LOCATION COHASSET CA
The Cohasset series consists of deep and very deep, well drained soils that formed in material weathered from volcanic rock. These soils are on volcanic ridges and mountain slopes in mountains and have slopes of 2 to 75 percent. The mean annual precipitation is about 38 inches and the mean annual air temperature is about 54 degrees F.
TAXONOMIC CLASS: Fine-loamy, mixed, active, mesic Ultic Haploxeralfs
TYPICAL PEDON: Cohasset loam - forested. (Colors are for dry soil unless otherwise stated.)
Oi--0 to 3 inches (0 to 8 cm); organic mat of fresh pine and fir needles, more decomposed with increasing depth; slightly acid (pH 6.1); abrupt smooth boundary.
A--3 to 7 inches (8 to 18 cm); brown (7.5YR 5/4) loam, dark reddish brown (5YR 3/4) moist; strong medium and fine granular structure; soft, very friable, nonsticky and nonplastic; few coarse roots, many very fine and fine, few medium pores; many rounded, hard concretions 2 to 3 mm in diameter; slightly acid (pH 6.1); abrupt smooth boundary. (3 to 6 inches thick)
AB--7 to 18 inches (18 to 44 cm); brown (7.5YR 5/4) loam, dark reddish brown (5YR 3/4) moist; strong medium and fine granular structure; slightly hard, friable, slightly sticky and slightly plastic; many very coarse roots; many pores; few rounded, hard concretions; moderately acid (pH 5.9); gradual wavy boundary. (7 to 16 inches thick)
BAt--18 to 32 inches (44 to 82 cm); brown (7.5YR 5/4) clay loam, dark reddish brown (5YR 3/4) moist; strong medium subangular blocky structure; hard, friable, slightly sticky and slightly plastic; many fine and very fine, few medium, and few coarse roots; many fine pores; thin continuous clay films line a few pores; strongly acid (pH 5.4); gradual irregular boundary. (6 to 20 inches thick)
Bt1--32 to 43 inches (82 to 110 cm); reddish brown (5YR 5/4) clay loam, reddish brown (5YR 4/4) moist; strong medium subangular blocky structure; hard, friable, slightly sticky and slightly plastic; common very fine and fine, few medium, and few coarse roots; many fine pores; thin continuous clay films line most pores; few weathered cobbles; strongly acid (pH 5.1); gradual smooth boundary. (8 to 15 inches thick)
Bt2--43 to 58 inches (110 to 148 cm); reddish brown (5YR 5/4) clay , reddish brown (5YR 4/4) moist; strong medium subangular blocky structure; hard, friable, slightly sticky and slightly plastic; common very fine and fine, few medium, and few coarse roots; many fine pores; a few weathered pebbles and cobbles; very strongly acid (pH 5.0); diffuse lower boundary. (10 to 20 inches thick)
Cr--58 to 63 inches (148 to 160 cm); light brownish gray weathered andesitic breccia with pale brown flecks and reddish brown staining and soil in cracks.
TYPE LOCATION: Tehama County, California; about 3 miles south of California Highway 36 to Little Giant Mill Road; on a west-facing slope of 24 percent at an elevation of 3,620 feet; 1/4 miles south of the north quarter corner of section 33, T.29 N., R.2 E. 121 degrees, 45 minutes 3 seconds west longitude, 40 degrees, 19 minutes 36.3 seconds north latitude, NAD 83.
RANGE IN CHARACTERISTICS: Depth to a paralithic or lithic contact of weathered rock ranges from 40 to 80 inches. The soil between depths of about 6 and 24 inches is usually moist; however, it is dry in all parts for 120 to 150 days from sometime in June through October. Mean annual soil temperature is between 54 and 59 degrees F. Coarse fragments are in all horizons and range up to 35 percent. The soil is influenced by amorphous material.
The A horizon is 10YR 5/4, 4/4, 4/2, 3/4, 3/3; 7.5YR 5/6, 4/6, 5/4, 4/4, 5/2, 4/2; 5YR 5/8, 4/8, 5/6, 4/6, 5/4, 4/4, 5/3, or 4/3. It is sandy loam, or loam, and may have gravelly or cobbly modifiers. It is slightly acid through strongly acid and contains concretions. This horizon is either too thin or value and chroma are too high to be umbric or mollic.
The Bt horizon is 7.5YR 5/8, 6/6, 5/6, 6/4, 5/4 or 4/6; 5YR 5/8, 4/8, 5/6, 4/6, 5/4, 4/4, 5/3, or 4/3 and 2.5YR 5/4. It is loam or clay loam and is gravelly or cobbly in some pedons. Clay content averages 25 to 35 percent and coarse sand and very coarse sand combined total 5 to 15 percent. Base saturation averages 35 to 50 percent usually decreasing with depth. It is medium acid through very strongly acid. Some pedons have a BC or C horizon.
COMPETING SERIES: These are the
Wohly soils. Boomer, Cle Elum,
Glenview, Holland, McGowan, Teanaway, and Wohly soils all average 50 to 75 percent base saturation in the control section. Casabonne, Centralia, Cherryhill, Cle Elum, Dalig, Fives, Gunn, Hood, Kalama, Latourell, McGowan, Para, Rosehaven, Speaker, Teanaway, Tigit, Trelk, Underwood, Varelum, Wilkeson and Wohly are all dry in the control section for less than 120 days in most years. Crozier and Hotaw soils are less than 40 inches to bedrock. Musick soils have more than 15 percent coarse plus very coarse sand in the control section.
GEOGRAPHIC SETTING: The soils are on volcanic ridges and mountain slopes comprised of volcanic mudflows, volcanic conglomerate, volcanic sandstone, tuff or extrusive volcanic rocks. Slopes are 2 to 75 percent. They are at elevations of about 800 to 5,500 feet. The climate is moist, subhumid with warm, nearly dry summers and cold, wet winters. Mean annual precipitation is 35 to 70 inches. Snow covers the higher elevations from December until March. The average January temperature is about 30 to 35 degrees F.; the average July temperature is about 63 to 68 degrees F; the mean annual temperature is about 45 to 58 degrees F. The average frost-free season is 100 to 250 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the
Lyonsville, McCarthy, and
Windy soils. Aiken soils have less than 35 percent base saturation in the argillic horizon. Ledmount soils have bedrock at less than 20 inches. McCarthy soils lack an argillic horizon. Lyonsville and Windy soils are at higher elevations and have soil temperatures less than 47 degrees F.
DRAINAGE AND PERMEABILITY: Well drained; slow to rapid runoff; moderate permeability.
USE AND VEGETATION: Used mainly for timber. Native vegetation is ponderosa pine, Douglas-fir, white fir, sugar pine, and incense-cedar with scattered black oak. Shrubs are prostrate ceanothus, whiteleaf and greenleaf manzanita, and deerbrush.
DISTRIBUTION AND EXTENT: Cascade, Sierra Nevada, and Coast Ranges of northern California and probably in southern Oregon. The soils are extensive in MLRA 22A and 22B.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California
SERIES ESTABLISHED: Tehama County, California, 1961.
Edits made after six SDJR projects - AEC
ADDITIONAL DATA: Typical pedon NSSL user pedon ID 54-CA-52-005, S90CA-109-108 (taxadjunct) and S72CA-055-005.
National Cooperative Soil Survey