FIRE EFFECTS
SPECIES: Bromus inermis | Smooth Brome 



IMMEDIATE FIRE EFFECT ON PLANT : 
Smooth brome is probably top-killed by fire.


DISCUSSION AND QUALIFICATION OF FIRE EFFECT : 
NO-ENTRY


PLANT RESPONSE TO FIRE : 
Early spring (late March-April) or late-season (late summer-fall) fire
can increase smooth brome productivity [62,65], especially when smooth
brome has become sod-bound.  Late spring fire generally damages
cool-season grasses such as smooth brome [8,82].  Old [93], Kirsch and
Kruse [71], and Blankespoor [15] have reported reductions in smooth
brome with late spring burning.

Old [93] attributed decreases in smooth brome after late April fire to
the advanced stage of development of smooth brome.  Rate of smooth brome
regrowth after fire cannot always be predicted based solely upon season
of burning and attendant phenological stage, however.  Blankenspoor and
Larson [16] cited soil moisture and nutrient levels and soil texture as
factors other than phenological stage that may affect smooth brome rate
of recovery.

In order to determine at which stage of growth smooth brome is most
susceptible to fire, Willson [124] prescribe-burned smooth brome at
tiller emergence (late March at the Mead, Nebraska, study site), tiller
elongation (mid-May), and heading (late May).  Late March fire had no
significant effect on smooth brome.  Mid-May or late May fire reduced
fall tiller density approximately 50 percent when compared to controls.

Examples of late spring fire:  Short- and mid-grass prairie of Pipestone
National Monument, Minnesota, was spring-burned (mid- to late April)
annually from 1983 to 1987.  The prairie had been severely degraded by
invasion of cool-season exotic grasses including smooth brome,
quackgrass (Elytrigia repens), and Kentucky bluegrass.  Fire severity
was low to moderate except in 1984, when high fuel levels were present.
Smooth brome postfire coverage was [11]:

             1984           1985          1987
             ----           ----          ----
season       spring        spring        summer  
cover (%)     21.3          22.4          26.4(a)
             -------------------------------------
             a = data pooled with quackgrass
 
Lack of flower and seed production was noted in the cool-season grasses
including smooth brome, while native warm-season grasses increased
height growth and seed production.  Height (cm) of smooth brome was
as follows [11]:

       Prefire                       Postfire
   --------------      -------------------------------------
        1983                1984            1985       1987
   ---------------     ---------------     ------     ------
   spring   summer     spring   summer     spring     summer    
     60       50         60       60         50         40

Smooth brome flowering was inhibited by a 2 May, 1972, prescribed fire in
Minnesota prairie [95].  

Examples of fire in seasons other than late spring:  On the Rathbun
Wildlife Area in southern Iowa, smooth brome is managed as ring-necked
pheasant cover.  Smooth brome showed a significant (P<0.05) increase in
percent coverage following September or April prescribed burning.
February burning resulted in a nonsignificant decrease in smooth brome
coverage, with significant declines in smooth brome frequency in some
years [51].  

A 22 April, 1983, prescribed fire on the Hillendale Game Farm of central
Pennsylvania increased smooth brome production.  On 5 October, 1983,
production was 69 kilograms per hectare on the unburned control and 612
kilograms per hectare on the burn [65].

In Iowa, three consecutive early spring (23-28 March, 1986; 11-12 April,
1987; 13-20 April, 1988) prescribed fires in pastureland excluded from
grazing had no significant effect on smooth brome.  On some plots,
atrazine was applied 7 to 10 days after burning; the fire plus atrazine
treatments had no significant effect on smooth brome [101].


DISCUSSION AND QUALIFICATION OF PLANT RESPONSE : 
Late spring burning has sometimes been only marginally effective in
controlling smooth brome [23,93].  Kirsh [70] reported that smooth brome
was actually stimulated by an early May prescribed fire.  This variable
response may be due, in part, to the fact that control effects have been
targeted against several cool-season exotic grasses rather than smooth
brome alone.  Since phenologies of cool-season grasses differ, timing of
a particular fire may reduce other cool-season species but not smooth
brome [16].

In a defoliation experiment, Harrison and Romo [58] found that smooth
brome regrowth was related to both growth stage and soil moisture
conditions.  After defoliation in the vegetative stage, smooth brome
resumed growth in 45 to 75 growing days when soil moisture was
favorable.  Smooth brome did not resume growth until the next growing
season after clipping in dry years.  When plants were defoliated during
reproduction, new tillers did not emerge until the next fall regardless
of soil moisture conditions.

Blankenspoor and Larson [16] used a prescribed fire and watering
treatment to determine smooth brome's response to late spring (9 May,
1989) fire under low and high soil moisture levels.  They found the
following changes in percent smooth brome biomass after treatment:

               Burned     Unburned
               ------     --------
high-water     -17.0       +10.5 
low-water       -8.2       +11.7
 
Decreases in the two burned treatments were significantly different
(p=0.05), but increases in the unburned treatments were not.  Apparently
when soil moisture is high, warm-season grasses are able to outcompete
fire-injured smooth brome for water.  With less soil moisture available,
warm-season grasses may be less able to take competitive advantage of
fire-injured smooth brome [16].

In the same study, Blankespoor and Larson [16] found that on unburned
plots, increases in smooth brome biomass were greatest on plots with low
initial smooth brome biomass.  This relationship approached significance
(p=0.06) for unburned, high-water plots and was strongly significant
(p=0.001) for unburned, low-water plots.  As a cool-season species with
substantial growth occurring early in the growing season, smooth brome
apparently encounters little competition from water-stressed,
warm-season plants in the absence of fire.


FIRE MANAGEMENT CONSIDERATIONS : 
If smooth brome is growing in association with a legume and an
increase in smooth brome productivity is desired, early spring rather
than late summer or early fall fire is generally recommended.
Late-season fire harms many legume species [62,74,94].

Fire control:  An important management goal in remnant prairie is to
maintain or increase diversity of native species and depress growth and
production of exotic invaders such as smooth brome.  Becker [11]
concluded that annual spring burning on Pipestone National Monument
prairie helped control smooth brome and other cool-season exotic
grasses, and that the structure, composition, and diversity of the
severely degraded native prairie was improved by annual burning.
Similarly, two consecutive spring fires on portions of an eastern South
Dakota tallgrass prairie where smooth brome was dominant reduced smooth
brome and Kentucky bluegrass coverage [15].

Blankespoor and Larson's [16] prescribed fire-water treatment study
suggests that prescribed late spring fire will most effectively control
smooth brome in wet years.  They recommend continuing a program of
prescribed burning through drier years, however.  Since they found that
smooth brome increased in importance without burning, and that increases
were greatest when initial smooth brome biomass was low, they concluded
that failing to burn smooth brome in dry years is likely to accelerate
its expansion.

For control, Willson [124] recommended burning smooth brome in late
spring after it has produced five or more green leaves per tiller;
unelongated tillers, which are not greatly damaged by fire, generally
have fewer than five green leaves per tiller.
 
Postfire plantings:  Smooth brome has been extensively planted to
increase forage and/or reduce erosion in burned areas
[14,29,34,35,61,79,106].  This practice has been questioned because
native species appear to be at least equally effective in reducing
erosion, and exotic grasses such as smooth brome may interfere with the
growth of native forbs and grasses [34].

Postfire plantings of smooth brome have been successful across a wide
range of habitats and climates.  For example, big sagebrush-threetip
sagebrush (Artemsia tridentata-A. tripartita) rangeland in Idaho was
burned in summer 1937 and seeded with one of six grasses to reduce
sagebrush cover and increase forage production.  On plots seeded to
smooth brome, smooth brome yield increased from 57 pounds per acre in
1940 to 148 pounds per acre in 1948.  Sagebrush coverage was lower on
smooth brome plots than on plots of any of the five other grasses
planted [14].

In Montana smooth broome seeded in after stand-replacing fire in
lodgepole pine (Pinus contorta) showed "fair" vigor (density of 4.4
plants/sq ft) on slopes with a southwestern exposure and "good" vigor
(density of 8.2 plants/sq ft) on slopes with a northeastern exposure
[45].

Litter accumulation:  Bleak [18] reported a 39 percent average rate of
decay of bagged smooth brome litter in direct contact with snow cover
over two consecutive winters.

Related categories for Species: Bromus inermis | Smooth Brome