LOCATION ROCKUS CA

Established Series
REV: BAL/ACF/ET/SAA
05/2016

ROCKUS SERIES

The Rockus series consists of moderately deep, well drained soils formed in colluvium and residuum derived from sandstone and mudstone. These soils are on mountains and have slopes of 9 to 50 percent. Mean annual precipitation is 1524 millimeters (59 inches) and the mean annual temperature is 12 degrees C (54 degrees F).

TAXONOMIC CLASS: Loamy-skeletal, mixed, superactive, mesic Xeric Haplohumults

TYPICAL PEDON: Rockus gravely loam - under a stand of annual and perennial grasses at 990 meters (3250 feet) elevation. When described on August 31, 2005 the soil was dry throughout. (Colors are for dry soil unless otherwise stated).

A1--0 to 6 centimeters (0 to 2 inches); brown (10YR 4/3) gravelly loam, dark brown (10YR 3/3) moist; moderate medium subangular blocky parting to strong very fine granular structure; slightly hard, very friable, nonsticky and nonplastic; many very fine and fine, and common medium roots; many very fine interstitial and common fine tubular pores; 25 percent gravel; very strongly acid (pH 4.6); abrupt smooth boundary.

A2--6 to 25 centimeters (2 to 10 inches); dark yellowish brown (10YR 4/4) gravelly loam, dark brown (10YR 3/3) moist; strong fine subangular blocky structure; slightly hard, very friable, nonsticky and nonplastic; many very fine, common fine and medium roots; many fine interstitial, and common fine tubular pores; 18 percent gravel; very strongly acid (pH 4.6); clear smooth boundary. (combined thickness of A horizons is 18 to 35 centimeters)

BA--25 to 33 centimeters (10 to 13 inches); yellowish brown (10YR 5/4) gravelly loam, dark yellowish brown (10YR 3/4) moist; strong medium subangular blocky structure; soft, very friable, nonsticky and nonplastic; many fine and medium, and common coarse and very coarse roots; common fine interstitial and tubular pores; 20 percent gravel, 5 percent cobbles; very strongly acid (pH 4.8); clear smooth boundary. (0 to 20 centimeters thick)

Bt1--33 to 61 centimeters (13 to 24 inches); yellowish brown (10YR 5/4) very gravelly loam, dark yellowish brown (10YR 3/4) moist; moderate fine subangular blocky structure; soft, very friable, slightly sticky and moderately plastic; common fine through coarse roots; common medium tubular pores; common distinct clay films on all faces of peds; 30 percent gravel, 20 percent cobbles; very strongly acid (pH 4.8); clear smooth boundary.

Bt2--61 to 71 centimeters (24 to 28 inches); yellowish brown (10YR 5/6) extremely gravelly loam, dark yellowish brown (10YR 3/6) moist; weak fine subangular blocky structure; slightly hard, very friable, slightly sticky and moderately plastic; many fine through coarse roots; common fine tubular pores; common distinct clay films on all faces of peds; 75 percent gravel, 5 percent cobbles; very strongly acid (pH 4.8); abrupt wavy boundary. (Combined thickness of Bt horizons is 35 to 80 centimeters)

R--71 centimeters (28 inches); very strongly cemented sandstone with fractures 20 to 50 centimeters (8 to 20 inches) apart.

TYPE LOCATION: Humboldt County, California; Murphy Meadows; USGS Maple Creek Quadrangle; 40.8319444 latitude and -123.8229722 longitude; UTM Zone 10 430611mE, 4520429mN; NAD 83.

RANGE IN CHARACTERISTICS:

Soil moisture: The soil moisture control section is dry from July 1st to October 15th and moist in all parts from November 15 to June 1st. This soil has a xeric soil moisture regime.

Soil temperature: The mean annual soil temperature is 10 to 15 degrees C (50 to 59 degrees F). The difference between mean summer and mean winter temperature is 6 to 10 degrees C. The soils have a mesic soil temperature regime.

Depth to lithic contact: 50 to 100 centimeters (20 to 40 inches).

Soil reaction: very strongly acid to moderately acid throughout the soil profile.

Base saturation (by sum of cations) is less than 35 percent above the lithic contact.

Organic carbon is 12kg or more in the upper cubic meter of the mineral soil or the upper 15 cm of the argillic has 0.9 percent or more organic carbon.

Surface fragments: 0 to 15 percent gravel

Particle Size Control Section (weighted average):
Clay: 15 to 30 percent.
Rock fragments: 35 to 80 percent gravel and 0 to 30 percent cobble

A horizons
Hue: 10YR or 2.5Y
Value: 3 through 5 dry; 2 or 3 moist
Chroma: 3 or 4 dry; 2 or 3 moist
Texture of the fine earth fraction: loam
Clay content: 10 to 20 percent
Rock fragments: 15 to 45 percent gravel and 0 to 10 percent cobble

Bt horizons
Hue: 10YR or 2.5Y
Value: 4 or 5 dry; 3 through 5 moist
Chroma: 2 though 6, dry or moist
Texture of the fine earth fraction: loam, silty clay loam, clay loam,
Clay content: 13 to 30 percent
Rock fragments: 30 to 80 percent gravel and 0 to 30 percent cobble

COMPETING SERIES: This is the Huysink soil. The Huysink soils are 100 to 150 centimeters deep.

GEOGRAPHIC SETTING: These soils occur on mountain slopes with slopes of 9 to 50 percent. They are on convex slope positions at elevations of 322 to 1206 meters (1056 to 3957 feet) on predominantly south and southwest facing slopes. These soils formed in colluvium and residuum from slightly metamorphosed sandstone and mudstone. The climate is subhumid with warm, dry summers and cool, wet winters. The mean annual precipitation is 1250 to 2032 millimeters (49 to 80 inches). Mean January temperature is about 7 degrees C; mean July temperature is about 15 degrees C; and the mean annual temperature is 10 to 15 degrees C (50 to 59 degrees F). The frost free period is about 240 to 280 days.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Flyat and Hawthorse series. Flyat soils are fine-loamy with less than 35 percent rock fragment in the particle size control section. Hawthorse soils are fine with more than 35 percent clay in the particle size control section. Flyat soils are on linear slope positions generally above Rockus soils. Hawthorse soils are on concave slope positions generally below Rockus soils.

DRAINAGE AND SATURATED HYDRAULIC CONDUCTIVITY: Well-drained; medium to high runoff; moderate to moderately high saturated hydraulic conductivity.

USE AND VEGETATION: This soil is mostly used for livestock grazing, wildlife habitat, and watershed. Natural vegetation is bristly dogtail grass, blue wildrye, soft brome and orchardgrass. Douglas-fir invades readily in the absence of fire.

DISTRIBUTION AND EXTENT: Siskiyou-Trinity Area, MLRA 5. The series is of small extent.

MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California

SERIES ESTABLISHED: Humboldt Del Norte area, California, 2005. The name is coined.

REMARKS: Diagnostic horizons and features include:

1. Umbric horizon - The zone from 0 to 25 centimeters (A1 and A2 horizon)
2. Argillic horizon - The zone from 33 to 71 centimeters (Bt1 and Bt2 horizons)
3. Lithic contact - The zone at 71 centimeters.
4. Particle size control section - The zone from 33 to 71 centimeters, averaging (by weight) 17 percent clay and 58 percent rock fragments.

ADDITIONAL DATA:

Nasis User Pedon ID: 05CA023605026

Soil classified using Keys to Soil Taxonomy, 12th edition.

National Cooperative Soil Survey
U.S.A.