State 1
Current Reference

Figure 12. Steep Skeletal 15-19" Site in the Lost River Range

Figure 13. Steep Skeletal 15-19" Site in the White Knob Mountains

The Reference state consists of three plant communities: The mountain big sagebrush (Artemisia tridentata var. vaseyana) dominated community, the mixed shrub community, and the mixed early sagebrush community. The mixed shrub community includes mountain big sagebrush, mountain snowberry (Symphoricarpos oreophilus), antelope bitterbrush (Purshia tridentata), chokecherry (Prunus virginiana), currant species (Ribes spp.) and saskatoon serviceberry (Amelanchier alnifolia). The mixed early sagebrush community consists of little sagebrush (Artemisia arbuscula var. longiloba) and black sagebrush (Artemisa nova). The dominant understory in all three communities is bluebunch wheatgrass (Pseudoroegnaria spicata). The mountain big sagebrush/bluebunch wheatgrass community is the most common community in the Reference State, and canopy cover is generally balanced between the sagebrush overstory and the bunch grass understory. The mixed shrub community often occurs as a result of very localized site condition variation. Small changes in surface fragment composition, slope shape, and site specific effective precipitation can allow for establishment of several additional overstory shrub species in outside of mountain big sagebrush. Composition and occurrence of shrub species in the mixed shrub community is variable and site specific. The mixed early sagebrush community in this ecological site is an indicator of increased coarse fragment volume within the 20 inch rooting zone of the soil profile (50cm). Although coarse fragments at this ecological site are already high, averaging above 35 percent in the top 20 inches, as the volume increases it can act as a root restriction. This creates favorable conditions for little and black sagebrush to establish. The presence of these species may also indicate a localized increase in calcium carbonate concentration in the soil profile resulting from limestone parent material. Processes (both natural and anthropogenic) that can result in state and community changes include fire, grazing, land use change, and occurrence of invasive species (Davies et al., 2011).

Characteristics and indicators. The transition between states at this ecological site is generally driven by relative annual effective precipitation and sagebrush killing disturbances or lack thereof. Historically, low to mixed severity fires occurred at relatively frequent fire return intervals of 10-25 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, often times 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 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 to high resilience as a result of the cryic soil temperature regime and xeric soil moisture regime. Resistance and resilience of a specific site has been attributed with 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. This is specifically true in terms of resisting or recovering from invasion post disturbance (Maestas et al., 2016).

Community 1.1
Mountain Big Sagebrush and Bluebunch Wheatgrass

Figure 14. Mountain Big Sagebrush/Bluebunch Wheatgrass Community in the Steep Skeletal 15-19" Reference State

This community is well adapted to the abiotic conditions of the Lost River Mountain LRU, specifically when soils are well drained, skeletal and steep. Mountain big sagebrush can occur on Mollisols, Aridisols, and Inceptisols, however, is most abundant on Mollisols (Innes, 2017). As seen in this community, mountain big sagebrush has the ability to form dense monocultures with little competition from other shrub species. The understory is dominated by bunchgrasses, primarily bluebunch wheatgrass, and to a lesser extent at the higher end of the effective precipitation range, Idaho fescue (Festuca idahoensis). Plant diversity in mountain big sagebrush dominated communities is higher than with any other big sagebrush species primarily due to high diversity in forb species (Innes, 2017), the most common being Indian paintbrush species (Castilleja), arrowleaf balsamroot (Balsamorhiza sagittata), and fleabane species (Erigeron). Mountain big sagebrush is the least drought tolerant of the big sagebrush species. On the landscape, transition from Wyoming big sagebrush and low sagebrush dominated communities to communities dominated by Mountain big sagebrush usually occurs along a gradient of increasing available soil moisture. Seedling establishment of mountain big sagebrush is highly dependent on available moisture and seedling mortality increases during periods of drought (Innes, 2017). Total annual production on this ecological in this community ranges from 600 to 1200 pounds per acre, averaging 850 pounds per acre. Canopy cover of mountain big sagebrush averages 20 percent and accounts for an average of 250 pounds per acre of annual production. Canopy cover of bluebunch wheatgrass averages 22 percent and accounts for 410 pound per acre of annual production. Although gaps in the canopy can exceed 6 feet, they are generally limited to less than 2 feet and occupy less than 6 percent of a 100 foot transect.

Resilience management. This community has moderately low resilience. Mountain big sagebrush is the least drought tolerant of the big sagebrush species. Mountain big sagebrush is highly flammable and fire typically kills plants within the disturbance area. Because this species reproduces 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, regeneration timespan increases and 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).

Community 1.2
Mixed Shrub and Bluebunch Wheatgrass

Figure 17. Steep Skeletal 15-19" Site: Community 1.2

Community 1.2 is much less common than Community 1.1 and moderately less common than Community 1.3. The Mixed Shrub Community is primarily influenced by very localized abiotic conditions. Although mountain big sagebrush usually remains the dominant overstory shrub, a diversity of other shrubs often including antelope bitterbrush (Purshia tridentata), chokecherry (Prunus virginiana), mountain snowberry (Symphoricarpos oreophilus), saskatoon serviceberry (Amelanchier alnifolia), and currant species (Ribes) may be present at varying population sizes. Antelope bitterbrush is also well suited to well drained permeable soils that are coarse textured or have a high concentration of cobbles and stones in the soil profile. It is usually found to be secondarily dominant to mountain big sagebrush. This species is often drawn to lava outcroppings and able to establish dry, rocky sites due to the presence of long taproot(s) (Zlatnik, 1999). When chokecherry is present on this ecological site, it is usually an indicator of a very localized increase in moisture with the soils remaining well drained (Johnson, 2000). This generally occurs on steep slopes and ravines near riverine systems in this LRU. Mountain snowberry, saskatoon serviceberry, and some currant species are highly adaptable to many of the conditions found on this ecological site (Aleksoff, 1999; Marshall, 1995; & Fryer, 1997). Bluebunch wheatgrass remains the primary understory species, with and increase of elk sedge (Carex geyeri) appearing towards the higher end of the relative annual effective precipitation range (19 inches).

Resilience management. This community has moderate resilience primarily attributed to the diversity in the shrub overstory. Having multiple species in the overstory reduces the chance of severe impact from insect and disease that often target a single species. Other natural disturbances such as frequent or severe fire and prolonged periods of drought will also differentially impact overstory species. Limited population loss reduces potential for increased erosion and establishment of invasive species following a disturbance. Bluebunch wheatgrass, which is the primary understory species in this ecological site is also very resilient to 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).

Community 1.3
Low Sage and Bluebunch Wheatgrass

The Low Sagebrush/Bluebunch Wheatgrass community within the Steep Skeletal 15 to 19 inch ecological site is rare, but generally indicates a very localized change in soil depth conditions or an increase in calcium carbonate concentration within the soil profile. Both black sagebrush (Artemesia nova) and little sagebrush (Artemesia arbuscula) are well adapted to soils that are shallow to a restrictive layer such as bedrock, clay, or tightly packed course fragments. The two species also establish well when the calcium carbonate equivalency approaches or is greater than 15 percent (Tilley & St. John [2], 2012). The two species are able to tolerate conditions of prolonged drought and limited moisture often occurring as co-dominant in the canopy. However, the more pronounced the localized restrictions become, the more likely it becomes that black sagebrush will dominate the shrub overstory (McArthur & Stevens, 2009). If depth to bedrock becomes less than 20 inches (50cm) or calcium carbonate equivalency becomes greater than 15 percent, transition occurs from the Steep Skeletal ecological site into a shallow site or a site that is strongly influenced by soil chemistry. Of the sites surveyed in this community, black sagebrush has tended to occupy a greater percentage of the canopy and account for a greater volume of the annual production when compared with little sagebrush. Gaps in shrub canopy average 37.5 percent, with 19 percent of those gaps greater than 3.1 feet in length. Total annual production in this community is slightly lower than that of Community 1.1 and 1.2, averaging just under 600 pounds per acre. Bluebunch wheatgrass is the primary understory species, accounting for up to 175 pounds per acre of production and 15 percent of the total canopy cover.

Resilience management. Resilience in this community is slightly higher than that of Community 1.1, as both black sagebrush and little sagebrush are more drought tolerant species than mountain big sagebrush. Resilience to insect and disease in this community is greater when the shrub canopy is more evenly populated by black and little sagebrush, decreasing the likelihood of complete die off in the event of a related disturbance.

Pathway 1.1A
Community 1.1 to 1.2

Mountain Big Sagebrush and Bluebunch Wheatgrass

Mixed Shrub and Bluebunch Wheatgrass

Transition from Community 1.1 to Community 1.2 is generally a result of localized abiotic conditions relating to relative annual effective precipitation (REAP), slope steepness, position on slope, and surface fragment. Slight increases in REAP, slope steepness greater than 50 percent, increase in surface fragment volume, or a combination of these factors can create conditions suitable to a wider range of shrub species outside of big and low sagebrush.

Context dependence. Transition to this community often occurs on the boundaries or transitional zones of the ecological site. As the slight changes in abiotic characteristics that allow for a more diverse shrub overstory become more pronounced, transition to a different ecological site will occur.

Pathway 1.1B
Community 1.1 to 1.3

Mountain Big Sagebrush and Bluebunch Wheatgrass

Low Sage and Bluebunch Wheatgrass

Transition from Community 1.1 to 1.3 is a result of slight localized changes to soil depth or chemistry within the rooting depth. Both low sage species, black and little sagebrush are well adapted to shallow and calcareous soils. Within Steep Skeletal 15 to 19 inch ecological sites, variations in depth to bedrock or localized increase in calcium carbonate concentration can result in shifts from a mountain big sagebrush dominated site to a site dominated by black sagebrush, little sagebrush, or a mixed population of the two. Mountain big sagebrush can still exist within the canopy of this community, however canopy cover is greatly decreased compared with that of Community 1.1.

Context dependence. The changes in abiotic conditions that drive the transition from Community 1.1 to 1.3 usually occur at or near the transition zones of other ecological sites. As these conditions become more prominent and reach certain levels, the ecological site changes.

State 2
Disturbed

Figure 21. Steep Skeletal 15-19" Ecological Site in the Disturbed State

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 frequent or severe wildfire; however, flooding, intense freeze events, and insect and disease can also occur. Of the big sagebrush species, mountain big sagebrush is particularly susceptible to stand replacing fires and often experiences complete canopy loss during moderate and severe wildfire events (Innes, 2017). Because this LRU exists primarily on publicly managed lands (US Forest Service, Bureau of Land Management, and State), 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 or chronic defoliation. 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 such as 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 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, continuing to increase until overstory canopy of sagebrush begins to return. However, local resilience of these sites in this state is highly dependent on current soil moisture availability, seed sources, timing and severity of the disturbance. In the instance of severe or frequent fire disturbance, bluebunch wheatgrass mortality can be significantly lower if the fire occurs in the spring as opposed to fall, and recovery can be impacted by quantity of immediate post fire precipitation (Zlatnik, 1999). More severe disturbances increase possibility of post disturbance invasion. The greater the establishment of invasives, the lower the site resilience becomes.

Community 2.1
Three Tip Sagebrush, Yellow Rabbitbrush and Bluebunch Wheatgrass

Figure 22. Community 2.1: Threetip Sagebrush Overstory with a Bluebunch Wheatgrass Understory

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 complete or nearly complete removal of the sagebrush overstory create opportunities for increased establishment and canopy cover of both native and non-native grasses and forbs, as well as disturbance tolerant shrubs. Threetip sagebrush has the ability to re-sprout from the roots or crown. In Eastern Idaho, threetip sagebrush has shown to have significant post fire sprouting potential. Repeated instances of fire disturbance promote continued increase and dominance of threetip sagebrush in the overstory canopy (Tirmenstein, 1999). Yellow rabbitbrush can quickly and aggressively establish on sites post disturbance and is considered as a seral species to sagebrush dominated overstory canopies. Although rabbitbrush populations are usually greatest within 15 years post disturbance, the species rarely becomes dominant except in the instance of repeated disturbance over short periods of time. After 15 years if no additional disturbance occurs, yellow rabbitbrush populations begin to diminish as they are replaced with sagebrush species (Tirmenstein, 1999). Bluebunch wheatgrass is rarely harmed by fire except during the most severe events. The species is able to reduce the amount of heat transfer to the root systems, promoting successful regrowth (Zlatnik, 1999 & Howard, 1997). Studies have shown 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).

Community 2.2
Mixed Grass and Forb

Figure 25. Mixed bunchgrass community with visible disturbance maintained sagebrush edge (Site 2021ID7032023)

Figure 26. Site: 2021ID7032023

The mixed grass and forb community is driven by the disturbance related removal of the primary overstory of sagebrush species. Both natural and anthropogenic disturbances that result in complete or nearly complete removal of the sagebrush overstory create opportunities for increased establishment and canopy cover of both native and non-native grasses and forbs, as well as disturbance tolerant shrubs. The primary sagebrush removing disturbance at this ecological site is fire. The frequency and severity of these fire disturbances is highly influenced by the overstory composition of the specific site in the reference state. The composition and extent of the sagebrush species in the overstory impacts that respective fire regime. At sites dominated either solely by black sage, alkali sage, or varying combinations of the two, fire return intervals are less frequent. Additionally, fires are usually low to moderate in severity and don't cover a large spatial extent (Steinberg, 2002 & Fryer, 2009). Black and alkali sagebrush dominated communities often lack fuels sufficient for frequent fire return intervals, severe fire events, or large fire events (Fryer, 2009). Steep Skeletal sites with an overstory canopy at least partially comprised with mountain big sagebrush are more susceptible to frequent fire return intervals, more severe fires, and often at a greater extent. Sites dominated by mountain big sagebrush communities have historically burned more frequently than sites dominated by other sagebrush species because the soil moisture and temperature regimes required by mountain big sagebrush are also more apt to produce an increased amount of fine fuels from other plant species (Innes, 2017).

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 are able to reduce the amount of heat transfer to the root systems, leaving them able to recover successfully (Zlatnik, 1999 & Howard, 1997). Studies have shown 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's bluegrass has been shown to fully re-establish post plowing disturbance events in as little as seven years after the plowing (Howard, 1997). Idaho fescue (Festuca Idahoensis) is less resilient to both fires and grazing. Idaho fescue can often survive low severity fires, however, moderate to severe fires are more destructive, resulting in a 30 year return to pre-disturbance levels. In terms of grazing disturbance, Idaho fescue is considered a decreaser and doesn't tolerate heavy grazing pressure well (Zouhar, 2000). Although many of the species in this state are at least somewhat resilient towards many of the disturbances encountered, available soil moisture, post disturbance weather, and rest from grazing all play an important role in how quickly a site can recover following a disturbance event. Both of the common shrub species found in this community at varying compositions are not only disturbance tolerant, but tend to increase with disturbance. Both yellow rabbitbrush and rubber rabbitbrush 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 can only become the dominant shrub species in highly disturbed systems (Terminstein, 1999).

Pathway 2.1A
Community 2.1 to 2.2

Three Tip Sagebrush, Yellow Rabbitbrush and Bluebunch Wheatgrass

Mixed Grass and Forb

Transition from Community 2.1 to 2.2 is a result of a severe sagebrush removing disturbance that eliminates the overstory shrub cover and discourages future shrub recovery. This transition is usually temporary as threetip sagebrush tends to sprout well following disturbances events (or repeated disturbance events) of low to moderate severity (Termenstein, 1999). If the disturbance were severe enough and existing threetip are unable to sprout, the transition to a mixed grass/fob community could be more permanent.

Context dependence. For this transition to occur, the causal disturbance must be severe enough to remove the overstory sagebrush canopy.

Pathway 2.2A
Community 2.2 to 2.1

Mixed Grass and Forb

Three Tip Sagebrush, Yellow Rabbitbrush and Bluebunch Wheatgrass

Transition from Community 2.2 to 2.1 is a result of time without a sagebrush canopy removing disturbance. Threetip sagebrush in particular has shown to vigorously sprout following disturbances of varying severities. In these instances, return to pre-disturbance canopy levels generally occurs within 25 to 40 years (Termenstein et al., 1999).

Context dependence. For threetip sagebrush canopy to return to dominance, a viable sprouting population or nearby seed source must exist on site.

State 3
Degraded

Figure 29. Site: 2021ID7033139 - Post fire disturbance invaded state

When a Steep Skeletal 15 to 19 inch site enters the degraded state, it is generally a result of post disturbance invasion by invasive species. This state can be driven by a particularly severe disturbance either in the form of frequent or severe fire, intensive grazing that results in chronic defoliation of vegetation, land use, or repeated disturbances of low to moderate severity over short periods of time. Proximity to seed source as well as seed transport vectors play a role in likelihood of post disturbance invasion.

Characteristics and indicators. In this state, total canopy cover and production values for mid to large sized bunchgrasses such as bluebunch wheatgrass will decrease. Traditional overstory cover and production of mountain big sagebrush and other shrubs will also decrease. These openings in the canopy will be filled with invasive annuals such as cheatgrass (Bromus techtorum) and more disturbance tolerant forbs such as phlox species, vetch species, an Indian paintbrush (Castilleja sp.). Continued disturbance will increase cover and production of these species. Productivity and canopy cover are lower than the reference state and shifted towards the understory grass species and forbs, particularly the invasive annuals.

Resilience management. This site has low resilience primarily due to the invasive species establishment. Cheatgrass is well adapted to post disturbance establishment, particularly after wildfire disturbances. Cheatgrass takes advantage of prolific seedbanks resilient to fire and its ability to rapidly establish when competition from native vegetation has been removed. Additionally, cheatgrass is able to alter fire regimes, shortening fire return intervals which provides a further advantage for cheatgrass and hinders re-establishment of native vegetation (Zouhar, 2003). Once fully established, restoration of sites invaded by cheatgrass either through natural or mechanical means has low success rates.

Community 3.1
Yellow Rabbitbrush and Cheatgrass

Figure 30. Site: 2021ID7033139

The Yellow Rabbitbrush and Cheatgrass (Chrysothamnus viscidiflorus/Bromus techtorum) community becomes dominant on a site in the Degraded State where native vegetation has been removed or severely altered by either natural or anthropogenic disturbances. Once cheatgrass has established, the species can outcompete the native vegetation that it replaced and promote feedback loops (such as shortened fire return intervals) that help perpetuate dominance (Zouhar, 2003). Yellow rabbitbrush is able to take advantage of its ability to aggressively sprout and rapidly grow following a disturbance. Once established in the overstory, yellow rabbitbrush needs continued frequent disturbances to stay dominant in the shrub overstory. In the absence of disturbance, yellow rabbitbrush will remain dominant for about 15 years before beginning to be replaced by shrub species from the reference community.

Resilience management. This community has high resilience as it is primarily disturbance driven. The dominant overstory and understory species are highly disturbance tolerant. Frequent disturbance regimes tend to perpetuate the dominance of this community.

Transition T1A
State 1 to 2

Current Reference

Disturbed

Transition from the reference to the disturbed state is primarily a mechanism of moderate to severe disturbance, both natural and anthropogenic. At this ecological site, the most likely disturbance to cause this transition is frequent or severe wildfire. Other disturbances include but are not limited to flooding events, freeze kill events, insect and disease, overgrazing that results in chronic defoliation, and mechanical brush removal.

Constraints to recovery. Primary constraint to recovery is distance to seed source and time. When the disturbance is severe enough 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 under ideal conditions (Innes, 2017). This time period can be greatly reduced through seeding and planting interventions.

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

Transition T1B
State 1 to 3

Current Reference

Degraded

The transition from the reference state to the Degraded state is primarily a mechanism of severe disturbance and post disturbance establishment of invasive species. The most likely disturbance events in this LRU associated with transition to this state are severe or frequent wildfire events and repeated overgrazing that results in chronic defoliation. Following a severe disturbance, invasive and disturbance tolerant species will rapidly establish, preventing native vegetation from recovering. Other possible disturbances include but are not limited to flooding events, freeze kill events, insect and disease, and mechanical brush removal.

Constraints to recovery. The most significant constraint to recovery in this state is establishment of non-native vegetation and disturbance tolerant plants. Once established, these species are able to outcompete native vegetation preventing those species from recovering to pre-disturbance levels. Effective treatment options are limited once significant populations of cheatgrass have established. Using prescribed or natural fire in conjunction with post fire seeding of native vegetation has shown success, however, reverting to cheatgrass canopy covers under five percent and returning to the reference state is highly unlikely (Zouhar, 2003).

Restoration pathway R2A
State 2 to 1

Disturbed

Current Reference

The most important mechanism driving restoration from the disturbed state to the reference is time without sagebrush removing disturbances and distance from overstory species (sagebrush) seed source. Seeding or planting of desired overstory species in the reference state can speed restoration efforts.

Context dependence. Restoration is highly dependent on time without disturbance. New sagebrush seedlings that are able to establish on a site are moderately sensitive to disturbances such as flood, freeze, and insect and disease. They are highly sensitive to herbivory and even low severity fire occurrence (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 T2A
State 2 to 3

Disturbed

Degraded

Transition from the disturbed state to the degraded state results from repeated low to moderate severity disturbances at frequent intervals or single high severity disturbance events. Invasive species and disturbance tolerant vegetation establish prior to native vegetation, preventing recovery to even disturbed state levels.

Constraints to recovery. Constraints to recovery primarily involve energy and resource expenditure to remove invasive species and return native plant cover. Once the degraded state is reached, invasive species such as cheatgrass have become well established on site. Eliminating these species and returning native plant cover is costly and resource intensive with low success rates.