Natural Resources
Conservation Service
Scenario model
Current ecosystem state
Select a state
Management practices/drivers
Select a transition or restoration pathway
- Transition T1B More details
- Transition T1C More details
- Transition T1A More details
- Transition T7A More details
- Restoration pathway R2A More details
- Transition T2A More details
- Transition T2B More details
- Transition T7A More details
- Restoration pathway R3A More details
- Transition T3A More details
- Transition T7A More details
- Transition T4A More details
- Transition T4B More details
- Transition T4C More details
- Transition T7A More details
- Transition T5A More details
- Transition T7A 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
The Reference State represents the best estimate of the natural range of variability that dominated the dynamics of the ecological site prior to European settlement. The Reference State (1.0) is dominated by cool-season grasses and subdominant warm-season grasses. Grazing, the lack of grazing, fire, and drought are the major drivers between plant communities. Continuous season-long grazing can push the site into a state dominated by warm-season shortgrasses (2.0). Non-use, no fire, and invasion of non-native cool-season grasses result in a transition to a Native/Invaded State (4.0).
Submodel
Description
The Shortgrass Sod State (2.0) is dominated by shortgrass species and upland sedges. This state is the result of grazing patterns that did not provide adequate recovery time for cool-season wheat and needlegrasses. The hydrologic function of this site is dramatically altered from the reference state. Runoff is high, and infiltration is low. State 2.0 is very resistant to change through grazing management alone.
Historically, rangeland mechanical treatment has been an option to improve forage production and plant species composition on this site. These mechanical treatments included contour furrowing, contour pitting, terracing, chiseling, and disking. The purpose of the treatments was to mechanically break up a sod-bound vegetative condition or compacted soils, resulting in less runoff and better infiltration. Many of these treatments were implemented during the 1930s through the 1970s. The results were mixed, primarily due to improper grazing management following the renovation practice. Another drawback, in addition to the cost, is that these practices result in a nearly permanently roughed ground surface.
Submodel
Description
This state is the result of very heavy, concentrated disturbance, such as concentrated rodent activity or livestock concentration. This state can also develop as a result of invasion by highly competitive or noxious weeds. Extended periods of drought accompanied by heavy grazing can also push an at-risk plant community phase to this state. In most cases, this state is dominated by pioneer perennial and annual grasses and forbs. The extent of bare ground is also much greater than in any other plant community phase.
Submodel
Description
The Native/Invaded State is dominated by native cool- and warm-season grasses. Subdominant species are non-native cool-season grasses. This state is in areas that are properly managed for grazing and possibly prescribed burning and in areas receiving occasional short periods of rest. If the native cool-season grasses decrease, a corresponding increase of non-native cool-season grasses can occur. The non-native cool-season grasses include Kentucky bluegrass, smooth brome, cheatgrass, field brome, and possibly crested wheatgrass.
Submodel
Description
This state is the result of invasion and dominance by non-native cool-season grass species. This state is characterized by the dominance of smooth brome and Kentucky bluegrass. Heavy grazing or long-term light grazing (understocked) tend to result in an increase of smooth bromegrass. Non-use and no fire tend to benefit Kentucky bluegrass because of an increasing thatch layer that effectively blocks the introduction of other plants into the system.
Accumulation of plant litter favors the more shade-tolerant introduced grass species. The nutrient cycle is impaired, and the result is typically a higher level of nitrogen, which also favors the introduced species. Increasing plant litter decreases the amount of sunlight reaching plant crowns, thereby shifting competitive advantage to shade-tolerant, introduced grass species. Studies indicate that biological activity is altered in the soil, and this shift apparently exploits the soil microclimate and encourages growth of the introduced grass species. Once the threshold is crossed, a change in grazing management alone cannot reduce the dominance of the invasive grasses. Preliminary studies indicate this threshold may exist when Kentucky bluegrass exceeds 30 percent of the plant community and native grasses represent less than 40 percent. Plant communities dominated by Kentucky bluegrass have significantly less cover and diversity of native grasses and forb species (Toledo et al., 2014).
Submodel
Description
Any plant community can transition to the Disturbed State (6.0). The two separate vegetative plant communities, Go-Back and Seeded, are highly variable in nature. They are derived through different management scenarios and are not related by succession. Infiltration, runoff, and soil erosion vary depending on the vegetation.
The Go-Back Plant Community (6.1) is in areas that were previously tilled for crop production and then abandoned. The plant community is greatly influenced by the plant communities on adjacent land. The Seeded Plant Community (6.2) is typically in areas that were tilled and then seeded to a perennial forage species or mix of species.
Submodel
Mechanism
Continuous season-long grazing, continuous seasonal grazing, or heavy grazing in combination with drought results in the Reference State transitioning to the Shortgrass Sod State (2.0). This transition is most likely to occur from the Western Wheatgrass-Buffalograss-Blue Grama Plant Community (1.2).
Mechanism
Heavy, continuous season-long grazing, frequent and severe defoliation, or heavy disturbance results in the Reference State transitioning to the Early Seral State (3.0).
Mechanism
Continuous summer seasonal grazing, long-term light grazing, or no use and no fire, and the subsequent invasion of non-native cool-season grasses, results in the Reference State (1.0) transitioning to the Native/Invaded State (4.0).
Mechanism
Heavy disturbance, including soil erosion, tillage, abandoning cropland, or seeding to improved pasture species, results in a transition to the Disturbed State (6.0).
Mechanism
Long-term prescribed grazing may potentially convert the Buffalograss-Blue Grama Sod Plant Community (2.1) to the Reference State (1.0). The transition is most probably to the Western Wheatgrass-Buffalograss-Blue Grama Plant Community (1.2), assuming adequate seed and vegetative sources are present. This transition could require significant time and inputs to achieve and, in the end, may not meet management objectives.
Relevant conservation practices
| Practice | External resources |
|---|---|
|
Prescribed Grazing |
Mechanism
Heavy, continuous season-long grazing, frequent severe defoliation, or heavy disturbance typically convert Plant Community 2.0 to the Early Seral State (3.0).
Mechanism
Long-term prescribed grazing that includes change in season of use, adequate time for recovery, and a return to normal precipitation patterns might transition Plant Community 2.0 to the Native/Invaded State (4.0). The direction of this transition towards the Native/Invaded State (4.0) is due to the invasion of non-native, cool-season perennial grasses. This transition may not be fast or feasible.
Relevant conservation practices
| Practice | External resources |
|---|---|
|
Prescribed Grazing |
Mechanism
Heavy disturbance, including soil erosion, tillage, abandoning cropland, or seeding to improved pasture species, results in a transition to the Disturbed State (6.0).
Mechanism
Removal of management-induced disturbance coupled with long-term prescribed grazing that includes change in season of use and adequate recovery time following grazing may return the Threeawn-Annual Plant Community (3.1) to the Shortgrass Sod State (2.0). Herbaceous weed control may also be needed. This transition could require significant time and input to achieve and, in the end, may not meet management objectives.
Relevant conservation practices
| Practice | External resources |
|---|---|
|
Prescribed Grazing |
|
|
Herbaceous Weed Control |
Mechanism
This transition results from removal of management-induced disturbance, herbaceous weed control, and prescribed grazing that includes proper stocking, change in season of use, and deferment that provides time for adequate recovery. The invasion of non-native cool-season perennial gasses likely transitions the Threeawn-Annuals Plant Community (3.1) to the Invaded State (5.0). This transition may not meet management objectives.
Relevant conservation practices
| Practice | External resources |
|---|---|
|
Prescribed Grazing |
|
|
Herbaceous Weed Control |
Mechanism
Heavy disturbance, including soil erosion, tillage, abandoning cropland, or seeding to improved pasture species, results in a transition to the Disturbed State (6.0).
Mechanism
Continuous season-long grazing, continuous seasonal grazing, or heavy grazing in combination with drought results in the Native/Invaded State (4.0) transitioning to the Shortgrass Sod State (2.0).
Mechanism
Heavy, continuous season-long grazing, frequent and severe defoliation, or heavy disturbance results in the Native/Invaded State (4.0) transitioning to the Early Seral State (3.0).
Mechanism
Heavy, continuous season-long grazing or long-term light grazing results in the Native/Invaded State (4.0) transitioning to the Invaded State (5.0). Extended periods of non-use and no fire result in build-up of a heavy litter layer, which favors cool-season non-natives grasses, such as Kentucky bluegrass and other non-native species, leading to the transition.
Mechanism
Heavy disturbance, including soil erosion, tillage, abandoning cropland, or seeding to improved pasture species, results in a transition to the Disturbed State (6.0).
Mechanism
Herbaceous weed control followed by long-term prescribed grazing may result in this plant community transitioning to the Native/Invaded State (4.0). The prescribed grazing should include proper stocking, change in season of use, and deferment that provides time for adequate recovery. This transition could require significant time and input to achieve and, in the end, may not meet management objectives.
Relevant conservation practices
| Practice | External resources |
|---|---|
|
Prescribed Burning |
|
|
Prescribed Grazing |
|
|
Herbaceous Weed Control |
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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