Warming intensified the effects of nitrogen addition on N_(2)O emissions from alpine meadow in the northern Qinghai-Tibet Plateau

Warming and nitrogen(N)addition may impact soil nitrous oxide(N_(2)O)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 N_(2)O emissions.We found that the N-addition greatly increased N_(2)O emissions by 77.4%in 2018 when compared to the control group.In contrast,warming showed little effect on N_(2)0 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 N_(2)0 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 N_(2)0 emissions,while diminished microbial carbon/nitrogen(MBC/MBN)(p<0.05)correlated with reduced N_(2)O emissions.Final results indicated that N-addition has a positive effect on N_(2)O 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 N_(2)O emissions of alpine meadows inthefuture.