气候变暖对东北玉米低温冷害分布规律的影响

Abstract

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 21st 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 21st 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.