Cool Loamy
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
Communities 1.1 and 1.2 are stable with a high cover of bluebunch wheatgrass/Idaho fescue and low to moderate cover of Wyoming big or threetip sagebrush. Both communities have a minor amount of threadleaf sedge which is native, but also rhizomatous. But when the dominant bunchgrasses exhibit low vigor and decline, sagebrush and threadleaf sedge increase and Japanese brome colonizes the disturbed sites. Dominate Reference State Species: Bluebunch wheatgrass, Idaho fescue, sagebrush (Wyoming big/threetip) At-risk Communities: • All communities in the reference state are at risk of invasive species. The seed source for Japanese brome or other invasive annual seed blows onto most sites annually. • Any community becomes at-risk of moving to State 3 when bluebunch wheatgrass and Idaho fescue have low vigor, the cover of sagebrush is expanding, and Japanese brome has colonized the site. • Any community is at risk when fire kills the Idaho fescue plants. The holes could quickly be filled by Japanese brome, cheatgrass or threadleaf sedge. The site should be inter-seeded that fall or early the following spring
Submodel
Description
State 2 represents a shrub-invasive annual grass community. Many native functional, structural groups have been altered or are missing. Annual grasses such as Japanese brome are present but secondary to the shrub and sedge components.
Submodel
Mechanism
The Reference State has only a minor amount of threadleaf sedge and no invasive species. In State 2 sagebrush and invasive annual grasses become dominant. Primary Trigger: Heavy grazing pressure (heavy grazing intensity, season-long grazing or frequent late-spring grazing) on bluebunch wheatgrass and Idaho fescue. Also, soil disturbances by rodents and badgers allow annual grasses to colonize. Ecological process. Consistent defoliation pressure (heavy grazing, season long grazing or frequent late spring grazing) The cover of sagebrush increases, and invasive annual grasses have colonized the site and become prominent. Indicators: increasing gaps between dominant bunchgrasses (bluebunch wheatgrass and Idaho fescue). Expanding cover of sagebrush and invasive species.
Mechanism
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. This requires a commitment of two years or more to kill threadleaf sedge and for weed control. 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 very shallow depth (about 1/8 inch is desired). Proper grazing management is essential to maintain the stand post-seeding. Secar Snake River wheatgrass, thickspike wheatgrass, Sherman big bluegrass, Sandberg bluegrass, and crested or intermediate wheatgrass are typical species seeded on Cool Loamy ecological site. The actual transition occurs when the seeded species have successfully established and are outcompeting the threadleaf sedge, shrubs and annual species for cover and dominance of resources.
Mechanism
This transition occurs when the cover of seeded grasses drops to less than 10% and invasive annual grasses have assumed a dominant position in the community. Primary trigger: heavy grazing pressure (heavy grazing intensity, season long grazing or frequent late spring grazing) reduces the vigor of the desirable seeded species. Ecological process: consistent defoliation pressure to desirable seeded grasses results in poor vigor, shrinking crowns and mortality. The competitive edge has shifted from seeded grasses to shrubs and annual grasses. Indicators: Declining cover for the seeded species. Increasing canopy gaps between desirable seeded species. Increasing cover of sagebrush and 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.