Grazing offsets the stimulating effects of nitrogen addition on soil CH(4) emissions in a meadow steppe in Northeast China

Grazing is the most common land use type for grasslands, and grazing may alter the impacts of the predicted enhancement of nitrogen deposition on soil CH(4) flux. To understand the effects of nitrogen addition, grazing, and their interactions on soil CH(4) flux, we conducted a field study on CH(4) flux in a meadow steppe in Northeast China from 2017 to 2018. We measured the soil CH(4) flux and soil physiochemical and vegetation parameters. The studied meadow steppe soil acted as a CH(4) source due to the legacy effects of an extreme rainfall event. During the experimental period, the average CH(4) fluxes were 7.8 ± 1.0, 5.8 ± 0.5, 9.3 ± 0.9 and 7.6 ± 0.6 μg m(-2) h(-1) for the CK (control), G (grazing), N (nitrogen addition) and NG (grazing and nitrogen addition) treatments, respectively. The cumulative CH(4) fluxes were 24.9 ± 2.6, 11.5 ± 4.9, 28.8 ± 4.2 and 17.8 ± 3.5 μg m(-2) yr(-1) for the CK, G, N and NG treatments, respectively. The N addition increased the average CH(4) flux by 19%, and the grazing treatment reduced it by 25%. The soil CH(4) flux was positively correlated with the 0–10 cm soil water filled pore space (P < 0.01), soil NH(4)(+)-N (P < 0.01) and soil NO(3)(-)-N (P < 0.01), but negatively correlated with the 0–10 cm soil temperature (P < 0.01), except for the sampling dates that were strongly influenced by the extreme rainfall event. The average CH(4) flux was significantly (P < 0.05) affected by the grazing and N addition treatments with the N addition treatment significantly (P < 0.05) increased the CH(4) flux, whereas grazing significantly (P < 0.05) decreased the CH(4) flux. Grazing offset the stimulating effects of N addition on CH(4) flux, and there was no difference (P = 0.79) in the CH(4) flux between the CK and NG plots. In summary, moderate grazing has the potential to reduce the negative impacts of N addition on CH(4) flux and can increase the capacity of the soil CH(4) sink in the studied meadow steppe.