In many forested landscapes across western North America, past fires often act as barriers to fire spread for a time and then, as live and dead fuels accumulate, reburn but with much lower severity than surrounding forested areas. In this project, we evaluated the interactions of past burn mosaics within recent large fire events in three study areas to support wildfire management decisions in semi-arid forests. A key inspiration for this project was a map of known fire starts within the 2006 Tripod Complex fire in North Central Washington State. Within the 175,000 acre fire area, over 300 active fire starts were suppressed between 1940 and 2005. In central Idaho, the 320,000-acre East Zone fire had a total of 977 recorded fire starts that were actively suppressed prior to the wildfire event. We conducted this study to better understand the role of past fires as a type of fuel reduction treatment and to also evaluate the long-term consequences of fire suppression.

With funding from the Joint Fire Sciences Program, we evaluated past fire mosaics and their interaction with subsequent large fire events. The study was designed to support the National Wildland Fire Cohesive Strategy and specifically address its goals to increase landscapes resiliency to fire and to improve firefighter safety.

Our project had two main tasks: •In Task 1, we used burn severity analysis to analyze the effect of past fires on subsequent fire spread and severity. •In Task 2, we used fire simulation modeling to ask how different wildfire management strategies (no suppression, partial suppression and full suppression) influences landscape patterns.