Natural Resources
Conservation Service
Ecological site F220XY204AK
Subalpine Forests Organic Wet Slopes
Last updated: 3/10/2025
Accessed: 03/31/2025
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): 220X–Alexander Archipelago-Gulf of Alaska Coast
This area is in the Southern Alaska Region and includes the higher elevations of the Coast, St. Elias, Chugach, and Kenai Mountains. The area makes up about 26,335 square miles. The terrain consists of steep, rugged, high-relief mountains. Glaciers and ice fields make up about 54 percent of the area. Unglaciated portions of the area are deeply incised with narrow to broad valleys. Flood plains and stream terraces on valley floors rapidly give rise to steep alluvial fans and mountain footslopes. Elevation ranges from sea level at the base of tidewater glaciers and ice fields to 18,008 feet at the summit of Mt. St. Elias (USDA 2006).
During the Pleistocene epoch, the area was covered with glacial ice. As the glacial ice melted, sediments were deposited by the melting ice. However, most of the original glacial deposits have eroded away or have been buried by colluvium and slope alluvium, which covers more than 90 percent of the present unglaciated landscape. The remaining glacial and glaciofluvial deposits and recent fluvial deposits are generally restricted to the bottoms of the larger valleys. 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 2006).
Miscellaneous (non-soil) areas make up more than 90 percent of this MLRA. The most common miscellaneous areas are rock outcrop, rubble land, chutes, and glaciers. The dominant soil orders in this area are Spodosols and Histosols. The soils in the area have a cryic soil temperature regime or a subgelic soil temperature class, a udic or aquic soil moisture regime, and mixed or amorphic mineralogy (USDA 2006).
While both alpine and subalpine plant communities characterize the vegetation in this area, most of the unglaciated terrain in this region is in the true alpine zone. Alpine vegetation consists of a variety of dwarf scrub and herbaceous communities. Low willow scrub is common in drainages. Lichens, scattered herbs, and dwarf shrubs dominate bedrock exposures and very shallow soils. In general, there is little or no plant growth at elevations above about 7,500 feet (USDA 2006). At lower elevations, subalpine vegetation consists of a variety of mountain hemlock and tall scrub communities. These subalpine plant communities typically occur at elevations between 1500 to 3000 feet (Boggs et al. 2010, Carstensen 2007, Jaques 1983; Martin et al. 1995).
The area is almost entirely undeveloped wild land. Remote wild-land recreation is the principal land use in this area. The rugged, high mountains, extensive glaciers and ice fields, and wilderness qualities of the area attract visitors from around the world. Small rural communities along the road system are the only permanent settlements. Part of the Wrangell-St. Elias Bay National Park and Preserve, the Glacier Bay National Park and Preserve, the Misty Fjords National Monument, the Chugach National Forest, and the Tongass National Forest are in this MLRA.
Classification relationships
National Vegetation Classification – Ecological Systems: Alaskan Pacific Maritime Subalpine Mountain Hemlock Woodland (CES204.143) (NatureServe 2015)
Ecological site concept
This subalpine site occurs on mountain slopes and depressions at the lowest subalpine bands of elevation and represents a transition from warmer coastal rainforests to colder subalpine forests. This site has a harsh climate where tree species from lower elevations like western hemlock are no longer dominant. The soils are wet for much of the growing season and are very poorly drained. These wet soils are Histosols and are formed in saturated organic material. Bedrock typically occurs within 15 to 35 inches.
The reference plant community is an open forest (25-60% cover) dominated by coniferous trees, ericaceous shrubs, and wetland indicator plant species. While mountain hemlock is the dominant tree species, western hemlock and Sitka spruce can also be an occasional stand component (Martin et al. 1995). Common understory species include oval-leaf blueberry, Alaska blueberry, deer cabbage, green false hellebore, strawberryleaf raspberry, deer fern, and fernleaf goldthread (Martin et al. 1995, Landfire 2009). The primary disturbance processes that maintain this plant community are exposure to cold temperatures, wind, blowdown, and avalanches (NatureServe 2018).
Associated sites
| F220XY338AK |
Subalpine Forests Dry Organic Slopes Occurs on similar bands of elevation on dry organic rich soils. |
|---|---|
| F220XY200AK |
Subalpine Forest Gravelly Dry Slopes Occurs on similar bands of elevation on dry soils, leading to differences in reference plant community assemblages.. |
Similar sites
| F220XY200AK |
Subalpine Forest Gravelly Dry Slopes Both sites occur in a similar band of elevation and have similar overstory and understory species. F220XY200AK has more productive trees and less wetland indicator species. |
|---|
Table 1. Dominant plant species
| Tree |
(1) Tsuga mertensiana |
|---|---|
| Shrub |
(1) Vaccinium ovalifolium |
| Herbaceous |
(1) Nephrophyllidium crista-galli |
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