Potential soil methane oxidation in naturally regenerated oak-dominated temperate deciduous forest stands responds to soil water status regardless of their age—an intact core incubation study

Abstract

Key message: Potential CH4 oxidation in the top soil layer increased with decreasing soil water content in spring but was inhibited during severe summer drought in naturally-regenerated oak-dominated temperate deciduous forest stands regardless of their age. No direct effect of mineral nitrogen on soil CH4 oxidation was found. Soil CH4 oxidation in temperate forests could be reduced by extreme climatic events. Context: The oxidation of atmospheric methane (CH4) by methanotrophic bacteria in forest soils is an important but overlooked ecosystem service. Aim: Our objective was to determine which factors drive variations in soil CH4 oxidation in oak-dominated temperate deciduous forest stands of different ages. Methods: Soil samples were collected in 16 stands aged 20 to 143 years in periods of high and low soil water content (SWC). The potential rate of soil CH4 oxidation was measured by incubating the first five centimetres of intact soil cores at 20 °C. Results: SWC was the main driver accounting for variations in CH4 oxidation. In spring, a two-fold reduction in SWC greatly increased CH4 oxidation. But when the soil was dry in late summer, a further reduction in SWC led to a decrease in CH4 oxidation in the top soil layer. No direct effect of mineral nitrogen on soil CH4 oxidation was found. Conclusions: With regard to soil CH4 oxidation, naturally regenerated forest stands contribute equally to climate change mitigation regardless of their age. Considering future climate scenarios for Europe, soil CH4 sink in temperate forests could be reduced, due to both an increase in the number of flooding episodes in spring and drier summers.