LOCATION GIBWELL CAEstablished Series
TAXONOMIC CLASS: Fine, mixed, active, isomesic Typic Hapludults
TYPICAL PEDON: Gibwell loamy sand - on a southwest facing slope of 14 percent- under Bishop pine, rhododendron, tanoak, golden chinquapin, hairy manzanita, glossyleaf manzanita and California huckleberry at 480 feet elevation. (Colors are for dry soil unless otherwise stated. When described on September 23, 1985, the soil was dry throughout).
0i--2 inches to 0; litter of Bishop pine and tanoak leaves and twigs.
E1--0 to 3 inches; gray (10YR 5/1) loamy sand, dark gray (10YR 4/1), moist; weak fine and medium subangular blocky structure; soft, very friable, nonsticky and nonplastic; slightly smeary; common very fine and fine and few medium roots; common very fine interstitial and very fine, fine and medium tubular pores; very strongly acid (pH 4.5); clear wavy boundary. (3 to 10 inches thick)
E2--3 to 7 inches; light gray (10YR 7/2) loamy sand, grayish brown (10YR 5/2) moist; weak medium subangular blocky structure; soft, very friable, nonsticky and nonplastic; slightly smeary; common very fine and few fine and medium roots; common very fine interstitial and tubular and few fine and medium tubular pores; extremely acid (pH 4.3); clear wavy boundary. (0 to 8 inches thick)
E3--7 to 12 inches; variegated light gray (2.5Y 7/2) and very pale brown (10YR 7/4) loamy sand, grayish brown (2.5Y 5/2) and yellowish brown (10YR 5/4) moist; weak fine and medium subangular blocky structure; soft, very friable, nonsticky and nonplastic; common very fine and fine and few medium roots; common very fine and fine tubular and common very fine interstitial pores; strongly acid (pH 5.5); abrupt wavy boundary. (0 to 8 inches thick)
Bt/E--12 to 18 inches; variegated brownish yellow (10YR 6/6) and light gray (10YR 7/2) clay loam; dark yellowish brown (10YR 4/4) and grayish brown (10YR 5/2) moist; moderate fine and medium subangular blocky structure; slightly hard, friable, sticky and plastic; common very fine, fine and medium and few coarse roots; common very fine tubular and interstitial pores; few thin clay films bridging sand grains; strongly acid (pH 5.5); abrupt wavy boundary. (2 to 7 inches thick)
Bt1--18 to 26 inches; yellowish brown (10YR 5/8) clay, dark yellowish brown (10YR 4/6) moist; strong medium and coarse subangular blocky structure; hard, very firm, sticky and plastic; common fine and medium and few coarse roots; common very fine and fine tubular and few very fine interstitial pores; many thin and moderately thick clay films on faces of peds and lining pores; strongly acid (pH 5.5); clear wavy boundary. (4 to 12 inches thick)
Bt2--26 to 42 inches; strong brown (7.5YR 5/8) sandy clay loam, strong brown (7.5YR 5/6) moist; massive; slightly hard, friable, slightly sticky and slightly plastic; few fine roots; common fine interstitial and few fine tubular pores; few thin clay films bridging sand grains; very strongly acid (pH 5.0); abrupt wavy boundary. (4 to 16 inches thick)
C--42 to 65 inches; pale yellow (2.5Y 7/4) loamy sand, light olive brown (2.5Y 5/4) moist; massive; soft, very friable, nonsticky and nonplastic; few fine roots; common very fine interstitial pores; strongly acid (pH 5.5).
TYPE LOCATION: Mendocino County, California; about 1750 feet north and 550 feet west of the southeast corner of sec. 32, T.18N., R.17W., MDBM; Fort Bragg quadrangle.
RANGE IN CHARACTERISTICS: Thickness of the solum ranges from 25 to 45 inches. Depth to bedrock is greater than 80 inches. The mean annual soil temperature is 50 to 56 degrees F. The difference between mean winter and summer temperatures is 6 to 9 degrees F. The soil between the depths of 13 and 25 inches is moist in all parts from November 1 to August 15 and is dry in some part from September 1 to October 1 in most years. The particle-size control section averages 35 to 50 percent clay. Base saturation (sum) ranges from 5 to 30 percent throughout. Soil reaction ranges from extremely through strongly acid (pH 4.3) through 5.5)
The E horizon is 2.5Y 6/2, 7/2; 10YR 5/1, 6/1, 6/2, 7/2, 7/3, 7/4, or 8/1. Moist color is 2.5Y 5/2; 10YR 3/1, 4/1, 4/2, 5/1, 5/2, 5/3, 5/4 or 6/2. Clay content ranges from 5 to 15 percent. In some pedons this horizon is slightly brittle when moist and slightly smeary.
The Bt horizon is 10YR 5/8, 6/6, 6/8; 7.5YR 5/6, 5/8 or 6/6. Moist color is 10YR 4/4, 4/6, 5/6, 5/8; 7.5YR 4/6, 5/6 or 5/8. It is sandy clay loam, clay loam, clay or sandy clay with 25 to 55 percent clay. Hard iron concretion content ranges from 0 to 5 percent.
The C horizon is 2.5Y 7/4; 10YR 6/6, 7/4, 7/6 or 7.5YR 6/6. Moist color is 2.5Y 5/4; 10YR 5/4, 5/6; 7.5YR 5/4, 5/6 or 5YR 4/6. It is sandy loam, loamy sand or sand with 5 to 15 percent clay. In some pedons the consistence of this horizon is fluffy or weakly cemented.
COMPETING SERIES: This is the Gibney (CA) series. Gibney soils contain low chroma mottles and high chroma mottles in the lower part of the series control section.
GEOGRAPHIC SETTING: The Gibwell soils occur on stabilized sand dunes. Slopes are 2 to 15 percent. Elevations are 250 to 700 feet. The soil formed in eolian sands. The climate is characterized by cool foggy summers and cool moist winters. A strong coastal fog influence limits the diurnal and annual range of temperature. Mean annual precipitation ranges from 40 to 65 inches. Mean January temperature is 48 degrees F.; mean July temperature is 57 degrees F.; and mean annual temperature is 53 degrees F. Frost-free season ranges from 270 to 330 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Cleone, Ferncreek, Gibney, Qunliven, and Shinglemill series. Cleone soils are coarse-loamy. Ferncreek and Gibney soils are somewhat poorly drained. Quinliven soils are moderately well drained. Shinglemill soils are poorly drained. The Ferncreek and Quinliven soils support commercial timber species.
DRAINAGE AND PERMEABILITY: Well drained, surface runoff under bare soil conditions is slow or medium. Slow permeability in the solum and rapid permeability in the substratum.
USE AND VEGETATION: This soil is used for homesite development, wildlife habitat and as watershed. Vegetation consists of Bishop pine, glossyleaf manzanita, hairy manzanita, rhododendron, golden chinquapin, California huckleberry and salal.
DISTRIBUTION AND EXTENT: Northern coastal California. The series is not extensive. MLRA 4.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California
SERIES ESTABLISHED: Mendocino County, California, Western part 1993.
REMARKS: Diagnostic horizons and features recognized:
Ochric epipedon (albic horizon) -- 0 to 12 inches (E1, E2, E3)
Argillic horizon -- 12 to 42 inches (Bt/E, Bt1, Bt2)
Particle-size control section -- 12 to 32 inches. Weighted average of 44 percent clay.
Soil was originally classified as a Tropudult. Taxonomy Handbook issue 8 deletes Tropudults and reclassifies them as Hapludults.
Many areas mapped as Gibwell soils were mapped as Noyo soils by the California Soil Vegetation Survey 1947-1950.