LOCATION STIRRUP WAEstablished Series
TAXONOMIC CLASS: Medial-skeletal over loamy-skeletal, amorphic over isotic Andic Humicryods
TYPICAL PEDON: Stirrup ashy sandy loam - under a coniferous forest on a 42 percent northwest-facing slope at an elevation of 3,620 feet. The soil was dry when described. (Colors are for dry soil unless otherwise stated. All textures are apparent field textures).
Oi--0 to 1 inch; partially decomposed forest litter; abrupt smooth boundary. (1/2 to 2 inches thick)
E--1 to 4 inches; light gray (7.5YR 7/1) ashy sandy loam, volcanic ash dark gray (5YR 4/1) moist; single grain, loose, nonsticky and nonplastic; few very fine and fine roots; very strongly acid (pH 5.0); abrupt wavy boundary. (1/2 to 3inches thick)
Bhs--4 to 8 inches; brown (7.5YR 5/4) gravelly medial sandy loam, (dominated by volcanic ash) dark brown (7.5YR 3/4) moist; moderate very fine subangular blocky structure; slightly hard, friable, slightly sticky and nonplastic, weakly smeary; common very fine, fine and few medium roots; 20 percent gravel; NaF pH 12.0; very strongly acid (pH 5.0); clear wavy boundary. (3 to 7 inches thick)
Bs--8 to 14 inches; yellowish brown (10YR 5/4) very gravelly medial loam, brown (7.5YR 4/4) moist; moderate very fine subangular blocky structure; slightly hard, friable, slightly sticky and nonplastic, weakly smeary; common very fine, fine and few medium roots; 40 percent gravel; NaF pH 12.0; very strongly acid (pH 4.8); clear wavy boundary. (6 to 10 inches thick)
Bw--14 to 24 inches; light yellowish brown (10YR 6/4) very gravelly medial loam, brown (10YR 4/3) moist; moderate very fine subangular blocky structure; slightly hard, friable, slightly sticky and nonplastic, weakly smeary; few very fine and fine roots; 50 percent gravel; NaF pH 11.5; very strongly acid (pH 4.8); clear wavy boundary (7 to 25 inches thick)
BC--24 to 36 inches; light yellowish brown (10YR 6/4) extremely gravelly medial sandy loam, dark yellowish brown (10YR 4/4) moist; weak very fine subangular blocky structure; soft, very friable, nonsticky and nonplastic, weakly smeary; few very fine roots; 70 percent gravel; NaF pH 10.6; very strongly acid (pH 5.0); clear wavy boundary. (0 to 12 inches thick)
2C--36 to 61 inches; pale yellow (2.5Y 7/4) extremely gravelly sandy loam, dark yellowish brown (10YR 4/4) moist; massive, soft, very friable nonsticky and nonplastic; 80 percent gravel; NaF pH 11.0; very strongly acid (pH 5.0).
TYPE LOCATION: Kittitas County, Washington; located about 1/4 mile west of Stampede Pass; about 0.3 miles west on Forest Service Road 212, Spur D. 100 feet south and 1,300 feet east of the northwest corner section 25, T. 21 N., R. 11 E.; USGS Stampede Pass, Washington topographic quadrangle; Latitude 47 degrees, 17 minutes, 28 seconds N. and Longitude 121 degrees, 21 minutes, 06 seconds W. (NAD83).
RANGE IN CHARACTERISTICS: The mean annual soil temperature is 39 to 45 degrees F. The soils are usually moist but are dry in all parts in the moisture control section for 15 to 30 consecutive days during the summer. The upper 25 to 36 inches of the particle-size control section has an estimated moist bulk density of 0.60 to 0.85 grams per cubic centimeter, volcanic glass content of 30 to 60 percent, acid oxalate extractable aluminum plus one-half iron of more than 2.0 percent and 15-bar water content of more than 12 percent. Solum thickness is 25 to 36 inches. The spodic horizon averages more than 6.0 percent organic carbon in the upper 4 inches and has ratio of free iron to carbon of about 0.47. Depth to bedrock is 40 to more than 60 inches.
The E horizon has hue of 5YR, 7.5YR or 10YR, value of 3 to 6 moist and chroma of 1 or 2 dry, 1 to 3 moist. Reaction is very strongly acid to moderately acid.
The Bhs horizon has hue of 7.5YR, 10YR, or 5YR, value of 3 or 4 moist and chroma of 4 to 6 dry. Texture is medial loam, medial sandy loam, gravelly medial loam or gravelly medial sandy loam. Reaction is very strongly acid to moderately acid.
The Bs horizon has hue of 7.5YR or 10YR and value of 3 or 4 moist. Texture is very gravelly medial loam, medial sandy loam, very cobbly medial sandy loam or very gravelly medial sandy loam. Reaction is very strongly acid to slightly acid.
The Bw horizon has hue of 10YR or 2.5Y, value of 4 or 5 moist and chroma of 3 or 4 moist or dry. Texture of the fine earth fraction is medial loam or medial sandy loam and is very cobbly, extremely cobbly, very gravelly, or extremely gravelly. Reaction is very strongly acid to slightly acid.
The BC horizon, when present has a fine earth texture of medial sandy loam, or medial loam and is extremely cobbly or extremely gravelly. Reaction is very strongly or strongly acid.
The 2C horizon has hue of 10YR or 2.5Y. Texture of the fine-earth fraction is sandy clay loam, sandy loam or loam and is extremely cobbly or extremely gravelly.
COMPETING SERIES: This is the Haywire series. Haywire soils have a lithic contact at 20 to 40 inches.
GEOGRAPHIC SETTING: Stirrup soils are on mountain slopes. Slopes are 5 to 85 percent. These soils formed in volcanic ash mixed with colluvium from andesite.and in some areas, sandstone. Elevation is 2,700 to 4,700 feet. The climate is characterized by cool dry summers and cool moist winters. The mean annual precipitation is 65 to 100 inches. The average January temperature is about 26 degrees F. and the average July temperature is about 59 degrees F. The mean annual temperature is 37 to 43 degrees F. The growing season at 28 degrees F is 130 to 170 days. The frost-free season is 35 to 80 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Gilpar and Nimue soils. Gilpar soils average less than 6 percent organic carbon in the upper part of the spodic horizon, are dry 30 to 45 days in the moisture control section and are on mountain side slopes. Nimue soils have more than 5 times as much organic carbon as free iron in the upper 12 inches of the spodic horizon and are on mountain side slopes.
DRAINAGE AND PERMEABILITY: Well drained; medium to rapid runoff; permeability is moderately rapid.
USE AND VEGETATION: These soils are used for timber production, wildlife habitat and watershed. Vegetation is Pacific silver fir, western hemlock and Douglas-fir with an understory of huckleberry, common beargrass, rusty menziesia, Oregongrape and princes pine.
DISTRIBUTION AND EXTENT: East slopes of the Cascade Mountains in western Kittitas County; MLRA 3. This series is of small extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Portland, Oregon
SERIES ESTABLISHED: Wenatchee National Forest, Kittitas County, Washington, 2003. Source of name is Stirrup Lake in western Kittitas County.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Albic horizon - the zone from 1 to 4 inches (E horizon)
Spodic horizon - the zone from 4 to 14 inches (Bhs and Bs horizon)
Andic properties - the zone from 1 to 36 inches
Particle-size control section - from 11 to 41 inches with the zone from 11 to 36 inches qualifying as medial-skeletal and the zone from 36 to 41 inches qualifying as loamy-skeletal. This pedon would classify as a medial-skeletal over loamy-skeletal family if such a contrasting particle-size class were in Soil Taxonomy. Some pedons may range to fragmental in the lower part of the particle-size control section however do not meet a contrasting particle-size class due to the lack of a 35 percent or more absolute rock fragment increase over the medial-skeletal layer above.
Depths to diagnostic horizons and features are measured from the top of the first mineral layer.
ADDITIONAL DATA: Partial laboratory data are available for this pedon. Soil survey sample #s S80WA-037-006; NSSL, Lincoln, NE.