
Natural Resources
Conservation Service
Ecological site AX001X01X412
Low Cryic Udic Dry Forest
Last updated: 5/15/2025
Accessed: 05/19/2025
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): 001X–Northern Pacific Coast Range, Foothills, and Valleys
This area consists of a long and narrow range of mountains with associated foothills and valleys that parallels the Pacific Ocean. This area is entirely within the Pacific Border Province of the Pacific Mountain System in Oregon and Washington. MLRA 1 is bounded on the north by the highest elevations of the Olympic Mountains and the strait of Juan de Fuca, and by the Klamath Mountains on the south. The Washington portion of this MLRA is primarily composed of young Tertiary sedimentary rocks (siltstone and sandstone) mixed with some volcanic rocks of the same age. Glacial till and outwash deposits are also found in the northern half of this area in Washington. Much of this area is accreted terrane formed by tectonic processes. The average annual precipitation ranges from 60 to 200 inches (1,525 to 5,580 millimeters), increasing with elevation. Most of the precipitation in this area occurs during low-intensity, Pacific frontal storms and is evenly distributed throughout fall, winter, and spring.
The dominant soil orders in this MLRA are Andisols, Inceptisols, and Ultisols. Soil depths broadly range from shallow to very deep. Soils are primarily well drained, however poorly drained soils may be found in depressional areas and on alluvial floodplains. Surface textures are typically medial and loamy or clayey. Soils in this area dominantly have a mesic or frigid temperature regime and a udic moisture regime. Soils with aquic moisture regimes and cryic temperature regimes also occur.
Ecological site concept
Low Cryic Udic Dry Forest sites occur on less stable landscape positions on glacial valley walls, ridges, mountain tops, and colluvial aprons in lower elevation areas within the cryic temperature zone. These sites are typically located on the leeward side of the Olympic mountains where precipitation is relatively low. Relatively high slope gradients limit water infiltration on these sites, generating runoff to more stable Low Cryic Udic Moist Forests, Wet Subalpine Meadows, and Cryic Aquic Shrublands. As a result, Low Cryic Udic Dry Forest sites characteristically exhibit lower production than similar Low Cryic Udic Forest and Low Cryic Udic Moist Forest sites.
Low Cryic Udic Dry Forest sites are characterized by an overstory canopy of mountain hemlock (Tsuga mertensiana) and Pacific silver fir (Abies amabilis), accompanied by an understory shrub community of thinleaf huckleberry (Vaccinium membranaceum), locally known as black huckleberry, and Cascade azalea. The most common herbaceous layer species are strawberryleaf raspberry (Rubus pedatus) and roughfruit berry (Rubus lasiococcus). Pipsissewa (Chimaphila umbellata), bride’s bonnet (Clintonia uniflora), white avalanche-lily (Erythronium montanum), Sitka valerian (Valeriana sitchensis), and twinflower (Linnaea borealis) are other common forbs on this site. Common beargrass (Xerophyllum tenax) is commonly found on this site.
Low Cryic Udic Dry Forest sites are readily differentiated from Frigid Udic Dry Forest sites by the low abundance of western hemlock (Tsuga heterophylla). If western hemlock is present on a Low Cryic Udic Dry Forest site, it will generally be limited to regenerating patches. High Cryic Udic Dry Forest sites are differentiated from Low Cryic Udic Dry Forest sites by the presence of subalpine fir (Abies lasiocarpa). Subalpine fir is generally absent on Low Cryic Udic Dry Forest sites but may occasionally be present in low abundance at the upper elevation range of the site.
Associated sites
AX001X01X306 |
Cryic Aquic Subalpine Wet Meadow Cryic Aquic Subalpine Wet Meadows may be found in depressions and seeps adjacent to or surrounded by Low Cryic Udic Dry Forest sites. Cryic Aquic Subalpine Wet Meadow sites are frequently ponded and lack tree cover. |
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AX001X01X411 |
Low Cryic Udic Moist Forest Low Cryic Udic Moist Forest sites may be found downslope of Low Cryic Udic Dry Forest sites. Low Cryic Udic Moist Forest sites may capture run-on water and have higher productivity. |
Similar sites
AX001X01X410 |
Low Cryic Udic Forest Low Cryic Udic Forests are typically located on the windward side of the Olympic mountains and on protected aspects. These sites receive higher effective precipitation and production is significantly higher than on Low Cryic Udic Dry Forest sites. |
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AX001X01X408 |
Frigid Udic Dry Forest Frigid Udic Dry Forest sites are found at lower elevations and lack mountain hemlock (Tsuga mertensiana). |
AX001X01X415 |
High Cryic Udic Dry Forest High Cryic Udic Dry Forest sites occur at higher elevations and are indicated by the presence of subalpine fir (Abies lasiocarpa). |
Table 1. Dominant plant species
Tree |
(1) Abies amabilis |
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Shrub |
(1) Rhododendron albiflorum |
Herbaceous |
(1) Xerophyllum tenax |
Legacy ID
F001XA412WA
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Ecosystem states
State 1 submodel, plant communities
Communities 1 and 5 (additional pathways)
1.1B | - | Minor disturbance |
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1.1A | - | High-intensity disturbance |
1.2A | - | Time without disturbance |
1.2B | - | High-intensity disturbance |
1.3A | - | Time without disturbance |
1.4B | - | High-intensity disturbance |
1.4A | - | Time without disturbance |
1.5A | - | Time without disturbance |
1.5B | - | High-intensity disturbance |