Natural Resources
Conservation Service
North Aspect, 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
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 State. Some rose may be present as well on north slopes. All the functional, structural groups have one or more native species present.
Reference State Community Phases:
1.1 Reference Idaho fescue
1.2 Shrub – Bunchgrass – Forb Rabbitbrush – bluebunch wheatgrass
Dominant Reference State Species:
Idaho fescue with bluebunch wheatgrass/Snake River wheatgrass as sub-dominant
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 Weeds – Shrub Yellow star-thistle, etc. – Rabbitbrush
Dominant Species in State 3:
Cheatgrass or broadleaf weeds (yellow star-thistle, etc.) and rabbitbrush
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. References: Boling M., Frazier B., Busacca, A., General Soil Map of Washington, Washington State University, 1998 Daubenmire, R., Steppe Vegetation of Washington, EB1446, 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 Ogle, Dan, Henson, James and Stannard, Mark. Plant guide for Idaho Fescue. Natural Resources Conservation Service, 2002 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 Tart, D., Kelley, P., and Schlafly, P., Rangeland Vegetation of the Yakima Indian reservation, August 1987, YIN Soil and Vegetation Survey Vallentine, John F. 1971. Range Development and Improvement. BYU Press, Provo, UT.
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