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Mechanical control on rangelands is defined as "the use of a tool to remove or destroy above and/or below ground plant material." There are numerous different ways to treat rangeland mechanically, and many considerations (e.g., species, sprouting ability, weather, topography, soil depth and type) for choosing the appropriate control. The form of mechanical control that is best suited to a particular situation depends on: 

Mechanical tools commonly employed to manage rangeland vegetation/brush: 

Grubbers. The use of a sharp, often U-shaped blades attached to a tractor, front-end loader, or excavator depending on needs and treatment area for severing brush roots below ground. The depth below ground and position where to sever in the root system for successful control can vary by brush species. Grubbing is generally effective at controlling and/or killing resprouting brush species (e.g., mesquite and catclaw acacia) in areas up to 100 to 250 tress/acre (Wiedemann, 1997). The machine size and tire type (e.g., rubber, tracks, off-road) should be considered during the planning process factoring in brush size and type, cost/acre, soil types, and sensitive cultural resources.  

Masticators. Mastication is a common technique in forest, woodland, and shrubland management, and is the process of shredding, grinding, or chopping trees/shrubs with specialized attachments most often on a skid steer loader or excavator. Mulched brush material falls onto the ground surface and can help to improve soil health and fertility via decomposition in more mesic environments. In fire-prone ecosystems, mastication is used for fuel management in reducing ladder fuels and slow the spread of wildfires. This control method would not be effective on resprouting brush species (e.g., mesquite, acacia, some Junipers).  

For detailed information including decision trees on masticator types for general management goals, see US Forest Service General Technical Report RMRS-GTR-381.

Chains. The use of chains (e.g., anchor or Ely chain) to alter rangeland vegetation is called "chaining". Chaining involves pulling a large chain, most often a section of marine anchor chain, between 2 tractors. Vegetation is either pulled out of the ground by the roots or broken off at ground level. Chaining is most effective on shrubs/trees as herbaceous material regenerates and recovers quickly following treatment. Chaining provides relatively quick results and allows large areas to be treated at a relatively low cost, however, it causes substantial soil disturbance that can lead to compaction or erosion. Trees or shrubs that resprout may require additional or follow-up treatment with herbicides or fire to actually kill the plants (see Integrated Brush Management Systems). 

Root Plows. A root plow is a heavy-duty, V-shaped blade that is pulled behind a tractor to sever the roots of trees/shrubs below the bud zone. Root plowing can control up to 90% of target plants when properly implemented; i.e. the blade is at the correct depth and it is done at the proper time of year. Unfortunately, root plowing also kills most herbaceous plants on site, especially when operating in areas of high tree density. Selective plowing can be used to sculpt the vegetation, improve wildlife habitat and enhance multiple use values on rangeland with fertile soils. 

Mowers. Mowing is generally applied to herbaceous vegetation to immediately remove biomass from an area. It can be used to prevent seed production in patches of invasive weeds or to increase visibility and ease of travel such as along highways or in recreation areas. Mowing causes minimal soil disturbance but does not necessarily kill the target plant and may cause harm to desirable vegetation as well. Repeated mowing may reduce resprouting trees and brush, however, it is most often combined with other treatments to achieve maximum control. Mowing is not suitable for rocky ground or areas with dense stands of large diameter trees. 

Rakes. Rakes are often used after chaining or root plowing to smooth and prep the site for revegetation or range seeding. Specially designed rakes allow for  brush to be stacked with minimal soil in piles. 

Range seeding, or rangeland seeding, is a tool for improving, developing, or altering a site's existing plant community through the application of seed. Seeding is typically done at the beginning or prior to the regional rainy season for restoring a portion of degraded rangeland to meet a specific management goal (e.g., forage production, erosion control). A site may be “prepped” prior to seeding by targeted grazing of weeds, amending soils with nutrients and microbes, removing invasive plants, or disking/tilling to rough up the soil surface to increase potential seed germination. Following a brush management treatment, range seeding can be used if seed sources of the desirable plant community has been lost, or in very low abundance. Areas impacted by wildfire or treated with prescribed burning can also be improved with range seeding. It is suggested to use a regionally appropriate and diverse seed mix of multiple grass, forb, and shrub species that are active in multiple different seasons (e.g., summer and spring) and have a variety of flower colors and sizes to maximize biodiversity and restoration success. There are many potential benefits for implementing range seeding including increased forage production, erosion control, wildlife and pollinator habitat, improving soil health, and invasive plant species resistance.

Most common seeding methods are broadcast and drill seeding. Broadcast seeding is a method where seed is spread and applied directly to the ground typically with a tractor, UTV/ATV, or by hand. In large area applications, broadcast seeding is used where terrain is too steep or rocky for drill seeding. Drill seeding uses machinery, often termed a “rangeland drill”, to place the seed in the soil at a determined depth in small furrows. Depth and rate of seeding will depend on the chosen species in the mix, where germination success can vary widely at depth between forbs, grasses, and shrubs. A bulking agent like rice hulls added to a seed mix can be used to account for differences in seed sizes and weights for impeding separation and aiding the even distribution of seeds.

Fertile islands and seedballs are also potential range seeding options, especially in more arid regions. Fertile Islands are a technique to improve seeding and germination success by selecting specific locations within a pasture (e.g., under shrub canopies, depressions, and rocky areas) with an increased potential for soil moisture accumulation and/or protection from insects and animals that can consume the seeds or seedlings. After seedling establishment, fertile islands can provide a future seed source for spread beyond the original seeded area. Seed balls are, as the name implies, ball-like structures of the seed mix combined with clay, compost, and water. The dry seed balls are spread in a treatment area and remain until sufficient rainfall occurs to remove the clay, where the seed makes soil contact during high soil moisture conditions with added nutrients from the compost. Seed balls can be relatively cheap to make and help deter loss of seed to wind and ants. 

Targeted grazing focuses specifically on vegetation management goals, as compared to solely livestock production. Managing vegetation occurs via targeted grazing with the application of specific type of livestock (e.g., cattle, sheep, or goats) to accomplish one or multiple vegetation goals (Launchbaugh and Walker, 2006). To meet a set goal, many factors come into play including the type and number of animals, distribution of livestock across the landscape, season and frequency of grazing/browsing, and the duration of grazing. 

There are many potential applications of targeted grazing, but frequently implemented for the management of invasive/noxious weeds like leafy spurge, yellow star thistle, and spotted knapweed, just to name a few. Additionally, appropriate timing, intensity, and distribution of grazers has been shown to slow the spread of wildfires through consumption of fine fuels, most notably in cheatgrass/downy brome (Diamond et al., 2009) and Lehmann lovegrass (Bruegger et al., 2016) invaded rangelands of the West. In steep and rocky terrain, where other vegetation management treatments (e.g., mechanical and herbicide) prove difficult, targeted grazing could be more cost-effective.

Implementing target grazing practices can provide beneficial secondary products and income to producers. Some of these products can include wool, goat milk, sale of lambs and kids, and/or contracting the livestock for use on other lands. Mixed herds (sheep and goats, for example) and mixed age types (breeding females and old wethers) can help to diversify the secondary revenue streams, as well as the types of vegetation you can target (brush vs forbs).      

Depending on the targeted grazers, producers and managers may also need special fencing (“goats go low”), herders or herding animals, additional waters, predator protection, and supplemental feed/protein. 

Grassland structure is maintained through multiple natural disturbance regimes. Natural disturbances can include grass utilization and trampling by herbivores and droughts that limit productivity and plant-plant competition for water. Fire, however, is potentially the most essential in promoting grass dominance while also reducing cover of encroaching shrubs/trees including the seedlings and saplings obscured in dense grass cover. Fire in native grasslands can aid in removing excess litter allowing grasses to recruit and establish, promote soil nutrient cycling, and help to manage invasive grasses and forbs. The benefits of fire can depend on the intensity (e.g., rate of spread and how hot the fire burns), where high intensity fires may lead to the loss of native plant species. Grasslands in the West are largely dependent on fire, but anthropogenic fire suppression has altered the historical, natural fire regimes. Thus, land managers can use prescribed fire to return fire back onto the landscape. 

Prescribed fire  

Prescribed fire, or controlled burning, is the use of systematically and purposefully planned fire to manage vegetation for the maintenance or improvement of wildlife habitat, reduction in brush cover that has encroached in a grassland, and/or remove excess fine fuels to increase grass cover. Historical fire regimes of a particular ecosystem can be reintroduced at various intervals to restore and/or maintain the biodiversity of a treated area. For reference, see the fire return intervals and regime characteristics by plant community type in the US by the US Forest Service.

The use of fire as a management tool can, as with rangeland management, be both an art and science. Implementing a prescribed fire often involves a lengthy planning and approval process, which can take many months or well beyond a year to develop a written plan, depending on the state and/or local burning laws and liability requirements. Depending on the specific land management goals, considerations are needed on livestock grazing rest for fuel accumulation (and after burning for recovery), labor/equipment needs, site preparation (e.g., firebreaks, coarse fuel management), and required city/town/neighbor/community notifications or approvals. Appropriate and safe weather conditions must exist for a prescribed fire to occur as well, where season, wind speed and direction, air temperature, relative humidity, smoke guidelines, and potentially many other factors will need to be considered before a safe ignition. 

Wildfire 

Wildfires are not planned. A wildfire can ignite naturally as with lightning or by humans (e.g., accidental, escaped campfires, arson). Additionally, a prescribed fire can become a wildfire if the fire escapes a planned burn area. Many grasslands, prairies, and forests across the West have evolved with fire as an important component of the ecosystem, and wildfire can be beneficial to the recruitment and establishment of native vegetation and habitat maintenance for wildlife. 

Historical wildfire suppression has led to an overabundance of fuels on many rangelands and forests with more frequent catastrophic wildfires in recent decades, where land management agencies often use mechanical thinning and mastication or even prescribed fire for excess fuel and brush removal. In recent decades, warmer temperatures combined with long-term droughts has extended fire seasons with higher frequencies and intensities of wildfires. Millions of acres are burned yearly, costing billions of dollars in wildland firefighting support, structural losses, and post-fire rehabilitation and restoration in the US. Urban development and increased population sizes has led to a boom in human-caused wildfires on public and private lands in recent years (Balch et al., 2017). Living in the wildland-urban interface increases your susceptibility to wildfire damage, but there are many techniques to help create “defensible space” and protect a property from wildfire.

For additional information, see the Fire topic pages in the Rangeland Ecology section. 

Cultural methods involve manipulating the timing, intensity, or duration of a land use or management action to achieve a desired vegetation composition and/or structure. Cultural control is most often employed to manage invasive weeds or deter undesirable species in traditional agriculture fields but also on rangeland landscapes. Targeted grazing, prescribed fire, and seeding desirable vegetation are the most common rangeland cultural methods (also see Related Resources below).

Cultural practices are often incorporated into an integrated approach in consideration with biological, cultural, and mechanical methods to maximize brush management goals. Selecting the appropriate cultural technique to meet your goal(s) can depend heavily on cost of implementation, but managers should also consider regional-, local-, and site-level soil, elevation, and weather (or climate) conditions to maximize efficacy in both short- and long-term time frames. 

A simplified example of a cultural method application includes seeding a desirable, competitive herbaceous species that can capture soil and water resources that aids in preventing resource capture by competing undesirable brush species following a mechanical practice. Considerations on the site suitability, species selection, and timing with precipitation (or the rainy season) for germination and establishment will be critical for seeding potential success.

Perhaps our first education about biological control came early with the nursery rhyme lines about the little old lady who swallowed organisms to catch the originally swallowed organism, (e.g. “the little old lady swallowed the spider to catch the fly and swallowed the bird to catch the spider and swallowed the cat to catch the bird”). The simple lesson from that nursery rhyme is that one seemingly simple biocontrol act may require successive unsustainable actions.  Biological control for vegetation management relies on organisms to manifest mortality, reduce health and thus reproduction and density, or out compete the undesired plants. Organisms used for this purpose can range from other desired plants to animals, insects, fish or those that cause disease in the undesired vegetation, such as bacteria, parasitoids or fungi. The most easily implemented biological control strategy on rangelands uses grazing animals (see targeted grazing) such as sheep, goats, cattle and horses (EPA 2008), for targeted grazing on the invasive plant. Humans could be considered as a biological control agent on mesquite encroachment for example (see also cultural methods), by employing alternative uses of mesquite; seed pods ground into flour or used as fodder for cattle, lumber, slash used to fill gullies or other water control structures, fuelwood, biofuel and biochar (Ellsworth et al. 2018). 

The use of biological control for woody plant encroachment is not typical, but there are some examples. Some success has been found by using mesquite seed eating insects such as bruchid beetles to control mesquite invasion in Australia and Argentina. Use of insects should be restricted if possible, to those native to the location and specialists on the target species to be controlled with rigorous testing done before introducing a non-native (Ellsworth et al. 2018). One of the most well-known introductions in the past decade was to control invasive Saltcedar. After rigorous testing and federal approval, the Tamarisk leaf beetle was successfully introduced into North America to control 1.5 million acres of Saltcedar (Tamarisk spp.) invaded and dominated riparian areas across thirteen states in the West (CATB 2012; Kauffman 2005). However, this biocontrol introduction has been so quickly successful at causing Saltcedar dieback that it has had subsequent consequences on the endangered Southwestern willow flycatcher that nests in riparian habitats. Use of such biocontrol measures require proactive monitoring and coordinated partnership restoration efforts to regain pre-invasion native vegetation to avoid a cascade of impacts on other species now relying on the invaded habitat.  

There are three primary strategies or approaches for biocontrol: classical, augmentation, and conservation. Classical biocontrol is an intentional introduction of a non-native agent for long-term control of a target organism (or plant) without the need for supplemental agent releases. Taking an augmentative approach entails a single large release of the biocontrol agent, where the agent does not reproduce or remain in an ecosystem long-term. Lastly, conservation biocontrol does not involve releasing an agent or pest, but rather supporting naturally occurring enemies of the target organism either through providing additional resources, modifying an ecosystem, or protecting the natural enemy to enhance the control. 

In the USA, any implementation of biocontrol that involves the release of a non-native agent should follow guidelines, permitting, and approvals as outlined by the US Department of Agriculture's Animal and Plant Health Inspection Service.

Brush (or shrub) encroachment is a global phenomenon whereby native and nonnative woody species displace grass species (Archer et al., 2017). The shift in a grass- to woody-dominated ecosystem results from complex interactions between many environmental drivers, physical controls, and historical land uses. A widespread conversion of grasslands to shrublands can significantly impact a variety of ecosystem processes and services such as soil erosion, water infiltration, and forage production (Archer & Predick, 2014). Range managers and land owners can employ several “brush management” treatments for reducing shrub/tree cover and help to restore encroached grasslands (Hamilton et al., 2004; Scifres et al., 1985).  

Brush management treatments are broken into four broad categories: biological, chemical, cultural, and mechanical. The following web resources details each method individually and for application in combination to maximize their effectiveness (e.g., Integrated Brush Management Systems) to meet management goals:

In 2018, a series of workshops were hosted in southeastern Arizona to discuss historical and current trends of brush cover; brush management methods and stories of application; and working collaboratively to apply their collective knowledge to meet brush cover goals. Details on this workshop series including agendas, presentations, and videos can be found here:

Much of the Western rangelands are a checkerboarded, interspersed land ownership of private, state and federal public lands. This creates difficulty in accomplishing landscape level vegetation management. One cultural tool that helps this diverse ownership with potentially conflicting opinions work together is Community-based Collaborative Conservation (Charnley, Sheridan and Nabhan 2014). These groups avert conflicts by focusing on evidence-based issues and group education (collaborative learning) in order to reach collective landscape level management decisions on shared goals regarding rangeland natural resources. Collaborative Conservation groups raise the voices of communities with concerns about impacts to their livelihoods because of environmental issues such as: landscape condition changes diminishing landscape productivity, erosion causing soil loss and water quantity and quality declines, endangered and threatened species management, wildfire mitigation and management, enforcement of regulations or fragmentation and development threats (Wilkins et al. 2020). Typically, these groups have a diverse representation of stakeholders from community members (producers, farmers and local residents) to industry and non-governmental organizations, universities as well as state and federal government agency representatives. Public land management agencies (e.g., U.S. Forest Service, Bureau of Land Management and U.S. Fish and Wildlife Service) also have cooperation and collaborative partnership policy mandates for many of their land planning processes. This brings collective action to implement rangelands maintenance and restoration solutions to often complex, cross boundary and interrelated environmental issues. 

Citations see Further Reading