Abstract:

Based on remote sensing images，spatial gradient variations of the representative vegetation classes in Tangjiahe Nature Reserve was quantitatively analyzed from east to west，south to north，and northwest to southeast by using GIS technology.The results showed that：Secondary deciduous broadleaved forest，evergreen broadleaved and deciduous broadleaved mixed forest，coniferous and broadleaved mixed forest and coniferous forest classes showed distinctive peaks and different gradient variations in different direction.Among them，with space change from northwest to southeast，gradient variations of evergreen broadleaved and deciduous broadleaved mixed forest are the most complex.There are fluctuant variation tendency for the number of patch and class area that change from “increasing at first” then “decreasing”then “increasing” to “decreasing at last” and change from “increasing at first” then “decreasing” to “decreasing at last” in the reserve.But the edge density and mean nearest neighbor distance have same variation tendency that change from “increasing at first” to “decreasing gradually at last” in the reserve.The two terminals of this direction have bigger degree of fragmentation with the higher values of proximity in the reserve，and in the middle it was opposite.With space change from north to south，gradient variations of coniferous forest is the simplest one due to decreasing class area，fragmentation and complexity.While the number of it be distributed relatively more on the two terminal of this direction and less in the middle.The research of spatial gradient variations which happened to the vegetation landscape in different direction will also provide important guiding significance for the useful protection and management of vegetation in Tangjiahe nature reserve after the serious earthquake.

Key words: Tangjiahe Nature Reserve, spatial gradient analysis, landscape pattern, vegetation landscape