Spatio-Temporal Pattern and Driving Forces of Grassland Change in West Jilin Province

Grassland had heavily degraded in west Jilin province during 1980-2000,and it is of great importance to the sustainable development of stockbreeding and eco-environment through study ing on spatio-temporal dynamic change of grassland in this region.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 in the past 20 years is interpreted and extracted,dynamic spatio-temporal change of grassland landscape patterns of Jilin province is analyzed.The results show:(1)In the past 20 years,40.70% of the grassland decreased,and grassland degradation is serious,especially for high coverage grassland with a net decreasing rate of 51.96%.(2)From 1980 to 1995,the total dynamic degree of grassland is accordant with the dynamic degree of high coverage grassland,so high coverage grassland has a strong effect on change of the whole grassland.During 1995-2000,both dynamic degree of various grasslands and total dynamic degree are negative,the speed of low coverage grassland degradation is the fastest,the total dynamic degree approximates the dynamic degree of high coverage grassland and moderate coverage grassland,and the two types of grasslands heavily affect change of the whole grassland.(3)Grassland is mainly converted into cropland and saline-alkalized land,the converted area reaches 475 799.43hm2 and 303 182.06hm2 respectively.(4)In the last 20 years,the center of gravity of all kinds of grasslands moved towards northeast direction,and in different phases,the change of center of gravity of each kind of grassland is irregular and multi-directional.As far as grassland degradation in the study area is concerned,natural factor takes certain driving action,but human actions are the dominating driving power.