LOCATION YORKNORTH               CA

Established Series
Rev.: JWH-ET
08/2016

YORKNORTH SERIES

The Yorknorth series consists of very deep, moderately well drained soils that formed in material weathered from chloritic schist and other sedimentary and metamorphic rocks. Yorknorth soils are on hills and mountains and have slopes of 2 to 50 percent. The mean annual precipitation is about 1650 millimeters and the mean annual temperature is about 14 degrees C.

TAXONOMIC CLASS: Fine, mixed, superactive, thermic Oxyaquic Argixerolls

TYPICAL PEDON: Yorknorth silt loam - on a south facing linear slope of 25 percent under grassland, at an elevation of 780 meters. (Colors are for dry soil unless otherwise noted.) When described on June 3, 2003, the soil was moist below 31 centimeters.

A--0 to 7 centimeters; brown (10YR 4/3) silt loam, very dark gray (10YR 3/1) moist; strong medium granular structure; slightly hard, very friable, nonsticky and nonplastic; common very fine roots throughout; 3 percent gravel; strongly acid (pH 5.5); abrupt wavy boundary. (20 to 50 centimeters thick)

Bt1--7 to 31 centimeters; grayish brown (2.5Y 5/2) silty clay loam, black (2.5Y 2.5/1) moist; strong coarse prismatic structure parting to strong medium subangular blocky; moderately hard, friable, moderately sticky and moderately plastic; common very fine roots throughout; common very fine tubular pores; very many clay films on faces of peds and in pores; 2 percent gravel; strongly acid (pH 5.4); gradual wavy boundary. (20 to 30 centimeters thick)

Bt2--31 to 51 centimeters; light brownish gray (2.5Y 6/2) silty clay loam, black (2.5Y 2.5/1) moist; common fine 10YR 6/4 mottles from sandstone; strong very coarse prismatic structure parting to strong medium subangular blocky; very hard, firm, moderately sticky and moderately plastic; common very fine roots throughout; common very fine tubular pores; very many clay films on faces of peds and in pores; 3 percent gravel; slightly acid (pH 6.2); clear wavy boundary. (10 to 25 centimeters thick)

Bt3--51 to 112 centimeters; gray (2.5Y 6/1) silty clay loam, dark gray (5Y 4/1) moist; common fine 10YR 6/4 mottles from sandstone; common coarse distinct olive brown (2.5Y 4/3) iron concentrations; moderate medium subangular blocky structure; extremely hard, firm, moderately sticky and moderately plastic; few very fine roots throughout;; many clay films and pressure faces on faces of peds; 5 percent gravel, 5 percent cobbles, and 1 percent stones; neutral (pH 7.2); gradual wavy boundary. (10 to 100 centimeters thick)

C1--112 to 160 centimeters; gray (2.5Y 6/1) clay loam, dark gray (5Y 4/1) moist; massive; extremely hard, firm, moderately sticky and moderately plastic; 100 percent pressure faces; 5 percent gravel; moderately alkaline (pH 7.9); gradual wavy boundary.

C2--160 to 190 centimeters; gray (2.5Y 6/1) extremely paragravelly loam, dark gray (N 4/0) moist; massive; extremely hard, firm, moderately sticky and moderately plastic; 60 percent paragravel and 5 percent cobbles; moderately alkaline (pH 8.0). (The combined thickness of the C horizons is 50 to 150 centimeters)

TYPE LOCATION: Humboldt County, California; about 1.5 miles southwest of Pratt Mountain; USGS Harris 7.5 minute quadrangle, California; WGS84 40.1030556 latitude and -123.709444 longitude; zone 10 0439452m E, 4439438m N, NAD 83.

RANGE IN CHARACTERISTICS:

Soil moisture: The soil moisture control section is dry in all parts for 45 or more consecutive days after the summer solstice and moist in all parts from November through May. The soil has a xeric soil moisture regime.

Soil Temperature: The mean annual soil temperature at 50 centimeters is 15 to 21 degrees C. The difference between mean summer and mean winter temperature is 6 degrees C or more. The soil has a thermic soil temperature regime.

Depth to Redoximorphic Features: 50 to 100 centimeters

Base saturation (by ammonium acetate): is greater than 71 percent in all horizons

Particle size control section (weighted average):
Rock fragments: 0 to 10 percent gravel, 0 to 5 percent cobbles
Pararock fragments: 0 to 10 percent
Clay content: 35 to 45 percent

Mollic epipedon: 25 to 100 centimeters thick

A horizon
Hue: 10YR or 2.5Y
Value: 4 or 5, 2 or 3 moist
Chroma: 1 through 4, 1 through 3 moist
Texture of fine earth: silt loam, loam, or silty clay loam
Rock fragments: 0 to 10 percent gravel
Clay content: 18 to 33 percent
Reaction: strongly to slightly acid

Upper Bt horizon
Hue: 10YR or 2.5Y, moist and dry
Value: 4 through 6, 2 through 4 moist
Chroma: 1 through 4, 1 through 3 moist
Texture of fine earth: clay loam, silty clay loam, silty clay, and clay
Rock fragments: 0 to 10 percent gravel
Clay content: 35 to 45 percent
Reaction: strongly to slightly acid

Lower Bt horizon
Hue: 10YR or 2.5Y, moist and dry
Value: 4 through 6, 2 through 4 moist
Chroma: 1 through 4, 1 through 3 moist
Texture of fine earth: clay loam, silty clay loam, silty clay, and clay
Rock fragments: 0 to 34 percent gravel, 0 to 10 percent cobbles and stones
Pararock fragments: 0 to 34 percent paragravel
Clay content: 30 to 45 percent
Reaction: moderately acid to neutral

Redoximorphic Features: fine and medium iron-manganese masses
Quantity: few to many
Hue: 10YR or 2.5Y
Value: 4 through 6
Chroma: 3 through 8

Redoximorphic features: fine and medium iron depletions
Quantity: none to common
Hue: 2.5Y or 5Y
Value: 4 or 5
Chroma: 1 or 2

C horizon
Hue: 2.5Y or 5Y, or N
Value: 4 to 6, 2.5 to 4 moist
Chroma: 0 to 3, moist or dry
Texture of fine earth: loam, clay loam, silty clay loam, clay
Rock fragments: 5 to 34 percent percent gravel, 0 to 10 percent cobbles
Pararock fragments: 0 to 34 percent paragravel
Clay content: 25 to 45 percent
Reaction: neutral to moderately alkaline

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

GEOGRAPHIC SETTING: Yorknorth soils are on mountain slopes. Slopes range from 2 to 50 percent. Yorknorth soils are on concave to linear slopes. Elevations range from 60 to 760 meters. These soils formed in colluvium and residuum. Landscapes dominated by Yorknorth soils have hummocky relief, sag ponds, slips, and intermittent springs. The climate is subhumid with warm, dry summers and cool, wet winters. Mean annual precipitation is 1525 to 2160 millimeters. Mean January temperature is about 11 degrees C, mean July temperature is about 21 degrees C, and the mean annual temperature is 13 to 15 degrees C. Frost free period is about 240 to 280 days.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Coolyork, Dryfield, and Witherell soils. Witherell soils have fractured bedrock above 50 centimeters and are on convex positions. Dryfield soils contain less than 35 percent clay in the control section and occur on linear to slightly convex positions. Coolyork soils have a mean annual soil temperature of less than 15 degrees C and are under forest vegetation.

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

USE AND VEGETATION: This soil is used for livestock grazing, watershed, and wildlife habitat. Vegetation is wild oat, slender oat, ripgut brome, soft brome, dogtsail grass, California oatgrass, blue wildrye, medusahead, rat-tail fescue, common sheep sorrel, hairy catsear, burclover, pale flax, pennyroyal,and western rush.

DISTRIBUTION AND EXTENT: Siskiyou-Trinity Area, MLRA 5. The soils are moderately extensive.

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

SERIES ESTABLISHED: Humboldt County, South Part, California, 2010. The name is coined.

REMARKS: Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon - the zone from 0 to 31 centimeters (A, Bt1 horizons)
Argillic horizon - the zone from 7 to 112 centimeters (Bt1, Bt2, and Bt3 horizons)
Particle size control section - the zone from 7 to 57 centimeters averages 36 percent clay and 7 percent fine sand and coarser by weight, and 6 percent gravel by volume (Bt1 and Bt2 horizons)
4. Oxyaquic feature - the zone from 51 to 190 centimeters (Bt3, C1, and C2 horizons)

ADDITIONAL DATA: NSSL Pedon 03N0874
NASIS User Pedon ID 03CA601148

This soil has a moist phase when used in MLRA 4B, where cooler summers are due to a marine layer influence.

Keys to Soil Taxonomy, 12th edition

---

National Cooperative Soil Survey
U.S.A.