LOCATION CHALKMOUNTAIN CA

Established Series
REV: JWH/JTB/ET
07/2016

CHALKMOUNTAIN SERIES

The Chalkmountain series consists of very deep, well drained soils formed in colluvium and residuum derived from sandstone and mudstone. Chalkmountain soils are on mountains. Slopes range from 15 to 50 percent. Mean annual precipitation is about 2160 millimeters and the mean annual temperature is about 13 degrees C.

TAXONOMIC CLASS: Loamy-skeletal, isotic, mesic Pachic Humixerepts

TYPICAL PEDON: Chalkmountain very gravelly loam on a north facing 35 percent slope under Douglas-fir and Oregon white oak with an understory of western swordfern, at an elevation of 690 meters. (Colors are for dry soil unless otherwise noted.) When described on 06/19/08, the soil was slightly moist throughout.

Oi--0 to 2 centimeters; slightly decomposed Douglas-fir needles and Oregon white oak leaves, black (10YR 2/1) moist; 85 percent fiber unrubbed, 60 percent fiber rubbed; slightly acid (pH 6.5); abrupt smooth boundary.

A1--2 to 20 centimeters; very dark grayish brown (10YR 3/2) very gravelly loam, black (10YR 2/1) moist; weak fine granular structure; slightly hard, very friable, nonsticky and nonplastic; common very fine and fine roots throughout; 45 percent gravel; strongly acid (pH 5.5); clear smooth boundary.

A2--20 to 67 centimeters; very dark grayish brown (10YR 3/2) very gravelly loam, black (10YR 2/1) moist; weak fine granular structure; slightly hard, very friable, nonsticky and nonplastic; common very fine, fine, and medium roots throughout; common very fine tubular pores; 40 percent gravel; moderately acid (pH 5.6); gradual smooth boundary.

A3--67 to 100 centimeters; very dark grayish brown (2.5Y 3/2) very gravelly sandy loam, black (10YR 2/1) moist; weak fine granular structure; slightly hard, very friable, nonsticky and nonplastic; common very fine roots throughout; few very fine tubular pores; 45 percent gravel; strongly acid (pH 5.5); gradual wavy boundary. (Combined thickness of the A horizons is 50 to 100 centimeters)

ABt--100 to 115 centimeters; dark grayish brown (2.5Y 4/2) very gravelly fine sandy loam, black (10YR 2/1) moist; weak fine granular structure; slightly hard, very friable, nonsticky and nonplastic; common faint clay films on rock faces; 50 percent gravel; moderately acid (pH 5.6); abrupt wavy boundary. (0 to 50 centimeters)

C1--115 to 145 centimeters; light olive brown (2.5Y 5/3) extremely gravelly coarse sandy loam, very dark brown (10YR 2/2) moist; massive; soft, loose, nonsticky and nonplastic; 68 percent gravel; moderately acid (pH 5.8); gradual wavy boundary.

C2--145 to 170 centimeters; brown (10YR 4/3) extremely gravelly sandy loam, light yellowish brown (2.5Y 6/3) moist; massive; soft, loose, nonsticky and nonplastic; 62 percent gravel; moderately acid (pH 5.8)

TYPE LOCATION: Humboldt County, California; located about 4 kilometers south of the town of Bridgeville; USGS Bridgeville quadrangle, CA; WGS84 40.4271667 latitude and -123.8182778 longitude; UTM zone 10 430589 mE, 4475492 mN; NAD 83.

RANGE IN CHARACTERISTICS:

Soil Temperature: The mean annual soil temperature at 50 centimeters is 10 to 14 degrees C. (50 to 58 degrees F.) and the difference between mean summer and mean winter soil temperatures is 6 to 9 degrees C. The soils have a mesic soil temperature regime.

Soil Moisture: The soil moisture control section, in normal years, is dry in all parts, for 45 or more consecutive days in the 4 months following the summer solstice and moist in all parts for 45 or more consecutive days in the 4 months following the winter solstice. The soils have a xeric soil moisture regime.

Thickness of the umbric epipedon: 50 to 100 centimeters thick

Base saturation by ammonium acetate is less than 60 percent between 25 and 75 centimeters

Surface fragments: 25 to 30 percent strongly cemented gravel

Particle size control section weighted average:
Clay content: 14 to 22 percent clay
Rock fragments: 35 to 59 percent strongly cemented sandstone gravel and 0 to 10 percent cobbles

A horizon:
Hue: 7.5YR, 10YR, or 2.5Y
Value: 3 to 5, 2 or 3 moist
Chroma: 1 to 3, dry or moist
Texture: loam or sandy loam
Clay content: 15 to 23 percent
Rock fragments: 25 to 59 percent
Reaction: strongly to moderately acid

B horizon: (when present)
Hue: 10YR or 2.5Y
Value: 5 to 7, 4 to 6 moist
Chroma: 4 to 6, dry or moist
Texture of fine earth: loam or sandy loam
Clay content: 10 to 27 percent
Rock fragments: 35 to 70 percent
Reaction: slightly to moderately acid

C horizon:
Hue: 10YR or 2.5Y
Value: 5 to 7, 4 to 6 moist
Chroma: 4 to 6, dry or moist
Texture of fine earth: loam or sandy loam
Clay content: 10 to 27 percent
Rock fragments: 35 to 70 percent
Reaction: slightly to moderately acid

COMPETING SERIES: These are the Forhaux, and Hiddenridge series. Forhaux soils have a difference between mean summer soil temperature and mean winter soil temperature of more than 9 degrees C. Hiddenridge soils are 100 to 152 centimeters deep to a lithic contact.

GEOGRAPHIC SETTING: Chalkmountain soils are on linear or concave positions on mountain slopes. Slopes are 15 to 50 percent. Elevations range from 490 to 914 meters. These soils formed in residuum and colluvium derived from sandstone and mudstone of the Franciscan Complex and the Yager terrain. The climate is subhumid with warm, dry summers and cool, moist winters. Mean annual precipitation is 1250 to 2280 millimeters and the mean annual temperature is 12 to 14 degrees C. The frost-free period is about 240 to 280 days. These soils are thought to be in areas which were previously grasslands and have been invaded by Douglas-fir.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Hoagland and Tannin soils. Hoagland and Tannin soils contain less than 35 percent coarse fragments. Tannin soils lack an umbric epipedon. Hoagland and Tannin soils are on similar landscape positions.

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

USE AND VEGETATION: This soil is used mainly for timber production, wildlife habitat, and for watershed. Natural vegetation is tanoak, Douglas-fir, white oak, Pacific madrone, California laurel, California huckleberry, and western swordfern.

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 County Soil Survey, Southern Part, California, 2010. The name is from Chalk Mountain.

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

1. Umbric epipedon: The zone from 2 to 100 centimeters. (A1, A2, A3 horizons)
2. Particle size control section: The zone from 27 to 102 centimeters averages 15 percent clay, by weight, and 42 percent gravel, by volume (A2 and A3 horizons)
3. Cambic horizon: 100 to 115 centimeters (ABt horizon)
4. Isotic feature: 15 bar water/clay is greater than 1.17 and the NaF pH is greater than 10.6 in all horizons.

ADDITIONAL DATA: NSSL Pedon No 09N0109, NSSL Pedon 09N0110 similar
NASIS User Pedon ID 08CA601982

Keys to Soil Taxonomy, 12th edition

National Cooperative Soil Survey
U.S.A.