LOCATION CHEWACK WAEstablished Series
TAXONOMIC CLASS: Ashy-skeletal over loamy-skeletal, glassy over isotic Xeric Vitricryands
TYPICAL PEDON: Chewack very stony ashy sandy loam, forestland on a northwest facing 46 percent slope, at 5,400 feet elevation in a subalpine fir, Engelmann spruce and lodgepole pine forest. (Colors are for dry soil unless otherwise stated. All textures are apparent field textures.)
Oe--0 to 2 inches; moderately decomposed needles, leaves and twigs; abrupt smooth boundary. (1 to 3 inches thick)
A--2 to 5 inches; light brownish gray (10YR 6/2) very stony ashy sandy loam, dark grayish brown (10YR 4/2) moist; weak fine and medium granular structure; soft, very friable, nonsticky and nonplastic; many very fine and fine roots and few medium and coarse roots; common fine irregular pores; 15 percent pebbles, 10 percent cobbles, and 10 percent stones; slightly acid (pH 6.4); clear wavy boundary. (1 to 3 inches thick)
Bw--5 to 25 inches; pale brown (10YR 6/3) very cobbly ashy sandy loam, brown (10YR 4/3) moist; weak fine subangular blocky structure; soft, very friable, nonsticky and nonplastic; common very fine and fine roots and few medium roots; common fine irregular pores; 20 percent pebbles, 20 percent cobbles, and 5 percent stones; NaF pH of 10.5; slightly acid (pH 6.2); gradual wavy boundary. (19 to 35 inches thick)
2C--25 to 62 inches; light gray (2.5Y 7/2) very cobbly coarse sandy loam, grayish brown (2.5Y 5/2) moist; massive; soft, very friable, nonsticky and nonplastic; common very fine and fine roots in the upper part; few irregular pores; 20 percent pebbles, 25 percent cobbles, and 5 percent stones; slightly acid (pH 6.2)
TYPE LOCATION: Okanogan County, Washington; about 14 miles north-northeast from the town of Winthrop, Washington; 400 feet west and 700 feet south of the northeast corner of section 9, T. 37 N., R. 22 E. (Latitude 48 degrees 43' 28"N, Longitude 120 degrees 04' 47"W)
RANGE IN CHARACTERISTICS: The mean annual soil temperature is 37 to 41 degrees F. The average summer soil temperature ranges from 42 to 46 degrees F. These soils are usually moist but are dry in all parts of moisture control section for 45 to 60 consecutive days following the summer solstice. Thickness of the mixed volcanic ash mantle ranges from 20 to 35 inches and has an estimated moist bulk density of 1.10 to 1.30 g/cc, volcanic glass content of 30 to 60 percent, acid-oxalate extractable aluminum plus one-half of the acid-oxalate extractable iron of 1.0 to 2.0 percent, and 15-bar water retention of 5 to 12 percent for air dried samples. The particle-size control section averages 35 to 60 percent rock fragments. Reaction is moderately acid to slightly acid throughout.
The A horizon has value of 5 or 6 dry, 4 or 5 moist, and chroma of 2 or 3 dry or moist.
The Bw horizon has chroma of 3 or 4 dry or moist. It is very cobbly ashy sandy loam or very gravelly ashy sandy loam. It has 20 to 30 percent pebbles, 10 to 20 percent cobbles and 5 to 10 percent stones.
The 2C horizon has value of 6 or 7 dry, 4 or 5 moist, and chroma of 2 or 3 dry or moist. It is very cobbly coarse sandy loam or very gravelly coarse sandy loam. It has 25 to 35 percent pebbles, 10 to 25 percent cobbles and 5 to 10 percent stones.
COMPETING SERIES: These are the Azwell, Bagmount, Burpeak, Fears, Hallihan, Naxing, Pird, Saydab and Tiptop series. Azwell and Saydab soils are 20 to 40 inches to a lithic contact. Bagmount soils are 20 to 40 inches to a paralithic contact. Fears, Pird and Tiptop soils have ashy-skeletal material greater than 40 inches thick. Hallihan soils have a bulk density of 0.85 to 0.95 g/cc in the particle-size control section. Naxing soils have an umbric epipedon. Burpeak soils are 40 to 60 inches deep to bedrock.
GEOGRAPHIC SETTING: Chewack soils are on back slopes of mountains at elevations of 4,400 to 6,400 feet. Slopes are 35 to 65 percent. These soils formed in a mixture of volcanic ash and granitic colluvium over ablation till. Precipitation ranges from 25 to 35 inches. The climate is characterized by cold, wet winters and cool, dry summers. The average January temperature ranges from 18 to 22 degrees F., and the average July temperature ranges from 52 to 58 degrees F. The average annual temperature ranges from 37 to 42 degrees F. The frost-free season is 60 to 85 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Doe, Myerscreek, Sitdown and Wapal soils. Doe soils have a frigid temperature regime. Myerscreek soils are formed in compact glacial till and have a 7 to 14 inch volcanic ash mantle. Sitdown soils are formed in sandy-skeletal ablation till or outwash with a 7 to 14 inch volcanic ash mantle. Wapal soils are frigid and are on southerly aspects.
DRAINAGE AND PERMEABILITY: Well drained, rapid to very rapid runoff; moderately rapid permeability.
USE AND VEGETATION: Used for timber production, wildlife habitat, recreation, livestock grazing and watershed. Native vegetation is subalpine fir, Engelmann spruce, lodgepole pine, Douglas-fir, grouse blueberry, black mountain huckleberry, silky lupine, heartleaf arnica, pachystima, sitka alder and pinegrass.
DISTRIBUTION AND EXTENT: Northcentral Washington. Series is of small extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Portland, Oregon
SERIES ESTABLISHED: Okanogan National Forest, Okanogan County, Washington, 2005.
REMARKS: Diagnostic horizons and features recognized in this soil are an ochric epipedon (A horizon) from the surface to 3 inches, an ashy-skeletal cambic (Bw) horizon from 3 to 23 inches over ablation till. The particle-size control section is the zone from 2 to 42 inches (A, Bw and part of the 2C horizon), ashy-skeletal from 2 to 25 inches and loamy-skeletal from 25 to 45 inches.