Abstract
We investigated the effects of elevated ozone concentration (E‐O 3 ) on CH 4 and N 2 O emission from paddies with two rice cultivars: an inbred Indica cultivar Yangdao 6 ( YD 6) and a hybrid one II ‐you 084 ( IIY 084), under fully open‐air field conditions in China. A mean 26.7% enhancement of ozone concentration above the ambient level (A‐O 3 ) significantly reduced CH 4 emission at tillering and flowering stages leading to a reduction of seasonal integral CH 4 emission by 29.6% on average across the two cultivars. The reduced CH 4 emission is associated with O 3 ‐induced reduction in the whole‐plant biomass (−13.2%), root biomass (−34.7%), and maximum tiller number (−10.3%), all of which curbed the carbon supply for belowground CH 4 production and its release from submerged soil to atmosphere. Although no significant difference was detected between the cultivars in the CH 4 emission response to E‐O 3 , a larger decrease in CH 4 emission with IIY 084 (−33.2%) than that with YD 6 (−7.0%) was observed at tillering stage, which may be due to the larger reduction in tiller number in IIY 084 by E‐O 3 . Additionally, E‐O 3 reduced seasonal mean NO x flux by 5.7% and 11.8% with IIY 084 and YD 6, respectively, but the effects were not significant statistically. We found that the relative response of CH 4 emission to E‐O 3 was not significantly different from those reported in open‐top chamber experiments. This study has thus confirmed that increasing ozone concentration would mitigate the global warming potential of CH 4 and suggested consideration of the feedback mechanism between ozone and its precursor emission into the projection of future ozone effects on terrestrial ecosystem.