Natural Resources
Conservation Service
SHALLOW GRAVELLY LOAM 9-11 P.Z.
Scenario model
Current ecosystem state
Select a state
Management practices/drivers
Select a transition or restoration pathway
- Transition T1a More details
- Transition T1b More details
- Transition T2 More details
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No transition or restoration pathway between the selected states has been described
Target ecosystem state
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State 1
Reference State
Reference State
Description
The reference state is representative of the natural range for variability under pristine conditions. This site is dominated by an evergreen shrub community. Community phase changes are primarily driven by long-term drought and infrequent wildfire. Historically, blackbrush associations were long-lived stable communities. Fire was infrequent and patchy due to low fuel loading. 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.
Submodel
Description
The invaded state is characterized by the presence of non-native annuals. A biotic threshold is crossed, with the introduction of non-natives that are difficult to remove from the system and have the potential to alter disturbance regimes significantly from their natural range of variability. Introduced annuals such as red brome, cheatgrass and redstem filaree have invaded the reference plant community. These non-natives annuals are highly flammable and promote wildfires where fires historically have been infrequent. Following a disturbance this state relies on the availability of a nearby seed source.
Submodel
Description
The tree state is characterized by the invasion of pinyon-juniper and tree cover greater than 20 percent. Lack of fire and other disturbance allows seedlings and saplings to infill and eventually dominate, 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. An abiotic threshold has been crossed changing the ecological dynamics of the site.
Submodel
Mechanism
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.
Mechanism
Continued lack of disturbance. Encroachment and establishment of pinyon and juniper. Tree canopy is 20 percent or greater and bare ground is increasing.
Model keys
Briefcase
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Ecological sites
Major Land Resource Areas
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.
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