LOCATION TECTAH CA

Established Series
Rev: JHP/JPS/ET
10/2016

TECTAH SERIES

The Tectah series consists of very deep, well drained soils formed in colluvium and residuum derived from sandstone, mudstone and metasedimentary rocks. Tectah soils are on mountains and have slopes of 0 to 50 percent. The mean annual precipitation is about 2160 millimeters (85 inches) and the mean annual temperature is about 11 degrees C (52 degrees F).

TAXONOMIC CLASS: Fine, mixed, semiactive, isomesic Typic Palehumults

TYPICAL PEDON: Tectah silty clay loam - on a south-facing, slightly convex slope of 35 percent under redwood, western hemlock, Douglas fir, tanoak, Pacific rhododendron, huckleberry, and salal at 366 meters (1200 feet) elevation. (Colors are for moist soil unless otherwise stated. When described July 6, 1982, the soil was moist throughout.)

Oi--0 to 5 centimeters (0 to 2 inches); fresh and slightly decomposed leaves, twigs and cones from redwood, Douglas-fir, tanoak, and hemlock; very strongly acid (pH 4.5). (0 to 6 centimeters thick)

A--5 to 30 centimeters (2 to 12 inches); dark yellowish brown (10YR 4/4) silty clay loam, light yellowish brown (10YR 6/4) dry; strong medium subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; common very fine, fine and medium, and few coarse roots; common very fine and fine irregular pores; 7 percent gravel; moderately acid (pH 5.6); gradual smooth boundary. (6 to 32 centimeters thick)

BAt--30 to 54 centimeters (12 to 21 inches); strong brown (7.5YR 4/6) silty clay loam, reddish yellow (7.5YR 7/6) dry; strong medium subangular blocky structure; hard, friable, slightly sticky and slightly plastic; common very fine, fine and medium, and few coarse roots; common very fine tubular and irregular pores; few distinct clay films in pores and on faces of peds; 4 percent gravel; moderately acid (pH 5.6); gradual smooth boundary. (0 to 38 centimeters thick)

Bt1--54 to 79 centimeters (21 to 31 inches); yellowish brown (10YR 5/6) silty clay, reddish yellow (7.5YR 7/6) dry; strong coarse subangular blocky structure; hard, friable, moderately sticky and moderately plastic; few very fine, fine, medium and coarse roots; common very fine tubular and irregular pores; many distinct clay films on faces of peds and in pores; 9 percent gravel; very strongly acid (pH 5.2); diffuse smooth boundary.

Bt2--79 to 115 centimeters (31 to 45 inches); yellowish brown (10YR 5/8) silty clay, yellow (10YR 7/6) dry; moderate coarse subangular blocky structure; hard, friable, moderately sticky and moderately plastic, few very fine, fine and medium roots; common very fine and fine tubular and few fine irregular pores; common distinct clay films on faces of peds and in pores; 7 percent gravel; very strongly acid (pH 5.1); diffuse smooth boundary.

Bt3--115 to 155 centimeters (45 to 61 inches); yellowish brown (10YR 5/8) silty clay loam, yellow (10YR 7/6) dry; moderate coarse subangular blocky structure; hard, friable, moderately sticky and moderately plastic; few very fine, fine and medium roots; common very fine tubular and irregular pores; common distinct clay films on faces of peds and in pores; 6 percent gravel; very strongly acid (pH 5.2); diffuse smooth boundary.

Bt4--155 to 185 centimeters (61 to 73 inches); yellowish brown (10YR 5/8) silty clay loam, yellow (10YR 7/6) dry; moderate coarse subangular blocky structure; hard, friable, moderately sticky and moderately plastic; few very fine, fine and medium roots; common very fine tubular and irregular pores; common faint clay films on faces of peds and in pores; 8 percent gravel; very strongly acid (pH 5.1). (Combined thickness of Bt horizons is 100 to 225).

TYPE LOCATION: Redwood National Park, Humboldt County, California; located approximately 14 kilometers southeast of the town of Orick, 152 meters southeast of junction between C-20 and C-Line Roads; southwest quarter, southeast quarter, Section 19, T. 10 N., R. 2 E., WGS84 Decimal degrees 41.2339139 latitude and -123.9915083 longitude; HBLM; USGS Bald Hills Quadrangle; UTM Zone 10 416908mE 4565198mN; NAD83.

RANGE IN CHARACTERISTICS:

Soil moisture: The soil is continuously moist in all parts in the soil moisture control section in most years, but it becomes nearly dry in the upper part from about September 15 to October 15 in most years. The soils have an udic moisture regime.

Soil temperature: The mean annual soil temperature is 10 to 13 degrees C (50 to 55 degrees F). The difference between mean summer and mean winter temperature is 2 to 4 degrees C.

Organic Matter: There is 12 to 20 kg per square meter of organic carbon to a depth of one meter.

Reaction is moderately or very strongly acid throughout. Base saturation is 5 to 35 percent between depths of 25 to 200 centimeters.

Particle-Size Control Section (weighted average):

Rock fragments: 0 to 30 percent gravel and 0 to 3 percent cobble.
Clay content: 35 to 50 percent clay.

O horizon

Hue: 10YR.
Value: 2 through 6 dry and moist.
Chroma: 1 through 4 dry and moist.

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

A horizon

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

Texture of fine earth: loam, silt loam, clay loam or silty clay loam.
Rock fragments: 0 to 13 percent gravel.
Clay content: 22 to 35 percent.

Bt horizon

Hue: 7.5YR, 10YR, or 2.5Y.
Value: 5 through 7 dry, 4 or 5 moist.
Chroma: 4 through 6 dry, 4 through 8 moist.

Texture of fine earth: clay loam, silty clay loam, silty clay or clay.
Rock fragments: 0 to 30 percent gravel and 0 to 3 percent cobbles.
Para rock fragments: 0 to 7 percent paragravel.
Clay content: 35 to 50 percent clay.

COMPETING SERIES: At this time there are no other series in this family.

GEOGRAPHIC SETTING: Tectah soils occur on broad ridges and mountain slopes. Slopes are 0 to 50 percent. Elevations are 24 to 702 meters (75 to 2300 feet). The soils formed in colluvium and residuum derived from sandstone, mudstone and metasedimentary rocks. The climate is humid with cool, foggy summers and cool, moist winters. Coastal influence limits the annual and diurnal range in temperature. Mean annual precipitation ranges from 1780 to 2550 millimeters (70 to 100 inches). Mean January temperature is about 9 degrees C; mean July temperature is about 14 degrees C; and the mean annual temperature is 10 to 13 degrees C (50 to 55 degrees F). Frost-free season is 240 to 280 days.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Ahpah, Coppercreek and Trailhead soils. Ahpah and Coppercreek soils are fine-loamy. Ahpah soils are 50 to 100 centimeters (20 to 40 inches) deep to a lithic contact and lack an argillic horizon. Trailhead soils have parasesquic mineralogy and hues redder than 7.5YR throughout the argillic horizon. The Ahpah soils are on convex slopes and on narrow ridge crests above the Tectah soils. The Coppercreek soils are on concave areas and on steeper slopes below the Tectah soils. The Trailhead soils are on broad, gentler slopes above the Tectah soils.

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

USE AND VEGETATION: This soil has been used for commercial timber, recreation, wildlife, and watershed. Natural vegetation consists of redwood, Douglas fir, western hemlock, tanoak, evergreen huckleberry, and Pacific rhododendron.

DISTRIBUTION AND EXTENT: California Coastal Redwood Belt; MLRA 4B. The series is not extensive.

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

SERIES ESTABLISHED: Humboldt Del Norte area, California 2007. Source of name is from Tectah Creek located about 15 kilometers east of the town of Orick.

REMARKS: Diagnostic horizons and features recognized in this pedon are:

1. Ochric epipedon - the zone from 0 to 30 centimeters (Oi& A horizons)
2. Argillic horizon - the zone from 30 to 185 centimeters (BAt, Bt1, Bt2, Bt3 & Bt4 horizons)
3. Ultisol feature - base saturation of less than 15 percent at the critical depth, 125 centimeters below the upper boundary of the argillic horizon
4. Humult feature - 15.7 kilograms per square meter of organic carbon to a depth of 1 meter
5. Palehumults feature - Clay remains at least 89 percent of its maximum to a depth of 185 centimeters
6. Particle-size control section - the zone from 30 to 80 centimeters, averages 39 percent clay, by weight, and 6 percent rock fragments, by volume. CEC/clay ratio averages 0.32, and DTA iron oxide 4 percent. Since associated soils have about two thirds as much gibbsite as iron oxide, gibbsite is estimated as approximately 3 percent. The sum of DTA iron oxide plus gibbsite is assumed to be less than 10 percent.

ADDITIONAL DATA: Soil profile sample 82-CA-12-04X was collected at the type location and analyzed at the University of California Soil Morphology Laboratory in Davis, California. Back-up sample 84-RNP-3 was collected at another Tectah profile in Redwood National Park. Sample 57-CA-08-02X was collected from a Tectah profile in Del Norte County and is described on pages 21-22 in Begg, et al (1984).

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

National Cooperative Soil Survey
U.S.A.