Shallow Clay
Scenario model
Current ecosystem state
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Management practices/drivers
Select a transition or restoration pathway
- Transition 1A More details
- Transition 1B More details
- Restoration pathway 2A More details
- Transition 3A More details
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No transition or restoration pathway between the selected states has been described
Target ecosystem state
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Description
This State represents what is believed to show the natural range of variability that dominated the dynamics of the ecological site prior to European settlement. This site in Reference, is dominated by cool-season grasses and sub-dominant warm-season grass. Grazing, the lack of grazing, and drought are the major drivers between plant communities. Continuous season-long grazing can push this plant community to a point where short grasses become the dominant functional group.
Submodel
Description
The Shortgrass State is dominated by warm-season shortgrass species and upland sedges. This state is the result of grazing patterns that did not provide adequate recover time for the mid and tall statured warm- and cool-season grasses. The hydrologic function of this site is dramatically altered. Runoff is high and infiltration is low. This State is very resistant to change through grazing management alone.
Submodel
Description
This State has been invaded by Kentucky bluegrass and/or smooth brome but not at the levels where the plant community is dominated by these species. This State is ‘At Risk’ of transitioning to the Invaded State (4.0) which is dominated by smooth brome and/or Kentucky bluegrass. Prescribed burning and/or chemical herbicides, and targeted grazing can be used to reduce the amount of smooth brome and Kentucky bluegrass in the plant community but it will not be completely removed. At this point a restoration pathway to the Reference State does not exist.
Submodel
Description
This state is the result of invasion and dominance of introduced species. This state is characterized by the dominance of Kentucky bluegrass and smooth brome, and an increasing thatch layer that effectively blocks introduction of other plants into the system. Plant litter accumulation tends to favor the more shade tolerant, introduced grass species. The nutrient cycle is also 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 soil biological activity is altered, 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 cause a reduction in the invasive grass dominance. Preliminary studies would tend to indicate this threshold may exist when Kentucky bluegrass exceeds 30 percent of the plant community and native grasses represent less than 40 percent of the plant community composition. Plant communities dominated by Kentucky bluegrass have significantly less cover and diversity of native grasses and forb species (Toledo, D. et al., 2014).
Submodel
Mechanism
Heavy continuous season-long grazing, heavy continuous seasonal grazing, and/or drought will shift this plant community to the Shortgrass State (2.0).
Mechanism
Invasion of non-native, cool-season grasses, no use, no fire or long-term light grazing will convert this plant community to the Native/Invaded State (3.0).
Mechanism
Long-term prescribed grazing that provides for proper stocking, change in season of use and adequate time for recovery, will move this plant community back to the Reference State (1.0), assuming an adequate seed/vegetative source is present. This could require significant time and input to achieve and a return to normal precipitation patterns, and in the end may not meet management objectives.
Mechanism
Heavy continuous season-long grazing, or no use and no fire, or long-term light grazing will cause a transition from the Native/Invaded State (3.0) to the Invaded State (4.0). The ecological threshold can be identified by the percentage of non-native cool-season species in the Plant Community. Preliminary studies would tend to indicate this threshold may exist when Kentucky bluegrass exceeds 30 percent of the plant community and native grasses represent less than 40 percent of the plant community composition (Toledo, D. et al., 2014). Smooth brome is assumed to follow a similar ecological threshold but is not documented scientifically.
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.