Soil salinization poses a great threat to sustainable land use and the limitation of greenhouse gas emissions. In this study, three saline alkali soils, saline soil[electrical conductivity (EC) 4.80 dS·m-1], high saline-alkaline soil (EC 2.60 dS·m-1), and low saline-alkaline soil (EC 0.74 dS·m-1) in the Hetao Irrigation District of Inner Mongolia were selected as research plots. Field experiments were conducted to study the uptake of methane (CH4) in the crop-growing season (April-October) for three years (2014-2016) using the static box method. There were significant differences in the soil CH4 uptake among the soil types in 2014 (F=18.0, P<0.001), 2015 (F=23.6, P<0.001), and 2016 (F=28.4, P<0.001). The uptake of CH4 by the soil decreases with increasing soil salinity. The accumulated CH4 uptake was 150.0 mg·m-2, 119.6 mg·m-2, and 99.9 mg·m-2 in the low saline-alkaline, high saline-alkaline, and saline soil in 2014, respectively. The cumulative uptake of CH4 was 27%, 28%, and 19% lower in the high saline-alkaline soil and 35%, 35%, and 53% lower in the saline soil than in the low saline-alkaline soil in 2014, 2015, and 2016, respectively. Redundancy analysis shows that the projection of the CH4 uptake flux and EC of saline-alkaline soil are in the positive direction, and in the opposite direction to the first principal component axis. The higher the soil EC, the lower the CH4 uptake flux. Soil EC was found to be the key factor controlling the uptakes of CH4, with a correlation coefficient (r) of -0.8809 (P<0.01, n=9).
Keywords: CH4 uptake; carbon sink; different saline-alkaline; electrical conductivity; saline-alkaline soils.