Controls on soil carbon dioxide and methane fluxes from a peat swamp vary by hydrogeomorphic setting

Abstract

AbstractCarbon dynamics of temperate peat swamps are a largely understudied component of wetland carbon cycling. Under a changing climate, hydrometeorological conditions may change, and understanding how peat swamps may be impacted is important. We investigated the importance of hydrogeomorphic setting on controlling soil carbon dioxide (CO2) and methane (CH4) fluxes from a temperate peat swamp in southern Ontario, Canada over a 3‐year period. We chose three different hydrogeomorphic settings: (a) a site with strong wetland‐stream interactions (i.e., an unconfined stream channel; unconfined), (b) a site with limited wetland‐stream interactions (confined), and (c) an interior site (no wetland–stream interaction). The differing hydrogeomorphic conditions between the sites resulted in differences in carbon fluxes. The unconfined site maintained a higher water table across all three study years, providing conditions that are not favourable to CO2 production. The confined and interior sites sustained a much lower water table, with conditions more conducive to CO2 efflux. The unconfined site also had the highest CH4 emissions due to the increased anoxic conditions favourable for CH4 production as a result of the higher water table position. Hydrogeomorphic setting was found to be important for understanding within site variation, suggesting the sites may respond differently to longer‐term shifts in environmental conditions. This may change relationships between sites if the responses are strong enough to significantly alter carbon fluxes, decomposition, and potential peat accumulation rates. It is important to understand the locally specific responses to environmental conditions within peat swamp ecosystems, in order to make future predictions about whole ecosystem function under changing conditions.