Variables that influence changes in fire severity and their relationship with changes between surface and crown fires in a wind-driven wildfire

The identification of the relationships between fire severities and fire types can be a new way to obtain knowledge about variables that cause transitions between surface and crown fires. In this study, we analyze the variables that influence fire severity and their relationship to changes in fire type in a wind-driven wildfire that burned under extreme conditions in the Northeast Iberian Peninsula. Ten of the 12 variables that affected severity were related to fuels, 1 was topographic, and 1 was related to fire spread. Not all changes in fire severity imply changes in fire type. Changes in green and scorched severities were not related to changes in fire type, but there was a strong relationship between changes in scorched and charred severities and the transition to active crown fires. The wind alignment and percentage of large trees contributed to the transition to charred severity and to the initiation of an active crown fire, whereas the cessation of an active crown fire and the transition to scorched severities were affected by tree density and the type of slope. The use of this methodology in other wildfires could provide a better understanding of the variables that influence the transitions to crown fires. © 2013 by the Society of American Foresters.