State 1
Reference State

Figure 12. Site ID: 2020ID7031184

The reference state consists of two dominant plant communities: The Black and Little Sagebrush (Artemisia nova & Artemisia arbuscula) dominated community and the Mixed Shrub/Bluebunch Wheatgrass community where overstory shrub canopy dominance is a mix of dwarf sagebrush species, big sagebrush species and other shrubs. The greatest difference between the two plant communities is composition and foliar cover of sagebrush (Artemisia) species. Mountain big sagebrush foliar cover increases on sites that are closer to the high end of the effective precipitation range (10 to 14 inches) and the calcium carbonate equivalency in the soil is lower, closer to minimum 15 percent concentrations outlined in the site concept. Processes (both natural and anthropogenic) that 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 shift between plant communities at this ecological site is generally driven by calcium carbonate concentration in soils, effective precipitation, and time since disturbance. 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 increased risk of severe, stand replacing fire occurrence. Removal of understory grasses can lessen the opportunities for low severity fires 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 frigid soil temperature regime and 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 frigid temperature regime and xeric moisture regime tend to have moderate diversity and production and are therefore more resilient, specifically in terms of resisting or recovering from invasion post-disturbance (Maestas et al., 2016). On the LRU scale, this site may also have increased resistance to invasion of annual grasses due to the calcium carbonate concentration found in the 10 to 25-centimeter range of the soil profile. Calcareous soils have shown to provide a deterrent to the establishment of invasive grasses such as Bromus tectorum (Miller et al., 2006).

Community 1.1
Black and Little Sagebrush and Bluebunch Wheatgrass Community

Figure 13. Site ID: 2020ID7033110

Figure 14. Canopy cover by plant type group: Site ID's: 2020ID7033110, 2021ID7033176.

This community is well adapted to the abiotic conditions of the Lost River Mountain LRU, specifically when soils are shallow to a restrictive layer such as bedrock, clay, or calcareous soils. Black (Artemisia nova) and little (Artemisia arbuscula) sagebrush thrive at dryer sites with soil conditions that create a root-restrictive layer through bedrock or soil chemistry. The more pronounced these conditions become, the more likely the community shifts towards a black sagebrush-dominated community (Tilley & St. John [2], 2012). At the landscape scale, mosaics between little and black sagebrush-dominated sites can represent slight localized differences in soil conditions and effective precipitation (McArthur & Stevens, 2009). Annual production in this community ranges between 400 and 750 pounds per acre, averaging 600 pounds per acre.

Resilience management. This community is moderately resilient. Black sagebrush and bluebunch wheatgrass are both drought-tolerant species, increasing their resistance to climate-related disturbances such as prolonged periods with below-average precipitation. However, with this ecological site occurring in the 10 to 14-inch effective precipitation range, recovery from other disturbances can be slow (Chambers et al., 2014).

Community 1.2
Mixed Shrub Overstory and Bluebunch Wheatgrass Community

Figure 17. Site ID: 2020ID7032169

Figure 18. Canopy cover by plant type group.

Figure 19. Production by plant type group.

The Mixed Shrub Overstory and Bluebunch Wheatgrass community decreases in little and black sagebrush canopy cover and increases in Wyoming big sagebrush (Artemisia tridentata spp. wyomingensis) and mountain big sagebrush (Artemisia tridentata spp vaseyana) when compared with Community 1.1. Grass and forb composition and canopy cover remain similar to Community 1.1 with a slight increase in production. This community occurs at sites that exist at the higher end of the climatic subset (10 to 14 inches) of the ecological sites' precipitation range. These sites also have a slightly lower concentration of calcium carbonates in the rooting zone of the soil profile, allowing mountain and Wyoming big sagebrush to outcompete little and black sagebrush. Production and canopy cover for this community are more evenly split between shrub and grass plant type groups. Shrub species account for a greater percentage of annual production and canopy cover than grass species. Annual production in this community ranges between 425 and 900 pounds per acre, averaging 750 pounds per acre.

Resilience management. Community 1.2 has moderate resilience. Resilience is gained through the increased diversity in the shrub and forb canopies. However, both big sagebrush species (Wyoming and mountain big sagebrush) are more susceptible to stand-replacing fires than little and black sagebrush-dominated communities. This is due to the increased fine fuel loading that occurs when big sagebrush is present on a site. Mountain big sagebrush and Wyoming big sagebrush are also less resistant to drought when compared with little and black sagebrush.

Pathway P1-2
Community 1.1 to 1.2

Black and Little Sagebrush and Bluebunch Wheatgrass Community

Mixed Shrub Overstory and Bluebunch Wheatgrass Community

Community transition from community 1.1 to community 1.2 is generally a result of localized abiotic conditions relating to effective precipitation, as well as depth and concentration of calcareous soils. Black sagebrush tends to dominate sites where calcareous soils are stronger and closer to the surface. As calcium carbonate concentrations decrease, deepen, and precipitation conditions become closer to the 14 inch boundary of relative effective annual precipitation, the likelihood of little sage emigrating or becoming dominant increases. As these conditions become really pronounced (nearing transitional areas) mountain big sagebrush (Artemisia tridentata spp. vaseyana) can be present in the overstory.

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

State 2
Disturbed State

Figure 22. Site ID: 2021ID7033140

The Disturbed state consists of one community and is characterized by a nearly complete to complete loss of overstory shrub canopy. Shrub canopy loss is a result of both natural and anthropogenic disturbances, however, the most common disturbance in this LRU that results in transition to the Disturbed state from the Reference state is moderate to severe fire events. 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. 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 that result in chronic defoliation following a fire disturbance event 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 near to complete loss of overstory sagebrush species (black sagebrush, little sagebrush, and mountain big sagebrush). A shift towards an increase in native and non-native disturbance-tolerant grasses and forbs is likely with removal of resource competition associated with sagebrush overstory. Additionally, the canopy cover of disturbance tolerant shrubs such as yellow rabbitbrush (Chrysothamnus viscidiflorus) and rubber rabbitbrush (Ericameria nauseosa) may increase. Severe disturbance events also increase the opportunity for invasion of annual grasses and weeds such as cheatgrass (Bromus tectorum) and thistle species. Percent canopy cover of invasive species is dependent on the distance of a seed source post-disturbance. Initial cover of invasive species stays below 5 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, and 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, and 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, and can eventually drive a transition to the Invaded state.

Community 2.1
Bunchgrass and Forb Community

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 near to 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. Fire is the primary disturbance responsible for removing sagebrush at this ecological site. The frequency and severity of fire disturbances are 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 cover small spatial extents (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). Shallow to Loamy Calcareous sites that are at the higher end of the 10 to 14-inch precipitation range with an overstory canopy at least partially comprised of mountain big sagebrush are more susceptible to frequent fire return intervals, more severe fires, and 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). Production in this community decreases from that of the Reference communities due to the loss of shrub overstory, however, production in the grass and forb functional groups increases. Production ranges from 225 to 700 pounds per acre, averaging 450 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's bluegrass (Poa secunda) are rarely harmed by fire events except for in the most severe instances. Both species are able to reduce the amount of heat transfer to the root systems, allowing post-fire 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) Although many of the species in this state are at least somewhat resilient towards many of the disturbances encountered, available soil moisture, weather, and rest from grazing all play an important role in how quickly a site can recover post-disturbance. 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 exists in relatively small numbers within the Reference State, it can only become the dominant shrub species in highly disturbed systems (Terminstein, 1999).

State 3
Invaded State

When a Shallow to Loamy, Calcareous ecological site transitions to the Invaded state, it is a result of post disturbance invasion by non-native and 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 black sagebrush, little sagebrush, 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, and Indian paintbrush (Castilleja sp.). Continued disturbance will increase cover and production of these species. Productivity and canopy cover is 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 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
Invasive Grass and Forb Community

The Invasive Grass and Forb Community become dominant on a site in the Invaded state where native vegetation has been removed or severely altered by either natural or anthropogenic disturbances. Once cheatgrass has been 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). Although much of the shrub overstory from the Reference state is removed, 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. The level of invasive species establishment is dependent on the severity of disturbances, amount of remaining native vegetation, and distance and transmission mechanisms for invasive species seed sources. Production in this community is moderately low, and may not consist of desirable grazing species. Production ranges from 300 to 650 pounds per acre, averaging 500 pounds per acre.

Resilience management. This site 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 T1-2
State 1 to 2

Reference State

Disturbed State

Transition from the Reference to the Disturbed state is primarily a mechanism of severe disturbance, both natural and anthropogenic. In this this ecological site, the most likely disturbance to cause this transition is frequent or severe wildfire events. Other disturbances include but are not limited to freeze kill, insect and disease, and mechanical brush removal.

Constraints to recovery. Primary constraint to recovery is distance to seed source. 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. This time period can be greatly reduced through seeding and planting interventions.

Context dependence. The primary factor driving likelihood of restoration success is post disturbance weather patterns. Prolonged period of drought can slow restoration processes, whereas 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 T1-3
State 1 to 3

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 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 R2-1
State 2 to 1

Disturbed State

Reference State

The most important mechanism driving restoration from the Disturbed to the Reference State 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 accelerate 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 this 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

Transition from the Disturbed state to the Invaded state occurs when non-native and invasive species are able to establish in place of native vegetation following a disturbance. Invasive species such as cheatgrass are able to take advantage of the available canopy space and resources that result from removal of native vegetation following a disturbance. The speed and extent of invasive species establishment is dependent on the severity of the disturbance, distance from invasive species seed sources, and dispersal methods of invasive species.

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. Often the species in this state disrupt disturbance regimes in a way that promotes further establishment . 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 R3-1
State 3 to 1

Restoration from the Invaded state to the Reference state is resource intensive and often unsuccessful, especially when cheatgrass is the primary invasive species. Once populations of invasive species exceed five percent canopy cover, mechanical and chemical treatments are required to effectively treat a site. Seeding or planting of native species following treatments is necessary to avoid re-invasion by non-desirable species.

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