摘要：Elevated tropospheric ozone (O<sub>3</sub>) concentration may substantially influence the below-ground processes of terrestrial ecosystems. Nevertheless, a comprehensive and quantitative understanding of O<sub>3</sub> impacts on soil CO<sub>2</sub> emission remains elusive, making the future sources or sinks of soil C uncertain. In this study, 77 pairs of observations (i.e., elevated O<sub>3</sub> concentration treatment versus control) extracted from 16 peer-reviewed studies were synthesized using meta-analysis. The results depicted that soil CO<sub>2</sub> efflux was significantly reduced under short-term O<sub>3</sub> exposure (≤1 year, <i>p</i> < 0.05), while it was increased under extended duration (>1 year, <i>p</i> < 0.05). Particularly, soil CO<sub>2</sub> emission was stimulated in nonagricultural ecosystems, in the free-air CO<sub>2</sub> enrichment (FACE) experiment, and in the soils of lower pH. The effect sizes of soil CO<sub>2</sub> efflux were significantly positively correlated with experimental duration and were significantly negatively correlated with soil pH, respectively. The ozone effect on soil CO<sub>2</sub> efflux would be enhanced at warm temperatures and high precipitation. The duration of O<sub>3</sub> exposure was the fundamental factor in analyzing O<sub>3</sub> impacts on soil CO<sub>2</sub> emission.
