Natural Resources
Conservation Service
Ecological site AX003X03F007
Glaciated Middle Cascades Cryic Udic Forest Group
Last updated: 5/10/2024
Accessed: 11/13/2024
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): 003X–Olympic and Cascade Mountains
The Cascade and Olympic Mountains (MLRA 3) include the west slope and parts of the east slope of the Cascades Mountains in Washington and Oregon. The Olympic Mountains in Washington State are also included. These mountains are part of a volcanic arc located at a convergent plate boundary. Volcanic rocks predominate but metamorphic and sedimentary rocks occur in the North Cascades and Olympic Mountains. Topography is generally dissected and steep, but some areas consist of constructional volcanic platforms and isolated stratovolcanoes. Elevation is usually 500 to 6000 feet but reaches to 14,410 ft at the summit of Mount Rainier. Many areas hosted alpine glaciers or ice sheets during the Pleistocene, and a few remain today.
Climate becomes cooler and more moist, with increasing elevation and latitude. Low elevations experience a long growing season and mild temperatures. High elevations can accumulate snowpack lasting into summer and frost may occur in any month. Average annual precipitation ranges from 60 to 180 inches in most areas. Most precipitation falls during the fall, winter, and spring during low-intensity frontal storms. Summers are relatively dry. Average annual temperature is 27 to 50 degrees F. The frost-free period is 10 to 180 days.
LRU notes
The Glaciated Western Cascades land resource unit (LRU C) is located in western Oregon and Washington. It is bounded by Snoqualmie Pass on the north, the North Santiam River on the south, and Puget Trough and the lower Willamette Valley on the west. Major rivers draining this LRU include the Green, Puyallup, Nisqually, Cowlitz, Lewis, Sandy, and Clackamas.
Bedrock consists mainly of volcanic rocks. Topography is generally dissected and steep. Low-relief areas often contain ancient and contemporary landslides. Alpine glaciation was widespread at the beginning of the Holocene. U-shaped valleys and cirque basins containing scoured bedrock are common (Noller, et al. 2016).
Soil moisture regime is mainly udic or aquic. Soil temperature regime ranges from mesic to cryic. Soils in this LRU may have lower clay content compared with those to the south. Inceptisols, Andisols, and Spodosols are common soil orders.
Conifer forest is the dominant vegetation. The natural fire regime is infrequent in most areas. At low to mid elevations, Douglas-fir (Pseudotsuga menziesii) is a long-lived, early-seral tree; western hemlock (Tsuga heterophylla) is an associated shade-tolerant tree. Red alder (Alnus rubra) is a short-lived, early-seral tree. It is ephemeral on uplands but persists on wet or repeatedly-disturbed sites. At high elevations, Noble fir (Abies procera) is an early-seral tree; Pacific silver fir (Abies amabilis) or mountain hemlock (Tsuga mertensiana) are associated shade-tolerant trees. Sitka alder (Alnus viridis ssp. sinuata) and vine maple (Acer circinatum) form persistent shrub fields on sites subject to very deep snowpack or avalanches. Subalpine and alpine wetlands typically support shrubby or herbaceous vegetation.
Classification relationships
• LANDFIRE: BPS 0111740 North Pacific Dry-Mesic Silver Fir-Western Hemlock-Douglas-fir Forest
Ecological site concept
This ecological site is found on steep mountain slopes. Climate is cold and moist. Soils are usually well drained and usually greater than 60 inches to a restrictive layer. Soil temperature regime is cryic, and soil moisture regime is udic. Soil parent material is usually volcanic ash and colluvium derived from andesite or basalt.
Associated sites
AX003X03C004 |
Glaciated Middle Cascades Frigid Udic Forest Group Lower on the landscape. |
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Similar sites
AX003X00F005 |
Western Middle Cascades Low Cryic Udic Forest Group Non-glaciated landforms. |
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Table 1. Dominant plant species
Tree |
(1) Abies amabilis |
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Shrub |
Not specified |
Herbaceous |
Not specified |
Legacy ID
F003XC007OR
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