LOCATION CUPVAR CAEstablished Series
TAXONOMIC CLASS: Fine, smectitic, mesic Haplic Durixererts
TYPICAL PEDON: Cupvar silty clay on a east facing 1 percent slope under a cover of perennial grasses and forbs at an elevation of 3710 feet. (Colors are for dry soil unless, otherwise stated. When described October 5, 1980, the soil was moist throughout)
A--0 to 3 inches; dark grayish brown (10YR 4/2) silty clay, very dark grayish brown (10YR 3/2) moist; moderate fine granular structure; very hard, firm, sticky and very plastic; common very fine roots; few very fine interstitial pores; neutral (pH 6.8); gradual smooth boundary.
Bss--3 to 21 inches; dark grayish brown (10YR 4/2) silty clay, very dark grayish brown (10YR 3/2) moist; strong coarse prismatic structure parting to strong medium angular blocky; extremely hard, firm, sticky and very plastic; many very fine and few fine roots; common very fine interstitial and tubular pores; common intersecting slickensides; neutral (pH 7.0); abrupt smooth boundary. (Combined thickness of the A horizon is 20 to 40 inches)
2Bkqm--21 to 25 inches; light yellowish brown (10YR 6/4) strongly cemented duripan, dark brown (10YR 3/3) moist; strong medium platy structure with thin continuous laminar capping 1/4 inch thick; extremely hard, very firm and brittle; many very fine tubular pores; violently effervescent with lime and silica segregated in filaments and slightly effervescent matrix; moderately alkaline (pH 8.4); abrupt smooth boundary. (3 to 10 inches thick)
2Bk--25 to 41 inches; light yellowish brown (10YR 6/4) fine sandy loam, dark brown (7.5YR 3/2 ) moist; weak fine subangular blocky structure; hard, friable, nonsticky and nonplastic; many very fine and common fine tubular and many very fine interstitial pores; slightly effervescent; moderately alkaline (pH 8.2); gradual smooth boundary.(15 to 25 inches thick)
2C--41 to 64 inches; light yellowish brown (10YR 6/4) fine sandy loam, dark brown (7.5YR 3/4) moist; massive; hard, friable, nonsticky and nonplastic; many very fine tubular pores; moderately alkaline (pH 8.0).
TYPE LOCATION: Lassen County, California; about 4.5 miles southeast of Fall River Mills, 4,500 feet east and 660 feet north of the southwest corner of section 19, T.36N. R.5E. Jellico NW (Hogback Ridge) Quadrangle (7.5 minute series).
RANGE IN CHARACTERISTICS: Depth to strongly cemented duripan ranges form 20 to 40 inches. The mollic epipedon is 20 to 40 inches thick. The mean annual soil temperature is 50 to 52 degrees F. The soil temperature exceeds 41 degrees F. from early March to early December (270 days) and exceeds 47 degrees F. from mid April to early November. The soil moisture control section (7 to 21 inches) is dry in all parts from mid June to mid October (ranges 120 to 130) and is moist in all parts from mid November to early May. The particle-size control section ranges from 40 to 60 percent clay. Cracks range from 1/2 to 1 1/2 inches wide. They remain open during a period from July to October and remain closed for the rest of the year. Few to common intersecting slickensides are in part of the A horizon.
The A and Bss horizon reaction is mildly alkaline or neutral. Organic matter ranges from 2 to 4 percent.
The Bk horizon is 10YR 6/4, 6/3, 5/3. It is sandy clay loam fine sandy loam, or sandy loam. Calcium carbonate equivalent ranges from 7 to 11 percent. Reaction is moderately alkaline or mildly alkaline.
COMPETING SERIES: These are the Aikman (ID), Carney (OR), Cuppy (T CA), Gerlach (T CA), Getrail (T CA), Jenny (CA), Lassen (CA), Lecrag (CA), Montague (CA), and Peasley (ID) series. Aikman, Lassen, and Peasley soils have hard bedrock within 40 inches. Carney and Getrail soils have weathered bedrock within 40 inches. Gerlach and Jenny soils are greater than 40 inches deep. Montague soils have a petrocalcic horizon. Lecrag soils do not have a duripan within 40 inches. Cuppy soils are ...
GEOGRAPHIC SETTING: Cupvar soils are in basins. Slopes are 0 to 2 percent. These soils formed in alluvium from extrusive igneous rock. Elevation is 3300 to 4500 feet. The climate is semiarid with warm dry summers and cold moist winters. Mean annual precipitation is 14 to 20 inches. Snowfall is 12 to 36 inches. The mean annual temperature is 48 to 50 degrees F. The mean January temperature is about 27 degrees F. The mean July temperature is about 67 degrees F. Frost-free period is 100 to 120 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Bieber, Esperanza and Pit soils. Bieber soils are shallow on intermound positions on terraces. Esperanza soils are deep on terraces. Pit soils are deep.
DRAINAGE AND PERMEABILITY: Moderately well drained; ponded to slow runoff; slow permeability. The soils are frequently flooded for periods of weeks in December through February. A water table is at 6 inches above the surface to a depth of 12 inches from December through February.
USE AND VEGETATION: This soil is mainly used for livestock grazing, crops, and pasture. The vegetation is Nevada bluegrass, bottlebrush squirreltail, and silver sagebrush.
DISTRIBUTION AND EXTENT: Northeastern California. The soils are not extensive. MLRA is 21.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California
SERIES ESTABLISHED: Lassen County, Intermountain Soil Survey Area, California 1994. Source of name is coined.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon- The zone from 0 to 21 inches (A, Bss).
Duripan- The zone from 21 to 25 inches (2Bkqm).