on farmlands, woodlands, and prairies. It grows to large sizes but is also found extensively as scrub forest. The best stands are in western Oregon and Washington-in the Cowlitz, Lewis, and Willamette River drainages-but stands or trees with substantial volume are found from British Columbia to central California. Dense dwarf or shrub stands of Oregon white oak, earlier identified as Quercus garryana var. breweri, and other stands previously identified as Q. garryana var. semota, form dense thickets over large areas in California (29,35,57,76,81). Similar dwarf or shrub forms grow to a more limited extent on severe sites in the rest of its range (57,79).
Oregon white oak is recognized as a distinct forest cover type (Society of American Foresters Type 233) and is listed as an associated species in at least eight other forest cover types (20): Pacific Douglas-Fir (Type 229), Port Orford-Cedar (Type 231), Redwood (Type 232), Douglas-Fir-Tanoak-Pacific Madrone (Type 234), Pacific Ponderosa Pine (Type 245), California Black Oak (Type 246), Knobcone Pine (Type 248), and Blue Oak-Digger Pine (Type 250). Its prominence and occurrence in these types, as well as in several others for which it is not specifically listed, vary widely.
Plant communities have been identified in parts of the Oregon white oak type. A Garry oak community of two types (oak parkland and scrub oak-rock outcrop), a Garry oak-arbutus, and an arbutus-Garry oak community have been defined in the Victoria, BC, metropolitan area (42). Four communities, ranked in order from wettest to driest, have been identified in white oak forests of the Willamette Valley: Oregon white oak/California hazel/western swordfern, Oregon white oak/sweet cherry/common snowberry, Oregon white oak/Saskatoon serviceberry/common snowberry, and Oregon white oak/Pacific poison-oak (73). These communities are floristically similar, being differentiated primarily by the relative coverage and frequency of a few shrub species. Five Oregon white oak communities identified in the North Umpqua Valley of Oregon were similar to the xeric Oregon white oak/Pacific poison-oak association of the Willamette Valley; a sixth was a riparian association dominated by Oregon white oak and Oregon ash (Fraxinus latifolia) (62). In California, four communities dominated by Oregon white oak were found in the Bald Hills woodlands of Redwood National Park (70) and three communities dominated by Oregon white oak or related hybrids were identified in a limited area on Bennett Mountain (75). The shin oak brush association, largely composed of Oregon white oak, is a distinctive plant community in Kern and Los Angeles Counties (76).
The composition of Oregon white oak communities varies greatly because of differences in soil, topography, and climate, and in fire and grazing histories. Because of proximity to farmlands, many communities include introduced forbs and grasses. Pacific poison-oak (Rhus diuersiloba) and common snowberry (Symphoricarpos albus) are probably the most widespread and characteristic shrub associates.
Species often found with Oregon white oak are listed in table 1. The listing is not exhaustive; it just indicates the great variety of common associates. Species associated with Oregon white oak in chaparral communities and on serpentine soils are listed in other sources (15,16,79).
|Abies grandis||Amorpha californica||Agropyron spicatum|
|Acer circinatum||Arctostaphylos columbiana||Agrostis spp.|
|Acer glabrum||Arctostaphylos manzanita||Allium spp.|
|Acer macrophyllum||Arctostaphylos media||Athysanus pusillus|
|Aesculus californica||Arctostaphylos uva-ursi||Avena barbata|
|Alnus rubra||Berberis aquifolium||Balsamorhiza deltoides|
|Amelanchier alnifolia||Berberis nervosa||Brodiaea spp.|
|Arbutus menziesii||Ceanothus cuneatus||Bromus spp.|
|Betula occidentalis||Ceanothus integerrimus||Camassia spp.|
|Castanopsis chrysophylla||Ceanothus velutinus||Carduus pycnocephalus|
|Cercocarpus betuloides||Cornus stolonifera||Carex spp.|
|Cornus nuttallii||Crataegus oxyacantha||Chlorogalum pomeridianum|
|Corylus cor