FIRE EFFECTS
SPECIES: Epilobium angustifolium | Fireweed 



IMMEDIATE FIRE EFFECT ON PLANT : 
Fire top-kills fireweed.  Seed in the surface organic layers is killed
by fire [74].  Surviving fireweed rhizomes vigorously sprout after a
fire [35,86].  Twenty to thirty days after fires in July and August
fireweed sprouted from rhizomes [195,199].


DISCUSSION AND QUALIFICATION OF FIRE EFFECT : 
NO-ENTRY


PLANT RESPONSE TO FIRE : 
Fireweed is an important off-site colonizer after fire [203,204].
Often, it is not present on a site before a fire but establishes during
the first postfire year [8,9,38,215].  Seedlings are initially present
in low amounts [155,174].  Colony growth continues via rhizome
expansion; some seedlings continue to establish as mineral soil
microsites open.

Initial establishment of fireweed seedlings usually exceeds expectations
of frequency based upon on-site preburn vegetation [141].  Following a
fire in eastern Siberian taiga, fireweed regenerated, and 79.5 percent
of fireweed individuals present sprouted from seed [212].

Fireweed is usually an increaser following fire [36,78,193,205].  Within
3 postfire months, fireweed was present at 3 percent frequency and 1
percent cover in central Alberta [7].  Fireweed slowly increases in
abundance, often with 100 percent frequency and 30 percent or more
cover, to peak on average postfire years 5 [18,39,51,63,80,155,170].  In
the Cascade Range, fireweed had significantly (p<0.05) different amounts
of cover at postfire years 3 to 5, but from years 11 to 16, there was no
significant (p>0.05) change in cover between burned and unburned areas
[160].  However, at 11 postfire years, fireweed was present at 91
percent frequency on upland sites in northwestern Oregon [165].  It was
not in the surrounding Douglas-fir-western hemlock (Tsuga heterophylla)
stand.  Fireweed was still one of the principal cover species 10 to 12
postfire years on severe fire sites in northern Idaho and western
Montana [45,140,147,203].  In other studies, the highest frequency for
fireweed was reached 17 to 20 years after fire [45,142,162].

Fireweed production may vary with severity of fire.  Severe fires remove
organic soil layers, exposing mineral soil which is an excellent seedbed
for fireweed.  Therefore, cover and density are greatest on severely
burned areas because of good seedling establishment [13,17,19,20,43].
Three years following an August fire, fireweed production steadily
increased from 423.8 air dried pounds per acre (475 kg/ha) on
low-severity burns to 1,478.4 air dried pounds per acre (1,657 hg/ha) on
high-severity burns [20].  However, fireweed was more dense 1 year after
fire in Wyoming on moderate-severity burns compared to high-severity
burns [6].

Initially, fireweed decreased after fire from preburn levels of cover
(20 percent) in a Douglas-fir stand in south-central Idaho [139].
However, by postfire year 3, cover had doubled the amount present
preburn.  Postfire years 5 to 8, fireweed cover plateaued at 84 to 88
percent [139].  Fireweed was expected to decline over the next 20 years
to preburn levels.

Fireweed is one of the most abundant forbs on most burned areas of
interior Alaska [138].  A series of severe fires in Alaska will convert
any forest type into a semipermanent herbaceous or shrub community [33].
The herbaceous communities are usually fireweed and grasses, such as
bluejoint reedgrass.

Immediately following burning of a white spruce type, fireweed can form
relatively stable communites with bluejoint reedgrass that may last 100
years in interior Alaska [137].  Following fire in black spruce (Picea
mariana) in the Northwest Territories, fireweed is the most prominent
plant and is one of several diagnostic species for the first stage of
recovery [26].  This stage may last 1 to 20 years [26].

In Engelmann spruce-subalpine fir communities (Picea engelmanni-Abies
lasiocarpa), fireweed was dominant on stands 1 to 10 postdisturbance
years; it declined on stands 11 to 80 postdisturbance years [71,189].
Following fire in the western hemlock/Douglas-fir zone in the Olymipic
Mountains, Washington, fireweed was common for stands 2 postfire years
[100].  However, it began to decline in frequency in stands 3 to 19
postfire years.  After about 30 years, fireweed had a low average
frequency (4 to 10 percent) with about 1 percent cover in burned-over
areas of different cover types, such as paper birch (Betula papyrifera),
aspen, and jack pine (Pinus banksiana) [168].  This pattern was seen in
Douglas-fir stands in the Cascade Range, Washington, aged 5 to 73 years
following logging and burning [135].  Fonda [75] found that fireweed
persisted under similar circumstances in stands 65 years or younger.
Fireweed began to decline in frequency as the crown of different forest
types closed in stands approximately 57 to 280 postfire years and was
absent in stands aged 290 to 515 postfire years [40,100,207].


DISCUSSION AND QUALIFICATION OF PLANT RESPONSE : 
NO-ENTRY


FIRE MANAGEMENT CONSIDERATIONS : 
In white spruce-aspen stands in Alberta, prescribed fire was not
effective for conifer regeneration after logging [119].  Heavy postfire
sprouting by aspen and fireweed inhibited white spruce seedling
establishment.  Light surface fires stimulated fireweed growth to 100
pounds per acre (111.9 kg/ha) within 3 months.

Fireweed and other forbs produced heavy cover following a severe fire in
Minnesota that inhibited jack pine growth [1].  Jack pine seedlings were
thin, light colored, and stunted.  Despite detrimental effects of
shading tree seedlings, herbaceous cover may provide higher microsite
humidity and suppress shrubs [2,151].

Fireweed effectively uptakes and recycles large amounts of nutrients
from burned-over areas [166].  Fireweed foliage had significantly
(p<0.05) higher levels of nutrients (potassium, magnesium, manganese,
phosphates, and zinc) on burned areas compared to unburned controls
[197].

Fire protection managers should consider using fireweed when they
require a species with low flammability rating (for rating factors see
Fire Ecology or Adaptations) [223].  Fireweed is included in the
narrow-leaved forb class for establishing fuel weights [31].

Following logging, slash may be bulldozed into piles.  Bulldozing
scarifies the soil, and slash piles burn very hot; fireweed readily
established in these open spots [14,218,222].  Fireweed had
significantly (p<0.05) higher frequency of occurrence on logged and
broadcast burned areas than on unburned areas [162].  Dense fireweed
stands protected slash from sun and wind during the fifth year after
cutting, reducing the probable rate of fire spread compared to the first
summer after cutting [159].  However, fireweed increases the rate of
fire spread with dead leaves and stems.

Burning, mechanical (e.g., tree cutting), biological (e.g., intense
sheep grazing), and chemical controls were applied to enhance big
huckleberry (Vaccinium membranaceum) communities on Mount Adams,
Washington.  These treatments had no significant (p>0.05) effect on
fireweed abundance during postdisturbance years 1 and 2 [156].  Fireweed
was significantly more abundant on burned plots postdisturbance year 5.
No other treatments had a significant (p>0.05) effect on fireweed
abundance after 5 years.

In Alberta, forage species, such as alfalfa (Medicago sativa) and
crested wheatgrass (Agropyron cristatum cv. Fairway) were seeded into
burned areas [5].  Fireweed successfully invaded the plantings and was
still present after five years.  Grasses aerially seeded on burns may
compete and displace fireweed.  In Montana, Pattee Canyon was aerially
seeded with commercial grasses following a fire.  Fireweed had low cover
values 10 years later [211].  Toth [211] suggested that orchardgrass
(Dactylis glomerata) had displaced fireweed.

Related categories for Species: Epilobium angustifolium | Fireweed