Loamy grassland
Scenario model
Current ecosystem state
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Management practices/drivers
Select a transition or restoration pathway
- Transition T1A More details
- Restoration pathway R2A More details
- Restoration pathway R2B 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 a grassland steppe with no invasive or exotic weed species. Grassland sites have no sagebrush and no bitterbrush. Rabbitbrush is present but a minor species in the reference State. All the functional, structural groups have one or more native species present.
Reference State Communities: 1.1 Bunchgrass and 1.2 Bunchgrass and Shrub.
Dominant Reference State Species: Bluebunch wheatgrass
Community 1.1, the Reference Community, is stable with a high cover of Idaho fescue and bluebunch wheatgrass and low cover of rabbitbrush. Community 1.2 happens when the dominant bunchgrasses exhibit lower cover. As the bunchgrasses decline the rabbitbrush increases.
At-risk Communities: • All communities in the reference state are at risk of moving to State 2. The seed source of cheatgrass, chervil and other invasive species is nearby and blowing onto most sites annually • Any community becomes at-risk of moving to State 3 when Idaho fescue and bluebunch have low vigor and annual bromes have colonized the site
Submodel
Description
Based on opportunity, State 2 represents a community dominated by either introduced forbs or invasive annual grasses. Opportunity refers to what seed in the seedbank and moisture available from year to year. Soil disturbances by rodents or badgers allow invasive species to colonize. Bunchgrasses which were dominant in the reference state are virtually missing in State 2 and the other native, functional-structural groups have been altered.
Communities for State 2: 2.1 Introduced Forb – Shrub Yellow star-thistle, etc. – Rabbitbrush 2.2 Annual Grass – Shrub Cheatgrass, etc. – Rabbitbrush Dominant Species in State 2: Annual bromes, yellow star-thistle, chervil, rabbitbrush, etc. Pathways within State 2 Result: there is a natural fluctuation between communities 2.1 and 2.2.
Primary Trigger: drier years favor the annual grasses while wetter years favor the introduced forbs/weeds.
Ecological process: in State 2 the seedbank of annual grasses and introduced forbs/weeds is full. In any given year one or more invasive species will have the opportunity to expand to become dominant or co-dominant. The next year a different species may have a similar opportunity.
Submodel
Description
State 3 represents a site that has been seeded to introduced grasses such as Sherman big bluegrass, crested wheatgrass, or intermediate wheatgrass.
Community for State 3: Introduced Seeded Grasses Dominant.
State 3 Species: Desirable seeded grasses with or without sagebrush and legumes.
Submodel
Mechanism
T1 Transition from Reference state to State 2 can go two different directions. Depending on what seed is in the seedbank and precipitation, either annual grasses or introduced forbs can dominate the site. Also, in State 2 rabbitbrush and rose make a significant increase.
Primary Trigger: Heavy grazing pressure (heavy grazing intensity, season long grazing or frequent late spring grazing) to bluebunch wheatgrass.
Ecological process. Consistent defoliation pressure to bluebunch wheatgrass cause poor vigor and shrinking crowns. This creates opportunity for invasive species and rabbitbrush. The seedbank of annual grass seed and introduced weed seed is full. In any given year one or more invasive species will have the opportunity to become dominant or co-dominant with rabbitbrush. The next year a different invasive species may have a similar opportunity. Drier years favor annual grasses and wetter years favor invasive forbs.
Indicators: increasing gaps between bluebunch wheatgrass plants. Invasive species first become established on disturbed areas and then expand to become dominant.
Mechanism
Result: Shift from State 2 back to State 1. This restoration transition does not occur without a significant commitment of time and resource inputs to restore ecological processes, native bunchgrasses and native forb species. The only difference between R2A and R2B is the selection of species. R1A uses introduced grasses while R2B uses native grasses such as Secar Snake River wheatgrass. 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 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 and Sandberg bluegrass are typical native grasses seeded on Loamy ecological site. Re-establishing the native forbs is much more problematic. Marginal success has been the result of two different methods: (1) seeding native grass and forbs at the same time, (2) seeding native grasses one year and then coming back the following year to seed the native forbs. The actual transition occurs when the seeded species have successfully established and are outcompeting the annual species for cover and dominance of resources.
Mechanism
Transition from State 2 (a community dominated by invasive annual species) to State 3, which is predominately introduced seeded grasses. 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 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. Sherman big bluegrass, crested wheatgrass, and intermediate wheatgrass are typical species seeded on Loamy ecological site. 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 seeded grass State 3 to State 2 which is dominated by invasive annual species. Primary Trigger: Chronic heavy grazing pressure (heavy grazing intensity, season long grazing or frequent late spring grazing) to seeded grasses.
Ecological process: Consistent defoliation pressure to bluebunch wheatgrass cause poor vigor, shrinking crowns and mortality. This creates opportunity for invasive species and rabbitbrush. The seedbank of annual grass seed and introduced weed seed is full. In any given year one or more invasive species will have the opportunity to become dominant or co-dominant with rabbitbrush. The next year a different invasive species may have a similar opportunity. Little of the resources remain for the desirable species.
Indicators: shrinking crowns and mortality of desirable species, increasing caps gaps between perennial species, increasing cover by annual grasses and increasing canopy by rabbitbrush/rose.
Model keys
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