FIRE EFFECTS
SPECIES: Quercus rubra | Northern Red Oak 



IMMEDIATE FIRE EFFECT ON PLANT : 
Northern red oak is apparently more susceptible to fire than many other
species of oak.  The tight, solid bark is typically more seriously
damaged than the rough, corky bark of species such as white oak [55].
Mortality is higher for smaller northern red than for larger trees
[112].  Large trees can survive bark scorch on up to 66 percent of their
circumference [98].  However, severe wildfires occasionally kill poleand
even sawtimber-sized individuals [101,131].  Pole-sized and larger
northern red oaks typically survive prescribed fires which top-kill the
plants [101].  Seedlings may be killed by such fires [101], but root
collars or belowground regenerative structures often survive even when
plants are top-killed.

Most acorns are characterized by a relatively high moisture content.  As
the moisture within the acorns is heated, the seeds swell and often
rupture [98].  Therefore, few acorns present on-site survive fire.


DISCUSSION AND QUALIFICATION OF FIRE EFFECT : 
Oaks tend to be less susceptible to fire during the dormant season [98].
Individuals of poor vigor are less likely to heal following fire-induced
injury than are healthy vigorous specimens.  Oaks growing in overstocked
stands typically exhibit lower vigor and are more susceptible to
fire-caused damage.  Crooked or leaning trees are particularly
susceptible to damage since the flames are more likely to be directly
below the stem, thereby increasing the amount of heat received by the
bark's surface.  Mortality or serious injury increases with greater fire
severity.  Mortality of seedlings may be correlated with temperatures
near the root collars [51].  [See FIRE CASE STUDY].

High mortality was reported after 8 years of biennial burning, although
mortality was not obvious until after the first 3 years.  A spring fire
killed 58 percent of existing northern red oak seedlings and caused
severe damage to the boles of some overstory trees [120].  However, an
"extremely hot" wildfire in Indiana, killed only 22 percent of
4-year-old plants [25].  The tops of 92 percent of 1-year-old northern
red oak seedlings were killed by a low-severity prescribed burn in
Wisconsin, but regenerative portions of 38 percent survived [25].

Northern red oak is generally more severely fire-scarred than many other
oaks [112].  When basal cambial tissue is seriously damaged by fire,
injuries often permit the entry of insects or decay that may ultimately
kill the tree [1,45,98,106].  Toole [132] reported that by the 2d year
after fire, 60 percent of wounded northern red oaks was infested by
insects.  Heart rot spread to 2.5 times the height of the bark
discoloration within 7 years of the fire.  Heart rot progressed more
slowly where the original fire scar represented less than 20 percent of
the tree's circumference and more rapidly where the fire scar was more
extensive.  Rouse [98] estimated that rot traveled up the bole of a
fire-damaged tree at 1.25 feet (0.4 m) per decade.

Mortality equations based on d.b.h., and the width and height of bark
blackening have been developed for northern red oak [71].  These
equations can be useful in predicting if a fire-damaged oak will
survive.


PLANT RESPONSE TO FIRE : 
Young northern red oaks commonly sprout vigorously from the stumps or
root collar after aboveground portions of the plant are killed by fire
[24,63].  Stem density is often increased as fire promotes sprouting and
reduces competition [25,91].  Johnson [51] reported that one to three
living stems may originate from a single root collar.  Frequent fire can
produce oak scrublands [25,52].  Hannah [43] reports 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.

Seedling sprouts are often particularly important in postfire
reestablishment, but seedling establishment may also occur [102].  Large
oaks that survive fire frequently serve as seed sources [43].  Dying
trees often produce a massive seed crop.  Acorns often germinate well on
mineral soil, and establishment may actually be favored in burned areas
[98].  Scheiner and others [103] reported 56 resprouts per acre (138/ha)
and 51 seedlings per acre (125/ha) after a fire in Michigan.

Rouse [98] reported that most large 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."

Specific response is presumably related to such factors as fire
severity, season of burn, and plant age and vigor.  Fire does not always
produce increases in northern red oak.  Van Lear and Waldrop [120]
reported that a spring fire in a northern red oak stand failed to
increase oak abundance in the understory.


DISCUSSION AND QUALIFICATION OF PLANT RESPONSE : 
Seedlings, saplings, and pole-sized individuals commonly sprout if
girdled by fire.  Damaged seedlings can often resprout several times and
may ultimately grow beyond the fire-susceptible stage [43].  Sprouting
ability appears to decrease as plants age.  Large trees much less likely
to sprout if severely damaged by fire.


FIRE MANAGEMENT CONSIDERATIONS : 
Prescribed fire:  Prescribed fire can be an important tool for
regenerating oak stands.  However, results do not always favor oak.
Crow [25] reported that "although there is abundant evidence of a
general relationship between fire and the occurrence of oak, prescribed
burning is not yet a viable silvicultural tool for regenerating oak
stands."  Most oaks sprout vigorously after fire, and competing
vegetation can be much reduced [43].  However, a single low-intensity
fire may have little impact on competing vegetation [25].  According to
Crow [25], a "commitment to frequent burning is needed to compensate for
decades of fire exclusion."  In the southern Appalachians, biennial
summer burns are usually most effective in promoting advance
regeneration.  Single pre- or post-harvest burns generally have
little effect [121].

Timber harvest and fire:  Fire can be used to control competing
herbaceous vegetation after timber harvest [18].  A series of cool or
low-severity prescribed fires prior to timber harvest can promote
advanced regeneration in oaks [121].

Fuels and flammability:  Wydeven and Kloes [131] reported that a "fairly
cool" fire in an uncut northern red oak stand produced flame lengths of
1 to 1.8 feet (0.3-0.56 m).  A "very hot" fire in a cut stand generated
flames 1.6 to 20 feet (0.5-6.0 m) high.

Related categories for Species: Quercus rubra | Northern Red Oak