Semidesert Shallow Sandy Loam (Utah Juniper, Blackbrush)
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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Description
This community has dense diverse biological crusts where the soil has less than 30% surface rock. This state includes the biotic communities that become established on the ecological site if all successional sequences are completed under the natural disturbance regimes. The reference state is generally dominated by blackbrush, Utah juniper, and two-needle-pinyon, however, depending on disturbance history, native grasses, forbs, or other shrubs may occupy significant composition in the plant community. The primary disturbance mechanism is climate fluctuation. 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. Typically, in the reference state this site will fluctuate between community phases 1.1 and 1.2; however once invasive plants establish, return to these community phases may not be possible.
Reference State: Plant communities influenced by insect herbivory, and climate fluctuations.
Indicators: A community dominated by Utah juniper and blackbrush where two-needle pinyon and native perennial grasses and forbs may also be present.
Feedbacks: Natural fluctuations in weather that allow for a self sustaining Utah juniper-blackbrush and native grass community. Insect herbivory, more frequent fire, or other disturbances that may allow for the establishment 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 establish.
Trigger: The establishment of invasive plant species.
Submodel
Description
The current potential state is similar to the reference state, however invasive species are now present in all community phases. This state is generally dominated by Utah juniper, two-needle pinyon, and blackbrush. Depending on the sites disturbance history, native perennial grasses, forbs, or other shrubs may be common in the sites understory. Primary disturbance mechanisms are thought to include long-term weather fluctuations, insect herbivory, improper livestock grazing and surface disturbances such as road and pipeline development and off road vehicle (OHV) use. Few disturbed sites have been located to date and so little data exists regarding them. The current potential state is still self sustaining but has less resistance to change due to lower resistance to disturbances and lower resilience following disturbances. Typically in the current potential state this site will fluctuate between community phases 2.1 and 2.2.
Current Potential State: Plant communities influenced by insect herbivory, weather fluctuations, and surface disturbances.
Indicators: A community dominated by Utah juniper and blackbrush where two-needle pinyon and native perennial grasses and forbs may also be present. Invasive grasses and forbs are present.
Feedbacks: Natural fluctuations in weather that allow for a self sustaining juniper-blackbrush and grass community.
Submodel
Mechanism
During periods of long-term drought, two-needle pinyon trees are susceptible to insect infestations which can cause them to decrease or die out in the community. Drought can also reduce native perennial grass production and eventually eliminate them from the system as well. Improper livestock grazing, although rare, and/or other surface disturbances can also cause the perennial herbaceous compoment of the plant community to deteriorate. These surface disturbances can also reduce or remove the sites naturally diverse biological crusts thus increase the susceptibility of the soil to erosion by wind and water. Non-native invasive species are more likely to enter the system during these periods. Once non-native species are present, 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.