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Vantage to Pomona Heights Chapter 3 230 kV Transmission Line Project FEIS Affected Environment PAGE 3-263 3.12.2.3 Fire Regime Groups and Fire Regime Condition Classes Fire regimes, fuel loads, and the composition and structure of vegetation have been altered by fire exclusion, livestock grazing, logging, and widespread establishment of exotic plants (Schmidt et al. 2002). Fire Regime Groups and Fire Regime Condition Classes (FRCC) have been developed as tools that land managers can use to assess the impacts that these alterations have on ecosystems. A natural or historical fire regime is a general classification describing the role fire would play across a landscape in the absence of modern human intervention, but includes the possible influence of burning by Native American groups. Fire Regime Groups are based on the average number of years between fires (also known as fire frequency or mean fire-return interval) combined with the severity (i.e., the amount of vegetation replacement) of the fire and its effect on the dominant overstory vegetation (Menakis et al. 2004; National Interagency Fuels, Fire, and Vegetation Technology Transfer [NIFTT] 2010). The five Fire Regime Groups are described in Table 3.12-1. Table 3.12-1 Fire Regime Groups and Descriptions GROUP FREQUENCY SEVERITY SEVERITY DESCRIPTION I 0 - 35 years Low/mixed Generally low-severity fires replacing less than 25% of the dominant overstory vegetation; can include mixed- severity fires that replace up to 75% of the overstory. II 0 - 35 years Replacement High-severity fires replacing greater than 75% of the dominant overstory vegetation. III 35 - 200 years Mixed/low Generally mixed severity; can also include low- severity fires. IV 35 - 200 years Replacement High-severity fires. V 200+ years Replacement/any severity Generally replacement-severity; can include any severity type in this frequency range. Source: NIFTT 2010 The majority of the Project study area is within Fire Regime Group III (68 percent), typically mixed-low severity fires that occur approximately every 35 to 200 years and Fire Regime Group IV (26 percent), typically high-severity replacement fires that occur approximately every 35 to 200 years. The remaining vegetated areas fall within Fire Regime Groups I, II, and V (one percent combined). Five percent of the Project study area is within the category water or barren and was not assigned to a Fire Regime Group. Fire return intervals for Wyoming big sagebrush shrub steppe communities have been estimated to span 50 to 240 years, falling into Fire Regime Groups III, IV, and V (Whisenant 1990; Baker 2006). The FRCC is an interagency, standardized tool to measure the degree of departure between historical and current fire regimes and vegetation structural conditions across differing vegetation types (Table 3.12-2). FRCC is an index that compares current with historical fire regimes and vegetation composition and structure to assess degree of departure on a scale from one (least departed) to three (most departed). It is important to note that FRCC is not a fire hazard metric, but instead measures ecological trends (Menakis et al. 2004; NIFTT 2010). The FRCC dataset was developed at a landscape scale by LANDFIRE using field-referenced data and Landsat imagery. Table 3.12-2 Fire Regime Condition Classes FIRE REGIME CONDITION CLASS DESCRIPTION FRCC 1 Ecosystems with low (<33%) departure from reference conditions and that are still within the estimated historical range of variation of a specifically defined reference period. Fire regimes are within a historical range and the risk of losing key ecosystem components is low. Vegetation attributes (species composition and structure) are intact and functioning within a historical range.