Nitrogen deposition accelerates greenhouse gas emissions at an alpine steppe site on the Tibetan Plateau

The increase in atmospheric N deposition can alter the exchange of greenhouse gas (GHG) between the biosphere and atmosphere. The effect of N deposition on GHG is poorly understood in alpine steppe. Therefore, we conducted a 4-year experiment with multilevel N addition of 0, 10, 20, 40, 80, 160 kg N ha(-1) using the static chamber and gas chromatographymethod to quantify responses of GHG fluxes and characterize the relationship between GHG fluxes andNaddition rate in Namco located in the alpine steppe in the central Tibetan Plateau (TP). Themean CO2 efflux, CH4 uptake, N2O emission during growing seasons across four years were 33.59 +/- 16.41mg C m(-2) h(-1), -56.42 +/- 29.20 mu g C m(-2) h(-1), 0.67 +/- 4.40 mu g N m-2 h-1 respectively. CO2 efflux increased 1.55-22.6%, CH4 uptake decreased 5.96-20.1%, N2O emission increased 37.3-133.5% with N addition. Wealso observed a critical threshold of 40 kgN ha(-1) a(-1) of Naddition abovewhich the increase rate of N2O emissionwould diminish. Our current results implied that under the background of future N deposition, N induced C sequestration might be offset by GHG balance causing a heating effect to the climate. (C) 2020 Elsevier B.V. All rights reserved.

Automated summary

The study conducted in alpine steppe found that atmospheric N deposition can alter the exchange of greenhouse gases, with N2O emissions increasing with increasing N addition rate, but diminishing after reaching a critical threshold of 40 kgN ha(-1) a(-1). This suggests that future N deposition may offset N-induced carbon sequestration, leading to a heating effect on the climate.