Effects of nitrogen and phosphorus enrichment on soil N2O emission from natural ecosystems: A global meta-analysis

Nitrogen (N) and phosphorous (P) enrichment play an important role in regulating soil N2O emission, but their interactive effect remains elusive (i.e. whether the effect of P or N enrichment on soil N2O emission varies between ambient and elevated soil N or P conditions). Here, we conducted a Bayesian meta-analysis across the global natural ecosystems to determine this effect. Our results showed that P enrichment significantly decreased soil N2O emission by 13.9% at ambient soil N condition. This N2O mitigation is likely due to the decreased soil NO3--N content (-17.6%) derived by the enhanced plant uptake when the P limitation was alleviated by P enrichment. However, this P-induced N2O (and NO3--N) mitigation was not found at elevated soil N condition. Additionally, N enrichment significantly increased soil N2O emission by 101.4%, which was associated with the increased soil NH4+-N (+41.0%) and NO3--N (+82.3%). However, the effect of N enrichment on soil N2O emission did not differ between ambient and elevated soil P subgroups, indicating that the P-derived N2O mitigation could be masked by N enrichment. Further analysis showed that manipulated N rate, soil texture, soil dissolved organic nitrogen, soil total nitrogen, soil organic carbon, soil pH, aboveground plant biomass, belowground plant biomass, and plant biomass nitrogen were the main factors affecting soil N2O emission under N enrichment. Taken together, our study provides evidence that P enrichment has the potential to reduce soil N2O emission from natural ecosystems, but this mitigation effect could be masked by N enrichment.