State 1
Reference

The Reference state consists of two dominant plant communities: The Little Sagebrush/Bluebunch Wheatgrass community and the Mixed Sagebrush/Bunchgrass community. The greatest difference between the two plant communities is the composition and foliar cover of sagebrush (Artemisia spp.) species. Wyoming big sagebrush (Artemisia tridentata ssp. wyomingensis) transitions to mountain big sagebrush at the higher end of the effective precipitation range (10 to 14 inches). Little sagebrush and black sagebrush (Artemisia nova) transition to big sagebrush species when the calcium carbonate concentration in the soil is focused lower in the soil profile or less calcareous, closer to the minimum 15 percent required in the site concept. Processes (both natural and anthropogenic) that can result in state and community changes include fire, grazing, land use change, and establishment of invasive species (Davies et al., 2011).

Characteristics and indicators. The shift between plant communities at this site is generally driven by calcium carbonate concentration in soils, effective precipitation, and sagebrush-killing disturbances or lack thereof. Historically, low to mixed-severity fires occurred at relatively frequent fire return intervals of 10 to 25 years, limiting sagebrush canopy density and creating a mosaic of sagebrush stands and more open grasslands (Knick, Holmes, & Miller, 2005). Exclusion of fire (in conjunction with climate change) increases sagebrush canopy cover and can lead to more severe stand-replacing fires, oftentimes at more frequent intervals. These severe fires can drive shifts to grassland communities as well as create opportunities for invasive species establishment (Roadhouse, Irvine, & Bowerstock, 2020; Knick et al., 2005). Improper grazing practices can also lead to an increase in sagebrush canopy cover and an increased risk of severe, stand-replacing fire occurrence. Removal of understory grasses can lessen the opportunities for low severity fire occurrence which leads to increased canopy densities and increases potential for severe fire disturbance events (Knick et al., 2005).

Resilience management. This site has moderate resilience as a result of the cryic soil temperature regime and the xeric soil moisture regime. Resistance and resilience of a specific site have been attributed to abiotic conditions favorable to plant growth and reproduction (Maestas et al. 2016). Soils that fall within the cryic (cold) temperature regime and xeric (wet) moisture regime tend to have higher diversity and production and are therefore more resilient, specifically in terms of resisting or recovering from invasion post-disturbance (Maestas et al., 2016). Although both black sagebrush and little sagebrush species are susceptible to fire damage and usually killed by fire events, fire events within these communities are usually rare. These communities generally lack the fine fuels required to carry fire, promoting relatively infrequent fire return intervals (Steinberg, 2002). Mountain big sagebrush is also highly susceptible to damage and mortality from fire events. These communities also tend to have higher fuel loading and carry fire more easily and frequently than the black and little sagebrush communities (Innes, 2017).

Community 1.1
Little Sagebrush/Bluebunch Wheatgrass

Community 1.1 is well adapted to the abiotic conditions of the Lost River Mountain LRU. Both little sagebrush (Artemisia arbuscula) and black sagebrush (Artemisia nova) have adaptations that allow them to thrive on the highly calcareous soils that form from limestone parent material. Little sagebrush more often dominates the canopy at this ecological site; however, it is not uncommon for the percent composition between black sagebrush and little sagebrush to be nearly equal. It is also possible that one of the two species is missing from the canopy completely. Black sagebrush prefers conditions where the highly calcareous soils are closer to the surface. Because the depth to calcareous soils in the Loamy Calcareous ecological site is 10 inches (25cm), little sagebrush can outcompete black sagebrush (McArthur & Stevens 2009; Tilley & St. John [2] 2012). Therefore, little sagebrush has a higher canopy cover and contributes more volume to overall ecological site production value. Little sagebrush/Bluebunch Wheatgrass communities can form in a mosaic distribution with other Community 1.2 across the range of relative effective annual precipitation. As effective precipitation increases and the concentration of calcium carbonates decreases, the overstory shifts to other sagebrush species and subspecies. Other bunchgrasses such as Idaho fescue (Festuca idahoensis) increase in canopy cover as available moisture increases. Production in Community 1.1 ranges from 400 to 850 pounds per acre, averaging 650 pounds per acre.

Resilience management. Resilience is moderate in Community 1.1. Black sagebrush and little sagebrush are both drought-tolerant species able to withstand periods of below-average precipitation. Bluebunch wheatgrass is well suited to the variable climate experienced in the Lost River Mountains and is resilient to many natural disturbances including drought and fire. Bluebunch wheatgrass has been shown to recover to pre-fire disturbance population levels in one to seven years post-disturbance. Under certain conditions, canopy cover and production can exceed pre-fire values (Zlatnik, 1999). Bluebunch wheatgrass is a decreaser, reducing canopy cover and production in relation to grazing pressure. Under heavy grazing pressure, the species will shift towards areas such as under the canopy of shrubs, opening the canopy for the establishment of rhizomatous grass species, invasive species, or bare ground.

Community 1.2
Mixed Sagebrush/Bunchgrass

Figure 13. Community 1.2: Site ID - 2019ID7031080

The Mixed Sagebrush/Bunchgrass community is well adapted to the abiotic conditions of the Lost River Mountain LRU. Wyoming big sagebrush and mountain big sagebrush can occur on Mollisols, Aridisols, and Inceptisols, however, are most abundant on Mollisols (Innes, 2017). Wyoming big sagebrush is well adapted to the drier conditions and often dominates sites at the lower end of the 10 to 14 inch climatic subset. Mountain big sagebrush becomes more prevalent at the upper end of the climatic subset, however, both species can be present on a site. Low sagebrush species (black and little sagebrush) have a higher canopy cover on sites with soils with a greater influence of calcium carbonates. In this community, all or a mix of these sagebrush species can be present on a site. The distinguishing feature between this community and Community 1.1 is the presence of big sagebrush species. The understory is dominated by bluebunch wheatgrass, though other bunchgrasses such as Sandberg bluegrass (Poa secunda) and Indian ricegrass (Achnatherum hymenoides) can be present in significant quantities. A variety of forbs such as spiny phlox (Phlox hoodii), stemless mock goldenweed (Stenotus acaulis) and varieties of Indian paintbrush (Castilleja spp.) occur in the understory as well. Production for this site is slightly higher than Community 1.1 due to the addition of big sagebrush species. Production ranges from 675 to 850 pounds per acre, averaging 675 pounds per acre.

Resilience management. This community has moderately low resilience. Mountain big sagebrush is the least drought tolerant of the big sagebrush species with Wyoming big sagebrush being slightly more drought tolerant. Both mountain and Wyoming big sagebrush are highly flammable and fire typically kills plants within the disturbance area. Because these species reproduce via seed that is dispersed through wind, water, and zoochory, distance from a viable source population plays a major role in post-disturbance regeneration. When disturbance events cover a large area spatially, the regeneration timespan increases and the likelihood of transitioning to another state or community increases (Innes, 2017). Slow regeneration can open windows for erosion to occur and invasive species to establish. Post-disturbance seeding and planting can increase restoration success. Bluebunch wheatgrass is a much more resilient species to the local disturbance regimes. The species is drought tolerant and usually is not killed except during the most severe wildfire events. During severe disturbances that remove the sagebrush overstory, bluebunch wheatgrass can persist as the dominant vegetation on this ecological site (Zlatnik, 1999). When Idaho fescue is the dominant understory or shares dominance in the understory, fire return intervals can be as frequent as 10 to 15 years. Severe fire events prompt a shift into the Disturbed state. The lower effective precipitation at this site (10 to 14 inches) also decreases this sites ability to successfully recover post-disturbance.

Pathway P1-2
Community 1.1 to 1.2

Little Sagebrush/Bluebunch Wheatgrass

Mixed Sagebrush/Bunchgrass

The primary driver that differentiates Community 1.1 and Community 1.2 is a slight increase in relative effective annual precipitation (REAP) or a decrease in the concentration of soil calcium carbonates. As carbonates occur deeper into the soil profile, or effective precipitation trends toward the higher end of the 10 to 14-inch range, overstory composition changes. It may still include the low sagebrush species but will also have big sagebrush species such as Wyoming big sagebrush and mountain big sagebrush occupying the canopy.

Context dependence. The abiotic conditions that result in community transitions from Community 1.1 to 1.2 are site-specific and not directly influenced by anthropogenic or biotic interactions.

State 2
Disturbed

The Disturbed state is a result of both natural and anthropogenic disturbance events that result in widespread sagebrush mortality at a given site. The primary natural disturbance resulting in sagebrush mortality at this ecological site is wildfire; however, intense freeze events, insect damage, and disease can also occur. Big sagebrush species and, to a lesser extent, little sagebrush species are highly susceptible to stand-replacing fires and often experience complete canopy loss during moderate and severe wildfire events (Innes, 2017; Tirmenstein, 1999). Because this LRU exists primarily on publicly managed lands (US Forest Service, Bureau of Land Management, and State of Idaho), widespread anthropogenic disturbance events are infrequent. Examples of anthropogenic disturbance events include brush management through sagebrush mowing or removal treatments, chemical treatments, or improper grazing techniques that result in high-intensity hoof disturbance. A combination of natural and anthropogenic disturbance is possible and can result in increased severity of disturbance, decreased resilience, and greater difficulty returning to the Reference state. For example, improper grazing practices post-fire disturbance can increase bare ground cover, increase erosion potential, and slow the reestablishment of grass species that preclude the return of overstory sagebrush canopy (Zlatnik, 1999).

Characteristics and indicators. The primary indicator of the Disturbed state is a near-complete loss of overstory sagebrush species, often replaced by shrub species that are able to take advantage of the local disturbance regime. Common replacement species include Artemisia tripartita (threetip sagebrush) and Chrysothamnus viscidiflorus (yellow rabbitbrush). A shift towards an increase in native and disturbance-tolerant grasses and forbs is likely with the removal of resource competition associated with the sagebrush overstory presence. Severe disturbance events also increase the opportunity for invasion of annual grasses and weeds such as cheatgrass (Bromus tectorum) and thistle species. The canopy cover percentage of these species is usually dependent on the distance of a seed source post-disturbance but mostly stays under five percent (Zlatnik, 1999).

Resilience management. Resilience in this state is moderate. Many of the post-disturbance grasses and shrubs that are common in this state establish quickly and reach a representative canopy within 10 years post-disturbance. Grasses and shrubs continue to increase until the overstory canopy of sagebrush begins to return. However, local resilience in this state is highly dependent on current soil moisture availability, seed sources, timing and severity of the disturbance. In the instance of fire disturbance, bluebunch wheatgrass mortality can be significantly lower if the fire occurs in the spring as opposed to fall. Recovery can be impacted by the quantity of immediate post-fire precipitation (Zlatnik, 1999). More severe disturbances increase the possibility of post-disturbance invasion. The greater the establishment of invasives, the lower the site resilience becomes

Community 2.1
Disturbance Shrub and Bunchgrass

Figure 16. Site: 2020ID7032179

Figure 17. Canopy Cover by Plant Type Group: Disturbance Shrub and Bunchgrass Community

Community 2.1 is driven by the disturbance-related removal of the primary overstory of sagebrush species. Both natural and anthropogenic disturbances that result in near complete removal of the sagebrush overstory create opportunities for increased establishment of both native and non-native grasses and forbs, as well as disturbance tolerant shrubs. In this community, the primary sagebrush removing disturbance at this ecological site is frequent or severe fire. The frequency and severity of these fire disturbances are highly influenced by the overstory composition of the specific site in the Reference state, prior to disturbance. The composition and extent of the sagebrush species in the overstory impacts that respective fire regime. Communities in the Reference state with mountain big sagebrush in the overstory are highly susceptible to stand-replacing fire events with fire return intervals ranging from five to 70 years (Innes, 2017; Termenstein, 1999). This increases the likelihood of transition from the Reference state to the Disturbed state (Community 2.1) following fire disturbances. In Community 2.1, the overstory is comprised of disturbance-tolerant shrubs at a reduced canopy. The primary overstory species include yellow rabbitbrush (Chrysothamnus viscidiflorus) and threetip sagebrush (Artemisia tripartita). Bunchgrasses, primarily bluebunch wheatgrass (Pseudoroegneria spicata), Idaho fescue (Festuca idahoensis) and Sandberg bluegrass (Poa secunda) primarily occupy the understory. Canopy cover of bunchgrasses is often higher early in the successional period following a disturbance, decreasing as the yellow rabbitbrush or threetip sagebrush canopy increases. Production at this site has a wide range which varies in relation to time since disturbance and the impact to the original canopy. Sites where shrub canopies have been removed can become highly productive in the grass and forb functional groups if conditions are ideal. Production ranges from 275 to 900 pounds per acre, averaging 500 pounds per acre.

Resilience management. This plant community is moderately resilient because the grasses and forbs that dominate the composition are resistant to a variety of disturbances and able to re-establish quickly in the event of more severe disturbances. Both bluebunch wheatgrass (Pseudoroegenaria spicata) and Sandberg bluegrass (Poa secunda) are rarely harmed by fire events except for in the most severe instances. Both plants can reduce the amount of heat transfer to the root systems, allowing successful regrowth (Zlatnik, 1999 & Howard, 1997). Studies show that in the absence of grazing, bluebunch wheatgrass-dominated systems are able to return to pre-fire production levels eight years post-disturbance (Zlatnick, 1999). Sandberg bluegrass has been shown to fully re-establish post-plowing events in as little as 7 years (Howard, 1997). Both yellow rabbitbrush and threetip sagebrush are often the first shrub species to re-establish on this ecological site following a disturbance and can increase in relation to the severity or frequency of the disturbance. Although yellow rabbitbrush can exist in relatively small numbers within the Reference state, it becomes the dominant shrub species in highly disturbed systems (Terminstein, 1999).

State 3
Invaded

Figure 19. Site ID: 2021ID7033160

The Invaded state is represented by a shift from native grasses and forbs in the understory to an understory dominated by invasive species. Transition to this state occurs after a severe disturbance that creates openings in the canopy for invasive species to establish. The primary invasive species that becomes dominant in the Invaded state is cheatgrass (Bromus tectorum). This state is especially prevalent on steep, rocky slopes where colluvial movement is active. As the soil is disturbed through the movement of material downhill, ideal conditions are presented for cheatgrass recruitment. Once established and a seed source is readily available, cheatgrass is well adapted to increasing its coverage area.

Characteristics and indicators. This state is indicated by any single invasive species occupying five percent or more of the canopy, or a group of invasive species occupying 10 percent of the canopy collectively.

Resilience management. This state exhibits low resilience due to the establishment of invasive and non-native species. Once established, non-native vegetation tends to increase in canopy cover and can often be promoted by further disturbances.

Community 3.1
Invasive Grass and Forb

Figure 20. Site ID: 2021ID703306

This community may resemble other communities within other states of the ecological site; however, will have a canopy cover of five percent or greater for a single invasive species, or 10 percent or greater for all invasive species on site. Production can be high, however may not occur in desirable species. The production range for this community is 300 to 750 lbs/acre, averaging 575 lbs/acre.

Resilience management. This community is perpetuated by continued, frequent disturbances. The invasive species that occupy the site thrive when disturbance regimes shift outside the historic range of variability.

Transition T1-2
State 1 to 2

Reference

Disturbed

Transition from the Reference to the Disturbed state is a mechanism of moderate to severe disturbance, both natural and anthropogenic. The most likely disturbance to cause this transition is wildfire. Other disturbances include but are not limited to freeze-kill events, insect damage, disease, overgrazing, and mechanical brush removal.

Constraints to recovery. The primary constraint to recovery is the distance to a seed source and time. When the disturbance is severe and the extent is great, seed source populations for sagebrush species may be removed from the vicinity. In this case, immigration and re-establishment of overstory sagebrush species can be slow. Re-establishment to pre-disturbance canopy cover and extent of mountain big sagebrush cover generally exceeds 25 years even in ideal conditions (Innes, 2017). The recovery time period can be greatly reduced through seeding and planting interventions.

Context dependence. The primary factors driving the likelihood of restoration success are post-disturbance weather patterns and distance from viable seed sources. Disturbances that cover a larger extent increase the distance to seed sources. Prolonged periods of drought can slow restoration processes. Alternately, average to above-average precipitation post-disturbance can greatly increase speed and success in the re-establishment of sagebrush species (Robin, 2017; Steinberg, 2002; and Fryer, 2009).

Transition T1-3
State 1 to 3

Reference

Invaded

The transition from the Reference state to the Invaded state is usually a result of vegetative canopy removing disturbances that create openings and opportunities for invasive species establishment. On steeper slopes, soil movement downslope that disturbs the surface creates ideal conditions for the establishment of invasive species, one of the most prominent species being cheatgrass. Once locally established, cheatgrass can further spread across a site.

Constraints to recovery. Constraints to recovery include the establishment speed of invasive species, prolonged periods of drought that diminish regeneration of desired species, loss of nutrient-rich topsoil due to increased erosion, and continued establishment and spread of invasive species.

Context dependence. Restoration success is dependent on invasive species composition and level of establishment. Removal of cheatgrass once significant establishment occurs can be resource-intensive with low success rates.

Restoration pathway R2-1
State 2 to 1

Disturbed

Reference

The most important mechanism driving restoration from the Disturbed state to the reference is time without sagebrush removing disturbance. Distance from overstory species (sagebrush) seed source can also impact the speed of restoration. Seeding or planting of desired overstory species found in the Reference state can speed restoration efforts.

Context dependence. Restoration is highly dependent on time without disturbance. New sagebrush seedlings are moderately sensitive to disturbances such as freeze-kill, insect damage, and disease. They are highly sensitive to herbivory and even low-severity fire events (Fryer 2009; Steinberg 2002). Seeding and planting of desired species can speed up the restoration process, however; regeneration success with or without planting is highly dependent on localized weather patterns during the restoration period. Periods of drought will slow the process significantly, whereas periods of above-normal precipitation aid in sagebrush regeneration and establishment (Innes 2017; Steinberg 2002; Fryer 2009).

Transition T2-3
State 2 to 3

Disturbed

Invaded

The transition from the Disturbed state to the Invaded state usually occurs if the disturbance that occurred removes native vegetative canopy cover creating opportunities for invasive species to establish in their place. Soil movement downslope that disturbs the surface creates ideal conditions for the establishment of invasive species, one of the most prominent species being cheatgrass. Once locally established, cheatgrass can further spread across a site.

Constraints to recovery. Constraints to recovery include: The establishment speed of invasive species; Prolonged periods of drought that diminish regeneration of desired species; Loss of nutrient-rich topsoil due to increased erosion; and Continued establishment and spread of invasive species.

Context dependence. Restoration success is dependent on invasive species composition and level of establishment. Removal of cheatgrass once significant establishment occurs can be resource intensive with low success rates.

Restoration pathway R3-1
State 3 to 1

Invaded

Reference

Restoration from the Invaded state to the Reference state requires removal of invasive species through treatment and often planting or seeding of native vegetation to prevent re-establishment.

Context dependence. The restoration process is resource intensive with low success rates if invasive species are well established. Planting or seeding of native vegetation after the removal of invasive species can increase overall restoration success.