Groundwater connectivity controls peat burn severity in the boreal plains

• Published in: Ecohydrology 2016-06, Vol.9 (4), p.574-584
• Main Authors: Hokanson, K. J., Lukenbach, M. C., Devito, K. J., Kettridge, N., Petrone, R. M., Waddington, J. M.
• Format: Article
• Language: English
• Subjects: boreal; carbon; groundwater; organic soil; peatland; smouldering; wildfire
• ISSN: 1936-0584; 1936-0592
• DOI: 10.1002/eco.1657

Wildfire is the largest disturbance affecting peatland ecosystems and can typically result in the combustion of 2–3 kg C m−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 ± 0.018 m) than peatland middles (0.057 ± 0.002 m). 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 ± 0.018 m) 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 ± 0.002 m). In an expansive peatland in a lacustrine clay plain, DOB at the margins bordering an isolated domed bog portion (0.186 ± 0.003 m, range: 0.0–0.748 m) was considerably greater than the DOB observed at fen margins with a longer groundwater flow path (