) mainly revealed differences between the herb and woody types. From the valley arid shrub and meadow zone to the mixed coniferous and deciduous forest zone, the vertical change of biodiversity structure is mainly controlled by habitat humidity, whereas the temperature gradient dominates the change from the mixed coniferous and deciduous forest zone to the alpine meadow zone. The vertical gradient of climate and the local heterogeneity of habitat are two groups of causal factors with different properties and scales of activity. Seventy seven percent of biodiversity variation was associated with the environmental indices, among which the cold index (CL) is most effective. Several hypotheses about the mechanisms of biodiversity patterns were supported by these results. It is also argued that, as modern environmental factors control the geographic pattern of biodiversity at Mt.Gongga, the effects of regional environmental changes and the history of the flora development should also be considered.