Wildlands

Wetlands

The refuge includes three major topographic features: the Yukon Flats at the center, the surrounding uplands, and the encircling highlands. The Yukon Flats, consisting of 6.5 million acres, consists of mostly flat to undulating lowlands dotted with shallow lakes, sloughs, and meandering and braided streams. Elevation is about 300 feet in the west and 600 to 900 feet in the north and east. The Yukon River is the principal drainage, dropping only 200 feet in elevation in 300 miles as it meanders across the Yukon Flats. The lower stretches of the Yukon’s tributaries are intricately braided streams with meandering channels, swelling in flood stage to cover vast areas.

Surrounding Uplands
The Yukon Flats are surrounded by uplands consisting of river terraces, alluvial fans, and flood plain deposits that rest on bedrock. It’s overall topography is gently rolling. Elevations do not generally exceed 1,200 to 1,300 feet.

Mountains
Encircling the entire Yukon Flats and its uplands are highlands and mountains. The Porcupine Plateau, an area of low ridges with gentle slopes and rounded-to-flat summits, lies along the northern and eastern boundary of the refuge. Elevations reach to 2,500 feet. The Chandalar, Sheenjek, and Coleen rivers drain the northern portion of the plateau; the Black and Little Black rivers, which originate in the Ogilvie Mountains southeast of the refuge, drain the area south of the Porcupine River. Along the western boundary of the refuge are the Hodzana Highlands, an area of 4,000-foot ridges drained by the Hadweenzic, Hodzana, and Dall rivers. The eastern Brooks Range lies north of the Hodzana Highlands and the Porcupine Plateau and is north of the refuge boundary. Bounding the Yukon Flats to the south are the Yukon–Tanana Uplands, of which the White and Crazy mountains are the northern extension. Summits in the White and Crazy mountains range from 3,000 to 4,100 feet in elevation. Birch and Beaver creeks are the major drainages on the northern side of the mountains.

View Physical Features Map (pdf)

Land Ownership
The refuge boundary encloses approximately 8,630,000 acres of federal lands and an additional 2,500,000 acres of selected and conveyed lands. The non-refuge lands belong to Doyon Regional Corporation, the villages of Beaver, Birch Creek, Chalkyitsik, Circle, Fort Yukon and Stevens Village, State of Alaska, and individual Native allotment holders.

View Land Ownership Map

Habitat
The predominant land cover type on the Yukon Flats National Wildlife Refuge is a mixture of open spruce forests, shrubs, and bogs. This ecoregion extends from the Yukon Flats eastward into Canada’s Old Crow basin. A southern portion of the refuge is classified as part of the Yukon-Tanana Uplands, and is characterized by sparse vegetation and coarse and fine rubble. Several factors influence the overall complexity of refuge habitats including: wildland fire, sediment deposition during periodic flooding, a braided drainage system, and discontinuous permafrost.

Trees
Forests predominate at lower elevations with timberline at 2,300 to 3,000 feet (700 to 900 m). Forest vegetation is characterized by five common tree species. Picea glauca (white spruce) reaches its optimum growth adjacent to stream channels, but is also found on a diversity of sites up to treeline. Picea mariana (black spruce) typically grows in open stands and is common on sites with restricted drainage, such as muskeg and north-facing slopes (usually with a shallow thaw zone). Betula papyrifera (white birch) is characteristically an upland species, and often occurs mixed with white spruce. Populus tremuloides (quaking aspen) predominates on well to extremely well drained south-facing slopes, while Populus balsamifera (balsam poplar) is primarily a riparian species forming forest communities often associated with Picea glauca.

Shrub communities
Shrub communities of Salix spp. (willow) and Alnus spp. (alder) are most abundant on riparian sites. Dwarf shrubs, Betula nana (dwarf birch), Ledum palustre (Labrador tea), Empetrum nigrum (crowberry), Vaccinium uliginosum (blueberry), and Dryas octopetala (mountain avens), are common above timberline. Dwarf shrubs, such as Chamaedaphne calyculata (leatherleaf) and Andromeda polifolia (bog rosemary), are typical of poorly drained organic soil, while others like Rosa acicularis (prickly rose), Viburnum edule (highbush cranberry), and Shepherdia canadensis (soapberry) are characteristic of well drained mineral soils in forests.

If you are interested in the diversity of willow species in interior Alaska, see the willow guide published in 2004 by the U.S. Fish and Wildlife Service and others. The Willows of Interior Alaska (pdf) is the result of an investigation to determine willow species and their distribution in Alaska. To obtain a hard copy of this guide contact us.

Herbaceous plants
Herbaceous plants, Eriophorum vaginatum (sheath cottongrass) and Carex bigelowii (Bigelow sedge), are most abundant in dwarf shrub-graminoid tussock tundra. Herbs also predominate as emergents on pond or lake margins – Carex aquatilis (water sedge) and Equisetum fluviatile (water horsetail) – and as aquatics such as Nuphar spp. (pond lily) and Potamogeton spp. (pondweed). Steep, treeless, south-facing bluffs often support Artemisia spp. (sagebrush) and Pulsatilla patens (pasque flower).

Last updated: July 22, 2008