LOAMY 10-12 P.Z.
Scenario model
Current ecosystem state
Select a state
Management practices/drivers
Select a transition or restoration pathway
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Transition T1
Introduction of annual non-native species.
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Transition T3
Repeated, widespread and severe fire.
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Transition T2
Absence of wildfire
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Transition T7
Loss of deep-rooted perennial bunchgrasses
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Restoration pathway R1
Rangeland seeding
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Transition T4
Catastrophic fire or a failed restoration attempt
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Restoration pathway R3
Brush management and seeding with native species
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Transition T6
Wildfire
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Transition T7
Decreasing grass species
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Restoration pathway R2
Rangeland seeding
More details -
No transition or restoration pathway between the selected states has been described
Target ecosystem state
Select a state
Description
The Reference State is a representative of the natural range of variability under pristine conditions. State dynamics are maintained by interactions between climatic patterns and disturbance regimes. Negative feedbacks enhance ecosystem resilience and contribute to the stability of the state. These include the presence of all structural and functional groups, low fine fuel loads, and retention of organic matter and nutrients. Plant community phase changes are primarily driven by fire, periodic drought and/or insect or disease attack.
Submodel
Description
This state is similar to the Reference State 1.0. Ecological function has not changed, however the resiliency of the state has been reduced by the presence of invasive weeds. This state has the same three general community phases. 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 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 non-natives’ high seed output, persistent seed bank, rapid growth rate, ability to cross pollinate and adaptations for seed dispersal.
Management would be to maintain high diversity of desired species to promote organic matter inputs and prevent the dispersal and seed production of the non-native invasive species.
Submodel
Description
Annual non-natives dominated site productivity and site resources. The dominance of non-native annuals control the spatial and temporal distribution of soil moisture, soil nutrients and energy resources. Remaining patches of sagebrush and/or perennial bunchgrass suffer from increased competition and narrowed fire return intervals.
Characteristics and indicators
This state experiences frequent fire due to increased cover and continuity of fine fuels. Fire is frequent enough to prevent the recovery of long-lived native perennials like big sagebrush. Disturbance tolerant shrubs may be present or increasing depending on time since disturbance. As cheatgrass increases, fire frequencies also increase to frequencies between 0.23 and 0.43 times a year; then even sprouting shrubs such as rabbitbrush will not survive (Whisenant 1990).
Submodel
Description
This state is characterized by a dominance of Utah juniper. Sagebrush and perennial bunchgrasses may still be present, but they are no longer controlling site resources. Soil moisture, soil nutrients and soil organic matter distribution and nutrient cycling have been spatially and temporally altered.
This state is relatively stable due to rapid growth rate and long life span of juniper.
Submodel
Description
This state is characterized by the dominance of shallow rooted perennial bunchgrass, which have replaced the deep-rooted perennial bunch grass typical of the site. Big sagebrush and rabbitbrush dominate the overstory. Bluegrass species dominate understory with non-native species present.
Characteristics and indicators
Sandberg bluegrass has been found to increase following fire likely due to its low stature and productivity (Daubenmire 1975). Sandberg bluegrass may retard reestablishment of deeper rooted bunchgrass. Reduced bunchgrass vigor or density provides an opportunity for Sandberg bluegrass expansion and/or cheatgrass and other invasive species to occupy interspaces.
Submodel
Description
This state is characterized by the dominance of non-native perennial wheatgrass species, like crested wheatgrass (Agropyron cristatum) or desert wheatgrass (Agropyron desertorum). Non-native perennial wheatgrass are frequently seeded following disturbance for erosion control and forage. Seeded perennials are long-lived and persistent and are capable of outcompeting native perennials and prohibit the return of pre-disturbance plant diversity. Soil nutrients , soil moisture, and organic matter distribution and cycling are primarily driven by introduced bunchgrasses. Native species, grass and forbs, may still be present in small amounts.
Submodel
Mechanism
Trigger: Introduction of annual non-native species
Slow variable: Over time the annual non-native plants 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: Repeated, widespread and severe fire.
Slow variables: Increased production and cover of non-native annual species over time.
Threshold: Loss of deep-rooted perennial bunchgrasses and shrubs truncates, spatially and temporally, nutrient capture and cycling within the community.
Mechanism
Trigger: Presence of juniper
Slow variables: Encroachment of juniper is primarily driven by lack of fire. This may also be coupled with prolonged drought and poor grazing management.
Threshold: Juniper is now controlling energy, moisture and nutrient resources Dominance of juniper results in decreased infiltration and increased runoff, reducing soil moisture and nutrient cycling. Sagebrush and perennial bunchgrass are reduced both vigor and reproductive capacity.
Mechanism
Trigger: inappropriate grazing management, prolonged drought or a combination.
Slow variable: Reduction of deep-rooted perennial bunchgrass through inappropriate grazing management, prolonged drought or a combination.
Threshold: Changes in the spatial and temporal patterns of infiltration and runoff effects soil moisture. Shallow-rooted perennial grasses are highly competitive for moisture and nutrient resources in the surface soil horizon.
Mechanism
Seeding drought tolerant species combined with grazing management/prescribed grazing.
Minimize soil disturbance and maximize non-native annual plant biomass removal during early spring. Continue to protect site from wildfire. Probability of success is low.
Mechanism
Trigger: Catastrophic fire causing a stand replacing event. Or a failed restoration attempt including inappropriate tree removal or rangeland seeding using soil disturbing practices.
Slow variables: Increased production and cover of non-native annual species under tree canopy.
Threshold: Closed tree canopy with non-native annual species in the understory changes the intensity, size and spatial variability of wildfires. Changes in community composition are driven by temporal changes in energy capture, soil moisture and nutrient cycling and result in the loss of perennial bunchgrasses and sagebrush.
Mechanism
Brush management treatments, physical or chemical. May be combined with seeding of native species using non-soil disturbing practices.
Mechanism
Trigger: Repeated, widespread and severe fire.
Slow variables: Increased production and cover of non-native annual species over time.
Threshold: Loss of shallow-rooted perennial bunchgrasses and shrubs truncates, spatially and temporally, nutrient capture and cycling within the community.
Mechanism
Trigger: Presence of juniper
Slow variables: Encroachment of juniper is primarily driven by lack of fire. This may also be coupled with prolonged drought and poor grazing management.
Threshold: Juniper is now controlling energy, moisture and nutrient resources Dominance of juniper results in decreased infiltration and increased runoff, reducing soil moisture and nutrient cycling. Sagebrush and perennial bunchgrass are reduced both vigor and reproductive capacity.
Model keys
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