HISTORY AND APPLICATIONS OF THE INTERMOUNTAIN GREENSTRIPPING PROGRAM Mike Pellant

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HISTORY AND APPLICATIONS OF THE
INTERMOUNTAIN GREENSTRIPPING
PROGRAM
Mike Pellant
between fire frequency and relative frequency of cheatgrass in southern Idaho. Greater fire frequencies were
also found to cause lower species richness in native communities. The trend of increased wildfire frequency on
cheatgrass rangelands observed by Stewart and Hull
(1949) is continuing today (Pellant 1990).
Cheatgrass was recognized as an "ecologic intruder" as
early as 1949 (Stewart and Hull 1949) and is now a major
component of the vegetation on over 17 million acres of
Great Basin rangelands (Pellant, in press). The ecological
and economic implications of the invasion of cheatgrass
and other alien weeds and the concurrent increase in
wildfires are enormous (Young and others 1987). The
adverse impacts of cheatgrass expansion and wildfire increases in the Intermountain area have recently received
national attention in a popular magazine (Devine 1993).
Although many consider this region a "lifeless desert,"
these rangelands support a wide variety of wildlife and
plant species, provide watershed and recreation values,
and support an important livestock industry. A proactive
wildfire management approach to reduce wildfire impacts
on natural and fiscal resources was needed to maintain
the character and ecosystem functions in the Intermountain area. The use of fire-resistant vegetation (greenstripping) to reduce wildfire spread offered an alternative
to reverse this trend.
ABSTRACT
The size and frequency of wildfires are rapidly increas-
in8 on rangelands in the Intermountain area of the Western
United States. One of the major contributors to increased
wildfires is alien annual grasses, primarily cheatgrass
(Bromus tectorum). Because these annual grasses dry
earlier than native species and are highly flammable, they
promote the rapid spread of fire. To reduce the size and
impact of rangeland wildfires, a wildfire presuppression
program called "greenstripping• was initiated in IOOho by
the Bureau ofLand Management in 1985. Greenstripping
is the strategic placement of30- to 400-ft-wide strips of
fire-resistant vegetation on fire-prone landscapes. To date,
461 mi (16,280 acres) of experimental and operational
greenstrips have been established. The objectives of the
greenstripping program include protecting native rangelands and private properties from wildfire damage, as
well as reducing fire suppression and rehabilitation costs.
INTRODUCTION
Wildfire impacts are of increasing concern to resource
managers and the public in the Great Basin Desert (northem Nevada, eastern Oregon, southern Idaho, and western
Utah) of the Intermountain West. Historically, wildfires
occurred at return intervals of 32-70 years in sagebrush
(Artemisia sp.) vegetation types in the Great Basin (Wright
and others 1979). However, the frequency and size of
wildfires today is considerably higher than historical
levels. Between 1984 and 1993, 2,909 wildfires burned
1,956,840 acres of rangeland in Idaho alone (USDI 1993).
Conversion of native, shrub-steppe vegetation to annual
grasses was initiated in the mid-1800's with overgrazing
by domestic livestock (Yensen 1980). A significant reduction in native herbaceous vegetation occurred and, concurrently, alien annual species were introduced and soon
dominated large areas within the Intermountain area
(Young and others 1972).
CheatgraSB is a wildfire hazard because it matures earlier than native species and provides easily ignited fuels
that promote a rapid rate offirespread (Stewart and Hull
1949). Whisenant (1990) found a significant correlation
BACKGROUND
The concept of using vegetation that resists burning
as a tool to reduce wildfire spread is not new. Early researchers working with crested wheatgrass (Agropyron
cristatum and A. sibericum) in southern Idaho recognized
the value of this introduced, perennial grass in lessening
the cheatgrass fire hazard (Hull and Stewart 1948; Stark
and others 1947). The practical benefit of crested wheatgrass as a fire control tool was recognized after an August
1949 wildfire northeast of Shoshone, ID. A 15,000-acre
wildfire burned to the perimeter of a crested wheatgrass
seeding and stopped, prompting the Bureau of Land Management (BLM) fire control officer to report, "The reseeded area of Owinza Butte, which has a good stand of
crested wheat, shows without doubt the value of this type
of planting in fire control work" (USDI 1948).
The establishment of vegetative fuel breaks in
cheatgrass rangelands was proposed in 1946 in Oregon
(Platt and Jackman 1946). These authors suggested that
cheatgrass rangelands be broken at suitable intervals,
especially along highways, with "strip plantings" of fireresistant vegetation such as crested wheatgr888.
Paper presented at the Symposium on Ecology, Management, and Restoration of Intermountain Annual Rangelands, Boise, ID, May 18-22, 1992.
Mike Pellant is an Ecologist and Greenstrip Program Manager, U.S.
Department of the Interior, Bureau of Land Management, Idaho State
Office, 3380 Americana Terrace, Boise, ID 83706.
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PROGRAM OBJECTIVE
Bureau of Land Management personnel in Idaho first
applied the concept of planting fire-resistant vegetation
along roadways in 1981-82 in the Shoshone District. A
25-mi system of crested wheatgrass "roadstrips" was
planted after a large wildfire (USDI 1982). Establishment of crested wheatgrass was poor because of annual
grass competition and large expanses of rocky, shallow
soils in the treatment area. However, results from early
research and wildfire contacts with aeedings were sufficiently promising that the BLM decided in 1985 to incorporate the use of fire-resistant vegetation into its Emergency Fire Rehabilitation program to reduce future fire
occurrences after an initial fire (USDI 1985).
The establishment of vegetative fuel breaks to reduce
wildfire spread is not limited to the Great Basin area.
In 1957, the "Fuel-Break Research and Demonstration
Program" was organized in southern California to expand
construction of wide fuel breaks in chaparral areas (Green
1977). Planting perennial grasses that remain green into
the summer was recommended for California firebreaks.
The objective of the greenstripping program is to slow
or atop the spread of wildfires by the strategic placement
of strips of fire-resistant vegetation on the landscape
(fig. 1). By reducing wildfire frequency and size, the following benefits are realized:
1. Reduced loss of plant diversity and shrub cover
on sagebrush-steppe and salt-desert shrublands. With
longer intervals between wildfires, loss of plant diversity,
especially shrubs, will be slowed on fire-prone landscapes
and eventually native species may increase (West 1978;
Whisenant 1990; Young and Evans 1978).
2. Reduced loss of private structures and properties
on urban/rural interfaces with public rangelands.
3. Reduced fire suppression and rehabilitation costa.
FUELS MANAGEMENT STRATEGY
Vegetative fuelbreaks, including greenatripa, are simply
fuels modification actions whereby vegetation that is
susceptible to igniting and carrying a fire is replaced by
vegetation that is less likely to ignite or carry a wildfire.
Standing dead material and current growth of plants and
litter constitute the bulk of rangeland fuels. Fuels are the
only element of the fire behavior triangle that can be influenced by management actions, as neither weather nor
topography are easily manipulated. By modifying fuel
properties, extreme fire behavior can be reduced.
Fuels available for combustion depend on the proportion of fuel that is dead, fuel particle size, moisture content, and fuel continuity (Anderson and Brown 1988).
With other factors being equal, the likelihood of a fire
start and rate of fire spread increases as fuel availability
BEGINNING OF THE
GREENSTRIPPING PROGRAM
In 1985, Idaho BLM personnel initiated the greenstripping program to reduce the impacts of wildfires. Strips of
fire-resistant vegetation are planted at strategic locations
on the landscape to slow or stop wildfires. The previous
section clearly indicates that the use of fire-resistant vegetation to reduce wildfire impacts is not a new concept.
Why did BLM initiate this new wildfire presuppression
program? The answer is simple: to incorporate improved
plant materials and new seeding and site preparation
equipment and technology into the implementation of
a vegetative fuel-break program. Greenstripping, a proactive approach to wildfire management, was implemented
to augment the reactive programs of fire suppression and
Emergency Fire Rehabilitation (Pellant 1990).
In 1987, two tasks were accomplished to formally implement the greenstripping program. Firat, an interagency
workgroup completed a handbook that identified greenstrip criteria and procedures (USDI 1987). Second, Congressional funding was obtained to establish operational
greenatrip projects and implement a cooperative research
program. Goals of the BLM's Intermountain Greenstripping and Rehabilitation Research Project are to evaluate
and select fire-resistant plant materials and equipment
to improve greenstripping and fire rehabilitation practices. Six research cooperators are currently working to
accomplish these goals.
In 1991, an internal evaluation of the greenstripping
program recommended program expansion to public land
in Utah, Oregon, and Nevada (USDI 1991). Pilot greenstrip projects were established in these three States in
1992-93, and multistate coordination on greenstrip projects
and research continues to this day. The author provides
technical assistance about greenstrip planning and implementation to other land managers in the Intermountain
area.
Figure 1-This greenstrip project near Mountain
Home, ID, was seeded with crested wheatgrass in
1985. Seedbed preparation on this 30-ft-wide
greenstrip was done with road patrol to reduce
weedy plant competition. Note absence of
cheatgrass in interspaces in this 1992 photo.
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increases. Rangelands infested with alien, annual grasses
are more prone to ignition and fire spread than native
rangelands, since the proportion of available, contiguous
fuels is higher on the former than the latter.
The effectiveness of greenstrips, or any fuels modification project, in reducing wildfire spread is enhanced by
three factors:
Disrupting Fuel Continuity-Fuel continuity can
be disrupted by replacing cheatgrass or other annual
grasses, which grow in a matlike pattern, with caespitose
grasses such as crested wheatgrass, which h ave large
spaces between individual plants (fig. 1). Spread of surface fires is interrupted in discontinuous fuels a nd can
be more easily suppressed (Anderson and Brown 1988).
Reducing Fuel Accumulations and VolatilityRangelands with a high density of shrubs generate longer
flame lengths and increase the probability of fire spotting
(Schmidt and Wakimoto 1988). The high monoterpene
and sesquiterpene content of sagebrush (Kelsey 1986) increases fire intensity in shrubs. Fire suppression actions
are easier and safer to carry out in light fuels than in
heavy fuels; for example, backfiring is less risky in perennial herbaceous vegetation than in dense stands of shrubs.
The probability of fires spreading laterally can be greatly
reduced if shrub stands are thinned to maintain a minimum distance of 10 ft between plants (Schmidt and
Wakimoto 1988).
Figure 2-Forage kochia plant (foreground) in a
marginally established greenstrip near Mountain
Home, 10 . Forage kochia is still green in this
August 1990 photograph. A wildfire started off
Interstate 84 (background) burned to this greenstrip and stopped because of the sparsity of contiguous fine fuels in the seeding.
watershed, and cultural and plant communities that are
at risk if disturbed. Both fire history and potential for
repeated wildfires are also considered.
High fire-frequency areas are generally associated
with cheatgrass and tend to reburn at frequent intervals
(Whisenant 1990). Greenstripping can break large blocks
of cheatgrass-infested rangeland into smaller, more manageable units, thereby reducing fire suppression costs and
spread of wildfires into unburned shrublands.
Increasing the Density of Plants With a Higher
Moisture Content-The length of time during the fire
season that fuels and fire behavior remain hazardous and
ignition potential is high is largely reflected in the moisture content of the various species in the plant community
(Anderson and Brown 1988). Increasing the proportion
of plants with high moisture and low volatile oil content
can reduce both the potential for ignition and rate of fire
spread.
Forage kochia (Kochia prostrata ), an introduced half
shrub, was found to have a fourfold and tenfold higher
moisture content in August 1992 than crested wheatgrass
and cheatgrass, respectively (USDI 1992). This plant is
effective in retarding wildfire spread and can compete
well in a weedy environment (fig. 2).
Land Ownership
Land ownership patterns are an important consideration in greenstrip planning. Greenstripping across
"checkerboard" land ownership patterns requires easements from private or State land owners. "Gaps" left
in greenstrips due to the presence of nonfederalland can
severely limit the effectiveness of a greenstrip in stopping
or slowing a wildfire.
PLANNING AND IMPLEMENTATION
A host of factors must be considered in the planning
and implementation of a greenstrip project. The use of an
interdisciplinary team that "designs" a greenstrip based
on a site-specific evaluation is essential. The following
factors should be considered when designing and implementing a greenstrip project.
Fire Behavior
Topography, vegetation types (fuel loads), and weather
patterns are fire behavior characteristics that must be
evaluated and incorporated into locating greenstrips on
the landscape. Expected fire behavior is included in the
design of a greenstrip project by considering prevailing
wind direction, slope, and fuel qua ntities and continuity.
Fire management specialists are included in the planning
process to ensure proper consideration of fire behavior
variables in selecting greenstrip locations.
Project Area
Selection of sites to implement greenstripping projects
is determined by an interdisciplinary team. This team
reviews land-use plans that identify high-value habitat,
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greenstrip project boundaries and compete with native
plants.
Fourwing saltbush (Atriplex canescens), a native shrub,
is occasionally used to enhance diversity of greenstrips
and to trap winter snowfall.
Soils
Soil productivity and the amount of surface rock affect
seeding establishment and persistence. Deeper soils generally support a better stand of seeded vegetation than
do rocky, shallow soils. Therefore, greenstrip width is increased to compensate for reduced density of greens trip
species on rocky or shallow soils.
Site Preparation and Seeding
Most sites selected for greenstripping are dominated
by weedy species such as cheatgrass, either as an annual
grass monoculture or as the dominant understory species
under sagebrush. Site preparation to reduce competition
from annual plants is required prior to seeding perennial
vegetation (Evans and Young 1977; Stark and others1947).
Evans (1961) reported that cheatgrass densities as low as
64 plants per square foot greatly increased mortality of
crested wheatgrass seedlings.
Mechanical, herbicidal, and burning treatments (or
combinations of them) are effective in controlling annual
species under the right conditions. Mechanical seedbed
preparation techniques have been used extensively and
evaluated in the greenstripping program. Disking is most
effective if the treatment is done in early spring prior to
cheatgrass seed maturity (fig. 3). Seeding greenstrip species with a rangeland drill is done in the fall following
the disking treatment. Labor and equipment costs to mechanically prepare seedbeds and distribute seed were estimated at $20 to $25 per acre by Pellant (1990). Hereports that these costs are considerably reduced ($8.50 per
acre for labor ) with the use of a disk chain that buries unwanted vegetation and distributes seed in one pass.
Use of fire as a site preparation technique can be effective if burning is done prior to seed dispersal by cheatgrass (Hull and Stewart 1948; Pechanec and Hull1945).
Costs to burn cheatgrass rangelands are generally under
$5 per acre.
Greenstrip Width
Greenstrip width generally varies from 30 to 400 ft
depending on fire prevention objectives, topography, expected fire behavior, and soils. Most greenstrip projects
in Idaho average 300 ft in width and have been seeded
along highways or railroads to reduce human-caused fire
starts and create a wider fire barrier. As fuel height and
volatility increase, greenstrip width should be increased
to reduce the potential for fire spotting that may occur
over the greenstrip.
Visual Impacts
Greenstrips can have a significant impact on the visual
characteristics of a landscape. Adverse visual impacts
can be minimized by avoiding straight-line seedings and
increasing plant and structural diversity in greenstrip
plantings.
Plant Materials
The selection of proper seed mixtures for greenstrip
plantings is critical for the successful establishment and
persistence of seeded species. General criteria for selecting species for rehabilitation are discussed by Plummer
and others (1968). Extensive research on reseeding abandoned farmland (Stark and others 1946) and cheatgrassinfested rangelands (Hull and Stewart 1948; Hull and
Holmgren 1964; lGomp and Hull 1971) is available for
planning greenstrip projects. Plants selected for seeding
greenstrip projects should also be:
1. Fire resistant during a majority of the wildfire season.
2. Drought tolerant and adapted to persist on semiarid
sites.
3. Palatable to herbivores.
4. Fire tolerant to survive occasional burns.
5. Capable of establishing and persisting in competition
with a nnual species.
Plant materials meeting all of these criteria are not
readily available. Introduced wheatgrasses (Agropyron
sp.), Russian wildrye (Elymusjunceus), dryland alfalfa
(Medicago sp.), Lewis flax (Linum lewisii), and small
burnett (Sa nguisorba minor) are the most common herbaceous species seeded in greenstrip projects.
Shrubs generally increase fuel loads and flammability,
increasing the probability that a greenstrip could be
breached by a wildfire. Therefore, use of shrubs in greenstrips is minimal. One exception is forage kochia, which
is limited in use only by seed availability and cost. There
are also concerns that this plant may spread outside of
Figure 3-Towner plow used to reduce annual
plant competition in May 1993 on a greenstrip
project near New Plymouth, ID. Rangeland drills
were used to plant a diverse greenstrip mixture
in October 1993.
66
Herbicides offer another alternative for cheatgrass control prior to seeding (Eckert and others 1974).
Several herbicides are being field tested in Idaho and
Nevada to determine their effectiveness in reducing
cheatgrass competition. Twenty-one herbicides are approved for use on public land to meet specific vegetation
treatment objectives (USDI 1991). Economics, environmental impacts, selectivity, and effectiveness are several
of many factors that must be cOnsidered prior to selecting
an herbicide for site preparation in cheatgrass-infested
rangelands.
In many respects, this situation is little changed 28 years
later. Therefore, it is probable that wildfire impacts will
continue to increase unless proactive measures, such as
greenstripping, are applied. Greenstripping is not the
ultimate solution to the cheatgrass-wildfire problem, but
one of many tools that must be applied to control wildfires
on rangelands dominated by annual plants.
ACKNOWLEDGMENTS
The author thanks Idaho BLM personnel who initiated
and contributed to the development of the greenstripping
program. Sue Phillips greatly improved the structure and
organization of this manuscript, while Bob Clark, Steve
Monsen, and Don Smurthwaite added editorial reviews.
Management
Livestock season-of-use and wildlife use patterns must
be considered in greenstrip planning. Livestock and wildlife are often attracted to green vegetation, causing overuse and eventual loss of palatable greenstrip plants. Additionally, greenstrips along roads or railways may attract
livestock and wildlife to the road or track, causing accidents.
An adequate period ofherbivore exclusion during the
plant establishment period is also essential. Seeding prescriptions for greenstrips should only include species that
will establish during the grazing exclusion period and species that will not be selectively overgrazed and eventually
lost from the greenstrip. However, livestock can serve a
useful role in proper greenstrip management by reducing
fine fuels through grazing and trampling.
REFERENCES
Anderson, Hal E.; Brown, James K. 1988. Fuel characteristics and fire behavior considerations in the wildlands.
In: Fischer, William C.; Amo, Stephen F., camps. Protecting people and homes from wildfire in the Interior
West: proceedings of the symposium and workshop;
1987 October 6-8; Missoula, MT. Gen. Tech. Rep.
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Forest Service, Intermountain Research Station:
124-130.
Bunting, S. C. 1985. Fire in sagebrush-grass ecosystems:
successional changes. In: Sanders, Ken; Durham, Jack,
eds. Rangeland fire effects-a symposium; 1984
November 27-29; Boise, ID. Boise, ID: U.S. Department
of the Interior, Bureau of Land Management, Idaho
State Office: 7-11.
Devine, Robert. 1993. The cheatgrass problem. The Atlantic. 271(5): 40-48.
Eckert, R. E., Jr.; Asher, J. E.; Christensen, M. D.; Evans,
R. A. 1974. Evaluation of the atrazine-fallow technique
for weed control and seeding establishment. Journal of
Range Management. 27: 288-292.
Evans, R. A. 1961. Effects of different densities of downy
brome (Bromus tectorum) on growth and survival of
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greenhouse. VVeeds.9:216-223.
Green, L. R. 1977. Fuelbreaks and other fuel modifications for wildland fire control. Agric. Handb. 499.
Washington, DC: U.S. Department of Agriculture,
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Hull, A. C., Jr. 1965. Cheatgrass-a persistent homesteader. In: Proceedings, cheatgr888 symposium; 1965
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Hull, A. C., Jr.; Holmgren, R. C. 1964. Seeding southern
Idaho rangelands. Res. Pap. INT-10. Ogden, UT: U.S.
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Hull, A. C., Jr.; Stewart, G. 1948. Replacing cheatgrasss
by reseeding with perennial grass on southern Idaho
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Kelsey, Rick G. 1986. Foliage biomass and crude terpenoid productivity of big sagebrush <Artemisia tridentata).
PROGRAM STATUS
From 1985 to the end of 1993, 451 mi (16,280 acres) of
greenstrips were seeded on public land in Idaho (PeDant
1993). Pilot greenstrip projects were completed in Oregon,
Nevada, and Utah in 1992 with technical assistance from
the Idaho Greenstrip Program Manager.
Two wildfires have burned into established greenstrip
projects. In 1988, a greenstrip project north of Grasmere,
ID, was effective in stopping a wildfire along 6 of 7 mi of
the contact area.
This allowed suppreBBion forces to concentrate their efforts on a fire front of only 1 mi instead of7. In 1990, a
greenstrip adjacent to a major interstate highway near
Mountain Home, ID, limited a wildfire to 15 acres (fig. 3).
From 1980 to 1989, the average area burned in the same
vicinity was 1,800 acres.
The Intermountain Greenstripping and Rehabilitation
Research Project has been transferred to the Department
of the Interior's National Biological Survey. Research is
continuing in 1994.
SUMMARY
The Intermountain landscape has been permanently
altered by the introduction and spread of alien annual
species, especially cheatgrass, which are more competitive
and flammable than native species. In 1965, a group of
land managers and research specialists met in Vale, OR,
to di8CU88 solutions to the management problems posed by
cheatgrass. Noted revegetation researcher, A. C. Hull, Jr.,
summed up the situation by stating, "The more cheatgrass
the more fire, and the more fire the more cheatgrass"
(USDI 1965).
67
In: McArthur, E. Durant; Welch, Bruce L., comps.
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and Chrysothamnus; 1984 July 9-13; Provo, UT. Gen.
Tech. Rep. INT-200. Ogden, UT: U.S. Department of
Agriculture, Forest Service, Intermountain Research
Station: 375-388.
Pechanec, J. F.; Hull, A. C., Jr. 1945. Spring forage lost
through cheatgrass fires. National Wool Grower. 35: 13.
Pellant, M. 1993. [Unpublished data]. On file at: Bureau
of Land Management, Idaho State Office, Boise, ID.
Pellant, Mike. 1990. The cheatgrass-wildfire cycle-are
there any solutions? In: McArthur, E. Durant; Romney,
Evan M.; Smith, Stanley D.; Tueller, Paul T., comps.
Proceedings-symposium on cheatgrass invasion, shrub
die-off, and other aspects of shrub biology and management; 1989 April 5-7; Las Vegas, NV. Gen. Tech. Rep.
INT-276. Ogden, UT: U.S. Department of Agriculture,
Forest Service, Intermountain Research Station: 11-17.
Platt, Kenneth; Jackman, E. R. 1946. The cheatgrass
problem in Oregon. Bull. 668. Corvallis, OR: Oregon
Agricultural Experiment Station. 48 p.
Plummer, A. P.; Christensen, D. R.; Monsen, S. B. 1968.
Restoring big game range in Utah. Publ. 68-3. Salt Lake
City, UT: Utah Division of Fish and Game. 183 p.
Schmidt, Wyman C.; W akimoto, Ronald H. 1988. Cultural
practices that can reduce fire hazards to homes in the
Interior West. In: Fischer, William C.; Arno, Stephen F.,
comps. Protecting people and homes from wildfire in
the Interior West: proceedings of the symposium and
workshop; 1987 October 6-8; Missoula, MT. Gen. Tech.
Rep. INT-251. Ogden, UT: U.S. Department of Agriculture, Forest Service, Intermountain Research Station:
131-141.
Stark, R. H.; Toevs, J. L.; Hafenrichter, A. L. 1946.
Grasses and cultural methods for reseeding abandoned
farmlands in southern Idaho. Bull. 267. Moscow, ID:
Idaho Agricultural Experiment Station. 36 p.
Stewart, G.; Hull, A. C., Jr. 1949. Cheatgrass {Bromus
tectorum L.)-an ecologic intruder in southern Idaho.
Ecology. 30(1): 58-74.
U.S. Department of the Interior, Bureau of Land Management. 1949. [Unpublished fire control records]. Shoshone,
ID: U.S. Department of the Interior, Bureau of Land
Management, Shoshone District Office. 7 p.
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Shoshone, ID: U.S. Department of the Interior, Bureau
of Land Management, Shoshone District Office. 10 p.
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Manual Handbook H-7142-1. Washington, DC: U.S.
Department of the Interior, Bureau of Land Management. 9p.
U.S. Department of the Interior, Bureau of Land Management. 1987. Draft greenstripping handbook. Boise, ID:
U.S. Department of the Interior, Bureau of Land Management, Idaho State Office. 80 p.
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Land Management, Idaho State Office. 10 p.
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on BLM lands in thirteen western states. Boise, ID:
U.S. Department of the Interior, Bureau of Land Management, Idaho State Office. 17 p.
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U.S. Department of the Interior, Bureau of Land Management, Idaho State Office. 27 p.
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Colorado Plateau. In: The sagebrush ecosystem: a symposium; 1978 April27-28; Logan, UT. Logan, UT: Utah
State University, College ofNatural Resources: 33-41.
Whisenant, Steven G. 1990. Changing fire frequencies on
Idaho's Snake River Plains: ecological and management
implications. In: McArthur, E. Durant; Romney,
Evan M.; Smith, Stanley D.; Tueller, Paul T., comps.
Proceedings-symposium on cheatgrass invasion, shrub
die-off, and other aspects of shrub biology and management; 1989 April 5-7; Las Vegas, NV. Gen. Tech. Rep.
INT-276. Ogden, UT: U.S. Department of Agriculture,
Forest Service, Intermountain Research Station: 1-7.
Wright, H. A.; Nuenschwander, L. F.; Britton, C. M.1979.
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plant communities: a state-of-the-art review. Gen. Tech.
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Yensen, D. A. 1980. A grazing history of southwestern
Idaho with emphasis on the Birds of Prey Study Area.
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Young, J. A.; Evans, R. A.; Major, J. 1972. Alien plants in
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