Natural Resources
Conservation Service
Loamy, Bunchgrass, 15-18" ppt.
Scenario model
Current ecosystem state
Select a state
Management practices/drivers
Select a transition or restoration pathway
-
Transition T1
grazing pressure
More details -
Transition T2
grazing pressure and precipitation
More details -
Restoration pathway R3
seed desirable species, and post-seeding weed control and management
More details -
Transition T4
grazing pressure
More details -
No transition or restoration pathway between the selected states has been described
Target ecosystem state
Select a state
Description
State 1 Narrative:
State 1 represents grassland steppe with no invasive or exotic weed species. Grassland sites have no sagebrush and no bitterbrush. Rabbitbrush and forbs are minor species in the Reference Community but more prominent in Community 1.2. All the functional, structural groups have one or more native species present.
Reference State Community Phases:
1.1 Bunchgrass Bluebunch wheatgrass
1.2 Shrub–Bunchgrass –Forb Rabbitbrush–Bluebunch wheatgrass–Unpalatable
Forbs
Dominant Reference State Species: Bluebunch / Snake River wheatgrass
At-risk Communities:
• Different communities have different degrees of risk
• All communities in the reference state are at risk of invasive species
• All communities in the reference state are at risk of moving to State 2. The seed source of invasive species is nearby and moving onto most sites annually.
• Any community is at risk when fire kills Idaho fescue plants. The holes could quickly be filled by invasive grass or weeds
• A community has moved to State 2 when cheatgrass or broadleaf weeds have colonized the site
• Any community becomes at-risk of moving to State 3 when Idaho fescue and bluebunch have low cover and cheatgrass or broadleaf weeds have colonized the site
Submodel
Description
State 2 Narrative:
State 2 represents a moderate invasion by invasive species and is the transition between State 1 and State 3. Native species are present and dominant, but invasive species have gained a foothold that they do not easily relinquish. Grazing pressure weakens the stand of native species allowing the invasive species to colonize and establish themselves in the community.
The invasion can be either cheatgrass or broadleaf weeds (yellow star thistle, chervil, etc.).
Submodel
Description
State 3 represents the situation where invasive species and rabbitbrush dominate the plant community. Based on opportunity, State 3 is dominated by either cheatgrass or alien broadleaf weeds. Opportunity refers to what seeds are in the seedbank and moisture available from year to year. Soil disturbances by rodents or badgers allow invasive species to colonize.
In State 3 native bunchgrasses which were dominant in the Reference State are virtually missing and the other native, functional-structural groups have been altered.
Community Phases for State 3:
3.1 Annual Grass – Shrub Cheatgrass – Rabbitbrush
3.2 Broadleaf Weed – Shrub Yellow star thistle, etc – Rabbitbrush
Community 3.1 is dominated by cheatgrass and rabbitbrush
Community 3.2 is dominated by broadleaf weeds and rabbitbrush
Submodel
Description
State 4 Narrative:
State 4 represents a stand of desirable introduced grasses such as Secar Snake River wheatgrass. Or intermediate wheatgrass The State 3 community has been eliminated and the site seeded to desirable grasses such as intermediate wheatgrass.
State 4 remains stable as long as a full stand is maintained (1.0 plant / sq. ft. or greater of the desired bunchgrasses)
Submodel
Mechanism
T1 Transition from Reference State with no invasive species to State 2 transitional is a stand of native plants with some invasive species. Previously the stand has not had alien species. The result of this transition is the presence of invasive species. Depending on seeds in the soil bank and what is growing nearby, either cheatgrass of broadleaf weeds enter the stand of native species. Also, in State 2 rabbitbrush makes a significant increase. Primary Trigger: grazing pressure (heavy grazing intensity, season long grazing or frequent late spring grazing) to bluebunch/Snake River wheatgrass and other palatable species. Ecological process: consistent defoliation pressure to bluebunch wheatgrass and other palatable species results in poor vigor, shrinking crowns and some plant mortality. The release of resources and niche space allows invasive species such as cheatgrass, yellow star thistle and chervil to colonize and establish. Indicators: decreasing cover of bluebunch wheatgrass and the presence of invasive species. Increasing gaps between bluebunch wheatgrass plants.
Mechanism
T2 Result: shift from native species with some invasive plants in State 2 to State 3 which is dominated by invasive species. T2 can go two directions, to annual greases Community 3.1 or to broadleaf weeds Community 3.2. Wetter years favor broadleaf weeds while drier years favor annual grasses. Rabbitbrush occurs on both communities. Primary Trigger: grazing pressure (heavy grazing intensity, season long grazing or frequent late spring grazing) to bluebunch wheatgrass and other palatable species Ecological process: consistent defoliation pressure to bluebunch wheatgrass and other palatable species results in poor vigor, shrinking crowns and some plant mortality. The release of resources and niche space allows rabbitbrush and invasive species such as cheatgrass, yellow star thistle and chervil to colonize and establish. This takes place in a series of retrogressions. The native species are weakened, the invasive species increase to fill the void, and an equilibrium at a lower ecological level has been reached. This continues until the community is dominated by rabbitbrush and invasive species rather than natives. Indicators: decreasing cover of native species and increasing cover of invasive species, rabbitbrush and rose
Restoration pathway R3
seed desirable species, and post-seeding weed control and management
Mechanism
R3 Transition from State 3 (a community dominated by invasive annual species) to State 4, which is predominately desirable seeded grasses (native or introduced). 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, crested wheatgrass, Covar sheep fescue, Whitmar wheatgrass and Sherman bluegrass are typical species seeded on Loamy, bunchgrass, 15-18” ppt. site in the Loess Hills. The actual transition occurs when the seeded species have successfully established and are outcompeting the annual species for cover and dominance of resources.
Mechanism
T4 Result: shift from State 4 seeded grass to State 3 which is dominated by invasive species. T4 can go to annual grass Community 3.1 or to broadleaf weeds Community 3.2. Wetter years favor broadleaf weeds while drier years favor annual grasses. Rabbitbrush occurs on both communities. Primary Trigger: grazing pressure (heavy grazing intensity, season long grazing or frequent late spring grazing) to desirable seeded species Ecological process: consistent defoliation pressure to seeded species results in poor vigor, shrinking crowns and some plant mortality. The release of resources and niche space allows rabbitbrush and invasive species such as cheatgrass, yellow star thistle and chervil to colonize and establish. This takes place in a series of retrogressions. The native species are weakened, the invasive species increase to fill the void, and an equilibrium at a lower ecological level has been reached. This continues until the community is dominated by rabbitbrush and invasive species rather than natives. Indicators: decreasing cover of seeded species and increasing cover of invasive species, rabbitbrush and rose Indicators: shrinking crowns and mortality of desirable species, increasing cover of invasive species and canopy cover of rabbitbrush References: Boling M., Frazier B., Busacca, A., General Soil Map of Washington, Washington State University, 1998 Caldwell, M.M., J.H. Richards, D.A. Johnson, R.S. Nowak, and R.S. Dzurec. Coping with Herbivory: Photosynthetic Capacity and Resource Allocation in Two Semiarid Agropyron bunchgrasses. Oecologia, 50:14-24. Daubenmire, R., Steppe vegetation of Washington, EB1446, Washington State University Cooperative Extension, 1970 Davies, Kirk, Medusahead Dispersal and Establishment in Sagebrush Steppe Plant Communities, Rangeland Ecology & Management, 2008 Environmental Protection Agency, map of Level III and IV Ecoregions of Washington, June 2010 Liston, A, B.L. Wilson, W.A. Robinson, P.S. Doescher, N.R. Harris, and T. Svejar. 2003. The Relative Importance of Sexula Reproduction Versus Clonal Spread in an Arid Bunchgrass. Oecologia 137:216-225 Miller, Baisan, Rose and Pacioretty, “Pre and Post Settlement Fire regimes in mountain Sagebrush communities: the Northern Intermountain Region Natural Resources Conservation Service, map of Common Resource Areas of Washington, 2003 Rapid Assessment Reference Condition Model for Wyoming Sagebrush, LANDFIRE project, 2008 Rocchio, Joseph & Crawford, Rex C., Ecological Systems of Washington State. A Guide to Identification. Washington State Department of Natural Resources, October 2015. Pages 156-161 Inter-Mountain Basin Big Sagebrush Rouse, Gerald, MLRA 8 Ecological Sites as referenced from Natural Resources Conservation Service-Washington FOTG, 2004 Soil Conservation Service, Range Sites for MLRA 8 from 1980s and 1990s Vallentine, John F. 1971. Range Development and Improvement. BYU Press, Provo, UT.
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