FIRE EFFECTS
SPECIES: Quercus alba | White Oak 



IMMEDIATE FIRE EFFECT ON PLANT : 
White oak is moderately resistant to fire [44,59].  Aerial portions may
be killed by fire [11], but underground regenerative structures
protected by overlying soil usually survive [10,76].  The rough, scaly
bark of white oak is more fire-resistant than the solid bark of many
other oaks [114].  Oaks typically become more fire resistant as the bark
thickens with age [51].

Most oaks will survive periodic fires.  In parts of the New Jersey Pine
Region, most white oaks 25 years and older possessed fire scars; four
fire scars were observed on a 65-year old tree [76].  However, frequent
fires can damange or kill white oaks, and recurrent fires at less than
8-year intervals could eliminate white oak [77].

Approximately 76 percent of white oaks were killed following fire in a
loblolly pine stand in Virginia [4], and an estimated 56.5 percent were
killed after a fire in a New Jersey pine-oak community [106].  Many of
the observed differences in susceptibility of oaks to fire can be
attributed to variation in fire severity and intensity, site
characteristics, plant age or size, form, vigor, season of burn, and
stocking levels [100].

Most acorns are characterized by a relatively high moisture content.  As
the moisture within the acorns is heated, the seeds swell and often
rupture [100].  Therefore, "average" fires kill all white oak acorns
present on-site [44].


DISCUSSION AND QUALIFICATION OF FIRE EFFECT : 
Oaks tend to be less susceptible to fire during the dormant season
[100].  Mean white oak mortality after fires in the dormant season was
23 percent, as compared with 69 percent after fires occurring in the
growing season.  Individuals of poor vigor are less likely to heal than
healthy vigorous specimens.  Oaks growing in overstocked stands
typically are less vigorous and thus more susceptible to fire damage.
Crooked or leaning trees are particularly susceptible to damage because
the flames are more likely to be directly below the stem, thereby
increasing the amount of heat received at the bark's surface.  Higher
fire intensity and severity increase mortality and serious injury.
Topographic factors such as aspect and slope can also influence
mortality [78].  Fire mortality also varies with the size of the tree;
fire is more likely to kill smaller white oaks than large ones [76].  A
fire in an oak-pine stand in New Jersey killed 44 percent of trees 1
inch in d.b.h., 5 percent of tree 2 to 4 inches in d.b.h., but no trees
greater than 5 inches in d.b.h. were killed [76].

Toole [117] reported that approximately 20 percent of white oaks
examined were uninjured by fire despite discolored bark.  Bark sloughed
off wounded white oaks within 5 years [117].  Following an early-season
fire in the Pine Barrens of New Jersey, some white oaks exhibited
partial crown mortality later in the summer, while others showed no
evidence of significant crown damage [14].  White oak is reportedly
susceptible to fire scars [93] which can permit the entry of insects or
decay that may ultimately kill the tree [100].  However, Kaufert [63]
reported that 50 percent of all fire scars on white oak had healed
within 15 years in a southern bottomland forest [63].  Studies suggest
that basal wounding does not affect growth rates [59].

Large white oaks can survive bark scorch up to two-thirds of their
circumferences [100].  Mortality equations based on d.b.h., and the
width and height of bark blackening have been developed for white oak
[55,78,86].  These equations can be useful in predicting if a
fire-damaged oak will survive [78].


PLANT RESPONSE TO FIRE : 
White oak commonly sprouts vigorously from the stump or root crown after
aboveground portions of the plant are damaged or killed [11,99].
Sprouting depends on such factors as plant vigor [84], genetic
composition, size, and fire severity and intensity.  White oak probably
stump-sprouts after moderate fires [51], and when completely top-killed,
underground portions often regenerate [100].  Hannah [51] reported that
the "best" sprouts often originate from buds located at or below ground
level.  These sprouts may be more vigorous and less susceptible to rot
or other damage.

White oak seedlings generally sprout after fire, and in many instances,
numbers remain essentially unchanged [97].  Damaged seedlings can often
resprout several times and may ultimately grow beyond the
fire-susceptible stage [51].  Seedlings often develop an enlarged root
crown after frequent fires [11,42].  Sprouting ability typically
decreases with increasing d.b.h. [64].  Pole-sized trees sprout readily
from stumps [32], but older, faster-growing, or taller trees often fail
to sprout [64].

Multiple sprouts, which resemble seedlings, commonly develop after fire
[75] and plant density is often increased.  In the southern
Appalachians, Keetch [65] reported an average of six to seven sprouts
per clump 4 years after fire and 10 to 15 per clump 2 years after
several consecutive fires.

White oak generally responds quickly to release [99].  Previously
suppressed individuals often grow rapidly into the understory soon after
fire [90].  Initial postfire sprout growth is also rapid, and prolific
seed production occurs at an early age [10,14].  Sprouts are commonly
present within one growing season after fire [13].

Rouse [100] reported that most surviving oaks are "capable of minimizing
fire-caused losses due to damaged cambium by rerouting the functions of
fire-killed portions within weeks after a fire."  Large oaks that
survive fire frequently serve as seed sources for burned areas [51];
dying trees often produce a massive seed crop [100].  Birds and mammals
may transport seeds from adjacent unburned areas, and seedling
establishment may occur.


DISCUSSION AND QUALIFICATION OF PLANT RESPONSE : 
Postfire increases in white oak have been documented as follows after
fire in a mixed hardwood community of Rhode Island [22]:

size class              burned                        unburned
                  density %   BA %              density %       BA %

overstory         42.7        23.40             23.6            27.60
1-10 ft. tall     42.4        -----             17.0            ----
< 1 ft. tall      42.3        -----             28.7            ----          


FIRE MANAGEMENT CONSIDERATIONS : 
Prescribed fire can be an important tool for regenerating oak stands.
Fire may favor seedling establishment by creating suitable seedbeds and
reducing competing vegetation [100].  A series of low-intensity
prescribed fires prior to timber harvest can promote advanced
regeneration [123].  In the southern Appalachians, biennial summer burns
are often most effective in promoting advance regeneration [123].
Single preharvest or postharvest burns generally have little effect
[123].

Protein content of white oak browse was higher during the year following
low- and high-intensity burns [36].  Calcium levels also tend to
increase in twigs on recently burned sites [11].  Changes in nutritive
value after fire have been documented [11,12,36].

Related categories for Species: Quercus alba | White Oak