Claypan
Scenario model
Current ecosystem state
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Management practices/drivers
Select a transition or restoration pathway
- Transition T1 More details
- Transition T2 More details
- Restoration pathway R1 More details
- Restoration pathway R2 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
This state represented the natural range of variability that dominated the dynamics of this ecological site. This state was dominated by cool season grasses. The primary disturbance mechanisms for this site in the reference condition included frequent fire and grazing by large herding ungulates. Timing of fires and grazing coupled with weather events dictated the dynamics that occurred within the natural range of variability. Cool season species decline and a corresponding increase in warm season grasses will occur.
Submodel
Description
This state represents the more common range of variability that exists with higher levels of grazing management but in the absence of periodic fire followed by short-term intensive grazing. This state is dominated by cool- and warm-season grasses. It can be found on areas that are properly managed with grazing and/or prescribed burning, and sometimes on areas receiving occasional short periods of rest. Cool-season species can decline and a corresponding increase in short, warm-season grasses will occur.
Submodel
Description
This state is the result of invasion and dominance of Kentucky bluegrass and/or smooth brome. This state is characterized by these two species and an increasing thatch layer that effectively blocks introduction of other plants into the system. Once the state is well established, even drastic events such as high intensity fires driven by high fuel loads of litter and thatch, will not result in more than a very short term reduction of these two species. These events may reduce the dominance of the sodgrasses, but due to the large amount of rhizomes in the soil there is no opportunity for the native species to establish and dominate before the sodgrasses rebound and again dominate the system.
Submodel
Mechanism
This is the transition from the native grass dominated reference state to a state that has been invaded by introduced cool-season grass species. When propagules of Kentucky bluegrass or some other non-native species are present, this transition occurs as natural and/or management actions favor a decline in the composition of warm and cool season native grasses and an increase in cool-season sodgrasses. This transition is compounded by a change in the historic grazing and fire regime where native herbivores would follow periodic fires with grazing. This historic grazing/fire sequence has largely been replaced by chronic season-long or heavy late season grazing. Complete rest from grazing and suppression of fire can also lead to this transition. The threshold between states is crossed when Kentucky bluegrass, Canada bluegrass, smooth brome, crested wheatgrass and/or other introduced species become established on the site. In some cases, these introduced species are part of functional/structural groups that were not present in the Reference State.
Mechanism
Complete rest from grazing and elimination of fire are the two major contributors to this transition, especially when smooth brome is present. Preliminary studies indicate this threshold may exist when Kentucky bluegrass exceeds 30% of the plant community and native grasses represent less than 40% of the plant community composition. The opportunity for high intensity spring burns is severely reduced by early green up and increased moisture and humidity at the soil surface and grazing pressure cannot cause a reduction in sodgrass dominance. Production is limited to the sod forming species. Infiltration continues to decrease and runoff increases, energy capture into the system is restricted to early season low producing species. Nutrient cycling is limited by root depth of the dominate species.
Mechanism
Long-term prescribed grazing (moderate stocking levels coupled with adequate recovery periods, or other grazing systems intended to treat specific species dominance, or periodic light to moderate stocking levels possibly including periodic rest) may lead this plant community phase over a threshold to the 2.0 Native Invaded Grass State. Pest management (i.e., herbicide) may also be needed to suppress cool-season invasive grasses. This will likely take a long period of time, possibly up to 10 years or more, and recovery may not be attainable. Success depends on whether native reproductive propagules, which may not always be readily visible, remain intact on the site.
Relevant conservation practices
| Practice | External resources |
|---|---|
|
Prescribed Grazing |
|
|
Integrated Pest Management (IPM) |
Mechanism
Significant intervention is required to shift plant community phase 4.1 into the Native Invaded State. The application of herbicides combined with range seeding or mechanical treatment combined with range seeding may be necessary to achieve this shift. A high level of grazing management would be required after these inputs in order to maintain the resulting plant community and prevent its return to community phase 4.1 or 3.1.
Model keys
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Ecological sites
Major Land Resource Areas
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.