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Natural Resources
Conservation Service
Ecological site F003XN952WA
Southern Washington Cascades High Cryic Deciduous Forest
Last updated: 5/10/2024
Accessed: 08/17/2024
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
Steep mountains and narrow to broad, gently sloping valleys characterize this MLRA. A triple junction of two oceanic plates and one continental plate is directly offshore from Puget Sound. Subduction of the oceanic plates under the westerly and northwesterly moving continental plate contributes to volcanic activity in the Cascade Mountains. Movement among these plates has resulted in major earthquakes and the formation of large stratovolcanoes. The Cascade Mountains consist primarily of volcanic crystalline rock and some associated metasedimentary rock. The mean annual precipitation is dominantly 60 to 100 inches, but it is 30 to 60 inches on the east side of the Cascade Mountains.
The soil orders in this MLRA are dominantly Andisols, Spodosols, and Inceptisols and minor areas of Entisols and Histosols. The soils are dominantly in the frigid or cryic temperature regime and the udic moisture regime. The soils generally are shallow to very deep, well drained, ashy to medial, and loamy or sandy. They are on mountain slopes and ridges.
Ecological site concept
This ecological site is in cold, moist areas at an elevation of more than 3,600 feet. It is in active avalanche chutes on debris cones of glacial-valley walls. The most common disturbances are avalanches, rockfalls, and debris flows. Wildfires are less common, but the steep slopes facilitate the rapid movement of fire to upslope areas.
The soils that support this site are in the cryic soil temperature regime and the udic soil moisture regime. They formed in mixed colluvium and volcanic ash. They are well drained and very deep. The soils are not subject to flooding or ponding. Soil moisture is not a limiting factor to forest growth because of the abundance of precipitation and the inherent water-holding properties of soils influenced by volcanic ash. A thin organic horizon that consists of decomposing twigs, needles, and litter is on the soil surface. This horizon helps to protect the soil from wind and water erosion.
As a result of the frequent disturbances, this site primarily supports early seral species such as Sitka alder (Alnus viridis ssp. sinuata) and vine maple (Acer circinatum). Common understory shrubs include Sitka mountain ash (Sorbus sitchensis var. sitchensis) and devilsclub (Oplopanax horridus).
Repeated avalanches do not allow for the establishment of a coniferous overstory. Seedlings of tree species such as Pacific silver fir (Abies amabilis), subalpine fir (Abies lasiocarpa), noble fir (Abies procera), Alaska cedar (Callitropsis nootkatensis), and mountain hemlock (Tsuga mertensiana) may encroach from the forested edges. Over time, the majority of these rigid-trunked trees will be snapped off by avalanches.
Associated sites
F003XN948WA |
Southern Washington Cascades Low Cryic Deciduous Forest Ecological site F003XN948WA, Southern Washington Cascades Low Cryic Deciduous Forest, is located at lower elevations compared to site F003XN952WA, Southern Washington Cascades High Cryic Deciduous Forest. Both sites are in active avalanche chutes. Ecological site F003XN948WA dominantly supports tree species such as Pacific silver fir and western hemlock. Site F003XN952WA dominantly supports species such as subalpine fir, mountain hemlock, and Alaska cedar. |
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Similar sites
F003XN948WA |
Southern Washington Cascades Low Cryic Deciduous Forest Ecological site F003XN948WA, Southern Washington Cascades Low Cryic Deciduous Forest, is located at lower elevations compared to site F003XN952WA, Southern Washington Cascades High Cryic Deciduous Forest. Both sites are in active avalanche chutes. Ecological site F003XN948WA dominantly supports tree species such as Pacific silver fir and western hemlock. Site F003XN952WA dominantly supports species such as subalpine fir, mountain hemlock, and Alaska cedar. |
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Table 1. Dominant plant species
Tree |
(1) Alnus viridis ssp. sinuata |
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Shrub |
(1) Sorbus sitchensis |
Herbaceous |
(1) Veratrum viride |
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