Thin Upland-South (16-18" PZ)
Scenario model
Current ecosystem state
Select a state
Management practices/drivers
Select a transition or restoration pathway
- Transition T1b More details
- Transition T1a More details
- Restoration pathway R2 More details
- Restoration pathway R3 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 the natural range of variability that dominates the dynamics of this ecological site. This state is dominated by warm-season grasses, with cool-season grasses being subdominant. In pre-European times, the primary disturbance mechanisms for this site in the reference condition included occasional fire and grazing by large ungulates. Timing of fires and grazing coupled with weather events dictated the dynamics that occurred within the natural range of variability. Taller cool- and warm-season grasses would have declined and a corresponding increase in short statured grass and grass-like species would have occurred. Today, a similar state 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.
Submodel
Description
This state is a result of overgrazing (individual plants of selected species being repeatedly grazed due to continuous grazing systems which allow for long paddock occupation periods). This type of grazing causes reduced vigor of the selected species (i.e., typically the most desired by grazing ungulates). As the photosynthetic area of these species is repeatedly removed, carbohydrate production needed for root respiration is inadequate, and the root systems of these species begin to falter. The shorter, more grazing tolerant species are given the advantage, and will dominate the site. In the early stages of this State, mid and tall grass remnants may be present in sufficient quantities to allow for recovery to the Reference State. Over time, this recovery will become less likely due to higher runoff and reduced infiltration.
Submodel
Description
This state consists of areas where tree canopy increases to a level that impedes the reproductive capability of the major native perennial grass species. The increase in tree canopy is a result of a disruption of the natural historic fire regime that kept the trees at an immature stage. This State is reached when mature tree canopy reaches about 25% or more. Tree canopy typically is dominated by ponderosa pine, but bur oak, eastern redcedar, and Rocky Mountain juniper may also be present in varying amounts.
Submodel
Mechanism
Encroachment and/or an increase in canopy cover of native coniferous tree species will lead this plant community phase over a threshold to the Conifer/Herbaceous State (State 3). This threshold will be crossed when tree canopy reaches about 25% or more of mature trees.
Mechanism
Heavy continuous grazing (stocking levels well above carrying capacity for extended portions of the growing season) or a combination of disturbances for extended periods of time will lead this plant community over a threshold and result in the 3.1 Sedge/Blue Grama/Fringed Sagewort Plant Community Phase within the Shortgrass Sod State (State 3).
Mechanism
Prescribed burning in conjunction with long-term prescribed grazing may lead this plant community across a threshold back to the Reference State (State 1). This would have to take place before the trees reach maturity and are still susceptible to fire, and reproductive propagules of the perennial grasses are still present. After trees reach maturity, a crown fire or timber harvest would be needed to move this plant community over the threshold back to the Reference State (State 1).
Relevant conservation practices
| Practice | External resources |
|---|---|
|
Prescribed Burning |
|
|
Prescribed Grazing |
Mechanism
Long-term prescribed grazing (moderate stocking levels coupled with adequate recovery periods, or other grazing systems such as high-density, low-frequency 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 Reference State (State 1). This will likely take a long period of time, possibly up to 10 years or more, and recovery may not be attainable. Under certain circumstances, the harsh conditions created by the shortgrass sod can lead to the elimination of invasive grass species such as Kentucky bluegrass.
Relevant conservation practices
| Practice | External resources |
|---|---|
|
Prescribed Grazing |
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.