State 1
Reference

The Reference state consists of three plant communities: the greasewood and basin wildrye community (1.1), the basin wildrye and greasewood community (1.2), and the basin wildrye and Gardner's saltbush community (1.3). Each plant community differs in percent composition and foliar cover of grasses and shrubs. Forbs are a minor component. The basin wildrye and greasewood plant community phase (1.2) is typically the early seral stages of this state. As greasewood becomes more dominant on this site, the site transitions to the greasewood and basin wildrye plant community (1.1). Drivers of these plant communities include: drought, fire, herbivory, and flood. To reach the greasewood and basin wildrye plant community, this ecological site must endure sufficient time without shrub killing events and overgrazing.

Community 1.1
Greasewood and Basin Wildrye

This plant community is the reference plant community. This community usually consists of basin wildrye 20 to 40 percent, rhizomatous wheatgrass 5 to 10 percent, Sandberg bluegrass 5 to 10 percent, other perennial grasses 5 to 10 percent, perennial forbs 5 to 10 percent, greasewood 10 to 50 percent, Gardner's saltbush 5 to 15 percent, and 5 to 10 percent other woody plants. Ground cover, by ocular estimate, varies from 60 to 75 percent. The total annual production (air-dry weight) of this state is about 1,000 pounds per acre, but it can range from about 700 pounds per acre in unfavorable years to about 1,300 pounds per acre in above average years. This plant community is extremely stable and well adapted to the Cool Central Desertic Basins and Plateaus climatic conditions. The diversity in plant species and additional moisture allows for high drought tolerance. This is a sustainable plant community (site/soil stability, watershed function, and biologic integrity). Events such as fire, flood, or continuous season long grazing will cause transitions to different plant communities and states. Shrub killing events such as fire will allow basin wildrye to become the dominant species and convert this plant community to the basin wildrye and greasewood plant community (1.2). Continuous season-long grazing will convert this plant community to the grazing resistant state in which basin greasewood and thickspike wheatgrass are the dominant plant species. Prolonged grazing reduces perennial bunchgrasses such as basin wildrye and increases rhizomatous grasses such as thickspike wheatgrass and Sandberg bluegrass.

Community 1.2
Basin Wildrye and Greasewood

This community usually consists of basin wildrye 20 to 40 percent, rhizomatous wheatgrass 5 to 10 percent, Sandberg bluegrass 10 to 20 percent, other perennial grasses 5 to 15 percent, perennial forbs 5 to 10 percent, greasewood 10 to 30 percent, Gardner's saltbush 5 to 15 percent, and 5 to 10 percent other woody plants. Ground cover, by ocular estimate, varies from 60 to 75 percent. The total annual production (air-dry weight) of this state is about 1,000 pounds per acre, but it can range from about 700 pounds per acre in unfavorable years to about 1,300 pounds per acre in above average years. This plant community is extremely stable and well adapted to the Cool Central Desertic Basins and Plateaus climatic conditions. The diversity in plant species and additional moisture allows for high drought tolerance. This is a sustainable plant community (site/soil stability, watershed function, and biologic integrity). Events such as fire, flood, or continuous season long grazing will cause transitions to different plant communities and states. Shrub killing events such as fire will allow basin wildrye to become the dominant species and convert this plant community to the basin wildrye and greasewood plant community (1.2). Continuous season-long grazing will convert this plant community to the grazing resistant state in which basin greasewood and thickspike wheatgrass are the dominant plant species. Prolonged grazing reduces perennial bunchgrasses such as basin wildrye and increases rhizomatous grasses such as thickspike wheatgrass and Sandberg bluegrass.

Pathway 1.1A
Community 1.1 to 1.2

Greasewood and Basin Wildrye

Basin Wildrye and Greasewood

Shrub removing events such as fire, flood, drought, or chemical or mechanical treatments

Context dependence. A transition to a grass dominated phase is most commonly caused by fire, flood, or other shrub killing events. This site must be rested from grazing after such events, or this site will transition to the grazing resistant state (2.1).

Pathway 1.2A
Community 1.2 to 1.1

Basin Wildrye and Greasewood

Greasewood and Basin Wildrye

Natural succession, rest from grazing, fire, flood, and other disturbances. Summer grazing also accelerates this transition as grasses are preferred over shrubs during the summer.

Context dependence. A transition from the basin wildrye/greasewood community to the greasewood/basin wildrye community occurs through natural succession over time. Rest from grazing and other disturbance events allows this community to become shrub dominant. Additionally, this plant community should be grazed in the summer as grasses are preferred over shrubs during this time. Reduction of grass accelerates progression to a shrub dominated community (1.1).

State 2
Grazing Resistant

This state develops as a result of continuous grazing by wildlife and domestic livestock. Dominant grasses include thickspike wheatgrass and Sandberg bluegrass. Greasewood has increased, with annual production often reaching 65 percent. Rubber and yellow rabbitbrush may occur but typically do not exceed 10 percent combined. The total annual production (air-dry weight) of this state is about 600 pounds per acre, but it can range from about 400 pounds per acre in unfavorable years to about 1100 pounds per acre in above average years. The state is moderately stable and somewhat vulnerable to excessive erosion. The biotic integrity of this plant community is usually intact. However, this state can be at risk depending on how far a shift has occurred in plant composition towards greasewood. The watershed is usually functioning. However, it can become at risk when canopy cover of greasewood and/or bare ground increases. Brush Management followed by deferment for 1 to 2 years as part of a prescribed grazing plan will eventually result in a plant community very similar to the reference plant community (greasewood and basin wildrye state). Care should be taken when planning brush management to consider wildlife habitat and critical winter ranges. Wildfire followed by heavy continuous season-long grazing will result in the invaded state.

Community 2.1
Greasewood and Thickspike Wheatgrass

This plant community is a result of continuous grazing. Basin wildrye and other perennial bunchgrasses have decreased, and rhizomatous grasses such as thickspike wheatgrass have increased. Greasewood is the dominant shrub, often reaching 50 percent canopy cover. Yellow rabbitbrush and rubber rabbitbrush may be present, but typically never exceed 10 percent production. Production is normally around 600 pounds per acre but ranges from 400 pounds per acre on below average years to 1100 pounds per acre on above average years. This plant community can return to the reference state or transition to the invaded state. To return to the reference state, brush management followed by deferment for 1 to 2 years as part of a prescribed grazing plan will eventually result in a plant community very similar to the greasewood and basin wildrye plant community (1.1). Care should be taken when planning brush management to consider wildlife habitat and critical winter ranges. A transition to the invaded state would be triggered by continuous heavy grazing and/or continuous heavy grazing after fire. Annuals such as cheatgrass and mustard may establish on the site, and the site may become more susceptible to erosion.

State 3
Invaded

This plant community is a result of heavy, season-long grazing by wildlife and livestock. Halogeton, Gardner’s saltbush, rhizomatous wheatgrass, and bare ground are also a major part of this state. Greasewood dominates, often exceeding 60 percent of the annual production. Sparse saline tolerant grasses and annual forbs make up the majority of the understory. The total annual production (air-dry weight) of this state is about 300 pounds per acre, but it can range from about 100 pounds per acre in unfavorable years to about 500 pounds per acre in above average years. The site is at risk and not well protected from excessive erosion. Grazing for wildlife and cattle has been reduced. The biotic integrity of this plant community is not intact. The amount of bare ground puts the watershed at risk for increased runoff. Chemical brush management and re-seeding followed by deferment for 1 to 2 years as part of a prescribed grazing plan may return this state to near reference plant community (greasewood and basin wildrye). Additional deferment may be necessary and should be prescribed on an individual site basis.

Community 3.1
Greasewood and Cheatgrass

This plant community is a result of continuous grazing, or continuous grazing after a disturbance event such as fire. Basin wildrye and other perennial bunchgrasses are likely not present on the site. Halogeton usually dominates this site. Rhizomatous grasses such as thickspike wheatgrass have increased, and cheatgrass may be present on the site. Greasewood is the dominant shrub, sometimes reaching up to 40 percent canopy cover. Gardner's saltbush has also increased but never reaches above 15 percent production. Yellow rabbitbrush and rubber rabbitbrush may be present, but typically never exceed 10 percent production. Production is normally around 400 pounds per acre but ranges from 200 pounds per acre on below average years to 600 pounds per acre on above average years. Bare ground may exceed 50 percent, which puts this site at risk for excessive erosion and runoff. This community will likely not return to the reference state without input. To return to the reference state, brush management and removal of halogeton through chemical or mechanical means will be necessary. Such treatments should be followed by deferment for two years or greater as part of a prescribed grazing plan. Such input will eventually result in a plant community very similar to the greasewood and basin wildrye plant community (1.1). Care should be taken when planning brush management to consider wildlife habitat and critical winter ranges.

Transition T1A
State 1 to 2

Reference

Grazing Resistant

Continuous grazing

Context dependence. A transition to the grazing resistant state depends on landform and severity of grazing, flooding, and fire. Narrow channels are usually more desirable to wildlife and livestock than surrounding upland areas, so these areas are grazed more intensely. Native bunchgrasses will be utilized quickly. Continuous grazing without rest will allow thickspike wheatgrass and greasewood to increase.

Transition T1B
State 1 to 3

Reference

Invaded

Continuous grazing without sufficient rest after disturbance events

Context dependence. Fire, flood, or other disturbance events followed by insufficient rest from grazing can trigger a transition from the reference state to the invaded state. Such a transition must occur rapidly and depends on severity of disturbance events and grazing. Landform also affects the likelihood of such a transition; narrow channels are less susceptible to fire, despite being more desirable to wildlife and livestock than surrounding upland areas. Severe flooding followed by erosion, grazing, and compaction are the primary mechanisms for transition in a narrow channel. Such events allow invasive plants such as cheatgrass and halogeton to establish. In larger and less concave areas such as a flood plane, fire followed by erosion, grazing, and compaction allow invasive plants to establish.

Restoration pathway R2A
State 2 to 1

Grazing Resistant

Reference

Rest from grazing

Context dependence. Restoration to reference state depends on land form, severity of grazing, flooding, and fire. In narrow channels, native shrubs and bunchgrasses may be harder to restore because these areas are grazed more intensely than nearby upland areas. Restoration of shrubs after fire and flooding events is less likely in narrow channels if these areas are continuously grazed by livestock and wildlife. In larger areas such as floodplains, restoration is more likely to succeed as long as the area is rested from grazing. Reseeding and/or mechanical treatments may be necessary if the understory is overtaken by Gardner's saltbush. Such practices may allow native bunchgrasses to reestablish.

Transition T2A
State 2 to 3

Grazing Resistant

Invaded

Continuous Grazing

Context dependence. As bare ground increases, invasive plants such as cheatgrass and halogeton establish on this site. A transition to the grazing resistant state depends on landform and severity of grazing, flooding, and fire. Disturbances such as fire will accelerate a transition from the grazing resistant state to the invaded state. Narrow channels are usually more desirable to wildlife and livestock than surrounding upland areas, so these areas are grazed more intensely and may become invaded more quickly.

Restoration pathway R3A
State 3 to 1

Invaded

Reference

Rest from grazing or rest from grazing with reseeding, mechanical, or herbicide treatments

Context dependence. Restoration to reference state depends on severity of prior disturbance events, grazing, landform, and prevalence of invasive plants. In narrow channels, native shrubs and bunchgrasses may be harder to restore because these areas are grazed more intensely than nearby upland areas. Restoration of shrubs after fire and flooding events is less likely in narrow channels if these areas are continuously grazed by livestock and wildlife. In larger areas such as floodplains, restoration is more likely to succeed as long as the area is rested from grazing. In all cases, additional input may be needed to restore native grasses and shrubs. Such input may include reseeding, herbicide treatments to remove cheatgrass and halogeton, and exclosure cages.

Restoration pathway R3B
State 3 to 2

Invaded

Grazing Resistant

Rest from grazing

Context dependence. Severity of grazing and compaction will determine how quickly shrubs and perennial bunchgrasses can reestablish. In some cases, annual grasses and undesirable forbs may completely dominate the site. Inputs such as herbicide treatment or prescribed fire may be necessary to return the state to the grazing resistant state, which will eventually return to the reference state.