Natural Resources
Conservation Service
Limy 10 to 14 Inch Precipitation Zone Lost River Mountains
Scenario model
Current ecosystem state
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Management practices/drivers
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- Transition T1A More details
- Transition T1B More details
- Restoration pathway R2A More details
- Transition T2A More details
- Restoration pathway R3A More details
- Transition T3A More details
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No transition or restoration pathway between the selected states has been described
Target ecosystem state
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Description
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 (Poa secunda), 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).
Dominant plant species
black sagebrush (Artemisia nova), shrub
little sagebrush (Artemisia arbuscula ssp. longiloba), shrub
bluebunch wheatgrass (Pseudoroegneria spicata), grass
Sandberg bluegrass (Poa secunda), grass
Submodel
Description
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 (Poa secunda) and rhizomatous wheatgrasses such as thickspike wheatgrass (Elymus lanceolatus), and western wheatgrass (Pascopyrum smithii). Openings in the canopy gaps vacated by bunchgrasses present opportunities for an increase in disturbance-tolerant forbs such as spiny phlox (Phlox hoodii), cushion phlox (Phlox pulvinata), 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.
Dominant plant species
black sagebrush (Artemisia nova), shrub
little sagebrush (Artemisia arbuscula ssp. longiloba), shrub
Sandberg bluegrass (Poa secunda), grass
spiny phlox (Phlox hoodii), grass
cushion phlox (Phlox pulvinata), grass
milkvetch (Astragalus), grass
Submodel
Description
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 (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. 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.
Dominant plant species
black sagebrush (Artemisia nova), shrub
little sagebrush (Artemisia arbuscula ssp. longiloba), shrub
yellow rabbitbrush (Chrysothamnus viscidiflorus), shrub
bluebunch wheatgrass (Pseudoroegneria spicata), grass
Sandberg bluegrass (Poa secunda), grass
Submodel
Mechanism
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).
Mechanism
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).
Mechanism
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.
Mechanism
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.
Mechanism
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).
Mechanism
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.
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