Spatial-temporal changes of vegetation in Qilian Mountains from 2000 to 2010 based on MODIS NDVI data and its affecting factors

A time series(2000-2010) data set of the Normalized Different Vegetation Index(NDVI) together with historical climate data were used to analyze spatial-temporal changes of vegetation and its affecting factors in Qilian Mountains.The results showed that: ①The maximum values of annual NDVI(MNDVI) has increased with an rate of 2.4%/10a since 2000.The greening area,stable area,and the degraded area accounted for 26.32%,66.42% and 7.26% of the total area respectively.MNDVI in the Lenglong Ridge,Laji Mt.,Datong Mt.,Daban Mt.,South Qinghai Mt.,Zongwulong Mt.,Tuolai Mt.,Xining basin and Huangshui valley increased.By contrast,MNDVI decreased in the Wushao Ridge,Zhuanglang River,Gulang river,Datong River,Shiyang River,Hei River and Shule River.②Temporal trends of MNDVI varied in different vegetation types.MNDVI increased significantly in shrubland,desert steppe,alpine grassland and alpine sparse meadow,while decreased significantly in deciduous broad-leaved forest,mixed forest and evergreen coniferous forest.MNDVI increase weakly in alpine shrub meadow and alpine meadow.③Vegetation changes in Qilian Mountains were mainly influenced by temperature and precipitation.Intensified human activities in local areas also profoundly impacted on vegetation.