Abstract:  Vegetation status represents the overall condition of regional ecological environment, hence vegetation coverage is often used to measure the effectiveness of ecological protection and restoration projects. Although numerous studies have reported the overall changes of vegetation coverage in the BeijingTianjin sandstorm source region, few studies have investigated the regional differences over the years. In this paper, we  calculated the annual vegetation coverage from 2000 to 2015 in the BeijingTianjin sandstorm source region using MODIS data, emphasizing the regional variations of   vegetation cover in different subzones through statistical and GIS technology. The results indicated that, during the study period, the annual vegetation coverage in the region increased from 35% to 45% with an average annual growth rate of 0.4%. Although vegetation coverage in the eight subzones presented similar growth trend, remarkable differences existed in the vegetation status and growth speed. The annual vegetation growth rates in the Jinbei mountain-hill and Yanshan mountain-hill-water-source-protection subzones exceeded 0.6%, however, lower than 0.2% annual growth rates were observed in the Otindag sandy land and Desert grassland subzones. In addition, higher degree of vegetation primarily distributed in the sandstorm source regions of Beijing, Chengde and Tianjin with  Shuozhou and Zhangjiakou showing higher growth rates, whereas the rates were lower than 0.1% in Wulanchabu and Baotou. Approximately 51% BeijingTianjin sandstorm source region saw growth rate increasing in 2015 compared to 2000, while the remaining areas experienced decline in the mid and western districts. In conclusion, this study confirmed that significant vegetation improvement has been made in the BeijingTianjin sandstorm source region, however,  some areas remain poorly covered, therefore more efforts should be directed to these areas towards ecological restoration.

Key words:  vegetation cover, NDVI, regional difference, BeijingTianjin sandstorm source area