LOCATION LASTANCE OREstablished Series
TAXONOMIC CLASS: Loamy-skeletal, isotic Typic Haplocryods
TYPICAL PEDON: Lastance stony fine sandy loam - forested. (Colors are for moist soil unless otherwise noted.)
0i--2 inches to 1 inch; needles, twigs, cones, leaves, etc.
0e--1 inch to 0; black (10YR 2/1) decomposed organic matter; many fine, medium and coarse roots; extremely acid (pH 3.8); abrupt wavy boundary. (0 to 5 inches thick)
E--0 to 1 inch; gray (10YR 5/1) stony fine sandy loam, light gray (10YR 6/1) dry; massive; soft, very friable, nonsticky and slightly plastic; 20 percent gravel, 5 percent cobbles, and 5 percent stones; many fine medium and coarse roots; many fine and very fine irregular pores; extremely acid (pH 4.0); abrupt wavy boundary. (1/2 to 3 inches thick)
Bs1--1 to 2 inches; dusky red (2.5YR 3/2) gravelly fine sandy loam, reddish brown (5YR 4/4) dry; massive; slightly hard, firm, nonsticky and slightly plastic; 20 percent gravel, 5 percent cobbles, and 5 percent stones, many fine, medium and coarse roots; many fine and very fine irregular pores; strongly acid (pH 5.0); abrupt wavy boundary. (1/2 to 2 inches thick)
Bs2--2 to 12 inches; dark brown (7.5YR 3/4), variegated with gray (10YR 5/1), dark brown (10YR 4/3), and brown (7.5YR 4/4) very cobbly fine sandy loam, brown (7.5YR 5/4) dry and crushed; weak fine and very fine subangular blocky structure; soft, very friable, nonsticky and slightly plastic; 20 percent cobbles, 35 percent gravel, and 2 percent stones; many fine medium and coarse roots; many very fine and fine irregular pores; strongly acid (pH 5.2); gradual wavy boundary. (8 to 15 inches thick)
C--12 to 60 inches; brown (7.5YR 4/4) extremely gravelly fine sandy loam, brown (10YR 5/4) dry and crushed; massive; soft, very friable, nonsticky and slightly plastic; 50 percent gravel, 25 percent cobbles, and 5 percent stones; common fine medium and coarse roots; many very fine and fine irregular pores; strongly acid (pH 5.5).
TYPE LOCATION: Multnomah County, Oregon; 50 feet south of the Bull Run River road, 1/4 mile west of the junction the with spur road to Bull Run Lake; SE1/4SW1/4 section 20, T. 1 S., R. 8 E. W. M.
RANGE IN CHARACTERISTICS: The mean annual soil temperature is 40 to 47 degrees F. The mean summer soil temperature is less than 47 degrees F. with an O horizon and full shade. The soils have a udic moisture regime but have a short dry period of less than 45 consecutive days during the summer. Depth to bedrock is 60 inches or more. Thickness of the solum ranges from 9 to 20 inches. The 10- to 40-inch control section is fine sandy loam with less than 10 percent clay and averages 35 to 80 percent rock fragments, dominantly gravel. The soils are extremely or very strongly acid in the E horizon, very strongly or strongly acid in the Bs1 horizon and strongly or medium acid in the Bs2 and C horizon.
The E horizon has value of 4 or 5 moist, 6 or 7 dry and chroma of 1 or less. It is loamy fine sand, fine sandy loam or silt loam. Stones cover up to 0.1 percent of the surface. Rock fragments range from 25 to 40 percent by volume.
The Bs horizon has hue of 5YR or 2.5YR in the upper part and 10YR, 7.5YR, or 5YR in the lower part, value of 3 or 4 moist, 4 or 5 dry, and chroma of 2 through 4 moist and dry. The upper part ranges from firm to very firm and the lower part from friable to very friable. Rock fragments range from 25 to 60 percent by volume.
The C horizon has hue of 10YR or 7.5YR, value of 5 or 6 dry and chroma of 3 or 4 moist and dry. It has 50 to 85 percent rock fragments, dominantly gravel.
COMPETING SERIES: These are the Conto, Dinzer, Homestead, Mt. Hood, and Tenex series. Dinzer soils have an intermittent E horizon less than one inch thick and have a very friable or friable Bs horizon in hue yellower than 5YR. Homestead and Tenex soils have a drier moisture regime than udic. Homestead soils have a thin loess mantle. Mt. Hood soils lack an upper spodic horizon having hue as red as 5YR or 2.5YR throughout and lack firm or very firm consistence. Conto soils lack coarse fragments in the Bs horizon.
GEOGRAPHIC SETTING: Lastance soils are on hillsides in glaciated valleys of the Cascade Mountains at elevations of 3,000 to 4,800 feet. Slope gradients range from 5 to 60 percent. The soils formed in colluvium and glacial till weathered mostly from olivine andesites and olivine-bearing basalt rocks of the Cascade andesite formation mixed with volcanic ash. The climate is humid and cool. The mean annual precipitation is 90 to 145 inches. The mean annual temperature is 38 to 45 degrees F., the mean January temperature is 29 degrees F., the mean July temperature is 57 degrees F. The frost-free season is less than 30 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the competing Dinzer soils and the Kinzel and Oneonta soils. Kinzel and Oneonta soils have umbric epipedons and lack a spodic horizon. DRAINAGE AND PERMEABILITY: Well drained; slow to rapid runoff; moderately rapid permeability.
USE AND VEGETATION: Timber production, recreation and wildlife. Vegetation is Douglas-fir, mountain hemlock, silver fir, noble fir, western redcedar, huckleberry, Pacific rhododendron and common beargrass.
DISTRIBUTION AND EXTENT: Cascade Mountains of northern Oregon. The series is of moderate extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Portland, Oregon
SERIES ESTABLISHED: Multnomah County, Oregon (Bull Run - Sandy Area), 1975.
ADDITIONAL DATA: Characterization data on one pedon (FS62Oreg-045-14 (1-4)) by Oregon State University (Unpublished).
NATIONAL COOPERATIVE SOIL SURVEY USA
NSTH 17, RECLASSIFICATION ONLY, 3/95