Upland Stony Loam (Wyoming sagebrush) South
Scenario model
Current ecosystem state
Select a state
Management practices/drivers
Select a transition or restoration pathway
- Transition T1A More details
- Transition T2A More details
- Transition T2B More details
- Transition T2C More details
- Restoration pathway R3A More details
- Transition T3A More details
- Transition T3B More details
- Restoration pathway R4A More details
- Restoration pathway R4B More details
- Transition T4A More details
- Transition T4B More details
- Transition T5A More details
- Transition T6A More details
- Transition T6B 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
The Reference State includes the plant communities that were best adapted to the unique combination of factors associated with the ecological site. It was in a natural dynamic equilibrium with the historic biotic, abiotic, and climatic factors on its ecological site in North America at the time of European immigration and settlement. This dominant aspect of the plant community is Wyoming big sagebrush and bluebunch wheatgrass. The community production by dry weight is 50 percent grass, 10 percent forbs, and 40 percent shrubs.
Submodel
Description
The Current Potential State is like the Reference State 1 with similar community phases. Ecological function has not changed; however, the resiliency of the state has been reduced by the presence of invasive weeds. Non-natives may increase in abundance but will not become dominant within this state. These non-natives can be highly flammable and can promote fire where historically fire had been infrequent. Negative feedbacks enhance ecosystem resilience and contribute to the stability of the state. These feedbacks include the presence of all structural and functional groups, low fine fuel loads, and retention of organic matter and nutrients. Positive feedbacks decrease ecosystem resilience and stability of the state. These include the nonnatives’ high seed output, persistent seed bank, rapid growth rate, ability to cross pollinate, and adaptations for seed dispersal. Additionally, the presence of highly flammable, non-native species reduces State resilience because these species can promote fire where historically fire has been infrequent leading to positive feedbacks that further the degradation of the system.
Submodel
Description
The Shrub State has two community phases and is the product of many years of heavy grazing during time periods harmful to deep-rooted perennial bunchgrasses. With a reduction in deep-rooted perennial bunchgrass competition, bluegrasses, and squirreltail will increase and become the dominant grass. Sagebrush dominates the overstory. Bitterbrush and/or rabbitbrush may be significant components. Sagebrush cover exceeds site concept and may be decadent, reflecting stand maturity and lack of seedling establishment due to competition with mature plants. Bare ground is also increasing. The shrub overstory and bluegrass understory dominate site resources such that soil water, nutrient capture, nutrient cycling, and soil organic matter are temporally and spatially redistributed.
Submodel
Description
The Tree State has two community phases that are characterized by the dominance of Utah juniper and singleleaf pinyon in the overstory. This state is identifiable by 30 to over 50 percent cover of Utah juniper and singleleaf pinyon. This stand exhibits a mixed age class. Older trees are at maximal height and upper crowns may be flat-topped or rounded. Younger trees are typically cone- or pyramidal shaped. Understory vegetation is sparse due to increasing shade and competition from trees.
Submodel
Description
The Annual State is characterized by the dominance of annual non-native species such as cheatgrass and tansy mustard in the understory. Rabbitbrush may dominate the overstory. Annual non-native species dominate the understory.
Submodel
Description
The Seeded State has two community phases a grass-dominated phase and a grass-shrub phase. The state is characterized by the dominance of seeded species such as smooth brome and crested wheatgrass. Other seeded species include forage kochia, Wyoming big sagebrush, and native and non-native perennial forbs.
Submodel
Mechanism
Trigger: This transition is caused by the introduction of non-native annual plants, such as cheatgrass, mustards, and bur buttercup.
Slow variables: Over time the annual non-native species will increase within the community.
Threshold: Any amount of introduced non-native species causes an immediate decrease in the resilience of the site. Annual non-native species cannot be easily removed from the system and have the potential to significantly alter disturbance regimes from their historic range of variation.
Mechanism
Trigger: To Community Phase 3.1: Repeated heavy growing season grazing will decrease or eliminate deep rooted perennial bunchgrasses, increase Sandberg bluegrass and favor shrub growth and establishment.
Slow variables: Long term decrease in deep-rooted perennial grass density.
Threshold: Loss of deep-rooted perennial bunchgrasses changes nutrient cycling, nutrient
redistribution, and reduces soil organic matter.
Mechanism
Trigger: Time and lack of disturbance or management action allows for Utah Juniper and singleleaf pinyon to dominate. This may be coupled with grazing management that favors tree establishment by reducing understory herbaceous competition for site resources
Slow variables: Over time the abundance and size of trees will increase.
Threshold: Trees dominate ecological processes and number of shrub skeletons exceed number of live shrubs.
Mechanism
Trigger: Fire and/or multiple fires lead to plant community phase 5.1, inappropriate grazing management that favors shrubs in the presence of non-native annual species leads to community phase 5.2.
Slow variables: Increased production and cover of non-native annual species.
Threshold: Loss of deep-rooted perennial bunchgrasses and shrubs truncates, spatially and temporally, nutrient capture and cycling within the community. Increased, continuous fine fuels from annual non-native plants modify the fire regime by changing intensity, size and spatial variability of fires.
Mechanism
Brush management such as mowing, coupled with seeding of deep-rooted native bunchgrasses will reduce the shrub overstory and release the perennial understory species. Presence of annual nonnative species increases the risk of transitioning to an annual state if this treatment fails.
Mechanism
Trigger: Time and a lack of disturbance or management action allows for Utah Juniper and singleleaf pinyon to dominate site. This may be coupled with grazing management that favors tree establishment by reducing understory herbaceous competition for site resources.
Slow variables: Over time the abundance and size of trees will increase.
Threshold: Trees overtop mountain sagebrush and out-compete shrubs for water and sunlight.
Shrub skeletons exceed live shrubs with minimal recruitment of new cohorts.
Mechanism
Trigger: To Community Phase 5.1: Severe fire. To Community Phase 5.2: Inappropriate grazing management in the presence of annual non-native species.
Slow variables: Increased production and cover of non-native annual species.
Threshold: Increased continuous fine fuels modify the fire regime by changing intensity, size, and spatial variability of fires. Changes in plant community composition and spatial variability of vegetation due to the loss of perennial bunchgrasses and sagebrush truncate energy capture spatially and temporally thus impacting nutrient cycling and distribution.
Mechanism
Tree removal and seeding of desired species. Tree removal practices that minimize soil disturbance are recommended. Probability of success declines with increased presence of nonnative annual species (Community Phase 4.2).
Mechanism
This restoration is recommended for phase 4.1 only due to the lack of understory in 4.2. Removal of the pinyon and juniper overstory through tree removal practices or a controlled burn, without seeding of grass species, would move this phase into a shrub state. If nonnative annuals are present, a controlled burn is not recommended.
Mechanism
Trigger: Fire reduces the tree overstory and allows for the annual non-native species in the understory to dominate the site. Soil disturbing treatments such as slash and burn may also reduce tree canopy and allow for non-native annual species to increase.
Slow variables: Over time, cover and production of annual non-native species increases.
Threshold: Loss of deep-rooted perennial bunchgrasses and shrubs changes temporal and spatial nutrient capture and cycling within the community. Increased, continuous fine fuels modify the fire regime by increasing frequency, size, and spatial variability of fires.
Mechanism
Tree removal and seeding of desired species. Tree removal practices that minimize soil disturbance are recommended. Probability of success declines with increased presence of nonnative annual species (Community Phase 4.2).
Mechanism
Seeding of deep-rooted bunchgrasses, coupled with brush management and/or herbicide. Probability of success is medium.
Mechanism
Trigger: Time and lack of disturbance or management action allows for Utah Juniper to dominate. This may be coupled with grazing management that favors tree establishment by reducing understory herbaceous competition for site resources
Slow variables: Over time, the abundance and size of trees will increase.
Threshold: Trees dominate ecological processes and number of shrub skeletons exceed number of live shrubs.
Mechanism
Trigger: Catastrophic fire.
Slow variables: Increased production and cover of non-native annual species.
Threshold: Increased continuous fine fuels modify the fire regime by changing intensity, size, and spatial variability of fires. Changes in plant community composition and spatial variability of vegetation due to the loss of perennial bunchgrasses and sagebrush truncate energy capture spatially and temporally, thus impacting nutrient cycling and distribution.
Model keys
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