Cool Loamy threetip sagebrush
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 sagebrush steppe with no invasive or exotic species. All the functional, structural groups have one or more species. Reference State Community Phases: 1.1 Reference Idaho fescue-bluebunch wheatgrass and threetip sagebrush 1.2 Shrub Steppe Threetip sage and Idaho fescue and bluebunch wheatgrass Communities 1.1 and 1.2 are stable with a high cover of Idaho fescue/bluebunch wheatgrass and low to moderate cover of threetip sage. 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, threadleaf sedge and threetip sage increase and Japanese brome colonizes the disturbed sites. Dominate Reference State Species: Threetip sagebrush, Idaho fescue, bluebunch wheatgrass 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 Idaho fescue and bluebunch have low vigor the cover of threadleaf sedge 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 threadleaf sedge or Japanese brome. The site should be inter-seeded that fall or early the following spring
Submodel
Description
State 2 represents a sedge-shrub 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. Community Phases for State 2: 2.1 Sedge-Shrub Threadleaf sedge-Threetip sage In Community 2.1, sod-forming threadleaf sedge has expanded to a position of dominance. Threetip sage has increased but is quite variable. In some instances, threetip sage is co-dominant and in other instances is secondary to threadleaf sedge. But when the dominant bunchgrasses exhibit low vigor and decline, threadleaf sedge and threetip sage increase. Japanese brome or ventenata may colonize the disturbed sites. The loss of soil biological crusts contributes to the invasion by annual grasses. Dominate Species in State 2: Threadleaf sedge, threetip sagebrush
Submodel
Description
State 3 represents sites that have been seeded. The site was no longer productive for intended uses. So, a commitment was made to kill existing stand and seed more desirable species. Control of threadleaf sedge would be critical to success.
Communities for State 3: 3.1 Seeded Grasses and 3.2 Shrub and Seeded Grasses Refer to narrative for R1
Dominant species in State 2: Desirable seeded grass species with or without a legume.
Submodel
Mechanism
The Reference State has only a minor amount of threadleaf sedge and no invasive species. In State 2 threadleaf sedge makes a significant increase along with threetip sage. Primary Trigger: Heavy grazing pressure (heavy grazing intensity, season long grazing or frequent late spring grazing) on Idaho fescue and bluebunch wheatgrass. Also, soil disturbances by rodents, badgers or rabbits allow annual grasses to colonize. Ecological process. The cover of threadleaf sedge and threetip sagebrush increase as the cover of the dominant bunchgrasses decline. Japanese brome or other invasive annual grasses may colonize disturbed areas and later, expands as opportunity presents itself. Indicators: increasing gaps between dominant bunchgrasses (Idaho fescue and bluebunch wheatgrass). Expanding cover of threadleaf sedge and threetip sage, and invasive species colonizing disturbed sites.
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
Desirable seeded species have low vigor and are declining. The cover of threadleaf sedge, threetip sage and invasive annuals is expanding. The competitive edge This transition occurs when the cover of dominant bunchgrasses drops to less than 10 percent threadleaf sedge has 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. Indicators: Declining vigor and cover for the seeded species. Increasing canopy gaps between perennial species. Increasing cover of threadleaf sedge, threetip sage and cover of exotic species.
Model keys
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