State 1
Reference

The Reference state has been determined by study of rangeland relic areas, areas protected from excessive disturbance, and areas under outside influences such as domestic livestock grazing and recreational uses.
Literature review, trends in plant communities under a variety of uses, and historical accounts also have been considered.

The reference state represents all plant communities and ecological dynamics of the upland loam Big sagebrush site. This state includes all biotic communities that become on the ecological site if all successional sequences are completed under the natural disturbance regime. This state is dominated by Basin and/or Wyoming big sagebrush with a diverse understory of native perennial grasses and native perennial and annual forbs. The nutrient cycling in native shrub-steppe ecosystems is characteristically ‘‘tight’’ (i.e. net concentrations of plant-available nutrients are low) because the broad spatial and temporal diversity of plants (woody and herbaceous) and soil microbes rapidly exploit nutrients as they are mineralized (Paschke et al., 2000). The primary disturbance mechanisms for this site in reference condition include fire, insect herbivory, and fluctuations in climate, such as drought or wet periods.

Prior to European settlement, fire return intervals were thought to be adequate enough to inhibit the encroachment of Pinyon and Utah juniper into the more productive deeper soils that support shrub steppe communities (Tausch 2002, Romme et al. 2007). However, as the number of years between fire events increases due to reduction in fine fuels or fire suppression, Pinyon and Utah juniper readily invade these communities. The time required to complete the transition of shrub steppe to a closed Pinyon and juniper woodland is variable. The transition is dependant on both the rate of tree establishment and site potential. Woodland presence at the landscape level also influences the rate of encroachment and closure on adjacent open areas

Reference state: Community phases maintained by fire, drought, insect herbivory, and time without disturbances. Indicators: A diverse and productive understory co-existing with a fluctuating canopy of big sagebrush.
Feedbacks: Infrequent, but regular droughts that result in a reduction of sagebrush cover. Higher than average precipitation cycles that maintains the episodic native plant reproductive cycles. Insect infestations and/or a fire regime sufficient enough to inhibit Pinyon and Utah juniper encroachment. Improper grazing that results in a loss of native herbaceous understory, the establishment of non-native invasive plants, and a reduction in the fire return interval.

At-risk Community Phase: All communities are at risk when native plants in the understory are stressed, and nutrients become available for non-natives to establish. However, plant community 1.3 is most at risk due Pinyon and Utah juniper encroachment.

Trigger: The establishment of non-native invasive plants and/or Increased establishment of Utah juniper and Pinyon to a point where they drive the ecological dynamics of the site.

Community 1.1
Big Sagebrush Shrubland with Grasses

This community phase is dominated by big sagebrush and a diverse understory of native perennial grasses and forbs. This phase supports cool and warm season grasses including Indian ricegrass, needle and thread, and galleta, along with several forbs. Dominance of warm or cool season herbaceous plants and forb production are dependent on the timing of precipitation, and can vary widely between years. Interspaces supporting highly developed lichen crusts are common, while bare ground is rare.

Community 1.2
Perennial Grassland with Big Sagebrush

This community phase is dominated by native perennial grasses and forbs, where big sagebrush is minimally present. As a result bare ground patches are small and rarely connected. Vegetative production is highest in this community of the reference state. Diverse and highly developed biological crusts are present throughout the site; moss is common under the few shrub canopies.

Community 1.3
Big Sagebrush Shrubland

This community phase is dominated by big sagebrush, where it typically measure greater than 37 percent cover. Pinyon and Utah juniper may have encroached, however does not yet control the ecological site dynamics. If Pinyon and Utah juniper are present, big sagebrush cover is expected to be less. The understory supports sparse native herbaceous vegetation, including forbs and perennial grasses. Biological crusts are typically well developed in the interspaces; however, bare ground is most common in this community phase.

Pathway 1.1A
Community 1.1 to 1.2

Pathway 1.1B
Community 1.1 to 1.3

Pathway 1.2A
Community 1.2 to 1.1

Pathway 1.3A
Community 1.3 to 1.2

State 2
Current Potential

The current potential state is very similar to the reference state in energy capture, nutrient cycling, hydrologic function and disturbance regime. The current potential state may include acclimatized, naturalized, or invasive nonnative species. With proper management, plant communities within the current potential state may be managed and used for various purposes by man without significant alteration in plant community composition or production. It includes all of the plant communities that exist in the reference state, but with the inclusion of nonnative species.
These plant communities with significant portions of invasive annuals are possible within this state. Continuous surface disturbances (improper grazing, off-highway-vehicle (OHV) use, recreational activities, etc.) can stress the native perennial plants and allow the non-natives species to increase. This shift in species composition could invoke another transition to a different state and affect the nutrient cycling, hydrologic function and soil stability. At this time there is no known way to completely remove the non-native plants from the site once they have become established. Therefore, this state is irreversibly altered from the reference state.

Current Potential state: Community phases maintained by fire, insects, drought, and time without disturbances.

Indicators: A diverse and productive understory dominated by native plants with non-native herbaceous plants co- existing under a canopy of big sagebrush.

Feedbacks: Infrequent, but regular droughts that reduce grass cover combined with sufficient moist cycles to maintain episodic reproductive cycles of native plants. Insect herbivory or fire return interval sufficient enough to inhibit Pinyon and juniper encroachment. Improper livestock grazing, that facilitates the loss of herbaceous understory, increasing non-native invasive plants, and causing a lengthened fire return interval).

At-risk community: Community 2.3 is the most at risk when Utah juniper and Pinyon have increase to a point where they drive the ecological dynamics of the site and have suppressed the understory.
Trigger – Increased Utah juniper and Pinyon, lack of understory, and increased erosion.

Community 2.1
Big Sagebrush Shrubland with Grasses

This community phase is dominated by big sagebrush with a diverse understory of native and non-native perennial grasses and forbs, including Indian ricegrass, galleta, and needle and thread. Non-native invasive species, such as cheatgrass and/or crested wheatgrass are present but in minimal amounts. This site supports highly developed lichen crusts and patches of bare ground are rare.

Community 2.2
Perennial Grassland with Big Sagebrush

This community phase is dominated by grasses (introduced and native) with little production and cover from big sagebrush. Native species dominate the herbaceous production, and include Indian ricegrass, galleta, needle and thread, and various native perennial and annual forbs. Vegetative production is usually high because grasses are able to respond to available nutrients and sunlight. Diverse and highly developed biological crusts are present throughout the site; moss is common under the few shrub canopies.

Community 2.3
Big Sagebrush Shrubland

This community phase is dominated by big sagebrush, where it typically measure greater than 37 percent cover. Pinyon and Utah juniper may have encroached, however does not yet control the ecological site dynamics. If Pinyon and Utah juniper are present, big sagebrush cover is expected to be less. The understory supports sparse native herbaceous vegetation, including forbs and grasses, both natives and non-natives. Biological crusts are typically well developed in the interspaces; however, bare ground is most common in this community phase.

Pathway 2.1A
Community 2.1 to 2.2

Pathway 2.1B
Community 2.1 to 2.3

Pathway 2.2A
Community 2.2 to 2.1

Pathway 2.3A
Community 2.3 to 2.2

State 3
Pinyon-Utah Juniper

This state is characterized by a dominance of Utah juniper and Pinyon, with some to very little understory depending on which community phase it is in. It typically occurs if there is a long interval between disturbances, accompanied by a nearby source for Pinyon and Utah juniper seeds. This state can persist for long periods of time until extreme conditions needed for wildfire occur or a management treatment is implemented.

Pinyon and Utah Juniper State: Community phases maintained, in a self-sustaining manner, over time without disturbance.
Indicators: A declining understory, coupled with a dense canopy of Pinyon and Utah juniper.
Feedbacks: Surface disturbance and other negative pressures (grazing, drought, etc.) that reduce the herbaceous understory, combined with a lack of disturbances that remove trees from the community. The removal of trees, which facilitates an increase in herbaceous plant production.
At-risk community – Community 3.1 is most at risk when Utah juniper and Pinyon have increased to a point where there is no longer an understory.
Trigger – Removal of trees.
Restoration Pathway – Active vegetation management that facilitates the removal of trees and allows for the reestablishment of desired native and introduced species.

Community 3.1
Pinyon and Utah Juniper with Understory

This community phase is dominated by a dense to almost closed canopy of trees with a minimal understory of big sagebrush, mixed perennial and invasive annuals grasses and forbs. Highly developed and diverse biological crusts are still present in the interspaces; however, the interspaces in this phase are typically barer than in the current potential state.

Community 3.2
Pinyon and Utah Juniper Woodland

This phase is represented by a closed canopy of trees with trace to no understory. The interspaces are lacking in developed biological crust due to increased erosion and uptake of moisture by the trees.

Pathway 3.1A
Community 3.1 to 3.2

Pathway 3.2A
Community 3.2 to 3.1

State 4
Seeded

This state results from a significant vegetation manipulation that may include prescribed burning, chaining, disking, mowing, or other technique, with the introduction of non-native perennial grasses such as Crested wheatgrass or Russian wildrye. The dominant understory plant species are the seeded grasses and forbs. The community dynamics are similar to the Current Potential State. Depending on the species used for the reseeding practice, the site could have more resistance to fire as well as better tolerance to grazing pressure. This state may persist for long periods of time. Typically, big sagebrush will reestablish in the seeding to significant proportions within 30 years. Under careful management, native grasses and forbs may reestablish in this plant community over time.
Actively manipulating plant communities in the invasive annuals or juniper invasion states to create a seeded range state is often the first step in assisted succession to restore natural plant communities back to the Current Potential State.

Seeded state: Community phases maintained by fire, drought, and time without disturbances.

Indicators: A developed perennial herbaceous understory of seeded species, typically non-natives, co-existing with a canopy of basin big sagebrush.

Feedbacks: Infrequent, but regular droughts that reduce grass cover. Moist cycles that maintain perennial bunch grasses. A fire regime sufficient to inhibit Pinyon and Utah juniper encroachment. Improper grazing resulting in a loss of the herbaceous understory, an increase in invasive plants, and an increase in the fire return interval.

At-risk community: Community 4.3 is the most at risk when Utah juniper and Pinyon have increased to a point where they drive the ecological dynamics of the site.

Restoration Pathway: proper domestic livestock grazing practices and the removal of trees that facilitates the reestablishment of native and introduced species.

Community 4.1
Seeded Grassland

This community phase is dominated by seeded grasses, with little to no production from big sagebrush. Typically this site has lower species diversity, but higher production than the current potential or reference state. The seeded grasses are able to respond favorably to the available nutrients, and effectively compete with and limit the invasive species. Commonly seen grasses include crested wheatgrass and Russian wildrye.

Community 4.2
Big Sagebrush Shrubland with Grasses

This community phase is represented by seeded species being co-dominant with big sagebrush. Bare interspaces supporting highly developed lichen crusts are common.

Community 4.3
Big Sagebrush Shrubland

This community phase is dominated by big sagebrush, where it typically measure greater than 37 percent cover. Pinyon and Utah juniper may have encroached, however does not yet control the ecological site dynamics. If Pinyon and Utah juniper are present, big sagebrush cover is expected to be less. The understory supports sparse native herbaceous vegetation, including forbs and grasses, both natives and non-natives. Biological crusts are typically well developed in the interspaces; however, bare ground is most common in this community phase.

Pathway 4.1A
Community 4.1 to 4.2

Pathway 4.2A
Community 4.2 to 4.1

Pathway 4.2B
Community 4.2 to 4.3

Pathway 4.3A
Community 4.3 to 4.1

State 5
Annual Invaded

This state is recognized by the predominance of invasive annuals. Invasive annuals have increased to a point where they influence or drive the disturbance regime and the nutrient cycle and energy flow, altering it from the regimes and cycles associated with sagebrush ecosystems. Research has shown that plant species differ substantially in their effects on soil water content and temperature and their effects on the frequency and intensity of disturbance. Once exotic plants like cheatgrass or Russian thistle have invaded a site fundamental nutrient cycling processes are known to change (Chapin et al., 1997). Cheatgrass invasion has been shown to alter the timing, distribution, and composition of organic matter inputs, as well as uptake of mineralized nutrients (Evans et al., 2001). Energy flow in this state is severely suppressed, with photosynthesis occurring only during a brief period in the spring. Cheatgrass invasion has also been shown to change the composition root pores, mycorrhizal associations, and assemblages of microbial species potentially affecting soil structure and the rate of soil organic matter decomposition (Belknap and Phillips, 2001). The altered disturbance regime and the loss of soil organic matter could create ecologically impoverished sites that are very difficult, if not impossible to restore to functionally diverse perennial herbaceous and woody communities.

Invasive Annuals State: Community phases maintained by fire, drought, livestock grazing; vegetation management, and time without disturbances.
Indicators: An annual grass or forb understory, where big sagebrush may or may not be present

Feedbacks: Short fire intervals, which maintain the annual grass and forb understory. Longer fire intervals, vegetation management, or livestock grazing that allows for the sagebrush overstory to reestablish.

At-risk community: Community 5.2 is the most at risk when cheatgrass or other annuals completely dominate the site, shortening the fire return interval, that maintains the annual grass/forb community.

Community 5.1
Big Sagebrush with Invasive Annual Understory

This community phase is dominated by an annual invasive understory with a big sagebrush canopy. Often, the sagebrush canopy is dense because disturbance factors have reduced the understory and nutrients are available. The interspaces are often bare, but may support slightly developed biological crusts.

Community 5.2
Invasive Annual Monoculture

This community phase is characterized by an almost a complete monoculture of cheatgrass or other invasive annuals. This state is typically self-enhancing and potentially perpetual state if fires continue to be frequent. This community is especially difficult for many of the traditional sagebrush wildlife species because forage and structural diversity is limiting. This community is also difficult to graze with domestic livestock because the forage availability is dependent on a singles species response to the time and amount of moisture.

Pathway 5.1A
Community 5.1 to 5.2

Pathway 5.2A
Community 5.2 to 5.1

Transition T1A
State 1 to 2

This transition from native perennial bunchgrass understory in the reference state to a state that has been invade by non-native species such as crested wheatgrass (blown in), cheatgrass, Russian thistle, and Annual wheatgrass. This transition occurs as natural and/or management actions favor establishment of non-native grasses and forbs, especially annuals. Some invasive plants can become established in undisturbed and healthy native plant communities. Possible events that can accelerate this transition include improper domestic livestock, severe surface disturbances, and extended droughts.

Transition T1B
State 1 to 3

This transition occurs from the big sagebrush shrubland community (1.3) into community 3.1. This occurs as Pinyon and Utah juniper increase to a point where they drive the ecological dynamics of the site. Shrub canopies can act as safe sites and facilitate the encroachment of Pinyon and Utah juniper into these deeper productive soils. Once established, trees are known to be capable of out-competing the remaining understory for nutrients and energy, thus reducing the shrubs and herbaceous understory even more. This process also facilitates the establishment of invasive annual plants such as Cheatgrass. This occurs through time without disturbances such as a fire or insect herbivory.

Transition T2A
State 2 to 3

This transition from a big sagebrush dominated community to a Pinyon and Utah juniper dominated community occurs when there is sufficient fire suppression and accelerated tree invasion to create a closed canopy. With a reduced fire potential this community enters into a perpetual tree dominated community unless there is significant energy inputs from outside influences.

Transition T2C
State 2 to 4

This pathway occurs after high amounts of energy inputs by man have been put into the system. Sagebrush and/or trees have been removed with vegetation manipulation techniques (chemical, mechanical, or fire) and introduced species that are adapted to the area and adapted to management needs have been established.

Transition T2B
State 2 to 5

This transition occurs when events favor the establishment and dominance of invasive annuals. Events could include increase fire return frequency (<5-20 years), improper grazing which reduces perennial bunch grasses, extended drought, increased surface disturbance through off road vehicle use, etc..

Transition T3B
State 3 to 4

This transition occurs through vegetation manipulation by man. Typically trees are removed through mechanical or chemical methods; the area is then re-seeded with grasses and forbs that are adapted to the area and to management needs.

Transition T3A
State 3 to 5

This transition occurs when events favor the establishment and dominance of invasive annuals. Events would likely include a catastrophic wildfire or other method of tree removal in a community that has a cheatgrass dominated understory.

Restoration pathway R4A
State 4 to 2

This pathway occurs as a result of long periods without disturbance and the community is allowed to develop ecosystem functions. This could be through prescribed grazing with domestic livestock to favor the development of native grasses over the introduced species (with proper time, timing, and amounts of grazing), and removal of the Utah juniper and Pinyon as they encroach.

Restoration pathway T4B
State 4 to 3

This transition from a big sagebrush and non-native seeded grassland dominated community to a Pinyon and Utah juniper dominated community occurs when there is sufficient fire suppression and accelerated Pinyon and Utah juniper invasion to create a closed canopy. With a reduced fire potential the site enters into a perpetual tree dominated community unless there is significant energy inputs from outside influences.

Transition T4A
State 4 to 5

This pathway occurs as a result of long periods without disturbance and the community is allowed to develop ecosystem functions. This could be through prescribed grazing with domestic livestock to favor the development of native grasses over the introduced species (with proper time, timing, and amounts of grazing), and removal of the Utah juniper and Pinyon as they encroach.

Transition T5B
State 5 to 3

This transition from a big sagebrush and invasive annual dominated community to a Pinyon and Utah juniper dominated community occurs when there is sufficient fire suppression and accelerated juniper invasion to create a closed canopy. With a reduced fire potential and a non-viable seed bank this community enters into a perpetual tree dominated community unless there is significant energy inputs from outside influences.

Transition T5A
State 5 to 4

Successful completion of this transition is difficult with current knowledge of adapted plants, soil preparation and seed techniques. Large amounts of input and management are required for the establishment of a perennial introduced/adapted grass. This pathway occurs when the invasive annuals are treated and removed from dominance and the desired species (typically non-native perennials that can successfully compete) are seeded and established. At this time, restoring from the invasive annuals state directly to a native grass community has not been successful possibly due to changes in the soil caused by the cheatgrass.