Analysis of spatial and temporal variation in potential summer maize yield and its response to climate change in the North China Plain

The North China Plain is a major food producing region in China and climate change could have beneficial or unbeneficial effects on food production in the region. To accurately assess the effect of climate change on potential yield of summer maize in different regions in the North China Plain, we simulated the growth of summer maize in the plain for the period 1979-2015 using regional implementation crop growth model WOFOST (WOrld FOod STudy). We also used China Meteorological Forcing Data (form the Institute of Tibetan Plateau Research of Chinese Academy of Science) as weather data input for the crop growth model. To analyze the spatial and temporal variations in potential summer maize yield in the North China Plain, simple linear regression and empirical orthogonal decomposition (EOF) methods were applied. Using grid-by-grid correlation analysis and singular value decomposition (SVD) methods, we analyzed the correlations between potential summer maize yield and temperature and the correlations between the potential summer maize yield and total daily solar radiation during the whole growth period, pre-silking stage and post-silking stage of maize. The results showed that potential summer maize yield generally increased from south to north in the range of 7 000-9 000 kg·hm^-2. While potential summer maize yield in the northwest part of the study area was more volatile, yield fluctuation was small in southern Beijing, Tianjin and central Hebei Province, with standard deviation less than 500 kg·hm^-2. Potential summer maize yield in northern Tangshan of Hebei Province, northwestern part of the study area and the eastern part of Shandong Peninsula had a fluctuating increasing trend for the study period, with a range of 200-600 kg·hm^-2·(10a)^-1 in most of these regions. Potential summer maize yield in the rest of the study area decreased, especially in central and southern Hebei Province, Tianjin, northwestern Shandong Province, northern Anhui Province, which was around 250 kg·hm^-2·(10a)^-1. Potential summer maize yield in western and northeastern parts of Hebei Province, northwestern part of Beijing and central and eastern parts of Shandong Province had a significant positive correlation (R=0.9) with temperature. Summer maize yield in these areas had increased over the past 37 years. The analysis suggested that the increase in summer maize yield in those places were driven by rising temperatures. Potential yield in southern and eastern parts of Beijing, Tianjin, central and southern parts of Hebei Province, southern parts of Tangshan and Qinhuangdao of Hebei Province, Shandong Province, eastern part of Henan Province, northern part of Anhui Province and northern part of Jiangsu Province had a significant positive correlation (R=0.8) with total solar radiation. At the same time, the shaded area of 99% confidence level (based on Student's t-test) for the post-silking stage was larger than that for the pre-silking stage. Also the correlation coefficients were more significant for the post-silking stage. Potential summer maize yield in most of these regions was on the decline, which was caused by the decline in total solar radiation in the regions. Furthermore, total radiation reduction mainly influenced the reproductive stage of summer maize. In conclusion, increase in temperature was the main factor driving the increase in potential summer maize yield. Also the decreasing total solar radiation was the main factor driving the decrease in potential summer yield in the North China Plain.