FIRE EFFECTS
SPECIES: Artemisia cana ssp. viscidula | Mountain Silver Sagebrush 



IMMEDIATE FIRE EFFECT ON PLANT : 
Fire effects on mountain silver sagebrush is not well documented.
Burning causes complete top-kill of plants regardless of the degree to
which aerial plant parts are consumed (fire intensity).  Studies on the
morphologically similar plains silver sagebrush indicate that the extent
to which plants survive burning is directly related to fire intensity
and severity.  Totally consumed plants sustain higher mortalities than
those less thoroughly burned.  This trend is further accentuated by
season of burning; more plants survive spring burns than fall burns
[37].  Apparently soil moisture and phenological stage at the time of
burning have a significant influence on plant survival [38].


DISCUSSION AND QUALIFICATION OF FIRE EFFECT : 
In general, mortality in silver sagebrush is directly related to fire
intensity and fire severity as effected by soil moisture content at the
time of burning.  White and Currie [37] conducted spring and fall burns
under comparable site conditions on a mixed-grass prairie in eastern
Montana.  Results indicate significant differences in the mortality of
plains silver sagebrush on spring versus fall burns.  Fall burning
produced a two- to three-fold increase in mortality over that of spring
burning.  Mortalities were greatest when high intensity burns coincided
with dry soil moisture conditions; conversely, most plants were able to
survive moderately intense burns when conducted under high soil moisture
conditions.  Apparently internal water stress in plants is increased as
the season progresses and soils dry out [38].  Soil moisture was
significantly diminished throughout the upper 23 inches (60 cm) of the
soil profile from early July through late September on study sites.

The degree to which this information applies to mountain silver
sagebrush is unkown.  Since soil moisture content appears to have a
significant impact on plant mortality, attempts at plant control through
the use of fire would necessitate dry conditions in order to be
effective.  Burning under the more mesic conditions associated with
mountain silver sagebrush sites may not achieve the desired effects.


PLANT RESPONSE TO FIRE : 
Information regarding the response of mountain silver sagebrush to fire
is lacking.  As a group, the silver sagebrush complex resprouts
vigorously following fire.  Postfire regeneration involves sprouting
from rootcrowns and rhizomes; new individuals are also established from
wind-dispersed seed [40,41].  Detailed fire response data has been
reported for plains silver sagebrush in Montana [37].  These studies
indicate that plant size prior to burning has little effect on
subsequent survival or regrowth; apparently postburn response varies in
relation to soil moisture conditions and season of burning.  Preburn
levels are quickly restored following most spring burning, and the
majority of plants survive and resprout vigorously due to the combined
effects of reduced fire severities and favorable moisture conditions.
Because of the adverse growing conditions, fall burning results in
significant decreases in plant numbers and has a more lasting effect
upon plant coverages [37].


DISCUSSION AND QUALIFICATION OF PLANT RESPONSE : 
Although not well-documented, most fire effects information on silver
sagebrush indicates that densities are rapidly regained and usually
enhanced following burning [7].  Recent detailed studies involving
plains silver sagebrush in Montana [37] indicate that increases in burn
intensity and severity tend to retard the resprouting abilities of
surviving plants.  Season of burning also has an influence on postfire
response.  Following spring burning sagebrush plants produced relatively
few (3 to 4) sprouts per plant.  Stem elongation was rapid, however.
Severely burned plants reached heights of at least 8 inches (20 cm)
within 3 months of burning, while less severely burned plants grew to
over 12 inches (30 cm).  Most plants were characterized by dense foliage
and a bushy growth form.  In contrast, fall burning resulted in plants
which produced more sprouts per plant but which had little regrowth.
Lightly burned plants had an average of 10 sprouts per plant but failed
to reach 8 inches (20 cm) within 3 months of breaking dormancy.  Plants
which were severely burned had only four sprouts per plant and averaged
less than 2.4 inches (6 cm) in length.

These results suggest that burning can be used to achieve a range of
management objectives within plains silver sagebrush stands.  On winter
ranges where this subspecies is a palatable forage, spring burning can
be used to enhance plant coverages and rejuvenate stands.  Where plant
control is deemed necessary, fall burning can drastically reduce
coverages.  The degree to which these results apply to mesic sites
dominated by mountain silver sagebrush is presently unknown.  Since soil
moisture conditions have a profound effect on postburn response, burns
must be precisely timed in order to have the desired effect on plant
densities.


FIRE MANAGEMENT CONSIDERATIONS : 
NO-ENTRY

Related categories for Species: Artemisia cana ssp. viscidula | Mountain Silver Sagebrush