Many parts of interior Alaska have a fire-dominated environment. It has been recognized that there are many beneficial effects of fire; consequently, the past fire control philosophy has been altered. Prescribed and controlled burning are being considered under the new approach. The more intense burns occur in the black spruce (Picea-Mariana) forests which are characterized by a thick organic layer and a shallow mineral soil underlain by permafrost. From field data, it is clear that both the thermal and moisture regimes undergo considerable alteration due to fire.