The reference state represents the plant communities and ecological dynamics of the desert shallow sandy loam, blackbrush site. 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, however depending on disturbance history, native grasses, forbs, or other shrubs may occupy significant composition in the plant community. The reference state is self sustaining and resistant to change due to high resistance to natural disturbances and high resilience following natural disturbances.
Reference State: Plant community resistant to fluctuations in climate.
Indicators: A community dominated by blackbrush where native perennial grasses and forbs may or may not be present.
Feedbacks: Natural fluctuations in climate that allow for a self sustaining blackbrush and native grass community. Any disturbance 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.
The current potential state is similar to the reference state, however invasive species are now present in all community phases of the current potential state. This state is generally dominated by blackbrush and Torrey's jointfir, however, depending on disturbance history, native grasses, forbs, or other shrubs may also commonly occupy the site. Primary disturbance mechanisms include weather fluctuations, native herbivore grazing, domestic livestock grazing, and surface disturbances such as road and pipeline development and off road vehicle (OHV) use. Due to lack of disturbed areas, the community responses to such disturbances are not well documented. The current potential state is still self sustaining; but can be losing resistance to change due to lower resistance to disturbances and lower resilience following disturbances. Where annual species such as cheatgrass is present, disturbances such as fire are more likely to occur.
Current Potential State: Plant community is resistant to weather fluctuations.
Indicators: A community dominated by blackbrush where 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 blackbrush and grass community. Improper livestock grazing may result in a decrease in perennial grasses.
Submodel
2.1. Blackbrush Shrubland with Perennial Grasses & Invasive Species.
Transition from Reference State (State 1) to Current Potential State (State 2).
This transition is from the native perennial warm and cool season grass understory in the reference state to a state that contains invasive species. Events may include any combination of improper livestock grazing, prolonged drought, and/or surface disturbances. However, invasive species such as cheatgrass have been known to invade intact perennial plant communities with little to no disturbances. Once invasive plants are found in the plant community a threshold has been crossed.
Model keys
Briefcase
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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.
) icon wherever it occurs. Drag and drop items to reorder. Cookies are used to store briefcase items between browsing sessions. Because of this, the number of items that can be added to your briefcase is limited, and briefcase items added on one device and browser cannot be accessed from another device or browser. Users who do not wish to place cookies on their devices should not use the briefcase tool. Briefcase cookies serve no other purpose than described here and are deleted whenever browsing history is cleared.
