FIRE CASE STUDIES
SPECIES: Pinus contorta var. latifolia | Rocky Mountain Lodgepole Pine 



CASE NAME : 
Table Mountain - Prescribed Crown Fire Study


REFERENCE : 
Woodard, P. M. 1977 [87]


SEASON/SEVERITY CLASSIFICATION : 
fall/severe


STUDY LOCATION : 
The study took place in the Cascade Mountains in central Washington,
approximately midway between the towns of Ellensburg and Wenatchee.


PREFIRE VEGETATIVE COMMUNITY : 
The study area is within the subalpine fir (Abies lasiocarpa) zone.  Two
adjacent but different-aged stands were burned.  One area was a
lodgepole pine (Pinus contorta) thicket about 100 years old.  The other
was an older, decadent stand of lodgepole pine with subalpine fir and
Engelmann spruce (Picea engelmannii) attaining dominance.  Each is
described below.  

Lodgepole pine thicket - Lodgepole pine was the overstory dominant, but
subalpine fir and Engelmann spruce were also principal components.
Subalpine fir and Engelmann spruce were codiminants in the intermediate
size classes.  Subalpine fir was the only tree regenerating under the
canopy.  Understory plants included elk sedge (Carex geyeri), Hood sedge
(C. hoodii), heartleaf arnica (Arnica cordifolia), broadleaf arnica (A.
latifolia), bigleaf lupine (Lupinus polyphyllus), and dwarf bilberry
(Vacciuium myrtillus).

Snag area - This was a decadent lodgepole stand, with subalpine fir and
Engelmann spruce dominating the overstory canopy.  Fir and spruce
codominated the intermediate size classes, but subalpine fir was the
only tree regenerating under the canopy.  Predominant understory plants
included subalpine fir, elk sedge, broadleaf arnica, and mosses
(Rhacomitrium canascens, Polytridum commune).


TARGET SPECIES PHENOLOGICAL STATE : 
NO-ENTRY


SITE DESCRIPTION : 
The burned area is a southwest-facing gentle slope at an elevation of
5,596 to 5,776 feet (1,706-1,761 m).  A total of 27 acres (10.9 ha) were
burned.

Climate:  The climate is typical of most areas within the subalpine
zone.  The winters are cold and wet and the summers cool and dry.  Frost
and freezing temperatures can occur during any month of the year.  Over
70 percent of precipitation falls as snow between October and March.  

Soil and duff:  The two stands have similar soils, but the soil in the
snag area is more fertile and better developed.  In both areas soils are
derived from basalt residium, have a clay-loam texture, and average 6
inches (15.2 cm) deep.  The effective rooting depth is about 20 inches
(51 cm) in the thicket area, and 20 to 40 inches (51-102 cm) in the snag
area.  On both areas, duff was generally from 1 to 4 inches (0.4-1.6 cm)
thick.  The mean depth of duff was 2.3 inches (5.9 cm) on the thicket
area, and 1.9 inches (4.9 cm) on the snag area.  

Fuel loading:  Prior to burning, mean fuel loads were as follows:  

          fuels                    thicket area         snag area
                                tons/acre tonnes/ha  tons/acre tonnes/ha

dead and down wood
0.0-0.25 inch (0.0-0.6 cm)         0.6        1.3       0.9       2.0
0.26-0.99 inch (0.6-2.5 cm)        2.1        4.6       2.9       6.4
1.0-3.0 inches (2.6-7.6 cm)        4.4        9.8       5.1      11.4
> 3.0 inches (7.6 cm) rotten      17.4       38.9      30.9      69.2
> 3.0 inches (7.6 cm) solid       17.0       38.1      50.1     112.1
litter                            41.4       92.7      89.8     201.2
duff                              32.5       72.8      30.0      67.1


FIRE DESCRIPTION : 
The fire was ignited by drip torches on September 30, 1975, taking
approximately 1 hour and 20 minutes to ignite the entire 27 acres (10.9
ha).  Actual fire prescriptions at the time of ignition were as follows:
 
ambient air temperature = 60 to 63 degrees F (16-17 C)
relative humidity = 19-21 percent
wind = calm gusts to 15.6 miles/hr (26 km/hr), from the south-southwest
days since last rain = 15
fine fuel moisture content = 13 percent

Within about 10 minutes after ignition, trees began to crown out.  Fire
behavior for each area is summarized below:  

Snag area - Crowning occurred throughout most of the snag area.  Flame
heights were estimated to be 125 feet (38 m) by one observer, and 50
feet (15 m) above the tops of 90 foot (27 m) crowns by two other
observers.  The fire consumed all small downed and dead wood from 0.0 to
1 inch (0-2.5 cm) in diameter, as well as needles and small twigs on
living standing trees.  Ninety-six percent of down and dead fuels less
than 3 inches (7.6 cm) in diameter were consumed.  In general, 90 to 100
percent of the duff layer was removed.  Many trees less than 3 inches
(7.6 cm) in diameter at the base were completely consumed, and nearly
all standing snags were blown down or burned down.  Where crowning
occurred, the only thing that remained immediately following the fire
was reddened soil, ash-covered soil, large-diameter logs, and dead
trees.  

Lodgepole thicket - Fire within the lodgepole thicket was much less
severe.  The crown fire which occurred within the snag area stopped when
it met the boundary of the lodgepole thicket.  Dead and down fuels less
than 3 inches (7.6 cm) in diameter were reduced by 70 percent.  Dead and
down fuels greater than 3 inches (7.6 cm) in diameter were reduced 34
percent.  Duff was reduced about 25 percent.


FIRE EFFECTS ON TARGET SPECIES : 
On portions of the burn where crowning occurred, all lodgepole pines
were killed.  In the lodgepole thicket area the fire did not crown, and
some trees survived.  In this area of Washington, Rocky Mountain
lodgepole pine is predominantly nonserotinous.  Within 1 year of the
fire, lodgepole seedlings became established on the burned area, but
were restricted to areas along the burn edge and near survivors within
the lodgepole thicket area.


FIRE MANAGEMENT IMPLICATIONS : 
Fire hazard and the potential for a high-intensity crown fire are high
in decadent lodgepole pine stands being taken over by shade-tolerant
associates.  The large accumulation of dead and down woody fuels burn
intensely, and the young conifers provide a fuel ladder to ignite the
crowns of overstory trees.  In this study, there was about twice as much
dead and down woody fuels in the snag area (area suffering a crown fire)
as in the thicket area (area experiencing ground fire).

In areas where lodgepole pine is largely nonserotinous, seed for
regeneration must come from survivors.  Lodgepole pine, however, is not
very fire resistant.  The occasional mature tree which survives fire,
those escaping fire in small, unburned pockets, and trees adjacent to
burned areas provide seed to colonize burned areas.  Because lodgepole
pine's seed dispersal distance is relatively short, seedling
establishment is restricted to areas around these seed trees.

Related categories for Species: Pinus contorta var. latifolia | Rocky Mountain Lodgepole Pine