State 1
Bluebunch Wheatgrass/Idaho Fescue/Sagebrush

The Bluebunch Wheatgrass/Idaho Fescue/Sagebrush State (State 1) is the reference community for the Limy Skeletal ecological site. The diverse mix of perennial grasses, and forbs make for a productive and stable site.

Characteristics and indicators. Bluebunch wheatgrass is the dominant herbaceous species on this site with an intermixed composition of mountain big sagebrush and black sagebrush providing the dominant woody cover. Lichen common in this community with ground covering forbs.

Resilience management. The vegetation that thrives in the harsh conditions of the Limy Skeletal ecological site create a plant community resistant to change. But once disturbed, the shift in the perennial grasses and shift in shrubs is difficult and takes time to recover, reducing the resiliency of the community.

Community 1.1
Bluebunch Wheatgrass/Spike Fescue/Sagebrush

Figure 8. Bluebunch wheatgrass and Columbia needlegrass are dominant with mountain big sagebrush and black sagebrush.

This is the Reference Community Phase. This state evolved with grazing by large herbivores and periodic fires. This plant community can be found on areas that are properly managed with grazing and/or prescribed burning, and on areas receiving periods of rest. The cyclical nature of the fire regime in this community prevents sagebrush from being the dominant landscape; however, the return interval is low. Tall and mid-stature cool-season grasses dominate the state. The major grasses include Bluebunch wheatgrass, spikefescue, Columbia needlegrass, Idaho fescue, and rhizomatous wheatgrasses. Mountain big sagebrush, black sagebrush, rubber rabbitbrush, and juniper are conspicuous elements of this state, occurring in a mosaic pattern, and making up 15% of the annual production. A variety of forbs also occur in this state and plant diversity is high (see Plant Composition Table). Annual production on this state ranges from 550 to 1000 pounds depending on climatic conditions. Average annual production is estimated at 750 pounds.

Resilience management. This plant community is extremely stable and well adapted to the Central Rocky Mountains 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
Mixed Shrub/Idaho Fescue

Figure 10. Idaho fescue and rhizomatous wheatgrasses have become the dominant herbaceous cover in this community.

Historically, this plant community evolved under grazing by large ungulates and a low fire frequency. Currently, it occurs under moderate, season-long grazing by livestock and is exacerbated by prolonged drought conditions. In addition, the fire regime for this site has been modified and extended periods without fire is now common. Shrubs are significant components of this plant community. Cool-season grasses make up the majority of the understory with the balance made up of miscellaneous forbs. Dominant grasses include Idaho fescue, bluebunch wheatgrass, prairie junegrass, Montana wheatgrass, and of less frequency Columbia needlegrass, and spike fescue. Grasses of secondary importance include bluegrasses and onespike oatgrass. Forbs commonly found in this plant community include hawksbeard, groundsel, balsamroot, asters, buckwheat, phlox, and penstemons. Shrubs such as mountain big and black sagebrushes, rubber rabbitbrush, fringed sagewort, and juniper can make up to 25% of the total annual production. When compared to the Reference Community Phase, mountain big and black sagebrush, rubber rabbitnbrush, fringed sagewort, bluegrasses, and rhizomatous wheatgrasses have increased. Production of specific species such as Columbia needlegrass and spike fescue has been reduced. Annual production ranges from 450 to 950 pounds; with average annual production of 700 pounds.

Resilience management. This plant community is resistant to change. The herbaceous species present are well adapted to grazing; however, species composition can be altered through long-term continuous season-long or year-long grazing. The herbaceous component is mostly intact and plant vigor and replacement capabilities are sufficient. Water flow patterns and litter movement is not uncommon especially on steeper slopes. Incidence of pedestalling is minimal but normal. 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/Spike Fescue/Sagebrush

Mixed Shrub/Idaho Fescue

Over time, moderate, continuous season-long grazing will reduce the vigor of the desirable tall and mid-stature cool-season grasses, and eventually reducing or removing them from the community. This decrease in the taller species, encourages Idaho fescue to become dominant in the community. Prolonged drought will exacerbate this transition.

State 2
Mixed Shrub/Perennial Grasses

After significant pressure on the herbaceous understory and with the lack of fire to rejuvenate the woody component, this State has shifted to a short-stature cool-season grasses with shrubs becoming a significant component of this state. Some of the preferred grasses have been reduced or are absent, and forbs (ground covering) have increased in the community. When compared to the Reference State, sagebrush, native bluegrasses, prairie junegrass, and rhizomatous wheatgrasses have increased. Most of the preferred grasses have been reduced and some are absent.

Characteristics and indicators. Dominant grasses include rhizomatous wheatgrasses, letterman's needlegrass, prairie junegrass, and of less frequency Columbia needlegrass, spike fescue, Idaho fescue and bluebunch wheatgrass. Grasses of secondary importance include slender wheatgrass, spike trisetum, one-spike oatgrass, and bluegrasses. Forbs commonly found in this plant community include balsamroot, agoseris, buckwheat, arnica, phlox, lupine, asters, and pussytoes. Fringed sagewort, mountain big sagebrush, black sagebrush, and juniper can make up to 30% of the total annual production.

Resilience management. This State is resistant to change without a major disturbance or inputs to start the change. But it is also at risk of degrading further and is susceptible to invasion due to the decreased herbaceous cover and increased woody structure.

Community 2.1
Mixed Shrub/Rhizomatous Wheatgrasses

Figure 11. Sagebrush and Montana wheatgrass dominated community on the Limy Skeletal ecological site.

This plant community currently is found under heavy continuous season-long grazing by livestock and protection from fire. Shrubs are a significant component of this plant community. Cool-season grasses make up the majority of the understory, but some of the preferred grasses have been reduced or are absent. Dominant grasses include rhizomatous wheatgrasses, Letterman's needlegrass, prairie junegrass. A noted decrease in Columbia needlegrass, spike fescue, Idaho fescue and bluebunch wheatgrass is seen. Grass species that may be more readily observed are slender wheatgrass, spike trisetum, one-spike oatgrass, and bluegrasses. Forbs commonly found in this plant community include balsamroot, agoseris, buckwheat, arnica, phlox, lupine, asters, pussytoes, common yarrow, and field chickweed. Rubber rabbitbrush, fringed sagewort, mountain big sagebrush, black sagebrush, and juniper can make up to 30% of the total annual production. When compared to the Reference State, sagebrushes, bluegrasses, prairie junegrass, and rhizomatous wheatgrasses have increased. Most of the preferred grasses have been reduced and some are absent. Sufficient Data has not been collected to establish Annual Production ranges at this time.

Resilience management. This plant community is resistant to change as the shrubs become more abundant. These areas may actually be more resistant to fire as less fine fuels are available and the bare ground between the shrubs is increased. The herbaceous component is not as diverse and plant vigor and species regeneration capabilities of some cool-season perennials are deficient. The removal of grazing does not seem to affect the plant composition or structure of the plant community. Soil erosion is accelerated because of increased bare ground. Water flow patterns and pedestalling is more noticeable. Infiltration is reduced and runoff is increased. Rill channels may be noticeable in the interspaces on steeper areas and gullies may be establishing where rills have concentrated down slope.

Community 2.2
Mixed Shrub/Bluegrasses

This plant community is the result of frequent and severe grazing and protection from fire. Shrubs are a dominant component of this plant community and annual production of shrubs can exceed 30%. Mountain big sagebrush, black sagebrush, rubber rabbitbrush, and bluegrasses are the primary components of the plant community as the preferred cool season grasses have been eliminated or greatly reduced. The dominant grasses are the bluegrasses such as Sandberg, mutton, big, and Canby. The interspaces between plants have expanded leaving the amount of bare ground more prevalent. When compared with the Reference State, the annual production is less, as the major cool-season grasses are reduced, but the shrub production has increased significantly and compensates for some of the decline in the herbaceous production. Sufficient Data has not been collected to establish Annual Production ranges at this time.

Resilience management. 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 shrubs is increased. The herbaceous component is not as diverse and plant vigor and species regeneration capabilities of cool-season perennials are deficient. The removal of grazing does not seem to affect the plant composition or structure of the plant community. 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.

Community 2.3
Rhizomatous Wheatgrasses/Bluegrasses

This plant community currently is found under heavy continuous season-long grazing by livestock and is perpetuated by either brush management or a wildfire, which removes or greatly reduces the shrubs. Some of the major cool-season bunchgrasses associated with this site have been reduced and some may have been removed. Dominant grasses include rhizomatous wheatgrasses, bluegrasses, prairie junegrass, and Montana wheatgrass. There may be incedential occurances of Columbia needlegrass, Idaho fescue, bluebunch wheatgrass, and spikefescue; however these species are greatly reduced. Forbs commonly found in this plant community include balsamroot, agoseris, buckwheat, arnica, phlox, lupine, asters, pussytoes, and field chickweed. Rubber rabbitbrush, fringed sagewort as well as pockets of mountain big sagebrush and black sagebrush can comprise as much as 15% of the total production. Overall, the shrub community has been impacted by the use or disturbances to this community. When compared to the Reference State, rhizomatous wheatgrasses, Montana wheatgrass, bluegrasses and fringed sagewort have increased. Columbia needlegrass, bluebunch wheatgrass, Idaho fescue, and sagebrush have decreased or have been removed. Production of the preferred cool-season grasses has been reduced. Sufficient Data has not been collected to establish Annual Production ranges at this time.

Resilience management. This plant community is resistant to change as the herbaceous species present are well adapted to grazing and if rubber rabbitbrush or fringed sagewort becomes the dominant shrub it is difficult for other shrubs to become established. However, species composition can be altered through long-term overgrazing. The herbaceous component is mostly intact, but some cool-season bunchgrasses associated with the site have been reduced or removed. Plant vigor and replacement capabilities are sufficient for some species but not all. Water flow patterns and litter movement is occurring but only on steeper slopes. Incidence of pedestalling is moderate to slight. Soils are mostly stable and the surface shows minimum soil loss. The watershed is functioning and the biotic community is partially intact.

Pathway CP2.1-2.2
Community 2.1 to 2.2

Frequent and Severe Grazing with the lack of fire or other brush control mechanisms will impact the herbaceous understory, allowing the sagebrush and other shrubs to increase in dominance on the site. This change in understory will convert the plant community to the Mixed Shrub/Bluegrasses Community Phase. The probability of this occurring is high and is especially evident on areas where drought or heavy browsing does not adversely impact the shrub stand.

Pathway CP2.1-2.3
Community 2.1 to 2.3

The driver for this transition is the removal or reduction in the woody cover, namely sagebrush from this community. Brush management or wildfire is the primary process with no change in the grazing impact that will convert this plant community to the Rhizomatous Wheatgrasses/Bluegrasses Community Phase.

Pathway CP2.2-2.1
Community 2.2 to 2.1

Prescribed grazing to allow rest (rest-rotation or deferred grazing) will encourage the desirable tall and mid-stature cool-season grasses to recover. With time, the shrub component may recover. If grass stands are too dense, they can shade out or inhibit sagebrush and other shrub species form establishing.

Pathway CP2.2-2.3
Community 2.2 to 2.3

Wildfire is a possible occurrence in this community, that removes the old growth sagebrush and may encourage sprouter species to increase. Impact to the herbaceous understory is generally minor. Severe or extended drought, insect infestations, or other natural disturbances can exacerbate the process. Brush management or prescribed fire will effectively remove or improve the woody cover, but if grazing management is in place with the brush removal the community will transition to the Rhizomatous Wheatgrasses/Bluegrasses Community Phase.

State 3
Invaded

Any disturbance provides an opportunity for aggressive species, such as many of our introduced invaders, to establish in a community. Catastrophic events or natural climatic events (drought, wildfire, etc) can be a source of this invasion.

Characteristics and indicators. The major indication of entering this State is the abundant or significant presence of an introduced species, whether invasive or just an invader. To meet the terms of abundant or significant, the presence has to account for greater than or equal to ten percent cover of the community. Species considered in this category are Kentucky bluegrass, smooth brome, or timothy for non-native invaders; or cheatgrass for invasive species. Thistle and common dandelion are other species of concern on this ecological site.

Resilience management. Once established, these aggressive and persistent species will exclude many of the native species and are extremely difficult to reduce or remove from the community. These species are able to tolerate repeated abuse and drastic climatic swings without losing their foothold in the community, creating a resistant and resilient community.

Community 3.1
Perennial Grasses/Non-Native Species

The Perennial Grasses/Non-Native Species Community Phase has maintained a representative sample of the perennial grasses and forbs that are typical of the site with a mixed shrub community. Non-native or invader species have established in the community and are a significant component in the community (10 percent or greater by foliar cover or 5 percent or greater by weight), and are prominent (referring to a more wide scale composition, not one isolated patch in an isolated portion of the landscape). Production of the desired perennial species is generally reduced but the total production is maintained or elevated due to the production potential of the non-native species. The species most common are smooth brome, Kentucky bluegrass, and common dandelion.

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. 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 non-native 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 3.2
Perennial Grasses/Invasive Species

The Perennial Grasses/Invasive Species Community Phase has maintained a fractured sample of the perennial grasses and forbs that are typical of the site with invasive species. This plant community evolved under frequent and severe grazing. The shrub component has been impacted and possibly removed by heavy browsing, wildfire or human means. Weedy annuals and bluegrasses are the most dominant plants. Invasive species, most commonly cheatgrass, hold a significant (10 percent or greater) composition of the landscape, and are prominent (referring to a more wide scale composition, not isolated patches on the landscape). Fringed sagewort and rubber rabbitbrush may be more abundant than other shrubs, as they are strong resprouters and may quickly re-establish the site after a disturbance. The interspaces between plants have expanded leaving the amount of bare ground more prevalent and more soil surface exposed to erosive elements. With the decrease or loss of most desirable mid-stature cool-season grasses, bluegrass will persist on the site (bluegrass includes natives: Sandberg, mutton, Canby, and big; as well as introduced species: Kentucky). Smooth brome, dandelion, and other introduced species will increase if present on the site. Other noxious weeds such as Canada thistle may invade the site if a seed source is available. Production of the desired perennial species is generally reduced but the total production is maintained or elevated due to the production potential of the invasive species.

Resilience management. Rangeland Health Implications/Indicators: This plant community is resistant to continued herbivory. Annuals and bluegrasses are effectively competing against the establishment of perennial cool-season grasses. Plant diversity is greatly altered and the herbaceous component is not intact. Recruitment of the major perennial grasses is not occurring and the replacement potential is absent. The biotic integrity is missing. The state is unstable and is not protected from excessive erosion. Rill channels and maybe even gullies may be present on site and adjacent areas are impacted by excessive runoff. Water flow patterns and pedestalling are obvious. The watershed is not functioning.

Pathway CP3.1-3.2
Community 3.1 to 3.2

Frequent and Severe Grazing will convert this plant community to a Perennial Grasses/Invasive Species Community Phase. Drought or a fire (man-made or wild) are drivers that will encourage this transition as well, if a seed source is present. If fringed sagewort and common yarrow are present more than likely it will persist in varying degrees as it is difficult to control.

State 4
Disturbed

Although to a much smaller extent than in lower elevations, there are areas that have been excavated for gravel, or have been accessed for irrigation convenience ditches or were part of a homestead. These areas have remnants of introduced species for haylands or have been left to recover and may be in at varying stages of succession. Or there are areas that are heavily impacted by recreational vehicles, parking, trails, roadways, or other land disturbances that have reduced or removed most native perennial vegetation and left a highly disturbed land. The Disturbed 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 result 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 highlight 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 Russian thistle, 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. The Disturbed State is highly variable and in a state of flux as the successional processes occur. Continued disturbance of these communities is a potential threat; and the communities are at high risk of transitioning to the Invaded State.

Community 4.1
Altered Lands

The title Disturbed Lands is encompassing two broad classifications of these land types. Go-back fields or tilled areas form Type one. The soils were once cultivated or were impacted by cultivation pracites 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 and introduced herbacous species as well as trees. Cottonwood breaks, elm, and other species of trees on tehs upland sites are key markers of old homestead locations. 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. A subset of Type one are those areas that were or currently are being impacted by recreation - camp sites, trails, parking areas, roadways. The varying stages of healing once abandoned, or the state of disturbance at each location leave a variable community. 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 and functional groups that are desired on the site. Soil erosion is variable depending on the disturbance regime that is occurring on the site and will vary with the specific community that has established on a specific location. Site-specific evaluation is needed to determine the water flow and pedestalling as well as infiltration and runoff potential and associated risks for each community.

Transition T1-2
State 1 to 2

Heavy, continuous, season-long grazing plus no fires or altered fire frequency will convert the plant community to the Mixed Shrub/Perennial Grasses State. This is especially evident on areas where drought or heavy browsing has adversely impact the shrub stand. The impacts required to force this transition are significant, and this does not happen in a short time period.

Constraints to recovery. The loss of sagebrush in some of these communities and the lack of necessary seed bank and recovery time are limiting factors for this State to recover.

Context dependence. The probability of this occurring is dependent on the density of Idaho fescue in the community, the shifts in use patterns historically, and the specific soil characteristics.

Transition T1-3
State 1 to 3

Fire, wild or prescribed, with no change in grazing management and seed source present allows for a rapid transition to the Invaded State. Drought or other catastrophic events will aid in this transition.

Constraints to recovery. The lack of effective treatment to eradicate or significantly control invasive species long term or to remove non-native species without impact to the native community limit the recovery of this State.

Restoration pathway R2-1
State 2 to 1

Prescribed grazing will convert this plant community to the Reference State, with time. 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. In addition, the removal of fire suppression will allow a somewhat natural fire regime to reoccur to more easily transition between this plant community and the Reference State. A prescribed fire treatment can be useful to hasten this transition if desired, or other means of brush management.

Transition T2-3
State 2 to 3

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. Fire is a primary means of provide the niche for cheatgrass to establish on this site.

Constraints to recovery. The nature of non-native (introduced) as well as invasive species, especially cheatgrass, once they are established, they are prolific reproducers and are hardy plants, making it costly and difficult (if even possible) to remove. The lack of key grass species also limits recover of this site.

Restoration pathway R3-4
State 3 to 4

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 there is a significant composition of non-native and invasive species that have established on a site.

Transition T4-3
State 4 to 3

Lack of management resulting in continued disturbance, catastrophic events, or failure in the restoration process are major causes for a disturbed or altered landscape to transition to an invaded state.

Constraints to recovery. The change in the soils and potentially the hydrology of the site as well as the presence on invasive species limit the recovery potential of this community.

Context dependence. Many of the altered landscapes may have non-native species initially, but the significant alteration of the soils with tillage or back-fill (pit reclamation) change the management response and hydrology of this ecological site.