FIRE EFFECTS
SPECIES: Arbutus menziesii | Pacific Madrone 



IMMEDIATE FIRE EFFECT ON PLANT : 
Madrone is a fire-sensitive species; aboveground portions are very
susceptible to fire mortality [4,10,63].  Low-intensity ground fires
usually top-kill madrone seedlings and sapling-sized stems [4].  Thin
bark provides little insulation from radiant heat, which usually kills
the cambium around the base of the stem [40].  Larger trees with thicker
bark frequently survive light underburning on favorable growth sites
within redwood and mixed-evergreen forests.  Although young, vigorous
trees usually exhibit bole injuries following burning, fire scars tend
to heal over rapidly.  Older madrones may initially survive light ground
fires; however, bole wounds facilitate the entry of insects and disease
and many fire-damaged trees eventually die [4].


DISCUSSION AND QUALIFICATION OF FIRE EFFECT : 
NO-ENTRY


PLANT RESPONSE TO FIRE : 
Vegetative regeneration: Following fires which kill aerial stems,
Pacific madrone initiates a rapid postburn recovery by sprouting from
adventitious buds located on an underground, globelike structure known
as a burl [31,58].  Burls may reach diameters of 8 inches (20 cm) or
more [26].  Since burls contain aggregations of buds, newly sprouted
madrones occur as "sprout clumps" [40].  Sprouts are quite tolerant of
direct sunlight and develop well in the initial postburn environment
[16].  After 10 years of growth on a good site in the northern Sierra
Nevada, Pacific madrone sprout clumps averaged 22 feet (6.7 m) in height
and 10.2 feet (3.1 m) in crown width with an average of 15 sprouts per
clump [39].

The initial postburn recovery is aggressive.  Pacific madrone sprouts
sometimes grow more than 5 feet (1.5 m) during the first postburn
growing season [39].  Although prolific spouting usually occurs during
the first 2 years following burning, sprout numbers are drastically
reduced between postburn years 2 and 3 as growth is concentrated into
multiple dominant stems.  Initial trends in postburn recovery of Pacific
madrone in northwestern California are presented below [66]:

                                              Years postburn
                                         1          2            3 


Average ht of tallest sprout            4.7        7.7         10.1 
     in clump (feet) 
Average crown diameter of sprout        4.5        6.8          7.6
     clump (feet)
Average sprouts per clump               17         16           13

Seedling regeneration:  Pacific madrone seedling establishemnt is
favored following fire.  Mineral soil seedbeds and light canopy
densities of the initial postburn environment are extremely conducive to
the successful establishment and growth of madrone seedlings [46,59].
On sites where fires are not too severe, abundant seed is available from
residual trees.  Off-site seed is also dispersed by mammals and birds.
Initial postburn seed production of sprouted madrones has not been
reported.  Minimum seed-bearing age of seedling-derived plants is 3 to 5
years [16].


DISCUSSION AND QUALIFICATION OF PLANT RESPONSE : 
Since sprout production is initially fueled by the residual root system,
postburn sprouting potential of madrone is strongly related to the size
and vigor of the parent tree.  Sprout clumps produced by larger diameter
parent trees are generally taller and wider in diameter than those of
smaller diameter parent trees; they also produce greater numbers of
resprouts [26,58,66].  Site quality apparently has almost no influence
on sprout clump development for at least 6 years after fire [58].
Limited observations on sites in southwestern Oregon indicate that
previous fires and the subsequent entry of pathogens can substantially
reduce the sprouting potential of parent trees greater than 17.2 inches
(43 cm) d.b.h. [58].


FIRE MANAGEMENT CONSIDERATIONS : 
Broadcast burning:  Where conifer regeneration is a primary management
concern, broadcast burning is generally an ineffective site preparation
tool following clearcutting in stands where madrone is widespread in the
understory.  Not only is madrone difficult to control with repeated
burning, but sprouts often grow faster than many associated hardwoods
[33,40].  Even though burning delays the recovery of madrone for
approximately one growing season, removal of logging debris promotes
sprouting by exposing basal buds to solar heating and permits sprouts to
grow unimpeded [40].  Sites where the preburn vegetation consists of low
conifer stocking combined with high densities of madrone are
particularly prone to the rapid development of a dense madrone
understory.

Underburning:  Pacific madrone seedlings establish readily following
logging and burning of conifer-hardwood stands [59].  Light underburning
at sometime during the rotation may minimize seedling establishment,
thereby reducing the density of madrones capable of sprouting after
future disturbances.  Control of madrone seed trees should accompany
such prescribed fire treatments (See Management slot under Value and Use
subframe.)

Hardwood management:  Burning should not be used as a method of slash
disposal in partially cut hardwood stands where madrone is managed for
timber production.  Instead, logging debris should be lopped and
scattered, or piled [40].

Wildlife management:  Burning initially increases the palatability of
Pacific madrone browse; spouts are utilized for up to 2 growing seasons
[11,61].

Related categories for Species: Arbutus menziesii | Pacific Madrone