LOCATION MCTOM CA+NVEstablished Series
TAXONOMIC CLASS: Sandy-skeletal, mixed Xeric Humicryepts
TYPICAL PEDON: McTom extremely stony loamy coarse sand--forest land. (Colors are for dry soil unless otherwise noted.) The soil surface is covered with 25 percent gravel, 5 percent cobbles, 15 percent stones, and 15 percent boulders.
Oi--0 to 2 inches; dark brown (10YR 3/3) very stony slightly decomposed plant material composed of fibrous needle litter, very dark grayish brown (10YR 3/2) moist; 15 percent cobbles, 25 percent stones, and 10 percent boulders; abrupt wavy boundary. (0 to 2 inches thick)
A1--2 to 8 inches; grayish brown (10YR 5/2) extremely stony loamy coarse sand, very dark grayish brown (10YR 3/2) moist; moderate fine subangular blocky structure parting to moderate fine granular; soft, very friable, nonsticky and nonplastic; many very fine, many fine, many medium, common coarse, and common very coarse roots; many very fine and fine interstitial pores; 20 percent gravel, 15 percent cobbles, and 25 percent stones; slightly acid; clear wavy boundary. (4 to 8 inches thick)
A2--8 to 18 inches; brown (10YR 5/3) extremely stony loamy coarse sand, very dark grayish brown (10YR 3/2) moist; moderate fine subangular blocky structure; soft, very friable, nonsticky and nonplastic; many very fine, fine, medium, coarse, and very coarse roots; many very fine and fine tubular and interstitial pores; 25 percent gravel, 20 percent cobbles, and 25 percent stones; moderately acid; clear wavy boundary. (6 to 12 inches thick)
Bw--18 to 34 inches; pale brown (10YR 6/3) extremely cobbly loamy coarse sand, brown (10YR 4/3) moist, weak medium subangular blocky structure; soft, very friable, nonsticky and nonplastic; common very fine, fine, medium, coarse, and very coarse roots; many very fine tubular and interstitial pores; 30 percent gravel, 30 percent cobbles, and 3 percent stones; moderately acid; clear wavy boundary. (10 to 20 inches thick)
Cr--34 to 44 inches; weathered granodiorite.
TYPE LOCATION: Mono County, California; on the Toiyabe National Forest in the Sweetwater Mountains about 0.75 mile southwest of the Middle Sister; in a nonsectionized township near the projected northeast corner of section 35, T. 8 N., R. 24 E.; USGS Desert Creek Peak 7.5 minute topographic quadrangle; 38 degrees 30 minutes 5.2 seconds north latitude and 119 degrees 18 minutes 7.1 seconds west longitude, NAD27.
RANGE IN CHARACTERISTICS:
Soil moisture - Usually moist in the moisture control section during late fall, winter, and spring; dry from July through early October for 60 to 80 consecutive days in the four months following the summer solstice; Typic xeric moisture regime.
Mean annual soil temperature - 35 to 40 degrees F.
Mean summer soil temperature - 44 to 47 degrees F.
Umbric epipedon thickness - 10 to 20 inches.
Depth to bedrock - 20 to 40 inches to a paralithic contact. The paralithic materials below the contact are weathered granitic rock such as granodiorite.
Particle-size control section - Clay content: Averages 3 to 8 percent;
Rock fragments: Averages 60 to 80 percent. Lithology of fragments is granodiorite.
A horizons
Value: 4 or 5 dry, 2 or 3 moist.
Chroma: 2 or 3, dry or moist.
Organic matter content: 1 to 3 percent.
Reaction: Moderately acid or slightly acid.
Bw horizon
Value: 6 or 7 dry, 4 or 5 moist.
Chroma: 3 or 4, dry or moist.
Texture: Extremely cobbly loamy coarse sand, extremely gravelly loamy coarse sand, or extremely stony loamy coarse sand.
Clay content: 3 to 8 percent.
Rock fragments: 60 to 80 percent.
Reaction: Moderately acid or slightly acid.
COMPETING SERIES: This is the Klauspeak series. Klauspeak soils are very deep and average less than 60 percent rock fragments in the particle-size control section.
GEOGRAPHIC SETTING: McTom soils are on mountains. They typically occur on backslope positions. They formed in residuum and colluvium derived from granodiorite. Slopes are 30 to 75 percent. Elevations range from 9,500 to 11,000 feet. The climate is subhumid-continental with cold, moist winters and cool, dry summers. The mean annual precipitation is 20 to 30 inches, the mean annual temperature is 33 to 38 degrees F., and the frost-free period is 30 to 60 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Bakscratch and Grandridge soils. Bakscratch soils have mollic epipedons, argillic horizons, and are shallow to paralithic contacts. Grandridge soils have mollic epipedons, argillic horizons, are shallow to paralithic contacts, and have a frigid temperature regime.
DRAINAGE AND PERMEABILITY: Somewhat excessively drained; high surface runoff; rapid permeability (high or very high saturated hydraulic conductivity).
USE AND VEGETATION: McTom soils are used for forest land, recreation, watershed, and wildlife habitat. The native vegetation is mainly a forest canopy of whitebark pine and limber pine with a sparse understory of various alpine forbs and some bluegrass.
DISTRIBUTION AND EXTENT: Eastern California and western Nevada, on the east side of the Sierra Nevada Range. These soils are not extensive with about 215 acres of the series mapped to date. MLRA 22A.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California
SERIES ESTABLISHED: Mono County (Toiyabe National Forest Area), California, 2006.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Organic soil material - The zone from the soil surface to 2 inches (Oi horizon).
Umbric epipedon - The zone from 2 to 18 inches (A1 and A2 horizons).
Paralithic contact - The boundary at 34 inches to underlying soft weathered bedrock (Cr layer).
Particle-size control section - The zone from 10 to 34 inches (Bw horizon and part of the A2 horizon).
The revision of December 2006 updated the taxonomic class from Xeric Dystrocryepts based on the tenth edition of the Keys to Soil Taxonomy, 2006.