Mountain Loam (mountain big sagebrush)
Scenario model
Current ecosystem state
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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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Restoration pathway R3a
Wildfire or application of 2, 4-D™ as an initial treatment, combined with prescribed grazing
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Transition T3a
tilling and re-seeding
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Transition T3b
Wildfire or brush management
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Transition T4a
Heavy continuous season-long grazing
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Transition T5a
heavy season-long grazing combined with natural succession
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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 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 co-dominated by mountain big sagebrush (Artemisia tridentata ssp. vaseyana) and a mixture of herbaceous species. Dominant grasses would have included bluebunch wheatgrass (Pseudoroegneria spicata), and basin wildrye (Leymus cinereus), and forbs would have included sticky purple geranium (Geranium viscosissimum), shortstem buckwheat (Eriogonum brevicaule), and lupines (Lupinus caudatus ssp. caudatus and L. argenteus), 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 is a shrub-steppe community where there is a co-dominance between mountain big sagebrush (and other minor shrubs) and a rather diverse mixture of herbaceous species. Dominant grasses are bluebunch wheatgrass and basin wildrye, and forbs include sticky purple geranium, shortstem buckwheat, and lupine species, 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 appropriate stocking rates and season of use. Conversely, heavy continuous season long livestock grazing and accelerated soil erosion will negatively impact the resiliency of this State.
Submodel
Description
Fire and heavy livestock grazing reduce native grasses. Shrubs, mainly mountain big sagebrush, will increase becoming super-dominant. Some low shrubs such as yellow rabbitbrush (Chrysothamnus viscidiflorus ssp. viscidiflorus), broom snakeweed (Gutierrezia sarothrae), and spineless horsebrush (Tetradymia canescens) may also increase. The stability of this State is maintained by the lack of a healthy, productive and diverse herb component capable of providing native seed source, soil stabilization, and soil moisture retention. The abundance of sagebrush seed source and lack of fire will also serve to maintain this State. Appropriate livestock grazing (correct stocking rate, timing, etc.) will help maintain the resiliency of this State, but continuous heavy livestock grazing will negatively impact the resiliency of this State.
Submodel
Description
This State is characterized by the dominance of seeded grasses such as intermediate wheatgrass, smooth brome, or orchardgrass. This State occurs when a decision is made to increase forage production by tilling and re-seeding introduced grasses. Periodic brush management is required to maintain the grass-dominance of this State. This resiliency of this State can be maintained by moderate grazing, high intensity short duration use. Conversely, continued heavy and accelerated soil erosion use will negatively impact the resiliency of this State.
Submodel
Description
The shrub component of this State is characterized by an increased amount of root-sprouting shrubs such as yellow rabbitbrush and spineless horsebrush, and a reduction in mountain big sagebrush as a result of sagebrush removal by pyric (fire) or chemical means. The stability of this State is maintained by the lack of sagebrush and the lack of a productive herbaceous component capable of providing native seed source. Proper livestock grazing (correct stocking rates and timing, etc.) will help maintain the resiliency of this community, but heavy season long livestock grazing will negatively impact its resiliency.
Submodel
Description
This State is characterized by the dominance of mountain big sagebrush and snowberry that is the result of natural succession combined with continuous heavy season long grazing. The shrub dominance is maintained by abundant shrub seed source and the lack of herb seed source. The stability of this State is also partially maintained by the fact that the longer-lived shrubs serve to protect the soil and provide abundant litter. Heavy season long livestock grazing will negatively impact the resiliency of this State. Earlier sheep grazing may have reduced the forb component to the extent that introduced grasses become established in the plant community in their place.
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 will cause a transition into the Mountain Big Sagebrush Super-dominance/Low Shrub State. The approach to this transition is indicated by a loss of perennial grass understory, an increase in the shrub component relative to grasses, and the bare soil exposure between shrubs and/or other evidence of accelerated soil erosion. The transition is triggered by sustained heavy season-long grazing.
Mechanism
Wildfire combined with prescribed grazing during only part of the non-growing season of the grasses and forbs will remove much of the dense sagebrush and allow the native perennial herbaceous species to re-establish.
Application of 2, 4-D™ combined with prescribed grazing during the non-growing season of the grasses and forbs will also remove much of the dense sagebrush and allow the native perennial herbaceous species to re-establish.
Mechanism
This transition occurs when a decision is made to increase forage production by tilling and re-seeding with intermediate wheatgrass (Thinopyrum intermedium), smooth brome (Bromus inermis), or orchardgrass (Dactylis glomerata).
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 or other root-sprouting shrubs such as spineless horsebrush will follow the removal of sagebrush in most circumstances. The herbaceous component may also increase after fire or brush beating.
Mechanism
Heavy continuous season-long grazing will reduce the herbaceous component, allowing the fast-growing unpalatable shrubs to re-establish. The approach to this transition is indicated by decreased grass vigor and an increase in shrub seedlings. This transition is triggered by excessive or improperly timed grazing of grasses.
Mechanism
Shrubs, mainly mountain big sagebrush and mountain snowberry (Symphoricarpos oreophilus), will come to dominate the community through natural succession as the length of time increases since the last shrub-killing disturbance. The approach to this transition is indicated by the presence of only older yellow rabbitbrush and spineless horsebrush, and the presence of sagebrush and snowberry seedlings. The trigger causing this transition is heavy season-long grazing combined with natural succession.
Model keys
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