Biogeoclimatic Zone

A biogeoclimatic zone is a geographical area (large ECOSYSTEM) with a relatively uniform macroclimate, characterized by a mosaic of vegetation, soils and, to a lesser extent, animal life reflecting that climate. Zones are usually named for the potential climatic climax or self-perpetuating vegetation established on mesic (average moisture) sites and zonal (climatically determined) soils. A zone may contain smaller vegetationally and environmentally more uniform ecosystems (subzones) that reflect differences in regional climate, soil moisture, soil nutrient status and environmental disturbance.

For example, in British Columbia, the Coastal Western Hemlock Zone is one of 14 biogeoclimatic zones. It occupies high precipitation areas up to 1000 m elevation west of the coastal mountains from the Washington to Alaska borders and beyond. Forests in this zone are dominated by western hemlock, often with co-dominant Pacific silver fir or western red cedar. Associated understory plants include salal and species of Vaccinium. Ten subzones are recognized within this large geographical area, reflecting gradations of continentality (hypermaritime to submaritime) and precipitation (very wet to dry). In the northern and wettest areas, Sitka spruce is an important tree, while in the southern or drier areas Douglas fir is more frequent. On extreme exposed coasts, stunted western hemlock, lodgepole pine and yellow cedar form complex mosaics with peat bogs.

In many areas, climatic climax plant communities have been replaced with various seral communities following agricultural clearing, logging, grazing, drainage or other human activities. These seral communities, rather than climax communities, may occupy large parts of biogeoclimatic zones such as the Coastal Douglas Fir Zone and the interior Ponderosa Pine and Bunchgrass zones.

The systems of ecological classification that are used for forest, range and wildlife management and for monitoring the impacts of climatic change in British Columbia are largely based in the concept of the biogeoclimatic zone and subzone.

Biogeoclimatic zones have been studied in several parts of Canada (BC, Alberta and the Yukon), the Hawaiian Islands, Japan (Hokkaido) and Indonesia.

See also VEGETATION REGIONS.

Author MICHAEL C.R. EDGELL

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Flora of North America
The FNA website features information on the names, taxonomic relationships, continent-wide distributions, and morphological characteristics of all plants native and naturalized found in North America north of Mexico.