Warming intensified the effects of nitrogen addition on N₂O emissions from alpine meadow in the northern Qinghai-Tibet Plateau

Warming and nitrogen (N) addition may impact soil nitrous oxide (N2O) emissions, but the relationship between plant community composition and soil microbial activities remains unclear. For a two-year field study in the Qinghai-Tibet Plateau, open-top chambers were used to quantify the effects of warming, N-addition, and their interactions on N2O emissions. We found that the N-addition greatly increased N2O emissions by 77.4% in 2018 when compared to the control group. In contrast, warming showed little effect on N2O emissions but did increase the activity of enzymes associated with soil nitrification and denitrification. A combined effect of warming and N-addition of resulted in 208.6% (2018) and 90.8% (2019) increase in N2O emissions, respectively, compared to the individual treatments of warming or N-addition. Global warming in alpine meadows is causally linked to increased legume biomass which is further intensified with the N-addition. Intensified legume biomass ( p < 0.05), soil moisture ( p < 0.001) and enzyme activity ( p < 0.001) had a positive effect on N2O emissions, while diminished microbial carbon/nitrogen (MBC/MBN) ( p < 0.05) correlated with reduced N2O emissions. Final results indicated that N-addition has a positive effect on N2O emissions, and the addition of warming further intensifies this effect. The increased dominance of legumes and microbial N content contributes to this effect. These outcomes suggest that warming and atmospheric N deposition can stimulate N2O emissions of alpine meadows in the future.