Steep Skeletal 15-19 Inch Precipitation Zone Lost River Mountains
Scenario model
Current ecosystem state
Select a state
Management practices/drivers
Select a transition or restoration pathway
- Transition T1A More details
- Transition T1B More details
- Restoration pathway R2A More details
- Transition T2A More details
-
No transition or restoration pathway between the selected states has been described
Target ecosystem state
Select a state
State 1
Current Reference
Description
The Reference state consists of three plant communities: The mountain big sagebrush (Artemisia tridentata var. vaseyana) dominated community, the mixed shrub community, and the mixed early sagebrush community. The mixed shrub community includes mountain big sagebrush, mountain snowberry (Symphoricarpos oreophilus), antelope bitterbrush (Purshia tridentata), chokecherry (Prunus virginiana), currant species (Ribes spp.) and saskatoon serviceberry (Amelanchier alnifolia). The mixed early sagebrush community consists of little sagebrush (Artemisia arbuscula var. longiloba) and black sagebrush (Artemisa nova). The dominant understory in all three communities is bluebunch wheatgrass (Pseudoroegnaria spicata).
The mountain big sagebrush/bluebunch wheatgrass community is the most common community in the Reference State, and canopy cover is generally balanced between the sagebrush overstory and the bunch grass understory. The mixed shrub community often occurs as a result of very localized site condition variation. Small changes in surface fragment composition, slope shape, and site specific effective precipitation can allow for establishment of several additional overstory shrub species in outside of mountain big sagebrush. Composition and occurrence of shrub species in the mixed shrub community is variable and site specific.
The mixed early sagebrush community in this ecological site is an indicator of increased coarse fragment volume within the 20 inch rooting zone of the soil profile (50cm). Although coarse fragments at this ecological site are already high, averaging above 35 percent in the top 20 inches, as the volume increases it can act as a root restriction. This creates favorable conditions for little and black sagebrush to establish. The presence of these species may also indicate a localized increase in calcium carbonate concentration in the soil profile resulting from limestone parent material.
Processes (both natural and anthropogenic) that can result in state and community changes include fire, grazing, land use change, and occurrence of invasive species (Davies et al., 2011).
Characteristics and indicators
The transition between states at this ecological site is generally driven by relative annual effective precipitation and sagebrush killing disturbances or lack thereof. Historically, low to mixed severity fires occurred at relatively frequent fire return intervals of 10-25 years, limiting sagebrush canopy density and creating a mosaic of sagebrush stands and more open grasslands (Knick, Holmes, & Miller, 2005). Exclusion of fire (in conjunction with climate change) increases sagebrush canopy cover and can lead to more severe stand replacing fires, often times at more frequent intervals. These severe fires can drive shifts to grassland communities as well as create opportunities for invasive species establishment (Roadhouse, Irvine, & Bowerstock, 2020; Knick et al., 2005).
Improper grazing practices can also lead to an increase in sagebrush canopy cover and increased risk of severe, stand replacing fire occurrence. Removal of understory grasses can lessen the opportunities for low severity fire occurrence which leads to increased canopy densities and increases potential for severe fire disturbance events (Knick et al., 2005).
Resilience management
This site has moderate to high resilience as a result of the cryic soil temperature regime and xeric soil moisture regime. Resistance and resilience of a specific site has been attributed with abiotic conditions favorable to plant growth and reproduction (Maestas et al. 2016). Soils that fall within the cryic (cold) temperature regime and xeric (wet) moisture regime tend to have higher diversity and production, and are therefore more resilient. This is specifically true in terms of resisting or recovering from invasion post disturbance (Maestas et al., 2016).
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 frequent or severe wildfire; however, flooding, intense freeze events, and insect and disease can also occur. Of the big sagebrush species, mountain big sagebrush is particularly susceptible to stand replacing fires and often experiences complete canopy loss during moderate and severe wildfire events (Innes, 2017).
Because this LRU exists primarily on publicly managed lands (US Forest Service, Bureau of Land Management, and State), widespread anthropogenic disturbance events are infrequent. Examples of anthropogenic disturbance events include brush management through sagebrush mowing or removal treatments, chemical treatments, or improper grazing techniques that result in high intensity hoof disturbance or chronic defoliation.
A combination of natural and anthropogenic disturbance is possible and can result in increased severity of disturbance, decreased resilience, and greater difficulty returning to the reference state. For example, improper grazing practices post fire disturbance can increase bare ground cover, increase erosion potential, and slow the reestablishment of grass species that preclude the return of overstory sagebrush canopy (Zlatnik, 1999).
Characteristics and indicators
The primary indicator of the disturbed state is a near complete loss of overstory sagebrush species, often replaced by shrub species that are able to take advantage of the local disturbance regime such as Artemisia tripartita (threetip sagebrush) and Chrysothamnus viscidiflorus (yellow rabbitbrush). A shift towards an increase in native and disturbance tolerant grasses and forbs is likely with the removal of resource competition associated with the sagebrush overstory presence. Severe disturbance events also increase the opportunity for invasion of annual grasses and weeds such as cheatgrass (Bromus tectorum) and thistle species. The canopy cover percentage of these species is usually dependent on distance of a seed source post disturbance, but mostly stays under five percent (Zlatnik, 1999).
Resilience management
Resilience in this state is moderate. Many of the post disturbance grasses and shrubs that are common in this state establish quickly and reach a representative canopy within 10 years post disturbance, continuing to increase until overstory canopy of sagebrush begins to return. However, local resilience of these sites in this state is highly dependent on current soil moisture availability, seed sources, timing and severity of the disturbance. In the instance of severe or frequent fire disturbance, bluebunch wheatgrass mortality can be significantly lower if the fire occurs in the spring as opposed to fall, and recovery can be impacted by quantity of immediate post fire precipitation (Zlatnik, 1999).
More severe disturbances increase possibility of post disturbance invasion. The greater the establishment of invasives, the lower the site resilience becomes.
Submodel
Description
When a Steep Skeletal 15 to 19 inch site enters the degraded state, it is generally a result of post disturbance invasion by invasive species. This state can be driven by a particularly severe disturbance either in the form of frequent or severe fire, intensive grazing that results in chronic defoliation of vegetation, land use, or repeated disturbances of low to moderate severity over short periods of time. Proximity to seed source as well as seed transport vectors play a role in likelihood of post disturbance invasion.
Characteristics and indicators
In this state, total canopy cover and production values for mid to large sized bunchgrasses such as bluebunch wheatgrass will decrease. Traditional overstory cover and production of mountain big sagebrush and other shrubs will also decrease. These openings in the canopy will be filled with invasive annuals such as cheatgrass (Bromus techtorum) and more disturbance tolerant forbs such as phlox species, vetch species, an Indian paintbrush (Castilleja sp.). Continued disturbance will increase cover and production of these species. Productivity and canopy cover are lower than the reference state and shifted towards the understory grass species and forbs, particularly the invasive annuals.
Resilience management
This site has low resilience primarily due to the invasive species establishment. Cheatgrass is well adapted to post disturbance establishment, particularly after wildfire disturbances. Cheatgrass takes advantage of prolific seedbanks resilient to fire and its ability to rapidly establish when competition from native vegetation has been removed. Additionally, cheatgrass is able to alter fire regimes, shortening fire return intervals which provides a further advantage for cheatgrass and hinders re-establishment of native vegetation (Zouhar, 2003). Once fully established, restoration of sites invaded by cheatgrass either through natural or mechanical means has low success rates.
Submodel
Mechanism
Transition from the reference to the disturbed state is primarily a mechanism of moderate to severe disturbance, both natural and anthropogenic. At this ecological site, the most likely disturbance to cause this transition is frequent or severe wildfire. Other disturbances include but are not limited to flooding events, freeze kill events, insect and disease, overgrazing that results in chronic defoliation, and mechanical brush removal.
Constraints to recovery
Primary constraint to recovery is distance to seed source and time. When the disturbance is severe enough and the extent is great, seed source populations for sagebrush species may be removed from the vicinity. In this case, immigration and re-establishment of overstory sagebrush species can be slow. Re-establishment to pre disturbance canopy cover and extent of mountain big sagebrush cover generally exceeds 25 years even under ideal conditions (Innes, 2017). This time period can be greatly reduced through seeding and planting interventions.
Context dependence
The primary factors driving likelihood of restoration success are post disturbance weather patterns and distance from viable seed source. Disturbances that cover larger extent increase distance to seed sources and prolonged periods of drought can slow restoration processes. Alternately, average to above average precipitation post disturbance can greatly increase speed and success in re-establishment of sagebrush species (Robin, 2017; Steinberg, 2002; and Fryer, 2009).
Mechanism
The transition from the reference state to the Degraded state is primarily a mechanism of severe disturbance and post disturbance establishment of invasive species. The most likely disturbance events in this LRU associated with transition to this state are severe or frequent wildfire events and repeated overgrazing that results in chronic defoliation. Following a severe disturbance, invasive and disturbance tolerant species will rapidly establish, preventing native vegetation from recovering. Other possible disturbances include but are not limited to flooding events, freeze kill events, insect and disease, and mechanical brush removal.
Constraints to recovery
The most significant constraint to recovery in this state is establishment of non-native vegetation and disturbance tolerant plants. Once established, these species are able to outcompete native vegetation preventing those species from recovering to pre-disturbance levels. Effective treatment options are limited once significant populations of cheatgrass have established. Using prescribed or natural fire in conjunction with post fire seeding of native vegetation has shown success, however, reverting to cheatgrass canopy covers under five percent and returning to the reference state is highly unlikely (Zouhar, 2003).
Mechanism
The most important mechanism driving restoration from the disturbed state to the reference is time without sagebrush removing disturbances and distance from overstory species (sagebrush) seed source. Seeding or planting of desired overstory species in the reference state can speed restoration efforts.
Context dependence
Restoration is highly dependent on time without disturbance. New sagebrush seedlings that are able to establish on a site are moderately sensitive to disturbances such as flood, freeze, and insect and disease. They are highly sensitive to herbivory and even low severity fire occurrence (Fryer, 2009 & Steinberg 2002).
Seeding and planting of desired species can speed up the restoration process, however, regeneration success with or without planting is highly dependent on localized weather patterns during the restoration period. Periods of drought will slow the process significantly, whereas periods of above normal precipitation aid in sagebrush regeneration and establishment (Innes, 2017; Steinberg 2002 & Fryer, 2009).
Mechanism
Transition from the disturbed state to the degraded state results from repeated low to moderate severity disturbances at frequent intervals or single high severity disturbance events. Invasive species and disturbance tolerant vegetation establish prior to native vegetation, preventing recovery to even disturbed state levels.
Constraints to recovery
Constraints to recovery primarily involve energy and resource expenditure to remove invasive species and return native plant cover. Once the degraded state is reached, invasive species such as cheatgrass have become well established on site. Eliminating these species and returning native plant cover is costly and resource intensive with low success rates.
Model keys
Briefcase
Add ecological sites and Major Land Resource Areas to your briefcase by clicking on the briefcase (
) icon wherever it occurs. Drag and drop items to reorder. Cookies are used to store briefcase items between browsing sessions. Because of this, the number of items that can be added to your briefcase is limited, and briefcase items added on one device and browser cannot be accessed from another device or browser. Users who do not wish to place cookies on their devices should not use the briefcase tool. Briefcase cookies serve no other purpose than described here and are deleted whenever browsing history is cleared.
Ecological sites
Major Land Resource Areas
The Ecosystem Dynamics Interpretive Tool is an information system framework developed by the USDA-ARS Jornada Experimental Range, USDA Natural Resources Conservation Service, and New Mexico State University.