LOCATION OBOSHIP CAEstablished Series
TAXONOMIC CLASS: Coarse-loamy, mixed, superactive, isothermic Pachic Haplustolls
TYPICAL PEDON: Oboship gravelly loam on northern 65 percent side slopes of mountain interfluves at an elevation of 1240 feet (378 meters) under continuous stands of oaks, toyon, crossosoma, ceanothus, lemonade sumac, and laurel sumac.(Colors are for dry soil observed on broken faces of peds unless otherwise noted).
Oi--0 to 1 inches, (0 to 3 cm); oak leaves and grasses; abrupt wavy boundary. (3 to 8 cm thick)
A--1 to 9 inches, (3 to 24 cm); dark grayish brown (10YR 4/2) gravelly loam, very dark brown (10YR 2/2) moist; 17 percent clay; strong coarse subangular blocky structure; soft, very friable, slightly sticky, slightly plastic; common fine and very fine roots; common fine low continuity interstitial and common very fine low continuity tubular pores; 1 percent rounded 75 to 250 millimeter cobbles and 10 percent rounded 2 to 75 millimeter gravel; moderately acid, pH 5.7 by pH meter 1:1 water; clear wavy boundary. (4 to 22 cm thick)
Bt1--9 to 22 inches, (24 to 56 cm); dark grayish brown (10YR 4/2) gravelly loam, very dark brown (10YR 2/2) moist; 18 percent clay; moderate medium angular blocky structure; soft, very friable, slightly sticky, slightly plastic; common fine and medium roots; common fine low continuity and very fine low continuity tubular pores; faint dark brown (7.5YR 3/3), moist, clay films on all faces of peds and 20 percent faint dark brown (7.5YR 3/3), moist, clay films on rock fragments; 1 percent rounded 75 to 250 millimeter cobbles and 20 percent rounded 2 to 75 millimeter gravel; moderately acid, pH 5.7 by pH meter 1:1 water; gradual wavy boundary. (18 to 44 cm thick)
Bt2--22 to 33 inches, (56 to 84 cm); light yellowish brown (10YR 6/4) very gravelly loam, dark yellowish brown (10YR 4/6) rubbed moist; 13 percent clay; moderate medium subangular blocky structure; slightly hard, very friable, moderately sticky, moderately plastic; common fine and very fine roots; common fine moderate continuity and very fine moderate continuity tubular pores; distinct dark brown (7.5YR 3/3), moist, clay films on all faces of peds and 20 percent distinct dark brown (7.5YR 3/3), moist, clay films on rock fragments; 5 percent rounded 75 to 250 millimeter cobbles and 30 percent rounded 2 to 75 millimeter gravel; slightly acid, pH 6.5 by pH meter 1:1 water; clear wavy boundary. (15 to 28 cm thick)
Bt3--33 to 60 inches, (84 to 153 cm); light yellowish brown (10YR 6/4) extremely gravelly loam, dark yellowish brown (10YR 4/6) rubbed moist; 17 percent clay; weak fine subangular blocky structure; slightly hard, firm, moderately sticky, moderately plastic; common very fine roots; 20 percent distinct dark brown (7.5YR 3/3), moist, clay films on rock fragments and 50 percent distinct dark brown (7.5YR 3/3), moist, clay films on all faces of peds; 20 percent rounded 75 to 250 millimeter cobbles and 65 percent rounded 2 to 75 millimeter gravel; neutral, pH 6.7 by pH meter 1:1 water; diffuse irregular boundary. (16 to 69 cm thick)
R--60 inches, (153 cm); very strongly cemented, quartz-diorite porphyry bedrock.
TYPE LOCATION: Santa Catalina Island, Los Angeles County, California, in the Channel Islands Soil Survey Area 33 degrees North latitude, 19 minutes, 17 seconds and 118 degrees, 19 minutes, 25 seconds West longitude, NAD83. - U.S.G.S Quad: Santa Catalina East.
RANGE IN CHARACTERISTICS: The mean annual soil temperature is 15 to 17 degrees Celsius (59 to 63 degrees F.) The difference between mean summer and mean winter temperatures ranged from 4 to 5 degrees Celsius. The soil moisture control section is dry in all parts from about mid-June to mid-November (about 150 days) and is usually moist the rest of the time.
The particle size control sections averages 15 to 18 percent clay.
The A horizon dry color is 10YR 4/2, 3/3, 5/3, 5/2, 7.5YR 5/3, moist color is 10YR 3/3, 3/2, 2/2, 7.5YR 2.5/2, 3/3.
Textures are loamy sand, sandy loam, gravely loam, loam.
Coarse fragments may be 0 to 20 percent fine gravels.
A2 horizon may be absent in some pedons.
The Bt1 horizon dry color is 10YR 4/2, 3/2, 7.5YR 4/4, Moist color is 10YR 3/3, 3/2, 2/2, 7.5YR 3/2.
Textures are loam, gravely loam, gravely sandy loam, gravely clay loam, sandy clay loam.
Coarse fragments may be 0 to 21 percent fine gravels.
The Bt2 horizon dry color is 10YR 6/4, 5/6, 5/4, 4/3, 7.5YR 4/4, Moist color is 10YR 4/4, 4/3, 2/2, 7.5YR 3/2.
Textures are gravely sandy loam, very gravely loam, clay loam, gravely clay loam, sandy clay.
Coarse fragments may be 0 to 35 percent fine gravels.
The Bt3 (Bt4 when present) horizon dry color is 10YR 6/4, 5/4, 4/6. Moist color is 10YR 4/3, 4/6, 4/4.
Textures are gravelly sandy clay loam,
Extremely gravelly clay loam, gravelly clay loam, extremely gravelly loam
Coarse fragments may be 30 to 85 percent fine gravels.
The C horizon (when present) dry color is 2.5Y. Moist color is 10YR 4/6, 4/4.
Textures are loamy sand, sandy loam, gravely loam, loam.
Coarse fragments may be 0 to 90 percent fine gravels.
The bedrock ranges from very rigid to hard and fractured quartz-diorite porphyry, diorite and intrusions of andesite.
The Bt horizons have clay films and bridging but rarely have the clay increase to meet the requirements for an argillic, however some do have an increase greater than three percent from the overlying horizon.
COMPETING SERIES: There are no competing series.
GEOGRAPHIC SETTING: Oboship soils formed on predominately north aspects under continuous stands of oak and chaparral in colluvium over residuum of quartz-diorite and diorite porphyry on complex side slopes of interfluves of hills and mountains on islands. This area contains some andesite dikes and fissures. Slopes range from 35 to 75 percent. Elevations are from sea level to 1732 feet (0 to 528 meters). The climate is characterized by warm, dry summers and cool, moist winters with potential fog common all year. The mean annual precipitation from 7 to 17 inches (178 to 432 mm), the mean annual temperature is 59 to 66 degrees F. (15 to 19 degrees C.), and the frost free season is 355 to 365 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Bosun, Nauti, Loadline, Flyer, Marpol and Express. Bosun soils are skeletal and typically found on the lower portion of slopes, Express, Nauti and Marpol soils are thermic under sage and grass and are coarse-loamy, fine-loamy and fine. Loadline soils are shallow and generally found on convex slope positions like crests of interfluves. Flyer soils are thermic and have an argillic. All these soils are found on hills and mountains.
DRAINAGE AND PERMEABILITY: well drained; medium runoff; moderate permeability.
USE AND VEGETATION: Wildlife habitat, recreation and building site development. Vegetation communities are predominately Island Chaparral, Coastal Sage Scrub and Island Woodland, Southern Riparian Woodland, also Non-native Scrub.
DISTRIBUTION AND EXTENT: Santa Catalina Island, Los Angeles County, California. The soil is not extensive. MLRA 20.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California.
SERIES ESTABLISHED: Santa Catalina Island, Los Angeles County, California, 2008.
REMARKS: The series name is coined. Diagnostic horizons and features recognized in this pedon:
Oboship soils are isothermic borderline isomesic. The iso classification dictates the moisture regime to not be xeric. These soils are possibly in the Aridic subgroup. Moisture control section data is needed for this classification.
Particle Size Control section for this pedon is 24 to 74 centimeters.
Mollic horizon extends from 3 to 56 centimeters deep. Typically the mollic horizon is finer than loamy fine sand.
Most pedons including the laboratory sample for the typical profile do not exhibit enough clay increase to qualify for an argillic horizon.
The O and surface A horizons are typically hydrophobic.
ADDITIONAL DATA:
Pedon information for this type location only:
Pedon Type: typical pedon for series Lab Source ID:
Pedon Purpose: full pedon description Lab Pedon #:06N0796