Desert Stony Loam (Shadscale-Bud Sagebrush)
Scenario model
Current ecosystem state
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Management practices/drivers
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- Transition T1A 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 represents the historic plant communities and ecological dynamics of the desert stony loam, shadscale-bud sagebrush 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, shadscale, and bud sagebrush. The primary disturbance mechanism is climate 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.
The reference state was determined by study of rangeland relic areas, areas protected from excessive disturbance and outside influences, such as grazing and recreation. Literature reviews, trends in plant community dynamics, and historical accounts are also considered.
Reference State: Community phases disturbed by climate fluctuations and insect herbivory.
Indicators: A site dominated by shadscale and bud sagebrush where James galleta, Indian ricegrass and sand dropseed may or may not be present.
Feedbacks: Extended periods of above average precipitation resulting in an increase in the native perennial plant vigor. Insect herbivory that reduces shrub vigor and allows grass production to increase.
At-risk Community Phase: All communities are at risk when nutrients are available for invasive plants to establish. Plant community 1.2 is especially at risk due to limited production and cover of understory grasses.
Trigger: Introduction of invasive plants to fill available niches.
Submodel
Description
The current potential state is similar to state one, however there are invasive species established in the understory—cheatgrass and halogeton being the most common. The primary disturbance mechanism is climate fluctuations; however livestock grazing may influence the ecological dynamics of the site.
Current Potential State: Plant communities disturbed by fluctuating climatic conditions insect herbivory, and livestock grazing.
Indicators: A site dominated by shadscale and bud sagebrush, where Indian ricegrass and sand dropseed may or may not be present. Invasive species are present.
Feedbacks: Fluctuations in climate allow for the maintenance of both shrubs and perennial grasses.
Submodel
Mechanism
Transition from Reference State (State 1) to Current Potential State (State 2).
This transition occurs as invasive species become established in the plant community. Common invasive species include cheatgrass, halogeton, and Russian thistle. Disturbances that may accelerate this transition include improper livestock grazing, surface disturbance and extended drought. Invasive species such as cheatgrass have also been known to invade an intact perennial plant community where no disturbance has occurred. Short wet spells when annuals are germinating can significiently increase their annual production.
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.