LOCATION DARKWOODS CA

Established Series
Rev: RV/ACF/WRR/BAL/ET
07/2016

DARKWOODS SERIES

The Darkwoods series consists of very deep, well drained soils formed in colluvium and residuum derived from sandstone, phyllite and schist. These soils are on mountains and have slopes of 15 to 110 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, semiactive, mesic Xeric Haplohumults

TYPICAL PEDON: Darkwoods very channery loam - under a stand of tanoak and Douglas-fir with an under story of California huckleberry, salal and swordfern. When described on April 10, 2001 the soil was moist throughout. (Colors are for dry soil unless otherwise stated).

Oi--0 to 4 centimeters (0 to 1.5 inches); slightly decomposed plant material; whole leaves do not break down with rubbing, abrupt smooth boundary.

Oe--4 to 8 centimeters (1.5 to 3 inches); very dark brown (10YR 2/2) moderately decomposed plant material, very dark brown (10YR 2/2) rubbed; 15 percent fibers, 5 percent fibers rubbed; moderately thick platy structure; soft, nonsticky, and nonplastic; very strongly acid (pH4.7); abrupt wavy boundary.

A--8 to 18 centimeters (3 to 7 inches);, yellowish brown (10YR 5/4), very channery silt loam, brown (7.5YR 4/4) moist; moderate fine granular structure; very friable, soft, nonsticky and, nonplastic; common very fine, fine, medium and coarse roots; many fine interstitial pores; 35 percent phyllite fragments; strongly acid, (pH 5.3); clear wavy boundary. (8 to 30 centimeters thick)

Bt1--18 to 40 centimeters (7 to 16 inches); light yellowish brown (10YR 6/4), very channery silt loam, dark yellowish brown (10YR 4/4) moist; weak fine subangular blocky structure; very friable, slightly hard, slightly sticky and slightly plastic; common very fine, fine and medium roots; many fine interstitial pores; few faint clay films on all faces of peds; 35 percent phyllite fragments; moderately acid, (pH 5.9); clear smooth boundary.

Bt2--40 to 78 centimeters (16 to 31 inches); brownish yellow (10YR 6/6), very channery loam, strong brown (7.5YR 4/6) moist; weak fine subangular blocky structure; very friable, slightly hard, slightly sticky and slightly plastic; common very fine, fine and medium roots; common fine tubular pores; few faint clay films on all faces of peds; 35 percent phyllite fragments; moderately acid, (pH 5.9),; clear smooth boundary.

Bt3--78 to 101 centimeters (31 to 40 inches); reddish yellow (7.5YR 7/6), very channery loam, strong brown (7.5YR 4/6) moist; weak fine subangular blocky structure; very friable, slightly hard, slightly sticky and slightly plastic; very few very fine, fine and common medium roots; common fine tubular pores; few faint clay films on all faces of peds; 50 percent phyllite fragments; moderately acid, (pH 5.6),; clear smooth boundary. (Combined thickness of the upper Bt horizons is 40 to 110 centimeters thick)

Bt4--101 to 134 centimeters (40 to 53 inches); reddish yellow (7.5YR 7/6), very channery loam, strong brown (7.5YR 4/6) moist; weak fine subangular blocky structure; very friable, slightly hard, slightly sticky and slightly plastic; very few fine and medium roots; common fine tubular pores; few faint clay films on all faces of peds; 50 percent phyllite fragments; moderately acid, (pH 5.6),; clear smooth boundary.

Bt5--134 to 170 centimeters (53 to 71 inches); very pale brown (10YR 7/4), very channery loam, yellowish brown (10YR 5/6) moist; weak fine subangular blocky structure; very friable, slightly hard, slightly sticky and slightly plastic; very few fine and medium roots; common fine tubular pores; few faint clay films on all faces of peds; 50 percent phyllite fragments; moderately acid, (pH 5.7). (Combined thickness of the lower Bt horizons is 25 to 75 centimeters)

TYPE LOCATION: Hoopa Tribal Lands, Humboldt County, California; USGS Hoopa topographic quadrangle. Big Hill Road to first left turn, go up across the ridge, 0.7 kilometers from the south crest of the ridge and up the bank to the next adjacent road cut. 400 meters west and 520 meters south of the northeast corner of Section 12, T. 9N, R. 4E, HB&M; WGS84 Decimal degrees 41.0942222 latitude, -123.6613333 longitude; UTM Zone 10, 444459mE, 4549427mN, 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 the mean summer and winter temperature is 6 degrees C. or greater. This soil has a mesic soil temperature regime.

Base saturation: by the ammonium acetate method is less than 35 percent at 143cm.

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

Particle size control section (by weighted average):

Clay: 20 to 35 percent.
Rock fragments: 35 to 70 percent gravel or channers and 0 to 10 percent cobbles.

Surface fragments: 0 to 35 percent gravel and 0 to 10 percent cobbles

A Horizon
Hue: 10YR or 7.5YR
Value: 4 through 7 dry, 2 through 5 moist.
Chroma: 3 through 6 dry, 2 through 6 moist.

Texture: loam or silt loam
Clay content: 15 to 25 percent
Rock fragments: 25 to 65 percent gravel or channers and 0 to 2 percent cobbles

Upper Bt Horizons
Hue: 10YR or 7.5YR
Value: 4 through 7 dry 4 through 6 moist.
Chroma: 4 through 6 dry, 4 through 8 moist.

Texture: loam, silt loam, or clay loam
Clay content: 20 to 35 percent
Rock fragments: 35 to 70 percent gravel or channers and 0 to 10 percent cobbles

Lower Bt Horizons
Hue: 10YR or 7.5YR
Value: 4 through 7 dry 4 through 6 moist.
Chroma: 4 through 6 dry, 4 through 8 moist.

Texture: loam or clay loam
Clay content: 15 to 30 percent
Rock fragments: 20 to 55 percent gravel or channers and 0 to 2 percent cobbles

Some pedons have C horizons

C Horizons
Hue: 10YR or 7.5YR
Value: 4 through 7 dry, 4 through 6 moist.
Chroma: 5 or 6 dry, 4 through 8 moist.

Texture: loamy sand or sandy loam
Clay content: 5 to 18 percent
Rock fragments: 35 to 65 percent gravel or channers

COMPETING SERIES: There are no competing series at this time.

GEOGRAPHIC SETTING: These soils occur on mountains with slopes of 15 to 110 percent at elevations of 19 to 1386 meters (62 to 4547 feet). These soils formed in colluvium and residuum derived from sandstone, schist, and phyllite. The climate is subhumid with warm dry summers and cool moist winters. The mean annual precipitation is 1250 to 2032 millimeters (49 to 80 inches). Mean annual air temperature is about 12 degrees C (54 degrees F). Mean summer temperature is 14 degrees C (58 degrees F) and the mean winter temperature is 7 degrees C (44 degrees F). The mean annual temperature is 9 to 15 degrees C (48 to 59 degrees F). The frost free season is about 150 to 250 days.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Firmountain, Oakside and Redtop soils. Redtop soils are fine with greater than 35 percent clay in the particle size control section. Firmountain soils are moderately deep, 50 to 100 centimeters to bedrock with fractures less than 10 centimeters apart. Oakside soils are shallow, 25 to 50 centimeters (10 to 20 inches) to bedrock with fractures greater than 10 centimeters apart.

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

USE AND VEGETATION: Used for timber production, wildlife habitat and watershed. Native vegetation is Douglas-fir, tanoak, Pacific madrone, salal, poison oak, bracken fern and modesty.

DISTRIBUTION AND EXTENT: Siskiyou-Trinity Area, MLRA 5. The series is not extensive.

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

SERIES ESTABLISHED: Humboldt and Del Norte Area, Humboldt County, California, 2007.

REMARKS: Diagnostic horizons and features include:

1. Ochric epipedon - The zone from 0 to 18 centimeters (Oi, Oe and A horizons)

2. Argillic horizon - The zone from 18 to 170 centimeters (Bt1, Bt2, Bt3, Bt4 and Bt5 horizons)

3. Particle-size control section - the zone from 18 to 68 centimeters, averages 23 percent clay, by weight, and 35 percent rock fragments, by volume.(Bt1 and Bt2 horizons)

4. Haplohumult feature - clay percentage drops from maximum of 24 percent to 18 percent at 101 centimeters.

ADDITIONAL DATA:

NSSL pedon number: 02N0572

NASIS User Pedon ID: 01CA023605624

Soil classified using the 12th Edition of the Keys to Soil Taxonomy.

National Cooperative Soil Survey
U.S.A.