Topographic Variation of Vegetation Types in Xiaohegou Nature Reserve of Sichuan Province

The variation of vegetation types in Xiaohegou Nature Reserve of Sichuan Province was studied based on its remote sensing images and digital elevation model(DEM) data.The results showed that ① as the elevation gradually increases,various vegetations appear and disappear in turn presenting a sequential distribution,and each of the vegetation types dominates at its corresponding elevation.The distribution of the vegetation types appears to correlate with the slope aspects.② Large areas of evergreen deciduous broadleaf forests and secondary deciduous broadleaf forests frequently occur on southwest-facing slopes and alpine shrubs and alpine meadows occupy the largest areas on southern-facing slope,whereas sub-alpine meadows rarely occur on flat land,north-facing slope and northwest slope.③ As the slope becomes sharp,the area proportions of various vegetation types differ with different slope-gradient ranges but the vegetation types are mainly secondary broadleaf deciduous forests and sub-alpine needle-leaf forest within various slope-gradient ranges and all the other vegetation types but sub-alpine meadows mainly distribute within the slope-gradient range of 20°~50°.