Desert Shallow Sandy Loam (Shadscale)
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
- Restoration pathway R4a 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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Description
The reference state was determined by study of rangeland relic areas, areas protected from excessive disturbance, and areas under land use influences, such as grazing and recreation. Literature reviews, trends in plant community dynamics, and historical accounts are also considered.
The reference state represents the historic plant communities and natural ecological dynamics of the desert shallow sandy loam, shadscale site. This state includes the biotic communities that become established on the ecological site if all successional sequences are completed under current climatic conditions; natural disturbances are inherent in its development. This state is dominated by warm season perennial grasses and shadscale. Perennial cool season grasses may or may not be present depending on soil development. The primary disturbance mechanism is weather fluctuations. The reference state is self sustaining and resistant to change due to high resistance to natural disturbances and high resilience following 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 disturbed by climate fluctuations.
Indicators: A site dominated by shadscale and galleta, where Indian ricegrass and sand dropseed may or may not be present.
Feedbacks: Extended drought resulting in a reduction of native perennial plant vigor. Normal fluctuations in weather allowing for the maintenance of both shrubs and perennial grasses.
At-risk Community Phase: All communities are at risk when nutrients are available for invasive plants to establish. Plant community 1.1 is especially at risk due to limited production and cover of understory grasses.
Trigger: Introduction of invasive plants to fill available niches.
Submodel
State 2
Current Potential State
Description
This state is similar to state one, however there are now non-native invasive species established in the understory—cheatgrass and halogeton being the most common. The primary disturbance mechanism is weather fluctuation; however livestock grazing now may influence the ecological dynamics of the site. The current potential state has less ability resist change and less resilience following disturbances.
Current Potential State: Plant communities disturbed by fluctuating weather conditions and livestock grazing.
Indicators: Site dominated by shadscale and galleta, Indian ricegrass and sand dropseed may also be present. Invasive species are now present.
Feedbacks: Extended drought, improper livestock grazing, and fire, resulting in a reduction of native perennial plant vigor. Normal fluctuations in weather and proper livestock grazing, allowing for the maintenance of both shrubs and perennial grasses.
At-risk Community Phase: All communities are at risk when nutrients are available for invasive plants to flourish. Community phase 2.1 is particularly at risk due to the decreased native perennial grass understory associated with this phase.
Trigger: Increased occurrence of invasive plants to fill available niches.
Submodel
Description
This state is dominated by invasive species—cheatgrass, halogeton, and Russian thistle being the most common. The primary disturbance mechanisms are fire, improper livestock grazing and drought. One or more invasive species has increased to a point where they influence or drive the disturbance regime and nutrient cycle. 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 invasive plants have established, a sites 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 can eventually create ecologically impoverished sites that are very difficult to restore to functionally diverse perennial herbaceous and woody communities. The competitiveness of the annual forbs and/or grasses, and the ability of these species to quickly establish after a disturbance, make this state extremely resistant to change and resilient after a disturbance.
Current Potential State: Plant communities disturbed by improper livestock grazing and drought.
Indicators: A site dominated by invasive plant species, such as cheatgrass and halogeton
Feedbacks: Time without disturbance which may enable some native vegetation to reestablish. Natural fluctuations in weather and fire if fine fuel accumulation is adequate, which allow for the continued dominance of invasive plant species.
At-risk Community Phase: Plant community 3.1 is most at risk because of declining native perennial vegetation.
Submodel
Description
This state is dominated by rubber rabbitbrush and broom snakeweed, with minimal occurrence of shadscale, Torrey mormontea, galleta, and other native perennial shrubs, grasses, and forbs. The primary disturbance mechanisms are improper livestock grazing, weather fluctuations, and mining or other surface disturbances. Rubber rabbitbrush and broom snakeweed have increased to a point where they influence or drive the disturbance regime and nutrient cycle. These alterations can eventually create ecologically impoverished sites that are very difficult to restore to functionally diverse perennial herbaceous and woody communities. The competitiveness of rubber rabbitbrush and broom snakeweed and the ability of these species to quickly establish after a disturbance make this state extremely resistant to change and resilient after a disturbance.
Rabbitbrush State: Plant communities disturbed by improper livestock grazing, mining disturbances, and other continued surface disturbances, such as road development, etc.
Indicators: A site dominated by broom snakeweed and rabbitbrush
Feedbacks: Time without disturbance which may enable limited native vegetation to reestablish. Natural fluctuations in climate, improper livestock grazing or continued surface disturbances which allow for the continued dominance of broom snakeweed and rubber rabbitbrush.
Restoration Pathway: Fall livestock grazing and insects may be used to control the establishment and dominance of rubber rabbitbrush. Time without surface disturbances and livestock grazing may allow for the reestablishment of native perennial shrubs and grasses without an increase in broom snakeweed; however this may take many years to accomplish.
Submodel
Mechanism
Transition from Reference State (State 1) to Current Potential State (State 2).
This transition occurs as non-native invasive species become established in the plant community. Common non-native invasive species include cheatgrass, halogeton, and Russian thistle. Disturbances that may accelerate this transition include improper livestock grazing, surface distrubance and/or extended drought. Invasive species such as cheatgrass have also been known to invade an intact perennial plant community, however, where no disturbance has occurred.
Mechanism
Transition from Current Potential State (State 2) to Invaded State (State 3).
This transition occurs as events favor the dominance of invasives species such as cheatgrass, Russian thistle, and halogeton. Events include drought and possibly fire; if fine fuel accumulation increases to a point where fire can carry through the current potential state. That fire could cause a transition into the invaded state.
Mechanism
Transition from Current Potential State (State 2) to Rabbitbrush State (State 4).
This transition occurs as events favor the increased dominance of rabbitbrush and broom snakeweed. Events typically include improper livestock grazing, mining or other large surface disturbance.
Mechanism
Restoration from Rabbitbrush State (State 4) to Current Potential State (State 2).
This restoration pathway occurs as events favor the reestablishment of native grasses, shrubs, and forbs. Fall livestock grazing and insects may be used to control the establishment and dominance of rubber rabbitbrush (Tirmenstein, 1999a); however care must be taken to allow for the reestablishment of native perennial shrub, grass, and forb species, without an increase in broom snakeweed which is enhanced by grazing pressures (Tirmenstein, 1999b). Time without surface disturbances and livestock grazing may allow for the reestablishment of native perennial shrubs and grasses without an increase in broom snakeweed; however this may take many years to accomplish.
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.