Mountain Shallow Loam (mountain big sagebrush)
Scenario model
Current ecosystem state
Select a state
Management practices/drivers
Select a transition or restoration pathway
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Transition T1A
introduction of exotic species
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Transition T2A
Lack of fire and continued heavy livestock grazing during the growing-season
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Transition T3A
application of 2, 4-D or spike
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Transition T3B
Wildfire or brush management, either by mechanical means or prescribed fire
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Restoration pathway R4A
Fire control and heavy grazing
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Restoration pathway R5A
Fire control and heavy grazing
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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 is a description of this ecological site just prior to Euro-American settlement but long after the arrival of Native Americans. The description of the Reference State was determined by NRCS Soil Survey Type Site Location information and familiarity with rangeland relict areas where they exist. The least modified plant community would have been dominated by a scattering of lower-statured mountain big sagebrush (Artemisia tridentata ssp. vaseyana) and a mixture of relatively patchy herbaceous species. Antelope bitterbrush (Purshia tridentata) and mountain snowberry (Symphoricarpos oreophilus) would have been present but less common shrub associates. Dominant grasses would have included bluebunch wheatgrass (Pseudoroegneria spicata), muttongrass (Poa fendleriana), and Columbia needlegrass (Achnatherum nelsonii), and forbs would have included tapertip hawksbeard (Crepis acuminata), arrowleaf balsamroot (Balsamorhiza sagittata), sticky purple geranium (Geranium viscosissimum), and shortstem buckwheat (Eriogonum brevicaule), among others (1.1). A more complete list of species by lifeform for the Reference State is available in the accompanying tables in the “Plant Community Composition by Weight and Percentage” section of this document.
Submodel
Description
State 2 is identical to State 1 in form and function, with the exception of the presence of non-native plants and animals, possible extinctions of native species, and a different climate. State 2 is a description of the ecological site shortly following Euro-American settlement. This state can be regarded as the current potential. This state is characterized by somewhat scattered mountain big sagebrush, antelope bitterbrush, and other minor shrubs with a mixture of herbaceous species. Dominant grasses are western wheatgrass (Pascopyrum smithii), with bluebunch wheatgrass, muttongrass, and Columbia needlegrass being slightly diminished from the Reference State. Forbs include tapertip hawksbeard, arrowleaf balsamroot, and sticky purple geranium, among others (2.1). A small component of non-natives will also be present. The resiliency of this State is maintained by a healthy, productive, and diverse plant community that can provide native seed sources and promotes soil stability, water infiltration, and soil moisture retention. Wildfire may also play a role in maintaining the balance between shrubs and herbs. The resiliency of this State will be maintained by a reduction in livestock numbers and season of use. Conversely, heavy continuous season long livestock and/or big game grazing will negatively impact the resiliency of this State.
Submodel
Description
In the absence of fire, but with continued heavy impacts from livestock grazing, the native herbaceous understory will markedly decrease, allowing the shrubs, mainly mountain big sagebrush, to become super-dominant and take over the site (3.1). The stability of this State is maintained by the abundance of seed source for sagebrush and other shrubs, and the lack of seed source for native perennial herbs, and possibly by soil erosion. The resiliency of this State can be maintained by reductions in animal numbers and seasons of use as long as soils are largely intact. Conversely, heavy season-long grazing by livestock and big game will negatively impact the resiliency of this State.
Submodel
Description
Perennial grasses will temporarily dominate the site (4.1) if chemicals (e.g. 2, 4-D, spike) are used to reduce the shrub component. This grass-dominated plant community can be sustained by re-application of chemical, re-seeding when necessary, and moderating the grazing by livestock during the growing season (4.1a). Fire control combined with continuous heavy season-long grazing will allow the site to eventually return to State 3.
Submodel
Description
Yellow rabbitbrush and some herbaceous species such as bluebunch wheatgrass, muttongrass, western wheatgrass and squirreltail (Elymus elymoides) (5.1) will increase following fire, whether prescribed or wild, or chemical removal of mountain big sagebrush. This State will be maintained by the recurrence of wildfire at short intervals, assuming that soils are largely intact. Fire control combined with continuous heavy season-long grazing will allow the site to eventually return to State 3.
Submodel
Mechanism
The simultaneous introduction of exotic species, both plants and animals, possible extinctions of native flora and fauna, and climate change has caused State 1 to transition to State 2. Reversal of such historic changes (i.e. a return pathway) back to State 1 is not practical.
Mechanism
Lack of fire and continued heavy livestock grazing during the growing-season of grasses can cause a transition into Mountain Big Sagebrush Super-dominance State. The approach to this transition is indicated by a loss of the perennial grass understory, an increase in the shrub component relative to the grasses, and an increase in bare soil exposed between the perennials. This transition is triggered by sustained heavy grazing in the growing season by livestock and big game use in winter.
Mechanism
With the application of 2, 4-D or spike, it may be possible to reduce the shrub layer and allow the perennial grasses to re-establish.
Mechanism
Wildfire or brush management, either by mechanical means or prescribed fire, will temporarily remove the mountain big sagebrush. However, an increase in yellow rabbitbrush (Chrysothamnus viscidiflorus) will follow the removal of sagebrush in most circumstances. The herbaceous component may also increase after fire or brush beating. The approach to this transition is indicated by the loss of desirable perennial species and a build up of fuel loads. This transition is triggered by wildfire or brush removal by mechanical or pyric (fire) means.
Mechanism
Fire control and heavy grazing will allow sagebrush to eventually re-establish, allowing the plant community to return to State 3.
Model keys
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