锡林河流域草原植被退化空间格局分析

利用TM遥感影像,结合地面植被调查,基于典型草原退化演替模式,绘制锡林河流域植被现状图,在地理信息系统支持下,研究了锡林河流域草原植被退化空间格局特征,得出全流域、上中下游及流域内不同地貌类型上不同草原退化等级的面积。全流域1999年放牧退化草原植被面积为7689.3km₂,占总流域面积的71.86%。根据草原退化指数计算得出全流域总草原退化指数为10901.8km₂草原退化单位,同时还计算了流域上中下游区域和流域内不同地貌类型的草原退化指数值。通过网格取样,绘制锡林河流域草原退化指数空间图,应用空间趋势面分析法绘制草原植被退化指数等值线图。结果表明:锡林河流域草原退化的空间格局较为复杂,首先与流域上中下游及不同地貌类型上人类放牧利用强度的差异相关,具体表现在流域中下游及河谷阶地、平原和丘陵区草原植被退化较为明显,其次,全流域有多个较为明显的草原植被严重退化中心区,均与人类高强度放牧利用有关。

Spatial pattern of steppe degradation in Xilin River Basin of Inner Mongolia

Steppe degradation is a major problem facing environment and animal husbandry in Inner Mongolia,China today.Using Landsat TM images of1999,and combining with field inves-tigation,and based on the diagnosis model of degradation succession of typical steppe in Inner Mongolia,the vegetation map in1999in the Xilin River Basin was compiled.Supported by ARC/INFO,the spatial pattern of steppe degradation was studied.The areas of steppe having different degradation degree throughout the Xilin River Basin,the upper,middle and lower reaches and different landform types were calculated.The total area of grazing degraded steppe in the Xilin River Basin in1999was7689.3km 2 ,71.86%of the total area basin.Light grazing degraded steppe was3678.8km 2 ,47.84%of the total grazing degraded steppe,medium grazing degraded steppe was1933.6km 2 ,25.15%of the total grazing degraded steppe,and heavy grazing degrad-ed steppe was2077.2km 2 ,27.01%of the total grazing degraded steppe.Based on the calculation formula of steppe degradation index,this paper calculated respectively the value of steppe degra-dation index of the whole basin,the upper,middle and lower reaches,and lower mountain,hill,lava tableland and high plain.Steppe degradation index per unit area of the upper,middle and lower reaches is middle reach>lower reach>upper reach;steppe degradation in dex per unit area of landforms is high plain >hill >lava tableland>lower mountain.With grid point sam pling on steppe vegetation degradation map,the value of steppe degradation index of each grid was calcu-lated,and the distribution map of steppe degradation index was compiled.The result is that the spatial pattern of steppe vegetation degradation in Xilin River Basin is complicated.Steppe degradation spatial pattern at large scale in the Xilin River Basin is related to human grazing in-tensity in the upper,middle and lower reaches and different landforms ,in the middle and low er reaches,steppe in river terrace,plain and hill area degraded obviously.Second,there are quite a number of central areas where steppe degraded seriously in the Xilin River Basin,which are all related to over-grazing.