FIRE EFFECTS
SPECIES: Quercus stellata | Post Oak 



IMMEDIATE FIRE EFFECT ON PLANT : 
In general, small post oaks are top-killed by low-severity fire, and
more severe fires top-kill larger trees and may kill rootstocks as well.

Growing-season fires tend to be more detrimental to post oak than
dormant-season fires.  In Texas, a winter headfire top-killed 20 percent
of a post oak and southern red oak understory; a late winter fire
top-killed just over 40 percent; a spring fire top-killed just under 40
percent; and a late summer fire top-killed 55 percent.  Winter fires
killed on average less than 2 percent of rootstocks; summer fires killed
on average less than 10 percent.  The top-kill was substantially greater
for oaks between 0.6 and 2.5 inches (1.5-6.4 cm) in diameter than those
between 2.6 and 4.5 inches (6.5-11.4 cm) in diameter.  Diameter was
measured 6 inches (15.2 cm) above the groundline [15].


DISCUSSION AND QUALIFICATION OF FIRE EFFECT : 
Post oak in a savanna is more likely to be killed by surface fires than
post oak in a forest because of the grass fuel load in the savanna.  In a
March surface fire in a central Oklahoma savanna, most post oaks smaller
than 1.6 inches (4 cm) in d.b.h. were top-killed and some trees up to
3.5 inches (9 cm) in d.b.h. were top-killed or severely damaged.  In the
adjacent post oak-blackjack oak forest, however, few woody stems larger
than 1 inch (2.5 cm) were top-killed [24].

In a post oak-eastern redcedar community, post oak is likely to be
killed by fire because the eastern redcedar is highly flammable and
fires tend to be hot.  In a severe fire in a post oak-eastern redcedar
community in the Wichita Mountains of Oklahoma, 92 percent of all trees
(post oak, blackjack oak, and eastern redcedar) greater than 3 inches
(7.6 cm) in d.b.h. were top-killed and only 13.5 percent of the post
oaks and blackjack oaks sprouted.  In the adjacent post oak-blackjack
oak forest, only 66 percent of trees greater than 3 inches (7.6 cm) were
top-killed by the fire and 70 percent sprouted [40].


PLANT RESPONSE TO FIRE : 
If top-killed by fire, post oak up to 10 inches (25 cm) in d.b.h. sprout
vigorously from the root crown [47].

Because of sprouting, fire tends to increase the number of understory
post oak stems.  Eight annual winter fires in Tennessee resulted in
2,000 stems per acre (4,940/ha) compared to 1,220 stems per acre
(3,010/ha) in the unburned control [49].  If the high fire frequency
continues, however, the stem density may decrease as root systems are
killed.  In a study on the Santee Experimental Forest in South Carolina,
43 years of periodic winter and summer low-severity fires and annual
winter and summer low-severity fires reduced the number of hardwood
stems (including post oak) between 1 and 5 inches (2.6-12.5) in d.b.h.
However, the number of stems less than 1 inch (2.5 cm) in d.b.h.
increased slightly under all treatments except annual summer fires.
Root systems were weakened and eventually killed by annual burning
during the growing season [53].

Fire wounds on surviving trees allow entry of fungi which can cause
heart rot decay [50]. 


DISCUSSION AND QUALIFICATION OF PLANT RESPONSE : 
NO-ENTRY


FIRE MANAGEMENT CONSIDERATIONS : 
Many present-day post oak-blackjack oak stands were former savannas.  In
the Wichita Forest Reserve in Oklahoma, the average age of stands
coincides with the advent of fire suppression in the reserve [10].
Forests may not revert back to savannas with prescribed burning because
post oak-blackjack oak forests are resistant to effects of fire once the
canopy closes and the grass fuel load is reduced [24].  Fire, in
conjunction with herbicides, may be effective at eliminating post oak
[48].

Prescribed fires are used to maintain grasslands.  Repeat summer fires
are effective at controlling woody species because they are hotter than
winter fires, and belowground carbohydrate reserves are lowest in the
summer [18].  Post oak growing within a pine forest can also be
controlled with prescribed fire [3,53].

Equations for the estimation of fire-caused mortality have been
developed for post oak.  In order to predict mortality, a manager needs
to know the tree d.b.h, the height of bark blackening, the width of bark
blackening 1 foot above the ground, and the season of fire.  The
equations should only be applied to trees between 3 and 16 inches
(7.6-40.6 cm) in d.b.h. [31].

Related categories for Species: Quercus stellata | Post Oak