LOCATION TEPONA CA

Established Series
Rev. FWH/FFH/JJJ/JPS
10/2016

TEPONA SERIES

The Tepona series consists of very deep, moderately well drained soils formed in marine deposits from mixed sources. Tepona soils are on marine terraces and have slopes of 0 to 9 percent. The mean annual precipitation is about 1500 millimeters (59 inches) and mean annual temperature is about 12 degrees C (54 degrees F).

TAXONOMIC CLASS: Coarse-loamy, mixed, superactive, isomesic Oxyaquic Humudepts

TYPICAL PEDON: Tepona loam on a southwest facing, linear slope of 2 percent under Sitka spruce, salmonberry, evergreen huckleberry and salal at an elevation of 15 meters (50 feet). (Colors are for moist soils unless otherwise stated. When described on May 24, 2007 the soil was moist throughout.)

Oi--0 to 4 centimeters (0 to 2 inches); very dark brown (10YR 2/2) slightly decomposed needles, leaves and twigs, very dark grayish brown (10YR 3/2) dry; 95 percent unrubbed, 85 percent rubbed; loose, loose, nonsticky and nonplastic; common very fine, fine, medium and coarse roots; many very fine and fine interstitial pores; moderately acid (pH 5.8); clear smooth boundary. (Thickness of the Oi horizon is 0 to 8 centimeters (0 to 3 inches))

A1--4 to 30 centimeters (2 to 12 inches); very dark brown (10YR 2/2) loam, very dark grayish brown (10YR 3/2) dry; weak fine and medium granular structure; soft, very friable, slightly sticky and slightly plastic; common very fine, fine, medium, coarse, and very coarse roots; many very fine and fine irregular pores and common very fine and fine tubular pores; very strongly acid (pH 5.0); gradual smooth boundary.

A2--30 to 64 centimeters (12 to 25 inches); very dark brown (10YR 2/2) loam, very dark grayish brown (10YR 3/2) dry; moderate very fine and fine subangular blocky; slightly hard, friable, slightly sticky and slightly plastic; many medium and coarse roots and common very fine, fine, and very coarse roots; many very fine and fine irregular pores and common fine and medium tubular pores; very strongly acid (pH 5.0); clear smooth boundary. (Combined thickness of the A horizons is 20 to 70 centimeters)

Bw1--64 to 88 centimeters (25 to 35 inches); dark brown (7.5YR 3/4) sandy loam, strong brown (7.5YR 5/6) dry; moderate fine subangular blocky structure; soft, very friable, nonsticky and nonplastic; common fine, medium, and coarse roots; common very fine and fine irregular pores and common very fine tubular pores; very strongly acid (pH 4.8); clear smooth boundary.

Bw2--88 to 105 centimeters (35 to 41 inches); dark yellowish brown (10YR 4/4) sandy loam, light yellowish brown (10YR 6/4) dry; single grain; loose, loose; nonsticky and nonplastic; common fine roots; many very fine and fine interstitial pores; common fine prominent strong brown (7.5YR 5/8) masses of iron accumulation in the matrix; very strongly acid (pH 5.0); clear smooth boundary. (Combined thickness of the Bw horizons is 40 to 90 centimeters)

C1--105 to 125 centimeters (41 to 49 inches); brown (10YR 4/3) sandy loam, light yellowish brown (10YR 6/4) dry; massive; soft, very friable, nonsticky and nonplastic; few fine and common medium roots; many very fine and fine interstitial pores; many fine and medium prominent strong brown (7.5YR 5/8) and yellowish red (5YR 5/6) masses of oxidized iron and common fine distinct dark gray (2.5Y 4/1) iron depletions in the matrix; strongly acid (pH 5.2); clear smooth boundary.

C2--125 to 152 centimeters (49 to 60 inches); dark grayish brown (2.5Y 4/2) sandy loam, light yellowish brown (2.5Y 6/4) dry; massive; soft, very friable, nonsticky and nonplastic; few very fine roots; many very fine and common fine interstitial pores; many fine and medium prominent strong brown (7.5YR 5/6) and brownish yellow (10YR 6/6) masses of oxidized iron and many fine and medium distinct dark gray (2.5Y 4/1) and gray (2.5Y 5/1) iron depletions in the matrix; strongly acid (pH 5.2). (Combined thickness of the C horizons is 20 to 60 centimeters)

TYPE LOCATION: Del Norte County, California; 5.5 kilometers (3.4 miles) north west of the town of Smith River, California; USGS Smith River Quadrangle; WSG84 41.9527778 latitude and -124.2052778 longitude, UTM Zone 10 400113mE 4645223mN; NAD83.

RANGE IN CHARACTERISTICS:

Soil moisture: The soil is usually moist in all parts in the soil moisture control section in most years, but becomes nearly dry in the upper part from about September 15 to October 15 in most years. The soils have an udic soil moisture regime and an oxyaquic regime subclass. A seasonal water table is present for 20 or more consecutive days or 30 or more cumulative days in most years within the zone from 75 to 100 centimeters (30 to 40 inches).

Soil temperature: The mean annual soil temperature is 11 to 13 degrees C (52 to 55 degrees F). The difference between mean summer and mean winter temperature is 2 to 4 degrees C. The soils have an isomesic temperature regime.

The umbric epipedon is 20 to 60 (25 to 54 inches) centimeters thick

Base Saturation, by ammonium acetate, is less than 60 percent between depths of 25 to 75 centimeters

Depth to redoximorphic features: 50 to 100 centimeters

Particle-Size Control Section (weighted average):

Clay content: 12 to 18 percent clay

O horizon

Hue: 10YR.
Value: 2 or 3, 3 through 5 dry
Chroma: 1 through 3 moist or dry

Texture: slightly decomposed organic material
Wood fragments: 0 to 35 percent
Reaction: moderately to very strongly acid

A horizon

Hue: 10YR
Value: 2 or 3, 3 through 5 dry
Chroma: 1 through 3, 2 or 3 dry

Texture of fine earth: loam, very fine sandy loam, sandy loam, or silt loam
Rock fragments: 0 percent gravel
Clay content: 10 to 25 percent
Reaction: very strongly to moderately acid

Bw horizon

Hue: 7.5YR, 10YR, or 2.5Y
Value: 3 through 5, 5 through 7 dry
Chroma: 3 through 6 moist and dry

Texture of fine earth: sandy loam or fine sandy loam
Rock fragments: 0 percent gravel
Clay content: 7 to 18 percent
Reaction: very strongly to moderately acid

Redoximorphic features:

Amount: many, common, or few
Kind: fine and medium masses of concentrated iron or iron-manganese masses in matrix
Hue: 7.5YR or 10YR
Value: 4 through 6
Chroma: 6 through 8

Amount: many, common, or few
Kind: fine and medium masses of depleted iron in matrix
Hue: 10YR or 2.5Y
Value: 4 or 6
Chroma: 1 or 2

C horizon

Hue: 10YR or 2.5Y
Value: 3 through 5, 5 or 6 dry
Chroma: 2 through 4, 1 through 4 dry

Texture of fine earth: sand, loamy fine sand, sandy loam, or fine sandy loam
Clay content: 2 to 13 percent
Reaction: very strongly to moderately acid

Redoximorphic features:

Amount: many or common
Kind: fine and medium masses of oxidized iron or iron-manganese masses in matrix
Hue: 5YR, 7.5YR, or 10YR
Value: 4 through 6 moist
Chroma: 6 through 8 moist

Amount: many, common, or few
Kind: fine and medium masses of depleted iron in matrix
Hue: 2.5Y
Value: 4 through 6
Chroma: 1 or 2

COMPETING SERIES: These are the Mystery soils. Mystery soils have buried A horizons.

GEOGRAPHIC SETTING: Tepona soils are on marine terraces. Slopes are 0 to 9 percent. The soils formed in marine sediments derived from mixed sources. Elevations are 4 to 183 meters (10 to 600 feet). A strong marine influence limits the diurnal and annual range of temperature. The climate is humid with cool, foggy summers and cool, wet winters. The mean annual temperature is 11 to 14 degrees C (52 to 57 degrees F). The mean annual precipitation is 890 to 2285 millimeters (35 to 90 inches). The frost-free period is 275 to 325 days.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Arcata and Halfbluff soils. Arcata and Halfbluff soils occur under cultivated or cleared conditions where the difference between mean winter and mean summer soil temperature is 6 degrees C or greater.

DRAINAGE AND SATURATED HYDRAULIC CONDUCTIVITY: Moderately well drained; surface runoff under bare soil conditions is moderate; saturated hydraulic conductivity is moderately high.

USE AND VEGETATION: This soil is used predominantly for timber production, recreation and urban development. Natural vegetation includes redwood with scattered Sitka spruce and red alder, salal, western swordfern, redwood sorrel, cascara and red huckleberry.

DISTRIBUTION AND EXTENT: Coastal Redwood Belts; MLRA 4B. The series is of small extent.

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

SERIES PROPOSED: Humboldt and Del Norte Counties Area, California, January 2013. The name is from Tepona Point north of Trinidad, California.

REMARKS: Diagnostic horizons and features recognized in this pedon are:
1. Umbric epipedon - the zone from 4 to 64 centimeters (A1 & A2 horizons).
2. Cambic horizon - the zone from 64 to 105 centimeters (Bw1 & Bw2 horizons).
3. Particle-size control section - the zone from 29 to 104 centimeters, averages 13 percent clay, and 38 percent fine sand or coarser, by weight. (A1, A2, Bw1 & Bw2 horizons).
4. Oxyaquic Dystrudepts - seasonal water table, aquic conditions for more than 30 days in most years within the zone from 88 to 152 centimeters (Bw2, C1 and C2 horizons)

ADDITIONAL DATA: California Soil-Vegetation Survey samples 63-CA-12-007 Humboldt County and 64-CA-08-003 was collected from similar pedons.
NASIS User Pedon ID 07CA605242
NSSL, Lincoln Lab sample number 08N0452

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

National Cooperative Soil Survey
U.S.A.