Burn severity alters peatland moss water availability: Implications for post-fire recovery

Wildfire is the largest disturbance affecting northern peatlands; however, little is known about how burn severity (organic soil depth of burn) alters post-fire hydrological conditions that control the recovery of keystone peatland mosses (i.e. Sphagnum). For this reason, we assessed the impact of burn severity on moss water availability by measuring soil tension (Ψ) and surface volumetric moisture content (θ) in burned and unburned portions of a peatland complex 2years after fire. We found that both high and low burn severity decreased post-fire water availability by altering peat hydrophysical properties (moisture retention and water repellency). Locations covered by Sphagnum fuscum prior to fire exhibited a decreasing post-fire water availability with an increasing burn severity. In contrast, the lowest water availability (Ψ>400cm, θ0·20m) in peatland margins and burn depths >0·05m in the middle of the peatland exhibited the highest water availability (Ψ