FIRE EFFECTS
SPECIES: Picea engelmannii | Engelmann Spruce 



IMMEDIATE FIRE EFFECT ON PLANT : 
Engelmann spruce is easily killed by fire.  It is very susceptible to
fire because it has (1) thin bark that provides little insulation for
the cambium, (2) a moderate amount of resin in the bark which ignites
readily, (3) shallow roots which are susceptible to soil heating, (4)
low-growing branches, (5) a tendency to grow in dense stands, (6)
moderately flammable foliage, and (7) heavy lichen growth [87].

Crown fires typically kill Engelmann spruce trees.  Engelmann spruce is
also very susceptible to surface fires because fine fuels which are
often concentrated under mature trees burn slowly and girdle the
thin-barked bole or char the shallow roots [20,31].  Some large
Engelmann spruce may survive light, surface fires, but these often die
later due to infection by wood-rotting fungi that enter through fire
scars [31].


DISCUSSION AND QUALIFICATION OF FIRE EFFECT : 
NO-ENTRY


PLANT RESPONSE TO FIRE : 
Following fire, Engelmann spruce reestablishes via seeds dispersed by
wind from trees surviving in protected pockets or from trees adjacent to
burned areas.  The rate of reestablishment is variable and depends on
the proximity of surviving cone-producing trees and seed production
during the year of the fire and immediate postfire years.  In general,
Engelmann spruce seedling establishment is very slow in areas burned by
large, continuous crown fires because much of the seed source is
destroyed.  However, on small burns or near pockets of surviving trees
within a large burn, Engelmann spruce usually establishes numerous
seedlings within 5 to 10 years [42,44].

In areas where Engelmann spruce is abundant and lodgepole pine scarce
before burning, Engelmann spruce establishes rapidly after fire if
sufficient numbers of seed trees survive or are near the burn.  If
lodgepole pine is present in the preburn community, it usually seeds in
aggressively, assuming a dominant role as it overtops any spruce
seedlings establishing on the site [24,28,42].  However, Engelmann 
spruce seedlings usually survive under the developing pine canopy
because of its shade tolerance.

Above 9,850 feet (3,000 m), lodgepole pine does not regenerate, and
burned areas remain open for several decades or longer.  Postfire
succession in this harsh, high-elevation zone (9,850 to 10,850 feet
[3,000-3,300 m]) proceeds very slowly.  Spruce slowly becomes
established as scattered seedlings [12].  It may take 100 to 200 years
before young spruce-fir forest covers the area.  However, conditions in
the upper parts of this zone sometimes make it difficult for tree
seedlings to establish and survive at all.  Here, grasses and sedges may
form a mat which prevents tree seeds from reaching mineral soil [85].
Burned fir-spruce forest is replaced by alpine tundra which can persist
for long periods of time [12].


DISCUSSION AND QUALIFICATION OF PLANT RESPONSE : 
Postfire Engelmann spruce seedling establishment is best on moist
surfaces where fire has consumed most or all of the duff leaving bare
mineral soil.  Seedlings do require some shade to survive; thus
regeneration after fire is best on sites where standing dead trees,
logs, or developing vegetation is present [73].  Engelmann spruce
postfire regeneration is poor on sites subjected to high light
intensities.  A 26,000 acre (64,200 ha) burn on a high-elevation site in
southwestern Colorado showed poor conifer regeneration 100 years after
the fire.  This was attributed to intense solar radiation which
inhibited photosynthesis, causing a high percentage of spruce seedlings
to die [75].  Postfire spruce regeneration is also poor where shrub and
herbaceous cover is dense, where exposed mineral soil is subject to
excessive evaporation, and where fire has only charred the duff [10].
Ash does not affect germination, but if it is deep, it can prevent a
seedling's roots from reaching mineral soil [62].

In northern Colorado, 3 years after a late August wildfire in a dense,
overmature stand composed of Engelmann spruce, subalpine fir, and
lodgepole pine, Engelmann spruce established 1,000 seedlings per acre
(2,470/ha) in burned areas that were than less than 0.1 acre (0.05 ha).
However, in the middle of the main burn, no Engelmann spruce seedlings
had established by 3 years after the fire [10].  In Colorado, Peet [66]
reported a 75-year-old burn that had good spruce regeneration near the
burn boundary, but only 218 yards (200 m) inside the burn edge, few
seedlings had established, and the area was still fairly open.

Day [24] sampled lodgepole pine-Engelmann spruce x white spruce hybrid
stands in southern Alberta that had established after fires that had
occurred 29 and 56 years prior to sampling.  He found that both pine and
spruce had initiated large numbers of seedlings imediately after the
fire.  Pine, however, had established more seedlings and rapidly outgrew
the spruce, forming a canopy that was three to four times taller than
the spruce canopy.  Pine seedling establishment had ceased by 30 years
after the fire, but spruce continued to establish seedlings.  Engelmann
spruce eventually dominates sites where spruce and pine come in together
after fire.


FIRE MANAGEMENT CONSIDERATIONS : 
After clearcutting Engelmann spruce stands, broadcast burning can be
used to prepare seedbeds for natural regeneration.  Broadcast burns
which remove most of the duff or organic matter and burn hot enough to
destroy some or all of the competing vegetation favor spruce seedling
establishment [72].  However, seedling establishment is poor or
nonexistent in areas where hot fires leave deep layers of ash or
generate such intense heat that rocks are fractured, such as under slash
pile fires [72,94].  For this reason, where large amounts of slash must
be burned, windrows or piles should be kept small and cover a minimal
portion of the area [3].  Engelmann spruce often occurs in cool and
moist locations which restricts the time of year when effective
broadcast burning can take place.  Prior to burning, duff must be dry
enough to ensure that it will be consumed.  Seedling establishment will
be inhibited on burns that only blacken the organic matter.  Some cull
logs and slash should be left in place to provide shade and protection
for developing seedlings [72].

Engelmann spruce stocking was greater than 50 percent and averaged 573
seedlings per acre (1415/ha) 5 years after broadcast burning in
clearcuts in northern Idaho where the uncut stand composition was 56
percent western larch, 22 percent Engelmann spruce, 15 percent mountain
hemlock, and 7 percent subalpine fir.  This broadcast burn exposed
mineral soil on 53 percent of the area [14].  In northwestern Montana,
Engelmann spruce seedling establishment was much greater on broadcast
burned clearcuts where burning exposed mineral soil than on unburned
clearcuts.  Eleven years after burning, stocking of Engelmann spruce
seedlings was 23 percent on burned cuts but only 1 percent on unburned
cuts.  Seventeen years after burning, stocking was 56 percent on burned
cuts but only 2 percent on unburned cuts [84].

Broadcast burning is generally not recommended following partial cutting
because residual Engelmann spruce trees are very fire sensitive.  

Related categories for Species: Picea engelmannii | Engelmann Spruce