LOCATION PTARMIGAN COEstablished Series
TAXONOMIC CLASS: Coarse-loamy, micaceous Typic Humicryepts
TYPICAL PEDON: Ptarmigan loam - grass vegetation. (Colors are for dry soil unless otherwise noted.)
01--2 inches to 1 inch; undecomposed organic material mainly roots, leaves, and stems of alpine grasses and sedges.
02--1 inch to 0; partially decomposed organic material like that of the horizon above.
A11--0 to 8 inches; very dark gray (10YR 3/1) loam, black (10YR 2/1) moist; moderate to strong medium and coarse granular structure; soft, very friable; thickly matted with grass roots; very strongly acid; clear wavy boundary. (6 to 10 inches thick)
A12--8 to 12 inches; dark grayish brown (10YR 4/2) sandy loam, very dark brown (10YR 2/2) moist; moderate fine and very fine subangular blocky structure that parts to moderate fine and medium granular; soft, very friable; 10 percent stones; very strongly acid; clear wavy boundary. (0 to 5 inches thick)
B2--12 to 25 inches; light yellowish brown (10YR 6/4) stony sandy loam, yellowish brown (10YR 6/4) moist; moderate fine subangular blocky structure; slightly hard, friable; very strongly acid; 15 percent stones; gradual wavy boundary. (9 to 15 inches thick)
C--25 to 30 inches; light yellowish brown (2.5Y 6/3) stony sandy loam, light olive brown (2.5Y 5/4) moist; massive; slightly hard, very friable; 30 percent stones; very strongly acid; gradual wavy boundary. (5 to 25 inches thick)
R--30 inches; gneiss and schist. Several feet thick.
TYPE LOCATION: Grand County, Colorado; approximately 1/2 mile west and slightly north of St. Louis Lake, Sec. 1, T. 3 S., R. 77 W.
RANGE IN CHARACTERISTICS: The thickness of the umbric epipedon ranges from 7 to 15 inches, thickness of solum ranges from 15 to 30 inches, and depth to bedrock ranges from 20 to 40 inches. The fine earth fraction of the control section is typically sandy loam but averages 3 to 18 percent, 10 to 40 percent silt, and 50 to 80 percent sand. Rock fragments range from 5 to 35 percent in the majority of the control section. The soils are extremely acid or strongly acid. The estimated average soil temperature is 28 to 32 degrees F., and the estimated average summer soil temperature is 40 to 45 degrees F. The moisture control section is dry for 60 to 90 days cumulative and is dry for 30 to 45 consecutive days in the summer.
The A horizon has hue of 2.5Y or 10YR, value of 2 through 5 dry, 1 through 3 moist, and chroma of 0 through 2. The horizon is less than 50 percent base saturated. Organic carbon ranges from 2 to 20 percent. Typically this soil has strong granular structure but it has weak subangular blocky structure in some pedons. It is soft or slightly hard.
The B2 horizon has hue of 10YR through 5YR, value of 5 through 7 dry, 4 through 6 moist, and chroma of 3 through 6. Typically this horizon has weak to moderate fine subangular blocky structure, but structure varies in both grade and class. Dry consistence is slightly hard to hard.
The C horizon has hue of 2.5Y or 10YR.
COMPETING SERIES: These are the Haverly and Strain series. Haverly soils are somewhat poorly or poorly drained. Strain soils have a paralithic contact above a depth of 40 inches.
GEOGRAPHIC SETTING: The Ptarmigan soils are on convex crests of mountains and ridges above timber line. Slope gradient ranges from 2 to 80 percent. The soils formed in material weathered residually or locally transported from gneiss and schist or similar bedrock. At the type location the average annual precipitation is 35 inches, most of which comes as snow. The average annual temperature is 28 degrees F., and the average summer temperature is 40 degrees F.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Mirror and Vasquez soils. Mirror soils have a loamy-skeletal control section. Vasquez soils are poorly drained.
DRAINAGE AND PERMEABILITY: Well drained; medium to rapid runoff; moderate to rapid permeability.
USE AND VEGETATION: These soils are used for grazing, or for recreational purposes. Vegetation is mainly grasses and sedges, including Kobresia, Volardi, alpine bluegrass, alpine fescue, and Geum.
DISTRIBUTION AND EXTENT: High mountainous areas of New Mexico, Colorado, Wyoming, and Montana. The series is of moderate extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana
SERIES ESTABLISHED: The Frazer Alpine Area, Grand County, Colorado, 1957.
REMARKS: Last updated by the state 4/77.
The mineralogy class was changed from paramicaceous to micaceous in 07/2010 by the National Soil Survey Center on request of the responsible MLRA regional office. The change was necessary based on the eleventh edition of the Keys to Soil Taxonomy, 2010.