Groundwater connectivity controls peat burn severity in the boreal plains

Wildfire is the largest disturbance affecting peatland ecosystems and can typically result in the combustion of 2-3kgCm^-2 of near-surface peat. We hypothesized that organic soil burn severity, as well as the associated carbon emissions, varies significantly as a function of hydrogeological setting due to groundwater impacts on peat bulk density and moisture content. We measured depth of burn (DOB) in three peatlands located along a hydrogeological and topographic gradient in Alberta's Boreal Plains. Peatland margins across all hydrogeological settings burned significantly deeper (0.245±0.018m) than peatland middles (0.057±0.002m). Further, hydrogeological setting strongly impacted DOB. A bog with an ephemeral groundwater connection in a coarse-textured glaciofluvial outwash experienced the greatest DOB at its margins (0.514±0.018m) due to large water table fluctuations, while a low-lying oligotrophic groundwater flow-through bog in a coarse-textured glaciofluvial outwash experienced limited water table fluctuations and had the lowest margin burn severity (0.072±0.002m). In an expansive peatland in a lacustrine clay plain, DOB at the margins bordering an isolated domed bog portion (0.186±0.003m, range: 0.0-0.748m) was considerably greater than the DOB observed at fen margins with a longer groundwater flow path (