Principles of the Classification

Classification principles of the Canadian National Vegetation Classification include:

1. Units define and describe vegetation using standardized criteria and nomenclature.

2. The classification consists of a full taxonomic vegetation hierarchy to permit descriptions of vegetation at various levels of generality. The classification is based on floristic, ecological, and physiognomic criteria, with the association as the basic classification unit and the alliance as a first-order grouping of associations. Provisionally, the 8-level hierarchy proposed for the USNVC is accepted for the CNVC, pending confirmation in Canadian vegetation conditions.

3. The classification will be integrated with spatial, or ecological land, classifications, using the association as the basic unit of integration.

4. Diagnostic features among the units are based upon vegetation characteristics that can be observed and measured objectively in the field, preferably using plot-based sampling methods. Wherever possible, units are developed from plot data adhering to the standards outlined in Chapter 5 of the guidelines document developed by the Ecological Society of America (ESA) Vegetation Classification Panel (2004). In the absence of high quality plot data, other information sources (e.g., incomplete plot data, literature sources, etc.) are used.

5. The units are concepts based upon characteristics of existing vegetation conditions. As much as possible, data are obtained from across the distribution range of the classification units in Canada, supplemented as necessary by additional range-wide information. Diagnostic and conceptual criteria are clearly stated and the ranges of variability of important attributes are clearly described. The quality of each classification unit is expressed by a confidence level designation, based on the relative quality of the data and the rigour of analysis used to define it.

6. The classification is designed to be updated and revised through a structured peer review process, as new information and type concepts become available. Periodic evaluation of the entire classification structure is encouraged.