Natural Resources
Conservation Service
Ecological site R222XY356AK
Alpine Dwarf Scrub Dry Gravelly Slopes
Last updated: 6/20/2019
Accessed: 04/24/2024
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): 222X–Southern Alaska Coastal Mountains
The Southern Alaska Coastal Mountains (MLRA 222) encompasses the Pacific Border Ranges and Coast Mountains physiographic provinces (Wahrhaftig 1965). Spanning approximately 26,355 square miles, the elevation ranges from sea level at the base of glaciers and ice fields to 18,008 feet at Mt. St. Elias (Figure 1). The MLRA was covered by glacial ice during the Pleistocene epoch, a time period spanning from 2.6 million to 11,700 years ago. During interglacial periods glacial extent was reduced, leaving behind various glacial deposits. Over time these deposits have been eroded or buried by colluvium and slope alluvium, which now covers more than 90 percent of the unglaciated landscape. Paleozoic, Mesozoic, and Lower Tertiary stratified sedimentary rocks, and occasionally Paleozoic intrusive rocks, underlie much of the area and are exposed on steep mountain slopes and ridges (USDA-NRCS 2006).
This landscape lies in the true alpine zone where glacial ice is, and has been, the dominant ground cover. Glacial ice encompassed all the MLRA during the Late Wisconsinan glaciation, 25,000 – 21, 000 years ago (Kauffman et al. 2011). Changes in climatic conditions following this period resulted in the recession of some glaciers and slowly exposed new surfaces for inhabitation by terrestrial ecosystems. Pioneer plant communities began to establish on the new substrate within the first 30 years and consisted mostly of evergreen, herbaceous dwarf shrubs with some pockets of low shrubs. These communities quickly transitioned to tall shrubs within 100 years of deglaciation. By approximately 13,000 years ago, four stable plant communities emerged across the non-glaciated landscape – ericaceous dwarf shrub, low shrub, tall shrub, and herbaceous communities – and form the present-day ecosystems (Boggs et al. 2010).
Classification relationships
USFS Ecoregion Province: Marine Mountains (M240), Forest-Meadow High (M242b) (Bailey 2007)
U.S. EPA Level III Ecoregion: Pacific Coastal Mountains (119) (Gallant et al. 2010)
National Vegetation Classification – Ecological Systems: Alaskan Pacific Maritime Alpine Sparse Shrub and Fell-Field (CES204.318) (NatureServe 2015)
Biophysical Settings: Alaskan Pacific Maritime Herbaceous Dwarf Shrubland (BpS 7816430) (LANDFIRE 2009)
Alaska Natural Heritage Program Landcover Class: Dwarf Shrub (Boggs et al. 2016)
Alaskan Vegetation Classification: Crowberry Dwarf Shrub Tundra (Viereck et al. 1992)
Ecological site concept
Alpine Dwarf Scrub Gravelly Slopes, Bedrock ecological sites occur on high-elevation mountain slopes that are exposed to harsh climatic conditions. The soils are gravelly Inceptisols that are well-drained and shallow, formed in colluvium over weathered residuum.
The reference vegetation on this ecological site is defined by a sparse cover of dwarf shrubs interspersed with large patches of bedrock and surface rock. Bog blueberry (Vaccinium uliginosum (Hook.) Coville) and black crowberry (Empetrum nigrum L.) are the dominant dwarf shrubs, and star reindeer lichen (Cladina stellaris (Opiz) Brodo) is the dominant non-vascular ground cover. Continuous exposure to cold temperatures, wind, and a short growing season maintain this plant community (LANDFIRE 2009).
Associated sites
R222XY352AK |
Alpine Dwarf Scrub Dry Organic Slopes Organic soils that are shallow to bedrock |
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R222XY357AK |
Alpine Dwarf Scrub Moist Gravelly Slopes Mineral soils that are shallow to bedrock, occurring on concave slope shapes |
Similar sites
R222XY357AK |
Alpine Dwarf Scrub Moist Gravelly Slopes Supports a similar dwarf shrub community but bedrock cover is less than 10 percent |
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Table 1. Dominant plant species
Tree |
Not specified |
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Shrub |
(1) Vaccinium uliginosum |
Herbaceous |
(1) Cladina |
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