Soil urease and catalase responses to ozone pollution are affected by the ozone sensitivity of wheat cultivars

Understanding the effects of elevated O 3 ( EO 3 ) on belowground process such as soil enzyme activities is essential to evaluate plant physiological reaction and soil processes (e.g. carbon and nitrogen turnover) under predicted increases in atmospheric O 3 . In this study, O 3 ‐induced changes in soil urease ( UA ) and catalase activities ( CTA ) under two contrasting wheat cultivars (O 3 ‐sensitive versus O 3 ‐tolerant) were investigated using a free‐air O 3 enrichment (O 3 FACE ) facility in China. EO 3 (60 ppb compared with 40 ppb in ambient O 3 ) generally increased UA under the O 3 ‐tolerant cultivar but reduced it under the O 3 ‐sensitive cultivar for different soil depths and growth stages. In contrast, the effects of EO 3 on CTA were not consistent and varied with soil depths and growth stages. These results suggest that the O 3 sensitivity of wheat cultivars plays an important role in determining the effects of EO 3 on soil enzyme activities. The contrasting responses of soil UA and CTA to EO 3 may alter the effect of projected increase in tropospheric O 3 on soil carbon and nitrogen turnover.