FIRE EFFECTS
SPECIES: Abies balsamea | Balsam Fir 



IMMEDIATE FIRE EFFECT ON PLANT : 
Balsam fir is the least fire-resistant conifer in the northeastern
United States [48].  Most fires kill balsam fir trees and destroy the
seeds [14].  Trees have thin, resinous, easily ignitable bark and
shallow roots [1,21].  Seeds have no endosperm to protect them from high
temperatures.  Cones are not necessarily destroyed by fire, but immature
seeds will not ripen on fire-killed trees.

If balsam fir trees are killed over extensive areas by summer fires, no
seed will be available to revegetate the burned area.  This occurred
following the 1936 wildfire on Isle Royale which burned 26,000 acres
(10,500 ha).  Most of the balsam fir trees were killed, and for 30 years
after the fire, balsam fir was largely absent from the burned area [27].


DISCUSSION AND QUALIFICATION OF FIRE EFFECT : 
NO-ENTRY


PLANT RESPONSE TO FIRE : 
Balsam fir is generally slow to reestablish after fire.  Because most
trees are killed by fire, it relies on rare survivors found in protected
pockets within the burn or trees from adjacent unburned areas to provide
seed for postfire seedling establishment.  Associates such as aspen,
paper birch, black spruce, and jack pine usually seed in aggressively
following fire and quickly dominate the site.  Balsam fir is usually
rare or absent for the first 30 to 50 years after fire, but thereafter
gradually establishes under the canopy of its seral associates
[2,14,20].


DISCUSSION AND QUALIFICATION OF PLANT RESPONSE : 
Fire creates seedbeds favorable for balsam fir germination and
establishment.  If seed is available, balsam fir readily establishes on
burned sites.  In northern Minnesota, balsam fir seedlings were
established within 5 years of a stand-destroying fire; seed originated
from an unburned mixed-conifer stand across a river [28].  Balsam fir
seedlings establish after fall fires that occur when seed is ripe and
still on the tree [11].


FIRE MANAGEMENT CONSIDERATIONS : 
Prescribed fire:  Prescribed fire can be used to convert balsam fir
forests to other species.  It is an important silvicultural tool in
spruce budworm-infested stands.  Burning infested stands eliminates the
unaffected balsam fir understory and prepares the site for other
commercial species, particularly black spruce [25].  In northern
Ontario, prescribed burning on sites pretreated by tramping (leveling
the dead trees with bulldozers) successfully prepared a spruce
budworm-killed balsam fir stand for planting [38].  Tramping aided fire
spread in this summer burn, when green herbaceous plants might otherwise
have hindered it.  The standing dead trees were dry before tramping.
Some large balsam fir boles were completely consumed and 55 percent of
balsam fir slash between 2.75 and 5 inches (7-13 cm) in diameter were
consumed.  Prescribed fires can also be used to kill balsam fir
seedlings and saplings in pine and mixed-wood types.  In these types,
low-intensity surface fires are sufficient to kill balsam fir saplings
[37].

Fire behavior:  Balsam fir tree mortality is often between 70 and 100
percent after the collapse of a spruce budworm outbreak [25].  These
altered forests are more flammable because the dead trees provide dry
aerial fuel and the newly exposed understory is drier than normal.  Fire
suppression in spruce budworm-killed stands is extremely difficult [25].
Experimental burns in spruce budworm-killed stands have been explosive.
In balsam fir stands with 30- to 90-year-old dead trees averaging 23 to
39 feet (7-12 m) in height, spring fires (before flushing of understory
vegetation), under conditions of high but not extreme fire danger,
burned with intensities as high as 38,000 KW/m and spread rates in
excess of 148 feet/minute (45 m/min.) [50].  Tree crown and surface fuel
consumption were nearly complete, and standing tree boles smoldered for
hours after the passage of the fire front.  These hot fires transport
large amounts of peeling bark, fine twigs, and branchlets in convection
columns which start spot fires downwind [49].

Decay after fire:  Fire-killed balsam fir deteriorates rather slowly.
Commercial salvage operations are possible for a number of years after
stand-killing fires [5].  However, budworm-killed trees quickly succumb
to wood-rotting fungi and are largely unusable after 1 to 3 years [34].

Related categories for Species: Abies balsamea | Balsam Fir