Elevated Tropospheric Ozone Concentration Alters Soil CO₂ Emission: A Meta-Analysis

• Main Authors: Enzhu Hu, Zhimin Ren, Sheng Xu, Weiwei Zhang
• Format: Article
• Language: English
• Published: MDPI AG 2021-04-01
• Series: Sustainability
• Subjects: elevated O₃ concentration; meta-analysis; soil CO₂ emission; climate change
• Online Access: https://www.mdpi.com/2071-1050/13/8/4571

Elevated tropospheric ozone (O₃) concentration may substantially influence the below-ground processes of terrestrial ecosystems. Nevertheless, a comprehensive and quantitative understanding of O₃ impacts on soil CO₂ emission remains elusive, making the future sources or sinks of soil C uncertain. In this study, 77 pairs of observations (i.e., elevated O₃ concentration treatment versus control) extracted from 16 peer-reviewed studies were synthesized using meta-analysis. The results depicted that soil CO₂ efflux was significantly reduced under short-term O₃ exposure (≤1 year, <i>p</i> < 0.05), while it was increased under extended duration (>1 year, <i>p</i> < 0.05). Particularly, soil CO₂ emission was stimulated in nonagricultural ecosystems, in the free-air CO₂ enrichment (FACE) experiment, and in the soils of lower pH. The effect sizes of soil CO₂ efflux were significantly positively correlated with experimental duration and were significantly negatively correlated with soil pH, respectively. The ozone effect on soil CO₂ efflux would be enhanced at warm temperatures and high precipitation. The duration of O₃ exposure was the fundamental factor in analyzing O₃ impacts on soil CO₂ emission.