Alkali Terrace
Scenario model
Current ecosystem state
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Management practices/drivers
Select a transition or restoration pathway
- Transition T1 More details
- Restoration pathway R1 More details
- Transition T2 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
State 1 Narrative:
State 1 represents grassland sites with no invasive or exotic species. All the functional, structural groups have one or more species.
By cover saltgrass dominates the Reference Community
By weight basin wildrye dominates the Reference Community
Reference State Community Phases:
1.1 Reference Basin wildrye – Saltgrass
1.2 Rhizomatous Saltgrass – Basin wildrye
Dominate Reference State Species:
Basin wildrye, saltgrass
At-risk Communities:
• All communities in the reference state are at risk of invasive species. Annual or biennial weeds and annual grass seeds blow onto most sites annually
Submodel
Description
State 2 Narrative:
State 2 represents the Alkali Terrace ecological site where invasive broadleaf weeds and invasive annual grasses have prominence. Basin wildrye is all but missing and saltgrass remains as a patchwork of spots and clumps.
State 2 can have two variations both with or without rabbitbrush:
1. Broadleaf annual or biennial weeds with saltgrass patches
2. Annual grasses with saltgrass patches
Community Phases for State 2:
Invasive broadleaf annual or biannual weeds with patches of saltgrass
Invasive annual grasses with patches of saltgrass
Some Invasive Species in State 2:
cheatgrass slender cinquefoil rabbitsfoot grass
foxtail barley pepperweed
.
Description
State 3 Narrative:
State 3 represents a site that has been seeded to desirable grasses such as basin wildrye, beardless wildrye, tall wheatgrass, or western wheatgrass.
Community Phases for State 3:
3.1 Seeded Grass
3.2 Shrub – Seeded Grass
Pathways within State 3
3.1a Result: Shift from Community 3.1 seeded grasses to community 3.2 shrub-seeded grasses.
Primary Trigger: Grazing pressure (heavy intensity, season long grazing, frequent late spring grazing) to desirable seeded grasses.
Ecological Process: With consistent grazing pressure, seeded grasses have poor vigor, shrinking crowns and some mortality. Rabbitbrush seed which blows onto the site establishes a crop of seedlings. Rabbitbrush cover expands as the shrubs grow.
Mechanism
T1 Result: Shift from Reference State to State 2 with invasive species
Primary Trigger: Grazing pressure (heavy intensity, season long grazing, frequent late spring grazing) to basin wildrye.
Ecological process: with consistent grazing pressure basin wildrye has poor vigor, shrinking crowns and mortality. Initially, saltgrass increases but then declines with further grazing pressure. Invasive species colonize and as the deterioration continues, eventually dominate the site.
Indicators: Increasing gaps between basin wildrye plants, decreasing cover of saltgrass and increasing cover of invasive species.
Mechanism
R1 Transition from State 2, a community dominated by invasive annual species, to State 3, which is predominately desirable seeded grasses. Species selection for the seeding is critical as the site is moderately saline-sodic.
This restoration transition does not occur without significant time and inputs to control weeds, prepare a seedbed, seed desirable species, and post-seeding weed control and management. It may take two years or longer to kill invasive annual species and remaining saltgrass, and to exhaust the seedbank of invasive weed seeds. Care must be taken to maintain soil structure so that the seedbed has many safe-sites for the seed. Seed placement must be managed to achieve seed-soil contact at a very shallow depth (about 1/8 inch is desired). Basin wildrye, beardless wildrye, tall wheatgrass, and western wheatgrass are typical species seeded on Alkali Terrace ecological site. Proper grazing management is essential to maintain the stand post-seeding.
The actual transition occurs when the seeded species have successfully established and are outcompeting the annual species for cover and dominance of resources.
Mechanism
T2 Result: Shift from State 3 seeded grasses to State 2 with invasive species
Primary Trigger: Grazing pressure (heavy intensity, season long grazing, frequent late spring grazing) to desirable seeded grasses.
Ecological Process: with consistent grazing pressure desirable grasses have poor vigor, shrinking crowns and mortality. This allows invasive species to colonize and then expand to a position of dominance.
Indicators: increasing gaps between basin wildrye plants, increasing cover of invasive species
Model keys
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Ecological site groups
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.