Key Laboratory for Vegetation Ecology, Ministry of Education Institute of Grassland Science, Northeast Normal University, Changchun, Jilin Province, China.
PLoS One. 2019 Dec 2;14(12):e0225862. doi: 10.1371/journal.pone.0225862. eCollection 2019.
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 CH4 flux. To understand the effects of nitrogen addition, grazing, and their interactions on soil CH4 flux, we conducted a field study on CH4 flux in a meadow steppe in Northeast China from 2017 to 2018. We measured the soil CH4 flux and soil physiochemical and vegetation parameters. The studied meadow steppe soil acted as a CH4 source due to the legacy effects of an extreme rainfall event. During the experimental period, the average CH4 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 CH4 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 CH4 flux by 19%, and the grazing treatment reduced it by 25%. The soil CH4 flux was positively correlated with the 0-10 cm soil water filled pore space (P < 0.01), soil NH4+-N (P < 0.01) and soil NO3--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 CH4 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 CH4 flux, whereas grazing significantly (P < 0.05) decreased the CH4 flux. Grazing offset the stimulating effects of N addition on CH4 flux, and there was no difference (P = 0.79) in the CH4 flux between the CK and NG plots. In summary, moderate grazing has the potential to reduce the negative impacts of N addition on CH4 flux and can increase the capacity of the soil CH4 sink in the studied meadow steppe.
放牧是草原最常见的土地利用方式，放牧可能会改变预测的氮沉降增加对土壤 CH4 通量的影响。为了了解氮添加、放牧及其相互作用对土壤 CH4 通量的影响，我们于 2017 年至 2018 年在中国东北的一个草甸草原进行了一项关于土壤 CH4 通量的田间研究。我们测量了土壤 CH4 通量以及土壤理化和植被参数。由于极端降雨事件的遗留效应，研究中的草甸草原土壤表现为 CH4 源。在实验期间，CK（对照）、G（放牧）、N（氮添加）和 NG（放牧和氮添加）处理的平均 CH4 通量分别为 7.8 ± 1.0、5.8 ± 0.5、9.3 ± 0.9 和 7.6 ± 0.6 μg m-2 h-1。CK、G、N 和 NG 处理的累积 CH4 通量分别为 24.9 ± 2.6、11.5 ± 4.9、28.8 ± 4.2 和 17.8 ± 3.5 μg m-2 yr-1。氮添加使平均 CH4 通量增加了 19%，放牧处理使 CH4 通量减少了 25%。土壤 CH4 通量与 0-10 cm 土壤水填充孔隙空间（P < 0.01）、土壤 NH4+-N（P < 0.01）和土壤 NO3--N（P < 0.01）呈正相关，但与 0-10 cm 土壤温度（P < 0.01）呈负相关，除了受极端降雨事件强烈影响的采样日期外。放牧和氮添加处理显著（P < 0.05）影响平均 CH4 通量，氮添加处理显著（P < 0.05）增加 CH4 通量，而放牧处理显著（P < 0.05）降低 CH4 通量。放牧抵消了氮添加对 CH4 通量的刺激作用，CK 和 NG 样地之间的 CH4 通量没有差异（P = 0.79）。总之，适度放牧有可能降低氮添加对 CH4 通量的负面影响，并增加研究草地土壤 CH4 汇的能力。
