Divergent terrestrial responses of soil N 2 O emissions to different levels of elevated CO 2 and temperature

Understanding the responses of soil nitrous oxide (N 2 O) emissions from terrestrial ecosystems to future CO 2 enrichment and warming is critical for the development of mitigation and adaptation policies. The effects of continuous increase in elevated CO 2 (EC) and elevated temperature (ET) on N 2 O emissions are not fully known. We synthesized 209 measurements from 70 published studies and carried out a meta‐analysis to examine individual and interactive effects of EC and ET on N 2 O emissions from grasslands, croplands and forests. On average, a significant increase of 23% in N 2 O emissions was observed under EC across all case studies. EC did not affect N 2 O emissions from grasslands or forests, but significantly increased N 2 O emissions in croplands by 38%. The extent of ET effects on N 2 O emissions was nonsignificant and there was no significant difference in N 2 O emission responses among these three terrestrial systems. ET only promoted N 2 O emissions in forest by about 32% when ET was less than 2°C. The interactive effect of EC and ET on N 2 O emissions was significantly synergistic, showing a greater increase than the sum of the effects caused by EC and ET alone. Our findings indicated that the combination of EC and ET substantially promoted soil N 2 O and highlighted the urgent need to explore its mechanisms to better understand N 2 O responses under future climate change.