Intensive forest harvest increases N2O emission from soil: A meta-analysis

A comprehensive evaluation of the impact of forest harvest on soil N2O flux at the global scale is currently unavailable. In this study, by using a global meta-analysis of 64 observations from 29 peer-reviewed publications over the last 30 years, we elucidated how forest harvest impacted soil N2O flux and related soil properties. Intensive forest harvest significantly increased soil N2O flux with a mean effect size of 0.85 and the increase was associated with elevated soil temperature, increased concentration of NO3−-N and decreased soil pH. The effect on soil N2O flux lasted for around six years, and soil N2O emission depended on existing forest types in the late stage (the recovery period >6 years) after harvest. Forest harvest clearly increased soil N2O flux, with effect size ranging 0.73–2.12, in broadleaf forests but did not significantly affect it in coniferous and mixed broadleaf-conifer forests. In addition, the time required for the complete recovery from harvest in terms of N2O flux was difficult to define because of the scarcity of long-term experiments. Overall, this study provides the first formal global-scale assessment on how forest harvest intensity, forest types and the time since harvest affect soil N2O flux. The findings of this study help to narrow the knowledge gap regarding the effect of forest harvest on soil N2O flux, and to facilitate decision making to decrease soil N2O emission post forest harvest.