Loamy, dwarf shrub, 18-24" ppt.
Scenario model
Current ecosystem state
Select a state
Management practices/drivers
Select a transition or restoration pathway
-
Transition T1a
grazing pressure
More details -
Transition T2a
grazing pressure
More details -
Restoration pathway R3a
restoration
More details -
Transition T4a
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 native grass-forb-dwarf shrub stands with no invasive or exotic weed species. The Palouse Hills have no sagebrush and no bitterbrush. All the functional, structural groups have one or more native species present.
Reference State Community Phases:
1.1 Reference Community Idaho fescue, bluebunch, native forbs
1.2 Forb-Grass Unpalatable native forbs, native grasses
Dominant Reference State Species: Idaho fescue, native forbs, bluebunch 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. Also, Kentucky bluegrass is aggressive with rhizomes or seed
• 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 Kentucky bluegrass has colonized the site
• Any community becomes at-risk of moving to State 3 when Idaho fescue and bluebunch have low cover and Kentucky bluegrass has colonized the site
Submodel
Description
State 2 represents transition between State 1 with no invasive species and State 3 which is dominated by invasive species. State 2 has a moderate invasion by invasive species, but native species are still present and dominant. 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 Kentucky bluegrass or a combination of invasive annual grasses (annual bromes, ventenata) and broadleaf weeds (Russian knapweed, Canadian thistle). Once retrogression allows Kentucky bluegrass there seems to be no reversal when grazing pressure is reduced or eliminated.
Submodel
Description
State 3 represents the situation where invasive species dominate the plant community.
Retrogression begins a weakened State 1 and then in State 2 the introduction and establishment of invasive species. The community stabilizes but at a lower ecological level. When the native species are further weakened the invasive species increase again. After a series of retrogressions, the stand becomes dominated by alien species.
Community 3.1 is mostly Kentucky bluegrass
Community 3.2 is either annual bromes or broadleaf weeds such as Russian thistle or Canadian thistle depending on sed source
Submodel
Description
State 4 represents a stand of desirable introduced grasses. The State 3 community has been eliminated and the site seeded to desirable grasses such as intermediate wheatgrass.
State 4 remains stable a long as a full stand is maintained (1.0 plant / sq. ft. or greater of the desired bunchgrasses)
Submodel
Mechanism
T1a Result: Transition from Reference State with no invasive species to State 2 with 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 Kentucky bluegrass or invasive annual grasses and broadleaf weeds enter the stand of native species.
Primary trigger: grazing pressure (heavy grazing intensity, season long grazing or frequent late spring grazing) Idaho fescue, bluebunch wheatgrass and other palatable species.
Ecological process: consistent defoliation pressure to Idaho fescue, bluebunch wheatgrass and other palatable species results in poor vigor, shrinking crowns and plant mortality. This gives invasive species such as Kentucky bluegrass, Russian knapweed and Canadian thistle the opportunity to colonize and establish.
Indicators: decreasing cover of Idaho fescue, bluebunch wheatgrass, and other palatable species, and the presence of invasive species where there have been none.
Mechanism
T2 Result: Transition from State 2 (mostly native species with some invasive species) to State 3 which is dominated by invasive species.
Primary trigger: grazing pressure (heavy grazing intensity, season long grazing or frequent late spring grazing) Idaho fescue, bluebunch wheatgrass and other palatable species.
Ecological process: consistent defoliation pressure to Idaho fescue, bluebunch wheatgrass and other palatable species results in poor vigor, shrinking crowns and plant mortality. This releases resources and niche space that invasives take advantage of. The transition can go two directions – to Kentucky bluegrass or to broadleaf weeds and annual bromes.
This transition takes place in a series of retrogressions. The palatable native species are weakened, and the invasive species increase to fill the void. After each retrogression the stand stabilizes but at a lower ecological level. Finally, the stand is dominated by invasive species rather than natives.
Indicators: decreasing cover of Idaho fescue and other native species and, increasing cover of invasive species.
Mechanism
R3a Transition from State 3 (a community dominated by invasive species) to State 4, which is predominately introduced seeded grasses with or without legumes.
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. Intermediate wheatgrass, orchardgrass, meadow brome, smooth brome and clover are typical species seeded on Loamy ecological site in the Palouse 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
T4a Result: shift from State 4 seeded grass to State 3 which is dominated by invasive species.
Primary Trigger: grazing pressure (heavy to severe grazing intensity, season long grazing or frequent late spring grazing) to desirable seeded grasses.
Ecological process: consistent defoliation pressure to seeded grasses results in poor vigor shrinking crowns and plant mortality. This releases resources and niche space that invasive species such as Kentucky bluegrass, Russian knapweed and Canadian thistle take advantage of.
In a series of retrogressions desirable seeded species are weakened and invasive species colonize and increase. After each retrogression the stand stabilizes but at a lower ecological level. Finally, the stand is dominated by invasive species rather than natives.
References:
Boling M., Frazier B., Busacca, A., General Soil Map of Washington, Washington State University, 1998
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
Lichthardt, Juanita and Mosely, Robert K., 1997 Status and Conservation of the Palouse Grassland in Idaho. Idaho Fish and Game, Boise, ID. USFS Purchase Order 14420-S-0395
Liston, A, B.L. Wilson, W.A. Robinson, P.S. Doescher, N.R. Harris, and T. Svejar. 2003. The Relative Importance of Sexual 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
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