LOCATION BRANSCOMB CAEstablished Series
TAXONOMIC CLASS: Loamy-skeletal, mixed, superactive, isomesic Ultic Hapludalfs
TYPICAL PEDON: Branscomb very gravelly loam - on a northeast facing slope of 60 percent under redwood, Douglas-fir, tanoak, swordfern and oxalis at 152 meters (500 feet) elevation. (Colors are for dry soil unless otherwise stated. When described November 14, 1979, the soil was moist throughout).
Oi--0 to 5 cm (0 to 2 inches); partially decomposed litter of redwood, Douglas fir and tanoak.
A--5 to 30 cm (2 to 12 inches); grayish brown (10YR 5/2) very gravelly loam, very dark brown (10YR 2/2) moist; strong fine and medium granular structure; slightly hard, very friable, slightly sticky and slightly plastic; few very fine and common fine, medium and coarse roots; many very fine and fine interstitial and few very fine tubular pores; 40 percent pebbles (2 to 25mm); strongly acid (pH 5.5); clear wavy boundary. (25 to 33 cm thick)
Bt1--30 to 46 cm (12 to 18 inches); pale brown (10YR 6/3) very gravelly loam, dark brown (10YR 3/3) moist; strong fine and medium granular structure; slightly hard, very friable, slightly sticky and slightly plastic; few very fine and common fine and medium roots; few very fine and fine tubular and common very fine and fine interstitial pores; common faint clay films on faces of peds; 35 percent pebbles (2 to 25mm), 5 percent angular cobbles (8 to 20cm); moderately acid (pH 6.0); gradual wavy boundary. (13 to 15 cm thick)
Bt2--46 to 69 cm (18 to 27 inches); very pale brown (10YR 7/3) very gravelly clay loam, dark yellowish brown (10YR 4/4) moist; moderate fine and medium subangular blocky structure; hard, friable, slightly sticky and slightly plastic; few very fine and common fine, medium, and coarse roots; few very fine tubular and common very fine and fine interstitial pores; common faint clay films on faces of peds and lining pores; 30 percent pebbles (2 to 25 mm), 5 percent angular cobbles (8 to 20 cm); very strongly acid (pH 4.5); gradual wavy boundary. (20 to 31 cm thick)
Bt3--69 to 132 cm (27 to 52 inches); very pale brown (10YR 7/4) very gravelly loam, yellowish brown (10YR 5/4) moist; moderate fine, medium and coarse angular blocky structure; hard, friable, slightly sticky and slightly plastic; few fine and medium roots; few very fine and fine interstitial pores; many distinct clay films on faces of peds and common faint clay films lining pores; 50 percent pebbles (2 to 50mm), 5 percent angular cobbles (8 to 20 cm); very strongly acid (pH 4.5); abrupt wavy boundary. (56 to 76 cm thick)
C--132 to 200 cm (52 to 79 inches); gravel; hard, fractured sandstone. Fractures are 5 to 20 millimeters apart and 1 to 2 millimeters wide.
TYPE LOCATION: Mendocino County, California; about 1,300 feet south and about 100 feet east of the northwest corner of section 12, T.19 N., R. 17 W., Branscomb quadrangle.
RANGE IN CHARACTERISTICS:
Soil temperature: 11 to 13 degrees C (51 to 56 degrees F). The difference between mean winter and mean summer soil temperature ranges from 2 to 3 degrees C.
Soil Moisture: The soil between the depths of 28 and 84 cm is moist in all parts from November 1 to August 1 and is dry in some parts from September 1 to October 1 in most years.
Depth to lithic material with fractures less than 10 centimeters apart: 100 to 150 centimeters
Particle Size control section (weighted average):
Rock fragments: 40 to 55 percent, mostly gravel
Clay content: 25 to 35 percent
A horizon:
Value: 4 or 5, 2 through 4 moist
Chroma: 2 through 4 dry or moist
Rock fragments: 35 to 45 percent gravel
Clay content: 15 to 27
Base saturation (ammonium acetate): 50 to 75 percent
Organic carbon content: 2 to 4 percent
Reaction: strongly or moderately acid
Bt horizon:
Hue: 10YR
Value: 6 or 7, 3 through 5 moist
Chroma: 3 or 4
Rock fragments: 35 to 60 percent
Texture: loam, clay loam
Clay content: 20 to 35 percent
Base saturation (ammonium acetate): 40 to 60 percent but less than 50 percent at some point in the argillic horizon. Base saturation is 40 to 55 percent at the contact with lithic material.
Reaction: very strongly through moderately acid
C horizon:
Rock fragments: 90 to 100 percent strongly cemented sandstone
COMPETING SERIES: There are no competing series in this family.
GEOGRAPHIC SETTING: Branscomb soils are on mountains adjacent to the Pacific coast. Slopes are 30 to 99 percent. Elevations are 3 to 245 meters. The soils formed in material weathered from sandstone. A strong coastal fog influence limits the diurnal and annual ranges of temperature. The climate is humid with cool foggy summers and cool moist winters. Mean annual precipitation ranges from 1000 to 1500 mm. Mean January temperature is 10 degrees C, mean July temperature is 13 degrees C, and the mean annual temperature is 12 degrees C. The frost-free period is 290 to 365 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Dehaven, Irmulco, Tramway and Usal, and Hotel soils. Dehaven soils do not have a mollic epipedon. Tramway soils are less than 40 inches deep. Irmulco and Usal soils are fine-loamy.
DRAINAGE AND PERMEABILITY: Well drained; runoff is high or very high; moderate permeability.
USE AND VEGETATION: This soil is used for timber production, wildlife habitat and watershed. Vegetation is grand fir, redwood, Douglas-fir, tanoak, swordfern, and oxalis.
DISTRIBUTION AND EXTENT: Northern coastal California. The series is not extensive. MLRA 4B.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California
SERIES ESTABLISHED: Mendocino County, California, Western Part, 1993.
REMARKS: The activity class was added to the classification in January of 2003. - ET
The depth class was changed to reflect the fracture spacing in the lithic material in January 2008. - ET.
Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon -- the zone from 5 to 30 cm (A)
Argillic horizon -- the zone from 30 to 133 (Bt1, Bt2, Bt3)
Lithic material - the boundary at 132 cm (C layer)
ADDITIONAL DATA: NSSL data is available for Type Location, pedon 80CA-045-016. (NSSL Sample #s 80P2458-2463)