LOCATION BISCARO CAEstablished Series
TAXONOMIC CLASS: Fine, smectitic, mesic Durinodic Xeric Paleargids
TYPICAL PEDON: Biscaro silt loam--on a 1 percent slope under black greasewood and basin big sagebrush at 4,420 feet elevation--rangeland. (Colors are for dry soil unless otherwise noted. When described on June 26, 1979, the soil was nearly dry below 3 inches.)
A--0 to 3 inches; light yellowish brown (2.5Y 6/3) silt loam, brown (10YR 4/3) moist; moderate thick and very thick platy structure; hard, very friable, slightly sticky and slightly plastic; few very fine roots; many very fine and common medium interstitial and vesicular pores; slightly alkaline (pH 7.5); abrupt wavy boundary. (2 to 6 inches thick)
Bt1--3 to 9 inches; pale brown (10YR 6/3) silty clay loam, brown (10YR 4/3) moist; moderate medium prismatic structure parting to strong medium and coarse angular blocky; very hard, friable, moderately sticky and moderately plastic; few very fine roots; common very fine tubular pores; many faint and distinct clay films on faces of peds and lining pores; SAR is 7; slightly alkaline (pH 7.5); clear wavy boundary.
Bt2--9 to 14 inches; light yellowish brown (10YR 6/4) silty clay, brown (10YR 4/3) moist; moderate fine and medium angular blocky structure; hard; friable, moderately sticky and moderately plastic; common very fine and few fine and medium roots; few very fine tubular pores; many faint and distinct clay films on faces of peds and lining pores; SAR is 11; slightly alkaline (pH 7.8); clear wavy boundary. (Combined thickness of the Bt horizons is 9 to 16 inches)
Bq--14 to 24 inches; pale yellow (2.5Y 8/4) loam, yellowish brown (10YR 5/4) moist; moderate fine, medium and coarse angular blocky structure; hard, firm and brittle, slightly sticky and nonplastic; few very fine, fine and medium roots; few very fine tubular pores; many faint and distinct silica coats with a shiny luster on faces of peds; slightly alkaline (pH 7.8); clear wavy boundary. (6 to 12 inches thick)
2Cq--24 to 38 inches; pale yellow (2.5Y 8/2) extremely paragravelly loam, light yellowish brown (2.5Y 6/4) moist; massive; hard, friable, slightly sticky and slightly plastic; pockets of many very fine and fine roots; common very fine tubular pores; 5 percent 10 to 20 mm durinodes near the upper boundary; 75 percent 5 to 20 mm diameter paragravel of highly weathered tuffaceous siltstone; slightly alkaline (pH 7.8); clear wavy boundary. (0 to 20 inches thick)
2Cr--38 to 60 inches; white (10YR 8/1) tuffaceous siltstone, light yellowish brown (2.5Y 6/4) moist, strong thick and very thick platy rock structure; few pockets of common very fine roots; few thin (0.5 to 1 mm) discontinuous horizontal silica laminae; noneffervescent rock matrix; strongly effervescent on faces of pararock fragments.
TYPE LOCATION: Lassen County, California; on The Tablelands west of Secret Valley; found by going about 7 miles south along the Karlo Road from its intersection with U.S. Highway 395, 2.5 miles south of Karlo, and 150 feet east of the road; about 2,200 feet west and 1,900 feet south of the northeast corner of section 25, T. 31 N., R. 14 E.; USGS Karlo 7.5 minute topographic quadrangle; 40 degrees 31 minutes 19 seconds north latitude and 120 degrees 20 minutes 25 seconds west longitude, NAD27.
RANGE IN CHARACTERISTICS:
Soil moisture - The soil moisture control section (about 5 to 28 inches) is moist in all parts from about December 1 to May 1. It is dry in all parts from June 1 to November 15 (168 days). The soil temperature exceeds 41 degrees from April 1 to December 1 (244 days) and exceeds 47 degrees from April 15 to November 15; Aridic moisture regime that borders on xeric.
Mean annual soil temperature - 48 to 52 degrees F.
Ochric epipedon thickness - 2 to 6 inches.
Depth to base of argillic horizon - 14 to 24 inches.
Depth to horizons with a firm, brittle matrix - 14 to 24 inches.
Depth to bedrock - 24 to 40 inches to a paralithic contact. The paralithic materials below the contact are soft, weathered tuffaceous siltstone or fine-grained sandstone. These geologic materials are composed dominantly of silt, very fine sand, or fine sand size particles.
Other features - An abrupt horizon boundary is normally present between the A horizon and the Bt1 horizon accompanied by an abrupt increase in clay content of at least 15 percent.
A horizon - Dry color: 10YR 6/2, 6/3, 7/2; 2.5Y 6/2, 6/3 or 7/2.
Moist color: 10YR 3/2, 3/3, 4/2, 4/3 or 2.5Y 4/2.
Texture: Silt loam, sandy loam, or clay loam. Overwash phases are recognized that are sandy loam or clay loam.
Clay content: 10 to 20 percent.
Reaction: Neutral through moderately alkaline.
Bt horizon - Dry color: 10YR 5/3, 6/2, 6/3, 6/4, 7/2, 7/3; 2.5Y 5/4 or 6/2.
Moist color: 10YR 3/4, 4/2, 4/3, 4/4, 5/3, 5/4; 2.5Y 4/2, 4/3 or 4/4.
Texture: Silty clay loam or silty clay.
Clay content: 35 to 50 percent.
Sand content: 5 to 20 percent.
Reaction: Neutral through moderately alkaline.
Sodicity (SAR): 8 to 12.
Bq horizon - Dry color: 10YR 6/3, 7/3, 7/4, 8/1, 8/2 or 2.5Y 8/4.
Moist color: 10YR 4/3, 4/4, 5/3, 5/4, 6/3; 2.5Y 4/4, 5/4 or 5Y 5/4.
Texture: Loam or silt loam.
Clay content: 15 to 25 percent.
Reaction: Slightly alkaline or moderately alkaline.
2Cq horizon (when present) - Dry color: 10YR 6/3, 7/3, 7/4, 8/1, 8/2 or 2.5Y 8/4.
Moist color: 10YR 4/3, 4/4, 5/3, 5/4, 6/3; 2.5Y 4/4, 5/4 or 5Y 5/4.
Texture: Extremely paragravelly loam or extremely paragravelly silt loam.
Clay content: 15 to 25 percent.
Pararock fragments: 60 to 85 percent paragravel of highly weathered tuffaceous rock.
Reaction: Slightly alkaline or moderately alkaline.
COMPETING SERIES: There are currently no other series in this family.
GEOGRAPHIC SETTING: Biscaro soils are on slightly dissected lake terraces. These soils formed in alluvium and residuum derived from interbedded tuffaceous siltstone and fine grained sandstone. Slopes are 0 to 2 percent. Elevation ranges from 4,400 to 5,350 feet. The climate is semiarid with cold, moist winters and warm, dry summers. The mean annual precipitation is 9 to 14 inches including 15 to 20 inches of snow. The mean annual temperature is 44 to 46 degrees F. The mean July temperature is about 64 degrees F. and the mean January temperature is about 26 degrees F. The frost-free period is 60 to 100 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Saddlerock and Termo soils. Saddlerock and Termo soils do not have bedrock within 40 inches of the soil surface and do not have horizons with a firm, brittle matrix. Saddlerock soils also have mollic epipedons and Termo soils have natric horizons.
DRAINAGE AND PERMEABILITY: Well drained; medium surface runoff; slow permeability. These soils are susceptible to frequent ponding for long duration from January through April with water up to 1.0 foot deep.
USE AND VEGETATION: Biscaro soils are used for rangeland, hayland, and pasture. The vegetation in native rangeland is black greasewood, basin big sagebrush, and bluegrass.
DISTRIBUTION AND EXTENT: Northeastern California. These soils are not extensive with about 5,100 acres of the series mapped to date. MLRA 23.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California.
SERIES ESTABLISHED: Lassen County (Susanville Area Soil Survey), California, 2000.
REMARKS: This revision of December 2003 updates the taxonomic class from Fine, smectitic, mesic Xeric Paleargids and recognizes the Bq horizon as meeting durinodic subgroup criteria.
Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon - The zone from the soil surface to 3 inches (A horizon).
Argillic horizon - The zone from 3 to 14 inches (Bt1 and Bt2 horizons).
Paleargid great group feature - The abrupt clay increase of more than 15 percent at 3 inches (between the A and Bt1 horizons).
Duric feature - The zone from 14 to 24 inches (Bq horizon).
Paralithic contact - The boundary at 38 inches to soft, weathered bedrock (2Cr layer).
Particle-size control section - The zone from 3 to 14 inches (Bt1 and Bt2 horizons).
ADDITIONAL DATA: The typical pedon at the series type location was reference sampled for the Soil Survey Laboratory (SSL), Lincoln, NE, as soil survey sample number S82CA-035-001-1 through 3. These were temporary horizon samples and the data are not stored in the SSL characterization database.