State 1
Reference

The Reference state of the Steep Loamy 15 to 19 inch ecological site consists of three dominant plant communities. Community 1.1 and 1.2 are dominated by a mountain big sagebrush (Artemisia tridentata ssp. vaseyana) overstory; however, Community 1.1 has a dominant understory of Idaho fescue (Festuca idahoensis) and the understory of Community 1.2 is dominated by bluebunch wheatgrass (Pseudoroegneria spicata). Community 1.1 is more predominant at sites closer to the higher end of the relative effective annual precipitation range (15 to 19 inches) as Idaho fescue is better adapted to slightly wetter conditions (Zouhar, 2000). In Community 1.3, a shift from a mountain big sagebrush-dominated overstory to a more diverse shrub overstory occurs. Bunchgrasses (Idaho fescue and bluebunch wheatgrass) remain the dominant understory. The characteristics of the Steep Loamy 15 to 19 inch ecological site allow for relatively high productivity and diversity in both the overstory and understory relative to many other ecological sites within the Lost River Mountain LRU. Processes (both natural and anthropogenic) that can result in state and community changes include frequent or severe fire, grazing that results in chronic defoliation, and land use changes (Davies et al., 2011).

Characteristics and indicators. The shift between communities at this ecological site is primarily driven by slight variations in local abiotic conditions. Shift in the understory composition from Idaho fescue to bluebunch wheatgrass is usually attributed to available moisture. Although Idaho fescue can be present closer to the 15 inch end of the relative effective annual precipitation range, bluebunch wheatgrass is better adapted to these conditions and tends to occupy a greater percentage of the canopy (Zouhar, 2000). Shift from an overstory canopy dominated by mountain big sagebrush to a mixed shrub overstory can result from slightly localized abiotic factors such as depth to bedrock and coarse fragment volume on the surface and throughout the soil profile. Biotic conditions including distance from seed source and resource competition can also play a role.

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 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, high production, and are therefore more resilient. This is specifically true 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 post-disturbance invasion due to the biodiversity generally present at the site. Sites with high biodiversity have been shown to exhibit increased resistance and resilience as a result of the differential impact of disturbances such as insects, disease, and fire on the variety of species present (Oliver et al., 2015).

Community 1.1
Mountain Big Sagebrush and Idaho Fescue

The Mountain Big Sagebrush and Idaho Fescue community is well adapted to the abiotic conditions found at the Steep Loamy 15 to 19 inch ecological site in the Lost River Mountain LRU. Both of the primary species thrive in loamy-based soil textures that lack carbonates and high volumes of coarse fragments, with the primary limiting factors being relative effective annual precipitation and slope steepness. Idaho fescue prefers slightly higher amounts of effective precipitation than the other grass species found at this ecological site and understories dominated by this species become more predominant on the upper end of the 15 to 19 inch climatic subset (Zouhar, 2000). Mountain big sagebrush has the greatest preference for sites with higher soil moisture availability. The species is commonly found on moderately deep to deep, well-drained Mollisols, and at higher elevations than other big sagebrush species (Innes, 2017). In this community, mountain big sagebrush tends to exist as a monoculture in the overstory; however, other species of shrubs may be present at less than five percent canopy cover. Production in this community is moderately high, ranging from 400 to 900 pounds per acre, with an average of just over 650 pounds per acre. Mountain big sagebrush foliar cover averages 30 percent, while Idaho fescue averages eight percent. Species of lupine (Lupinus spp.) and arrow leaf balsamroot (Balsamorhiza sagittata) each average between two to seven percent canopy cover.

Resilience management. Mountain big sagebrush is the primary overstory species in the Reference state. It exhibits low to moderate resistance but moderate to high resilience. Mountain big sagebrush is the least drought tolerant of the big sagebrush species. Mountain big sagebrush foliage is highly flammable and is among the most productive of sagebrush species so fuel loading and continuity are high (Innes, 2017). This increases susceptibility to severe wildfire events at more frequent intervals which can slow recovery. Fires in mountain big sagebrush stands tend to be stand-replacing. When Idaho fescue is the dominant understory, fire return intervals can be as frequent as 10 to 15 years. Although Idaho fescue fares better than mountain big sagebrush during fire events, mortality averages between 20 and 50 percent and can exceed 75 percent after severe events (Zouhar, 2000). Severe fire events can prompt a shift into the Disturbed state. Resilience at this site is deemed moderate to high due to the ability of mountain big sagebrush to quickly re-establish canopy cover post-disturbance. Under moderate to ideal conditions, mountain big sagebrush can return to pre-disturbance levels relatively quickly compared to other big sagebrush species (Innes, 2017). The additional effective precipitation received at this site (15 to 19 inches) adds resilience. Available moisture is key component of successful recovery (Chamber et al., 2014).

Community 1.2
Mountain Big Sagebrush and Bluebunch Wheatgrass

The Mountain Big Sagebrush and Bluebunch Wheatgrass community is more prevalent on the lower end of the 15 to 19 inch climatic subset of the Loamy ecological site. Bluebunch wheatgrass can thrive under a broad range of moisture conditions and is one of the most drought-resistant native bunchgrasses (Zlatnik, 1999). These adaptations often allow bluebunch wheatgrass to become the dominant understory at the drier sites in the 15 to 19 inch climatic subset. Although both Idaho fescue and bluebunch wheatgrass populations can be present in this community, canopy cover and percentage of total production will be higher for bluebunch wheatgrass. Mountain big sagebrush remains the dominant overstory species. Other shrub species that may be present at a limited canopy cover include mountain snowberry (Symphoricarpos oreophilus), yellow rabbitbrush (Chrysothamnus viscidiflorus), and antelope bitterbrush (Purshia tridentata). Production in this community is moderately high, ranging from 650 to 1,000 pounds per acre, with an average of 850 pounds per acre. Mountain big sagebrush foliar cover averages 25 percent, while bluebunch wheatgrass averages 20 percent. Idaho fescue is sub-dominant in the understory averaging eight percent canopy cover. Species of lupine (Lupinus spp.), arrowleaf balsamroot (Balsamorhiza sagittata) and phlox (Phlox spp.) contribute zero to three percent of canopy cover respectively.

Resilience management. With mountain big sagebrush being the primary overstory species, this community in the Reference state exhibits low to moderate resilience. Of all the big sagebrush species, mountain big sagebrush is the least drought tolerant. Sagebrush foliage is highly flammable and because they are among the most productive of sagebrush species, fuel loading and continuity are higher (Innes, 2017). This increases susceptibility to severe wildfire events at more frequent intervals which can slow recovery. Fires in mountain big sagebrush stands tend to be stand replacing and under poor conditions, recovery to pre-fire levels can exceed 75 years (Innes, 2017). Bluebunch wheatgrass usually survives fires because its buds are protected. Fire return intervals are generally less than 30 years depending on overstory and related vegetation. Recovery of bluebunch wheatgrass from fire is rapid, generally returning to pre-disturbance populations in less than five years (Zlatnik, 1999). Although bluebunch populations may survive severe fire events, if the mountain big sagebrush overstory is removed, this can prompt a shift into the Disturbed state. The additional relative effective annual precipitation received at this site (15 to 19 inches) adds resilience. Available moisture is key component of successful post-disturbance recovery (Chamber et al., 2014).

Community 1.3
Mixed Mountain Shrub and Bunchgrass

Community 1.3 shifts from the mountain big sagebrush-dominated overstory to a more diverse overstory that includes a variety of mountain shrub species. The mixed shrub community is primarily influenced by very localized abiotic conditions. Although mountain big sagebrush usually remains the dominant overstory shrub, other shrubs often including antelope bitterbrush (Purshia tridentata), chokecherry (Prunus virginiana), mountain snowberry (Symphoricarpos oreophilus), Saskatoon serviceberry (Amelanchier alnifolia) and currant species (Ribes spp.) may be present at varying population sizes. Mountain snowberry, usually secondary in dominance to mountain big sagebrush in this community is well suited to sandy and clay loam soils at varying elevations, both under acidic and basic soil conditions (Aleksoff, 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 Geyer's sedge (Carex geyeri) appearing towards the higher end of the effective precipitation range (19 inches). Production in this community can be moderately high, with a wide range from 450 to 1,300 pounds per acre, with an average of 900 pounds per acre. Mountain big sagebrush foliar cover averages between 10 to 15 percent, mountain snowberry ranges from five to 20 percent, and Idaho fescue/bluebunch wheatgrass averages 10 to 15 percent canopy cover. Species of lupine (Lupinus spp.) and arrowleaf balsamroot (Balsamorhiza sagittata) contribute zero to five percent to total canopy cover.

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 insects and diseases that often target a single species. Other natural disturbances such as fire and prolonged periods of drought will also impact overstory species differentially. Limited population loss reduces the potential for increased erosion and the establishment of invasive species following a disturbance. Bluebunch wheatgrass, which is one of 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).

Pathway 1.1A
Community 1.1 to 1.2

Mountain Big Sagebrush and Idaho Fescue

Mountain Big Sagebrush and Bluebunch Wheatgrass

Differences in understory dominance between Idaho fescue (1.1) and bluebunch wheatgrass (1.2) are generally attributed to slight localized variations in effective precipitation at this ecological site. Idaho fescue is better suited for conditions found at the higher end of the 15 to 19 inch relative effective annual precipitation range, while bluebunch wheatgrass is more drought tolerant and better able to cope with conditions at lower effective precipitation (Zouhar 2000; Zlatnik 1999). When the ecological site occurs at the higher end of the effective precipitation range, Idaho fescue is more likely to dominate the understory both in canopy cover percentage and production value.

Pathway 1.1B
Community 1.1 to 1.3

Mountain Big Sagebrush and Idaho Fescue

Mixed Mountain Shrub and Bunchgrass

The transition from the mountain big sagebrush-dominated shrub overstory to the mixed shrub overstory is primarily a mechanism in slight variations in localized abiotic conditions. Mountain big sagebrush prefers soil conditions that are moderately deep to deep and well drained (Innes, 2017). Slight variations in site soil characteristics and other abiotic conditions can increase favorability for other shrub species to establish and share site dominance. These species include antelope bitterbrush, mountain snowberry, chokecherry, and occasionally Saskatoon serviceberry.

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 frequent or severe wildfires; however, intense freeze events, insect damage, and disease can also occur. Both mountain big sagebrush and basin big sagebrush are particularly 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 or chronic defoliation of vegetation. 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 can take advantage of the local disturbance regime such as threetip sagebrush (Artemisia tripartita) and yellow rabbitbrush (Chrysothamnus viscidiflorus). 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 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 are established quickly and reach a representative canopy within 10 years post-disturbance. These species continue to increase until the 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 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 invasion. The greater the establishment of invasives, the lower the site resilience becomes.

Community 2.1
Bunchgrass and Forb

The mixed grass and forb community is driven by the removal of the primary overstory of sagebrush species. Both natural and anthropogenic disturbances that result in the 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 removal disturbance at this ecological site is fire. The frequency and severity of these 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. Steep Loamy sites with an overstory canopy at least partially comprised of mountain big sagebrush are more susceptible to frequent fire return intervals, more severe fires, and often to 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 is moderately high, ranging from 370 to 1075 pounds per acre, with an average of 865 pounds per acre. Mountain big sagebrush foliar cover averages nearly five percent, while bluebunch wheatgrass averages over 20 percent.

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 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, enabling successful regrowth (Zlatnik, 1999; Howard, 1997). Studies have shown that in the absence of grazing, bluebunch wheatgrass-dominated systems can return to pre-fire production levels in eight years (Zlatnick, 1999). Sandberg 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 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, and rest from grazing all play an important role in how quickly a site can return following the disturbance. The resilience of mountain big sagebrush populations is highly dependent on the severity of disturbance and distance from a seed source. Mountain big sagebrush communities are significantly impacted in all but the lowest severity fire events. This often leaves little remaining sagebrush canopy on sight or nearby as a viable seed source. Additionally, mountain big sagebrush is reliant on favorable weather patterns and moisture availability to increase seed establishment and success (Innes, 2017).

State 3
Degraded

When a Steep Loamy 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 fire, intensive grazing, or land use, or repeated disturbances of low to moderate severity over short periods. Proximity to a seed source as well as seed transport vectors play a role in the 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 generally 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 spp.). Continued disturbance will increase the 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 the ability to rapidly establish when competition from native vegetation has been removed through disturbance. Additionally, cheatgrass can 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 Annual Grass

The invasive annual grass 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 (Bromus techtorum) 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). In this LRU, yellow rabbitbrush is another species that is often 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 state. Production in this community is moderately high, ranging from 475 to 1,025 pounds per acre, with an average of just over 800 pounds per acre. Mountain big sagebrush and yellow rabbitbrush both average five percent foliar cover. Cheatgrass canopy cover can be as high as 70 percent. Species of lupine (Lupinus sp.) and arrow leaf balsamroot (Balsamorhiza sagittata) each average between 0 to 5 percent canopy cover respectively.

Resilience management. This community in the Degraded state is primarily disturbance-driven. The dominant overstory and understory species are highly disturbance tolerant. Frequent disturbance events tend to perpetuate the dominance of this community. Once cheatgrass has fully established, returning to the disturbed or Degraded state is very difficult and resource-intensive.

Transition T1A
State 1 to 2

Reference

Disturbed

The transition from the Reference state to the Disturbed state is a result of both natural and anthropogenic disturbance regimes. The primary disturbance regime likely to impact this ecological site is moderate to severe fire occurrence. Fire return intervals in the reference communities are often driven by the dominant understory species. This can be less than 30 years in bluebunch wheatgrass communities and 15 years for Idaho fescue (Innes 2017; Zouhar, 2000).

Constraints to recovery. The primary constraint to recovery is the distance to a seed source. Most fire events are fatal to mountain big sagebrush and when the disturbance is severe enough and the extent is large, 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 period can be greatly reduced through seeding and planting interventions. Bluebunch wheatgrass is resistant to fire and generally unharmed in all but the most severe events. Idaho fescue is less resistant, increasing the time needed to return to pre-disturbance levels.

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

Transition T1B
State 1 to 3

Reference

Degraded

The transition from the Reference state to the Degraded state is a result of a disturbance event (or multiple disturbance events) followed by the establishment of invasive species, primarily cheatgrass. The likelihood of this transition increases when multiple disturbance events occur with little time for recovery, or following especially severe disturbance events.

Constraints to recovery. Once cheatgrass begins to establish on a site, it can grow and reproduce rapidly often forming a monoculture (Zouhar, 2003). Once established, complete removal of the species from a site is difficult, costly, and resource intensive, limiting restoration options. Success is increased by identifying sites early in the transition and beginning treatment before cheatgrass populations become significant.

Restoration pathway R2A
State 2 to 1

Disturbed

Reference

The most important mechanism driving restoration from the Disturbed state to the Reference state is time without a 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 can establish on a site are moderately sensitive to disturbances such as freeze-kill, insect damage, 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

The transition from the Disturbed state to the Degraded state is more likely than a direct transition from the Reference to the Degraded state. The transition occurs when a disturbance removes most or all of the native shrub overstory and grass understory, creating available space for invasive species establishment. Once established, many invasive species such as cheatgrass can promote feedback loops that increase their dominance over time.

Constraints to recovery. The primary constraint to recovery is the successful removal of invasive species. Once established, the successful removal of cheatgrass and other invasive species is a resource-intensive process. Time without disturbance and seeding/planting interventions of native vegetation can aid in recovery.

Context dependence. Factors that contribute to restoration success include the level of invasive species establishment, intervention methods, and post-treatment weather patterns. A prolonged period of drought can slow restoration processes, whereas average to above-average precipitation post-disturbance can greatly increase speed and success in the re-establishment of sagebrush species (Robin, 2017; Steinberg, 2002; Fryer, 2009).

Restoration pathway R3A
State 3 to 2

Degraded

Disturbed

The most important factor in restoration from the Degraded state to the Disturbed state is the removal of invasive annual grasses and the re-establishment of native grasses. Depending on the level of invasive species presence, this may only be achieved using mechanical interventions and seeding.

Context dependence. Restoration is dependent on time without disturbance and favorable planting conditions. 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 and bunchgrass regeneration and establishment (Innes 2017; Steinberg 2002; Fryer, 2009).