Dry Loamy
Scenario model
Current ecosystem state
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Management practices/drivers
Select a transition or restoration pathway
- Transition T1 & T2 More details
- Transition T3 & T4 More details
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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 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
Reference State Community Phases:
1.1 Reference Bluebunch wheatgrass – Wyoming sagebrush / spiny hopsage
1.2 Bunchgrass Bluebunch wheatgrass
1.3 Heavy sage Wyoming sagebrush/ spiny hopsage-bluebunch wheatgrass
Dominate Reference State Species:
bluebunch wheatgrass and Wyoming big sagebrush with spiny hopsage and Sandberg bluegrass
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
• Any community is at risk when shrub cover is high (40percent or more) and there is little to no bluebunch
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 annuals such as cheatgrass, Russian thistle and mustard. Most of the native functional, structural groups are still represented by one or more species.
Invasive species 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 and other invasives make 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.
Communities 2.1 and 2.2 have significant amounts of native and invasive species. 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:
Community 2.1 Shrub – invasive species – native grass
Community 2.2 Invasive annual grass and broadleaf weed
Dominate State 2 Species:
Invasive species, Wyoming big sagebrush/spiny hopsage
Submodel
Description
State 3 Narrative:
State 3 represents 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 and other shrubs
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
Mechanism
T1 Result: transition from Community 1.3 in the Reference State with no invasive species to Community 2.1 in State 2 which is a mix of invasive and native species. This is a continuation of the decline that started with Pathway 1.2a. In Community 2.1 shrubs, native bunchgrasses and invasive species are co-dominant.
Primary Trigger: grazing pressure to bluebunch wheatgrass. A secondary trigger would be a year with high moisture and a micro-flush of cheatgrass and other invasive species
Ecological process. Consistent defoliation pressure to bluebunch wheatgrass results in poor vigor, shrinking crowns and some mortality. Most sites in the Reference State have some scattered cheatgrass seed as the seed blows onto most site annually. 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.
Indicators: The occurrence of annual grasses on sites where they had been absent. Reduced cover and distance between bluebunch wheatgrass plants.
T2 Result: shift from Community 1.2 in Reference State with no invasives species to community 2.2 in State 2 with a mix of native and invasive species. This is a continuation of the decline that started with Pathway 1.1a. This transition occurs when invasive species have colonized the site and are successfully reproducing.
Primary Trigger: a repeat of moderate-severity fire. Repeated fire is more common in south Central Washington than elsewhere in MLRA 007X.
Ecological Process: fire kills remaining sagebrush and spiny hopsage plants. This second fire is also detrimental to bluebunch wheatgrass plants and the exhibit poor vigor, shrinking crowns and mortality.
Primary Trigger: moderate-severity fire happens again.
Mechanism
T3 Result: shift from Community 2.1 (mix of native and invasive species) in State 2 to Community 3.1 (shrub-invasive species) in State 3. This is a continuation of the chain of decline which started with Pathway 1.2a and Transition T1. This transition occurs when the cover of native bunchgrasses is less than 10 percent and invasive species cover is at least 40 percent.
Primary Trigger: heavy grazing pressure (heavy grazing intensity, season-long grazing or frequent late-spring grazing) to bluebunch wheatgrass and the entire community.
Ecological Process: defoliation pressure continues and remaining bluebunch wheatgrass suffer mortality. Invasive species and shrubs expand via new seedlings to assume shared a position of codominance.
T4 Result: Shift from Community 2.2 (native and invasive species mix) in State 2 to Community 3.2 (cheatgrass dominated) in State 3.
Primary Trigger: moderate-severity fire happens again. Repeated fire is more common in south Central Washington than elsewhere in MLRA 007X.
Ecological process: the last vestiges of native species are replaced by cheatgrass and other invasive species.
Model keys
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Ecological site groups
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