Habitat

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(Adam Grimm/ USFWS)

The Yukon Flats has a subarctic climate characterized by seasonal extremes of temperature and daylight. The refuge includes three major topographic features: the Yukon Flats at the center, the surrounding uplands, and the encircling highlands. The Yukon River bisects the refuge, sculpting the alluvial plain that’s known for its abundance of waterfowl during the summer breeding season.


The Yukon Flats

The Yukon Flats span about half of the refuge’s total area and consist of mostly flat to undulating lowlands dotted with shallow lakes, sloughs, and meandering and braided streams. The majestic Yukon River is the dominant feature of this landscape, dropping only 200 feet in elevation as it meanders 270 miles across the Flats. The lower stretches of the Yukon’s tributaries are intricately braided streams with meandering channels, swelling with spring floods to cover vast areas and replenishing the region’s lakes, ponds, and marshes. These spring floods maintain the area’s high value as productive habitat for migratory waterfowl and other wildlife.

Surrounding Uplands and Highlands

The uplands surrounding the Yukon Flats begin as a long slope gradually rising between 150 and 600 feet to the base of the encircling highlands. The uplands and highlands each make up about 25% of the refuge’s area. The northern and eastern boundaries of the refuge feature the Porcupine Plateau, an area of low ridges with gentle slopes and rounded-to-flat summits reaching 2,500 feet at peak elevation. Along the western boundary of the refuge are the Hodzana Highlands, an area of 4,000-foot ridges. Beyond the refuge boundary lays the Brooks Mountain Range to the north of the Hodzana Highlands and the Porcupine Plateau. Bounding the Yukon Flats to the south are the Yukon–Tanana Uplands and the White and Crazy mountains.

Vegetation

A mixture of open spruce forests, shrubs, and bogs dominate the Yukon Flats National Wildlife Refuge. The refuge has a short growing season, averaging 81 days at Fort Yukon. Despite this, lush vegetation quickly populates the Flats in summer due to long hours of daylight and warm temperatures. When winter draws to a close and the Flats warm, the previous year’s vegetation rapidly decomposes, providing essential nutrients for new vegetation to flourish. Although the refuge experiences low levels of precipitation, plenty of water is available during the short growing season because of snowmelt, spring flooding, low evaporation rates, and the fact that the permanently frozen subsoil does not absorb excess water.

Fire on the Yukon Flats is essential to maintaining healthy plant and wildlife communities. The Yukon Flats boreal forest is an excellent example of a fire-dependent ecosystem that experiences repetitive, long-term cycles of burning and regeneration. Disturbance by fire maintains a diversity of plant species by interrupting natural succession and preventing the landscape from being dominated by climax species. The most common source of fire on the Yukon Flats is lightening. Combined with low precipitation, high summer temperatures, and the presence of highly flammable fuel, lightening commonly ignites wildland fires that can burn several hundred thousand acres at a time.

View a Physical Features Map

Learn More about the Willows of Interior Alaska

Learn More about Managing Fire on the Yukon Flats

Learn More about Weather on the Yukon Flats