The Existing Vegetation Type (EVT) layer is mapped using decision tree models, field data, Landsat imagery, elevation, and biophysical gradient data. Decision tree models are developed separately for each of the three lifeforms -tree, shrub, and herbaceous and are then used to generate lifeform specific EVT layers.
The LF-GAP Map Units Descriptions provide descriptions for each LF EVT including species, distribution and classification information. Vegetation map units are primarily derived from NatureServe's Ecological Systems classification, alliances of the U.S. National Vegetation Classification (USNVC), the National Land Cover Database and LF specific types.
LF uses EVT in several subsequent layers, including the development of the fuel layers.
New and Improved LF Auto-Keys: LF is gearing up for LF remap - learn about the redesign of the Auto-Keys process, which is used to determine existing vegetation type classification based on plot data in the LFRDB — Developing Auto-Keys for LF Vegetation Mapping: 2014-2015 CONUS Project Report