Corridor effect of the spatial changes of landscape patterns in arid areas： A case study of the river corridor areas in the middle and lower reaches of Tarim River

The river corridor areas in the middle and lower reaches of the Tarim River are dominated by the traditional green corridors along the river section from the Qara Reservoir in Yuli County to the Taitema Lake in Ruoqiang County, which plays an important role in the social and economic development in the Tarim River Wate＇rshed with a extremely significant ecological functions. The buffer zones perpendicular to the watercourse were defined along both riversides at a 5-km interval beginning from the watercourse （10 km wider） using the method of the buffer zone analysis. The landscape pattern indexes of each buffer zone were calculated, and the indexes of the main landscape patterns were analyzed so as to reveal the radiative effect and the characteristics of the river corridors on landscape and patch levels. The results show that the radiative width is generally 30 km in the study area, and can be up to 50-70 km in subregion FG1 because the study area is located in two drainage basins, with an ecological interstitial zone between them. The landscapes of woodlands and wetlands are generally distributed within the 10 km buffer zone （it means that the buffer zone is 5 km away from the watercourse; the same hereafter） along both riversides. Moreover, the closer the buffer zone is to the watercourse, the higher the patch density and the largest patch index are. In the ecological and environmental regeneration for the study area, the extent of ecological effect of the river corridors must be fully considered, and the projects must be scientifically and rationally planned and designed.