LOCATION OBISPO CAEstablished Series
TAXONOMIC CLASS: Clayey, magnesic, thermic Lithic Haploxerolls
TYPICAL PEDON: Obispo clay, rangeland. (Colors are for dry soil unless otherwise noted.)
A11--0 to 2 inches; very dark gray (10YR 3/1) clay, black (10YR 2/1) moist; strong fine granular structure; very hard, firm, sticky and plastic; common very fine and few medium roots; few fine tubular and interstitial pores; mildly alkaline (pH 7.5); abrupt smooth boundary. (0 to 2 inches)
A12--2 to 11 inches; very dark gray (10YR 3/1) clay, black (10YR 2/1) moist; moderate coarse subangular blocky structure; very hard, firm, sticky and plastic; common very fine and few medium roots; few very fine tubular and interstitial pores; mildly alkaline (pH 7.5); abrupt wavy boundary. (6 to 20 inches)
R1--11 to 18 inches; black (N 2/0), yellowish brown (10YR 4/6), and olive (5Y 4/4) serpentinite, dug with handtools without difficulty but does not slake in water; few thin clay films coat fracture faces that are more than 1/2 inch and less than 8 inches apart and less than 1 mm in width. Few very fine roots in fractures; abrupt wavy boundary. (0 to 12 inches)
R2--18 inches; black (N 2/0), yellowish brown (10YR 4/6), and olive (5Y 4/4) serpentinite; fractures are more than 1 inch and less than 12 inches apart and less than 1 mm in width.
TYPE LOCATION: San Luis Obispo County, California; approximately 3,600 feet west and 295 feet south of the SW corner of section 34, T. 30 S., R. 12 E. MDB&M.
RANGE IN CHARACTERISTICS: Depth to a lithic contact is 8 to 20 inches. The soil below the depth of about 4 inches is usually moist between sometime in November and sometime in May and usually dry the rest of the year. The mean annual soil temperature is about 61 degrees to 65 degrees F.
The A horizon is gray, grayish brown, dark gray, dark grayish brown, very dark gray or very dark grayish brown (10YR 5/1, 5/2, 4/1, 4/2, 3/1, 3/2). Moist colors are very dark gray, very dark grayish brown, black or very dark brown (10YR 3/1, 3/2, 2/1, 2/2.) This horizon is usually clay but is clay loam with more than 35 percent clay in some pedons. It contains up to 35 percent by volume serpentinite pebbles and cobbles. Reaction is neutral through moderately alkaline. The calcium to magnesium ratio is assumed to be low.
COMPETING SERIES: These are the Climara, Delpiedra, Dubakella, Hambright, Lopez, Montara, Permanente, and Plaskett series in other families. Climara soils have a lithic contact at a depth of 28 to 40 inches, have cracks that extend to a depth of 20 inches or more and have intersecting slickensides. Delpiedra and Dubakella soils have an argillic horizon. Hambright, Lopez, Permanente and Plaskett soil shave more than 35 percent rock fragments in the control section. Also, Permanente and Plaskett soils have a soil temperature less than 59 degrees F. Henneke soils have an argillic horizon and have 35 to 50 percent rock fragments. Montara soils have less than 35 percent clay.
GEOGRAPHIC SETTING: Obispo soils are on hilly to very steep foothills and mountains and have slopes of 15 to 75 percent. They formed in residual material weathered from serpentinite at elevations of 200 to 2,500 feet. The climate is dry, subhumid mesothermal with warm, dry summers and cool, wet winters. the mean annual precipitation is 16 to 35 inches. The average January temperature is 52 degrees F.; the average July temperature is about 63 degrees F.; the average annual temperature is 56 to 60 degrees F. The frost-free season is 275 to 350 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Cibo, Clear Lake, Cropley, Diablo, Gazos, Lodo and Los Osos soils. Cibo, Clear Lake, Cropley, Diablo, Gazos, and Los Osos soils are deeper than 20 inches to any lithic or paralithic contact. Also, Cibo, Clear Lake, Cropley and Diablo soils have cracks that extend below 20 inches and have slickensides; Gazos soils have 20 to 30 percent clay in the control section and Los Osos soils have an argillic horizon. Lodo soils have 18 to 35 percent clay throughout and have mixed mineralogy.
DRAINAGE AND PERMEABILITY: Well drained; rapid and very rapid runoff; slow permeability. Steep areas adjacent to rock outcrops may persist for several months after the end of the rainy season.
USE AND VEGETATION: Used for grazing, wildlife, watershed and recreation. Naturalized and native vegetation is annual and perennial grasses and forbs with a few brush species such as sagebrush.
DISTRIBUTION AND EXTENT: Coast Range of California. The soils are inextensive.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California
SERIES ESTABLISHED: San Luis Obispo County, Coastal Part, California.