NDVI variation and coupling analysis with climate change in northwest of China based on GIS and RS

The paper researched temporal-spatial variation of NDVI and analyzed coupling with climate changes in the northwest of China from 1982 to 2006 years based on the GIS and remote sencing. The results show that the NDVI of alpine meadow and deciduous needle-leaf forests increased with a rate of p=0.21%/10 a, the NDVI was ascending (p=0.27%/10 a) which attributed to the growing season delayed. Air temperature increased in Qinghai-Tibet Plateau, the south of Tianshan mountains in spring and northern Xinjiang\Hanzhong in autumn, and the range of variation of precipitation was great in boundary of semi-humid and semi-arid. The correlation coefficient was 0.62 between NDVI and temperature in the Yellow River and Yangtze River source regions. There was a great correlations between NDVI and precipitation in Hexi-Alxa\southern Xinjiang with a coefficient of 0.65. NDVI decline was attributed to precipitation too much in the Hanzhong, Qilian, Tianshan mountains in summer and autumn; NDVI of the cold regions was more sensitive to the changes of temperature and the NDVI was not raised sharply until the average monthly temperature reached to 8℃. NDVI began to decline when the temperature was more than 22℃. The NDVI came to the peak with temperature rising (19–20℃) in the non-cold and arid regions. NDVI was linear increment with the rising of precipitation, if the temperature conditions met the needs of vegetation growth in the cold region .The threshold value of monthly precipitation was 60 mm (start) and 220 mm (stop) in the arid region; The changing of NDVI was lag when the air temperature and precipitation changed in North of China .