Broad-scale alterations of historical fire regimes and vegetation dynamics have occurred in many landscapes in the U.S. through the combined influence of land management practices, fire exclusion, ungulate herbivory, insect and disease outbreaks, climate change, and invasion of non-native plant species. The LANDFIRE Project produces maps of simulated historical fire regimes and vegetation conditions using the LANDSUM landscape succession and disturbance dynamics model. The LANDFIRE Project also produces maps of current vegetation and measurements of current vegetation departure from simulated historical reference conditions. These maps support fire and landscape management planning outlined in the goals of the National Fire Plan, Federal Wildland Fire Management Policy, and the Healthy Forests Restoration Act.Data Summary:Succession Classes categorize current vegetation composition and structure into up to five successional states defined for each LANDFIRE Biophysical Settings (BpS) Model. An additional category defines uncharacteristic vegetation components that are not found within the compositional or structural variability of successional states defined for each BpS model, such as exotic species. These succession classes are similar in concept to those defined in the Interagency Fire Regime Condition Class Guidebook (www.frcc.gov). The presumed historical reference conditions for the succession classes in each BpS model are simulated using the vegetation and disturbance dynamics model LANDSUM (Keane et al. 2002, Keane et al. 2003, Keane et al. 2005, Pratt et al. 2005). The current successional classes and their simulated historical reference conditions are compared to assess departure of vegetation characteristics; this departure can be quantified using methods such as Fire Regime Condition Class (FRCC). Five successional classes, "A" (1) - "E" (5) define successional states represented within a given BpS model. 'UN' (6) represents uncharacteristic native vegetation for the BpS model on which these vegetation conditions are found. These are taken to represent vegetation cover, height, or composition that would not have been expected to occur on the BpS during the reference condition period. 'UE' (7) represents uncharacteristic exotic vegetation for the BpS model on which these vegetation conditions are found. Additional data layer values were included to represent Water (111), Snow / Ice (112), Barren (131), and Sparsely Vegetated (132). Urban (120) and Agriculture (180) are provided to mask out such areas from analysis of vegetation departure. To use this layer for assessing vegetation departure from simulated historical reference conditions, it is necessary to combine this layer with LANDFIRE BpS and LANDFIRE Map Zone data layers. The subsequent combination of Map Zone, Bps, and Succession Class can then be found within LANDFIRE Simulated Historical Reference Condition tables. Caution is warranted in assessing vegetation departure across Map Zone boundaries, as the classification schemes used to produce BpS and Succession Classes may vary slightly between adjacent Map Zones. Furthermore, reference conditions are simulated independently for each Map Zone, resulting in potentially unique measurements of reference conditions for a given BpS between adjacent Map Zones. Holsinger, L., R.E. Keane, B. Steele, M.C. Reeves, and S.D. Pratt. 2005. Assessing departure of current vegetation conditions from historical simulations of vegetation across large landscapes. Chapter 11 in: The LANDFIRE Prototype Project: nationally consistent and locally relevant geospatial data and tools for wildland fire management. M.G. Rollins, Technical Editor. USDA Forest Service, Rocky Mountain Research Station, Missoula Fire Sciences Laboratory. RMRS-GTR-[In prep.] Keane, R.E., R. Parsons, and P. Hessburg. 2002. Estimating historical range and variation of landscape patch dynamics: limitations of the simulation approach. Ecological Modeling 151: 29-49. Keane, R.E., G.J. Cary, and R. Parsons. 2003. Using simulation to map fire regimes: an evaluation of approaches, strategies, and limitations. International Journal of Wildland Fire 12: 309-322. Keane, R.E., L. Holsinger, and S. Pratt. 2006. Simulating historical landscape dynamics using the landscape fire succession model LANDSUM version 4.0. USDA Forest Service, Rocky Mountain Research Station, Missoula Fire Sciences Laboratory. RMRS-GTR-171CD. Pratt, S.D., L. Holsinger, and R.E. Keane. 2005. Modeling historical reference conditions for vegetation and fire regimes using simulation modeling. Chapter 10 in: The LANDFIRE Prototype Project: nationally consistent and locally relevant geospatial data and tools for wildland fire management. M.G. Rollins, Technical Editor. USDA Forest Service, Rocky Mountain Research Station, Missoula Fire Sciences Laboratory. RMRS-GTR-[In prep.]