. Vegetation of Oregon and Washington. Botany Oregon Ecology; Botany Washington (State) Ecology. rise to a wide variety of soils. Well-developed soils are generally brown with loamy surface horizons and clay loam subsoils. The most widely distributed great soil group is the Reddish Brown Lateritic. These soils occupy low to moderate elevations throughout the province. Less common soils in drier locations include Sols Bruns Acides, Noncalcic Brown, and Western Brown Forest soils. On the higher peaks, Lithosol, Rock- land, and Podzol soils predominate. At lower elevations, soils formed under gra
. Vegetation of Oregon and Washington. Botany Oregon Ecology; Botany Washington (State) Ecology. rise to a wide variety of soils. Well-developed soils are generally brown with loamy surface horizons and clay loam subsoils. The most widely distributed great soil group is the Reddish Brown Lateritic. These soils occupy low to moderate elevations throughout the province. Less common soils in drier locations include Sols Bruns Acides, Noncalcic Brown, and Western Brown Forest soils. On the higher peaks, Lithosol, Rock- land, and Podzol soils predominate. At lower elevations, soils formed under grassland vege- tation fall within the Grumusol and Prairie great soil groups. These soils are extensive in central Jackson County. Alluvial and Humic Gley soils occupy low-lying depressions and scattered areas along principal streams. Willamette Valley Province The Willamette Valley is a broad structural depression oriented north-south and situated in Oregon between the Coast Ranges on the west and the Cascade Range on the east. The valley is approximately 200 kilometers long, extending from the Columbia River to Cot- tage Grove where the two mountain ranges converge. Valley width generally ranges from 30 to 50 kilometers. Topographically, the val- ley is characterized by broad alluvial flats sep- arated by groups of low hills (, Portland, Chehalem, Eola, Salem, and Coburg Hills) (fig. 6). The valley floor has a very gentle, north-facing slope; elevation increases from 50 meters at Salem to only 129 meters at Eugene, 130 kilometers to the south. As a result, the Willamette River is a sluggish stream with many meanders, especially from Oregon City southward. The Willamette Valley is bordered on the west by a variety of sedimentary and volcanic rocks of Eocene age. They include submarine pillow basalts, conglomerates, and tuffaceous sandstones and siltstones which are actually eastward extensions of Coast Ranges forma- tions. In the southern portion of the valley, these Eocene
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