Ahklun Mountains, 16,700 mi2 (43,300 km2)
Land-surface form.--Groups of rugged steep-walled mountains with sharp summits 2,000-5,000 ft (600-1,500 m) high, separated by broad flat valleys and lowlands, rise abruptly above the lowlands and low hills to the north and east. The mountains consist of strongly deformed sedimentary and volcanic rocks, with some bodies of schist. There are many narrow glacial lakes in U-shaped canyons. A few small cirque glaciers are found at the highest elevations.
Climate.--The marine-phase tundra climate (described above for the Bering Tundra [Southern] Province) is characterized by cold winters and cool, short summers. Average daily temperatures range from a minimum of 3F (-16C) to a maximum of 18F (-8C). Mean summer temperatures have daily lows around 46F (8C) and highs around 61 to 66F (16 to 19C). Annual precipitation ranges from 39 in (1,000 mm) in the lowlands to over 78 in (2,000 mm) in the higher mountains, with a pronounced summer maximum. Average annual snowfall ranges from 78 to 196 in (2,000 to 5,000 mm), with a similar seasonal pattern.
Vegetation.--Alpine tundra predominates in the mountains, whereas moist tundra communities occupy valley bottoms. Black spruce forest vegetation dominates some hills and ridges. Forests of white spruce, paper birch, and alder cover low hills along major rivers.
Soils.--Principal soils are Inceptisols. Mountain soils are formed in very stony and gravelly colluvium material over bedrock. Valley soils are formed over glacial till. Permafrost occurs sporadically.
Fauna.--Beaver are abundant mammals, with large numbers harvested annually.
Blackpoll warblers are common breeders in conifer stands in river valleys.
Wood frogs have been reported.
Sockeye salmon are the most abundant fish, but chum, king, and silver salmon are also numerous.