Documentation of the modeling of potential vegetation at three spatial scales using biophysical settings in the Columbia River Basin assessment area

This report describes the application of a vegetation model to predict potential vegetation over the 822,922 km b2 s of the Columbia River Basin (CRB) assessment area at 3 scales. Topographic relief in the CRB assessment area ranges from 23 m (75 ft) to 4203 m (13,785 ft), with vegetation types that include desert grasslands in low elevation valleys and basins and alpine communities on some of the high peaks. A regional hierarchical classification of the Western U.S. vegetation (Bourgeron and Engelking, 1994) was used to derive potential vegetation (PV) type classes along moisture and temperature gradients at three distinct scales (section, regional and coarse). Elevation, slope and aspects settings were assigned to the PV classes at the section level. These settings were used to assign each 1 km x 1 km DEM pixel to the most probable PV class. GIS technology was used to aggregate these section level mapping units into the regional level map and the coarse level map. All maps were reviewed for their general approximation of PV cover over the CRB assessment area.