Abstract: Based on the 1961-2010 daily weather data from 15 meteorological stations, and by using climate tendency rate, partial correlation analysis, and linear regression analysis, in combining with the inverse distance weighting (IDW) method of GIS spatial analysis techniques, this paper quantitatively analyzed the reference crop evapotranspiration (ET₀) in eastern Gansu at different temporal and spatial scales, and studied the spatiotemporal variation patterns of the ET₀ and related climatic affecting factors. In the recent 50 years in eastern Gansu, the mean annual ET₀ presented a weak downward trend. The summer ET₀ decreased significantly, being the main reason for the decrease of the mean annual ET₀, the spring ET₀ increased remarkably, while the ET₀ in winter and autumn had no obvious change trend. The mean monthly ET₀ showed a unanimous single peak. Spatially, the mean annual ET₀ was larger in northern and central areas, but smaller in western areas. The spring ET₀ showed an increasing trend in most areas, the summer ET₀ showed a decreasing trend in the whole eastern Gansu, while the ET₀ in winter and autumn had no obvious change trend. The ET₀ was negatively correlated with relative humidity and precipitation, but significantly positively correlated with temperature, sunshine hours, and wind speed. Sunshine hours, wind speed, and relative humidity were the main climatic factors affecting the ET₀ in eastern Gansu.

Key words: global change, soil microorganism, carbon and nitrogen cycle., field manipulative experiment