Natural Resources
Conservation Service
Ecological site F236XY152AK
Boreal Forest Volcanic Loamy Swales
Last updated: 2/13/2024
Accessed: 11/14/2024
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.
Figure 1. Mapped extent
Areas shown in blue indicate the maximum mapped extent of this ecological site. Other ecological sites likely occur within the highlighted areas. It is also possible for this ecological site to occur outside of highlighted areas if detailed soil survey has not been completed or recently updated.
MLRA notes
Major Land Resource Area (MLRA): 236X–Bristol Bay-Northern Alaska Peninsula Lowlands
The Bristol Bay-Northern Alaska Peninsula Lowland Major Land Resource Area (MLRA 236) is located in Western Alaska. This MLRA covers approximately 19,500 square miles and is defined by an expanse of nearly level to rolling lowlands, uplands and low to moderate hills bordered by long, mountain footslopes. Major rivers include the Egegik, Mulchatna, Naknek, Nushagak, and Wood River. MLRA 236 is in the zone of discontinuous permafrost. It is primarily in areas with finer textured soils on terraces, rolling uplands and footslopes. This MLRA was glaciated during the early to middle Pleistocene. Moraine and glaciofluvial deposits cover around sixty percent of the MLRA. Alluvium and coastal deposits make up a large portion of the remaining area (Kautz et al., 2012; USDA, 2006).
Climate patterns across this MLRA shift as one moves away from the coast. A maritime climate is prominent along the coast, while continental weather, commonly associated with Interior Alaska, is more influential inland. Across the MLRA, summers are general short and warm while winters are long and cold. Mean annual precipitation is 13 to 50 inches, with increased precipitation at higher elevations and areas away from the coast. Mean annual temperatures is between 30 and 36 degrees F (USDA, 2006).
The Bristol Bay-Northern Alaska Peninsula MLRA is principally undeveloped wilderness. Federally managed land includes parts of the Katmai and Aniakchak National Parks, and the Alaska Peninsula, Becharof, Togiak and Alaska Maritime National Wildlife Refuges. The MLRA is sparsely populated. Principal communities include Dillingham, Naknek, and King Salmon. Commercial fishing in Bristol Bay and the Bering Sea comprises a major part of economic activity in the MLRA. Other land uses include subsistence activities (fishing, hunting, and gathering) and sport hunting and fishing (USDA, 2006).
Ecological site concept
This boreal ecological site is on swales on forested plains. Site elevation ranges from 30 to 600 feet above sea level. Slopes are nearly level to gentle (0 - 6 percent). Soil hydrology and tree propagule pressure shape the vegetation on this landform. Closed swales are collection sites for precipitation and snow melt. Soils are somewhat poorly drained and wet soil conditions restrict vegetation during the important early growing season.
The reference state supports two communities. The reference plant community is characterized as a mixed forest (Viereck et al., 1992). It is composed of a white spruce and birch in the overstory with an understory of low shrubs, ferns and bluejoint. Areas of increased wetness typically cannot support trees. These areas are most commonly found in the center of swales. Both communities can coexist in a single swale and are relatively stable unless shifts to water inputs or ponding depth change.
Associated sites
F236XY115AK |
Boreal Forest Loamy Moist Slopes F236XY115AK describes the forested plains and hill backslopes. The swales described by this site (F236XY152AK) are features on the forested plain. |
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Similar sites
R236XY151AK |
Subarctic Open Willow Loamy Plain Swales R236XY151AK describes swales in the maritime climate zone of MLRA 236. While underlying hydrological processes are the same in both sites, R236XY151AK is noted for the lack of trees. |
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Table 1. Dominant plant species
Tree |
(1) Picea glauca |
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Shrub |
(1) Rubus pedatus |
Herbaceous |
(1) Dryopteris expansa |
Click on box and path labels to scroll to the respective text.
Ecosystem states
State 1 submodel, plant communities
1.1a | - | Ponding. |
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1.2a | - | Normal time and growth without disruptive ponding. |