Natural Resources
Conservation Service
POTR5/SYOR2/BRMA4-ELTR7
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
- 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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Description
The Reference State 1.0 is a representative of the natural range of variability under pristine conditions. This site has four general community phases; a mature woodland phase, a sucker/sapling phase, an immature woodland phase and an over mature woodland 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, 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. Periodic wildfires prevent over-mature aspen stands and maintain a naturally stratified mosaic of even-aged aspen stands in various stages of successional development. Many aspen stands are even-aged because of the rapid reproduction by suckering after a major disturbance such as fire. In the absence of fire, harvest, or similar events, aspen stands become uneven-aged. Uneven-aged stands form under stable conditions where the overstory gradually disintegrates with disease or age, and is replaced by suckers. Uneven-aged stands also occur where individual clones gradually expand into adjacent grasslands or shrublands. Harvesting/cutting of older age classes (that are more suspectible to insects) may minimize damage and larger clear-cut areas may retard conifer infill.
Submodel
State 2
Current Potential State
Current Potential State
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 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.
Harvesting/cutting of older age classes (that are more susceptible to insects) may minimize damage and larger clear-cut areas may retard conifer infill. Season-long herbivory will diminish/eliminate successful aspen establishment and may accelerate establishment of conifers and other woody species. Aspen stands will generally establish is domestic and wild herbivory is restricted to use of leaders on less than 40% of the number of suckers present.
Submodel
Description
This state is characterized by one community phase dominated by Rocky Mountain white fir. Limber pine may also be present. Aspen may be present in trace amounts however trees are decadent and little to no regeneration is occurring. The conifer stand may be a variety of ages depending on harvesting and cutting history and natural regeneration. Aspen and potential for root suckering has been eliminated due to repeated stress from the management regime. Duff build-up can retard conifer germination while fossorial animal activity can provide conifer germination sites. Occurrence of surface fire scorches new seedlings but usually does not kill older conifer trees with thicker bark. Understory vegetation is sparse. Negative feedbacks enhance ecosystem resilience and contribute to the stability of the state. These feedbacks include the dense canopy cover of conifer creating a shade rich environment that facilitates the germination and establishment of conifers and retards the growth and suckering of aspen. Positive feedbacks decrease ecosystem resilience and stability of the state. These include high fuel loads from canopy closure and dead and down wood leading to the potential for stand-replacing fire.
Submodel
Mechanism
Trigger: This transition is caused by the introduction of non-native plants, such as Kentucky bluegrass, smooth brome, thistles and common dandelion. Conifers may also invade. Slow variables: Over time the annual non-native species and conifers will increase within the community. Threshold: Any amount of introduced non-native species causes an immediate decrease in the resilience of the site. A change in the natural fire return interval allows conifers to increase.
Mechanism
Trigger: Time and a lack of disturbance allow conifer trees to establish, grow and mature. Slow variables: Over time the abundance and size of trees will increase. Threshold: Conifer composition is greater than 60% of the stand and conifer height exceeds aspen height. Aspen are decadent and dying with little to no regeneration. Little understory vegetation remains due to competition with trees for site resources.
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.
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