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JAPANESEBROMEINTHENORTHERN
GREAT PLAINS
M. R. Haferkamp
J.A. Young
E. E. Grings
M.G. Karl
R. K. Heitschmidt
M. D. MacNeil
ABSTRACT
To develop a better understanding of these relationships,
we began a series of studies in 1990. In separate experiments we examined (1) environmental effects on Japanese
brome seed germination, (2) effects of Japanese brome on
western wheatgrass production, (3) comparative herbage
quality profiles of Japanese brome and western wheatgrass,
and (4) effects of simulated grazing on herbage and root
production of Japanese brome plants.
Japanese brome (Bromus japonicus) is an alien annual
grass that has become an important component ofplant
communities in the Northern Great Plains. This paper reports preliminary results of studies begun in 1990 examining the environmental effects on Japanese brome seed germination, effects of Japanese brome on western wheatgrass
production, comparative herbage quality profiles for Japanese brome and western wheatgrass (Pascopyrum smithii),
and effects of simulated grazing on herbage and root production of Japanese brome.
METHODS
Research was conducted on the Fort Keogh Livestock
and Range Research Laboratory near Miles City, MT. Regional topography ranges from rolling hills to broken badlands with small intersecting ephemeral streams flowing
into large rivers located in broad, nearly level valleys. Indigenous vegetation on the 55,000-acre research station is a
grama-needlegrass-wheatgrass (Bouteloua-Stipa-Agropyron)
mix (Kuchler 1964). Long-term annual precipitation averages 13.3 inches with about 60 percent received during the
April through August period. Temperatures often exceed
100 °F during summer and decrease to --40 °F or less during winter. The average frost-free period is 150 days.
INTRODUCTION
Japanese brome (Bromus japonicus) is an alien annual
grass that has become a dominant species of some mixed
prairie plant communities in the Northern Great Plains
(Haferkamp and others 1993; Whisenant 1990). Its life
cycle is somewhat shorter in duration than coexisting perennial grass species such as western wheatgrass (Pascopyrum smithii). Further, as with all annual grasses, annual herbage production is erratic (Hull and Pechanec
1947). Moreover, when present on rangelands, Japanese
brome plants may shift the period of peak forage production, causing an earlier decline in overall forage quality
(Cook and Harris 1952). Thus, the presence of Japanese
brome may negatively impact livestock production.
Perpetuation of Japanese brome on rangelands requires
completion of the plant's life cycle beginning with seed germination, continuing through seedling emergence and establishment, and terminating with plant maturation and
seed dissemination. Determining how environmental conditions affect the life cycle of Japanese brome plants and
their interactions with other plant species is critical for
development of grazing management strategies to both
reduce the prevalence and efficiently use brome-infested
rangelands.
Germination
Paper presented at the Symposium on Ecology, Management, and Restoration of Intermountain Annual Rangelands, Boise, ID, May 18-21, 1992.
M. R. Haferkamp, E. E. Grings, M. G. Karl, R. K. Heitschmidt, and M. D.
MacNeil are Range Scientist, Nutritionist, Postdoctoral Range Scientist, Research Leader, and Research Geneticist, respectively, U.S. Department of
Agriculture, Agricultural Research Service, Fort Keogh Livestock and
Range Research Laboratory, Miles City, MT 69301; J. A Young is a Range
Scientist, U.S. Department of Agriculture, Agricultural Research Service,
Reno, NV 89512.
398
Incubation temperatures, collection dates, and postharvest storage and light conditions were varied so as to
span a range of environmental conditions that might be
encountered in the field. Seeds were collected in summer
in Oklahoma and in summer, fall, and winter in eastern
Montana. Summer collections were stored in a laboratory
at room temperature. Fall and winter collections were
divided into thirds and stored in either an unheated warehouse or a freezer, or ovendried at 115 °F for 6 to 35 days
and then stored in a desiccator at room temperature.
Summer collections from 1990 and 1991 were initially
incubated in a series of 55 constant and alternating temperatures ranging from 32 to 104 °F, which were divided
into combinations related to selected seedbed environments (Young and others 1973). Tests were initiated about
6 months following seed collection, and four replications of
25 seeds of each collection were incubated for 4 weeks in
closed dishes arranged in a randomized-block design. Seeds
were considered germinated when the radicle was at least
0.2 inch long.
Summer collections from Oklahoma and Montana and fall
and winter collections from Montana were incubated in two
temperature regimes beginning in January 1992. A warm
regime consisted of 28 days with alternating 12-hour periods of 46 and 73 °F, and a cool+warm regime consisted of
10 days at 32 and 50 °F followed by 18 days at 46 and 73 °F.
Light was provided by cool-white fluorescent bulbs during
the 12-hour 50 and 73 °F temperature periods. The summer,
fall, and winter seeds were also incubated at 46 and 73 °F
in total darkness or alternating 12-hour periods of light and
dark. Seed treatments were arranged in a randomized-block
design with four to eight replications consisting of 100 seeds
incubated in each dish. Seeds were considered germinated
when the coleoptile and radicle were each at least 0.2 inch
long.
Competition
Table 1-Germination characteristics of Japanese brome seed
collected in eastern Montana in the summers of 1990-91
Percent and
standard deviation1
Characteristic
Mean of all regimes
Mean of regimes with
some germination
Regimes with some germination
Regimes with optimum germination
Mean of optima
Maximum germination
1Means
71 (4.2)
74 {4.3)
96 (1.4)
32 (8.0)
99 (1.1)
100 {1.1)
and standard deviations are based on eight values.
in 32 percent of the regimes and mean of optima was 99 percent. The maximum germination was 100 percent.
Maximum germination of Japanese brome seed occurred
in regimes representing moderate and cold seedbed conditions, with germination being somewhat depressed in very
cold and warmer-than-moderate temperatures (fig. 1}. Responses were similar between years and similar to those reported by Young and others (1984} for downy brome (Bromus
tectorum). In those studies, seeds germinated best at coldfluctuating, fluctuating, and moderate seedbed conditions,
and germination was depressed at very cold temperatures.
When summer, fall, and winter collections were compared,
summer collections germinated rapidly to greater than 90
percent regardless of temperature (table 2}. Fall and winter collections stored in the warehouse germinated greater
than 70 percent in the warm regime, but germination was
reduced to less than 20 percent in the cool+warm regime,
Three treatments were applied in a randomized-block
design with 10 replications at two locations. Japanese
brome plants were left intact inside a 10.6-square-foot
circle, a portion (about 50 percent) were removed, or all
were removed. Weeding of plants occurred during late
spring and early summer. In early July, biomass of westem wheatgrass, Japanese brome, and all other vegetation
was clipped at ground level inside a 2.4-square-foot circle
located in the center of each plot.
Forage Quality
Replicated samples of Japanese brome inflorescences
and herbage and western wheatgrass herbage were collected during June, July, and August 1990 and 1991 from
pastures at Fort Keogh (Haferkamp and others 1993). Collected samples were ovendried, ground, and analyzed for
nitrogen content and in vitro digestible organic matter.
Cold Period
16 hr °F
Simulated Grazing
32
Japanese brome seedlings grown from seed were planted
in greenhouse boxes in late winter. Clipping treatments
were begun in late June 1991 and early May 1992 and continued for about 60 days. Plants were either not clipped
(control) until the end of the study or clipped to a 3-inch or
6-inch stubble height every week or every 2 weeks. Treatments were arranged in a randomized-block design with
five replications. All clipped herbage and remaining shoots
were dried and weighed. At the termination of the study,
roots were washed free of soil, dried, and weighed.
36
Warm Period 8 hr °F
50
59
68
77
cold
83b
50
59
68
77
88
95
Germination
104
Mean germination for the 55 temperature regimes for
Japanese brome was 71 percent (table 1). Over 95 percent
of all temperature regimes supported some germination, and
the mean germination for regimes where some germination
occurred was 74 percent. Optimum germination, defined as
germination not lower than maximum observed minus onehalf confidence interval at O.Ollevel ofprobability, occurred
397
95
104
widely fluctuating
61c
41
RESULTS
86
~~~~~~~~~~~--~~~------,
Figure 1-5eedbed requirements of Japanese
brome seed collected in eastern Montana during
the summers of 1990 and 1991. Means are based
on eight values. Mean germinations followed by
the same letter are not significantly different at the
0.01 level of probability as determined by Duncan's
Multiple Range Test.
Table 2-Maximum germination in two temperature regimes for Japanese brome seed collected In
Oklahoma and Montana In summer 1991 and In Montana In fall and winter 1991. Summer
collections were stored in a laboratory at room temperature and fall and winter collections
were stored in an unheated warehouse. Germination studies were begun In January 1992
Oklahoma
July7
Temperature
Montana
Nov. 21
July 12
Dec.30
--------------------Peroent------------------199
100
32 and 50 °F + 46 and 73 °F
46 and 73°F
18
88
92
100
5
71
LSD0•05 c 4.3
'Means are based on eight replications of 100 seeds.
suggesting these seeds may have entered a dormant state
when incubated at 32 °F. Similar results were reported for
downy brome seeds collected in Montana (Warg 1938) and
Japanese brome seeds collected in Kentucky (Baskin and
Baskin 1981).
When the presence of light was studied, we found darkness, as might be encountered under a dense litter cover,
enhanced 7-day germination up to 35 percent, but light
improved 28-day germination up to 31 percent, and wintercollected seeds were more sensitive to light than fall collections (figs. 2 and 3). If ovendried seeds are excluded, over
40 percent of the seeds collected in fall and winter and over
90 percent of summer collections germinated in darkness.
Thus, it is apparent that seeds may germinate readily under a dense litter cover that restricts essentially all light
and reduces moisture evaporation, as was suggested by
Whisenant (1990). Care must be taken, however, when
forming hypotheses relative to field germination and emergence, since the spectral composition of radiation incident
on the seed can be affected by many factors such as time of
day, seasonal meteorological conditions, snow cover, shallow burial in soil, and transmission characteristics of the
overstory vegetation (McDonough 1977).
KEY
100
~
•••• ~---··---
80
,.:::::::..... ·-· ----- ·•
c
0
;
c
,
60
~CD 40
I
0
....
'
'
C!J
s
!#~,-::'
,•
I
,'
,,.. .
,, .
,
,,
I
II ' '
''
I'
,'
Forage quality of Japanese brome varies with time and
plant part. In early May, when inflorescences are emerged,
crude protein concentrations in whole plants range from 12
§:
·-G·· OVen-dry
80
c
0
--9-· Fr. .zer
;
~ Warehouae
i
c
60
CD
40
....~
20
"
..... Freezer
... ... 4'
Forage Quality
100
-•-· Oven-dry
/,
In competition studies, trends suggest western wheatgrass production was reduced with the presence of Japanese brome, but the reduction was not statistically significant in 1991 (fig. 4). In 1992, standing crop of western
wheatgrass was increased by total removal of Japanese
brome, but not by partial removal. Total standing crop
was significantly reduced during both years by an average
of 284 pounds per acre at one location and 643 pounds per
acre at the other by the total removal of brome.
Precipitation was probably the most important factor
affecting the variation in western wheatgrass response in·
1991 and 1992. Total precipitation measured on these sites
during April, May, and June 1991 (13.2 inches or 203 percent of normal) was three times the amount received on
either site in 1992 (4 inches or 62 percent of normal).
1
,'
''
'1,'
20
Competition
....,.._. Warehouae
- .. • · Oven-dry
..... Freezer
0
0
7
14
21
7
28
Time (Days)
14
21
28
Time (Days)
Figure 2-Germlnation of Japanese brome seed collected in November, stored in an unheated warehouse, ovendried, or frozen; and incubated in
February 1992 for 28 days in a 46n3 °F temperature
regime in darkness or with light for 12 hours at the
high temperature. Means are based on eight values.
Filled symbols represent the dark regime.
Figure 3-Germlnation of Japanese brome seed collected in December, stored in an unheated warehouse,
ovendried, or frozen; and incubated in February 1992
for 28 days in a 46n3 °F temperature regime In darkness or with light for 12 hours at the high temperature.
Means are based on eight values. Filled symbols represent the dark regime.
398
-
.,
2500
0
al
.0
2000
~
ril.1
1m!'
,}
Weelern Whoatgraaa
14
-
Western Wheatgrass
-
Japanese Bromo
,
Japanese Brame
SeedHeads
'~----
12
Japanese Bromo
~
Other
~
Leaves & Stems
10
~
a. 1500
.,.,
...u
0
01
.~
c
,1
"0
c:
0...
Cl
............
6
1:1
2
0
al
U5
8
Q.
/"'
~
1000
"i
4
500
',, ________ ............ _,,,, .......... __ _
···-,,,,
..... .._______
,_
2
0
so 100
Hyp lex
0
0
so 100
N2B
1991
0
50 100
0
Hyplex
1992
0~------~------~~------._----~
so 100
N2B
6/27
7/27
8/23 6/21
7/16
1990
8/12
1991
Figure 4-Peak standing crops of western wheatgrass, Japanese brome, and other species growing
in competition plots in 1991 and 1992 at the Hyplex
and N2B sites on Fort Keogh. Japanese brome removal percentages were 0, 50, and 100. Means
are based on 10 values.
Figure 5-Percentage crude protein of Japanese
brome and western wheatgrass plants growing at
the N2B site on Fort Keogh. Means are based on
12 values.
to 15 percent; concentrations in western wheatgrass plants
range from 15 to 22 percent. Later in the growing season,
intact inflorescences or seed heads are relatively high in
quality, and may be higher or similar in quality to herbage
of western wheatgrass (figs. 5 and 6). Herbage quality of
Japanese brome, however, decreases from relatively high
when plants are in the seedling stage to low when plants
are mature.
The profiles of quality varied between the 2 years presented in figures 5 and 6. This phenomenon is generally
related to the pattern of precipitation (fig. 7), with quality
declining most rapidly as the soil dries and plants begin
maturing. In contrast, during a cool-wet growing season,
forage quality may remain high for longer periods as it
did in 1991. For comparison, 9 percent crude protein is
the suggested level for a 1,100-pound beef cow consuming
4.4 pounds forage per 220 pounds body weight with average milking ability during the first 90 to 120 days postpartum (National Research Council1984).
greatest for unclipped controls. Frequency of clipping did
not generally affect any component as much as intensity
of clipping.
More than twice as much biomass was produced in the
herbage and root components when plants remained vegetative rather than reproductive. When clipping was begun on vegetative plants, tillers averaged 23 per plant
and increased to only 26 per plant by the end of the study.
Tillers increased from 7 to 8 per control plant becoming reproductive during the study; th ey increased from 9 to 26
per clipped plant during the same period. Thus, plants remaining in the vegetative state continued to produce new
Simulated Grazing
~
When plants in the clipping study remained vegetative,
all clipping regimes or intensities reduced production of
roots, herbage, and total biomass (fig. 8). Increasing the
intensity of clipping significantly reduced herbage and total biomass, and although similar trends occurred with root
biomass, differences were not significant. Increasing the
frequency of clipping from every 2 weeks to weekly did not
significantly reduce biomass production.
When plants produced reproductive s hoots, increasing
intensity of clipping significantly reduced total herbage
weight, and reduced total biomass for all but the plants
clipped to 6 inches every week (fig. 8). Root weights were
similar for unclipped controls and both clipping frequencies at 6 inches, but weights were significantly less for
plants clipped at 3 inches. Weight of inflorescences was
0
110
-
Western Wheatgrass
-
Japanese Bromo
Seed Heads
80
---· Japanese Bromo
leaves & Stems
70
~
0
60
50
40
2:
30
20
10
0
6/27
7/27
8/23 6/21
1990
Figure 6--Percentage in vitro digestible organic
matter of Japanese brome and western wheatgrass plants growing at the N2B site on Fort
Keogh. Means are based on 12 values.
399
7/16
1991
8/12
7
c:;;al
.s::;
D
Monlhly
-
82yoor
6
average
5
0
~
c
4
0
!
3
·c:;
2
'Ci.
~
[)_
J
F MA M J J A S 0 N 0 J F MA M J J A S 0 N 0
1990
1991
Year
Figure 7-Precipitation recorded during 1990 and
1991 at Frank Wiley Airfield, Miles City, MT.
1.75
-Herbage
1.50
.J:l
x0
1.25
I ll
al
0
1.00
c
H
Seed Heads
~ Roots
:::l
~
cIll
0::
0.75
0.50
0.25
0.00
2wk
lwk
1991
2wtt
lwk
2wk
1wk
2wlt
1•k
1992
Figure 8-Weights of herbage, seedheads, and roots
produced by nonclipped control Japanese brome
plants grown in the greenhouse and plants clipped at 3
or 6 inches on a weekly or biweekly schedule. Means
are based on five values.
leaves; plants that became reproductive responded to clipping by producing new tillers. Tiller production takes longer
than leaf production, and would therefore result in lower
yields.
CONCLUSIONS
As with downy brome, complete germination of all seeds
in one season is rare. Seeds that are not disseminated, or
do not germinate in fall, overwinter and potentially enter a
state of secondary dormancy, induced by imbibition of water
at cold temperatures. Only a small proportion may germinate before the next fall when secondary dormancy is removed with the warm temperatures of summer.
The germination process appears to shift in response to
moisture and temperature from one in which most seeds
germinate at once to one in which seed germination is delayed with only a few seeds germinating at any one time.
These processes result in a carry-over of a large number
of viable seeds from year to year, complicating control of
Japanese brome through conventional means. Japanese
brome seed germination characteristics also aid its future
invasion and perpetuation on rangelands in the Northern
Great Plains.
Total standing crop was reduced consistently and significantly both years by removal of Japanese brome at both competition study sites. However, Japanese brome appears to
have reduced production of western wheatgrass only when
the supply of moisture was insufficient to meet the demands
of both species. Thus, Japanese brome appears to be adding to the total forage base, and we can expect a short-term
decline in forage production when it is absent. Quality of
forage is relatively high when plants are immature or if we
only consider inflorescences. Once plants mature and inflorescences are grazed, however, the remaining herbaceous
component is of much poorer quality than western wheatgrass herbage. As the data show, the profile of forage quality varies with species and maturation, with the latter being
controlled to some degree by the pattern of precipitation.
Although not examined in this study, Japanese brome
competition may have a cumulative effect on western wheatgrass plants when encountered during a period of several
years. In addition, western wheatgrass plants may respond
to competition differently with or without clipping or grazing. Answering these questions will require additional
research.
The clipping data suggest biomass production of vigorously growing Japanese brome plants can be reduced by
frequent, intensive clipping. Thus, management of this
annual growing on Northern Great Plains rangelands can
impact the amount of forage produced. Effective control
of Japanese brome will be more difficult, however, because
some seed was produced even with severe treatments.
ACKNOWLEDGMENTS
The authors express appreciation to Dr. Jerry Volesky
for seed collection; Kevin Peterson, Bill Creamer, Bryon
Bennett, Cheryl Murphy, JoAnn Gresens, Ellen Martens,
and several summer aides for assistance with sample collection and processing; Debra Palmquist for statistical analysis; and Mary Ellen French for preparation of graphics.
The results of this series of studies are important because
the characteristics of Japanese brome they describe indicate it may be a component of Northern Great Plains rangelands for years to come. Germination studies showed temperature is likely not a limiting factor for fall germination
of Japanese brome seed disseminated in summer or fall.
If soil moisture is adequate, high levels of germination will
often occur during the initial fall period. This results in the
emergence of a large population of Japanese brome seedlings that can overwinter and renew growth early the following spring.
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