Analysis Of Spatial-Temporal Change Of NDVI And Its Driving Factors In Eastern Alxa

On account of the global climate change and the improvement of ecological protection in recent years, great changes had happened on desert vegetation coverage of Alxa in Inner Mongolia. In order to understand the change of Alxa desert vegetation and its driving factors accurately and provide basic data for the region ecosystem protection and utilization, we took Eastern Alxa as example, in which the desert vegetation coverage was better. We used the MODIS-NDVI data from 2001 to 2015 to analyze the climate fluctuation and the trend of vegetation in difierent periods, and discussed the factors of climate and human drive NDVI changes. The main research results were as follows:1. The annual average air temperature and annual precipitation of Eastern Alxa were not significant upward in volatility from 2001 to 2015. The tendency rate was 0.34℃/10a and 0.35 mm/10a. There were biggish differences in the growing season. The data displayed that both temperature and precipitation in 8,9 June showed no significant decline, and the tendency rate were 0.43℃/10 a,8.09 mm/10a and 8.09 mm/10 a.2. Eastern Alxa NDVI was rising in general from 2001 to 2015. And the annual change rate was 0.0068/10a. On the spatial, NDVI had an up trend in the eastern steppe desert and north-central typical desert, no significant change on northern typical desert and southwestern desert, a downtrend in central Ulan bub. desertd and northern typical desert.3. Eastern Alxa NDVI showed significant stage change from 2001 to 2015. And in most area, NDVI increasing rate was faster than that of in the first 10 years from 2011 to 2015, in which the region of steppe desert and typical desert had relatively significant fluctuations.4. The relationships between Eastern Alxa NDVI and temperature in the same period were not significant. But there was a positively correlated relationship between NDVI and precipitation in annual and growing season. NDVI had obvious lag effect on precipitation which delayed 1 to 6 months in average. Precipitation was one of the important climate driving factors on NDVI changes. NDVI had weaker lag effect on temperature. But in August, NDVI had a significantly negative correlation with the everage temperature before 1 and 2 month, which showed that at the beginning of growing season, high temperature counted against to the growth of the desert vegetation.