The Possible Effects of Global Warming on Cropping Systems in China Ⅹ. The Possible Impacts of Climate Change on Climatic Suitability of Spring Maize in the Three Provinces of Northeast China
【Objective】The variabilities of distribution patterns of spring maize climatic suitability in the three provinces of Northeast China under climate change were studied, and the results will provide a scientific basis for spring maize cropping distribution in the region. 【Method】In this research, the year 1981 was taken as a time node and divided the period 1961-2010 into two sub-periods. The historical climate data from 74 meteorological stations in these three provinces from 1961 to 2010 were used. According to the agro-meteorological indices, the possible northern limit changes of spring maize in Northeast China were analyzed. The rain-fed yields in each station in the potential cropping region of spring maize were assessed by APSIM-Maize model year by year. On the basis of statistical methods, the variabilities of the rain-fed yield level and stablity zones were investigated. In summary, the variability of distribution patterns of spring maize climatic suitability were studied. 【Result】In the period from 1981 to 2010, the possible northern limit of spring maize moved with a northwestward shift of 158.3-285.8 km, and the possible planting area increased by 3.87*10~4 km~2(4.91% of the whole land area in Northeast China) than during the period from 1961 to 1980. During the period 1981-2010, the percentage of the very high, high and moderately high rain-fed yield zones of spring maize in the possible planting area increased from 81.14% to 86.66%, but the percentage of the very high, high zones decreased from 36.61% to 34.82% and the moderately high zone increased from 44.53% to 51.85%. Meanwhile, the percentage of the marginally high zone decreased from 18.86% to 13.34%. Generally, the rain-fed yield per unit area reduced by 40 kg·hm~(-2) in the research area. However, the total rain-fed yield increased by 7.0% with possible planting area increase, especially the high and moderately high rain-fed yield zones. The percentage of the very stable, stable and moderately stable rain-fed yield zones of spring maize in the possible planting area increased from 80.20% to 89.28%. Meanwhile, the percentage of the very stable and stable rain-fed yield zones increased from 40.97% to 49.97%, but the percentage of the marginally stable rain-fed yield zone decreased from 19.80% to 10.72%. The percentage of the suitability and moderately suitable climatic zones increased from 61.09% to 83.00%, but the percentage of the very suitable climatic zone decreased from 18.83% to 6.67%. Meanwhile, the percentage of marginally suitability zone decreased from 20.08% to 10.33%. The rain-fed yield per unit area obtained stably reduced by 171 kg·hm~(-2) in the research region. However, the total rain-fed yield obtained stably increased by 2.6% with possible planting area increase, especially the suitable and moderately suitable climatic zones. 【Conclusion】Under the background of climate change, the possible northern limit of spring maize moved northwestward with an increasing possible planting area in Northeast China. If there were no changes of varieties, cultivation and management, the percentage of the very high rain-fed yield zones in the possible planting area decreased and the yield per unit area reduced. However, the total rain-fed yield increased with the possible planting area increase. The stability of rain-fed yield increased with a greater percentage of the very stable and stable rain-fed yield zones in the possible planting area increased. In the potential cropping area of spring maize in Northeast China, the percentage of the climatic suitability and moderately suitability zones increased, but the percentage of the very suitable climatic zone decreased. The rain-fed yield per unit area obtained stably reduced. However, the total rain-fed yield obtained stably increased with the possible planting area increase in the research region, especially the suitable and moderately suitable climatic zones.