FIRE EFFECTS
SPECIES: Rhododendron macrophyllum | Pacific Rhododendron 



IMMEDIATE FIRE EFFECT ON PLANT : 
Pacific rhododendron appears to be top-killed by most fires.  The
shallow rootcrown could be heat-killed during severe fires, thus killing
the entire plant.  Low severity fires may allow the survival of basal
stem buds, accounting for observations of its increased survival
following such fires [11,20].


DISCUSSION AND QUALIFICATION OF FIRE EFFECT : 
NO-ENTRY


PLANT RESPONSE TO FIRE : 
Following fire, Pacific rhododendron sprouts from stem bases or
rootcrowns and new seedlings may establish [3,20,62].  There is a marked
decrease in cover and frequency immediately after fire followed by a
slow, gradual increase [10,11,48,58].  In the western Cascade Mountains
of Oregon, Pacific rhododendron is a residual species following light
fires but very scarce after more severe fires [11].  Nevertheless in
this area, evidence of past fires is shown by brushfields that include
Pacific rhododendron [53].  In Asia rhododendron seedlings rapidly
colonize open areas after fire [35] and Pacific rhododendron's tiny,
winged seeds might allow expansion from surviving plants.


DISCUSSION AND QUALIFICATION OF PLANT RESPONSE : 
Several studies that have used permanent plots to follow vegatation
changes after logging and burning in Oregon and Washington demonstrate
that Pacific rhododendron is fire-sensitive.  Two studies following
slash burning compared burned and unburned plots.  In the first study,
most plots were burned lightly or moderately by fall fires.  Samples
taken during the first 16 years after slash burning show Pacific
rhododendron to be dominant on twice as many unburned plots as burned
plots.  Where it did attain significant cover on burned plots, Pacific
rhododendron had resprouted by the second season after fire [39,40].  A
second study found cover of Pacific rhododendron to be 30.5 percent on
unburned plots and 4.9 percent on burned plots 11 to 16 years following
fire [49].

Results of another postfire study demonstrated a slow increase in
frequency of Pacific rhododendron from the first to the fifth and sixth
growing seasons [58].  A comparison of old-growth western hemlock -
Douglas-fir stands with 2- to 40-year-old stands found mean cover values
of Pacific rhododendron decreased from 13 percent to 0.4 percent 2 years
after broadcast burning and gradually increased to 6.8 percent at 40
years [48].  Early recovery of Pacific rhododendron on three clearcuts
that were treated with medium-intensity fall fires was as follows [11]:

                                  Cover (%)      Frequency (%)

Before logging:                   8.5            29.5
Year 1 after logging:             1.0            18.0
Year 1 after slash fire:          0.2            13.1
Year 2 after slash fire:          0.8            11.5
Year 5 after slash fire:          1.8            14.8


FIRE MANAGEMENT CONSIDERATIONS : 
Since Pacific rhododendron is reduced by fire [20], burning after
logging results in better conifer stocking [57].  However, communities
with Pacific rhododendron as a dominant are frequently on infertile
soils that are sensitive to the effects of fire [27,28].  Moderate to
hot slash fires can cause damage to these soils and loss of nutrients,
especially nitrogen [27,28].

Related categories for Species: Rhododendron macrophyllum | Pacific Rhododendron