Time series analysis of vegetation cover in north piedmont of Yinshan Mountain

North piedmont of Yinshan Mountain is a typical fragile ecology zone and important eco-shelter in north China, therefore, to monitor and analyze its dynamics of vegetation cover is an important entrance to study response of global change in this area even the ecotone. Based on annual SPOT4/VEGETATION images of this area from 1998 to 2003, we did time series analysis on dynamics of annual maximum NDVI, which reflected dynamics of vegetation cover condition, and then drew three conclusions: Firstly, the whole area annual maximum NDVI was degenerated continuously from year 1999 to 2001, while was improved continuously in the next two years. Secondly, when it comes to woodland, grassland and cropland, the order of the annual maximum NDVI and their change in a year both were: cropland>woodland>grassland, while the order of change in 1998-2003 was: woodland>cropland>grassland; Besides, cropland and woodland annual maximum NDVI in year 2003 had middling and slight improvement respectively, compared with those of year 1998, while grassland had middling degeneration. Thirdly, annual maximum NDVI of the whole area in year 2001 had serious degeneration, compared with that of year 1998, except for middle Damao Banner, east Duolun County and southeast Shangdu County, while that of 2003 had middling or high improvement, compared with that of year 2001, except for northwest Damao Banner and sporadic spots of east Duolun County. On the whole, annual maximum NDVI of year 2003 had middling degeneration in the northwest of this area, while degeneration and improvement coexisted in other places, compared with that of year 1998