Natural Resources
Conservation Service
Alkali Flat (Black Greasewood)
Scenario model
Current ecosystem state
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Management practices/drivers
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- Transition T1A More details
- Transition T2A 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 represents the plant communities and ecological dynamics of the Alkali Flat (greasewood) site. The Reference State includes the biotic communities that become established on the ecological site if all successional sequences are completed under the natural disturbance regime. The Reference State is generally dominated by black greasewood and bottlebrush squirreltail. 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 variable due to disturbance intensity. Once invasive plants establish, return to the reference state may not be possible.
Reference State: Black greasewood/bottlebrush squirreltail state with natural fluctuations that form either a shrubland or grassland aspect following fire in the natural disturbance history.
Indicators: A community dominated by greasewood and bottlebrush squirreltail.
Feedbacks: Improper livestock grazing of perennial grasses and/or other disturbances that may allow for the establishment of invasive species.
At-risk Community Phase: This state is at risk when native plants are stressed and nutrients become available for invasive plants to establish.
Trigger: The establishment of invasive plant species
Submodel
State 2
Current Potential State
Current Potential State
Description
The Current Potential State is similar to the Reference State, however, invasive grasses and/or forbs are now present in all community phases. This state is still dominated by an canopy of black greasewood. bottlebrush squirreltail, Indian ricegrass and basin wildrye are still the primary perennial grass species, however, cheatgrass, mustard species, and other non-native invasive species now make up a significant portion of the herbaceous layer.
Primary disturbance mechanisms include, fire, drought, and domestic livestock grazing. Timing of these disturbances dictates the ecological dynamics that occur. The Current Potential State is still self sustaining but is losing resistance to change due to lower resilience following disturbances. When disturbances occur, the rate of recovery is variable depending on severity.
Current Potential State: Black greasewood/ bottlebrush squirreltail state with variations caused by fire, insect damage and/or drought. Invasive plants are present.
Indicators: A community dominated by greasewood and/or bottlebrush squirreltail where native perennial grasses and forbs are also present. Invasive grasses and/or forbs are present.
Feedbacks: Frequent disturbances that may allow the dominance of annual invasive species such as cheatgrass to dominate.
At-risk Community Phase: As increased disturbance frequency allows for the dominance of annual grasses, such as cheatgrass, this community is at greater risk.
Trigger: Reoccurring disturbance that results in a dominance of annual grasses in the herbaceous layer.
Submodel
State 3
Range Seeding State
Range Seeding State
Description
The Range Seeding State occurs when the site is plowed or disked and planted to various rangeland grasses. Tall wheatgrass, crested wheatgrass, and Russian wildrye are the most commonly seeded species. These seedings can range from successful with few invasive species to failed with few seeded species and dominated by invasive species. Common invasive species are Russian thistle, cheatgrass, tansy mustard, broom snakeweed, alyssum, fivehorn smotherweed, and annual Cryptantha.
Invasive Forb State: Range seeding community phases influenced by livestock grazing practices and weather cycles.
Indicators: Perennial rangeland seeding with annual, invasive forbs and grasses present in various amounts.
Feedbacks: Livestock grazing practices and weather cycles that maintain or degrade the range seeding and suppress or increase the non-native annuals present in the community.
Trigger: An increase of cheatgrass and other annuals that may shorten the sites fire interval, decrease perennial seeding production and increase bare ground.
Submodel
Mechanism
This transition is from the black greasewood/squirreltail community phase in the Reference State to a state that now contains non-native, invasive species. Events may include the establishment of invasive grasses and forbs, and an increase in black greasewood, broom snakeweed, and green rabbitbrush. Factors that drive such events include, improper livestock grazing of perennial grasses, prolonged drought, and the presence of a seed source for invasive species. Invasive species such as cheatgrass however have been known to invade intact perennial plant communities with little to no disturbance. Once invasive species are found in the plant community a threshold has been crossed.
Mechanism
This transition is from the Current Potential State to a seeded rangeland community phase. Site is plowed, disked and/or burned, and seeded to adapted rangeland species including tall wheatgrass, crested wheatgrass, or Russian wilrye. Factors that drive such events include, proper livestock grazing of perennial grasses, sufficient moisture for seeding establishment, and adequate control of unwanted invasive species. Once site is converted, 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.
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