LOCATION IOWITHLA                AK

Established Series
SAS/TJR/SJN
05/2022

IOWITHLA SERIES

The Iowithla series consists of very deep, moderately well drained soils formed in loamy, sandy, and gravelly alluvium on flood plains. Slopes are 0 to 5 percent. The mean annual precipitation is about 690 millimeters and the mean annual air temperature is about 0.6 degrees C.

TAXONOMIC CLASS: Sandy-skeletal, mixed Typic Dystrocryepts

TYPICAL PEDON: Iowithla silt loam, located on a flood plain with a slope of 1 percent and elevation of 47 meters; when described on August 22nd, 2010 the soil was moist throughout (Colors are for moist soil unless otherwise noted)

Oi--0 to 4 cm; slightly decomposed plant material; very friable, nonsticky, nonplastic; common fine roots, common medium roots, common coarse roots, and many very fine roots; strongly acid (pH 5.5); clear smooth boundary

A--4 to 9 cm; dark brown (7.5YR 3/3) silt loam; 20 percent sand; 75 percent silt; 5 percent clay; weak fine granular structure; very friable, nonsticky, nonplastic; common fine roots, common medium roots, and many very fine roots; very strongly acid (pH 4.5); clear smooth boundary

Bw--9 to 24 cm; brown (10YR 4/3) silt loam; 35 percent sand; 60 percent silt; 5 percent clay; weak fine subangular blocky structure; very friable, nonsticky, nonplastic; common fine roots, common medium roots, and many very fine roots; 2 percent fine light olive brown (2.5Y 5/3) iron depletions and 5 percent fine yellowish red (5YR 4/6) masses of oxidized iron with diffuse boundaries; very strongly acid (pH 4.8); abrupt smooth boundary

2C--24 to 183 cm; extremely gravelly coarse sand; 98 percent sand; 1 percent silt; 1 percent clay; single grain; loose, nonsticky, nonplastic; common fine roots and common very fine roots; 85 percent gravel; moderately acid (pH 5.7)

TYPE LOCATION: Dillingham Census Area, Alaska; Located in the Village of New Stuyahok; 59.4552778 degrees north latitude and 157.3150000 degrees west longitude.

RANGE IN CHARACTERISTICS:
Mean annual soil temperature - 0.9 to 2.5 degrees 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 cambic horizon - 18 to 30 cm
Thickness of redox concentrations - 8 to 30 cm

All mineral horizons-
Reaction - 4.4 to 6.1

Particle-size control section-
Clay content - 0 to 5 percent
Rock fragments - 65 to 85 percent

Oi horizon
Thickness - 3 to 4 cm
Reaction - 5.3 to 5.5

A horizon
Hue - 7.5YR to 2.5Y
Value - 3 or 4
Chroma - 2 or 3
Fine earth texture - Silt loam or silt
Clay content - 4 to 8 percent
Reaction - 4.4 to 4.5
Rock fragments - 0 percent
Thickness - 3 to 5 cm

Bw horizon
Hue - 10YR or 2.5Y
Value - 3 or 4
Chroma - 3
Fine earth texture - Silt loam or silt
Clay content - 1 to 7 percent
Reaction - 4.8 to 5.0
Rock fragments - 0 percent
Thickness - 10 to 17 cm

2C horizon
Hue - 10YR or 2.5Y
Value - 4 or 5
Chroma - 1 to 3
Fine earth texture - Coarse sand or sand
Clay content - 0 to 5 percent
Reaction - 5.7 to 6.1
Rock fragments - 65 to 85 percent total; 65 to 83 percent medium and coarse gravels, and 0 to 11 percent fine gravels
Thickness - 159 to 163 cm

COMPETING SERIES: These are the Elting, Mirror Lake, Priestlake, and Tolby soils. Elting soils formedin eolian deposits over outwash in mountains over 2,244 feet in elevation with slopes of up to 48 percent. Mirror Lake soils formed in glacial till and are found on slopes ranging from 10 to 70 percent. Priestlake soils have a mean annual soil temperature of 4 to 6 degrees C and are found on steep mountain uplands. Tolby soils are also found on sleep mountain slopes.

GEOGRAPHIC SETTING:
Parent material - Organic material over coarse-loamy alluvium over sandy and gravelly alluvium
Landform - Flood plains
Slope - 0 to 5 percent
Elevation - 23 to 55 meters
Climate - Cool summers; cold winters, August and September are the wettest months
Mean annual precipitation - 669 to 771 mm
Mean annual air temperature - 0.3 to 0.7 degrees C
Frost free duration - 85 to 140 days

GEOGRAPHICALLY ASSOCIATED SOILS:
Kokwok - Well drained, coarse-loamy over sandy or sandy-skeletal, and similar landform
Nunachuak - Very poorly drained, silty and loamy alluvium, low flood plains
Orgter - Very poorly drained, formed in organic parent material, stream terraces
Ekvik - Well drained, formed in colluvium and glacial outwash, bluffs

DRAINAGE AND SATURATED HYDRAULIC CONDUCTIVITY: (Ksat)
Drainage class - Moderately well drained
Saturation in normal years - Within 75 cm of the soil surface for less than two weeks during the growing season
Flooding - Occasional and brief
Ponding - Frequent and brief
Ksat - Moderately high in the coarse-loamy alluvium and very high in the sandy and gravelly alluvium
Redoximorphic features in the Bw horizon are associated with spring thaw conditions where water is perched on top of hard frost. This layer is moist, not wet, during the growing season.

USE AND VEGETATION:
Use - Wildlife habitat and subsistence
Potential natural vegetation - Western maritime forest composed of paper birch, white spruce, Kenai birch, bluejoint grass, horsetails, spreading woodfern, alder, spirea, highbush cranberry, and moss

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 - 29 to 104 cm
Soil moisture regime - Udic
Ochric epipedon
Cambic horizon - A and Bw horizons
Redox concentrations - Bw horizon

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National Cooperative Soil Survey
U.S.A.