Interactive effects of depth and temperature on CH4 and N2O flux in a shallow podzol

Measuring and modelling the efflux of greenhouse gases from soils is crucial for gauging ecosystem responses to climate and land-use change, and potential contributions and feedbacks to gas emissions. Upland soils with high amounts of organic matter can produce large effluxes of CH4 and potentially N2O, and therefore understanding the sensitivity of such fluxes to changes in climate (e.g. temperature) is of importance. Here we consider the role of shallow podzols in the temperature response of CH4 and N2O efflux using a simple laboratory incubation. Such soils have a shallow peat layer overlain by coarse organic matter, and by splitting and incubating these layers across a 1–30 °C temperature ramp, we observed a significant negative temperature response for both gases, and a gas-dependent effect on the presence of a between-layer difference. Given these observations, there is a need to consider the temperature sensitivity of near surface layers as distinct, and to recognise the potential for shallow podzols to have a strong source–sink transition across temperature ranges.