Loamy, sagebrush
Scenario model
Current ecosystem state
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Management practices/drivers
Select a transition or restoration pathway
- Transition T1 More details
- Transition T2 More details
- Restoration pathway R1 More details
- Restoration pathway R2 More details
- Transition T3 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 Narrative:
State 1 represents sagebrush steppe with no invasive or exotic weed species. All the functional, structural groups have one or more native species. A diverse native perennial community is more resistant to invasive annual species such as cheatgrass.
Reference State Community Phases:
1.1 Reference Bluebunch wheatgrass-Wyoming sagebrush
1.2 Bunchgrass Bluebunch wheatgrass
1.3 Heavy sage Wyoming sagebrush-bluebunch wheatgrass
1.4 Depauperate Wyoming sagebrush-Sandberg bluegrass
Dominate Reference State Species:
Wyoming big sagebrush, bluebunch wheatgrass
At-risk Communities:
• All communities in the reference state are at risk of moving to State 2. The seed source of cheatgrass is nearby and blowing onto most sites annually
• Community Phase 1.4, the depauperate community (sagebrush-Sandberg bluegrass), has little to no bluebunch wheatgrass, and is therefore, at considerable risk of moving to State 3 which is dominated by annual species
• Any Loamy community is at risk when bluebunch cover is low (< 10%) and cheatgrass cover is becoming co-dominant (40% or more).
• Any community is at risk when sagebrush cover is high (40%+) and there is little to no bluebunch
• Community 1.4, and any site with low cover of bluebunch wheatgrass, and any site with moderate to heavy cover of cheatgrass should be seeded after a fire
Submodel
Description
State 2 Narrative:
State 2 represents a gradation along the transition between Reference State and State 3. State 2 is sagebrush steppe with the inclusion of invasive annual grasses such as cheatgrass. All the native functional, structural groups are still represented by one or more species.
Cheatgrass seed blows onto most sites annually seeking an opportunity to invade and colonize. With each loss of a native perennial plant, the site becomes less and less resistant to invasion. When cheatgrass makes seed for the next generation, the site has been colonized and will likely remain a component of the community. The loss of biological soil crusts is also a contributing factor to the invasion by cheatgrass.
For communities 2.1, 2.2, and 2.3 the amount of cheatgrass is minor. Cheatgrass is more prominent in community 2.4. Once a community has been invaded by cheatgrass the chance of going back to State 1 is small. This state can occur with or without sagebrush.
Community Phases for State 2:
Same as Reference State.
Dominate State 2 Species:
Wyoming big sagebrush – bluebunch wheatgrass
Pathways within State 2
The pathways in State 2 are basically the same as in the Reference State. Community 2.4 is most at risk of transitioning to State 3.
Submodel
Description
State 3 Narrative:
State 3 represents communities dominated by invasive annual species and has crossed a biological threshold. Virtually all the native functional, structural groups are missing. This state can occur with or without sagebrush.
Community Phases for State 3:
3.1 Shrub – Annual Grass Sagebrush – cheatgrass
3.2 Annual Grass Cheatgrass
Dominate State 3 Species:
Cheatgrass with or without sagebrush
The main species can include cheatgrass, Japanese brome, medusahead, ventenata, mustard, prickly lettuce and diffuse knapweed. This state can occur with or without sagebrush.
Submodel
Description
State 4 Narrative:
State 4 represents a site that has been seeded to desirable grasses such as Secar Snake River wheatgrass, Sherman big bluegrass, crested wheatgrass or intermediate wheatgrass. State 4 has two community phases that are stable if they maintain 0.8 plant / sq. ft. or greater of the desired bunchgrasses
Community Phases for State 4:
4.1 Seeded Grasses
4.2 Shrub – Seeded Grasses
Dominate State 4 Species:
Desirable seeded grasses with or without sagebrush and legumes
Submodel
Mechanism
T1 Result: transition from Reference State to State 2 (shrub steppe w/ a few annuals). The Reference State does not have invasive species. State 2 has the same communities but with minor additions of invasive annual grasses such as cheatgrass.
Ecological process. Most sites in the Reference State have some scattered cheatgrass seed. This seed is waiting for enough moisture to germinate and to compete with the native species for space, light and moisture. When the right year happens even pristine communities in the Reference State are susceptible to colonization by cheatgrass.
Primary Trigger: The transition occurs during a high moisture year that causes a micro-burst of cheatgrass and is the principle means of colonization. A second trigger would be spots of soil disturbance.
Indicators: The occurrence of annual grasses on sites where they had been absent.
Mechanism
T2 Result: Transition from State 2 to State 3 which is dominated by annuals. This transition occurs once the cover of bluebunch wheatgrass decline to less than 10% while invasive species cover is 40% or more.
Primary Trigger: Chronic heavy grazing, season-long grazing, or late spring grazing. Note: chronic season-long grazing in 1880s-1940s created thousands of acres of annual grass-sagebrush community, and then fire turned that into annual grasses.
Ecological Process: Consistent defoliation pressure to bluebunch wheatgrass causes poor vigor, shrinking crowns and plant mortality. Native species are all but eliminated while invasive species such as annual bromes have the competitive advantage. With more and more of the soil surface and upper soil rooting surface open, opportunistic, exotic weeds take advantage of the available niche space to colonize and expand until they dominate the community.
The site has lost its primary species that stabilize and protect the soil from wind and water erosion and has also lost the ability to retain sufficient soil moisture for many of the native perennial species.
Indicators: Decreasing cover of bluebunch wheatgrass and increasing cover of invasive annual species. Increasing distance between bunchgrass plants. Decreasing soil organic matter, soil water retention, limited water infiltration and percolation in the soil profile.
Mechanism
R1 Transition from State 3 (a community dominated by invasive annual species) to State 4, which is predominately desirable seeded grasses.
This restoration transition does not occur without significant time and inputs to control weeds, prepare a seedbed, seed the desirable species, and post-seeding, to control weeds and manage grazing. This requires a commitment of two years or more for weed control and seedbed preparation. 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, thickspike wheatgrass, Sherman big bluegrass, Sandberg bluegrass, and crested or 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
R2 Result: Shift from State 3 back to State 2. This restoration transition does not occur without a significant commitment of time & resource inputs to restore ecological processes, native bunchgrasses, Wyoming sagebrush and native forb species.
Shifting from State 3 to State 4: If the goal is to restore back to a native plant community, State 3 must first be shifted to State 4. It will take two years or longer to kill annual species and to exhaust the seedbank of invasive species. Site will then need to be seeded to perennial species such as crested wheatgrass to restore soil properties before native species can survive and thrive on site. The seeded species rebuild some of the basic soil properties including increased soil organic matter, increased soil moisture, and likely would also require the soil’s pore spaces, bulk density and soil microorganisms to return before the native species that used to survive in this ecological site can return. The site would also need several years of no significant fires and proper grazing management as well to establish and maintain desirable species plant vigor. See narrative for R1 transition above.
Shifting from State 4 to State 2: This assumes that the shift from State 3 to State 4 has been successful. Introduce grasses must be killed before native species are seeded. The seeding of native species should occur in two steps: (1) a seeding of native bunchgrasses so that broadleaf weeds may be controlled, (2) a re-introduction of sagebrush and native forbs. The site would also need several years of no significant fires and proper grazing management as well to ensure plant establishment and vigor. See narrative for R1 transition above.
Mechanism
T3 Result: shift from seeded grass State 4 to State 3 which is dominated by invasive annual species.
Primary Trigger: This transition occurs when chronic grazing pressure has removed too much of the seeded bunchgrass cover allowing invasive annual species to colonize the site. As this continues the competitive advantage goes to the exotic species which are opportunistic and take most of the site’s resources. Little of the resources remain for the desirable species.
Secondary Trigger: Frequent fires or a severe fire that removes too much of the perennial bunchgrass cover and gives the competitive advantage back to the invasive species.
Ecological Process: Consistent defoliation pressure to seeded grasses cause poor vigor, shrinking crowns and plant mortality. With more and more of the soil surface and upper soil rooting surface open, opportunistic, exotic weeds that take advantage of the available niche space to colonize and expand until the dominate the community.
Indicators: shrinking crowns and mortality of desirable species, increasing gaps between seeded plants, and increasing cover by annual grasses.
References:
Boling M., Frazier B., Busacca, A., General Soil Map of Washington, Washington State University, 1998
Daubenmire, R., Steppe Vegetation of Washington, EB1446, March 1968
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
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
Tart, D., Kelley, P., and Schlafly, P., Rangeland Vegetation of the Yakima Indian reservation, August 1987, YIN Soil and Vegetation Survey
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