LANDFIRE 2022 Vegetation Departure (VDep) CONUS

LANDFIRE’s (LF) 2022 Vegetation Departure (VDep) product categorizes departure between current vegetation condition and reference vegetation condition, according to the methods outlined in the Interagency Fire Regime Condition Class Guidebook (FRCC Guidebook (Hann et al 2010)). VDep differs from the FRCC Guidebook, however, because it is based on the departure of current vegetation condition only, whereas the FRCC Guidebook approach includes departure of current fire regimes for the reference period. For VDep, summary units are defined as a BioPhysical Setting (BpS) with identical reference condition values regardless of map zone. For example, when a BpS is present in map zone 1, 2, 4, 5, 6 and 8, the reference conditions for this BpS are identical in map zones 1, 2, 4, 5, and 8, those map zones become a summary unit for VDep computation. Since reference conditions are unique for this BpS in map zone 6, it is a separate summary unit for calculating VDep. Within each BpS summary unit, we compare the reference percentage of each Succession Class (SClass) to the current percentage, then the smaller of the two is summed to determine the similarity index for the BpS. This value is then subtracted from 100 to determine the departure value, VDep value is always between 0 and 100, with 100 representing maximum departure. Reference conditions are derived from quantitative vegetation dynamics models that mimic native, pre-European colonization disturbance regimes. The current conditions are derived from the corresponding LF 2022 SClass data for each BpS. The proportion of the landscape occupied by each SClass, in each BpS unit, within each summary unit represents current condition of that SClass in VDep calculation. VDep is based entirely on the remaining area of each BpS unit that is occupied by valid SClasses. Each pixel in a BpS within a summary unit has the same VDep value.