Ogilvie-Mackenzie alpine tundra

• Category: Grassland, Tundra, and Human Biomes.
• Geographic Location: North America.
• Summary: This biome is home to the unique Ogilvie mountain lemming, and is a distinctive combination of ecozones with diverse terrains.

The Ogilvie-Mackenzie Alpine Tundra biome is located in a mountainous band from the Alaska-Yukon border southeastward to the border of the Yukon-Northwest Territories. This taiga-cordillera region corresponds in the north to the North Ogilvie Mountains, the Mackenzie Mountains running east to west through the Yukon, and southward to the Selwyn Mountains of the Northwest Territories (NWT). The northern part extends across a section of the Ogilvie and Wernecke mountains and the connected intermontane basins.

The middle section includes the westernmost parts of the Ogilvie and Wernecke mountains, the Backbone Ranges of the interior, and the Canyon Ranges of the east. The southern region lies in the rain shadow of the Selwyn Mountains. On the Yukon-NWT border is a mountainous area that includes the Selwyn and the southern portion of the Mackenzie Mountains. The Ogilvie-Mackenzie Alpine Tundra is predominately a wilderness area with no permanent settlements.

The biome is classified as tundra; it spans 80,500 square miles (208,400 square kilometers) and features a continental sub-Arctic climate. This type of climate has long, cold winters and short, cool summers. The average annual temperature of the Ogilvie-Mackenzie Alpine Tundra ecoregion is around 27 degrees F (minus 3 degrees C). Winter temperatures range from minus 3 to minus 7 degrees F (minus 19 to minus 22 degrees C), while the average summer temperature is 48 degrees F (9 degrees C). In the winter, frigid temperatures of minus 58 degrees F (minus 50 degrees C) are common. Annual precipitation ranges from 12 to 30 inches (30 to 75 centimeters), with the higher elevations receiving significantly more precipitation.

The Ogilvie-Mackenzie Alpine Tundra biome is composed of a diverse collection of terrains that range from rounded and flat-top hills, to extremely rugged and steep mountainous areas, to alpine and glacial valley areas. Portions of the Ogilvie and Wernecke mountains are unglaciated here. The valleys and river bottoms are V-shaped in the unglaciated areas, and U-shaped in areas carved out by glaciers.

The tundra is covered predominately by sub-Arctic and subalpine coniferous forests, followed by Arctic-alpine tundra and rocklands, with the smallest area being lakes and wetlands. Most of the terrain of the northern part of the region lies from 3,000 to 4,400 feet (900 to 1,350 meters) elevation. Moving in a southeastern direction, several peaks reach 6,890 feet (2,100 meters), with the highest elevation being Mount Keele—9,678 feet (2,950 meters)—in the Selwyn Mountains. The North Ogilvie and Mackenzie Mountains have continuous permafrost, while the Selwyn Mountains region has irregular, patchy, low-ice-content permafrost.

Flora and Fauna

The Ogilvie-Mackenzie Alpine Tundra biome is characterized by Arctic-alpine tundra at higher elevations and subalpine-sub-Arctic coniferous forests at lower elevations. Tree species include paper birch, balsam fir, trembling aspen, balsam poplar, lodgepole pine, dwarf birch, and willows (blue-green and net-veined). Alpine fir, black and white spruce, and dwarf birch are commonly stunted, crooked, bent, and twisted (sometimes called krummholz). Much of the alpine and talus slopes are devoid of vegetation.

Existing vegetation consists of: lichens (fruticose, crustose, rock tripe, and reindeer), herbs (alpine blueberry, lupine, osha, mountain tobacco, horsetail, and northern Labrador tea), moss (feather and peat), forbs (entire-leaf mountain-avens, three-toothed saxifrage, and naked-stem wallflower), saxifrages (prickly, purple, and yellow mountain), ericaceous shrubs (Arctic bell-heather, white dryas, mountain bearberry, and bog cranberry—dwarfed in alpine regions), and sedge. Cottongrass is common in wetter areas and at higher elevations. All vegetation is vulnerable to frost at any time.

Most of the fauna found in this region are at their northern range limit. Amphibians here are the wood frog, western toad, and striped chorus frog. There are no reptiles. Common mammals include Dall’s sheep, moose, mountain goats, and mule deer. Caribou herds are found in this region, such as the northern mountain woodland caribou and Yukon’s only boreal caribou. Predators common to the area are wolverines, grizzly and black bears, red foxes, wolves, lynxes, and martens.

A unique mammal, that may be the only one exclusive to the Yukon, is the Ogilvie mountain lemming. Other small animals include Arctic ground and northern flying squirrels, beavers, hares (snowshoe and tundra), American and collared pikas, short-tailed weasels, hoary marmots, bushy-tailed wood rats, mice (meadow jumping and deer), least chipmunks, singing voles, and bats (little brown myotis).

An abundance of avian species makes the region home, such as sparrows (Lincoln, violet-green, cliff, chipping, and Savannah), dark-eyed juncoes, pine grosbeaks, white-winged crossbills, Alder flycatchers, blackpolls, snow buntings, wandering tattlers, horned larks, gray-crowned rosy finches, Townsend’s solitaires, water and American pipits, warblers (tree and yellow), rusty blackbirds, flycatchers (olive-sided and yellowbellied), and thrushes (varied, northern water gray-cheeked, and Swainson).

Year-round residents include common ravens, ptarmigans (rock, willow, and the rare white-tailed), gray jays, and chickadees (black-capped and boreal). Common birds of prey are great horned and short-eared owls, bald and golden eagles, American kestrels, peregrine falcons, Northern harriers, and gyrfalcons.

Waterfowl can be found in the low elevations near lakes and rivers, and in the limited wetlands. These are summer breeding and nesting areas for waterfowl species such as Canada geese, northern pintails, trumpeter swans, loons (common, Pacific, and red-throated), mergansers (common and red-breasted), horned grebes, American widgeons, surf scoters, Northern shovelers, ducks (mallard, long-tailed, and harlequin), scaups (greater and lesser), green-winged teals, and Barrow’s goldeneyes.

Human Impact

Land use in the Ogilvie-Mackenzie Alpine Tundra area consists mostly of big game, sport, and subsistence hunting and trapping; as well as tourism, recreational activities, and natural resource exploration. The area is considered to be 86 percent intact. Just 13 percent of the ecoregion is protected. Protected areas include Nahanni National Park Reserve, Nááts'ihch'oh National Park Reserve, and Ni'iinlii'njik Territorial Park. Threats to the area are mainly in the form of mining and increased road-building connected to natural resource development. Roads damage the fragile vegetation, as well as open the area to multiple human activities. Beyond the road-system areas, disturbance to the area is minimal.

Bibliography

Benke, Arthur C., and Colbert E. Cushing, eds. Rivers of North America. Maryland Heights, MO: Academic Press, 2005.

Noss, Reed. "Ogilvie-Mackenzie Alpine Tundra." One Earth, 2022, www.oneearth.org/ecoregions/ogilvie-mackenzie-alpine-tundra/. Accessed 4 Dec. 2024.

Reilly, Michael. “Arctic Tundra Holds Global Warming Time Bomb.” Discovery News, August 25, 2008.

Ricketts, T., E. Dinerstein, D. Olson, C. Loucks, W. Eichbaum, and D. DellaSalla, et al. Terrestrial Ecoregions of North America: A Conservation Assessment. Washington, DC: Island Press, 1999.

Smith, S. et al. “Ogilvie-MacKenzie Alpine Tundra.” WWF, www.worldwildlife.org/ecoregions/na1116. Accessed 4 Dec. 2024.