Short-term elevated O3 exerts stronger effects on soil nitrification than does CO2, but jointly promotes soil denitrification

Atmospheric CO2 and O3 concentrations have been increasing, with important consequences on the biogeochemical cycle in agroecosystems. However, little is known about the interactive effect of elevated CO2 and O3 on soil nitrogen cycling processes mediated by soil microbes. We conducted open-top chamber facilities to assess the impacts of short-term elevated CO2 and O3 on soil nitrification and denitrification rates, and the abundances of soil N cycling-related genes for two rice cultivars (Nanjing 5055 vs. Wuyujing 3) in paddy soil. Elevated CO2 potentially increased the abundance of nitrification-related genes (AOA amoA + 40.9