Ozone Pollution Increases CO2 and N2O Emissions in Ozone‐sensitive Wheat System

Abstract

Core Ideas Elevated O3 (EO3) effects on GHG flux and GWP from O3‐sensitivity wheat systems were studied.EO3 reduced belowground biomass of O3‐sensitive (SW) and O3‐tolerant (TW) wheat cultivars.O3‐sensitivty of wheat cultivar affected responses of gaseous C and N emission and GWP to EO3.SW wheat would release more freshly assimilated C, adding GHG emission and GWP under EO3. The effects of elevated O3 (EO3) on greenhouse gas (GHG) emissions and global warming potential (GWP) from wheat systems with differential O3 sensitivity are not well understood. The nitrous oxide (N2O), methane (CH4), and carbon dioxide (CO2) emissions from cropping (CP) and bare soil or root‐free (BS) plots, GWP, GWP per unit yield, and biomass and its allocation to belowground between O3‐sensitive (cultivar YN19) and tolerant (cultivar Y15) wheat (Triticum aestivum L.) systems were investigated at EO3 and ambient O3 (AO3) with an open‐air O3 fumigation system. Results indicated that a 50% elevation above AO3 significantly reduced belowground biomass of the two cultivars. The EO3 significantly increased the cumulative emissions of CO2 and N2O but did not change that of CH4 in YN19 CP. For BS, it significantly increased the emission of CO2 but decreased that of CH4 and N2O. The EO3 significantly increased the GWP and GWP per unit yield in YN19 CP but reduced the GWP in BS. The O3 sensitivity of wheat cultivar affected the responses of gaseous C and N emission, GWP and GWP per unit yield to EO3. The O3‐sensitive wheat cultivar would release more freshly assimilated C, increasing cumulative GHG emissions, GWP and GWP per unit yield in response to O3 stress, when compared to the O3 O3‐tolerant wheat cultivar. Our results suggest that EO3 may impair soil C and N sequestration in an O3 O3‐sensitive wheat–soil system in view of lower root biomass but higher CO2 and N2O emissions under EO3.