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What is the Biogeoclimatic Ecosystem Classification?

BEC stands for Biogeoclimatic Ecosystem Classification system

The Biogeoclimatic Ecosystem Classification system was first developed by Dr. V.J. Krajina of the Department of Botany, University of British Columbia. In the 1970’s, the Biogeoclimatic Classification system was adopted by the British Columbia Ministry of Forests as a method to classify and manage sites on an ecosystem-specific basis.

As the name implies, the system incorporates three distinct levels into the classification of ecosystems in BC. “Bio” indicates the biological nature of the ecosystem. This can be observed in BEC by looking at the vegetation potential on a site. “Geo” indicates the use of soils and geology in the classification. We determine this aspect of BEC by analyzing soil pits and determining the soil texture and geology of the site. Finally, “climatic” involves overriding climatic factors in the classification. For instance, many of us have experienced that the coast of BC is wetter, the north interior is drier and colder and the southern interior is hotter. The combination of geology, vegetation and climate concepts form the basis for division of Biogeoclimatic Zones in British Columbia. Together, the three levels Bio, Geo and Climatic are used to classify any site in BC into an ecosystem. In British Columbia, there are 14 biogeoclimatic zones identified.

Together, the three levels Bio, Geo and Climatic are used to classify any site in BC into an ecosystem. In British Columbia, there are 14 biogeoclimatic zones identified.


The Concept of Ecosystem

In BEC, the ecosystem is defined as the interactions between climate and soil that determine the vegetation potential on a site. Prevailing climate in any given area will determine the average amount of rainfall, temperature and growing-degree days that will occur on a site. The soils will determine whether a site receives moisture from adjacent hillslope, drains moisture excessively (eg sandy soils), has an abundance of soil nutrients or is depleted in soil nutrients. The combination of prevailing climate and soil type can be used to predict the potential vegetation community that may develop in any given area of the province. In BEC, ecosystems are described in terms of potential plant community or what the species composition might look like at maturity.

Zones, Subzones, Variants and Phases

Zones:
BEC Zones are the highest level of classification and represent areas of broad macroclimate. They are generally named after dominant tree species and a descriptor of the general climate or region. Examples include the Coastal Western Hemlock Zone, Interior Douglas-fir Zone and Boreal White and Black Spruce Zone.

Example: CWH – Coastal Western Hemlock
ESSF – Engelmann Spruce Subalpine fir

Subzones:
Subzones are divisions of zones that further define the climate of an area. On the coast, subzones are divided based on climate and continentality (the relative influence of the marine environment on the terrestrial environment). In the interior, subzones are divided based on climate and precipitation.

Variants are divisions of subzones that are slightly wetter, drier, cooler or hotter than other areas in the subzone.

Phases are used periodically to account for subtle changes in variants that are a result of different topography. Examples can include cold air drainage sites, south facing aspects and local rain shadow. These sites may be extensive within a variant but not large enough nor climatically different enough to justify creating a separate variant.

A full Biogeoclimatic ecosystem label that has a zone, subzone, variant and phase would look like:

IDFdk1a – Thompson dry, cool Interior Douglas-fir variant, grassland phase

 

 

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