The Reference State has been determined by study of rangeland relic areas, areas protected from excessive disturbance, and influences such as grazing and recreational uses. Through literature review, historical accounts and observations of trends in plant community dynamics under a variety of uses have been considered. Community phases, community pathways, states, transitions, and thresholds, have been determined through similar studies and experience.
This state represents the natural range of variability that historically dominated the dynamics of this ecological site. This state includes the biotic communities that would be expressed on the ecological site if all successional sequences were completed without modern disturbances under the present environmental conditions; natural disturbances are inherent in its development. This state is dominated by pinyon and Utah juniper with a well developed understory of native shrubs, perennial grasses and perennial and annual forbs. The primary disturbance mechanisms for this site in the reference condition include drought and insects.
Reference State: Community phases maintained by drought and insect pathogen cycles
Indicators: A community dominated by twoneedle pinyon and Utah juniper, where shrubs, and native perennial grasses and forb production is variable.
Feedbacks: Infrequent but regular droughts that reduce pinyon cover. Disturbances that may allow for the establishment of invasive species.
At-risk Community Phase: this community is at risk when native plants are stressed and nutrients become available for invasive plants to establish.
The current potential state is similar to the reference state; however invasive species are present. This state is generally dominated by Utah juniper and twoneedle pinyon, however depending on disturbance history, native grasses, forbs, or other shrubs may dominate the site. Primary disturbance mechanisms include insect herbivory, 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 documented and are not currently included in the state and transition model. The current potential state is still self sustaining; but is losing resistance to change due to lower resistance to disturbances and lower resilience following disturbances, and new drastic disturbances such as fire being more likely to occur.
Current Potential State: Community phases maintained by drought and insect herbivory cycles
Indicators: A community dominated by twoneedle pinyon and Utah juniper, where shrubs, and native perennial grasses and forb production is variable.
Feedbacks: Infrequent, but regular droughts to reduce tree cover.
T1a – 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 include intense continuous grazing of perennial grasses, prolonged drought, and surface disturbances, etc. 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.
