State 1
Reference

The prominent cover of bluebunch wheatgrass and other mid-stature cool-season bunchgrasses with perennial forbs and a mix of Wyoming big sagebrush, black sagebrush and winterfat make for a productive and stable site.

Characteristics and indicators. Bluebunch wheatgrass is the dominant herbaceous species on this site with Wyoming big sagebrush as the dominant woody cover. Black sagebrush is common on this ecological site, but there is a specific zones within the Rim subset that black sagebrush is more dominant (tied directly to the dolomite and limestone related areas). Lichen provide a significant soil cover in combination with other cryptogamic crusts.

Resilience management. The hardiness of the vegetation that thrive within the harsh conditions of the soil characteristics of the Limy Skeletal ecological site create a plant community resistant to change. But once disturbed, the herbaceous component of this site is difficult to restore, reducing the resiliency of the community.

Community 1.1
Bluebunch Wheatgrass/Needle and Thread/Sagebrush

Figure 8. Bluebunch wheatgrass and needle and thread are dominant on this Limy Skeletal Site.

This plant community is the interpretive plant community for the Limy Skeletal ecological site and is considered to be the Reference Plant Community. This state evolved with grazing by large herbivores and infrequent periodic fires. This plant community can be found on areas that are properly managed with grazing and on areas receiving occasional short periods of rest. The potential vegetation is about 75% grasses or grass-like plants, 10% forbs, and 15% woody plants. This state is dominated by cool season mid-grasses.

The major grasses include bluebunch wheatgrass, needle and thread, Indian ricegrass, and rhizomatous wheatgrasses (Western and Thickspike). Other grasses occurring in this state include bottlebrush squirreltail, prairie junegrass, and Sandberg bluegrass. Wyoming big sagebrush and black sagebrush are an important element of this state, occurring in a mosaic pattern, and making up 5 to 15% of the annual production. Winterfat is common in the community as are a variety of forbs.

The total annual production (air-dry weight) of this state is about 325 lbs./acre, but it can range from about 150 lbs./acre in unfavorable years to about 450 lbs./acre in above average years.

Resilience management. This plant community is extremely stable and well adapted to the Northern Intermountain Desertic Basins climatic conditions. The diversity in plant species is high across this community which allows for a high drought tolerance. This is a sustainable plant community (site/soil stability, watershed function, and biologic integrity).

Community 1.2
Perennial Grasses/Wyoming Big Sagebrush

Figure 10. Broom snakeweed and Sandberg bluegrass have replaced needle and thread, and the bluebunch wheatgrass has decreased in this community.

Historically, this plant community evolved under grazing and a low fire frequency. Currently, it is found under moderate, season-long grazing by livestock and will be exacerbated by prolonged drought conditions. This plant community is still dominated by cool-season grasses, while short warm-season grasses and miscellaneous forbs account for the balance of the understory. Sagebrush (Wyoming big sagebrush and black sagebrush) is the larger part of the overall production and accounts for the majority of the upper canopy.

The bluebunch wheatgrass is still abundant in the community, with needle and thread although they are decreasing. Rhizomatous wheatgrasses, bottlebrush squirreltail, Sandberg bluegrass are increasing. Forbs commonly found in this plant community include scarlet globemallow, fringed sagewort, and spiny phlox. Wyoming big sagebrush and black sagebrush can make up to 25 percent of the annual production. The upper canopy of sagebrush and lower canopy of grasses and forbs provide a diverse plant community.

When compared to the Reference Community 1.1, the change in sagebrush accompanied by the increase of blue grama, threadleaf sedge, and plains prickly pear cactus are indicators of a transition. Indian ricegrass will only occur in trace amounts under the sagebrush canopy or within the patches of prickly pear. In addition, the amount of winterfat may or may not have changed depending on the season and species of use.

The total annual production (air-dry weight) of this state is about 250 pounds per acre, but it can range from about 150 lbs./acre in unfavorable years to about 400 lbs./acre in above average years.

Resilience management. Rangeland Health Implications/Indicators: The herbaceous component is mostly intact and plant vigor and replacement capabilities are sufficient. Water flow patterns and litter movement may be occurring but only on steeper slopes. Incidence of pedestalling is minimal. Soils are mostly stable and the surface shows minimum soil loss. The watershed is functioning and the biotic community is intact. This plant community is resilient, but is subject to change. The herbaceous species present are well adapted to grazing; however, species composition can be altered through long-term year-long or continuous season-long grazing or natural and man-made disturbances.

Pathway 1.1A
Community 1.1 to 1.2

Bluebunch Wheatgrass/Needle and Thread/Sagebrush

Perennial Grasses/Wyoming Big Sagebrush

Moderate, continuous season-long grazing will convert the plant community to the Perennial Grass/Sagebrush Community Phase. Prolonged drought will exacerbate this transition. The continuous use reduces the key mid-stature bunchgrasses such as bluebunch wheatgrass, needle and thread, and Indian ricegrass; allowing the short-stature bunchgrasses and sod-formers to increase in the community.

Pathway 1.2A
Community 1.2 to 1.1

Perennial Grasses/Wyoming Big Sagebrush

Bluebunch Wheatgrass/Needle and Thread/Sagebrush

Prescribed grazing or possibly long-term prescribed grazing, will allow recovery to the Reference Community Phase. Rotational grazing with deferment is implemented as part of the prescribed method of use. Prescribed fire or brush management may encourage rejuvination of sagebrush and will remove old standing growth of bluebunch wheatgrass and other bunchgrasses. Consideration of the risk of invasive species needs to be taken before using prescribed fire on this community.

State 2
Sod Bound

The Sod Bound state with sagebrush is a low-stature community that has shifted from the cools-season bunchgrasses to warm-season tillering grasses (blue grama) with intermixed grass-like species (threadleaf sedge).

Characteristics and indicators. Wyoming big sagebrush and black sagebrush are still the prominent woody cover for this site, however there may be a notable composition of winterfat. Season of use and species of grazing ungulate will be a factor affecting this cover. The sagebrush cover is still dwarfed or droughty in appearance and generally has been reduced in vigor by the shift in hydrology of this community. Most other mid and short-stature cool-season bunchgrasses are limited to within the canopy of the sagebrush or within the protective ring of cactus clumps.

Resilience management. The dense root map of blue grama and threadleaf sedge make this community extremely resistant to change, and resilient to disturbance. Although the establishment of blue grama and threadleaf sedge is a slow process, it will recover with time. Removal of grazing or disturbance does not provide a shift in the herbaceous cover within this community. The overall health and vigor of both the herbaceous as well as woody cover will improve with the removal of the grazing pressure or disturbance from the community. Blue grama's wide-spread increase in many ecological sites within the Big Horn Basin is hypothesised to be a response to shifts in timing of precipitation and seasonal warm-up patterns over the last 100 years.

Community 2.1
Sod-formers/Sagebrush

Figure 13. Threadleaf sedge community on the Limy Skeletal ecological site.

This plant community is the result of frequent and severe (year-long or continuous season-long) grazing, which has adversely affected the perennial grasses as well as impacted the shrub component. Other factors that can affect this community include drought, shift in climate, wildlife browsing and alternative uses.

A dense sod of blue grama with patches of threadleaf sedge dominates this state. Prickly pear cactus will increase in the community, and can limit livestock's ability to access grazable forage. Sagebrush has been reduced or in some cases removed, while rubber rabbitbrush may persist in the community. Wyoming big sagebrush has been noted to decrease first in a community while black sagebrush appears to be more resilient on the landscape.

When compared to the Reference Communities, blue grama and threadleaf sedge have increased. Prickly pear cactus has invaded. All cool-season mid-grasses, forbs, and most shrubs have been greatly reduced. Production has significantly decreased.

The total annual production (air-dry weight) of this state is about __ pounds per acre, but it can range from about __ lbs./acre in unfavorable years to about __ lbs./acre in above average years.

Resilience management. Rangeland Health Implications/Indicators: This community is at risk of transition to a completely sod-bound community as explained above, as the sod is extremely resistant to change and continued frequent and severe grazing or the removal of grazing does not seem to affect the plant composition or structure of the sod-formers, but it will eventually remove the shrub component from the plant community. The biotic integrity of this state is not functional and plant diversity is extremely low. The plant vigor is significantly weakened and replacement capabilities are limited due to the reduced number of cool-season grasses. This sod-bound plant community is very resistant to water infiltration. While this sod protects the site itself, off-site areas are affected by excessive runoff that can cause rills and gully erosion. Water flow patterns are obvious in areas of bare ground and pedestalling is apparent along the sod edges. Rill channels are noticeable in the interspaces and down slope. The watershed may or may not be functioning, as runoff may affect adjoining sites.

State 3
Bare Ground

Figure 14. Historic use and drought has removed the herbaceous lower canopy, leaving sagebrush as the only cover.

The loss of most of the herbaceous understory in the community leaves a barren and generally decadent (in appearance) stand of Wyoming big sagebrush and black sagebrush. Lichen and cryptogramic crust cover may or may not be in tact, health of this living soil cover is dependent on the type of disturbance and period of recovery following the disturbances that has lapsed.

Characteristics and indicators. The dominance of sagebrush cover, with a mix of there short shrubs, with the lack of most herbaceous cover is the characteristics of the Sagebrush/<a class="species-link" href="https://plants.usda.gov/core/profile?symbol=2BARE" target="_blank" title="Open in plants.usda.gov"><i>Bare Ground</i></a> State. Remnant populations of perennial grasses will occur in the canopy of sagebrush or within the protective niche within cactus clumps.

Resilience management. The lack of native propagates and the limitations of this calcic soil restrict the ability of most native species to recover, lowering the resiliency of this State. This ecological state is at risk of transitioning to an invaded state due to the lack of soil cover and competitive native species.

Community 3.1
Sagebrush/Bare Ground

Figure 15. Historic use and drought have removed the lower canopy leaving sagebrush as the only cover in this community.

This plant community is the result of frequent and severe grazing and drought. Sagebrush dominates this plant community, with an absence of most perennial grasses. Forbs may be present, especially lower growing annual forbs. Wyoming big sagebrush and black sagebrush are the major vegetative cover.

The dominant grasses are bottlebrush squirreltail, Sandberg bluegrass, and blue grama. Cactus often invades. The interspaces between plants have expanded leaving the amount of bare ground more prevalent. As compared with the Reference State, the annual production declines, with the loss of herbaceous production.

Shrub production may fluctuate slightly; however, the historic presumption of shrub increasing significantly has not been documented. Overall sagebrush cover maintains or may increase slightly, but age and density of the canopy cover will vary over time.

The open interspaces leave this site vulnerable to weedy annual species such as cheatgrass to occupy the site if a seed source is available. If invasive species gain a foothold, they push the state across a threshold into the Invaded State.

The total annual production (air-dry weight) of this state is about __ pounds per acre, but it can range from about __ lbs./acre in unfavorable years to about __ lbs./acre in above average years.

Resilience management. Rangeland Health Implications/Indicators: This plant community is resistant to change as the stand becomes more decadent. These areas hold a lower fire threat because of the lack of fine fuels and the increase of bare ground between sagebrush plants. Plant diversity is moderate to poor. The plant vigor is diminished and replacement capabilities are limited due to the reduced number of cool-season grasses. Plant litter is noticeably less when compared to reference communities. Soil erosion is accelerated because of increased bare ground. Water flow patterns and pedestalling are obvious. Infiltration is reduced and runoff is increased. Rill channels may be noticeable in the interspaces and gullies may be establishing where rills have concentrated down slope.

State 4
Invaded

The Invaded State has a range of variability that is distinguished by its population of invasive or introduced (non-native) species that has successful established and become significant within the composition of the community. A significant component of this community initially is comprised of the native species that comprise the reference communities.

Characteristics and indicators. The composition by weight of ten percent or more of an invasive species is the factor tipping a community over the threshold into the Invaded State. The community can be relatively intact, having a representative composition of native species similar to the Reference State, but with a significant composition (minimum of five percent) cover of an invasive species or mix of invasive species. Cheatgrass is the most significant threat at this time; however, there are other aggressive non-native species that pose a concern on this ecological site. These species include field cottonrose, mustards, Russian thistle, and Kochia.

Resilience management. The competitive edge of most invasive species makes this site resistant to change and resilient following disturbance. Cheatgrass has been seen to respond with a positive potential following disturbances (fire, mechanical).

Community 4.1
Perennial Grasses/Invasive Species/Sagebrush

The Perennial Grasses/Invasive Species/Sagebrush phase has maintained a representative sample of the perennial grasses and forbs that are typical of the site with the accompanying sagebrush composition (Wyoming big sagebrush and black sagebrush).

The invasive species are present and hold a significant (10 percent or greater) composition of the landscape, and are prominent on the site (referring to a more wide scale composition, not one isolated patch in an isolated portion of the landscape).

Production of the desired perennial species of this site is generally reduced but the total production is maintained or elevated due to the production potential of many of the annual or invasive species.

Resilience management. Rangeland Health Implications/Indicators: This plant community is resistant to change. These areas may be more prone to fire as fine fuels are more available and the bare ground between the sagebrush plants is decreased. Plant diversity is moderate to poor. The plant vigor is diminished and replacement capabilities are limited due to the reduced number of cool-season grasses. Plant litter is noticeably more when compared to reference communities due to the potential biomass produced by the invasive species (species dependent). Soil erosion is variable depending on the species of invasion and the litter accumulation thus associated, this variability also applies to water flow patterns and pedestalling. Infiltration is reduced and runoff is increased due to loss of perennial vegetation and root density.

Community 4.2
Invasive Species/Sagebrush

This community phase is the at-risk community. As the native populations of perennial grasses and forbs become weakened, the site becomes invader driven, and irreversible. If environmental or management stressors or disturbances occur to remove the shrub component, the site crosses a threshold to State 6, Annual Grasses/Invaders.

The sagebrush is able to compete and maintain a strong community under a heavy infestation level unless fire or disturbance of any nature weakens the plant. The canopy of the sagebrush serves as a protective niche for native grass species allowing them to persist. But the herbaceous native community is low in resistance and even lower in resilience. The invasive community is a highly resistant and resilient community.

Resilience management. Rangeland Health Implications/Indicators: This plant community is resistant to change as the stand becomes more decadent. These areas may be more prone to fire as fine fuels are more available and the bare ground between the sagebrush plants is decreased. Plant diversity is poor. The plant vigor is diminished and replacement capabilities are limited due to the reduced number of cool-season grasses. Plant litter is noticeably more when compared to reference communities due to the potential biomass produced by the invasive species (species dependent). Soil erosion is variable depending on the species of invasion and the litter accumulation thus associated. The variability of the water flow and pedestalling as well as infiltration and runoff is determined again by the species that establishes on this site.

Pathway 4.1A
Community 4.1 to 4.2

Frequent or Severe Grazing, Drought, Disturbances (mechanical) and Wildfire – Drought, wildfire, or other climatic stresses on the system can continue to stress the native species reducing their ability to maintain their footprint in the plant community. This continued stress or the complication with mechanical disturbances or, frequent or severe grazing or pressure from wildlife and livestock can reduce the natives to an nonviable or unsustainable population and allow the invasive species to dominate the site, specifically cheatgrass (downy brome).

State 5
Degraded

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.
Mechanical disturbances and reclamation practices using non-native species could qualify some stages of this state to be considered as a land use shift. The end result in either case is the shift in potential and response in management so that it is no longer similar to the reference community. The potential shifts are highly variable, so a dynamic state was captured to detail the altered communities that exist on the landscape.

Characteristics and indicators. The soil disturbance and mechanical or physical removal of the vegetative canopy is the key characteristic of the Disturbed State. The initial indicators are the primary successional species that establish following a disturbance including kochia, six weeks fescue, and sunflowers. These initial colonizers will then be followed by any seeded species, or other species from within the locations seed bank.

Resilience management. This State is highly variable and in a state of flux as the successional processes occur. The continued disturbance of these areas is a potential threat. This State is at high risk of transitioning to the Invaded State.

Community 5.1
Disturbed Lands

The title Disturbed Lands is encompassing two broad classifications of these land types. Go-back fields are referring to sites that were once cultivated or have had minor surface disturbance, and have since been left to natural processes. Homestead and abandoned farming sites can be identified on the landscape (through photo-tone shifts in aerial photographs) and are generally a mix of natives that have moved into disturbed sites or a co-mingling of introduced species and natives. These sites are difficult to reclaim, generally due to the introduced species that persist on the landscape. And once reclaimed, do not tend to respond to the natural disturbance regimes in the same manner that a native, mechanically undisturbed site would respond. The Limy Skeletal ecological site was not typically farmed specifically, but was influenced by homesteading or irrigation processes. The extent of this type is limited on the landscape.

In a similar process, mined lands or lands affected by energy development including gravel or mineral excavation pits, transmission corridors, transportation corridors and oil and gas development sites provide a host of successional processes. Many times, these locations are re-exposed to disturbance frequently by mechanical means leaving annual weeds and primary successional species as the dominate canopy. Older, established sites or abandoned locations, have established communities similar to those expected on go-back fields and may be stable in nature.

The growth curve of this plant community will vary depending on the species that are selected for seeding. For a more accurate portrait of the growth curve for the seeded community, the species used and the climatic tendencies of the region must be considered.

Resilience management. Rangeland Health Implications/Indicators: The plant community is variable and depending on the age of the stand and the stage of successional tendencies that the location is in will determine how stable (resilient/resistant) the community is. Plant diversity is generally strong, but is usually lacking in the structural groups that are desired on the site. Soil erosion is variable depending on the disturbance regime that is occurring on the site and again on the specific community that has established on a specific location. The variability of the water flow and pedestalling as well as infiltration and runoff is determined again by the species that establishes on this site.

Transition T1A
State 1 to 2

Frequent and severe (year-long or continuous season-long ) grazing or compaction from surface traffic, will convert the plant community to a Sod-former Plant Community. The impact to of frequent or repeated hits during grazing, hoof impact, and lack of rest for recovery weakens and removes the key grass species in the community. As the mid-stature grasses decline, blue grama is able to increase and alter the hydrology of the site.

Constraints to recovery.The dense root mat formed by blue grama and threadleaf sedge alters the hydrology, effectively removing moisture from the site, limiting the available resources for other native species. The dense sod also limits the available soil space for seedling establishment. Interpspaces between sod patches are prone to erosion and runoff (limited infiltration of moisture).

Transition T1B
State 1 to 3

Frequent and severe grazing plus no fire on soils with limited soluble salts, will convert the plant community to the Sagebrush/<a class="species-link" href="https://plants.usda.gov/core/profile?symbol=2BARE" target="_blank" title="Open in plants.usda.gov"><i>Bare Ground</i></a> Plant Community. This is especially evident on areas with historically higher precipitation and the sagebrush stand is not adversely impacted by drought or heavy browsing. Grazing impacts to the herbaceous cover repeatedly removes it from the community leaving a sagebrush dominated community. Drought, insect damage, and other natural disturbances can assist in this transition.

Constraints to recovery.The lack of a seed bank and the harsh environment of the soils limits seedling establishment and survival. The unpredictable and variable spring precipitation also limits success of recovery for the Limy Skeletal ecological site.

Transition T2A
State 2 to 4

Drought, Frequent or severe grazing, Disturbance – Drought as the only factor or drought with grazing intensity together can work to weaken or kill Wyoming big sagebrush on the landscape, and once it has declined or been removed from an area it is not known if or how long it will take for it to come back without cultural methods, which do not carry a reliable success rate. 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 open this closed community to potential invasive species, especially when there is a readily available seed source for those invasive species.

Constraints to recovery.The dense sod of threadleaf sedge will continue to impact the hydrology and competition for limited resources in this community limiting the potential for recovery. The lack of other key herbaceous species also is a constraint on this site. The inability, at this time, to eradicate cheatgrass does not allow for a complete recovery of an invaded community.

Restoration pathway R3A
State 3 to 1

Brush management with prescribed grazing or rest allows for this community to improve. Trials completed in the local area have demonstrated the ability for these Limy Skeletal ecological sites to recover herbaceous cover following a sagebrush mowing treatment. The recovery is dependent on the remnant population the is present, the current weather patterns, and timing.

Transition T3A
State 3 to 4

Drought, soil disturbances, or high-intensity grazing with a seed source present can open the soil surface and weaken the sod allowing invasive species to establish. Although not common, fire can provide the niche for cheatgrass to establish on this site.

Constraints to recovery.Once invasive species, especially cheatgrass, establish, it is costly and difficult (if even possible) to remove. The lack of the key grass species also limits recover of this site.

Restoration pathway R4A
State 4 to 5

Integrated Pest Management, with Seeding the site to a native mixture - Success is not known to have occurred, and is rated to be low and highly variable for the rate of control of most species. Cheatgrass is one of the most invasive species for many of these sites, although there are other challenges. With intensive weed control and inputs this community can resemble an at-risk community within the reference state, but it is not possible to reach the reference community condition once annuals have established on a site.

Transition T5A
State 5 to 4

Frequent or Severe Grazing, Disturbance with a seed Source, or Drought - Any disturbance that occurs or stress that is placed on the herbaceous cover, weakens the canopy and allows for invasive species to establish if a seed source is present. This State is at high risk of transitioning to an Invaded State. The challenge of successful seedings on a calcareous soil opens the community to invasion.

Constraints to recovery.The challenge of eradicating or reducing invasive species such as cheatgrass prevents recovery of most invaded communities without significant inputs for weed control, seeding with long-term grazing management.