Additive effects dominate phosphorus offsetting positive effects of nitrogen to terrestrial ecosystem N2O emissions

Nitrous oxide (N2O) emissions from terrestrial ecosystem significantly contribute to global warming and are substantially influenced by nitrogen (N) and phosphorus (P) additions. Yet, the precise interactive effects of N and P addition on N2O emissions remain poorly understood. We synthesized 714 observations from 198 publications to evaluate the response of N2O emission rates to N and P addition across terrestrial ecosystems. Our results revealed that N and nitrogen + phosphorus (NP) additions increased N2O emissions by 122.5 % and 64.5 %, respectively. In contrast, P addition alone reduced N2O emissions by 16.3 %. Akaike mixed model weights identified ecosystem type as a factor commonly influencing N2O emissions under added N, P, and NP. Predominantly additive interactions between N and P additions drove N2O emission responses, rather than synergistic or antagonistic interactions. Antagonistic effects were exclusively observed in cropland ecosystems. Collectively, these findings demonstrate that N and P addition exhibit independent and additive effects on N2O emissions in terrestrial ecosystems. This implies that the stimulatory effect of N and the inhibitory effect of P can be quantitatively combined to improve predictions of N2O emissions under nutrient enrichment scenarios.