SHALLOW SILTY 5-8 P.Z.
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 T3A More details
- Restoration pathway R3A More details
- Transition T3B More details
- Restoration pathway R4A More details
- Transition T4A More details
- Transition T5A More details
- Transition T5B 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 1.0 is a representative of the natural range of variability under pristine conditions. The Reference State has two general community phases: a shrub-grass dominant phase and a shrub dominant phase. 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. This site is very stable, with little variation in plant community composition. Plant community changes would be reflected in production response to long term drought or herbivory. Wet years will increase grass production, while drought years will reduce production. Shrub production will also increase during wet years; however, extreme growing season wet periods has been shown to cause shadscale death.
Submodel
Description
This state is similar to the Reference State 1.0 with the addition of a shadscale and sprouting shrub dominated community phase. 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 non-natives’ high seed output, persistent seed bank, rapid growth rate, ability to cross pollinate, and adaptations for seed dispersal.
Submodel
Description
This state has one community phase that is characterized by shadscale, bud sagebrush or a sprouting shrub overstory with very little to no understory. The site has crossed a biotic threshold and site processes are being controlled by shrubs. Shrub cover exceeds the site concept and may be decadent, reflecting stand maturity and lack of seedling establishment due to competition with mature plants. The shrub overstory dominates site resources such that soil water, nutrient capture, nutrient cycling and soil organic matter are temporally and spatially redistributed. Bare ground has increased.
Submodel
Description
This state consists of two community phases; an annual species dominant state and a shadscale/rabbitbrush dominant state with an annual understory. In this state, a biotic threshold has been crossed and state dynamics are driven by the dominance and persistence of the annual plant community which is perpetuated by a shortened fire return interval. The herbaceous understory is dominated by annual non-native species such as cheatgrass and halogeton. Bare ground may be abundant. Resiliency has declined and further degradation from fire facilitates a cheatgrass and sprouting shrub plant community. The fire return interval has shortened due to the dominance of cheatgrass in the understory and is a driver in site dynamics.
Submodel
Description
This state has one community phase which is characterized by a dominance of seeded species most commonly forage kochia. Other seeded species such as crested wheatgrass and Russian wildrye may be present on the site. Annual non-native species are present to increasing.
Submodel
Description
This state consists of one community phase. This state is characterized by the loss of vegetative cover, redistribution and loss of the soil surface, as well as, increasing cover of desert pavement. Feedbacks contributing to the stability of this state include soil loss, nutrient loss, soil surface degradation and increased area, distribution and connectivity between patches of bare soil. This state has only one community phase, described below.
Submodel
Mechanism
Trigger: This transition is caused by the introduction of non-native annual plants, such as halogeton, mustards and cheatgrass.
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: Inappropriate grazing management and/or prolonged drought will decrease or eliminate deep rooted perennial bunchgrasses and favor shrub growth and establishment.
Slow variables: Long term decrease in grass density and reduced native species (shrub and grass) recruitment rates. Increased reproduction of non-native invasive species.
Threshold: Loss of deep-rooted perennial bunchgrasses changes nutrient cycling, nutrient redistribution, and reduces soil organic matter.
Mechanism
Trigger: Fire and/or soil disturbing treatments such as drill seeding and plowing. An unusually wet spring may facilitate the increased germination and production of cheatgrass leading to its dominance within the community.
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
Trigger: Fire and/or soil disturbing treatments such as drill seeding and plowing.
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
Shrub management and seeding of desired species with minimal soil disturbance. This pathway has a low probability of success due to the arid climate of these sites (see Ecological Dynamics and Disturbance Response, Fire Ecology).
Mechanism
Trigger: Multiple fires and/or failed seeding and other soil disturbing treatments such as drill seeding, roller chopper, Lawson aerator etc.
Slow variables: Increased, continuous fine fuels modify the fire regime by changing intensity, size and spatial variability of fires.
Threshold: Increased wind erosion resulting in soil loss preventing the establishment of native perennials. 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
Seeding of perennial species. This pathway has a low probability of success due to the arid climate of these sites (see Ecological Dynamics and Disturbance Response, Fire Ecology).
Mechanism
Trigger: Severe drought, multiple fires (typically occurring within 15 years) or inadequate rest and recovery from defoliation, coupled with soil loss and redistribution caused by an intense rain or wind event.
Slow variables: Long term decrease in grass density and reduced native species (shrub and grass) recruitment rates. Long term soil movement and soil loss.
Threshold: Increased overland flow and reduced soil moisture due to extensive bare ground.
Mechanism
Trigger: Catastrophic fire
Slow variable: Increased production and cover of non-native annual species.
Threshold: Cheatgrass or other non-native annuals dominate the understory.
Model keys
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