Quercus garryana

Fagaceae -- Beech family

    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

More info for the term: nonnative species

Oregon white oak is native to western North America. It occurs from Vancouver Island, British Columbia (49 °N latitude), to southern California (34 °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 [40]. 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 [69] 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 [87].

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 [130].

(key to state/province abbreviations)
UNITED STATES CA OR WA
CANADA BC

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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 [15]:

1 Northern Pacific Border

2 Cascade Mountains

3 Southern Pacific Border

4 Sierra Mountains

5 Columbia Plateau

The range of Oregon white oak spans more than 15° of latitude  from just below the 50th parallel on Vancouver Island in Canada  south nearly to latitude 34° N. in Los Angeles County, CA.  South of Courtenay, BC, Oregon white oak is common in the eastern  and southernmost parts of Vancouver Island and on adjacent  smaller islands from near sea level up to 200 m (660 ft) or more  (47). It is not found on the British Columbia mainland except for  two disjunct stands in the Fraser River Valley (28). In  Washington, it is abundant on islands in Puget Sound and  distributed east and west of the Sound and then south and east to  the Columbia River at elevations up to 1160 m (3,800 ft) (68).  Oregon white oak is widespread at lower elevations in most of the  Willamette, Umpqua, and Rogue River Valleys of western Oregon  (67,68). It is also common in the Klamath Mountains and on inland  slopes of the northern Coast Ranges in California to San  Francisco Bay but infrequent from there southward to Santa Clara  County (29).

    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.

Quercus garryana Douglas ex Hook.:
Canada (North America)
United States (North America)

Note: This information is based on publications available through Tropicos and may not represent the entire distribution. Tropicos does not categorize distributions as native or non-native.

Canada

Origin: Unknown/Undetermined

Regularity: Regularly occurring

Currently: Unknown/Undetermined

Confidence: Confident

United States

Origin: Unknown/Undetermined

Regularity: Regularly occurring

Currently: Unknown/Undetermined

Confidence: Confident

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.

More info for the terms: shrub, tree

This description provides characteristics that may be relevant to fire ecology, and is not meant for identification. Keys for identification are available (e.g. [40,62,63,64,101]).

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 [102]. 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 [59]. A shrub form is also noted from the southernmost populations [102]. Thilenius [139] 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 [60]. Male flowers are catkins that are produced on the current year's growth [63]. Female flowers are solitary or in clusters and appear in the leaf axils of new twigs [59]. 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 [102]. 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 [82].

Belowground description: Oregon white oak produces a central taproot and many lateral roots in the top 12 inches (30 cm) of soil [60]. Roots have ecto- and endomycorrhizal associations [100,152].

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 [31].

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. × subconvexa are described in [101]. Brewer's oak. © Michael Charters www.calflora.net

Trees or shrubs , deciduous, trees to 15(-20) m, with solitary trunks, shrubs to 0.1-3 m, multitrunked. Bark light gray or almost white, scaly. Twigs brown, red, or yellowish, 2-4 mm diam., densely puberulent with spreading hairs or glabrate. Buds brown or yellowish, ovoid or fusiform and apex acute, 2-12 mm, glandular-puberulent or densely pubescent. Leaves: petiole 4-10 mm. Leaf blade obovate, elliptic or subrotund, moderately to deeply lobed, 25-120(-140) × 15-85 mm, base rounded-attenuate or cuneate, rarely subcordate, often unequal, margins with sinuses usually reaching more than 1/2 distance to midrib, lobes oblong or spatulate, obtuse, rounded or blunt, larger lobes usually with 2-3 sublobes or teeth, veins often ending in retuse teeth, secondary veins yellowish, 4-7 on each side, the more distal veins often branching within distal lobes, apex broadly rounded; surfaces abaxially light green or waxy yellowish, often felty to touch, densely to sparsely covered with semi-erect or erect, simple and (2-)4-8-rayed, fasciculate hairs 0.1-1 mm, secondary veins raised, adaxially bright or dark green, glossy or somewhat scurfy because of sparse stellate hairs. Acorns 1-3, subsessile, rarely on peduncle to 10(-20) mm; cup saucer-shaped, cup-shaped, or hemispheric, 4-10 mm deep × 12-22 mm wide; scales yellowish or reddish brown, often long-acute near rim of cup, moderately or scarcely tuberculate, canescent or tomentulose; nut light brown, oblong to globose, (12-)25-30(-40) × (10-)14-20(-22) mm, apex blunt or rounded, glabrous or often persistently puberulent. Cotyledons distinct. 2 n = 24.

Quercus douglasii Hooker & Arnott var. neaei (Liebmann) A. de Candolle; Q. garryana var. jacobi (R. Brown ter) Zabel; Q. jacobi R. Brown ter; Q. lobata Née var. breweri (Engelmann) Wenzig; Quercus neaei Liebmann

More info for the terms: association, resistance

Dry prairies, wooded slopes, rocky bluffs, and montane coniferous forests all provide Oregon white oak habitat [40,63,101].

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 °F (-11 to 10 °C), and high July temperatures are often 60 to 84 °F (16-29 °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 [102].

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 [106].

Oregon: Oregon white oak woodlands in central Oregon occupy sites receiving 12 to 59 inches (300-1,500 mm) of precipitation/year [154]. 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 [116].

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 °F (-9.4 °C), and summer temperatures average 70 °F (21 °C). Mean spring and fall temperatures average 50 °F (10 °C) and 54 °F (12 °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 °F (-20 °C). The freezing resistance of buds was 5 °F (-15 °C) [122].

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 [85].

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 °F (22 °C), and less than 1.2 inches (30 mm) of precipitation in the driest summer month [73]. On southern Vancouver Island, Oregon white oak habitats receive 24 to 47 inches (600-1,200 mm) of precipitation per year [119].

Elevation:

Elevation tolerances for Oregon white oak and varieties

Elevation (feet)

Variety, if applicable California Entire range   1,000-5,000 [62,101,106] 0-3,900 [128], up to 7,500 in southernmost range [102] Brewer's oak 2,000-6,200 [62,101] 2,000-6,200 [40,106] Q. g. var. garryana 980-5,900 [62] 0-5,900 [40,62] Q. g. var. semota 2,500-5,000 [101] 2,500-5,900 [40,101]

Soils: Oregon white oak occurs on a variety of soils ranging from dry to very moist and poorly to rapidly draining. Gravelly and heavy clay substrates are tolerated [102,106,128].

In Castle Crags State Park, the Oregon white oak/cheatgrass plant association occurs on cobbly alluvial soils [133]. In the northern California Coast Ranges, Oregon white oak occurs on well-drained, slightly acidic loams [67]. 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 [33].

Oregon white oak woodlands in the Willamette Valley occur on well-drained, moderately deep, acidic soils of igneous, alluvial, or sedimentary origin [139]. 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 [100].

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) [73]. 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 [119].

More info for the terms: association, fern, mesic, natural, tiller, xeric

Oregon white oak is a dominant species in the following vegetation types and plant
communities:

California:

• 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 [25]

• Oregon oak woodland in Coast Ranges

• mixed north slope cismontane woodland in the valleys and lower slopes of the Klamath and North
  Coast ranges [65]

• Oregon white oak woodland vegetation type in north coast areas [161]

• Oregon white oak/common snowberry (Symphoricarpos albus) in Bald
  Hills of Redwood National Park

• Oregon white oak/Columbian larkspur (Delphinium trolliifolium) in draws and
  on moist sites in Redwood National Park's Bald Hills [135,136]

• Oregon white oak/orchardgrass (Dactylis glomerata) in Bald Hills of Redwood National Park

• Oregon white oak/bristly dogstail grass (Cynosurus echinatus) in heavily
  grazed areas in Redwood National Park's Bald Hills [135,136]

• Oregon white oak/cheatgrass (Bromus tectorum) plant association in
  Shasta County's Castle Crags State Park [133]

• Oak brush vegetation in Kern, Tulare, Butte and Shasta counties, dominated by
  Q. g. var. semota [65]

Oregon:

• 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 [127]

• Douglas-fir-Oregon white oak/poison-oak on the Tiller Ranger District in the southern
  Cascade Range [11]

• 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 [116]

• Oregon ash (Fraxinus latifolia)-Oregon white oak/common snowberry on the Muddy Creek floodplain in
  northwestern Oregon's Finley Wildlife Refuge [96]

• Oregon white oak-Pacific madrone (Arbutus menziesii)/poison-oak/bristly dogstail
  grass

• Oregon white oak-Oregon ash/sweetbriar rose/common rush (Rosa eglanteria/Juncus effusus) within the
  interior valleys of the Umpqua
  River basin [127]

• 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
  Valley [139]

• Oregon white oak-birchleaf mountain-mahogany (Cercocarpus montanus var. glaber)
  in the Umpqua and/or Rogue river watersheds [116]

• Oregon white oak/Scotch broom/creeping bentgrass (Cytisus scoparius/Agrostis stolonifera)
  in the Myrtle Island Research Natural Area [140]

• Oregon white oak/Saskatoon serviceberry (Amelanchier alnifolia)/common snowberry in
  the Willamette Valley [139]

• Oregon white oak/poison-oak/medusahead (Taeniatherum caput-medusae)-bristly dogstail
  grass

• Oregon white oak/poison-oak/bristly dogstail grass

• Oregon white oak/poison-oak/orchardgrass
  within the Interior Valleys of the Umpqua River Basin [127]

• Oregon white oak/poison-oak on xeric sites in the Willamette Valley [139]

• Oregon white oak/woods strawberry (Fragaria vesca) on Tiller and Steamboat Ranger Districts in
  the southern Cascade Range [11]

• Oregon white oak/California brome (Bromus carinatus)

• Oregon white oak/bristly dogstail grass in the Umpqua and/or Rogue River watersheds [116]

Oregon and Washington:

• 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 [22]

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 [85]

British Columbia:

• Oregon white oak/hollyleaved barberry (Mahonia aquifolium) [35,36]

• Oregon white oak/oceanspray (Holodiscus discolor) [74]

• Oregon white oak/pink honeysuckle (Lonicera hispidula)

• Oregon white oak/large camas (Camassia leichtlinii)

• Oregon white oak/miner's lettuce (Claytonia perfoliata) [35,36]

• Oregon white oak/broadleaf stonecrop (Sedum spathulifolium)

• Oregon white oak/common chickweed (Stellaria media) [74]

• 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/Alaska oniongrass (Melica subulata) [35,36]

• Oregon white oak/ripgut brome (Bromus diandrus ssp. rigidus)

• Oregon white oak/poverty brome (B. sterilis) [74]

Epling's oak
is a dominant species in the following vegetation types of California:

• Epling's oak/poison-oak

• Epling's oak/spreading hedgeparsley (Torilis arvensis)

• Epling's oak/California fescue (Festuca californica) on Bennett
  Mountain in Sonoma County [145]

More info on this topic.

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 [126]:

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

421 Chokecherry-serviceberry-rose

422 Riparian

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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 [37]:

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

231 Port-Orford-cedar

232 Redwood

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

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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 [77] 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

K033 Chaparral

K034 Montane chaparral

K050 Fescue-wheatgrass

K051 Wheatgrass-bluegrass

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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):

ECOSYSTEMS [44]:

FRES20 Douglas-fir

FRES21 Ponderosa pine

FRES27 Redwood

FRES28 Western hardwoods

FRES34 Chaparral-mountain shrub

FRES35 Pinyon-juniper

FRES36 Mountain grasslands

Oregon white oak can grow on a wide variety of sites, but on good  sites it is often crowded out by species that grow faster and  taller. Hence, Oregon white oak is most common on sites that are  too exposed or droughty for other tree species during at least  part of the year, including inland valleys and foothills, south  slopes, unglaciated and glaciated rocky ridges, and a narrow  transition zone east of the Cascades between conifer forest and  treeless, dissected plateau. Although usually considered a xeric  species, Oregon white oak also commonly occurs in very moist  locations-on flood plains, on heavy clay soils, and on river  terraces. These locations appear to have two common  characteristics-standing water or a shallow water table during a  lengthy wet season and gravelly or heavy clay surface soils that  probably are droughty during the extended dry season. The  distribution of Oregon white oak gives evidence that it can  withstand both lengthy flooding and drought.

    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).

Oregon white oak grows in diverse climates, ranging from the cool,  humid conditions near the coast to the hot, dry environments in  inland valleys and foothill woodlands. Records from 48 climatic  observation stations within or bordering its range indicate that  Oregon white oak has endured temperature extremes of -34° to  47° C (-30° to 116° F) (45,47,53,77). Average  annual temperatures range from 8° to 18° C (46° to  64° F); average temperatures in January, from -11° to  10° C (13° to 50° F); and in July, from 16°  to 29° C (60° to 84° F).

    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.

Oregon white oak is found in pure, closed-canopy stands; in  mixture with conifers or broad-leaved trees; and as scattered  single trees or groves on farmlands, woodlands, and prairies. It  grows to large sizes but is also found extensively as scrub  forest. The best stands are in western Oregon and Washington-in  the Cowlitz, Lewis, and Willamette River drainages-but stands or  trees with substantial volume are found from British Columbia to  central California. Dense dwarf or shrub stands of Oregon white  oak, earlier identified as Quercus garryana var. breweri,  and other stands previously identified as Q. garryana  var. semota, form dense thickets over large areas in  California (29,35,57,76,81). Similar dwarf or shrub forms grow to  a more limited extent on severe sites in the rest of its range  (57,79).

    Oregon white oak is recognized as a distinct forest cover type  (Society of American Foresters Type 233) and is listed as an  associated species in at least eight other forest cover types  (20): Pacific Douglas-Fir (Type 229), Port Orford-Cedar (Type  231), Redwood (Type 232), Douglas-Fir-Tanoak-Pacific Madrone  (Type 234), Pacific Ponderosa Pine (Type 245), California Black  Oak (Type 246), Knobcone Pine (Type 248), and Blue Oak-Digger  Pine (Type 250). Its prominence and occurrence in these types, as  well as in several others for which it is not specifically  listed, vary widely.

    Plant communities have been identified in parts of the Oregon  white oak type. A Garry oak community of two types (oak parkland  and scrub oak-rock outcrop), a Garry oak-arbutus, and an  arbutus-Garry oak community have been defined in the Victoria,  BC, metropolitan area (42). Four communities, ranked in order  from wettest to driest, have been identified in white oak forests  of the Willamette Valley: Oregon white oak/California  hazel/western swordfern, Oregon white oak/sweet cherry/common  snowberry, Oregon white oak/Saskatoon serviceberry/common  snowberry, and Oregon white oak/Pacific poison-oak (73). These  communities are floristically similar, being differentiated  primarily by the relative coverage and frequency of a few shrub  species. Five Oregon white oak communities identified in the  North Umpqua Valley of Oregon were similar to the xeric Oregon  white oak/Pacific poison-oak association of the Willamette  Valley; a sixth was a riparian association dominated by Oregon  white oak and Oregon ash (Fraxinus latifolia) (62). In  California, four communities dominated by Oregon white oak were  found in the Bald Hills woodlands of Redwood National Park (70)  and three communities dominated by Oregon white oak or related  hybrids were identified in a limited area on Bennett Mountain  (75). The shin oak brush association, largely composed of Oregon  white oak, is a distinctive plant community in Kern and Los  Angeles Counties (76).

    The composition of Oregon white oak communities varies greatly  because of differences in soil, topography, and climate, and in  fire and grazing histories. Because of proximity to farmlands,  many communities include introduced forbs and grasses. Pacific  poison-oak (Rhus diuersiloba) and common snowberry (Symphoricarpos  albus) are probably the most widespread and characteristic  shrub associates.

    Species often found with Oregon white oak are listed in table 1.  The listing is not exhaustive; it just indicates the great  variety of common associates. Species associated with Oregon  white oak in chaparral communities and on serpentine soils are  listed in other sources (15,16,79).

                       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

Because of their attractiveness as food,  seed crops of Oregon white oak are often decimated quickly (12).  Larvae of the filbertworm (Melissopus latiferreanus) and  the filbert weevil (Curculio occidentalis) damage crops  even before acorns ripen (23). Maturing or ripe acorns are  consumed by woodpeckers, pigeons, doves, jays, wood ducks, mice,  chipmunks, squirrels, pocket gophers, woodrats, deer, bear, and  other wildlife, as well as by domestic animals.

    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.

More info for the terms: cover, density, fire frequency, fire severity, fire use, fire-return interval, frequency, fuel, ladder fuels, litter, nonnative species, presence, restoration, severity, succession

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 [3]. Nonnative, sensitive, and rare plant or wildlife species also need consideration. Many rare plants [20] and vulnerable, threatened, or endangered butterflies [50] 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 [69], 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 [3]. 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 [136]. 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 [88].

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 [49].

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 °F (74-213 °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 [86].

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 [113]. 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  

stem density

Ash
(surficial 2 cm dry ash from Oregon white oak logs) 8.5a 4.0a No ash 49.5b 10.5b Heat
(60 °C for 10 minute, prior to planting) 33.5a 11.0a No heat 49.5b 3.5b 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 [57].

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 [149]. In the same area, Thysell and Carey [141] 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 [141].

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 [45]. 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 [134].

More info for the terms: basal area, cover, density, fire management, fire use, natural, nonnative species, prescribed fire, shrubs, top-kill, tree

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 °F (19 °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 [135].
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 [72].
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 [120]:

Oregon white oak sprout dimensions on cut or burned sites in the 2nd and 3rd posttreatment years

Time since treatment (years)Sample sizeHeight of tallest sprout in a clump (feet)Crown diameter of sprouting clump (feet)Number of sprouts/clumpmeanrangemeanrangemeanrange2 506.64.4-11.26.82.9-12.3181-573499.26.1-12.88.23.5-12.3101-25
Sugihara and Reed [134], 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 [134].
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
°F (10-20 °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 m²/ha.
Stand structure:
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 on early, late-, and twice-burned sites

Early LateTwiceDensity reductions
(m²/ha)0.7 0.62.1Mortality
(stems/ha)9491523
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 soilsTreatmentSurvival (%)Cover (%)Height (cm)Ash
(surficial 2 cm dry ash from Oregon white oak logs)20a4.2a1.2aNo ash36.5b7.1b2.4bHeat
(60 °C for 10 minute,
prior to planting)286.41.6No heat28.54.92
Averages with different letters within survival, cover, and
height columns are significantly different (P<0.001, P<0.007, and P<0.001,
respectively).

More info for the terms: fire severity, natural, prescribed fire, root crown, severity, tree

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 [134] 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 [120]. 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 [114]. 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 [135]. 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. © 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 [114].

More complete summaries of the studies identified in Oregon white oak sprout and/or seedling regeneration are presented below.

More info for the term: top-kill

Oregon white oak mortality is rare following fire. The bark on mature trees is sufficient to withstand cambial kill from fire in open woodlands [2]. 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 [141] 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.

More info for the terms: adventitious, geophyte, initial off-site colonizer, root sucker, secondary colonizer, tree

POSTFIRE REGENERATION STRATEGY [129]:
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)

More info for the terms: density, fire cycle, fire exclusion, fire frequency, fire regime, fire-resistant species, fire-return interval, forbs, frequency, fuel, root crown, severity, succession, top-kill, tree

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 [2]. 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 [135]. 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" [85]. White [158] 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 [132]. 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 [138].

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 [18]. 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 [2]. 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), [78] (southwestern Oregon), [83] (southwestern Washington), and [147] (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 [68]. 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 [137].

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 [13]. 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 [27].

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 [45].

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 [7] California chaparral Adenostoma and/or Arctostaphylos spp. <35 to <100 [107] cheatgrass Bromus tectorum 109,157] California montane chaparral Ceanothus and/or Arctostaphylos spp. 50-100 western juniper Juniperus occidentalis 20-70 pinyon-juniper Pinus-Juniperus spp. <35 [107] Pacific ponderosa pine* Pinus ponderosa var. ponderosa 1-47 [7] 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 [107] interior live oak Quercus wislizenii <35 [7] redwood Sequoia sempervirens 5-200 [7,39,132] western redcedar-western hemlock Thuja plicata-Tsuga heterophylla >200 [7] *fire return interval varies widely; trends in variation are noted in the species review

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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 [85].

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 [41]. A study conducted in Fort Lewis, Washington, suggested shade was beneficial to Oregon white oak seedling growth [105].

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 [32].

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 [13].

More info for the terms: basal area, competition, cover, density, hypogeal, litter, monoecious, root crown, shrub, tree, xeric

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 [32]. 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 [62]. 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) [118].

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 [160] 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 [135].

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 [26]. 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 [32].

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 [48]. 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 [108].

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 [154]. 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 [26]. 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 [41]. 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 [154].

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 [46] 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 [102]. The potential for seed predation and desiccation is high without burial [41]. 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 [41].

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 [43]. In central Oregon, Douglas's squirrels were observed burying Oregon white oak acorns about 0.8 inch (2 cm) deep [154]. 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 [121]. Pennoyer [34] 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 °F (30 °C) during the day and 70 °F (21 °C) at night was 77% to 100% [16].

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 [61].

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 [41]. 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 [154].

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 [105].

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 m²) on high- than on low-intensity (19.1 seedlings/100 m²) grazed sites. However, sapling density was slightly (9.3 saplings/100 m²) higher on high-intensity than on low-intensity (10.8 seedlings/100 m²) 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 [67].

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 [102]. 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 [32]. The abundance and "vigor" of sprouts typically increases with increased parent plant size [102].

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More info for the terms: geophyte, phanerophyte

RAUNKIAER [112] LIFE FORM:
Geophyte
Phanerophyte

More info for the terms: shrub, tree

Tree-shrub

Oregon white oak has been classed  as intermediate in tolerance, intolerant, and very intolerant of  shade (47). Perhaps such a range of tolerance best describes its  status in different situations. Clearly, it is not tolerant of  over-topping by Douglas-fir and associated conifers. Dead oaks  often found beneath Douglas-fir canopies bear witness that they  could not endure the shade (40,72). In some locations and   situations, Oregon white oak perpetuates itself, indicating that  it can reproduce adequately in its own shade. Branch development  on open-grown trees may be very dense. Sparse development of side  branches in closed stands provides evidence, however, that it  should be classed as intolerant of shade.

    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).

Oregon white oak has a deep taproot and a  well-developed lateral system; it is very windfirm even in wet  areas. Fast taproot extension and sparse development of laterals  are shown by seedlings in the first few weeks of growth. Despite  formation of a deep taproot, a high percentage of oak roots are  found in upper soil layers. Only 11 percent of the total number  of oak roots were found below 76 cm (30 in) in deep Willakenzie  soil (38). In contrast, 28 percent of the total Douglas-fir roots  in the same soil were found below 76 cm (30 in).

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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 [102]. 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 [40].

Oregon white oak sprouts  abundantly from dormant buds on cut stumps, root collars, and  along exposed trunks. Sprouts provide the most certain way to  obtain natural regeneration. In 3 years, stump sprouts in 49  clumps in northwestern California averaged 10 per clump; height  of the tallest sprout averaged 2.8 in (9.2 ft) and crown diameter  per clump 2.5 in (8.2 ft) (52). Larger stumps produced more  sprouts, larger clumps, and faster growing shoots. The spread of  Oregon white oak by root sprouts has been noted in widely  separated instances (28,68,69,70,71,74). In general, the rooting  or layering of oak cuttings is difficult, and there is no reason  to believe that Oregon white oak would be easier to reproduce by  these methods than other oaks.

Acorns of Oregon white oak must be  kept moist until they germinate. In nature, moisture is  maintained by a layer of leaves or through shallow insertion into  soil from impact, rodent activity, animal trampling, or other  soil disturbances. A moisture content of 30 percent or more must  be maintained in cool regulated storage to maintain seed  viability. Storage conditions have not been determined  specifically for Oregon white oak; several methods recommended  for keeping seeds moist should be suitable (46,65).

    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 crops may be heavy  but are considered irregular. The large acorns, typically about 3  em (1.2 in) long and half as wide, mature in one season and ripen  from late August to November. The age when a tree first bears  fruit, the age of maximum production, and the average quantity  produced have not been determined. In one collecting effort,  about 18 kg (40 lb) of acorns per hour could be hand-picked from   the ground under woodland trees between Redding and Weaverville,  CA. The yield was estimated to be 5 to 9 kg (10 to 20 lb) each  for trees 3 to 9 in (10 to 30 ft) tall and 15 to 30 cm (6 to 12  in) in diameter; production for this fair crop was about 560  kg/ha (500 lb/acre) (81). Northeast of Mount Shasta, a fair crop  the same year yielded about 23 kg (50 lb) of acorns from a single  tree 8 in (25 ft) in height and crown spread. In the Willamette  Valley, acorns were dispersed from September to November, and  three crops ranged from failure to 1737 kg/ha (1,550 lb/acre)  ovendry-weight basis (12). Large crops of acorns are also  produced by shrubby forms of Oregon white oak, but density of the  stands can make collection difficult.

    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).

Oregon white oak flowers somewhat  later in the spring than many of its associates. Flowering has  been noted in March, April, May, and June (72,74), but the  seasonal span is probably greater over the wide range of  latitudes and elevations where this species occurs. Flowers  appear concurrently with new leaves and extension of twig growth.

    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.

Under favorable conditions, mature  Oregon white oak trees are 15 to 27 in (50 to 90 ft) tall and 60  to 100 cm (24 to 40 in) in d.b.h. (34,48,72,73). A maximum height  of 36.6 m (120 ft), crown spread of 38.4 in (126 ft), and  diameter of 246 cm (97 in) at d.b.h. are on record (2,35).  Typically, open-grown trees have short holes bearing very large,  crooked branches that form dense, rounded crowns (fig. 3). Such   trees occupy much space but do not produce much volume for  commercial use, except for fuel. In contrast, forest-grown trees  70 to 90 years old have slim, straight holes, fine side branches,  and narrow crowns (60). Trees measured in northwestern California  had average form classes of 63 and 68 (34). Branchwood of trees  over 60 cm (24 in) in d.b.h. averaged 24 percent of total cubic  volume. Trees of better form are probably developing now because  young stands are more even aged and better stocked than those in  the past, but such stands are limited in extent and widely  scattered.

    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).

Though Oregon white oak populations in Washington are disjunct and  scattered, the chemical and morphological characteristics of  their foliage are similar (71). Genetic differences appear so  minor that seed distribution from a common source by Indians has  been postulated. Ecotypic variation was observed in top and root  growth of young seedlings from seed collections made from  Corvallis, OR, southward (43). First-year seedlings from northern  sources were taller and heavier.

    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).

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 0
Specimens with Barcodes: 2
Species With Barcodes: 1

Information on state-level protected status of plants in the United States is available at Plants Database.

Canada

Rounded National Status Rank: NNR - Unranked

United States

Rounded National Status Rank: NNR - Unranked

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.

More info for the terms: basal area, cover, hardwood, nonnative species, prescribed fire, restoration, selection

Conservation:
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 [2] "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
year".

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 [42]. Because Oregon white oak is often an indicator of culturally
important sites in western Washington [131], 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 [125] 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 [94]). Establishing a reference condition,
often the first step to restoration, is challenging without native flora [94].
However, many sources address Oregon white oak management and conservation.
Harrington and Devine [56] 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 [80]. 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 [151].
Climate change:
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 [95].
Diseases/pests:
Diseases affecting Oregon white oak in California are identified and
described in [111].
Silviculture management:
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 [54]. Similar management goals are reported in the 1950s from northwestern California.
In a 1955 paper, Roy [120] 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 [156].
There are regression equations useful for
predicting Oregon white oak height in Oregon. Larsen and Hann [79] 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 [155].

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.

The wood of Oregon white oak is dense, with specific gravity  ranging from 0.52 to 0.88 when ovendry (66), has moderate  strength in static bending tests, but does not absorb shocks well  (47). It rates high in compression and shear strength and is  outstanding among 20 northwestern woods in tension and side  hardness tests (47). The heartwood is at least as durable as that  of white oak (Quercus alba) (58). Pallets made from  Oregon white oak compare favorably in strength with those made  from other species (66) and are higher in withdrawal resistance  for nails or staples (41).

    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.