FRRR Draft PEIS Virtual Public Meeting
4: What are the Desired Fuel and Fire Behavior Conditions?
Historical Conditions
Fire behavior can be described as either mixed or stand replacement severity and varying intensities. Historically wildfire would have burned in sagebrush communities every 10 to 250 years. Fires were also often small, between 1 and 500 acres, and would burn in a patchy manner with mixed severity, leaving islands and fingers of unburned vegetation. The following figure shows the progression of fire severity, from low-severity, non-lethal fires to the high-severity, stand-replacement fires. Larger fires were rare but did occur when fuel loading increased due to successive years of precipitation and weather and high winds aligned. Currently wildfires are getting large more frequently and burning thousands or hundreds of thousands of acres because of continuous fuel loads of cheatgrass. Please refer to Section 3.2.2 and Appendix H, Section H.3 in the FRRR DPEIS for more information.
Progression of Fire Severity
Current Conditions
More recently, fire return intervals have shortened, with some areas are burning every 1 to 5 years due to the increase in invasive annual grasses. Some areas have burned up to 7 times in the last 20 years.
Fire behavior is described as stand replacement severity and high intensity. Fuels are continuous and cure earlier in the season, increasing receptible fuels allowing for larger patch sizes, regardless of wind and weather conditions (see Progression of Fire Severity figure shown above). In areas of pinyon-juniper encroachment, historic vegetation mosaics have been replaced with dense, closed canopy stands which increases fuel loading and results in lethal high-severity crown fires.
Fire Regimes
Fire regimes are characterized by fire return intervals and interactions between vegetation, fire spread, fire effects and spatial context. Several maps presented in the FRRR Draft PEIS display historic fire return interval (Appendix A, Map 13 in the FRRR DPEIS) and fire regimes (Appendix A, Map 14 in the FRRR DPEIS) across the analysis area pre-settlement. These historical conditions are representative of desired vegetation conditions described in Station 3, What are the Desire Vegetation Conditions?, of the virtual public meeting. The Fire Regime Group Descriptions and Acres table presented below also represents pre-settlement conditions. For more information on the different types of fire regimes within the project area please reference Section 3.2.2 and Appendix H, Section H.3 of the FRRR Draft PEIS.
Fire Regime Group Descriptions and Acres
For more information on the FRRR Draft PEIS please contact Ammon Wilhelm, 208-373-4000.
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