LOCATION IVERSEN CAEstablished Series
TAXONOMIC CLASS: Fine, mixed, active, isomesic Typic Haplustults
TYPICAL PEDON: Iversen loam - on a southeast facing slope of 10 percent under Douglas fir, redwood, tanoak, Bishop pine, and madrone at 1200 feet elevation. (Colors are for dry soil unless otherwise stated. When described on July 31, 1984, the soil was moist below 7 inches).
Oi--1 inch to 0; litter of Douglas-fir and redwood.
A1--0 to 3 inches; yellowish brown (10YR 5/4) loam, dark brown (7.5YR 3/4) moist; moderate fine and medium subangular blocky structure, slightly hard, friable, slightly sticky and slightly plastic; common very fine, fine and medium roots; common very fine interstitial and very fine and fine tubular pores; 5 percent hard angular pebbles (2-10mm); slightly acid (pH 6.5); clear wavy boundary. (3 to 6 inches thick)
A2--3 to 7 inches; light brown (7.5YR 6/4) loam, strong brown (7.5YR 4/6) moist; moderate fine, medium and coarse subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; common very fine, fine, medium and coarse roots; common very fine interstitial and tubular and few fine tubular pores; moderately acid (pH 5.8); clear wavy boundary. (0 to 5 inches thick)
Bt1--7 to 10 inches; reddish yellow (7.5YR 6/6) clay, strong brown (7.5YR 5/6) moist; strong coarse and very coarse subangular blocky structure; hard, firm, very sticky and very plastic; few very fine and fine and common medium and coarse roots; common very fine and fine tubular pores; common moderately thick and thick clay films on faces of peds and lining pores; very strongly acid (pH 5.0); clear wavy boundary. (3 to 20 inches thick)
Bt2--10 to 22 inches; reddish yellow (7.5YR 6/6) clay; strong brown (7.5YR 5/6) moist; strong medium, coarse and very coarse angular blocky structure; very hard, very firm, sticky and very plastic, few very fine and fine, and common medium and coarse roots; common very fine and fine tubular pores; many moderately thick and thick clay films on faces of peds and lining pores; 2 percent hard angular, subrounded and round pebbles (2-10mm); very strongly acid (pH 5.0); clear wavy boundary. (4 to 15 inches thick)
Bt3--22 to 37 inches; strong brown (7.5YR 5/6) gravelly clay, strong brown (7.5YR 4/6) moist; strong coarse angular blocky structure; hard, firm, sticky and very plastic; few fine and common medium and coarse roots; common very fine and few fine tubular pores; many moderately thick and thick clay films on faces of peds and lining pores; 20 percent slightly hard and hard angular sandstone pebbles (2-50mm); very strongly acid (pH 5.0); abrupt irregular boundary. (0 to 15 inches thick)
Crt--37 to 46 inches; interlayered soft through slightly hard sandstone and soft, highly weathered sandstone and shale; fractures are 10 to 50mm apart and 1 to 10mm wide; few fine and medium roots in fractures; clay films on fracture faces. Rock slakes in water.
TYPE LOCATION: Mendocino County, California; about 1200 feet north and 950 feet west of the southeast corner of sec. 5,T.11N., R.15W., MDBM, Gualala quadrangle.
RANGE IN CHARACTERISTICS: Thickness of the solum and depth to paralithic contact ranges from 20 to 40 inches. The mean annual soil temperature is 53 to 57 degrees F. The difference between mean summer and mean winter temperature is 4 to 9 degrees F. The soil between the depths of 6 and 20 inches is moist in all parts from November 1 to June 1 and is dry in all or some parts from July 1 to October 1 in most years. The particle-size control section averages from 40 to 55 percent clay. Clay mineralogy is dominated by 1 to 1 lattice clays.
The A horizon is 10YR 5/3, 5/4; 7.5YR 5/4 or 6/4. Moist color is 7.5YR 3/4, 4/4, 4/6 or 5/4. Clay content ranges from 18 to 27 percent. Gravel content ranges from 0 to 10 percent. Reaction is moderately or slightly acid.
An E horizon is present at the surface in some pedons. It is 10YR 7/1, 7/2 or 8/1. Moist color is 10YR 6/1, 6/2 or 7/2. It is sandy loam with 10 to 20 percent clay. Reaction is strongly or moderately acid.
The Bt horizon is 10YR 6/6, 7/6; 7.5YR 5/6 or 6/6. Moist color is 10YR 4/6, 5/6, 6/6; 7.5YR 4/6 or 5/6. It is clay loam, clay or gravelly clay. Clay content ranges from 27 to 60 percent. Gravel content ranges from 0 to 20 percent. Base saturation (sum) ranges from 25 to 45 percent, and is less than 35 percent in the lower part of the horizon. Reaction is very strongly or strongly acid.
COMPETING SERIES: There are no competing series.
GEOGRAPHIC SETTING: Iversen soils are on ridgetops and upper sideslopes of coastal hills and mountains. Slopes are 2 to 30 percent. Elevations are 600 to 1300 feet. The soils formed in material weathered from sandstone and shale. The climate is humid with cool foggy summers and cool moist winters. A moderate marine influence limits the diurnal and annual range in temperature. The Iversen soils are associated with a ridge system in Southern Mendocino County that was subjected to intensive clearing, burning and subsequent erosion in the late 1800's and in the early part of this century. It is probable that the Iversen soils represent a truncated version of the original deeper forest soils. They have been relatively undisturbed for 40 to 60 years now and are reforming A horizons. Mean annual precipitation is 45 to 55 inches. Mean January temperature is about 50 degrees F., mean July temperature is about 58 degrees F. and the mean annual temperature is about 54 degrees F. The frost-free period is about 250 to 320 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Havensneck, Fishrock, Ferncreek, and Quinliven soils. Fishrock and Havensneck soils are on similar landscape positions. Fishrock soils are less than 20 inches deep to lithic contact. Havensneck soils have a fine-loamy particle-size control section. Ferncreek and Quinliven soils are on marine terraces adjacent to the ridge system on which Iversen soils formed. Ferncreek and Quinliven soils are greater than 60 inches deep and have udic soil moisture regimes.
DRAINAGE AND PERMEABILITY: Well drained; surface runoff under bare soil conditions is slow through rapid; slow permeability.
USE AND VEGETATION: This soil is used for homesite development, timber production and as watershed. Vegetation consists of Douglas-fir, redwood, tanoak, Bishop pine, madrone and California huckleberry.
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 in this pedon are:
Ochric epipedon - the zone from 0 to 7 inches (A1, A2)
Argillic horizon - the zone from 7 to 37 inches (Bt1, Bt2, Bt3)
Paralithic contact - the boundary with soft bedrock at 37 inches.
Many areas mapped as the Iversen soil were mapped as the Noyo soil by the California Soil Vegetation Survey 1947-1950
The activity class was added to the classification in February of 2003. Competing series were not checked at that time. - ET