MAHOGANY SAVANNA 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
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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 represents the natural range of variability under pristine conditions. The reference state has three general community phases: a tree-shrub dominant-phase, a sprouting shrub and 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 long-term drought, and/or insect attack.
Submodel
State 2
Current Potential State
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.
Submodel
Description
This state has two community phases a grass-dominated phase and a sprouting shrub-dominated phase. The primary characteristic of this state is a lack of mountain mahogany resulting from a severe wildfire. 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 competition from deep rooted perennial bunchgrass and become the dominant grass. Annuals, Sandberg bluegrass, and sprouting shrubs dominate site resources such that soil water, nutrient capture, nutrient cycling, and soil organic matter are temporally and spatially redistributed.
Submodel
Mechanism
Trigger: This transition is caused by the introduction of non-native annual plants, such as cheatgrass, mustards, and thistle.
Slow variables: Over time annual non-native species 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: High-severity or stand-replacing fire that significantly reduces or eliminates mountain mahogany and sagebrush. Bunchgrass plants significantly damaged by the fire may be further reduced or eliminated with inappropriate post-fire grazing management. Sandberg bluegrass becomes the dominant grass.
Slow variable: Cover and production of Sandberg bluegrass and/or annual non-natives will increase. Reduction of soil organic matter input, resulting in decreased soil water.
Threshold: Loss of mahogany overstory, sagebrush, and deep-rooted perennial bunchgrasses changes nutrient cycling, nutrient redistribution, and reduces soil organic matter. Increased, continuous fine fuels modify the fire regime by changing intensity, size and spatial variability of fires.
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.