This feature class contains attribute information from ten mid-level existing vegetation maps (1:100,000) prepared for the Tongass National Forest to provide up-to-date and more complete information about vegetative communities, structure, and patterns across the Forest. Approximately 4.6 million acres, 3.5 million acres of which are terrestrial and inland waterbodies and rivers, were mapped through a partnership between the Geospatial Technology and Applications Center (GTAC), Tongass National Forest, and the Alaska Regional Office. The Tongass National Forest and their partners prepared the regional classification system, identified the desired map units (map classes) and provided general project management. GTAC provided project support and expertise in vegetation mapping.

The modeling units (mapping polygons) were characterized with the following vegetation attributes: 1) vegetation type; 2) tree canopy cover; 3) trees per acre (TPA) for trees ≥ 1’ tall; 4) trees per acre for trees ≥ 6” diameter at breast height (DBH); 5) quadratic mean diameter (QMD) for trees ≥ 2” DBH; 6) quadratic mean diameter for trees ≥ 9” DBH; 7) thematic tree size; 8) biomass for trees ≥ 2” DBH; 9) gross board feet (GBF) for trees ≥ 9” DBH; and 10) stand density index (SDI) for trees ≥ 9” DBH. The minimum map feature depicted on the map is 0.25 acres. All map products were designed according to the Forest Service mid-level vegetation mapping standards to be stored in the Forest GIS and National databases. This map product was generated using imagery primarily acquired in 2019 – 2022, reference information collected in the summers of 2019 – 2022, and LiDAR data from 2018. Therefore, the final map can be considered indicative of the existing vegetation conditions found within the project boundary in 2022.

Note that the forest structure metrics will be more reliable within the LiDAR extent versus outside. Outside the LiDAR extent these metrics were extrapolated using more coarse spectral and topographic data. Therefore, it is important for a product user to understand whether they are within the LiDAR acquisition area as indicated by the "Source_Extent" field to ascertain the ultimate reliability of a particular structure metric.

For more detailed information on mapping methodology please see the Ketchikan-Misty Fjords Ranger District Existing Vegetation Project Report.