The compound effects of drought and high temperature stresses will be the main constraints on maize yield in Northeast China

Compound climate extremes such as drought and high temperature have a greater impact on agricultural production than the individual extremes. An increasing frequency and intensity of the compound climate extremes has been observed and projected under climate change, yet partitioning the total impacts to individual ones on crop yield has not been well assessed. In this study, we assessed the compound and separate effects of drought and high temperature on maize yield under 9 climate-year types (CYTs) with different combinations of precipitation and temperature in Northeast China (NEC). The well-validated Agricultural Production Systems Simulator (APSIM) model was used to simulate the maize yield, driven by historical (1981-2017) and future climate data (2021-2060). The results show that CYTs of warm (warm-dry, warm-wet, warm) are prominent in the future under both Representative Concentration Pathway (RCP) 4.5 and 8.5 scenarios. However, CYT of warm-wet increased mostly (11.5%) under RCP8.5, while warm-dry increased most (12.3%) under RCP4.5. The magnitude of maize yield loss caused by the compound of high temperature and drought (18.75%) is higher than the individual ones (drought 17.32% and high temperature 1.27%). There are variations in the effects of stresses on maize yield among CYTs and the yield reductions by the compound effects of drought and high temperature were warm-dry > warm > rainless > warm-wet > normal > cold-dry > cold > rainy > cold-wet. In addition, the yield loss was negatively correlated with T_max and VPD_max but positively correlated with Prec. These findings imply the importance of fully considering the selection of heat and drought-resistant varieties and implementing supplementary irrigation for future climate mitigation strategies during maize production in NEC.