LOCATION LASSEN CAEstablished Series
TAXONOMIC CLASS: Fine, smectitic, mesic Leptic Haploxererts
TYPICAL PEDON: Lassen clay--on a west facing convex slope of 15 percent under medusahead, bullthistle, bulbous bluegrass, tumble mustard, lupine, and cheatgrass at 2,670 feet elevation--rangeland. (Colors are for dry soil unless otherwise noted. When described on September 11, 1973, the soil was dry above 7 inches and moist below).
A--0 to 4 inches; dark grayish brown (10YR 4/2) clay, very dark grayish brown (10YR 3/2) moist; strong medium subangular blocky structure parting to strong fine angular blocky; very hard, firm, very sticky and very plastic; many very fine and fine roots; vertical cracks are 1 to 2 inches wide and 1 to 3 feet apart; 5 percent gravel, 2 percent cobbles; slightly alkaline (pH 7.5); abrupt smooth boundary. (2 to 6 inches thick)
Bw--4 to 9 inches; dark grayish brown (10YR 4/2) clay, very dark grayish brown (10YR 3/2) moist; strong coarse prismatic structure; extremely hard, very firm, very sticky and very plastic; few very fine and fine roots; few very fine discontinuous tubular pores; weakly expressed continuous pressure faces; vertical cracks are 1 to 2 inches wide and 1 to 3 feet apart; 5 percent gravel and 2 percent cobbles; slightly alkaline (pH 7.5); clear smooth boundary. (3 to 7 inches thick)
Bss--9 to 26 inches; dark grayish brown (10YR 4/2) clay, very dark grayish brown (10YR 3/2) moist; strong coarse prismatic structure parting to some wedge-shaped peds; extremely hard, very firm, very sticky and very plastic; few very fine and fine roots; few discontinuous pores; strongly expressed pressure faces and many small intersecting slickensides; vertical cracks are 1/8 to 1 inch wide; 5 percent gravel and 2 percent cobbles; slightly alkaline (pH 7.5); abrupt wavy boundary. (13 to 22 inches thick)
BC--26 to 28 inches; dark grayish brown (2.5Y 4/2) gravelly clay, dark grayish brown (2.5Y 4/2) moist; massive; extremely hard, very firm, very sticky and very plastic; few very fine and fine roots; few very fine and fine discontinuous tubular pores; strongly expressed pressure faces; 25 percent gravel; slightly alkaline (pH 7.5); abrupt wavy boundary. (1 to 5 inches thick)
R--28 inches; volcanic rock of Tertiary age.
TYPE LOCATION: Siskiyou County, California; in the Shasta Valley about 9 miles northeast of Montague and just east of where the Ager-Willow Creek Road curves slightly to the west; about 400 feet north and 70 feet west of the southeast corner of section 16, T. 46 N., R. 5 W.; USGS Bogus Mountain 7.5 minute topographic quadrangle; 41 degrees 49 minutes 53 seconds north latitude and 122 degrees 25 minutes 12 seconds west longitude, NAD27.
RANGE IN CHARACTERISTICS:
Soil moisture - The soil temperature exceeds 41 degrees F. from early March to late December about 270 to 300 days and exceeds 47 degrees F. from early April to mid November about 210 to 225 days. The soil has cracks 1 to 10 cm wide to a depth of 20 to 26 inches. The cracks open and close each year. They remain open from July through October about 90 to 120 days and are closed the rest of the year.
Mean annual soil temperature - 48 to 54 degrees F.
Mollic epipedon thickness - 20 to 35 inches; includes the Bw and Bss horizons.
Depth to bedrock - 20 to 40 inches to a lithic contact.
Particle-size control section - Clay content: 35 to 60 percent; Rock fragments: 5 to 35 percent, mainly gravel and cobbles with a few stones. Lithology of fragments are volcanic rocks such as andesite or basalt.
Vertical cracks - Reversible, trans-horizon cracks at least 1 cm wide extend from the soil surface to a depth of about 26 inches.
A and Bw horizons - Dry color: 10YR 3/2, 3/3, 4/2, 4/3, 5/2, 5/3; 7.5YR 3/2, 4/2, 5/2; 5YR 3/2, 3/3, 4/2, 4/3, 5/2, 5/3.
Moist color: 10YR 2/2, 3/2, 3/3,; 7.5YR 3/2; 5YR 2/2, 3/2, 3/3.
Texture: Clay, cobbly clay, stony clay, or very stony clay.
Clay content: 35 to 60 percent.
Organic matter content: 1 or 2 percent.
Reaction: Neutral or slightly alkaline.
Bss and BC horizons - Dry color: 2.5Y 4/2, 4/4; 10YR 3/3, 3/4, 4/2, 4/3, 4/4, 5/2, 5/3; 7.5YR 4/2, 4/4, 5/2; 5YR 4/2, 4/3, 4/4; colors are mostly lithochromic.
Moist color: 2.5Y 3/2, 4/2, 4/4; 10YR 3/2, 3/3, 3/4, 4/2, 4/3, 4/4, 5/2, 5/3; 7.5YR 3/2, 4/2, 4/4, 5/2; 5YR 3/2, 3/3, 3/4, 4/2, 4/3, 4/4.
Texture: Clay loam, clay, gravelly clay, gravelly clay loam, cobbly clay, or cobbly clay loam.
Clay content: 35 to 60 percent.
Reaction: Neutral through moderately alkaline.
Slickensides and other vertic features: Slickensides occur in the Bss horizon and pressure faces are common throughout the profile unless there is an Ap horizon.
COMPETING SERIES: These are the Aikman, Breadloaf (T), Karcal, and Shafer (T) series.
Aikman soils are dry 60 to 90 consecutive days after the summer solstice. Breadloaf soils are moderately deep to paralithic contacts. Karcal soils have ochric epipedons and cambic horizons. Shafer soils have mollic epipedons 7 to 20 inches thick and are moderately deep to paralithic contacts.
GEOGRAPHIC SETTING: Lassen soils are on hills and lava plateaus. These soils formed in residuum and colluvium derived from Tertiary volcanic rock. Slopes are 2 to 50 percent. Elevations range from 2,000 to 5,400 feet. The climate is semiarid or subhumid with cold, moist winters and warm, dry summers. The mean annual precipitation is 12 to 20 inches with a seasonal snowfall of 8 to 36 inches. The mean January temperature is about 34 degrees F., the mean July temperature is about 68 degrees F., and the mean annual temperature is 45 to 52 degrees F. The frost-free period is 80 to 140 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Bogus, Kuck, Mary, Pit, Terwilliger soils. Bogus soils have thick mollic epipedons, argillic horizons, and paralithic contacts at depths of 60 to 80 inches. Kuck soils have mollic epipedons, argillic horizons, and paralithic contacts at depths of 20 to 40 inches. Mary soils are fine-loamy, have ochric epipedons, and have argillic horizons. Pit soils have moist chroma of 1 or less in the upper part of the A horizon and are poorly drained. Terwilliger soils have ochric epipedons and argillic horizons.
DRAINAGE AND PERMEABILITY: Well drained; high surface runoff; slow permeability.
USE AND VEGETATION: Lassen soils are used primarily for livestock grazing. Some cultivated areas are used for the production of dryland and irrigated small grains, hay and pasture. The vegetation is principally bluebunch wheatgrass, Idaho fescue, Sandberg bluegrass. Some areas have a very few scattered juniper and black oak or white oak. Other areas may be dominantly medusahead.
DISTRIBUTION AND EXTENT: Northern California. These soils are moderately extensive. MLRA 21.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California.
SERIES ESTABLISHED: Siskiyou County (Shasta Valley Area), California, 1919.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon - The zone from the soil surface to 26 inches (A, Bw, and Bss horizons).
Slickensides - The zone from 9 to 26 inches (Bss horizon).
Lithic contact - The boundary at 28 inches to underlying bedrock (R layer).
Particle-size control section - The zone from 10 to 28 inches (BC horizon and part of the Bss horizon).