Temporal And Spatial Distribution And Comprehensive Risk Assessment Of Maize Delayed Chilling Injury In Northeast China

Northeast China is an important corn production base,with planting area accounting for 40.1% of the whole country.Chilling injury is one of the main agrometeorological disasters in Northeast China.Because of the insufficient heat condition in spring,the delayed chilling injury is easy to occur,which results in the decrease of corn quality and yield.Under the climate background of global warming,extreme weather phenomenon increases.In this study,the boundary value of average temperature anomaly index in growing season was improved to analyze the temporal and spatial distribution of delayed cold damage of Spring Maize in Northeast China.The calculation forms of risk factors,such as risk,exposure,vulnerability and regional disaster prevention and mitigation capability index were defined by means of moving average simulation and deviation standardization,and the risk assessment model of delayed cold damage was built on this basis.The results were as follows:(1)The order of the coefficient of variation of heat condition in growth period was: 90's > 80's > early 21's,which showed the distribution situation of high in Northwest and low in Southeast.The starting date of stable passing through the 10? limit was 0.1d ahead of the average year,and the ending date was about 0.15 d behind.The heat condition decreased with the increase of latitude,and extended from the 1980 s to the early 21 st century.(2)From 1981 to 2015,the occurrence frequency of cold injury in Northeast China was the highest in 1980 s,and showed a trend of fluctuation and decrease with time.The number of stations of severe cold injury was the highest in 1981-1996,and the occurrence of mild cold injury was higher than that of severe and moderate cold injury in 1997-2015.The frequency of chilling injury in different degrees was greatly reduced.The descending trend of the ratio of chilling injury stations was: severe > moderate > mild,but there were still areas with severe chilling injury in the early 21 st century when the frequency of chilling injury was generally reduced.According to the analysis of M-K mutation test,1997 was the mutation year of the average temperature value in the growth season of Northeast China,and it was also the mutation year of the sequence of low and severe cold injury stations.Since 1997,the monthly average accumulated temperature significant increased in the growth period of Northeast China,the number of cold injury stations decreased significantly,and the decline trend was very significant in the early 21 st century.(3)From 1981 to 2015,the occurrence frequency of mild and moderate chilling injury in Northeast China was generally low,below 40%,while that of severe chilling injury was high,the most serious in 1980 s,the second in 1990 s,and below 30% in early 21 st century.The occurrence frequency of severe chilling injury decreased with time.The high incidence areas of mild cold injury were Liaoning,the West and the middle of Jilin;the high incidence areas of moderate cold injury were located in Liaoning Province,the southwest of Jilin Province and the south part of the East four League of Inner Mongolia;the high frequency areas of severe cold injury were concentrated in the North of Heilongjiang,the north of Inner Mongolia and the Baishan mountains of the east of Jilin Province,and the frequency of severe cold injury in the northeast was decreasing from northwest to Southeast Trend.(4)Regional distribution of risk: the eastern part of Heilongjiang and the northern part of Inner Mongolia were in the high-risk area,Mudanjiang City,Chaoyang City,Huludao City and Chifeng City were in the sub high value area,gradually reducing to the middle and west of Jilin,and the risk coefficient of most areas at the junction of Jilin and Inner Mongolia was below 0.0025.The comprehensive risk assessment model of cold injury determined in this study could be used to assess the risk possibility of cold injury of Spring Maize in Northeast China,and provide reference for the time arrangement of agricultural production sowing and the reasonable layout of farming.