FIRE CASE STUDIES
SPECIES: Picea mariana | Black Spruce 



CASE NAME : 
Lowland Black Spruce Experimental Burns/Manitoba



SEASON/SEVERITY CLASSIFICATION : 
spring/light
spring/moderate


STUDY LOCATION : 
The study took place 60 miles (97 km) east-southeast of Winnipeg,
Manitoba.  


PREFIRE VEGETATIVE COMMUNITY : 
The community was a 100-year-old black spruce stand averaging 2,180
trees per acre (5,387/ha).  Hummocks and depressions were covered with a
continuous moss carpet.  Feather mosses (Pleurozium schreberi,
Hylocomium splendens) comprised 88 percent of this ground cover and
sphagnum mosses (Sphagnum spp.) 12 percent.  Scattered shrubs including
Labrador-tea (Ledum groenlandicum), bog birch (Betula glandulosa),
shrubby cinquefoil (Potentilla fruiticosa), and prickly rose (Rosa
acicularis) collectively made up 20 percent of the ground cover.  Other
scattered shrubs and herbs included meadow horsetail (Equisetum
pratense), mountain cranberry (Vaccinium vitis-idaea), twinflower
(Linnaea borealis), creeping snowberry (Gaultheria hispidula),
bunchberry (Cornus canadensis), and coltsfoot (Petasites spp.).

The area was logged 2.5 years before the experimental burns were
conducted.  The logging operation removed only merchantible timber,
leaving 800 trees per acre (1,977/ha).  Slash was 10 to 25 inches deep
(25-64 cm) and covered 52 percent of the ground.  Under the slash was a
litter layer of fallen needles about 3 inches (8 cm) deep. The logging
operation reduced feather moss cover from 88 to 41 percent, sphagnum
moss cover from 12 to 6 percent, and shrub cover from 20 to 10 percent,
but increased grass cover from 10 to 20 percent, and sedge cover from 10
to 30 percent.  


TARGET SPECIES PHENOLOGICAL STATE : 
NO-ENTRY


SITE DESCRIPTION : 
The site was typical of many lowland black spruce peatlands.  It was
situated on a gentle transition gradient between a well-drained upland
and a poorly drained muskeg.  The ground had 10- to 18-inch-high (25-46
cm) peaty hummocks and intermittent depressions.  Extending to 10 inches
(25 cm) below the depressions was the upper peat, which was mostly
comprised of fibrous undecomposed debris.  Below this was 16 inches (40
cm) of well-decomoposed mucky peat over fine-textured mineral soil.


FIRE DESCRIPTION : 
Two areas were burned under different fire prescriptions, resulting in a
light-severity and moderate-severity burn.  Conditions before igniting
each burn were as follows:

                    light-severity burn        moderate-severity burn

date                    May 17, 1967                May 29, 1967
cloud cover (%)             90                          70
air temp (F/C)            72/22                       75/24
relative humidity (%)       32                          31
wind speed (mph/kph)       9/14                        9/14
wind direction             west                       southeast

The average flame height for both fires was 3 feet (1 m) with occasional
trees crowning up to 40 feet (12 m).  In general fires destroyed slash,
surface litter, and aerial parts of vegetation including feather mosses
and some sphagnum mosses.  Stumps and discarded logs were only partially
consumed.  

The moderate-severity burn occurred about 2 weeks later than the
light-severity burn when fuels were drier.  Peat under exposed feather
mosses was dry to a depth of 1 inch (2.5 cm) on May 17, and to a depth
of 3 inches (8 cm) on May 29.  Although burning exposed 95 percent of
the peat on both burns, fire burned deeper into peat on the
moderate-severity burn.  On the light-severity burn, average depth of
burning was 3 (8 cm) inches on hummocks and 2 inches (5 cm) in
depressions.  On the moderate-severity burn, average depth of burning
was 7 inches (18 cm) on hummocks and 4 inches (10 cm) in depressions.


FIRE EFFECTS ON TARGET SPECIES : 
Of the residual black spruce trees left after logging, all were killed
by the fire.  Smaller trees were completely consumed, while larger trees
were scorched.  Cones in the upper crowns of scorched trees were
unharmed and were responsible for good seedfall after the fire.  Five
growing seasons after the fires, stocking was 94 percent on the
moderate-severity burn and 70 percent on the light-severity burn.
Seedling density 5 years after burning was 16,129 per acre (39,856/ha)
on the moderate-severity burn and 3,075 per acre (7,598/ha) on the
light-severity burn.  On both burned areas nearly all seedlings were
found on exposed peat.  A small percentage were found on sphagnum.  The
average seedling height 5 years after burning was 11 inches (28 cm) on
the moderate-severity burn and 8 inches (20 cm) on the light-severity
burn.  


FIRE MANAGEMENT IMPLICATIONS : 
Burning following timber harvest can be used for the successful
regeneration of black spruce on lowland sites.  Black spruce will
establish quickly from natural seedfall if adequate seed trees are
present and the fuels are sufficiently dry to ensure moderately deep
burning.  



FIRE CASE STUDIES
SPECIES: Picea mariana | Black Spruce 



CASE NAME : 
Washington Creek Experimental Fires/Fairbanks, AK



SEASON/SEVERITY CLASSIFICATION : 
summer/intense


STUDY LOCATION : 
The study was conducted at the Washington Creek Fire Study and Training
Area, about 25 miles (40 km) north of Fairbanks, Alaska. 


PREFIRE VEGETATIVE COMMUNITY : 
The preburn community was a 70-year-old unevenly spaced black spruce
(Picea mariana) stand with a small amount of paper birch (Betula
papyrifera), green alder (Alnus viridis ssp. crispa), scouler willow
(Salix scouleriana), and Alaska willow (S. alaxensis) scattered
throughout.  Low shrubs included mountain cranberry (Vaccinium
vitis-idaia), bog blueberry (V. uliginosum), and Labrador-tea (Ledum
groenlandicum).  Moss cover ranged from 72 to 85 percent.  

The study area was divided into five units, of which four were burned.
Density, height, and diameter of trees on the four burned units prior to
ignition is presented below:

                                      Unit #
                       1L          2            3            4L

Density (stems/acre)

black spruce trees    1376       2214         1692          901
paper birch trees      0          300           32           47
black spruce saplings  603        790         3546          759
paper birch saplings   0           32          0             0

Avg height of black
spruce (feet/meters) 11.2/3.4   11.2/3.4     11.5/3.5     10.2/3.1 

Avg diameter of
black spruce (in/cm)  1.9/4.8    1.9/4.8      2.0/5.0      1.7/4.3


TARGET SPECIES PHENOLOGICAL STATE : 
NO-ENTRY


SITE DESCRIPTION : 
The burned area was on a ridgetop that sloped to the southeast.
Elevation was approximately 1,700 feet (520 m).  The soil was a shallow
Fairplay silt loam with shattered bedrock and stones at a depth of 8 to
20 inches (20-50 cm).  No permafrost was present.  The five units, four
burn and one control, ranged in size from 0.22 to 0.37 acres (0.09-0.15
ha), each separated by a fireline several yards wide.


FIRE DESCRIPTION : 
                      Units burned on July 22

One unit was burned on July 22, following a rainless period from July 16
to July 22.  The organic layer was high in water content from heavy
rains which fell before July 16.  Conditions before ignition were as
follows:

fuel stick moisture content = 6.6 percent
relative humidity = 32 percent
wind speed and direction = 0-5 mph (0-8 kph), south-southeast 
temperature = 76 degrees F (24 C)

Burning in unit 2:  The fire was ignited at 11:52 am.  Heat developed
rapidly and the fire quickly spread to the crowns.  The fire moved
across the unit in 7 minutes.  The fire was hot from 0 to 10 feet (0-3
m) above the ground, but not within the forest floor.  Most of the
organic layer was not consumed.

                     Units burned on August 26

Three units were burned in the afternoon on August 26.  To measure the
effects of high intensity fire, 2 of the units (1L and 4L) were loaded
with additional fuel.  Black spruce cut from the fire lines which
bordered the units was laid in rows within these units in June, 1975,
more than 1 year before burning.  Unit 1L had 23,636 pounds/acre (26,500
kg/ha) of loaded fuel.  Unit 4L had 13,914 pounds/acre (15,600 kg/ha) of
loaded fuel.  A total of 16 mm of precipitation fell between August 1
and August 26.  Conditions before ignition were as follows:

fuel stick moisture content = 6.6 percent
relative humidity = 40 percent
wind speed and direction = 6-8 mph (9.6-12.8 kph), south-southeast
temperature = 66 degrees F (19 C)

Burning in unit 1L:  This unit was ignited at 12:42 pm.  Fire spread to
tree crowns within 1 minute.  Burning in tree crowns was spotty except
for the center of the unit.  Where crowning occurred in one area, flames
reached to 52 feet (16 m).  Most active burning was over within 16
minutes, but fire continued to burn in the organic layer for several
hours.

Burning in unit 4L:  This unit was ignited at 2:13 pm.  The fire
completed its run across the unit in 6 minutes.  This fire burned the
hottest of the 4 units burned.  The loaded fuel added to the spread and
intensity of the fire and to the depth in which fire burned into the
organic layer.

Burning in unit 3:  This unit was ignited at 3:01 pm, and burned
primarily as a slow moving ground fire.  It took 29 minutes to burn
across the unit.  This was the coolest of the 4 fires.

Indicators of fire intensity and severity for all units is presented
below: 

                                              Burn Unit
                                      1L      2        3       4L
avg. water evaporation
from 250 ml water
cans (ml)                             65      5       16      107

highest temp (C)      height
recorded from heat   
sensitive paints at   2.75 m          66     288      66      454
different heights     2.25 m          66     288      66      454
                      1.75 m          66     288     121      454
                      1.25 m         121     288     121      660
                       .75 m         121     288     121      660
                       .25 m         288     288     288      660
                     6-15 cm         288     288     288      454
                      0-5 cm         288     121     288      454
     2-3 cm in organic layer         ---      43     288      121

highest temp (C)       depth in 
recorded by heat     organic layer 
sensitive pellets    
                       surface       >83     >83     >83      >83
                       5 cm           43      43      43       69
                      10 cm          <43     <43     <43      <73

Effect on forest floor 

Thickness before burning (cm)       21.6    19.8    23.2     22.4
Thickness after burning (cm)        11.6    14.9     7.8      7.2
Reduction in thickness (percent)    43      24      61       62

percentage of forest floor in
forest floor fire severity classes

(based on ten 1-m2 plots)
heavily burned                      24.0     2.0    37.0     49.4
moderately burned                   25.0     0.2    11.9      6.1
lightly burned                      37.5    97.1    49.3     34.5
scorched                             7.5     0.7     1.8      0
unburned                             6.0     0       0        0

(based on ten 10-m-long transects)
heavily burned                      34.2     2.1    36.8     58.0
moderatley burned                   21.0    16.0    16.0     17.0
lightly burned                      36.1    75.0    42.0     24.9
scorched                             1.0     6.9     4.5      0.1
unburned                             7.7     0       1.7      0


FIRE EFFECTS ON TARGET SPECIES : 
Because it was difficult to tell if trees were dead or alive immediately
after the fire, damage to black spruce trees and saplings was recorded
as a percentage of needles consumed.  Needle consumption by unit is
listed below:

needles consumed        unit 1L      unit 2      unit 3      unit 4L

   (percent)                     (percentage of trees)
    76-100                33           47           9          39
    51-75                 32           16          38          55
    26-50                 28           22          44           6
     0-25                  7           14           9           0

                                (percentage of saplings)
    76-100                76           62          43          78
    51-75                 16           15          38          20
    26-50                  8            8          17           2
     0-25                  0           14           2           0

In general, more needles were consumed on saplings than on tall trees,
indicating that the fires were more intense under the crowns of the
trees.  

The fires caused black spruce cones to open and shed seed.  Seedfall
began immediately after the fires on August 26.  Seedfall in unit 4L was
much lower than in the unburned control.  The fire in this unit may have
been intense enough to consume many cones.  In the other units, seedfall
in September and October was higher than in the unburned control.


FIRE MANAGEMENT IMPLICATIONS : 
Prescribed fires can simulate moderately severe wildfires in black
spruce stands.  Within these burns, aboveground vegetation was almost
completely killed, and the forest floor displayed a mosaic of different
burning severities.  These four fires show that the moisture content of
forest floor materials is extremely important in controlling the
severity of burning in black spruce stands.

Black spruce seedfall begins shortly after fire.  This should result in
abundant seedling establishment beginning in postfire year 1.

Related categories for Species: Picea mariana | Black Spruce