Smooth Brome

This species has been spread worldwide through seed production for pasture and fodder.

Awnless Brome, as interpreted here, is part of a species complex grading into awned and/or hairy forms especially in Asia. It shows quite clear connections with Bromus stenostachyus Boiss. and the Caucasian Bromus biebersteinii Roem. & Schult. Its distinction from Bromus confines is also rather ill-defined.

A very useful fodder grass introduced into the British Ises and North America for this reason.

Perennial, with spreading rhizomes. Culms loosely tufted, erect, 50–120 cm tall, glabrous or retrorsely hairy below nodes. Leaf sheaths glabrous or shortly hairy; leaf blades flat, 20–30 cm × 4–8 mm, both surfaces and margins scabrid, glabrous or margins sparsely ciliate, apex acuminate, ligule 1–2 mm. Panicle dense at first, spreading after anthesis, 10–20 cm; branches 3–5 per node, up to 10 cm, scabrid, each bearing 2–6 spikelets. Spikelets 15–25 mm, florets 6–12; rachilla internodes 2–3 mm, spinulose; glumes lanceolate, margins membranous, lower glume 4–7 mm, 1-veined, upper glume 6–10 mm, 3-veined; lemmas oblong-lanceolate,8–12 mm, 5–7-veined, glabrous, base scabrid, apex obtuse or emarginate; awn up to 3–4 mm, or awnless; palea shorter than lemma, keels ciliate. Anthers 3–4 mm. Fl. and fr. Jul–Sep. 2n = 14, 28, 56.

Rhizomatous perennial; culms solitary or loosely tufted, up to 120 cm high. Leaf-blades up to 35 cm long, 4-8 mm wide, glabrous or sparsely ciliate on the margins; sheaths glabrous or very shortly pubescent. Panicle 10-20 cm long, usually rather dense, occasionally loose and open. Spikelets narrowly oblong, 8-13-flowered, 15-30(-35) mm long, pallid or slightly purple-tinged; glumes narrowly lanceolate, glabrous, the lower 3.5-8 mm long, 1-nerved, the upper 6-11 mm long, 3-nerved; lemmas oblong-lanceolate, the lower 9.5-13 mm long, 5-7-nerved, usually glabrous or often sparsely hairy at the base, rarely sparsely appressed hirsute all over, truncate at the tip, shortly and bluntly 2-toothed, awnless or with an awn up to 1.5 mm long, rarely the awn as much as 4-6 mm; palea almost as long as the lemma, ciliate on the back and keels or glabrous on the back; rhachilla pubescent; anthers (3-)3.5-5.5(-7) mm long.

Gansu, Guizhou, Hebei, Heilongjiang, Jiangsu, Jilin, Liaoning, Nei Mongol, Qinghai, Shaanxi, Shandong, Shanxi, Sichuan, Xinjiang, Xizang, Yunnan [Japan, Kashmir, Kazakhstan, Kyrgyzstan, Mongolia, Tajikistan, Uzbekistan; SW Asia (Caucasus), Europe].

Distribution: Kashmir; Europe and temperate Asia.

Fl. & Fr.Per.: June-August.

Gullies on slopes, roadsides, river banks, dominant species of mountain meadows; 1000–3500 m.

Bromopsis inermis (Leysser) Holub; Bromus pskemensis Pavlov; Zerna inermis (Leysser) Lindman.

More info for the terms: competition, cool-season, fire use, prescribed fire, warm-season

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.

Lyon's Research Paper (Lyon 1971) provides further information on
prescribed fire use and postfire response of plant species including
smooth brome.

smooth brome
Austrian brome
awnless brome
bromegrass
Hungarian brome
Russian brome

More info for the term: cover

The cover value of smooth brome has been rated as follows [40]:

                           UT     CO     WY      MT      ND
upland game birds        fair    ----   ----    good    good
waterfowl                fair    ----   ----    ----    fair
small nongame birds      good    fair   ----    fair    fair
small mammals            good    fair   ----    good    ----

More info for the term: cool-season

Smooth brome is an exotic, cool-season grass from 1.3 to 3.2 feet
(0.4-1.0 m) tall.  Blades are flat.  The inflorescence is an open
panicle from 2.4 to 6.8 inches (6-17 cm) long bearing 6 to 11-flowered
spikelets.  Lemmas have short awns ( less than 2 mm) or are unawned [53,54,61].

Two principle types of smooth brome are recognized, the northern and
southern.  The northern type is weakly rhizomatous, with leaves well up
on the stem and short glumes.  A few northern cultivars are actually
bunchgrasses.  The southern type is strongly rhizomatous, with leaves
near the base of the stem and long glumes.  Other notable differences
are earlier spring growth of the southern type and more even growth of
the northern type through the growing season [55].

In a meadow in West Virginia on shallow silty loam, smooth brome roots
grew to a depth of 18 inches (46 cm), with most of the root biomass
occurring in the first 3 inches (7.6) of soil.  (Average root
productivity was 717.7 lbs/acre inch at 0-3 inches below ground [52].)
Witte [127] found roots as long as 9.4 feet (2.87 m).

Due to cloning, smooth brome is a long-lived species.  Plantings have
persisted for at least 60 years [98].

Smooth brome is native to Eurasia.  In North America it occurs from
Alaska and all the Canadian provinces and territories south to southern
California and New Mexico, northern Oklahoma, and North Carolina
[6,61,67,90,99,110].

More info for the terms: fire regime, litter

Most smooth brome cultivars are rhizomatous [56,110], and survive fire
by sprouting from rhizomes.  Weakly rhizomatous or bunchgrass types
probably regenerate after fire primarily by tillering.  Rates of
postfire recovery probably differ between cultivars, with rhizomatous
types recovering more quickly than bunchgrass types, but such
differences have not been documented in the literature.

Periodic early spring or fall fire promotes rhizomatous smooth brome by
removing litter from sod-bound plants [56,110].

FIRE REGIMES :
Find fire regime information for the plant communities in which this
species may occur by entering the species name in the FEIS home page under
"Find FIRE REGIMES".

More info for the terms: association, cool-season, cover, forbs, litter, stand-replacing fire, tiller

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 (Artemisia 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 brome 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.

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More info for the term: hemicryptophyte

Hemicryptophyte

More info for the term: cover

Smooth brome is widely adapted to a variety of sites.  It is common in
riparian zones, valley bottoms, and dryland sites.  [48,56,119].  It is
adapted to all soil textures [49,55,90], although it may not thrive on
sand or heavy clay [119].  Smooth brome tolerates acid soils; it
comprised the dominant cover on a coal spoil of pH 4.5 in British
Columbia [56].  It does not grow on soils that are more than moderately
alkaline [55].  It is fairly saline tolerant [56].  Smooth brome grows
best on moist, well-drained soils [49], but tolerates poorly drained
soils [32].  Smooth brome is best adapted to regions receiving more than
15 inches (380 mm) of annual precipitation [98,119].  Eleven inches (280
mm) of annual precipitation is the minimum that will support smooth
brome without irrigation [98].

Some cultivars of smooth brome are adapted to northern latitudes and
high elevations [60,102].  Smooth brome persists to about 9,000 feet
(2,743 m) elevation in the northern Rocky Mountains [24,119] and to
about 11,000 feet (3,300 m) in the central and southern Rocky Mountains
[119].  General elevational ranges in several states are:

     from 7,000 to 10,000 feet (2,134-3,048 m) in Arizona [69]
     below 8,900 feet (2,700 m) in California [61]
     from 4,500 to 10,000 feet (1,372-3,048 m) in Colorado [57]
     from 4,096 to 10,352 feet (1,280-3,235 m) in Utah [121]

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This species is known to occur in association with the following cover types (as classified by the Society of American Foresters):

More info for the term: cover

   Smooth brome occurs in most SAF Cover Types.

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This species is known to occur in the following ecosystem types (as named by the U.S. Forest Service in their Forest and Range Ecosystem [FRES] Type classification):

   Smooth brome occurs in most FRES ecosystems.

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This species is known to occur in association with the following Rangeland Cover Types (as classified by the Society for Range Management, SRM):

More info for the term: cover

   Smooth brome occurs in most SRM Cover Types.

Smooth brome is probably top-killed by fire.

More info for the terms: cover, herbaceous, seed

Livestock:  Smooth brome cultivars have been bred for nutritional
quality and adaptation to selected climates.  This has made smooth brome
one of the most important exotic forage grasses in the United States and
Canada.  It is widely planted in pastures and rangelands from Texas to
Alaska and Yukon Territory [87,88,110].

Wildlife:  Grazing wildlife utilize smooth brome to varying degrees,
depending upon wildlife species and smooth brome quality.  Elk use it as
a winter food [63].  Mule deer in central Utah were found to use it only
lightly [7], but deer utilization of smooth brome is generally
considered good [40,110].  Geese [26] and small rodents such as pocket
gophers [81] also graze smooth brome.  The seeds may not be preferred by
granivores.  Everett and others [46] found that when offered the seed of
18 herbaceous species, deer mouse selected smooth brome seed the least.

Smooth brome provides cover for birds and small mammals [10].  Ducks,
[33,78], gray partridge [27], American bittern, northern harrier, and
short-eared owl [41] use it as nesting cover.

More info for the term: graminoid

Graminoid

More info for the terms: association, cool-season, fire exclusion, forbs, forest, grassland, litter, prescribed fire, restoration, rhizome, seed

Range:  Smooth brome's tolerance to grazing is generally rated as high
[56].  It is highly adaptable, having persisted in many of the habitats
where it was planted to increase forage production including
pinyon-juniper (Pinus-Juniperus spp.) [39], quaking aspen (Populus
tremuloides) [21], and subalpine and alpine ranges [56,102].  It has
persisted on old saltgrass (Distichlis spicata) meadows with saline
soils once the saltgrass was removed [84,85].

Smooth brome may not tolerate grazing on all habitat or site types.
Currie and Smith [36] reported that smooth brome planted on
low-fertility ponderosa pine (Pinus ponderosa) forest soils in Colorado
declined under even light-intensity cattle grazing.  They speculated
that smooth brome is more likely to persist under cattle grazing on
fertile soils.

Laycock and Conrad [77] used cattle to test several grazing systems on
rangeland seeded to crested wheatgrasses (Agropyron cristatum and A.
desertorum) and smooth brome in mountain big sagebrush (Artemisia
tridentata spp. vaseyana) habitat in Utah.  They found that average
cattle weight gain was the same under all systems, but heavy June
grazing in alternate years best promoted grass production.

Ungulates in Yellowstone National Park utilized smooth brome growing in
association with other graminoids and forbs, but did not graze smooth
brome where it grew in a monoculture [48].

Forestry:  In British Columbia, height and biomass of lodgepole pine
(Pinus contorta var. latifolia) seedlings established from a mix of
lodgepole pine seed and smooth brome and other grass seed were less
than height and biomass of lodgepole pine seedlings established from
lodgepole pine seed sown alone [28].

Native grassland restoration:  Smooth brome dominates many native
grasslands and old fields [2].  Masters and Vogel [82] stated that on
tallgrass prairie, it is usually found in areas with a history of
overgrazing and/or fire exclusion.  Grassland restoration efforts often
include controlling smooth brome with cool-season grass herbicides such
as atrazine and glyphosate, mowing, and/or prescribed fire [73].

Anderson [2] found that near Lincoln, Nebraska, fall application of
glyphosate helped control smooth brome.  Atrazine may not be as
effective; other studies [83,96] have reported that while atrazine
controlled other exotic cool-season grasses, it did not significantly
reduce smooth brome.

Establishment and maintenance:  Seed handling and planting guidelines
for smooth brome are available [49,116,117].  Cultivars adapted to
selected environments and/or regions are sold commercially
[56,103,104,108,119,123].

Smooth brome requires fertile soil in order to maintain nutritional
quality.  On infertile soils it needs periodic fertilization or a
companion nitrogen fixer.  On rangelands smooth brome is usually planted
in a mix with alfalfa (Medicago sativa), yellow sweet clover (Melilotus
officinalis), or other legume species.  Fertilization affects growth
allocation:  Watkins [120] found that fertilizers increased leaf and
shoot growth but reduced rhizome and root growth.

Rhizomatous cultivars become sod-bound after several years unless litter
is removed by grazing and/or fire [56,110].

More info for the term: fresh

The National Academy of Sciences [89] found the nutritional content of
fresh, flowering smooth brome in the United States was as follows:

dry matter (%)         27.1
ash (%)                 1.9
crude fiber (%)         8.3
ether extract (%)       0.9
N-free extract(%)      13.2
protein (%, N x 6.25)   2.8
digestible energy (Mcal/kg)
  cattle                0.79
  domestic sheep        0.78

Nutritional content of fresh smooth brome in immature, early bloom,
milk, dough, overripe, and weathered stages, and of cured smooth brome
in each stage, is also available [89].

The nutritional value of smooth brome for wildlife has been rated as
follows [40]:
                         UT     CO     WY     MT     ND
elk                    good    good   ----   poor   ----
mule deer              good    fair   ----   ----   poor
white-tailed deer      ----    ----   ----   ----   poor
upland game birds      good    ----   ----   ----   poor
small nongame birds    fair    ----   ----   ----   ----
waterfowl              fair    ----   ----   fair   ----
small mammals          good    good   ----   ----   ----

     AK  CA  CO  CT  DE  HI  ID  IL  IN  IA
     KS  KY  ME  MD  MA  MI  MN  MO  MT  NE
     NV  NH  NJ  NM  NY  NC  ND  OH  OK  OR
     PA  RI  TN  TX  UT  VT  WA  WV  WI  WY
     DC  AB  BC  MB  NB  NF  NT  NS  ON  PE
     PQ  SK  YT

Early growth of smooth brome is highly palatable.  Palatability and
nutritional quality drop rapidly after flowering.  Fall green-up
provides palatable forage later in the year [110].

The palatability of smooth brome has been rated as follows [40]:

                    UT       CO       WY       MT       ND
cattle             good     good     good     good     good  
domestic sheep     good     good     good     good     good
horses             good     good     good     good     good

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More info for the terms: phenology, seed

Smooth brome undergoes fall green-up.  Inflorescences are initiated
during cool, short fall days [90].  In colder climates, smooth brome is
dormant in winter.  It may remain green year-round in southern climates
[76].  Spring growth begins early in the season [110,107].  Lengthening
culms expose the panicles in late spring to early summer [90], and
smooth brome flowers in summer.  In Minnesota, flowering occurred from
early to late June [80,86].  It occurred in late May or early June in
Ames, Iowa, with later, sporadic flowering [72].  Phenology is delayed
in northern latitudes and high elevations.  Smooth brome on the Wasatch
Plateau of Utah flowers 85 to 102 days after snowmelt [44].  Seed
matures in early to late summer [49].  Smooth brome grows throughout the
growing season when soil water is adequate.  Under dry soil conditions
it becomes dormant, but it resumes growth when soils moisten [16].

More info for the terms: cool-season, cover, density, fire severity, frequency, fuel, prescribed fire, seed, severity, tiller, warm-season

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 less than 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].

More info for the terms: herb, rhizome, tussock

   Rhizomatous herb, rhizome in soil
   Tussock graminoid

More info for the terms: cool-season, cover, fresh, seed, stratification

Smooth brome reproduces by seed, rhizomes, and tillers.  Spread by seed
has been rated moderate, and vegetative spread has been rated good [97].

Smooth brome is usually cross-pollinated [72,86], although it may
self-fertilize from different spikelets of the same plant [86].  McKone
[72] found that seed set was significantly lower in smooth brome than in
other brome species.  Insect herbivory has been cited as a factor
reducing seed set in smooth brome [86,91].  Seed yield of smooth brome
broadcast-planted in Michigan 174 pounds per acre when grown with
alfalfa and 121 pounds per acre when grown alone [122].  Seed has
remained viable for 22 months to over 14 years [49,55].  Seed stored in
a shed for 19 years showed 20 percent germination [66].  Seed requires
stratification to germinate.  Germinative capacity of fresh, stratified
seed has varied from 83 to above 95 percent in the laboratory [49].
Optimal temperatures for germination in the greenhouse were from 68 to
86 degrees Fahrenheit (20-30 deg C) [49].  Like all cool-season species,
however, smooth brome can germinate at lower temperatures.  Bleak [17]
reported that smooth brome seed sown in late fall to early winter in
central Utah germinated and produced roots and shoots under deep snow
cover.  Light enhances germination but is not required [49].

Seedling growth is rapid [56,59].  Knobloch [72], who described
germination and seedling development in detail, reported that 54 days
after sowing, greenhouse-grown seedlings had 150-millimeter-long roots,
five leaves, and had begun tillering.  Baker and Jung [9] found that
under greenhouse conditions, the optimal day temperature for growth was
between 64.9 and 76.8 degrees Fahrenheit (18.3-24.9 deg C), and that food
reserves were depleted less with low night temperatures than with warm
night temperatures.  Cultivars differ in rate of growth and drought
tolerance [30].

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This species can be found in the following regions of the western United States (according to the Bureau of Land Management classification of Physiographic Regions of the western United States):

    1  Northern Pacific Border
    2  Cascade Mountains
    3  Southern Pacific Border
    4  Sierra Mountains
    5  Columbia Plateau
    6  Upper Basin and Range
    7  Lower Basin and Range
    8  Northern Rocky Mountains
    9  Middle Rocky Mountains
   10  Wyoming Basin
   11  Southern Rocky Mountains
   12  Colorado Plateau
   13  Rocky Mountain Piedmont
   14  Great Plains
   15  Black Hills Uplift
   16  Upper Missouri Basin and Broken Lands

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More info for the terms: cover, grassland, shrubs

Smooth brome generally invades after disturbance and persists
[19,20,37].  It is a common invader of disturbed prairie throughout the
Great Plains [112,125,126].  In Yellowstone National Park, Wyoming,
smooth brome cover was similar in young eastern cottonwood (Populus
deltoides), mature eastern cottonwood, and grassland areas [19].  Boggs
and Weaver [20] reported that along the Yellowstone River, moderate
grazing increased the occurrence of shrubs in mature eastern cottonwood,
and severe grazing converted the area to smooth brome, timothy (Phleum
pratense), and Kentucky bluegrass (Poa pratensis).

Smooth brome tolerates moderate shade to full sun [49,56]

More info for the term: introgression

The currently accepted scientific name of smooth brome is Bromus inermis
Leyss. Infrataxa are [54,61,68]:

Bromus inermis subsp. inermis Leyss
Bromus inermis subsp. inermis var. divaricatus Rohlena
Bromus inermis subsp. inermis var. inermis Leyss

Kartesz [68] recognizes Pumpelly brome as a subspecies of B. inermis, B.
inermis ssp. pumpellianus (Scribn.) Wagnon. FEIS follows the treatment
of other authorities in recognizing Pumpelly brome as a separate
species, B. pumpellianus Scribn. [54,58,61,67,115,121]. (A literature
summary of B. pumpellianus is available in FEIS.) Considerable
hybridization and introgression have occurred between smooth brome, an
introduced species, and Pumpelly brome, a native species [5,53,121].
Smooth brome does not hybridize with other North American species [4].

Smooth brome has been extensively used for rehabilitation.  It is cold
hardy and fairly resistant to saline soils and drought [117].  The
ability of most cultivars to spread rhizomatously makes smooth brome a
good soil binder [56,103,104].  It is recommended for erosion control
and streambank and stream bottom stabilization in all areas of the
United States except the Southeast [104,118].  Southern cultivars tend
to be more strongly rhizomatous than northern cultivars, and generally
give the best erosion control [64].  Some southern cultivars will grow
in northern latitudes of the United States [25].  Smooth brome has also
been successful in rehabilitating mined lands [38,43], game ranges
[51,65], roadsides [42], and ski areas [12].  Smooth brome establishes
on high-elevation sites [56].  It can be an aggressive colonizer on many
sites, however, and may crowd out native species [107].

Smooth brome showed poor survivorship on semiarid canyonland in
northwestern Idaho that was disked and seeded with several grass species
to remove yellow starthistle (Centaurea solstitialis) [92].

inermis: unarmed, without spines

Perennials, Terrestrial, not aquatic, Rhizomes present, Rhizome elongate, creeping, stems distant, Stems nodes swollen or brittle, Stems erect or ascending, Stems solitary, Stems caespitose, tufted, or clustered, Stems terete, round in cross section, or polygonal, Stem internodes hollow, Stems with inflorescence less than 1 m tall, Stems, culms, or scapes exceeding basal leaves, Leaves mostly cauline, Leaves conspicuously 2-ranked, distichous, Leaves sheathing at base, Leaf sheath mostly closed, Leaf sheath smooth, glabrous, Leaf sheath and blade differentiated, Leaf blades linear, Leaf blades 2-10 mm wide, Leaf blades mostly flat, Leaf blades mostly glabrous, Leaf blades scabrous, roughened, or wrinkled, Ligule present, Ligule an unfringed eciliate membrane, Inflorescence terminal, Inflorescence an open panicle, openly paniculate, branches spreading, Inflorescence a contracted panicle, narrowly paniculate, branches appressed or ascending, Inflorescence solitary, with 1 spike, fascicle, glomerule, head, or cluster per stem or culm, Inflorescence branches more than 10 to numerous, Flowers bisexual, Spikelets pedicellate, Spikelets laterally compressed, Spikelet 3-10 mm wide, Spikelets with 3-7 florets, Spikelets with 8-40 florets, Spikelets solitary at rachis nodes, Spikelets all alike and fertille, Spikelets bisexual, Spikelets disarticulating above the glumes, glumes persistent, Spikelets disarticulating beneath or between the florets, Glumes present, empty bracts, Glumes 2 clearly present, Glumes equal or subequal, Glumes distinctly unequal, Glumes shorter than adjacent lemma, Glumes 1 nerved, Glumes 3 nerved, Lemmas thin, chartaceous, hyaline, cartilaginous, or membranous, Lemma 5-7 nerved, Lemma glabrous, Lemma body or surface hairy, Lemma apex dentate, 2-fid, Lemma awnless, Lemma margins thin, lying flat, Lemma straight, Palea present, well developed, Palea membranous, hyaline, Palea shorter t han lemma, Palea longer than lemma, Palea 2 nerved or 2 keeled, Palea keels winged, scabrous, or ciliate, Stamens 3, Styles 2-fid, deeply 2-branched, Stigmas 2, Fruit - caryopsis, Caryopsis ellipsoid, longitudinally grooved, hilum long-linear, Caryopsis hairy at apex.

Bromus inermis is a species of the true grass family (Poaceae). This rhizomatous grass is native to Europe and considered invasive in North America.

The plant is characterized by an erect, leafy, long-lived perennial, 46 to 91 cm (1+1⁄2 to 3 ft) tall, rhizomatous and commonly producing a dense sod. It starts growth in early spring; flowers May to July; reproduces from seeds, tillers, and rhizomes. It may regrow and re flower in the fall if moisture is sufficient. The leaves are glabrous or occasionally pubescent, particularly on the sheaths; blades 20 to 38 cm (8 to 15 in) long, 0.6 to 1.3 cm (1⁄4 to 1⁄2 in) wide, flat, with a raised and keeled midrib below; sheaths closed, except near collar, and papery when dry; leaves rolled in the bud; ligates up to 0.3 cm (1⁄8 in) long, rounded, and membranous; auricles absent.