Heat from a fire does not readily penetrate soil. Prescribed burning has no effect on the physical and chemical properties of soil. It does not consume the lower layer of litter, which protects the soil from rain and the sun. Forest fires don't always kill the timber. Larger trees have thicker bark to protect the cambium and needles are higher above the heat source.
Some forest fires burn with low intensities where fuels are light or are moist.
Even though the trees are not killed outright, they can be damaged and growth can be retarded if all of the litter is consumed, especially hardwoods. They are weakened and may die later as a result of insects, drought, or windthrow due to a partial killing of the root system. They are destructive because they are generally very intense, producing high temperatures on the tree boles and tree crowns. Conditions contributing to large, intense wildfires are drought, low humidity, high winds, and large amounts of fuel. Fires under these conditions also create their own adverse weather conditions as they get larger with preheating of the fuels, higher winds, and updrafts.