The reference state is representative of the natural range for variability under pristine conditions. Primary natural disturbance mechanisms affecting this ecological site are infrequent wildfire, prolonged drought and insect attack. Historically, infrequent wildfire occured due to the natural build up of woody fuels and lightning strikes. Plant communities of this site are stable, long-lived and dynamic in response to changes in disturbance regimes and weather patterns.
The invaded state is characterized by the presence of non-natives in the understory. Ecological function has not been compromised at this time, however the presence of non-natives has reduced ecological resilience of the site. A biotic threshold has been crossed with the introduction of non-natives that are very difficult to remove from the system and have the potential to significantly alter disturbance regimes from their historic range of variation. These non-natives annuals are highly flammable and can 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
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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.