STUDIES ON THE NORTH AGROCLIMATIC BOUNDARIES OF WINTER WHEAT IN LIAONING, BEIJING AND HEBEI
辽京冀冬麦农业气候北界的研究

A mathematical model about dividing the north agroclimatic boundaries of winter wheat in Liaoning, Beijing and Hebei has been set up in this paper.Spatial climatic equations were used to estimate temperature normals of any point in this region.The agroclimatic equation of death percentage of winter wheat was then applied to the point estimates of winter survival.Death percentages of each grid representing a square area (10×10km) on the topographic maps of 1:1,000,000 scale were computed by the mentioned equations. AII these death percentages were then classified into three classes (<20%, 20-40% and>40%)by computer and printed out by LPT.The demarcation between the first class and the second one is called the safe planting boundary of winter wheat and the other demarcation is the potential planting boundary.The results indicated that the safe planting boundary is similar to the natural boundary in the 1950's in the same area.In the potential planting region, winter wheat should take protective measure with great care so as to reduce the freeze damage.