Sandy (Sy) Big Horn Basin Rim
Scenario model
Current ecosystem state
Select a state
Management practices/drivers
Select a transition or restoration pathway
-
Transition T 1-2
Frequent or high-intensity herbivory on a community weakens the ability for the grasses to persist, especially during prolonged drought. Low vigor in grasses and lack of fire shifts the composition to a more pronounced sagebrush community. In time, sagebrush will increase in density (lack of perennial grass cover), preventing the recovery without intervention.
More details -
Transition T 1-3
Long duration, high-intensity grazing reduces the bunchgrass component and encourages threadleaf sedge and blue grama. Prolonged drought stresses the plants, opening the canopy, and allows these short-statured sod-forming grasses to fill in the interspaces. The shallow, dense root mats will continue to spread over time. The removal of sagebrush with animal impacts, fire or brush management aids in establishing this sod-former community.
More details -
Restoration pathway R 2-1
Removal or thinning of the sagebrush by mechanical or chemical means, or by fire, leaving remnant populations of desired native perennial grass species allows the recovery to the Reference State, if climatic variables cooperate and rest occurs for seed development and seedling establishment.
More details -
Transition T 2-3
Sod-forming species such as threadleaf sedge and blue grama can tolerate high levels of use and will maintain as other native species decline. This decline creates a sagebrush–sod-former community that is resistant to change with management. Impacts to sagebrush by disease or insect damage will shift this to the secondary community phase.
More details -
Transition T 2-4
Seed sources are prevalent for cheatgrass, knapweed, and other invasive species. Stress to the native community from drought; events such as wildfire (prescribed burning) and other forms of brush management; or ground/soil disturbance, including impacts by grazing large herbivores or recreation creates a niche for invasive or undesirable weeds. This invasion will start small and spread each year if not addressed immediately.
More details -
Transition T 3-4
The interstitial spaces within the patchy canopy of sod-formers leaves areas for weedy species to establish, especially with disturbance or within high traffic areas.
More details -
Restoration pathway R 4-5
Integrated pest management plan or other intense weed control program with seeding will be necessary to overcome a severe weed infestation. Preparing the seedbed and using improved varieties, native seed, or introduced species suited for the management use intended may be the only way to overcome some invasive species.
More details -
Transition T 5-4
In the reclamation or restoration process, or after land disturbance, if no management is put into place to prevent a reoccurrence or a new infestation of weeds, the community will revert back or transition to an invaded state. Wildfire, prescribed burning, drought, or frequent and severe overutilization can be a disturbance that either opens the canopy or introduces the species to the location.
More details -
No transition or restoration pathway between the selected states has been described
Target ecosystem state
Select a state
Description
The reference state (State 1) for the Sandy ecological site is dominated by mid-stature, cool-season bunchgrasses. This state persisted under grazing by large ungulates and was a resource for forage and habitat for a variety of wildlife.
Characteristics and indicators
The Bunchgrass/Sagebrush State (State 1Reference) is characterized by the prominent cover of needle and thread (15-30 percent composition) and Indian ricegrass. Rhizomatous wheatgrasses and prairie Junegrass are common, with 10 percent or less cover of Wyoming big sagebrush. Minor components to the overall composition is made up of Sandberg bluegrass, bottlebrush squirreltail, sand dropseed, threeawn, blue grama, and threadleaf sedge.
Resilience management
Prescribed grazing or managed use to provide forage removal and to help incorporate litter helps for this suit of communities to persist on the landscape and to maintain vigor.
Submodel
Description
Persistence of drought with frequent overuse leads to a decline of the herbaceous species, creating the Wyoming Big Sagebrush/Bare Ground State. Wyoming big sagebrush creates a zone of protection for understory of herbaceous species. Sagebrush and other woody species provide shade, moisture reserves, and protection from herbivory. A select array of herbaceous cover will persist in this understory and may maintain vigor in difficult conditions.
Characteristics and indicators
Sagebrush or woody vegetative cover is the prominent characteristic of this state. The understory of herbaceous cover is generally lacking or sparse in the woody cover interspaces. The woody canopy does provide a "niche" for some herbaceous species to persist.
Resilience management
This state can be exacerbated by insects and other human disturbances. The total woody canopy (foliar) cover does not necessarily increase in this community, but the percent composition by weight (annual production) is influenced by the decrease of herbaceous vegetation and the relative stability of the woody species production, creating the appearance of increased canopy cover of sagebrush.
Risk of wildfire is minimal due to the lack of fine fuels within the understory, but the canopy of the woody vegetation can easily carry a fire under specific weather conditions. Depending on the prescription of use, trailing and other erosional patterns are highly visible in this state. The loose or coarser texture of these soils allows for increased wind scour and drifting/mounding to occur with more open ground between canopy “patches,” that further hinders fire movement.
Protection from wildfire and use, on a long-term perspective, can aid in the transition of a Reference Community (1.1 or 1.2) to this state as sagebrush becomes dense and decadent reducing the ability for the herbaceous component to maintain vigor. The loss of herbaceous cover leads to increased bare ground and sagebrush cover. As the site continues to weaken, the sagebrush cover is susceptible to attack by insects, disease, and old age; which can remove it from the system increasing the risk of invasion or transition to a more degraded state.
The overall arid nature of coarse textured soils exacerbates the impact of drought and reduces the resilience and resistance of this site during extended dry periods. The presence of yucca on this site is not frequent, but when it does occur, it can easily become a concern, especially if frequently grazed in the winter. The growth habits of the yucca plant produces pedestalling and drift/scour patterns on the landscape. The level of variability of species in this state (State 2) remains abundant; however, only one-well defined community will be provided here, with discussion of transitions or variances from this community.
Submodel
Description
Tillering, mat-, or sod-forming species are native and common in many communities within the Big Horn Basin. Blue grama and threadleaf sedge are the dominant grass or grass-like species within this functional group. Both species are a native component of the Reference Community; however, the tendency is for these species to increase with prolonged drought or under grazing pressure, becoming dominant. As the dominant species, they alter the hydrology of the site, increasing surface runoff. The dense and restrictive root system inhibits movement of water through and funnels surface flow around the edge of the “grass clumps,” concentrating flow into channel-like patterns, creating a drier environment for native grass species and forbs to persist.
Characteristics and indicators
The major canopy cover is comprised of blue grama and threadleaf sedge. Sagebrush and yucca may be present as well as a few other shrubs; however, most woody canopy and other herbaceous species are few. Pricklypear cactus tends to increase in this State.
Resilience management
Blue grama and threadleaf sedge tend to be resistant to management once established on the landscape. Mechanical treatment of the soil is one of the few tools found to have a strong success in altering this community once established.
Submodel
Description
Cheatgrass or downy brome (Bromus tectorum) is an aggressive annual invader that threatens rangelands across the west, including Wyoming. The ability of cheatgrass to persist through the winter under a blanket of snow and grow early allow it to take advantage of early spring precipitation and snowmelt (winter annual). Multiple growth cycles throughout a year leaves a thick litter (duff) layer and builds a significant seedbank. This annual invader has an aggressive growth habit that creates a hostile environment for most native species, including sagebrush. Climatic shifts, changes in management, and exposure to human activity are a few of the explanations for the current flush and rapid expanse across the western United States.
Although cheatgrass is the most prevalent large-scale threat for rangeland managers, a variety of thistles and knapweeds, in combination with other aggressive invaders such as whitetop (hoary cress), black henbane, field bindweed, and leafy spurge are increasing in density and frequency. Each species produces their own set of challenging management issues. As new species are identified, or as other species become more prevalent on a large-scale, the community dynamics in this state will shift in response to the concerns of the identified species.
Characteristics and indicators
This state is characterized by the presence and then dominance of invasive/non-native species. The competitive nature of annuals and other invasive species, creates a complex environment that inhibits control, and makes it implausible to attain complete eradication once an invasive species has established on the landscape. Increased access, increased travels of individuals, and other natural and man-made disturbances has opened the door for invasion in most native communities.
Resilience management
The lack of tools to achieve complete eradication, and variable success on long-term reduction of most invasive species has led to this state being resilient and resistant to change.
Submodel
Description
Difficulties in maintaining delivery systems and dependable supply of irrigation water has limited the economic feasibility to maintain all farmed lands. Increased energy development and the expansion of recreational land uses (including hunting) has changed the face of rangelands. The broken nature of the rim provides more topographic relief for movement of wild game, yet access is still easy to moderate for wheeled traffic. Although the disturbance footprints within this LRU are not as contiguous as within the core, old homestead locations, abandoned crop fields, roads, recreational facilities, and energy development have left their marks.
Disturbance to these highly erodible soils (whether it was mechanical, cultural, or natural) reduced the resilience or resistance to support native vegetation or the ability to respond to management in the same manner as an undisturbed site. Changes to soil structure and hydrologic processes reduce the stability and ability to recover. Reclamation or restoration of an area will not replace the original function and factors to an undisturbed state. These "altered" lands may, after significant inputs and time, resemble the Reference Communities (1.1 or 1.2), but they will respond and function the same as the Reference State.
One catastrophic event or several smaller disturbances can lead to the transition to the Altered State from any identified state within the State-and-Transition Model. The soils have not been altered to the extent that they are outside the site characteristics, but the potential has shifted enough that it will not respond the Reference State. Location or site-specific investigation is needed to determine if a disturbed or reclaimed area still meets site characteristics.
The time required to allow the redevelop ment of structure and the cryptogrammic crust, as well as any impact to chemistry, is beyond the natural function of management. The initial flush of vegetation is kochia and Russian thistle and mustards, a successional plant community. The site begins its own recovery, but the time required to return to the original conditions (pre-disturbance) is outside of feasible consideration. The site, however, may become similar in composition to the Reference State, but the integrity of the soil is altered, changing the potential of the site.
Characteristics and indicators
This state is characterized by a landscape that has been mechanically manipulated or had significant soil disturbance. Early successional plant communities, evidence of farming (field edges, cultivation rows, etc.) or the presence of introduced species (crested wheatgrasses, russian wildrye, etc.) are indicators of this state.
Submodel
Mechanism
Frequent and severe grazing (year-long) or drought with the absence of brush management or wildfire- The conversion to a Wyoming Big Sagebrush/Bare Ground Plant Community is a response to extended periods of stress, both climatic and human-induced. Frequent or high-intensity herbivory weakens the ability for desirable grasses to persist, especially during periods of prolonged drought. The composition will shift to predominantly Wyoming big sagebrush as the herbaceous cover declines. Over extended periods of time, the sagebrush canopy will increase in density, preventing the recovery without intervention. The illusion of crossing the threshold to State 2 is captured with fluctuating precipitation patterns affecting production of prominent plants within this system. A marked loss of herbaceous cover and diversity, increased bare ground, and lack of litter over multiple monitoring cycles provides the evidence that the transition to State 2 has occurred, and is not an annual climatic response. It is important to recognize that the number of actual sagebrush plants may not increase to cause this shift. Rather the loss of herbaceous composition and increase in the canopy cover of woody species is the larger factor (creates the illusion of increased number of plants when it is the size and age that is more likely to change).
Constraints to recovery
The possible lack or limited seed-sources for the key mid-stature, cool-season bunchgrasses is the major recovery constraint for this State.
Mechanism
Frequent grazing (yearlong), brush management, or fire with droughtSevere and frequent grazing (by livestock or any other large ungulates) reduces vigor and presence of key species. As needle and thread and Indian ricegrass begin to decline, shorter-statured grasses become dominant. Animal disturbance (hoof impact) reduces the bunchgrass component through damage to the crown of the plant, but also in some instance by allowing repeated defoliation of the desirable species, reducing recovery potential and ground cover for insulation and snow catch. The damage and repeated defoliation weakens, and over time, removes select species. The open canopy and hoof impact encourages species that are tolerant to trampling and that can utilize the small bursts of spring and summer moisture, these species are generally mat or sod-forming species such as blue grama and threadleaf sedge. Prolonged drought stresses the plants and opens the canopy for these short-statured grasses to fill in the interspaces. The shallow, dense root mats will continue to spread over time. The added removal of sagebrush with animal impacts, fire, or brush management may open the canopy more and aid in establishing this sod community. Season of use and intensity of grazing (time and timing) is a trigger that can reduce the risk of transitioning, or if done poorly can force the transition to occur rapidly. The Reference State (1.1 and 1.2) is dominated by cool-season species. Provided the area receives good spring moisture, growth and maturity of these plants can happen quickly within the first two weeks of June, while blue grama is just beginning. By alternating when the community is grazed, providing periods of rest during the critical initial green-up and growth in the spring, and allowing recovery time before the community is grazed again within the year, allows the bunchgrasses and rhizomatous grasses to maintain vigor and production. This also allows for summer use when the warm-season grasses are growing (blue grama) which will help to utilize this species and maintain cover.
Constraints to recovery
The resiliency of the mat-forming (sod-forming) grasses is the recovery constraint for this transition. Blue grama and threadleaf sedge, once established in significant composition, are resistant to management changes and require some level of mechanical manipulation to allow other native species to increase (re-establish) in this community.
Mechanism
Prescribed grazing with brush management or wildfire—Treatment to thin or rejuvenate the sagebrush canopy is necessary to allow and encourage native perennial grasses to respond to improved moisture and sunlight. Prescribed grazing is required in conjunction with brush management to prevent overuse of the exposed grasses allowing this community to recover.
Treatment will vary depending on the current composition of grasses remaining and the potential threats to the location. Removal or thinning of the sagebrush within this community will help to reduce competition, encouraging grass and forb recovery if the disturbance or overuse (recreational or grazing pressure) is reduced. Drought may prolong the time required for recovery.
Mowing or mulching sagebrush trials have shown a strong response by grasses with little to no recovery time post-treatment. The resulting community with these treatments is driven by the dominant species within the community pre-treatment. Climate and treatment conditions during and following a fire has a larger impact on the community. It is crucial to investigate the immediate and surrounding areas of a treatment site to ensure no invasive species (cheatgrass) are present.
Context dependence
In some instances, when sagebrush canopy is not excessive but the understory of herbaceous species is lacking, seeding of native cultivars may be necessary to encourage the grasses to re-establish.
Relevant conservation practices
| Practice | External resources |
|---|---|
|
Brush Management |
|
|
Prescribed Burning |
|
|
Critical Area Planting |
|
|
Grazing Land Mechanical Treatment |
|
|
Range Planting |
|
|
Heavy Use Area Protection |
|
|
Integrated Pest Management (IPM) |
|
|
Upland Wildlife Habitat Management |
|
|
Early Successional Habitat Development/Management |
|
|
Planned Grazing System |
|
|
Native Plant Community Restoration and Management |
|
|
Prescribed Grazing |
|
|
Grazing Management Plan |
Mechanism
Drought, disease or insect damage, overuse, or fireSod-forming species such as blue grama and threadleaf sedge can tolerate high levels of use and will maintain as other native species decline. Hoof action or compaction inhibits more desirable native species, allowing the sod-formers to become dominant, creating a sagebrush/sod community that is resistant to change by grazing management. Impacts to sagebrush by disease or insect damage, as well as drought or herbivory, will shift this community to the secondary community phase with cactus as a subdominant cover with blue grama and threadleaf sedge.
Extended periods of drought in combination with a change in the amount and timing of precipitation and spring snowmelt has allowed the warm-season grass, blue grama, to out-compete cool-season natives such as needle and thread. Climate change is widely debated and speculated; however, the documented shifts in climatic curves, as well as large-scale transitions to this community under different management scenarios, highlights climate as a key player – not just use and management. Further research is needed to identify the factor for each site-specific situation.
Constraints to recovery
The loss of or lack of woody canopy, primarily sagebrush, and the need for mechanical treatment to reduce/remove the sod-formers are the major constraints for recovery of this state.
Mechanism
Fire (wild or prescribed), frequent or severe grazing, drought with insect damage/brush managementThroughout most of this LRU, there are seed sources present for cheatgrass, knapweed, and other invasive species. Removal or thinning of the canopy and displacement of the soil surface by disturbance (fire, drought, disease/insect damage to sagebrush, or ground/soil disturbance including impacts by grazing large herbivores or recreational activities), creates a niche for invasive/undesirable weeds.
Invasions start with one or two isolated plants, that if caught can be treated and an infestation avoided; however, when unseen or ignored, the population grows exponentially with time. In some cases, once the invasive species are established, they can create their own habitat, reducing the ability for native species to compete for the limited resources.
The open canopy of the Sagebrush/Bare Ground State is vulnerable to invasive species without further influence. With continued overuse, drought, or insect damage or disease, the invasive species will establish and quickly dominate a location. The threshold species in this system is Wyoming big sagebrush, which protects the remnants of the perennial native grasses, allowing them to persist.
Constraints to recovery
The inability to eradicate or achieve long-term control of most invasive species is the constraint to recovery for this State transition.
Mechanism
Frequent and severe grazing, drought, disturbance with a seed source presentResistance to invasion of the sod-dominated community is presumed due to the lack of extensive bare ground and the aggressive and persistent nature of blue grama and threadleaf sedge. This community also has a minimal risk of wildfire because of the lack of fine fuels and reduced sagebrush canopy. The increased interspatial pattern of these communities leaves exposed soil that is vulnerable to invasion by undesirable species. Increased pressure from overuse and drought work to weaken the sod or mat-like community of low-statured grasses, opening more surface to invaders, such as cheatgrass and knapweeds. If a seed source is available, ground disturbance by herbivores or man-induced, allows invasive species to find a way into the community. Once established in the community, the extent of spread is limited, but it is still extremely difficult to manage, and eradication is not feasible. Once the invasive species have become prevalent on the landscape (>5 percent composition), the community crosses the threshold into the Invaded/Sagebrush State (State 4).
Constraints to recovery
The lack of sufficient tools to eradicate or gain long-term control of most invasive species is the constraint to recovery for this state.
Mechanism
Integrated pest management, with seedingIntegrated pest management and intense weed control as part of seedbed preparation and after seeding will be necessary to overcome a severe weed infestation. Preparation of the target area and utilization of improved varieties, native seed, or (where appropriate) introduced species suited for intended land use increase the success of removing the invasive species. Success of reestablishing a native or desired plant community on a large scale is not documented. Small-scale attempts are rated to be low and highly variable for the rate of control of most species. The limited success and difficulties in reestablishing sagebrush also limit the site potential. Due to the need to till (turn the soil) for seedbed preparation reduces soil stability by breaking down soil structure and alters the hydrologic cycle by changing the infiltration and percolation rates of the soil. The alteration of the soil properties prevents the soils from reacting the same to management and environmental changes, so transitions to a reclaimed or altered state (State 5).
Relevant conservation practices
| Practice | External resources |
|---|---|
|
Critical Area Planting |
|
|
Grazing Land Mechanical Treatment |
|
|
Integrated Pest Management (IPM) |
|
|
Upland Wildlife Habitat Management |
|
|
Early Successional Habitat Development/Management |
|
|
Planned Grazing System |
|
|
Native Plant Community Restoration and Management |
|
|
Prescribed Grazing |
|
|
Invasive Plant Species Control |
|
|
Grazing Management Plan |
|
|
Herbaceous Weed Control |
Mechanism
No use, fire (wild or prescribed), frequent or severe grazing, drought with seed source presentPost-disturbance and during reclamation processes, management is required to prevent a reoccurrence or a new infestation of weeds. Wildfire, prescribed burning, drought, or frequent and severe overutilization by herbivores can be a source of the disturbance that either opens the canopy or introduces the species to the location. Extended periods of non-use can create loose soils, reducing vigor and health of the native population. The resulting die-back allows the community to become vulnerable to weed invasions. This invasion triggers the transition to the Invaded State.
Constraints to recovery
The inability to or the financial cost of the inputs to eradicate or successfully control invasive species is one contraint to recovery. Another is the seed selection to compete with the invasive species that are affecting the site.
Model keys
Briefcase
Add ecological sites and Major Land Resource Areas to your briefcase by clicking on the briefcase (
) icon wherever it occurs. Drag and drop items to reorder. Cookies are used to store briefcase items between browsing sessions. Because of this, the number of items that can be added to your briefcase is limited, and briefcase items added on one device and browser cannot be accessed from another device or browser. Users who do not wish to place cookies on their devices should not use the briefcase tool. Briefcase cookies serve no other purpose than described here and are deleted whenever browsing history is cleared.
Ecological sites
Major Land Resource Areas
The Ecosystem Dynamics Interpretive Tool is an information system framework developed by the USDA-ARS Jornada Experimental Range, USDA Natural Resources Conservation Service, and New Mexico State University.