FIRE EFFECTS
SPECIES: Sisymbrium altissimum | Tumblemustard 



IMMEDIATE FIRE EFFECT ON PLANT : 
Tumblemustard is readily killed by fires of any intensity [6,19,20,21].
Extensive stands of tumblemustard are not usually able to carry a fire
[10].


DISCUSSION AND QUALIFICATION OF FIRE EFFECT : 
NO-ENTRY


PLANT RESPONSE TO FIRE : 
Burns within sagebrush-grassland or pinyon-juniper communities are
rapidly invaded by tumblemustard [15,18,20,21].  This highly mobile
"tumbleweed" is capable of widespread seed dispersal; adjacent unburned
areas can also serve as seed sources [6,13].  Tumblemustard can be an
important component of early postburn vegetation, especially on sites
where herbaceous perennials have been significantly reduced [27].
Burning exposes bare soil which is condusive to seed germination [1].
Although initial establishment may be low, plant densities increase
dramatically for 1 to 2 years, and extensive stands are sometimes
formed.  After 2 to 3 years, overcrowding significantly reduces mustard
survival and seed production, and plants are rapidly replaced by more
competitive species, typically cheatgrass.


DISCUSSION AND QUALIFICATION OF PLANT RESPONSE : 
Piemeisel [20,21] described secondary succession on abandoned farmland
in Idaho as progressing from dominance by Russian thistle to
tumblemustard to cheatgrass.  He indicated that initial dominance by any
one of these species is a function of efficient seedbed saturation.
Tumblemustard was not, however, a significant component following a fire
in a degraded big sagebrush/Thurber needlegrass (Artemisia
tridentata/Stipa thruberiana) community in Nevada [30].  Although
maximum frequencies occurred shortly after burning, tumblemustard was
suppressed by a sparse stand of cheatgrass that had established during
the first postfire season.

Initial establishment of tumblemustard is also influenced by the amount
of perennial herbaceous cover present in the preburn community.  Burns
in the drier sagebrush habitat types (Artemisia tridentata ssp.
wyomingensis and A. tridentata ssp. tridentata) are particularly
susceptible to mustard invasion [10].  Not only is mustard more
competitive on these drier sites, but herbaceous perennial cover is
naturally low at any successional stage [4].  Tumblemustard was unable
to establish dominance following a wildfire in a protected foothills
grassland in Montana despite an abundance of seed from adjacent mustard
stands.  Although plant coverages were significantly higher than on
unburned areas, maximum coverages reached only 3 percent 2 years after
the fire [1].

Studies of postburn vegetation in pinyon-juniper woodlands indicate that
tumblemustard reaches highest coverages during early-mid (4- to
8-year-old burns) to mid (14- to 17-year-old burns) successional stages
[15].  Apparently this species is more competitive on drier sites within
these communities, since frequencies were greatest on south- and
west-facing slopes.  Furthermore, when burns were seeded, tumblemustard
had a significantly higher occurrence on unseeded sites than seeded
sites.


FIRE MANAGEMENT CONSIDERATIONS : 
NO-ENTRY

Related categories for Species: Sisymbrium altissimum | Tumblemustard