Nitrification, denitrification, and related functional genes under elevated <scp>CO₂</scp>: A meta‐analysis in terrestrial ecosystems

Summary

This meta-analysis synthesised 879 observations from 46 independent elevated CO₂ experiments to assess how rising atmospheric CO₂ affects soil nitrification and denitrification processes and their associated microbial functional genes. Elevated CO₂ consistently increased potential nitrification (+28%), bacterial amoA gene abundance (+62%), and denitrification genes (nirK +25%, nirS +27%, nosZ +32%), with synergistic effects when combined with warming, increased precipitation, or nitrogen addition. The findings suggest that regional climate conditions—particularly mean annual temperature and precipitation—will modulate the magnitude of these responses, with potential implications for soil N₂O emissions under future climate scenarios.

Regional applicability

The meta-analysis is global in scope and does not report United Kingdom-specific data. However, findings are applicable to temperate regions including the United Kingdom, particularly regarding how anticipated increases in precipitation and warming may amplify soil nitrogen cycling changes under elevated CO₂. The significant interactions with nitrogen addition are particularly relevant to UK arable and mixed farming systems where nitrogen fertiliser use is substantial.

Key measures

Gross and potential nitrification rates; potential denitrification rates; abundances of archaeal amoA, bacterial amoA, nirK, nirS, and nosZ functional genes; interaction effects with elevated temperature, precipitation, drought, and nitrogen addition

Outcomes reported

The meta-analysis quantified responses of nitrification, denitrification, and related functional genes to elevated CO₂ across 879 observations from 58 publications. It examined how elevated CO₂ alone or in combination with temperature, precipitation, drought, and nitrogen addition affects soil nitrogen cycle processes and N₂O emission pathways.

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