State 1
Reference

The Reference state holds a healthy mix of bluebunch wheatgrass, needle and thread, as well as Indian ricegrass, rhizomatous wheatgrasses, and a minor extent of the sod-former 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 and threadleaf sedge to needle and thread and western wheatgrass 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 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.

Community 1.1
Bluebunch Wheatgrass/Needle and thread/Sagebrush

Figure 8. Bluebunch wheatgrass and needle and thread community on an eroded fan remnant. Mix of black sagebrush and Wyoming big sagebrush are present.

This plant community is the interpretive plant community for this site and is considered to be the Reference Plant Community. This state evolved with grazing by large herbivores. The fire role on this site is reduced by the lack of dense cover to carry a fire; although not a major role, there is still a risk for fire in this community following a year with high productivity. This plant community can be found on areas that are properly managed with grazing with areas receiving occasional short periods of rest. The potential vegetation is about 75% grasses or grass-like plants, 15% forbs, and 10% woody plants. This state is dominated by cool season mid-grasses. The major grasses include bluebunch wheatgrass, needle and thread, and Indian ricegrass. Rhizomatous wheatgrasses (Montana, Western, and Thickspike) are intermediate grasses on this community. Other grasses occurring in this state include prairie junegrass, needleleaf sedge, and Sandberg bluegrass. Sagebrush is a conspicuous element of this state, occurring in a mosaic pattern, and making up 5 to 10% of the annual production. Black sagebrush is dominant, but small areas of Wyoming big sagebrush will occur. Winterfat and fringed sagewort are a common component found on this site. A variety of forbs also occurs in this state and plant diversity is high (see Plant Composition Table). The total annual production (air-dry weight) of this state is about 400 lbs./acre, but it can range from about 250 lbs./acre in unfavorable years to about 600 lbs./acre in above average years.

Resilience management. This plant community is extremely stable and well adapted to the Central Rocky Mountains foothill climatic conditions. The diversity in plant species allows for high drought tolerance. This is a sustainable plant community (site/soil stability, watershed function, and biologic integrity).

Community 1.2
Perennial Grasses/Sagebrush

Figure 11. Post-fire, bluebunch wheatgrass and Sandberg bluegrass are robust with broom snakeweed and fringed sagewort. Black sagebrush has a small holding and is beginning to recover in the community.

Figure 12. Wyoming big sagebrush is prevalent with only small disbursements of black sagebrush on this bluebunch wheatgrass, western wheatgrass, and Sandberg bluegrass community.

The Perennial Grasses/Sagebrush Community Phase is found under moderate, season-long grazing by livestock and will be exacerbated by prolonged drought conditions. Historically, this plant community evolved under grazing and a low fire frequency. The plant community maintains a cool-season grass dominant component, while tillering sedges and miscellaneous forbs account for the balance of the understory. Black sagebrush is now a conspicuous part of the overall production and accounts for the majority of the over story. Rubber rabbitbrush and Wyoming big sagebrush to a lower degree, may be present in the overstory. Sagebrush can make up to 25% of the annual production. The dominant grass is bluebunch wheatgrass, with rhizomatous wheatgrasses, Sandberg bluegrass, needleleaf sedge, and threadleaf sedge increasing on the site. Forbs commonly found in this plant community include scarlet globemallow, salsify, fringed sagewort, and spiny phlox. The over story of sagebrush and understory of grasses and forbs provide a diverse plant community. Plains pricklypear cactus will be present, but occurs in small isolated patches. Indian ricegrass and needle and thread have decreased and may occur in only trace amounts under the sagebrush canopy or within cactus clumps. Winterfat is common, but different seasons and species of use will reduce its vigor. The total annual production (air-dry weight) of this state is about 450 pounds per acre, but it can range from about 250 lbs./acre in unfavorable years to about 700 lbs./acre in above average years.

Resilience management. Rangeland Health Implications/Indicators: 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 improper management and disturbance causing decadence and decrease in vigor of the vegetative cover. 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.

Pathway 1.1A
Community 1.1 to 1.2

Bluebunch Wheatgrass/Needle and thread/Sagebrush

Perennial Grasses/Sagebrush

Moderate, continuous season-long grazing will convert the plant community to the Perennial Grass/Sagebrush Plant Community. Prolonged drought will exacerbate this transition. The stressers reduce the mid-stature grasses such as bluebunch wheatgrass, needle and thread, Indian ricegrass; allowing the short-statured grasses and sod-formers to increase in dominance in the community.

Pathway 1.2A
Community 1.2 to 1.1

Perennial Grasses/Sagebrush

Bluebunch Wheatgrass/Needle and thread/Sagebrush

Prescribed grazing or possibly long-term prescribed grazing, will allow recovery of this plant community to the Reference community. The probability of this occurring is high especially if rotational grazing along with short periods of rest is implemented as part of a prescribed method of use. The limiting soil properties will slow recovery of this site, so change will not occur immediately following implementation of a changed grazing strategy. However, the community will respond to changes in precipitation relatively quickly and with marked differences.

State 2
Sod Bound

Threadleaf sedge is a sod-forming species that exist as a component of the perennial vegetation naturally (in reference communities) in the ecological site. The general tendency of threadleaf sedge is to increase under grazing pressure, becoming dominant. The alteration of the site by the root mats hinder other native grasses reducing their presence in the community.

Characteristics and indicators. This state is characterized by the dominance of threadleaf sedge 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. Threadleaf sedge, a sod-forming species, is hardy and resilient. Once threadleaf sedge has established a dense root-mat the upland sedge is extremely difficult to remove from a site without significant inputs. The dense root mat alters the natural hydrologic process of the community, moving moisture off-site and limiting the potential for other species to recover.

Community 2.1
Threadleaf Sedge/Sagebrush

Figure 15. Remnants of bluebunch wheatgrass are still present, however, threadleaf sedge is dominant in the gaps within the community.

This plant community is the result of frequent and severe year-long grazing, which has adversely affected the perennial grasses as well as impacted the shrub component. Other factors that can affect the shrubs include drought, heavy browsing, and other surface disturbances. A dense sod of threadleaf sedge dominates this state. Sagebrush has been reduced to small patches, and rubber rabbitbrush is present. When compared to the Reference State (State 1), threadleaf sedge, has increased. Pricklypear cactus has increased. Cool-season mid-stature grasses, forbs, and most shrubs have been greatly reduced. Production has been significantly decreased. The total annual production (air-dry weight) of this state is not available. At this time, sufficient data has not been collected to provide dependable production.

Resilience management. Rangeland Health Implications/Indicators: This community is at risk of losing the shrub component from the plant community. The biotic integrity 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 immediate area, 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 inter-spaces and down slope. The watershed may or may not be functioning, as runoff may affect adjoining sites.

State 3
Sagebrush/Bare Ground

Figure 17. Herbaceous cover is within the crown or near black sagebrush plants with open or near barren interspaces in this community.

Figure 18. Increased bare ground and lack of grasses in this community is classic for Community Phase 3.1.

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 woody canopy, of sagebrush or rabbitbrush, and within the protection of pricklypear cactus.

Characteristics and indicators. A sagebrush canopy with limited understory cover is the major characteristic of this community. The lack of herbaceous understory and maturity of the sagebrush and shrub canopy is prominent on the landscape. These factors also create the dominance in production of sagebrush, not specifically an increase in the total number of plants. The change is more of a factor of the closed canopy of mature stands of sagebrush and other shrubs.

Resilience management. Variable climatic patterns and limitations of this calcareous soil hinders plant establishment and vigor. Impact to the herbaceous cover, reducing and potentially removing understory cover, will take time and resources to improve the community. Those species that are able to persist within protective niches in the community influence the recovery potential.

Community 3.1
Sagebrush/Bare Ground

The Sagebrush/Bare Ground Community Phase is the result of drought and frequent and severe (continuous, season-long or year-long) grazing. Sagebrush dominates this plant community, and the preferred cool-season grasses have been greatly reduced. The cool-season grass remnants commonly found in the understory of the sagebrush or within cactus clumps are bluebunch wheatgrass, Sandberg bluegrass, western wheatgrass and six-weeks fescue. The interspaces between plants have expanded leaving the amount of bare ground more prevalent. The open interspaces leave this site vulnerable to weedy annual species, such as Cheatgrass, to occupy the community if a seed source is available. If invasive species gain a foothold, they force the state across a threshold into the Invaded State. The total annual production (air-dry weight) of this state is not available. At this time, sufficient data has not been collected to provide dependable production.

Resilience management. Rangeland Health Implications/Indicators: This plant community is resistant to change as the stand becomes more decadent. These areas may actually be more resistant to fire as less fine fuels are available and the bare ground between the sagebrush plants is increased. Continued frequent and severe grazing does not seem to affect the composition or structure of the plant community. Removal or protection from grazing shows only minor improvement, and any significant change will take time and will be dependent on the seed bank available. 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

Invasive plant species are a permanent concern on rangelands and their management. New species are discovered and listed continually, and new methods of treatment are under development that will alter the information in this section. Currently, the foothills within the Big Horn Basin, are prone to cheatgrass, and several varieties of thistles, knapweeds, 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.

Characteristics and indicators. The significant presence of invasive species (cheatgrass or thistles) or other non-native weedy species within the community is the indication that there has been a shift to this State. Significant is quantified as five percent composition by cover within the community.

Resilience management. The resiliency of most invasive species to persist through significant disturbance create a challenging regime for treatment. Long-term weed management plans are needed to maintain control of many of the invasive species, and eradication is extremely difficult if possible.

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 black sagebrush composition. The invasive species are present and hold a significant (five 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

Black sagebrush is able to maintain a community under a heavy infestation level unless fire or insect/disease weakens the plant. The canopy of the sagebrush serves as a protected niche in the system that can hold native grass species and help them to persist. But the system is low in resistance and even lower in resilience.

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 associated litter accumulation. Potential for pedestalling as well as infiltration and runoff is also determined by the species that establishes.

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. Complication with mechanical disturbances or, frequent and severe grazing pressure from wildlife and livestock can reduce the natives to an nonviable or unsustainable population and allow the invasive species to dominate the site.

State 5
Degraded

The Degraded State could be drafted as a stand-alone box within the state and transition model diagram. No matter which a State an ecological site originally is ranked in, once the community is mechanically disturbed, or suffers a catastrophic or significant natural disaster that alters the soil properties (erosional, depositional, hydrological or chemical), the recovery 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, a location has not been altered out of the current ecological site concept, but the potential has shifted enough that it is no longer comparable to the reference community. In response to the change in potential and the variability, a dynamic State was captured to detail the altered communities that exist on the landscape.

Characteristics and indicators. The key indication of a transition to this State is the primary successional phase following major soil disturbance, or the presence of introduced species (seeded varieties).

Resilience management. The resiliency and resistance of the established community is a direct relation to the extent of the disturbance/alteration, the species that are established and the maturity of the stand.

Community 5.1
Disturbed Lands

The title Disturbed Lands is encompassing three 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 color-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. Reclaimed communities do not respond disturbances the same as a native, mechanically undisturbed site would respond. Mined lands or lands affected by energy development including transmission corridors, transportation corridors and 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 last type of Disturbed lands are a variety of seeded introduced species. Although this could be considered reclaimed or restored, these communities were seeded to introduced or improved varieties. Many plantings were monocultures, or completed in alternating rows, not in a mixture. Crested wheatgrass was a species used frequently for reclamation throughout Wyoming and many of these communities persist today. Although there are areas where native species from neighboring sites are starting to slowly extend into the crested wheatgrass stands, many times, these stands remain as a monoculture until a disturbance occurs to open the canopy slightly to provide a more tolerable niche. Russian wildrye and varieties of rhizomatous and bunch-wheatgrasses have also been used to help compensate for the chemistry of these soils. Although the success of vegetative seedings are moderate due to unpredictable precipitation events, there are successful re-seeded sites.These communities will transition or mature as the stand density declines with lack of management or inputs, the canopy opens and allows natives, if present, to begin to establish. Although each planting is highly variable on the exact composition that will be present, they appear to be stable and can be productive sites. 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.

Community 5.2
Reclaimed Lands

Reclamation practices have shifted greatly over the last several decades from introduced varieties to native seedings. As mentioned in the community phase above, as these introduced seedings mature and the stands open, they can be characteristically similar to a reference community. The current interpretation of the definition of reclaimed or restored communities are seedings of natural occurring species to mimic or mirror the Reference Community Phase as closely as possible. This excludes the use of non-native species and allows for a more similar ecological response than what is expected with non-native species. These seedings will not replicate the reference community in response to management due to the change in soil dynamics. Mechanical disturbance for seedbed preparation and seeding, shifts soil structure, infiltration and potentially water holding capacity affecting their response to management. There are situations where these communities may respond very similar to reference. The growth curve of this plant community will vary depending on the species that are selected as the reclamation seed mix. 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: Seeding mixtures will determine the plant community resistant to change and resilience to threat of invasive species and to erosion. Many of the stands established during seeding are diversity poor, but are better than the monocultures that were planned historically. Many seeded sites may be prone to fire as they mature as many of the cultivated seeds produce more biomass (possibly more litter) and thus may create more fine fuels to fuel a fire. Soil erosion is variable depending on the establishment of the seeding, how it is seeded, and mechanical procedures put in place. 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 5.1A
Community 5.1 to 5.2

Seeding, Brush Management, Integrated Pest Management, Prescribed grazing management – With the proper mechanical improvements and the follow-up through establishment and then maintenance, a disturbed site can be improved and managed. However, climatic limitations and soil chemistry limit the success of seeding treatments. Depending on the site location, invasive species are a risk to most sites within the lower foothills and create a moderate success potential for this process.

Pathway 5.2A
Community 5.2 to 5.1

No use, No Fire, Long Term Prescribed Grazing, Frequent or Severe Grazing. The lack of maintenance of a community or further disturbance by grazing or other, will cause a decline in vigor and a shift in composition. Since the community and soils are altered from the Reference State due to plowing, mining, or other similar disturbances, the plant community will not follow the same expected shifts as a native community and will resemble the disturbed lands plant composition.

Transition T1A
State 1 to 2

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 threadleaf sedge is difficult to reduce to allow other native species to establish on a site. The alteration to the hydrologic properties by threadleaf sedge further creates a dry and hostile environment for most mid-stature cool-season grasses.

Transition T1B
State 1 to 3

Frequent and severe grazing will convert the plant community to the 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.

Transition T1C
State 1 to 4

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.

Transition T2A
State 2 to 4

Threadleaf sedge has 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.

Restoration pathway R3A
State 3 to 1

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.

Transition T3A
State 3 to 4

A combination of long-term drought or a canopy disturbance will convert the Sagebrush/Bare Ground State to the Invaded State, if an invasive 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.

Restoration pathway R4A
State 4 to 5

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.

Transition T5A
State 5 to 4

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.