Biogeoclimatic zones of British Columbia

The biogeoclimatic zones of British Columbia are a classification system used by the British Columbia Ministry of Forests for the Canadian province's many different ecosystems. The classification system 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 American Environmental Protection Agency (EPA). The system of biogeoclimatic zones was partly created for the purpose of managing forestry resources, but is also in use by the British Columbia Ministry of Environment 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."^[1][2]

The biogeoclimatic zones of British Columbia are:

Alpine Tundra

Alpine Tundra in the Coast Range, near Whistler Mountain

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: in the southwest it starts at 1,600 metres (5,200 ft), in the southeast, 2,250 metres (7,380 ft), in the north from 1,500 metres (4,900 ft), and in the northwest it can start as low as 1,000 metres (3,300 ft).^[3] 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 0 °C (32 °F) to 4 °C (39 °F), and even in summer the average temperature does not exceed 10 °C (50 °F). The zone sees heavy precipitation, usually in the form of snow.^[3]

Trees 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 see a larger variety of plant species. Higher elevations are exclusively the realm of the lichens.^[3]

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.^[3]

Spruce—Willow—Birch

Found only in the north of the province, this zone occurs in the sub-alpine of the Interior Mountains.^[4]

White spruce is the most abundant conifer in the Spruce-Willow-Birch (SWB) zone, except at the upper (parkland) elevations, where subalpine fir dominates. Engelmann spruce and hybrid white × Engelmann spruce is a primary feature distinguishing the SWB from the more southerly ESSF zone.

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).^[5]

Boreal White and Black Spruce

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).^[5]

Sub-Boreal Pine—Spruce

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 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).^[5]

Sub-Boreal Spruce

Interior spruce (mostly hybrid white × Engelmann, with some pure white spruce) is dominant throughout 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).^[5]

Engelmann Spruce—Subalpine Fir

Over most of southern British Columbia, spruce dominates the canopy of mature stands in the Engelmann Spruce-Subalpine Fir (ESSF) zone, while subalpine fir is most abundant in the understorey. At higher elevations, particularly in the north and in wet, heavy snowfall areas, subalpine fir dominates and spruce is a minor component. In southern British Columbia, the spruce is pure Engelmann, but white spruce characteristics become increasingly evident northward, first only at lower elevations, then at all elevations. At the northern limits of the ESSF, Engelmann spruce characteristics are rare.

Subalpine fir is ubiquitous in the ESSF and is the most common associate of spruce throughout. Lodgepole pine is the most common seral species. Deciduous species, such as trembling aspen, paper birch, and black cottonwood, are present but uncommon. Whitebark pine and, in southeastern British Columbia only, limber pine and alpine larch occur in association with spruce, especially in the driest ecosystems, usually at high elevations, where spruce is not abundant. At low elevations in the ESSF, associates of spruce are Douglas-fir, western redcedar (Thuja plicata), western hemlock (Tsuga heterophylla) and western white pine. Mountain hemlock and amabilis fir (Abies amabilis) are also found with spruce in the ESSF, principally adjacent to the Mountain Hemlock Zone. The dominant plant community in the ESSF has an understorey of ericaceous shrubs, mainly Rhododendron albiflorum, Vaccinium membranaceum, and Menziesia ferruginea, with Vaccinium ovalifolium in high-precipitation areas and V. scoparium in dry areas. Ribes lacustre, Oplopanax horridus and Lonicera involucrata are common shrubs on moist to wet sites. Herbs characteristic of the ESSF forest include Valeriana sitchensis, Gymnocarpium dryopteris, Rubus pedatus, Streptopus roseus, Veratrum viride, Athyrium filix-femina, Cornus canadensis, Lycopodium annotinum, Tiarella spp. and Arnica cordifolia. Dominant bryophytes are Pleurozium schreberi, Dicranum spp., and Barbilophozia spp. Lichens are abundant on the forest floor and include Peltigera spp., Nephroma arcticum, and Cladonia spp. At the upper parkland elevations of the ESSF, closed forest and tree islands of spruce and subalpine fir are interspersed with moist herb meadows and drier ericaceous heath. The meadows typically include the herbs: Valeriana sitchensis, Veratrum viride, Senecio triangularis, Lupinus arcticus, Thalictrum occidentale, Epilobium angustifolium, Pedicularis bracteosum, Castelleja miniata, Erigeron peregrinus, Carex spp. and Luzula spp. Subalpine heath includes Empetrum nigrum, Cassiope mertensiana, C. tetragona, Phyllodoce empetriformis, P. glandulifera, and Vaccinium caespitosum (Coates et al. 1994).^[5]

Montane Spruce

Overlooking Browne Lake on a Calm Rainy Morning in Late Autumn

Occurs at mid elevations in the south and central interior in the lee of the coast mountains. Climate characterized by cold winters and short warm summers. Dominated by Engelmann spruce and Subalpine Fir. Provides important summer and fall habitat for deer and moose and important winter habitat for mountain caribou.^[4]

Ponderosa Pine

White spruce or white × Engelmann hybrids are found only rarely within the Ponderosa Pine (PP) zone, and occur in cool, moist, sheltered situations, e.g., steep, north-facing canyon headwalls (Coates et al. 1994).^[5]

Interior Douglas-fir

Hybrid Engelmann × white spruce is secondary to Douglas-fir, and occurs mainly in wetter subzones and at higher elevations transitional to the Montane Spruce, Sub-Boreal Spruce, and Engelmann Spruce–Subalpine Fir Zones.

The most common associate of spruce is Douglas-fir, which dominates the zone. Lodgepole pine is abundant in the Interior Douglas-fir (IDF) zone but tends to be present only in small amounts on the wetter spruce sites. Western redcedar, western larch, and grand fir (Abies grandis) occur together with spruce, particularly in the southeastern part of the zone. Trembling aspen, paper birch, and black cottonwood are common seral species. Mixed shrub or horsetail-dominated plant communities are typical of moist, rich ecosystems that include spruce. Common shrub associates include: Ribes lacustre, Lonicera involucrata, Cornus sericea, Rosa acicularis, Symphoricarpos albus and Acer glabrum. The well-developed herb layer contains Linnaea borealis, Cornus canadensis, Aralia nudicaulis, Actaea rubra, and Osmorhiza chilensis, together with Equisetum and Carex spp. on wetter sites. Bog forests with Sphagnum spp., Ledum groenlandicum, and Gaultheria hispidula are infrequent but usually have a tree canopy of pure spruce (Coates et al. 1994).^[5]

Coastal Douglas-fir

Coastal Douglas fir is often predominant is Southern Coastal British, particularly on Eastern Vancouver Island, The Gulf Islands, and the Sechelt Peninsula. It is often located to artbutus trees in the Gulf Islands, and is the Climax species for this biome, largely a "Csb" Cool Dry-Summer Mediterranean, sometimes call "Sub Mediterranean" climate zone.

Interior Cedar—Hemlock

Interior spruce is a common secondary component of Interior Cedar-Hemlock (ICH) forests. It is most abundant in the northern and eastern parts of the zone, close to the Sub-Boreal Spruce Zone, or at high elevations bordering the Engelmann Spruce–Subalpine Fir Zone. It is least abundant in drier parts of the ICH. White spruce, Engelmann spruce, and their hybrids are all present, Engelmann spruce dominating in southeastern British Columbia, particularly at high elevations, and white spruce dominating in the north. In the coast–interior transition of northwestern British Columbia, interior spruce hybridizes with Sitka spruce.

The ICH has a greater diversity of tree species than any other interior zone. Western hemlock and western redcedar are the climax dominants, and interior spruce often accompanies them as a secondary component. Subalpine fir is a major associate to the north. Black cottonwood, lodgepole pine, trembling aspen, and paper birch are found with spruce in seral communities throughout most of the zone. In the central and southern ICH, spruce may also occur in association with Douglas-fir, western larch, western white pine, and grand fir. A typical spruce or redcedar–spruce stand on a seepage ecosystem has a diverse shrub layer dominated by Oplopanax horridus, Ribes lacustre, Cornus sericea, Acer glabrum, Rubus parviflorus, Viburnum edule, and Lonicera involucrata. Characteristic herbs include Gymnocarpium dryopteris, Athyrium filix-femina, Tiarella unifoliata, Viola glabella, Circaea alpina, Streptopus spp., Osmorhiza chilensis, Dryopteris assimilis, and Actaea rubra. On swampier sites, Lysichiton americanum, Equisetum spp., and Rhytidiadelphus triquetrus and Hylocomium splendens are found. Seral communities on mesic sites in the north of the ICH have a mixed overstorey of spruce, subalpine fir, lodgepole pine, paper birch, and trembling aspen. Typical shrubs are: Rubus parviflorus, Viburnum edule, Rosa acicularis, Paxistima myrsinites, Amelanchier alnifolia, Shepherdia canadensis, Alnus viridis, and Vaccinium membranaceum. Major herbs include: Cornus canadensis, Clintonia uniflora, Aralia nudicaulis, Lathyrus nevadensis, Rubus pubescens, Smilacina spp., Orthilia secunda, Osmorhiza chilensis, and Petasites palmatus. The moss carpet is dominated by Rhytidiadelphus triquetrus, Ptilium crista-castrensis, Pleurozium schreberi, and Hylocomium splendens (Coates et al. 1994).^[5]

See also

• List of forest regions and districts of British Columbia

References

• Biogeoclimatic zones of British Columbia (map), BC Ministry of Forests website

External links

• Web Atlas: Biogeographic Zones of British Columbia, Simon Fraser University Geography Dept.