The Variations in NDVI of different vegetation types in Xinjiang and its relation to climate factors

The NOAA/AVHRR NDVI data, as an important index, is universally used to analyze vegetation dynamic growth and global climate change. In order to explore the interannual variation in various vegetation types, this study analyzes the temporal dynamic of Normalized Difference Index (NDVI) for 10 vegetation types in Xinjiang and investigates the relationships between NDVI and climatic variables over the period of 1982-2003. The results demonstrate that: 1) Average NDVI of the study area increased significantly at rates of 0.58% each year in the growing season (April-October), 0.53% in the spring (March-May), 0.50% in the summer (June-August) and 0.65% in autumn (September-November). The interannual variation of NDVI in growing season, spring, summer, and autumn were increased significantly (P0.01). 2) Then the coefficient of correlation(r) (P0.05 or P0.01) was gained to describe relationship between NDVI and climatic variable. The NDVI of 5 vegetation types were related significantly with precipitation (P0.05), the types were broadleaf forest, desert, grassland, herbosa and meadow. The vegetation types related significantly with temperature were coniferous forest, shrub, alpine swamp and alpine vegetation. The correlation of NDVI value with the precipitation and temperature was not significant in growing season of farmland. 3) The NDVI of most vegetation was correlated significantly to temperature (P0.05) in spring, and to precipitation in summer, the increase of NDVI correlated to interaction of precipitation and temperature in autumn.