Impact of warming and nitrogen addition on soil greenhouse gas fluxes: A global perspective

Global warming and nitrogen (N) deposition have a profound impact on greenhouse gas (GHG) fluxes and consequently, they also affect climate change. However, the global combined effects of warming and N addition on GHG fluxes remain to be fully understood. To address this knowledge gap, a global meta-analysis of 197 datasets was performed to assess the response of GHG fluxes to warming and N addition and their interactions under various climate and experimental conditions. The results indicate that warming significantly increased CO₂ emissions, while N addition and the combined warming and N addition treatments had no impact on CO₂ emissions. Moreover, both warming and N addition and their interactions exhibited positive effects on N₂O emissions. Under the combined warming and N addition treatments, warming was observed to exert a positive main effect on CO₂ emissions, while N addition had a positive main effect on N₂O emissions. The interactive effects of warming and N addition exhibited antagonistic effects on CO₂, N₂O, and CH₄ emissions, with CH₄ uptake dominated by additive effects. Furthermore, we identified biome and climate factors as the two treatments. These findings indicate that both warming and N addition substantially impact soil GHG fluxes and highlight the urgent need to investigate the influence of the combination of warming and N addition on terrestrial carbon and N cycling under ongoing global change.