LOCATION FIRMOUNTAIN CA

Established Series
REV: WRR/ACF/BAL/ET/JH
04/2015

FIRMOUNTAIN SERIES

The Firmountain series consists of very deep, well drained soils formed in colluvium and residuum derived from phyllite and schist. Firmountain soils are moderately deep to bedrock with fractures less than 10 centimeters apart. These soils are on mountains and have slopes of 30 to 110 percent. Mean annual precipitation is 1905 millimeters (75 inches) and the mean annual temperature is 12 degrees C (54 degrees F).

TAXONOMIC CLASS: Loamy-skeletal over fragmental, mixed, superactive, mesic Typic Dystroxerepts

TYPICAL PEDON: Firmountain very channery loam- under a stand of tanoak, Douglas-fir, canyon live oak and Pacific madrone with a surface cover of 5 percent channers. When described on April 12, 2001, the soil was moist throughout. (Colors are for dry soil unless otherwise stated).

Oe--0 to 7 centimeters; very dark brown (10YR 2/2) moderately decayed plant material, very dark brown (10YR 2/2) rubbed, very dark brown (10YR 2/2) moist; 90 percent fibers, 30 percent fibers rubbed; slightly acid, (pH 6.2),; abrupt smooth boundary. (0 to 10 centimeters thick)

A--7 to 25 centimeters (3 to 10 inches); light gray (10YR 7/2) broken face, very channery loam, dark yellowish brown (10YR 4/4) broken face, moist; weak fine subangular blocky structure; very friable, soft, slightly sticky and slightly plastic; moderately few very fine and common coarse roots throughout; many fine interstitial pores; 55 percent flat subangular phyllite fragments; strongly acid, (pH 5.2); clear wavy boundary. (5 to 20 centimeters thick)

Bw1--25 to 60 centimeters (10 to 24 inches); very pale brown (10YR 7/4) broken face, very channery loam, dark yellowish brown (10YR 4/6) broken face, moist; weak medium subangular blocky structure; very friable, soft, slightly sticky and slightly plastic; few very fine and common medium and coarse roots throughout; common fine tubular and many fine interstitial pores; 45 percent flat subangular phyllite fragments; strongly acid, (pH 5.3); clear smooth boundary.

Bw2--60 to 90 centimeters (24 to 35 inches); very pale brown (10YR 7/4) broken face, very channery loam, dark yellowish brown (10YR 4/6) broken face, moist; weak medium subangular blocky structure; very friable, soft, slightly sticky and slightly plastic; common medium and very coarse roots; many fine interstitial pores; 50 percent flat subangular phyllite fragments; very strongly acid, (pH 5.3); abrupt smooth boundary. (Combined thickness of Bw horizons is 50 to 85 centimeters)

C--90 to 172 centimeters (35 to 68 inches); Channers; 90 percent channers; highly fractured phyllite bedrock; fractures 5 to 10 centimeters apart; very strongly acid, (pH 5.3).

TYPE LOCATION: Humboldt County, California; along Big Hill Road, approximately 1.5 kilometers east of the turn off to Hostler Point. USGS Hoopa topographic quadrangle; 760 meters west and 400 meters north of the southeast corner of Section 7, T. 8N, R.5E, HB&M; 41 degrees 5 minutes 11.4 seconds north latitude and 123 degrees 39 minutes 9.1 seconds west longitude; UTM Zone 10, 445193mE, 4548564mN, NAD 83; WGS84 Decimal degrees 41.0865000 latitude, -123.6525278 longitude

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 mean winter temperature is 6 degrees C or greater. This soil has a mesic soil temperature regime.

Depth to lithic materials: 50 to 100 centimeters (20 to 40 inches)
Depth to bedrock: greater than 150 centimeters (60 inches).

Surface fragments: 0 to 10 percent gravel or channers, 0 to 5 percent cobbles and 0 to 5 percent stones

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

Particle Size Control Section (by weighted average):
Clay: 10 to 30 percent
Rock fragments:
Upper Part - 35 to 65 percent gravel or channers and 0 to 10 percent cobbles
Lower Part - 90 to 100 percent gravel or channers

A Horizon

Hue: 10YR
Value: 4 through 7 dry, 3 through 6 moist
Chroma: 2 through 5 dry, 3 through 6 moist
Texture of fine earth fraction: loam.
Clay Content: 10 to 25 percent
Rock fragment: 35 to 55 percent gravel or channers and 0 to 5 percent cobbles

Bw Horizon

Hue: 10YR, 7.5YR, or 2.5Y
Value: 6 or 7 dry, 2 through 6 moist
Chroma: 2 through 6 dry or moist
Texture of fine earth fraction: loam or clay loam.
Clay content: 10 to 30 percent.
Rock fragments: 35 to 65 percent gravels or channers and 0 to 10 percent cobbles.

C horizon
Hue: 10YR, 7.5YR, or 2.5Y
Value: 6 or 7 dry, 2 through 6 moist.
Chroma: 2 through 6 dry or moist.
Texture of the fine earth fraction: loam.
Clay content: 10 to 25 percent.
Rock fragments: 90 to 100 percent gravels or channers.

COMPETING SERIES: There are no competing series in this family..

GEOGRAPHIC SETTING: These soils occur on mountains with slopes of 30 to 110 percent at elevations of 65 to 1272 meters (213 to 4104 feet). These soils formed in colluvium and residuum derived from schist and phyllite. The climate is subhumid with warm, dry summers and cool, wet winters. The mean annual precipitation is 1524 to 2290 millimeters (60 to 90 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 13 degrees C (48 to 59 degrees F). The frost free season is about 150 to 250 days.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Darkwoods, Redtop, and Oakside soils. Darkwoods soils have an argillic horizon with increasing clay content with depth and presence of clay films. Redtop soils are fine with greater than 35 percent clay in the particle size control section. Oakside soils are 25 to 50 centimeters (10 to 20 inches) to bedrock. Darkwoods and Redtop soils are generally found on linear to concave slope positions. Oakside soils are generally found on strongly convex slope positions.

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 with tanoak, Pacific madrone, salal, Cascade barberry, bracken fern and poison oak.

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

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

SERIES PROPOSED: Northern Humboldt Area, Humboldt County, California, 2012. Proposed 2001.

REMARKS: Diagnostic horizons and features include:

1. Ochric epipedon - The zone from 0 to 25 centimeters (Oe and A horizons)
2. Cambic horizon - The zone from 25 to 90 centimeters (Bw1 and Bw2 horizons)
3. Particle size control section - The zone from 25 to 100 centimeters, averaging (by weight) 11 percent clay and 40 percent rock fragments over 90 percent rock fragments.

ADDITIONAL DATA:

NSSL pedon number: 02N0573

Nasis User Pedon ID: 01CA023605625
Soil classified using Keys to Soil Taxonomy, 11th edition.

National Cooperative Soil Survey
U.S.A.