Abstract: The spatial pattern of aboveground biomass is an important content of species distribution pattern, whereas the environmental heterogeneity caused by the topographical differences in the scope of small scales is the environmental basis for the formation and evolution of this pattern. Based on the field survey in August 2011 and with the help of GIS and SPLUS software, the generalized additive model (GAM) was applied to study the spatial distribution pattern of S. chamaejasme population in degraded alpine grassland, and to quantitatively analyze the response mechanisms of the spatial pattern of S. chamaejasme’s aboveground biomass to topographical factors. Topographical factors had definite effects on the aboveground biomass of S. chamaejasme, with the sequence of aspect > slope > elevation > plane curvature > profile curvature. The contribution degree of aspect and slope to the spatial pattern of S. chamaejasme’s aboveground biomass was 3.75 and 1.48, respectively, while the contribution of other topographic factors was relatively lower. The aboveground biomass of S. chamaejasme had a uniform distribution in the gradients of elevation, plane curvature, and profile curvature, but presented an opendown parabola tendency in aspect gradient and an openup parabola tendency in slope gradient. The relationships between the spatial heterogeneity of S. chamaejasme’s aboveground biomass and topographic factors reflected the response mechanisms and growth strategies of S. chamaejasme under the effects of the redistribution of water and heat conditions.

Key words: Hongchiba region, Ecological restoration, Niche, Interspecies general overlap, Interspecies specific overlap