Thin Loamy (Tlo) LRU 44A-A
Scenario model
Current ecosystem state
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Management practices/drivers
Select a transition or restoration pathway
- Transition T1A More details
- Transition T1B More details
- Transition T1C More details
- Restoration pathway R2A More details
- Transition T2A More details
- Transition T2B More details
- Restoration pathway R3A More details
- Restoration pathway R3B More details
- Transition T3A More details
- Restoration pathway R4A More details
- Restoration pathway R4B More details
- Restoration pathway R4C 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
This state is characterized by cool-season bunchgrasses and is represented by three communities that differ mainly in the percent composition of bluebunch wheatgrass and woody canopy cover (predominantly Wyoming big sagebrush). Forbs are a minor component in this state.
Submodel
Description
This state is characterized by having to < 10% bluebunch wheatgrass and < 50% canopy cover. State 2 is represented by two communities that differ in the percent canopy cover of woody species. Production in this state is considerably lower than in the Taller Bunchgrass State (1). Some native plants tend to increase under prolonged drought and/or heavy grazing practices. A few of these species may include prairie junegrass, Sandberg bluegrass, western yarrow, scarlet globemallow, hairy goldenaster, and fringed sagewort.
Submodel
Description
The single community described below characterizes this state.
Submodel
Mechanism
The Taller Bunchgrass State (1) transitions to the Altered State (2) if bluebunch wheatgrass falls below 10% species composition. The trigger for this transition is the loss of taller bunchgrasses, which creates a shift in species composition towards lower productive species, especially needleandthread. This transition can occur from any community within the Taller Bunchgrass State (1), it is not dependant on an increase of woody canopy cover, but on the decrease of bluebunch wheatgrass production. The driver for this transition is improper grazing management and/or long-term drought leading to a decrease in bluebunch wheatgrass composition to < 10%.
Mechanism
The Taller Bunchgrass State (1) transitions to the Sparsely Vegetated State (3) if plant canopy cover declines to < 25% and bluebunch wheatgrass decreases to below 10% by dry weight. The trigger for this transition is the loss of taller bunchgrasses, which creates open spots of bare soil. Soil erosion is accompanied by decreased soil fertility driving transitions to the Sparsely Vegetated State. There are several other key factors signaling the approach of transition T1B: increases in soil physical crusting, decreases in cover of cryptogamic crusts, decreases in soil surface aggregate stability, and/or evidence of erosion, including water flow patterns, development of plant pedestals, and litter movement. The driver for this transition is improper grazing management and/or long-term drought leading to a decrease in rough fescue composition to < 10%.
Mechanism
Regardless of grazing management, without some form of weed management (chemical, mechanical, or biological control), the Taller Bunchgrass State (1) can transition to the Invaded State (4) if aggressive invasive species, such as spotted knapweed and cheatgrass are introduced, even if the herbaceous component of the reference community is thriving. Healthy plant communities are most resilient to invasives. Long-term stress conditions for native species (e.g., overgrazing, drought, and fire) accelerate the process. If populations of invasive species reach critical levels, the site transitions to the Invaded State. The driver for this transition is the presence of aggressive invasive species.
Mechanism
Restoration of the Altered State to the Taller Bunchgrass State requires substantial energy input. The drivers for this restoration pathway are removal of woody species, restoration of native herbaceous species by reseeding bluebunch wheatgrass.
Mechanism
Removal of shrubs without proper grazing management can lead to an increase in bare ground and erosion of the fertile surface horizon and the site can degrade to the Sparsely Vegetated State (3). The driver for this transition is brush management without proper grazing management.
Mechanism
Removal of shrubs can lead to an increase in bare ground. If invasive species are present, bare ground offers opportunity for invasive species to fill open areas, leading to the Invaded State (4). The driver for this transition is brush management in presence of invasive species.
Mechanism
The Sparsely Vegetated State (3) has lost soil or vegetation attributes to the point that recovery to the Taller Bunchgrass State (1) will require reclamation efforts such as soil rebuilding, intensive mechanical treatments, and/or revegetation. The drivers for this restoration pathway are reclamation efforts and proper grazing management. The trigger is restoration efforts.
Mechanism
The Sparsely Vegetated State (3) has lost soil or vegetation attributes to the point that recovery to the Altered State (2) will require reclamation efforts such as soil rebuilding, intensive mechanical treatments, and/or reseeding in recommended areas only. If the reclamation efforts are performed without reseeding bluebunch wheatgrass, under unfavorable climatic conditions, or without proper grazing management, the site will return to the Altered State.
Mechanism
Invasive species can occupy Sparsely Vegetated State (3) and drive it to the Invaded State (4). The Altered Bunchgrass State is at risk of this transition occurring if invasive propagules are present. The driver for this transition is the presence of critical population levels (> 25%) of invasive species. The trigger is the presence of propagules of invasive species.
Mechanism
Restoration of the Invaded State (4) to the Taller Bunchgrass State (1) requires substantial energy input. The drivers for this restoration pathway are removal of invasive species, restoration of native bunchgrass species, ongoing management of invasives, and proper grazing management. Without maintenance, invasive species are likely to return (probably rapidly) because of the presence of propagules in the soil, increases in soil disturbance. The drivers for this reclamation pathway are treatments to reduce or remove invasive/noxious species in combination with favorable growing conditions. The trigger is invasive species control.
Mechanism
Weed management without reseeding desirable, taller bunchgrasses, favorable climatic conditions, or proper grazing management will lead to the Altered State (2).
Mechanism
If invasive species are removed without sufficient remnant populations of reference community species (particularly rough fescue), a site in the Invaded State (4) is likely to return to the Sparsely Vegetated State (3) instead of the Taller Bunchgrass State (1). The driver for the reclamation pathway is weed management without reseeding. The trigger is invasive species control.
Model keys
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