. Vegetation of Oregon and Washington. Botany Oregon Ecology; Botany Washington (State) Ecology. pus densiflora, Arbutus menziesii, and Quer- cus kelloggii; and (3) understory shrubs such as Quercus chrysolepis, Berberis nervosa, Rhus diversiloba, and Rosa gymnocarpa. Ceanothus integerrimus and Arctostaphylos viscida characterized the understory on driest sites. Gratkowski11 indicates the major coni- fers on the valley floor in this area are Pinus ponderosa and Libocedrus decurrens with Arctostaphylos viscida and Ceanothus cuneatus as understory dominants. In the floristically poorer eastern S
. Vegetation of Oregon and Washington. Botany Oregon Ecology; Botany Washington (State) Ecology. pus densiflora, Arbutus menziesii, and Quer- cus kelloggii; and (3) understory shrubs such as Quercus chrysolepis, Berberis nervosa, Rhus diversiloba, and Rosa gymnocarpa. Ceanothus integerrimus and Arctostaphylos viscida characterized the understory on driest sites. Gratkowski11 indicates the major coni- fers on the valley floor in this area are Pinus ponderosa and Libocedrus decurrens with Arctostaphylos viscida and Ceanothus cuneatus as understory dominants. In the floristically poorer eastern Siskiyou Mountains, Waring (1969) recognized a Pond- erosa Pine Type as the most xeric of his conif- erous types. Pseudotsuga menziesii, Arbutus menziesii, and, sometimes, Abies concolor were associated with the Pinus ponderosa. Arctostaphylos patula, A. viscida, A. nevaden- sis, Achillea millefolium var. lanulosum, Soli- dago canadensis, Apocynum pumilum, and Lupinus spp. typified the understory. Grasslands. — There are extensive areas of grassland in the Interior Valley Zone. Some of these were created by settlers and latter-day farmers through clearing or burning or both (fig. 71). Other grasslands occupy sites that appear incapable of supporting tree growth, , grass balds associated with Grumusols or lithosolic, extremely xeric, southerly exposed slopes. Almost all grassland areas (and Quer- cus savanna) have been heavily grazed by domestic livestock — cattle, sheep, or angora goats —and are extensively used as unim- proved pastureland today (fig. 72). The nature of the original grassland com- munities is strictly conjectural, since grazing and introduction of alien species have altered all stands to some degree. Turner (1969) has suggested these grasslands probably looked similar to parts of the "California annual-type grassland" with Danthonia californica and Stipa spp. typical dominant species. Habeck (1961) provided a list of grasses which may have be
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