气候变暖对东北玉米低温冷害分布规律的影响

利用东北地区48个农气站1961-2010年气象资料和近20多年玉米生育期资料,建立生育阶段热量指数和冷害指数,分析气候变暖对东北玉米4个生育阶段热量及低温冷害分布格局的影响。结果表明:热量指数总体表现为明显的增加趋势;平均温度、热量指数的年代际变化特征明显,中晚、晚熟区的上升趋势均小于早、中熟区;冷害频率总体表现为明显的减小趋势;气候变暖对两个熟型区域4个生育阶段的冷害影响并不一致,早、中熟区的冷害平均频率最大值均出现在20世纪60年代,中晚、晚熟区的冷害平均频率最大值均出现在70年代,两个熟型区域的最小值均出现在21世纪初。研究结果可为未来东北地区调整玉米种植制度和生产布局,为适应气候变化和趋利避害提供科学依据。

The impacts of global climatic change on chilling damage distributions of maize in Northeast China

To assess variations of the thermal conditions and chilling damage distributions of maize in Northeast China under the global climatic change, in this study, we defined a heat index and a chilling damage index of growing stage, based on the daily meteorological data of 1961-2010 over 48 agro-meteorolgical stations in Northeast China and the maize growth records over the recent 20 years. The entire growing period of maize was divided into four stages: 1) from emergence to seven-leaf, 2) from emergence to tasseling, 3) from emergence to milky ripening, and 4) from emergence to maturation. Different maturation types of maize in Northeast China were also taken into account and the impacts of global climate warming on the thermal status and chilling damage distributions of different types of maize during their four growing stages were analyzed and evaluated.The results show that the heat indices in the four growing stages exhibit in general a rising trend, with the heat amount in the early 21^st centuary being the largest and supposedly most advantageous for maize growth, over the recent 50 years. However, the increased heat, i.e., the climate warming, affects the thermal and chilling situations differently for different maturation types of maize. Specifically, the heat index increases and the chilling index drops for areas with maize ripening in the middle of the season. In contrast, the heat index drops and the chilling index increases over the areas with maize ripening late of the season. An in-the-middle situation occurs in the areas with middle-late-season ripening maize. This indicates that climate warming benefits the most the middle-season ripening maize while it is disadvantageous to the late-season ripening maize.It is found that the area-averaged temperature and heat index for each of the four growing stages of maize have significant interdecadal variations. The lowest temperature and heat index occurred in the 1960s for the early-middle-season ripening maize, whereas they showed up in the 1970s for the middle-late-season ripening maize. The rising trend of the heat index for the early-middle-season ripening maize is stronger than that for the middle-late-season ripening maize.The frequency of the chilling damage to maize during the four growing stages shows an overall decreasing trend, and a significant reduction of frequency appears in the 1980s. The impacts of the global warming on the maize in Northeast China differ for different ripening types of maize during their varied growing stages. The highest chilling frequency is found in the 1960s for the early-middle-season ripening maize while the chilling is most frequent in the 1970s for the middle-late-season ripening maize. For both types of maize, the least frequent chilling events are observed in the early 21^st centuary. The results obtained in this study is expected to provide scientific insights and basis for adjusting the maize cropping system and distribution in Northeast China to adapt to climate change, and to mitigate the chilling damage and associated losses.