Overwintering Fires Can Occur in Both Peatlands and Upland Forests with Varying Ecological Impacts

Climate warming is increasing the prevalence of overwintering ‘zombie’ 
fres, which are expected to occur primarily in peatlands, undermining 
carbon storage through deep burning of organic soils. We visited 
overwintering fres in Northwest Territories, Canada, and Interior Alaska, 
United States, and present feld measurements of where overwintering 
fres are burning in the landscape and their impact on combustion severity 
and forest regeneration. Combustion severity hotspots did not generate 
overwintering, but peat and woody biomass smouldering both supported 
overwintering, leading to wintertime smouldering in both treed peatlands 
and upland forests. These fndings create challenges for fre managers 
and uncertainty about carbon emissions, but forest regeneration was 
not compromised.