Changes Of Maize Planting Limits And Risk Assessment Of Chilling Injury In Northeast China

As one of the main corn-producing areas in China,northeast China is located in the fragile climate zone of middle and high latitudes and faces the severe challenge of climate change.In recent years,global climate warming has increased the heat in the middle and high latitudes,and some regions have blindly moved north to plant medium and late maturing maize varieties in pursuit of high yield.However,the increase in climate volatility has led to the aggravation of the potential threat of meteorological disasters.Affected by global warming,extreme meteorological disasters may occur frequently and recur in the future,among which chilling injury has shown an increasing frequency in local areas since the 21 st century,which will bring great risks to regional food security.Therefore,paying attention to the change of maize planting boundary in northeast China and the law of chilling risk under the background of climate change can provide theoretical reference for the distribution of food security.In this research,the chilling injury of maize in northeast China was taken as the research object,based on the accumulated temperature index to represent the planting limits of different varieties,meteorological observation data,and statistical data were used reveal the changing rules of planting boundaries and the chilling effects.Firstly,mathematical-statistical methods such as the mann-kendall test and climate trend rate were used to analyze the characteristics of maize planting boundary change;The risk assessment model of chilling injury was constructed from the hazard and vulnerability of risk forming factors,and the influence scope of the chilling risk was defined by buffer zone;Finally,the boundary change and chilling injury risk were estimated under the emission scenarios of RCP4.5 and RCP8.5,and the variation of planting boundarychilling injury risk was simulated by using surface fitting.The main results are as follows:(1)In the past 60 years,the temperature in northeast China has increased significantly,and the planting boundaries of different varieties of corn have shifted from north to east.Among them,the boundary changes of middle and late varieties have affected the most extensive areas,and the actual planting area change rate of corn in this region has shown a significant trend of increase.The potential maize planting area calculated based on the threshold index ?10? was significantly correlated with the actual planting area,showing a lag period of 10 years.(2)The characteristics of corn chilling injury risk in the historical period are as follows: the corn chilling injury risk in northeast China shows a decreasing trend in time and gradually decreases from north to south in space;meanwhile,the potential planting area and the actual planting area are increasing,the regional exposure is enhanced,and the adaptability of the northern region is also improving.According to the comprehensive analysis,from 1980 to 2017,the middle and high value areas of cold damage risk gradually extended from the central and western regions to the northern regions,which coincided with the northward trend of maize planting limit,and the cold damage risk was relatively high within 20-40 km of the geometric centerline of the limit change.(3)Comparison of the boundary change and the cold damage risk estimation under different emission paths: the late variety boundary showed a small southward shift in the warming slowing period compared with the significant warming period,and the exposure of maize in the warming slowing period was increased due to the 10-year lag of the potential planting area;Therefore,the risk of chilling injury in the warming slowing period is 0.06?0.09 higher than that in the significant warming period,which will lead to an increase in the reduction rate by 0.04?0.05,and a more significant increase in the risk in the RCP8.5 emission path;The simulation of surface fitting shows that the trend of boundary-risk shifting to the north is significant,and the high latitude area becomes the area with the significant increase of chilling injury risk,and the fitting effect is good.This study makes up for the lack of research foundations for the impact of climate change on crop distribution and disaster risk assessment,and reveals the impact of changes in corn planting boundaries and cold damage risk in Northeast China,to provide a theoretical basis for regional crop distribution and ensuring food security.