LOCATION ORNBAUN CAEstablished Series
TAXONOMIC CLASS: Fine-loamy, mixed, superactive, isomesic Ultic Haplustalfs
TYPICAL PEDON: Ornbaun loam - on a west facing convex slope of 50 percent under redwood and Douglas fir at 800 feet elevation. (Colors are for dry soil unless otherwise stated. When described May 8, 1978, the soil was moist throughout.)
Oi--0.5 inch to 0; litter of redwood and Douglas fir.
A--0 to 3 inches; light yellowish brown (10YR 6/4) loam, dark yellowish brown (10YR 3/4) moist; weak fine subangular blocky and weak medium granular structure; hard, friable, slightly sticky and slightly plastic; common fine and few very fine and coarse roots; few very fine and fine interstitial and few fine tubular pores; 5 percent soft subangular pebbles (2 to 20 mm); moderately acid (pH 5.6); clear wavy boundary. (2 to 5 inches thick)
BAt--3 to 9 inches; light brown (7.5YR 6/4) loam, dark yellowish brown (7.5YR 4/4) moist; weak fine angular blocky structure; hard, firm, sticky and plastic; common fine, and few very fine, medium and coarse roots; few very fine interstitial and common fine tubular and interstitial pores; few thin clay films bridging mineral grains; 2 percent soft subangular pebbles (2 to 20 mm); strongly acid (pH 5.5); clear wavy boundary. (4 to 7 inches thick)
Bt1--9 to 25 inches; variegated reddish yellow (7.5YR 7/6)and light brown (7.5YR 6/4) loam, strong brown (7.5YR 5/6) moist; moderate fine and medium angular blocky structure; hard, firm, sticky and plastic, common fine and few very fine, medium and coarse roots; few very fine interstitial and common fine tubular and interstitial pores; common moderately thick clay films on faces of peds and lining pores; moderately acid (pH 5.6); gradual wavy boundary. (10 to 20 inches thick)
Bt2--25 to 40 inches; variegated light brown (7.5YR 6/4) and yellowish red (5YR 5/6) gravelly loam, strong brown (7.5YR 5/6) moist; weak fine and medium angular blocky structure; hard, firm, sticky and plastic; common fine, few very fine, coarse and very coarse roots; few very fine and fine interstitial pores; common moderately thick clay films on peds and in pores; 16 percent soft subangular pebbles (2 to 75 mm); strongly acid (pH 5.5); gradual wavy boundary. (10 to 20 inches thick)
Bt3--40 to 50 inches; variegated reddish yellow (5YR 6/6) and pink (7.5YR 7/4) clay loam, yellowish red (5YR 4/6) and strong brown (7.5YR 5/6) moist; weak fine angular blocky structure; very hard, very firm, sticky and very plastic; few fine, medium, and coarse roots; few very fine tubular pores; many moderately thick clay films on faces of peds; 14 percent soft subangular pebbles (2 to 75 mm); strongly acid (pH 5.4); clear irregular boundary. (5 to 10 inches thick)
Bt4--50 to 59 inches; variegated reddish yellow (5YR 6/6) and pink (7.5YR 7/4) clay loam, yellowish red (5YR 4/6) and strong brown (7.5YR 5/6) moist; weak fine angular blocky structure; very hard, very firm, sticky and very plastic; few fine, medium and coarse roots; few very fine tubular pores; many moderately thick clay films on faces of peds; 10 percent soft subangular pebbles (2 to 75 mm); strongly acid (pH 5.2); abrupt irregular boundary. (5 to 10 inches thick)
Cr--59 to 61 inches; soft, fractured sandstone; fractures are about 1 to 3 mm wide and about 10 cm apart.
TYPE LOCATION: Mendocino County, California; about 1 mile south of the town of Boonville; 1,800 feet east and 1900 feet south of the northwest corner of section 14, T.13 N., R.14 W.; Ornbaun Valley Quandrangle.
RANGE IN CHARACTERISTICS: Thickness of the solum and depth to a lithic or paralithic contact is 40 to 60 inches. The mean annual soil temperature ranges from 50 to 56 degrees F. The difference between mean summer and mean winter temperature ranges from 5 to 9 degrees F. The soil between depths of 6 and 17 inches is moist in all parts from November 1 to June 1 and is dry in some or all parts from July 1 to October 1 in most years. The particle-size control section averages from 25 to 35 percent clay and from 15 to 35 percent soft fragments of sandstone. Base saturation ranges from 40 to 75 percent throughout the soil.
The A horizon is 10YR 5/2, 5/4, 6/2, 6/3 or 6/4. Moist color is 10YR 2/2, 3/3, 3/4, 4/3, 4/4, 5/3, 5/4, or 7.5YR 3/2. Soft sandstone fragments content ranges from 0 to 10 percent. Where mollic colors occur, the layer is too thin to meet the requirements for a mollic epipedon. Reaction ranges from strongly acid through slightly acid.
The Bt horizon is 10YR 6/4, 6/6, 7/3, 7/4; 7.5YR 6/4, 6/6 7/4, 7/6; 5YR 5/6 or 6/6. Moist color is 10YR 4/6, 6/4; 7.5YR 4/4, 4/6, 5/6, 6/4, 6/6, 7/6; 5YR 4/6 or 5/6. It is loam or clay loam. Clay textures are below the particle-size control section. Clay content ranges from 20 to 50 percent (increasing with increasing depth). Soft sandstone fragment content ranges from 0 to 35 percent. Fragments slake in water. Reaction ranges from very strongly acid through moderately acid.
COMPETING SERIES: These are the Cabrillo (CA), Crispin (CA), Inverness (CA) and Zeni (CA) soils. Inverness soils have C horizons above a paralithic contact and contain 5 to 20 percent mica flakes. Crispin and Zeni soils are 20 to 40 inches deep to a paralithic contact. Cabrillo soils are very deep.
GEOGRAPHIC SETTING: The Ornbaun soils occur on hills and mountains. Slopes are 9 to 75 percent. Elevations range from 200 to 2,500 feet. The soils formed in material weathered from feldspathic or micaceous sandstone and mudstone. The climate is subhumid with cool foggy summers and cool moist winters. A moderate coastal fog influence limits the diurnal and annual range of temperature. Mean annual precipitation ranges from 40 to 70 inches. Mean January temperature is about 50 degrees F; mean July temperature is about 60 degrees F; and the mean annual temperature is about 53 degrees F. The frost-free period is 220 to 320 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the competing Zeni and the Casabonne, Dehaven, Hotel, Irmulco, Kibesillah, Pardaloe, Tramway, Woodin, Wohly and Yellowhound soils. The Hotel, Kibesillah, Tramway, Woodin, Wohly and Zeni soils are moderately deep. Casabonne, Pardaloe, Woodin and Wohly have a xeric mesic moisture temperature regime. Dehaven, Hotel, Irmulco and Tramway soils have a udic moisture regime. Dehaven, Hotel, Kibesillah, Pardaloe, Woodin and Yellowhound soils have a loamy-skeletal particle-size control section.
DRAINAGE AND PERMEABILITY: Well drained; surface runoff under bare soil conditions is medium to very rapid; moderate permeability.
USE AND VEGETATION: This soil is used for timber production, wildlife habitat and watershed. Vegetation consists of Douglas-fir, redwood, tanoak, madrone and California huckleberry.
DISTRIBUTION AND EXTENT: Northern coastal California. The series is moderately extensive. MLRA 4.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California
SERIES ESTABLISHED: Mendocino County, California, Eastern Part 1985.
REMARKS:
Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon - the surface layer from 0 to 3 inches.
Argillic horizon - the zone from 9 to 59 inches (Bt1, Bt2, Bt3, Bt4 horizons)
Paralithic material, when present, has a similar available water capacity and bulk density to the overlying B horizon. Soft sandstone fragments in the Bt horizon are not recognized in the textural class as they do not affect engineering properties in the same manner as hard gravels.
The activity class was added to the classification in February of 2003. Competing series were not checked at that time. - ET
ADDITIONAL DATA: Complete lab characterization of typical pedon: NSSL Lab Sample Nos. - 80P2469-2475.