Very Shallow Steep Sandy Slopes 12-14 P.Z.
Scenario model
Current ecosystem state
Select a state
Management practices/drivers
Select a transition or restoration pathway
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Transition T1A
Trigger: Introduction of non-native annual species.
More details
Slow variables: Over time the annual non-native plants will 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. -
Transition T1B
Trigger: Time and a lack of disturbance allow trees to dominate site resources; might be coupled with inappropriate grazing management that favors shrub and tree dominance.
More details
Slow variables: Over time the abundance and size of trees will increase.
Threshold: Singleleaf pinyon canopy cover is greater than 50 percent. Little understory vegetation remains due to competition with trees for site resources. -
Transition T2A
Trigger: Time and a lack of disturbance allow trees to dominate site resources; might be coupled with inappropriate grazing management that favors shrub and tree dominance.
More details
Slow variables: Over time the abundance and size of trees will increase.
Threshold: Pinyon canopy cover is greater than 30 percent. Little understory vegetation remains due to competition with trees for site resources. -
Transition T2B
Trigger: Catastrophic crown fire facilitates the establishment of non-native, annual weeds.
More details
Slow variables: (a) An increase in tree crown cover, (b) a loss of perennial understory and (c) an increase in annual non-native species.
Threshold: Cheatgrass or other non-native annuals dominate understory. Loss of deep-rooted perennial bunchgrasses changes: (a) spatial and temporal nutrient cycling, (b) nutrient redistribution, and (3) reduces soil organic matter. Increased canopy cover of trees allows severe stand-replacing fire. The increased seed bank of non-native, annual species responds positively to post-fire conditions facilitating the transition to an Annual State. -
Restoration pathway R3A
Manual or mechanical thinning of trees coupled with seeding. Probability of success is highest from community phase 3.1.
More details -
Transition T3A
Trigger: Catastrophic fire reduces the tree overstory and allows for the annual non-native species in the understory to dominate the site. Soil disturbing treatments such as slash and burn might reduce tree canopy and allow for non-native annual species to increase.
More details
Slow variables: Over time, cover and production of annual non-native species increases.
Threshold: Loss of deep-rooted perennial bunchgrasses and shrubs changes temporal and spatial nutrient capture and cycling within the community. Increased, continuous fine fuels modify the fire regime by increasing frequency, size, and spatial variability of fires. -
No transition or restoration pathway between the selected states has been described
Target ecosystem state
Select a state
Description
The Reference State 1.0 is representative of the natural range of variability under pristine conditions. This Reference State has four general community phases: an old-growth woodland phase, a shrub-herbaceous phase, an immature tree phase, and an infilled tree 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: (a) the presence of all structural and functional groups, (b) low fine fuel loads, and (c) retention of organic matter and nutrients. Plant community phase changes are primarily driven by fire, periodic long-term drought, and/or insect or disease attack. Fires are typically small and patchy due to low fuel loads. This fire type will create a plant community mosaic that will include all or most of the following community phases within this state.
Submodel
Description
The Current Potential State 2.0 is similar to the Reference State 1.0, with four general community phases: (1) an old-growth woodland phase, (2) a shrub-herbaceous phase, (3) an immature tree phase, and (4) an infilled tree phase. Ecological function has not changed, however the resiliency of the state has been reduced by the presence of non-native species. These non-natives, particularly cheatgrass, can be highly flammable and promote fire where historically fire had been infrequent. Negative feedbacks enhance ecosystem resilience and contribute to the stability of the state.
These include: (a) the presence of all structural and functional groups, (b) low fine fuel loads and (c) retention of organic matter and nutrients. Positive feedbacks decrease ecosystem resilience and stability of the state. These include: (a) the non-natives’ high seed output, (b) persistent seed bank, (c) rapid growth rate, (d) ability to cross pollinate, and (e) adaptations for seed dispersal. Fires within this community with the small amount of non-native annual species present are likely still small and patchy due to low fuel loads. This fire type will create a plant community mosaic that will include all or most of the following community phases within this state.
Submodel
Description
This state has two community phases characterized by the dominance of singleleaf pinyon in the overstory. This state is identifiable by: (1) greater than 50 percent cover of singleleaf pinyon, and (2) a mixed age class. Older trees are at maximal height and upper crowns may be flat-topped or rounded. Younger trees are typically cone- or pyramidal-shaped. Understory vegetation is sparse due to increasing shade and competition from trees.
Submodel
Description
This community is characterized by the dominance of annual non-native species such as cheatgrass and tansy mustard in the understory. Rabbitbrush or other sprouting shrubs might dominate the overstory. Annual non-native species dominate the understory. Ecological dynamics are significantly altered in this state. Annual non-native species create a highly combustible fuel bed that shortens the fire return interval. Nutrient cycling is spatially and temporally truncated as annual plants contribute significantly less to deep soil carbon. This state was not observed in MLRA 26 during field work for this project, however it is possible given increased fire activity in these sites and their proximity to known annual states of sagebrush ecological sites. We refer the reader to the report for Disturbance Response Group 21 for MLRA 28A and 28B.
Submodel
Mechanism
T1A: Transition from Reference State 1.0 to Current Potential State 2.0
Trigger: Introduction of non-native annual species.
Slow variables: Over time the annual non-native plants will 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: Time and a lack of disturbance allow trees to dominate site resources; might be coupled with inappropriate grazing management that favors shrub and tree dominance.
Slow variables: Over time the abundance and size of trees will increase.
Threshold: Singleleaf pinyon canopy cover is greater than 50 percent. Little understory vegetation remains due to competition with trees for site resources.
Mechanism
Trigger: Time and a lack of disturbance allow trees to dominate site resources; might be coupled with inappropriate grazing management that favors shrub and tree dominance.
Slow variables: Over time the abundance and size of trees will increase.
Threshold: Pinyon canopy cover is greater than 30 percent. Little understory vegetation remains due to competition with trees for site resources.
Mechanism
Trigger: Catastrophic crown fire facilitates the establishment of non-native, annual weeds.
Slow variables: (a) An increase in tree crown cover, (b) a loss of perennial understory and (c) an increase in annual non-native species.
Threshold: Cheatgrass or other non-native annuals dominate understory. Loss of deep-rooted perennial bunchgrasses changes: (a) spatial and temporal nutrient cycling, (b) nutrient redistribution, and (3) reduces soil organic matter. Increased canopy cover of trees allows severe stand-replacing fire. The increased seed bank of non-native, annual species responds positively to post-fire conditions facilitating the transition to an Annual State.
Mechanism
Manual or mechanical thinning of trees coupled with seeding. Probability of success is highest from community phase 3.1.
Mechanism
Trigger: Catastrophic fire reduces the tree overstory and allows for the annual non-native species in the understory to dominate the site. Soil disturbing treatments such as slash and burn might reduce tree canopy and allow for non-native annual species to increase.
Slow variables: Over time, cover and production of annual non-native species increases.
Threshold: Loss of deep-rooted perennial bunchgrasses and shrubs changes temporal and spatial nutrient capture and cycling within the community. Increased, continuous fine fuels modify the fire regime by increasing frequency, size, and spatial variability of fires.
Model keys
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