These rasters represent output from the Boreal ALFRESCO (Alaska Frame Based Ecosystem Code) model. Boreal ALFRESCO operates on an annual time step, in a landscape composed of 1 x 1 km pixels, a scale appropriate for interfacing with mesoscale climate and carbon models. The last four digits of the file name specifies the year represented by the raster. For example a file named Age_years_historical_1990.tif represents the year 1990. Cell values represent the age of vegetation in years since last fire, with zero (0) indicating burned area in that year. Coverage of this dataset includes much of the state of Alaska (but does exclude Southeastern AK, Kodiak Island, portions of the Alaska Peninsula, and the Aleutian Islands). ALFRESCO simulates the responses of subarctic and boreal vegetation to transient climatic changes. The model assumptions reflect the hypothesis that fire regime and climate are the primary drivers of landscape-level changes in the distribution of vegetation in the circumpolar arctic/boreal zone. Furthermore, it assumes that vegetation composition and continuity serve as a major determinant of large, landscape-level fires. Files from years 1860-2006 use a variety of historical datasets for model spin up and calibration to most closely match historical wildfire dynamics. Files from years 2007-2099 use the Hadley (HAD_CM3) Global Climate model and the A1B emissions scenario for projecting future vegetation ages. The HAD_CM3 model was chosen based on it being the mean predictor of climate.
