Natural Resources
Conservation Service
Claypan (Cp) 10-14" PZ Frigid
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 T1C More details
- Restoration pathway R2A More details
- Transition T2A More details
- Transition T2B More details
- Transition T3A More details
- Restoration pathway R4A More details
- Restoration pathway R4B More details
- Restoration pathway R4C More details
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No transition or restoration pathway between the selected states has been described
Target ecosystem state
Select a state
Description
Reference State consists of two plant communities. The first is dominated by deep-rooted bunchgrasses, and rhizomatous grasses. The second community is co-dominated by bunchgrasses, shrubs and rhizomatous grasses. These communities regularly transition in response to varying climatic conditions and minor disturbances.
The Reference State exists where grazing by livestock and wildlife has historically been light to moderate and grazing events have been short. This reduces the opportunity for grazing regrowth and maintains.
Submodel
Description
This state is characterized by having less than 10 percent bluebunch wheatgrass by dry weight. It is represented by one community. Production in this state can be similar to that in the Reference State (1). Some native plants increase under prolonged drought or heavy grazing practices. This may include western wheatgrass, needle and thread, Sandberg bluegrass, scarlet globemallow, hairy false goldenaster, and prairie sagewort.
Submodel
Description
Shortgrass-Shrub State lacks mid-statured bunchgrasses. Western wheatgrass, blue grama, Sandberg bluegrass, and prairie Junegrass are dominant grasses. Increasers like broom snakeweed and prickly pear cactus are almost as productive as the larger sagebrush shrubs. Larger shrub species that remain are heavily hedged. This state will be treated as terminal (e.g., restoration will likely be impossible or unsuccessful and require major energy inputs).
Submodel
Description
The Invaded State is identified by being in the exponential growth phase of invader species where control is a priority. Dominance (or relative dominance) of noxious or invasive species reduces species diversity, forage production, wildlife habitat, and site protection. A level of 10 percent invasive species composition by dry weight indicates that a substantial energy input will be required to shift to a grassland state (herbicide, mechanical treatment) even with a return to proper grazing management or favorable growing conditions. Prescriptive grazing can be used to manage invasive species. In some instances, carefully targeted grazing (sometimes in combination with other treatments) can reduce or maintain species composition of invasive species.
Submodel
Mechanism
The Reference State (1) transitions to the Rhizomatous Grass State (2) if bluebunch wheatgrass, by dry weight, decreases to below 10 percent by weight or if bare ground cover is increased beyond 20 percent. The driver for this transition is the loss of taller bunchgrasses, which creates open areas in the plant canopy with bare soil. Soil erosion reduces soil fertility, driving transitions to the Rhizomatous Grass State. There are several other key factors signaling the approach of transition T1A increases in soil physical crusting, decreases in the cover of cryptogamic crusts, decreases in soil surface aggregate stability, and evidence of erosion, including water flow patterns, the development of plant pedestals, and litter movement. The trigger for this transition is improper grazing management or long-term drought, leading to a decrease in bluebunch wheatgrass composition to less than 10 percent by weight and a reduction in total plant canopy cover.
Mechanism
The Reference State (1) transitions to the Shortgrass-Shrub State (3) when bluebunch wheatgrass is removed from the plant community. Needle and thread is subdominant to short-statured bunchgrasses such as Sandberg bluegrass. The trigger for this transition is the loss of taller bunchgrasses, which creates open spaces with bare soil. Soil erosion reduces soil fertility, driving transitions to the Shortgrass-Shrub State. There are several other key factors signaling the approach of transition T1B increases in soil physical crusting, decreases in the cover of cryptogamic crusts, decreases in soil surface aggregate stability, and evidence of erosion, including water flow patterns, the development of plant pedestals, and litter movement. The drivers for this transition are improper grazing management, intense or repeated fires, or heavy human disturbance. Rapid transition is generally realized when livestock are confined to small pastures for long periods.
Mechanism
Healthy plant communities are most resistant to invasion. However, regardless of grazing management, without some form of active weed management (chemical, mechanical, or biological control) and without prevention, the Reference State (1) can transition to the Invaded State (4) in the presence of aggressive invasive species, such as spotted knapweed, leafy spurge, and cheatgrass. The Central Rocky Mountain Valleys tend to resist invasion by cheatgrass; however, repeated heavy grazing or intense human activities can open the interspaces of the bunchgrass community and allow for encroachment. Long-term stress conditions for native species (e.g., overgrazing, drought, and fire) accelerate this transition. If populations of invasive species reach critical levels, the site transitions to the Invaded State. The trigger for this transition is the presence of aggressive invasive species. The species composition by dry weight of invasive species approaches 10 percent.
Mechanism
The Rhizomatous Grass State (2) has lost soil or vegetation attributes to the point that recovery to the Reference State (1) may require reclamation efforts such as soil rebuilding, intensive mechanical and cultural treatments, or revegetation. Examples of mechanical treatment may be brush control. Cultural treatments may include prescribed grazing, targeted brush browsing, or prescribed burning. Prescribed grazing tactics may include a rest or deferred-season rotation with light or moderate grazing intensity. Low-intensity prescribed fires were used to reduce competitive increasers like needle and thread and Sandberg bluegrass. A low-intensity fire will also reduce Wyoming big sagebrush densities. Fire should be carefully planned or avoided in areas prone to annual grass infestation. The drivers for this restoration pathway are reclamation efforts and proper grazing management.
Mechanism
As improper grazing management continues, the vigor of bunch grasses will decrease, and the shorter grasses and shrubs will increase towards the Shortgrass-Shrub State (3). Prolonged drought will provide a competitive advantage to shrubs, allowing them to become co-dominant with grasses. The shrub canopy will increase. Key transition factors include an increase in native shrub canopy cover, a reduction in bunchgrass production, a decrease in total plant canopy cover and production, increases in mean bare patch size, increases in soil crusting, decreases in the cover of cryptobiotic crusts, decreases in soil aggregate stability, or evidence of erosion, including water flow patterns and litter movement.
Mechanism
Invasive species can occupy the Rhizomatous Grass State (2) and drive it to the Invaded State (4). This state is at risk if invasive seeds or other viable materials are present. The driver for this transition is more than 10 percent of the dry weight of invasive species. The trigger is the presence of seeds and/or other viable material from invasive species.
Mechanism
Invasive species can occupy the Shortgrass-Shrub State (3) and drive it to the Invaded State (4). The Shortgrass-Shrub State is at risk of this transition occurring if invasive seeds or viable material are present. The driver for this transition is the presence of critical population levels of invasive species. The trigger is the presence of seeds or viable material from invasive species. The Shortgrass-Shrub State has sufficient bare ground that the transition could occur simply due to the presence or introduction of invasive seeds or viable material. This is particularly true of aggressive invasive species such as spotted knapweed and cheatgrass. This transition could be assisted by overgrazing (failure to adjust stocking rate to declining forage production), a long-term lack of fire, or an extensive drought.
Mechanism
Restoration of the Invaded State (4) to the Reference State (1) requires substantial energy input. The drivers for the restoration pathway are removing invasive species, restoring native bunchgrass species, persistent management of invasive species, and proper grazing management. Without continued control, invasive species are likely to return (probably rapidly) from the presence of seeds or other viable material in the soil and management-related practices that increase soil disturbance. If the site has transitioned from the Reference State to the Invaded State, the amount of time and resources necessary to transition back to the Reference State may be less than for a site that transitioned from the Rhizomatous Grass State. Sites transitioning from the Rhizomatous Grass State (2) will require more inputs to reestablish native bunchgrasses before they resemble the Reference State (1). Sites that have transitioned from the Shortgrass-Shrub State (3) to the Invaded State (4) may severely lack soil and vegetative properties that will allow for restoration to the Reference State. Hydrologic function damage may be irreversible, especially with accelerated gully erosion.
Mechanism
If invasive species are removed before remnant populations of bunchgrass have been drastically reduced, the Invaded State (4) can return to the Rhizomatous Grass State. The driver for the reclamation pathway is weed management without reseeding. Continued integrated pest management will be required as many of the invasive species that can occupy the Invaded State have extended dormant seed life. The trigger is invasive species control.
Mechanism
If invasive species are removed, the site could return to the Shortgrass-Shrub State (3). Without sufficient remnant populations of preferred plants, the Invaded State (4) is not likely to return to any other states. The driver for the reclamation pathway is weed management without reseeding. The trigger is invasive species control. The invading species cause a significant increase in soil loss due to a lack of ground cover (Lacey et al., 1989).
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.
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