National Standards for the Floristic Levels of Vegetation Classification in the United States: Associations and Alliances

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not applicable

Maintenance authority

not applicable


The objective of this project is to develop floristic-level standards for the classification of vegetation in the United States using associations and alliances as defined in the FGDC Vegetation Classification Standards (FGDC-STD-005, October 1997).  While the existing approved standard defines association and alliance, it does not provide standards for naming and classifying vegetation at these levels.  This project will develop standards for doing so as Part II of the FGDC Vegetation Classification Standards: Floristic Levels of Vegetation Classification in the United States:  Associations and Alliances.


The floristic-level standards of a national vegetation classification will be FGDC data content standards.  The standards will include:

  • Inventory and plot standards:  to establish criteria for the collection of vegetation plot data, the purpose of field sampling, and the standards for vegetation plot data.
  • Standards for the documentation and characterization of vegetation units:  to formalize a standard format for documentation, characterization, and review in support of recognized units in the classification system.
  • Nomenclature standards:  based on the scientific names of the diagnostic (dominant, differential, indicator, or character) species and follow FGDC nomenclature standards;
  • Standards for data management (dissemination and archiving):  to establish an overall system for data management, archiving, and dissemination.

These standards will be used to classify and catalog plant communities, and will be important for predicting ecological processes such as productivity, successional patterns, or other complex properties of natural phenomena. The classification will provide a consistent conceptual matrix for integrating, understanding and communicating the ecological context for management decisions concerning biodiversity.  We expect that such a classification system will play a prominent role in guiding research and extrapolation of findings, in ecosystem management and planning, in resource conservation, and in predicting outcomes from environmental change.

The standards are for classification of existing, not potential, vegetation and are based upon vegetation condition at the optimal time during the growing season.  The vegetation types are defined on the basis of species composition within types.  The standards are for vegetation classification, not landscape, ecosystem, or site classification.  The classification will include the full range of plant communities, i.e., natural as well as anthropogenic.

The standards for the lower levels of the National Vegetation Classification are based on actual floristic(vegetation) composition.   The data used to describe alliance and association types must be collected in the field using standard and documented sampling methods.  The alliance and association units are derived from these field data.  These floristically-based classes will be nested under the physiognomic classes of the hierarchy presented in the FGDC Vegetation Classification Standards (FGDC-STD-005, October 1997).  All floristic-level standards will be a subset of the existing FGDC Vegetation Classification Standards.

Sponsored by

Vegetation Subcommittee

Project history

Document Version Date Custodian
FGDC Standards Working Group