Nulato Hills, Kuskokwim Mountains, Nushagak-Big River Hills, 55,000 mi2 (142,400 km2)
Land-surface form.--This area includes low mountains and hills interspersed with valleys. Elevations range from 980-1,970 ft (300-600 m) on ridges in the north to 4,920 ft (1,500 m) in the south. Much of the area exhibits glacial features, but in the north only the higher peaks were once covered by glaciers. Deep, narrow valleys are prevalent.
Climate.--The climate is transitional from maritime to extreme continental. Winters are milder and summers cooler than in the interior. The average January temperature is about 4F (-16C), and the average July temperature is just above 50F (10C). The growing season is 4 months. Average annual precipitation is about 16 in (400 mm); precipitation is heaviest in late summer, when there are heavy rains. Snowfall ranges from 59 to 78 in (1,500 to 2,000 mm).
Vegetation.--Black spruce forest vegetation is dominant in this area. Many hills and ridges, however, support only a tundra vegetation consisting of sedges and shrubs. There are forests of white spruce and paper birch on the hills overlooking the Yukon and Kuskokwim Rivers. Alpine meadow vegetation is predominant at higher elevations.
Soils.--The dominant soils are Inceptisols.
Fauna.--The fauna of the lowland forests are similar to those in surrounding tayga regions. There are low to moderate populations of brown bears. River otters are found throughout major river drainages. Northern bog lemmings populate wet alpine and subalpine meadows.
Alpine tundra provides habitat for horned larks, surfbirds, and white-tailed ptarmigan. Sharp-shinned hawks and golden eagles are common avian predators.