JD Shallow 9-12 PZ
Scenario model
Current ecosystem state
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Management practices/drivers
Select a transition or restoration pathway
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Transition T1A
Introduction of non-native annual plants
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Transition T2A
Chronic improperly managed grazing or prolonged time without fire
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Transition T2B
Catastrophic fire, soil disturbing treatments or prolonged improperly managed grazing in the presence of non-native annual species
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Transition T2C
Time and lack of disturbance or management action
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Restoration pathway R3A
Shrub management and seeding of native species coupled with minimal soil disturbance
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Transition T3A
Catastrophic fire, soil disturbing treatments or prolonged improperly managed grazing in the presence of non-native annual species
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Transition T3B
Time and a lack of disturbance or management action
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Restoration pathway R3B
Brush management such as mowing, coupled with seeding of deep rooted non-native wheatgrasses
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Restoration pathway R4A
Reduction of annual grasses through management actions such as herbicide, prescribed grazing, or mowing, and seeding of desired species
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Restoration pathway R4A
Seeding of deep-rooted bunchgrasses
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Restoration pathway R5B
Tree removal practices with minimal soil disturbance
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Transition T5A
Catastrophic, stand replacing fire or inappropriate tree removal practices with soil disturbance
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Restoration pathway R5A
Tree removal and seeding of desired non-native wheatgrass species
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Transition T6A
Repeated, heavy, growing season grazing, severe fire
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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 is representative of the natural range of variability for the site under pristine conditions. The reference state is a bunchgrass shrubland. 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 are maintained by ecosystem processes and structural elements such as the presence of all structural and functional plant groups, the retention of organic matter and the maintenance of plant community cover. Plant community phase changes are primarily driven by infrequent fire and/or periodic drought.
Submodel
Description
This state is similar to the Reference State. Ecological function has not changed fundamentally, however the resiliency of the site has been reduced by the presence of invasive plants. Additionally, livestock herbivory may be present as a disturbance process and changes in climate may be altering ecological dynamics. Non-native plant species may increase in abundance but will not become dominant or control ecological processes within this state. These species 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 are maintained by ecosystem processes and structural elements such as the presence of all structural and functional groups, and retention of organic matter and nutrients. Positive feedbacks driven by plant community invasion decrease ecosystem resilience and stability of the state. These include exotic plant species' high seed output, persistent seed bank, rapid growth rate, ability to cross pollinate, and adaptations for seed dispersal. Plant community phase changes are primarily driven by infrequent fire, periodic drought and ungulate herbivory.
Current potential plant communities mirror those of the above Reference State 1.0 yet with the addition of a low level of invasive exotic plant invasion and influences of livestock herbivory. Livestock herbivory may result in decreases in deep rooted perennial grasses, and related increases in shallow rooted perennial grasses (such as Sandberg's bluegrass) and shrubs, among other changes.
Description
Within this state, site resources are primarily controlled by shrub species and western juniper. Native perennial grass composition has been reduced considerably. Sprouting and non-sprouting shrubs as well as western juniper are present. Exotic herbaceous species are often present.
Multiple plant community phases are likely within this state, influenced by livestock herbivory and fire. Sagebrush cover exceeds site concept and may be decadent, reflecting stand maturity and lack of seedling establishment due to competition with mature plants. Sprouting species such as rabbitbrush and broom snakeweed as well as non-sprouting species such as big sagebrush may be dominant. The dominance of site resources by the shrub overstory and Sandberg bluegrass understory leads to a temporal redistribution of soil water, nutrient capture, nutrient cycling and soil organic matter. Western juniper may increase and begin to influence the understory vegetation.
Description
Within this state, site resources are primarily controlled by exotic annual and perennial herbaceous species. Native perennial grass composition has been greatly diminished. Shrub species and western juniper may also be present. Overtime, with increasing invasion, soil stabilizing perennial root biomass will be decreased. Bare ground will increase potentially increasing erosion even on this low slope site during extreme weather events.
Multiple plant communities are possible within this state, all of which are dominated by invasive annual grasses such as cheatgrass and medusahead as well as invasive annual and perennial forbs. Invader shrub species such as broom snakeweed may also be common
Description
This state is characterized by a dominance of young juniper (less than 100 years old) in the overstory. Big 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 cycling have been spatially and temporally altered due to competition from Juniper as well as altered community structure. Juniper encroachment can decrease cover of grasses and shrubs by reducing light availability and altering site hydrology through increased interception of precipitation, reduced infiltration and increased erosion. Bare ground will increase and erosion may be increased even on this low slope site during extreme weather events.
Multiple plant community phases may occur within this state, defined in part by the degree of juniper encroachment and the relative composition of other structural and functional groups. Non-native annual plants are likely present in all phases.
Description
Within this state, site resources are primarily controlled by introduced range grasses such as crested wheatgrass (Agropyron cristatum). Multiple community phases may occur within this state and will include different compositions of native and invasive shrub and grass species and western juniper. Similar to ecological dynamics within other states of this site, shrub species and western juniper will increase with greater time since fire and herbivory pressure. While introduced range grasses may provide some analogous ecological functions to native perennial grasses, they may outcompete native grasses in the long-term.
Mechanism
Trigger(s): This transition is caused by the introduction of non-native annual plants, such as
cheatgrass, medusahead, and mustards.
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.
Constraints to recovery
Altered Processes/Feedback Mechanisms: 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(s): Chronic improperly managed grazing or prolonged time without fire sufficient enough for the deep rooted perennial grass seedbank to diminish, and grazing resistant and/or fire intolerant shrubs to increase.
Slow variables: Long term decrease in deep-rooted perennial grass density.
Altered Processes/Feedback Mechanisms: Loss of deep-rooted perennial bunchgrasses changes nutrient cycling, nutrient redistribution, and reduces soil organic matter.
Mechanism
Trigger(s): Catastrophic fire, soil disturbing treatments or prolonged improperly managed grazing in the presence of non-native annual species; competitive increase in medusahead through lack of active management.
Slow variables: Increased production and cover of non-native annual species; increased
production and cover of medusahead as a percentage of the non-native total annual grass
production and total cover.
Altered Processes/Feedback Mechanisms: Loss of deep-rooted perennial bunchgrasses and shrubs truncates, spatially and temporally, nutrient capture and cycling within the community.
Constraints to recovery
Increased, continuous fine fuels from annual non-native plants modify the fire regime by changing intensity, size and spatial variability of fires.
Mechanism
Trigger(s): Time and lack of disturbance or management action allows for western juniper to dominate.
Slow variables: Over time the abundance and size of trees will increase.
Altered Processes/Feedbacks: Trees dominate ecological processes.
Context dependence
This may be coupled with grazing management that favors tree establishment by reducing understory herbaceous competition for site resources.
Mechanism
Shrub management and seeding of native species coupled with minimal soil disturbance, potentially requiring the use of herbicide.
Context dependence
Risk of failure may be high due to droughty nature of the site, shallow soils and low resilience.
Mechanism
Trigger(s): Catastrophic fire, soil disturbing treatments or prolonged improperly managed grazing in the presence of non-native annual species; competitive increase in medusahead through lack of active management.
Slow variables: Increased production and cover of non-native annual species; increased
production and cover of medusahead as a percentage of the non-native total annual grass
production and total cover.
Altered Processes/Feedback Mechanisms: 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.
Constraints to recovery
Increased, continuous fine fuels modify the fire regime by changing intensity, size and spatial variability of fires
Mechanism
Trigger(s): Time and a lack of disturbance or management action allows for western juniper 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.
Altered Processes/Feedback Mechanisms: Trees dominate ecological processes.
Mechanism
Brush management such as mowing, coupled with seeding of deep rooted non-native wheatgrasses. Targeted herbicide treatments may be necessary to facilitate this restoration pathway.
Context dependence
If non-native annual grasses are present, restoration attempts causing soil disturbance will likely initiate a transition to an annual state
Mechanism
Reduction of annual grasses through management actions such as herbicide, prescribed grazing, or mowing, and seeding of desired species.
Context dependence
Risk of failure may be high due to droughty nature of the site and low resilience.
Mechanism
Seeding of deep-rooted bunchgrasses. Targeted herbicide treatments are often necessary to facilitate this restoration pathway.
Context dependence
The probability of success is extremely low due to the low resilience of the site.
Mechanism
Tree removal practices with minimal soil disturbance.
Mechanism
Trigger(s): Catastrophic, stand replacing fire or inappropriate tree removal practices with soil disturbance will cause a transition to the Invaded State.
Slow variables: Increased production and cover of non-native annual species under tree canopies.
Altered Processes/Feedback Mechanisms: Changes in plant community composition and spatial variability of vegetation due to the loss of perennial bunchgrasses and sagebrush truncate energy capture and impact nutrient cycling and distribution.
Constraints to recovery
Closed tree canopy with non-native annual species dominant in the understory changes the intensity, size and spatial variability of fires.
Mechanism
Tree removal and seeding of desired non-native wheatgrass species. Tree removal practices with minimal soil disturbance are recommended. Herbicide treatment may be necessary.
Context dependence
Probability of success declines with increased presence of non-native annual species.
Mechanism
Trigger(s): Repeated, heavy, growing season grazing will decrease or eliminate deep rooted perennial bunchgrasses, increase Sandberg bluegrass and favor shrub growth and establishment. Severe fire will remove sagebrush overstory, decrease perennial bunchgrasses and enhance Sandberg bluegrass.
Slow variables: Long term decrease in deep-rooted perennial grass density.
Altered Processes/Feedbacks: Loss of deep-rooted perennial bunchgrasses changes nutrient cycling, nutrient redistribution, and reduces soil organic matter.
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.