LOCATION MOUNTOM                 CA

Established Series
Rev. VB/ET/JJJ/MAV
06/2016

MOUNTOM SERIES

The Mountom series consists of very deep, very poorly drained soils formed in hydrophytic plant material over alluvium from mixed rock sources. Mountom soils are on alluvial fans and have slopes of 0 to 5 percent. The mean annual precipitation is about 150 mm and the mean annual temperature is about 16.1 degrees C.

TAXONOMIC CLASS: Loamy, mixed, euic, mesic Terric Haplohemists

TYPICAL PEDON: Mountom peaty muck, under perennial grasses and forbs, at an elevation of 1,381 meters. When described on 7/19/90 the soil was saturated throughout. (Colors are for moist, rubbed soil unless otherwise noted)

Oe1--0 to 5 cm; black (10YR 2/1) mucky peat, dark gray (10YR 4/1) dry; partially decomposed hemic material, 75 percent unrubbed and 30 percent rubbed fibers; neutral pH 6.6); clear smooth boundary. (5 to 10 cm thick)

Oe2--5 to 30 cm; very dark brown (10YR 2/2) mucky peat, dark gray (N 4/0) dry; partially decomposed hemic material, 80 percent unrubbed and 40 percent rubbed fibers; moderately acid (pH 6.0); clear smooth boundary. (20 to 36 cm thick)

Oe3--30 to 46 cm; black (10YR 2/1) mucky peat, dark gray (10YR 4/1) dry; partially decomposed hemic material, 35 percent unrubbed and 20 percent rubbed fibers; massive; slightly acid (pH 6.2); clear wavy boundary. (13 to 25 cm thick)

Oa--46 to 64 cm; very dark brown (10YR 2/2) mucky peat, gray (10YR 5/1) dry; partially decomposed hemic material, 15 percent unrubbed and 5 percent rubbed fibers; massive; 10 percent mineral material; 1 percent gravel; slightly acid (pH 6.2); abrupt smooth boundary. (13 to 38 cm thick)

2C--64 to 122 cm; dusky red (2.5YR 3/2) gravelly sandy loam, weak red (2.5YR 5/2) dry; massive; slightly hard, friable, slightly sticky and slightly plastic; common very fine and fine roots; common very fine and fine interstitial and few very fine tubular pores; 25 percent gravel; slightly alkaline (pH 7.4); abrupt smooth boundary. (13 to 64 cm thick)

3Cdg--122 to 165 cm; dark olive gray (5Y 3/2) dense sandy clay loam, olive gray (5Y 5/2) dry; massive; extremely hard, very firm, moderately sticky and moderately plastic; few very fine roots; few fine and medium tubular pores; 10 percent gravel; slightly alkaline (pH 7.4).

TYPE LOCATION: Inyo County, California; about 8 miles northwest of Bishop in Round Valley; 900 feet south and 50 feet west of the northeast corner of section 21, T. 6 S., R. 31 E., M.D.B.M. USGS Rovana 7.5 minute topographic quadrangle;; latitude 37 degrees 25 minutes 01 seconds N and longitude 118 degrees 34 minutes 07 seconds W; WGS84 Decimal Degrees 37.416944 latitude, -118.5686111 longitude.

RANGE IN CHARACTERISTICS: The mean annual soil temperature is about 13.3 degrees C. The thickness of the organic layers is 61 to 112 cm. Depth to the dense Cd horizon is 74 to 127 cm. Unrubbed fiber averages 60 to 80 percent and rubbed fiber averages 20 to 40 percent in the surface tier. The subsurface tier averages 15 to 30 percent unrubbed fiber and 10 to 20 percent rubbed fiber.

The Oe horizon color is 10YR 2/1, 2/2 or 2.5Y 2/0. Dry color is 10YR 4/1, 5/1 or 2.5Y 4/0. Reaction is neutral to moderately acid in .01 M CaCl.

The Oa horizon color is 10YR 2/2 or 2/1. Dry color is 10YR 4/1 or 5/1. This horizon contains 1 to 5 percent gravel. Reaction is slightly acid or neutral.

The 2C horizon color is 2.5Y 3/0 or 3/2. Dry color is 2.5Y 5/0 or 5/2. Texture is gravelly sandy loam, with 15 to 30 percent gravel. Reaction is neutral to mildly alkaline.

The 2Cd horizon color is 5Y 3/2 or 3/1. Dry color is 5Y 5/1 or 5/2. Textures are clay loam or sandy clay loam and contain 5 to 15 percent gravel. Moist consistence is firm or very firm. Reaction is slightly to moderately alkaline.

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

GEOGRAPHIC SETTING: The Mountom soils formed in hydrophytic plant material over alluvium from mixed rock sources. They are on hummocky alluvial fans downslope from springs along fault lines. Elevations are 1,345 to 1,435 meters. Slopes are 0 to 5 percent. The mean annual precipitation is 100 to 200 mm. The mean annual temperature is 15 to 17.2 degrees C. The frost-free season is 140 to 180 days.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Conway, Dehy and Roundval soils. Artray, Dehy and Roundval soils lack the organic surface layers.

DRAINAGE AND PERMEABILITY: Very poorly drained; slow runoff; very slow permeability. Depth to the water table is 15 cm above the surface to 30 cm below the surface all year. Frequently flooded for long durations from January to December.

USE AND VEGETATION: Used primarily for livestock grazing and wildlife habitat. The dominant vegetation is rushes and sedges.

DISTRIBUTION AND EXTENT: Valleys of east central California. These soils are of small extent in MLRA 29.

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

SERIES PROPOSED: Inyo County, California. Benton-Owens Valley Soil Survey Area, 1994.

REMARKS: The name comes from nearby Mount Tom. The MAAT would suggest thermic, but the MAST averages mesic due to the cooling effect of the high water table.

Diagnostic horizons and other soil properties recognized in the profile are:

Histic epipedon: Zone from the 0 to 64 cm (Oe1, Oe2, Oe3, Oa)

1. Organic layers
a. Surface tier 0 to 30 cm - 75% identifiable plant
parts and bulk density 0.1 -0.2 g/cm3.
b. Subsurface tier 30 to 64 cm - 25% identifiable
plant parts.
c. Pyrophosphate extractable color assumed to have value
less than 7 based on similar Medihemist soils in other
areas.
d. The pH in .01 CaCl is >4.5 throughout the O horizon.

2. Mineral layers fall within the control section of 0 to 130 cm.
a. The portion of the control section between 64 and 130 cm (the lower part of the subsurface tier and all
of the bottom tier) is mineral soil and averages about
10% clay and 23% gravel (loamy).

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National Cooperative Soil Survey
U.S.A.