Juniper Savanna
Scenario model
Current ecosystem state
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Management practices/drivers
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- Transition T1A 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 is representative of the natural range of variability prior to Euro-American settlement conditions. Community phase changes are primarily driven by time, drought, and infrequent wildfire. State dynamics are maintained by interactions between climatic patterns and disturbance regimes. Natural disturbances under pristine conditions included periodic burning set by native peoples, drought, insect attack, and herbivory by native fauna.
The reference state has three general community phases a perennial grass dominant phase, a perennial grass-shrub mixture with scattered trees and a shrub-dominant phase with some tree infilling. Disturbance favors the grass-dominated and grass-shrub phases and less frequent disturbance favors the shrub-dominated phase.
Submodel
Description
This state is similar to the Reference State. 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. 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. Additionally, the presence of highly flammable, non-native species reduces State resilience because these species can promote fire where historically fire has been infrequent leading to positive feedbacks that further the degradation of the system.
Submodel
Mechanism
Trigger: This transition is caused by the introduction of non-native annual weeds, such as cheatgrass, mustard and halogeton.
Slow variables: 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.
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.