Quercus lobata Née

valley oak
valley white oak
California white oak
water oak
weeping oak
white oak
roble

Valley oak in the Santa Monica Mountains National Recreation Area is
reproducing poorly and is targeted for a long-term monitoring program to
access the health of valley oak populations and communities [20].

More info for the terms: monoecious, natural, tree

Valley oak is a long-lived, flood- and drought-tolerant, monoecious,
deciduous tree [28.56,53]. It is the largest North American oak
[34,53,61] Trees are typically 30 to 75 feet (10-25 m) tall and from 1.8
to 2.4 feet (0.5-0.7 m) in d.b.h. but may become much larger [13,53]. A
record tree in Gridley measures 9.3 feet (2.8 m) in d.b.h. [13], and
Griffin [30] reported a 138-foot (30 m) valley oak at the Hastings
Natural History Reservation of Carmel Valley. Large oaks are usually
hollow or rotten in the center, making exact age determinations
impossible. Age estimates of very large trees range from 400 to 500+
years [8.30]. Mature stands are typically from 100 to 200 years old
[8].

The crowns of open-grown trees are very broad [30]. Valley oaks have a
highly branched growth habit. The oaks are sensitive to chloride
aerosol, and trees growing less than 4 miles (7 km) inland tend to be
scrubby and flagged [55]. Valley oak typically has several vertical
roots that tap groundwater and extensive horizontal root branches
[28,31]. Vertical root depth has been measured as deep as 80 feet (262
m) in some individuals [45]. Acorns are long (1.2 to 2.0 inches [3-5
cm]) and slender (0.5 to 0.8 inch [1.2-2.0 cm]). The bark is thick and
deeply furrowed [53].

Valley oak is endemic to California. It is distributed from Shasta
County south through the Central Valley and lower-elevation foothills
and valleys of the Sierra Nevada and Coast Ranges to Los Angeles County
[34,71]. It also occurs on Santa Cruz and Santa Catalina Islands [46].

More info for the terms: fire regime, litter, root crown, woodland

Valley oak has a number of strategies which enable it to survive fire.
Mature trees are fire resistant, while top-killed seedlings and saplings
sprout from the root crown [30,32]. The symbiotic relationship between
this species and animals which store acorns underground favors postfire
species regeneration, as buried acorns usually survive fire [15].

Historically, valley oak woodland burned on approximately a yearly
basis. Lightning usually struck the taller, older oaks. These hollow,
punky oaks were frequently the source of fire ignition once hit. Fires
were typically hot but burned quickly, carried by dry grasses and oak
litter, with few downed woody fuels [74].

FIRE REGIMES :
Find fire regime information for the plant communities in which this
species may occur by entering the species name in the FEIS home page under
"Find FIRE REGIMES".

More info for the terms: fire suppression, litter, shrubs, woodland

The threat of severe fire has greatly increased where valley oak
woodlands border coniferous forests. Due to fire suppression, these
woodlands frequently contain an understory of conifer saplings and small
trees, with a deep litter of oak leaves, needles, cones, and downed
woody fuels [32].

Prescribed burning would increase valley oak numbers. Near coniferous
forests, fire would eliminate invading conifers such as Coulter and
ponderosa pine from valley oak woodland [32]. At lower elevations,
populations of live oaks and shrubs such as buckthorn (Rhamnus spp.) and
sumac (Rhus spp.) continue to increase in valley oak woodland in the
absence of fire [12,31]. Some authorities, however, fear that postfire
recovery of valley oak may be impaired under drought conditions [74],
and prescribed burning is not recommended in years of low precipitation.

Fire scars provide entry points for various heart-rot fungi. Badly
fire-scarred trees are susceptible to windthrow [60].

Scrub jays help facilitate postfire regeneration, as they prefer burn
areas as acorn-caching sites [54].

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More info for the term: phanerophyte

Phanerophyte

More info for the terms: cover, forest, habitat type, herbaceous, lichen, mesic, shrub

Valley oak grows in the deep, rich soil typical of floodplains and
valley floors [34,43]. Slope rarely exceeds 35 percent [2]. Soil
textures include silty loam, clayey loam, and sandy clay loam. Valley
oaks near undammed waterways receive annual inputs of silty alluvium
[39]. The oaks depend on water-table access [14]. Best growth is
attained when water tables are about 33 feet (10 m) below the surface
[5]. They will tolerate poorly drained soil and wet seeps [11,41].
Valley oaks in riparian forests receive subsurface irrigation.
Historically, these forests were inundated about every 5 years [26].
Where distribution overlaps with other oaks, valley oaks are found on
the more mesic sites with deeper soils [48].

The oaks grow in a Mediterranean climate, characterized by wet, mild
winters and hot, dry summers. Coastal valley oaks receive from 20 to 80
inches (51-203 cm) of annual precipitation; inland populations receive
from 6 to 30 inches (14-76 cm) [7]. Fog is common along the coast in
summer and inland during winter [29]. Elevation ranges from sea level
to a maximum of 5,100 feet (1,700 m) in the Tehachapi Mountains [30].

Plant associations: Overstory associates not listed as SAF COVER TYPES
include Fremont cottonwood, white alder (Alnus rhombifolia), arroyo
willow (Salix lasiolepsis), valley willow (S. goodingii), Oregon ash
(Fraxinus latifolia), Hind's walnut (Juglans hindsii), California black
walnut (J. californica), California buckeye (Aesculus californica), box
elder (Acer negundo), Coulter pine (Pinus coulteri), interior live oak,
Engelmann oak (Quercus engelmannii), and pin oak (Q. plaustris). Common
exotics are eucalyptus (Eucalyptus spp.), tree-of-heaven (Ailanthus
altissima), and fig (Ficus caria) [5,12,30,36,40].

Shrub associates include poison-oak (Toxicodendron diversilobium),
coffeeberry (Rhamnus californica), redberry (R. crocea), Mexican tea
(Chenopodium ambrosiodes), California blackberry (Rubus vitifolius),
coyotebush (Baccaris pilularis var. consanguinea), California rose (Rosa
californica), buckbrush (Ceanothus cuneatus), birchleaf
mountain-mahogany (Cercocarpus betuloides), squawbush (Rhus trilobata),
and Mexican elderberry (Sambucus mexicana) [1,9,12,53].

Herbaceous associates include bermuda grass (Cynodon dactylon), purple
needlegrass (Stipa pulchra), Harding grass (Phalaris tuberosa var.
stenoptera), wild oat (Avena fatua), pine bluegrass (Poa scabrella),
soft chess (Bromus mollis), yellow star thistle (Centaurea
solstitialis), annual agoseris (Agoseris heterophylla), golden brodiaea
(Brodiaea lutea), and California melicgrass (Melica californica). The
state-endangered California hibiscus (Hibiscus californicus) occurs
within the valley oak riparian forest habitat type [9,11,21,35,64].

Other: Creeping woody plants using valley oak for vertical support
include wild grape (Vitis californica); poison-oak often assumes this
growth form as well [39]. Mistletoe (Phoradendron villosum) is a common
valley oak parasite [60]. Physconia detersa is frequently the dominant
lichen on valley oak bark [68].

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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):

221 Red alder
222 Black cottonwood - willow
223 Sitka spruce
232 Redwood
233 Oregon white oak
234 Douglas-fir - tanoak - Pacific madrone
245 Pacific ponderosa pine
246 California black oak
249 Canyon live oak
250 Blue oak - Digger pine
255 California coast live oak

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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):

FRES20 Douglas-fir
FRES21 Ponderosa pine
FRES24 Hemlock - Sitka spruce
FRES27 Redwood
FRES28 Western hardwoods
FRES42 Annual grasslands

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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 terms: forest, shrub

K001 Spruce - cedar - hemlock forest
K005 Mixed conifer forest
K006 Redwood forest
K009 Pine - cypress forest
K010 Ponderosa shrub forest
K011 Western ponderosa forest
K026 Oregon oakwoods
K029 California mixed evergreen forest
K030 California oakwoods
K048 California steppe

More info for the terms: crown fire, moderate-severity fire, surface fire

Moderate-severity fire top-kills seedlings and saplings. Larger valley
oaks are resistant to such fire. Moderate-severity fire on the Chews
Ridge of the Santa Lucia Range in Monterey County killed only one valley
oak larger than 12 inches (30 cm) d.b.h. [32]. Trees suffering basal
burning are most likely to be killed [59]. Hot surface fire may kill
large trees with extensive internal rot. During the Chews Ridge Fire,
mortality occurred when the interior punky wood of older valley oaks
ignited, leaving exterior bark uncharred. Trees less than 20 inches (50
cm) in d.b.h. are usually killed by hot surface fires. Crown fire will
kill a large number of valley oak of all size classes. Forty-eight
percent of valley oak were killed on portions of the Chews Ridge where
crowning occurred [32].

More info for the terms: cover, cover type, density, forest, woodland

Remaining valley oak riparian and woodland areas comprise critical
habitat which is intensively used by wildlife. Collectively, valley oak
riparian forests support 67 nesting bird species, more than any other
California habitat for which data are available [23]. The
state-threatened Swainson's hawk is closely associated with riparian
habitat in the Central Valley, where these hawks use large valley oaks
as nesting sites [66]. Other animal species living within the valley
oak riparian forest cover type and in danger of extirpation include the
state-threatened greater sandhill crane, the state-endangered
yellow-billed cuckoo, and the federally-threatened elderberry longhorn
beetle [26,40]. In addition, these forests provide habitat for rare
remnant populations of ringtail in the Central Valley [9]. Valley oak
woodlands support much wildlife as well. The valley oak woodland of the
Tehachapi Mountains supports 45 species of birds. Valley oaks there are
preferred foraging substrate for the northern oriole, housewren, and
acorn woodpecker [12]. The valley oak woodland of the Bobelaine Audubon
Sanctuary near the Feather River has a mean density of 16 birds per acre
(40 birds/ha), with 35 species present. The area is preferred wintering
grounds for various sparrows and the dark-eyed junco [51].

Valley oak is used by various cavity-nesting and cavity-storing birds
and mammals [50]. It supplies browse for livestock, black-tailed deer,
lagomorphs, and various rodents. Pocket gopher, California ground
squirrel, and deer mouse are heavy consumers of valley oak seedlings.
Acorns are an important diet item of the California ground squirrel,
pocket gopher, scrub jay, yellow-billed magpie, acorn woodpecker,
black-tailed deer, feral pig, and of cattle. Roots are consumed by
feral pig and pocket gopher [30,35,75].

More info for the terms: association, codominant, cover, forest, grassland, hardwood, natural, phase, shrub, tree, woodland

This species dominates two plant communities: the valley oak woodland
and the valley oak riparian forest. It is often the only tree in valley
oak woodland, which are composed of grassy savannas with large, widely
spaced oaks. The valley oak woodland and the annual grassland are
closely associated, and together form a mosaic over portions of
California's low-elevation rangeland [41]. Historically, the associated
grassland was probably dominated by perennial bunchgrasses [37]. Valley
oak woodland, once extensive, has largely been cleared for farmland and
now occurs in scattered remnant patches. Isolated trees are sometimes
found in cultivated fields [77].

Valley oak riparian forest occurs on levees and the highest parts of
floodplains [38,40]. Canopies are open to densely closed; shrub cover
may be as great as 70 percent [13]. Historically, these forests
extended 0.6 to 5.0 miles (1-8 km) on each side of major rivers [5,38].

Valley oak riparian forest merges with Fremont cottonwood (Populus
fremontii) riparian forest near waterways and with valley oak woodland
on upland sites [39]. In foothill oak (Quercus spp.) woodlands, the
valley oak phase merges with the California black oak (Quercus
kelloggii), coast live oak (Q. agrifolia), or interior live oak (Q.
wislizeni) phases [2]. Valley oak is an indicator of rich, deep
alluvial soils that comprise some of the most fertile farmland in the
world [41,62].

Publications listing valley oak as a dominant or codominant species in
habitat typings are as follows:

A classification system for California's hardwood rangelands [2].
Blue oak communities in California [3].
Association types in the North Coast Ranges of California [16].
Riparian vegetation and flora of the Sacramento Valley [17].
Oak woodland [31].
Vegetation and floristics of Pinnacles National Monument [35].
Terrestrial natural communities of California [39].

More info for the term: tree

Tree

More info for the terms: cover, cover type, forest, natural, series, woodland

The valley oak cover type currently occupies an estimated 274,000 acres
(109,600 ha). About 86 percent of this is privately owned, and
miscellaneous federal agencies manage most of the land containing the
other 14 percent. National Forests contain only a trace. Fifty-two
percent of the valley oak type is in sawtimber stands; 48 percent is in
poletimber and sapling stands [13]. Valley oak cover was once
extensive, extending through lowlands and into foothills [7]. Jepson
[42] reported 400 square miles (91,040 sq km) of valley oak woodland
covering the eastern San Joaquin Valley in 1910. Valley oak riparian
forest currently occupies about 12,000 acres (4,856 ha) on the
Sacramento River System, approximately 1.5 percent of original acreage
[38].

The greatest problem facing valley oak managers is lack of sapling
recruitment. Due to a number of factors, most young valley oak die
before reaching sexual maturity [30,61]. Obstacles to sapling
recruitment are discussed in REGENERATION. Another major management
concern is loss of mature trees. Valley oak have died in some areas
because of greatly lowered water tables. In other areas, the
accumulation of saline irrigation runoff has killed oaks. Mature trees
are sensitive to overwatering, pruning, grade changes, and blankets of
asphalt covering the root system [61]. Trees are resistant to
short-term drought; mature trees suffer drought damage only when a
series of dry seasons lower water tables to extreme depths [28].

Oak diseases cause scant mortality in valley oak under natural
conditions. Most valley oaks are infected with the heart-rot fungus
Armillaria mellea, but it is usually fatal to only very old trees. It
is nearly always fatal, however, to orchard trees planted in fields
recently cleared of oaks [60]. Acorns are frequently infested with
filbert worm (Melissopus latiferreanus) and filbert weevil (Curculio
occidentis). Fifty-eight percent of insect-infested acorns germinate
and develop normally [43].

Where present, rooting feral pigs cause considerable damage. In the
valley oak woodland of Pinnacles National Monument, over 9 percent of
total valley oak cover was destroyed by feral pigs. Managers had the
community fenced off to exclude pigs [35].

Valley oak are not adapted to snow, and the heavy, wet snowfalls that
sometimes occur within their range cause considerable limb breakage
[29].

The percent composition of valley oak acorns is as follows [76]:

moisture 40.57 ash 1.08
crude protein 2.82 calcium 0.08
crude fiber 7.84 phosphorus 0.06
fat 4.25 tannins 3.85

Information on the nutritional value of valley oak browse is sparse.
The mineral value of mature leaves for black-tailed deer is rated as
follows [67]:

phosphorus: fair
calcium: good
phosphorus/calcium ratio: fair (0.20:0.86)

CA

More info for the term: mast

Native Americans used valley oak acorns for making meal [4]. During the
last century, domestic pigs were driven to Central Valley oak woodlands
for mast feedings [61].

Valley oak acorns are selectively chosen by acorns predators over those
of other species, probably because of their large size [70].

The palatability of mature valley oak browse has been rated as poor for
cattle; useless for horses; poor to useless for sheep and goats; and
fair to poor for black-tailed deer [63].

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Valley oak seasonal development is as follows:

catkins emerge: March to April [53]
leaves emerge: March [14]
acorns ripe: October to November [15]
leaves fall: November [14]

More info for the terms: natural, root crown

Griffin [32] found that valley oak greater than 26.4 inches (66 cm) in
d.b.h. did not produce root crown sprouts following the Chews Ridge
Fire. Ninety-three percent of trees with basal sprouts were between 4.0
and 15.6 inches (10-39 cm) in d.b.h. Where fire was moderate, sprouts
averaged 18 inches (45 cm) in height at postfire year 1. Trees sapling-
size or larger had grown a large number of epicormic sprouts as well.
Where fire was severe, surviving valley oaks produced mostly basal
sprouts, averaging 19 inches (47 cm) in height. A minority (21 percent)
of saplings and larger trees grew epicormic sprouts, but many epicormic
sprouts were dying by the end of postfire year 1. Many small trees had
severe basal scars where bark was peeling off. Trees with burned crowns
grew no epicormic sprouts. Basal sprouts of such oaks, however, were
taller than those from any other class of fire, averaging 24 inches (59
cm) in height.

Literature describing postfire natural regeneration and long-term fire
recovery of valley oak woodlands are lacking. There are currently no
reports of fire research conducted in valley oak riparian forests.

More info for the terms: ground residual colonizer, secondary colonizer

Tree with adventitious-bud root crown/root sucker
Ground residual colonizer (on-site, initial community)
Secondary colonizer - off-site seed

More info for the terms: competition, forbs, hypogeal, natural, root crown, seed, tree

Sexual: Valley oak is wind pollinated. Catkins are frost sensitive and
are sometimes killed by freezing temperatures [29]. The age of sexual
maturity and maximum acorn production are not recorded in the literature.
Trees growing in full sun produce the greatest number of acorns [43].
Seeds mature in 1 year [15]. Acorns collected at the Bobelain Audubon
Sanctuary were 58 percent viable; loss of viability was attributed to
insect predation [43]. There is no dormancy requirement. Some acorns
germinate before falling off the parent tree, and many others germinate
soon afterward [27,65]. Seed-caching animals which bury acorns, such as
scrub jay and California ground squirrel, are important to species
survival. Acorns buried by these animals have a greater chance of
germination and successful establishment, as predation of acorns is
usually high [15]. At the Hastings Natural History Reservation, Griffin
[32] reported 100 percent consumption of acorns on the ground. Some
acorns, however, remained until spring when black-tailed deer and cattle
were excluded from the area.

Germination is hypogeal. Seedling emergence is best in seedlings buried
2 to 4 inches (5-10 cm). Shallowly-buried acorns usually desiccate or
are dug up by seed predators [70]. Seedlings grow best in partial shade
or on northern aspects; seedling survival is low on southern aspects
[32]. Valley oak is less browse-resistant than competing live oaks, and
current levels of herbivory are too high to permit significant seedling
recruitment on most sites [6,30]. Random plot samples taken throughout
valley oak's range showed sapling-to-mature tree ratios of 1:10 or worse
[52]. Exceptions are in localized ecotonal and riparian areas [43].
Loss of seedlings due to pocket gopher root herbivory is high [34].
Pocket gopher populations in the Central Valley, once controlled by
drownings during seasonal inundations, have greatly increased following
the building of flood-control dams. Aboveground herbivory by pocket
gopher and other animals causes much mortality as well. Recruitment at
one unproductive site in the Santa Monica National Recreation Area began
once cattle were excluded and weeds removed from around germinants [71].
Seedlings are sensitive to competition from grasses and forbs,
particularly annual grasses. Where soil moisture is limiting, annual
grasses outcompete valley oak seedlings for water [21]. Once saplings
grow above the browse line, mortality is low [30].

Vegetative: Valley oak seedlings and saplings sprout from the root
crown following damage to aboveground portions of the plant [30].
Mature trees do not have this ability, but often grow epicormic sprouts
following damage to branches [32].

More info on this topic.

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):

3 Southern Pacific Border
4 Sierra Mountains

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More info for the terms: climax, hardwood, secondary colonizer

Valley oak is intermediate in shade tolerance [49]. It is a climax
species in floodplain riparian forests; it is also a secondary colonizer
there [69]. On swales denuded by gold dredging on the Merced River,
valley oak seedlings established under the shade of young willows.
Since no parent trees were nearby, it is believed that the oak seedlings
grew from animal-buried acorns [78].

Most authorities classify valley oak woodlands as fire climax, and seral
to mixed hardwood or coniferous forests in the absence of fire
[12,18,30,31,39].

The currently accepted scientific name of valley oak is Quercus lobata
Nee. in the subgenus Quercus or white oak [46,53,72]. Recognized
varieties are as follows [53]:

Q. lobata var. lobata
Q. lobata var. agillara Jeps.
Q. lobata var. insperata Jeps.
Q. lobata var. turbinata Jeps.
Q. lobata var. walteri Jeps.

Valley oak hybridizes with the following species:

x Q. douglasii (blue oak): Q. Xjolonensis Sargent [41,46]
x Q. turbinella ssp. californica (desert scrub oak): Q. Xmunzii
Tucker [41,46]
x Q. dumosa (California scrub oak): Q. Xtowneii Palmer [46,72]
x Q. engelmannii (Engelmann oak] [72]
x Q. garryana (Oregon white oak) [72]

MacDonald oak (Q. macdonalii), found on the Channel Islands, is
recognized by some authorities as a distinct species resulting from
hybridization between valley and California scrub oak [53,72,73].

More info for the terms: forbs, forest, tree, woodland

There is great interest among public and private managers to restore as
much valley oak woodland and riparian forest as possible, and
revegetation projects are numerous [25,26,54,56,58]. Due to heavy acorn
and seedling predation, however, mortality of newly-established
populations often approaches 100 percent on project sites [1,30].
Enclosing plants in a protective device such as wire caging is
recommended until tree height exceeds the browse line. The
effectiveness of various protective devices has been detailed in the
literature [19,33]. Trees are established from nursery stock or from
acorn plantings. Nursery-grown trees planted in the Sepulveda Wildlife
Reserve of Los Angeles County showed good survival during their first
year [57]. Trees grown from on-site acorn plantings, however, usually
establish a deeper taproot and produce earlier top-growth than
transplanted nursery stock [33]. Irrigating seedlings for the first few
years greatly increases survival and growth rates [19]. The Nature
Conservancy is currently restoring 50 acres (20 ha) of valley oak
woodland on an old field on the Consumnes River Preserve of Sacramento
County. Seedlings on this project site attained a height of 4 feet (1.2
m) in the first year, and survival was 95 percent in the first 3 years.
Seedlings were protected from aboveground herbivory and watered every 2
weeks during summer. Grasses and forbs near valley oak seedlings were
weeded [33,34]. In contrast, seedlings at the Hopland Field Station
(Hopland, California), protected from herbivory but left unwatered and
unweeded, attained little or no top-growth in the first year [19].
Fertilizing seedlings is not recommended because it stimulates growth of
competing grass species over growth of the oaks [1]. Acorn collecting
methods and detailed cultivation techniques are described in the
literature [11,19,54,65].

Valley oak lumber has a propensity to crack and warp while drying, and
is often stained by fungus. These problems, however, can be overcome,
and there is a small commercial market for the lumber in the manufacture
of cabinets. The wood is occasionally used for wine barrels.
Historically, it was primarily used as firewood and as a source of
commercial charcoal. Valley oak wood was also utilized in the
construction of the steamboats that once ran the Sacramento and San
Joaquin Rivers, and as keel blocks during World War II [34,62,74].