Influence of climate warming in winter on the winter wheat cultivable area in Shanxi Province

Based on the daily mean temperature data of 70 meteorological stations in Shanxi Province from 1970 to 2012, the negative accumulated temperature in winter, average monthly temperature in January and extreme minimum temperature were computed and their changing trends were analyzed in this paper using linear trend estimation method, and their abrupt change points were observed by means of accumulated variance method and contours of the negative accumulated temperature in winter, average monthly temperature in January and extreme minimum temperature were compared respectively after being divided into two groups according to the abrupt change points. The results showed that the negative accumulated temperature in winter showed a remarkable decrease, and the average monthly temperature in January and extreme minimum temperature did not increase significantly. Changes were found between the two groups, the negative accumulated temperature decreased by 103.4oC, and the average monthly temperature in January and extreme minimum temperature rose by 0.7oC and0.9oC, respectively. The negative accumulated temperature and extreme minimum temperature played a key role, which are the thresholds that the winter wheat Province could be planted or not. Under climatic warming, the winter wheat cultivable area and the reliable planting area expanded by 2.9×106hm2(increased by 52%) and 2.3×106hm2(rose by 79%), respectively.