Big Sagebrush, Crested Wheatgrass, and
Grazing on Gravel-Cobble Pediments of the
Duchesne River Formation and Quaternary
Deposits in Uintah County, Utah
Allen Huber
Sherel Goodrich
Abstract—Pediment surfaces of the Duchesne River Formation
near Lapoint and Quaternary deposits at Grouse Creek, Uintah
County, Utah, provide rather uniform habitat conditions on which
to contrast the abundance of crested wheatgrass (Agropyron
cristatum) on seeded areas and adjacent unseeded areas. Although
crested wheatgrass has persisted as a dominant for over 40 years
where it was seeded at one study site, it has spread less than
0.32 km (0.2 mile) into native plant communities from seeded areas
of this study. At 15.25 meters (50 feet) from the plow line, crested
wheatgrass showed over a six-fold decrease in abundance. Where
cattle (Bos taurus) have grazed in winter only, crested wheatgrass
stands have persisted for 33 years with very little Wyoming big
sagebrush recruitment into the seeded area. In nearby crested
wheatgrass seedings, Wyoming big sagebrush has returned to
persistent wheatgrass stands after spring and early summer grazing was initiated. Crested wheatgrass has also demonstrated the
capability to successfully suppress cheatgrass in Wyoming and
mountain big sagebrush communities. Spring and early summer
grazing by cattle is indicate as a tool to achieve sagebrush cover
where it is desired in crested wheatgrass stands.
Over the past several decades, land managers and private
land owners have turned over vast acres of native vegetation
in the Intermountain region and seeded these areas into
crested wheatgrass (Agropyron cristatum). Crested wheatgrass was selected to improve early season forage production
for livestock, for its ease in establishment, tolerance to
drought, and for its ability to adapt to various habitats and
precipitation zones. After seeding, crested wheatgrass has
demonstrated the ability to establish monocultures in sagebrush communities with annual precipitation less than
30.5 cm (12 inches). Land managers have found that sagebrush recruitment in crested wheatgrass seedings is possible when influenced by various grazing techniques (Laycock
and Conrad 1981; Evans and others 1986; Angell 1998).
Time of recovery for sagebrush following treatment and
seeding of crested wheatgrass is apparently variable, but
Winward (1991) found that recovery of sagebrush following
In: McArthur, E. Durant; Ostler, W. Kent; Wambolt, Carl L., comps. 1999.
Proceedings: shrubland ecotones; 1998 August 12–14; Ephraim, UT. Proc.
RMRS-P-11. Ogden, UT: U.S. Department of Agriculture, Forest Service,
Rocky Mountain Research Station.
Allen Huber is Rangeland Manager, Duchesne District, Ashley National
Forest, U.S. Department of Agriculture, Duchesne, UT 84021. Sherel
Goodrich is Forest Ecologist, Ashley National Forest, U.S. Department of
Agriculture, Vernal, UT 84078.
USDA Forest Service Proceedings RMRS-P-11. 1999
burn treatments vary from 12 years in the mountain big
sagebrush (Artemisia tridentata ssp. vaseyana var.
pauciflora) type to over 40 years in the drier Wyoming big
sagebrush (Artemisia tridentata ssp. wyomingensis) type.
Whisenant (1990) indicated a fire interval of 60 to 110 years
for presettlement Wyoming big sagebrush. Hull and Klomp
(1966) studied the invasive nature of crested wheatgrass
from original seedings into adjacent native sagebrush communities in Idaho. They observed crested wheatgrass plants
growing in the native community as far as 122 m from the
plow line 30 years after mechanical treatment and seeding.
Monsen (1994) found the fire resistant capabilities of crested
wheatgrass could be used to alter fire intervals in cheatgrass
systems.
In Uinta Basin, Utah, numerous communities of Wyoming
and mountain big sagebrush have been mechanically treated
and seeded with crested wheatgrass. Four sagebrush sites
with sharp boundaries between treated and untreated areas
were selected for this study. Objectives of this research were
to determine the invasive nature of crested wheatgrass from
treatment areas into native plant communities, its ability to
suppress cheatgrass (Bromus tectorum) at a common site,
shrub recruitment into seeded areas following treatment, and
the timely use of grazing to influence sagebrush recovery.
Study Sites _____________________
Four sites were included in this study. These sites are
located at Lapoint Bench, Flat Iron Bench, and near Grouse
Creek in Uintah County, Utah. The study sites at Lapoint
Bench (two sites) and Flat Iron Bench (one site) are about
2.4 km east-northeast of Lapoint and 16 km west of Vernal.
The sites are located on relatively flat, uniform stream
pediment surfaces of the Duchesne River Formation. These
pediment surfaces consist of a gravel-cobble layer that
protects these sites from the erosive action that carved
relatively shallow, highly dissected canyons adjacent to the
pediment surfaces. The elevations at these three sites are
approximately 1,760 meters (5,770 ft). Lapoint and Flat Iron
Benches are located between the Lapoint Climate Station
and the Vernal Climate Station. The elevation, latitude, and
vegetation of the study sites and climate stations are similar. Mean annual precipitation at the Lapoint Climate
Station (1948-1961) of 17.7 cm (8.25 inches) and the Vernal
Climate Station (1928-1992) of 17.5 cm (8.16 inches) indicate mean annual precipitation at the study sites are between 17-19 cm (8-9 inches) (Ashcroft and others 1992).
181
Sagebrush from these pediments have been identified
with an ultraviolet light test as Wyoming big sagebrush
(Goodrich and others, these proceedings). Wyoming big
sagebrush-grass communities dominate the landscape below the pinyon-juniper belt where these pediment surfaces
occur. Soils of the Aridisol order are typical for these areas.
Soils with a higher content of sand and/or gravel typically
support a understory dominated by needle-and-thread grass
(Stipa comata var. comata). Soils with less sand and/or
gravel typically support more bottlebrush squirreltail (Elymus elymoides). Sites that support needle-and-thread grass
appear to be more resistant to cheatgrass invasion than sites
that support mostly bottlebrush squirreltail.
On Lapoint Bench, the Eakins site was plowed and seeded
with crested wheatgrass in ca. 1970. Wyoming big sagebrush kill due to treatment was nearly 100 percent. Sheep
grazed the Eakins site late winter to early summer from
1970 to ca. 1980. Since 1980, the site has been grazed
annually by cattle during the late spring and early summer
months. Grazing pressure by cattle is generally moderate
(40 to 50% use by weight). The Huber site was plowed and
aerially seeded with crested wheatgrass in fall 1985. The kill
of Wyoming big sagebrush following the plow treatment was
only about 70%. Due to the abundance of cheatgrass, the site
was burned with prescribed fire the following year. After
fire, about 90 percent of Wyoming big sagebrush originally
at the area prior to both treatments was killed. Crested
wheatgrass was reseeded with a drill following the burn and
it replaced cheatgrass as the dominate at the site. Spring
and early summer (May and June) cattle grazing was initiated 3 years following the burn treatment and has been
employed annually for the past 9 years. Forage utilization by
cattle at the Huber site is generally over 60 percent (Huber
1998, personal communication). The site at Flat Iron Bench
was plowed and seeded with crested wheatgrass in 1965 by
the Bureau of Land Management. Wyoming big sagebrush
kill was essentially 100 percent. Approximately 2,400 head
of sheep were permitted to graze the site early spring and
late fall from time of treatment to 1975. The allotment was
converted to cattle in 1975 but was not grazed until 1982.
Since this time, cattle have grazed the area from midNovember to the end of January (Nelson 1998, personal
communication). Antelope and sage grouse utilize these
wyoming big sagebrush sites year round. These areas are
also considered important winter range for deer and elk. At
all three sites, a sharp boundary between treated and
untreated areas in similar habitat exists. These circumstances provided an opportunity to sample the advancement
of crested wheatgrass from treated areas into untreated
areas. Also, the reestablishment of Wyoming big sagebrush
in treated areas under different grazing schemes were
sampled.
The study site at Grouse Creek is approximately 8.8 km
east of Elk Horn Guard Station and 10.1 km north of Tridell.
The site is located on Quaternary stream pediments. Elevation at the Grouse Creek site is 2,164 meters (7,100 ft). The
site is located between the Elk Horn Climate Station and
Maeser 9 NW Climate Station (15 km west). They are about
equal in latitude and position at the base of the Uinta
Mountains to each other and to the study site. Mean annual
precipitation at Elk Horn (1910-1930) of 34.1 cm (13.41
inches) (Martin and Corbin 1930) and Maeser 9 NW of 34.4 cm
182
(13.55 inches) (Ashcroft and others 1992) indicates mean
annual precipitation at the site is between 34.3 and 35.6 cm
(13.5 and 14.0 inches).
The Grouse Creek site is located above the pinyon-juniper
belt. Sagebrush samples from the area applied to the ultraviolet light test were identified as mountain big sagebrush
(Goodrich and others, these proceedings). Associated plants
at the site include serviceberry (Amelanchier alnifolia),
bitterbrush (Purshia tridentata), yellowbrush (Chrysothamnus viscidiflorus var. lanceolatus), and thickspike wheatgrass (Elymus lanceolatus).
In 1956, the area north of the National Forest boundary
fence, which is administered by the Ashley National Forest,
was mechanically treated to reduce sagebrush and seeded
with a seed mix that included crested wheatgrass and
smooth brome (Bromus inermis). Crested wheatgrass established and persisted as a dominate plant in the seeding.
Forest data indicate that smooth brome was as a minor
component in the community during the 1980’s and 1990’s
(Ashley National Forest, unpublished data). The area south
of the fence, owned by the Ute Indian Tribe, was not treated
and remained in native vegetation. In 1988, both sides of the
fence were burned during the Whiterocks wildfire, which
burned approximately 16,000 acres. The Grouse Creek site
is included in the Mosby Mountain summer cattle allotment.
The grazing season ranges from mid-June to mid-September
under a rest rotation system. Grazing intensity is generally
moderate (40 to 50% utilization). Adjacent Ute Tribal land
receives light grazing intensity (under 40% utilization) from
cattle during most seasons of the year. The Grouse Creek
area is also considered critical late winter and early spring
habitat for elk and deer. The contrast of seeded and nonseeded
range on opposite sides of the fence provided an opportunity
to evaluate the advancement of crested wheatgrass into the
nonseeded area after 42 years following treatment.
Methods & Results ______________
A total of five belt-plots of 0.9 m (3 ft) wide were established parallel to the plow line at each of the four study sites.
Their lengths varied due to topographical limitations. The
length of transects were 137.0 m (450 ft) at the Eakins and
Huber sites, 152.5 m (500 ft) at the Grouse Creek site, and
61.0 m (200 ft) at the Flat Iron site. Of the five transects, four
were established 15.25 m (50 ft), 30.5 m (100 ft), 61.0 m
(200 ft), and 122.0 m (400 ft) from the plow line into the
untreated area, and one transect was established 15.25 m
(50 ft) from the plow line into the area plowed and seeded
with crested wheatgrass. Crested wheatgrass plants were
counted in each belt-plot and standardized to determine
density of crested wheatgrass plants inside treated areas
and outside treated areas of native vegetation at standard
distances from the plow line (table 1). Crown cover for
Wyoming big sagebrush was measured by line intercept
along transect beltlines at the Flat Iron, Eakins, and Huber
study sites. Crown cover for mountain big sagebrush and
other woody plants at Grouse Creek was measured by line
intercept along five 30.5 m (100 ft) beltlines at study 43-16,
which is located ca. 91.5 m (300 ft) north of study site (Ashley
National Forest, unpublished data). A total of one-hundred
50 cm2 (19.69 inches2) sample plots were established along
USDA Forest Service Proceedings RMRS-P-11. 1999
Table 1—Number of crested wheatgrass plants per 1⁄10 hectare (10 m2) 15.25 meters inside treatment
areas seeded with crested wheatgrass and 15.25, 30.5, 61.0, and 122.0 meters outside
treatment areas in native vegetation.
Study site
Year of
treatment
15.25 m
inside
15.25 m
outside
30.5 m
outside
61.0 m
outside
122.0 m
outside
Grouse Creek
Flat Iron
Eakins
Huber
1956
1966
1970
1985
594
701
935
1088
97
160
216
20
77
93
65
11
39
37
12
6
23
3
1
0
the 15.25 m (50 ft) transects inside and outside of treatment
at the Huber study site. Summed nested frequency was
determined for all grass species as outlined by the U.S.
Department of Agriculture, Forest Service (1993).
The number of crested wheatgrass plants per 1⁄10 hectare
was 6.1 (Grouse Creek), 4.4 (Flat Iron), 4.3 (Eakins), and
54.4 (Huber) times fewer at 15.25 m outside the treatment
than at 15.25 m inside the treatment. The number of plants
per 1⁄10 hectare outside the treatment decreased substantially at further distances from the plow line as indicated in
table 1. No crested wheatgrass plants were observed outside
the treatment 129.5 m (425 ft) from the plow line at the
Eakins and Huber sites, 183.0 m (600 ft) from plow line at
Flat Iron, and 322.0 m (1,056 ft) from plow line at Grouse
Creek. Density of crested wheatgrass plants were greater in
the younger treatment areas and fewer in the older treatment areas. At the Grouse Creek and Huber sites, the
majority of crested wheatgrass plants established outside
the treatment area were found along shallow drainages that
run perpendicular to the transects and plow line. Seed
distribution of crested wheatgrass from the treatment into
the adjacent native community appeared to be primarily a
result of surface water flow. At the Flat Iron and Eakins
sites, seed distribution appears to be more of a function of
wind, especially at the Eakins site where the plow line runs
perpendicular to normal wind patterns and the untreated
area is downwind from the treatment area. Crested wheatgrass plants found in the unseeded areas of the four study
sites did not display highly invasive or otherwise weedy
features, but appeared for the most part as scattered plants
among natives with little indication of initiating a major
shift in plant community function. Cheatgrass, however,
was observed in abundance in the native communities at all
four study sites. At the Huber site, frequency of cheatgrass
was significantly higher (nearly 10 times greater) 15.25 m
outside the treatment than 15.25 m inside the treatment
(table 2).
Outside the treatment area, presence of cheatgrass was
higher on alluvial surfaces where bottlebrush squirreltail is
the most common native grass. On gravel pediment surfaces, where needle-and-thread grass is more abundant,
presence of cheatgrass was much lower. Information from
this study indicates that needle-and-thread grass sites are
less susceptible to cheatgrass than bottlebrush squirreltail
sites in Wyoming big sagebrush communities. In the treatment area at the Huber site, the ability of crested wheatgrass to suppress cheatgrass was much greater than that of
native species. A dense stand of cheatgrass formed at the
Huber site when crested wheatgrass failed to germinate
following the initial plow and seeding. Following the second
treatment, crested wheatgrass at the site germinated and
has been successful in suppressing cheatgrass as indicated
by the frequency data in table 2 above.
At Grouse Creek, cheatgrass was observed in abundance
in the native plant community. Outside the treatment,
cheatgrass formed a nearly continuous, fine, highly flammable fuel within the thickspike wheatgrass-mountain big
sagebrush community. Similar to the Huber site, crested
wheatgrass successfully suppressed cheatgrass in the treatment area. With the potential to increase fire frequency,
cheatgrass presents a major risk to ecological function of the
native plant community. The risk of crested wheatgrass to
ecological function of the native plant community appears to
be low after 42 years. Trend of native shrubs (table 3)
following the 1988 Whiterocks fire demonstrates compatibility of crested wheatgrass with function of native plants at
this site.
Although crested wheatgrass remains the dominant herbaceous species in the treatment area, native shrubs in the
treatment appear to be functioning similar to those outside
Table 2—Summed nested frequencya for six grassesb at 15.25 meters inside treatment
area and 15.25 meters outside treatment area at the Huber study site.
Transect
Inside treatment
Outside treatment
AGCR
STCO
ELEL
STHY
BRTE
HIJA
303
12
17
94
2
68
7
3
24
236
27
0
a
Nested frequency scores were derived from 100 nested plots of 5 X 5 cm, 25 X 25 cm, 25 X 50 cm,
and 50 X 50 cm along each 137.0 m transect. Maximum score possible is 400. The treatment area was
plowed and seeded with crested wheatgrass in 1985.
b
Agropyron cristatum (AGCR), Stipa comata (STCO), Elymus elymoides (ELEL), Stipa hymenoides
(STHY), Bromus tectorum (BRTE), and Hilaria jamesii (HIJA).
USDA Forest Service Proceedings RMRS-P-11. 1999
183
Table 3—Percent crown covera for six shrubsb from Grouse Creek
treatment area seeded with crested wheatgrass in 1956.
Year
ARTR
PUTR
AMAL
CHVI
GUSA
CHNA
1987
1988c
1991
1995
1997
1998
16.1
0.0
0.1
0.6
1.3
1.4
12.3
0.0
3.9
8.9
10.3
13.0
1.4
0.0
1.4
4.3
4.1
5.6
0.2
0.0
1.7
2.5
2.7
2.5
0.1
0.0
0.3
0.1
0.0
0.0
0.0
0.0
0.0
0.0
0.3
0.1
a
Crown cover estimates were derived from line intercept data.
b
The six shrubs are: Artemisia tridentata ssp. vaseyana var. pauciflora
(ARTR), Purshia tridentata (PUTR), Amelanchier alnifolia (AMAL), Chrysothamnus viscidiflorus (CHVI), Gutierrezia sarothrae (GUSA), and Chrysothamnus
nauseosus (CHNA).
c
area burned during the 1988 Whiterocks wildfire.
the treatment (i.e., percent canopy cover and density). Ten
years after fire, bitterbrush, serviceberry, and yellowbrush
are nearly equal to or exceed preburn crown cover percentages. Although slower to return than sprouting shrubs,
mountain big sagebrush appears to be returning at expected
rates following fire. Species richness data indicates that the
total number of species in the treatment area is relatively
high (30 taxa). This value is consistent with Tart (1996). He
2
found that the number of plant taxa per 375 m plot in
mountain big sagebrush communities in central Wyoming
ranged from 11 to 39 taxa with a mean of 27.
Shrub recruitment and species richness values in the
crested wheatgrass treatment at Grouse Creek may be
influenced by livestock grazing, however, cattle grazing at
the site was not addressed in this study. At the Flat Iron,
Eakins, and Huber sites, the return of wyoming big sagebrush in crested wheatgrass treatments appear to be influenced by livestock grazing (table 4).
Crested wheatgrass established and has maintained a
monoculture community at Flat Iron for 32 years in the
absence of spring and summer livestock grazing. Treatment
of Wyoming big sagebrush at the site resulted in essentially
100% kill of the shrub. Information from the site indicates
that recruitment of Wyoming big sagebrush at the margins
of the treatment is currently nonexistent. The Eakins and
Huber sites are grazed by cattle during the boot stage of
phenology. Recruitment of sagebrush at these sites is apparent. Treatment of Wyoming big sagebrush was nearly
100 percent at the Eakins site and about 90 percent at the
Huber site. Although internal as well as external recruitment
Table 4—Percent crown covera of Wyoming big sagebrush inside
treatments seeded with crested wheatgrass and outside
treatments at the Flat Iron, Eakins, and Huber study sites.
Study site
Flat Iron
Eakinsc
Huberc
a
Outside
Inside
1966
1970
1985
12.7
21.7
20.2
0.00
2.40
1.00
Crown cover estimates were derived from line intercept data.
Grazed by cattle during winter only.
Grazed by cattle late spring and summer.
b
c
b
Year of
treatment
184
of sagebrush at these sites are apparent, spring and summer
grazing appear to initiate or at least accelerate the return of
wyoming big sagebrush into the crested wheatgrass treatments.
Discussion and Management
Implications ____________________
Information from the four study sites indicate that although crested wheatgrass has a high capacity to persist in
original seedings, it has not demonstrated highly invasive or
otherwise weedy features demonstrated by other exotics
such as cheatgrass. Where crested wheatgrass has entered
native plant communities, it appears to have little modifying
influence on community composition and function. Cheatgrass presents a high risk to community composition and
function in big sagebrush communities (Billings 1994;
Peters and Bunting 1994). In the Uinta Basin, crested
wheatgrass has demonstrated a higher capability to suppress cheatgrass in these communities than native species.
Crested wheatgrass can provide a reliable means of altering
high fire frequency and other undesirable features of cheatgrass systems.
Following plowing and seeding, crested wheatgrass established and maintained a monoculture community in the
absence of spring livestock grazing in Wyoming big sagebrush communities with little or no shrub recruitment.
Sagebrush recruitment is apparent in treatments where
livestock grazing in spring and early summer is employed.
Information from the Flat Iron, Eakins, and Huber sites
indicate that timely grazing by cattle can be used as a tool to
promote recruitment of Wyoming big sagebrush in crested
wheatgrass seedings where desired. In the mountain big
sagebrush community at Grouse Creek, crested wheatgrass
did not form a monoculture. Although it remained a
dominante grass, shrub recruitment in the treatment was
apparent and appeared to function similar to shrubs in
adjacent native communities. Species richness in the treatment was relatively high. Summer livestock grazing at
Grouse Creek has probably promoted shrub recruitment.
Coupled with livestock grazing, crested wheatgrass seedings
can be managed for return of sagebrush in communities
altered by cheatgrass invasion.
References _____________________
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