Fire severity strongly shapes soil enzyme activities in terrestrial ecosystems: insights from a meta-analysis

Background and aims: Fire has profound consequences for biogeochemical processes, largely mediated by soil enzyme activities (EAs). As climate-induced wildfire activity intensifies, understanding the influence of fire severity on soil EAs has become increasingly critical due to the dual role of fire in disrupting and restructuring ecosystem functions. Methods: In this study, a meta-analysis was conducted to assess the impact of fire severity on soil EAs with 368 field studies across 86 publications. Based on this, further analysis was conducted on the differences in soil EAs across ecosystems following varying fires severities. Additionally, the driving mechanisms of soil EAs in response to fires of different severities were explored. Results: The results revealed that fire severity (low, moderate, and high) was the dominant factor influencing soil EAs, with increasingly negative effects observed along the gradient low- to high-severity fires. Among ecosystem type, forest and shrubland ecosystems exhibited greater sensitivity to fire severity, whereas grasslands showed comparatively minimal response. Fire effects on soil EAs were primarily driven by fire-induced reductions in soil microbial biomass and organic matter, with soil EAs showing a significant positive correlation to both variables. Notably, moderate-severity fires were associated with post-fire recovery, with soil EAs recovering and eventually exceeding pre-fire levels. Conclusion: This study provides critical insights into how fire severity shapes soil EAs, advancing our understanding of soil functional dynamics and ecosystem recovery following fire disturbances. These findings offer a theoretical foundation for the development of ecosystem restoration strategies to mitigate the impacts of fire severity.