Divergent terrestrial responses of soil N2O emissions to different levels of elevated CO2 and temperature

Understanding soil nitrous oxide (N2O) emissions responses from terrestrial ecosystems to future CO2 enrichment and warming is critical for the development of mitigation and adaptation policies. The continuous increase of elevated CO2 (EC) and elevated temperature (ET) effects on N2O 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 N2O emissions from grasslands, croplands, and forests. On average, a significant increase of 23% in N2O emission was observed under EC across all case studies. A sharp increase in the N2O emissions was noticed in the response to EC under less than 150 ppm enrichment levels. Nonetheless, a significant but weak negative response of N2O emission to EC was examined. Compared with non-significant responses of grassland and forest, EC resulted in the highest increase (38%) in N2O emission of cropland. The extent of ET effect on N2O e...