Increased CO2 and decreased CH4 emissions in response to drying of northern peatlands: experimental observations vs. model simulations

Abstract:

Undisturbed peatlands in the high latitudes have acted as a large carbon sink because low temperatures and saturated soil conditions inhibit carbon decomposition. As air temperature has risen during the last decades, however, this vast amount of carbon stock in Arctic and Boreal peatlands is potentially subject to increased decomposition, not only due to increased temperatures but also due to soil drying. Drying follows permafrost thaw or enhanced evapotranspiration, and exposes upper peat soil horizons to aerobic decomposition. Here, we use a version of the Organizing Carbon and Hydrology In Dynamic Ecosystems model modified to northern peatlands (ORCHIDEE-PEAT-METHANE) to simulate CO₂ and CH₄ fluxes in response to peatland drying. By adjusting key parameters that are associated with CO₂ and CH₄ fluxes, we simulate CO₂ and CH₄ fluxes of 6 peat sites in Arctic and Boreal region, within which drainage manipulation experiments were carried out. Drying peatlands generally decreased CH₄ emission but increased CO₂ emission, and the magnitude of this change depended on the intensity of drainage. We will present the simulation results of all 6 different sites, and how they differ among one another, especially how sensitive they are to drying intensity.