Natural Resources
Conservation Service
Ecological site R224XY743AK
Subalpine Scrub Dry Slopes Ecological Site Group
Last updated: 6/13/2025
Accessed: 10/19/2025
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): 224X–Cook Inlet Lowlands
Major Land Resource Area (MLRA) 224X consists of lowlands and lower mountain slopes of the Susitna and Matanuska Valleys, western Kenai Peninsula, and west side of Cook Inlet. It makes up about 10,965 square miles (28,400 square kilometers). The terrain is a broad expanse of braided flood plains, high gradient rivers, rolling plains, terraces and hills bordered by the surrounding mountains. This MLRA contains a large percentage of Alaska's total population and includes the most extensive road systems in the state. Major rivers include the Susitna, Yentna, Little Susitna, Matanuska, Kenai, and Deep Creek that all drain into Cook Inlet. Large lakes include Tustumena and Skilak.
Climate is highly variable ranging from temperate maritime to continental subarctic. Winter arctic weather systems are common in the northern portion of the MLRA. The average annual precipitation ranges from 15 to 60 inches (380 to 1,525 millimeters). The average annual snowfall is about 60 to 120 inches (150 to 305 centimeters). The average annual temperature is about 27 to 36 degrees F (-3 to 2 degrees C). The freeze-free period averages 65 to 160 days, decreasing with elevation.
Vegetation ranges from spruce/birch forests in the lowlands to subalpine scrubland at high elevations. Saltwater meadows along the coast and wetlands and extensive marsh occur throughout the lowlands across the valley. In most years precipitation is adequate for crops, with limited irrigation. Major rivers are affected by high sediment-laden glacial meltwater and ice dam damage and flooding is a risk during spring thaw. Water is hard or very hard, with high potential levels of iron, but is otherwise of excellent quality. Alpine vegetation is associated with the adjacent Cook Inlet Mountains MLRA (223X).
The dominant soil orders in this MLRA are Spodosols, Histosols, Entisols, and Inceptisols. Water, riverwash, beaches, and other miscellaneous (non-soil) areas are 15 percent of this MLRA. Glacial and volcanic ash wind-blown deposits influence much of area, while fluvial deposits are common in riparian areas.
The MLRA is visited by a great number of migrating birds and supports large populations of waterfowl. Most of the rivers and streams are important spawning grounds for salmon (Chinook, coho, and red salmon). Peonies, hay, potatoes, and hardy vegetables are important agriculture with a few dairy and beef cattle farms present. Commercial logging and subsistence firewood gathering are locally important, as is subsistence gathering. Other major industries in the area include commercial fishing, fish processing, and oil and gas extraction. Tourism and wildland recreation are becoming increasingly important.
The major resource concerns are water erosion and water quality. Aquifers are highly susceptible to contamination from runoff. The intrusion of seawater can be a problem along Cook Inlet. Rapid development and off-road recreation are creating significant damage to the wildlands.
LRU notes
This MLRA is a transitional zone between temperate maritime and continental subarctic climatic zones to the south and areas of arctic winter weather patterns to the north. With this transition, there are major variations in climatic influences and vegetative responses. With further soil survey and vegetative surveys, this MLRA will be evaluated for potential Land Resource Unit (LRU) development.
Ecological site concept
• This subalpine ecological site occurs on hillslope, ridges, and mountain slopes.
• Soils formed in loess and/or volcanic ash over gravelly till, outwash and/or residuum.
• Soils range from shallow to very deep, with depth controlled by bedrock.
• Soils do not flood or pond. These well drained soils have a deep or no observable water table during the growing season.
• Reference state vegetation is a mosaic dominated largely by Sitka alder scrubland with small patches of grass and forb herbaceous meadows. No known disturbance transitions or community pathways exist between these two plant communities.
Associated sites
| R223XY706AK |
Alpine scrub wet depressions and drainageways Occurs in adjacent high-elevation drainages. |
|---|---|
| R224XY741AK |
Subalpine Herbaceous Wet Slopes Ecological Site Group Occurs on adjacent subalpine slopes with wetter soils that support herbaceous meadows. |
| R224XY742AK |
Subalpine Scrub Moist Slopes Ecological Site Group Occurs on adjacent subalpine slopes with wetter soils that support low scrub willow. |
Similar sites
| R228XY705AK |
White spruce/alder scrub unstable slopes Associated with similar alder dominant vegetation but on slopes to the North in MLRA 228X (Interior Alaska Mountains). |
|---|---|
| R224XY742AK |
Subalpine Scrub Moist Slopes Ecological Site Group Both 742 and 743 support shrubby plant communities. Ecological site group 742 supports low scrub communities dominated by willow. |
Table 1. Dominant plant species
| Tree |
Not specified |
|---|---|
| Shrub |
(1) Alnus viridis ssp. sinuata |
| Herbaceous |
(1) Calamagrostis canadensis |
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