LOCATION ZYGORE OR+WAEstablished Series
TAXONOMIC CLASS: Loamy-skeletal, isotic, frigid Andic Dystrudepts
TYPICAL PEDON: Zygore gravelly medial loam, forested. (Colors are for moist soil unless otherwise noted.)
Oi--0 to 3 inches; slightly decomposed needles, twigs, leaves, cones.
A1--3 to 9 inches; dark brown (7.5YR 3/2) gravelly medial loam, brown (7.5YR 4/2) dry; moderate fine and very fine granular structure; slightly hard, friable, slightly sticky and slightly plastic; weakly smeary; many very fine, fine and medium roots; many very fine and fine irregular pores; 15 percent gravel and 5 percent cobbles; 10 percent 2mm to 10mm concretions; moderately acid (pH 5.9); clear wavy boundary. (3 to 10 inches thick)
A2--9 to 13 inches; dark brown (7.5YR 3/2) gravelly medial loam, brown (7.5YR 4/3) dry; moderate fine subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; weakly smeary; many very fine and fine roots; many very fine tubular pores; 15 percent gravel and 5 percent cobbles; 10 percent 2mm to 10mm concretions; moderately acid (pH 5.8); clear wavy boundary. (2 to 12 inches thick)
2Bw--13 to 22 inches; dark brown (7.5YR 3/3) very cobbly loam, brown (7.5YR 4/4) dry; moderate fine and very fine subangular blocky structure; slightly hard, very friable, slightly sticky and slightly plastic; common very fine roots; many very fine tubular pores; 15 percent cobbles, 15 percent gravel and 5 percent stones; 10 percent 2mm to 10mm concretions; moderately acid (pH 6.0); gradual wavy boundary. (6 to 18 inches thick)
2BC--22 to 37 inches; brown (7.5YR 4/4) very cobbly loam, brown (7.5YR 5/4) dry; weak medium subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; common very fine roots; many very fine tubular pores; 25 percent cobbles, 15 percent gravel and 5 percent stones; slightly acid (pH 6.2); gradual wavy boundary. (6 to 18 inches thick)
2C--37 to 63 inches; brown (7.5YR 4/4) extremely cobbly loam, brown (7.5YR 5/4) dry; massive; hard, friable, slightly sticky and slightly plastic; common very fine and fine roots; many very fine tubular pores; 35 percent cobbles, 25 percent gravel and 5 percent stones; slightly acid (pH 6.2).
TYPE LOCATION: Multnomah County, Oregon; about 1/4 mile north of Larch Mountain Road, in the SE1/4 SW1/4 SE1/4 section 34, T. 1 N., R. 5 E.
RANGE IN CHARACTERISTICS: The mean annual soil temperature is estimated to range from 43 to 47 degrees F. These soils are usually moist and are dry for less than 45 consecutive days in all parts between depths of 4 and 12 inches. The solum has hue of 10YR or 7.5YR. The solum is 30 to 50 inches thick. Depth to bedrock or highly fractured bedrock commonly is more than 60 inches. Rock fragments range from 10 to 20 percent gravel and 5 to 20 percent cobbles in the A horizon and from 15 to 30 percent gravel, 15 to 40 percent cobbles, and 0 to 5 percent stones in the B and C horizons, increasing with increasing depth. Moist bulk density is 0.85 to 0.95 grams per cubic centimeter throughout.
The A horizon has hue of 10YR or 7.5YR, with value of 2 or 3 moist, 4 or 5 dry, and chroma of 2 or 3 moist and dry. It is medial silt loam or medial loam and is gravelly or cobbly. This horizon has moderate or strong granular or subangular blocky structure. It has an estimated acid oxalate extractable aluminum plus one-half iron of 1.0 to 3.0 percent and less than 2.0 cmol per kg fine earth of 1N KCL extractable aluminum. Organic matter is 6 to 12 percent.
The Bw horizon has hue of 10YR or 7.5YR with value of 3 or 4 moist, 4 through 6 dry, and chroma of 3 or 4 moist. It is loam or silt loam, has less than 18 percent clay and commonly is very cobbly. This horizon has weak or moderate subangular blocky structure.
The C horizon has hue of 10YR or 7.5YR with value of 3 or 4 moist, 4, 5 or 6 dry, and chroma of 3, 4, 5 or 6 moist and dry. It is very cobbly or extremely cobbly loam.
COMPETING SERIES: These are Fernwood and Tinker series. Fernwood soils are 20 to 40 inches deep to lithic bedrock. Tinker soils are 20 to 40 inches to a cemented or compacted C1 horizon and are moderately well drained.
GEOGRAPHIC SETTING: Zygore soils are on dissected mountainous areas at elevations of 1,500 to 3,000 feet. Slopes range from 5 to 90 percent. The soils formed in colluvium weathered from andesite and basalt mixed with volcanic ash. The climate is characterized by cool wet winters and warm moist summers. The mean annual precipitation is 70 to 100 inches. The mean annual temperature is 44 to 45 degrees F., the mean January temperature is 30 degrees F., the mean July temperature is 60 degrees F. The frost-free period is 45 to 110 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Aschoff and the Bull Run soils. These soils have mesic soil temperature and are at lower elevations or on associated south-facing slopes. Also, Bull Run soils lack rock fragments.
DRAINAGE AND PERMEABILITY: Well drained; moderate permeability.
USE AND VEGETATION: These soils are used for timber production, recreation and wildlife habitat. Native vegetation is western hemlock, Douglas fir, grand fir, red alder, western redcedar, vine maple, red huckleberry, salal, swordfern, Oregon oxalis, and forbs.
DISTRIBUTION AND EXTENT: Cascade Mountains in northwestern Oregon and S. W. Washington;MLRA 3, 6. The series is of moderate extent.
MLRA OFFICE RESPONSIBLE: Portland, Oregon
SERIES ESTABLISHED: Multnomah County, Oregon, 1977.
REMARKS: Classification changed 6/98 based on 1998 Keys to Soil Taxonomy. Competing series have not been revised.
Diagnostic horizons and features recognized in this pedon;
Umbric epipedon - from 3 to 22 inches (A1, A2, and Bw horizons)
Particle-size control section - from 13 to 43 inches (Bw, BC, and upper 6 inches of C horizon) with a weighted average of 46 percent rock fragments.
Andic feature - from 3 to 13 inches having a moist bulk density of 0.85 to 0.95 grams per cubic centimeter and estimated acid oxalate aluminum plus one-half iron of 1.0 to 3.0 percent, 15-bar moisture of 15 to 20 percent, phosphate retention of 75 to 85 percent, and volcanic glass content of 5 to 30 percent.
ADDITIONAL DATA ON ANDIC PROPERTIES NEEDED ON THIS SERIES TO CONFIRM CLASSIFICATION OF ANDIC SUBGROUP OR ANDISOL. CLASSIFICATION SHOULD BE SIMILAR TO THE MESIC COUNTERPART OF THIS SERIES CALLED ASCHOFF AND THE FRIGID, MODERATELY DEEP SERIES CALLED DOUGAN.