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

Abstract

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.

Keywords

• Alpine meadow
• Community composition
• Nitrogen addition
• Nitrous oxide flux
• Qinghai‒Tibet Plateau
• Warming