Research On Vegetation Changing And Reaction To Climate In Northwest China In The Past 22 Years

The study areas of this paper are Forest, Grassland,Oasis, Rainfed agriculture in Northwest China. The data are used from GIMMS dataset 8km AVHRR NDVI from 1982 to 2003. By dividing three stages of Spring, Summer, Autumn, the paper analyzes the change characteristic of vegetation and the condition that the vegetation change respond to the climate factors(temperature and precipitation) in Northwest China during the past 22 years. It does make sense to ecological environment protections and research in Northwest China. Main conclusions are as follows:1) Coinciding to the protection condition, the vegetation reduces from southeast to northwest. Forest, grassland, oasis, spring wheat rainfed agriculture regions' NDVI annual figures are single peak pattern, otherwise, winter wheat rainfed agriculture regions' NDVI annual figures are double peak pattern;and different vegetation have different change characteristic ofNDVI_s , the forest regions' NDVI are downtrend, grassland regions' NDVI are uptrend,rainfed agriculture regions' NDVI are unchanged , oasis regions' NDVI increased remarkably. Oasis regions have irrigation conditions and interannual fluctuation is the least.2) The vegetation is increased in most Northwest China in the past 22 years. The increased regions account for 20. 5% of Northwest China, which distribute in most Xinjiang and Hexi corridor of Gansu province oasis, irrigation regions along the Yellow River and grassland regions in Qinghai province. Oasis regions increased remarkably. The decreased vegetation regions account for 4. 8%, which distribute eastern part of Northwest China.3) The degree which vegetations sensitive to temperature is reduced in turn with: forest—oasis —grassland—rainfed agriculture. And the degree that sensitive to precipitation is grassland-forest—rainfed agriculture—oasis.4) The forest vegetation's growth depend on temperature more than on precipitation in spring, but the increase of temperature and the decrease of precipitation is disadvantage the growth in summer;the grassland vegetation's growth especially depend on temperature;precipitation is the mainly factor that influence the rainfed agriculture vegetation's growth;the oasis' growth is interrelated to temperature and precipitation is not a key factor in its growth.