State 1
Reference State

The Reference State is a representative of the natural range of variability under pre-Euro settlement conditions. State dynamics are maintained by interactions between climatic patterns and disturbance regimes. Negative feedbacks enhance ecosystem resilience and contribute to the stability of the state. These include the presence of all structural and functional groups, low fine fuel loads, and retention of organic matter and nutrients. Community phase changes are primarily driven by fire, periodic drought and/or insect or disease attack.

Community 1.1

Figure 1. T. Stringham, NV 769, MU 1390, 4_26_2016

This community phase is characteristic of a mid-seral plant community. It is dominated by Idaho fescue and bluebunch wheatgrass and mountain big sagebrush. Basin wildrye and an assortment of perennial forbs are common.

Resilience management. Pre-settlement fire return intervals in mountain big sagebrush communities varied from 15 to 25 years (Burkhardt and Tisdale 1969, Houston 1973, and Miller et al. 2000). Mountain big sagebrush is killed by fire (Neunschwander 1980, Blaisdell et al. 1982) and does not resprout (Blaisdell 1953). Post fire regeneration occurs from seed and will vary depending on site characteristics, seed source, and fire characteristics.

Community 1.2

This community phase is characteristic of a post-disturbance, early seral community phase. Idaho fescue, bluebunch wheatgrass and other perennial grasses dominate. Depending on fire severity, rabbitbrush, Utah serviceberry (Amelanchier utahensis), desert peach (Prunus andersonii) and mountain snowberry (Symphoricarpos orbiculatus) may increase after fire due to their ability to sprout. Depending on fire severity or intensity of Aroga moth infestations, patches of intact sagebrush may remain. Perennial forbs may increase post-fire but will likely return to pre-burn levels within a few years.

Resilience management. Big sagebrush is killed by fire and post fire regeneration occurs from seed and will vary depending on site characteristics, seed source, and fire characteristics. The effect of fire on bunchgrasses relates to culm density, culm-leaf morphology, and the size of the plant. The initial condition of bunchgrasses within the site along with seasonality and intensity of the fire all factor into the individual species response. For most forbs and grasses the growing points are located at or below the soil surface providing relative protection from disturbances which decrease above ground biomass, such as grazing or fire. Mature Idaho fescue plants are commonly reported to be severely damaged by fire in all seasons (Wright et al. 1979). Initial mortality may be high (in excess of 75%) on severe burns, but usually varies from 20 to 50 percent (Barrington et al 1988). Bluebunch wheatgrass has coarse stems with little leafy material, therefore the aboveground biomass burns rapidly and little heat is transferred downward into the crowns (Young 1983). Uresk et al. (1976) reported burning increased vegetative and reproductive vigor of bluebunch wheatgrass. Thus, bluebunch wheatgrass is considered to experience slight damage to fire but is more susceptible in drought years (Young 1983).

Community 1.3

Figure 3. P. Novak-Echenique, NV777, MU581, 4_28_2010

Decadent sagebrush dominates the overstory and the deep-rooted perennial bunchgrasses in the understory are reduced either from competition with shrubs and/or from herbivory. Sandberg bluegrass and/or squirreltail may increase and become dominant the grass on the site.

Resilience management. As fire frequency decreases, sagebrush will increase and the potential for encroachment by piñon and juniper also increases. This community phase is at-risk of crossing an ecological threshold due to redistribution of nutrient, energy and moisture resources.

Pathway 1.1a
Community 1.1 to 1.2

Fire will decrease or eliminate the overstory of sagebrush and allow for the perennial bunchgrasses to dominate the site. Fires will typically be low severity resulting in a mosaic pattern due to low fuel loads. A fire following an unusually wet spring or a change in management may be more severe and reduce sagebrush cover to trace amounts. Removal of sagebrush overstory allows perennial grasses and forbs to dominate this community phase. A severe infestation of Aroga moth could also cause a large decrease in sagebrush.

Context dependence.Pre-settlement fire return intervals in mountain big sagebrush communities varied from 15 to 25 years (Burkhardt and Tisdale 1969, Houston 1973, and Miller et al. 2000). Mountain big sagebrush is killed by fire (Neunschwander 1980, Blaisdell et al. 1982) and does not resprout (Blaisdell 1953).

Pathway 1.1b
Community 1.1 to 1.3

Time and lack of disturbance such as fire allows for sagebrush to increase and become decadent. Long-term drought, herbivory, or combinations of these will cause a decline in perennial bunchgrasses and fine fuels leading to a reduced fire frequency allowing big sagebrush to dominate the site.

Pathway 1.2a
Community 1.2 to 1.1

Time and lack of disturbance will allow the mountain big sagebrush to recover and increase.

Context dependence.Post fire regeneration occurs from seed and will vary depending on site characteristics, seed source, and fire characteristics. Mountain big sagebrush seedlings can grow rapidly and may reach reproductive maturity within 3 to 5 years (Bunting et al. 1987). Mountain big sagebrush may return to pre-burn density and cover within 15-20 years following fire, but establishment after severe fires may proceed more slowly (Bunting et al. 1987).

Pathway 1.3a
Community 1.3 to 1.1

A low severity fire, Aroga moth or combinations will reduce the sagebrush overstory and create a sagebrush/grass mosaic with sagebrush and perennial bunchgrasses codominant.

Context dependence.Mountain big sagebrush is killed by fire and does not resprout. Post fire regeneration is dependent on available seed source.

Pathway 1.3b
Community 1.3 to 1.2

Fire will decrease or eliminate the overstory of sagebrush and allow for the perennial bunchgrasses to dominate the site. Fires will typically be low severity due to low fine fuel loads. A fire following an unusually wet spring or a change in management may be more severe and reduce sagebrush cover to trace amounts. A severe infestation of Aroga moth could also cause a large decrease in sagebrush within the community, giving a competitive advantage to the perennial grasses and forbs.

Context dependence.Mountain big sagebrush is killed by fire (Neunschwander 1980, Blaisdell et al. 1982) and does not resprout (Blaisdell 1953). Post fire regeneration occurs from seed and will vary depending on site characteristics, seed source, and fire characteristics.

State 2
Current Potential State

This state is similar to the Reference State 1.0. Ecological function has not changed, however the resiliency of the state has been reduced by the presence of invasive weeds. Non-natives may increase in abundance but will not become dominant within this State. These non-natives can be highly flammable, and can promote fire where historically fire had been infrequent. Negative feedbacks enhance ecosystem resilience and contribute to the stability of the state. These include the presence of all structural and functional groups, low fine fuel loads and retention of organic matter and nutrients. Positive feedbacks decrease ecosystem resilience and stability of the state. These include the non-natives’ high seed output, persistent seed bank, rapid growth rate, ability to cross pollinate and adaptations for seed dispersal.

Community 2.1

This community phase is characteristics of a mid-seral plant community. It is similar to the Reference Community Phase 1.1 with non-native species present in trace amounts.
Dominant species include Idaho fescue, bluebunch wheatgrass, basin wildrye, and mountain big sagebrush. Non-natives, annuals or perennials, are present but not dominant in the understory.

Resilience management. Pre-settlement fire return intervals in mountain big sagebrush communities varied from 15 to 25 years (Burkhardt and Tisdale 1969, Houston 1973, and Miller et al. 2000). The introduction of annual weedy species, like cheatgrass, may cause an increase in fire frequency and eventually lead to an annual dominated community.

Community 2.2

Figure 4. T. Stringham, NV769, MU1390, 4_26_2010

This community phase is characteristic of a post-disturbance, early seral community phase where non-native species are present. Idaho fescue, bluebunch wheatgrass and other perennial grasses dominate post wildfire. Douglas rabbitbrush, mountain snowberry, desert peach and Utah serviceberry may be resprouting. Depending on disturbance frequency/intensity patches of intact sagebrush may remain. Perennial forbs and sprouting shrubs may increase post-fire but will likely return to pre-burn levels within a few years. Annual non-native species are stable or increasing within the community.

Resilience management. The effect of fire on bunchgrasses relates to culm density, culm-leaf morphology, and the size of the plant. The initial condition of bunchgrasses within the site along with seasonality and intensity of the fire all factor into the individual species response. For most forbs and grasses the growing points are located at or below the soil surface providing relative protection from disturbances which decrease above ground biomass, such as grazing or fire. Thus, fire mortality is more correlated to duration and intensity of heat which is related to culm density, culm-leaf morphology, size of plant and abundance of old growth (Wright 1971, Young 1983). The introduction of annual weedy species, like cheatgrass, may cause an increase in fire frequency. Competition for moisture and nutrient resources between natives and non-natives can be significant post-wildfire.

Community 2.3
(At Risk)

Figure 5. Plant community 2.3

Figure 6. Plant community 2.3

Mountain big sagebrush, other shrubs, and bare ground increase in cover. Idaho fescue and bluebunch wheatgrass decrease. Sandberg bluegrass may be increasing. Cheatgrass and other non-native species are stable to increasing. Juniper and pinyon may be present as a result of encroachment from neighboring sites, resulting from lack of disturbance.

Resilience management. Lack of disturbance allows sagebrush to dominate the plant community. Eventually, piñon and juniper will also increase in cover and density. As shrubs and trees dominate site resources the herbaceous understory is severely reduced. As bare ground patches increase and become interconnected soil erosion will increase.

Pathway 2.1a
Community 2.1 to 2.2

Fire will decrease or eliminate the overstory of sagebrush and allow for the perennial bunchgrasses to dominate the site. Fires will typically be small and patchy due to low fuel loads. A fire following an unusually wet spring or a change in management may be more severe and reduce sagebrush cover to trace amounts. A severe infestation of Aroga moth could also cause a large decrease in sagebrush overstory.

Context dependence.Pre-settlement fire return intervals in mountain big sagebrush communities varied from 15 to 25 years (Burkhardt and Tisdale 1969, Houston 1973, and Miller et al. 2000). The introduction of annual weedy species, like cheatgrass, may cause an increase in fire frequency.

Pathway 2.1b
Community 2.1 to 2.3

Time and lack of disturbance allows sagebrush to increase and become decadent. Chronic drought will reduce fine fuels and leads reduced fire frequency allowing big sagebrush to dominate the site. Pinyon and juniper may also be increasing in cover and density.

Context dependence.Inappropriate grazing management, coupled with prolonged drought, will further reduce the perennial bunchgrass understory. Sandberg bluegrass may increase in the understory depending on grazing management. Excessive sheep grazing favors Sandberg bluegrass; however, where cattle are the dominant grazers, cheatgrass often increases.

Pathway 2.2a
Community 2.2 to 2.1

Time and lack of disturbance allows for establishment and growth of sagebrush. The establishment of big sagebrush may take many years.

Context dependence.Post fire regeneration occurs from seed and will vary depending on site characteristics, seed source, and fire characteristics. Mountain big sagebrush seedlings can grow rapidly and may reach reproductive maturity within 3 to 5 years (Bunting et al. 1987). Mountain big sagebrush may return to pre-burn density and cover within 15-20 years following fire, but establishment after severe fires may proceed more slowly (Bunting et al. 1987). Presence of non-native annuals significantly increase competition for soil moisture and nutrient resources, which can be detrimental for shrub seedlings.

Pathway 2.3a
Community 2.3 to 2.1

Low severity fire reduces sagebrush overstory and allows for the understory perennial grasses to increase. Due to low fuel loads, fires will likely be small creating a mosaic pattern. Management that reduces shrubs will allow for the perennial bunchgrasses in the understory to increase. Heavy late-fall/winter grazing may cause mechanical damage to sagebrush thus promoting the perennial bunchgrass understory. Brush treatments with minimal soil disturbance will also decrease sagebrush and release the perennial understory. Annual non-native species are present and may increase in the community.

Pathway 2.3b
Community 2.3 to 2.2

(At Risk)

Fire will decrease or eliminate decadent overstory of sagebrush/native trees and allow for the perennial bunchgrasses to dominate the site. Fires will typically be high intensity due to the dominance of sagebrush resulting in removal of the overstory shrub community. Annual non-native species respond well to fire and may increase post-burn.

Context dependence.Mountain big sagebrush is killed by fire (Neunschwander 1980, Blaisdell et al. 1982) and does not resprout (Blaisdell 1953). Post fire regeneration occurs from seed and will vary depending on site characteristics, seed source, and fire characteristics. Mountain big sagebrush seedlings can grow rapidly and may reach reproductive maturity within 3 to 5 years (Bunting et al. 1987). Mountain big sagebrush may return to pre-burn density and cover within 15-20 years following fire, but establishment after severe fires may proceed more slowly (Bunting et al. 1987). The introduction of annual weedy species, like cheatgrass, may cause an increase in fire frequency and eventually lead to an annual dominated community. Brush management without soil disturbance may also reduce sagebrush overstory and allow for perennial bunchgrasses to increase.

State 3
Shrub State

This state is characterized by the loss of deep rooted-perennial bunchgrasses. It is a product of many years of excessive utilization during time periods harmful to perennial bunchgrasses. Lack of competition allows Sandberg bluegrass to increase and become the dominant grass on this site.

Characteristics and indicators. Ecological processes (soil hydrology, nutrient cycling, and energy capture) are being controlled by the shrub component of the plant community along with Sandberg bluegrass in the understory.

Community 3.1

Figure 7. Loamy Slope 12-14 3.1 (024XY021NV) T. Stringham Ap

Shrub cover exceeds site concept and may be decadent, reflecting stand maturity and lack of seedling establishment due to competition with mature plants. Deep-rooted perennial bunchgrasses may be present in trace amounts or absent from the community. Sandberg bluegrass and annual non-native species increase, and the amount of bare ground increases. Utah juniper and singleleaf pinyon may be present as a result of encroachment from neighboring sites and lack of wildfire. Non-native annuals are stable to increasing

Resilience management. As bare ground increases and deep-rooted herbaceous perennials are reduced this site is at risk of increased soil erosion. Increased run off and soil erosions contributes to the stability of this community phase and prevents the establishment and survival of native perennials.

Community 3.2

This community phase is characteristics of a post-fire plant community. Bluegrass is dominant, annual non-native species may be present and increasing but are not dominant. Depending on fire severity trace amounts of sagebrush, snowberry and/or rabbitbrush may be present.

Resilience management. Resilience of this community phase is reduced due to lack of deep-rooted perennial species. The dominance of Sandburg's bluegrass controls site resources. Including the spatial distribution of soil moisture, resulting lower rates of infiltration, increased runoff and reduced soil moisture storage.

Pathway 3.1a
Community 3.1 to 3.2

Fire, heavy fall grazing causing mechanical damage to shrubs, and/or brush treatments with minimal soil disturbance, will greatly reduce the overstory shrubs to trace amounts and allow for Sandberg bluegrass to dominate the site. Non-native annuals, such as cheatgrass, are stable or increasing.

Context dependence.Mechanism by which sagebrush is removed will be the primary driver related to abundance of cheatgrass. Cheatgrass will increase significantly following a wildfire or any soil disturbing practice.

Pathway 3.2a
Community 3.2 to 3.1

Absence of disturbance and natural regeneration over time allows for sagebrush and other shrubs to recover. The regeneration of big sagebrush may take many years.

Context dependence.Mountain big sagebrush is killed by fire (Neunschwander 1980, Blaisdell et al. 1982) and does not resprout (Blaisdell 1953). Post fire regeneration occurs from seed and will vary depending on site characteristics, seed source, and fire characteristics. Depending on fire severity, rabbitbrush, Utah serviceberry (<a class="species-link" href="https://plants.usda.gov/core/profile?symbol=AMUT" target="_blank" title="Open in plants.usda.gov"><i>Amelanchier utahensis</i></a>), desert peach (<a class="species-link" href="https://plants.usda.gov/core/profile?symbol=PRAN2" target="_blank" title="Open in plants.usda.gov"><i>Prunus andersonii</i></a>) and mountain snowberry (<a class="species-link" href="https://plants.usda.gov/core/profile?symbol=SYOR" target="_blank" title="Open in plants.usda.gov"><i>Symphoricarpos orbiculatus</i></a>) may increase after fire due to their ability to sprout.

State 4
Annual State

This state has two community phases which are characterized by the dominance of annual non-native species such as cheatgrass and tumble mustard in the understory. Sagebrush and/or rabbitbrush dominate the overstory.

Community 4.1

Figure 8. Loamy Slope 12-14 Phase 4.1 T. Stringham April 20

Annual non-native plants such as tumble mustard and cheatgrass dominate the site.

Community 4.2

Mountain big sagebrush and/or rabbitbrush dominate the overstory. Annual non-native species, likely cheatgrass, dominate the understory. Understory may be sparse.

Pathway 4.1a
Community 4.1 to 4.2

Time and a lack of disturbance will allow for recovery of mountain big sagebrush and/or rabbitbrush. This community phase pathway is unlikely to occur due to the ability of cheatgrass to out-compete sagebrush seedlings.

Pathway 4.2a
Community 4.2 to 4.1

Fire, brush management, or Aroga moth infestation will reduce or eliminate the sagebrush component on this site and allow for annual non-native species to dominate.

State 5
Tree State

This state has two community phases that are characterized by the dominance of Utah juniper and singleleaf pinyon in the overstory. Big sagebrush and perennial bunchgrasses may still be present, but they are no longer controlling site dynamics in this state. Soil moisture, soil nutrients and soil organic matter distribution and cycling have been spatially and temporally altered.

Community 5.1

Figure 9. T. Stringham, NV775, MU3561, 8_24_2010

Utah juniper and singleleaf pinyon dominate the overstory. Mountain big sagebrush and rabbitbrush are minor components of the understory. Sandberg bluegrass is present. Deep rooted perennial bunchgrasses are present but declining. Annual non-native species are present or co-dominant in the understory. Pedestalling, sheet, and rill erosion are increasing.

Community 5.2

Figure 10. Loamy Slope 12-14 Phase 5.2 T. Stringham April 2010

Figure 11. Loamy Slope 12-14 Phase 5.1 T. Stringham April 2010

Utah juniper and singleleaf pinyon dominate the overstory. The understory is sparse and bare ground may be significant. This community is not likely to change without human interference or a severe wildfire that will transition it to an Annual State 4.0.

Pathway 5.1a
Community 5.1 to 5.2

Absence of disturbance over time will eventually allow the pinyon and juniper trees to increase and mature severely affecting the understory.

Transition T1A
State 1 to 2

Trigger: Introduction of annual non-native species. Slow variable: Over time the annual non-native plants will increase within the community decreasing organic matter inputs from deep-rooted perennial bunchgrasses resulting in reductions in soil water availability for perennial bunchgrasses. Threshold: Any amount of introduced non-native species causes an immediate decrease in the resilience of the site. Annual non-native species cannot be easily removed from the system and have the potential to significantly alter disturbance regimes from their historic range of variation.

Transition T2A
State 2 to 3

Trigger: To Community Phase 3.1: Loss of deep rooted perennial bunchgrasses and an increased Sandberg bluegrass, muttongrass, and shrub growth and establishment. To Community Phase 3.2: Severe fire in community phase 2.3 will remove sagebrush overstory, decrease perennial bunchgrasses and enhance Sandberg bluegrass and muttongrass. Annual non-native species will increase. Slow variables: Prolonged drought, excessive herbivory or both result in long term decrease in deep-rooted perennial grass density reducing organic matter inputs and infiltration reduced soil water. Threshold: Loss of deep-rooted perennial bunchgrasses changes nutrient cycling, redistributes runoff, and reduces soil organic matter.

Transition T2B
State 2 to 4

Trigger: Reoccurring, severe, wildfires and/or soil disturbing treatments such as drill seeding, roller chopper or Lawson aerator will eliminate perennial natives. Slow variable: Increased production and cover of non-native annual species. Threshold: Loss of deep-rooted perennial bunchgrasses and shrubs changes nutrient capture and cycling within the community. Increased, continuous fine fuels modify the fire regime by changing intensity, size and spatial variability of fires.

Transition T2C
State 2 to 5

Trigger: Absence of disturbance natural regeneration over time and presence of pinyon and/or juniper seed source Slow variables: Increased establishment and cover of juniper trees. Reduced cover and establishment of sagebrush and perennial bunchgrasses Threshold: Trees overtop big sagebrush and out-compete shrubs and bunchgrasses for water and sunlight. Juniper trees control the distribution of energy, nutrient and moisture resources.

Restoration pathway R3A
State 3 to 2

Brush management and seeding with native species. Care should be taken to minimize soil disturbance. Probability of success is low.

Transition T3A
State 3 to 4

Trigger: Multiple severe wildfires and/or soil disturbing treatments Slow variables: increased cover and seed production by annual non-natives coupled with reduced cover and vigor of Sandburg's bluegrass. Threshold: Increased, continuous fine fuels modify the fire regime by changing intensity, size and spatial variability of fires. Changes in plant community composition and spatial variability of vegetation due to the loss of perennial bunchgrasses and sagebrush truncate energy capture and impact the nutrient cycling and distribution.

Transition T3B
State 3 to 5

Trigger: Presence of a pinyon/juniper seed source, coupled with absence of natural disturbance, excessive herbivory and prolonged drought. Slow variable: Over time the abundance and size of trees increase, reducing the understory due to competition for light and moisture resources. Threshold: Trees dominate ecological processes including moisture, nutrient and energy capture. This results in reduced infiltration, increased runoff and redistribution of soil and nutrients off site.

Restoration pathway R5A
State 5 to 3

Tree removal with a bluegrass dominated understory. Use of soil disturbing practices will mostly likely result in transition to an annual dominated state.

Transition T5A
State 5 to 4

Trigger: Catastrophic wildfire or Inappropriate tree removal practices such as chop and burn when annual non-natives such as cheatgrass are present Slow variables: Increased seed production and cover of annual non-native species. Threshold: Increased, continuous fine fuels caused by the dominance of non-native annuals modify the fire regime by changing frequency, intensity, size and spatial variability of fires.