定居放牧方式下归一化植被指数(NDVI)的空间变化特征

MODELING THE SPATIAL PATTERN OF NORMALIZED DIFFERENCE VEGETATION INDEX (NDVI) UNDER A POST-NOMADIC SEDENTARY GRAZING SYSTEM

利用遥感数据 ,对内蒙古锡林河流域定居放牧方式下归一化植被指数 (N DVI)的空间变化特征进行了分析 ,结果表明 :1)定居放牧方式下 ,N DVI随定居点距离的变化格局经历了 3个阶段。第一阶段 ,草场处于原生阶段 ,N DVI不随距离变化 ;第二阶段 ,定居点附近开始局部退化 ,N DVI随距离增加而增大 ;第三阶段 ,退化区域扩大 ,N DVI不随距离变化。2 )在草场局部退化阶段 ,N DVI随距离的变化呈对数函数规律 ,定居点的放牧区具有放牧半径、原生 N DVI值、N DVI变化率等特征。

The effects of human activities on the spatial pattern of grassland vegetation in Xilin River Basin (XRB), Inner Mongolia were studied using satellite remote sensing data. The impacts of changes from a nomadic to settled pastoral lifestyle on grassland vegetation were evaluated by relating the value of normalized difference vegetation index ( NDVI ) at a point around a village to the distance between the point and the center of the village. Under sedentary grazing practices, the NDVI changes in the vicinity of villages occupy three phases. In the first phase, grasslands maintain homogeneity within the grazing area centered at village, and NDVI does not change with the distance from the center of village. In the second phase grasslands near the village begin to degrade and NDVI increases with distance. At the final phase, grassland degradation extends to the whole grazing area and NDVI does not change with distance. For the second phase, the change of NDVI can be estimated as logarithmic function of distance. The model implicated several important characteristics to spatially define the grazing area of a settled village, including grazing radius, background NDVI and rate of change in NDVI .