Natural Resources
Conservation Service
Ecological site F006XD004WA
Mesic Xeric Slopes and Plateaus (Oregon White Oak-Ponderosa pine Hot Dry Herb/Shrub)
Last updated: 9/11/2023
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): 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) 6.8 - Oak-Conifer Eastern Cascades - Columbia Foothills
This LRU occurs predominantly on structural benches, hillslopes, plateaus, canyons, and terraces. The soils are dominantly in the Mollisols and Alfisols taxonomic order, with minor areas of Inceptisols and Andisols. Soil parent materials are dominantly colluvium and residuum from basalt with a component of loess and volcanic ash. Taxonomic soil climate is primarily a mesic temperature regime with minor areas with a frigid temperature regime. The moisture regime is xeric with average annual precipitation of about 23 inches.
Other LRU'S where the site occurs: CRA 6.6 - Yakima Plateau and Slopes
Classification relationships
HOG211 (WEN) – Oregon White Oak/pinegrass-elk sedge (QUGA/CARU/CAGE)
Yakima Nation
#30 – Ponderosa pine – Oregon White Oak/elk sedge (PIPO-QUGA/CAGE)
#31 – Ponderosa pine – Oregon White Oak/bitterbrush (PIPO-QUGA/PUTR2)
Ecological site concept
These ponderosa pine – Oregon white oak sites are located on the foot slopes and mid – steep slopes on the southern portion of CRA 6.6 and eastern half of CRA 6.8. Two plant associations are included in this ecological site: QUGA-PIPO/CAGE and QUGA-PIPO/PUTR. The CAGE site is located on moderate to flat terrain and the PUTR site is located on steeper south facing slopes. The dominant overstory is a mix of ponderosa pine and Oregon white oak and the dominant understory regeneration is oak with some pine. Quaking aspen clumps can occur and Douglas-fir can be found in the overstory and understory, however the site is too hot and dry for Douglas-fir dominance.
Associated sites
F006XB004WA |
Mesic Xeric Foothills and Mountain Slopes (Ponderosa Pine Hot Dry Shrub Grass) On cooler sites, slightly moister sites. |
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F006XB001WA |
Frigid Xeric Mountain Slopes (Douglas-fir Moderately Dry Shrub/Herb) On cooler, moister sites with northerly aspects. |
Similar sites
F006XD003WA |
Mesic Xeric Slopes and Flood Plains (Oregon white oak-Ponderosa Pine Hot Moderately Dry Shrub) On moister sites. |
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Table 1. Dominant plant species
Tree |
(1) Quercus garryana |
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Shrub |
Not specified |
Herbaceous |
Not specified |
Click on box and path labels to scroll to the respective text.
Ecosystem states
T1A | - | Fire suppression |
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T1B | - | Land conversion |
R2A | - | Selective thinning and prescribed burning |
R3A | - | Intensive planting and inter-seeding |