William, the closed canopy of the stands of Ponderosa Pine and other conifers along with the steep slopes and drought conditions combined with the fire caused the needles to be cooked (Scorched) thus killing the trees. Historically, in a natural setting, the average fire interval under a Ponderosa Pine stand was around seven years. Fire suppression efforts has allowed increased fuel buildups and more dense stands (more trees per acre) to cause more intense fires. The steep slopes caused the heat buildup to rapidly rise along the slope under the closed canopy concentrating the heat in the needles but did not burn long enough to cause the soil to be sterilized in most places along the Hermosa Cliffs.