Stony
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 Community 1.1 is dominated by bluebunch wheatgrass with some sagebrush.
Community 1.2 is even more strongly bunchgrass dominated.
Community 1.3 has a heavy sage canopy but bluebunch remains a vital component in the community.
Communities 1.1, 1,2 and 1.3 have enough bluebunch wheatgrass to shift to the other two communities and back again. These three community phases have high amounts of bunchgrass cover and are at low risk of moving to State 3
Community 1.4, Depauperate, is dominated by sagebrush with Sandberg bluegrass as sub-dominate. There is not enough bluebunch remaining for community 1.4 to shift back to the other communities in the reference state.
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 Stony community is at risk when bluebunch cover is low (less than 10 percent) and cheatgrass cover is becoming co-dominant (40 percent or more).
• Any community is at risk when sagebrush cover is high (40percent or more) 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 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 crust is also contributes to 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.
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 annual bromes, mustard, prickly lettuce and diffuse knapweed.
Pathways within State 3
3.1a Result: shift from shrub-cheatgrass to cheatgrass.
Causes: Moderate intensity fire kills most or all sagebrush. Cheatgrass and other invasive species fully occupy the site.
Submodel
Description
State 4: Seeded Grasses
Note: Stony ecological sites have mild to moderate equipment limitations due to surface rock.
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 0.8 plant / sq. ft. or greater of the desired bunchgrasses is maintained.
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 with 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-flush 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: Shift 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 percent while invasive species cover is at least 40 percent. This transition can occur with or without sagebrush in the community. Community 2.4 has limited amount of bluebunch wheatgrass and is the community most at risk and is also the pathway for crossing the threshold from State 2 into State 3. Community 2.4 is the segue between State 2 and State 3.
Primary Trigger: Chronic heavy grazing, season-long grazing, or late spring grazing. Native species are all but eliminated. 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. A secondary trigger would be frequent fires that weaken the entire community. In either case, annuals such as cheatgrass have the competitive advantage. 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.
Ecological Process: Consistent defoliation pressure to bluebunch wheatgrass causes 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: Decreasing cover of bluebunch wheatgrass and increasing cover of invasive annual species. Increasing distance between native bunchgrasses. Decreasing soil organic matter, soil water retention, limited water infiltration and percolation in the soil profile.
Mechanism
Recovery
Most Stony ecological site soils have surface rock and rock throughout the profile. Other soils do not have surface rock but are shallow to bedrock. Equipment limitations that will cause issues and some treatment options may not be feasible on some sites.
R1 Result: Shift from State 3 (a community dominated by invasive annual species) to State 4, which is predominately desirable seeded grasses.
This transition occurs when active management decisions are attempted to alter the annual dominated state to one with perennial bunchgrasses, even if they are not native. 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, thickspike wheatgrass, Sherman big bluegrass, Sandberg bluegrass, and crested or Siberian wheatgrass are typical species seeded on Stony 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 4 back to State 2. This restoration transition is not likely to occur without a significant commitment of time and resource inputs to restore ecological processes, perennial 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. 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. Introduced grasses must be killed before the seeding of native species. 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.
Mechanism
T3 Result: Shift from seeded grass to State 3 which is dominated by invasive annual species.
Primary Trigger: This transition occurs when chronic heavy grazing has removed too much of the perennial 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 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 caps gaps between perennial species, increasing cover by annual grasses.
Model keys
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The Ecosystem Dynamics Interpretive Tool is an information system framework developed by the USDA-ARS Jornada Experimental Range, USDA Natural Resources Conservation Service, and New Mexico State University.