Variation in fuel structure of boreal fens

Wildfire frequency and severity in boreal peatlands can be limited by wet fuel conditions, but increases in burn severity can occur when lower water table positions cause drying of fuels. To date, most studies on northern peatland fires have focused on ombrotrophic bogs. Though minerotrophic fens are the most common type of peatland in North America, the influence of fuel structure and loading on potential fire behaviour in boreal fens is poorly understood. To investigate the potential for widespread flame front propagation across boreal fens, we quantified the fuel components present in three generalized boreal fen types (open, shrub, and treed fens) in northern Alberta, Canada. The loadings of aerial fuels, tall shrubs, and downed woody debris varied significantly among fen types. Fuel loads tended to be smallest in the open fens and largest in the treed fens. Open and shrub fens had larger loads of total surface fuels relative to treed fens, with short-statured shrubs being the dominant contributor to surface fuel load. Based on our observations of available fuel loads, each of the fen types may support moderate-to high-intensity fire following long-term drying, which may not only consume some fraction of the aboveground biomass, but also provide a substantial downward pulse of energy to initiate smouldering in the organic layer.