Assessing the spatio-temporal tropospheric ozone and drought impacts on leaf growth and grain yield of wheat across Europe through crop modeling and remote sensing data

Water stress and ozone are known to cause yield loss of wheat across Europe when acting as individual stressor. There is a growing evidence that these stressors cause synergistic effects on yield when they are combined. Analyzing spatio-temporal leaf growth dynamics and grain yield in responses to variability of climate and ozone conditions, especially focusing on water stress and ozone in wheat growing areas in EU, is rarely done. Three crop models (LINTULCC2, WOFOST, and DO3SE) which have different degrees of complexity and input requirements were calibrated and validated using experimental data from Spain describing the response of wheat plants to single and combination of ozone and/or water stress. Modeling performance of three models was then evaluated for 360 locations across EU using remote sensing green leaf area index (GLAI) from Sentinel-2 images and statistical grain yield data. Water stress or ozone alone caused grain yield reduction by 19% and 17%, respectively. Both observation and modeling simulation results showed that the combination of these two factors led to a further yield loss (10-17%). We conclude that combinations of drought stress and ozone can result in bigger effects on yield than the two stresses separately. The well-calibrated process based models could be used to test adaptation practices to both air pollution and climate change scenario combinations with further improvements that are needed in modelling leaf growth dynamics.