LOCATION BOHNA CAEstablished Series
TAXONOMIC CLASS: Fine-loamy, mixed, superactive, thermic Typic Argixerolls
TYPICAL PEDON: Bohna loam - on a south facing slope of 15 percent with oak and annual grass cover at 4,300 feet elevation. (Colors are for dry soil unless otherwise stated. When described on August 1, 1977, the soil was dry).
O1---2 inches to 0; decomposed oak and grass litter.
A11--0 to 4 inches; brown (10YR 5/3) loam, very dark grayish brown (10YR 3/2) moist; moderate fine and medium granular structure; slightly hard, friable, nonsticky and slightly plastic; many very fine roots; many very fine tubular pores; neutral (pH 6.8); gradual wavy boundary. (3 to 9 inches thick)
A12--4 to 8 inches; brown (10YR 5/3) loam, very dark grayish brown (10YR 3/2) moist; moderate medium granular structure; slightly hard, friable, nonsticky and slightly plastic; many fine roots; many very fine tubular pores; neutral (pH 6.8); gradual wavy boundary. (3 to 5 inches thick)
B1--8 to 19 inches; brown (10YR5/3) loam, dark brown (10YR 3/3) moist; weak medium subangular blocky structure; slightly hard, firm, slightly sticky and slightly plastic; few medium and common very fine roots; common fine tubular pores; neutral (pH 6.6); gradual wavy boundary. (10 to 12 inches thick)
B21t--19 to 36 inches; strong brown (7.5YR 5/6) sandy clay loam, brown (7.5YR 4/4) moist; moderate medium subangular blocky structure; hard, firm, sticky and plastic; ;common fine tubular pores; few thin clay bridges between mineral grains, and few thin clay films in tubular pores and on peds; neutral (pH6.6); gradual wavy boundary. (16 to 31 inches thick)
B22t--36 to 44 inches; strong brown (7.5YR 5/6) sandy clay loam, brown (7.5YR 4/4) moist; massive; slightly hard, friable, slightly sticky and slightly plastic; common moderately thick and thin yellowish red (5YR 5/6 and 4/6) clay bridges between mineral grains; slightly acid (pH 6.4); diffuse irregular boundary. (8 to 16 inches thick)
Cr--44 inches; yellowish red (5YR 5/6 and 4/6) weathered granitic materials with relic rock structure.
TYPE LOCATION: Kern County, California; Sequoia National Forest Greenhorn Ranger District. 100 feet north of Forest Service road 25S04, about 0.3 miles south of the intersection with F.H. 52 (Highway 1550. NW 1/4, NE 1/4, ec. 26, T. 25 ., R. 31 E., MDB&M.
RANGE IN CHARACTERISTICS: Depth to a paralithic contact of weathered granitic rock ranges from 40 to 73 inches. The soil between depths of about 7 and 20 inches usually becomes moist in all parts in late October or November and remains moist until mid-May. The soil is dry in all parts the rest of the year. Mean annual soil temperature varies from 59 to 62 degrees F. Base saturation ranges from 80 to 100 by (NH4OAc) throughout.
The A horizon has dry color of 10YR or 7.5YR 5/2, 5/3, or 5/4, and moist color of 10YR or 7.5YR 3/2 or 3/3. It is loam or sandy loam. It is weak or moderate granular. It is neutral or slightly acid.
The B2t horizon has dry color of 10YR or 7.5R 4/4, 4/6, 5/4, 5/6, 6/4, or 6/6, and moist color of 10YR or 7.5YR 4/4, 4/7, 5/4, or 5/6. It is sandy clay loam or loam with strong or moderate subangular blocky structure, or some may be massive. Percent clay averages from 20 to 25 throughout the upper 20 inches of this horizon. This horizon has less than 15 to 20 percent angular sand fragments. It is neutral or slightly acid.
COMPETING SERIES: These are the Ballard, Chualar, Gilroy, Pinto, Shimmon, Soper and Tehachapi series. Ballard soils have clay loam or sandy clay loam B2t horizons which contain 20 to 35 percent siliceous shale fragments. Chualar soils contain 20 to 25 percent angular sand fragments in the B2t horizon. In addition Chualar soils formed in alluvium on slopes of less than 9 percent. Gilroy soils have a lithic contact at a depth of 20 to 40 inches. Pinto soils have an A2 horizon with an abrupt lower boundary. Shimmon and Soper soils have a paralithic contact at depths of 20 to 40 inches. Tehachapi soils have B2t horizons averaging 25 to 35 percent clay.
GEOGRAPHIC SETTING: Bohna soils are on foothills, mountain slopes and ridges. Slopes are 5 to 75 percent. They formed in material weathered from Mesozoic granite. Elevations are 1,600 to 5,000 feet. The climate is semiarid with cool moist winters and warm dry summers. Mean annual precipitation is 20 to 35 inches. Mean annual temperature is 62 degrees F, and the frost-free season is 150 to 260 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Ahwahnee, Auberry, and Cieneba series. Ahwahnee soils have a paralithic contact at depths of 20 to 40 inches. Auberry soils have an ochric epipedon. Cieneba soils are less than 20 inches deep.
DRAINAGE AND PERMEABILITY: Well drained; medium to rapid runoff; slow permeability.
USE AND VEGETATION: Used for rangeland, wildlife land, and recreation land. Vegetation is an oak-grass or chaparral cover type consisting of blue oak, canyon live-oak, interior live-oak, Digger pine, wedgeleaf ceanothus, mountain mahogany, Freemont silk-tassel, Mariposa manzanita, and annual grasses.
DISTRIBUTION AND EXTENT: The upper parts of the granitic foothills on the western slopes of the southern Sierra Nevada Mountains of California. The soils are not extensive (about 9,500 acres).
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California
SERIES ESTABLISHED: Sequoia National Forest Area, Kern County, California 1981. Name is taken from Bohna Creek.
REMARKS: The activity class was added to the classification in January of 2003. Competing series were not checked at that time. - ET
Last revised by the state on 9/80.