However, the relationship between weather and fire severity, and the relationships between fire severity, carbon fluxes and climate feedbacks are not well known. The greatest carbon loss due to fire results from post-fire decomposition rather than combustion during the fire. This causes high CO2 efflux in well-aerated sites and large efflux of methane and N2O where thawing of permafrost creates waterlogged soils. Nitrogen retention initially depends more on retention in microbial biomass rather than regrowing vegetation. Fire severity is the major factor determining post-fire vegetation type.
Fire causes threshold changes in energy exchange with the atmosphere.
Immediately following fire, there is an increase in winter albedo and decrease in summer albedo, combined with reduced ET and increased runoff. ET than unburned stands, with a net reduction in runoff. The net change at the watershed scale is sensitive to the fate of permafrost.