Spatiotemporal characteristics of heat and rainfall changes in summer maize season under climate change in the North China Plain

Significant climate change has occurred across the North China Plain in the past few decades, corresponding to global climate change. Climate change during the growth period of summer maize has caused far-reaching impacts on production in the region, which is one of the most vital summer maize production regions in China. Based on observation data from 49 meteorological stations and 27 agro-meteorological stations, this paper analyzed growth degree days (GDD), heat degree days (HDD) and rainfall, and their climatic trend rates for the vegetative growth phase, vegetative and reproductive growth phase, productive growth phase and whole growth period of summer maize in the North China Plain for the period 1961?2010. The results showed that both GDD and HDD increased from northeast to southwest of the North China Plain. However, rainfall decreased from southeast to northwest of the plain. The climatic trend rates of GDD, HDD and rainfall from 1961 to 2010 in the North China Plain were 8.14 ℃·d·10a^-1, 2.45 ℃·d·10a^-1 and 10.75 mm·10a^-1, respectively. Furthermore, GDD decreased during the vegetative growth phase, increased during vegetative and reproductive growth phase, reproductive growth phase and whole growth period of summer maize in northern region of the North China Plain for the period 1961-2010. However, the reverse trends were noted for the southern of the plain. HDD increased in the north but decreased in the southern of the North China Plain. Rainfall decreased in the north but increased in the south for all the growth stages. Consequently, high temperature and drought posed significant risks to summer maize production in the north Hebei Province, Beijing City and Tianjin City in the north of the North China Plain. However, the risks of temperature and drought decreased for most of Henan Province and southern Shandong Province in the south of the North China Plain for the period 1961-2010.