State 1
Bunchgrass/Sagebrush

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.

Community 1.1
Bluebunch Wheatgrass/Rhizomatous Wheatgrsases/Wyoming Big Sagebrush

Figure 8. Bluebunch dominated community on a Limy Upland ecological site.

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, rhizomatous wheatgrasses (Western and Thickspike), needle and thread, and Indian ricegrass. Other grasses occurring in this state include bottlebrush squirreltail, prairie junegrass, and Sandberg bluegrass. Wyoming big sagebrush is a conspicuous element of this state, occurring in a mosaic pattern, and making up 5 to 10% of the annual production. Winterfat is 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 300 lbs./acre, but it can range from about 125 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 allows for 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 11. Bluebunch wheatgrass, threadleaf sedge, and Sandberg bluegrass are prominent 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. Wyoming big sagebrush is now a conspicuous part of the overall production and accounts for the majority of the over story. The dominant grass is bluebunch wheatgrass, with Sandberg bluegrass, bottlebrush squirreltail, blue grama, and threadleaf sedge increasing on the site. Forbs commonly found in this plant community include scarlet globemallow, fringed sagewort, and spiny phlox. Wyoming big sagebrush can make up to 25% of the annual production. The over story of sagebrush and understory of grasses and forbs provide a diverse plant community. Plains prickly pear cactus will be present, but occurs in small isolated patches. Indian ricegrass and rhizomatous wheatgrass has 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 200 pounds per acre, but it can range from about 125 lbs./acre in unfavorable years to about 400 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 CP1.1-1.2
Community 1.1 to 1.2

Bluebunch Wheatgrass/Rhizomatous Wheatgrsases/Wyoming Big Sagebrush

Perennial Grasses/Wyoming Big Sagebrush

Moderate, continuous season-long grazing will convert the plant community to the Perennial Grass/Wyoming Big Sagebrush Plant Community. Prolonged drought will exacerbate this transition. The stressers reduce the bunchgrasses such as Bluebunch Wheatgrass, Needleandthread, Indian ricegrass; allowing the solitary growth and sod-formers to increase in dominance in the community.

Pathway CP1.2-1.1
Community 1.2 to 1.1

Perennial Grasses/Wyoming Big Sagebrush

Bluebunch Wheatgrass/Rhizomatous Wheatgrsases/Wyoming Big 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 deferred grazing is implemented as part of prescribed method of use.

State 2
Sod-former State

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.

Community 2.1
Blue Grama/Threadleaf Sedge/Wyoming Big Sagebrush

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 blue grama with patches of threadleaf sedge dominates this state. Wyoming big sagebrush has been reduced to small patches, and rubber rabbitbrush is present. When compared to the Reference State (State 1), blue grama and threadleaf sedge, have increased. Prickly pear cactus has invaded. Cool-season mid-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 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 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.

Community 2.2
Blue Grama/Threadleaf Sedge/Cactus

Drought or continued pressure removes the remaining shrubs, leaving a sod of blue grama with patches of threadleaf sedge and cactus as the main ground cover. Prickly pear cactus can become dense enough to reduce the ability for livestock to graze the limited forage. Wyoming big sagebrush has been generally removed from the site with only isolated occurrences. Rubber rabbitbrush is significantly reduced, but will persist in the community. Compared to the Reference Community 1.1, Community 2.2 has increased in blue grama and threadleaf sedge, cactus has invaded, and cool-season grasses, forbs, and shrubs have been greatly reduced or removed. Production has been 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 sod bound community 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 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 the bare ground areas 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.

Pathway CP2.1-2.2
Community 2.1 to 2.2

Frequent or Severe Grazing, Drought/Insect Damage, Fire/Wildfire – The Wyoming big sagebrush component of this community is the at risk species. Sagebrush will decrease under drought, and if grazing pressures persist through season or year-long patterns, becoming decadent and then dying. The sod-dominated community reduces the ability for sagebrush to propagate, also leading to a recession of the already limited sagebrush component. Although rare in occurrence, due to lack of fine fuels and canopy cover, fire will remove the shrub canopy as well. Cactus increases, and in some cases, rubber rabbitbrush will increase as sagebrush recedes. Recent drought periods (past ten years) have had an impact on the health and vigor of blue grama and threadleaf sedge. The dense root structure of the sod-forming plants is reduced allowing other species to establish.

State 3
Sagebrush/Bare Ground State

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.

Community 3.1
Wyoming Big Sagebrush/Bare Ground

This plant community is the result of drought and frequent and severe 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, bottlebrush squirreltail, Sandberg bluegrass, and needle and thread. 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 site if a seed source is available. If invasive species gain a foothold, they push the state across a threshold into an invaded or annual grass 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 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 or the removal of grazing does not seem to affect the composition or structure of the plant community. 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 State

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.

Community 4.1
Perennial Grasses/Invasive Species/Wyoming Big Sagebrush

The Perennial Grasses/Invasive Species/Wyoming big sagebrush phase has maintained a representative sample of the perennial grasses and forbs that are typical of the site with the accompanying Wyoming big sagebrush composition. The invasive species are present and hold a significant (10% 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/Wyoming Big Sagebrush

Wyoming big sagebrush is able to maintain a community under a heavy infestation level unless fire or disturbance of any nature 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 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 CP4.1-4.2
Community 4.1 to 4.2

Frequent or Severe Grazing, Drought, Disturbances (mechancial) 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.

State 5
Degraded State

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.

Community 5.1
Disturbed Lands Plant Communities

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 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. In a similar process, 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 is the “introduced grass plantings”. Although this could be considered reclaimed or restored, there are sites that were seeded to introduced or improved species, such as crested wheatgrass, smooth brome, or tall wheatgrass in a monoculture. 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 Plant Communities

Reclamation practices have shifted greatly over the last several decades. 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. Bozosky Russian wildrye and varieties of rhizomatous and bunch-wheatgrasses have also been used in mixes to help compensate for the chemistry of these soils. Although the success of vegetative seedings are low in this LRU, due to the low precipitation and timing of precipitation events, there are limited areas along pipeline corridors, well sites or pad sites, and along transportation corridors where re-seeded sites have succeeded. As mentioned in the community phase above, as these seedings mature and the stands open, they can be characteristically similar to other disturbed sites. Where under the more current, and understood definition of reclaimed or restored, sites are planted to as close to a natural occurring plant community 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. Again, these seedings will not replicate the reference community in response to management due to the change in soil dynamics with mechanical disturbance, seedbed preparation and seeding, but they can be very similar. 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 CP5.1-5.2
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 Basin and create a low success potential for this process.

Pathway CP5.2-5.1
Community 5.2 to 5.1

No use, No Fire, Long Term Prescribed Grazing, Frequent or Severe Grazing. In general, if a site is not maintained with the conditions of which the species are adapted under, a decline in vigor will occur and then a shift in composition will occur. Since the site is altered from reference state in soils due to plowing, mining, or other similar disturbances, the plant community will not follow the same expected shifts of a native community and this will refer back to a community more reflective of a disturbed plant composition.

Transition T1-2
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 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.

Transition T1-3
State 1 to 3

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.

Transition T1-4
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 T2-4
State 2 to 4

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.

Restoration pathway R3-1
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 T3-4
State 3 to 4

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.

Restoration pathway R4-5
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 T5-4
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.