The reference state is representative of the natural range of variability under pristine conditions. It is dominated by an evergreen shrub community with a significant amount of perennial grass. Plant community phase changes are primarily driven by periodic wildfire, insect/disease attack and long-term drought. Plant community dynamics are driven by interactions between climatic patterns and disturbance regimes.
This state is characterized by the presence of non-native species in the understory. Introduced annuals such as cheatgrass have invaded the plant community. A biotic threshold is crossed with the introduction of non-native annuals that are difficult to remove from the system and have the potential to significantly alter disturbance regimes from their historic range of variation. These non-native annuals are highly flammable and can promote wildfire where fires historically have been infrequent. Recovery of sagebrush to pre-fire conditions is dependent on available seed source and favorable weather conditions and may take an extended period of time.
This state is characterized by the invasion of pinyon and juniper and tree cover of greater than 20 percent. Lack of fire, insect/disease attack and drought allows seedlings and saplings to infill and eventually dominate the plant community, changing the ecological dynamics of the site. Non-native annuals may or may not be present in the understory. This state experiences reduced infiltration and increased runoff during precipitation events, diminishing soil moisture. Feedbacks contributing to the stability of this state include reduced understory vegetation resulting from decreased soil moisture and overstory shading.
Introduction of non-native species due to a combination of factors including: 1) surface disturbance, 2) changes in the kinds of animals and their grazing patterns, 3) drought and/or 4) changes in fire history.
Continued lack of disturbance. Encroachment and establishment of pinyon and juniper. Tree canopy is greater than 20 percent and bare ground is increasing.
Continued lack of disturbance. Encroachment and establishment of pinyon and juniper. Tree canopy is greater than 20 percent and bare ground is increasing.
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.
