Natural Resources
Conservation Service
Thin Claypan (Tcp) Dry Grassland
Scenario model
Current ecosystem state
Select a state
Management practices/drivers
Select a transition or restoration pathway
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Transition T1A
prolonged drought, improper grazing, or a combination of these factors
More details -
Transition T1B
The introduction of aggressive perennial grasses (mostly crested wheatgrass)
More details -
Transition T1C
Conversion to annual cropland
More details -
Restoration pathway R2A
range seeding, grazing land mechanical treatment, timely moisture, proper grazing management (management intensive and costly)
More details -
Transition T2A
introduction of weedy species; combined with drought and/or improper grazing management
More details -
Transition T2B
conversion to annual cropland
More details -
Transition T3A
conversion to annual cropland
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Transition T4A
cessation of annual cropping
More details -
Transition T5A
conversion to annual cropland
More details -
No transition or restoration pathway between the selected states has been described
Target ecosystem state
Select a state
State 1
Reference
Reference
Description
The Reference state consists of two communities. The dynamics of this state are driven by the combined influences of climate, grazing, and fire. Dense clubmoss may be present in any of the communities within this state; however, its density is highly variable and the dynamics of this species are not well understood (Romo and Bai, 2004; Romo, 2011). Research has shown that its density is affected by drought, fire, and hoof action by grazing animals (Coupland, 1950; VanDyne and Vogel, 1967; Clarke et al., 1947). However, its abundance may vary greatly from site to site without discernable reason. In general, this state is characterized by a predominance of mid-statured, cool-season rhizomatous grasses. As ecological conditions decline; mid-statured grasses decrease and are replaced by short-statured grasses such as blue grama and Sandberg bluegrass. Plant Community 1.2 is dominated by blue grama and rhizomatous wheatgrasses, although wheatgrasses decrease in this community. Sandberg bluegrass also increases in Plant Community 1.2, as does prairie sagewort. Drought, improper grazing management, or a combination of these factors can transition this state to the Shortgrass state.
Dominant plant species
western wheatgrass (Pascopyrum smithii), grass
blue grama (Bouteloua gracilis), grass
Submodel
Description
The Shortgrass state consists of two communities. The dynamics of this state are driven by long-term drought, improper grazing management, or a combination of these factors. Rhizomatous wheatgrasses have low production and poor vigor in this state. Prairie sagewort is common. Blue grama increases with long-term improper grazing at the expense of cool-season midgrasses (Coupland, 1961; Biondini and Manske, 1996; Derner and Whitman, 2009). Reductions in stocking rates can reduce blue grama cover and increase the cover of cool-season midgrasses, although this recovery may take decades (Dormaar and Willms, 1990; Dormaar et al., 1994). Dense clubmoss may or may not be present in this state and the dynamics of this species are not well understood. In some cases, it is abundant on heavily grazed areas, but in others, it is rare or absent. Its abundance varies greatly from site to site without a discernable reason, therefore, it is not considered a reliable indicator of past grazing use (Montana State College, 1949). Annual bromes are also present in this state. They are naturalized but usually do not have a significant ecological impact; however, their abundance varies depending on precipitation and germination conditions.
Submodel
Description
The Invaded state (3) occurs when invasive plant species, primarily crested wheatgrass, invade adjacent native grassland communities. An estimated 20 million acres of crested wheatgrass have been planted in the western U.S. (Holechek, 1981). Since the 1930s, crested wheatgrass has been planted to improve forage for livestock (Roglers and Lorenz, 1983; Laycock, 1988). Beginning in the mid-1980s, crested wheatgrass was often seeded on lands enrolled in the Conservation Reserve Program (CRP; Roath, 1988; DeLuca and Lesica, 1996). Crested wheatgrass is extremely drought tolerant, establishes readily on a variety of soil types, has high seedling vigor, and provides highly productive early-season forage for livestock (Roglers and Lorenz, 1983). Once established, monocultures of crested wheatgrass can persist for at least 60 years (Krzic et al., 2000; Henderson and Naeth, 2005), as crested wheatgrass stands resist the recruitment of native plant species (Looman and Heinrichs, 1973; Henderson and Naeth, 2005; Fansler and Mangold, 2011).
Crested wheatgrass produces abundant seeds that can dominate the seedbank of invaded grasslands, although crested wheatgrass cover decreases with increasing distance from seeded areas (Henderson and Naeth, 2005; Heidinga and Wilson, 2002). The early growth of crested wheatgrass allows this species to take advantage of early-season soil moisture, which may result in competitive exclusion of native cool-season rhizomatous wheatgrasses and bunchgrasses such as needle and thread and prairie Junegrass (Christian and Wilson, 1999; Heidinga and Wilson, 2002; Henderson and Naeth, 2005). If already established, the warm-season, mat-forming blue grama may compete successfully with crested wheatgrass, although the ability of blue grama to persist in invaded stands is unknown due to its low seed production and narrow germination requirements (Coupland, 1950; Heidinga and Wilson, 2002; Lauenroth et al., 1994). Reduced soil quality, reduced plant species diversity, and simplified structural complexity (Dormaar et al., 1995; Henderson and Naeth, 2005) result in a state that is substantially departed from the Reference state (1).
Dominant plant species
crested wheatgrass (Agropyron cristatum), grass
blue grama (Bouteloua gracilis), grass
Submodel
Description
The Annual Cropland state (4) occurs when land is put into cultivation. Major crops in MLRA 52 include winter and spring wheat, as well as barley.
Submodel
Description
The Post Cropland state (5) occurs when cultivated cropland is abandoned and allowed to either re-vegetate naturally or is seeded back to perennial species for livestock grazing or wildlife use. This state can transition back to the Cropland state (4) if the site is returned to cultivation.
Submodel
Mechanism
The Reference state (1) transitions to the Shortgrass state (2) when cool-season rhizomatous wheatgrasses become rare and contribute little to production. Shortgrasses, particularly the warm-season, mat-forming blue grama, as well as Sandberg bluegrass, dominate the plant community. Prolonged drought, improper grazing practices or a combination of these factors weaken the resilience of the Reference state (1) and drive its transition to the Shortgrass state (2).
Context dependence
Drought may accelerate or exacerbate change. Soils are particularly susceptible to erosion when dry.
Transition T1B
The introduction of aggressive perennial grasses (mostly crested wheatgrass)
Mechanism
The Reference state (1) transitions to the Invaded state (3) when aggressive perennial grasses, particularly crested wheatgrass, invade the Reference state (1). These communities are often adjacent to seeded pastures. Exotic plant species dominate the site in terms of cover and production. Site resilience has been substantially reduced and other rangeland health attributes such as the reproductive capacity of native grasses and soil quality have been substantially altered from the Reference state (Henderson and Naeth, 2005; Smoliak and Dormaar, 1985; Dormaar et al., 1995).
Context dependence
Close proximity to a seed source increases the likelihood of encroachment by invasive species.
Mechanism
The Reference state (1) will transition to the Cropland state (4) when the site is placed into cultivation with crops such as winter and spring wheat and barley.
Context dependence
Drought may accelerate or exacerbate change. Cropped soils are particularly susceptible to erosion during drought.
Restoration pathway R2A
range seeding, grazing land mechanical treatment, timely moisture, proper grazing management (management intensive and costly)
Mechanism
Blue grama can resist displacement by other species (Dormaar and Willms, 1990; Laycock, 1991; Dormaar et al., 1994; Lacey et al., 1995). A reduction in livestock grazing pressure alone may not be sufficient to reduce the cover of blue grama in the Shortgrass state (2) (Dormaar and Willms, 1990), and mechanical treatments may be necessary (Hart et al., 1985). Therefore, returning the Shortgrass state (2) to the Reference state (1) can require considerable cost, energy, and time.
Context dependence
Drought may inhibit recovery despite management inputs. Reseedings are more likely to fail during drought.
Transition T2A
introduction of weedy species; combined with drought and/or improper grazing management
Mechanism
The Shortgrass state (2) transitions to the Invaded state (3) when aggressive perennial grasses such as crested wheatgrass invade the Shortgrass state (2). This transition can occur when native plant communities are adjacent to seeded pastures. Exotic plant species, particularly crested wheatgrass, dominate the site in terms of cover and production. Crested wheatgrass can outcompete native grasses (Vaness and Wilson, 2007), weakening site resilience and impacting rangeland health attributes such as the reproductive capacity of native grasses (Henderson and Naeth, 2005) and soil quality (Smoliak and Dormaar, 1985; Dormaar et al., 1995).
Context dependence
Close proximity to a seed source increases likelihood of encroachment by invasive species.
Mechanism
The Shortgrass state (2) transitions to the Cropland state (4) when the site is placed into cultivation with crops such as winter and spring wheat and barley.
Context dependence
Drought may accelerate or exacerbate change. Cropped soils are particularly susceptible to erosion during drought.
Mechanism
The transition from the Invaded state (3) to the Annual Cropland state (4) occurs when the site is placed into cultivation with crops such as winter and spring wheat and barley.
Context dependence
Drought may accelerate or exacerbate change. Cropped soils are particularly susceptible to erosion during drought.
Mechanism
The transition from the Annual Cropland state (4) to the Post Cropland state (5) occurs with the cessation of cultivation. The site may also be seeded to perennial forage species such as crested wheatgrass and alfalfa or a mix of native species.
Context dependence
Drought may inhibit recovery despite management inputs. Reseedings are more likely to fail during drought.
Mechanism
Tillage or application of herbicide followed by seeding of cultivated crops, such as winter wheat, spring wheat, and barley, transitions the Post Cropland state (5) to the Cropland state (4).
Context dependence
Drought may accelerate or exacerbate change. Cropped soils are particularly susceptible to erosion during drought.
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