LOCATION ZWAGG OR
Established Series
Rev. MHF/RTS/RWL
01/2013
ZWAGG SERIES
The Zwagg series consists of moderately deep, well drained soils formed in residuum and colluvium from metasedimentary or metavolcanic rock. Zwagg soils occur in open grassland areas on broad ridgetops and side slopes of coastal hills and mountains. Slopes are 0 to 90 percent. The mean annual precipitation is about 110 inches. The mean annual temperature is about 54 degrees F.
TAXONOMIC CLASS: Coarse-loamy, isotic, isomesic Pachic Humudepts
TYPICAL PEDON: Zwagg loam, pasture, on an 18 percent south-facing slope at an elevation of 960 feet. (Colors are for moist soil unless otherwise noted.)
A1--0 to 8 inches; black (10YR 2/1) loam, dark grayish brown (10YR 4/2) dry; strong fine granular structure; slightly hard, friable, nonsticky and nonplastic; weakly smeary; many fine and very fine roots; many fine and very fine irregular pores; 10 percent gravel; very strongly acid (pH 5.0); clear smooth boundary.
A2--8 to 15 inches; very dark brown (10YR 2/2) loam, dark grayish brown (10YR 4/2) dry; strong fine granular structure; slightly hard, friable, nonsticky and nonplastic; weakly smeary; many fine and very fine roots; many fine and very fine irregular pores; 10 percent gravel; very strongly acid (pH 4.8); clear smooth boundary.
A3--15 to 21 inches; very dark brown (10YR 2/2) loam, grayish brown (10YR 5/2) dry; moderate fine granular structure; slightly hard, friable, nonsticky and nonplastic; weakly smeary; many fine and very fine roots; many fine and very fine irregular pores; 10 percent gravel; very strongly acid (pH 4.8); gradual smooth boundary. (Combined thickness of the A horizon ranges from 20 to 25 inches)
Bw--21 to 25 inches; dark grayish brown (10YR 4/2) very gravelly loam, brown (10YR 5/3) dry; weak very fine subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; weakly smeary; common fine and very fine roots, many fine and very fine irregular pores; 55 percent gravel; very strongly acid (pH 4.6); gradual wavy boundary. (3 to 8 inches thick)
R--25 inches; sandstone.
TYPE LOCATION: Curry County, Oregon; located about 1100 feet south and 1800 feet east of the northwest corner of section 10, T. 41 S., R. 13 W. (Latitude 42 degrees, 02 minutes, 39 seconds N; Longitude 124 degrees, 14 minutes, and 00 seconds W)
RANGE IN CHARACTERISTICS: The mean annual soil temperature is 54 to 59 degrees F. The difference between mean summer and mean winter soil temperature varies from 5 to 9 degrees F. The soils are usually moist and are dry for less than 45 consecutive days between 4 and 12 inches in the four months following the summer solstice. The particle-size control section averages 12 to 18 percent clay. Depth to bedrock is 20 to 40 inches. The umbric epipedon is 20 to 25 inches thick.
The A horizon has value of 2 or 3 moist, 4 or 5 dry and chroma of 1 or 2 moist and dry. It is loam with 12 to 18 percent clay. It has 5 to 15 percent gravel. Organic matter is 4 to 8 percent.
The Bw horizon has hue of 10YR or 2.5Y, value of 4 or 5 moist and dry, and chroma of 2 or 3 moist and 3 or 4 dry. It is gravelly loam or very gravelly loam with 12 to 18 percent clay. It has 30 to 60 percent gravel.
COMPETING SERIES: This is the
Arcata series. Arcata soils are very deep to bedrock.
GEOGRAPHIC SETTING: Zwagg soils occur in open grassland areas on broad ridgetops and side slopes of coastal hills and mountains. Slopes are 0 to 90 percent. The soils formed in residuum and colluvium derived dominantly from metasedimentary or metavolcanic rock of the Dothan Formation. Elevation is 200 to 1300 feet. The climate is humid, characterized by warm wet winters and warm moist summers with fog. A strong marine influence limits the diurnal and annual range of temperature. The mean annual precipitation is 90 to 130 inches. The mean annual temperature is 50 to 57 degrees F. The frost-free period is 240 to 300 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the
Bosland,
Dulandy,
Floras,
Guerin,
Loeb,
Macklyn,
Vondergreen, and
Wedderburn soils. These soils are also occur on ridgetops and side slopes of coastal hills and mountains. Bosland soils are fine-loamy. Dulandy soils are loamy-skeletal. Floras soils are 40 to 60 inches deep to a paralithic contact and are fine textured. Guerin soils are 10 to 20 inches deep to a lithic contact and are loamy-skeletal. Loeb, Macklyn, and Vondergreen soils have argillic horizons. Wedderburn soils are 40 to 60 inches deep to a lithic contact and are fine-loamy.
DRAINAGE AND PERMEABILITY: Well drained; moderate permeability.
USE AND VEGETATION: The soils are used mainly for pasture, limited homesite development, recreation, and wildlife habitat. Most areas have been cleared of native vegetation. In those remaining areas, the vegetation is Douglas fir, red alder, tanoak, cascara buckthorn, evergreen huckleberry, salmonberry, and western azalea.
DISTRIBUTION AND EXTENT: Coastal hills and mountains of southwestern Oregon; MLRA 4. The series is of small extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California
SERIES ESTABLISHED: Curry County, Oregon; 1995. The source of the name is Zwagg Island off the south coast of Oregon, near Brookings.
REMARKS: Diagnostic horizons and features in this pedon include:
Umbric epipedon - from the surface to 21 inches. (A1, A2, and A3 horizons)
Humitropepts feature - base saturation (assumed) of less than 50 percent by ammonium acetate in some subhorizon between 10 and 40 inches. Organic carbon is 19.6 kg/square meter to a depth of 25 inches (lithic contact).
National Cooperative Soil Survey
U.S.A.