Shallow Loamy-North (18-22" PZ)
Scenario model
Current ecosystem state
Select a state
Management practices/drivers
Select a transition or restoration pathway
- Transition T1A More details
- Transition T1B More details
- Transition T1C More details
- Restoration pathway R2A More details
- Restoration pathway R3A More details
- Transition T3A More details
- Transition T4A 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 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 the Reference State (1.0) is dominated by warm-season grasses, with cool-season grasses being subdominant. In pre-European times, the primary disturbance mechanisms 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. 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 prescribed burning and sometimes on areas receiving occasional short periods of rest. The Reference State is very susceptible to invasion of non-native cool-season grasses and the encroachment of conifers from adjacent sites.
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 (1.0). 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 percent or more. Tree canopy typically is dominated by ponderosa pine, but bur oak, and Rocky Mountain juniper may also be present in varying amounts.
Submodel
Description
The Native/Invaded State is dominated by native cool- and warm-season grasses, and subdominant non-native cool-season grasses. It can be found on areas that would appear to be properly managed with grazing and possibly prescribed burning. Extended periods of non-use and no fire, or long-term light grazing can result in the invasion and establishment of non-native cool-season grasses onto this site. If the native cool-season grasses decline a corresponding increase of non-native cool-season grasses can occur. The non-native cool-season grasses will include, smooth brome, Kentucky bluegrass, cheatgrass, and field brome.
Submodel
Mechanism
Continuous grazing (stocking levels above carrying capacity for extended portions of the growing season); continuous seasonal grazing (spring or fall); or heavy grazing in combination with drought will result in a transition from the Reference State (1.0) to the Shortgrass Sod State (2.0). This transition will most likely occur from the Rhizomatous Wheatgrass-Needle and Thread/Sedge/Blue Grama Plant Community (1.3).
Mechanism
Encroachment or an increase in canopy cover of native coniferous tree species; and no fire will lead the Reference State (1.0) to the Conifer/Herbaceous State (3.0). This threshold will be crossed when tree canopy reaches approximately 25 percent or more of mature trees.
Mechanism
Continuous seasonal grazing (summer); long-term light grazing; or no use and no fire, and the invasion of non-native cool-season grasses will transition the Reference State (1.0) to the Native/Invaded State (4.0).
Mechanism
Long-term prescribed grazing including proper stocking rates, change in season of use, adequate time for recovery; and a return to normal precipitation patterns following drought will transition the Shortgrass Sod State (2.0) to the Reference State (1.0). This transition may not be fast or feasible.
Relevant conservation practices
| Practice | External resources |
|---|---|
|
Prescribed Grazing |
Mechanism
Prescribed burning or mechanical brush management in conjunction with long-term prescribed grazing may lead the Conifer/Herbaceous State (3.0) to the Reference State (1.0). This would need 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 high-intensity fire or timber harvest may be needed to move the Conifer/Herbaceous State (3.0) to the Reference State (1.0). Herbaceous weed control may also be needed for treatment of weedy species.
Relevant conservation practices
| Practice | External resources |
|---|---|
|
Brush Management |
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Prescribed Burning |
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Prescribed Grazing |
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Herbaceous Weed Control |
Mechanism
Invasion of non-native cool-season grasses; fire, mechanical brush management, or prescribed burning to remove conifers will transition the Conifer/Herbaceous State (3.0) to the Native/Invaded State (4.0).
Relevant conservation practices
| Practice | External resources |
|---|---|
|
Brush Management |
|
|
Prescribed Burning |
Mechanism
Encroachment or an increase in canopy cover of native coniferous tree species, and no fire will shift the Native/Invaded State (4.0) to the Conifer/Herbaceous State (3.0). This threshold will be crossed when tree canopy reaches approximately 25 percent or more of mature trees.
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.