Physiographic features

Physiographic Features
This ecological site occurs mainly on hillslopes, lower mountain slopes, outwash terraces and stream terraces. Parent materials are primarily till, outwash or colluvium and residuum from metamorphic rock with a mantle of volcanic ash and loess.

Landscapes: Mountains
Landforms: mountain slopes and avalanche chutes

Elevation:
Total range = 675 to 2200 m
(2,215 to 7,215 feet)
Central tendency = 1190 to 1660 m
(3,895 to 5,435 feet)

Slope (percent):
Total range = 0 to 80 percent
Central tendency = 25 to 45 percent

Water Table Depth:
>200cm
(>80 in)

Flooding:
Frequency: None
Duration: None

Ponding:
Frequency: None
Duration: None

Aspect: 165-190-325
Central tendency: 140-190-225

Table 2. Representative physiographic features

Table 3. Representative physiographic features (actual ranges)

Climatic features

Climatic Features

During the spring and summer, a circulation of air around a high-pressure center brings a prevailing westerly and northwesterly flow of comparatively dry, cool and stable air into the region. As the air moves inland, it becomes warmer and drier which results in a dry season beginning in the late spring and reaching a peak in mid-summer. In the fall and winter, a circulation of air around two pressure centers over the ocean brings a prevailing southwesterly and westerly flow of air into the Pacific Northwest. This air from over the ocean is moist and near the temperature of the water. Condensation occurs as the air moves inland over the cooler land and rises along the windward slopes of the mountains or highlands. This results in a wet season beginning in October, reaching a peak in winter, then gradually decreasing in the spring.

The elevation within the LRU varies from approximately 1,000 feet in the lower river valleys to about 7,200 feet in the higher mountains. The annual precipitation increases from 9 inches in the valleys to over 48 inches in the highest mountains. Winter season snowfall averages about 43 inches. Both rainfall and snowfall increase with elevation. Snow can be expected after the first of November and to remain on the ground from the first of December until March or April.

In January, the average maximum temperature is near 29° F and the minimum temperature is 14° F. Minimum temperatures from -5° to -20°F are recorded almost every winter and temperatures ranging to -25° F have been recorded. In July, the average maximum temperature is 81° and the minimum temperature 47° F. Maximum temperatures reach 100° F on a few afternoons each summer and temperatures as high as 108° F have been recorded. The average date of the last freezing temperatures can be expected by early-June and after early-September in the warmer areas.
(Compiled from WRCC: Climate of Washington and available station data)

Frost-free period (days):
Total range = 75 to 125 days
Central tendency = 90 to 105 days

Mean annual precipitation (cm):
Total range = 425 to 1590 mm
(17 to 63 inches)
Central tendency = 525 to 1120 mm
(21 to 44 inches)

MAAT (C)
Total range = 1.5 to 7.9
(35 to 46 F)
Central tendency = 3.8 to 5.8
(39 to 42 F)

Climate stations: none

Influencing water features

Water Table Depth:
>200cm
(>80 in)

Flooding:
Frequency: None
Duration: None

Ponding:
Frequency: None
Duration: None

Soil features

Representative Soil Features
This ecological site is associated with the Brickel, Crocamp, Pelican, Tenas, and Vitrandic Dystrocryepts components. The soils are Haploxerandic Humicryepts, Vitrandic Dystrocryepts, Vitrandic Haplocryolls, Vitrandic Haploxerolls, and Vitrixerandic Humicryepts. These soils have developed in till, colluvium and residuum from granite, metamorphic and andesite rocks. Most sites have a surface influenced by volcanic ash and loess. Volcanic ash layers are mixed at lower elevations and form distinct, moderately thicker layers at higher elevations.

Parent Materials:
Kind: volcanic ash, loess, till,
Origin: mixed
Kind: colluvium, residuum
Origin: granite, metamorphics, andesite

Surface Texture: (<2mm fraction)
(1) Ashy-Loam
(2) Ashy-Sandy Loam
(3) Ashy-Fine Sandy Loam

Surface Fragments

Table 4. Representative soil features

Table 5. Representative soil features (actual values)

References

• . USNVC [United States National Vegetation Classification]. 2019. United States National Vegetation Classification Database, V2.03. Federal Geographic Data Committee, Vegetation Subcommittee, Washington DC.. USNVC: http://usnvc.org/.

• Gerald, R. 2004. NRCS - Washington; Interim Ecological Site Descriptions for Rangeland.

• Rocchio, J.F. and R.C. Crawford. 2015. Ecological systems of Washington State. A guide to identification. Washington Department of Natural Resources.. Natural Heritage Report.. Washington Department of Natural Resources, Natural Heritage Program, Olympia, WA. 1–397.

Contributors

Stephanie Shoemaker
Brian Gardner

Approval

Curtis Talbot, 10/15/2020