Choppy Sands 22-25" PZ
Scenario model
Current ecosystem state
Select a state
Management practices/drivers
Select a transition or restoration pathway
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Transition T1A
Frequent and severe defoliation, land disturbance, wind erosion.
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Transition T1B
Woody encroachment with no fire or brush management
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Restoration pathway R2A
Removal of disturbance with long-term (>10 years) prescribed grazing.
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Restoration pathway R3A
Prescribed burning, timber harvest, brush management.
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No transition or restoration pathway between the selected states has been described
Target ecosystem state
Select a state
Description
The Reference State (1) describes the range of vegetative community phases that occur on the Choppy Sands 22-25" PZ ecological site where the range of natural variability under historic conditions and disturbance regimes is mostly intact. The Reference State developed under the combined influences of climatic conditions, periodic fire activity, grazing by large herbivores, and impacts from small mammals and insects. High perennial grass cover and production allows for increased soil moisture retention, vegetative production and overall soil quality.
The Reference State includes four community phases which are the Reference Community (1.1), the Degraded Native Grass Community (1.2), the At-Risk Community (1.3), and the Excessive Litter Community (1.4). The Reference Community serves as a description of the native plant community that occurs on the site when the natural disturbance regimes are intact or closely mimicked by management practices. The Degraded Native Grass and the At-Risk Communities result from management decisions that are unfavorable for a healthy Reference Community. The Excessive Litter Community occurs when herbivory and fire are removed from the landscape.
Submodel
Description
The Eroded State (2) can be reached from any plant community in the Reference State (1). This state is the result of heavy disturbance. This heavy disturbance is usually frequent and severe defoliation. The Eroded State can also develop with vehicle traffic, livestock trailing or other heavy disturbances. Long-term drought or dormant season wildfire coupled with the heavy disturbance will accelerate the move to the Eroded State. The Eroded State (2) includes two plant communities which are the Active Blowout Community (2.1) and the Early Seral Community (2.2).
Submodel
Description
The Invaded Woody State (3) is the result of woody encroachment. Once the tree canopy cover reaches 15 percent with an average tree height exceeding five feet, the threshold to the Invaded Woody State has been crossed. Woody species are increasing due to the lack of prescribed fire, brush management, or other woody tree removal. Typical ecological impacts are a loss of native grasses, reduce diversity of functional and structural groups, reduced forage production, and reduced soil quality. Prescribed burning, wildfire, timber harvest and brush management will move the Invaded Woody State toward the Reference State (1). The Invaded Woody State includes the Invaded Woody Community (3.1).
Submodel
Mechanism
The Eroded State (2) can be reached from any plant community of the Reference State (1). The Eroded State occurs with frequent and severe defoliation. Heavy, continuous grazing most often causes this transition, but it can also occur with rotational grazing when plants are not given adequate growing season recovery time before the paddocks or pastures are re-grazed. This process is accelerated when accompanied by additional disturbances, such as dormant season wildfire or extended drought. Heavy disturbance, such as vehicle traffic or livestock trailing can also cause this transition. The reduction in plant canopy and litter cover allows wind erosion to develop, creating large areas of blowing sand.
Mechanism
Long-term (more than ten years) disruption of the natural fire regime and the encroachment of invasive exotic and native woody species with no woody species management will cause the Reference State (1) to cross the threshold to the Invaded Woody State (3).
Mechanism
The Eroded State (2) can be restored to the Reference State (1) with long term grazing management (10 or more years) that incorporates adequate growing season recovery periods. When either human-caused disturbance or livestock concentration caused the transition from the Reference State, removal of the disturbance along with appropriate grazing management is needed. The slope, aspect, and size of the area, as well as the relative abundance of perennial plants, will influence the amount of time required to reach the Reference Community.
Mechanism
The Invaded Woody State (3) can be restored to the Reference State (1) through prescribed burning, wildfire, timber harvest, or brush management. The forb component may initially increase following tree removal. Ongoing brush management such as hand cutting, chemical spot treatments, or periodic prescribed burning is required to prevent a return to the Invaded Woody State. The heavier the existing canopy cover, the greater the energy input required to return to the Reference State. The amount of time required for the herbaceous vegetation of the Reference State to return depends upon the severity and duration of the encroachment.
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.