FIRE CASE STUDIES
SPECIES: Eriophorum vaginatum | Sheathed Cottonsedge 



CASE NAME : 
Regeneration/Imurak Lake Fire/Seward Peninsula


REFERENCES : 
Racine, C. H. 1979 [44]
Racine, C. H. 1981 [66]
Racine, C. H.; Johnson, L. A.; Viereck, L. A. 1987 [45]


SEASON/SEVERITY CLASSIFICATION : 
summer/low to moderate severity


STUDY LOCATION : 
The Imurak Lake area is located in the central part of the Seward
Peninsula of Alaska (65 deg 35 min N., 163 deg 20 min W.).  It is within
the Bering Land Bridge National Monument and is administered by the
National Park Service.  At the time of the fire, it was administered by
the Bureau of Land Management.  Study sites were on the southwest slope
of Nimrod Hill (Bendelben C-3 quadrangle on USGS topographical map)
[1,2].


PREFIRE VEGETATIVE COMMUNITY : 
Sheathed cottonsedge tussocks dominated the footslope of Nimrod Hill.
Sheathed cottonsedge frequency was 10 percent; density was 34 shoots per
square meter.  Areas between tussocks were occupied by dwarf shrubs,
mosses, and lichens.  Dwarf shrubs present were bog Labrador tea (Ledum
palustre), cloudberry (Rubus chamaeorus), mountain cranberry (Vaccinium
vitis-idaea), bog blueberry (V. uliginosum), crowberry (Empetrum
nigrum), and dwarf arctic birch (Betula nana).  Mosses were Sphagnum
spp., Dicranum elongatum, Hypnum pratense, and Aulocimium palustre.
Also present were reindeer lichens (Cladonia gracilis, C. rangiferina),
caribou lichens (Cetraria cuclata), and dogtooth lichen (Peltigera
aphthosa).  Imurak Lake was downslope from this sheathed
cottonsedge-ericaceous shrub community.  A dwarf arctic birch-ericaceous
shrub community was upslope [1,2,3].


TARGET SPECIES PHENOLOGICAL STATE : 



SITE DESCRIPTION : 
Imurak Lake Fire study sits were located along a topographic transect
from the bottom to the top of Nimrod Hill.  Slope was gentle (1-9%) on
the footslope where the sheathed cottonsedge-ericaceous shrub community
occurred.  Footslope elevation was 1,100 to 1,350 feet (335-411 m).
Soil was moist.  Texture of the soil mineral fraction was silty
clay-loam.  Frost depth was 11.6 inches (29 cm).  The organic layer was
3.6 to 17.2 inches (19-43 cm) thick [1,2].


FIRE DESCRIPTION : 
The Imurak Lake Fire was ignited by lightning.  Fire was moderate to
severe in the dwarf arctic birch-ericaceous shrub community.  It moved
downslope from that community into sheathed cottonsedge-ericaceous
shrub, where it lowered to light and moderate severity [1,2].


FIRE EFFECTS ON TARGET SPECIES : 
Sheathed cottonsedge-ericaceous shrub tundra had the fastest postfire
regeneration rates of all plant communities burned, with 15 to 20
percent cover at postfire year 1.  Sheathed cottonsedge cover averaged
17.4 percent; average density of mature plants was 3.5 shoots per square
meter.  Tussocks on old frost scars apparently sprouted more vigorously
than tussocks on other substrates and produced more flowers at postfire
year 2.  Distinction between sheathed cottonsedge seedlings and Carex
spp. seedlings was difficult at postfire year 1 because they were less
than 0.4 inch (1 cm) tall.  Total sedge seedling density, however, was
greater than 100 per square meter.  After 7 postfire years, evidence of
fire was difficult to detect, except for the change in species
composition.  Sheathed cottonsedge increased in importance as a result
of fire [1].


FIRE MANAGEMENT IMPLICATIONS : 
Postfire peat thickness was 9.6 to 12 inches (24-30 cm), a reduction of
2 to 6 inches (5-15 cm) from prefire thickness.  Depth of thaw increased
12 to 14 inches (30-35 cm).  Postfire frost action created new frost
scars and renewed old ones [1].

The Imurak Lake Fire demonstrates how fire benefits sheathed
cottonsedge.  The fire renewed growth of senescent tussocks.  Increased
depth of active soil layer and availability of fresh frost scars created
opportunity for seedling establishment.  Increased soil nutrients
allowed for vigorous growth of seedlings and sprouting tillers [1].

Heavy equipement was driven across the Imurak Lake Burn the spring
following the fire.  It left deep tracks and ruts (up to 10 inches [25
cm] deep) and exposed mineral soil.  Racine [1] recommended that because
burned tundra is particularly susceptible to disturbance, off-road
vehicle traffic be prohibited except in winter when soils are frozen.

Related categories for Species: Eriophorum vaginatum | Sheathed Cottonsedge