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Ahklun and Kilbuck Mountains

↑About the Ahklun and Kilbuck Mountains

The Ahklun and Kilbuck Mountains are a steep but relatively low mountain range in southwestern Alaska, between Bristol Bay and Kuskokwim Bay. The region includes a number of rugged islands, the largest of which is Hagemeister Island, followed by High Island and Crooked Island. Some smaller islands, such as Round Island and Summit Island, could be included here but are not because the boundaries of the US EPA data are too coarse to capture these small islands. Although in our classification scheme this region is considered part of the Marine West Coast Forest, the vegetation here is transitional between those forests and the more open cover in bordering regions of Alaska Tundra.

The region has a humid subarctic climate throughout, with both oceanic and continental influences. Precipitation is unusually high for the location so far north, and increases with elevation. The oceanic influence, which moderates climate, is strongest in the south and east portions of this region, whereas the northwest-facing portions of this region, even at lower elevations, have a harsher climate, particularly with spring temperatures being slower to warm up. At sea level, significant snow falls October through April, and snowfall is even higher at higher elevations, accumulating more as temperatures stay below freezing for a larger portion of the year. There are small areas of glaciers at the highest elevations, but much less than in the Alaska Range farther east or even the Alaska Peninsula Mountains farther southeast. The glaciers here have been retreating and melting rapidly in recent years. About 10% of the glaciers have been completed eliminated in the past 50 years, and the total area covered by glaciers has been reduced to about half its extent in the 1950's-70's. At the current rate, this region will be have no remaining glaciers by about the year 2100. Although this process was occurring before human influence, it has been greatly accelerated by human-induced climate change.

The terrain here consists of small groupings of steep, rugged mountains separated by broad, flat valleys. Most of the mountains stretch to around 5,000 ft or 1,500m, lower than mountains farther east and south. This area has eroded enough for the valleys to coalesce into a well-connected network of broad bottomlands, some of which are filled with lakes. Many of the lakes are long, narrow, and deep; such lakes are more common on the eastern side of this region, with a few in the interior. The western portion has smaller lakes and ponds. Streams are steep and flow radially out of the mountains, and then combine into slightly larger, slow-moving, winding streams in the valleys. Because of the glacial topography, the streams are small relative to the valleys they inhabit.

The mountains themselves consist of a mix of sedimentary and older volcanic rocks, which have themselves been deformed. The topography reflects heavy glaciation of the region that carved deep U-shaped valleys, but with the glaciers mostly retreating in this interglacial period. Soils here are very different in the mountains from the bottomlands. The mountains tend to have poorly-developed rocky and gravely soil, formed mostly from colluvium over bedrock. The valleys have slightly richer soils formed on glacial till. There is discontinuous permafrost throughout.

The vegetation here grades between forests and tundra. Dwarf scrub communities cover most of the mountains. Lower mountain slopes and valleys support taller scrub growth interspersed with more herbaceous vegetation; willow, alders, and birches are dominant on these sites. Some sites in valley bottoms support white spruce (Picea glauca) and hardwoods, with low, poorly-drained sites opening into sedge-tussock tundra meadows. Vegetation and forests are densest in the east and south portions of this region; the western portions are relatively more barren, with lower scrub, more open tundra, and minimal trees. As the climate warms, vegetation cover in this region will likely increase and it will take on more characteristics of the Marine West Coast Forest ecoregion.

This region is sparsely populated, with most of the population located along the coast or in broader lowland areas nearby. Togiak is the largest settlement, followed by Manokotak, and other settlements include Goodnews Bay and Aleknagik. Quinhagak is located here in our classification scheme, but it is in a broad, flat area close to the border of this region with the Subarctic Coastal Plains. All of these settlements have less than 1,000 people. The land use here is minimal, mostly consisting of subsistence and recreational hunting and fishing. There is some mineral mining. Togiak was once home to the largest commercial Herring fishery in Alaska, but the market for that fish collapsed and there is virtually no commercial fishing there any more.

This region is bordered to the northwest along the coast by the Subarctic Coastal Plains, a low, flat region covered in tundra and lacking forests. It is bordered to the southeast by the Bristol Bay-Nushagak Lowlands, another low, flat region covered in tundra, but that region is more sheltered and supports more plant biodiversity. The rest of the region borders the Alaska Boreal Interior inland, a diverse region where the cover is also transitional between forest and tundra, but that region tends to be lower-elevation and also has escaped glaciation and tends to be unusually high in plant biodiversity. Parts of this region alternately border the low and flat Interior Bottomlands, or the Interior Forested Lowlands and Uplands, which are relatively more rugged but tend to be lower and less rugged than this region.