State 1
Reference State

The Reference State is a representative of the natural range of variability under pristine 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. Plant community phase changes are primarily driven by fire, periodic drought and/or insect or disease attack.

Characteristics and indicators. This state is dominated by basin big sagebrush and bluebunch wheatgrass.

Community 1.1
Community Phase

This community phase is characteristic of a mid-seral plant community and is dominated by basin big sagebrush and bluebunch wheatgrass. Thurber's needlegrass, bottlebrush squirreltail, and antelope bitterbrush are also common on this site. Composition by weight is approximately 60-70 percent grass, 5-10 percent forbs and 20-30 percent shrubs.

Community 1.2
Community Phase

This community phase is characterized by a post-disturbance, early seral, plant community. Sagebrush and other shrubs are reduced, or patchy. Perennial bunchgrasses and forbs dominate the visual aspect of the plant community. Disturbance tolerant shrubs such as rabbitbrush and antelope bitterbrush will sprout from the root-crown following low and medium intensity wildfire and may begin to dominate the plant community 2 to 5 years post-disturbance.

Resilience management. Basin big sagebrush does not sprout after fire. Because of the time needed to produce seed, it is eliminated by frequent fires (Bunting et al. 1987). Basin big sagebrush establishes on a site primarily by off-site seed or seed from plants that survive in unburned patches. 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).

Community 1.3
Community Phase

Natural regeneration and absence of disturbance over time allows sagebrush to mature and dominate the plant community. Perennial bunchgrasses and forbs are reduced in both vigor and productivity due to competition for light, moisture and nutrient resources.

Pathway 1.1a
Community 1.1 to 1.2

Low severity fire creates sagebrush/grass mosaic; higher intensity fires significantly reduce sagebrush cover and lead to early seral community dominated by grasses and forbs. Frequency and intensity of wildfire is primarily driven by cover and amount of herbaceous vegetation. Under pre-Eurosettlement conditions fire return interval is estimated to be between 20 and 50 years.

Pathway 1.1b
Community 1.1 to 1.3

Time, absence of disturbance and natural regeneration over time allows sagebrush to dominate site resources. This community phase pathway may be coupled with drought and/or herbivory further reducing herbaceous understory.

Pathway 1.2a
Community 1.2 to 1.1

Time, absence of disturbance and natural regeneration over time allows sagebrush to recover. Recovery of sagebrush depends on the availability of a local seed source (patches of mature shrubs) as well as precipitation patterns favorable for germination and seedling recruitment. Sagebrush seedlings are susceptible to less than favorable conditions for several years. Completion of this community phase pathways may take decades.

Context dependence. Approximately 90% of big sagebrush seed is dispersed within 30 feet (9 m) of the parent shrub (Goodrich et al. 1985) with maximum seed dispersal at approximately 108 feet (33 m) from the parent shrub (Shumar and Anderson 1986). Therefore, regeneration of basin big sagebrush after stand replacing fires is difficult and dependent upon proximity of residual mature plants and favorable moisture conditions (Johnson and Payne 1968, Humphrey 1984).

Pathway 1.3a
Community 1.3 to 1.1

Low intensity, patchy wildfire or insect infestation would reduce sagebrush overstory creating a mosaic on the landscape. Perennial bunchgrasses and forbs dominate disturbed patches due to an increase in light, moisture and nutrient resources.

Pathway 1.3b
Community 1.3 to 1.2

Wide spread wildfire removes sagebrush and allows perennial bunchgrasses and forbs to dominate.

State 2
Current Potential

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. 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.

Resilience management. Best management will maintain high diversity of desired species to promote organic matter inputs and prevent the dispersal and seed production of the non-native invasive species.

State 3
Sagebrush-bluegrass state

This state is characterized by the dominance of shallow rooted perennial bunchgrass, which have replaced the deep-rooted perennial bunch grass typical of the site. Big sagebrush and rabbitbrush dominate the overstory. Bluegrass species dominate understory with non-native species present.

Characteristics and indicators. Sandberg bluegrass has been found to increase following fire likely due to its low stature and productivity (Daubenmire 1975). Sandberg bluegrass may retard reestablishment of deeper rooted bunchgrass. Reduced bunchgrass vigor or density provides an opportunity for Sandberg bluegrass expansion and/or cheatgrass and other invasive species to occupy interspaces.

State 4
Annual State

Annual non-natives dominated site productivity and site resources. The dominance of non-native annuals control the spatial and temporal distribution of soil moisture, soil nutrients and energy resources. Remaining patches of sagebrush and/or perennial bunchgrass suffer from increased competition and narrowed fire return intervals.

Characteristics and indicators. This state experiences frequent fire due to increased cover and continuity of fine fuels. Fire is frequent enough to prevent the recovery of long-lived native perennials like big sagebrush. Disturbance tolerant shrubs may be present or increasing depending on time since disturbance. As cheatgrass increases, fire frequencies also increase. As cheatgrass increases, fire frequencies also increase to frequencies between 0.23 and 0.43 times a year; then even sprouting shrubs such as rabbitbrush will not survive (Whisenant 1990).

State 5
Seeded State

This state is characterized by the dominance of non-native perennial wheatgrass species, like crested wheatgrass (Agropyron cristatum) or desert wheatgrass (Agropyron desertorum). Non-native perennial wheatgrass are frequently seeded following disturbance for erosion control and forage. These seed species are long-lived and persistent in the plant community and are able compete with native perennial bunchgrass spatial and limited soil moisture resource. Native species, grass and forbs, may still be present in small amounts.

Community 5.1
Community Phase

This community phase is characteristic of a successful restoration attempt. Crested wheatgrass, forage kochia, or other non-native seeded species dominate. Big sagebrush may be present. Annual non-natives present.

Community 5.2
Community Phase

This community phase is characterized by the recovery of big sagebrush. Crested wheatgrass is persistent and dominates understory. Annual non-native species are present but do not dominate.

Pathway 5.1a
Community 5.1 to 5.2

Time, absence of disturbance and natural regeneration over time allows sagebrush to increase.

Pathway 5.2a
Community 5.2 to 5.1

Insect infestation, wildfire, brush management or other shrub removing disturbance that does not disturb the soil surface. Soil disturbing practices have the potential to significantly increase annual non-natives.

Transition T1
State 1 to 2

Trigger: Introduction of annual non-native species Slow variable: Over time the annual non-native plants increase within the community. 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 T2
State 2 to 3

Trigger: inappropriate grazing management, prolonged drought or a combination. Slow variable: Reduction of deep-rooted perennial bunchgrass and increased cover of shallow-rooted perennial grasses and shrubs. Threshold: Changes in the spatial and temporal patterns of infiltration and runoff effects soil moisture. Shallow-rooted perennial grasses are highly competitive for moisture and nutrient resources in the surface soil horizon.

Context dependence. Loss of deep-rooted perennial bunchgrasses

Transition T3
State 2 to 4

Trigger: Repeated, widespread and severe fire. Slow variables: Increased production and cover of non-native annual species over time. Threshold: Loss of native perennial bunchgrasses and shrubs truncates, spatially and temporally, nutrient capture and cycling within the community.

Restoration pathway R1
State 3 to 2

Seeding with native species followed by prescribed grazing Minimize soil disturbance and maximize non-native annual plant biomass removal during early spring. Combine prescribed grazing with seeding of native species. Continue to protect site from wildfire. Probability of success is extremely low.

Transition T4
State 3 to 4

Trigger: Repeated, widespread and severe fire. Slow variables: Increased production and cover of non-native annual species over time. Threshold: Loss of native perennial bunchgrasses and shrubs truncates, spatially and temporally, nutrient capture and cycling within the community.

Restoration pathway R4
State 3 to 5

Seeding with drought tolerant, non-native, species. May be combined with brush management or herbicide application.

Restoration pathway R2
State 4 to 2

Seeding with native species followed by prescribed grazing Minimize soil disturbance and maximize non-native annual plant biomass removal during early spring. Combine prescribed grazing with seeding of native species. Continue to protect site from wildfire. Probability of success is extremely low.

Restoration pathway R3
State 4 to 5

Seeding with drought tolerant, non-native, species. May be combined with brush management or herbicide application.