Chapter 7
Ecological Subregions of the United States
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Aleutian Oceanic Meadow - Heath

Three Sections have been delineated in this Province:

These Sections are located in southwestern Alaska, and, as their names describe, include the Alaska Peninsula, Aleutian Islands, and part of Kodiak Island. The area of these Sections is about 22,200 mi2 (57,500 km2).

M127A--Alaska Peninsula

Geomorphology. The Aleutian Range consists of rounded east-trending ridges surmounted at intervals by rugged volcanoes. The mountains were heavily glaciated during the Pliestocene epoch. This Section is bordered to the north by the Bristol Bay Lowlands where the Aleutian Mountains become increasingly submerged southwestwardly, forming the Aleutian Islands. Elevation ranges from sea level to 8,530 ft (2,600 m).

Lithology and Stratigraphy. The Aleutian Mountains consist of segments of the peninsular terrane, which includes mildly folded and faulted late Mesozoic sedimentary rocks, locally intruded by granitic rocks and surmounted at intervals by volcanic piles dating from the late Tertiary to the recent age. Many volcanoes have calderas. A major fault extends along the north side of the eastern part of the range, separating the sedimentary rocks from the granitic batholith on the north.

Soil Taxa. Dominant soils are Typic Haplocryands and Typic Vitricryands. Most of the glacial deposits are mantled with volcanic ash and scoria and are very easily eroded. Soils are shallow on mountain peaks, rock escarpments, and colluvial slopes. Some depressions are filled with fibrous peat.

Potential Natural Vegetation. The vegetation is primarily alpine tundra heath meadows and barrens, with willow and alder occurring at lower elevations and along drainages.

Fauna. The Alaska Peninsula provides significant staging and migration habitat for waterfowl in the spring and fall. Numerous Steller sea lion rookeries and hauling grounds occur along the coast. Sea otters are also common along the coast. Large populations of brown bears live here, partially in response to the large salmon runs which are dominated by pink, chum, and silver salmon.

Climate. Average annual precipitation ranges from 24 to 65 in (610 to 1,650 mm). Average annual temperature ranges from 33 to 40 oF (1 to 4 oC). The growing season lasts approximately from May 10 to September 30 in low-lying areas. Killing frosts can occur any day of the year at higher elevations.

Surface Water Characteristics. Glacially fed streams flowing to the Pacific are short and steep, while those flowing to the Bering Sea are longer and have braided channels. Many lakes occur along the northern portion, held in by end moraines; many lake bottoms extend well below sea level. Wetlands occupy less than 3 percent of the area.

Disturbance Regimes. Ocean-spawned storms rack coastal areas with high wind and heavy rains.

Land Use. Human occupation is restricted to the shorelines. The region is primarily used for subsistence and recreational hunting and fishing.

Cultural Ecology. Aleuts inhabit the west and the Alutiiq Eskimos occupy the east.

Compiled by Alaska Region.

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Section M127B--Aleutian Islands

Geomorphology. The Aleutian Islands are made up of a chain of volcanic islands perched atop the crest of a submarine ridge. Topography varies from wave-beaten level platforms near sea level, to intensely glaciated mountains indented with fjords and bordered by cliffs. The islands gradually emerge above sea level to the northeast forming the Alaska Peninsula. Elevation rises from sea level to greater than 6,230 ft (1,900 m).

Lithology and Stratigraphy. The linear chain of volcanoes on the north side of the islands is of late Cenozoic age and includes many calderas. The remainder of the islands appear to be emerged parts of tilted fault blocks, consisting chiefly of faulted and folded Cenozoic volcanic rocks, which include locally mildly metamorphosed as well as granitic intrusions of Cenozoic age. The submarine topography of the Aleutian Ridge reveals to be complexly block faulted along its crest.

Soil Taxa. Dominant soils are Typic Haplocryands and Typic Vitricryands. Most soils formed in deposits of volcanic ash or scoria over basaltic bedrock. Bare rock and rubble occur on the steep slopes of volcanic cones, peaks, and high ridgetops. With increasing distance from active volcanoes, volcanic material generally grades from coarse lapili and scoria to fine sands. Organic soils occupy depressions and some broad valley bottoms.

Potential Natural Vegetation. Vegetation consists of alpine tundra heath meadows. Lichen communities prevail on windswept ridges. Moist tundra meadows occur at lower elevations and are dominated by grass, sedge, and scattered willows and birch.

Fauna. This Section is rich in bird life and marine mammals, but has few large land mammals. Several species of auklet (i.e., Cassin's, crested, least, and parakeet) are common breeders. The whiskered auklet is an uncommon breeder but occurs only in this Section in Alaska. Red-legged kittiwakes are also unique to this Section, nesting mainly on Buldir and Bogoslof Islands. The entire population of the endangered Aleutian Canada goose nests here. Nearly all of the world's population of Emperor geese winter in the Aleutians. Winter wrens and rosy finches are common breeders along rocky beaches. The introduction of foxes, rats, cats, and dogs resulted in severe reductions of ground-nesting birds. Northern fur seal rookeries are used for breeding and pupping. Numerous Steller sea lion rookeries and hauling grounds occur along the coast. Sea otters also are common along the coast. Sockeye and pink salmon are the most numerous fish species in this Section.

Climate. Average annual precipitation ranges from 32 to 65 in (810 to 1,650 mm). Average annual temperature ranges from 36 to 39 oF (2 to 4 oC). The growing season extends approximately from June 1 through September 15.

Surface Water Characteristics. Streams in the Aleutian Islands are short and swift. Many plunge into the sea over waterfalls. Volcanoes of porous rock have stream courses that are filled with water only during exceptionally heavy rains. Many lakes occupy irregular ice-carved basins in rolling topography on glaciated islands. Numerous ponds were enlarged when ice, expanded by freezing, shoved the banks aside to form ramparts of soils and turf. Lakes fill a few volcanic craters and calderas. Wetlands occupy 11 percent of the area.

Disturbance Regimes. These islands are frequently affected by intense storms, spawning high winds, and heavy rains.

Land Use. Settlements are sparse and restricted to the coastline. The region is used primarily for subsistence and recreational hunting and fishing. Native plant communities have been negatively affected by the introduction of exotic species.

Cultural Ecology. Aleuts occupy this Section.

Compiled by Alaska Region.

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Section M127C--West Kodiak Island

Geomorphology. The Kodiak Mountains are mostly glaciated, with broad, smooth ridges that extend northwestward. The coastline is extremely irregular, having many fjords and islands. The western part of the island has many broad U-shaped valleys. Elevation ranges from sea level to 4,270 ft (1,300 m).

Lithology and Stratigraphy. Kodiak Island occurs within the Chugach terrane and is comprised of complexly deformed, weakly metamorphosed Upper Cretaceous graywacke and slate, with disrupted assemblages of chert, gabbro, ultramafic rocks, and basalt. Older greenstones and schist lie along the northwest coast. The main divide is granitic batholith. Northeast-trending belts of downfaulted and eroded Tertiary rocks lie on the southeast side and make up the Trinity Islands. With the occurrence of moraines and ice margin ridges, it appears that ice from the Alaska Peninsula Section banked up against the western shore of the West Kodiak Island Section.

Soil Taxa. Dominant soils are Typic Haplocryands and Typic Vitricryands. Most of the glacial deposits are mantled with ejecta from the 1912 eruption of Mount Katmai and Novarupta. Soils are shallow on mountain peaks, rock escarpments, and colluvial slopes. Some depressions are filled with fibrous peat.

Potential Natural Vegetation. The vegetation is primarily alpine tundra heath meadows and barrens with moist and wet sedge meadows occuring at lower elevations. Shrub thickets occur along some drainages.

Fauna. Saltwater bays provide habitat for Aleutian terns and harlequin ducks. Shoreline rocks and cliffs support black-legged kittiwakes, horned and tufted puffins, black oystercatchers, and common murres. The Kodiak brown bear is the world's largest carnivore. Five other land mammals are native to the island: red fox, river otter, short-tailed weasel, little brown bat, and tundra vole. Successful introductions of other land mammals include: Sitka black-tailed deer (1924-34), beaver (1925), snowshoe hare (1934), and mountain goat (1952-53). Steller sea lions are common in coastal waters around Kodiak Island. All five species of North American Pacific salmon are present in the Kodiak area; pink, chum, and sockeye are the most abundant. Arctic char are the most widely distributed resident or anadromous fish on Kodiak Island. Other native species include steelhead and rainbow trout.

Climate. Average annual precipitation ranges from 50 to 70 in (1,270 to 1,780 mm). Average annual temperature ranges from 38 to 41 oF (3 to 5 oC). The growing season lasts approximately from May 10 to September 30 in low-lying areas. Killing frosts can occur any day of the year at higher elevations.

Surface Water Characteristics. Glacially fed streams are short and steep and many are less than 10 miles long. Lakes and ponds are scattered over the glacially sculptured landscapes. Wetlands occupy less than 11 percent of the area.

Disturbance Regimes. Storm events are the primary source of natural disturbance. Wildfires are rare.

Land Use. Human occupation is restricted to the shorelines, with the city of Kodiak having the highest population. The region is primarily used for subsistence and recreational hunting and fishing.

Cultural Ecology. Alutiiq Eskimos presently occupy this Section.

Compiled by Alaska Region.

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