LOCATION SIKU AK
Established Series
MPS
11/2024
SIKU SERIES
Depth class: very deep
Drainage class: poorly drained
Parent material: mossy organic material over gravelly loamy colluvium derived from mudstone or graywacke
Landscape: mountains
Landform: mountain slopes
Slopes: 0 to 25 percent
Mean annual precipitation: about 400 mm (16 in)
Mean annual air temperature: about -4 degrees C. (25 degrees F.)
Frost-free period: 70 to 90 days
TAXONOMIC CLASS: Loamy-skeletal, mixed, superactive, acid, subgelic Typic Gelaquepts
TYPICAL PEDON: Siku gravelly silt loam in a mossy and low shrub alpine community on an east facing linear, convex microhigh on a backslope on a slope of 18 percent at an elevation of 470m (1542 ft)
Oi1--0 to 9 cm (0 to 4 in); slightly decomposed plant material; dark brown (7.5YR 3/3) broken face moist, brown (7.5YR 5/3) broken face dry; many very fine and fine roots throughout; moderately acid (pH 5.6); clear smooth boundary. (5 to 12 cm, 2 to 5 in thick)
Oi2--9 to 22 cm (4 to 9 in); slightly decomposed plant material; black (7.5YR 2.5/1) broken face moist, dark gray (7.5YR 4/1) broken face dry; many very fine, fine, and medium roots throughout; slightly acid (pH 6.1); abrupt smooth boundary. (10 to 15 cm, 4 to 6 in thick)
Bg1--22 to 47 cm (9 to 19 in); gravelly silt loam; dark gray (10YR 4/1) broken face moist; gray (10YR 6/1) broken face dry; weak medium subangular blocky structure; friable, slightly hard, nonsticky, nonplastic; nonsmeary; common fine roots throughout; few very fine dendritic tubular pores; 8 percent cobbles, 20 percent gravel; 7 percent 3 mm ice lenses; strongly acid (pH 5.5); clear smooth boundary. (20 to 30 cm, 8 to 12 in thick)
Bg2--47 to 100 cm (19 to 39 in); very gravelly silt loam; dark gray (10YR 4/1) broken face moist, gray (10YR 6/1) broken face dry; weak medium subangular blocky structure; friable, slightly hard, nonsticky, nonplastic; nonsmeary; moderately few fine roots throughout; few very fine dendritic tubular pores; 10 percent fine prominent irregular reddish brown (5YR 4/4), moist, masses of oxidized iron in matrix; 35 percent gravel and 5 percent cobbles; strongly acid (pH 5.4); gradual smooth boundary. (25 to 60 cm, 10 to 24 in thick)
Cg--100 to 200 cm (39 to 79 in); very gravelly silt loam; dark gray (10YR 4/1) broken face moist, gray (10YR 6/1) broken face dry; massive; friable, slightly hard, nonsticky, nonplastic; nonsmeary; few very fine irregular pores; 40 percent gravel and 10 percent cobbles; strongly acid (pH 5.5)
TYPE LOCATION: Nulato Hills - Continental Divide and Blackburn Hills Soil Survey Area, Alaska; latitude 64.4951908, longitude -160.2600110, datum WGS84, UTM north 7152797.33 and UTM east 439466.20, zone 4, datum WGS84.
RANGE IN CHARACTERISTICS:
Soil moisture regime: aquic
Soil temperature regime: gelic
Mean annual soil temperature: -1 to 0 degrees C. (30 to 32 degrees F.)
Thickness of folistic epipedon: 15 to 27 cm (6 to 11 in)
Thickness of cambic horizon: 45 to 90 cm (18 to 35 in)
Depth to reduced matrix: 15 to 27 cm (6 to 11 in)
Depth to redoximorphic concentrations: 34 to 67 cm (13 to 26 in)
Oi horizons:
Hue: 7.5YR or 10YR
Value: 2 to 3 moist, 4 or 5 dry
Chroma: 1 to 3
Texture: slightly decomposed material
Organic matter: 60 to 90 percent
Reaction class: moderately acid to neutral (pH 5.6 to 7.3)
A horizon (when present)
Hue: 10YR
Value: 2 to 4 moist, 4 to 6 dry
Chroma: 2 or 3
Texture: silt loam
Sand: 15 to 52 percent
Silt: 35 to 84 percent
Clay: 3 to 13 percent
Rock fragments: 0 to 14 percent
Gravels: 0 to 14 percent
Organic matter: 2 to 4 percent
Reaction class: very strongly acid to moderately acid (pH 4.5 to 6)
Bg1 horizon:
Hue: 10YR or 2.5Y
Value: 4 or 5 moist, 6 or 7 dry
Chroma: 1 or 2
Texture: silt loam, loam or their gravelly analogues
Sand: 15 to 52 percent
Silt: 31 to 80 percent
Clay: 3 to 17 percent
Rock fragments: 15 to 50 percent
Gravels: 10 to 35 percent
Cobbles: 5 to 15 percent
Organic matter: 0.5 to 4 percent
Reaction class: very strongly acid to moderately acid (pH 4.5 to 6)
Bg2 horizon:
Hue: 10YR or 2.5Y
Value: 4 or 5 moist, 6 or 7 dry
Chroma: 1 or 2
Texture: silt loam, loam or their gravelly and cobbly analogues
Sand: 15 to 52 percent
Silt: 31 to 80 percent
Clay: 3 to 17 percent
Rock fragments: 35 to 50 percent
Gravels: 15 to 40 percent
Cobbles: 0 to 35 percent
Organic matter: 0.5 to 4 percent
Reaction class: very strongly acid to strongly acid (pH 4.5 to 5.5)
Cg horizon:
Hue: 10YR or 2.5Y
Value: 4 or 5 moist, 6 or 7 dry
Chroma: 1 or 2
Texture: silt loam, loam or their gravelly and cobbly analogues
Sand: 15 to 52 percent
Silt: 36 to 80 percent
Clay: 2 to 12 percent
Rock fragments: 35 to 60 percent
Gravels: 20 to 50 percent
Cobbles: 5 to 35 percent
Organic matter: 0.5 to 3 percent
Reaction class: strongly acid to slightly acid (pH 5.1 to 6.5)
COMPETING SERIES: There are no competing series.
GEOGRAPHIC SETTING:
Elevation: 50 to 775 meters (165 to 2545 feet)
Parent material: mossy organic material over gravelly loamy colluvium derived from mudstone or graywacke
Landform: mountain slopes
Slopes: 0 to 25 percent
Mean annual precipitation: 300 to 600 mm (12 to 24 in)
Mean annual air temperature: -6 to -1 degrees C. (21 to 30 degrees F.)
Frost free period: 70 to 90 days
GEOGRAPHICALLY ASSOCIATED SOILS: These are the
Aagiak,
Apun,
Fluffle,
Iyyagrik,
Kunjik,
Niakuk,
Niilgik,
Nunanjiak,
Sagvaktuk,
Savik,
Stovecreek, and
Urgiilik soils.
Aagiak soils have aquic conditions starting between 25 to 50 cm, have an umbric epipedon, lack a cambic horizon, have a cryic soil temperature regime, and occur on mountainflanks, lower third
Apun soils have permafrost, have a histic epipedon, have cryoturbation, lack a cambic horizon, have a coarse-loamy particle size class, have a nonacid reaction class, and occur on footslopes, terraces and saddles
Fluffle soils have an ochric epipedon, have a coarse-loamy particle size class, have a cryic soil temperature regime, have a nonacid reaction class, and occur on flood plains
Iyyagrik soils lack aquic conditions, have a lithic contact at depths between 100 to 150 cm (40 to 60 in), have a mollic epipedon, have a cryic soil temperature regime, lack a cambic horizon, and occur on mountainflanks, upper third
Kunjik soils lack aquic conditions, have a lithic contact at depths between 50 to 100 cm (20 to 40 in), have a fragmental layer starting at depths between 27 to 104 cm (11 to 41 in), have an ochric epipedon, have a loamy-skeletal over fragmental particle size class, have a cryic soil temperature regime, and occur on ridges
Niakuk soils lack aquic conditions, have a lithic contact at depths between 100 to 150 cm (40 to 60 in), have a fragmental layer starting at depths between 20 to 73 cm (8 to 29 in), have an ochric epipedon, have a coarse-loamy over fragmental particle size class, have a cryic soil temperature regime, and occur on mountainflanks, upper and center thirds
Niilgik soils have permafrost, have a histic epipedon, have cryoturbation, lack a cambic horizon, have a coarse-silty particle size class, and occur on footslopes
Nunanjiak soils lack aquic conditions, have a paralithic contact at depths between 100 to 150 cm (40 to 60 in), have an umbric epipedon, have andic soil properties, can have spodic materials, have a medial over loamy-skeletal particle size class, have a cryic soil temperature regime, and occur on head slopes and mountainflanks, center third
Sagvaktuk soils lack aquic conditions, have an ochric epipedon, have a coarse-loamy particle size class, have an isotic mineralogy class, have a cryic soil temperature regime, and occur on drainageways on valleys
Savik soils lack aquic conditions, have a lithic contact at depths between 25 to 50 cm (10 to 20 in), have a fragmental layer starting at depths between 13 to 40 cm (5 to 15 in), have an umbric epipedon, lack a cambic horizon, have a fragmental particle size class, and occur on nose slopes or mountainflanks, upper third on knife ridges
Stovecreek soils have an umbric epipedon, have a coarse-loamy particle size class, have a nonacid reaction class, have a cryic soil temperature regime, lack an organic surface and occur on drainageways
Urgiilik soils lack aquic conditions, have a lithic contact at depths between 50 to 100 cm (20 to 40 in), have a fragmental layer starting at depths between 25 to 91 cm (10 to 36 in), have an ochric epipedon, have a cryic soil temperature regime, and occur on side slopes and mountainflanks, center third
DRAINAGE AND SATURATED HYDRAULIC CONDUCTIVITY:
Drainage class: poorly drained
Saturation during normal years-- saturated between 0 and 25 cm during the growing season
Saturated Hydraulic Conductivity: very high in the Oi horizons, moderately high to high in the Bg and Cg horizons
Permeability: rapid to very rapid in the Oi horizons, moderate to moderately rapid in the Bg and Cg horizons
Runoff: very high
USE AND VEGETATION:
Use: wildlife habitat, recreation, and subsistence
Native vegetation: Bigelow's sedge, sphagnum, bog blueberry, turgid aulacomnium moss, dwarf birch, moss, splendid feather moss, Schreber's big red stem moss, black crowberry, cloudberry, tealeaf willow, Flavocetraria cucullate, marsh Labrador tea, tussock cottongrass, field horsetail, cup lichen, reindeer lichen
DISTRIBUTION AND EXTENT: MLRA 240, Nulato Hills-Southern Seward Peninsula Highlands. The series is of moderate extent.
SOIL SURVEY REGIONAL OFFICE (SSRO) RESPONSIBLE: Wasilla, Alaska
SERIES ESTABLISHED: Nulato Hills - Continental Divide and Blackburn Hills Soil Survey, Alaska, 2024.
REMARKS: Diagnostic features and horizons recognized in this profile include:
Particle-size control section: 47 to 122 cm (19 to 48 in)
Folistic epipedon: 0 to 22 cm (0 to 9 in) (Oi1 and Oi2 horizons)
Cambic horizon: 22 to 100cm (9 to 39 in) (Bg1 and Bg2 horizons)
Reduced matrix: 22 to 200cm (9 to 79 in) (Bg1 and Bg2 horizons)
Redoximorphic concentrations: 47 to 100 cm (19 to 39 in) (Bg2 horizon)
Aquic conditions: 22 to 200 cm (9 to 79 in) (Bg1, Bg2, and Cg horizons)
ADDITIONAL DATA:
User pedon ID: 2021AK180739
National Cooperative Soil Survey
U.S.A.