Winter wheat yield was positively correlated with Tmean in northern China including Zone I and Zone II, however was negatively correlated with Tmean in southern China including Zone III and Zone VIII (Fig. 3). In northwestern China, spring wheat yield was negatively correlated with Tmean in Zone VI, but positively correlated with Tmean in high altitude Zone VII. The positive (neg-ative) correlations suggested that yield was positively (negatively)affected by increase in Tmean.