LOCATION POTRMOUND IDEstablished Series
TAXONOMIC CLASS: Loamy-skeletal, isotic Vitrandic Humicryepts
TYPICAL PEDON: Potrmound extremely stony ashy loam, supporting a aspen-lodgepole pine/mountain snowberry community type, woodland; on a 12 percent convex slope at an elevation of 6,060 feet. (Colors are for dry soils unless otherwise stated).
A1--0 to 16 inches; dark grayish brown (10YR 4/2) extremely stony ashy loam, very dark brown (10YR 2/2) moist; moderate fine granular structure; soft, very friable, nonsticky and nonplastic; many very fine through coarse roots; many very fine irregular pores; 5 percent cobbles and 80 percent stones; moderately acid (pH 5.8); abrupt wavy boundary. (4 to 16 inches thick)
A2--16 to 24 inches; brown (10YR 5/3) extremely stony ashy loam, dark brown (7.5YR 3/2) moist; weak medium subangular blocky structure parting to week fine granular; soft, very friable, nonsticky and nonplastic; many very fine through coarse roots; common very fine irregular and many very fine tubular pores; 5 percent cobbles and 80 percent stones; slightly acid (pH 6.2); clear wavy boundary. (8 to 14 inches thick)
A3--24 to 30 inches; brown (10YR 5/3) extremely stony ashy loam, dark brown (7.5YR 3/2) moist; weak medium subangular blocky structure; soft, very friable, nonsticky and nonplastic; common very fine through coarse roots; common very fine tubular pores; 5 percent gravel and 80 percent stones; moderately acid (pH 5.8); clear wavy boundary. (0 to 10 inches thick)
Bw--30 to 39 inches; pale brown (10YR 6/3) extremely stony ashy loam, brown (10YR 4/3) moist; weak medium subangular blocky structure; soft, very friable, nonsticky and nonplastic; common very fine through medium roots; common very fine tubular pores; 5 percent gravel and 80 percent stones; slightly acid (pH 6.2); abrupt irregular boundary. (7 to 16 inches thick)
R--39 inches; hard basalt.
TYPE LOCATION: Fremont County, Idaho; approximately 12 miles northeast of Ashton, about 300 feet north and 200 feet east of the southwest corner of section 2, T. 10 N., R 43 E; Latitude - 44 degrees, 12 minutes, 58 seconds North; Longitude - 111 degrees, 21 minutes, 27 seconds West.
RANGE IN CHARACTERISTICS:
Umbric epipedon thickness - 20 to 30 inches.
Depth to hard bedrock - 20 to 40 inches.
Percent clay in the particle-size control section - 10 to 18 percent.
Volcanic glass content - 5 to 30 percent in the 0.02 to 2.0 mm size fraction
Ammonium oxalate extractable Al plus 1/2 Fe - 0.1 to 1.0 percent
Phosphate retention - 20 to 50 percent
Mean annual soil temperature - 39 to 41 degrees F.
Mean summer soil temperature - 56 to 59 degrees F.
Moisture control section - between 8 and 24 inches; dry throughout the moisture control section for 30 to 45 consecutive days during the four months following the summer solstice
Reaction - moderately acid or slightly acid.
A horizons
Hue - 7.5YR or 10YR
Value - 4 or 5 dry, 2 or 3 moist
Chroma - 2 or 3 dry or moist
Clay content - 10 to 18 percent
Rock fragment content - 60 to 90 percent
Gravel - 5 to 20 percent
Cobbles - 0 to 45 percent
Stones - 20 to 80 percent
Base saturation by ammonium acetate - 30 to 50 percent
Bw horizon
Hue - 7.5YR or 10YR
Value - 5 or 6 dry, 3 or 4 moist
Texture - ashy loam or ashy silt loam
Clay content - 10 to 18 percent
Rock fragment content - 60 to 90 percent
Gravel - 0 to 10 percent
Cobbles - 0 to 45 percent
Stones - 20 to 90 percent
Base saturation by ammonium acetate - 30 to 80 percent
COMPETING SERIES: These are the Prong and Rhylow series. Prong soils receive 50 to 70 inches of annual precipitation. Rhylow soils are very deep.
GEOGRAPHIC SETTING: Potrmound soils are on pressure ridges of lava flows on caldera floors. They formed in loess and volcanic ash intermixed with residual basalt rock fragments. Slopes range from 4 to 35 percent. Elevations range from 5,900 to 6,500 feet. The mean annual precipitation is 20 to 28 inches and the mean annual temperature is 37 to 40 degrees F. The frost free period is less than 70 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Islandpark, and Spliten series. Islandpark soils occur in swales between pressure ridges. They have an albic horizon with less than 15 percent rock fragments to depths of 40 inches or more. Spliten soils occur on gently sloping pressure ridges and are less than 20 inches deep over hard bedrock.
DRAINAGE AND PERMEABILITY: Well drained; slow to rapid runoff; moderately rapid permeability.
USE AND VEGETATION: Potrmound soils are used for wildlife habitat, woodland and recreation. The potential native vegetation is a Douglas fir/common snowberry plant association.
DISTRIBUTION AND EXTENT: Southeastern Idaho. The soils of this series are of moderate extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana.
SERIES ESTABLISHED: Targhee National Forest, Fremont County, Idaho, 1997.
REMARKS: Location coordinates determined by Global Positioning System.
Diagnostic horizons and features recognized in this pedon are:
Umbric epipedon - the zone from the mineral soil surface to 30 inches (the A1, A2 and A3 horizons).
Cambic horizon - the zone from 30 to 39 inches (the Bw horizon).
Particle-size control section - the zone from 10 to 39 inches (part of the A1 horizon, the A2 and A3 horizons and Bw horizons).
Vitrandic subgroup feature - the zone from the mineral soil surface to 39 inches (A1, A2, A3 and Bw horizons)
Moisture regime - udic.
ADDITIONAL DATA: NSSL S92ID-043-079.
The 3/2008 description reflects a change in classification from Loamy-skeletal, isotic Vitrandic Dystrocryepts to Loamy-skeletal, isotic Vitrandic Humicryepts due to revision of the cryepts great groups and subgroups. The competing series section was not updated and should be reviewed after all the cryepts have been re-classified.
3/31/08- In review of this description and corresponding lab analysis, further investigation is needed to determine dominant base saturation to classify as Inceptisol (mollic vs. umbric epipedon).