Different soil moisture control of net methane oxidation and production in organic upland and wet forest soils of the Pacific coastal rainforest in Canada

In a changing climate, understanding how soil hydrology impacts greenhouse gas dynamics will be important for the future management of the soils in the forests on the Canadian Pacific west coast. In a laboratory study, the impact of soil hydrology on potential net methane (CH4) exchange rates and the abundance of methanotrophs (CH4 oxidation) and methanogens (CH4 production) in upland and water-saturated wet soils were investigated. CH4 oxidation and production rates were highest in the wet soils, which corresponded to higher numbers of methanotrophs and methanogens, indicating a link between the microbial abundance and CH4 exchange rates. Also, CH4 production was induced in the upland soils, indicating the presence of methanogens. The optimum soil moisture content for CH4 oxidation was highest in upland soils and the wet soils sustained higher CH4 oxidation rates over a broader range of soil moisture. These results underline the importance of the soil hydrological controls of CH4 oxidation in contrasting soils and forest types, which deserves further attention in field-based studies.