BOTANICAL AND ECOLOGICAL CHARACTERISTICS
SPECIES: Quercus alba | White Oak 



GENERAL BOTANICAL CHARACTERISTICS : 
White oak is a medium to large, spreading, deciduous tree which commonly
reaches 60 to 80 feet (18-24 m) in height [31,53,131].  On favorable
sites, individuals may grow to more than 100 feet (30 m) in height and
exceed 5 feet (1.5 m) in diameter [19,108].  White oak is slow-growing
and long-lived (up to 600 years) [35].

White oak is monoecious [131].  Yellowish staminate catkins are borne at
the base of new growth, whereas reddish pistillate catkins grow in the
axils of new growth [119,131,148].  The short-stalked, glabrous, ovoid
acorns are tan to brown [31,53,108].  Acorns are generally borne in
pairs [31].  The rough, warty cup covers approximately 33 to 50 percent
of the nut [31,55,131].


RAUNKIAER LIFE FORM : 
   Undisturbed State:  Phanerophyte (mesophanerophyte)
   Undisturbed State:  Phanerophyte (megaphanerophyte)
   Burned or Clipped State:  Phanerophyte (nanophanerophyte)
   Burned or Clipped State:  Chamaephyte
   Burned or Clipped State:  Hemicryptophyte
   Burned or Clipped State:  Crytophyte (geophyte)


REGENERATION PROCESSES : 
White oak reproduces through seed and by vegetative means.  Both modes
of regeneration appear to be important.

Seed:  White oak produces good acorn crops at erratic intervals.  Good
crops have been reported at 4- to 10-year [148] and at 3- to 5-year
intervals [118].  Vigorous crowned trees greater than 20 inches d.b.h.
(51 cm) generally produce the best seed crops [57].  Pollen, which is
produced in abundance, is dispersed by wind, but generally travels less
than 656 feet (200 m) [46,58].  Plants generally bear fruit between 50
and 200 years of age, but open-grown trees on good sites may produce
seed as early as 20 years of age [99,148].  Reproduction from seed can
occur when (1) large seed trees are present within 200 feet (61 m), (2)
litter cover is moderate, and (3) the site receives at least 35 percent
of full sunlight [148].

Seeds of white oak do not store well [16].  Seed longevity is less than
1 year; white oak is not considered a seed banker [60].  Viability in
storage declines from 90 percent for fresh seed to 7.0 percent for seed
stored for 6 months [16].  Only 14 to 18 percent of the total seed
produced may be sound [148].  Many acorns are damaged or destroyed by
insects [144] or bird and mammal seed predators.  Several studies have
reported that animals consumed 72 to 83 percent of all white oak acorns
[135].  In years of poor acorn production, the entire seed crop may be
eliminated [148].

Acorn production:  Acorn production varies annually with the individual
tree or stand [148].  Certain trees tend to produce larger acorn crops
on a consistent basis [119].  Weather conditions, and tree size and vigor,
also influence acorn production.  An individual oak 69 feet (21 m) tall
with a d.b.h. of 25 inches (63.5 cm) produced more than 23,000 acorns in
a favorable year [148].  However, most forest-grown trees produce less
than 10,000 acorns annually.  Annual yields may range from 0 to 202,000
acorns per acre (500,000/ha) [148].  Acorn production may be reduced by
cool April temperatures [119] and drought [118].

Seed dispersal:  In parts of Michigan, the blue jay is the primary
dispersal agent of white oak [60].  Blue jays commonly exhibit a
preference for burying acorns in bare open areas which are well suited
for germination [60].  Gray squirrels are also important dispersal
agents in many locations and are the only known long-distance disperser
[35,148].  The now-extinct passenger pigeon may have effected
long-distance dispersal of many eastern oaks [21].  Wind and gravity
also aid in seed dispersal [148].

Germination:  White oak acorns do not exhibit dormancy [16].  In
storage, seeds germinate readily at temperatures of 33 to 37 degrees F
(1-3 deg C) [16].  Under natural conditions, acorns begin germinating
soon after they fall [35].  Acorns require a cover of litter for good
germination and seedling establishment [86].  Acorns without such
protection are often damaged or killed by frost or drought [86].
Germination capacity ranges from 50 to 99 percent [148].

Seedling establishment:  Seedling establishment is generally limited to
years of abundant acorn production [148].  Light to moderate litter
cover and periods of full sunlight are required for establishment.
Establishment is best on loose soils [30].

Vegetative regeneration:  White oak exhibits a number of modes of
vegetative regeneration.  Vigorous sprouting from the stump or root
crown is commonly observed after fire, mechanical damage, and other
types of disturbance.  Sprouting generally decreases with increasing
stem diameter [64], although trees up to 80 years of age occasionally
retain the ability to sprout [42].  Small poles, saplings, and even
seedlings sprout readily if cut or burned [51].  Stump-sprouting by
diameter class has been reported as follows [99]:

      d.b.h. (inches)   percent of stumps likely to sprout

      2 to 5                        80
      6 to 11                       50
      12 to 16                      15
      16 +                           0          
      
Repeated sprouting is commonly observed [125].  Seedlings often develop
an "s"-shaped curve at ground level, which helps protect dormant buds
from fire [100].  Root stools develop under the ground surface after
repeated fires or herbivory.  These root stools, made up of callus
tissue filled with dormant buds, typically sprout vigorously in the
absence of further disturbance [100].

Seedling sprouts persist beneath the forest canopy even in the absence
of disturbance.  Although the top dies back every few years, the root
system continues to develop and plants may persist for up to 90 years or
more [99].  As the forest canopy is opened, the seedling sprouts grow
rapidly [99].  Epicormic branches or water sprouts often develop from
dormant buds located on the boles [16,23].  Buds are stimulated to
sprout by sudden shifts in light intensity, partial removal of the
crown, and a loss of plant vigor [16].  Bud dormancy in oaks is largely
controlled by auxins rather than by levels of carbohydrate reserves
[125].  Apical dominance can restrict the development of belowground
buds when buds survive on aboveground portions of the plant.  Sprouting
is reduced by low light levels [125] and decreases as the stand ages
[82].  McIntyre [82] reported that the number of sprout groups decreases
from poor to good sites.

Silviculture:  Oaks often regenerate poorly after timber harvest.
Hannah [51] reported that the use of natural seedbeds and standard
silvicultural practices are often ineffectual in promoting oak
regeneration.  The presence of vigorous advanced regeneration is
essential for producing good stands of oaks after timber harvest
[29,88,102].  For adequate regeneration of oaks, advanced regeneration
of at least 4.5 feet (1.4 m) in height should number at least 435 per
acre (1,074/ha) prior to harvest [99,102].  A series of selection cuts
can produce stands with several age classes and can generate sufficient
advanced regeneration for well-stocked postharvest stands.  Initial cuts
should reduce overstory densities to no less than 60 percent stocking
[102].  Reduction of competing understory species may also be necessary
in some instances [102].

Mechanical treatment:  Sprouts tend to be larger and taller when white
oaks are cut during the dormant season [64].  Sprout growth by season
has been reported in detail [64].


SITE CHARACTERISTICS : 
White oak grows in rich uplands, moist bottomlands, along streams, on
hammocks, sinks, sandy plains, and on dry, gravelly slopes
[17,28,30,99,116].  It occurs on all upland aspects, and slope positions
[99], but in the southern Appalachians, it exhibits best growth on
northern lower slopes and in coves [32].  White oak is absent on
ridgetops with shallow soil, on poorly drained flats, and on very wet
bottomlands [99].  Latitude, aspect, and topography are important
factors influencing the distribution of white oak within its range [99].
White oak grows in a variety of dry to mesic woodland communities [131]
including pine-oak-hickory woods, beech-maple, and mixed hardwood
forests [30,131].  It also occurs in relatively open post oak savanna
[110] and oak savanna codominated by bur oak [8].

Plant associates:  White oak grows in pure or mixed stands in the
Southeast [38] but towards the northern portion of its range it rarely
occurs in pure stands [57].  Important tree associates are numerous and
include beech (Fagus grandifolia), sugar maple, black cherry (Prunus
serotina), white ash (Fraxinus americana), yellow poplar, shortleaf pine
(Pinus echinata), loblolly pine (P. taeda), eastern white pine (P.
strobus), jack pine (P. banksiana), eastern hemlock, sweet gum, black
gum (Nyssa sylvatica), American basswood (Tilia americana), shagbark
hickory (Carya ovata), and other hickories (Carya spp.)  [28,57,83,110].
Scarlet oak, post oak, bur oak, black oak, and northern red oak are also
important associates [99], Upland oaks and hickories are the most common
associates [99].  Many herbaceous species grow in association with white
oak.

Climate:  White oak is often associated with a cool, temperate,
continental climate [12] but can grow under a variety of climatic
regimes [99].  Mean average temperatures range from 45 degrees F (7 deg
C) in the North to 70 degrees F (21 deg C) in eastern Texas and northern
Florida [32].  Annual precipitation averages 80 inches (203 cm) in the
southern Appalachians but is less than 30 inches (77 cm) in southern
Minnesota [99].  Growing season length ranges from 5 months in the North
to 9 months in the South [99].

Soils:  White oak grows on a wide variety of soils [28] derived from
many types of parent materials [42].  It grows on silty loam, clay loam,
silty clay loam, fine sand, and loamy clay [12,43,110] but grows best on
deep, well-drained loamy soils.  Low soil-nutrient levels limit growth
of white oak only on sandy soils [99].  White oak is common on rocky
soils [116].

Elevation:  White oak grows from sea level to 5,900 feet (0-1,800 m)
[38].  In the North, it generally grows under 500 feet (152 m) in
elevation, but in the southern Appalachians, it grows as a "scrub tree"
at 4,500 feet (1,372 m) [99].  It is absent from higher elevations in
the northern Appalachians.  In the Smoky Mountains, two populations are
separated by an elevational gap of 1,000 feet (305 m) [130].  White oak
grows below 2,000 feet (610 m) in the Cumberland Mountains [130].


SUCCESSIONAL STATUS : 
White oak readily regenerates after disturbances such as fire or logging
and often assumes prominence in mid to late seral stages [2,61].  In the
North, white oak is commonly seral to sugar maple and other species
characteristic of mixed mesophytic stands [42].  In much of its range,
it is succeeded by beech and other shade-tolerant species on
well-drained second bottoms and in protected coves [99].  White oak is a
pioneer on frequently burned sites in southern Wisconsin [8], and in
Michigan, readily colonizes agricultural land 15 years after abandonment
[54].  In much of the eastern deciduous woodlands, forests formerly
dominated by white oak, beech, red maple, yellow poplar, and northern
red oak are now being replaced by more shade-tolerant species such as
sugar maple and American basswood [8,91].

White oak cannot regenerate successfully beneath a dense canopy and in
many areas, grows in forests transitional to climax sugar maple or mixed
mesophytic forests [2,34].  Because of the longevity of white oak,
climax development proceeds very slowly [2].  White oaks may persist on
exposed sites within climax stands [8].

White oak is considered a climax tree in oak-hickory stands in the
central and southern hardwood forest zone [99].  It grows as a climax
dominant or codominant on certain lower elevation sites in the Smoky
Mountains [130] and occurs in climax pine-oak forests of New Jersey
[77].  It also assumes importance in climax floodplain oak-hickory
forests of Tennessee [107].  White oak is represented in mixed hardwood
old growth stands of northwestern Ohio [12].  Old-growth oak-hickory
forests of southern Michigan [50], and in old-growth oak communities of
eastern Tennessee [81].  Pine-oak forests cyclically replace
beech-magnolia forests after disturbance in parts of southeastern Texas
[47] and Louisiana.


SEASONAL DEVELOPMENT : 
Leaves begin to develop and new shoots are initiated in mid-March to
late May, depending on geographic location [99].  The timing of bud
break is largely dependent on latitude [99] but also depends on soil
nutrient levels [18] and weather.  Bell and others [18] observed delayed
budbreak on copper, lead, and zinc-mineralized sites.  Most vegetative
growth takes place during the spring, with up to 50 percent of seedling
height growth attained in April [99].  Fowells [42] reported that
seedling height growth was 90 percent complete by July 1.  Plants may
become dormant in late fall, although leaves commonly persist into
winter [28].

Flowering generally occurs in spring when the new leaves are elongating
[32] but varies according to latitude, weather conditions, and with the
genetic composition of individual trees [99,104,105].  Flowering can
occur from late March to May [99] or June [103].  In Pennsylvania,
pistillate catkins emerge in late April or May, approximately 5 to 10
days after the emergence of staminate flowers [105].  Sharp and Chisman
[104] observed trees within the same population flowering early (May 5
to May 11) and late (May 13 to May 19).  Three distinct waves of
flowering (early, middle, and late) have been reported.  Warm weather
speeds up floral development, which begins after exposure to minimum
temperatures of 50 degrees F (10 deg C) for at least 10 days [104].
Pollen is generally shed within 3 days, but light winds can accelerate
shedding [104].  Pollen shedding is often delayed by prolonged rainy
weather [104].  

Acorns typically ripen approximately 120 days after pollination [99].
In Pennsylvania, embryos generally begin development after July 24, grow
rapidly by August 4, and reach full size by August 25 [105].  Acorns
fall from the trees by September or October [99,105].  Generalized
flowering and fruit ripening dates by geographic location are as
follows:

Location          Flowering         Fruit ripe        Authority

PA                April-May         ----              Sharp and Sprague 1967
NC, SC            April             Sept.-Nov.        Radford and others 1968
New England       May 21-June 3     ----              Seymour 1985
Blue Ridge Mtns.  April-May         ----              Wofford 1989
Adirondack Mtns.  May               Sept.             Chapman & Besette 1990  
nc Great Plains   May               Oct.              Stephens 1973           
WV                ----              Oct. 3            Park 1942

Related categories for Species: Quercus alba | White Oak