Sandy Gravel (SyGr)
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 as crested wheatgrass and Kentucky bluegrass.
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Transition T2A
Prolonged drought, improper grazing management, or a combination of these factors
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Transition T2B
Displacement of native species by non-native invasive species (crested wheatgrass, noxious weeds, etc.)
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Transition T2C
Conversion to cropland
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Restoration pathway R3A
Range seeding, grazing land mechanical treatment, timely moisture, proper grazing management (management intensive and costly)
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Transition T3B
Conversion to cropland
More details -
Transition T4A
Conversion to cropland
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Transition T5A
Cessation of annual cropping
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Transition T6A
Conversion to cropland
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 one community phase characterized by mid-statured bunchgrasses. This state is considered extinct and is included here for historical reference purposes.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 cover and production. In general, this state was resilient to grazing; however, localized areas likely received heavy grazing, which resulted in the species composition shifting to short-statured species. Fire most likely resulted in short-term shifts in species composition to more warm-season grasses such as blue grama and fewer cool-season bunchgrasses.
Submodel
Description
The Contemporary Reference State (2) contains two community phases characterized by mid-statured bunchgrasses. It evolved under the combined influences of climate, grazing, and fire, with climatic variation having the greatest influence on cover and production. This state differs from the historical reference state in that it is influenced by introduced plant species and has altered fire and grazing regimes. In general, this state is resilient to grazing and fire, although these factors can influence species composition in localized areas. Lesser spikemoss, also known as dense clubmoss (Selaginella densa), may occur in some areas; its dynamics on this site are not well understood.
Submodel
Description
The Shortgrass State (3) consists of one community phase. The dynamics of this state are driven by long-term drought, improper grazing management, or a combination of these factors. Shortgrasses increase with long-term improper grazing at the expense of cool-season midgrasses (Coupland, 1961; Biondini and Manske, 1996). In particular, communities of blue grama can alter soil properties, creating conditions that resist establishment of other grass species (Dormaar and Willms, 1990; Dormaar et al., 1994). Reductions in stocking rates can reduce shortgrass cover and increase the cover of cool-season midgrasses, although this recovery may take decades (Dormaar and Willms, 1990; Dormaar et al., 1994).
Submodel
Description
The Invaded State (4) occurs when invasive plant species invade adjacent native grassland communities and displace the native species. Data suggest that native species diversity declines significantly when invasive species exceed 30 percent of the plant community. The non-native perennial grass crested wheatgrass is the greatest concern on this ecological site. Crested wheatgrass has been planted on an estimated 20 million acres in the western U.S. since the 1930s (Holechek, 1981). 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). Plant communities dominated by crested wheatgrass have significantly less cover of native grass and forb species (Heidinga and Wilson, 2002). Invasive grass species can invade relatively undisturbed grasslands, and it is not clear what triggers them to displace native species. Proximity to seeded areas is likely a major contributing factor as crested wheatgrass cover decreases with increasing distance from seeded areas (Heidinga and Wilson, 2002).
Noxious weeds such as leafy spurge are not widespread in MLRA 53A, but they can be a concern in localized areas. 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
Description
The Cropland State (5) occurs when land is put into cultivation. Major crops in MLRA 53A are small grains such as wheat.
Submodel
Description
The Post-Cropland State (6) occurs when cultivated cropland is abandoned and allowed to either revegetate naturally or is seeded back to perennial species for grazing or wildlife use. This state can transition back to the Cropland State (5) if the site is put back into cultivation.
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
Prolonged drought, improper grazing practices, or a combination of these factors weaken the resilience of the Contemporary Reference State (2) and drive its transition to the Shortgrass State (3). The Contemporary Reference State (2) transitions to the Shortgrass State (3) when mid-statured grasses become rare and contribute little to production. Shortgrasses such as blue grama and prairie Junegrass dominate the plant community.
Mechanism
The Contemporary Reference State (2) transitions to the Invaded State (4) when aggressive perennial grasses or noxious weeds displace native species. The most common concern is crested wheatgrass, which is a widespread invasive species in the Northern Great Plains (Henderson and Naeth, 2005). The precise triggers of this transition are not clear, but data suggest that invasion from adjacent seedings is a major contributing factor (Heidinga and Wilson, 2002). In addition, other rangeland health attributes, such as reproductive capacity of native grasses and soil quality, have been substantially altered.
Mechanism
Tillage or application of herbicide followed by seeding of cultivated crops, such as winter wheat, spring wheat, and barley, transitions the Contemporary Reference State (2) to the Cropland State (5).
Mechanism
A reduction in livestock grazing pressure alone may not be sufficient to reduce the cover of shortgrasses in the Shortgrass State (3) (Dormaar and Willms, 1990). Blue grama, in particular, can resist displacement by other species (Dormaar and Willms, 1990; Laycock, 1991; Dormaar et al., 1994; Lacey et al., 1995. Intensive management such as reseeding and mechanical treatment may be necessary (Hart et al., 1985), but these practices are labor intensive and costly. Therefore, returning the Shortgrass State (3) to the Contemporary Reference State (2) may require considerable energy and cost and may not be feasible within a reasonable amount of time.
Mechanism
Tillage or application of herbicide followed by seeding of cultivated crops, such as winter wheat, spring wheat, and barley, transitions the Shortgrass State (3) to the Cropland State (5).
Mechanism
Tillage or application of herbicide followed by seeding of cultivated crops, such as winter wheat, spring wheat, and barley, transitions the Invaded State (4) to the Cropland State (5).
Mechanism
The transition from the Cropland State (5) to the Post-Cropland State (6) occurs with the cessation of cultivation. The site may also be seeded to perennial forage species. Such seedings may be comprised of introduced grasses and legumes, or a mix of native species.
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.