Methane uptake by saline-alkaline soils with varying electrical conductivity in the Hetao Irrigation District of Inner Mongolia, China

Soil salinization adversely affects sustainable land use and limitation of greenhouse gas emission. Methane (CH4) uptake and the specific activity of methanotrophs in three saline-alkaline soilsS1, electrical conductivity (EC) 4.80dSm(-1); S2, EC 2.60dSm(-1); and S3, EC 0.74dSm(-1)were observed and measured across crop phenological development in the Hetao Irrigation District of Inner Mongolia, China. There were significant differences in CH4 uptake between the three soil types. The cumulative uptake of CH4 was 97.97mgm(-2), 109.49mgm(-2), and 150.0mgm(-2) in S1, S2, and S3, respectively. Cumulative CH4 uptake was 35%, 35%, and 53% lower in S1 than in S3, and was 27%, 28%, and 19% lower in S2 than in S3 in 2014, 2015, and 2016, respectively. Differences in CH4 uptake were driven by the different specific activities of the methanotrophs in the three soils, of which the key controlling factor was soil EC. The findings demonstrate that saline-alkaline soils with high EC led to low CH4 uptake and thereby significantly increased the total greenhouse effect of CH4.