This ecoregion encompasses much of south-central Yukon and a part of east-central Alaska. There are a number of disjunct outliers of this ecoregion in central Alaska.
The ecoclimate of this ecoregion can be described as a combination of alpine, subalpine and boreal northern Cordilleran. The region experiences short cool summers (mean temperature 10°C to 10.5°C), and long, cold winters (mean temperature -20°C to -23°C), but there is great variation about monthly means. The coldest temperature in North America (-63°C) was officially recorded in this ecoregion on the Kluane Plateau. Mean annual precipitation is lowest in the valleys within the rain shadow of the coastal ranges (less than 300 mm) and increases in the interior ranges and plateaux (up to 600 mm) (ESWG 1995).
This ecoregion contains mountain ranges with many high peaks, and extensive, rolling to undulating hills and plateaus, moderately to deeply incised. These ranges are separated by wide valleys and lowlands, whose topography ranges from level to undulating. Almost all of the area was affected by glaciation. Most of the region lies between 900 m and 1500 m asl, with peaks reaching between 2100 m and 2400 m in elevation. Permafrost is common in many parts of the ecoregion, particularly in the north and at higher elevations, but becomes more sporadic and discontinuous to the southwest toward the coast (ESWG 1995) .
White and black spruce (Picea glauca and P. mariana) form the most common forest types, usually within a matrix of aspen (Populus tremuloides) or dwarf willow (Salix spp.), birch (Betula spp.) and ericaceous (Ericaceae) shrubs. These forests are usually open and extensive. Black spruce-scrub willow-birch are dominant in poorly drained sites, particularly in the lowlands, and black spruce, willow and paper birch (Betula papyrifera) prevail on slopes underlain by permafrost. Balsam poplar (P. balsamifea) occur on some floodplains. Lodgepole pine (Pinus contorta) and alpine fir (Abies lasiocarpa) are also present, depending on time since disturbance and local conditions. At the higher elevations, sparsely vegetated alpine and subalpine communities consist of mountain avens (Dryas hookeriana), dwarf willow, birch, ericaceous shrubs, graminoid species (Gramineae and Cyperaceae) and mosses (ESWG 1995).
Characteristic wildlife include caribou (Rangifer tarandus), grizzly and black bear (Ursus arctos and U. americanus), Dall’s sheep (Ovis dalli), moose (Alces alces), beaver (Castor canadensis), red fox (Vulpes fulva), wolf (Canis lupus), hare (Lepus spp.), common raven (Corvus corax), rock and willow ptarmigan (Lagopus mutus and L. lagopus), and golden eagle (Aquila chrysaetos) (ESWG 1995).
Significant ecological phenomena include some possible Beringia floristic elements on south-facing, low-elevation slopes along the Yukon River valley. Parts of the ecoregion represent unglaciated terrain, while unique periglacial landforms exist in some of the uplands.
Habitat Loss and Degradation
Approximately 85 percent of this ecoregion was estimated to remain intact. Mining and road development are the primary human factors contributing to habitat loss. In parts of the ecoregion, valley bottoms, which contain the most productive habitats, have been significantly altered by mining activities. In fact, most of the 15 percent habitat loss in this ecoregion represents degradation of valley bottoms.
Remaining Blocks of Intact Habitat
Large blocks of intact habitat remain, although these increasingly have roads dissecting them.
Degree of Fragmentation
Much of the ecoregion (in Yukon) is taiga and boreal forest. Alpine areas are disjunct, although this is the natural condition. Roaded valleys are more problematic as these create barriers or interfere with seasonal movement of large mammals.
Degree of Protection
There are no protected areas in the Yukon, but the following areas exist in Alaska:
•Yukon-Charley Rivers National Preserve - eastern Alaska
•Streese National Conservation Areas - eastern Alaska
•White Mountains National Recreation Area - eastern Alaska
•Arctic National Wildlife Refuge -small part of the northeastern portion of the ecoregion in Alaska
Note: Many of the upland (alpine) outliers in this ecoregion in western Alaska are not protected and are not part of the lowland preserves surrounding them.
Types and Severity of Threats
Mining continues to expand and there is already a small amount of logging in the southwestern (Yukon) portion of the ecoregion with possible plans to increase logging of these northern forests.
Suite of Priority Activities to Enhance Biodiversity Conservation
•Recovery of ’40 Mile’ and ‘Aistiakik’ caribou herds
•Upgrade protection standards of the MacArthur Game Sanctuary (Yukon) to exclude mineral exploration and mining.
•Establish Wellesley Lake candidate protected area.
•Canadian Arctic Resources Committee
•Canadian Nature Federation
•Canadian Parks and Wilderness Society, Yukon Chapter
•Friends of Yukon Rivers
•World Wildlife Fund Canada
•Yukon Conservation Society
Relationship to other classification schemes
The Interior Yukon/Alaska Alpine Tundra includes the Klondike Plateau, the Ruby Ranges, and the Yukon Plateau-North (TEC 172, 174 and 176) (Ecological Stratification Working Group 1995). This region includes Central and Eastern Yukon and Kluane Boreal forest regions ( 26a, b and c) and Tundra vegetation (Rowe 1972).
Prepared by: S. Smith, J. Shay, J. Peepre, K. Kavanagh, M. Sims, G. Mann.