The climate change and its ecosystem effect in the upper yellow river

Based on meteorological and hydrological data collected from 1961 to 2004,NOAA/AVHRR NDVI data with 8times8 km spatial resolution from 1982 to 2003, climate change and its ecosystem effect are analyzed in the upper yellow river in this paper. The results showed that the change trend of temperature in the upper yellow river was consistent with global warming, and the increasing rate of annual mean soil temperature was higher than that of air temperature. Annual precipitation presented fluctuant change. Annual maximum frozen soil depth and annual runoff tends to decrease over the past 40 years, especially in 1990s.Dry and warming trend takes place both in climate and soil in the region, especially in soil. The drainage area of upper yellow river is an ecosystem fragility area, and it is sensitive to climate change. Our analyses indicated that grassland main growth periods are from May to October,NDVI peak value appeared in July in drainage area of the upper yellow river. Annual NDVI peak value and NDVI mean value could reflect preferably climate changes, and the trends of them appeared increased in some degree among oscillations in the past 20 years, which meant a better condition for vegetation growth or longer growing days in the study area. Furthermore, the temperature exhibits a more remarkable relativity than precipitation in the area.