LOCATION ROLPH AK
Established Series
SAS/TJR/SJN
02/2022
ROLPH SERIES
The Rolph series consists of very deep, well drained soils formed in loess on rises of plains and on shoulders of hills. Slopes range from 2 to 10 percent. The mean annual precipitation is about 615 millimeters and the mean annual air temperature is about 0.5 degrees C.
TAXONOMIC CLASS: Coarse-silty, isotic Typic Humicryepts
TYPICAL PEDON: Rolph highly organic silt loam, located on a plain rise with a slope of 2 percent and elevation of 17 meters; when described on September 17th, 2007 the soil was moist throughout (Colors are for moist soil unless otherwise noted)
Oi--0 to 5 centimeters; slightly decomposed plant material; common very fine and fine roots, common medium roots, and many coarse roots; moderately acid, pH 6.0; clear smooth boundary
A/Cjj--5 to 38 centimeters; 80 percent very dark grayish brown (10YR 3/2) and 20 percent brown (10YR 4/3) highly organic silt loam; 20 percent sand; 75 percent silt; 5 percent clay; weak fine granular structure; very friable, nonsticky, nonplastic; common very fine and fine roots, common medium roots, and common coarse roots; 1 percent nonflat 5 to 76 millimeter fragments; very strongly acid, pH 4.9; clear smooth boundary
Bw/Cgjj--38 to 105 centimeters; 75 percent yellowish brown (10YR 5/4) and 25 percent dark grayish brown (2.5Y 4/2) silt loam; 20 percent sand; 75 percent silt; 5 percent clay; moderate medium subangular blocky structure; friable, nonsticky, nonplastic; common very fine and fine roots, common medium roots, and common coarse roots; 10 percent medium dark brown (7.5YR 3/3), moist, masses of oxidized iron with clear boundaries; 2 percent nonflat 5 to 76 millimeter fragments; strongly acid, pH 5.1; gradual smooth boundary
C--105 to 183 centimeters; 65 percent light olive gray (5Y 6/2) silt loam; 30 percent sand; 65 percent silt; 5 percent clay; massive; friable, nonsticky, nonplastic; few very fine and fine roots, few medium roots, and few coarse roots; 5 percent medium strong brown (7.5YR 4/6), moist, iron-manganese nodules with sharp boundaries and 30 percent coarse strong brown (7.5YR 4/6), moist, masses of oxidized iron with sharp boundaries; 5 percent nonflat 5 to 76 millimeter fragments; strongly acid, pH 5.5
TYPE LOCATION: Dillingham Census Area, Alaska; 2 kilometers south-southeast of the Village of Ekuk; 58.7963889 degrees north latitude and 158.5497222 degrees west longitude.
RANGE IN CHARACTERISTICS:
Mean annual soil temperature - 0.5 to 1.7 C (cryic soil temperature regime)
Soil moisture control section - Dry less than 45 consecutive days from June to October (udic soil moisture regime)
Thickness of umbric epipedon - 33 to 95 cm
Thickness of cambic horizon - 67 to 85 cm
All mineral horizons-
Reaction - 4.9 to 6.6
Particle-size control section-
Clay content - 3 to 8
Rock fragments - 0 to 10 percent
Oi (or Oe) horizon
Thickness - 2 to 9 cm
A/Cjj horizon
Hue - 10YR
Value - 2 to 4
Chroma - 1 to 3
Fine earth texture - Highly organic silt loam or highly organic silt
Clay content - 3 to 8 percent
Reaction - 4.9 to 5.3
Rock fragments - 0 to 1 percent subrounded coarse and medium gravels
Thickness - 6 to 88 cm
Bw/Cgjj horizon
Hue - 7.5YR to 2.5Y
Value - 2.5 to 5
Chroma - 1 to 4
Fine earth texture - Silt loam, silt, or loamy very fine sand
Clay content - 3 to 8 percent
Reaction - 5.1 to 5.8
Rock fragments - 0 to 10 percent rounded medium and coarse gravels
Thickness - 48 to 85 cm
C horizon
Hue - 10Y or 5Y
Value - 3 to 6
Chroma - 1 or 2
Fine earth texture - Silt loam, silt, sandy loam, or very fine sandy loam
Clay content - 3 to 10 percent
Reaction - 5.5 to 6.3
Rock fragments - 0 to 30 percent subrounded medium and coarse gravels
Thickness - 8 to 78 cm
COMPETING SERIES: There are no competing series
GEOGRAPHIC SETTING:
Parent material - Herbaceous organic material over coarse-silty cryoturbate over coarse-silty loess
Landform - Rises on plains, and hills
Slope - 2 to 10 percent
Elevation - 10 to 45 meters
Climate - Cool summers; cold winters, August and September are the wettest months
Mean annual precipitation - 612 to 628 mm
Mean annual air temperature - 0.3 to 0.7 degrees C
Frost free duration - 85 to 140 days
GEOGRAPHICALLY ASSOCIATED SOILS:
Clarks point - No umbric epipedon present, andic soil properties and spodic horizon, similar landform position
Kanakanak - No umbric epipedon present, andic soil properties and spodic horizon, rises and talfs on plains
Flounder - Aquic conditions within 40 cm, very steep slopes on coastal bluffs
Nushagak - Aquic conditions at surface, talfs on plains
DRAINAGE AND SATURATED HYDRAULIC CONDUCTIVITY: (Ksat)
Drainage class - Well drained
Saturation in normal years - None
Flooding - None
Ponding - None
Ksat - Moderately high to high throughout the mineral soil material, except for moderately high in the A/Cjj horizon
Redoximorphic features in the Bw/Cgjj horizon are the product of spring thaw where water perches on top of hard frost. This horizon is moist, not wet, during the growing season.
USE AND VEGETATION:
Use - Wildlife habitat
Potential natural vegetation - Western maritime scrubland composed of alder, ferns, and grass
DISTRIBUTION AND EXTENT: Bristol Bay Lowlands; MLRA 236; small extent
SOIL SURVEY REGIONAL OFFICE (SSRO) RESPONSIBLE: WASILLA, ALASKA
SERIES ESTABLISHED: Nushagak-Mulchatna Watershed Soil Survey, Dillingham Census Area, Alaska, 2019
REMARKS:
Particle-size control section - 30 to 105 cm
Umbric epipedon - A/Cjj horizon
Soil moisture regime - Udic
Cambic - A/Cjj and Bw/Cgjj horizons
Cryoturbation - A/Cjj and Bw/Cgjj horizons
National Cooperative Soil Survey
U.S.A.