State 1
Reference

Figure 11. Limy 10-14" Ecological Site

The Reference state in the Limy ecological site consists of four communities: the black sagebrush (Artemisia nova) community, the little sagebrush (Artemisia arbuscula longiloba) community, the mixed overstory community where black sagebrush and little sagebrush are co-dominant, and the bluebunch wheatgrass (Pseudoroegnaria spicata) dominated community. Although the Black Sagebrush/Bluebunch wheatgrass community is the typical community associated with this site due to it's tolerance of calcareous soils derived from limestone, it is not the most common. Range for black sagebrush in the Lost River Mountain LRU is limited as a result of it's climatic requirements. Although black sagebrush has been shown to successfully establish in frigid soil temperature and xeric soil moisture regimes, the species tends to be more prominent in areas that border mesic and aridic. Available moisture increases rapidly with elevation gain in the Lost River Mountain LRU, creating conditions more favorable to black sagebrush/little sagebrush mixed communities, or communities with overstories dominated by little sagebrush (Steinberg, 2002; Fryer, 2009).

The primary driver in community change in the ecological site is local climatic conditions, however, processes (both natural and anthropogenic) that can result in community changes. These include but are not limited to frequent or severe fire occurrence, grazing that results in chronic defoliation limiting regrowth, land use change, and occurrence of invasive species (Davies et al., 2011). These processes can result in sagebrush overstory removal, shifting to community 1.4, the bluebunch wheatgrass dominated community. The low to moderate severity disturbances can decrease sagebrush populations leading to local (although usually temporary) dominance of bunchgrass populations.

Production values in the Reference state of this ecological site can be wide ranging depending on local site conditions and seasonal weather patterns and trends. Total production varies from 400 to 1200 pounds per acre, with average production at 719 pounds per acre.

Characteristics and indicators. Overstory sagebrush canopy cover in this state is generally high, averaging 15 percent canopy cover regardless of sagebrush species dominance. The understory is dominated by bluebunch wheatgrass, Sandberg bluegrass (<a class="species-link" href="https://plants.usda.gov/core/profile?symbol=POSE" target="_blank" title="Open in plants.usda.gov"><i>Poa secunda</i></a>), and a mix of drier climate forbs. Bluebunch wheat grass canopy cover can vary, ranging from five to 40 percent. The higher end usually occurs in community 1.4. Lack of diversity at this site can be attributed to soil chemistry. Because calcium carbonate equivalency is greater than 15 percent in the top four inches (10 centimeters) of the soil profile, plants must be specifically adapted to those conditions to establish populations. The lack of diversity favors the bunchgrass understory by decreasing competition and allowing for higher canopy cover and production of the species. Although effective precipitation at this site is low (10 to 14 inches), site production can exceed 1000 pounds per acre with over half of that attributed to bluebunch wheatgrass and other grasses present.

Resilience management. This site has moderate resilience resulting from the frigid temperature regime and xeric 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 frigid temperature regime and xeric moisture regime present moderately favorable conditions for regeneration and production and therefore promote moderate resilience post disturbance. This is specifically true in terms of resisting or recovering from site invasion after a disturbance has occurred (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 zero to four inch (0 to 10cm) range of the soil profile. Calcareous soils have shown to provide a deterrent to establishment of invasive grasses such as Bromus techtorum (Miller et al., 2006).

Community 1.1
Black Sagebrush and Bluebunch Wheatgrass

Figure 12. Black sagebrush/bluebunch wheatgrass community

This community is well adapted to the abiotic conditions of the Lost River Mountain LRU, specifically when soils are shallow to calcareous soils. Although composition, foliar cover, and production at this ecological site can vary throughout the shrub overstory, black sagebrush tends to occur more often as a singular dominant overstory species. Black sagebrush thrives at dryer sites, making it more common on the Southern end of the LRU and near the borders with the Lost River Valley LRU where relative annual effective precipitation (REAP) is lower. The more pronounced these dry climatic and calcareous soil 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 REAP (McArthur & Stevens, 2009).

This community is drought-tolerant and plant mortality is generally low during extended periods of lower than average precipitation. Black sagebrush communities can form in a mosaic distribution with the other communities in this state (1.2, 1.3, & 1.4) across the range of relative annual effective precipitation. Black sagebrush-dominated sites are generally more common at the lower end of the effective precipitation range (10 inch), and cover of little sagebrush tends to increase towards the upper end of 14 inches (Tilley & St. John [2], 2012).

Of the surveys and site visits completed in this community, average foliar cover of black sagebrush is 20 percent, with bluebunch wheatgrasse averaging eight percent. Although canopy cover of black sagebrush is higher than bluebunch in this community, plant production is more evenly split. Bluebunch wheatgrass (and other minor grasses) averages 45 percent of the site production value, while black sagebrush and other minor shrubs account for 55 percent. Forbs are a minor community component, averaging one to three percent canopy cover.

Basal gaps are numerous, but minimal in length (one to three feet). Surface gravel cover is usually high compared to other ecological sites in the LRU reaching as high as 50 percent, and exposed bare ground can be extensive, with a maximum near 55 percent.

Resilience management. This community has moderate resilience as a result of the frigid soil temperature regime and xeric soil moisture regime. These conditions are moderately favorable for regeneration and production relating to post disturbance recovery (Maestas et al., 2016). Local site conditions can play a significant role in site resilience. Black sagebrush communities in montane environments are more resistant to annual grass invasion than in valleys and lowlands, and annual grass establishment post disturbance can vary based on moisture patterns, location, and seed source vicinity. Under certain conditions, annual grass invasion (specifically by Bromus techtorum - cheatgrass) can drive conversion from black sagebrush to annual grassland communities (Steinberg, 2002). However, the calcareous soils present at this site may provide additional resistance to annual grass establishment. Calcareous soils have shown to provide a deterrent to establishment of invasive grasses such as Bromus techtorum (Miller et al., 2006).

Community 1.2
Little Sagebrush and Bluebunch Wheatgrass

Figure 15. Little Sagebrush/Bluebunch Wheatgrass Community

In community 1.2, the dominant overstory species shifts from black sagebrush to Artemisia arbuscula var. longiloba (little sagebrush). Like community 1.1, this community is also well adapted to the abiotic conditions in the Lost River Mountain LRU, specifically in the Limy ecological site. Similar to black sagebrush, little sagebrush is tolerant of the highly calcareous surface soils present which are derived from the limestone parent material. The shift in overstory canopy from black to little sagebrush is at least in part a result of increased coarse fragments in the rooting zone. Little sagebrush has shown to typically grow where a root restricting layer is present in the form of a claypan, bedrock, or in the case of this LRU, where coarse fragments in the soil consisting of cobbles and gravels exceed 30 percent (Steinberg, 2002).

Like Community 1.1, the primary understory species is bluebunch wheatgrass. Bluebunch wheatgrass can be a dominant understory grass at many different elevation and precipitation levels across the LRU. It is tolerant of calcareous soils and primarily occupies the sagebrush canopy gaps in well drained soils where it can receive full sunlight (Zlatnick, 1999).

Of the surveys completed in this community of the Limy ecological site, average canopy cover of little sagebrush is 15 percent, while cover of bluebunch wheatgrass is 25 percent. Gaps in vegetation canopy per 100 foot transect averaged a total of 47 feet with gaps ranging in size from one to six feet.

Resilience management. This community is moderately resilient. Little sagebrush and bluebunch wheatgrass are both drought-tolerant species which increases resistance to climate-related disturbances such as prolonged periods with below average precipitation. However, with this site occurring in the 10 to 14 inch effective precipitation range, recovery from other disturbances can be slow (Chambers et al., 2014). Slow returns to pre-disturbance conditions can create opportunities for erosion to occur and invasive species to establish. Additional resistance to invasion of annual grasses can be attributed to the calcareous soils. Calcareous soils, when high enough in the soil profile, have been shown to act as a deterrent towards the establishment of invasive annual grasses (Miller et al., 2006).

Community 1.3
Mixed Black and Little Sagebrush

Figure 18. Mixed Black and Little Sagebrush Community

Community 1.3 is a co-dominated overstory that includes both little and black sagebrush. This is usually represented in a mosaic across the ecological sites and often represents slight local differences in soil depths or volume of coarse fragments in the soil profile. While both species can tolerate calcareous soils, black sagebrush tends to establish better when calcium carbonate equivalency is higher and soils are deeper to a root-restricting layer. Little sagebrush establishes better where soils are shallow to a root restriction. In this LRU, root restrictions generally consist of bedrock or a high volume of coarse fragments (gravels and cobbles) in the soil profile (Steinberg, 2002; Tilley and St. John [2], 2012). Canopy cover between the two sagebrush species can vary on any given site with one of the two comprising the majority of cover. They can also exist in nearly equal canopy cover distribution.

Similar to Communities 1.1 and 1.2, the dominant understory species is bluebunch wheatgrass. Bluebunch wheatgrass can be a dominant understory grass at many different elevation and precipitation levels across the LRU. It is tolerant of calcareous soils and primarily occupies the sagebrush canopy gaps in well drained soils where it can receive full sunlight (Zlatnick, 1999). Other perennial grasses such as Poa secunda (Sandberg bluegrass) can exist within this community, generally at less than five percent of the total canopy cover.

Total annual production at this site is similar to that of Communities 1.1 and 1.2 ranging from 400 to 1200 pounds per acre with average annual production of 650 pounds per acre. Average combined canopy cover of little and black sagebrush is near 20 percent. Combined perennial grass understory (Sandberg bluegrass and bluebunch wheatgrass) average 25 percent.

Resilience management. This community is slightly more resilient than communities 1.1 and 1.2 . The increased diversity of the mixed overstory canopy provides additional protection against insect and disease disturbances that could potentially only impact one of the two species. However, with this site occurring in the 10 to 14 inch effective precipitation range, recovery from other disturbances can be slow (Chambers et al., 2014). Slow returns to pre-disturbance conditions can open opportunities for erosion to occur and invasive species to establish. Additional resistance to invasion of annual grasses can be attributed to the calcareous soils. Calcareous soils, when high enough in the soil profile, have shown to act as a deterrent towards the establishment of invasive annual grasses (Miller et al., 2006).

Community 1.4
Bluebunch Wheatgrass and Little Sagebrush

Figure 21. Bluebunch Wheatgrass/Little Sagebrush

This community is characterized by a change in dominant foliar cover from sagebrush (black sagebrush, little sagebrush, or a combination of the two) to a dominant foliar cover of bunchgrasses including bluebunch wheatgrass and Sandberg bluegrass. The shift in dominant foliar cover to bunchgrasses can be a result of local site characteristics that allow the bunchgrasses to establish and minimize additional growth of sagebrush, or by a sagebrush mortality event. These events can include fire, flooding, intense freezing periods, insect and disease, or anthropogenic disturbances. These sagebrush mortality events are of a low to moderate-severity nature, leaving behind enough sagebrush plants to maintain a reduced population and seed source. Severe disturbance events that remove the majority or all of the sagebrush population in an area generally move the ecological site into state three, the Disturbance state.

Production values within this community are wide-ranging, having the ability to outproduce Communities 1.1 and 1.2 due to the increased opportunity for bunchgrass establishment. At the high end of the production range (1200 pounds per acre), grasses can account for over half of the total production value (650 pounds per acre).

Resilience management. This community is moderate to highly resilient when bluebunch wheatgrass dominates the canopy cover and production at the ecological site. 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 numbers in one to seven years post disturbance and, under certain conditions, canopy cover and production of the species 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 occurring in more protected areas such as the under the canopy of shrubs, opening the canopy for rhizomatous grass species, invasive species, or bare ground establishment. If grazing pressure is significant enough in intensity and duration, this ecological site will shift into the Grazing Resistant state.

Pathway 1.1A
Community 1.1 to 1.4

Black Sagebrush and Bluebunch Wheatgrass

Bluebunch Wheatgrass and Little Sagebrush

The transition from community 1.1 to 1.4 is a result of a sagebrush removal disturbance. These disturbances can be either anthropogenic or naturally occurring. Natural disturbances include low to moderate severity fire, sagebrush die-off events from freeze kill, drought, or prolonged saturation (flooding). Anthropogenic disturbances include mechanical or chemical brush thinning, land conversion, and herbivory. These disturbances are not severe enough to remove entire sagebrush populations, which would transition the site to the disturbed state.

Context dependence.Climatic variation such as prolonged periods of drought or above average temperatures can result in a higher likelihood of a fire-related disturbance occurring at this ecological site. The likelihood or severity of insect and disease disturbances specific to these sagebrush species has not been shown to increase in relation to climatic factors (Evers et al., 2013).

Pathway 1.2A
Community 1.2 to 1.4

Little Sagebrush and Bluebunch Wheatgrass

Bluebunch Wheatgrass and Little Sagebrush

The transition from community 1.2 to 1.4 is a result of a sagebrush removal disturbance. These disturbances can be either anthropogenic or naturally occurring. Natural disturbances include low to moderate severity fire, sagebrush die-off events from freeze kill, drought, of prolonged saturation (flooding). Anthropogenic disturbances include mechanical or chemical brush thinning, land conversion, and herbivory. These disturbances are not severe enough to remove entire sagebrush populations, which would transition the site to the disturbed state.

Context dependence.Climatic variation such as prolonged periods of drought or above average temperatures can result in a higher likelihood of a fire-related disturbance occurring at this ecological site. The likelihood or severity of insect and disease disturbances specific to these sagebrush species has not been shown to increase in relation to climatic factors (Evers et al., 2013).

Pathway 1.3A
Community 1.3 to 1.1

Mixed Black and Little Sagebrush

Black Sagebrush and Bluebunch Wheatgrass

Shifting from Community 1.3 (Mixed Back and Little Sagebrush community) to Community 1.1 (Black Sagebrush community) is primarily a result of a sagebrush removing disturbance that would only impact the low sagebrush species. This would likely be the result of an insect or disease disturbance that only targeted a single species or a mechanical treatment aimed at removing a single species.

Context dependence.Little evidence suggests that climatic factors such as drought or increased average temperature play a role in the insect and disease-related disturbances that impact sagebrush (Evers et al., 2013). Therefore, these events are considered cyclical and more dependent on time and spatial influences.

Pathway 1.3B
Community 1.3 to 1.2

Mixed Black and Little Sagebrush

Little Sagebrush and Bluebunch Wheatgrass

Shifting from Community 1.3 (Mixed Black and Little Sagebrush community) to Community 1.2 (Little Sagebrush community) is primarily a result of a sagebrush removing disturbance that would only impact the black sagebrush species. This would likely be the result of an insect or disease-related disturbance that only targeted a single species or a mechanical treatment aimed at removing a single species.

Context dependence.Little evidence suggests that climatic factors such as drought or increased average temperature play a role in the insect and disease-related disturbances that impact sagebrush (Evers et al., 2013). Therefore, these events are considered cyclical and more dependent on time and spatial influences.

Pathway 1.3C
Community 1.3 to 1.4

Mixed Black and Little Sagebrush

Bluebunch Wheatgrass and Little Sagebrush

The transition from Community 1.3 to 1.4 is a result of a sagebrush removal disturbance. These disturbances can be either anthropogenic or naturally occurring. Natural disturbances include low to moderate-severity fire, sagebrush die-off events from freeze kill, drought, or prolonged saturation (flooding). Anthropogenic disturbances include mechanical or chemical brush thinning, land conversion, and herbivory. These disturbances are not severe enough to remove entire sagebrush populations, which would transition the site to the disturbed state.

Context dependence.Climatic variation such as prolonged periods of drought or above average temperatures can result in a higher likelihood of a fire-related disturbance occurring at this ecological site. The likelihood or severity of insect and disease disturbances specific to these sagebrush species has not been shown to increase in relation to climatic factors (Evers et al., 2013).

Pathway 1.4A
Community 1.4 to 1.1

Bluebunch Wheatgrass and Little Sagebrush

Black Sagebrush and Bluebunch Wheatgrass

The transition from Community 1.4 to Community 1.1 requires time without a sagebrush removing disturbance. In the absence of disturbance, sagebrush species will repopulate the site. The timeframe of this transition is highly dependent on local climate and weather conditions, as well as distance to seed source.

Context dependence.This transition requires time without a sagebrush removing disturbance. Disturbances that occur when the sagebrush overstory is developing can delay or restart the transition back to Community 1.1.

Pathway 1.4B
Community 1.4 to 1.2

Bluebunch Wheatgrass and Little Sagebrush

Little Sagebrush and Bluebunch Wheatgrass

The transition from Community 1.4 to Community 1.2 requires time without a sagebrush removing disturbance. In the absence of disturbance, sagebrush species will repopulate the site. The timeframe of this transition is highly dependent on local climate and weather conditions, as well as distance to seed source.

Context dependence.This transition requires time without a sagebrush removing disturbance. Disturbances that occur when the sagebrush overstory is developing can delay or restart the transition back to Community 1.2.

Pathway 1.4C
Community 1.4 to 1.3

Bluebunch Wheatgrass and Little Sagebrush

Mixed Black and Little Sagebrush

Transition from Community 1.4 to Community 1.3 requires time without a sagebrush removing disturbance. In the absence of disturbance, sagebrush species will repopulate the site. The timeframe of this transition is highly dependent on local climate and weather conditions, as well as distance to seed source.

Context dependence.This transition requires time without a sagebrush removing disturbance. Disturbances that occur when the sagebrush overstory is developing can delay or restart the transition back to Community 1.3.

State 2
Grazing Resistant

When a Limy site in the Lost River Mountain LRU enters the Grazing Resistant state, the primary shift occurs in the understory vegetation. Grazing pressure that results in chronic defoliation from livestock, native ungulates, or a combination of the two drives a shift from the cool-season bunchgrasses present in the Reference state (primarily bluebunch wheatgrass) towards rhizomatous wheatgrasses, short stature bunchgrasses, and ground covering forbs. This state is generally a result of current or historic improper grazing practices that potentially included higher stocking rates and repeated heavy grazing during the growing season.

Characteristics and indicators. In this state, total canopy cover and production values for mid-statured size bunchgrasses such as bluebunch wheatgrass will decrease. These understory grasses will be relegated to the protected areas under the sagebrush canopies where they are sheltered from grazing. As they are removed from the canopy gaps, they will be replaced with grazing-resistant short-stature bunchgrasses like Sandberg bluegrass (<a class="species-link" href="https://plants.usda.gov/core/profile?symbol=POSE" target="_blank" title="Open in plants.usda.gov"><i>Poa secunda</i></a>) and rhizomatous wheatgrasses such as thickspike wheatgrass (<a class="species-link" href="https://plants.usda.gov/core/profile?symbol=ELLA3" target="_blank" title="Open in plants.usda.gov"><i>Elymus lanceolatus</i></a>), and western wheatgrass (<a class="species-link" href="https://plants.usda.gov/core/profile?symbol=PASM" target="_blank" title="Open in plants.usda.gov"><i>Pascopyrum smithii</i></a>). Openings in the canopy gaps vacated by bunchgrasses present opportunities for an increase in disturbance-tolerant forbs such as spiny phlox (<a class="species-link" href="https://plants.usda.gov/core/profile?symbol=PHHO" target="_blank" title="Open in plants.usda.gov"><i>Phlox hoodii</i></a>), cushion phlox (<a class="species-link" href="https://plants.usda.gov/core/profile?symbol=PHPU5" target="_blank" title="Open in plants.usda.gov"><i>Phlox pulvinata</i></a>), vetch species (Vicia sp.) and Indian paintbrush species (Castilleja sp.). Opportunities for invasive annual grasses increase as competition from native grasses are removed from the canopy structure. Depending on how well grazing-resistant rhizomatous and bunchgrasses occupy the canopy gaps, an increase in bare ground cover usually occurs. This can lead to increased erosion and decreased infiltration, decreasing available moisture at the site. Because of this, productivity and canopy cover will be lower than at the reference state.

Resilience management. Resilience in this state is lower than in the Reference state, primarily due to the decrease in available moisture and the opportunity for invasive species recruitment. The ability to recover from disturbance in rangeland systems has shown to be related to local climatic conditions. As available moisture increases and temperature decreases, resilience to disturbance increases (Chambers, et al. 2014). Resilience to erosion and invasive species establishment would be dependent on how well rhizomatous grasses and forbs occupy the bare ground spaces left by the removal of bunchgrasses. Rhizomatous grasses are mat-forming and if able to establish relatively quickly, can aid in reducing erosion. Additionally, if native rhizomatous grasses and forbs are able to quickly establish, this decreases the ability of invasive annual grasses such as cheatgrass to occupy bare soil openings within the site.

Community 2.1
Little Sagebrush and Rhizomatous Wheatgrass

This plant community is identified by its sagebrush overstory and diminished short stature bunch grass and rhizomatous wheatgrass understory. The shrub overstory will consist of black sagebrush, little sagebrush, or a combination of the two. Within this state and community, the bluebunch wheatgrass dominated understory present in the Reference State is replaced by short stature bunchgrasses such as Sandberg bluegrass and rhizomatous wheatgrasses. Remaining bluebunch wheatgrass is concentrated tightly under sagebrush canopies where it is protected from grazers.

Sagebrush canopy cover will often be higher than that of the reference state as opportunities for sagebrush to migrate into the openings left by previous bluebunch wheatgrass plants are created. Sagebrush canopy cover in the Reference communities ranges between 10 to 31 percent and 14 to 35 percent in the grazing resistant community.

The diminished understory in this community also leads to lower annual production values. Production in the reference state ranges from 400 to 1200 pounds per acre, whereas production in the Grazing Resistant state ranges from 200 to 535 pounds per acre. The greatest difference is caused by the decrease in bluebunch wheatgrass density. Bluebunch wheatgrass accounts for 150 to 250 pounds per acre in the Reference communities, and decreases to zero to 50 pounds per acre in the Grazing Resistant state.

Resilience management. This community has moderate resilience, mostly in relation to the understory grass species that replace bluebunch wheatgrass in the Reference communities. Sandberg bluegrass is a highly drought-resistant species of bunchgrass that is also resistant to grazing stress. Even when tilled, Sandberg bluegrass is able to re-establish to pre-disturbance levels within seven years (Howard, 1997). Although not as resilient to grazing pressures as Sandberg bluegrass, the rhizomatous wheatgrasses that can occur on this site can tolerate moderate grazing that does not result in complete or chronic defoliation. On upland sites, Western wheatgrass is considered to be a decreaser under heavy grazing pressure when annual precipitation is under 20 inches, however, it switches to an increaser when annual precipitation is over 20 inches (Tirmenstein, 1999). Alternately, resilience in this community is lowered through the decrease in available soil moisture that occurs from the shift to rhizomatous grasses and the increase in bare soil cover (Chambers, 2014).

State 3
Disturbed

Figure 26. Fire Disturbed Limy Ecological Site

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, and insect and disease can also occur. 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 eliminating the shrub overstory.

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 defoliate new growth following a 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).

The primary contributor to production is bluebunch wheatgrass and can consist of nearly 80 percent of the total depending on local site conditions.

Characteristics and indicators. The primary indicator of the Disturbed state is a nearly complete to complete loss of overstory sagebrush species (black sagebrush and little sagebrush). 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. Additionally, canopy cover of disturbance-tolerant shrubs such as yellow rabbitbrush (<a class="species-link" href="https://plants.usda.gov/core/profile?symbol=CHVI8" target="_blank" title="Open in plants.usda.gov"><i>Chrysothamnus viscidiflorus</i></a>) and rubber rabbitbrush (<a class="species-link" href="https://plants.usda.gov/core/profile?symbol=ERNA10" target="_blank" title="Open in plants.usda.gov"><i>Ericameria nauseosa</i></a>) may increase. Severe disturbance events also increase the opportunity for invasion of annual grasses and weeds such as cheatgrass (<a class="species-link" href="https://plants.usda.gov/core/profile?symbol=BRTE" target="_blank" title="Open in plants.usda.gov"><i>Bromus tectorum</i></a>) 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, and continue 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 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 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 3.1
Mixed Grass and Forb

Figure 27. Limy site in disturbed state due to past wildfire event

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 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 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 the 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 little sagebrush communities often lack fuels sufficient for frequent fire return intervals, severe fire events, or large fire events (Fryer, 2009). Total annual production in this state ranges from 200 to 675 pounds per acre, averaging 410 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 (<a class="species-link" href="https://plants.usda.gov/core/profile?symbol=POSE" target="_blank" title="Open in plants.usda.gov"><i>Poa secunda</i></a>) are rarely harmed by fire events except for in the most severe instances. Both plants are able to reduce the amount of transfer to the root systems, leaving them able to regrow 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 bluegrass has been shown to fully re-establish post plowing disturbance events in as little as seven years after the plowing (Howard, 1997). Although many of the species in this state are at least somewhat resilient to many of the disturbances encountered, available soil moisture, weather, and rest from grazing play an important role in how quickly a site can recover. Both of the common shrub species found in this community 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).

Transition T1A
State 1 to 2

Reference

Grazing Resistant

The transition from the Reference state to the Grazing Resistant state is a product of current or historical improper grazing practices. Continual overstocking and overgrazing during critical growing periods can result in a significant functional and compositional shift in the understory vegetation of the Limy ecological site. In perennial bunchgrasses such as bluebunch wheatgrass, which is the dominant understory vegetation in the Reference state, repeated overgrazing weakens the underground structures through undernourishment caused by the continual removal of photosynthetic tissue (Daubenmire, 1940). This eventually results in the death of these grasses, opening that position for more grazing resistant grasses like Sandberg bluegrass, or bare soil. Because most of this LRU exists on publicly managed lands with regulated grazing policies, new transitions to this state are rare. Historical practices and regulations may have differed, leading to the current existence of this state.

Constraints to recovery.Constraints to recovery include: o Continued improper grazing techniques o Prolonged periods of drought that diminish regeneration of desired species o Loss of nutrient rich top soil due to increased erosion o Establishment of invasive species

Context dependence.Restoration efforts can be greatly influenced by precipitation patterns. Successful regeneration of Reference state understory species is highly dependent on moisture received after restoration efforts. Rates of successful establishment of bluebunch wheatgrass and Sandberg bluegrass increase when available moisture is high during the critical periods post regeneration (Zlatnik, 1999; Howard, 1997).

Transition T1B
State 1 to 3

Reference

Disturbed

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

Constraints to recovery.The primary constraint to recovery is distance to a 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 the likelihood of restoration success is weather patterns. A prolonged period of drought can slow restoration processes, whereas average to above average precipitation can greatly increase speed and success in the re-establishment of sagebrush species (Innes, 2017; Steinberg, 2002; and Fryer, 2009).

Restoration pathway R2A
State 2 to 1

Grazing Resistant

Reference

The primary mechanism of restoration back to the Reference state is time without grazing. Seeding of desired Reference state species can speed up the restoration process.

Context dependence.The time frame for restoration is highly dependent on variations in localized weather patterns. Prolonged periods of drought can dramatically increase time required to return to the Reference state, whereas periods of above normal precipitation can decrease that time frame. Grazing practices that are infrequent and of light intensity, mimicking natural historic grazing patterns, will not impact the restoration pathway. However, continuous early-season grazing at moderate to high intensity will perpetuate the Grazing Resistant state.

Transition T2A
State 2 to 3

Grazing Resistant

Disturbed

The transition from the Grazing Resistant to the Disturbed state is a result of moderate to severe sagebrush removing disturbances. These can include both natural and anthropogenic disturbances, however unlike the Reference state, the possibility of moderate to severe fire events is reduced as a result of the diminished understory composition present in the Grazing Resistant state.

Restoration pathway R3A
State 3 to 1

Disturbed

Reference

The most important mechanism driving restoration from the Disturbed state to the Reference state is time without sagebrush removing disturbances and distance from a 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 site are moderately sensitive to disturbances such like intense freeze events, 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. 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 T3A
State 3 to 2

Disturbed

Grazing Resistant

The transition from the Disturbed state to the Grazing Resistant state results from improper grazing practices. Plant communities in the Disturbed state are particularly vulnerable to heavy grazing in the years immediately following the disturbance that caused the transition from the Reference state to the Disturbed state. If bunchgrasses are unable to establish, plant composition could shift to higher volumes of grazing-resistant, rhizomatous grass species.

Context dependence.Years of drought or below average precipitation in combination with improper grazing can speed transition to the Grazing Resistant state.