LOCATION BRITTON CAEstablished Series
TAXONOMIC CLASS: Clayey, mixed, superactive, mesic, shallow Andic Haploxerepts
TYPICAL PEDON: Britton silty clay loam--on a south-facing 20 percent slope under a cover of ponderosa pine and black oak at an elevation of 3,000 feet--forestland. (Colors are for dry soil unless otherwise noted. When described October 1978, the soil was dry throughout.)
A--0 to 3 inches; light brownish gray (10YR 6/2) silty clay loam, very dark grayish brown (10YR 3/2) moist; moderately fine subangular blocky structure; soft, very friable, slightly sticky and moderately plastic; many very fine and fine roots; many very fine tubular pores; 1 percent gravel; 8.4 NaF pH; moderately acid (pH 6.0); abrupt smooth boundary. (2 to 4 inches thick)
Bw1--3 to 8 inches; light brownish gray (10YR 6/2) silty clay loam, dark grayish brown (10YR 4/2) moist; moderate medium subangular blocky structure; soft, very friable, slightly sticky and moderately plastic; many very fine and fine roots; many very fine and fine tubular and interstitial pores; 10 percent gravel and 2 percent cobbles; 8.2 NaF pH; strongly acid (pH 5.5); clear wavy boundary. (3 to 6 inches thick)
Bw2--8 to 15 inches; light brownish gray (10YR 6/2) gravelly silty clay loam, dark grayish brown (10YR 4/2) moist; moderate medium subangular blocky structure; soft, very friable, slightly sticky and moderately plastic; many very fine and fine and few coarse roots; many very fine and fine tubular and interstitial pores; 20 percent gravel and 5 percent cobbles; 8.1 NaF pH; strongly acid (pH 5.4); abrupt wavy boundary. (5 to 10 inches thick)
Cr--15 to 28 inches; highly fractured soft diatomite.
TYPE LOCATION: Shasta County, California; about 4 miles E of McArthur-Burney Falls State Park, 50 feet NW of dirt road, 3,000 feet W and 300 feet N from the SE corner of sec. 25, T. 37 N., R. 3 E. (Pondosa Quadrangle, 15 minute series)
RANGE IN CHARACTERISTICS:
Soil moisture - The soil moisture control section is dry in all parts from early July to early November (120-130 days) and is moist in all parts from mid November to mid-May; The soil temperature exceeds 41 degrees F. from early March to late December (300 days) and exceeds 47 degrees F. from mid-April to mid-November; Xeric moisture regime.
Mean annual soil temperature - 48 to 50 degrees F.
Depth to base of cambic horizon - 10 to 20 inches.
Depth to bedrock - 10 to 20 inches to a paralithic contact. The paralithic materials below the contact are weathered and fractured diatomite or water-laid tuff.
Particle-size control section - Clay content: 35 to 45 percent; Rock fragments: 15 to 35 percent, mainly pebbles.
Reaction - Moderately acid to strongly acid and acidity increases with depth.
Other features - Mineralogy is mixed with small amounts of halloysitic and montmorillonitic clays. The 15 bar water to clay ratio ranges from 0.61 to 0.78. NaF pH is 8.4 to 7.9 and decreases with depth. Base saturation by ammonium acetate ranges from 70 to 90 percent and increases with depth. The CEC to clay ratio ranges from 0.64 to 0.87. Volcanic glass content ranges from 30 to 50 percent in the A horizon and the Bw1 horizon, but the fine-earth fraction has less than 30 percent particles that are coarse silt through very coarse sand in size.
The A horizon color is 10YR 6/1, or 6/2. Moist color is 10YR 3/2, or 3/3. Texture is silty clay loam or silt loam with 25 to 30 percent clay and 0 to 15 percent rock fragments, mostly gravel. Organic matter content ranges from 3 to 7 percent.
The Bw horizon color is 10YR 6/2, 7/2 or 8/2. Moist color is 10YR 3/4, 4/2, 4/3 or 4/4. The clay content is 30 to 40 percent clay and 0 to 15 percent rock fragments in the upper part and 35 to 40 percent clay and 15 to 35 percent rock fragments in the lower part. Organic matter content ranges from 1 to 2 percent in the upper part and .5 to 1 percent in the lower part.
COMPETING SERIES: There are no competing series in this family.
GEOGRAPHIC SETTING: Britton soils are on hills. These soils formed in slope alluvium weathered from diatomite or water-laid tuff. Slopes are 2 to 50 percent. Elevation is 2,700 to 3,200 feet. The climate is subhumid with cold, moist winters and warm, dry summers. The mean annual precipitation is 16 to 35 inches. Snowfall is 36 to 60 inches. The mean annual temperature is 45 to 48 degrees F., mean January temperature is about 31 degrees F., and the mean July temperature is about 66 degrees F. The frost-free period is 80 to 100 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Arkright and Burney soils. Arkright soils are fine-loamy and 20 to 40 inches deep to a lithic contact on plateaus. Burney soils are fine-loamy and are greater than 60 inches deep on plateaus.
DRAINAGE AND PERMEABILITY: Well drained; very high surface runoff; slow permeability.
USE AND VEGETATION: Britton soils are used mainly for forestland, livestock grazing, and recreation. The vegetation is mainly a forest canopy of ponderosa pine, Oregon white oak, and California black oak with an understory of skunkbush sumac, antelope bitterbrush, and needlegrass.
DISTRIBUTION AND EXTENT: Modoc Plateau of northeastern California. These soils are not extensive with about 2,500 acres mapped, mainly around the Lake Britton area. MLRAs 21 and 22.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California.
SERIES ESTABLISHED: Shasta County, California, Intermountain Soil Survey Area, 1994.
REMARKS: This revision of March 2001 updates the taxonomic class from Clayey, mixed, mesic, shallow Vitrandic Xerochrepts. Additional lab work is needed to determine oxalate extractable iron and aluminum values on this series to verify the new subgroup.
Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon - The zone from the soil surface to 7 inches (A horizon and part of the Bw1 horizon).
Cambic Horizon - The zone from 3 to 15 inches (Bw1 and Bw2 horizons).
Paralithic contact - The boundary at 15 inches to underlying soft, fractured bedrock (Cr layer).
Particle-size control section - The zone from 10 to 15 inches (part of the Bw2 horizon).
ADDITIONAL DATA: This pedon is sampled by the Lincoln Lab and U.C. Davis Lab in 1981. Pedon number is 81-45-199X for Davis and the NSSL# is S81CA-089-003, pedon # 81P0716.