LOCATION CHUU AK

Established Series
SDB/MJS
08/2025

CHUU SERIES

Depth class: very deep
Drainage class: somewhat poorly drained
Parent material: calcareous loess
Landscape: mountains
Landform: terraces on river valleys
Slopes: 1 to 10 percent
Mean annual precipitation: about 350 mm (14 in)
Mean annual air temperature: about -2 degrees C. (28 degrees F)
Frost-free period: 32 to 103 days

TAXONOMIC CLASS: Coarse-loamy, mixed, superactive Aquic Cumulic Haplocryolls

TYPICAL PEDON: Chuu very fine sandy loam, in a balsam poplar community on a south facing linear, linear terrace on a slope of 4 percent at an elevation of 176m (575 ft).

Oi--0 to 4 cm (0.0 to 1.6 in); slightly decomposed plant material, dark brown (7.5YR 3/4) moist; common very fine, common fine and medium roots; noneffervescent; slightly alkaline (pH 7.8); clear smooth boundary (2 to 19 cm, 1 to 7 in).

A--4 to 26 cm (1.6 to 10.2 in); very fine sandy loam, very dark brown (7.5YR 2.5/2) moist; moderate fine granular structure; soft, very friable, nonsticky, nonplastic; nonsmeary; common very fine, fine, medium, coarse, and very coarse roots throughout; noneffervescent; slightly alkaline (pH 7.5); clear smooth boundary (9 to 45 cm, 4 to 18 in).

Bw--26 to 56 cm (10.2 to 22.0 in); silt loam, dark brown (7.5YR 3/3) moist; moderate medium subangular blocky structure; slightly hard, friable, nonsticky, nonplastic; nonsmeary; common very fine, fine, medium, coarse, and very coarse roots throughout; 10 percent medium irregular (10yr 4/3) masses of reduced iron with clear boundaries in matrix; noneffervescent; moderately alkaline (pH 7.9); gradual smooth boundary (20 to 40 cm, 8 to 16 in).

BC--56 to 122 cm (22.0 to 48.0 in); silt loam, dark brown (7.5YR 3/4) moist; weak fine subangular blocky structure; soft, very friable, nonsticky, nonplastic; nonsmeary; common fine roots throughout; 15 percent fine prominent irregular (10yr 4/2) masses of reduced iron with clear boundaries in matrix and 30 percent medium distinct irregular (7.5yr 4/6) masses of oxidized iron with clear boundaries in matrix; slight effervescence; moderately alkaline (pH 8.1); abrupt smooth boundary (10 to 80 cm, 4 to 31 in).

Cg--122 to 200 cm (48.0 to 59.1 in); silt loam, bluish black (10B 2.5/1) moist; massive; soft, very friable, nonsticky, nonplastic; nonsmeary; slight effervescence; moderately alkaline (pH 8.3). (16 to 159 cm, 6 to 63 in).

TYPE LOCATION: North Copper River Soil Survey Area, Alaska; latitude 61.51611, longitude -144.43765, UTM 6822955.42 north and UTM 636307.71 east, zone 6, Datum WGS84.

RANGE IN CHARACTERISTICS:

Soil moisture regime: aquic
Soil temperature regime: cryic
Mean annual soil temperature: 0 to 5 degrees C. (32 to 41 degrees F)
Thickness of organic material: 2 to 19 cm (1 to 7 in)
Thickness of mollic epipedon: 29 to 85 cm (11 to 33 in)
Depth to redoximorphic concentrations: 36 to 104 cm (14 to 41 in)

Oi and Oe horizon:
Hue: 7.5YR or 10YR
Value: 2 to 3
Chroma: 1 to 3
Texture: slightly decomposed organic material, moderately decomposed organic material.
Organic matter: 60 to 90 percent
Reaction class: slightly alkaline to moderately alkaline (pH 7.4 to 8.4)

A horizon:
Hue: 7.5YR or 10YR
Value: 2 to 3
Chroma: 1 to 3
Texture: silt loam, or very fine sandy loam
Sand: 20 to 55 percent
Silt: 40 to 75 percent
Clay: 3 to 15 percent
Rock fragments: 0 percent
Organic matter: 2.7 to 7.2 percent
Reaction class: slightly alkaline (pH 7.4 to 7.8)

Bw horizon:
Hue: 7.5YR or 10YR
Value: 3 to 4
Chroma: 2 to 3
Texture: silt loam
Sand: 20 to 47 percent
Silt: 50 to 74 percent
Clay: 3 to 15 percent
Rock fragments: 0 percent
Organic matter: 1 to 3 percent
Reaction class: slightly alkaline to moderately alkaline (pH 7.4 to 8.4)

C and BC horizons:
Hue: 2.5Y or 5Y
Value: 3 to 4
Chroma: 1 to 4
Texture: silt loam
Sand: 20 to 45 percent
Silt: 50 to 75 percent
Clay: 5 to 18 percent
Rock fragments: 0 percent
Organic matter: 0.1 to 2 percent
Reaction class: moderately alkaline (pH 7.9 to 8.4)

COMPETING SERIES: These are the Benitocreek (AK), Broadycreek (OR), Cablab (NV, ID), and Pappascreek (MT, WY) soils.
Broady creek, Cablab, and Pappascreek have alluvial parent material as parent material, and have more than 15 percent gravel in the C horizons.
Benitocreek soils are somewhat poorly drained, have a mollic epipedon, have a lithic contact within 200 cm (79 in), and occur on mountain slopes and glacial valley floors.

GEOGRAPHIC SETTING:
Elevation: 100 to 600 meters (330 to 1970 ft)
Parent material: calcareous loess
Landform: terraces on river valleys
Slopes: 1 to 10 percent
Mean annual precipitation: 300 to 800 mm (12 to 31 in)
Mean annual air temperature: -4 to 1 degrees C (25 to 34 degrees F)
Frost free period: 32 to103 days

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Alterationcreek, Chitina, Coppercenter, Haggardcreek, Manker, Rocklake, and Tonsina soils.
Alterationcreek soils are well drained, have silt loam textures, have bedrock at a depth between 101 and 154 cm, and occur on hillslopes and mountain valleys.
Chitina soils are well drained, have very deep (>40 cm, >16 in) mollic epipedons, and occur on loess covered hillsloeps and stream terraces.
Coppercenter soils are poorly drained permafrost soils, have a histic epipedon, and occur on hillslopes.
Haggardcreek soils are well drained, have a folistic epipedon, have a silt loam or gravelly silt loam surface texture, there are bedrock within 2 meters of the soil surface, and occur on hillslopes and mountain slopes.
Manker soils have permafrost, a cryoturbated horizon, lack a lithic contact, and occur on north facing slopes
Rocklake soils are less than 50cm deep to bedrock, they occur on occurs on escarpments and ridges on mountain sides
Tonsina soils are well drained, have very deep (>40 cm, >16 in) mollic epipedons, silt loam surface textures, they have marginally coarser textures at depth than the Chitina soils, they occur on till plains and hills.

DRAINAGE AND SATURATED HYDRAULIC CONDUCTIVITY:
Drainage class: somewhat poorly
Saturated Hydraulic Conductivity: very high in the O horizon, high in the A horizon, and moderately high in the B and C horizons.
Permeability: very rapid in the O horizon, moderately rapid in the A horizon, moderate in the B and C horizons.
Runoff: very high

USE AND VEGETATION:
Use: wildlife habitat, recreation, and subsistence
Native vegetation: Balsom poplar, prickly rose, meadow horsetail

DISTRIBUTION AND EXTENT: MLRA 228, Interior Alaska mountains.
Extent: limited

SOIL SURVEY REGIONAL OFFICE (SSRO) RESPONSIBLE: Wasilla, Alaska

SERIES ESTABLISHED: North Copper River Soil Survey, Alaska, 2024.

REMARKS: Diagnostic features and horizons recognized in this profile include:

Particle-size control section: 29 to 104 cm (11 to 41 in)

Mollic epipedon: 4 to 29 cm (2 to 11 in) (A horizon)

Free carbonates horizon: 56 to 200 cm (22 to 79 in) ( B, BC, and C horizon)

Redoximorphic concentrations: 56 to 200 cm (22 to 79 in) (BC, and C horizon)

Redoximorphic depletions: 56 to 200 cm (22 to 79 in) (BC, and C horizon)

ADDITIONAL DATA:

User pedon Id: 2018AK261011

National Cooperative Soil Survey
U.S.A.