Choppy Sandhills (CS)
Scenario model
Current ecosystem state
Select a state
Management practices/drivers
Select a transition or restoration pathway
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Transition T1A
Introduction of non-native grass species, such crested wheatgrass.
More details -
Transition T2A
Improper grazing management, warmer and drier climatic conditions.
More details -
Transition T2B
Displacement of native species by non-native invasive species (Crested Wheatgrass, noxious weeds, etc.)
More details -
Restoration pathway R3A
Critical area seeding, proper grazing management (management intensive and costly); or cooler, moister climatic conditions
More details -
Transition T3B
Recolonization of site by non-native species (Crested Wheatgrass, noxious weeds, etc.)
More details -
No transition or restoration pathway between the selected states has been described
Target ecosystem state
Select a state
Description
The Historic Reference State (1) contains four plant communities characterized by predominantly climate-driven eolian processes. This state is considered extinct and is included here for historical reference purposes. It evolved under the combined influences of climate, grazing, and fire (with climatic variation having the greatest influence on site stability, dune evolution, and vegetative cover). It is hypothesized that fire reduced shrub cover in this state. Most community phases in this state were resilient to light grazing, although localized areas may have experienced destabilization due to heavy grazing.
Submodel
Description
The Contemporary Reference State (2) contains four plant communities characterized by predominantly climate-driven eolian processes. Evidence suggests that climatic variation has the greatest influence on site stability, dune evolution, and vegetative cover and that this site is sensitive to small shifts in climate (Muhs and Wolfe, 1999; Wolfe and Lemmen, 1999). This state is considered representative of dominant climate patterns of the last 100 to 150 years, which generally have induced dune stabilization in the Northern Great Plains throughout the 20th century (Wolfe et al., 2001). This state differs from the Historic Reference State in that it is influenced by introduced plant species and has altered fire and grazing regimes. It is hypothesized that this state may have greater shrub cover due to the elimination of fire. In general, this state is resilient to light grazing, although grazing can influence site stability in localized areas. Non-native species, predominantly crested wheatgrass, typically comprise less than 10 percent of the plant community in this state.
Submodel
Description
The Destabilized State (3) consists of two plant communities. The dynamics of this state are driven by long-term drought, improper grazing management, or a combination of these factors. Evidence suggests that landscape-scale destabilization and reactivation of dunes are largely due to warmer and drier climatic conditions (Muhs and Wolfe, 1999; Wolfe et al., 2001). Removal of vegetation due to improper grazing, particularly when it occurs over multiple years and on a widespread scale, may also destabilize the site.
Submodel
Description
The Invaded State (4) occurs when invasive plant species invade adjacent native grassland communities and displace the native species. Data suggest that the diversity of native species declines significantly when invasive species exceed 30 percent of the plant community. Crested wheatgrass has been planted on an estimated 20 million acres in the western U.S. since the 1930s (Holechek, 1981) and is the greatest concern on this ecological site. It is extremely drought tolerant, establishes readily on a variety of soil types, has high seedling vigor, and can dominate the seedbank of invaded grasslands (Rogler and Lorenz, 1983; Henderson and Naeth, 2005). Invasive grass species can invade relatively undisturbed grasslands, but it is not clear precisely what triggers them to displace native species. Reduced plant species diversity, simplified structural complexity, and altered biologic processes result in a state that is substantially departed from both the Reference State (1) and the Contemporary Reference State (2).
Noxious weeds such as leafy spurge are not widespread in MLRA 53A, but they can be a concern on this ecological site. These species are very aggressive perennials. They typically displace native species and dominate ecological function when they invade a site. In some cases, these species can be suppressed through intensive management (herbicide application, biological control, or intensive grazing management). Control efforts are unlikely to eliminate noxious weeds, but their density can be sufficiently suppressed so that species composition and structural complexity are similar to that of the Contemporary Reference State (2). However, cessation of control methods will most likely result in recolonization of the site by the noxious species.
Submodel
Mechanism
Introduction of non-native grass species occurred in the early 20th century. The naturalization of these species in relatively undisturbed grasslands, coupled with changes in fire and grazing regimes, transitions the Reference State (1) to the Contemporary Reference State (2).
Mechanism
Improper grazing management can weaken the resilience of the Contemporary Reference State (2) and drive its transition to the Destabilized State (3). A shift to warmer, drier climatic conditions will also trigger the transition to the Destabilized State (3). The Contemporary Reference State (2) transitions to the Destabilized State (3) when soil loss exceeds vegetative recovery and dune activity reactivates on a larger scale.
Mechanism
The Contemporary Reference State (2) transitions to the Invaded State (4) when aggressive perennial grasses or noxious weeds displace native species and dominate the site. The most common concern is crested wheatgrass, which is a widespread invasive species in the Northern Great Plains (Heidinga and Wilson, 2002; Henderson and Naeth, 2005). The precise triggers of this transition are not clear, and further investigation is required. In addition, other rangeland health attributes, such as reproductive capacity of native grasses and soil quality, have been substantially altered.
Mechanism
A reduction in livestock grazing pressure alone may not be sufficient to reestablish stable vegetative cover in the Destabilized State (3). Intensive management such as critical area seedings may be necessary, but these practices are labor intensive and costly. In some cases, a shift to cooler, drier climate conditions may be required to facilitate a return the Contemporary Reference State (2). Returning the Destabilized State (3) may require considerable energy and cost and may not be feasible within a reasonable amount of time.
Relevant conservation practices
| Practice | External resources |
|---|---|
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Critical Area Planting |
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Prescribed Grazing |
Mechanism
The Destabilized State (3) transitions to the Invaded State (4) when aggressive perennial grasses or noxious weeds displace native species and dominate the site. The most common concern is crested wheatgrass, which is a widespread invasive species in the Northern Great Plains (Heidinga and Wilson, 2002; Henderson and Naeth, 2005). The precise triggers of this transition are not clear, and further investigation is required. In addition, other rangeland health attributes, such as reproductive capacity of native grasses and soil quality, have been substantially altered.
Model keys
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