U.S. Joint Fire Science Program


Date of this Version


Document Type



Fire Science Brief, Issue 10, July 2008


US government work.


In Alaska, the unusually warm, dry summer of 2004 brought wildfires that burned a record setting 6.7 million acres, mostly in the flammable black spruce forests of the interior. Less fl ammable deciduous tree species were known to sometimes replace black spruce in areas where fire was severe enough to burn away the organic layer. Based on study of the 2004 fires, researchers developed methods for measuring the depth of pre-fi re organic layers, and predicting patterns of post-fire regeneration and future forest flammability. They investigated how variations in site moisture and organic layer consumption affect subsequent patterns of postfi re vegetation recovery. At sites with low to moderate moisture, fire severity can determine whether black spruce will regenerate or shift to a less flammable, deciduous dominated successional trajectory. Frequent fi re can eventually cause high moisture sites to dry out and favor a deciduous system, supporting the idea that prescribed fire can be used to create deciduous fi re breaks. This knowledge will help inform strategies for both wildfire suppression and prescribed fire that can potentially reduce future flammability in black spruce ecosystems at landscape scales.