The Possible Effects of Global Warming on Cropping Systems in China Ⅺ. The Variation of Potential Light-Temperature Suitable Cultivation Zone of Winter Wheat in China Under Climate Change
【Objective】 In the context of climate change, China needs to address critical challenges relating to the agricultural development and food security. Wheat is one of China's three major grain crops, which plays an important role in Chinas food security. The variation of potential light-temperature suitable cultivation zone of winter wheat in China under climate change was studied, which would provide an important scientific reference for the rational distribution of winter wheat. 【Method】 In this research, the correction step by step method was used to calculate the potential light-temperature yield of winter wheat in each year. The year 1981 was taken as a time node and divided the period 1961-2010 into two sub-periods. Combined with the indices of the potential light-temperature yield level and the stability, the variation of the potential light-temperature yield level and the stability zones were investigated. In summary, the variation of the boundaries and distributions of the potential light-temperature suitable cultivation zones of winter wheat in China under climate change was studied. 【Result】 Compared with the period 1961-1980, during 1981-2010, the percentage of the very high and high potential yield zones in the study area increased by 6.33% and 7.42%, respectively, but the percentage of moderately high and marginally high potential yield zones decreased by 10.50% and 3.24%, respectively. During 1981 to 2010, the percentage of the very stable potential yield zone in the study area decreased by 25.76%, but the percentage of stable, moderately stable and marginally potential yield zones increased by 12.09%, 10.34% and 3.31%, respectively. The boundary of the very suitable zones moved northward and westward. The southern boundary of the very suitable zones moved northward from the central part of Anhui Province to the northwest portion of Shandong Province, and the western boundary of the very suitable zones extended westward from the southwest part of Shanxi Province to the northwest part of Shaanxi Province; The boundary of the suitable zones moved northeastward, and the maximum spatial displacement was in the eastern part of Sichuang Province to the southwest part of Shaanxi Province, moving by about 835.63 km. The spatial displacement of the potential suitable cultivation zone of winter wheat caused the changes of the winter wheat actual cropping area. Compared with the period 1961-1980, during 1981-2010, the percentage of the very suitable and suitable zones of winter wheat in the study area decreased by 4.49% and 4.75%, respectively, while the percentage of moderately suitable and marginally suitable zones increased by 7.17% and 2.06%, respectively. The potential yield per unit area increased by about 513 kg·hm~(-2) in average in each suitable cultivation zone. However, the total potential yield reduced by 1 504*10~4 t in the study area compared with 1961-1980 because of the reduction of the area in the very suitable and suitable zones of winter wheat, which caused the total potential yield in these two cultivation zones reduced by 5 108*10~4 t and 5 896*10~4 t, respectively.