Natural Resources
Conservation Service
Ecological site F006XA005WA
Cool Frigid Xeric Mountain Slopes
(Douglas-fir Cool Moderately Dry Shrub/Herb)
Last updated: 4/01/2025
Accessed: 07/11/2026
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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): 006X–Cascade Mountains, Eastern Slope
Major Land Resource Area (MLRA): 006X–Cascade Mountains, Eastern Slope.
Stretching from northern Washington to southern Oregon, MLRA6 encompasses the mountain slopes, foothills, elevated plateaus and valleys on the eastern slopes of the Cascade mountains. This MLRA is a transitional area between the Cascade Mountains to the west and the lower lying Columbia Basalt Plateau to the east. Situated in the rain shadow of the Cascade Crest, this MLRA receives less precipitation than portions of the cascades further west and greater precipitation than the basalt plateaus to the east. Geologically, the majority of the MLRA is dominated by Miocene volcanic rocks, while the northern portion is dominated by Pre-Cretaceous metamorphic rocks and the southern portion is blanketed with a thick mantle of ash and pumice from Mount Mazama. The soils in the MLRA dominantly have a mesic, frigid, or cryic soil temperature regime, a xeric soil moisture regime, and mixed or glassy mineralogy. They generally are moderately deep to very deep, well drained, and loamy or ashy. Biologically, the MLRA is dominated by coniferous forest, large expanses of which are dominated by ponderosa pine, Douglas-fir or lodgepole pine. Areas experiencing cooler and moister conditions include grand fir, white fir, and western larch while the highest elevations include pacific silver fir, subalpine fir and whitebark pine. Economically, timber harvest and recreation are important land uses in these forests. Historically, many of these forests would have experienced relatively frequent, low and mixed severity fire favoring the development of mature forests dominated by ponderosa pine or Douglas-fir. In the southern pumice plateau forests, less frequent, higher severity fire was common and promoted the growth of large expanses of lodgepole pine forests.LRU notes
Major Land Resource Area: 6 – Cascade Mountains, Eastern Slopes
Modal Land Resource Unit (LRU): Common Resource Area (CRA) 6.3 - Okanogan Pine / Fir Hills
This LRU occurs predominantly on slopes of mountains. The soils are dominantly in the Andisols and Inceptisols taxonomic order. Soil parent materials are dominantly colluvium and residuum from igneous, sedimentary, and metamorphic rock, and glacial till, with a mantle or mixture of volcanic ash in the upper part. Taxonomic soil climate is a frigid temperature regime and xeric moisture regime with average annual precipitation of about 24 inches.
Other LRU'S where the site occurs:
CRA 6.2 - Pasayten / Sawtooth Highland
CRA 6.5 - Chiwaukum Hills and LowlandsClassification relationships
Forest Service Plant Associations:
CDS832 - Douglas-fir/low huckleberry (PSME/VAMY2)
CDS811 - Douglas-fir/huckleberry (PSME/VACCI)
CDS831 – Douglas-fir/dwarf huckleberry (PSME/VACA)Associated sites
F006XA001WA Cool Frigid Xeric Ashy Slopes (Douglas-fir Cool Dry Grass)
Higher elevation. Understory is dominated by pinegrass Occurs on southerly aspects.
F006XA003WA Cryic Xeric Mountain Slopes (Subalpine fir Cool Moderately Dry Shrub/Herb)
Cooler, higher elevation sites.
Similar sites
F006XA001WA Cool Frigid Xeric Ashy Slopes (Douglas-fir Cool Dry Grass)
Higher elevation. Understory is dominated by pinegrass Occurs on southerly aspects.
Table 1. Dominant plant species
Tree Not specified
Shrub Not specified
Herbaceous Not specified
