Western Canada can be divided into four major geographical areas: the Pacific coast, the mountainous interior, the plains of Alberta, and the arctic. Within each of these four main areas are distinct vegetation zones, the boundaries of which are determined by factors such as precipitation, latitude, and altitude.
Coastal regions that receive more than 1,000 millimeters (40 inches) of rain annually are dominated by temperate rainforest—predominantly evergreens. Just 0.02 percent of the world’s land area is temperate rainforest and a full 25 percent of this amount is located in British Columbia. Coastal forest is mostly hemlock, western red cedar, Sitka spruce, and, in drier coastal areas, Douglas fir.
The Queen Charlottes’ rainforest is thickly covered in spongy, pale green moss, which grows alongside coastal Douglas fir. In the region’s subalpine areas you’ll find mountain hemlock.
With vast elevation changes, naturally the flora is diverse, ranging from the cacti of Canada’s only desert in the Okanagan Valley to the equally hardy flowering plants that cling to glaciated peaks, coming alive with color for a few short weeks of summer.
The montane forest holds the greatest diversity of life of any vegetation zone and is prime winter habitat for larger mammals. But this is also where most development occurs and therefore the habitat is often much changed from its natural state.
In the southern portion of interior British Columbia, valleys are cloaked in montane forest to an elevation of about 1,500 meters (4,900 feet). Drier and south-facing areas support a mixture of Douglas fir and ponderosa pine in the south-central region.
Farther east in the Canadian Rockies, aspen, balsam poplar, and white spruce thrive. Englemann spruce take hold at higher elevations and to the north. Lodgepole pine is common throughout. The first species to appear after fire, its seed cones are sealed by a resin that is melted only at high temperatures. When fire races through the forest, the resin melts and the cones release their seeds. Large tracts of fescue grassland are common in the very driest areas.
Subalpine forests occur where temperatures are lower and precipitation higher than in the montane. In the Canadian Rockies, this is generally 1,500–2,200 meters (4,900–7,200 feet) above sea level. In the southern interior of British Columbia, it begins (and ends) at higher elevations. The upper limit of the subalpine zone is the treeline. The climax species are Engelmann spruce and subalpine fir, although as in the montane, extensive forests of lodgepole pine occur in areas that have been scorched by fire in the last 100 years.
At higher elevations, stands of larch are seen. Larches are deciduous conifers. Unlike other evergreens, their needles turn a burnt-orange color each fall, producing a magnificent display for photographers.
The alpine zone extends from the treeline to mountain summits. The upper limit of tree growth south of the 60th parallel varies between 1,800 and 2,400 meters (5,900–7,900 feet) above sea level, dropping progressively to the north until it meets the treeless tundra of the Northwest Territories. Vegetation at these high altitudes occurs only where soil has been deposited. Large areas of alpine meadows burst with color for a short period each summer as lupines, mountain avens, alpine forget-me-nots, avalanche lily, moss campion, and a variety of heathers bloom.
East of the Canadian Rockies, the mountains dramatically give way to seemingly endless plains. Although the average elevation is 1,000 meters (3,300 feet) above sea level, the land is incredibly flat; in the southeast corner of Alberta, the Cypress Hills rise 500 meters (1,600 feet) above the surrounding land, yet are the highest point between the Canadian Rockies and Labrador, 5,000 kilometers (3,100 miles) distant. While it certainly isn’t obvious at first, the plains are made up of the following three vegetation zones.
Southern Alberta is dominated by prairie, the warmest and driest of Canada’s ecological zones. The land is flat, open grassland, with trees supported only where water flows. Along most waterways, cottonwood, aspen, and poplar provide welcome shade for larger mammals (including Homo sapiens) while willows clog riverbanks. Water from these rivers is pumped up from the valley floors and diverted by canals across the prairies, making widespread agriculture possible. Native grasses such as rough fescue and grama survive without a helping hand. Amid the seemingly desolate landscape, colorful flowers such as the wild rose can be found.
Unique to Canada, this area is a transition zone between the prairie grassland to the south and the boreal forest to the north. As the name suggests, trembling aspen (named for light, flattened leaves that “tremble” in even the slightest wind) is the climax species, but much of this zone has been given over to agriculture. Best known for it mammal populations, Elk Island National Park is one of the few remaining areas of this unique habitat.
Technically, the boreal forest, cutting a wide swath across western Canada, is part of the “plains.” Encompassing almost half of Alberta and continuing into northern British Columbia and the two territories, the landscape is certainly flat. But it’s also heavily treed. Only a few species of trees are able to adapt at these northern latitudes. In the southern part of the boreal forest, aspen and balsam poplar dominate.
Farther north, conifers such as white spruce, lodgepole pine, and balsam fir are more common, with jack pine growing on dry ridges, and tamarack also present. The entire forest is interspersed with lakes, bogs, and sloughs, where black spruce and larch are the dominant species. In drier, upland areas the lush undergrowth is home to raspberries, saskatoons, and buffalo berries. To the north, where drainage is generally poor, the ground cover is made up of dense mats of peat.
The Treeline and Beyond
The treeline is a convoluted line that designates the northernmost extent of tree growth. It occurs below the 60th parallel in Eastern Canada, crossing the Arctic Circle some 500 kilometers (300 miles) north of Yellowknife before running along the top of the continent and into Alaska. It varies in latitude due to elevation—as a generalization it begins farther north as latitude descends.
The treeline is not a line of trees as the name might suggest, but a transition in vegetation types (sometimes called taiga) that may be up to 100 kilometers (62 miles) wide. Where trees do grow in this transition, they are predominantly evergreens of the boreal forest, and because of little precipitation and a short growing season (70–80 frost-free days annually), are almost always stunted. Black spruce, white spruce, jack pine (the most northerly of the pines), and aspen are the most common trees found here. White birch is the only deciduous tree able to withstand the region’s climate.
Above the treeline, in an area of continuous permafrost, is the arctic biome—the tundra. Here a unique selection of vegetation has successfully adapted to the region’s extreme seasonal changes of temperature and sunlight, as well as to its lack of precipitation (less than the Sahara Desert). Where water and wind have deposited soil, usually in depressions or along the banks of rivers, the vegetation is more varied.
Almost all plants are perennials, able to spring to life quickly after a winter of hibernation. Brightly colored flowers such as yellow arctic poppies, purple saxifrage, pink rhododendrons, and white heather carpet entire landscapes during the short summer. Willows are one of the few woody plants to survive on the otherwise treeless tundra; they’re found across the Arctic mainland along with ground birch and Labrador tea.
Other areas are almost completely devoid of soil, supporting little more than arctic ferns, lichens, and mosses. Low temperatures here restrict bacterial action, and as a result, the soil is lacking in the nitrogen necessary for plant growth. Occasional oases of lush vegetation mark spots where the soil received a nitrogen boost—as from a rotting animal carcass or the detritus of an ancient Inuit campsite.
© Andrew Hempstead, from Moon Western Canada, 3rd Edition