| In the recent fifty years, there were obviously 3 year periods for the short-term climatic yield, and 89 year and 1617 year periods for long-term climatic yield in Gansu province. The technical yield is not only determined by the agro-technological level and the diaster resistance ability of human, but also influenced by climatic factors. With the expansion of the time scale, the effect of climatic factors tends to be weakened, while that of agro-technologies tends to be increased. Within three years, the effect of climate is larger than that of technologies; form three to seven years, the effect of agro-technologies goes up rapidly; when time scale is over eight years, the effect of agro-technologies becomes dominant. For a longer time scale, the relative importance of climatic factors and agro-technologies is not only related to the time scale, but also to the mutation of climate and technologies. |