Saline Upland (SU) LRU 01 Subset A
Scenario model
Current ecosystem state
Select a state
Management practices/drivers
Select a transition or restoration pathway
- Transition T1A More details
- Transition T1B More details
- Restoration pathway R2A More details
- Transition T2A More details
- Restoration pathway R3A More details
- Restoration pathway R3B More details
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No transition or restoration pathway between the selected states has been described
Target ecosystem state
Select a state
Description
The Reference State of this ecological site consists of two known potential plant communities, the Reference Community (1.1) and the Wheatgrass Community (1.2). These are described below but are generally characterized by a mid-statured, cool-season grass community with limited shrub production. Community 1.1 is dominated by basin wildrye and bluebunch wheatgrass and is considered the reference, while Community 1.2 has a codominance of basin wildrye, bluebunch wheatgrass, and western wheatgrass with an increase in basin big sagebrush. These communities may meld into each other due to the varying conditions that occur in southwest Montana, particularly during dry cycles.
Submodel
Description
State 2, Shortgrass State, has been altered by long-term unmanaged, heavy grazing. In this State, drought conditions may speed the departure from reference.
Submodel
Description
The site is invaded when more than five percent of the total production is from non-native exotic species, such as cheatgrass and any occurrence of ventenata.
Due to the complex relationships between plants and soil biota and their influence on site stability, hydrology, and biotic integrity, restoration from the invaded state will never return to the reference state. To restore an invaded state would require a considerable input of energy and capital to match the reference plant community, but the hydrology and soil biota would not be those of the reference state. Often, the invasive species seedbank is not eliminated, which will allow for a fast conversion back to the invaded state.
Submodel
Mechanism
The Reference State (1) transitions to the Altered State (2) if basin wildrye, by dry weight, decreases to below 10% or if bare ground cover is increased beyond 20%. The driver for this transition is loss of taller bunchgrasses, which creates open areas in the plant canopy with bare soil. Soil erosion results in decreased soil fertility, driving transitions to the Altered State. There are several other key factors signaling the approach of transition T1A: increases in soil physical crusting, increase of rhizomatous grasses, 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 trigger for this transition is improper grazing management and/or long-term drought leading to a decrease in basin wildrye composition to <15% and reduction in total plant canopy cover.
Mechanism
Rapid invasion of the Reference State is often a result of repeated heavy disturbance from non-managed grazing (often combined with prolonged drought), stressing native bunchgrasses. Seeds of non-native grasses and forbs readily germinated in the bare ground between bunchgrass culms.
Mechanism
The Shortgrass State (2) has lost soil or vegetation attributes to the point that recovery to the Reference State (1) will require reclamation efforts such as soil rebuilding, intensive mechanical and cultural treatments, and/or revegetation (via seeding or sprig planting in the case of basin wildrye). Examples of mechanical treatment may be brush control, while cultural treatments may include prescribed grazing, targeted brush browsing, or prescribed burning. Low-intensity prescribed fires can be used to reduce competitive increasers like needle and thread and Sandberg bluegrass. A low-intensity fire will also reduce big sagebrush densities. In areas prone to annual grass infestation, fire should be carefully planned or avoided. The drivers for this restoration pathway are reclamation efforts along with proper grazing management.
Mechanism
With continued disturbance, the Shortgrass State can degrade, losing the majority of the native bunchgrasses as well as reducing the native rhizomatous grasses. Invasive species take advantage of these plant gaps. The trigger is the presence of invasive species such as cheatgrass, ventenata, and leafy spurge.
Mechanism
Restoration of the Invaded State (3) to the Reference State (1) requires substantial energy input. The drivers for the restoration pathway are the removal of invasive species, restoration of native bunchgrass species, persistent management of invasive species, and proper grazing management. Without continued control, invasive species are likely to return (probably rapidly) due to the presence of seeds and/or other viable material in the soil and management related practices that increase soil disturbance. If invaded by conifer encroachment, treatment depends on the condition of the rangeland.
Sites that have transitioned from the Rhizomatous State (2) to the Invaded State (3) may be severely lacking in soil and vegetative properties that will allow for restoration to the Reference State. Hydrologic function damage may be irreversible, especially with accelerated gully erosion.
Mechanism
If invasive species are removed before remnant populations of bunchgrass are drastically reduced, the Invaded State (3) can revert to the Rhizomatous state. The driver for the reclamation pathway is weed management without reseeding. Continued Integrated Pest Management (IPM) will be required as many of the invasive species that can occupy the Invaded State have extended dormant seed life. The trigger is invasive species control.
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.