SOUTH SLOPE 8-12 P.Z.
Scenario model
Current ecosystem state
Select a state
Management practices/drivers
Select a transition or restoration pathway
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Transition T1A
Introduction of non-native species
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Transition T2A
Loss of deep-rooted perennial bunchgrass
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Transition T2B
Severe repeated wildfire or soil disturbance
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Restoration pathway R3A
Seeding with native species
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Transition T3A
Repeated/severe wildfire and/or failed restoration attempt
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Restoration pathway R3B
Brush management, seeding, low success probability
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Restoration pathway R4A
Seeding, management techniques, low probability success
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Transition T5A
Increased size and frequency of wildfires
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No transition or restoration pathway between the selected states has been described
Target ecosystem state
Select a state
Description
The Reference State 1.0 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.
Characteristics and indicators
Fire is the principal means of renewal of decadent stands of Wyoming big sagebrush. Wyoming big sagebrush communities historically had low fuel loads, and patchy fires that burned in a mosaic pattern were common at 10 to 70 year return intervals (West and Hassan 1985, Bunting et al. 1987). (Davies et al 2007) suggest fire return intervals in Wyoming big sagebrush communities were around 50 to 100 years. Wyoming big sagebrush is killed by fire and only regenerates from seed. Recovery time for Wyoming big sagebrush may require 50 to 120 or more years (Baker 2006). Post-fire hydrologic recovery and resilience is primarily influenced by pre-fire site conditions, fire severity, and post-fire weather and land use that relate to vegetation recovery.
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. 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 is a product of the absence of wildfire, prolonged drought, combined with many years of heavy grazing during time periods harmful to perennial bunchgrasses. Sandberg bluegrass increases with a reduction in deep-rooted perennial bunchgrass competition and may become the dominate grass. The loss of structural and functional groups affects ecosystem functioning and can result in soil surface instability and soil loss.
Sagebrush dominates the overstory and exceeds site concept. It may be decadent, reflecting stand maturity and lack of seedling establishment due to competition with mature plants. Spiny hopsage and/or rabbitbrush may be a significant component of this state. 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 exceeds the site concept and soil and precipitation are being redistributed off site.
Submodel
Description
This community is characterized by the dominance of annual non-native species and a narrowed fire return interval. Sprouting shrubs such as rabbitbrush, shadscale, broom snakeweed and Spiny hopsage may be common, depending on time since disturbance.
Submodel
Description
This state is characterized by the dominance of introduced wheatgrass species. Forage kochia and other desired seeded species including. Wyoming big sagebrush and native and non-native forbs may be also be present. 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.
Submodel
Mechanism
Trigger: This transition is caused by the introduction of non-native annual weeds, such as cheatgrass, mustards, bur buttercup and halogeton.
Slow variables: Over time the annual non-native plants 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: Absence of wildfire, prolonged drought, and/or excessive, long-term, herbivory during periods harmful to perennial bunchgrasses, or a combination of all.
Slow variables: Long term reduction in deep-rooted perennial grass density, reproduction, and vigor.
Threshold: Loss of deep-rooted perennial bunchgrasses results in spatial and temporal nutrient changes to nutrient cycling, water infiltration and redistribution. This reduces soil organic matter and soil moisture storage.
Mechanism
Trigger: Multiple severe wildfires and/or soil disturbing treatments that removes deep-rooted native perennials
Slow variables: Increased seed production and cover of annual non-native species.
Threshold: Increased, continuous fine fuels modify the fire regime by changing frequency, 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 and impact the temporal and spatial aspects of nutrient cycling and distribution.
Mechanism
Brush management with minimal soil disturbance, coupled with seeding of deep-rooted perennial native bunchgrasses. Probability of success very low.
Mechanism
Trigger: Repeated/severe wildfire and/or failed restoration attempt using soil disturbing practices
Slow variables: Increased production and cover of non-native annual species and loss of native perennials.
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
Brush management with minimal soil disturbance, coupled with seeding of desired species, usually introduced wheatgrasses. Restoration attempts causing soil disturbance will likely initiate a transition to an annual state. Probability of success very low.
Mechanism
Seeding of deep-rooted introduced bunchgrasses and other desired species; may be coupled with brush management and/or herbicide. Probability of success is extremely low.
Mechanism
Trigger: Multiple severe wildfires and/or soil disturbing treatments that removes deep-rooted perennials.
Slow variables: Increased production and cover of non-native annual species
Threshold: Increased, continuous fine fuels modify the fire regime by changing frequency, 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 and impact the temporal and spatial aspects of nutrient cycling and distribution.
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.