Natural Resources
Conservation Service
North Aspect, Dwarf Shrub, 18-24" 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 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 Idaho fescue
1.2 Forb – Grass unpalatable native forbs – native grasses
1.3 Dwarf Shrub snowberry – rose
Dominant Reference State Species: Idaho fescue and a wide variety of forbs
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 vigor 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 with 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 seed source
Indicators: the occurrence of invasive species where there has been none.
Submodel
Mechanism
T1 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) to Idaho fescue 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 Transition from State 2 with some invasive species to State3 which is dominated by invasive species Primary trigger: grazing pressure (heavy grazing intensity, season long grazing or frequent late spring grazing) Idaho fescue 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. Recovery Seeding is not an option for North Slope as most locations are too steep to seed. 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 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
Model keys
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Ecological site groups
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