FIRE CASE STUDIES
SPECIES: Pinus banksiana | Jack Pine 



CASE NAME : 
Regeneration after prescribed fire in a seed-tree system


REFERENCE : 
Chrosciewicz, Z. 1988 [24]


SEASON/SEVERITY CLASSIFICATION : 
Summer backfire/moderate-severity


STUDY LOCATION : 
The study was conducted on an upland till site at latitude 53 deg 52 min
N.  and longitude 105 deg 4 min W., about 15 miles (24 km) by road
northeast of Candle Lake in central Saskatchewan.


PREFIRE VEGETATIVE COMMUNITY : 
The original stand of 82-year-old jack pine with a small amount of black
spruce (Picea mariana) and trembling aspen (Populus tremuloides) was
logged to leave eight jack pine seed trees per acre (20/ha).  The seed
trees had well-developed crowns, ranged in height from 60 to 70 feet
(18-21 m), and were 8 or more inches (20 cm) in d.b.h.  About 95 percent
of the forest floor was covered by Schrebers moss (Pleurozium
schreberi).  Also present was bristly club-moss (Lycopodium annotinum),
twinflower (Linnaea borealis var. americana), and bunchberry (Cornus
canadensis).  American green alder (Alnus crispa) growing up to 6.6 feet
(2 m) tall was present in the understory.  The slash averaged 1 foot
(0.3 m) in depth and provided 71 percent intermittent ground cover.


TARGET SPECIES PHENOLOGICAL STATE : 
NO-ENTRY


SITE DESCRIPTION : 
The terrain was nearly flat with a slight south-southwest aspect.  The
glacial till soil varied downward from sandy loam to sandy clay loam.
The soil moisture regime was fresh to moderately moist, and the humus
(including surface moss and litter) averaged 2.8 inches (7.1 cm) in
depth.


FIRE DESCRIPTION : 
Weather:  At the time of the fire, the air temperature ranged from 70 to
82 degrees Fahrenheit (21-28 deg C), relative humidity 43 to 61 percent,
and wind speed 2 to 6 miles per hour (3-10 km/h) at 4 feet (1.2 m) above
the ground and 3 to 10 miles per hour (5-16 km/h) at 33 feet (10 m)
above the ground out of the southwest.

Fuel moisture:  Preburn moisture content of the forest floor duff
averaged 95 percent in exposed locations and 200 percent in locations
shaded by slash.  The Duff Moisture Code (DMC) was 37 and the Fine Fuel
Moisture Code (FFMC) was 80.  Preburn moisture content of the cured pine
needles averaged 11 percent and the cured pine branches less than 0.8
inch (2 cm) in diameter averaged 15 percent.

Fire and burn characteristics:  During the most active period of
burning, flame heights averaged 3 feet (1 m) above the ground.  The fire
crowned in a few seed trees.  

All aerial parts of minor vegetation were completely burned.  Only
stumps, logs, and some branch wood remained in a surface-charred state.
The forest floor humus depth was reduced to 1.7 inches (4.2 cm).  After
the fire, the forest floor was 9 percent exposed mineral soil, 88
percent partially burned humus, and 3 percent undisturbed original
humus.


FIRE EFFECTS ON TARGET SPECIES : 
More than 70 percent of the jack pine seed trees showed varying degrees
of crown scorch immediately after the fire, and eventually most seed
trees died.  Some cones on seed trees opened within 1 or 2 days of the
fire, while others opened more slowly.  Overall seed shedding was
expected to last up to 3 years.

Jack pine regeneration was inventoried four growing seasons after the
fire.  Stocking averaged 4,939 seedlings per acre (12,195/ha).  Twenty
percent of the seedlings grew on exposed mineral soil and 80 percent on
partially burned humus.  The dominant seedlings averaged 1.5 feet (0.47
m) in height.  The tallest seedlings (2.3 feet [0.71 m]) more than
doubled in height in the next two growing seasons, averaging over 1 foot
(0.3 m) height growth per year.  Most of the jack pine seedlings
successfully competed with American green alder, aspen (Populus spp.),
and Bebb willow (Salix bebbiana).  In a few locations, dense canopies of
aspen sprouts overtopped the jack pine and retarded its height growth.


FIRE MANAGEMENT IMPLICATIONS : 
The study demonstrates that prescribed burning in conjunction with a
seed-tree system can successfully regenerate jack pine.  Enough heat was
generated from burning logging slash and the other fuel present to open
serotinous cones in the seed trees.  Jack pine regenerated successfully
on partially burned humus because of adequate precipitation during the
postfire growing seasons.  Had the fire been followed by a drought,
seedlings may have only survived on mineral seedbeds.
 

Related categories for Species: Pinus banksiana | Jack Pine