Analyzing fuel treatments and fire hazard in the Pacific Northwest

Ph.D. Dissertation Abstract by Morris Johnson (2008)

The effect of thinning and surface fuel treatments on fire hazard was tested using the Fire and Fuel Extension to the Forest Vegetation Simulation (FFE-FVS) on 45,162 stands from throughout the dry forests in the western United States. A matrix of 13 treatments was designed to test responses to different fire types. The treatments were patterned after the principles of a fire-safe forest. These four principles are to (1) reduce surface fuels, (2) increase height to live crown (3) decrease crown density, and (4) leave big trees of resistant species (Agee and Skinner 2005). A total of 698,140 projections resulted from evaluating stands based on four thinning densities (124, 247, 494, and 741 tph), three surface fuel treatments (leave slash, extract slash, prescribed fire), and no action. The effect of thinning treatments on surface fire stands was consistent across all blocks: most (on average, 80%) did not change after treatment. In conditional surface fire stands, thinning generated surface fire, passive crown fire, and active crown fire stands: passive crown fire transitioned to surface fire stands, and active crown fire stands transitioned to surface fire, conditional surface fire and passive crown fire stands. Furthermore, the 124 and 247 tph thinning treatments were more effective than the 494 and 741 tph treatments. I could not compare effects of surface fuel treatments effects on fire hazard because of limitations of the model. I next explored the potential fire hazards of implementing restoration thinning treatments, with and without surface fuel treatments in the Cedar River Municipal Watershed (47°23'N, 121°41'W), using FFE-FVS and FlamMap. FlamMap's minimum travel time model indicates that slash generated from thinning treatments may increase potential area burned. I also used FlamMap's treatment optimization model to identify areas that, if treated, could reduce wildfire spread. Extreme weather conditions generated the largest area burn.