Grasslands occupy 40% of global land surface, which greenhouse gases (GHG) emissions are receiving more and more attention. Although there have studied that grazing and nitrogen deposition solely affects soil GHG flux of grassland, the effects of their interaction with accurate stocking rate and N deposition rate (future scenarios) are still unknown. We set up the dual factors trials of grazing of 4 stocking rage (0, 2.7, 5.3, 8.7 sheep ha-1) and N deposition of two levels (0, 10 kg N m-2 yr-1) in typical steppe in the Loess Plateau from 2012–2017. We hypothesized that low N addition has little effect on CH4 fluxes at low nitrogen deposition level, but that this would increase N2O over time, and rotational grazing has little influence on soil GHG flux.
Results/Conclusions
Results showed that typical steppe was a CH4 sink and a N2O resource. Soil CH4 rather than N2O flux existed an obvious interannual variations. With the increasing experiment years, mean methane flux variations was -0.13± 0.11 μg m-2 min-1 in 2012 and 0.58 ug m-2 min-1 in 2017. The soil CH4 and N2O fluxes was insensitive to low N deposition. Grazing had significant effect on soil CH4 flux, but no soil N2O flux. 5.3 sheep/ha grazing reduced soil CH4 uptake by 2.5 times probably due to appropriate rotational grazing maintaining stable above-ground biomass. Our preliminary results suggest that stable N deposition level may have little impacts on soil CH4 and N2O fluxes in the future; light rotational grazing mitigate GHG emissions of typical steppe.