Methane uptake in salt-affected soils shows low sensitivity to salt addition

Methane oxidation in aerated soils is a significant sink for atmospheric methane (CH4). Salt-affected soils are extensively present and constitute about 7% of total land surface. However, our knowledge about CH4 turnover between the atmosphere and the saline soils is very limited. In order to evaluate the potential of CH4 consumption in saline soils, CH4 fluxes were measured in intact cores of the slightly (ECe = 3.2 mS cm−1), moderately (ECe = 7.1 mS cm−1) and extremely (ECe = 50.7 mS cm−1 and 112.6 mS cm−1) saline soils from the Yellow River Delta, China. CH4 uptake of cores from the slightly saline soil ranged from 14 to 24 μg CH4–C m−2 h−1, comparable to those in the non-saline forest soils with similar texture. CH4 uptake of cores from the moderately saline soil was only about 6% of that in the slightly saline soil. CH4 uptake was too low to be measurable in the extremely saline soil. Compared with the non-saline soil, CH4 uptake in the saline soils was much less sensitive to salt, suggesting the higher salt-tolerance of CH4 oxidizers in the saline soil. The result also indicated an underestimate in CH4 uptake for the naturally-occurring saline soils by adding salt to non-saline soils. These results should be useful to study the global CH4 budget and to explore the physiological and ecological characteristics of methanotrophic bacteria in the salt-affected soils.