利用马尔柯夫过程预测锡林河流域草原退化格局的变化

以我国北方典型草原模式地段之一的锡林河流域草原为研究对象,根据研究区两个时期遥感影像解译的植被类型图衍生出草原植被退化图。在对草原退化图统一网格化后,计算各网格草原退化指数,并加以分级,确定不同草原退化等级之间转移概率,并应用马尔柯夫模型预测锡林河流域草原退化格局的演变趋势。结果表明:如果不采取防止草地退化的根本性措施,草原退化态势还将继续下去。以每个网格草原退化指数值为各网格草原退化状况划分依据,以3km×3km网格为统计单元,在流域总面积为10701km₂情况下,预测结果是:2005年,锡林河流域草原退化为3级的网格总面积是3776km₂,占流域总面积的35.29%;4、5级网格面积之和为5427km₂,达到流域总面积的50.71%。2025年,锡林河流域草原退化为3级的网格面积总和是3389km₂,占流域总面积的31.67%;4、5级网格面积之和为6406km₂,达到流域总面积的59.86%。

Forecast on changes of steppe degradation patterns in the Xilin River Basin, Inner Mongolia: an application of Markov process

At present,steppe degradation is a major environmental problem in Inner Mongolia of China,resulting in desertification and reduction of steppe productivity.However,data on area, change and forecast of steppe degradation is inadequate at regional level.Steppe in the Xilin River Basin is one of the typical patterns in pastoral area of northern China,it is also one of the most important husbandry bases in Inner Mongolia and an UNESCO/MAB Biosphere Reserve.Using Landsat TM images of1985and1999,and combining with field community investi-gation,we compiled steppe vegetation maps in1985and1999of the Xilin River Basin.Further,according to the model of degradation succession of typical steppe in Inner Mongolia,we com-piled steppe degradation maps.Supported with ARC/INFO and ARC/VIEW,grid sampling on steppe degradation map was finished,the size of each grid is3km×3km.Based on steppe degra-dation index(SDI)aggregating the information of area and grade of steppe degradation developed by the authors,the SDI of each grid was calculated.The values of SDI were divided into five grades to indicate the degree of steppe degradation increase.In1999,the total area of grids where the value of SDI is3is3924km 2 ,36.67%of the total area of the Xilin River Basin;the total area of grids where the value of SDI is4and5is5049km 2 ,47.18%of the total area.Then,the translation probability matrix from1985to1999of different grade of degraded steppe was calculated.With application of Markov process,the changing trend of steppe degra-dation pattern in the Xilin River Basin was forecasted.The results showed that if no fundmental measures are taken to prevent steppe degradation in this region,the trend of degradation will continue.That is to say,the area of steppe at grades1,2and3will decrease,and that of grades4and5will increase.Up to2025,the total area of grids where the value of SDI is3is3389km 2 ,31.67%of the total area of the Xilin River Basin;the total area of grids where the value of SDI is4and5is6406km 2 ,59.86%of the total area.