The heat stress during anthesis and the grain-filling period of spring maize in Northeast China is projected to increase toward the mid-21st century

Against the background of global warming, heat stress have become more frequent, which adversely affects the growth and development of spring maize plants in Northeast China. In order to adapt the regional maize production to climate change, it is imperative to understand the spatio-temporal characteristics of heat stress. In this study, we analyzed three of the indices for heat stress, including the number of heat stress days, heating degree days (HDD, the total heat degree-days during critical stages), and the percentage of stations with heat stress. From 1981 to 2019, the number of heat stress days varied greatly among the study years, ranging from 0 to 14 and 27 days, respectively. The average HDD was 7.8 °C∙d and 5.0 °C∙d from 1981 to 2000, respectively, and the main hot-spots of heat stress occurred in the southwest regions. Moreover, compared with 1981-2000, the region of HDD during anthesis higher than 10 oC∙d in 2041-2060 under SSP1-2.6 and SSP5-8.5 climate scenarios increased by 9.1~50.1% and 0.1~28.6%. The average HDD during the critical stages from 2041 to 2060 under SSP5-8.5 climate scenario, even 1.5 times than 1981-2000. HDD during maize anthesis and the grain-filling period showed an overall increasing trend with years. About 19% and 58% of the study locations showed heat stress during the past 39 years, respectively. Therefore, heat stress during anthesis and the grain-filling period for spring maize in Northeast China is projected to increase towards the mid-21st century. This article is protected by copyright. All rights reserved.