Loamy (Ly) Wind River Basin Rim
Scenario model
Current ecosystem state
Select a state
Management practices/drivers
Select a transition or restoration pathway
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Transition T1A
Frequent or high intensity herbivory on a community weakens the ability for the grasses to persist, especially during prolonged drought. With the weakened grasses and with prevention or lack of fire, the composition will shift to mostly sagebrush, and with time sagebrush will increase in density preventing the recovery without intervention.
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Transition T1B
Long duration, high intensity grazing reduces the bunchgrass component and encourages the mat or sod-forming species such as threadleaf sedge and blue grama. Prolonged drought stresses the plants, and opens the canopy for these two quick responding plants 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-former community.
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Restoration pathway R2A
Removal or thinning of the sagebrush by mechanical, chemical or fire with remnant populations of the native perennial desired species will lead to this community. Provided, sufficient time is given for recovery of plants and conditions are optimal for seed development and seedling establishment. Frequent use of this community during the dormant season will work to reduce the sagebrush through trampling and grazing-tolerant. B but may encourage lower stature more tolerant species and not the more desired species.
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Transition T2A
Sod-forming species such as threadleaf sedge and blue grama are able to 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.
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Transition T2B
Seed sources are prevalent for cheatgrass, knapweed, and other invasive species. Stress to the native community from drought; events such as wildfire or prescribed burning and other forms of brush management; or ground/soil disturbance including impacts by grazing large herbivores or recreation that open the canopy and break the surface of the soil, a niche for invasion by undesirable weeds is presented. This invasion will start small and spread each year if not addressed immediately.
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Transition T3A
The interstitial spaces within the patchy canopy of sod-formers leaves areas for weedy species to establish, especially with disturbance or high traffic areas.
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Restoration pathway R4A
Integrated pest management plan and intense weed control after and possibly before seedbed preparation will be necessary to overcome a severe weed infestation. Using either improved varieties, native seed, or in some cases, an introduced species suited for the management use intended may be the only way to overcome some invasive species.
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Transition T5A
In the reclamation or restoration process, or after a land disturbance occurs, if no management is put into place to prevent a re-occurrence 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 grazing by large herbivores can be a source of the disturbance that either opens the canopy and/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 for the Loamy Wind River Basin Core ecological site is chracterized by the dominance of rhizomatous wheatgrasses, with the scattered overstore of Wyoming big sagebrush State (State 1). This state was maintained with the grazing of large ungulates, mainly wild/feral horses, deer, and antelope; as well as domestic livestock use. This area was historically sheep and has shifted to predominately cattle, however there are still localized bands of sheep that utilize allotments within the LRU. Fire has had only a minor roll within this LRU. Small, lightening induced burns occur, but with no significant frequency.
Characteristics and indicators
Rhizomatous Wheatgrasses/Sagebrush State (State 1 - Reference) is characterized by the key species including: 15% or less composition by cover of Wyoming big sagebrush, rhizomatous wheatgrasses (western and thickspike) (<30%), needleandthread, and Indian ricegrass, with and isolated areas of bluebunch wheatgrass. Minor component to the overall composition are Sandberg bluegrass, bottlebrush squirreltail, prairie junegrass, blue grama, and threadleaf sedge.
Submodel
Description
The remaining herbaceous understory utilizes the moisture and shelter provided by the canopy of Wyoming big sagebrush to maintain vigor in difficult conditions. Persistence of drought and/or frequent over use by livestock and/or wildlife leads to a decline of the herbaceous understory, creating the Wyoming Big Sagebrush / Bare Ground State. Total sagebrush canopy increases in percent composition by cover. With the decrease of herbaceous vegetation production, the canopy of sagebrush appears to increase.
Lack of fine fuels to carry a fire leave this state at a minimal risk of wildfire. However, with the right weather conditions (dry, hot winds), the sagebrush canopy may easily carry a fire. Depending on the current livestock management, trailing and other erosional patterns may be highly visible in this state. The production and function of this state can be altered by the health and vigor of the sagebrush, establishment of other woody species and the intensity of the herbivory.
Long-term protection from wildfire and grazing can advance the transition of a reference community (1.1 or 1.2) to this state (2). As sagebrush becomes dense and mature, the herbaceous component declines in vigor, bare ground and sagebrush cover increase. Further decline in this state, leaves the sagebrush cover susceptible to attack by insects, disease, and general old age. This community is now at risk of invasion or transition to a more degraded state. There is a high level of variability of species in this state, which will shift in response to precipitation or in response to past management. The most representative community is discussed below.
Characteristics and indicators
Wyoming big sagebrush is a significant component (> 25%) of the plant community and the preferred mid-stature cool season grasses have been eliminated or greatly reduced. Sandberg bluegrass and western wheatgrass are prominant, but usually within the crown of sagebrush or prickly pear cactus. The interspaces have expanded, leaving significant bare ground.
Submodel
Description
The degraded condition of this State is driven by the loss of hydrologic function and species diversity with the increase of sod-forming grasses, mainly blue grama with a smaller component of threadleaf sedge. This site is the result of long-term season long grazing by large ungulates; but long term exclosures also suggest a possible response or impact of shifts in historic weather patterns.
Characteristics and indicators
The dominant sod-forming grass that currently exists within this LRU is blue grama with intermixed areas of threadleaf sedge. Both are species that persist as a component of the perennial vegetation naturally (in reference communities) within this ecological site. The general tendency is for these species to increase with prolonged drought or under grazing pressure, becoming dominant. Hydrology of the site is altered by increased surface runoff from the dense shallow root system that inhibits the movement of water through the soil. The sod patches will direct surface flow around the edge of the mat concentrating flow into channel like patterns, creating a difficult or harsh environment for native grass species and forbs to persist.
Submodel
Description
Cheatgrass or downy brome (Bromus tectorum) is the invader that has the greatest concern for most land managers. This invader has an aggressive growth habit that creates a harsh environment for most native species, including sagebrush. Multiple growth cycles throughout a year leaves a thick litter (duff) layer and builds a significant seedbank. The ability to persist through the winter under snow and sprout early gives it the advantage over native species for the early spring precipitation and snowmelt. Shifts in climatic patterns, 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 threat most prevalent to rangelands on a large scale, a variety of thistles, knapweeds (spotted, Russian, etc.), and whitetop (hoary cress) are increasing in density and frequency, creating their own set of challenging management issues. As more or new invasive species are found or identified within the Wind River Basin, the community dynamics in this state will continue to shift in response to the species-specific concerns.
Characteristics and indicators
This state is characterized by the presence of an invasive/non-native species. Extended periods of drought alone; or in combination with severe grazing, insect damage, or wildfire has weakened the native composition of the community opening the canopy for invasion. The competitive nature of annuals and other invasive species, the loss of diversity, changes to the potential of a site due to allelopathy or other deterrent characteristics of invasive species, and risks or limitations associated with the various invasive species creates a hostile environment for both native species and grazers.
Resilience management
The resilience and resistance of the invaders create a management roadblock that is usually financially driven. Once an invasion reaches a threshold, many land managers have no choice but to learn to utilize what they have rather than to try to treat or improve the site, specifically in relation to cheatgrass control.
Submodel
Description
The arid nature of this region has played a major role in the development and transitions in land use over time. Landscapes accessible by irrigation water and equipment were farmed and many were later abandoned and left to return to rangeland. Other landscapes were treated with a variety of practices to manage or eradicate sagebrush. Tillage of the soil, change in hydrology caused by the loss of vegetative structure, constant climatic fluctuations, and advancements in seed sources have created this altered state.
Once a soil has been disturbed, whether it was mechanical, cultural, or natural the change in soil structure, hydrologic function, and possibly stability prevent a site from supporting the native vegetation or responding to management the same as the reference site. Reclamation or restoration of an area will not replace the original function and factors that made the original location respond as it did. So these "altered" lands may, after significant inputs and time, look similar to the Reference communities (1.1 or 1.2), but they will not be able to respond or function the same way as the Reference community.
The disturbed or degraded state could be shown as a stand-alone box within the state and transition model diagram. No matter what state a location is classified, once the site has experienced an event that has altered the soil properties (erosional, depositional, hydrological or chemical), the site potential is altered. Consideration of this state for an alternate ecological site would be reasonable. In some cases (site by site consideration), a re-correlation of a location may be the best solution. However, in many cases, the soils have not been altered beyond the current site characteristics. However, the potential has shifted enough that it is no longer truly comparable to the reference state.
Tillage of a site, alters the soil structure, depletes the biota of the soil and dries the profile. The loss of soil structure changes the water holding capacity of the soil, and the mixing may remove argillic or clay bulges, which may increase the movement through the soil, and reduce the available water capacity. The time required for soil to recover and re-establish the healthy biota is highly variable depending on the climatic conditions following the event.
The initial flush of weedy vegetation (kochia, Russian thistle, and mustards) is the initial step in the recovery process. Although they are only successional species, they provide organic material, nutrient flow and erosional protection. However, they lack the perennial structure and root system to fully stabilize the site. When the seeded area establishes, the site may become similar in composition to reference. However, the integrity of the soil has been altered, changing potential of the site. A dynamic state was depicted to detail the altered communities that exist on the landscape.
Characteristics and indicators
Soil disturbances, indications of seeding (rows, presence of strong stands of improved grass species or selective seeded species - crested wheatgrass, Russian wildrye, etc.), or the prominent cover of early successional plants (kochia, russian thistle, mustards) are strong indicators or characteristics of a disturbed/degraded or altered landscape.
Submodel
Mechanism
Frequent and Severe Grazing (Year-long) or Drought - Frequent or high intensity herbivory weakens the ability for the grasses to persist, especially during prolonged drought. The weakened herbaceous component in combination with lack of fire provides the opportunity for sagebrush to become dominant. Over time, the sagebrush density and lack of understory will prevent recovery without intervention. The conversion to a Wyoming Big Sagebrush/Bare Ground State is a response to extended periods of stress, both climate and/or human induced. Intensive grazing with minimal to no recovery period begins the transition, and with added climatic stress, species diversity and productivity is lost, and the community crosses into the Sagebrush/Bare ground State. The illusion of crossing the threshold to State 2 can be found during non-typical precipitation years for communities dominant in needleandthread. The loss of species density and diversity, increased bare ground and decreased litter are the indicators that a true transition has occurred.
Constraints to recovery
Lack of seed source is the only major constraint for recovery of this community.
Mechanism
Frequent Grazing (Yearlong), Brush Management or Fire with Drought – Severe and frequent grazing reduces vigor and abundance of key species. As rhizomatous wheatgrasses, and needleandthread decline, short-statured grasses become dominant. Long duration, high intensity herbivory reduces the mid-stature bunchgrasses through repeated defoliation as well as physical damage to the crown and growth points of the plants. The open canopy and soil condition encourages species that are tolerant to heavy trampling and frequent defoliation. These species are generally the mat or sod-forming species of blue grama and threadleaf sedge. Prolonged drought or climatic stress may also encourage the sod-formers to fill in the interspaces. The shallow, dense root mats will continue to spread over time.
Constraints to recovery
The persistence and resilience of the root mat formed by sod-forming species as well as the alteration to hydrology make the recovery process unfeasible.
Mechanism
Prescribed Grazing with Brush Management or Wildfire - Treatment to thin the canopy to allow the native vegetation to respond to improved moisture and sunlight followed by prescribed grazing to prevent overuse of the exposed grasses will help this community recover. Treatment will vary depending on the specific 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 grasses and forb recovery. Post treatment grazing management is critical for successful long-term recovery. 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. Weather and treatment conditions during and following a wildfire will also influence the community. Prior to treatment, carefully checking the immediate and surrounding area will help ensure little or no invasive species (cheatgrass) is present.
Relevant conservation practices
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Brush Management |
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Fence |
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Livestock Pipeline |
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Prescribed Grazing |
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Pumping Plant |
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Grazing Land Mechanical Treatment |
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Heavy Use Area Protection |
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Spring Development |
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Integrated Pest Management (IPM) |
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Watering Facility |
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Water Well |
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Upland Wildlife Habitat Management |
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Early Successional Habitat Development/Management |
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Livestock Use Area Protection |
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Planned Grazing System |
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Prescribed Grazing |
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Invasive Plant Species Control |
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Grazing Management Plan |
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Pumping plant powered by renewable energy |
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Intensive Management of Rotational Grazing |
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Prescriptive grazing management system for grazed lands |
Mechanism
Drought, Disease, Insect Damage, Severe Grazing, or Fire - Sod-forming species such as blue grama and threadleaf sedge are able to tolerate high levels of grazing use and will maintain as other native species decline. Hoof action or compaction inhibits more desirable native species, allowing the sod-formers to become more dominant on the landscape. This decline creates a sagebrush / sod-former community that is resistant to change with grazing management. Impacts to sagebrush by disease or insect damage, as well as drought or herbivory, will shift state 2 to the secondary community phase with cactus as a subdominant species with blue grama.
Constraints to recovery
Compaction, altered hydrology, and the lack of seed-source are the major constraints for this site to recover. The ability to reduce the dense root-mat of a sod-former inhibits the transition back to bare ground scenario.
Mechanism
Fire (wild), Frequent or Severe Grazing, Drought with Insect Damage or Brush Management – Throughout most of this LRU there is a seed source present in the soil for cheatgrass, knapweed, and other invasive species. Stress to the native plant community creates a niche for invasion by undesirable or weedy species. Several causes of stress include drought, wildfire, prescribed burning and other forms of brush management, ground and soil disturbance from intensive grazing by large herbivores, or recreational activities. Documentation has shown that often the invasion starts with one or two isolated plants. If these plants can be treated early, a full infestation of the site can be avoided. However, if these plants are undetected, ignored, or further stress or disturbance occurs, the population soon grows exponentially. In some cases the invasive species, once established, can create its own habitat, forcing the weaker native species out. The open canopy of the Sagebrush/Bare Ground State is vulnerable to invasive species without further influence. With continued over-use, drought, insect damage or fire, 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 cool-season native grasses, allowing them to persist on the landscape.
Constraints to recovery
The ability to recover and remain in this degraded state, is the lack of vegetation. The significance of the bare ground in State 2 is prone to or encourages invasion by non-native or aggressive species. To remove these species and then maintain their removal is difficult without shifting the community to another state completely. (State 1,3, or 5). The second constraint is the ability to control the invasive weed without the thought to susceptibility. Cheatgrass has not been successfully eradicated from a community, rendering a recovery back to state 2 impossible at this time.
Mechanism
Frequent and Severe Grazing, Drought, Disturbance with a seed source present - The chance of wildfire is reduced with the loss of fine fuels and reduced sagebrush canopy. Increased pressure from severe grazing and drought combine to weaken the sod or mat-like community of low stature grasses, making the site vulnerable. Continued disturbance opens the bare ground or interspaces to annuals and other 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, it is extremely difficult to manage and may not be feasible to completely remove them from the community. Once the invasive species have become prevalent (>5% composition) on the landscape, the community crosses the threshold into the Invaded/Sagebrush State (State 4).
Constraints to recovery
The only significant constraint to recovery, is the ability to remove/eradicate the noxious weed/invasive weed that has invaded the community.
Mechanism
Integrated Pest Management, with seeding - Integrated pest management plan or intense weed control after and possibly before seedbed preparation will be necessary to overcome a severe weed infestation. Preparing a seedbed (tilling) and using either improved varieties, native seed, or in some cases, an introduced species suited for the management use intended may be the only way to overcome some invasive species. Success of re-establishing a native or desired plant community on a large scale has not been documented. Small-scale attempts are rated to be low and highly variable for the rate of control of most species. Possibly, a site could be established to look similar to an at-risk community within the reference state. However, it is still not possible to reach the reference community condition once annuals have established on a site. The need to till the soil or to prepare the seedbed for planting the native species, 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 soils, the change in the plant community and the risk of re-invasion of the site will prevent it from reacting in the same manner to management and environmental changes as an unaltered native community. Therefore, it remains in the reclaimed state/community phase 5.2.
Relevant conservation practices
| Practice | External resources |
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Critical Area Planting |
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Prescribed Grazing |
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Grazing Land Mechanical Treatment |
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Range Planting |
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Heavy Use Area Protection |
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Integrated Pest Management (IPM) |
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Upland Wildlife Habitat Management |
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Early Successional Habitat Development/Management |
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Planned Grazing System |
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Prescribed Grazing |
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Invasive Plant Species Control |
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Grazing Management Plan |
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Prescriptive grazing management system for grazed lands |
Mechanism
No Use, Fire (wild or prescribed), Frequent or severe Grazing, Drought with Seed Source Present – In the reclamation or restoration process, or after a land disturbance occurs, 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 grazing by large herbivores can be a source of the disturbance that either opens the canopy and/or introduces the species to the location. Extended periods of non-use creates a decadent community with a large proportion of dead growth persisting around the crown of the plants, reducing vigor and production. As the plants begin to dieback, the community becomes vulnerable to weed invasions. The reverse of the non-use scenario, it has been found that frequent or severe grazing, drought, or fire can open the canopy to invasion as well. This invasion triggers the transition to an invaded state.
Context dependence
The disturbance of cause of the infestation and the seed sources that are available/introduced are the driving factors for the specifics of this transition.
Model keys
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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.