LOAMY 14-16 P.Z.
Scenario model
Current ecosystem state
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Management practices/drivers
Select a transition or restoration pathway
- Transition A More details
- Transition A More details
- Transition B More details
- Restoration pathway A More details
- Transition A More details
- Restoration pathway A 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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State 1
Reference State
Description
The Reference State is a representative of the natural range of variability under pristine conditions. The reference state has three general community phases: a shrub-grass dominant-phase, a perennial 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. 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 with four 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 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 two community phases: a mountain big sagebrush-dominated phase and a rabbitbrush-dominated phase. This state is a product of many years of heavy grazing during time periods harmful to perennial bunchgrasses. Sandberg bluegrass will increase with a reduction in deep rooted perennial bunchgrass competition and become the dominant grass on this site. Sagebrush dominates the overstory and rabbitbrush may be a significant component. Sagebrush cover exceeds site concept and may be decadent, reflecting stand maturity and lack of seedling establishment due to competition with mature plants.
Submodel
Description
This state has one community phase that is dominated by deep-rooted perennial forbs. This state may be the result of many years of abusive grazing allowing the perennial forbs to increase. It may also be compounded by fire. This may occur as “pockets” or inclusions within other states of the same site, and can appear to be localized. The positive feedbacks in this state include the presence of a competitive functional group that possesses deep-rooted taproots and strong lateral roots, the sprouting ability of roots or root crown, high seed production and the ability to monopolize soil moisture.
Submodel
Mechanism
Trigger: Introduction of annual non-native species.
Slow variable: Over time the annual non-native plants will increase within the community decreasing organic matter inputs from deep-rooted perennial bunchgrasses resulting in reductions in soil water availability for perennial bunchgrasses.
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: Inappropriate grazing will decrease or eliminate deep rooted perennial bunchgrasses, increase Sandberg bluegrass and favor shrub growth and establishment. To Community Phase 3.2: Severe fire in community phase 2.3 will remove sagebrush overstory, decrease perennial bunchgrasses and enhance Sandberg bluegrass. Annual non-native species will increase.
Slow variables: Long term decrease in deep-rooted perennial grass density resulting in decreased organic matter inputs and reduced soil water.
Threshold: Loss of deep-rooted perennial bunchgrasses changes nutrient cycling, nutrient redistribution, and reduces soil organic matter.
Mechanism
Trigger: Inappropriate grazing management and/or fire promote mule ears and other perennial forbs to dominate the site. Persistent spring grazing after a fire will suppress perennial grasses and promote forb production.
Slow variable: Increasing density of perennial forbs and soil erosion.
Threshold: Loss of deep-rooted perennial bunchgrasses and shrubs changes nutrient capture and cycling within the community and reduced organic matter inputs and soil water.
Mechanism
Brush management with minimal soil disturbance/seeding of desired species.
Relevant conservation practices
| Practice | External resources |
|---|---|
|
Brush Management |
|
|
Range Planting |
Mechanism
Trigger: Fire in combination with inappropriate grazing management can eliminate Sandberg bluegrass understory and transition to 4.1.
Slow variable: Increasing density of perennial forbs and soil erosion.
Threshold: Loss of deep-rooted perennial bunchgrasses and shrubs changes nutrient capture and cycling within the community and reduced organic matter inputs and reduced soil water.
Model keys
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Ecological sites
Major Land Resource Areas
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.