The reference state is representative of the natural range of variability under pristine conditions. The reference state is dominated by a long-lived evergreen shrub community with an understory of cool and warm season perennial bunchgrasses, as well as, annual and perennial forbs. Plant community phase changes are primarily driven by long term drought. Historically, fire is rare in this system, but can have long-term impacts on plant community dynamics. Reproduction and recruitment are episodic, based on favorable environmental conditions (Pendleton and Meyer 2004). Very old stands of blackbrush may have established hundreds to thousands of years ago under very different climatic conditions and will take a considerable amount of time to recover following disturbances.
The invaded state is characterized by a blackbrush community with non-native annuals in the understory. A biotic threshold has been crossed, with the introduction of non-native annuals that are difficult to remove from the system and have the potenital to alter disturbance regimes significantly from their natural or historic range of variability. These non-natives annuals are highly flammable and promote wildfires where fires historically have been infrequent.
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.
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.
