The biogeoclimatic zones of British Columbia are units of a classification system used by the British Columbia Ministry of Forests for the Canadian province's fourteen different broad, climatic ecosystems. The classification system, termed Biogeoclimatic Ecosystem Classification, exists independently of other ecoregion systems, one created by the World Wildlife Fund and the other in use by Environment Canada, which is based on one created by the Commission for Environmental Cooperation (CEC) and also in use by the US Environmental Protection Agency (EPA). The system of biogeoclimatic ecosystem classification was partly created for the purpose of managing forestry resources, but is also in use by the British Columbia Ministry of Environment and Climate Change Strategy and other provincial agencies. A biogeoclimatic zone is defined as "a geographic area having similar patterns of energy flow, vegetation and soils as a result of a broadly homogenous macroclimate."
All zones are officially abbreviated in capital letters (AT for Alpine Tundra, BWBS for Boreal White and Black Spruce, and so on). Subzones, which are divisions of zones based on more regional climates, have their connotative codes in lower case with the first letter denoting relative moistness and the second relative temperature; thus the northeastern BWBS with its warm thundery summers has been mapped as BWBSmw for "moist warm" while the Alsek Ranges subzone in the northwestern panhandle, stormy in all seasons with winds blowing from glaciers, is BWBSvk for "very wet cool." Subzones may be divided into variants, each of which is denoted by a number. For example, the numerous variants of the Interior Cedar—Hemlock moist warm subzone are designated as ICHmw1, ICHmw2, etc. A variant may be divided into phases, such as ICHmc1a, the amabilis fir phase of the Interior Cedar—Hemlock moist cold subzone.
The biogeoclimatic zones of British Columbia are:
Alpine Tundra (AT)
The Alpine Tundra zone is the harshest and least-populated biozone in the Province. It occupies the high elevations of mountainous areas, and is especially common in the Coast Range. The elevation range of this zone varies by area and is influenced both by latitude and by snowfall: in the extremely snowy southwest it starts at and in the less snowy southeast, . In the relatively dry north, the AT starts at , and in the more snowy northwest it can start as low as . Most life is found in the lower ranges of the zone.
The terrain in this zone is dominated by ice, snow, rock, and glaciers. Glacier-related features like cirques, talus, alpine lakes and moraine are common. Climate is a major barrier to life; the growing season is extremely short. Mean average temperature usually ranges from to , and even in summer the average temperature does not exceed . The zone sees heavy precipitation, usually in the form of snow.
Tree species are rarely found in this zone, and when they do grow, they take the low, sprawling Krummholz form. Shrubs are common, especially dwarf evergreen species like partridgefoot, kinnikinnick, crowberry, lingonberry, and alpine-azalea. Grasses, heath, and sedges are also present. Wetter areas and calcareous substrates see a larger variety of plant species. Higher elevations are exclusively the realm of the lichens.
Due to its harsh winters, few animals live in the zone year-round. However, in the spring, summer, and fall, many species are found. Mountain goats, big-horned sheep, stone sheep, Roosevelt elk, blacktailed deer, mule deer, elk, and caribou all take advantage of summer growth in the zone. Grey wolves follow the ungulates. Bears, such as black and grizzly, enjoy the many berries of the alpine meadows in the zone. Smaller mammals like the wolverine, hoary marmot, the endangered Vancouver Island marmot, Arctic ground squirrel, and the Siberian lemming are present. Birds of prey include the golden eagle and gyrfalcon. Ground birds such as the ptarmigan nest in the alpine zone, while other bird species like the snow bunting and rosy finch venture upwards from the treeline.
Spruce—Willow—Birch (SWB)
Found only in the north of the province, this zone occurs in the sub-alpine of the Interior Mountains.
White spruce is the most abundant conifer in the Spruce—Willow—Birch (SWB) zone, except at the upper (parkland) elevations, where subalpine fir dominates. Spruces with Engelmann spruce or hybrid white × Engelmann spruce characteristics may be present, especially in areas transitional to ESSF; if they are more abundant than white spruce, the site is mapped as ESSF. Subalpine fir is the most common associate of white spruce in the SWB zone. Black spruce (Picea mariana), lodgepole pine and trembling aspen (Populus tremuloides) are relatively minor associates. Many spruce stands are quite open, with a well-developed shrub layer dominated by a variety of willows (Salix glauca, S. planifolia, S. scouleriana, S. bebbiana) and scrub birch (Betula glandulosa). Other common shrubs include Potentilla fruticosa, Shepherdia canadensis, Empetrum nigrum, Vaccinium vitis-idaea, V. caespitosum and Ledum groenlandicum. Common herbs are Linnaea borealis, Festuca altaica, Epilobium angustifolium, Lupinus arcticu and Mertensia paniculata. In addition to the feather mosses Pleurozium schreberi and Hylocomium splendens, the forest floor contains a diversity of lichens (Coates et al. 1994).Coates, K.D.; Haeussler, S.; Lindeburgh, S.; Pojar, R.; Stock, A.J. 1994. Ecology and silviculture of interior spruce in British Columbia. Canada/British Columbia Partnership Agreement For. Resour. Devel., Victoria BC, FRDA Rep. 220. 182 p.
Boreal White and Black Spruce (BWBS)
White spruce is the predominant tree species in the Boreal White and Black Spruce (BWBS), except in the Fort Nelson area where the poorly drained lowlands are dominated by black spruce. Engelmann spruce is absent, though some white × Engelmann hybrids may occur at southern margins of the zone bordering the SBS zone.
Mixed stands of white spruce and trembling aspen (often with a minor component of balsam poplar [Populus balsamifera], birch (Betula papyrifera, B. neoalaskana) or lodgepole pine) are the most common components of forest cover on warm mesic sites in the BWBS. On colder sites, e.g., on north-facing slopes, pure white spruce or mixtures of white and black spruces dominate. Lodgepole pine is the typical associate of white spruce on coarse-textured parent materials, while balsam poplar–spruce mixtures are frequent on floodplains. Subalpine fir is common in western parts of the zone, but is rare east of the Rockies. Wetland black spruce stands often have a minor component of slow-growing white spruce. Typical vegetation in boreal white spruce stands includes the common shrubs Rosa acicularis, Viburnum edule, Shepherdia canadensis, Salix bebbiana, and Alnus viridis, with Ribes triste and Lonicera involucrata on wet sites, and Ledum groenlandicum and Vaccinium vitis-idaea on cold sites. Characteristic herbs are Linnaea borealis, Rubus pubescens, Mertensia paniculata, Petasites palmatus, Pyrola asarifolia, Cornus canadensis and Calamagrostis canadensis, with Equisetum spp. on wet sites. The thick carpet of moss is of Hylocomium splendens, Pleurozium schreberi and Ptilium crista-castrensis, and the lichen Peltigera aphthosa (Coates et al. 1994).
Sub-Boreal Pine—Spruce (SBPS)
White spruce is a distant second in importance to lodgepole pine in the Sub-Boreal Pine-Spruce zone (SBPS). It occurs most commonly in the understorey to pine, but scattered stands dominated by white spruce can be found on moist sites. Pure Engelmann spruce is absent, and any hybrids appear to have mainly white spruce characteristics.
Lodgepole pine is the most common associate of white spruce in the SBPS. White spruce also occurs with trembling aspen in seral stands, and mixtures of black and white spruces occupy cold low-lying sites. Floodplain stands of black cottonwood (Populus balsamifera ssp. trichocarpa) and white spruce occur uncommonly.
Typical understorey vegetation of moist spruce ecosystems includes the shrubs Lonicera involucrata, Rosa acicularis, Shepherdia canadensis, Juniperus communis, Salix glauca, Betula glandulosa, Ribes lacustre, R. hudsonianum and Viburnum edule, and the herbs Cornus canadensis, Linnaea borealis, Epilobium angustifolium, Petasites palmatus, Fragaria virginiana, Equisetum arvense, Calamagrostis canadensis and Mitella nuda. In addition to the usual feather mosses (Pleurozium schreberi, Hylocomium splendens and Ptilium crista-castrensis) the moss layer characteristically includes Aulacomnium palustre and Peltigera, Cladina and Cladonia lichens (Coates et al. 1994).
Sub-Boreal Spruce (SBS)
Interior spruce (mostly hybrid white × Engelmann, with some pure white spruce) is dominant throughout the many subzones of the Sub-Boreal Spruce (SBS) zone.
Lodgepole pine is the most common associate of interior spruce in the SBS. Subalpine fir is abundant in cooler, moister subzones. Trembling aspen and Douglas-fir (Pseudotsuga menziesii var. glauca) are often found with spruce on warmer, drier, more southerly subzones. Black cottonwood is the main associate of interior spruce on active floodplain sites, and mixtures of white and black spruces are common on wetlands.
Understorey vegetation in mesic spruce stands typically includes a moderately well-developed shrub layer dominated by Vaccinium membranaceum, Rubus parviflorus, Viburnum edule, Rosa acicularis, Alnus viridis, a variety of herbs (Cornus canadensis, Clintonia uniflora, Rubus pubescens, Rubus pedatus, Arnica cordifolia, Maianthemum racemosa, Orthilia secunda, Aralia nudicaulis) and a well-developed carpet of feathermosses (Pleurozium schreberi, Ptilium crista-castrensis, Hylocomiium splendens, Rhytidiadelphus triquetrus). Wetter spruce sites have Lonicera involucrata, Cornus sericea, Gymnocarpium dryopteris, Tiarella trifoliata, Equisetum arvense and Mnium mosses. Characteristic species of spruce bog, fen, or swamp ecosystems are Salix spp., Betula glandulosa, Ledum groenlandicum, Carex spp. and Sphagnum moss (Coates et al. 1994).
Mountain Hemlock (MH) In coastal areas the MH is transitional between productive low-elevation forests and treeless alpine tundra (AT). Unlike the interior high-elevation transition zones (SWB, ESSF), spruce is usually scarce or absent and mountain hemlock is abundant. Yellow cedar is also common, especially in the more maritime areas. The most common fir is Pacific silver fir and subalpine fir may also be plentiful. Fir is absent on Haida Gwaii. Some western hemlock may be present, especially at lower elevations where its proportion of hemlock cover may reach 50%. If western hemlock cover exceeds 50% of total hemlock cover, the site is considered to be within the CWH.R. Green and K. Klinka (1994). A Field Guide for Site Identification and Interpretation for the Vancouver Forest Region Land Management Handbook Number 28, page 68
The westernmost subzone, wet hypermaritime (MHwh) on Haida Gwaii, is atypical for its absence of fir and relative abundance of spruce. In this case the spruce is Sitka spruce, which forms a site series with mountain hemlock and reedgrass on fresh rich sites. Mainland sites formerly mapped as MHwh are being reevaluated.Allen Banner et al (2014). A Field Guide to Ecosystem Classification and Identification for Haida Gwaii. Land Management Handbook Number 68, page 80
Windward moist maritime (MHmm1) is dominated by mountain hemlock and Pacific silver fir. Yellow cedar places third in abundance and western hemlock becomes increasingly significant with decreasing elevation. Leeward moist maritime (MHmm2) has all of the windward tree species, plus subalpine fir.
Engelmann Spruce—Subalpine Fir (ESSF)