FIRE EFFECTS
SPECIES: Pseudotsuga menziesii var. menziesii | Coast Douglas-Fir 



IMMEDIATE FIRE EFFECT ON PLANT : 
Trees:  Crown fires commonly kill all trees over extensive areas.  Hot
ground fires that scorch tree crowns and char tree boles kill variable
proportions of coast Douglas-fir [3].  Rapidly spreading ground fires
tend to inflict more damage to Douglas-fir crowns, while slow spreading
ground fires are damaging to the bole and can kill trees through cambial
heating [60].  Crown scorching from summer fires is more damaging than
late summer or fall fires because more buds are killed.  During late
summer the buds are set and subsequent-year needles are well protected
[75].  Seedlings and saplings are susceptible to and may be killed by
even low-intensity ground fires [74].

Seed:  Temperatures in excess of 140 degrees F (60 C) are lethal to
Douglas-fir seeds.  Thus most seeds on the forest floor will be
destroyed by fire [35].  Crown fires will kill seeds in green cones;
however, green cones are relatively good insulators and are not highly
flammable, and fires that not excessively hot often only scorch the
cones.  Seeds can mature in scorched cones on fire-killed trees, and
later disperse onto the burned area [35].


DISCUSSION AND QUALIFICATION OF FIRE EFFECT : 
The Hoh Fire in June 1978 burned 1,230 acres (500 ha) of montane and
subalpine coniferous forests.  The montane forest was composed primarily
of 400- to 500-year-old western hemlock and Douglas-fir.  About 10
percent of this forest type was consumed by a crown fire, while most of
the remaining forest experienced a hot ground fire with considerable
crown scorching.  All trees less than 10 feet (3 m) tall were killed.
Mortality of overstory trees was high, but Douglas-fir suffered the
least.  The fire reduced the basal area of all species as follows:

        bigleaf maple 100 %
        western hemlock 80%
        western redcedar 50 %
        sitka spruce 50 %
        coast Douglas-fir 33%

Ninety-one percent of western hemlock overstory trees were killed,
compared with 62 percent of Douglas-fir [3].


PLANT RESPONSE TO FIRE : 
Seedling establishment following fire is dependent on the spacing and
number of surviving seed trees.  Seedling establishment following large
stand-destroying fires is slow because seed trees are killed over
extensive areas.  After the Tillamook Fire in northwestern Oregon,
seedlings were restricted to areas around scattered survivors and near
the burn edge [77].  Conversely, Douglas-fir can quickly establish a new
cohort of seedlings if there are numerous, well-spaced surviving seed
trees within the burned area.  Conifer seedlings were abundant after the
Hoh Fire in Olympic National Park, where 38 percent of mature
Douglas-fir survived.  Three years after this fire, there were about
3,400 conifer seedlings per acre (8,400/ha), about half of which were
Douglas-fir [34].  In the northern Cascades, Douglas-fir seedling
frequency was between 80 and 100 percent on three different 4-year-old
burns ranging in size from 55 to 410 acres (22-166 ha) [52].


DISCUSSION AND QUALIFICATION OF PLANT RESPONSE : 
NO-ENTRY


FIRE MANAGEMENT CONSIDERATIONS : 
Natural regeneration following slash burning:  The effects of slash
burning on coast Douglas-fir seedling establishment are contradictory.
Some researchers report greater stocking on burned areas, while others
report greater stocking on unburned areas [57].  It appears that
Douglas-fir is favored by slash burning on mesic and wetter sites in the
western hemlock zone.  On dry sites, natural regeneration following
broadcast burning is unpredictable, and often poor, due to high soil
temperatures and moisture stress [17].

Following broadcast slash burning in clearcuts in the Coast and Cascade
Ranges in Oregon and Washington, 90 percent of the area is typically
moderately or lightly burned, which provides good seedbeds [53,57].
Severe burning, which retards Douglas-fir regeneration because of
altered physical and chemical soil properties, occurrs on less than 10
percent of the area.  This is typically where burning stumps produce
intense heat [17].  Minore [55] found that 5-year-old coast Douglas-fir
seedling height was lower on sites where slash was piled and burned than
on broadcast burned sites.

On erodible granitic soils of the Klamath National Forest, hand planted
Douglas-fir seedlings were 7 times more numerous on unburned than on
burned plots, 6 years after planting [67].

Models:  Peterson and Arbaugh [60] present a model for predicting
postfire survival of coast Douglas-fir in the Cascades.  The model uses
crown and bole damage variables to predict survival.

Salvage logging:  Typically less than 3 percent of all merchantable
timber in coast Douglas-fir stands is consumed by forest fires.
Deterioration rates vary with tree size and wood type.  Very little
sapwood can be salvaged 3 years after fire, but heartwood deteriorates
more slowly.  Salvage has been carried out for 1 to 2 years in
young-growth stands, 4 to 7 years in intermediate stands, and for 5 to
10 years in old-growth stands [37].

Duff reduction:  Duff consumption by prescribed burning can be predicted
using weather and fuel variables on cut-over Douglas-fir sites.
Generally, most duff is burned when the moisture content of the upper
duff is below 30 percent.  When the upper duff layer exceeds 120 percent
moisture content no combustion takes place.  Between these values, the
percentage of duff consumed depends on the amount and moisture content
of fine woody fuels [44,62].

Related categories for Species: Pseudotsuga menziesii var. menziesii | Coast Douglas-Fir