Limy Upland (LiU) Big Horn Basin Rim
Scenario model
Current ecosystem state
Select a state
Management practices/drivers
Select a transition or restoration pathway
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Transition T1-2
Severe and frequent grazing (continuous season-long or year-long) with drought encourages the sod-forming species to establish and then out-compete the more desirable mid-stature cool-season bunchgrasses.
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Transition T1-3
Grazing impacts to the herbaceous cover weakens and eventually removes the grasses from the community leaving a mixed shrub community.
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Transition T1-4
Disturbances such as season-long continuous grazing, drought, or fire with a seed source present provides invasive species the opportunity to establish in the Reference State.
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Transition T2-4
Drought or surface impact will provide the niche for invasive species to establish and transition the sod-former community to an Invaded State.
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Restoration pathway R3-1
Long-term grazing management with incorporation of rest to allow recovery with assistance with seeding of desirable species are needed to restore this community.
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Transition T3-4
Drought and canopy disturbance with seed sources present encourages the transition to the Invaded State.
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Restoration pathway R4-5
Integrated pest management, long-term grazing management with seeding is required to reclaim or restore to a non-invaded state.
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Transition T5-4
The lack of management or seeding failure allow the re-invasion of this site.
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No transition or restoration pathway between the selected states has been described
Target ecosystem state
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State 1
Bunchgrass/Sagebrush
Description
The Reference State holds a healthy mix of bluebunch wheatgrass, rhizomatous wheatgrasses, as well as Indian ricegrass, needle and thread, and to a minor extent sod-formers such as blue grama and threadleaf sedge.
The high calcium carbonates in the soils reduces the differences between coarser textured soils to finer textured soils. A minor shift between Indian ricegrass, blue grama and threadleaf sedge to needle and thread, western wheatgrass, and bottlebrush squirreltail does occur between sandier textures to clay loam textures. The lack of significant distinction limits the ability to separate the two communities into individual ecological sites, so the range of plant composition will capture this characteristic within the plant community tables.
Characteristics and indicators
The reference state is characterized by the dominance of bluebunch wheatgrass, at 50% or less composition by weight, with Wyoming big sagebrush at 10% or less composition by weight. The droughty nature of these soils reduces the plant cover and maintains a higher level of bare ground than a soil with no chemistry. Lichen is a common soil cover that is found to indicate elevated levels of carbonates in the soil.
Resilience management
Although bluebunch wheatgrass and sagebrush are resilient species, they are at-risk when subjected to continuous season-long or year-long grazing. Once they are removed from a community they can be difficult to recover.
Submodel
Description
Blue grama and threadleaf sedge are sod-forming species that exist as a component of the perennial vegetation naturally (in reference communities) in the ecological site. The general tendency of these species is to increase under grazing pressure, becoming dominant. The species that gains dominance appears to be dependent on which species is more prevalent in the community before the negative pressures are applied.
Characteristics and indicators
This state is characterized by the dominance of these sod-formers and the lack of a most other cool-season bunchgrasses is distinct on the landscape. The lack of sagebrush and increasing cactus cover is also characteristic of the Sod-Former State (State 2).
Resilience management
Sod-forming species, blue-grama and threadleaf sedge alike, are hardy and resilient. Once they have established a dense root-mat they are extremely difficult to remove from a site without significant inputs. They also alter the natural hydrologic process of a community limiting the potential for other species to recover.
Submodel
Description
If continued pressure or disturbance occurs on the vulnerable community within the reference state (State 1), it can be forced into the Sagebrush/Bare Ground State. Over time, drought or grazing pressures on this state will reduce the herbaceous plant cover to occurrences under the canopy of Wyoming Big sagebrush or similar shrub species (rabbitbrush) and within the protection of prickly pear cactus.
Characteristics and indicators
A sagebrush canopy with limited understory cover is the major characteristic of this community. There is a misnomer that claimed an increase in brush cover, however, the lack of understory will give the perception of increased shrub cover.
Resilience management
The soil conditions are limiting for plant establishment, and the climatic variables within this area are also challenging. Once the understory is reduced, it will take time and resources to improve the site. The existing understory species will have an influence on the recovery potential of a community.
A Wyoming big sagebrush community with a scare understory of bottlebrush squirreltail was located. There were trace amounts of bluebunch wheatgrass, Sandberg bluegrass, and annual forbs. Production was low and Wyoming big sagebrush was at approximately 25% canopy. Bureau of Land Management (BLM), completed a variety of treatments over three years. The trials showed that the timing and climate during the trial determined which species would thrive. The mowing treatments during this trial occurred at optimal germination conditions for bottlebrush squirreltail. So the mowing treatment acted as a seed dispersal process allowing the plant species to flourish.
Submodel
Description
Invasive plant species are a permanent concern with rangelands and management. Each year new species are discovered and will alter this section as they are. Currently within the Big Horn Basin there are several varieties of thistles, knapweeds, milkweeds, mustards and others that create a management issue for livestock and ecology. In areas where there has been a disturbance, natural or man-made, these species can gain a place in the landscape and are difficult to impossible to eradicate. Because of this it becomes a battle to maintain control with annual or prolonged management of the weed species, and preventing further shifts or changes to the native composition.
Submodel
Description
The Degraded state could be drafted as a stand-alone box within the state and transition model diagram. No matter what state a site originally is ranked in, once the site is mechanically disturbed, or suffers a catastrophic or significant natural disaster that alters the soil properties (erosional, depositional, hydrological or chemical), the site potential is altered. To consider this as an alternate ecological site would not be unreasonable. In some cases (site by site consideration), a re-correlation of a location may be the best solution. But in many cases, the site has not been altered out of the current site, but the potential has shifted enough that it is no longer truly comparable to the reference community. So a dynamic state was captured to detail the altered communities that exist on the landscape.
Submodel
Mechanism
Frequent and severe grazing (yearlong grazing) will convert the plant community to the Sod-Former/Sagebrush State. Drought or the shift in precipitation timing and spring warm up has also encouraged the shift to short-statured sod-forming grasses.
Constraints to recovery
The dense root system of blue grama and threadleaf sedge are difficult to reduce to allow other native species to establish on a site. The alternation of hydrologic properties of these sod-former further creates a dry and hostile environment for most mid-stature cool-season grasses.
Mechanism
Frequent and severe grazing will convert the plant community to the Big Sagebrush/Bare Ground Plant Community. This conversion is found on areas where the sagebrush stand is not adversely impacted by drought or heavy browsing, but the herbaceous species have been weakened or removed from the system.
Constraints to recovery
The limited or lack of seed sources for the desired mid-stature cool-season bunchgrasses and the natural soil conditions that provide a harsh environment for seed germination restrict the ability for this community to recover.
Mechanism
Frequent and severe grazing, fire, drought, or disturbance with introduction of a seed source will allow this plant community and any of the states to shift to the Invaded State. There is a high risk of crossing the threshold into the Invaded State, especially with the continued increase of invaders in high traffic areas and the persistence of drought which opens the plant community to aggressive species like cheatgrass.
Constraints to recovery
The difficulty in reducing and inability to eradicate cheatgrass is the main constraint to recovery. The limiting characteristics of the soils also restricts establishment of desirable species.
Mechanism
Blue grama and threadleaf sedge have been seen to die back or die out with prolonged drought opening the canopy and the community’s vulnerability to invasive species. Disturbance by mechanical means or human activities that break the root masses or disturb the soil surface provide the potential niche for invasive species to establish, especially when there is a readily available seed source for those invasive species.
Constraints to recovery
The limited ability to eradicate invasive species such as cheatgrass limits the ability for this community to recover.
Mechanism
The use of herbivory during the dormant season with the introduction of native seed sources to encourage the re-establishment of grasses to this community is one means of assisting with recovery of the Sagebrush/Bare Ground State. Rest and long-term grazing management are needed to allow the recovery of native species.
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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Upland Wildlife Habitat Management |
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Prescribed Grazing |
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Grazing Management Plan |
Mechanism
A combination of long-term drought or a canopy disturbance will convert the sagebrush/bare ground plant community to the Invaded State, if an invader species seed source is present.
Constraints to recovery
The challenge of eradicating or reducing and maintaining an invaded plant community while encourage native species has not been successfully accomplished, especially on these droughty soils.
Mechanism
Integrated pest management with an intensive ground treatment to remove/eradicate the invasive species is the first process in restoring this community. The removal of the invasive species is then followed by seeding with long-term grazing management and weed management to restore or reclaim an invaded community to a native community. Success is extremely limited and is only known to have been completed on small scale areas.
Relevant conservation practices
| Practice | External resources |
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Cover Crop |
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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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Upland Wildlife Habitat Management |
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Early Successional Habitat Development/Management |
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Invasive Plant Species Control |
Mechanism
The lack of weed management, further ground disturbance or seeding failure allow the invasive species to re-establish transitioning a reclaimed site back to an invaded state.
Constraints to recovery
The limited capabilities to control invasive species is the main constraint to recovery. However, the limiting characteristics of the soil also inhibit the establishment of native species that could help reduce the threat of invasive species.
Model keys
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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.