LOCATION SCOAP WAEstablished Series
TAXONOMIC CLASS: Loamy-skeletal, isotic, frigid Vitrandic Haploxerolls
TYPICAL PEDON: Scoap gravelly ashy loam - woodland. (Colors are for dry soil unless otherwise stated.)
Oi--0 to 2 inches; black (10YR 2/1) moist; loose, partially decomposed organic litter, composed of needles, leaves, twigs, bark and cones; slightly acid (pH 6.4); abrupt smooth boundary. (2 to 4 inches thick)
A1--2 to 9 inches; dark grayish brown (10YR 4/2) gravelly ashy loam, very dark brown (10YR 2/2) moist; weak fine and medium granular structure; slightly hard, friable, slightly sticky and slightly plastic; common fine and medium, few coarse roots; common fine pores; 25 percent gravel; neutral (pH 6.6); clear wavy boundary. (5 to 8 inches thick)
A2--9 to 15 inches; grayish brown (10YR 5/2) gravelly ashy loam, very dark grayish brown (10YR 3/2) moist; weak fine and medium subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; common fine and medium, few coarse roots; common fine pores; 25 percent gravel; slightly acid (pH 6.4); clear wavy boundary. (5 to 13 inches thick)
Bw1--15 to 28 inches; brown (10YR 5/3) gravelly loam, dark brown (10YR 3/3) moist; weak fine and medium subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; common fine and medium, few coarse roots; common fine pores; 25 percent gravel; slightly acid (pH 6.4); clear wavy boundary. (5 to 15 inches thick)
Bw2--28 to 35 inches; pale brown (10YR 6/3) very cobbly loam, dark yellowish brown (10YR 3/4) moist; weak fine and medium subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; common fine and medium, few coarse roots; common fine pores; 20 percent gravel and 25 percent cobbles; slightly acid (pH 6.4); clear wavy boundary. (4 to 8 inches thick)
BC--35 to 45 inches; light yellowish brown (10YR 6/4) very cobbly loam, dark yellowish brown (10YR 3/4) moist; massive; hard, friable, slightly sticky and slightly plastic; common fine and medium, few coarse roots; common fine pores; 20 percent gravel and 30 percent cobbles; slightly acid (pH 6.4); clear wavy boundary. (7 to 10 inches thick)
C--45 to 60 inches; very pale brown (10YR 7/4) very stony loam, brown (10YR 4/3) moist; massive; hard, friable, slightly sticky and slightly plastic; few fine, medium and coarse roots; few fine pores; 10 percent gravel, 15 percent cobbles and 25 percent stones; slightly acid (pH 6.4).
TYPE LOCATION: Stevens County, Washington; about 3 miles southeast of Gifford; 1,400 feet south and 2,300 feet east of the northwest corner of sec. 12, T. 32 N., R. 37 E., W.M. 33T-79.
RANGE IN CHARACTERISTICS: The mean annual soil temperature is 44 to 46 degrees F. The mollic epipedon is 20 to 30 inches thick. These soils are usually moist but are dry in all parts between a depth of 8 to 24 inches for 60 to 75 consecutive days following the summer solstice. The upper 10 to 20 inches has an estimated moist bulk density of 1.20 to 1.50 g/cc, volcanic glass content of 5 to 20 percent, acid-oxalate extractable aluminum plus one-half of the acid-oxalate extractable iron of 0.4 to 1.0 percent, and 15-bar water retention of 5 to 12 percent for air dried samples. The control section has 8 to 12 percent clay and averages 35 to 50 percent rock fragments. Base saturation (by sum of cations) is assumed to be less than 75 percent in some part between 10 and 30 inches.
The A horizon has value of 4 or 5 dry, 2 or 3 moist, and chroma of 1 to 3 moist and dry. It is ashy silt loam, ashy loam or ashy sandy loam and has 5 to 30 percent rock fragments. Reaction is neutral or slightly acid.
The Bw horizon has value of 4 to 6 dry, 3 or 4 moist, and chroma of 3 or 4 moist and dry. It is loam, sandy loam, or silt loam and is gravelly, very gravelly, or very cobbly. It is 20 to 40 percent gravel and 0 to 30 percent cobbles.
The C horizon has value of 5 to 7 dry, 3 through 5 moist, and chroma of 3 or 4 moist and dry. It is loam or sandy loam and is very cobbly, very stony, or very gravelly. It is 10 to 50 percent gravel and 5 to 40 percent cobbles and stones.
COMPETING SERIES: These are the Cassal, Cherrycreek, Eastpine, Egyptcreek, Fredonyer, Longs, Midpeak, Mineral, Peahke, Shalrock, Shilling, Umatilla, and Yellcreek. Cassal soils have distinct redox features at 30 to 45 inches. Cherrycreek and Longs soils are 40 to 60 inches to a lithic contact and have more than 12 percent clay in the particle-size control section. Eastpine, Egyptcreek, Fredonyer, Midpeak, Mineral, Peahke, and Shalrock soils are 20 to 40 inches to a lithic contact. Shilling soils have a mollic epipedon 10 to 20 inches thick and have 18 to 27 percent clay in the particle-size control section. Umatilla soils have more than 25 percent clay in the particle-size control section. Yellcreek soils have a mollic epipedon 7 to 15 inches thick and have 50 to 80 percent rock fragments in the particle-size control section. Soils in the similar mixed, superactive family classification are the Dogtown, Frint, Hogranch, Magill Pelican, and Wellscreek series. Dogtown soils are dry 45 to 60 days following the summer solstice. Frint,and Magill soils are 20 to 40 inches deep to a lithic contact. Hogranch soils are dry 85 to 95 days following the summer solstice. Pelican soils are dry 75 to 90 days following the summer solstice. Wellscreek soils have a mollic epipedon 10 to 20 inches thick and 18 to 30 percent clay in the particle-size control section.
GEOGRAPHIC SETTING: Scoap soils are on glaciated uplands, outwash terraces and mountainsides at elevations of 1,500 to 4,800 feet. Slopes are 5 to 65 percent. The soils formed in glacial till and colluvium with a component of loess and volcanic ash in the upper part. Scoap soils are in a continental climate with warm, dry summers and cool, moist winters. Average annual precipitation is 18 to 25 inches. Average annual temperature is 41 to 45 degrees F. The frost-free season is 90 to 120 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Aits, Dehart, Donavan, Inkler, Maki, Raisio, Rufus, and Stevens soils. Aits, Donavan and Stevens soils are coarse-loamy. Dehart soils do not have a mollic epipedon and are on mountains. Aits soils are on glaciated mountains. Donavan soils are on toeslopes, footslopes, and backslopes of mountains. Inkler soils have an admixture of volcanic ash in the upper part of the particle-size control section with a bulk density of 0.85 to 0.95 g/cc and are on foothills and mountains. Maki and Raisio soils are 20 to 40 inches deep to a lithic contact and Maki soils are also calcareous. Maki soils are on south-facing glaciated uplands and mountain sides. Rufus soils are 10 to 20 inches deep to a lithic contact. Raisio, Rufus, and Stevens soils are on south-facing sideslopes and ridgetops of mountains.
DRAINAGE AND PERMEABILITY: Well drained; very slow to very rapid runoff; moderate permeability.
USE AND VEGETATION: These soils are used primarily for timber production and grazing and some is used for dryland cropland and pasture. Potential natural vegetation includes Douglas- fir, ponderosa pine, and western larch with an understory of pinegrass, mallow ninebark, common snowberry, Oregon-grape, snowbrush ceanothus, creambush oceanspray, bluebunch wheatgrass, lupine, and prairie junegrass.
DISTRIBUTION AND EXTENT: Eastern, Washington; MLRA 43. The series is of small extent.
MLRA OFFICE RESPONSIBLE: Bozeman, Montana
SERIES ESTABLISHED: Stevens County, Washington, 1978.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon - the zone from 2 to 28 inches (A1, A2 and Bw1 horizons)
Cambic horizon - the zone from 28 to 35 inches (Bw2 horizon)
Vitrandic feature - the zone from 2 to 15 inches
Depth to diagnostic horizons and features are measured from the top of the first mineral layer.