Modeling the effects of tropospheric ozone on wheat growth and yield

Elevated tropospheric ozone (O-3) concentrations can negatively impact wheat growth by reducing photosynthesis and accelerating leaf senescence. Future global O-3 concentrations are expected to increase in many regions, which will further limit global wheat production. However, few crop models consider the effects of O-3 stress on wheat. We incorporated the effects of O-3 stress on photosynthesis and leaf senescence into the DSSAT-NWheat crop model and reproduced an observed experiment and reported yield declines from the literature. Simulated wheat yields decreased as daily O-3 concentrations increased above 25 ppb, with yield losses ranging from 0.26% to 0.95% per ppb O-3 increase, depending on the cultivar O-3 sensitivity. The model reproduced known wheat physiological responses from the combination of O-3 stress with water deficit and elevated atmospheric CO2 concentration. Increased water deficit stress and elevated atmospheric CO2 both reduce the negative impact of O-3, but yield benefits from elevated CO2 can be lost due to elevated O-3 concentrations. The O-3-modified NWheat model simulates the effects of O-3 stress on wheat growth and yield in interaction with other growth factors and can be used for studies on climate change and O-3 impacts.