The Fire Regime Condition Class (FRCC) Departure Index data product uses a range from 0 to 100 to depict the amount that current vegetation has departed from simulated historical vegetation reference conditions (Hann and Bunnell 2001; Hardy and others 2001; Barrett and others 2010; Holsinger and others 2006). This departure results from changes to species composition, structural stage, and canopy closure. It is important to note that the LANDFIRE FRCC layer represents the departure of current vegetation conditions from simulated historical reference conditions, which is only one component of the FRCC characterization outlined in Barrett and others (2010). LANDFIRE simulates historical vegetation reference conditions using the vegetation and disturbance dynamics model LANDSUM (Keane and others 2002; Keane and others 2006; Pratt and others 2006). Current vegetation conditions are derived from a classification of LANDFIRE layers of existing vegetation type, cover, and height.