Semidesert Sand (Fourwing Saltbush)
Scenario model
Current ecosystem state
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Management practices/drivers
Select a transition or restoration pathway
- Transition T1a More details
- Transition T2a More details
- Transition T2b More details
- Transition T2c More details
- Restoration pathway R3a More details
- Transition T3b More details
- Transition T3a More details
- Transition T4b More details
- Transition T4a More details
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No transition or restoration pathway between the selected states has been described
Target ecosystem state
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State 1
Reference State
Description
The reference state has been determined by the study of rangeland relic areas and areas protected from excessive disturbance such as improper livestock grazing and high impact recreation. Literature reviews, trends in plant community dynamics, and historical accounts have also been considered.
This state represents the natural range of variability that dominates the dynamics of this ecological site. This state includes the biotic communities that would become established if all successional sequences were completed under the natural disturbance regime. The state is dominated by perennial warm and cool season grasses and a diverse shrub community. Utah juniper has been known to invade this site when it is in close proximity to a juniper stand. Due to the aggressive competitiveness of Utah juniper, blowout areas are common where these species occur. Primary disturbance mechanisms for this site include fire, grazing by native herbivores, prolonged rodent activity, insect herbivory, alluvial deposits and changes in the sites drainage patterns. These disturbances coupled with weather events dictate the dynamics that occur within the natural range of variability. The reference state is self sustaining and resistant to change due to high resistance to natural disturbances and high resilience after natural disturbances. When natural disturbances occur, the rate of recovery is relatively rapid due to niches being filled with highly adapted native vegetation.
Reference State: Community phases influenced by infrequent fire, native herbivore grazing, insect herbivory, alluvial deposits, time without disturbance, and climate.
Indicators: A well developed native perennial warm and cool season grass community with a diverse shrub overstory, when present.
Feedbacks: Establishment of non-native invasive species in the understory. Infrequent but regular fires that maintain the perennial bunch grass understory and the establishment of shrubs.
At-risk Community Phase: All communities are at risk for invasion by non-native plants; however plant community 1.3 and 1.4 are most at risk due to decreased species cover and diversity in the understory. 1.4 also is at risk due to changes in disturbance regime.
Trigger: Establishment of non-native plant species
Submodel
States 1, 5 and 2 (additional transitions)
1.1. Perennial Grassland
1.5. Active Dunes
1.2. Perennial Grassland/Shrubland
State 2
Current Potential State
Description
This state is similar to the reference state except that non-native plants are now present in all plant community phases. The primary disturbance mechanisms can be natural or human induced. Events, such as improper livestock grazing, prolonged rodent activity, changes in historic fire regimes, OHV overuse, insect herbivory, or drought may influence this site. A shift in species composition will affect the nutrient cycling, soil-water relationships, hydrology, and soil stability. Dominant grasses include both warm and cool season; however many times heavy spring grazing will remove the cool season grasses and heavy late summer and early fall grazing will remove the warm season grasses. Utah juniper is also still a common invader of the shallow soil components, creating blowout areas and increasing erosion. This state is losing resistance to disturbances and resilience after disturbance. Invasive plants are beginning to fill the niches and establish on the site.
Current Potential State: Plant communities influenced by both natural and man influenced events, including rodent activity, OHV overuse, livestock grazing, insect herbivory, fire, time with out disturbances, and climatic fluctuations.
Indicators: A perennial cool and warm season grass understory with fourwing saltbush forming the dominant visual aspect, when present. Non-native species are now present in all plant communities.
Feedbacks: Extended drought, improper livestock grazing, or other disturbance that changes the ecological dynamics of the site. Infrequent but regular fires or properly managed domestic livestock grazing to maintain the understory and the establishment of shrubs.
At-risk Community Phase: All communities are at risk; however plant community 2.3 is most at risk due to its limited understory.
Trigger: Disturbance that facilitates the dominance of invasive forbs and/or grasses.
Submodel
State 3
Sand Sagebrush State
Description
This state is characterized by the dominance of sand sagebrush, where invasive and desirable species may or may not be present in the understory. Primary disturbance mechanisms include improper livestock grazing and drought which reduces the understory limiting it to occurring directly under the shrub canopy. This creates large bare interspaces which are susceptible erosion. Time without disturbances may cause this site to reestablish some of its understory. Due to sand sagebrush’s resilience and ability to establish after a disturbance this state may be very persistent. This shrub is an avid resprouter and thus after disturbances, such as fire or alluvial sand deposits, it is able to reestablish relatively fast when compared to other vegetation (McWilliams, 2003). Once established it can proliferate and dominate the site reducing the ability of other perennial shrubs to obtain the nutrients needed for survival.
Sand Sagebrush State: Plant communities influenced by time without disturbances, drought, and livestock grazing.
Indicators: A site dominated by sand sagebrush, where invasive and desirable species may or may not be present in the understory.
Feedbacks: Extended drought, improperly managed livestock grazing, or other disturbance that result in a reduction of the understory and subsequent increased occurrence of invasive plant species. Properly managed livestock grazing and normal precipitation fluctuations that allow for the maintenance of the understory and shrub canopy.
At risk Community: All communities are at risk; however these sites may be very stable do to the behavior of sand sagebrush and its resilience after disturbances. Plant community 3.2 is most at risk due to absence of a developed understory and its increased erosion potential.
Trigger: Cheatgrass invasion, creating a decrease in the fire return interval (every 5-10 years)
Submodel
Description
This state is characterized by the dominance of invasive forbs/shrubs. These species may include, but are not limited to Russian thistle, cheatgrass, tansy mustard, broom snakeweed, annual stickseed, or annual Cryptantha. One or more invasive species has increased to a point where they influence or drive the disturbance regime and nutrient cycle. Russian thistle and/or cheatgrass are the most likely of these species to establish and dominate. Russian thistle is a prolific reproducer—one plant can produce up to 250,000 seeds, which are dispersed by the wind causing the dead plant to “tumble” across the landscape. While generally considered an unwanted weed, Russian thistle may actually help disturbed sites recover more quickly. If topsoil is present, Russian thistle roots are invaded by mycorrhizal fungi and because this plant does not form associations with the fungi the root and plant are killed. This causes increased mycorrhizal fungi in the soil and an increased chance for other plants to establish through the aid of these fungi associations. Yet, managers must be aware that that without proper management other invasive annuals, such is cheatgrass may become established instead of the desirable native species. If topsoil is missing the mycorrhizal fungi, Russian thistle can persist for relatively long periods of time (Howard, 1992). Cheatgrass has an entirely other effect on the soil/plant/water relationships. Research has shown that plant species differ substantially in the effects on soil water content and temperature, and in their effects on the frequency and intensity of disturbance. After cheatgrass has invaded a site fundamental nutrient cycling processes, root pores, mycorrhizal associations, microbial species, and soil organic material changes (Chapin et al. 1997; Belnap and Phillips, 2001). These alterations may eventually create ecologically impoverished sites that are very difficult to restore to functionally diverse perennial herbaceous and woody communities. The competitiveness of the invasive species and the ability of these species to quickly establish after a disturbance make this state extremely resistance to change and resilient after a disturbance.
Invasive Forb State: Community phases influenced by improper grazing and weather cycles.
Indicators: A complete understory of invasive forbs and/or broom snakeweed where native perennial shrubs, grasses, and forbs are minimally present.
Feedbacks: Improper livestock grazing and weather cycles that maintain the dominance of invasive forbs/shrubs with minimal decrease in occurring native perennial grasses, shrubs, and forbs. Increased occurrence of cheatgrass, decreasing the fire return interval. Flooding and alluvial deposits that facilitates the establishment of sand sagebrush.
Trigger: The increased establishment of cheatgrass, caused by a decrease in the fire return interval, which facilitates the continued removal of other grasses, shrubs, and forbs.
Submodel
Description
This state’s ecological processes are driven by the dominance of cheatgrass, where native and invasive plant species may or may not be present. Cheatgrass dramatically affects the soil/plant/water relationships of a site. Research has shown that plant species differ substantially in the effects on soil water content and temperature, and in their effects on the frequency and intensity of disturbance. After cheatgrass has invaded a site the fundamental nutrient cycling processes, root pores, mycorrhizal associations, microbial species, and soil organic material changes (Chapin et al. 1997; Belnap and Phillips, 2001). These alterations may eventually create ecologically impoverished sites that are very difficult to restore to functionally diverse perennial herbaceous and woody communities. The competitiveness of cheatgrass and its ability to quickly establish after a disturbance make this state extremely resistance to change and resilient after a disturbance.
Annual Grass State: Community phases maintained, in a self-sustaining manner, by frequent fire.
Indicators: A site where ecological processes are driven by cheatgrass
Feedbacks: A self sustaining disturbance regime of frequent fire.
Submodel
Mechanism
Transition from Reference State (State 1) to Current Potential State (State 2).
This transition is from the native perennial bunchgrass understory in the reference state to a state that has non-native invasive plants present in the understory. This transition occurs as natural and/or management actions favor a decline in native perennial grasses and an increase in invasive plant species. Possible events include poorly managed domestic livestock, extended droughts, fire, etc. Cheatgrass, however, has been known to establish in intact perennial vegetation communities that have experienced little disturbances either caused naturally or by human activities. Once non-native plants have established, a threshold had been crossed.
Mechanism
Transition from Current Potential State (State 2) to Sand Sagebrush State (State 3).
This transition occurs when events favor the establishment and dominance of sand sagebrush. Events typically include a flood with alluvial deposits. This changes the water drainage patterns of a site and results in a dominance of sand sagebrush due to its ability to establish and flourish on sites with shorter disturbance regimes (McWilliams, 2003). This transition results in a new state rather than another plant community like in the reference state, due the presence of invasive species present in the current potential state. This transition causes the site’s ecological dynamics to not only be controlled by sand sagebrush, but also the invasive forbs and grasses that will be present in the understory.
Mechanism
Transition from Current Potential State (State 2) to Invaded State (State 4).
This transition occurs when events favor the increased establishment and dominance of invasive plant species. Events include any type of surface disturbance, such as fire, improper domestic livestock grazing, OHV overuse, and drought. Once invasive species drive the ecological dynamics a threshold has been crossed.
Mechanism
Transition from Current Potential State (State 2) to Annual Grass State (State 5).
This transition is from the current potential state into a state dominated by cheatgrass. This transition occurs as events favor the increased establishment and dominance of cheatgrass. Typically this occurs as a series of fires which lead to an increase in cheatgrass and a subsequent decrease in the fire return interval. Once cheatgrass drives the ecological dynamics of the site a threshold has been crossed.
Mechanism
Restoration from Sand Sagebrush State (State 3) to Current Potential State (State2).
This restoration pathway occurs as sites stabilize and fourwing saltbush, winterfat, and Cutler mormontea are able to reestablish on the sites. Events triggering this event usually are changes in the sites drainage pathways or time without disturbances. This pathway may take many years to accomplish, and may not be possible with current knowledge.
Mechanism
Transition from Sand Sagebrush State (State 3) to Invasive Forb State (State 4).
This transition occurs if community 3.1 does not progress into community 3.2. Removal of the sand sagebrush by drought or drainage pattern changes may facilitate a transition into state 4. Once invasive forbs regain control over the ecological dynamics a threshold has been crossed.
Mechanism
Transition from Sand Sagebrush State (State 3) to Annual Grass State (State 5).
This transition occurs as fire removes the shrub canopy. Cheatgrass typically invades the interspaces and once this species dominates a site, the amount and continuity of fine fuels increases until fire can start to eliminate the shrub/forb/perennial grass component. Once cheatgrass drives the ecological dynamics a threshold has been crossed.
Mechanism
Transition from Invasive Forb State (State 4) to Sand Sagebrush State (State 3).
This transition occurs when events favor the establishment and dominance of sand sagebrush. Events typically include a flood with alluvial deposits. This changes the water drainage patterns of a site and results in a dominance of sand sagebrush due to its ability to establish and flourish on sites with shorter disturbance regimes (McWilliams, 2003).
Mechanism
Transition from Invasive Forb State (State 4) to Annual Grass State (State 5).
This transition occurs as events favor the replacement of the invasive forbs with cheatgrass. Sites that are dominated by tansy mustard in the invaded state may actually facilitate this transition, due to its ability to provide the litter needed for the germination of cheatgrass. The fire return interval decreases due to increased fine fuel accumulations facilitating the dominance of cheatgrass. Once cheatgrass dominates and drives the ecological dynamics of the site a threshold has been crossed.
Model keys
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The Ecosystem Dynamics Interpretive Tool is an information system framework developed by the USDA-ARS Jornada Experimental Range, USDA Natural Resources Conservation Service, and New Mexico State University.