. Vegetation-soil units in the central Oregon juniper zone. Botany Oregon Ecology; Plant-soil relationships Oregon; Junipers Oregon. The Area Physiography The central Oregon juniper zone includes approximately 108,000 acres in Crook, Des- chutes, and Jefferson Counties where western juniper is a major component of the vegetation. This area is one of three physiographic sub- divisions of the Northwest representative of the pinyon-juniper zone in the Western United States. -Although no pinyon pines occur in the Cregon area, other features are similar to the broad parent zone. Soils are generally
. Vegetation-soil units in the central Oregon juniper zone. Botany Oregon Ecology; Plant-soil relationships Oregon; Junipers Oregon. The Area Physiography The central Oregon juniper zone includes approximately 108,000 acres in Crook, Des- chutes, and Jefferson Counties where western juniper is a major component of the vegetation. This area is one of three physiographic sub- divisions of the Northwest representative of the pinyon-juniper zone in the Western United States. -Although no pinyon pines occur in the Cregon area, other features are similar to the broad parent zone. Soils are generally shallow and stony. The climate is characterized by high summer temperatures, cool winters, high winds, low relative humidity, and low annual precipitation, In the study area, the zone grades to the ponderosa pine zone, where mois- ture is more effective, and to the sagebrush or grassland zones of less effective moisture. The three physiographic ^subdivisions are based on soil parent materials (fig. 1). In the study area, soils are derived from wind-laid and mixed igneous and pumice sands or, where these materials do not comprise the actual par- ent material, pumice is scattered throughout the soil profile. Where pumice is present, but not as a major soil forming material, it is found mostly in the A horizon. The pumice probably originated from Mount Mazama (site of Crater Lake), 100 miles southwest of Bend, when the volcano exploded approximately 8,000 years ago (Williams 1942). Some pumice may have originated from more recent eruptions of New- berry Crater (site of Paulina and East Lakes), located 25 miles south of Bend. The igneous sands, mostly from andesite, rhyolite, or basalt, were transported from dry lakebeds by south- westerly winds. A second physiographic subdivision of the Oregon juniper zone has soils derived mostly Figure 1 .—Distribution of the physiographic sub- divisions of the juniper zone in eastern 2. Please note that these images are extracted fr
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