Land use 1
Rangeland

Range is the dominant land use for this site and provides the most diverse ecosystem services. Range is land on which the historic and introduced vegetation is predominantly grasses, grass-like plants, forbs or shrubs managed as a natural ecosystem. Range may include natural grasslands, savannas, shrublands, tundra, alpine communities, marshes and meadows.

Characteristics and indicators. This landuse consists of diverse native plant communities dominated by Wyoming big sagebrush and perennial cool season grasses that provide for site stability, hydrologic function, and biotic integrity of the site.

State 1.1
Reference State

Figure 7. Reference State

The Reference State consists of two plant communities: the Big Sagebrush/Bunchgrass community and the Bunchgrass/Big Sagebrush community. Each plant community differs in percent composition and foliar cover of bunchgrasses and shrubs. The dominant shrub is Wyoming big sagebrush. Dominant bunchgrasses include needle and thread, Indian ricegrass, and bluebunch wheatgrass. Forbs are a minor component. Two important processes occur in the reference state and result in plant community changes: 1) sagebrush-killing disturbances such as herbivory, drought, freeze-kill, snow mold, and to a lesser extent, fire; and 2) time without those disturbances, generally referred to as "natural succession." Fire is thought to have been infrequent due to low fine fuel loads, but when it occurred it was small acreage and stand replacing (Innes 2019). Fire Return Intervals are difficult to estimate due to little direct evidence of fire from pre-settlement times, but what information does exist suggests over 200 years for low fuel sites in the Wyoming Basin (Innes 2019).

Characteristics and indicators. The shift between plant community phases is dependent upon sagebrush-killing disturbances, and without them it will increase even with proper grazing management that includes light to moderate utilization, adequate recovery, and periodic critical growth period rest. Improper grazing management that includes high utilization, inadequate recovery, and continuous season-long grazing may accelerate the rate of increase for the shrub component. Management actions or treatments are not typically prescribed or used to mimic the natural disturbance regime due to fragile nature of the soils and lower productivity potential on this site. Treatments that do exist many times have goals for increased leader growth on shrubs for big game winter range. Prescribed fire is not used due to ownership patterns and lack of fine fuels (Clause and Randall, 2014).

Resilience management. This site has moderate to moderately high resilience due to its aridic ustic (ustic bordering on aridic) soil moisture regime and frigid bordering on cryic temperature regime (Chambers et.al. 2014). Precipitation is typically low, but more effective with cooler temperatures and present when needed during the critical growth period (May through June). The site can usually recover after minor disturbance but is susceptible to delays in recovery during extreme climatic events such as drought. The site has moderately high resistance to invasion by annual grasses because of climate limitations (dry and cold). The site may be susceptible to invasion after extreme disturbance during warmer climatic periods or on southeast aspects and concave microtopography. On a local scale, this site is more susceptible to annual weed invasion than sites with heavier soil textures.

Community 1.1.1
Big Sagebrush/Bunchgrass

This plant community is well adapted to Cool Central Desertic Basins and Plateaus climatic conditions. The diversity in plant species allows for drought tolerance, and natural plant mortality is very low. Perennial plants that dominate this site have strong, healthy root systems that allow production to increase significantly with favorable moisture conditions. Abundant plant litter is available for soil building and moisture retention. Plant litter is properly distributed with very little movement off-site. This plant community provides for soil stability and a properly functioning hydrologic cycle. The Big Sagebrush/Bunchgrass Community can occur across the entire ecological site or can occur in a mosaic with the Bunchgrass/Big Sagebrush Community. This plant community occurs in the absence of sagebrush killing disturbances and with grazing that mimics the historic herbivory regime (light, episodic, and associate with mid-size ungulate migration). Wyoming big sagebrush is dominant with foliar cover ranging from 15% to 25%. At this sagebrush canopy level in this precipitation zone, there is some competition between the shrub over-story and the herbaceous under-story (Winward, 2007). A Big Sagebrush/Bunchgrass Community with a degraded under-story is an “at-risk” community that could transition to the Grazing Resistant State. There are some canopy gaps, but most are small (1-2 feet) with some moderate in size (3-6 feet). Rock cover on the soil surface is common and often armors the site against soil erosion. Many plant inter-spaces have canopy or litter cover. Production of grasses is lower than in the Bunchgrass/Big Sagebrush community.

Community 1.1.2
Bunchgrass/Big Sagebrush

This plant community is well adapted to Cool Central Desertic Basins and Plateaus climatic conditions. The diversity in plant species allows for drought tolerance, and natural plant mortality is very low. Perennial plants that dominate this site have strong, healthy root systems that allow production to increase significantly with favorable moisture conditions. Abundant plant litter is available for soil building and moisture retention. Plant litter is properly distributed with very little movement off-site. This plant community provides for soil stability and a properly functioning hydrologic cycle. The Bunchgrass/Big Sagebrush Community can occur across the entire ecological site or can occur in a mosaic associated with the disturbance cycle at any given time and location with the Big Sagebrush/Bunchgrass Community. This plant community occurs after a recent sagebrush killing disturbances and with grazing that mimics the historic herbivory regime (light, episodic, and associate with mid-size ungulate migration). Mid-stature cool season bunchgrasses dominate and sagebrush is sub-dominant with foliar cover ranging from 5% to 15%. At this sagebrush canopy level in this precipitation zone, there is little, if any, competition between the shrub over-story and the herbaceous under-story. In fact, there is evidence to suggest that the under-story receives more benefit from the sage over-story than negative effects (Winward, 2007). There are some canopy gaps, but most are small (1-2 feet) with some moderate in size (3-6 feet). Rock cover on the soil surface is common and often armors the site against soil erosion. Many plant inter-spaces have canopy or litter cover. Production of grasses is higher than in the Big Sagebrush/Bunchgrass community.

Pathway P1.1.1-1.1.2
Community 1.1.1 to 1.1.2

This pathway occurs after a sagebrush killing event, such as drought, freeze-kill, snow mold and/or herbivory, insects or disease. Fire is infrequent on this site due to low fine fuel loads.

Context dependence. This pathway relies upon close to normal precipitation and temperature as well as a grazing regime that is low to moderate intensity. If extreme conditions/disturbances such as hot temperatures, drought, catastrophic fire, or high intensity grazing occur, there is risk of a transition to either the Grazing Resistant or Disturbed State depending upon severity and cumulative disturbance. A successful pathway is contingent upon a grazing regime that allows for periodic critical growth period rest (May-June). The historic herbivory regime was light and episodic, sometimes including spring/fall migration patterns by mid-size ungulates who "ride the green wave" from winter to summer ranges (Aikens et.al. 2017).

Pathway P1.1.2-1.1.1
Community 1.1.2 to 1.1.1

Natural succession (time without a sagebrush killing event).

Context dependence. The time period for this pathway is dependent upon weather events such as drought and above normal precipitation years. Drought results in a slower pathway while favorable precipitation can result in a faster pathway. A grazing regime that mimics the historic regime (light intensity, episodic grazing events) will not alter the pathway, but a continuous grazing regime at moderate to heavy intensity can accelerate the pathway and puts the plant community at-risk of transitioning to the Grazing Resistant State if maintained over long periods of time.

State 1.2
Grazing Resistant State

Figure 12. Grazing Resistant State

The Grazing Resistant State consists of two plant communities: the Big Sagebrush/Short-stature Grass community and the Short-stature Grass/Big Sagebrush community. There has been a shift in understory functional/structural group dominance. Due to herbivory pressure or possibly catastrophic drought, there is a shift from mid-stature cool-season bunchgrasses to short-stature cool-season bunchgrasses, rhizomatous wheatgrasses, and grass-likes. Canopy gap interspace and bare ground has increased from the Reference State, while herbaceous foliar cover has decreased.

Characteristics and indicators. There are fewer mid-size bunchgrasses and they are typically found under the shrub canopy where they are protected from herbivory. The shrub canopy inter-spaces are occupied by grazing tolerant grasses as well as patches of bare ground that are often connected. Drier site conditions result in lower productivity and less herbaceous production potential. In many cases, the transition to the Grazing Resistant State may have occurred many decades ago during an era of higher stocking rates and continuous grazing during the growing season. However, continual grazing during the critical growth period (roughly May through June) at proper stocking rates will facilitate the transition to this state or maintain it as a stable state.

Resilience management. Site resilience is lower than the Reference State. Site hydrology has been modified due to moisture being utilized by shallower rooting species. Therefore, the site is drier earlier in the season, lower in diversity, and unable to recover as quickly after a disturbance such as drought. This state is more drought-prone, and therefore sees wider productivity swings during dry versus wet years. Site resistance to invasion by annual grasses is similar to the reference state, although there are more niches for undesirable annual forbs such as desert alyssum or annual invasive grasses such as cheatgrass to become established during favorable (hot/dry) conditions on southeastern aspects and concave micro-topography.

Community 1.2.1
Big Sagebrush/Short-stature Grass

This plant community is characterized as Wyoming big sagebrush dominated with a diminished understory. The understory has lost many of the mid-stature cool-season bunchgrasses, and they have been replaced with short-stature bunchgrasses such as Sandberg bluegrass, rhizomatous wheatgrasses and grass-likes, and mat-forming forbs. Shrub foliar cover is often greater than 15 percent and typically comprising greater than 30 percent of total annual production (species composition by dry weight). Areas that catch and retain snow are more likely to have higher shrub cover. Herbaceous production and foliar cover has decreased. A small amount of annual invasive grasses such as cheatgrass could occur on south aspects, mostly less than five percent foliar cover. There is often a slight increase in sprouting shrubs (less than 10 percent composition by weight). The site is typically adequately protected from soil erosion due to surface rock fragments and high sage cover. Hydrologic Function has been altered through higher than normal sagebrush canopy. Biotic Integrity is reduced due to low vegetative production, relative dominance of structural/functional groups , and potentially invasive species if present. Total annual production ranges from 200 to 600 pounds per acre with a Representative Value (RV) of 400 pounds per acre. Productivity is highly variable and fluctuates drastically in response to drought and wet cycles.

Community 1.2.2
Short-stature grass/Big Sagebrush

This plant community is characterized by a dominance of short-stature grasses such as Sandberg bluegrass, rhizomatous grasses and grass-likes, and mat-forming forbs. A sagebrush killing event has happened recently, and Wyoming big sagebrush foliar cover is typically less than 15 percent. A small amount of annual invasive grasses such as cheatgrass could occur on south aspects, mostly less than five percent foliar cover. There is often a slight increase in bare ground. The site is typically adequately protected from soil erosion due to surface rock fragments and high sage cover. Hydrologic Function has been altered through increased bare ground. Biotic Integrity is reduced due to low vegetative production, relative dominance of structural/functional groups , and potentially invasive species if present. Total annual production ranges from 200 to 600 pounds per acre with a Representative Value (RV) of 400 pounds per acre. Productivity is highly variable and fluctuates drastically in response to drought and wet cycles. This plant community is at-risk of transitioning to the Disturbed State with additional disturbance such as heavy grazing, sagebrush treatment, or ground-disturbing activity.

Pathway P1.2.1-1.2.2
Community 1.2.1 to 1.2.2

Sagebrush killing event, mainly natural and climatic events such as herbivory, drought, prolonged soil saturation, freeze-kill, or snow mold. Fire is not typically a driver in this state due to the lack of fine fuels in the under-story. Anthropogenic sagebrush treatments is another potential drivers, but is not common on this site.

Context dependence. If extreme conditions/disturbances such as hot temperatures, drought, or high intensity grazing occur, there is risk of a transition to the Disturbed State depending upon severity and cumulative disturbance. Prolonged drought and improper grazing (high intensity, season-long) can accelerate the pathway back to a sagebrush dominated plant community.

Pathway P1.2.2-1.2.1
Community 1.2.2 to 1.2.1

Natural succession (time without a sagebrush killing event).

Context dependence. The time period for this pathway is dependent upon weather events such as drought and above normal precipitation years. Drought results in a faster pathway while favorable precipitation can result in a slower pathway. A grazing regime that mimics the historic regime (light intensity, episodic grazing events) will not alter the pathway, but a continuous grazing regime at moderate to heavy intensity can accelerate the pathway.

State 1.3
Disturbed State

The disturbed state is a result of soil-disturbing activities outside of the normal disturbance regime expected for this site. Examples are high intensity hoof action, anthropogenic activity, rodent activity, or frequent flooding, which includes occasional irrigation. It may also occur after brush management (or multiple consecutive treatments) preceded or followed by improper grazing techniques that include high-intensity grazing use without appropriate recovery periods.

Characteristics and indicators. There is a shift toward sprouting shrub dominance and increased bare ground with diminished under-story and litter. Both green (Chrysothamnus viscidiflorus) and rubber rabbitbrush (Ericameria nauseosus) may be present. Along with a shift in shrub species, the herbaceous under-story also shifts toward more disturbance tolerant species such as thickspike wheatgrass (Elymus lanceolatus ssp. lanceolatus) and needleleaf sedge (Carex duriuscula). Annual weeds such as bur buttercup (Ceratocephala testiculata), flixweed (Descurainia sophia), and lambsquarter (Chenopodium album), and invasive annual grasses such as cheatgrass (Bromus tectorum) can be present in small amounts (less than five percent composition by dry weight).

Resilience management. Site resilience is lower than the Reference State or Grazing Resistant State. Site hydrology has been modified due to moisture being utilized by shallower rooting species. Therefore, the site is drier earlier in the season and unable to recover as quickly after a disturbance. However, existing shrub canopy and remnant perennial vegetation provide some amount of resiliency. Site resistance to invasion by annual grasses is lower due to niches in the understory for establishment as well as coarse soil surface textures. Episodic moisture is more suited to annual life forms during drought.

Community 1.3.1
Rabbitbrush/Short-stature grass

Rabbitbrush dominates with foliar cover often exceeding 20 percent, typically making up over 30 percent of total annual production (species composition by dry weight). Short-stature perennial grasses such as thickspike wheatgrass and needleleaf sedge are dominant. Annual grasses or forbs are more common on southeastern aspects and concave microtopography. Common annuals include desert alyssum, flixweed, and occasionally cheatgrass if a seed source has been introduced to the site. The understory has decreased and bare ground exceeds 40 percent. Bunchgrasses are limited to the protected areas under shrubs. The site is typically adequately protected, but wind erosion can occur, resulting in scouring and deposition. Biotic Integrity is reduced due to low vegetative production, relative dominance and unexpected structural/functional groups, and potentially invasive species if present. Total annual production ranges from 100 to 400 pounds per acre with a Representative Value (RV) of 200 pounds per acre.

Transition T1.1-1.2
State 1.1 to 1.2

Reference State

Grazing Resistant State

Herbivory pressure in excess of normal Reference State conditions. Typical scenarios include moderate to high intensity continuous spring grazing or low intensity season-long grazing.

Constraints to recovery. Recovery is inhibited by continued herbivory pressure, reduced seedbank, and drought conditions. Annual grasses may occur in small amounts when on southeast aspects and concave micro-topography.

Context dependence. Warmer and drier climate trends contribute to uncertainty of restoration efforts. Coarse soil textures put this site at risk of transitioning to the Disturbed State with continued or additive disturbances.

Transition T1.-1.3
State 1.1 to 1.3

Soil-disturbance outside of the normal disturbance regime expected for this site. Examples include high intensity fire, high intensity hoof action, anthropogenic activity (e.g. mechanical and chemical treatments), recreational activities, or rodent activity. Extreme herbivory in combination with catastrophic drought may be a trigger for this transition as well.

Constraints to recovery. Persistent drought conditions, and herbivory pressure are constraints to recovery to the Reference State. Recovery is further inhibited by consecutive disturbances repeated over a relatively short time period and prolonged drought conditions. There is a risk of annual invasion on southeastern aspects and concave micro-topography.

Context dependence. This transition typically occurs after multiple consecutive disturbances. Warmer and drier climate trends contribute to uncertainty of restoration efforts.

Transition T1.2-1.3
State 1.2 to 1.3

Soil-disturbance outside of the normal disturbance regime expected for this site. Examples include high intensity fire, high intensity hoof action, anthropogenic activity (e.g. mechanical and chemical treatments), rodent activity, or prolonged soil saturation, typically occasional irrigation. Extreme herbivory in combination with catastrophic drought may be a trigger for this transition as well.

Constraints to recovery. Persistent drought conditions, and herbivory pressure are constraints to recovery to the Reference State. Recovery is further inhibited by consecutive disturbances repeated over a relatively short time period and prolonged drought conditions. There is a risk of annual invasion on southeastern aspects and concave microtopography.

Context dependence. This transition typically occurs after multiple consecutive disturbances. Warmer and drier climate trends contribute to uncertainty of restoration efforts.

Land use 2
Other - Mineral Extraction Lands

Land that is barren, sandy, rocky, or that is impacted by the extraction of natural resources, such as minerals, gravel or sand, coal, shale, rock, oil, or natural gas.

Characteristics and indicators. This land use can be many things, but in this LRU is most often associated with oil and gas development. Barren land. A land cover/use category used to classify lands with limited capacity to support life and having less than 5 percent vegetative cover. Vegetation, if present, is widely spaced. [NRI-87] Typically, the surface of barren land is sand, rock, exposed subsoil, or salt-affected soils. Subcategories include salt flats; sand dunes; mud flats; beaches; bare exposed rock; quarries, strip mines, gravel pits, and borrow pits; river wash; oil wasteland; mixed barren lands; and other barren land. [NRI-92]

State 2.1
Reclaimed

The Reclaimed State is highly variable based on weather conditions during reclamation activities, the management practices used to implement the reclamation, the seed mix, and timing/method of stockpiling topsoil during the disturbance.

Characteristics and indicators. The most common scenario is a reclaimed oil and gas well pad planted to crested wheatgrass (Agropyron cristatum) without appropriate topsoil stockpiling. If topsoil is stockpiled, it may have been stored for too long and/or stored too deep resulting in fewer soil microorganisms. Over time, Wyoming big sagebrush will spread into the reclaimed area, but the understory will be dominated by introduced species. Biological soil crusts are minimal, further exposing the soil surface to erosional forces as well as impairing carbon, nutrient, and water cycles.

Resilience management. Resilience is lower than the Reference State, but with best management practices, a certain amount of resilience can be restored. Successful reclamation will result in reduced soil erosion and improved hydrologic function. Biotic integrity is highly variable. Because soil disturbance previously occurred on the site and soil surface textures are coarse, resistance to invasive species is low.

State 2.2
Annuals/Bare Ground

The Annuals/Bare Ground community occurs after severe disturbance, most often physical soil disturbance that removes topsoil, but it can also occur as a transition from the Eroded State after severe drought, flooding, pests, or disease, leaving the site with no perennial vegetation.

Characteristics and indicators. Populations of annual weedy forbs can reach critical levels and impact the ecological processes on the site until restoration or reclamation of the site occurs. As part of succession, all sites that are severely disturbed go through this plant community as part of the restoration process, but the time in this plant community phase is largely dependent on the use of restoration Best Management Practices (BPMs) and climate cycles. Biological soil crusts are non-existent, further exposing the soil surface to erosional forces as well as impairing carbon, nutrient, and water cycles.

Resilience management. Site resilience is at its lowest, and recovery is largely dependent on management practices and weather patterns. Resistance to invasion is at its lowest, and the site is vulnerable to all of the common annual weedy forbs such as Russian thistle (Salsola tragus)), flixweed (Descurainia sophia), lambsquarter (Chenopodium album), and halogeton (Halogeton glomeraturs) as well as invading species such as cheatgrass (Bromus tectorum) and existing or newly emerging noxious weed threats.

Restoration pathway R2.2-2.1
State 2.2 to 2.1

Reclamation efforts include re-seeding. In cases where heavy equipment caused the disturbance, contouring and/or deep ripping may be necessary to provide a suitable site for re-seeding. Care must be taken to stockpile and replace surface layers separately from the subsurface. Prescribed grazing and restricting vehicle traffic on the site is necessary to facilitate successful seeding of perennial species.

Context dependence. Drought conditions and/or herbivory pressure may hinder restoration efforts, and multiple seeding efforts may be necessary if failure is caused by drought. Mulch can be effective for soil moisture retention and erosion control. Soil limitations include depth and care must be used to stockpile soil surface for later use in site reclamation and restoration.

Conversion C1-2
Land use 1 to 2

The conversion from Range to Other - Mineral Extraction Lands occurs when vegetation and soil is manipulated for the purpose of mineral extraction. Common practices are oil and natural gas pad and pipeline infrastructure, gravel pits, and road construction. Vegetation and topsoil is removed and topsoil is often stockpiled for on or off-site reclamation.

Conversion C2-1
Land use 2 to 1

Conversion from Other - Mineral Extraction Lands to Range occurs, sometimes over a long period of time, as part of the restoration process after mineral extraction. There is low potential for recovery without significant inputs of energy and resources, especially if topsoil has been removed. Seed mixes that mimic an adjacent “reference area” rather than the site potential as described in the Reference State (1.1) will often result in a plant community resembling the Grazing Resistant State (1.2) due to inappropriate seed mixes and pre- and post-seeding grazing management that does not provide adequate recovery and periodic critical growth period rest.