The Reference State has been determined by study of rangeland relic areas, areas protected from excessive disturbance, and areas under 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, thresholds, and restoration pathways 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 have been expressed on the ecological site if all successional sequences were completed without interferences by man under the present environmental conditions; natural disturbances are inherent in its development. It was in a natural dynamic equilibrium with the historic biotic, abiotic, climatic factors at the time of European immigration and settlement. The dominant aspect of this site is Pinyon and Utah juniper with an understory of roundleaf buffaloberry and associated grasses. Fluctuations in species compositions and relative production may change from year to year dependant upon abnormal precipitation or other climatic factors. The primary disturbance mechanisms for this site in reference condition include drought, and natural surface disturbances.
Reference state: Community phases maintained by climate fluctuations, natural surface disturbances, and time. Indicators: A well developed understory co-existing with a canopy of older Pinyon and Utah juniper.
Feedbacks: Infrequent, but regular droughts to reduce tree cover and allow for a productive herbaceous understory. The loss of native herbaceous understory species that results in opportunities for erosion.
At-risk Community Phase: All communities are at risk when native plants in the understory are stressed, and nutrients become available for non-natives to establish.
Trigger: Decrease of native plants in the understory and the introduction of non-native plants to fill the available niches.
Submodel
1.1. Pinyon and Utah Juniper Woodland with Understory
This state is very similar to the reference state, except that non-native grasses and/or forbs are now present in all phases. The current potential state may include naturalized or invasive non-native species. The primary disturbance mechanisms include all those found in the reference state as well as human induced disturbances, including improper domestic livestock grazing and recreation activities, including off highway vehicle (OHV) overuse. Plant communities within the current potential state are more likely managed and used for various purposes by man, without significant alteration in plant community composition or production. In time, continued surface disturbances, will likely stress the native plant species and allow for non-native species to increase. This shift in species composition could affect nutrient cycling, hydrology, and soil stability. At this time there is no known way to effectively remove the non-native plants from this site, once they have become established. Therefore this site is often irreversibly altered from the reference state.
Current Potential state: Community phases influenced by climate, surface disturbances, and domestic livestock grazing.
Indicators: A well developed understory co-existing with a canopy of older Pinyon and Utah juniper.
Feedbacks: Infrequent, but regular droughts to reduce tree cover and allow for a productive herbaceous understory. The loss of native herbaceous understory species that results in opportunities for erosion.
Submodel
2.1. Pinyon and Utah Juniper Woodland with Understory
This transition from the native perennial bunchgrass and shrub understory in the reference state to a state that has been invaded by naturalized species such as crested wheatgrass (blown in), cheatgrass, and annual wheatgrass. This transition occurs as natural and/or management actions favor an increase in non-native grasses and forbs, especially annuals. Possible events include the mere presence of invasive species, improper livestock grazing, seeding introduced species nearby, extended droughts, and surface disturbances combined with an available seed source of non-native species.
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.
