B. tectorum has been introduced to southern
Russia, west central Asia, North America,
Japan,
South Africa, Australia,
New Zealand,
Iceland, and
Greenland.) 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. In Canada,
B. tectorum has been identified as an invasive weed in all provinces, and is extremely prevalent in Alberta and British Columbia .
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. 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. 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. 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.
A. cristatum is much easier to establish than the native perennials and has been shown to be a strong competitor of
B. tectorum. However,
A. cristatum can exhibit invasive behavior and is a strong competitor of native perennials. 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, However, the late application puts the native perennial vegetation at risk, as they may be coming out of
dormancy. 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. 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. Fall burns may also promote select grasses and fire-resilient plants. 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.
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. 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. 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. In addition to providing erosion control, BSC is vital for
nutrient cycling and
carbon fixation. 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.
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. 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. The life strategies of these three grasses differ in such a way that they provide constant interaction and competition with
B. tectorum. 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. 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. If an area burns, the
B. tectorum cover and
biomass do not increase as was once thought, but recover to previous levels. Increased fires, because of
B. tectorum, may serve to maintain, not increase, the
B. tectorum population by preventing the natives from establishing. ==References==