Shallow Loam
Scenario model
Current ecosystem state
Select a state
Management practices/drivers
Select a transition or restoration pathway
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Transition T1A
Disturbance (human, mechanical, or animal), Continuous grazing of perennial grasses and black sagebrush
More details -
Restoration pathway R2A
Brush removal and seeding
More details -
Transition T2A
Repeated fires within a short timespan, Disturbance (human, mechanical, or animal), Continuous grazing of perennial grasses and black sagebrush
More details -
No transition or restoration pathway between the selected states has been described
Target ecosystem state
Select a state
Description
The Reference State is a shrubby grassland and consists of black sagebrush, western wheatgrass, other grasses, and scattered shrubs. Western wheatgrass, sideoats grama, prairie Junegrass, and squirreltail contribute to a sparse grassland appearance. Black sagebrush has a noticeable place on this site under the Reference State. Fluctuations in species composition and relative production may change depending on precipitation and other climatic factors. Black sagebrush communities historically experienced an extended fire-return interval due to widely-spaced shrubs and low herbaceous (fine-fuel) production. The establishment of sagebrush occurs solely from seed, and recruitment pulses are episodic and based on favorable climatic conditions. Browsing of black sagebrush needs monitoring to ensure it does not become too heavy and that new and young seedlings are establishing in numbers high enough to replace the current stand. Drought can compound the problem of heavy browsing (Winward, 2004). Continuous grazing, which allows repetitive grazing of the desirable species, eventually leads to a decrease in the following species from the plant community: western wheatgrass, sideoats grama, prairie Junegrass, Arizona fescue, and needle and thread. Undesirable species that increase from continuous grazing include blue grama, rabbitbrush, and black sagebrush. If these species continue to dominate, severe site deterioration will follow.
Submodel
Description
The Cushion Plant State is present following frequent and heavy browsing of black sagebrush during the winter. The crowns of heavily-browsed black sagebrush become rounded instead of the typical irregular, spreading, U-shape. Black sagebrush can be almost level with the ground after severe browsing (Fryer, 2009). This state is at risk for excessive wind and water erosion, and the biotic integrity is also compromised. The bare ground cover increases in this state, and the interspaces between plants are more sizeable. Black sagebrush is still present on the site and may dominate the total shrub cover. However, black sagebrush is approximately 2 to 4 inches in height rather than the typical 4 to 12 inches. Plants such as western wheatgrass, yellow rabbitbrush, and low-growing forbs dominate the site in the Cushion Plant State.
Submodel
Mechanism
There are several drivers for this transition. The first driver for this transition is long-term, excessive, year-long livestock grazing. Trampling and bedding (especially by large flocks of domestic sheep), prolonged animal bedding, salting, watering, and use of handling locations can accelerate this transition. The second driver is long-term damage caused by trail and road development or excessive trail development. The third driver is long-term herbivory by wildlife and upland species that diminish the shrubs and grass. Herbivory can happen on sites located on ridges and hills where the snow melts and allows for year-round use by livestock and wildlife. The only plants remaining are those tolerant of drought, infertile soil, mechanical disturbances, and herbivory. A combination of all three drivers in varying proportions can also trigger this transition.
Mechanism
The driver for this restoration pathway is grazing only during the non-growing season for the herbaceous component and wildlife management. The broadcast reseeding of native perennial forbs and grasses must accompany this management regime to trigger the pathway.
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.