FIRE EFFECTS
SPECIES: Pseudotsuga macrocarpa | Bigcone Douglas-Fir 



IMMEDIATE FIRE EFFECT ON PLANT : 
Fire kills bigcone Douglas-fir seeds.  Most authorities claim that
seedlings and saplings are killed by fire [10,14,18].  One study,
however, showed that small burned trees sprouted following a fire of
unreported severity in the Transverse Ranges [23].  The immediate effect
of fire on young trees is therefore unclear, but mortality rates
probably vary according to fire severity [22].  Pole- and
sawtimber-sized trees are fire resistant.  Aerial photographs of burns
in the eastern Transverse Ranges show that 60 percent of bigcone
Douglas-fir escaped defoliation during the period from 1938 to 1975
[23].  An additional 15 percent were scorched but not killed.
Twenty-five percent of the trees were killed outright.

The branchlets of defoliated trees are usually killed.  Large main
branches generally survive moderate-severity fire, but may be killed
when severely burned.  Trunks of severely burned trees are often
protected from fatal damage by their thick bark [18].  Bigcone
Douglas-firs growing sympatrically with canyon live oaks suffer less
fire damage than other bigcone Douglas-firs.  These oak seems to act as
a buffer against the intense heat of chaparral fires burning into the
bigcone Douglas-fir community [22,23].  


DISCUSSION AND QUALIFICATION OF FIRE EFFECT : 
NO-ENTRY


PLANT RESPONSE TO FIRE : 
Most sprouting occurs on trees scorched by surface fire.  Trees
subjected to crown fire rarely sprout [22].  Aerial photographs taken
over the Meyer and Bear Burns of the Transverse Ranges at postfire years
1 and 2 showed that scorched stands with persistent dead foliage
sprouted, but severely burned stands were killed.  Field study of stands
in the Village Burn (severity unreported) near Mount Baldy in the
Transverse Ranges revealed sprouting in pole-sized trees and saplings as
small as 10 feet (3 m) in height.  All sprouts died on a number of such
smaller individuals after postfire year 1, but other trees regained full
crowns within 2 to 3 years [23].  The seed-producing ability of bigcone
Douglas-fir is impaired for years [19].

Postfire natural regeneration generally takes decades.  A survey of
Transverse Range burns showed natural regeneration was almost
nonexistent in recent burns.  No offspring were found in burns less than
19 years old.  Seedlings and saplings were most evident in burned areas
free of further fire for 50 or more years.  Bigcone Douglas-fir probably
requires the development of an overstory before shade-tolerant seedlings
will establish.  Seed dispersal into these shaded areas is usually a
reproductive barrier following stand-replacing fires where all potential
parent trees are killed.  Long-distance seed dispersal is inefficient in
bigcone Douglas-fir [23].


DISCUSSION AND QUALIFICATION OF PLANT RESPONSE : 
NO-ENTRY


FIRE MANAGEMENT CONSIDERATIONS : 
Despite its ability to develop new crowns, bigcone Douglas-fir is not
favored by frequent fire.  Repeated fire depletes energy reserves and
enlarges old wounds, and mortality is high in trees subjected to such
fire regimes [18].  Bolton and Vogl [3] speculate that trees subjected
to frequent fire loose their ability to sprout.  In contrast to most
conifers, however, fire-damaged trees are usually free from bark beetle
attacks [10].  Bigcone Douglas-fir is adapted to a regime of long,
fire-free intervals [7].  Frequent fire increases the number and density
of the chaparral and woodland species in the spaces between bigcone
Douglas-fir trees [14].  Occasional circumstances of stand defoliation,
however, select in its favor because of its sprouting habit [23].  The
interfaces of chaparral and bigcone Douglas-fir forests are in constant
flux as environmental factors of fire, drought, precipitation, and
erosion assert themselves [32].

The desiccating Santa Ana foehn winds that sweep the Santa Ana and San
Jacinto mountains represent a fire danger to bigcone Douglas-fir trees.
Santa Ana winds are capable of carrying fire downward from upslope mixed
coniferous forests [28,32].

Related categories for Species: Pseudotsuga macrocarpa | Bigcone Douglas-Fir