Ecohydrological Controls on post-fire Sphagnum moss recovery in Boreal Shield peatlands

Northern peatlands are critical carbon sinks, and wildfire is the largest disturbance within the Boreal ecozone. The return of a peatland to a carbon sink and the post disturbance resilience of peatlands depends greatly on the ecohydrological recovery and reestablishment of Sphagnum mosses.

We examined post-fire moss accumulation and moss moisture stress (soil water tension, soil moisture) in triplicate burned and unburned Boreal Shield Sphagnum dominated peatland types (shallow, deep peatland middle, and deep peatland margin). Additional climatological and geophysical measurements were taken to identify ecohydrological controls on post-fire Sphagnum recovery.

The soil water tension exceeded 100 mbar (an established physiological threshold for Sphagnum) when the water table was lost from the peat profile, which only occurred in the shallowest peatlands. We found no significant difference in the moss moisture stress between the burned and unburned landscapes 5-years post fire. Depth of burn, remnant post-fire soil depth, and post-fire soil accumulation did not show a significant relationship with soil water tension 5-years post fire. Rather, current peat depth best explained moss moisture stress in burned and unburned landscapes, suggesting a peat depth threshold, above which Sphagnum drought resilience increases. Our ongoing research seeks to identify the critical depth threshold for greater moss resilience in a natural, disturbed, and recovering environment through Hydrus-1D modelling with the aim to provide researchers and practitioners information to maximise peatland ecosystem recovery through post-fire restoration.