Abstract:

Based on the SPOT-VGT normalized difference vegetation index (NDVI) dataset, SRTM digital elevation model (DEM), and metrological data accumulated during the years from 1999 to 2013 in four observatory stations in the Wuliangsuhai Basin, Inner Mongolia, analyses were performed for inter-annual changes in vegetation coverage in the region and their elevation effect, and at the mean time exploration was done of responses of the vegetation to climate changes through comparing changes in annual mean temperature and annual precipitation. Results show that (1) on the whole, the basin was quite low in vegetation coverage, with a multi-year mean of NDVI being 0.213; however, vegetation coverage in 94.8% areas of the basin exhibited an apparent rising trend, and the trend in 51.8% areas of the region passed the 99% confidence level (a statistical variable calculated by the non-parametric Mann-Kendall test of Z>2.32); and the annual mean NDVI was 22.4% areas in 2013 than in 1999; (2) vegetation coverage in the region declined with rising elevation and annual NDVI change rate also varied significantly with elevation, exhibiting a declining trend around 1 000 m in elevation and rising trends in all the others; and (3) variation of annual mean NDVI in the region was significantly and positively related to annual mean precipitation (P<0.05), but negatively to annual mean temperature (P>0.05).

Key words: climate change, vegetation coverage, altitudinal gradient, NDVI, Inner Mongolia