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Natural Resources
Conservation Service
Ecological site R237XY220AK
Western Alaska Maritime Mosaic Loamy Hummocks
Last updated: 7/23/2020
Accessed: 08/17/2024
General information
Provisional. A provisional ecological site description has undergone quality control and quality assurance review. It contains a working state and transition model and enough information to identify the ecological site.
MLRA notes
Major Land Resource Area (MLRA): 237X–Ahklun Mountains
The Ahklun Mountains Major Land Resource Area (MLRA 237) is in western Alaska (fig. 3). This MLRA covers approximately 14,555 square miles, and it includes the mountains, hills, and valleys of the Kilbuck Mountains in the north and the Ahklun Mountains in the south. Except for the Kilbuck Mountains and the highest ridges of the Ahklun Mountains, the MLRA was extensively glaciated during the Pleistocene (Kautz et al., 2004). Today, a few small glaciers persist in mountainous cirques (Gallant et al., 1995). The present-day landscape and landforms reflect this glacial history; glacial moraines and glacial drift cover much of the area (USDA-NRCS, 2006). The landscape of the MLRA is primarily defined by low, steep, rugged mountains cut by narrow-to-broad valleys. Flood plains and terraces of varying sizes are common at the lower elevations in the valley bottoms. Glacially carved valleys host many lakes. Togiak Lake is one of the largest lakes in the region. It is 13 miles long and about 9,500 acres in size. Major rivers include the Goodnews, Togiak, Kanektok, Osviak, Eek, and Arolik Rivers. Where the Goodnews and Togiak Rivers reach the coast, the nearly level to rolling deltas support numerous small lakes.
This MLRA has two distinct climatic zones: subarctic continental and maritime continental (fig. 4). The high-elevation areas are in the subarctic continental zone. The mean annual precipitation is more than 75 inches, and the mean annual air temperature is below about 27 degrees F (-3 degrees C) in extreme locations. The warmer, drier areas at the lower elevations are in the maritime continental zone. The mean annual precipitation is 20 to 50 inches, and the mean annual air temperature is about 30 to 32 degrees F (-0.2 to 1.2 degrees C) (PRISM). This climatic zone is influenced by both maritime and continental factors. The temperatures in summer are moderated by the open waters of the Bering Sea, and the temperatures in winter are more continental due to the presence of ice in the sea (Western Regional Climate Center, 2017). The seasonal ice reaches its southernmost extent off the coast of Alaska in Bristol Bay (Alaska Climate Research Center, 2017). The western coast of Alaska is also influenced by high winds from strong storms and airmasses in the Interior Region of Alaska (Hartmann, 2002).
The Ahklun Mountains MLRA is principally undeveloped wilderness. Federally managed lands include the Togiak and Alaska Maritime National Wildlife Refuges. The MLRA is sparsely populated, but it has several communities, including Togiak, Manokotak, Twin Hills, and Goodnews Bay. Togiak is the largest village. It has a population of approximately 855, most of which are Yup’ik Alaska Natives (U.S. Census Bureau, 2016). Major land uses include subsistence activities (fishing, hunting, and gathering) and wildlife recreation (USDA-NRCS, 2006; Kautz et al., 2004).
Ecological site concept
Ecological site R237XY220AK is associated with moderately well drained soils. It is on earth hummocks in linear to slightly concave depressions of broad outwash plains in the southern part of the Ahklun Mountains area. The major disturbance is the formation of earth hummocks. The micro-topographic low areas are subject to ponding. The site does not support an alternate state.
This ecological site supports an earth hummock mosaic consisting of two communities distinguished by the micro-high and micro-low areas. Both of these areas support many low and dwarf shrubs, including bog blueberry (Vaccinium uliginosum), dwarf birch (Betula nana), and marsh Labrador tea (Ledum palustre ssp. decumbens). The micro-low positions typically are wet and support hydrophilic species, and the micro-high areas support dense concentrations of low and dwarf shrubs and many lichens.
Associated sites
R237XY222AK |
Western Alaska Maritime Scrubland Loamy Hummocks Ecological sites R237XY220AK and R237XY222AK are on earth hummocks of outwash plains. The sites are differentiated by the height of the earth hummocks and reference state communities. Ecotonal plant communities that have characteristics from more than one ecological site are in areas where these sites abut. |
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Similar sites
R237XY222AK |
Western Alaska Maritime Scrubland Loamy Hummocks Ecological sites R237XY220AK and R237XY222AK are on earth hummocks. Site R237XY220AK is in linear to slightly concave depressional areas of outwash plains, and site R237XY222AK is in linear to convex areas on talfs of plains and treads of terraces. The plant communities on the well drained, coarse textured soils associated with site R237XY222AK are on smaller earth hummocks and are similar in both the micro-high and micro-low areas. |
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Figure 1. The micro-high and micro-low areas of the rolling earth hummocks support many of the same plant species, but the micro-topographic areas support different indicator species.
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Figure 2. Some of the earth hummocks support dense willow.
Table 1. Dominant plant species
Tree |
Not specified |
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Shrub |
(1) Vaccinium uliginosum |
Herbaceous |
Not specified |
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Ecosystem states
State 1 submodel, plant communities
1.1A | - | Frost heave collapse |
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1.2A | - | Frost heave |