{{Short description|Species of grass}} {{multiple issues| {{globalize|date=November 2017}} {{lead extra info|reason=information about its native growth|date=May 2019}} }} {{Speciesbox | image = Bromus tectorum — Flora Batava — Volume v13.jpg | image_caption = | genus = Bromus | species = tectorum | authority = L. | synonyms = ''Anisantha tectorum'' <small>(L.) Nevski</small> }}
'''''Bromus tectorum''''', known as '''downy brome''', '''drooping brome''',<ref name=BSBI07>{{BSBI 2007 |access-date=2014-10-17}}</ref> or '''cheatgrass''', is a winter annual grass native to Europe, southwestern Asia, and northern Africa, but has become invasive in many other areas. It now is present in most of Europe, southern Russia, Japan, South Africa, Australia, New Zealand, Iceland, Greenland, North America, and western Central Asia.<ref name=":20" /> In the eastern US, ''B. tectorum'' is common along roadsides and as a crop weed, but usually does not dominate an ecosystem.<ref name=":16">{{Cite web|url=https://www.fs.fed.us/database/feis/plants/graminoid/brotec/all.html|title=Bromus tectorum|website=www.fs.fed.us|access-date=2017-11-29|archive-date=2017-05-02|archive-url=https://web.archive.org/web/20170502121131/https://www.fs.fed.us/database/feis/plants/graminoid/brotec/all.html|url-status=live}}</ref> It has become a dominant species in the Intermountain West and parts of Canada, and displays especially invasive behavior in the sagebrush steppe ecosystems, where it has been listed as noxious weed.<ref name=":16" /> ''B. tectorum'' often enters the site in an area that has been disturbed, and then quickly expands into the surrounding area through its rapid growth and prolific seed production.<ref name=":4">{{Cite journal|last1=Blank|first1=RR|last2=Morgan|first2=T|last3=Allen|first3=F|date=2015|title=Suppression of annual Bromus tectorum by perennial Agropyron cristatum: roles of soil nitrogen availability and biological soil space|journal=AoB Plants|volume=7|article-number=plv006|pmc=4340153|pmid=25603967|doi=10.1093/aobpla/plv006}}</ref>
The reduction of native plants and the increased fire frequency caused by ''B. tectorum'' prompted the United States Fish and Wildlife Service (USFWS) to examine if the greater sage-grouse needed to be listed as a threatened or endangered species due to habitat destruction. After the review was completed by the USFWS, Secretarial Order 3336 was signed with the goal of reducing the threat of rangeland fires and preserve habitat by reducing downy brome.
Research has shown that ecosystems with a healthy biological soil crust and native plant community are resistant to ''B. tectorum'' invasion.<ref name=":4" /><ref name=":3" /><ref name=":15" /> In areas where ''B. tectorum'' is invasive, treatments that are being researched/used by land managers to control ''B. tectorum'' include seeding of native plants and non-native bunchgrasses to outcompete ''B. tectorum,'' herbicides, and prescribed burns. The effectiveness of these treatments is tightly linked to the timing of the water availability at the site. With precipitation shortly after herbicide and seeding treatments increasing the success,<ref name=":17">{{Cite journal|last1=Sebastian|first1=DJ|last2=Sebastian|first2=JR|last3=Nissen|first3=SJ|last4=Beck|first4=KG|date=2016|title=A Potential New Herbicide for Invasive Annual Grass Control on Rangeland|journal=Rangeland Ecology & Management|volume=69|issue=3|pages=195–198|doi=10.1016/j.rama.2015.11.001|s2cid=87912010}}</ref><ref name=":18">{{Cite journal|last1=Bakker|first1=JD|last2=Wilson|first2=SD|last3=Christian|first3=JM|last4=Li|first4=X|last5=Ambrose|first5=LG|last6=Waddington|first6=J|s2cid=54752821|date=2003|title=Contingency of grassland restoration on year, site, and competition from introduced grasses|journal=Ecological Applications|volume=13|pages=137–153|doi=10.1890/1051-0761(2003)013[0137:cogroy]2.0.co;2}}</ref> and overall high precipitation increases ''B. tectorum'' growth, causing the treatment effects to be statistically insignificant.<ref name=":17" /> thumb|A sagebrush ecosystem in southern Idaho after ''B. tectorum'' has established
==Description== ''Bromus'' comes from a Greek word for a type of oat, and ''tectorum'' comes from the Latin possessive form of ''tector'', which means "of the overlayment (roof)".<ref name=":20">{{Cite journal|last1=Upadhyaya|first1=MK|last2=Turkington|first2=R|last3=McIlvride|first3=D|date=1986|title=THE BIOLOGY OF CANADIAN WEEDS. 75. Bromus tectorum|journal=Canadian Journal of Plant Science|volume=66|issue=3|pages=689–709|doi=10.4141/cjps86-091|doi-access=free}}</ref> ''Bromus tectorum'' is a winter annual grass native to Eurasia usually germinating in autumn, overwintering as a seedling, then flowering in the spring or early summer.<ref name=":0">{{Cite journal|last1=Duncan|first1=CA|last2=Jachetta|first2=JJ|last3=Brown|first3=ML|last4=Carrithers|first4=VF|last5=Clark|first5=JK|last6=Ditomaso|first6=JM|last7=Lym|first7=RG|last8=McDaniel|first8=KC|last9=Renz|first9=MJ|date=2004|title=Assessing the Economic, Environmental, and Societal Losses from Invasive Plants on Rangeland Wildlands|journal=Weed Technology|volume=18|pages=1411–1416|first10=PM|last10=Rice|doi=10.1614/0890-037x(2004)018[1411:ateeas]2.0.co;2|s2cid=86198927 }}</ref> ''B. tectorum'' may be mistaken for a bunchgrass because it may send up shoots that give it the appearance of having a rosette.<ref name=":19" /> In areas where it is growing in dense stands, the plant will not form this rosette-like structure, but instead is single-culmed (stalked).<ref name=":19" />
The stems are smooth (glabrous) and slender.<ref name=":20" /> The leaves are hairy (pubescent) and have sheaths that are separate except at the node, where the leaf attaches to the stem.<ref name=":20" /> It typically reaches {{convert|40|–|90|cm|in|abbr=on}} tall, though plants as small as {{convert|2.5|cm|in|abbr=on}} may produce seed.<ref name=":19" /> The flowers of ''B. tectorum'' are arranged on a drooping panicle with about 30 spikelets with awns and five to eight flowers each.<ref name=":20" /><ref name=":19" /> It is cleistogamous (self pollinating, non-opening flower) with no evident outcrossing.<ref>{{cite journal|last=Valliant|first=M. T.|author2=Mack, R. N.|author3=Novak, S. J.|date=July 2007|title=Introduction history and population genetics of the invasive grass ''Bromus tectorum'' (Poaceae) in Canada|journal=American Journal of Botany|volume=94|issue=7|pages=1156–1169|doi=10.3732/ajb.94.7.1156|pmid=21636483|doi-access=free}}</ref> ''B. tectorum'' has a fibrous root system with few main roots that do not reach more than a foot into the soil, and has wide-spreading lateral roots that make it efficient at absorbing moisture from light precipitation episodes.<ref name=":5">{{Cite journal|last1=Taylor|first1=K|last2=Brummer|first2=T|last3=Rew|first3=LJ|last4=Lavin|first4=M|last5=Maxwell|first5=BD|date=2014|title=Bromus tectorum Response to Fire Varies with Climate Conditions|url=https://scholarworks.montana.edu/xmlui/handle/1/8948|journal=Ecosystems|volume=17|issue=6|pages=960–973|doi=10.1007/s10021-014-9771-7|bibcode=2014Ecosy..17..960T|s2cid=2077322|archive-date=2020-07-27|access-date=2019-07-12|archive-url=https://web.archive.org/web/20200727050403/https://scholarworks.montana.edu/xmlui/handle/1/8948|url-status=live}}</ref> It has the capability to reduce soil moisture to the permanent wilting point (minimal soil moisture required for a plant not to wilt) to a depth of {{convert|70|cm|in|abbr=on}}, reducing competition from other species.<ref>{{cite journal|last=D'Antonio|first=C M|author2=Vitousek, P M|s2cid=86250355|title=Biological Invasions by Exotic Grasses, the Grass/Fire Cycle, and Global Change|journal=Annual Review of Ecology and Systematics|date=November 1992|volume=23|issue=1|pages=63–87|doi=10.1146/annurev.es.23.110192.000431|jstor=2097282|url=https://tede.ufrrj.br/jspui/handle/jspui/4237|archive-date=2023-08-28|access-date=2023-01-21|archive-url=https://web.archive.org/web/20230828142006/https://tede.ufrrj.br/jspui/handle/jspui/4237|url-status=live}}</ref>
===Seeds=== The seeds ripen and disperse in the late spring and early summer.<ref name=":19" /> They are dispersed by wind, small rodents, or attachment to animal fur, within a week of maturity.<ref name=":19" /> They are also moved as a contaminant in hay, grain, straw, and machinery.<ref name=":19" /> ''B. tectorum'' is an abundant seed producer, with a potential in excess of 300 seeds per plant; seed production per plant is dependent on plant density. Under optimal conditions, ''B. tectorum'' may produce 450 kg of seed per hectare (400 pounds per acre) with about 330,000 seeds/kg (150,000 seeds/pound).<ref name=":19" /> As the seed of ''B. tectorum'' ripen, the plant turns from green to purple to straw-colored.<ref name=":19" />
''B. tectorum'' seeds demonstrate rapid germination as soon as the seed lands in appropriate conditions.<ref name=":19" /> If winter rainfall is limiting and germination is inhibited, but spring moisture is adequate, then seeds will germinate in the spring, and the plants will flower that summer.<ref name=":19" /> The seeds maintain high viability (ability to germinate under optimal conditions) in dry storage, lasting over 11 years. In the field, under buried conditions, seeds lose their viability in 2–5 years. Seeds can withstand high soil temperatures, and the primary limit to germination is inadequate moisture. Germination is best in the dark or diffuse light. They germinate most quickly when covered with soil, but do not need to be in contact with bare soil. Some leaf litter cover generally improves germination and establishment of seedlings. Seedlings emerge rapidly from the top 2.5 cm (1 in) of soil, and a few plants emerge from depths of 8 cm (3 in), but not from seeds 10 cm (4 in) below the surface.<ref>{{cite web|title=Bromus tectorum|url=http://www.fs.fed.us/database/feis/plants/graminoid/brotec/all.html|work=Fire Effects Information System|publisher=USDA Forest Service|access-date=30 September 2012|archive-date=2 October 2012|archive-url=https://web.archive.org/web/20121002175422/http://www.fs.fed.us/database/feis/plants/graminoid/brotec/all.html|url-status=live}}</ref>
==Taxonomy== The scientific name ''Bromus tectorum'' was given to the species by Carl Linnaeus in ''Species Plantarum'', which was published in 1753. According to Plants of the World Online, it has 57 synonyms, including four that were reclassifications into another genus. It has no accepted varieties.<ref name="POWO">{{cite POWO |id=394163-1 |title=''Bromus tectorum'' L. |access-date=13 November 2024}}</ref>
==Habitat== ''B. tectorum'' grows in many different climates. It is found primarily in the {{convert|150|–|560|mm|in|abbr=on}} precipitation zone.<ref name=":19" /> It can grow in almost any type of soil, including B and C horizons of eroded areas and areas low in nitrogen.<ref name=":19" /> ''B. tectorum'' is quick to colonize disturbed areas.<ref name=":19">{{Cite journal|last1=Klemmedson|first1=JO|last2=Smith|first2=JG|date=1964|title=Cheatgrass (Bromus Tectorum L.)|journal=Botanical Review|volume=30|issue=2|pages=226–262|doi=10.1007/bf02858603|bibcode=1964BotRv..30..226K |s2cid=43876700}}</ref> It is most often found on coarse-textured soils and does not grow well on heavy, dry, and/or saline soils. It grows in a relatively narrow range of soil temperatures; growth starts at {{convert|2.0|-|3.5|°C|°F}} and slows when temperatures exceed {{convert|15|°C|°F}}.<ref>{{cite web|url=http://jan.ucc.nau.edu/~plants-c/forage/chea.shtml|title=Forage Grasses of the Colorado Plateau Cold Desert|publisher=Northern Arizona University|access-date=30 September 2012|archive-date=11 May 2015|archive-url=https://web.archive.org/web/20150511005623/http://jan.ucc.nau.edu/~plants-c/forage/chea.shtml}}</ref>
==Status as an exotic weed== thumb|left|Cheatgrass in Elko, Nevada ''B. tectorum'' has been introduced to southern Russia, west central Asia, North America, Japan, South Africa, Australia, New Zealand, Iceland, and Greenland.<ref name=":16" /> It was first found in the United States (where it is known as downy brome or cheatgrass<ref>How To Get Rid Of Cheatgrass? [https://padoutdoor.com/how-to-get-rid-of-cheatgrass/ "Cheatgrass"] {{Webarchive|url=https://web.archive.org/web/20200104045155/https://padoutdoor.com/how-to-get-rid-of-cheatgrass/ |date=2020-01-04 }}, Pad Outdoor</ref>) in 1861 in New York and Pennsylvania, and by 1928, ''B. tectorum'' had spread to all parts of the United States (including Hawaii and Alaska), except for Florida and portions of Alabama, Georgia, and South Carolina. ''B. tectorum'' is most abundant in the Great Basin and Columbia Basin, and is part of the introduced species that replaced California native plants in the California Floristic Province's grasslands and other habitats.<ref>{{cite web|title=Invasive Plant Inventory|url=http://www.cal-ipc.org/ip/inventory/pdf/Inventory2006.pdf|publisher=California Invasive Plant Council|year=2006|access-date=2012-09-30|archive-url=https://web.archive.org/web/20080510142427/http://www.cal-ipc.org/ip/inventory/pdf/Inventory2006.pdf|archive-date=2008-05-10}}</ref> In Canada, ''B. tectorum'' has been identified as an invasive weed in all provinces, and is extremely prevalent in Alberta and British Columbia .<ref name=":20" /><ref>{{Cite web|url=https://www.cabi.org/isc/datasheet/10036|title=Bromus tectorum (downy brome)|website=www.cabi.org|access-date=2017-11-29|archive-date=2017-12-01|archive-url=https://web.archive.org/web/20171201032256/https://www.cabi.org/isc/datasheet/10036|url-status=live}}</ref>
===Invasive species=== In the US, it grows on rangelands, pastures, prairies, fields, waste areas, eroded sites, and roadsides. It is much reviled by ranchers and land managers. ''B. tectorum'' seeds are also a critical portion of the diet of the chukar and grey partridge, which have been introduced to the US. Intensive sheep browsing of ''B. tectorum'' in early spring has been used as a fire fuels-reduction strategy in the hills adjacent to Carson City, Nevada.<ref>{{cite news|title=Forest Service Use Sheep to Reduce Fire Hazard|url=http://www.fs.usda.gov/detail/htnf/news-events/?cid=STELPRDB5292546|archive-url=https://web.archive.org/web/20131227224814/http://www.fs.usda.gov/detail/htnf/news-events/?cid=STELPRDB5292546|archive-date=December 27, 2013|newspaper=USDA Forest Service|date=April 12, 2011}}</ref> Because of rangeland fires and the invasion of ''B. tectorum'', in 2010. the United States Fish and Wildlife Service (USFWS) considered the possibility of extending the protections of the Endangered Species Act to the greater sage-grouse.<ref name=":1">{{Cite journal|last=Jewel|first=Sally|date=2015|title=Secretarial Order 3336|url=https://www.forestsandrangelands.gov/rangeland/documents/SecretarialOrder3336.pdf|journal=Department of the Interior}}</ref> The primary focus of Secretarial Order 3336, signed in 2015 in response to the USFWS status review, was to reduce threats to greater sage-grouse habitat by reducing the frequency and severity of rangeland fire.<ref name=":1" /> Specifically, Secretarial Order 3336 focused on how reducing ''B. tectorum'' could reduce the frequency and extent of rangeland fires. Since the review of the status of the greater sage-grouse by the USFWS in 2010 and the implementation Secretarial Order 3336, the bulk of the research focusing on ''B. tectorum'' ecology and control has been completed.
''Bromus tectorum'' has demonstrated a quantitative and qualitative response to recent and near-term changes in the concentration of atmospheric carbon dioxide. Laboratory experiments have shown that above-ground biomass increased 1.5–2.7 gram per plant for every 10 part per million (ppm) increase above the 270 ppm preindustrial baseline.<ref name="ziska05" /> On the qualitative side, rising carbon dioxide decreased the digestibility and potential decomposition of ''B. tectorum''. In addition to stimulation of biomass, rising carbon dioxide may also increase the above-ground retention of ''B. tectorum'' biomass by decreasing removal by animals or bacteria.<ref name="ziska05" /> Ongoing increases in atmospheric carbon dioxide may contribute significantly to ''B. tectorum'' productivity and fuel load, with subsequent effects on wildfire frequency and intensity.<ref name=ziska05/><ref name=natcons08/>
''B. tectorum'' has been shown to benefit from endophytic colonization by morels (''Morchella sextelata'', ''M. snyderi'') in western North America.<ref name=baynes12/>
=== Treatment options ===
==== Seeding ==== The availability of native seed always is a limiting factor in restoration of sagebrush ecosystems after a rangeland fire. Little is understood about the germination requirements of native species. This lack of understanding is complicated by the episodic nature of establishment in arid grasslands.<ref name=":18" /><ref>{{Cite journal|last1=Elseroad|first1=AC|last2=Rudd|first2=NT|date=2011|title=Can Imazapic Increase Native Species Abundance in Cheatgrass (Bromus tectorum) Invaded Native Plant Communities?|journal=Rangeland Ecology & Management|volume=64|issue=6|pages=641–648|doi=10.2111/rem-d-10-00163.1|hdl=10150/642911|s2cid=55840671|hdl-access=free}}</ref> In response to the limited availability of native seed, land managers have been seeding ''Agropyron cristatum,'' a perennial bunchgrass native to Russia and Asia. The use of seeding another non-native to control an exotic, problem species is called assisted succession.<ref name=":8">{{Cite journal|last1=Cox|first1=RD|last2=Anderson|first2=VJ|date=2004|title=Increasing Native Diversity of Cheatgrass-Dominated Rangeland through Assisted|journal=Journal of Rangeland Management|volume=57|issue=2|pages=203–210|doi=10.2307/4003920|jstor=4003920|hdl=10150/643523|hdl-access=free}}</ref> ''A. cristatum'' is much easier to establish than the native perennials and has been shown to be a strong competitor of ''B. tectorum.''<ref name=":4" /><ref name=":9">{{Cite journal|last1=Davies|first1=KW|last2=Boyd|first2=CS|last3=Nafus|first3=AM|date=2013|title=Restoring the Sagebrush Component in Crested Wheatgrass–Dominated Communities|journal=Rangeland Ecology & Management|volume=66|issue=4|pages=472–478|doi=10.2111/rem-d-12-00145.1|hdl=10150/642734|s2cid=59127764|hdl-access=free}}</ref>
However, ''A. cristatum'' can exhibit invasive behavior and is a strong competitor of native perennials.<ref name=":4" /><ref>{{Cite journal|last1=Brummer|first1=TJ|last2=Taylor|first2=KT|last3=Rotella|first3=J|last4=Maxwell|first4=BD|last5=Rew|first5=LJ|last6=LAvin|first6=M|date=2016|title=Drivers of Bromus tectorum Abundance in the Western North American Sagebrush Steppe|url=https://scholarworks.montana.edu/xmlui/handle/1/12644|journal=Ecosystems|volume=19|issue=6|pages=986–1000|doi=10.1007/s10021-016-9980-3|bibcode=2016Ecosy..19..986B|s2cid=15485664|archive-date=2020-07-27|access-date=2019-07-12|archive-url=https://web.archive.org/web/20200727051118/https://scholarworks.montana.edu/xmlui/handle/1/12644|url-status=live}}</ref> The reason it is used, regardless of its invasive behavior, is because it restores some function to a perennial grassland. ''A. cristatum'' is resistant to wildfire and it is suitable forage for cattle and wildlife,<ref name=":8" /> but the intensive control that would be needed to establish a native plant community in an ''A. cristatum'' monoculture would cause disturbances that would also increase the invasive species it was planted to outcompete.<ref name=":9" /> An alternative to using ''A. cristatum'' as a placeholder species in assisted succession is to establish it alongside foundation species such as sagebrush. Adding sagebrush would diversify the ecosystem and provide habitat for sagebrush obligates,<ref name=":9" /> but this would mean accepting the possibility that the native plant community may never establish.
==== Herbicides ==== A majority of research in 2011-2017 has focused on the use of herbicides to control ''B. tectorum'' and their effect on native plant communities. When using herbicides to suppress winter annual grasses, the two most important factors that influence success are application timing and residual soil activity. Application timing is split into three main categories - pre-emergence in the fall before ''B. tectorum'' germinates, early postemergence in early spring when ''B. tectorum'' is a seedling, and late postemergence in late spring after ''B. tectorum'' is mature.
To be most effective, postemergence application needs to be done as late in the spring as possible to ensure that the herbicide treatment hits the majority of the ''B. tectorum'' population.<ref name=":10">{{Cite journal|last1=Sebastian|first1=DJ|last2=Nissen|first2=SJ|last3=Sebastian|first3=JR|last4=Beck|first4=KG|date=2017|title=Seed Bank Depletion: The Key to Long-Term Downy Brome ( Bromus tectorum L.) Management|journal=Rangeland Ecology & Management|volume=70|issue=4|pages=477–483|doi=10.1016/j.rama.2016.12.003|s2cid=90622245|hdl=10150/667449|hdl-access=free}}</ref> However, the late application puts the native perennial vegetation at risk, as they may be coming out of dormancy.<ref name=":10" /> Herbicides with no residual soil activity are not generally used because they are only effective in the year of application. If the herbicide has no residual soil activity, the herbicide must be applied postemergence in the early spring, but pre-emergence application is preferred because it is less likely to harm the native vegetation.
Studies have suggested that herbicide usage may select for warm-season grasses and decrease the abundance of cool-season grasses.<ref name=":10" /> Five main herbicides are used to control ''B. tectorum'' - imazapic, rimsulfuron, tebuthiuron, glyphosate, and indaziflam. The bulk of the recent research, though, has been done on glyphosate, indaziflam, and imazapic.
Glyphosate has no residual soil activity and must be used postemergence, which limits its control of ''B. tectorum'' to one year. For effective control, it must be applied to the same area for more than five years to get ahead of seed production to prevent recolonization.<ref name=":10" /> Imazapic is the herbicide most widely used by land managers for ''B. tectorum'' control. Of the herbicides listed, it is also the most commonly studied. Imazapic is preferred because it can be applied both pre- and postemergence, is approved for rangeland use, and has residual soil activity that allows for one- to two-year control.<ref name=":11">{{Cite journal|last1=Sebastian|first1=DJ|last2=Nissen|first2=SJ|last3=De|first3=J|last4=Rodrigues|first4=S|date=2016|title=Pre-emergence Control of Six Invasive Winter Annual Grasses with Imazapic and Indaziflam|journal=Invasive Plant Science and Management|volume=9|pages=308–316}}</ref> Indaziflam is one of the newest herbicides, licensed in 2010. It has a residual soil activity of 2–3 years. and it is also useful against many other invasive grasses. Not only does it reduce the abundance and biomass of ''B. tectorum'', but it also reduces the highly flammable litter that ''B. tectorum'' produces.<ref name=":17" /> In early trials, it has consistently outcompeted imazapic.<ref name=":11" /> As of 2017, indaziflam has not been approved for use outside of residential and commercial properties.
==== Prescribed burning ==== Prescribed burning alone reduces ''B. tectorum'' biomass for about two years.<ref name=":13">{{Cite journal|last1=Kessler|first1=KC|last2=Nissen|first2=SJ|last3=Meiman|first3=PJ|last4=Beck|first4=KG|date=2015|title=Litter Reduction by Prescribed Burning Can Extend Downy Brome Control|url=https://mountainscholar.org/bitstream/10217/88563/1/Kessler_colostate_0053N_12741.pdf|journal=Rangeland Ecology & Management|volume=68|issue=4|pages=367–374|doi=10.1016/j.rama.2015.05.006|hdl=10217/88563|s2cid=53650291|hdl-access=free}}</ref> The goal of a prescribed burn in a ''B. tectorum''-invaded area is to remove the highly flammable plant litter in a controlled manner. The timing of prescribed burns can affect the variety and amount of returning vegetation. Spring burns may result in a significant reduction of native vegetation, but fall burns have been shown to increase species richness.<ref name=":12">{{Cite journal|last1=Brockway|first1=DG|last2=Gatewood|first2=RG|last3=Paris|first3=RB|s2cid=15695486|date=2002|title=Restoring fire as an ecological process in shortgrass prairie ecosystems: initial effects of prescribed burning during the dormant and growing seasons|journal=Journal of Environmental Management|volume=65|issue=2|pages=135–152|doi=10.1006/jema.2002.0540|pmid=12197076}}</ref> Fall burns may also promote select grasses and fire-resilient plants.<ref name=":12" /> Another control for ''B. tectorum'' burns is consideration for the densities and fire adaptations of nearby foliage.<ref name=":21">{{Cite journal|last1=Baynes|first1=Melissa|last2=Newcombe|first2=George|last3=Dixon|first3=Linley|last4=Castlebury|first4=Lisa|last5=O'Donnell|first5=Kerry|title=A novel plant–fungal mutualism associated with fire|journal=Fungal Biology|language=en|volume=116|issue=1|pages=133–144|doi=10.1016/j.funbio.2011.10.008|pmid=22208608|year=2012}}</ref> In some cases, the existence of adjacent morchella can trigger mutual relationships such as increased fiber, and by extension, fuels that nurture the return of cheatgrass.<ref name=":21" /> Similarly, when densely packed conifers begin infilling sagebrush communities, the understory perennial vegetation is reduced; when these areas are burned, the succession is dominated by ''B. tectorum'' in favor of taller grasses, making burns situationally inferior.<ref>{{Cite journal|last1=Williams|first1=Rachel E.|last2=Roundy|first2=Bruce A.|last3=Hulet|first3=April|last4=Miller|first4=Richard F.|last5=Tausch|first5=Robin J.|last6=Chambers|first6=Jeanne C.|last7=Matthews|first7=Jeffrey|last8=Schooley|first8=Robert|last9=Eggett|first9=Dennis|title=Pretreatment Tree Dominance and Conifer Removal Treatments Affect Plant Succession in Sagebrush Communities|journal=Rangeland Ecology & Management|language=en|volume=70|issue=6|pages=759–773|doi=10.1016/j.rama.2017.05.007|year=2017|s2cid=90945715|hdl=10150/667481|hdl-access=free}}</ref>
==== Water availability and treatment success ==== Water availably has a large impact on the success of ''B. tectorum'' treatments. In years of high precipitation, ''B. tectorum'' recruitment and biomass will increase and may render the treatment ineffective.<ref name=":13" /> In most long-term ''B. tectorum'' studies. precipitation differences between years are speculated to be the cause of variation in effectiveness.<ref name=":13" /><ref name=":14">{{Cite journal|last1=Munson|first1=SM|last2=Long|first2=AL|last3=Decker|first3=C|last4=Johnson|first4=KA|last5=Walsh|first5=K|last6=Miller|first6=ME|date=2015|title=Repeated landscape-scale treatments following fire suppress a non-native annual grass and promote recovery of native perennial vegetation|journal=Biological Invasions|volume=17|issue=6|pages=1915–1926|doi=10.1007/s10530-015-0847-x|bibcode=2015BiInv..17.1915M |s2cid=15819903}}</ref> However, well-timed precipitation after herbicide application can increase the amount of herbicide absorbed into the soil. When herbicide is applied to an area and ''B. tectorum'' litter is on the ground, much of the herbicide is absorbed into the litter and some adheres to the litter. The litter creates a blanket that ''B. tectorum'' can germinate under even after herbicide application.<ref name=":13" />If rain occurs shortly after herbicide application, then some of the herbicide trapped in the litter can be released and work into the soil.<ref name=":13" /> The rain may also allow native species to overcome herbicide impacts.<ref name=":14" /> Increased precipitation in early spring may increase the success of seeding by increasing the germination rate of native grasses and remove ''B. tectorum'''s competitive advantage.<ref name=":8" />thumb|Invasive ''B. tectorum'' on Spruce Mountain, Nevada
=== Characteristics of a resistant native community === A positive correlation is seen between native vegetation communities and biological soil crust (BSC).<ref name=":2">{{Cite journal|last1=Dettweiler-Robinson|first1=E|last2=Bakker|first2=JD|last3=Grace|first3=JB|date=2013|title=Controls of biological soil crust cover and composition shift with succession in sagebrush shrub-steppe|journal=Journal of Arid Environments|volume=94|pages=96–104|doi=10.1016/j.jaridenv.2013.01.013|bibcode=2013JArEn..94...96D|s2cid=83802623}}</ref> BSC is composed of cyanobacteria, algae, lichens, and mosses living on the soil. In arid regions, BSCs colonize the spaces between plants, increase the biodiversity of the area, are often the dominant cover, and are vital in ecosystem function.<ref name=":3">{{Cite journal|last1=Belnap|first1=J|last2=Phillips|first2=SL|last3=Troxler|first3=T|date=2006|title=Soil lichen and moss cover and species richness can be highly dynamic: The effects of invasion by the annual exotic grass Bromus tectorum, precipitation, and temperature on biological soil crusts in SE Utah|journal=Applied Soil Ecology|volume=32|issue=1|pages=63–76|doi=10.1016/j.apsoil.2004.12.010|bibcode=2006AppSE..32...63B}}</ref> In addition to providing erosion control, BSC is vital for nutrient cycling and carbon fixation.<ref name=":3" /> Fire and trampling by cattle are the major threats to the BSC communities, and once disturbed, decades or even centuries may be needed for BSC to reform.<ref name=":2" /><ref name=":3" /> A decline in the health of the BSC community serves as an early-warning indicator for ''B.s tectorum'' invasion. If the BSC community is healthy, then it will impede ''B. tectorum'' germination and reduce the likelihood of invasion.<ref name=":3" /><ref name=":15">{{Cite journal|last1=Song|first1=G|last2=Li|first2=X|last3=Hui|first3=R|date=2017|title=Effect of biological soil crusts on seed germination and growth of an exotic and two native plant species in an arid ecosystem|journal=PLOS ONE|volume=12|issue=10|article-number=e0185839|doi=10.1371/journal.pone.0185839|pmid=28977018|pmc=5627943|bibcode=2017PLoSO..1285839S|doi-access=free}}</ref> If a disturbance in the biological soil crust occurs, though, and ''B. tectorum'' is able to establish, then it will impede the recovery of the BSC community.<ref name=":2" />
Native perennial grasses have roots that often reach four feet into the soil. These roots provide organic matter, which feeds the soil organisms that assist in water and nutrient cycling in arid ecosystems and improve soil quality.<ref name=":6">{{Cite journal|last1=Thill|first1=DC|last2=Beck|first2=KG|last3=Callihan|first3=RH|date=1983|title=The Biology of Downy Brome (Bromus tectorum)|journal=Weed Science|volume=32|pages=7–127|doi=10.1017/S0043174500060185|s2cid=88235742 }}</ref> ''Bromus tectorum'' has a shallow, spreading root system, which makes it much more efficient at absorbing moisture from light precipitation episodes and disrupts nutrient cycling.<ref name=":5" /><ref name=":6" /> Several studies have shown that native plant biomass, especially that of bunchgrasses, negatively affects ''B. tectorum'' cover and biomass,<ref name=":4" /><ref>{{Cite journal|last1=Baughman|first1=OW|last2=Meyer|first2=SE|last3=Aanderud|first3=ZT|last4=Leger|first4=EA|date=2016|title=Cheatgrass die-offs as an opportunity for restoration in the Great Basin, USA: Will local or commercial native plants succeed where exotic invaders fail|journal=Journal of Arid Environments|volume=124|pages=193–204|doi=10.1016/j.jaridenv.2015.08.011|bibcode=2016JArEn.124..193B|doi-access=free}}</ref><ref>{{Cite journal|last1=Prevéy|first1=JS|last2=Seastedt|first2=TR|date=2015|title=Effects of precipitation change and neighboring plants on population dynamics of Bromus tectorum.|url=https://www.dora.lib4ri.ch/wsl/islandora/object/wsl%3A5404|journal=Oecologia|volume=179|issue=3|pages=765–775|doi=10.1007/s00442-015-3398-z|pmid=26227366|bibcode=2015Oecol.179..765P|s2cid=15887595|archive-date=2024-12-05|access-date=2020-08-30|archive-url=https://web.archive.org/web/20241205115124/https://www.dora.lib4ri.ch/wsl/islandora/object/wsl%3A5404|url-status=live}}</ref> suggesting that a diverse native perennial community is more resistant to ''B. tectorum'' invasion.
Studies have identified ''Poa secunda, Pseudoroegneria spicata,'' and ''Achnatherum thurberianum'' as key grasses for ''B. tectorum'' resistance.<ref name=":7">{{Cite journal|last1=Leffler|first1=AJ|last2=Monaco|first2=TA|last3=James|first3=JJ|last4=Sheley|first4=RL|date=2016|title=Importance of soil and plant community disturbance for establishment of Bromus tectorum in the Intermountain West, USA|journal=NeoBiota|volume=30|pages=111–125|doi=10.3897/neobiota.30.7119|doi-access=free}}</ref><ref>{{Cite journal|last1=Reisner|first1=MD|last2=Grace|first2=JB|last3=Pyke|first3=DA|last4=Doescher|first4=PS|date=2013|title=Conditions favoring Bromus tectorum dominance of endangered sagebrush steppe ecosystems|journal=Journal of Applied Ecology|volume=50|issue=4|pages=1039–1049|doi=10.1111/1365-2664.12097|s2cid=73573936 |doi-access=free|bibcode=2013JApEc..50.1039R }}</ref> The life strategies of these three grasses differ in such a way that they provide constant interaction and competition with ''B. tectorum.''<ref name=":7" /> ''P. spicata'' and ''A. thurberianum'' are deep rooted and complete most of their growth in the late spring, and ''P. secunda'' is shallow rooted and completes most of its growth in the late winter and early spring.<ref name=":7" />
Perennial grass ecosystems are less prone to burning. ''B. tectorum'' has been historically thought to create a positive feedback loop. However, Taylor, et al. (2014) suggest that fire alone does not promote ''B. tectorum.''<ref name=":5" /> If an area burns, the ''B. tectorum'' cover and biomass do not increase as was once thought, but recover to previous levels.<ref name=":5" /> Increased fires, because of ''B. tectorum'', may serve to maintain, not increase, the ''B. tectorum'' population by preventing the natives from establishing.
==References== {{Reflist|refs=
<ref name=ziska05>{{citation | doi = 10.1111/j.1365-2486.2005.00992.x | url = https://naldc-legacy.nal.usda.gov/naldc/download.xhtml?id=8709&content=PDF | title = The impact of recent increases in atmospheric CO<sub>2</sub> on biomass production and vegetative retention of cheatgrass (''B. tectorum''): Implications for fire disturbance. | last1 = Ziska | first1 = L.H. | last2 = Reeves III | first2 = J.B. | last3 = Blank | first3 = R.R. | year = 2005 | journal = Global Change Biology | volume = 11 | issue = 8 | pages = 1325–1332 | s2cid = 84746686 | access-date = 2018-12-29 | archive-date = 2020-07-27 | archive-url = https://web.archive.org/web/20200727051539/https://naldc-legacy.nal.usda.gov/naldc/download.xhtml?id=8709&content=PDF | url-access = subscription }}</ref> <ref name=natcons08>{{citation | url = http://www.tncfire.org/crosscutting_fandi.htm | title = Global Fire Initiative: Fire and Invasives | publisher = The Nature Conservancy | access-date = 2008-12-12 | archive-url = https://web.archive.org/web/20090412054533/http://www.tncfire.org/crosscutting_fandi.htm | archive-date = 2009-04-12 }}</ref>
<ref name=baynes12>{{cite journal| author=Baynes, M. A.| author2=Newcombe, G.| author3=Dixon, L.| author4=Castlebury, L.| author5=O'Donnell, K.| name-list-style=amp| title=A novel plant-fungal mutualism associated with fire| journal=Fungal Biology| date=January 2012| volume=116| number=1| pages=133–144| doi=10.1016/j.funbio.2011.10.008| pmid=22208608| url=http://www.fs.fed.us/rm/pubs_other/rmrs_2012_baynes_m001.pdf| archive-date=2014-11-06| access-date=2012-04-13| archive-url=https://web.archive.org/web/20141106032151/http://www.fs.fed.us/rm/pubs_other/rmrs_2012_baynes_m001.pdf| url-status=live}}</ref>
}}
==External links== {{Commons category|Bromus tectorum}} * [https://web.archive.org/web/20060923103823/http://www.npwrc.usgs.gov/resource/plants/exoticab/scotbrot.htm npwrc.usgs.gov: USGS profile] * [http://www.plants.usda.gov/java/profile?symbol=BRTE plants.usda.gov: USDA Plants Profile — ''Bromus tectorum'' (Downy Brome)] {{Webarchive|url=https://web.archive.org/web/20120601051129/http://plants.usda.gov/java/profile?symbol=BRTE |date=2012-06-01 }} * [https://www.invasivespeciesinfo.gov/terrestrial/plants/downy-brome Species Profile- Downy Brome (''Bromus tectorum'')], National Invasive Species Information Center, United States National Agricultural Library — ''lists general information and resources for Downy Brome.'' * [https://www.nytimes.com/2012/07/31/science/earth/a-fungus-emerges-as-weapon-against-cheatgrass.html ''Out West, 'Black Fingers of Death' Offer Hope Against an Invader''] July 30, 2012 The New York Times * https://www.forestsandrangelands.gov/rangeland/documents/SecretarialOrder3336.pdf * https://www.sagegrouseinitiative.com/roots/ * [https://www.fs.fed.us/database/feis/plants/graminoid/brotec/all.html Fire Effects Information System], United States Forest Service * [http://extension.colostate.edu/docs/pubs/natres/06310.pdf Cheatgrass and Wildfire], Colorado State University * [https://www.cabi.org/isc/datasheet/10036 CABI Invasive Species Compendium] * {{PFAF|Bromus tectorum}}
{{Taxonbar|from=Q164128}} {{Authority control}}
tectorum Category:Bunchgrasses of Africa Category:Bunchgrasses of Asia Category:Bunchgrasses of Europe Category:Flora of Lebanon Category:Plants described in 1753 Category:Botanical taxa named by Carl Linnaeus Category:Grasses of Lebanon