Natural Resources
Conservation Service
Scenario model
Current ecosystem state
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Management practices/drivers
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- Transition T1A More details
- Restoration pathway R2A More details
- Transition T3A 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 represents Alkali Terrace 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 represents Alkali Terrace where invasive broadleaf weeds and/or 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 biennial 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 perennial pepperweed
Submodel
Description
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
Submodel
Mechanism
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
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). Species that can tolerate the saline-sodic conditions include basin wildrye, beardless wildrye, tall wheatgrass, and western wheatgrass. 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
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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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.
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