Yukon Interior dry forests
Kusawa, Yukon Territory, Canada Photograph by J. Peepre
The Yukon interior dry forests ecoregion lies chiefly within the Yukon Territory, with a minor element extending into extreme northwestern British Columbia, in Canada. The Yukon River is a principal catchment basin of the ecoregion. This taiga dominated ecoregion contains much of the human population in the Yukon, including parts of most major highways in the Yukon Territory.
The climate in this ecoregion in the Yukon interior can be characterized as cold and semiarid. Mean annual temperature is around -3°Celsius (C), mean summer temperature is 11°C, and mean winter temperature ranges between -16.5°C and -19°C. The southern portion of the ecoregion lies within the rain-shadow of the St. Elias Mountains. Mean annual precipitation is in the range of 225-400 millimetres (mm), increasing with elevation and in the northeast.
The Yukon Plateau is the dominant physiographic feature. It comprises groups of rolling hills and plateaus, separated by broad, but incised valleys. Elevations in this ecoregion are generally above 1000 metres (m) above mean seal level, with some smaller peaks in the south. Low ice-content permafrost occurs in a sporadic discontinuous pattern here, affecting some areas of microhabitat, but not others nearby.
Biological characteristics
Due to the severe climate of this ecoregion, coupled with history of recent pre-Holocene glaciation, there is a low species richness in the Yukon interior dry forests. With a total of only 175 vertebrate species present, there is an absence of reptiles and presence of only three amphibian taxa here.
Flora
White and Black Spruce (Picea glauca and P. mariana) form the dominant tree species. Lodgepole Pine (P. contorta) often invades arid sites and areas recently inflicted with wildfires. South-facing slopes at low elevations are often characterized by grassland communities. Scrub birch (Betula sp.) and willow (Salix spp. ) occur up to elevation of the tree line, which is usually defined by the presence of Sub-alpine Fir (Abies lasiocarpa).
In the colder alpine regions, Hooker's Eight-petal Mountain-avens (Dryas hookeriana), dwarf shrubs, forbs, grasses and lichens constitute the main vegetative cover. Due to the relatively dry interior climate, forests are frequently renewed from recurring natural fires such that young successional communities are most common. This ecoregion contains one of the most northern areas on the continent with grassland communities. The juxtaposition of these grasslands with northern boreal forest creates an unusual association of plant communities.
Mammals
Characteristic wildlife species include Caribou (Rangifer tarandus), Moose (Alces alces), Hoary Marmot (Marmota caligata); Mountain Goat (Oreamnos americanus), Stone’s and Dall’s sheep (Ovis dalli spp.), Grizzly and Black Bear (Ursus arctos and U. americanus), Gray Wolf (Canis lupus), Coyote (Canis latrans), American Beaver (Castor canadensis), Arctic Ground Squirrel (Spermophilus parryii) and hares (Lepus spp).
Columbia Spotted Frog. Source: Phil Myers/EoL Amphibians
There are three anuran species present in the Yukon interior dry forests: Columbia Spotted Frog (Rana luteiventris), a taxon that breeds in sedge fens and beaver ponds; Wood Frog (Lithobates sylvaticus), a water breeder that overwinters under logs or leaves; Western Toad (Anaxyrus boreas), a taxon in the northern limit of its range in this ecoregion. WWF had earlier asserted the Black Toad (Anaxyrus exsul) to occur in the ecoregion, but all other sources state the taxon only is found in the USA.
Birdlife
A number of avian species are found in the Yukon interior dry forests, including the Raven (Corvus corax), Ptarmigans (Lagopus spp.) and Golden Eagle (Aquila chrysaetos).
Conservation Status
Yukon interior dry forests: scene along a rare access road. @ C.Michael Hogan
Habitat Loss and Degradation
It is estimated that approximately 75 percent of the ecoregion remains intact. Most of the disturbed habitat is considered to be altered, with only a small amount of area heavily altered. Factors leading to habitat loss include forestry and mining activities, urban growth around Whitehorse, and major transportation corridors.
Remaining Blocks of Intact Habitat
Most of the ecoregion, particularly the higher elevation portions of the Yukon interior dry forests, can be considered as intact habitat. Valley bottoms are the units that have been most extensively developed for human settlement, roads, and resource exploitation.
Degree of Fragmentation
Habitat fragmentation in this ecoregion has principally resulted from the construction of major transportation corridors through the lower elevations. Susceptibility is high for some species with seasonal migrations or movements between habitat types, especially large carnivores such as the Gray Wolf, woodland caribou and Dall’s sheep.
Types and Severity of Threats
Threats to biodiversity are increasing rapidly in this ecoregion. Timber harvesting has begun and is yet to be well-regulated or planned in the Yukon. Mining activity is significant in some parts of the ecoregion and a number of wildlife species are in serious decline. A government-sanctioned wolf kill has been occurring in this area for the past few years; because of the large range of the Gray Wolf, actions of both Canada and the USA are important for the Gray Wolf in this ecoregion. There are administrative efforts in the USA promoted by the Obama administration as of 2013 to remove further protection of wolves; notably, the U.S. Fish and Wildlife Service has removed three experts from the Gray Wolf protection review panel, because these experts have spoken out in favor of continuing protection of the species.
Suite of Priority Activities to Enhance Biodiversity Conservation
- The highest priority activity is to establish a new protected area following the Kusawa Lake territorial park proposal.
- Ending control programs for taking of carnivores can be permanently ended in order to enhance robustness of the ecoregion.
Conservation Partners
- Canadian Nature Federation
- Canadian Parks and Wilderness Society, Yukon Chapter
- Friends of Yukon Rivers
- World Wildlife Fund Canada
- Yukon Conservation Society
Degree of Protection
There are no large protected areas yet established in this ecoregion.
- Charlie Cole Creek Ecological Reserve, southern Yukon Territory - 1.62 square kilometres (km2)
- Nisutlin River Delta National Wildlife Area (not fully protected), southern Yukon Territory - 5.28 km2
References
- William J. Cody. 2000. Flora of the Yukon Territory, National Research Press, ISBN 0-660-18110-X
- C. Michael Hogan. 2008. Black Spruce: Picea mariana, GlobalTwitcher.com, ed. Nicklas Stromberg, November, 2008
- Jean-Paul Pinard. 2007. Wind Climate of the Whitehorse Area. ARCTIC 60 (3): 227–237.
- R.F. Powers, M.B. Adams, J.D. Joslin, J.N. Fisk. 2005. Non-Boreal Coniferous Forests of North America. In Andersson, F. Coniferous Forests (1st ed.). Amsterdam: Elsevier. ISBN 9780444816276.
- Kirsten Stade. 2013. Gray Wolf Peer Review Panel Purged by Agency: U.S. Fish and Wildlife forces contractor to axe scientists due to sign-on letter. Public Employees for Environmental Responsibility (PEER)
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