LOCATION GIBNEY CAEstablished Series
TAXONOMIC CLASS: Fine, mixed, active, isomesic Typic Hapludults
TYPICAL PEDON: Gibney loam - on a southwest facing slope of 2 percent under Bishop pine at 520 feet elevation (colors are for dry soil unless otherwise stated. When described on August 14, 1984, the soil was dry to a depth of 4 inches, slightly moist between 4 and 9 inches, and moist from 9 to 63 inches).
Oi--3 inches to 0; litter of bishop pine and manzanita
A1--0 to 4 inches; pale yellow (2.5Y 7/4) loam, yellowish brown (10YR 5/4) moist; moderate fine and medium subangular blocky structure parting to weak fine granular; soft, very friable, sticky and slightly plastic; many very fine and fine and common medium and coarse roots; common very fine and fine tubular and common very fine interstitial pores; 10 percent hard subrounded dark reddish brown (5YR 2.5/2)and black (5YR 2.5/1) nodules (2-30mm); moderately acid (pH 5.6); clear wavy boundary. (2 to 8 inches thick)
A2--4 to 9 inches; pale yellow (2.5Y 7/4) loam, yellowish brown (10YR 5/4) moist; moderate fine and medium subangular blocky structure parting to weak fine granular; slightly hard, very friable, sticky and plastic; common very fine,fine, medium and coarse roots; common very fine and fine tubular and common very fine interstitial pores; 5 percent hard, subrounded, dark reddish brown (5YR 2.5/2) and black (5YR 2.5/1) nodules (2-10mm); moderately acid (pH 5.9); clear wavy boundary. (0 to 6 inches thick)
Bt1--9 to 15 inches; brownish yellow (10YR 6/6) sandy clay loam, yellowish brown (10YR 5/6) moist; moderate very fine ,fine, medium and coarse subangular blocky structure; slightly hard, firm, sticky and plastic; common very fine and fine and few medium roots; common very fine tubular and interstitial pores; few thin clay films on faces of peds and bridging mineral grains; extremely acid (pH 4.3); gradual wavy boundary. (4 to 10 inches thick)
Bt2--15 to 29 inches; yellowish brown (10YR 5/8) clay loam, yellowish brown (10YR 5/6) moist; strong fine, medium and coarse subangular blocky structure; hard, firm, sticky and plastic; few very fine and fine roots; common very fine tubular and interstitial pores; common thin and moderately thick clay films on faces of peds and lining pores, and bridging mineral grains; extremely acid (pH 4.3); gradual wavy boundary. (6 to 18 inches thick)
Btv1--29 to 40 inches; yellowish brown (10YR 5/8) clay, yellowish brown (10YR 5/6) moist; common medium and coarse distinct strong brown (7.5YR 5/6) mottles, strong brown (7.5YR 5/6) moist, and common medium prominent red (2.5YR 4/8) mottles, red (2.5YR 4/6) moist; strong fine, medium and coarse angular blocky structure; hard, firm, very sticky and plastic; few very fine, fine and medium roots; few very fine tubular and interstitial pores; many thin and moderately thick clay films on faces of peds, lining pores and bridging mineral grains; most red color is the soft natural plinthite, that is firm when moist; 5 percent hard subrounded yellowish red (5YR 4/6) nodules, (20 to 60 mm); very strongly acid (pH 4.5); gradual wavy boundary. (0 to 15 inches thick)
Btv2--40 to 55 inches; brownish yellow (10YR 6/6) clay, yellowish brown (10YR 5/6) moist; many medium and coarse distinct strong brown (7.5YR 5/6) mottles, strong brown (7.5YR 5/6) moist, common medium and coarse prominent red (2.5YR 4/8) mottles, red (2.5YR 4/8) moist, and common medium and coarse prominent light gray (2.5Y 7/2) mottles, light yellowish brown (2.5Y 6/4) moist; strong fine, medium and coarse angular blocky structure; hard, firm, sticky and plastic; few very fine and fine roots; few very fine tubular and interstitial pores; many thin and moderately thick clay films on faces of peds, lining pores and bridging mineral grains; most red color is soft natural plinthite, that is firm when moist; 10 percent hard platelike yellowish red (5YR 4/6) nodules that are 5 to 10 mm thick, 20 to 100 mm long and 10 to 40 mm wide; extremely acid (pH 4.1); abrupt irregular boundary. (0 to 16 inches thick)
Btv3--55 to 63 inches; light gray (2.5Y 7/2) sandy clay loam, light brownish gray (2.5Y 6/2) moist; common coarse prominent strong brown (7.5YR 5/8) mottles, strong brown (7.5YR 5/6) moist, and common medium prominent red (2.5YR 4/8) mottles, yellowish red (5YR 4/6) moist; massive; slightly hard, firm, slightly sticky and slightly plastic; few very fine roots; common very fine interstitial and few very fine tubular pores; few moderately thick clay films on nodules; most red color is soft natural plinthite that is firm when moist; 10 percent hard and very hard subangular yellowish red (5YR 4/6) nodules (50-200mm); very strongly acid (pH 4.5).
TYPE LOCATION: Mendocino County, California; about 400 feet north and 2600 feet east of the southwest corner of sec. 21,T.l7N., R.17W., MDBM, Mendocino quadrangle.
RANGE IN CHARACTERISTICS: Thickness of the solum is greater than 60 inches. Depth to bedrock is greater than 80 inches. The mean annual soil temperature is 50 to 56 degrees F. The difference between mean summer and mean winter temperature varies from 6 to 9 degrees F. The soil between the depths of 9 and 21 inches is moist in all parts from November 1 to August 1 and is dry in some part from September 1 to October 1 in most years. The particle-size control section averages 35 to 45 percent clay. Hard iron nodule content ranges from 0 to 15 percent throughout.
The A horizon is 2.5Y 6/4, 7/2, 7/4; 10YR 6/2, 6/3, 6/4 or 7/2. Moist color is 2.5Y 5/2, 6/4; 10YR 4/3, 4/4, 5/2, 5/3, 5/4 or 6/3. The horizon may be smeary and may be brittle when moist. Clay content ranges from 7 to 15 percent. Subrounded nodules (2-30mm) range from 0 to 15 percent. Reaction is very strongly to moderately acid.
The Bt horizon is 5Y 7/2,; 2.5Y 7/2; 10YR 5/6, 5/8, 6/4, 6/6, 7/3 or N 7/0. Moist colors are 5Y 6/2, 6/3; 2.5Y 6/2; 10YR 4/6, 5/4, 5/6, 5/8 or N 5/0. Mottle colors are 2.5Y 7/2; 10YR 6/6, 7/1, 8/1; 7.5YR 5/6, 5/8 or 2.5YR 4/8. Moist mottle colors are 2.5Y 6/4; 10YR 5/4, 6/8, 7/2, 8/1; 7.5YR 5/6, 5/8; 5YR 4/6; 2.5YR 4/6 or 4/8. Low chroma grayish colors occur with higher chroma brownish colors and reddish colors in a regularly occurring reticulate pattern. This pattern occurs within a depth of 30 to 50 inches. It is clay, sandy clay, clay loam, or sandy clay loam. Clay content ranges from 30 to 60 percent. The horizon contains 0 to 20 percent soft plinthite. Hard iron nodules are commonly 2 to 30mm in diameter but may range to 200mm in the lowest part of the horizon. Base saturation (sum) ranges from 5 to 30 percent. Clay mineralogy is dominated by 1 to 1 lattice clays. Reaction is extremely or very strongly acid.
COMPETING SERIES: This is the Gibwell (CA) series. Gibwell soils lack mottling.
GEOGRAPHIC SETTING: The Gibney soils occur on marine terraces. Slopes are 2 to 15 percent. Elevations are 200 to 750 feet. The soils formed in marine sediments. The climate is humid with cool foggy summers and cool moist winters. A strong marine influence limits the diurnal and annual range of temperature. Mean annual precipitation varies from 40 to 65 inches. Mean January temperature is 48 degrees F., mean July temperature is 57 degrees F., and the mean annual temperature is 53 degrees F. The frost-free period is 270 to 330 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the competing Gibwell soils and the Aborigine, Blacklock and Shinglemill soils. All are adjacent to Gibney soils on marine terraces. Aborigine and Blacklock soils support extreme pygmy vegetation. Aborigine soils are saturated with water above 10 inches for extended periods during the winter and are very poorly drained. Blacklock soils are shallow to an iron cemented hardpan. Shinglemill soils have low chroma mottles between 10 and 30 inches and are poorly drained.
DRAINAGE AND PERMEABILITY: Somewhat poorly drained; the soil is saturated with water for extended periods following episodes of heavy rain from December through April. The saturated zone starts between the depths of 30 and 50 inches and extends to greater than 60 inches. The soil is not saturated above 60 inches from summer through early fall. Surface runoff under bare soil conditions is slow or medium; slow permeability.
USE AND VEGETATION: This soil is used for wildlife habitat, watershed, recreation, and homesite development. Vegetation consists of Bishop pine, glossyleaf manzanita, California huckleberry, rhododendron, Mendocino cypress and bear grass.
DISTRIBUTION AND EXTENT: Northern coastal California. The series is not extensive. MLRA 4.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California
SERIES ESTABLISHED: Mendocino County, California, Western Part, 1993.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon - the zone from 0 to 9 inches (A1, A2)
Argillic horizon - the zone from 9 to 63 inches (Bt1, Bt2,Btv1, Btv2, Btv3)