FIRE EFFECTS
SPECIES: Pinus resinosa | Red Pine 



IMMEDIATE FIRE EFFECT ON PLANT : 
Thick bark allows mature red pine (50 years old or 50 feet tall) to
survive relatively intense surface fires.  Red pine are killed by crown
fires or by surface fires that result in considerable crown scorch [33].
Moderate-intensity surface fires (<200 Btu/s/ft [<692 kW/m]) do not
scorch the crowns of mature red pine.  A large red pine may survive a
surface fire intensity of 500 Btu/s/ft (1,730 kW/m), but this intensity
is probably the highest red pine can withstand [40].  In a study in New
England, many red pines less than 4 inches (10 cm) survived their first
surface fire [10].

Two stands, in which 96 percent of the red and white pines were 9 inches
(23 cm) in diameter or larger, were prescribed burned in late spring
(May 31 and June 15).  The percent crown scorch was estimated after the
fire, and 1 year later mortality was assessed.  There was no mortality
in trees with less than 46 percent crown scorch.  Mortality was 50
percent in the 81 to 85 percent crown scorch class and 100 percent in
trees with more than 96 percent crown scorch [27].

An April surface fire in a 47-year-old red pine plantation in Minnesota
resulted in less mortality than the abovementioned study.  The red pine
were 50 to 60 feet (15.2-18.3 m) tall, and most trees were between 6 and
11 inches (15-28 cm) in d.b.h.  One and a half years after the fire,
mortality was 40 percent in the 95 to 100 percent crown scorch class, 14
percent in the 75 to 95 percent crown scorch class, and 8 percent or
less in those pines with less than 75 percent crown scorch.  The fire
took place while the new shoots were still in the terminal buds.
Mortality would probably have been higher if the fire had occurred after
the buds had opened but before the next year's buds had formed [36].

A laboratory study in August, in which red pine seedlings were exposed
to different temperature regimes for 4 minutes, demonstrated even less
mortality with high percentages of needle scorch.  The seedlings
withstood up to 90 percent needle scorch with only 10 to 20 percent
mortality.  The author suggests that there may be two lethal
temperatures, one that kills needles and one that kills terminal buds.
Therefore, percent needle scorch may not be directly related to
mortality in red pine [27].

A completely developed seed may survive in a cone in the crown after a
surface fire that completely killed the crown foliage, but an
undeveloped seed is unlikely to complete its development under these
conditions [40].


DISCUSSION AND QUALIFICATION OF FIRE EFFECT : 
In natural red pine stands, crown fires are rare because stands are
open.  However, dense plantation stands up to 50 feet (15.2 m) tall are
at high risk of intense crown fire.  Red pine is highly flammable and
crown fires can reach intensities up to 6,500 BTU/s/ft (22,500 kW/m) [40].


PLANT RESPONSE TO FIRE : 
Fire provides red pine with conditions necessary for regeneration,
specifically a bare or lightly covered mineral seedbed free of brushy
competition and an open canopy.  A summer surface fire averaging 200 to
500 Btu/s/ft (692-1,730 kW/m) with small scale variations in intensity
to ensure the survival of some seed trees is ideal for regeneration
[40].  However, not all canopy-opening fires result in red pine
recruitment because good seed crops are infrequent [10].  Red pine
establishment is sometimes delayed for up to 10 years after a fire [3].
In one study, seedling counts at postfire year 1 correlated positively
with fire severity, exposure of mineral soil, and reduction of shrub
weight per acre [39].

A thick organic layer is an unfavorable seedbed because germinants are
farther from a constant water supply and the mineral soil.  The higher
the fire severity, the more organic material is removed.  However, fire
also consumes seeds and rhizomes and thus reduces the early postfire
herbaceous cover which serves to shelter the young seedlings from heat.
Initially, as the amount of postfire shelter is reduced by increasing
fire severity, red pine survival decreases.  Eventually, however, the
reduction in organic matter depth is sufficient to compensate for the
lack of shelter, and the survival of red pine increases.  Establishment
is highest when mineral soil is exposed [37].

A study of slash pine (Pinus elliottii) showed that if the crown is
partially scorched, a loss in growth can be expected, possibly as much
as 1 year's growth in the first 2 postfire years.  The author believes
these results are applicable to red pine [15].



DISCUSSION AND QUALIFICATION OF PLANT RESPONSE : 
NO-ENTRY


FIRE MANAGEMENT CONSIDERATIONS : 
Prescribed fire is used for red pine site preparation.  In the
shelterwood system, two fires conducted in consecutive years are
recommended before the first partial cut.  A fire conducted after the
partial cut may be too hot because of slash and may cause mortality of
the remaining trees.  The first fire should be in the spring before
understory leaves emerge so that the fire will be hot enough to remove
most of the soil surface organic material [41].  Sufficient duff is
removed only when the moisture content is less than or equal to 60
percent [40].  A second fire after the leaves emerge helps reduce
competition.  A suggested reasonable fire intensity for preparing a
seedbed and controlling competition is 116 to 173 Btu/s/ft (400-600
kW/m) [41].  Van Wagner [40] states that 200 Btu/s/ft (692 kW/m) is the
upper limit of intensity to avoid crown scorch in 70- to 80-foot (21-24
m) red pine.  This intensity is lower than is ideal for natural
regeneration because trees do not need to be killed to open up the
canopy in a shelterwood system.

Two consecutive annual fires in a 90-year-old red and white pine stand
in Ontario improved the initial conditions necessary for pine
regeneration.  The fires were low in intensity (22 to 23 Btu/s/ft [78-79
kW/m]) and did not harm the overstory.  The litter layer was consumed
and the understory was changed from one dominated by balsam fir saplings
to one dominated by herbaceous species.  However, the understory will
revert back to prefire conditions unless some of the canopy is removed
in a shelterwood cut [28].

The red pine cone beetle, and possibly the red pine cone moth, can be
controlled by prescribed fire.  Adults overwinter on the forest floor
and are vulnerable to low-severity ground fires from late October to
early May.  Because the decrease in the red pine cone beetle might
result in an increase in other pests, such as the red pine coneworm, the
prescribed burning treatment should be limited to years with heavy cone
production [29].

Equations have been developed to predict the forest floor fuel weight
and the litter weight in red pine stands from the basal area [9].

Related categories for Species: Pinus resinosa | Red Pine