LOCATION SWEETMOUNT CAEstablished Series
TAXONOMIC CLASS: Loamy-skeletal, mixed, superactive Pachic Argicryolls
TYPICAL PEDON: Sweetmount very gravelly sandy loam--rangeland. (Colors are for dry soil unless otherwise noted.) The soil surface is covered with 25 percent gravel, 5 percent cobbles, 3 percent stones, and 1 percent boulders.
A--0 to 2 inches; grayish brown (10YR 5/2) very gravelly sandy loam, very dark grayish brown (10YR 3/2) moist; moderate fine subangular blocky structure; soft, very friable, nonsticky and nonplastic; few very fine roots; many very fine interstitial pores; 35 percent gravel; slightly acid; clear wavy boundary. (2 to 7 inches thick)
Bt1--2 to 8 inches; grayish brown (10YR 5/2) very gravelly loam, very dark grayish brown (10YR 3/2) moist; moderate fine and medium subangular blocky structure; soft, very friable, slightly sticky and slightly plastic; many very fine and fine roots; common very fine tubular and interstitial pores; few faint clay bridges between sand grains; 40 percent gravel and 15 percent stones; slightly acid; clear wavy boundary. (4 to 8 inches thick)
Bt2--8 to 16 inches; grayish brown (10YR 5/2) very gravelly loam, very dark grayish brown (10YR 3/2) moist; moderate fine and medium subangular blocky structure; slightly hard, very friable, moderately sticky and moderately plastic; many very fine, fine, medium and coarse roots; common very fine tubular and interstitial pores; common faint clay bridges between sand grains; 35 percent gravel, 5 percent cobbles, and 10 percent stones; neutral; clear wavy boundary. (7 to 12 inches thick)
Bt3--16 to 24 inches; brown (10YR 5/3) very gravelly clay loam, dark brown (10YR 3/3) moist; moderate medium and coarse subangular blocky structure; slightly hard, very friable, moderately sticky and moderately plastic; common very fine and fine roots; common very fine tubular and interstitial pores; many distinct clay films on faces of peds and lining pores; 40 percent gravel and 5 percent cobbles; neutral; clear wavy boundary. (6 to 12 inches thick)
Bt4--24 to 33 inches; brown (10YR 5/3) very gravelly clay loam, dark brown (10YR 3/3) moist; strong fine and medium angular blocky structure; slightly hard, friable, moderately sticky and moderately plastic; common very fine and fine roots; common very fine tubular and interstitial pores; many distinct clay films on faces of peds and lining pores; 40 percent gravel and 5 percent cobbles; neutral; clear wavy boundary. (6 to 12 inches thick)
Bt5--33 to 39 inches; light brownish gray (10YR 6/2) very gravelly clay loam, dark grayish brown (10YR 4/2) moist; strong medium angular blocky structure; hard, friable, moderately sticky and moderately plastic; few very fine and fine roots; common very fine tubular pores; many distinct clay films on faces of peds and lining pores; 40 percent gravel and 5 percent cobbles; 20 percent paragravel; neutral; clear wavy boundary. (4 to 10 inches thick)
Bt6--39 to 55 inches; light yellowish brown (10YR 6/4) extremely gravelly clay, dark yellowish brown (10YR 4/4) moist; moderate medium angular blocky structure; hard, firm, very sticky and very plastic; few very fine and fine roots; common very tine tubular pores; many distinct clay films on faces of peds and lining pores; 60 percent gravel and 5 percent cobbles; 20 percent paragravel; neutral; clear irregular boundary. (10 to 20 inches thick)
Crt--55 to 65 inches; weathered andesitic tuff; illuvial clay lines fractures.
TYPE LOCATION: Mono County, California; on the Toiyabe National Forest in the Sweetwater Mountains about 2 miles southwest of Lobdell Lake; approximately 1,150 feet north and 400 feet west of the southeast corner of section 30, T. 7 N., R. 24 E.; USGS Chris Flat 7.5 minute topographic quadrangle; 38 degrees 25 minutes 12.7 seconds north latitude and 119 degrees 22 minutes 35.4 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 - 42 to 46 degrees F.
Mean summer soil temperature - 52 to 59 degrees F.
Mollic epipedon thickness - 24 to 36 inches; includes the Bt1 through Bt4 horizons.
Depth to base of argillic horizon - 40 to 60 inches.
Depth to bedrock - 40 to 60 inches to a paralithic contact. The paralithic materials below the contact are weathered andesitic rock.
Particle-size control section - Clay content: Averages 18 to 27 percent; Rock fragments: Averages 35 to 60 percent, mainly gravel. Lithology of fragments are volcanic rocks such as andesite, tuff, or tuff-breccia.
Other features - Clay content increases steadily with depth and is typically more than 27 percent in the lower part of the argillic horizon.
A horizon - Value: 4 or 5 dry, 2 or 3 moist.
Chroma: 2 or 3, dry or moist.
Organic matter content: 2 to 4 percent.
Reaction: Slightly acid or neutral.
Bt1 and Bt2 horizons - Value: 4 or 5 dry, 2 or 3 moist.
Chroma: 2 or 3, dry or moist.
Texture: Very gravelly loam, very gravelly sandy clay loam, or very gravelly clay loam.
Clay content: 18 to 27 percent.
Rock fragments: 35 to 60 percent.
Organic matter content: 1 to 3 percent.
Reaction: Slightly acid or neutral.
Bt3 horizon - Clay content: 27 to 35 percent.
Rock fragments: 35 to 60 percent.
Organic matter content: 1 to 3 percent.
Reaction: Slightly acid or neutral.
Bt4 and Bt5 horizons - Value: 5 or 6 dry, 3 or 4 moist.
Chroma: 3 or 4, dry or moist.
Clay content: 27 to 35 percent.
Rock fragments: 35 to 60 percent.
Pararock fragments: 0 to 20 percent paragravel.
Reaction: Slightly acid or neutral.
Bt6 horizon - Value: 5 or 6 dry, 3 or 4 moist.
Chroma: 3 or 4, dry or moist.
Texture: Extremely gravelly clay or very gravelly clay loam.
Clay content: 35 to 50 percent.
Rock fragments: 50 to 80 percent.
Pararock fragments: 5 to 20 percent paragravel.
Reaction: Slightly acid or neutral.
COMPETING SERIES: These are the Angelwhine, Aspetill, Badwater, Bickmore, Bluebell, Booneville, Buena Vista, Dab, Dailybasin (T), Delhew, Hawkinspeak, Keman, Littlemud (T), Lostcannon, Monibasin, Parkalley (T), Parkay, Redbird, Rutherford, and Woodhurst series.
Angelwhine, Aspetill, Dab, Delhew, Keman, Lostcannon, and Monibasin soils are very deep and do not have subhorizons of the argillic horizon with 27 to 50 percent clay. Badwater soils are very deep and are dominated by boulders in the particle-size control section. Bickmore, Bluebell, Buena Vista, Hawkinspeak, Littlemud, Rutherford, and Woodhurst soils are moderately deep to lithic contacts. Booneville soils are very deep and have mean annual soil temperature of 36 to 40 degrees F. Dailybasin soils have an ustic moisture regime. Parkalley soils are very deep, have the base of the argillic horizon between 28 and 35 inches from the soil surface, and are dominated by flagstones. Parkay soils average 27 to 35 percent clay in the particle-size control section. Redbird soils are very deep, average 27 to 35 percent clay in the particle-size control section, and have horizons with identifiable secondary carbonates within 40 inches of the soil surface.
GEOGRAPHIC SETTING: Sweetmount soils are on mountains. They typically occur on shoulder positions. They formed in residuum and colluvium derived from andesite, tuff, or tuff-breccia. Slopes are 4 to 30 percent. Elevations range from 8,000 to 10,000 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 36 to 42 degrees F., and the frost-free period is 30 to 60 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the competing Dab and Hawkinspeak soils and the Sumeadow soil. Sumeadow soils are very deep and have umbric epipedons.
DRAINAGE AND PERMEABILITY: Well drained; high surface runoff; slow permeability (moderately low or moderately high saturated hydraulic conductivity).
USE AND VEGETATION: Sweetmount soils are used for rangeland, recreation, watershed, and wildlife habitat. The native vegetation is mainly mountain big sagebrush, snowberry, and western needlegrass.
DISTRIBUTION AND EXTENT: Eastern California, on the east side of the Sierra Nevada Range. These soils are not extensive with about 3,100 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:
Mollic epipedon - The zone from the soil surface to 33 inches (A, Bt1, Bt2, Bt3, and Bt4 horizons).
Argillic horizon - The zone from 2 to 55 inches (Bt1, Bt2, Bt3, Bt4, Bt5, and Bt6 horizons).
Paralithic contact - The boundary at 55 inches to underlying soft, weathered bedrock (Crt layer).
Particle-size control section - The zone from 2 to 22 inches (Bt1 and Bt2 horizons and part of the Bt3 horizon).