Mountain Stony Loam (mountain big sagebrush)
List model
Reference State
Mountain Big Sagebrush/ Introduced Non-natives State
Mountain Big Sagebrush Super-dominance State
Native Perennial Grasses State
Mountain big sagebrush / Unpalatable forbs state
Yellow rabbitbrush State
Utah Juniper Invaded State
Scenario model
Current ecosystem state
Select a state
Management practices/drivers
Select a transition or restoration pathway
-
Transition T1A
introduction of exotic species
More details -
Transition T2A
Lack of fire and continued heavy livestock grazing during the growing season
More details -
Restoration pathway R3A
cool-season prescribed fire to remove sagebrush, followed by deferment of livestock grazing and reseeding of desirable species
More details -
Transition T3A
the application of 2, 4-D™ to reduce the shrub layer and allow the native perennial grasses to re-establish
More details -
Transition T3B
wildfire or mechanical removal of sagebrush accompanied by heavy grazing
More details -
Transition T3C
continued suppression of fire and heavy continuous livestock grazing
More details -
Transition T4A
heavy livestock grazing and fire exclusion
More details -
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 dominant plant communities found on these sites would have depended on the time since last wildfire and activity of pocket gophers (Thomomys spp.). The first phase immediately following wildfire (1.3a) would have been dominated by a mixture of native perennial forbs and grasses including tapertip hawksbeard (Crepis acuminata), arrowleaf balsamroot (Balsamorhiza sagittata), sticky purple geranium (Geranium viscosissimum), shortstem buckwheat (Eriogonum brevicaule), bluebunch wheatgrass (Pseudoroegneria spicata), slender wheatgrass (Elymus trachycaulus), and Letterman’s needlegrass (Achnatherum lettermanii) (1.1). When present, pocket gophers would have substantially reduced the forb component (1.1a) creating a grass-dominated phase (1.2). With increased time since the last wildfire (1.2a), mountain big sagebrush (Artemisia tridentata spp. vaseyana) would have ultimately regained its dominance on the site (1.3). Several other mountain shrub species would have also been present including antelope bitterbrush (Purshia tridentata) and mountain snowberry (Symphoricarpos oreophilus). 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. The relative amount of shrubs, grasses, and forbs depends upon the length of time elapsed since the last wildfire and the presence of pocket gophers. Immediately following fire (2.3a), the site will be in a mixed forb-grass phase (2.1). If pocket gophers remove the forbs (2.1a), the site could become grass-dominated (2.2). Sagebrush will re-establish 20 to 30 years after fire (2.2a), becoming dominant while still retaining much of its mixed perennial herbaceous understory (2.3). Dominant grasses are western wheatgrass (Pascopyrum smithii), with slightly diminished bluebunch wheatgrass, slender wheatgrass, and Letterman’s needlegrass (compared to the Reference State). Forbs include tapertip hawksbeard, arrowleaf balsamroot, and sticky purple geranium, among others. A small component of non-native species may also occur. This State is maintained by periodic wildfire and by a healthy, productive, and diverse plant community that can provide native seed sources and promotes soil stability, water infiltration, and soil moisture retention. The resiliency of this State can be maintained by reductions in livestock numbers and seasons of grazing, but heavy continued grazing during the growing season will negatively impact the resiliency of this State.
Submodel
Description
In the absence of fire, and 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 an abundance of mountain big sagebrush seed source and a lack of native perennial herb seed source. The paucity of the herbaceous understory may allow accelerated soil erosion to occur. The resiliency of this State can be maintained by reductions in livestock numbers and seasons of grazing, but heavy continued grazing during the growing season will negatively impact the resiliency of this State.
Submodel
Description
Native perennial grasses such as western wheatgrass and Letterman’s needlegrass will temporarily dominate the site (4.1) if chemicals (e.g. 2, 4-D™) are used to reduce the shrub and forb components. This grassland can be sustained by re-application of chemical, re-seeding with native seed when necessary, and moderating the livestock grazing during the growing season of the grasses (4.1a). Continued heavy livestock grazing will negatively impact the resiliency of this State.
Submodel
Description
If heavy livestock grazing continues, the grasses will be depleted once again, allowing the sagebrush and unpalatable forbs to regain dominance. The approach to this transition is indicated by an increase in sagebrush seedlings, a loss of perennial grasses, and an increase in unpalatable forbs. This transition is triggered by heavy livestock grazing and fire exclusion.
Submodel
Description
Yellow rabbitbrush and some common disturbance-following herbaceous species such as houndstongue (Cynoglossum spp.), tarweed (Madia spp.), and mule-ears (Wyethia amplexicaulis) will increase following fire (6.1), whether prescribed or wild, and chemical removal of mountain big sagebrush. This State could be maintained by periodic fire.
Submodel
Description
If the suppression of wildfire continues, particularly during droughty periods, and neighboring stands of Utah juniper exist, juniper will eventually move into these sites. Mountain big sagebrush and other lower shrubs will still be present initially, but with time will be outcompeted by the invading juniper trees (7.1). This State is maintained by juniper outcompeting understory species and by accelerated soil erosion. A cool-season prescribed burn will serve to remove juniper temporarily, allowing the understory to recover.
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 will cause a transition to the Mountain Big Sagebrush Super-dominance State. The approach to this transition is indicated by a loss of perennial grass understory and an increase in shrub component relative to grasses and forbs. Grasses will consist of a residual population occurring closely under larger shrubs. The trigger causing this transition is sustained heavy grazing over the growth season.
Mechanism
The Mountain Big Sagebrush Super-dominance State can be returned to the Mountain Big Sagebrush/ Introduced Non-natives State by applying a cool-season prescribed fire to remove sagebrush. This needs to be followed by a deferment of livestock grazing and reseeding of desirable species.
Mechanism
With the application of 2, 4-D™ it may be possible to reduce the shrub layer and allow the native perennial grasses to re-establish. This seems similar to Restoration Pathway R3a described below; however the difference is that this is produced by application of herbicides which also knock out many forbs.
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) is expected in most circumstances. The herbaceous component will also increase after fire or brush beating. The approach to this transition is indicated by an increase in rabbitbrush seedlings. The transition is triggered by wildfire or mechanical removal of sagebrush accompanied by heavy grazing.
Mechanism
With continued suppression of fire and heavy continuous livestock grazing, the site may slowly be invaded by Utah juniper (Juniperus osteosperma). The approach to this transition is indicated by the increasing presence of juniper seedlings. This transition is triggered by overgrazing and fire exclusion.
Mechanism
If heavy livestock grazing continues, the grasses will be depleted once again, allowing the sagebrush and unpalatable forbs to regain dominance. The approach to this transition is indicated by an increase in sagebrush seedlings, a loss of perennial grasses, and an increase in unpalatable forbs. This transition is triggered by heavy livestock grazing and fire exclusion.
Model keys
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