Sandy 14-17" PZ
Scenario model
Current ecosystem state
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Management practices/drivers
Select a transition or restoration pathway
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Transition T1A
Long-term (>10 years), heavy defoliation through grazing or haying.
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Transition T1B
Woody encroachment with no fire or brush management.
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Transition T1C
Tillage to facilitate production agriculture.
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Restoration pathway R2A
Long-term (>15 years) prescribed grazing with adequate growing season recovery time. This restoration may not be feasible.
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Transition T2A
Woody encroachment with no fire or brush management.
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Transition T2B
Tillage to facilitate agriculture.
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Restoration pathway R3A
Prescribed burning, timber harvest, brush management.
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Restoration pathway R3B
Prescribed burning, timber harvest, brush management.
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Restoration pathway R3C
Prescribed burning, timber harvest, brush management.
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Transition T4A
Woody encroachment with no fire or brush management.
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No transition or restoration pathway between the selected states has been described
Target ecosystem state
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Description
The Reference State (1) describes the range of vegetative communities that occur on the Sandy 14-17" 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. Natural fire played a significant role in the succession of this site by limiting the extent of shrubs. Wildfires have been actively controlled in recent times, reducing plant species diversity, especially forb diversity.
The Reference State includes three community phases which are the Reference Community (1.1), the At-Risk Community (1.2) and the Excessive Litter Community (1.3), The Reference Community serves as a description of the native plant community that naturally occurs on the site when the natural disturbance regimes are intact or closely mimicked by management practices. The At-Risk Community results from management actions that are unfavorable for a healthy Reference Community. The Excessive Litter Community occurs when herbivory and fire are eliminated from the landscape.
Submodel
Description
The Shortgrass State (2) transitioned from the Reference State (1) and much of the native warm-season tall- and midgrass components have been replaced by warm-season shortgrasses and upland sedges. This State is the result of long-term grazing management that did not provide adequate recovery time for warm-season tall- and midgrasses and mid-statured cool-season grasses. This management is typically heavy, continuous, season long grazing but heavy, rotational grazing with inadequate growing season recovery periods can also cause this transition. Over time, repeated annual haying during the rapid growth period of warm-season tallgrasses with inadequate growing recovery periods will also cause this transition.
The loss of warm-season tall- and midgrasses negatively impacts energy flow, nutrient cycling, and hydrologic function. Runoff is higher and infiltration is lower than the Reference State. This state is very resistant to change. The Shortgrass State includes the Shortgrass Community (2.1).
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 a grass dominated state. If the Invaded Woody State transitioned from the Shortgrass State (2) or the Sodbusted State (4), the land cannot return to the Reference State (1) as the native plant community, soils, and hydrologic function had been too severely impacted prior to the woody encroachment to allow the return to the Reference State through woody species removal alone. The Invaded Woody State includes one community, the Invaded Woody Community (3.1).
Submodel
Description
The threshold to the Sodbusted State (4) is crossed as a result of mechanical disturbance to facilitate production agriculture. If farming operations are suspended, the site can be seeded to native grasses resulting in the Reseeded Native Grass Community (4.1), be seeded to a tame pasture forage mixture resulting in the Seeded Pasture Community (4.2) or be abandoned with no seeding which will result in the Natural Reclamation Community (4.3). Permanent alterations of the soil, plant community, and hydrologic cycle make restoration to the Reference State (1) extremely difficult, if not impossible.
Submodel
Mechanism
The Reference State (1) transitions to the Shortgrass State (2) in response to long-term (greater than ten years), heavy, repeated defoliation of the key forage species (sand bluestem and prairie sandreed) by grazing or haying. This change typically occurs with long-term heavy, continuous season long grazing but heavy rotational grazing without adequate recovery periods may also cause this transition.
The Reference State loses a significant proportion of warm-season, tall- and midgrasses and crosses a threshold to the Shortgrass State. Deep rooted plants are replaced by shallow rooted, sod-forming grasses which tend to form root mats and water infiltration is reduced. Forage production and plant species diversity has declined. Initially, the plant community will be a mosaic, with shortgrass and mixed grass communities intermingled but as the management continues the plant community becomes dominated by shortgrasses and non-native cool-season grasses such as cheatgrass or Kentucky bluegrass may be significant.
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 can cause the Reference State (1) to transition to the Invaded Woody State (3).
Mechanism
The Reference State (1) has been significantly altered by tillage to facilitate production agriculture. When the land is no longer cropped, the resulting state is the Sodbusted State (4). The disruption to the plant community, the soil, and the hydrology of the system make restoration to a true Reference State unlikely.
Mechanism
Long-term (more than 15 years) prescribed grazing with adequate growing season recovery periods will move the Shortgrass State (2) toward the Reference State (1). The amount of time required for, and feasibility of this restoration depends upon the abundance of warm-season tall- and midgrasses and cool-season bunch grasses remaining in the plant community. This restoration may not be feasible.
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 can cause the Shortgrass State (2) to transition to the Invaded Woody State (3).
Mechanism
The Shortgrass State (2) has been significantly altered by tillage to facilitate production agriculture. When the land is no longer cropped, the resulting state is the Sodbusted State (4).
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. Land that transitioned to the Invaded Woody State from the Shortgrass State (2) or the Sodbusted State (4) cannot be restored to the Reference State through the removal of woody species as the native plant community, soils, and hydrologic function have been too severely impacted for that restoration to occur with brush management alone.
Mechanism
The Invaded Woody State (3) can be restored to the Shortgrass State (2) 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 Shortgrass State to return depends upon the severity and duration of the encroachment. Land that transitioned to the Invaded Woody State from the Shortgrass State cannot be restored to the Reference State through the removal of woody species as the native plant community, soils, and hydrologic function have been too severely impacted for that restoration to occur with brush management alone.
Mechanism
The Invaded Woody State (3) can be restored to the Sodbusted State (4) 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 Sodbusted State by management practices. Land that transitioned to the Invaded Woody State from the Sodbusted State cannot be restored to the Reference State (1) through the removal of woody species as the native plant community, soils, and hydrologic function have been too severely impacted for that restoration to occur with removal of brush alone.
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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.