MONITORING TEMPORAL AND SPATIAL CHANGES OF LAND USE AND LAND COVER BASED ON REMOTE SENSING IN THE HILLY REGION OF CENTRAL SICHUAN BETWEEN 1989 AND 2009
In recent years, under the background of government policy and the development of social economy, land use in hilly region of central Sichuan has changed drastically. Especially the Changzhi soil erosion control project that has been carried out since 1989 and the policy of converting from farm land to forest which has been carried out after flooding disaster in 1998, have seriously affected the land use in hilly region of central Sichuan between 1989 and 2009. In order to detect these changes and acquire the land use information, this study was conducted in Lizixi basin which is the typical area in hilly region of central Sichuan. Supervised classification was applied to the processing procedure of TM, SPOT data in 1989, 1999 and Rapideye data in 2009. The results were further improved by visual interpretation. The overall classification accuracy reaches 88.33% and the kappa is 0.8350. The elevation was classified into five grades to detect the land use distribution in different elevation gradients in 2009. Post-classification comparisons of the classified images indicated that the major change consists that the cultivated land is decreasing and forest is increasing. The force factor of these changes may be the policy of converting from farmland to forest. Because of the labor shortage, 53.29% of the decreased cultivated land has changed to abandoned arable land which is covered by lush grass and mainly distribute on the halfway up to the hill. The urban area has enlarged 7 times due to the large number of migrants from rural to urban. Overall these changes reflect the regional policies and human activities are the major and important force factors of changes in the hilly region of central Sichuan during last two decades.