LOCATION LURNICK OREstablished Series
TAXONOMIC CLASS: Clayey-skeletal, isotic Andic Dystrocryepts
TYPICAL PEDON: Lurnick gravelly medial loam, woodland. (Colors are for moist soil unless otherwise noted.)
Oi--0 to 1 inch; organic litter of needles, leaves and twigs.
A1--1 to 5 inches; very dark grayish brown (10YR 3/2) gravelly medial loam, grayish brown (10YR 5/2) dry; moderate fine and very fine granular structure; soft, very friable, slightly sticky and slightly plastic; weakly smeary; many fine and medium roots; many very fine irregular pores; 35 percent fine concretions and gravel; strongly acid (pH5.2); clear smooth boundary.
A2--5 to 10 inches; dark brown (10YR 3/3) gravelly medial loam, grayish brown (10YR 5/2) dry; moderate fine and very fine subangular blocky structure; soft, very friable, slightly sticky and slightly plastic; weakly smeary; many fine and medium roots; many very fine tubular pores; 30 percent fine concretions and gravel; very strongly acid (pH 4.8); clear wavy boundary. (Combined thickness of the A horizon is 4 to 9 inches)
Bw1--10 to 16 inches; brown (10YR 4/3) gravelly silty clay loam, light yellowish brown (10YR 6/4) dry; moderate fine and medium subangular blocky structure; hard, firm, moderately sticky and moderately plastic; many fine and medium roots; many very fine tubular pores; 30 percent fine gravel; very strongly acid (pH 4.8); clear wavy boundary.
Bw2--16 to 22 inches; brown (10YR 4/3) very gravelly silty clay, light yellowish brown (10YR 6/4) dry; moderate fine and medium subangular blocky structure; hard, firm, moderately sticky and moderately plastic; many very fine, fine and medium roots; common very fine tubular pores; 45 percent fine and medium gravel; very strongly acid (pH 4.8); clear wavy boundary.
Bw3--22 to 31 inches; dark yellowish brown (10YR 4/4) very gravelly silty clay, very pale brown (10YR 7/4) dry; weak fine subangular blocky structure; hard, firm, very sticky and very plastic; few fine and medium roots; common very fine tubular pores; 60 percent fine and medium gravel; very strongly acid (pH 4.8); abrupt wavy boundary. (Combined thickness of the Bw horizon is 10 to 30 inches)
Cr--31 inches; yellowish brown (10YR 5/4) weakly cemented, partially weathered siltstone with a few thin intrusions of soil material in the interstices.
TYPE LOCATION: Polk County, Oregon; located about 2 miles northwest of Black Rock; in the SE1/4 NE1/4 section 16, T.8S., R.7W.; Laurel Mountain, OR 7.5 minute USGS quad; NAD 1927.
RANGE IN CHARACTERISTICS: The mean annual soil temperature is 42 to 47 degrees F., and the mean summer soil temperature is less than 47 degrees F. with an O horizon present. The soils are usually moist and are dry in the moisture control section less than 45 consecutive days during the summer following the summer solstice in most years. Depth to the paralithic contact and solum thickness ranges from 20 to 40 inches. The particle-size control section has 35 to 80 percent rock fragments, including both channer shaped fragments (shaly textural modifiers) and angular or subangular fragments (gravelly or cobbly textural modifiers). The particle-size control section has 35 to 50 percent clay (see Remarks) The solum is very strongly acid or strongly acid. Hue is 10YR or 7.5YR.
The A horizon has value of 3 or 4 moist, 5 or 6 dry and chroma of 2 to 4 moist, 2 to 4 dry. Texture of the fine-earth fraction is medial loam with 18 to 25 percent clay by field estimate. It has 10 to 35 percent gravel, 5 to 40 percent cobbles, and 0 to 5 percent stones. It has moist bulk density less than 1.0 g/cm3, phosphate retention of 75 to 95 percent, and acid oxalate extractable aluminum plus one-half iron of 1.0 to 2.0 percent.
The Bw1 horizon has value of 3 to 5 moist, 4 to 6 dry and chroma of 3 to 5 moist and dry. Texture of the fine-earth fraction is typically clay loam or silty clay loam with 27 to 40 percent clay. It has 15 to 55 percent gravel, 20 to 50 percent cobbles, 0 to 10 percent stones, 0 to 30 percent paragravel, and 0 to 10 percent paracobbles.
The Bw2 and Bw3 horizons have value of 4 to 6 moist, 5 to 7 dry and chroma of 3 to 6 moist and dry. Texture of the fine-earth fraction is typically silty clay loam or silty clay with 35 to 50 percent clay. It has 15 to 55 percent gravel, 30 to 50 percent cobbles, 0 to 10 percent stones, 0 to 30 percent paragravel, and 0 to 10 percent paracobbles.
The BC horizon, if present, has value of 4 to 6 moist, 5 to 7 dry and chroma of 4 to 8 moist or dry. Texture of the fine-earth fraction is typically silty clay loam or silty clay with 35 to 50 percent clay. It has 15 to 45 percent gravel, 30 to 50 percent cobbles, 0 to 10 percent stones, 0 to 30 percent paragravel, and 0 to 20 percent paracobbles.
COMPETING SERIES: There are no competing series.
GEOGRAPHIC SETTING: Lurnick soils occur on summits, ridgetops, shoulder slopes, and backslopes of mountains. Elevations are 1,800 to 4,100 feet. Slopes are 3 to 90 percent. The soils formed in fine textured residuum and colluvium weathered from siltstone, shale and sandstone of the Tyee and Flournoy Formations. The climate is characterized by cold wet winters and cool moist summers. The mean annual temperature is 41 to 45 degrees F. The mean January temperature is 31 degrees F. and the mean July temperature is 55 degrees F. The mean annual precipitation is 90 to 180 inches. The frost-free period is 60 to 110 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Cruiser, Luckiamute, Maryspeak(T), Mulkey, Valsetz and Yellowstone soils. All of these soils occur on mountains. Cruiser soils have andic soil properties, are deeper than 40 inches to bedrock, have hue of 5YR, and are medial. Luckiamute and Yellowstone soils are less than 20 inches deep to a lithic contact. Luckiamute soils are loamy-skeletal and have 18 to 35 percent clay in the particle-size control section. Maryspeak soils are sandy-skeletal and greater than 60 inches deep to bedrock. Mulkey soils are in a medial family and have andic soil properties. Valsetz soils are 20 to 40 inches deep to a lithic contact, have andic soil properties, and are medial-skeletal. Yellowstone soils have andic soil properties and are medial-skeletal.
DRAINAGE AND PERMEABILITY: Well drained; moderately slow permeability.
USE AND VEGETATION: The Lurnick soils are used mainly for timber production, recreation, wildlife habitat, and watersheds. The potential native vegetation is noble fir, Pacific silver fir, western hemlock, Douglas fir, vine maple, salal, Pacific rhododendron, western brackenfern, blue and red huckleberry, common beargrass and cascade Oregongrape.
DISTRIBUTION AND EXTENT: Central portion of the Coast Range Mountains in Oregon; MLRA 1. The series is of small extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Portland, Oregon
SERIES ESTABLISHED: Polk County, Oregon, 1977.
REMARKS: Diagnostic horizons and features recognized in this pedon include:
Ochric epipedon
Cambic horizon - from a depth of 10 to 31 inches (Bw1, Bw2, and Bw3 horizons).
Particle-size control section - from a depth of 10 to 31 inches (Bw1, Bw2, and Bw3 horizons).
Andic feature - from a depth of 1 to 10 inches (A1 and A2 horizons).
Paralithic feature - weakly cemented, partially weathered siltstone bedrock at a depth of 31 inches (Cr horizon).
The current lower elevational range for this series of 1,800 feet is considerably lower than that of the geographically associated soils (3,000 to 4,100 feet). Upon further investigation and field observations in Polk County, the elevation range is likely to be revised so as to be consistent with all the geographically associated soils.
The official type location is located in Polk County and is currently considered as clayey-skeletal. The modal pedon for the adjacent Benton County is loamy-skeletal (based on lab data of 2.5 X 15-bar water = 30 percent clay) and is recognized as a taxadjunct to the series. All associated soils both at the official type location and in Benton County have less than 35 percent clay in their particle-size control sections. In addition, there is a small extent of the Lurnick soil concept currently recognized and therefore, points to a need for further investigation as to the family particle-size class to use.
Classification revised 9/03 from clayey-skeletal, isotic Typic Dystrocryepts to clayey-skeletal, isotic Andic Dystrocryepts based on the Keys to Soil Taxonomy, 8th Edition and supporting lab data.
Depth to diagnostic horizons and features are measured from the top of the first mineral horizon.