Natural Resources
Conservation Service
Ecological site F006XA007WA
Warm Frigid Xeric Mountain Slopes (Douglas-fir Warm Dry Shrub/Herb)
Last updated: 9/11/2023
Accessed: 11/21/2024
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): 006X–Cascade Mountains, Eastern Slope
Major Land Resource Area (MLRA): 006X–Cascade Mountains, Eastern Slope.
Stretching from northern Washington to southern Oregon, MLRA 6 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
Common Resource Area (CRA) 6.4 - Chelan Tephra Hills
This LRU occurs predominantly on slopes of foothills and mountains. The soils are dominantly in the Inceptisols and Mollisols taxonomic orders, with some Alfisols and Andisols . 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 primarily a frigid or mesic temperature regime and xeric moisture regime with average annual precipitation of about 28 inches.
Other LRU'S where the site occurs:
CRA 6.3 - Okanogan Pine / Fir Hills
CRA 6.5 - Chiwaukum Hills and Lowlands
CRA 6.6 - Yakima Plateau and Slopes
Classification relationships
CDS411 - Douglas-fir/Pachistima (PSME/PAMY)
CDS629 - Douglas-fir/Mountain Snowberry (PSME/SYOR)
CDS653 - Douglas-fir/Bearberry (PSME/ARUV)
CDS654 - Douglas-fir/Bearberry-Bitterbrush (PSME/ARUV-PUTR)
Ecological site concept
This ecological site is classified as Douglas-fir Warm Moderately Dry Shrub/Herb. The dominant tree species is Douglas-fir occurring on upper or middle warm dry slopes. Ponderosa pine is also a key tree component. Other tree species capable of being on site include lodgepole pine and western larch. Elevation ranges from 1400 to 4300 feet and precipitation ranges from 20 to 35 inches.
The following USFS plant associations are included in this ecological site:
Douglas-fir/Pachistima (PSME/PAMY)
Douglas-fir/Mountain Snowberry (PSME/SYOR)
Douglas-fir/Bearberry (PSME/ARUV)
Douglas-fir/Bearberry-Bitterbrush (PSME/ARUV-PUTR)
Douglas-fir/Pinemat Manzinita (PSME/ARNE) – Included from Yakima Indian Reservation
Associated sites
F006XA001WA |
Cool Frigid Xeric Ashy Slopes (Douglas-fir Cool Dry Grass) On cooler, higher elevation sites. |
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F006XA002WA |
Mesic Xeric Hill Slopes and Terraces (Ponderosa Pine Hot Dry Grass) On warmer, drier sites. |
F006XB001WA |
Frigid Xeric Mountain Slopes (Douglas-fir Moderately Dry Shrub/Herb) On moister, higher elevation sites. Associated in southern Chelan, Kittitas and Norther Yakima Co. |
Similar sites
F006XB001WA |
Frigid Xeric Mountain Slopes (Douglas-fir Moderately Dry Shrub/Herb) On moister, higher elevation sites. Associated in southern Chelan, Kittitas and Norther Yakima Co. |
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Table 1. Dominant plant species
Tree |
(1) Pseudotsuga menziesii |
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Shrub |
(1) Symphoricarpos oreophilus |
Herbaceous |
(1) Calamagrostis rubescens |
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Ecosystem states
State 1 submodel, plant communities
1.1B | - | Time. Lack of frequent ground fire |
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1.2A | - | Time |