Chapter 6
Ecological Subregions of the United States



Ahklun Mountains Tundra - Meadow

One Section has been delineated in this Province:

It is located in southwestern Alaska, bordering the Bering Sea. The area of this Section is about 16,700 mi2 (43,300 km2).

Section M126A---Ahklun Mountains

Geomorphology. A group of rugged steep-walled mountains having sharp summits separated by broad, flat valleys and lowlands. This Section includes the Pribilof Islands. Elevation ranges from sea level to greater than 4,920 ft (1,500 m).

Lithology and Stratigraphy. The area occurs within the Togiak terrane, consisting of late Mesozoic island arc and deep ocean volcanic rocks. These rocks are cut by great northeast-trending faults, along which many of the valleys have been eroded by glacial ice.

Soil Taxa. Principal soils are Histic Pergelic Cryaquepts, Pergelic Cryaquepts, Typic Cryochrepts, Humic Cryorthods, Pergelic Cryorthods, Typic Cryumbrepts, and Pergelic Cryumbrepts. Mountain soils formed in very stony and gravelly colluvium material over bedrock, whereas valley soils formed in glacial till.

Potential Natural Vegetation. Alpine tundra heath meadows and barrens predominate in the mountains, whereas moist tundra sedge-tussock meadows occur in valley bottoms. Black spruce forest vegetation dominates some hills and ridges. Forests of white spruce, paper birch, and alder cover the low hills along the major rivers.

Fauna. Blackpoll warblers are common breeders in conifer stands in river valleys. Beaver are abundant, supporting a large annual harvest. Wood frogs have been reported to occur. Sockeye salmon are the most abundant fish. Chum, king, and silver salmon are also numerous. Rainbow trout are a common resident fish in this Section.

Climate. Average annual precipitation ranges from 19 to 25 in (480 to 640 mm). Average annual temperature ranges from 29 to 33 oF (-2 to 1 oC). The growing season extends approximately from May 15 to September 10.

Surface Water Characteristics. Water is adequate to abundant in most of the area, but may be deficient in midsummer in the northern portion. Permafrost exists in most low-lying soils and in high mountains, but it is generally absent in soils covered by forests. Wetlands occupy up to 55 percent of the area.

Disturbance Regimes. Occurrence of wildfires is low.

Land Use. Human population is low and dispersed. Recreational and subsistence hunting and fishing are the main uses.

Cultural Ecology. Yupik Eskimos reside here.

Compiled by Alaska Region.