2.0 Classification and Mapping Concepts

Ecosystem classification provides the taxonomic framework for describing the nature and pattern of ecological units within a landscape. Ecosystem mapping uses the classification to depict the spatial distribution of the ecological units. This section describes the classification hierarchy and how it is used in TEM.

Three ecosystem integration levels are combined in TEM (Figure 2.1): the regional ecosystem level, where the classification units are ecosections and biogeoclimatic subzones and variants; the local ecosystem level, where site series is the classification; and the vegetation developmental level, where structural stages and seral community types are used.

Ecosystem units, described in more detail below, are a conceptual group of sites that are similar enough to be grouped together as one mapping individual. In TEM, this is a combination of site and vegetation developmental units. It is important to remember however, that the ecosystem unit is an abstract unit of classification, which, each time it is mapped, will have a certain range of characteristics that make it unique from other ecosystem units.

Map units represent mapped portions of the landscape (Valentine, 1986). Each unit is established as a result of applying a classification to a map polygon. Ecosystem maps contain three kinds of map units: ecoregion map units, biogeoclimatic map units, and ecosystem map units. An ecosystem map unit contains either predominantly one mapping individual (simple map unit) or more than one (compound map unit). Each may also contain a certain proportion of other ecosystem units which are unmappable at the scale of mapping (Valentine, 1986). Ecoregion and biogeoclimatic map units are always mapped as simple map units.

Figure 2.1 Levels of ecosystem integration and classification in terrestrial ecosystem mapping

2.1 Ecoregion Units

The ecoregion classification developed and mapped for British Columbia provides a systematic view of the broad geographic relationships of the province (Demarchi et al., 1990; Demarchi, 1993). This "regional" classification is based on the interaction of macroclimatic processes (Marsh, 1988) and physiography (Holland, 1976; Mathews, 1986). It is a hierarchical system, stratifying the province according to five levels:

Ecodomain	This is an area of broad climatic uniformity (e.g., the Humid Temperate Ecodomain is one of three ecodomains occurring in British Columbia).
Ecodivision	This is an area of broad climatic and physiographic uniformity (e.g., the Humid Maritime and Highlands is one of seven ecodivisions occurring within British Columbia).
Ecoprovince	This is an area with consistent climate, relief, and plate tectonics (e.g., the Coast and Mountains Ecoprovince is 1 of 10 ecoprovinces occurring in British Columbia).
Ecoregion	This is an area with major physiographic and minor macroclimatic variation (e.g., the Pacific Ranges is one of 39 terrestrial ecoregion units occurring in British Columbia).
Ecosection	This is an area with minor physiographic and macroclimatic variation (e.g., the Eastern Pacific Ranges is one of 101 terrestrial ecosection units occurring in British Columbia).

Ecodomains and ecodivisions are very broad and place British Columbia in a global context. Ecoprovinces, ecoregions, and ecosections are progressively more detailed and narrow in scope and relate the province to other parts of North America, or segments of the province to each other.

The ecosection is the classification unit depicted in terrestrial ecosystem mapping. At present, British Columbia is mapped to the ecosection level at two scales of presentation: 1:2 000 000 (Demarchi, 1993) and 1:250 000 (BC Ministry of Forests, 1995).

Ecosections represent map delineations at the highest level of ecosystem generalization on a terrestrial ecosystem map, and are mapped as simple units that stratify the landscape into broad physiographically and climatically uniform units. Ecosections are named after specific geographic or physiographic features.

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