William I. Stein
Oregon white oak (Quercus garryana), a broadleaved deciduous hardwood common inland along the Pacific Coast, has the longest north-south distribution among western oaks-from Vancouver Island, British Columbia, to southern California. It is the only native oak in British Columbia and Washington and the principal one in Oregon. Though commonly known as Garry oak in British Columbia, elsewhere it is usually called white oak, post oak, Oregon oak, Brewer oak, or shin oak. Its scientific name was chosen by David Douglas to honor Nicholas Garry, secretary and later deputy governor of the Hudson Bay Company.
General: Oak Family (Fagaceae). Quercus garryana, a native deciduous tree up to 30 m tall throughout much of its range in the Pacific Northwest, has an open, rounded crown. However, in the southern part of its range, including interior California, it also is a shrub up to 5 m tall, which is treated as var. breweri (Engelm.) Jepson. The mature bark is brownish gray and shallowly fissured in a checker-like pattern. Leaves are oblong to obovate, 8-15 cm long, and deeply lobed (5-7 rounded lobes). The upper surfaces are shiny and dark green, but the lower surfaces are pale green. Like all oaks, Oregon oak is monoecious and wind-pollinated. The acorn cups are composed of thick, tubercled scales. The one-seeded nuts are 2-3 cm long, ovoid, and mature in one year. Flowering takes place from March to May. Fruits mature between August and November. Color images, line drawings, and a description can be found in Farrar (1995).
Oregon white oak, Garry oak, Brewer’s oak, chêne de Garry; three varieties are recognized for this species: Quercus garryana var. garryana, Quercus garryana var. breweri, and Quercus garryana var. semota
Regularity: Regularly occurring
Regularity: Regularly occurring
Oregon white oak is native to western North America. It occurs from Vancouver Island, British Columbia (49 Â°N latitude), to southern California (34 Â°N latitude) [102,128]. Oregon white oak occurs primarily west of the Cascade Range but populations are scattered east of the Cascade Range [63,64].
Distribution of varieties: Brewer's oak is found in the Siskiyou region of California and Oregon and may occur in the northern Sierra Nevada. The most widely distributed variety is Q. g. var. garryana, which occupies habitats from British Columbia south to possibly Los Angeles County. In the southernmost reaches, Q. g. var. garryana is restricted to riparian sites. Quercus garryana var. semota occupies western slopes of the Sierra Nevada and northern slopes of the Tehachapi Mountains, and reaches its northern limit in southern Oregon . Flora of North America provides a distributional map of Oregon white oak and its varieties.
Past and present distributions: Oregon white oak habitat loss is reported throughout its range. A 1998 Pacific Northwest Ecosystem Consortium cited in  indicated that Oregon white oak woodlands and savannahs in the Willamette Valley of Oregon have declined to less than 15% of their pre-European settlement extent. In British Columbia, comparisons of early survey records and current occurrence reports indicate that Oregon white oak habitat loss has exceeded 95%. Habitat loss is primarily a result of European settlers that suppressed fires, altered land use, and introduced nonnative species and heavy grazing .
In Oregon white oak's easternmost distributions, habitat protection and Oregon white oak conservation alternatives may be limited. Slightly more than 83% of Oregon white oak habitat is privately owned, and none is under permanent protection in southeastern Oregon and/or eastern California .
States or Provinces
Regional Distribution in the Western United States
This species can be found in the following regions of the western United States (according to the Bureau of Land Management classification of Physiographic Regions of the western United States):
BLM PHYSIOGRAPHIC REGIONS :
1 Northern Pacific Border
2 Cascade Mountains
3 Southern Pacific Border
4 Sierra Mountains
5 Columbia Plateau
In small tree and shrub sizes, Oregon white oak extends inland to just east of the Cascade Range, mainly in the Columbia River and Pit River drainages (29,50,67,68,71). It has a scattered distribution the entire length of the western Sierra Nevada south to the Tehachapi Mountains in Kern and northern Los Angeles Counties where it forms extensive brush fields at elevations up to 2290 m (7,500 ft) (29,76).
-The native range of Oregon white oak.
This species is known from California, Washington, Oregon, and British Columbia. For current distribution, please consult the Plant Profile page for this species on the PLANTS Web site.
Aboveground description: Oregon white oak is a deciduous tree or sometimes a shrub. Growth form can be affected by regional and site conditions. Oregon white oak may be 30 to 100 feet (8-30 m) tall with a solitary trunk or up to 20 feet (5 m) tall with many trunks [40,62,63,64]. In tree form, Oregon white oak's DBH is typically 24 to 40 inches (61-100 cm), although a DBH of 97 inches (250 cm) was reported in a review . Oregon white oak trunks have thick, furrowed, scaly bark [63,110]. A short, crooked, and sometimes creeping form is described in rocky habitats with shallow soils [60,110]. At high-elevation sites in eastern Oregon and Washington, a "shrubby" growth form is typical . A shrub form is also noted from the southernmost populations . Thilenius  described "forest-form" and "savannah-form" trees in Willamette Valley. Forest-form trees were fairly tall with ascending branches near the crown and a DBH often less than 24 inches (60 cm). These trees grew in closed-canopy woodlands with nearly 1,045 trees/ha. Savannah-form trees had DBH measurements often exceeding 3 feet (1 m), massive branches, and spreading crowns. These trees grew in open woodlands with 17 trees/ha.
Leaves are moderately to deeply lobed and measure up to 6 inches (15 cm) long. Generally there are 3 to 7 pinnate lobes. Margins are entire or with 2 to 3 teeth [40,59,63,110]. Occasionally, trees produce a second set of summer leaves . Male flowers are catkins that are produced on the current year's growth . Female flowers are solitary or in clusters and appear in the leaf axils of new twigs . Oregon white oak produces large acorns that measure 0.8 to 1.2 inches (2-3 cm) long and mature in a single growing season [40,106]. Five hundred years is the estimated Oregon white oak lifespan . Growth rates evaluated in an 80-year-old Oregon white oak-Douglas-fir stand in Oregon State's McDonald-Dunn Forest decreased by over half after the first 20 years of life. Overtopping by Douglas-fir may have affected growth .
Root systems of 27 Oregon white oak trees from 1.3 to 60.7 feet (0.4-18.5 m) tall and 3 to 95 years old were excavated from coarse-textured glacial outwash soils in Fort Lewis, Washington. Soils were 75% to 85% gravel at the C horizon (30 to <80 inches (70-<200 cm)). Total taproot length for seedlings (x=7 years), small trees (x=22 years), and large trees (x=93 years) was 38 inches (96 cm), 79.9 inches (203 cm), and 80.3 inches (204 cm), respectively. Taproots grew horizontally for at least part of their length and were highly bent once they reached the C horizon. Just one large tree had a taproot extending beyond 68.9 inches (175 cm) deep. Taproot dominance decreased with plant age. Seedlings and small trees have primary taproots and small-diameter lateral roots. Large tree taproots were tapered, and the shallow lateral roots were extensive and large .
|Varieties and hybrids: Brewer's oak is a spreading, clonal shrub up to 20 feet (5 m) tall with smooth bark. Leaves are 1 to 4 inches (3-9 cm) long, and acorns are less than 1 inch (3 cm) long [40,62,101,106]. Quercus garryana var. garryana is a tree that may reach 70 feet (20 m) tall with large leaves that measure 3 to 5.5 inches (7-14 cm) long [40,62]. The description of Q. g. var. semota is much like that of Brewer's oak, but acorns are typically larger [40,101]. Epling's oak, Howell's oak, and Q. Ã subconvexa are described in .|
|Brewer's oak. Â© Michael Charters www.calflora.net|
Puget Lowland Forests Habitat
Cope's giant salamander is found in the Puget lowland forests along with several other western North America ecoregions. The Puget lowland forests occupy a north-south topographic depression between the Olympic Peninsula and western slopes of the Cascade Mountains, extending from north of the Canadian border to the lower Columbia River along the Oregon border. The portion of this forest ecoregion within British Columbia includes the Fraser Valley lowlands, the coastal lowlands locally known as the Sunshine Coast and several of the Gulf Islands. This ecoregion is within the Nearctic Realm and classified as part of the Temperate Coniferous Forests biome.
The Puget lowland forests have a Mediterranean-like climate, with warm, dry summers, and mild wet winters. The mean annual temperature is 9°C, the mean summer temperature is 15°C, and the mean winter temperature is 3.5°C. Annual precipitation averages 800 to 900 millimeters (mm) but may be as great as 1530 mm. Only a small percentage of this precipitation falls as snow. However, annual rainfall on the San Juan Islands can be as low as 460 mm, due to rain-shadow effects caused by the Olympic Mountains. This local rain shadow effect results in some of the driest sites encountered in the region. Varied topography on these hilly islands results in a diverse assemblage of plant communities arranged along orographically defiined moisture gradients. Open grasslands with widely scattered trees dominate the exposed southern aspects of the islands, while moister dense forests occur on northern sheltered slopes characterized by Western red cedar (Thuja plicata), Grand fir (Abies grandis), and Sword fern (Polystichum munitum) communities.
There are only a small number of amphibian taxa in the Puget lowland forests, namely: Cope's giant salamander (Dicamptodon copei); Monterey ensatina (Ensatina eschscholtzii); Long-toed salamander (Ambystoma macrodactylum); Western redback salamander (Plethodon vehiculum); Northwestern salamander (Ambystoma gracile); Pacific chorus frog (Pseudacris regilla); Coastal giant salamander (Dicamptodon tenebrosus); Rough-skin newt (Taricha granulosa); the Vulnerable Spotted frog (Rana pretiosa); Tailed frog (Ascopus truei); and Northern red-legged frog (Rana aurora).
Likewise there are a small number of reptilian taxa within the ecoregion: Common garter snake (Thamnophis sirtalis); Western terrestrial garter snake (Thamnophis sirtalis); Northern alligator lizard (Elgaria coerulea); Western fence lizard (Sceloporus occidentalis); Northwestern garter snake (Thamnophis ordinoides); Sharp-tailed snake (Contia tenuis); Yellow-bellied racer (Coluber constrictor); and Western pond turtle (Clemmys marmorata).
There are numberous mammalian taxa present in the Puget lowland forests. A small sample of these are:Creeping vole (Microtus oregoni), Raccoon (Procyon lotor), Southern sea otter (Enhydra lutris), Mink (Mustela vison), Coyote (Canis latrans), Black-tailed deer (Odocoileus hemionus), Pallid bat (Antrozous pallidus), and Harbour seal (Phoca vitulina).
A rich assortment of bird species present in this ecoregion, including the Near Threatened Spotted owl (Strix occidentalis), Turkey vulture (Cathartes aura), Bald eagle (Haliaeetus leucocephalus), Blue grouse (Dendragapus obscurus), as well as a gamut of seabirds, numerous shorebirds and waterfowl.
Climate: Oregon white oak's westernmost habitats experience more mild, maritime climates than those farther east. Throughout Oregon white oak's range, low January temperatures typically range from 13 to 50 Â°F (-11 to 10 Â°C), and high July temperatures are often 60 to 84 Â°F (16-29 Â°C). Summer droughts are moderate to extreme, and annual precipitation ranges from 10 to 100 inches (250-2,500 mm). Oregon white oak trees are somewhat resistant to snow and ice damage .
California: Warm summers, freezing winter temperatures, and annual precipitation ranges of 20 to 50 inches (510-1,300 mm) are reported in Oregon white oak habitats in California .
Oregon: Oregon white oak woodlands in central Oregon occupy sites receiving 12 to 59 inches (300-1,500 mm) of precipitation/year . In southwestern Oregon, the Oregon white oak-Douglas-fir/blue wildrye vegetation type receives an average of 46 inches (1,160 mm) of precipitation/year and 5.5 inches (140 mm) in the dry season from May to September. Oregon white oak/birchleaf mountain-mahogany vegetation receives the least average amount of dry season precipitation1.6 inches (40 mm)/dry season .
The climate is mild in the Willamette Valley. Annual precipitation averages about 40 inches (1,000 mm), and most comes from November to May. Snow is rarely present for more than a few weeks. From June to September, conditions are dry. Winter temperatures rarely drop below 15 Â°F (-9.4 Â°C), and summer temperatures average 70 Â°F (21 Â°C). Mean spring and fall temperatures average 50 Â°F (10 Â°C) and 54 Â°F (12 Â°C), respectively [52,139]. One-year-old Oregon white oak stems collected from mature trees near Corvallis, Oregon, had a freezing resistance, defined as the lowest temperature at which no injury was sustained, of -4 Â°F (-20 Â°C). The freezing resistance of buds was 5 Â°F (-15 Â°C) .
Washington: In Washington's Wenatchee National Forest, Oregon white oak woodlands occupy some of the hottest and driest areas, where less than 20 inches (500 mm) of precipitation/year is common .
British Columbia: The climate in Oregon white oak habitats of British Columbia is described as maritime to submaritime, dry summer, cool mesothermal. Characteristic of this climate is an average temperature in the warmest month of less than 72 Â°F (22 Â°C), and less than 1.2 inches (30 mm) of precipitation in the driest summer month . On southern Vancouver Island, Oregon white oak habitats receive 24 to 47 inches (600-1,200 mm) of precipitation per year .Elevation:
Elevation tolerances for Oregon white oak and varieties
|Variety, if applicable||California||Entire range|
|1,000-5,000 [62,101,106]||0-3,900 , up to 7,500 in southernmost range |
|Brewer's oak||2,000-6,200 [62,101]||2,000-6,200 [40,106]|
|Q. g. var. garryana||980-5,900 ||0-5,900 [40,62]|
|Q. g. var. semota||2,500-5,000 ||2,500-5,900 [40,101]|
In Castle Crags State Park, the Oregon white oak/cheatgrass plant association occurs on cobbly alluvial soils . In the northern California Coast Ranges, Oregon white oak occurs on well-drained, slightly acidic loams . Nutrients in the top 3 feet (1 m) of soil from Oregon white oak and Brewer's oak woodlands in California's Humboldt and Shasta counties is provided in .
Oregon white oak woodlands in the Willamette Valley occur on well-drained, moderately deep, acidic soils of igneous, alluvial, or sedimentary origin . Quercus garryana var. garryana in southwestern Oregon grew on serpentine and nonserpentine alluvial soils; however, the site with the greatest concentrations of serpentine elements also supported Brewer's oak. Soil fertility was lower but Oregon white oak ectomycorrhizal diversity was higher on serpentine than alluvial soils .
In British Columbia, Oregon white oak is indicative of very dry (moisture deficit 3.5-5 months of year) to moderately dry soils (moisture deficit 1.5-3.5 months) . On southern Vancouver Island, Oregon white oak habitats have Sombric Brunisol soils with deep, dark surface horizons and bedrock layers at 20- to 30-inch (40-80 cm) depths .
Key Plant Community Associations
Oregon white oak is a dominant species in the following vegetation types and plant
forest chaparral with Brewer's oak and "scrubby" Oregon white oak
Bald Hills woodlands with tree-form Oregon white oak in the North Coast Ranges 
Oregon oak woodland in Coast Ranges
mixed north slope cismontane woodland in the valleys and lower slopes of the Klamath and North
Coast ranges 
Oregon white oak woodland vegetation type in north coast areas 
Oregon white oak/common snowberry (Symphoricarpos albus) in Bald
Hills of Redwood National Park
Oregon white oak/orchardgrass (Dactylis glomerata) in Bald Hills of Redwood National Park
Oregon white oak/cheatgrass (Bromus tectorum) plant association in
Shasta County's Castle Crags State Park 
Oak brush vegetation in Kern, Tulare, Butte and Shasta counties, dominated by
Q. g. var. semota 
Douglas-fir (Pseudotsuga menziesii)-Oregon white oak/poison-oak-western sword fern
((Toxicodendron diversilobum-Polystichum munitum) in the interior valleys of the Umpqua River basin 
Douglas-fir-Oregon white oak/poison-oak on the Tiller Ranger District in the southern
Cascade Range 
Oregon white oak-Douglas-fir/sheep fescue (Festuca ovina)
Oregon white oak-Douglas-fir/blue wildrye (Elymus glaucus) in the Umpqua and/or Rogue
river watersheds 
Oregon ash (Fraxinus latifolia)-Oregon white oak/common snowberry on the Muddy Creek floodplain in
northwestern Oregon's Finley Wildlife Refuge 
Oregon white oak-Pacific madrone (Arbutus menziesii)/poison-oak/bristly dogstail
Oregon white oak-Oregon ash/sweetbriar rose/common rush (Rosa eglanteria/Juncus effusus) within the
interior valleys of the Umpqua
River basin 
Oregon white oak/California hazelnut (Corylus cornuta var. californica)/western sword fern
on mesic sites in the Willamette Valley
Oregon white oak/sweet cherry (Prunus avium)/common snowberry in the Willamette
Oregon white oak-birchleaf mountain-mahogany (Cercocarpus montanus var. glaber)
in the Umpqua and/or Rogue river watersheds 
Oregon white oak/Scotch broom/creeping bentgrass (Cytisus scoparius/Agrostis stolonifera)
in the Myrtle Island Research Natural Area 
Oregon white oak/Saskatoon serviceberry (Amelanchier alnifolia)/common snowberry in
the Willamette Valley 
Oregon white oak/poison-oak/medusahead (Taeniatherum caput-medusae)-bristly dogstail
Oregon white oak/poison-oak/bristly dogstail grass
Oregon white oak/poison-oak/orchardgrass
within the Interior Valleys of the Umpqua River Basin 
Oregon white oak/poison-oak on xeric sites in the Willamette Valley 
Oregon white oak/woods strawberry (Fragaria vesca) on Tiller and Steamboat Ranger Districts in
the southern Cascade Range 
Oregon white oak/California brome (Bromus carinatus)
Oregon white oak/bristly dogstail grass in the Umpqua and/or Rogue River watersheds 
westside oak woodlands and dry Douglas-fir forests in the Willamette
Valley, Puget lowlands, and Klamath Mountains
ponderosa pine (Pinus ponderosa) forests and woodlands on eastern
slopes of the Cascade Range in eastern Oregon and Washington 
Oregon white oak/beaked hazelnut (Corylus cornuta)-common snowberry
Oregon white oak/bluebunch wheatgrass (Pseudoroegneria spicata)
Oregon white oak/pinegrass-elk sedge (Calamagrostis rubescens-Carex geyeri) in
the Wenatchee National Forest 
Oregon white oak/oceanspray (Holodiscus discolor) 
Oregon white oak/pink honeysuckle (Lonicera hispidula)
Oregon white oak/large camas (Camassia leichtlinii)
Oregon white oak/broadleaf stonecrop (Sedum spathulifolium)
Oregon white oak/common chickweed (Stellaria media) 
Oregon white oak/dicranum moss-shortspur seablush (Dicranum scoparium-Plectritis congesta)
Oregon white oak/rhacomitrium-Wallace's spikemoss (Rhacomitrium canescens-Selaginella wallacei)
Oregon white oak/Sierra pea (Lathyrus nevadensis)
Oregon white oak/California brome
Oregon white oak/blue wildrye
Oregon white oak/long-stolon sedge (Carex inops)
Oregon white oak/ripgut brome (Bromus diandrus ssp. rigidus)
Oregon white oak/poverty brome (B. sterilis) 
is a dominant species in the following vegetation types of California:
Epling's oak/spreading hedgeparsley (Torilis arvensis)
Epling's oak/California fescue (Festuca californica) on Bennett
Mountain in Sonoma County 
Habitat: Rangeland Cover Types
This species is known to occur in association with the following Rangeland Cover Types (as classified by the Society for Range Management, SRM):
More info for the term: cover
SRM (RANGELAND) COVER TYPES :
101 Bluebunch wheatgrass
109 Ponderosa pine shrubland
110 Ponderosa pine-grassland
201 Blue oak woodland
202 Coast live oak woodland
203 Riparian woodland
207 Scrub oak mixed chaparral
208 Ceanothus mixed chaparral
209 Montane shrubland
412 Juniper-pinyon woodland
416 True mountain-mahogany
Habitat: Cover Types
This species is known to occur in association with the following cover types (as classified by the Society of American Foresters):
More info for the term: cover
SAF COVER TYPES :
207 Red fir
210 Interior Douglas-fir
211 White fir
213 Grand fir
220 Rocky Mountain juniper
221 Red alder
229 Pacific Douglas-fir
230 Douglas-fir-western hemlock
233 Oregon white oak
234 Douglas-fir-tanoak-Pacific madrone
238 Western juniper
243 Sierra Nevada mixed conifer
244 Pacific ponderosa pine-Douglas-fir
245 Pacific ponderosa pine
246 California black oak
248 Knobcone pine
249 Canyon live oak
250 Blue oak-foothills pine
255 California coast live oak
Habitat: Plant Associations
This species is known to occur in association with the following plant community types (as classified by Küchler 1964):
More info for the term: shrub
KUCHLER  PLANT ASSOCIATIONS:
K002 Cedar-hemlock-Douglas-fir forest
K005 Mixed conifer forest
K006 Redwood forest
K007 Red fir forest
K009 Pine-cypress forest
K010 Ponderosa shrub forest
K011 Western ponderosa forest
K012 Douglas-fir forest
K014 Grand fir-Douglas-fir forest
K024 Juniper steppe woodland
K025 Alder-ash forest
K026 Oregon oakwoods
K028 Mosaic of K002 and K026
K029 California mixed evergreen forest
K030 California oakwoods
K034 Montane chaparral
This species is known to occur in the following ecosystem types (as named by the U.S. Forest Service in their Forest and Range Ecosystem [FRES] Type classification):
FRES21 Ponderosa pine
FRES28 Western hardwoods
FRES34 Chaparral-mountain shrub
FRES36 Mountain grasslands
Soils and Topography
Oregon white oak grows on soils of at least four orders: Alfisols, Inceptisols, Mollisols, and Ultisols. Specific soil series include Hugo and McMahon in coastal northern California and Goulding near Santa Rosa (75,78). In Oregon's Willamette Valley, Oregon white oak is found on soils derived from alluvial deposits (poorly drained gray brown Amity and Dayton series), sedimentary rocks (deep, welldrained brown Steiwer, Carlton, Peavine, Bellpine, Melbourne, and Willakenzie series), and basic igneous rocks (brown or reddish, moderately deep, well-drained Nekia, Dixonville, and Olympic series) (22,38,67,73). A subsurface clay layer that restricts water penetration is characteristic of soils in most of these series. White oak stands near Dufur in eastern Oregon grow in soils derived from basalt and andesite (32); in southern Oregon, they grow in soils derived from andesite, granite, and serpentine (79). On the southeastern tip of Vancouver Island, BC, seven soils supporting a vegetational sequence of grass, Oregon white oak, and Douglas-fir were gravelly loams or gravelly sandy loams that developed on young, nonhomogeneous parent materials (11).
Soils under Oregon white oak stands are generally acidic, ranging in pH from 4.8 to 5.9 (11,75,78). Bulk densities ranging from 0.61 to 1.45 have been measured (73,78). Many white oak stands grow on gentle topography; only one-fourth of those examined in the Willamette Valley were on slopes greater than 30 percent (73).
Average annual precipitation ranges from 170 mm (6.7 in) at Ellensburg, WA, east of the Cascades to 2630 mm (103.5 in) at Cougar, WA, west of the Cascades. Precipitation at the southern end of the range of Oregon white oak (Tehachapi) averages 270 mm (10.6 in), similar to that at northerly locations east of the Cascades-Ellensburg, Yakima, and Goldendale in Washington and The Dalles and Dufur in Oregon. Average annual snowfall ranges from little, if any, at several locations to 417 cm (164 in) at Mineral in Tehama County, CA. Average precipitation in the growing season (April through September) ranges from 30 mm (1.2 in) at Tehachapi, CA, and Ellensburg, WA, to 630 mm (24.8 in) at Cougar, WA. Length of average frost-free season (above 0° C; 32° F) ranges from 63 days at Burney in Shasta County, CA, to 282 days at Victoria, BC.
Oregon white oak is typically found on rocky slopes or valleys, including floodplains, at elevations below 1500 meters. The species has a broad tolerance of soil types and has adapted to thin soils in rocky terrain as well as deep well developed sandy loams in valley settings. Most often it thrives in areas with rainfall exceeds 70 centimeters per annum.
Where sustained fire suppression strategies prevail, Douglas fir will encroach, and eventually dominate, mixeed oak wooodlands where Oregon white oak is a dominant or sub-dominant tree.
Adaptation: Oregon oak is best developed as a tree on slopes and valleys below 1500 m where annual rainfall exceeds 30 inches. The range in climate is considerable, extending from the relatively cool, moist Fraser Valley of British Columbia to the summer-dry Coast Ranges north of San Francisco and the foothills of the Sierra Nevada in California. Oregon oak takes the form of a shrub on nutrient-poor soils (e.g., serpentine) and drier sites, often forming clonal thickets. It is tolerant of freezing conditions and also has a broad tolerance of substrates, which vary from rocky, thin soils of ridges to the deep loams and clays of valley bottoms. Common associates in mixed forests include madrone, Douglas fir, tanbark oak, and yellow pines. In the coastal mountains and in the absence of fire, Douglas fir gradually replaces Oregon oak. Throughout much of its range, Oregon oak reproduces extensively by basal sprouts, which often develop after fires. Thus, Oregon Oak is often associated with local grasslands maintained by fire. In some areas seedlings develop into multi-stemmed plants, which may live up to 10 years, until a single shoot becomes dominant. Like most oaks, Oregon oak has an obligate relationship with mycorrhizal fungi, which provide additional moisture and nutrients.
Seed Preparation: Oak seeds do not store well and consequently seeds should be planted soon after maturity. Nuts are considered ripe when they separate freely from the acorn cap and fall from the tree. Care should be taken to collect local fruits, because they may be adapted to local environmental conditions. Viable nuts may be green to brown, and have unblemished walls. Nuts with discoloration or sticky exudates, and small holes caused by insect larvae, should be discarded.
Direct Seeding: Seeds may be planted at the beginning of the winter. Once the site is chosen, prepare holes that are 10 inches in diameter and 4-5 inches deep. One gram of a slow-release fertilizer should be placed in the bottom and covered by a small amount of soil. Place 6-10 acorns in each hole at a depth of 1-2 inches. Rodents or birds should use temporary enclosures to minimize herbivory. A simple enclosure can be constructed from a one-quart plastic dairy container with the bottom removed and a metal screen attached. Towards the end of the first season, seedlings should be thinned to 2 or 3 per hole and to one seedling by the second season. Supplemental watering may be necessary if a drought of 6 weeks or more occurs during the spring.
Container Planting: Seeds may be planted in one-gallon containers, using well-drained potting soil that includes slow-release fertilizer. Tapered plastic planting tubes, with a volume of 10 cubic inches, may also be used. Seeds should be planted 1-2 inches deep and the soil kept moist and aerated. Seedlings should be transplanted as soon as the first leaves open and become firm, which generally occurs in spring. Planting holes should be at least twice as wide and deep as the container. Seedlings may require watering every 2-3 weeks during the first season. Care should be taken to weed and mulch around young plants until they are 6-10 inches tall.
Associated Forest Cover
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).
Table 1- Trees, shrubs, and herbs associated with Oregon white oak in different parts of its range¹ Trees Shrubs Herbs 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 cornuta Cytisus scoparius Collinsia spp. Crataegus douglasii Gaultheria shallon Crocidium multicaule Fraxinus latifolia Hedera helix Cynosurus echinatus Heteromeles arbutifolia Holodiscus discolor Dactylis glomerata Juniperus scopulorum Osmaronia cerasiformis Danthonia californica Libocedrus decurrens Philadelphus lewisii Delphinium menziesii Lithocarpus densiflorus Physocarpus capitatus Dentaria californica Pinus contorta Purshia tridentata Dodecatheon hendersonii Pinus monticola Rhus diversiloba Dryopteris arguta Pinus ponderosa Ribes sanguineum Elymus glaucus Pinus sabiniana Rosa eglanteria Eriogonum nudum Populus tremuloides Rosa gymnocarpa Eriophyllum lanatum Populus trichocarpa Rosa nutkana Erythronium oregonum Prunus avium Rubus laciniatus Festuca spp. Prunus emarginata Rubus parviflorus Fritillaria lanceolata Prunus virginiana Rubus procerus Galium spp. Pseudotsuga menziesii Rubus ursinus Holcus lanatus Pyrus communis Spiraea betulifolia Hypericum perforatum Pyrus fusca Spiraea douglasii Lathyrus spp. Pyrus malus Symphoricarpos albus Lomatium utriculatum Quercus agrifolia Symphoricarpos mollis Lonicera ciliosa Quercus chrysolepis Symphoricarpos rivularis Lotus micranthus Quercus douglasii Vaccinium ovatum Lupinus spp. Quercus kelloggii Vaccinium parvifolium Melica geyeri Rhamnus purshiana Viburnum ellipticum Mimulus spp. Salix spp. Montia spp. Sambucus cerulea Nemophila heterophylla Taxus brevifolia Osmorhiza spp. Thuja plicata Phacelia linearis Tsuga heterophylla Platyspermum scapigera Umbellularia californica Plectritis spp. Poa pratensis Polystichum munitum Pteridium aquilinum Ranunculus spp. Sanicula crassicaulis Sedum spathulifolium Sherardia arvensis Silene californica Sisyrinchium douglasii Stipa spp. Thysanocarpus curvipes Trifolium tridentatum Vicia americana Viola ocellata Zigadenus venenosus ¹ Sources: 4,10,11,13,20,22,24,28,31,32,35,42,47,54,62,63,67,69,70,71,72,73,75,78
Diseases and Parasites
Wind, wet snow, and freezing rain damage Oregon white oak less than associated hardwoods, but in tests it showed only moderate resistance to cold. Dormant buds collected northwest of Corvallis, OR, withstood -15° C (5° F) and twigs -20° C (-40 F) without injury (55).
Large Oregon white oaks are obviously fire resistant; they have withstood annual or periodic fires for years. But small oaks may be killed or badly damaged by fire, as evidenced by the increased density and spread of oak stands since the advent of fire control.
More than 110 pathogens have been found on the leaves, twigs, trunk, or roots of Oregon white oak (59). Most are of minor consequence; many are saprophytes. Leaf-spot, mildew, and anthracnose fungi sometimes attack the foliage, but control methods have been suggested for only one-an anthracnose disease (Gnomonia quercina). In 1968, this fungus caused moderate to severe dying of leaves and possibly death of oak trees in southern Pierce County, WA (14). Premature browning of foliage is occasionally widespread in the Willamette Valley, but the causes and effects have received only incidental attention. The hairy mistletoe is common on Oregon white oak in Oregon and California, forming conspicuous, rounded growths in the upper crown. Its effect on growth and vigor of this host is undetermined. The white pocket root and butt rot (Polyporus dryophilus) and the shoestring root rot (Armillaria mellea) are probably the most damaging rots found in Oregon white oak. Its heartwood is generally very durable; stumps and even relatively small stems may remain intact for years.
Although Oregon white oak is host to hundreds of insect species (19), damage is usually not severe, and loss of trees to insect attack is uncommon. The western oak looper (Lambdina fiscellaria somniaria) is probably the most damaging insect on white oak from Oregon north to British Columbia. In some years, oaks over large areas in the Willamette Valley are defoliated (23). The damage is temporary since the trees leaf out the next year and outbreaks are not sustained. The western tent caterpillar (Malacosoma californicum) and the Pacific tent caterpillar (M. constrictum) are widely distributed defoliators with a preference for oaks. Several species of aphid, particularly Teberculatus columbiae, feed on the underside of oak leaves; the snowy tree cricket (Oecanthus fultoni) lives in open-grown oaks and associated species; and several leafrollers (Abebaea cervella and Pandemis cerasana) are found on Oregon white oak. Oregon white oak is the principal host for R. cerasana, an introduced leafroller causing sporadic defoliation that is now maintaining a relatively high population and slowly extending its range around Victoria, BC (17). Many gall wasps are found on oaks; those prominent on Oregon white oak include Andricus californicus, which forms large, persistent, applelike galls on twigs; Bassettia ligni, which causes seedlike galls under the bark of branches that often girdle and kill the branch; Besbicus mirabilis, which forms mottled, spherical galls on the underside of leaves; and Neuroterus saltatorius, which forms mustard-seed-like galls on lower leaf surfaces that drop in the fall and jump around like Mexican jumping beans caused by activity of the enclosed larvae (18,23).
Only incidental damage by animals has been noted on vegetative parts of Oregon white oak. Douglas squirrels and western gray squirrels sometimes debark small branches infested by gall wasp larvae (64). Damage is scattered and may involve as much as one-fourth of a tree's crown. Gophers and other burrowing animals, which are abundant on forest borders, damage some roots. Livestock inflict some trampling and feeding damage on young oaks.
Fire Management Considerations
The use of fire in Oregon white oak habitats is often complicated by their proximity to urban areas, associated nonnative, rare, or sensitive plant and wildlife species, and understory fuel composition. Appropriate fire use requires clearly defined management goals.
General challenges: There are numerous factors to consider when using fire to manage Oregon white oak habitats. Urban areas near Oregon white oak communities affect the timing and control of fire . Nonnative, sensitive, and rare plant or wildlife species also need consideration. Many rare plants  and vulnerable, threatened, or endangered butterflies  are associated with Oregon white oak communities on Vancouver Island. In addition to the needs of rare and/or sensitive species are the unique needs of wildlife species in Oregon white oak habitats. For instance, acorn woodpeckers use large-sized trees for granaries , and wild turkeys in Washington's southern Klickitat County use Oregon white oak and Oregon white oak-ponderosa pine communities as brood habitat and Douglas-fir habitats for roosting. These studies suggest that stand structure and diversity at various scales may affect wildlife habitat suitability. See Importance to Livestock and Wildlife for more on Oregon white oak habitat characteristics that attract wildlife.
Nonnative species: Reintroduction of fire in Oregon white oak communities is often complicated by the presence of nonnative species and their response to fire . The response of nonnative species is variable and likely affected by fire timing and severity. In Oregon white oak woodlands of Redwood National Park's Bald Hills, the most heavily grazed community (Oregon white oak/bristly dogstail grass) had the highest percentage of nonnative species, and the most recently burned community (Oregon white oak/common snowberry) had the highest percentage of native species . On Vancouver Island's Cowichan Garry Oak Reserve, burning and mowing increased the cover of dominant nonnative grasses. Sites were evaluated in the first or second posttreatment year. Native plant recruitment on treated sites was limited by propagule dispersal, and sites lacking native species may require seeding .
In western Oregon, many nonnative species including thistles (Cirsium spp.), Scotch broom, purple foxglove (Digitalis purpurea), St Johnswort (Hypericum perforatum), English holly (Ilex aquifolium), Himalayan blackberry (Rubus discolor), and evergreen blackberry (R. laciniatus) were more frequent following canopy release. Of the 8 nonnative species studied, all but English ivy (Hedera helix) were more frequent on thinned or clearcut logged sites than control sites .
In the Cowichan Garry Oak Reserve, the prefire diversity affected the level of invasibility of Oregon white oak savannahs. Low-diversity savannah plots had more invading species and more Scotch broom and thistles present after fire than did high-diversity plots. Plots burned twice, once in July and again in October, and maximum soil surface temperatures during the fires ranged from 170 to 415 Â°F (74-213 Â°C). Invasibility was determined by seeding native species that were absent from most treated plots. Seeded species did not establish in unburned plots, and in burned plots the survival of seeded species increased with decreased species richness. Recruitment of Scotch broom and thistles that were not seeded into plots was significantly (P<0.0001) greater in low-diversity than in high-diversity burned plots. Postfire Scotch broom cover increased by 250% in low-diversity plots .
Increases in Scotch broom following fire may be related to soil heating. In greenhouse studies, Scotch broom stem density was significantly greater in heat treated soils. All other associated species were negatively impacted by ash and heat. Study findings are summarized in the table below. Heat did not affect Oregon white oak seedling survival, cover, or height. For more on the effects of heat and ash on Oregon white oak, see Acorn survival and emergence . Additional information on Scotch broom and its heat scarified seed is available.
|Stem density/container of Oregon white oak associated species and Scotch broom grown in heat and ash treated soils|
|Treatment||All associated species||Scotch broom|
(surficial 2 cm dry ash from Oregon white oak logs)
(60 Â°C for 10 minute, prior to planting)
|Averages for ash and heat treatments within the all competitor column are significantly different (P<0.001 and P<0.006), respectively. Ash and heat treatments for Scotch broom are also significantly different (P<0.01 and P<0.001), respectively.|
Fuels: Composition of the understory vegetation and litter can affect fire behavior and thus prescribed fire procedures in Oregon white oak vegetation. In mixed Oregon white oak-Douglas-fir stands in Annadel State Park, grasses were lacking. With Oregon white oak and Douglas-fir litter as the primary surface fuel, fire carries only under the driest conditions .
Presence of Scotch broom may increase fire severity in Oregon white oak stands. Prescribed fires in Fort Lewis, Washington, plant communities with mature Scotch broom produced higher soil surface temperatures than those in Idaho fescue prairies, Oregon white oak woodlands, or on sites with newly established Scotch broom populations . In the same area, Thysell and Carey  noted that sites with a dense understory of Oregon white oak, Douglas-fir, and Scotch broom may produce more "damaging" fires than oak savannah sites. Mature Scotch broom may provide ladder fuels into Oregon white oak crowns. In the study area, researchers observed mature fire-killed Oregon white oak, although not commonly .Restoration fire management: Fire frequency and fire distribution can likely be manipulated to manage or maintain prairies, savannahs, mixed woodlands or a combination of these types. With the removal of Native American burning practices in the Willamette Valley, Oregon white oak savannahs quickly succeeded to closed-canopy Oregon white oak woodlands, and Oregon white oak woodlands became Douglas-fir-dominated forests [51,52,68]. On Vancouver Island, Oregon white oak and Douglas-fir establishment in prairies occurred after Native American burning ceased . In Redwood National Park, prescribed fires produced high mortality of young Douglas-fir trees less than 10 feet (3 m) tall. To limit the succession of Oregon white oak woodlands to Douglas-fir-dominated forests, a fire-return interval of 10 years or less, a time less than that required for Douglas-fir to reach 10 feet (3 m), is needed .
Broad-scale Impacts of Plant Response to Fire
Generally, Oregon white oak is not killed by fire, and often sprouts and
seedlings occur on burned sites. However, for a fire-adapted species seen as a candidate
for recovery through fire use, there are
relatively few fire effects studies. The Comprehensive fire effects study described in this section provides the most in-depth analysis of Oregon white oak regeneration following fire
available to date (2007).
The study provides information on acorn survival and emergence, sprout production, and
stand structure in communities with a nonnative species component. Nonnative
species are common in Oregon white oak habitats, and understanding
fire effects in communities with nonnative species is important to the future management of this species. See Nonnative species for more information.
Prescribed fires in oak woodlands in the Bald Hills of Redwood National Park top-killed Oregon white oak trees that were
less than 10 feet (3 m) tall. Fires were low-severity backing and head fires
that spread at 0.6 to 0.9 m/minute, had an average flame height of 1
foot (0.3 m) and a maximum height of 3.9 feet (1.2 m). At the time of burning, relative humidity averaged
55%, air temperature averaged 66 Â°F (19 Â°C), and winds ranged from 0 to 3.2 km/hour. Of the 20 closely-monitored Oregon white
oak trees, all less than 10 feet (3 m) tall were top-killed and sprouting "vigorously from
the base" 10 months following the fire. Trees 10 feet (3 m) or
taller showed little damage or sprouting. Researchers noted some scarring by
this fire. Acorns collected from the ground and from the canopy on unburned
sites had germination percentages of 99.2% and 100%, respectively.
On burned sites, 52.6% of acorns collected from the ground germinated, and 100%
of the acorns from the canopy germinated .
Nearly all burned Brewer's oak shrubs sprouted in burned chaparral
vegetation in the lower Kern River Watershed of the Sequoia National Forest.
The fire burned in July in "ancient" stands that had not burned for at least 90 years
prior to this fire and in "mature" stands that had not burned for 50 or 60 years before
the July fire. In ancient and mature stands, 94.2% and 99% of Brewer's oak sprouted
in the first postfire year .
Sprout production measured as clump diameter, number of sprouts/clump,
and height of sprouts increased with increased diameter of the parent tree on 2-
and 3-year-old burned or clearcut sites in California's Humboldt and Trinity
counties. Burned and logged sites were analyzed together, so differences between
fire and logging on spout production are not discernable. Both sprout height
and sprout clump diameter increased with increased time since treatment, while
the number of sprouts/clump decreased with increasing time since
treatment. Study findings are summarized in the table below :
Oregon white oak sprout dimensions on cut or burned sites in the 2nd and 3rd posttreatment years
|Time since treatment (years)||Sample size||Height of tallest sprout in a clump (feet)||Crown diameter of sprouting clump (feet)||Number of sprouts/clump|
Sugihara and Reed , through
studies of regeneration following prescribed fires in Redwood National Park,
observed and summarized several regeneration phenomena. They found that sprouting is "more intense" from
40-year-old than 70-year-old Oregon white oak trees. Sprouts grow rapidly and may reach 3
feet (1 m) in a single year. Seedlings, however, may take 10 years or more to reach 3 feet (1 m)
tall. Sprouts may occur 7 to 10 feet (2-3 m) from the base of the parent tree,
producing increased Oregon white oak coverage on burned sites. Researchers also found that fires
can stimulate basal sprouting without top-killing stems .
On 2-year-old prescribed-burned sites in the Oak Patch Natural Area Preserve, Oregon white oak seedlings were more
common on high-severity burned sites, and sprouts were concentrated on
low-severity burned sites. Seedlings occurred on areas where logs
had burned and soil carbon and nitrogen concentrations
were low. Seedlings were associated with species characteristic of very disturbed areas, such as stinking willie
(Senecio jacobaea), common velvetgrass (Holcus lanatus), and fireweed (Chamerion
angustifolium). Oregon white oak sprouts were associated with native species
such as baldhip rose (Rosa gymnocarpa),
Saskatoon serviceberry, salal (Gaultheria shallon), and cascara (Rhamnus
purshiana). Findings suggest that seedling regeneration may depend on
severely burned microsites. However, these conditions often produce habitats for
nonnative species, too [2,3,4]. For additional
information on the effects of fire on nonnative species in Oregon white oak communities, see Nonnative species.
There was no damage to mature trees following spring or fall fires in Fort Lewis, Washington.
Fire effects were evaluated in the first postfire year on sites that burned
every 3 to 5 years. Temperatures ranged from 50 to 70
Â°F (10-20 Â°C), relative humidity levels were 20% to 50%, and
wind speeds were less than 5 km/hour at the time of burning. Nearly all top-killed
Oregon white oak sprouted. Only 3 clumps of 5 to 10 stems that were less than 3 feet (1 m) tall and 2
trees with a DBH of 2 to 4 inches (5-10 cm) were killed. Mature trees were undamaged,
and top-kill was concentrated in stems that were less than 3 feet (1 m) tall and
0.8 inch (2 cm) in diameter [148,149].
Comprehensive fire effects study:
Numerous aspects of Oregon white oak regeneration were evaluated on early (February-April),
late (August-October), and twice- (2 early or late-season fires within 6 years) burned woodland and conifer
fringe stands in Fort Lewis, Washington. There were 4 early, 4 late-, and 3 twice-burned sites, and time since
fire ranged from 1 to 6 years. The basal area in unburned areas averaged 18.1 mÂ²/ha.
Relative percent reductions in stem basal area from prescribed fire were similar for Oregon white oak, Douglas-fir, and
ponderosa pine. However, small and medium size classes of Oregon white oak and
medium to large size classes of Douglas-fir and ponderosa pine contributed
most to basal area reductions. Small, medium, and large size classes were
defined as 0.04 to 4 inch (0.1-10 cm), 4 to 20 inch (10.1-50 cm), and >20 inch (50 cm)
DBH, respectively. Twice-burned had the
greatest reductions in Oregon white oak basal area and density. Single-fire sites accounted for the
majority of Douglas-fir and ponderosa pine densities and basal area. Results suggest that frequent fires (at least 3
in 10 years) create oak savannahs,
and less than 2 fires/decade produce dense Oregon white-oak and/or mixed sapling thickets. Study findings
are summarized in the table below [113,114].
Oregon white oak mortality and
|Density reductions |
Regeneration: Sprouts outnumbered seedlings
4:1 on burned sites. Thirty-nine percent of 874 burned Oregon white oak that were breast height or taller
sprouted. Sprout production increased with decreased basal area and increased crown
scorch produced by the fire. Sprouting was related to
tree size, too. The average DBH of sprouting Oregon white oak was about 4 inches (9 cm) less than
nonsprouting Oregon white oak (P<0.001).
Heights of sprouting trees were approximately 11 feet (3.5 m) less than that of
nonsprouting Oregon white oak (P<0.001), and
the crown scorch of sprouting Oregon white oak was nearly double that of
nonsprouting Oregon white oak (P<0.001). Overall, large trees
with minimal scorch, growing in areas with little to no change in stand basal area,
produced few sprouts [113,114].
There were Oregon white oak seedlings on 7 of the 11 burned sites. Just 3% of
Oregon white oak seedlings
were found in open conditions (beyond tree canopies). Seedling density was lowest
under Oregon white oak canopies and highest beneath Douglas-fir (P=0.057). Most
Oregon white oak seedling regeneration (>75%)
occurred under the canopy of Douglas-fir trees with a DBH of 20 inches (50 cm) or
more [113,114]. The importance of Douglas-fir in Oregon white oak seedling emergence may affect
management decisions in mixed conifer-Oregon white oak forests.
Acorn survival and emergence:
In Fort Lewis, Washington, researchers conducted experiments on the survival, germination, and establishment of
Oregon white oak acorns in the field and in the greenhouse. In 1999 no acorns
were left on the soil surface after 75 days. In 2000, seeds were buried and
predation decreased. Of those surviving acorns, emergence was significantly
greater (P=0.022) in soils with char than in ash or unburned areas. However, Oregon
white oak seedling mass was greatest when grown in ash. In greenhouse studies, acorn survival and
growth were compared in soils treated with ash and heat before planting. Survival, cover, and
height of seedlings from acorns planted in ash were significantly lower than in soils without ash.
Heat did not affect Oregon white oak seedling
survival, cover, or height. Study results are summarized in the table below.
In an additional greenhouse study, researchers found
that Scotch broom stem density was significantly greater on heat-treated soils,
a finding that complicates fire management in Oregon white oak habitats. For additional
information regarding management challenges in Oregon white oak habitats with nonnative species, see Fire Management Considerations [113,114].
|Survival, cover, and height of Oregon white oak seedlings grown in heat and ash treated soils|
|Treatment||Survival (%)||Cover (%)||Height (cm)|
(surficial 2 cm dry ash from Oregon white oak logs)
(60 Â°C for 10 minute,
prior to planting)
Averages with different letters within survival, cover, and
height columns are significantly different (P<0.001, P<0.007, and P<0.001,
Plant Response to Fire
| Sprouts: When top-killed, Oregon white oak sprouts from the roots or root crown [2,3,4,120,134]. Abundance or "intensity" of sprouting may be affected by tree age, tree diameter, crown scorch, and/or fire severity. Following a fire in Redwood National Park, Sugihara and Reed  reported sprouts produced 7 to 10 feet (2-3 m) away from the parent stem. They noted that sprouting was more "intense" from 40-year-old than 70-year-old trees. After cutting and burning in California's Humboldt and Trinity counties, sprout clump diameter, number of sprouts/clump, and sprout height increased with increased parent tree diameter . Following prescribed fires in Fort Lewis, Washington, the crown scorch of sprouting Oregon white oak was significantly (P<0.001) greater than that of nonsprouting Oregon white oak . Two years after a prescribed fire in Washington's Oak Patch Natural Area Preserve, Oregon white oak sprouts were concentrated on sites that burned at low severity [2,3,4]. |
Seedlings: Seedlings on burned sites are reported in several fire studies [2,3,4,114]. It is unclear whether seedlings were from on-site sources or from caches made on recently burned sites. Researchers in Redwood National Park found that acorns in the canopy were unaffected by low-severity prescribed fire, but scorched or charred acorns on the ground had germination percentages nearly half that of unburned acorns . There is some evidence that time since fire may affect Oregon white oak acorn production. For more information, see Seed production.
|Oregon white oak sprout. Â© Br Alfred Brousseau, |
Saint Mary's College.
Oregon white oak seedling emergence may be related to fire severity, substrate, and/or canopy coverage. Seedlings were most common on high-severity burned sites in the Oak Patch Natural Area Preserve, suggesting that severely burned microsites are important to seedling regeneration [2,3,4]. On burned sites in Fort Lewis, Washington, Oregon white oak seedling emergence was high in soils with char and low in ash substrates; however, seedling mass was greatest in ash. Seedling densities were also affected by canopy composition .
More complete summaries of the studies identified in Oregon white oak sprout and/or seedling regeneration are presented below.
Immediate Effect of Fire
Oregon white oak mortality is rare following fire. The bark on mature trees is sufficient to withstand cambial kill from fire in open woodlands . There are 2 reports of saplings over 10 feet (3 m) tall resisting top-kill in low-severity fires [135,148]. However, Thysell and Carey  observed fire-killed mature Oregon white oaks, although rarely, after a severe fire fueled by a dense understory of Oregon white oak, Douglas-fir, and Scotch broom in Fort Lewis, Washington.
POSTFIRE REGENERATION STRATEGY :
Tree with adventitious bud/root crown/soboliferous species root sucker
Geophyte, growing points deep in soil
Initial off-site colonizer (off-site, initial community)
Secondary colonizer (on-site or off-site seed sources)
Fire adaptations: Oregon white oak is a fire-resistant species; typically, saplings over 10 feet (3 m) tall resist even top-kill. Mortality from fire is rare, and root crown sprouts are common following top-kill in even the smallest size classes [134,135,148,149]. Mature tree bark is sufficient to withstand surface fires in open conditions . If top-killed, Oregon white oak rapidly sprouts from the root crown and/or roots [2,3,4,120,134]. Acorns in the canopy survive low-severity fires, but scorched acorns on the ground have reduced germination . Animal dispersal of acorns (see Seed dispersal and Importance to Livestock and Wildlife) onto burned sites is likely.
FIRE REGIMES: The persistence of Oregon white oak communities is dependent on periodic fire. Native Americans maintained open Oregon white oak stands through frequent fall burning. The loss of Oregon white oak-dominated habitats to conifer-dominated forests is in large part the result of increased fire-return intervals since European settlement and the subsequent elimination of Native American burning.
Historical fire-return intervals: Numerous researchers have suggested that Oregon white oak woodlands and savannahs burned frequently based on the fire adaptations of woodland species and the susceptibility of later successional conifer species. Because pre-European fires were fueled by gasses and forbs, they were "flashy and of low duration" and did not normally scar trees, making fire regime reconstruction difficult. However, a fire-return interval of 5 to 10 years likely would have restricted conifer encroachment [1,2]. Dry, hot sites occupied by Oregon white oak in Washington's Wenatchee National Forest burned in low-severity fires at intervals "judged to be in the 5 to 30 year range" . White  reports that Oregon white oak in Oregon's Klamath Mountains is adapted to a 3- to 20-year fire-return interval.
Past fire frequencies were estimated at 4.5, 7.5, and 13.3 years for the presettlement (before 1875), settlement (1875-1897), and postsettlement (1898-1940) periods, respectively, in the Bull Creek Watershed of California's Humboldt Redwoods State Park. Basal sprouts and fire-scarred stumps in old growth redwood-Douglas-fir forests were used to determine fire frequency. When watershed zones were used to estimate fire frequency, estimates were approximately twice that reported for the entire study area for all time periods, suggesting spatial variability in fire frequencies . The fire cycle increased dramatically after 1905 in a 5,745-acre (2,325 ha), mixed-conifer forest with Oregon white oak in California's Shasta-Trinity National Forest. From 1628 to 1995, 184 fire years were recorded. Fires burned primarily in the mid-summer or fall. The pre-European fire cycle of 19 years increased to 238 years after 1905. A large increase in young Douglas-firs coincided with fire exclusion .
Native American burning: The most extensively studied Oregon white oak communities burned by Native Americans are those in the Willamette Valley, which were probably burned annually or nearly annually. The Willamette Valley has been described as the most intensely fire-managed environment in the aboriginal Northwest . Based on ethnohistorical evidence (ethnographic and archeological, published and unpublished sources) the Native people of the Willamette Valley burned grasslands and Oregon white oak savannahs nearly every year in low-severity late summer or early fall fires. The earliest recorded fire date for Native burning was 2 July, and the latest was 20 October. Likely sites in Oregon white oak woodlands were burned only after acorns were collected [17,19]. The frequency of Native American fires in Oregon white oak communities is difficult to determine, and annual burning is not considered likely by Agee . Fires in the Willamette Valley served several purposes, most related to maintaining food sources of mule deer, tarweed (Madia spp.) seeds, and insects. Large-scale burning in the Willamette Valley was eliminated when the Kalapuya, Umpqua, and Tahelma people were sent to the Grande Ronde Reservation in 1855 [17,19].
Several additional references provide strong evidence of frequent Native American burning in Oregon white oak habitats. For additional information on evidence of burning and potential reasons for burning, see [84,93] (California),  (southwestern Oregon),  (southwestern Washington), and  (British Columbia).
From historical and current written accounts, maps, and aerial photos, researchers compared Willamette Valley vegetation in 1853 to that in 1969. Much of what was Oregon white oak savannahs became dense woodlands, and areas that were oak woodlands became Douglas-fir forests. Changes occurred with decreased fire frequency and European settlement . Findings were similar from aerial photos and data collected in past surveys of the valley's Monmouth Township. In 1850 approximately 8% of the township was closed-canopy Oregon white oak woodlands, and 50% was open Oregon white oak savannahs. In 1955, closed-canopy Oregon white oak woodlands increased to 24% of the township [51,52].
Decreased fire frequency: Changes in stand density and composition, chiefly due to the encroachment of Douglas-fir, are common in Oregon white oak communities since fire exclusion.
Researchers have extensively studied Oregon white oak woodlands in California [134,135,136] and have summarized changes in all aspects of historic and current woodland FIRE REGIMES. Since the mid-1800s the management and composition of these woodlands have changed substantially. With the elimination of frequent Native American burning, Douglas-fir encroachment ensued. Nonnative grasses, which dry earlier than native herbs, were introduced with European settlement. Although earlier-curing fuels occur in Oregon white oak communities, fires continue to burn predominantly in the summer or early fall, like in the early 1800s. Fire frequency is much reduced from the historic annual or nearly annual frequency. Fire size historically ranged from 20 to 200 acres (10-100 ha) and presently averages less than 20 acres (10 ha). The spatial complexity of fuels was low historically due to nearly uniform herbaceous vegetation in the understory of Oregon white oak woodlands. The encroachment of Douglas-fir has increased vertical fuel loads. Short fire-return intervals and a lack of heavy fuels supported lower severity fires than occur presently. Historically, surface fires and only occasional torching occurred in Oregon white oak communities; currently, however, torching is more common, and crown fires are possible with extreme fire weather conditions .
Rapid invasion of oak (Quercus spp.) woodlands by Douglas-fir began in the early 1940s in Annadel State Park. Researchers found that Douglas-fir establishment paralleled increased oak density and canopy closure, which coincided with fire exclusion in the Park . For a more detailed summary of this study, see Succession to coniferous forest. In the Fox Hollow Research Area in Willamette Valley, researchers found that forest structure and composition changed considerably from the 1800s to the mid-1970s. Prior to 1850 warm dry ponderosa pine- and Oregon white oak-dominated sites had estimated tree densities of 70/ha. The same sites in the mid-1970s supported an estimated 1,179 trees/ha. Douglas-fir dominated the seedling layer (74%). Researchers attributed changes in forest structure and composition largely to decreased fire frequency .
Oregon white oak and Douglas-fir establishment on Rocky Point, Vancouver Island, was facilitated through fire exclusion. Tree ring analyses and fire scar data from relatively undisturbed prairies, Oregon white oak woodlands, and coniferous forests allowed researchers to reconstruct stand composition and structure. Oregon white oak establishment began on prairies in 1850 and peaked in 1890. Minor Douglas-fir establishment began in 1890. From 1950 on, recruitment was almost exclusively by coniferous species. Researchers found that there were significantly (P<0.001) fewer Oregon white oak seedlings on plots with a coniferous overstory than those without. There were few saplings, indicating that seedlings were eventually unsuccessful. Browsing, nonnative grasses (orchardgrass, colonial bentgrass, and sweet vernalgrass (Anthoxanthum odoratum)), or climate change may have affected sapling development. A search for fire-scarred trees revealed no scarring fire since about 1850 .
Additional factors to Oregon white oak declines: Fire exclusion was not the only factor associated with changes and declines in Oregon white oak communities. Past silvicultural management decisions also affected Oregon white oak. See Silviculture management for a discussion of other factors affecting Oregon white oak declines.
The following table provides fire return intervals for plant communities and ecosystems where Oregon white oak is important. For further information, see the FEIS review of the dominant species listed below.
|Community or Ecosystem||Dominant Species||Fire Return Interval Range (years)|
|grand fir||Abies grandis||35-200 |
|California chaparral||Adenostoma and/or Arctostaphylos spp.||<35 to <100 |
|California montane chaparral||Ceanothus and/or Arctostaphylos spp.||50-100|
|western juniper||Juniperus occidentalis||20-70|
|pinyon-juniper||Pinus-Juniperus spp.||<35 |
|Pacific ponderosa pine*||Pinus ponderosa var. ponderosa||1-47 |
|mountain grasslands||Pseudoroegneria spicata||3-40 (x=10) [6,7]|
|coastal Douglas-fir*||Pseudotsuga menziesii var. menziesii||40-240 [7,99,117]|
|Pacific coast mixed evergreen||Pseudotsuga menziesii var. menziesii-Lithocarpus densiflorus-Arbutus menziesii||<35-130 [7,23]|
|California oakwoods||Quercus spp.||<35|
|Oregon white oak||Quercus garryana||3-30 [1,2,85,132]|
|California black oak||Quercus kelloggii||5-30 |
|interior live oak||Quercus wislizenii||<35 |
|redwood||Sequoia sempervirens||5-200 [7,39,132]|
|western redcedar-western hemlock||Thuja plicata-Tsuga heterophylla||>200 |
More info for the terms: climax, density, fire regime, succession, tree
Oregon white oak is considered a pioneer and a disturbance "climax" species. It is often the first invader on prairies, but without periodic disturbance it is replaced by conifers. However, site conditions can affect the persistence and successional status of Oregon white oak. On very dry sites, Oregon white oak may dominate without disturbance [102,128]. On the Wenatchee National Forest, Oregon white oak occurs in dry areas with gravelly, stony soils. Here is it both a pioneer and a climax species, since coniferous species, primarily Douglas-fir and ponderosa pine, do not regenerate well. Stands with Douglas-fir and ponderosa pine emerging above the Oregon white oak canopy occur only on the most "favorable" sites .
Shade tolerance: Mature Oregon white oaks are not considered shade tolerant. However, developmental stage affects shade tolerance, and presumably shade tolerance decreases with age. In a study of Oregon white oak seedlings in Metchosin, researchers found that seedling mortality was not affected by overstory vegetation and that shade intolerance developed sometime after the seedling stage . A study conducted in Fort Lewis, Washington, suggested shade was beneficial to Oregon white oak seedling growth .
While growth of Oregon white oak seedlings may be unaffected or favored by shade, tree growth in shade is often restricted. Following the removal of Douglas-fir canopy trees in western Washington, Oregon white oak in the "suppressed" midstory responded rapidly with increased growth, epicormic branching, and acorn production. Treatments involved the removal of Douglas-fir within a full radius and a half radius of the study tree's height. Oregon white oak DBH growth was significantly greater on 3-year-old (P=0.003) and 5-year-old (P<0.001) treated sites. Epicormic branching in the first and second posttreatment years averaged 9.3 new branches in full-radius plots, 7.1 in half-radius plots, and 1.2 in control plots .
Succession to coniferous forest: Conditions fostering the transition from Oregon white oak woodlands to coniferous forests are well described in a study in California's Sonoma Mountains. In Annadel State Park, researchers analyzed mixed Oregon white oak-Douglas-fir stands. Oregon white oak trees were consistently older than Douglas-fir trees, indicating recent conifer invasion. Although Douglas-fir regeneration had occurred since 1910, researchers noted 2 establishment "surges". The first, in the early 1940s, corresponded to improved fire detection and suppression through technological advancements and the utilization of prison inmates as firefighters. A second Douglas-fir establishment flush occurred in the early 1970s, when the Park was established, livestock were removed, and a Douglas-fir seed source was available due to the 1940s establishment. Prior to the practice of excluding fire in the early 1900s, Annadel State Park experienced widespread frequent fires. Researchers indicated that Douglas-fir establishment coincided with increased Oregon white oak density and canopy closure, which coincided with fire regime changes in the Park .
Oregon white oak reproduces sexually through acorn production [32,135] and asexually through root, root crown, and epicormic sprouting. Root and/or root crown sprouts are common following fire or cutting [102,134]. Epicormic sprouts occur following disturbance and canopy release . Oregon white oak seedlings can sprout following shoot mortality [41,61].
Pollination: Oregon white oak flowers are wind pollinated.
Breeding system: Oregon white oak is monoecious . An Oregon white oak genetics study in British Columbia revealed outcrossing rates near 100%, but levels of "correlated mating", described as siblings of a common mother sharing a common father, were significant (P≤0.05) .
Seed production: Acorn production by Oregon white oak is variable. Studies indicate that stand density, light availability, tree age, and time since fire may affect production. Irregular acorn production is reported by many [106,135,160]. In California, Wolf  observed heavy acorn production by Brewer's oak and Q. g. var. semota in some years and practically none in others. In the Bald Hills of Redwood National Park, researchers evaluated Oregon white oak acorn production for 5 years. Production was moderate to heavy 1 year. No acorns were produced in another year. Light and light to moderate crops were reported for 2 years and 1 year, respectively .
Possible factors affecting production: Studies suggest that Oregon white oak acorn production increases with increased sunlight, but that variable production is commonplace. On Oregon's William L. Finley National Wildlife Refuge, production was 602 kg/ha in 1976, 131 kg/ha in 1977, and 0 kg/ha in 1978. In producing years nearly 40% more acorns were produced in savannahs than in closed-canopy woodlands, but these differences were not significant (P>0.05). A search for acorns in the rest of the Willamette Valley during the nonproducing year revealed low acorn production throughout the Willamette Valley . Acorn production increased following the removal of Douglas-fir canopy trees in western Washington. Neighboring Douglas-fir trees within a full radius and a half radius of the study tree's height were removed. In posttreatment years 2 and 4, when acorn crops were greatest, production was significantly greater (P<0.05) for full and half release treatments than for control trees. Increased sunlight appeared to increase acorn production, because those crown portions receiving direct sunlight had the most acorns. Epicormic branches that appeared following canopy release produced acorns 5 years after sprouting .
Oregon white oak acorn production varied with tree age and time since fire in western Washington and Oregon. A single season of production by 248 trees, 11 to over 300 years old, on 60 sites was evaluated. Acorn production was estimated visually using a method based on a 1 to 4 scale developed by Graves . Nonproducing trees produced no acorns. Light producing trees had acorns that were visible only after very close examination. Moderate producers had readily visible acorns, but the entire tree was not covered. Heavy producers had acorns covering the entire tree and limbs that sagged with acorn weight. Nearly 50% of the trees produced no acorns; 34% produced light crops and 19% produced moderate crops. No trees produced heavy crops. Production was greatest for trees at least 60 years old, growing with little "competition" on well-watered, well-drained sites. Researchers assessed competition levels through stand basal area, individual tree shape, and crown contact. Trees less than 20 years old did not produce acorns, but production increased with age until trees were nearly 80 years old, when production leveled off. The oldest tree (>300 years) produced no acorns. On sites that burned 1 year earlier, 71% of trees were nonproducing. On sites unburned for 20 years and sites burned 2 to 4 years earlier, 48% of trees were nonproducing. Sites burned 6 to 10 years earlier had 18% non- and 41% moderate producing trees, respectively .
Seed predation: While seed production is variable, seed predation is ubiquitous. Fallen acorns are quickly cached, consumed, or infected by wildlife and insects. In central Oregon, insect larva were common in fallen acorns . In Oregon white oak savannahs and woodlands on the William L. Finley National Wildlife Refuge, 80% of acorns were removed by 25 November in 1976, and 99% were removed by 3 November in the following year . In Metchosin on Vancouver Island, acorn predation was highest in areas with moderate to high tree, extensive shrub, and low herbaceous cover. Predation was lowest in habitats with high herbaceous and low to moderate shrub and tree cover . The substantial utilization of Oregon white oak acorns is also discussed in Seed banking and Importance to Livestock and Wildlife.
Seed dispersal: Oregon white oak acorns are dispersed by many agents; dispersal distance is often greatest through active transport by birds and shortest through passive movement by gravity. In central Oregon, 41 of 116 painted acorns were located in the spring. The maximum dispersal distance of these acorns, likely the result of gravity and rolling, was 21.8 feet (6.65 m) from the trunk. Most acorns were found beneath the canopy. In the same area, Douglas's squirrels, western gray squirrels, blue jays, Steller's jays, and Lewis's woodpeckers dispersed acorns. Douglas's squirrels carried acorns approximately 30 feet (8 m) before burying them. On 2 occasions blue jays transported acorns almost 1,000 feet (300 m) before consuming the acorns. Steller's jays typically carried acorns 1,000 to 1,300 feet (300-400 m) into conifer-dominated sites. Sometimes acorns were dropped, other times consumed. Lewis's woodpeckers often transported acorns 100 to 200 feet (30-50 m) into Oregon white oak- or western juniper (Juniperus occidentalis)-dominated habitats before dropping or consuming them .
Populations of Oregon white oak near Yale, British Columbia, are nearly 100 miles (200 km) from the main distribution of the species on Vancouver Island. After assessing all possible sources for this disjunct population, Glendenning  suggested that long-distance acorn dispersal by band-tailed pigeons was most likely.
Seed banking: Long term seed survival in the soil is unlikely, as Oregon white oak seed is viable for just 1 year . The potential for seed predation and desiccation is high without burial . On southern Vancouver Island, 53% to 100% of acorns on the soil surface were removed. Of those acorns that survived predation on the soil surface, most dried out and died. Mortality of acorns buried under litter or in soil was less than 17% in all but one habitat .
Numerous wildlife species cache and bury Oregon white oak acorns. Unrecovered caches are likely an important source of Oregon white oak germination. On southern Vancouver Island, researchers found that Steller's jays transported and hid acorns singly in scattered locations. Of 151 acorns, 68% were buried under moss or litter, and 24% were buried in the soil. Emergence was significantly greater (P<0.05) for buried acorns than for those left on the surface. Nearly half of Steller's jay hoards were in habitats characterized as small clumps of overlapping Oregon white oak, Pacific madrone, and Douglas-fir canopies, conifer sapling patches within Oregon white oak stands, or in riparian areas. However, when 2,700 acorns were planted in all available habitats, emergence was greatest in those habitats chosen less often by Steller's jays . In central Oregon, Douglas's squirrels were observed burying Oregon white oak acorns about 0.8 inch (2 cm) deep . Western gray squirrels in Fort Lewis, Washington, gathered and buried Oregon white oak acorns in August and September. Acorns were buried separately under or near the source tree . Pennoyer  found Oregon white oak acorns 11 times in a total of 63 dusky-footed woodrat nests near Corvallis, Oregon. Nest material may offer protection from desiccation, and acorns may germinate if not recovered.
Germination: Oregon white oak seed germinates readily given warm, moist conditions, and stratification is unnecessary [16,102,105]. Germination is limited by predation, desiccation (see Seed Banking), and fire (see Fire Effects).
Germination is hypogeal and typically complete in 2 to 5 weeks. Germination of Oregon white oak acorns in loam soils maintained at 86 Â°F (30 Â°C) during the day and 70 Â°F (21 Â°C) at night was 77% to 100% .
Seedling establishment/growth: There is conflicting information among studies regarding the conditions most conducive to Oregon white oak seedling recruitment. Even on the same site, conditions beneficial for germination are often not conducive to seedling growth, and conditions favorable to seedling establishment are different from those benefiting sapling growth.
Sites with increased light availability had more Oregon white oak seedlings than did those with less light in west-central Willamette Valley. Seedlings, defined as multistemmed plants that lacked a single dominant stem, were dense and occupied patches of up to 1 acre (0.5 ha) in size in open sites harvested 15 to 25 years ago. Seedlings and saplings were sparsely scattered on unharvested sites. Seedlings were smaller and grew more slowly than saplings, defined as those plants with a single dominant stem. Seedling growth averaged 1.8 inches (4.6 cm)/year), and sapling growth averaged 6.2 inches (15.7 cm)/year. Seedlings had multiple stems, and this morphology persisted for up to 20 years. Researchers observed seedlings with 21-year-old taproots and 9-year-old aboveground stems, indicating that dieback and sprouting occurred multiple times before seedlings transitioned into saplings. Seedling taproots averaged 22.2 inches (56.3 cm) long, and taproot diameter averaged 0.5 inch (1.2 cm) at 0.8 inch (2 cm) depths. Taproots grew an average of 2.9 inches (7.3 cm)/year, and growth generally increased with penetration depth. Over 3.5 years, 3 of 23 marked seedlings died from taproot severing by pocket gophers. Seedling and saplings were rarely browsed .
In Metchosin, seedling mortality was not associated with overstory vegetation, but acorn survival was positively associated with dense herbaceous cover and low shrub and tree cover (see Seed predation). Habitats favoring acorn survival and germination were poor habitats for seedling survival. Shade did not encourage or reduce seedling growth, and browsed seedlings sprouted. The majority of seedling mortality was the result of desiccation and was concentrated on south-facing slopes. However, researchers noted that many seedlings survived dry conditions . Rapid taproot development likely helps Oregon white oak seedlings tolerate xeric conditions [61,102]. In central Oregon, a study of age structure and climate data indicated that Oregon white oak regeneration was favored during dry periods in mixed Douglas-fir-ponderosa pine-Oregon white oak forests .
A study in Fort Lewis, Washington, suggested that shade was beneficial to Oregon white oak seedling growth. Seedlings from acorns collected in Fort Lewis, Washington, and grown in greenhouse conditions were later moved to either full sun or shade (50% full sun) conditions in an outdoor nursery. At 1 year old, seedlings were transplanted on a Fort Lewis prairie site dominated by Idaho fescue (Festuca idahoensis) and colonial bentgrass (Agrostis capillaris). Most seedlings transplanted in September died, but most planted in early November, mid-January, and early March survived. Seedlings grown in outdoor nursery shade were damaged in full sun conditions in the prairie. At the end of the first field growing season, shoot mortality was 11% in the shade and 85% in the sun, regardless of the nursery growing conditions. Shoot mortality was considered a result of moisture stress, and yellowing and browning appeared first in the full sun area. Shoot mortality is not equivalent to seedling mortality, and a number of seedlings with dead shoots had live roots and root crown buds .
When sites with low and high historical grazing intensities in northern California's Coast Ranges were compared, researchers found that Oregon white oak seedling density was greater (33.5 seedlings/100 mÂ²) on high- than on low-intensity (19.1 seedlings/100 mÂ²) grazed sites. However, sapling density was slightly (9.3 saplings/100 mÂ²) higher on high-intensity than on low-intensity (10.8 seedlings/100 mÂ²) grazed sites. Researchers suggested that herbivore removal of surrounding vegetation may encourage Oregon white oak seedling development, but grazers may negatively affect Oregon white oak sapling growth .
Vegetative regeneration: Oregon white oak produces epicormic, root, and root crown sprouts [41,61,102,134]. Root crown sprouts are common following aboveground stem mortality . Oregon white oak seedlings sprout following shoot mortality that may or may not be the result of a disturbance [41,61]. Epicormic sprouts occur following disturbance and canopy release . The abundance and "vigor" of sprouts typically increases with increased parent plant size .
Growth Form (according to Raunkiær Life-form classification)
More info for the terms: geophyte, phanerophyte
RAUNKIAER  LIFE FORM:
Reaction to Competition
Oregon white oak functions as both a seral and a climax species. It is long lived, reproduces from both seeds and sprouts, forms nearly pure stands, and can endure great adversities. In fact, it rates as a climax species because it has greater ability than other species to establish itself and persist where yearly or seasonal precipitation is sparse, where soils are shallow or droughty, or where fire is a repeated natural occurrence.
Geologic and floristic evidence indicates that Oregon white oak associations have evolved through successive eras as components of relatively and pine-oak forests, have repeatedly advanced northward from a locus in the southwestern United States and northwestern Mexico, and have repeatedly retreated as North American climates warmed and cooled (16). The most recent northward advance ended about 6,000 years ago; the more and vegetation types, including oak woodlands, are now being replaced by conifer forest favored by the climatic trend toward cooler and moister conditions.
The seral role of Oregon white oak is illustrated by major changes occurring in the Willamette Valley. Open oak woodlands, savannas dotted with oaks, and grasslands were prominent and widespread before the territory was settled; fires-natural as well as those set by Indians-maintained these open conditions (30,31,36,44,61). Post-settlement exclusion of fire permitted development of closed-canopy white oak stands that are typically of two ages-large spreading trees, now 270 to 330 years old, are scattered among smaller trees of narrow form, 60 to 150 years old (73). Where not restricted by agricultural practices, young oaks continue to encroach into grassland. But, in turn, many oak stands are being invaded and superseded by bigleaf maples or conifers, mainly Douglas-fir (fig. 4). A similar sequence of events is occurring in the northern oak woodland, a distinctive Oregon white oak type in California (5,51,69). Unless steps are taken to reverse present trends, the Oregon white oak type will continue to become a less prominent part of the western flora. A reduction in species diversity will also occur, for open-canopy communities have a more varied composition than closed conifer communities (13).
Life History and Behavior
Oregon white oak flowers are produced with leaves in the spring (April-June) [63,101,110]. In the southern and northern part of Oregon white oak's range, flowers may appear as early as March and as late as June, respectively. Acorns require a single growing season to mature and ripen from August to November . Flowering in Oregon white oak varieties is similar; most flower in the spring. However, Brewer's oak flowering may be slightly delayed compared to Q. g. var. garryana and Q. g. var. semota .
The acorns are large and heavy, averaging about 5 g each (85/lb). Viability has been better than 75 percent in the few samples tested (46), but the usual quality of the seeds is unknown. The seeds are not dormant; they will germinate soon after dispersal if subjected to warm, moist conditions. They will also germinate prematurely in low-temperature stratification. Normally, seeds retain viability only until the next growing season; chances of extending the viability period have not been determined.
Seedlings of Oregon white oak generally appear in the spring. Germination is hypogeal, and the rapid development of a deep taproot is believed responsible for their ability to establish in grass. Shoot development is relatively slow but can be greatly accelerated with long photoperiods (43). Seedlings are not produced now for forest plantings, but raising them in containers is readily possible. Direct seeding of acorns should also prove successful if seeds and young seedlings are protected from rodents and other predators. In at least some circumstances, natural reproduction from seed seems to occur readily (13,28,35).
Seed Production and Dissemination
The heavy seeds disseminate by gravity only short distances from the tree crowns, except on steep slopes. Local transport is attributed primarily to the food-gathering activities of animals. In the past, Indians-and also pigeons-may have been responsible for long-distance colonization of Oregon white oak (28,71).
Flowering and Fruiting
The species is monoecious, bearing slim, staminate flowers (catkins) that emerge from buds on existing twigs and also appear on the basal end of developing twigs (64). Some catkins associated with new twig growth just originate from the same bud; others are located as much as 5 mm (0.2 in) from the base on new growth. Catkins are pale yellow tinged with green. Fully extended catkins vary greatly in length-in one collection, from 3 to 10 cm (1.2 to 3.9 in). Catkins of the same twig and cluster are in various stages of development-some are fading before others reach full size. The faded dry catkin is light brown and fragile.
The closed pistillate flowers are small, deep red, and covered with whitish hairs (64). They appear in axils of developing leaves, either single and sessile or as many as five or six on a short stalk up to 2 cm (0.8 in) long. Two flowers are often located at the base of the stalk and several along and at its tip. Basal flowers may be open while others on the stalk are still tiny and tightly closed. Flower openings are narrow; the interior elements are greenish to yellowish. Flowers were found on new growth that had extended only 1 cm (0.4 in) or up to 12 cm (4.7 in); most flowers were on new growth 4 to 7 cm (1.6 to 2.8 in) long. Flowering appears at its fullest when the first leaves are about half size; when leaves approach full size, catkins are withered. On a single tree, flowering seems to be a short event, perhaps a week long, as leaves develop quickly once growth starts.
Individual trees are known to flower abundantly, but observations are needed on the regularity of flowering and on the variability within and between stands and locations.
Growth and Yield
Resource inventories of various intensities indicate that the Oregon white oak type occurs on at least 361 400 ha (893,000 acres) in California, Oregon, and Washington and, as a species, comprises 26.2 million in' (926 million ft') or more of growing stock (7,8,9,10,21,25,26,27). As a component of woodland and other vegetation types, Oregon white oak is found on an additional 299 100 ha (739,000 acres) in California and in sizeable, undefined areas in Oregon and Washington. In California, the mean stand growing-stock volume in the type was 76.9 m³/ha (1,099 ft³/acre), and the maximum found was 314.7 m³/ha (4,498 ft³/acre).
Oregon white oak generally grows slowly in both height and diameter, but there are exceptions. Limited data from widely separated locations indicate that six to eight rings per centimeter (16 to 20/in) is a common rate for slower growing Oregon white oaks (28,68,72,75). For example, trees in a full stand 47 to 70 years old on deep Willakenzie soil at Corvallis, OR, averaged 14 in (46 ft) in height, 15 cm (6.0 in) in d.b.h., and eight rings per centimeter (20/in) in radial growth (38). Oregon white oak has the capability, however, of growing faster than five rings per centimeter (13/in) (31,48,72,80). In the Cowlitz River Valley, the fastest rate shown on large stumps was 1.9/cm (4.9/in); in the Willamette Valley, the rate averaged 4.6/cm (11.8/in) for four forest-grown trees 95 to 135 years old that averaged 24 in (80 ft) tall and 48 cm (19 in) in d.b.h.
Basal area of Oregon white oak stands has ranged from 8.0 to 60.8 m² /ha (35 to 265 ft²/acre), with up to 19.3 m²/ha (84 ft²/acre) additional basal area of other species present. In these and other stands averaging 10 cm (4 in) or more in d.b.h., number of oak stems ranged from 10 to 2,800/ha (4 to 1,133/acre) (1,4,31, 62,69,70,72,75). Volumes for stands on different sites and of different ages are not known. One 80-year-old stand that averaged 160 trees 9 cm (3.6 in) and larger in d.b.h. would yield about 94.5 m³/ha (15 cords/acre) (60).
Molecular Biology and Genetics
Quercus garryana hybridizes naturally with four other oaks. Quercus x subconvexa Tucker (Q. durata x garryana), a small tree found in Santa Clara and Marin Counties, CA, is noteworthy because of its morphologically dissimilar parents-Q. garryana is a deciduous tree, Q. durata an evergreen shrub, and the hybrid is tardily deciduous (74). Quercus x howellii Tucker (Q. dumosa x garryana) is also a small tree found in Marin County and a hybrid between a deciduous tree and an evergreen or tardily deciduous shrub or tree. Quercus x eplingii C. H. Muller (Q. douglasii x garryana), a tree with deciduous leaves, is found in Lake and Sonoma Counties, CA (75). Hybrids between Q. garryana and Q. lobata are also found in Sonoma County (4).
Statistics of barcoding coverage: Quercus garryana
Public Records: 0
Specimens with Barcodes: 2
Species With Barcodes: 1
National NatureServe Conservation Status
Rounded National Status Rank: NNR - Unranked
Rounded National Status Rank: NNR - Unranked
NatureServe Conservation Status
Rounded Global Status Rank: G5 - Secure
Please consult the PLANTS Web site and your State Department of Natural Resources for this plant’s current status, such as, state noxious status and wetland indicator values.
There is considerable concern about the future of Oregon white oak habitats. Recent and rapid losses
of habitat have prompted the need for the protection, recovery, and restoration
of Oregon white oak woodlands and savannahs. According to Agee  "without
prescriptive treatment, up to 50% of threatened oak woodlands could be beyond
help by the year 2010," and the "window of opportunity narrows every
Oregon white oak ecosystem conservation is necessary for the protection of associated
species and culturally important historical sites. Many plant and animal species at
risk of local or global extinction are associated with Oregon white oak communities. Lists of these species are
presented in . Because Oregon white oak is often an indicator of culturally
important sites in western Washington , the loss of these
communities could also mean a loss of artifacts, historical evidence, as well as an
appreciation or understanding of the practices of Native people.
Conservation of Oregon white oak vegetation is difficult for several reasons. Scott
and others  report that only a very small portion of Oregon white oak's geographic distribution is
currently protected. In British Columbia, 40% to 76% of the understory species in
Oregon white oak communities
are nonnative and make up 59% to 82% of the understory cover (Erickson 1996
and Roemer 1995, cited in ). Establishing a reference condition,
often the first step to restoration, is challenging without native flora .
However, many sources address Oregon white oak management and conservation.
Harrington and Devine  provide guidelines for
releasing Oregon white oak from overtopping conifers. They include information on stand selection,
release types, treatment season, and concerns or problems with associated nonnative species. Guidelines for
Oregon white oak woodland preservation and management in Washington that include
future land use practices, prescribed fire, and selective harvest are described
in . Information on determining management goals,
considering ecosystem structure and function, reevaluating management effects, identifying tradeoffs,
and setting management priorities in Oregon white oak woodlands is provided in .
Using existing relationships between the distributions of oak species, the prevailing climates
within these distributions, and 3 general climate change models, researchers
suggest that predicted changes in climate will not significantly impact the
distribution of oaks in California .
Diseases affecting Oregon white oak in California are identified and
described in .
Decreased fire frequencies in Oregon white oak habitats are not solely
responsible for declines in Oregon white oak. Past silvicultural management
decisions also contributed to declines.
In a study conducted near Oregon State College in the Willamette Valley,
researchers designed several treatments to increase conifer production on Oregon
white oak-dominated sites. Researchers indicated that Oregon white oak "stands
were poor producers of forest products because of exceptionally
slow growth". Treatments to increase productivity of Oregon white
oak-dominated woodlands included clearcutting, burning, planting to pasture, underplanting with Douglas-fir, thinning and underplanting to Douglas-fir, and
clearcutting and planting to Douglas-fir . Similar management goals are reported in the 1950s from northwestern California.
In a 1955 paper, Roy  indicated that hardwood sprouts following logging or fire
are "pernicious" and "capture ground area which otherwise
could be used to grow conifers". He also suggests that "treatments
may be necessary to obtain adequate stocking of desired conifers".
Guidelines for herbicides use to control Oregon white oak
in reforestation and/or timber production efforts are provided in .
There are regression equations useful for
predicting Oregon white oak height in Oregon. Larsen and Hann  provide
equations for predicting Oregon white oak height in southwestern Oregon using
DBH, basal area, or site indices as the independent variables. Equations to
predict height using DBH of Oregon white oak trees in west-central
Willamette Valley are given in .
Cultivars, improved and selected materials (and area of origin)
This species can be acquired from nurseries throughout its range that deal in native plants. Contact your local Natural Resources Conservation Service (formerly Soil Conservation Service) office for more information. Look in the phone book under ”United States Government.” The Natural Resources Conservation Service will be listed under the subheading “Department of Agriculture.”
Natural regeneration, through sprouting and seed germination, is promoted by fire, which contributes to expansion and persistence of Oregon oak stands. Continued disturbance by fire may result in pure stands that are often associated with an understory of grasses or scattered shrubs. Oregon oak is not as susceptible to oak crown and root rot fungi (e.g., Inonotus, Ganoderma, and Laetiporus) as other oaks, unless disturbed by changes that include irrigation. Activities that disturb or compact soil around large trees, especially in urban settings, should be avoided.
Relevance to Humans and Ecosystems
Other uses and values
Native people of the western United States utilized Oregon white oak; acorns were often an important food source. Salish groups of the Puget Sound ate Oregon white oak acorns after bitter tannins were removed through soaking. They also used Oregon white oak bark in treatments for tuberculosis and other ailments [110,146]. Since Oregon white oak provided important foods to early inhabitants, Storm  indicates that mature Oregon white oak stands can be used to find culturally important sites in western Washington. In northern California, Native people considered Oregon white oak acorns sweet and palatable . In Mendocino County, California, acorns made up a large portion of Native people's diets. Male tribe members beat acorns from the tree, and women collected them in baskets. Acorns were dried, ground into meal, and made into bread or soup .
Oregon white oak is an attractive landscape plant in the Pacific Northwest. The hardiness, branching pattern, and white bark of Oregon white oak and Brewer's oak are appealing characteristics .
Wood Products: Oregon white oak wood is strong, hard, and close grained. In the past it was used for ships, wagons, and railroad ties . Characteristics of Oregon white oak as a fuelwood are provided in . Today Oregon white oak is used to make furniture, flooring, veneer, boxes, crates, pallets, and caskets . Oregon white oak has been used for fence posts . Additional information regarding the decay resistance of Oregon white oak is available in . For more on the uses, characteristics, and properties of Oregon white oak wood and factors that may affect these characteristics, see [82,104].
Importance to Livestock and Wildlife
Many wildlife species utilize Oregon white oak as a food source and for cover, perching, nest material, and nest sites . In a 1940 review, Van Dersal  indicates that ring-necked pheasants, band-tailed pigeons, ruffed grouse, gray sapsuckers, California woodpeckers, Lewis's woodpeckers, American black bears, mule deer, dusky-footed woodrats, and Douglas ground squirrels utilize Oregon white oak. Van Dersal's list is not exhaustive.
Variable Oregon white oak acorn production (see Seed production) may have affected findings in short-term usage studies.
Cattle: Cases of cattle being poisoned by Oregon white oak are often related to other extenuating circumstances. In southern Oregon, 30 of 117 steers became ill when grazing in Oregon white oak woodlands and savannahs. Calves were observed feeding under Oregon white oak trees where acorns were likely abundant because of an earlier severe storm. Green acorns likely made cattle ill. Weather events that dislodge an abundance of acorns, a lack of more palatable forage, and/or young grazing animals are often associated with reports of oak poisoning in cattle .
Domestic sheep: Domestic sheep grazing on Mt Hood appeared to prefer Oregon white oak acorns (Coville 1898, cited in ).
Deer: Oregon white oak provides habitat and food for young and old white-tailed and mule deer. The oak-Pacific madrone cover type was used most frequently (33%) by 11 white-tailed deer fawns. Fawns averaged 5.7 days old when collared and were monitored during the summer in Oregon's lower northern Umpqua River Watershed. Male fawns used the type more than female fawns . In the Klickitat Basin of Washington, McCorquodale  found that 66 radio-collared, migratory Columbian black-tailed deer preferred (P<0.05) winter habitats with an overstory dominated or codominated by Oregon white oak. Preference was determined by use versus availability. The lack of snow, abundance of forage, availability of acorns, and associated shrubs and arboreal lichens likely affected preference .
In the William L. Finley National Wildlife Refuge, Oregon white oak acorns made up 9% to 93% of the weight of 4 Columbian black-tailed deer stomachs . Brewer's oak receives heavy to moderate mule deer use and makes up a bulk of fall mule deer diets in California's western Glenn County .
Large mammals: The stomachs of mountain lions collected in the winter from Oregon's western Cascade Range did not contain Oregon white oak, but researchers noted that Oregon white oak was recovered from mountain lions collected at other times of the year. Whether or not Oregon white oak consumption was purposeful or incidental was not reported .
Small mammals: A variety of small mammals utilize Oregon white oak habitats and feed on Oregon white oak acorns and/or seedlings. In Oregon white oak-dominated sites in Fort Lewis, Washington, the most abundant small mammals, listed in order of decreasing abundance, were deer mice, vagrant shrews, Trowbridge's shrews, and creeping voles . Oregon white oak woodlands are also important habitat for western gray squirrels in Fort Lewis. High-use stands had 34% Oregon white oak and 53% Douglas-fir in the overstory. Low-use stands had 53% Oregon white oak and 43% Douglas-fir in the canopy. Use was lower in stands with high Scotch broom abundance. Researchers observed western gray squirrels digging and foraging for Oregon white oak acorns from November to March and gathering and burying acorns in August and September .
Oregon white oak was found 11 times in 63 dusky-footed woodrat nests near Corvallis, Oregon . In the William L. Finley National Wildlife Refuge, small mammals took 61% of the Oregon white oak acorns available in savannahs and 96% in closed-canopy woodlands . In west-central Willamette Valley, 3 of 23 marked Oregon white oak seedlings died from taproot severing by pocket gophers . An additional discussion of small mammals that feed on Oregon white oak acorns and disperse acorns is provided in Seed dispersal.
Game birds: Wild turkeys are common in Oregon white oak habitats of Oregon and Washington. Of 2,288 wild turkeys located in southern Wasco County, Oregon, 18.6% were in Oregon white oak, 15.2% in ponderosa pine-Oregon white oak, and 18.2% in ponderosa pine-Douglas-fir-Oregon white oak stands. Use of these habitats occurred year-round . In Washington's Klickitat County, 4 wild turkey broods were monitored using radio transmitters from mid-May to early July. Broods used Oregon white oak and ponderosa pine-Oregon white oak habitats more than expected based on their availability (P<0.05). Douglas-fir forests and nonforested habitats were used less than expected. Oregon white oak and ponderosa pine-Oregon white oak communities supported a diverse understory, which likely provided escape cover, and many open areas with insects and herbaceous foods .
Other birds: Numerous studies suggest that Oregon white oak communities provide important breeding, nesting, and foraging sites. In 5 Oregon white oak stands in western Oregon, the Shannon-Weaver avian diversity was 2.46 to 3.13, depending on the season. The researcher noted that these levels of diversity were greater than those reported for many other forest communities . In south-central Washington, bird abundance was high in study sites dominated by a mixture of small Oregon white oak and ponderosa pine trees and in pure Oregon white oak stands . Species richness was greater in Oregon white oak woodlands than in any age class of Douglas-fir forests in the Cascade Range of south-central Washington (Manuwal 1991, cited in ). In northwestern Humboldt County, California, Oregon white oak acorns made up the bulk of band-tailed pigeon's fall diet .
In mixed Douglas-fir-hardwood forests of western Oregon, researchers observed 140 Oregon white oak trees with excavated cavities, indicating use by cavity-nesting birds in the area . Oregon white oak woodlands in south-central Washington provided important nesting habitat for Nashville warblers . Large-sized Oregon white oak trees are important to acorn woodpeckers in Benton County, Oregon. Granaries were located in areas where Oregon white oak basal area averaged 50.1 mÂ²/ha, and the DBH of surrounding Oregon white oak trees averaged 25.5 inches (64.7 cm). Large tree conservation may be important in managing acorn woodpeckers .
Of 17 bird species surveyed in fragmented Oregon white oak woodlands on Vancouver Island, 2 species, the brown-headed cowbird and chipping sparrow, favored Oregon white oak woodlands over Douglas-fir forests. The size of many bird populations was related to patch size and human population densities, suggesting that protection of woodlands and forests from urbanization is important to bird management .
In the Willamette Valley, researchers found more breeding neotropical migrants in Oregon white oak woodlands than in coniferous forests. Western wood-pewee, Lazuli bunting, and Cassin's vireo were not found regularly in coniferous forests. Acorn woodpeckers, downy woodpeckers, white-breasted nuthatches, black-capped chickadees, northern flickers, and Bewick's wrens are cavity-nesting species, and large-diameter open-grown Oregon white oak trees provided more cavities than did Douglas-fir forests. White-breasted nuthatches were negatively correlated (R = -0.65) with increasing Douglas-fir cover, and populations are in decline in the Willamette Valley. Researchers indicate that "conservation of Oregon white oak habitats is critical to the maintenance of populations of several avian species in the Willamette Valley" . An additional discussion of birds that feed on Oregon white oak acorns and often disperse acorns is provided in Seed dispersal.
Amphibians and reptiles: Many amphibians and reptiles occur in Oregon white oak meadows in the Georgia Depression of British Columbia. The "rarely observed" sharp-tailed snake has a distribution closely resembling Oregon white oak's, and sharp-tailed snake persistence may depend on Oregon white oak habitat conservation .
Palatability/nutritional value: Oregon white oak is considered good to fair browse for deer, poor to "useless" for cattle, domestic sheep and goats, and "useless" for horses . In a review, Van Dersal  reports that Oregon white oak protein levels are similar to those in alfalfa (Medicago sativa). Oregon white oak leaves collected from lower crowns in Humboldt County, California, averaged 11.4% protein in the dry season (June-October) and 12% in the wet season (November-July). Acid soluble lignin concentrations averaged 15.1% and 21.1% in the dry and wet seasons, respectively. Total sugar concentrations were very similar in the dry (4.6%) and wet seasons (4.5%) . Oregon white oak acorns collected from sites near Weaverville, California, were 3% protein, 3.4% fat, 9.1% fiber, 52.5% nitrogen-free extract, and 1.4% ash .
Cover value: Oregon white oak trees and shrubs provide important cover and shade for livestock and wildlife. This topic has been addressed briefly in Importance to Livestock and Wildlife.
Specialty items, fenceposts, and fuel are now the primary uses of Oregon white oak. The wood is considered one of the best fuels for home heating and commands top prices. It has been used for flooring, interior finish, furniture, cooperage staves, cabinet stock, insulator pins, woodenware, novelties, baskets, handle stock, felling wedges, agricultural implements, vehicles, and ship construction (60). Consumption of Oregon white oak totaled 12 454 m³ (2,185,000 fbm) exclusive of fuel in 1910 but has since declined (60).
Although Oregon white oak is not grown commercially for landscape purposes, scattered native trees, groves, and open stands are highly valued scenic assets in wildland, farm, park, and urban areas (35,42,49,56). Mistletoe is a scenic growth on Oregon white oaks that is collected and sold as a decorative and festive minor product.
Until recent times, meal or mush made from acorns of many oaks (including Oregon white oak) was a common Indian food (35,71,81). When crops were heavy, white oak acorns were also gathered and stored by local ranchers for feed, mainly for hogs. Livestock forage for acorns and prefer those of white oaks to black oaks (81). The leaves have a protein content of 5 to 14 percent (35,56), and Oregon white oak is rated as good to fair browse for deer but poor for domestic livestock.
Oregon white oak woodlands and forests provide favorable habitat for wildlife (6) and also produce substantial amounts of forage for sheep and cattle (33). Infrequently, cattle are poisoned by foraging on oak; one instance involving Oregon white oak has been documented (37).
Oak-dominated forests in the western part of the Willamette Valley in Oregon have a higher diversity of birds in all seasons than adjacent conifer forests (3). Oregon white oak and ponderosa pine-Oregon white oak associations are preferred brood habitats for Merriam's wild turkey in south-central Washington (39).
Greenhouse experiments have shown that Oregon white oak is a good host for the gourmet truffle, Tuber melanosporum (43). The feasibility of managing Oregon white oak stands for truffle production, as many oak stands are managed in Europe, is being investigated.
Wildlife: Oregon oak is a valuable source of food and cover for wildlife. Gray squirrels, deer, and livestock eat acorns and the leaves of young shoots and sprouts.
Ethnobotanic: Native Americans used Acorns as a food staple.
Construction: In the Pacific Northwest, large trees were preferred for shipbuilding, railroad ties, and construction. Resistance to decay also contributed to its use as fence posts. The wood continues to be important to cottage furniture and cabinet industries.
Quercus garryana, the Garry oak, Oregon white oak or Oregon oak, is a tree species with a range stretching from southern California to southwestern British Columbia. It grows from sea level to 210 metres (690 ft) altitude in the northern part of its range, and at 300 to 1,800 metres (980 to 5,910 ft) in the south of the range in California. The tree is named after Nicholas Garry, deputy governor of the Hudson's Bay Company, 1822–35.
In British Columbia, the Garry oak occurs on the Gulf Islands and southeastern Vancouver Island, from west of Victoria along the east side of the island up to the Campbell River area. There are also small populations along the Fraser River on the British Columbia mainland.
In Washington state, it grows on the west side of the Cascade Range, particularly in the Puget Sound lowlands, the northeastern Olympic Peninsula, Whidbey Island and the San Juan Islands. It also grows in the foothills of the southeastern Cascades and along the Columbia River Gorge.
In California, the garryana variety grows in the foothills of the Siskiyou and Klamath Mountains, the Coast Ranges of Northern California, and of the west slope of the Cascades. The semota variety grows in the Sierra Nevada and Coast Ranges as far south as Los Angeles County.
There are three varieties:
- Quercus garryana var. garryana – tree to 20 (30) m. British Columbia south along the Cascades to the California Coast Ranges.
- Quercus garryana var. breweri – shrub to 5 m; leaves velvety underneath. Siskiyou Mountains.
- Quercus garryana var. semota – shrub to 5 m; leaves not velvety underneath. Sierra Nevada.
It is a drought-tolerant tree, typically of medium height, growing slowly to around 20 m (occasionally as high as 30 m) or as a shrub to 3 to 5 metres (9.8 to 16.4 ft) tall. It has the characteristic oval profile of other oaks when solitary, but is also known to grow in groves close enough together that crowns may form a canopy. The leaves are deciduous, 5–15 cm long and 2–8 cm broad, with 3-7 deep lobes on each side. The flowers are catkins, the fruit a small acorn 2–3 cm (rarely 4 cm) long and 1.5–2 cm broad, with shallow, scaly cups.
The Oregon white oak is commonly found in the Willamette Valley hosting the mistletoe Phoradendron flavescens. It is also commonly found hosting galls created by wasps in the family Cynipidae. 'Oak apples', green or yellow ball of up to 5 cm in size, are the most spectacular. They are attached to the undersides of leaves. One common species responsible for these galls is Cynips maculipennis. Other species create galls on stems and leaves. Shapes vary from spheres to mushroom-shaped to pencil-shaped.
While the invasive plant disease commonly called Sudden Oak Death attacks other Pacific Coast native oaks, it has not yet been found on the Garry oak. Most oak hosts of this disease are in the red oak group, while Garry oak is in the white oak group.
Garry oak is the only native oak species in British Columbia, Washington, and northern Oregon. In these areas, Garry oak woodlands are seral, or early-successional – they depend on disturbance to avoid being overtaken by Douglas-fir (Pseudotsuga menziesii). The disturbance allowing Garry oak to persist in an area that would otherwise succeed to coniferous forest was primarily fire. Natural wildfires are relatively common in the drier portions of the Pacific Northwest where Garry oak is found, but fire suppression has made such events much less common. In addition, early settlers' records, soil surveys, and tribal histories indicate that deliberate burning was widely practiced by the indigenous people of these areas. Fire perpetuated the grasslands that produced food sources such as camas, chocolate lily, bracken fern, and oak; and that provided grazing and easy hunting for deer and elk. Mature Garry oaks are fire-resistant, and so would not be severely harmed by grass fires of low intensity. Such fires prevented Douglas-fir and most other conifer seedlings from becoming established, allowing bunch grass prairie and Garry oak woodland to persist. Fire also kept oak woodlands on drier soils free of a shrub understory. Wetter oak woodlands historically had a substantial shrub understory, primarily snowberry.
- Propertius duskywing butterfly Erynnis propertius, sole larval food plant is oak
- Bucculatrix zophopasta leaf-mining moth, sole larval food plant is oak
- Lewis woodpecker Melanerpes lewis
- Slender billed nuthatch Sitta carolinensis aculeata
- Sharp tailed snake Contia tenuis
- Western gray squirrel Sciurus griseus
- Western tanager Piranga ludoviciara
- Western wood peewee Contopus sordidulus
- Western bluebird Sialia mexicana
- Sessile trillium Trillium parviflorum
- Banded cord-moss Entosthodon fascicularis
- Apple moss Bartramia stricta
- (liverwort) Riccia ciliata
Garry oak woodlands create a landscape mosaic of grassland, savanna, woodland, and closed-canopy forest. This mosaic of varied habitats, in turn, allows many more species to live in this area than would be possible in coniferous forest alone. Parks Canada states that Garry oak woodlands support more species of plants than any other terrestrial ecosystem in British Columbia. It grows in a variety of soil types, for instance, rocky outcrops, glacial gravelly outwash, deep grassland soils, and seasonally flooded riparian areas.
The Donation Land Claim Act of 1850 encouraged Anglo settlement of Washington and Oregon, and marked the beginning of the end of regular burning by Indians of the area (Perdue IN Dunn and Ewing). The arrival of Europeans also reduced the number of natural fires that took place in Garry oak habitat. With fire suppression and conversion to agriculture, Garry oak woodlands and bunch grass prairies were invaded by Douglas-fir, Oregon ash (Fraxinus latifolia), and imported pasture grasses. Oaks were logged to clear land for pasture, and for firewood and fence posts. Livestock grazing trampled and consumed oak seedlings. By the 1990s, more than half the Garry oak woodland habitat in the South Puget Sound area of Washington was gone. On Vancouver Island, more than 90% was gone. Remaining Garry oak woodlands are threatened by urbanization, conversion to Douglas-fir woodland, and invasion by shrubs, both native and nonnative (Scotch broom Cytisus scoparius, sweetbriar rose Rosa eglanteria, snowberry Symphoricarpos albus, Indian plum Oemleria cerasiformis, poison-oak Toxicodendron diversilobum, English holly Ilex aquifolium, bird cherry Prunus avens). Conversely, oak groves in wetter areas that historically had closed canopies of large trees are becoming crowded with young oaks that grow thin and spindly, due to lack of fires that would clear out seedlings.
Although the wood has a beautiful grain, it is difficult to season without warping, and therefore the Garry oak has not historically been regarded as having any commercial value and is frequently destroyed as land is cleared for development. However, Garry oaks and their ecosystems are the focus of conservation efforts, including in communities such as Oak Bay, British Columbia, which is named after the tree, and Corvallis, Oregon. Moreover, recently the wood, which is similar to that of other white oaks, has been used experimentally in Oregon for creating casks in which to age wine. It is above all an excellent firewood.
In Oak Bay, British Columbia, a fine of up to $10,000 may be issued for each Garry oak tree cut or damaged.
- "GOERT". Garry Oak Ecosystems Recovery Team. Retrieved 3 February 2011.
- "Burke Herbarium". University of Washington. Retrieved 3 February 2011.
- Franklin and Dyrness (1988). Natural Vegetation of Oregon and Washington. Corvallis, Oregon: Oregon State University Press. ISBN 0-87071-356-6.
- "USDA PLANTS Database". United States Department of Agriculture. Retrieved 3 February 2011.
- Haggard, Peter and Judy (2006). Insects of the Pacific Northwest. Portland, Oregon: Timber Press. ISBN 978-0-88192-689-7.
- APHIS. "Phytophthora ramorum host list". USDA. Retrieved 6 February 2011.
- Dunn and Ewing (1997). Ecology and Conservation of the South Puget Sound Landscape. Seattle: The Nature Conservancy.
- Lea; Miles; McIntosh (2006). "Garry Oak Ecosystem Recovery Team Colloqium".
- Parks Canada. "Garry Oak Ecosystems". Retrieved 7 February 2011.
- Barnes, Marc (November 2003). "Bald Hill Oak Restoration". Oregon Oak Communities Working Group. Retrieved 11 August 2013.
- "What is the best firewood to burn". Firewoodresource. Retrieved 14 October 2012.
- "Trees on Your Property - An Information Guide to Oak Bay’s Tree Protection Bylaw" (PDF). Oak Bay B.C. Retrieved 18 April 2012.
Names and Taxonomy
Comments: Kartesz (1999) and Flora North America recognize three varieties of Quercus garryana: variety breweri, variety semota, and the typical. An unpublished data set from Kartesz 2004 recognizes a variety fruticosa and not a variety breweri. Flora North America mentions no variety fruticosa.
The scientific name of Oregon white oak is Quercus garryana Dougl. (Fagaceae) [40,62,64,70]. As
the common name suggests, Oregon white oak belongs to
the white oak subgenus (Lepidobalanus) .
Quercus garryana var. breweri (Engelm.) Jepson , Brewer's oak
Quercus garryana var. garryana
Quercus garryana var. semota (Jepson) [47,70], Oregon white oak
Quercus ÃÂ eplingii C. H. Muller [47,62,101,106,144], Epling's oak
(Oregon white oak ÃÂ blue oak (Q. douglasii))
Quercus ÃÂ howelii Tucker [101,143,144], Howell's oak
(Oregon white oak ÃÂ Nuttall's scrub oak (Q. dumosa))
Quercus ÃÂ subconvexa Tucker [40,62,101,143,144]
(Oregon white oak ÃÂ leather oak (Q. durata))
Brewer's oak hybridizes with deer oak (Q. sadleriana) [62,144].
Quercus garryana var. garryana hybridizes with scrub oak (Q. berberidifolia) 
and valley oak (Q. lobata) [62,144]. There may be introgression of Q. garryana var. semota and valley oak
in isolated locations of distribution overlap .
According to Govaerts and Frodin , Q. ÃÂ subconvexa and Howell's oak describe the same
hybrid―Oregon white oak ÃÂ Nuttall's scrub oak.
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