FIRE CASE STUDIES
SPECIES: Marchantia polymorpha | Liverwort 



CASE NAME : 
The effects of experimental fires on black spruce forests


REFERENCE : 
Dyrness, C. T.; Norum, R. A. 1983 [19]


SEASON/SEVERITY CLASSIFICATION : 
Summer/light to severe fires


STUDY LOCATION : 
The site lies within the W 1/2 sec. 12, and the NE 1/4 sec. 13, T4N,
R2W, of the Fairbanks Meridian, Alaska.
 


PREFIRE VEGETATIVE COMMUNITY : 
Before burning, the vegetation was an open black spruce (Picea
mariana)/feather moss (Pleurozium schreberi) forest.  The mature, open
black spruce tree layer comprised a mosaic of two dominant age-classes
of about 85 and 140 years.  Some of the seven units burned included
small groups of trembling aspen (Populus tremuloides) and scattered
paper birch (Betula papyrifera).  The tall shrub layer was represented
by scattered American green alder (Alnus viridis ssp. crispa), willows
(Salix spp.), and prickly rose (Rosa acicularis).  The most common
low-growing shrubs were mountain cranberry (Vaccinium vitis-idaea), bog
blueberry (V. uliginosum), crowberry (Empetrum nigrum), and bog Labrador
tea (Ledum groenlandicum).  The herbaceous layer was sparse but the
entire forest floor was covered with feather mosses.


TARGET SPECIES PHENOLOGICAL STATE : 
NO-ENTRY


SITE DESCRIPTION : 
The total burned area covered approximately 32 acres (13 ha).  The
elevation was 1,575 to 1,706 feet (480-520 m).  The slope was 10 to 15
percent, and the aspect was generally southeast to south from a main
ridge running southwest to northeast.  The position of the fires was on
the upper third of the slope.  The soil in the experimental area was
silty loam, somewhat poorly drained in shallow loess over schist
bedrock.  Before the fire, a forest floor layer 8 to 12 inches (20-30
cm) thick was present.  The mineral soil was made up of a very
dark-brown silty loam surface horizon underlain by a yellowish-brown,
stony (30-50 percent by volume), silty loam subsoil.  Bedrock was
generally within 29 inches (75 cm) of the surface.


FIRE DESCRIPTION : 
Seven units of approximately 5 acres (2 ha) each were burned between
July 19 and August 8, 1978.  The woody fuels on the forest floor were
meager and scattered and therefore contributed little to fire behavior
or subsequent fire effects.  Fire behavior within the units ranged from
slowly moving surface fires to rapidly advancing crown fires.  The crown
fires were passive, making the transition after hot surface fire had
passed beneath the trees.  Consequently, the surface fires determined
the rate of spread, and the crown fires followed, with flames reaching
50 feet (15 m) or more.  Most of the units were completely covered by
fire and had burned down to glowing combustion within an hour after
being ignited.  Weather conditions during the fires were as follows:

                                            Unit
                            1     2     3     4     5     6     7
                          --------------------------------------------
Temperature (deg C)        23    21    24    21    22    21    26  
Relative humidity          42    33    30    54    42    33    36
Wind (mph)                1-4   5-8   4-6   1-2   3-6   3-5   3-5 
Wind direction            SSW    SW    SW    SW   SSW    SW   SSW
Rate of spread (ft/min)   1.5   3.7   3.8   1.0   4.0    --   5.9 
Flame length (ft)         1.9   2.5   3.5   0.5   2.2    3.0  2.2


FIRE EFFECTS ON TARGET SPECIES : 
M. polymorpha was not present in the prefire vegetation.  In heavily
burned areas, M. polymorpha, fire moss (Ceratodon purpureus), and
fireweed (Epilobium angustifolium) dominated the postfire community for
the first 3 years.  M. polymorpha maintained a biomass of about 15 to 20
grams per square meter throughout that period.


FIRE MANAGEMENT IMPLICATIONS : 
M. polymorpha invades heavily burned areas by light, wind-borne spores.
Competition from sprouters on lightly burned sites will prevent or limit
M. polymorpha colonization.  Sites must be severely burned if M.
polymorpha establishment is desired in the postfire community.

Related categories for Species: Marchantia polymorpha | Liverwort