The Classification System is an FGDC standard through the physiognomic (first 5 levels). Work continues through the USGS-NPS Vegetation Mapping Program, in association with USGS/BRD (CBI), USGS/BRD (GAP), EPA (EMAP), U.S. Fish and Wildlife Service, National Park Service, NatureServe, The Nature Conservancy, Ecological Society of America (Vegetation Section), and the FGDC Vegetation Subcommittee on the floristic levels (lower 2 levels) of the standard. The lower levels of the Classification have several thousand cover types and associations to date. Work will continue for an indefinite period as new classes are proposed and existing classes are refined or aggregated.

Standardized National Vegetation Classification System; protocol document for the USGS-NPS Vegetation Mapping Program

The Federal Geographic Data Committee's Information on The National Vegetation Classification Standard

NatureServe "Terrestrial Vegetation of the United States"

Specifications and Requirements

• The system must be based on a sound scientific approach that is a logical progression from historical methods
• The approach must be repeatable and based on standard field and data analysis methods
• The system should be broadly accepted both nationally and internationally
• The system must classify existing biological associations that repeat across the landscape
• The classification units must be ecologically meaningful.
• The classification must be mappable from imagery.
• The classification system must be hierarchically organized such that it can be applied at multiple scales.
• The system must identify classification units that are appropriately scaled to meet objectives for biodiversity conservation, as well as resource and ecosystem management needs.
• The system must be flexible and open ended such that it will allow for additions, modifications and continuous refinement.
• The system must be well documented.
• The system should be able to be cross-walked between other frequently used systems.

Illustrated example of a classification, through association level

System: Terrestrial/Aquatic - (hydrological regime)

Class - Woodland - (spacing & height of dominant form)

Subclass - Evergreen Woodland - (morphological & Phenological similarity)

Group - Temperate Evergreen Needle-leaved - (climate latitude, growth form, leaf form)

Formation - Evergreen needle-leaved forest with conical crowns - (mappable units)

Alliance (or cover type) - Abies lasiocarpa Forest (dominant species)

Association (or community) - Abies lasiocarpa/Vaccinium scoparium [Subalpine fir/Grouseberry] (subdominant or associated species with similar ecological processes)

Abies lasiocarpa/Vaccinium scoparium forest

USGS-NPS Vegetation Mapping Program