Climate change effects on peatland decomposition and porewater dissolved organic carbon biogeochemistry

Carbon accumulation and storage is a defining characteristic of peatland ecosystems. Decomposition of peat releases dissolved organic carbon (DOC) to receiving waters and can be an important fraction of the peatland carbon budget, along with being an important modifier of downstream water quality. Changes in temperature and hydrological processes under future climate scenarios are expected to impact decomposition processes in peatlands with unclear ramifications for both the quantity and the quality of the DOC released. We experimentally examined the individual and interactive effects of increased temperature, elevated atmospheric carbon dioxide concentration, and lower water table position on peatland decomposition and the quantity and quality of porewater DOC in intact, replicated peat monoliths in a full factorial design. Decomposition rates and porewater DOC concentrations significantly increased under elevated temperature conditions; however, the quality of this carbon was variable, showing signs of both increased lability and recalcitrance. Lowered water table treatments also increased decomposition rates, although the high water conditions prompted greater porewater DOC concentrations and lability. It is expected that elevated decomposition rates under future climate scenarios will alter porewater DOC quantity in peatlands; however, we suggest that contributions from the aboveground system are needed to fully understand changes in DOC quality and subsequent ecosystem dynamics.