Natural Resources
Conservation Service
Semidesert Very Shallow Sandy Loam (Blackbrush)
Scenario model
Current ecosystem state
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Management practices/drivers
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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 describes the historic plant communities and natural ecological dynamics of the Semidesert Very Shallow Loam, Blackbrush 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 composed of a broad mixture of shrubs including blackbrush, littleleaf mountain mahogany, Mexican cliffrose and Torrey jointfir. Perennial cool and warm season grasses and perennial forbs are present in small amounts.
This 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: Plant communities affected by precipitation and run-on moisture fluctuations.
Indicators: A site dominated by various shrub species, where James galleta and Indian ricegrass may also 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.
Trigger: Introduction of invasive plants to fill available niches.
Submodel
State 2
Current Potential State
Current Potential State
Description
The Current Potential State is similar to the Reference Sate except that non-native species are now present. This state describes the plant communities that have or could become established on this ecological site under various successional sequences and disturbance conditions.
This state is composed of a broad mixture of shrubs including blackbrush, shadscale, littleleaf mountain mahogany, Mexican cliffrose and Torrey jointfir. Perennial cool and warm season grasses and perennial forbs are present in small amounts. Red brome, Russian thistle, various mustard species and other non-native species are present.
The primary disturbance mechanisms are the shrub layer density; the amount of invasive species present, the amount of run-on moisture and weather fluctuations. The current potential state is still self-sustaining but may be losing its resistance to change due to the impact of disturbances with less resilience following those disturbances.
Definitions:
Current Potential State: Plant communities influenced by shrub canopy density, long term weather fluctuations, and periodic fire. Invasive species are present in various amounts.
Indicators: A community dominated various shrubs and James galleta. The density of the shrub canopy determines the amount and composition of the other native and introduced grasses and forbs that may be present.
Feedbacks: Natural fluctuations in weather patterns that allow for a self sustaining mixed shrub and native grass community. Prolonged drought and/or other disturbances that may allow for the increase of invasive species.
At-risk Community Phase: All communities are at risk when native plants are stressed and nutrients become available for invasive plants to increase.
Trigger: A reduction of perennial grass and forb species combined with an increase of invasive plant species.
Submodel
Mechanism
This pathway describes the affects of the presence of a seed source of invasive and/or non-native species that become established by any combination of surface spot fire activity, drought, and improper livestock grazing. A threshold is passed when invasive and/or non-native species become established.
Mechanism
This pathway describes the affects of the presence of a seed source of invasive and/or non-native species that become established by any combination of surface spot fire activity, drought, and improper livestock grazing. A threshold is passed when invasive and/or non-native species become established.
Mechanism
This transitional pathway describes the affects of long term drought, heavy wildlife browsing and the establishment of invasive species such as red brome and/or Russian thistle. A threshold is crossed when invasive species become established.
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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