Invasive annual grasses, such as cheatgrass (Bromus tectorum) and medusahead (Taeniatherum caput-medusae), are one of the most significant stressors to rangeland ecosystems in the western U.S. Their expansion and dominance across this area are the most damaging ecosystem agents on this iconic landscape.
Many invasive plants thrive in disturbed areas and are easily spread through various pathways and vectors. In the western U.S., disturbed landscape can take the form of areas changed by human development, improper grazing, and burned by wildfire. Roads and trails, and the vehicles that travel them, transmission corridors, and fuel breaks all serve as pathways and vectors that help spread these unwanted invaders. Once an invasive plant becomes established in an area, it can quickly spread across the landscape. Invasive plant species can become ecologically dominant, creating near-monocultures that result in reduced wildlife habitat, recreational opportunities, livestock forage, and altered fire regimes. Even after landscape disturbances are removed from areas dominated by these plants, these invasive annual grasses can remain the dominant plant.

Cheatgrass originated in Europe or Eurasia and medusahead in the Mediterranean region. Both were introduced to the U.S. in the mid- to late-1800's as a contaminant in seed and straw. Both species germinate in the fall and early spring, grow rapidly and in high numbers making them highly competitive with native species.
Plants native to the sagebrush landscape may not recover from disturbances that allow invasive annual grasses to over-run them, even decades later. In these areas, elimination of invasive annual grasses is very difficult because the limited number of remaining native plants are unable to produce seeds and seedlings that can compete with these invasive annual grasses. In addition, the thick thatch produced by annual grasses kills biological soil crusts (lichens, mosses and cyanobacteria) that once filled the soil interspaces between the native grasses and shrubs.
The conversion of a diverse native ecosystem to simple invasive grass-dominated ecosystems degrades the ecosystem processes leading to soil erosion, less water in the soil for plant growth, and changes in nutrient cycling, making a less productive land that is much harder to restore to what it was before the invasion.
Land managers are tasked with controlling cheatgrass and medusahead, but resources are limited for invasive plant management. They face difficult decisions on how to use their limited resources. Do they target high-risk pathways and vectors of invasion for efficiency, focus on specific invasive plant patches that are feasible to control, or treat the periphery of a large invasion to slow and contain the spread? Innovative approaches that capitalize on the targeted ecosystem’s resilience to disturbance and resistance to invasive plant invasion is needed to achieve long-term ecosystem conservation and restoration goals for invasive plant-dominated landscapes.
Researchers at the USGS have and continue to develop a wide variety of tools and systems, and answer questions, that help tribal, federal, state, industry, and private land managers design and implement sustainable rangeland practices along with effective restoration and rehabilitation projects. Studies focus on finding ways to control cheatgrass and medusahead through use of herbicides, soil bacteria, and targeted grazing. On-going research also answers questions about the resistance of an ecosystem to an invasive plant, including the suitability of the ecosystem’s climate and soils for establishment and persistence of the invasive plant, and the capacity of the native plant community to prevent increases in the invasive plant’s population through factors such as competition, herbivory, and ability of native plants, including biological soil crusts, to adapt to environmental conditions. They develop solutions to help land managers bolster or support the ecosystem's resilience, or ability to bounce back from a disturbance.

Notable contributions include:
Exotic Brome-Grasses in the Western U.S. Edited and contributed to the authoritative source of information on exotic annual Bromus in arid and semi-arid ecosystems of the western U.S.
Indicators of Rangeland Health. Development of the best, most consistent, and comparable method to determine rangeland health. This method is widely used by multiple land management agencies and highly
valued by ranchers.
Right Seed at the Right Place and Time. Tests of seed sources used in BLM restoration efforts changed seed transfer guidelines and enhanced seeding success. Our data helps the BLM, the largest purchaser of
wildland seed globally, buy the right kind and amount of seed.
Conservation Efforts Database. Constructed a data system that helped the USFWS determine if stakeholder conservation efforts were enough to avoid an Endangered Species Act listing of the Greater sage-grouse.
Restoration of biological soil crusts. Tests of species for restoration, impacts of grazing and fire are of interest to BLM, USFWS, and USFS managers to enhance restoration successes.
Browse the Publications and Data and Tools tabs to find USGS publications related to invasive annual grasses.
Check out the News tab for plain language descriptions of USGS studies and publications.
Click the Multimedia tab for pictures and maps.
Visit the team pages for the scientists working on invasive annual grasses.
Restoration and Ecology of Arid Lands Team (FRESC)
Wildlife Ecology and Conservation Biology Team (FRESC)
Fire Ecology in Dynamic Ecosystems Team (FRESC)
Plant-Soil-Environment Laboratory (FRESC)
If you are unable to access a product or publication online, you can request a copy by sending an email with your contact information and the publication's citation to fresc_outreach@usgs.gov or call (541) 750-1030.
Survival data of transplanted sagebrush (Artemesia tridentata) seedlings in relation to vegetative, organismal, and topographic conditions after megafire
Biological soil crust cover from the Taylor Grazing Act exclosures
Tackifier impacts on growth of Great Basin mosses Bryum argenteum and Syntrichia ruralis, a growth chamber study, 2017-2018
The Sagebrush Biome Range Extent, as Derived from Classified Landsat Imagery
Disturbance characteristics, vegetation and biocrust cover from the northern Great Basin (USA) 2012-2013
Fuels Database for Intact and Invaded Big Sagebrush (Artemisia tridentata) Ecological Sites
Vegetation cover data used from the Soil Vegetation Inventory Method (SVIM) for Southwest Idaho
Exotic and perennial grass cover for pastures in the Soda Fire (2016)
Combined wildfire dataset for the United States and certain territories, 1870-2015
Nitrogen cycling rates from sagebrush and cheatgrass-invaded soils in the Northern Great Basin (2008)
If you are unable to access a product or publication online, you can request a copy by sending an email with your contact information and the publication's citation to fresc_outreach@usgs.gov or call (541) 750-1030.
Plant community trajectories following livestock exclusion for conservation vary and hinge on initial invasion and soil-biocrust conditions in shrub steppe
The effects of cheatgrass invasion on US Great Basin carbon storage depend on interactions between plant community composition, precipitation seasonality, and soil climate regime
Intra-site sources of restoration variability in severely invaded rangeland: Strong temporal effects of herbicide-weather interactions; weak spatial effects of plant-community patch type and litter
Post-fire management-scale trials of bacterial soil amendment MB906 show inconsistent control of invasive annual grasses
Weed-suppressive bacteria applied as a spray or seed mixture did not control Bromus tectorum
Weed-suppressive bacteria have no effect on exotic or native plants in sagebrush-steppe
Weed-suppressive bacteria fail to control bromus tectorum under field conditions
Operationalizing resilience and resistance concepts to address invasive grass-fire cycles
An experimental test of weed-suppressive bacteria effectiveness in rangelands in southwestern Idaho, 2016–18
Resiliency of biological soil crusts and vascular plants varies among morphogroups with disturbance intensity
A conservation paradox in the Great Basin—Altering sagebrush landscapes with fuel breaks to reduce habitat loss from wildfire
Fire and grazing influence site resistance to Bromus tectorum through their effects on shrub, bunchgrass and biocrust communities in the Great Basin (USA)
If you are unable to access a product or publication online, you can request a copy by sending an email with your contact information and the publication's citation to fresc_outreach@usgs.gov or call (541) 750-1030.
Land Treatment Exploration Tool
The Land Treatment Exploration Tool is designed for resource managers to use when planning land treatments. The tool provides useful summaries of environmental characteristics of planned treatment areas and facilitates adaptive management practices by comparing those characteristics to other similar treatments within a specified distance or area of interest. Provisional Software.
Plain language descriptions for some related USGS products and publications.
New Invasive Annual Grass Book Addresses Critical Questions for the Western U.S.
- Overview
Invasive annual grasses, such as cheatgrass (Bromus tectorum) and medusahead (Taeniatherum caput-medusae), are one of the most significant stressors to rangeland ecosystems in the western U.S. Their expansion and dominance across this area are the most damaging ecosystem agents on this iconic landscape.
Many invasive plants thrive in disturbed areas and are easily spread through various pathways and vectors. In the western U.S., disturbed landscape can take the form of areas changed by human development, improper grazing, and burned by wildfire. Roads and trails, and the vehicles that travel them, transmission corridors, and fuel breaks all serve as pathways and vectors that help spread these unwanted invaders. Once an invasive plant becomes established in an area, it can quickly spread across the landscape. Invasive plant species can become ecologically dominant, creating near-monocultures that result in reduced wildlife habitat, recreational opportunities, livestock forage, and altered fire regimes. Even after landscape disturbances are removed from areas dominated by these plants, these invasive annual grasses can remain the dominant plant.
Sources/Usage: Some content may have restrictions. Visit Media to see details.Cheatgrass (Bromus tectorum) is the dominant exotic annual grass species on semi-arid rangelands of the western hemisphere. Photo by Justin L. Welty, USGS Cheatgrass originated in Europe or Eurasia and medusahead in the Mediterranean region. Both were introduced to the U.S. in the mid- to late-1800's as a contaminant in seed and straw. Both species germinate in the fall and early spring, grow rapidly and in high numbers making them highly competitive with native species.
Plants native to the sagebrush landscape may not recover from disturbances that allow invasive annual grasses to over-run them, even decades later. In these areas, elimination of invasive annual grasses is very difficult because the limited number of remaining native plants are unable to produce seeds and seedlings that can compete with these invasive annual grasses. In addition, the thick thatch produced by annual grasses kills biological soil crusts (lichens, mosses and cyanobacteria) that once filled the soil interspaces between the native grasses and shrubs.
The conversion of a diverse native ecosystem to simple invasive grass-dominated ecosystems degrades the ecosystem processes leading to soil erosion, less water in the soil for plant growth, and changes in nutrient cycling, making a less productive land that is much harder to restore to what it was before the invasion.
Land managers are tasked with controlling cheatgrass and medusahead, but resources are limited for invasive plant management. They face difficult decisions on how to use their limited resources. Do they target high-risk pathways and vectors of invasion for efficiency, focus on specific invasive plant patches that are feasible to control, or treat the periphery of a large invasion to slow and contain the spread? Innovative approaches that capitalize on the targeted ecosystem’s resilience to disturbance and resistance to invasive plant invasion is needed to achieve long-term ecosystem conservation and restoration goals for invasive plant-dominated landscapes.
Researchers at the USGS have and continue to develop a wide variety of tools and systems, and answer questions, that help tribal, federal, state, industry, and private land managers design and implement sustainable rangeland practices along with effective restoration and rehabilitation projects. Studies focus on finding ways to control cheatgrass and medusahead through use of herbicides, soil bacteria, and targeted grazing. On-going research also answers questions about the resistance of an ecosystem to an invasive plant, including the suitability of the ecosystem’s climate and soils for establishment and persistence of the invasive plant, and the capacity of the native plant community to prevent increases in the invasive plant’s population through factors such as competition, herbivory, and ability of native plants, including biological soil crusts, to adapt to environmental conditions. They develop solutions to help land managers bolster or support the ecosystem's resilience, or ability to bounce back from a disturbance.
Sources/Usage: Some content may have restrictions. Visit Media to see details.Medusahead (Taeniatherum caput-medusae) seed heads have long barbed “hairs” called awns that can cause injury to grazing animals. Photo by Justin L. Welty, USGS Notable contributions include:
Exotic Brome-Grasses in the Western U.S. Edited and contributed to the authoritative source of information on exotic annual Bromus in arid and semi-arid ecosystems of the western U.S.
Indicators of Rangeland Health. Development of the best, most consistent, and comparable method to determine rangeland health. This method is widely used by multiple land management agencies and highly
valued by ranchers.Right Seed at the Right Place and Time. Tests of seed sources used in BLM restoration efforts changed seed transfer guidelines and enhanced seeding success. Our data helps the BLM, the largest purchaser of
wildland seed globally, buy the right kind and amount of seed.Conservation Efforts Database. Constructed a data system that helped the USFWS determine if stakeholder conservation efforts were enough to avoid an Endangered Species Act listing of the Greater sage-grouse.
Restoration of biological soil crusts. Tests of species for restoration, impacts of grazing and fire are of interest to BLM, USFWS, and USFS managers to enhance restoration successes.
Browse the Publications and Data and Tools tabs to find USGS publications related to invasive annual grasses.
Check out the News tab for plain language descriptions of USGS studies and publications.
Click the Multimedia tab for pictures and maps.
- Science
Visit the team pages for the scientists working on invasive annual grasses.
Restoration and Ecology of Arid Lands Team (FRESC)
The focus of our research is on the restoration and monitoring of the plants and soils of the Intermountain West. Our lab is part of the Snake River Field Station, but is located in Corvallis, Oregon. Research topics include fire rehabilitation effects and effectiveness, indicators of rangeland health, invasive species ecology, and restoration of shrub steppe ecosystems.Wildlife Ecology and Conservation Biology Team (FRESC)
Wildlife respond to changes in their environment, some of which are dramatic and others subtle. To fully understand the factors that drive changes in populations and communities, we need better information on wildlife ecology in natural and human-altered landscapes. We conduct research and provide technical assistance to address applied questions about the ecology and conservation of wildlife...Fire Ecology in Dynamic Ecosystems Team (FRESC)
Understanding how fire and other disturbances affect ecosystem health and resiliency is critically important for land managers and for society as a whole.Plant-Soil-Environment Laboratory (FRESC)
We produce basic and applied science needed to manage landscapes in ways that make them resistant and resilient to stressors such as wildfire, exotic plant invasions, drought, and temperature extremes. These stressors impact ecosystem productivity and functioning and pose costly risks to human health and safety in the western United States. We team with other state and federal agencies to find... - Data
If you are unable to access a product or publication online, you can request a copy by sending an email with your contact information and the publication's citation to fresc_outreach@usgs.gov or call (541) 750-1030.
Survival data of transplanted sagebrush (Artemesia tridentata) seedlings in relation to vegetative, organismal, and topographic conditions after megafire
This dataset contains information on the survival of individual sagebrush seedlings, stands of seedlings and the vegetative and topographic conditions in which they were planted.Biological soil crust cover from the Taylor Grazing Act exclosures
Seven exclosures that were part of the original 28 Taylor Grazing Act exclosures across northern Nevada were surveyed for cover of biological soil crusts in May 2018. Surveys consisted of 15 quadrats both inside and outside of the exclosures. Quadrats were used to measure biocrust cover via point-intercept at 39 vertices within each quadrat. Cattle grazing outside of the exclosures was characterizTackifier impacts on growth of Great Basin mosses Bryum argenteum and Syntrichia ruralis, a growth chamber study, 2017-2018
The dataset supports a larger study that examined the impacts of three tackifiers (guar, psyllium, and polyacrylamide) on growth of two dryland mosses (Bryum argenteum and Syntrichia ruralis). Moss fragments were grown in petri dishes and subjected to individual tackifiers in one of three possible concentrations (0.5x, 1x, or 2x) of the respective manufacturer's recommended application rate. DistiThe Sagebrush Biome Range Extent, as Derived from Classified Landsat Imagery
This feature estimates the geographic extent of the sagebrush biome in the United States. It was created for the Western Association of Fish and Wildlife Agency's (WAFWA) Sagebrush Conservation Strategy publication as a visual for the schematic figures. This layer does not represent the realized distribution of sagebrush and should not be used to summarize statistics about the distribution or precDisturbance characteristics, vegetation and biocrust cover from the northern Great Basin (USA) 2012-2013
Fifteen fires from the Chronosequence dataset (see Knutson et al. 2014) were visited in 2012 and 2013 and surveyed for cover of lichens and mosses. Fires were selected to cover the range of average precipitation for each of three water years following fire, fire severity, time since fire, season of ignition, total acres burned and grazing intensity. Cattle grazing was characterized by distance froFuels Database for Intact and Invaded Big Sagebrush (Artemisia tridentata) Ecological Sites
The Fuels Guide and Database for Big Sagebrush Ecological Sites was developed as part of the Joint Fire Sciences Program project "Quantifying and predicting fuels and the effects of reduction treatments along successional and invasion gradients in sagebrush habitats" (Shinneman and others, 2015). The research was carried out by the U.S. Geological Survey (USGS) Forest and Rangeland EcosyVegetation cover data used from the Soil Vegetation Inventory Method (SVIM) for Southwest Idaho
The US Department of Interior's (USDI) Bureau of Land Management (BLM) has a long history of soil and vegetation monitoring of public rangelands it manages. However, historical monitoring data have been stored and managed at the field, district, or state level, making them difficult to compile and analyze. BLM's Soil Vegetation Inventory Method (hereafter SVIM) program occurred between 1977 and 19Exotic and perennial grass cover for pastures in the Soda Fire (2016)
The point data file ("Soda Fire Point and Pasture Data (2016).Point Data.csv") includes 2016 vegetative cover values of exotic annual grass and perennial grass measured within three different types of plots for 75 pastures in the Soda Fire, which burned in 2015: 6m2 plot using a grid-point intercept photo software, SamplePoint (Booth et al. 2006), 1m2 quadrat using an unguided rapid ocular estimatCombined wildfire dataset for the United States and certain territories, 1870-2015
The increase in wildfires, particularly in the western U.S., represents one of the greatest threats to multiple native ecosystems. Despite this threat, there is currently no central repository to store both past and current wildfire perimeter data. Currently, wildfire boundaries can only be found in disparate local or national datasets. These datasets are generally restricted to specific locationsNitrogen cycling rates from sagebrush and cheatgrass-invaded soils in the Northern Great Basin (2008)
This dataset contains data supporting the paper: DeCrappeo, N.M., DeLorenze, E.J., Giguere, A.T., Pyke, D.A., and Bottomley, P.J. Fungal and bacterial contributions to nitrogen cycling in cheatgrass-invaded and uninvaded native sagebrush soils of the western USA (accepted at the journal Plant and Soil). The purpose of the study was to evaluate the relative contributions of soil bacteria and fungi - Multimedia
- Publications
If you are unable to access a product or publication online, you can request a copy by sending an email with your contact information and the publication's citation to fresc_outreach@usgs.gov or call (541) 750-1030.
Filter Total Items: 35Plant community trajectories following livestock exclusion for conservation vary and hinge on initial invasion and soil-biocrust conditions in shrub steppe
Adjustments or complete withdrawal of livestock grazing are among the most common conservation actions in semiarid uplands, but outcomes can vary considerably with ecological context. Invasion by exotic annual grasses and the excessive wildfire they promote are increasing threats to semiarid shrub-steppe, and plant-community response to livestock exclusion in these areas may be complicated by theThe effects of cheatgrass invasion on US Great Basin carbon storage depend on interactions between plant community composition, precipitation seasonality, and soil climate regime
Annual-grass invasions are transforming desert ecosystems in ways that affect ecosystem carbon (C) balance, but previous studies do not agree on the pattern, magnitude and direction of changes. A recent meta-analysis of 41 articles and 386 sites concludes that invasion by annual grasses such as cheatgrass (Bromus tectorum L) reduces C in biomass across the Great Basin (Nagy et al., 2021). ReanalysIntra-site sources of restoration variability in severely invaded rangeland: Strong temporal effects of herbicide-weather interactions; weak spatial effects of plant-community patch type and litter
Invasions by exotic annual grasses (EAGs) are replacing native perennials in semiarid areas globally, including the vast sagebrush-steppe rangelands of western North America. Efforts to eradicate EAGs and restore perennials have had mixed success, especially in relatively warm and dry areas where EAGs had high dominance prior to intervention. Greater consideration of the ecological sources of variPost-fire management-scale trials of bacterial soil amendment MB906 show inconsistent control of invasive annual grasses
Rangeland managers need tools to control invasive annual grasses, particularly following wildfire. We assessed responses of native and invasive/exotic grasses to the MB906 soil amendment containing live cultures of a purportedly weed-suppressive strain of the bacterium Pseudomonas fluorescens (“WSB”). MB906 was applied alone and in combination with the pre-emergent herbicide imazapic on >3000 ha aWeed-suppressive bacteria applied as a spray or seed mixture did not control Bromus tectorum
We conducted two case studies testing effectiveness of a soil-borne bacteria, Pseudomonas fluorescens strain D7, in controlling Bromus tectorum (cheatgrass) and in affecting the density of sown desirable seedlings. We conducted two case studies testing D7’s ability to control of B. tectorum (cover, biomass and density) when mixed with native seeds sown after a fire and when sprayed on a native comWeed-suppressive bacteria have no effect on exotic or native plants in sagebrush-steppe
Approaches and techniques for control of exotic annual grasses are a high priority in rangelands including sagebrush steppe. Strains of the soil bacterium Pseudomonas fluorescens have been proposed to be selectively pathogenic to multiple species of exotic annual grasses (“Pf,” weed-suppressive bacteria, “WSB”). However, defensible tests of the target and nontarget effects of these WSB strains inWeed-suppressive bacteria fail to control bromus tectorum under field conditions
The exotic winter annual grass Bromus tectorum L. (downy brome or cheatgrass) infests millions of hectares of western rangelands. Weed-suppressive bacteria (ACK55 and D7 strains of Pseudomonas fluorescens Migula 1895) have been shown to reduce B. tectorum populations in eastern Washington. Unfortunately, outside of Washington, little is known about the efficacy of these or other weed-suppressive bOperationalizing resilience and resistance concepts to address invasive grass-fire cycles
Plant invasions can affect fuel characteristics, fire behavior, and fire regimes resulting in invasive plant-fire cycles and alternative, self-perpetuating states that can be difficult, if not impossible, to reverse. Concepts related to general resilience to disturbance and resistance to invasive plants provide the basis for managing landscapes to increase their capacity to reorganize and adjust fAn experimental test of weed-suppressive bacteria effectiveness in rangelands in southwestern Idaho, 2016–18
Approaches and techniques for control of exotic annual grasses are a high priority in sagebrush-steppe and other rangelands. Strains of the soil bacterium Pseudomonas fluorescens (Pf) have been proposed to be selectively pathogenic to multiple species of exotic annual grasses with effects evident by the second year, and with no effect on native or desirable species including native bunchgrasses. HResiliency of biological soil crusts and vascular plants varies among morphogroups with disturbance intensity
Background and aimsDisturbance affects the ability of organisms to persist on a site, and disturbance history acts as a filter of community composition. This is true for vascular plants and morphological groups of biocrusts, which respond differently to disturbance. Although functioning arid ecosystems include both groups, filtering of morphological groups of biocrusts has not previously been compA conservation paradox in the Great Basin—Altering sagebrush landscapes with fuel breaks to reduce habitat loss from wildfire
Interactions between fire and nonnative, annual plant species (that is, “the grass/fire cycle”) represent one of the greatest threats to sagebrush (Artemisia spp.) ecosystems and associated wildlife, including the greater sage-grouse (Centrocercus urophasianus). In 2015, U.S. Department of the Interior called for a “science-based strategy to reduce the threat of large-scale rangeland fire to habitFire and grazing influence site resistance to Bromus tectorum through their effects on shrub, bunchgrass and biocrust communities in the Great Basin (USA)
Shrubs, bunchgrasses and biological soil crusts (biocrusts) are believed to contribute to site resistance to plant invasions in the presence of cattle grazing. Although fire is a concomitant disturbance with grazing, little is known regarding their combined impacts on invasion resistance. We are the first to date to test the idea that biotic communities mediate the effects of disturbance on site r - Web Tools
If you are unable to access a product or publication online, you can request a copy by sending an email with your contact information and the publication's citation to fresc_outreach@usgs.gov or call (541) 750-1030.
Land Treatment Exploration Tool
The Land Treatment Exploration Tool is designed for resource managers to use when planning land treatments. The tool provides useful summaries of environmental characteristics of planned treatment areas and facilitates adaptive management practices by comparing those characteristics to other similar treatments within a specified distance or area of interest. Provisional Software.
- News
Plain language descriptions for some related USGS products and publications.
New Invasive Annual Grass Book Addresses Critical Questions for the Western U.S.
BOISE, Idaho — Bromus species – such as cheatgrass – are exotic annual grasses that have become the dominant annual grasses in the western hemisphere. Their spread and impacts across the western U.S. continue despite the many attempts by land managers to control these species.Filter Total Items: 16 - Partners