Introduction to the CNVC Hierarchy

The vegetation of Canada can be described using various criteria – ecological, floristic, physiognomic, or combinations of these factors. The Canadian National Vegetation Classification uses the same eight-level classification hierarchy as the United States National Vegetation Classification. This hierarchy, which has been developed by an international group of scientists from the western hemisphere, uses physiognomic criteria at the upper levels, floristic criteria at the lower levels, and combinations of these factors through the middle levels to classify the diversity of natural and semi-natural vegetation. The hierarchy, with an example unit for each level, is as follows:

Canadian National Vegetation Classification Hierarchy Levels with Examples

Natural Vegetation Hierarchy	Example
Upper Levels
1 – Formation Class	Scientific Name: Mesomorphic Tree Vegetation
1 – Formation Class	Colloquial Name: Mesomorphic Forest and Woodland
2 – Formation Subclass	Scientific Name: Boreal Tree Vegetation
2 – Formation Subclass	Colloquial Name: Boreal Forest and Woodland
3 - Formation	Scientific Name: Boreal Lowland and Montane Tree Vegetation
3 - Formation	Colloquial Name: Low Elevation and Montane Boreal Forest and Woodland
Mid Levels
4 – Division	Scientific Name: Picea glauca & P. mariana – Populus tremuloides - Pinus contorta & P. banksiana Division
4 – Division	Colloquial Name: North America Low Elevation and Submontane Boreal Forest and Woodland
5 – Macrogroup	Scientific Name: Picea glauca & P. mariana – Populus tremuloides - Pinus contorta - Abies lasiocarpa Macrogroup
5 – Macrogroup	Colloquial Name: Western North America Boreal Conifer and Hardwood Forest and Woodland
6 - Group	*Scientific Name:* Picea glauca – Populus tremuloides (Pinus contorta) / Hyolocomium splendens Group
6 - Group	Colloquial Name: Western North America Boreal Dry-Mesic Mesotrophic White Spruce - Aspen (Lodgepole Pine) Forest
Lower Levels
7 – Alliance	Scientific Name: Picea glauca – Pinus contorta – Populus tremuloides / Hylocomium splendens Alliance
7 – Alliance	Colloquial Name: White spruce – Lodgepole pine – Trembling Aspen / Stairstep Moss Alliance
8 – Association	Scientific Name: Picea glauca / Hylocomium splendens
8 – Association	Colloquial Name: White Spruce / Stairstep Moss

A summary definition for each level is available here. The hierarchy is fully described in the United States Federal Geographic Data Committee publication National Vegetation Classification Standard.

The hierarchy has not yet been fully developed for Canada. The focus of the CNVC has been on developing and describing the associations. A working version of the hierarchy has been initiated, but will not be available until it has had further supporting work and has been agreed upon by the CNVC partners. The first four levels of the proposed hierarchy for Canadian natural and semi-natural vegetation are shown here.