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

Abstract Methane oxidation in aerated soils is a significant sink for atmospheric methane (CH 4 ). Salt-affected soils are extensively present and constitute about 7% of total land surface. However, our knowledge about CH 4 turnover between the atmosphere and the saline soils is very limited. In order to evaluate the potential of CH 4 consumption in saline soils, CH 4 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. CH 4 uptake of cores from the slightly saline soil ranged from 14 to 24 μg CH 4 –C m −2  h −1 , comparable to those in the non-saline forest soils with similar texture. CH 4 uptake of cores from the moderately saline soil was only about 6% of that in the slightly saline soil. CH 4 uptake was too low to be measurable in the extremely saline soil. Compared with the non-saline soil, CH 4 uptake in the saline soils was much less sensitive to salt, suggesting the higher salt-tolerance of CH 4 oxidizers in the saline soil. The result also indicated an underestimate in CH 4 uptake for the naturally-occurring saline soils by adding salt to non-saline soils. These results should be useful to study the global CH 4 budget and to explore the physiological and ecological characteristics of methanotrophic bacteria in the salt-affected soils.