Effect of High-Temperature Events When Heading into the Maturity Period on Summer Maize (Zea mays L.) Yield in the Huang-Huai-Hai Region, China

The predicted increase in the frequency of extreme climatic events in the future may have a negative effect on cereal production, but our understanding of the historical trends of high-temperature events associated with climate change and their long-term impact on summer maize yield is limited. Based on an analysis of historical climate and summer maize yield data from 1980 to 2016 in the Huang-Huai-Hai (3H) region of China, we calculated two high-temperature event indices, namely, high-temperature hours (HTH) and high-temperature degrees (HTD, the sum of the differences between 35 degrees C and above), and then investigated the temporal trend of high-temperature events from maize heading to maturity and their impact on the yield of summer maize. Our results indicated that the air temperature showed a significant upward trend when heading into the maturity period of summer maize in the 3H region from 1980-2016 and that the increase was greater in the northern Huang-Huai-Hai (N3H) region than in the southern Huang-Huai-Hai (S3H) region. The intensity of high-temperature events when heading into the maturity period increased considerably from 1980 to 2016 in the 3H region, especially in the S3H region. The HTH and HTD increased by 1.30 h and 0.80 degrees C per decade in the S3H region, respectively. Moreover, a sensitivity analysis of panel data showed that the increases in HTH and HTD when heading into the maturity period had a consistent negative effect on yield in S3H and N3H regions; this effect was more obvious in the S3H region. In the S3H region, a 1 h increase in HTH was found to be associated with a 0.45-1.13% decrease in yield and a 1 degrees C increase in HTD could result in a yield loss of 1.34-4.29%. High-temperature events were detrimental to summer maize production, and the severity of this effect was projected to increase in the 3H region. In this study, we used two indices (HTH and HTD) to quantify the impact of high-temperature events on summer maize yield during the critical growth phase (heading to maturity) at a small timescale (hours and days). The results of this study can provide a reference for policymakers to use in the formulation of corresponding climate change adaptation strategies.