Abstract: Maize is the most important grain crop in China, and North China Plain is the main production area of summer maize. The maize production has been threatened by the rapid increase of extreme temperature events in the context of climate change. The characteristics and risk probability of heat injury during the flowering period of summer maize were analyzed, based on the meteorological data from 40 weather stations in North China Plain from 1980 to 2019, in order to deal scientifically with heat injury and ensure the high and stable yield of summer maize. The daily maximum temperature during summer maize flowering period with more than 35℃ for more than 3 days was taken as the index of heat injury, and the grades of heat injury would be divided into slight, moderate and server levels in terms of the occurrence time and duration of heat injury. The characteristics of heat injury during the flowering period of summer maize were analyzed by the occurrence times and the stations ratio of heat injury occurrence in the study area. Moreover, the risk probability of heat injury was evaluated using the theory of information diffusion. The results indicated that: (1) the period of 2010−2019 had more serious effects of heat injury during the flowering period, which showed the characteristics of successive occurrence and spatial expansion of heat injury. The most serious heat injury happened in Henan province, which the station ratio of heat injury occurrence reached 60.7% during 2010−2019, and increased by 51.4% compared with 2000−2009. The climate tendency rate of heat injury occurrence times in Zhengzhou, Gushi and Nanyang regions reached about 0.2 times·(10y) −1 (P<0.01); (2) The high-risk areas of heat injury during the flowering period of summer maize happened in Henan province and western Shandong. A wide range, high frequency and severe severity of heat injury took place in Henan province, and the proportions of areas with severe heat injury with more than 10% and more than 5% were 66% and 18%, respectively. The slight heat injury was the main meteorological disaster in the west of Shandong province, and its risk probability was more than 10%. The risk of heat injury in the Beijing-Tianjian-Hebei area and eastern Shandong province was lower compared with Henan province, and its risk of slight and moderate heat injury was less than 5%.

Key words: Summer maize, Flowering period, Heat injury, Information diffusion theory, Risk probability