Research on Dynamic Change of Grassland in West Jilin Province

By using three-period(1980,1995,2000) remote sensing images and with the support of RS and GIS,spatial information of grassland landscape in west Jilin province from 1980 to 2000 is extracted,spatio-temporal dynamics of grassland and change of grassland landscape patterns are analyzed.The results show:①From 1980 to 2000,40.70% of grassland decreased,and grassland seriously degraded.Grassland is mainly converted into cropland and saline-alkalized land,conversion area reaches 475 799.43 hm~2 and 303 182.06 hm~2 respectively;②From 1980 to 2000,total dynamic degree of grassland is a minus value.During 1980~1995,high coverage grassland has a strong effect on change of whole grassland.During 1995~2000,high and moderate coverage grasslands heavily affect change of whole grassland;③In the last twenty years,the centroids of all kinds of grasslands moved towards northeast direction,and in different phases,the centroids change of each kind of grassland are irregular and multi-directional;④During 1980~2000,on the whole,total number of patches,mean patch area,mean patch perimeter and dominance index have a decrease tendency,mean patch fractal dimension little changes and its value is approximate 1,the whole dynamics of fragmentation indices of various grasslands has an increase trend,and fragmentation degree is more serious,the whole pattern becomes complication.As far as grassland degradation in the study area is concerned,natural factor takes some driving acting,but human actions are dominating driving power.