Subalpine Stony Loam (snowfield sagebrush)
Scenario model
Current ecosystem state
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Management practices/drivers
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- Transition T1a More details
- Transition T2a More details
- Transition T3a More details
- Transition T3b 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
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 shrub would have been snowfield sagebrush (Artemisia spiciformis) (Shultz 2006). A lush perennial understory would have been composed of grasses including slender wheatgrass (Elymus trachycaulus), spike fescue (Leucopoa kingii), Columbia needlegrass (Achnatherum nelsonii), and nodding brome (Bromus anomalus). Forbs would have included sticky purple geranium (Geranium viscosissimum), Fendler’s meadow-rue (Thalictrum fendleri), Nevada pea (Lathyrus lanszwertii), and sulphur-flower buckwheat (Eriogonum umbellatum var. umbellatum) among many others. A more complete list of species by lifeform for the Reference State is available in accompanying tables in the “Plant Community Composition by Weight and Percentage” section of this document. The time elapsed since last wildfire would have been the driving factor behind the relative abundance of shrubs relative to the associated understory. Following a recent wildfire (1.2a), an herbaceous dominant phase would have been found (1.1). As the time since last fire increased (1.1a), the shrub component would have increased (1.2).
Submodel
Description
State 2 is very similar to State 1 in form and function, with the exception of the presence of non-native plants and animals, possible extinctions of some 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 primary shrub is snowfield sagebrush. The native perennial herbs are slightly reduced due to impacts from heavy seasonal grazing, but the species would likely still include those present in the Reference State (State 1). A small component of non-native introduced annuals are now also present including Douglas’ knotweed (Polygonum douglasii), mountain tarweed (Madia glomerata), and Kentucky bluegrass (Poa pratensis). 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. The maintenance this State will be encouraged by a reduction in livestock grazing pressure. Conversely, continued heavy livestock grazing during the growing season will negatively impact the resiliency of this State.
Submodel
Description
Snowfield sagebrush has grown denser and taller in areas that have received nearly a century-long period of heavy livestock grazing during growing season of herbs and where fire has been suppressed (T2a). Introduced annuals such as common dandelion (Taraxacum officinale), mountain tarweed, and Douglas’ knotweed have become abundant in the understory. The stability of this less desirable State is maintained by the lack of a healthy, productive and diverse herb component capable of providing native seed source and soil moisture retention. Heavy growth-season livestock grazing will negatively impact the resiliency of this State.
Submodel
Description
This state is dominated by native perennial herbs, either pure grasses or mixed forbs and grasses (4.1). If shrubs are removed by chemical means, the forb component will also be removed leaving only the native perennial grasses. If prescribed fire is used to remove shrubs, this will provide an equal opportunity for both grasses and forbs to respond. If keeping the shrubs back is desirable, then re-treatment using fire or chemicals may be necessary (4.1a). The resiliency of this State will be maintained by reductions in livestock grazing. Accelerated soil erosion will reduce the resiliency of this State.
Submodel
Mechanism
T1a: from State 1 to State 2 (Reference State to Snowfield Sagebrush/ Introduced Non-natives State)
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, but because this plant community is particularly resilient, it may be possible to achieve a plant community that is almost identical to the Reference State.
Mechanism
T2a: from State 2 to State 3 (Snowfield Sagebrush/ Introduced Non-natives State to Snowfield Sagebrush Super-dominance State)
Prolonged lack of fire and heavy continuous season-long grazing (which occurred at many sites particularly between the 1860s and the 1950s), creates a shrub-dominated site where introduced annuals begin to replace the native herbaceous species. The approach to this transition is indicated by an increase in size, age class, and density of sagebrush and by a reduction in the understory. The trigger causing this transition is heavy growing season livestock grazing. If seed sources for desirable native species are still present, it may be possible to avoid or reverse this transition with a reduction in growing season livestock grazing.
Mechanism
T3a: from State 3 to State 4 (Snowfield Sagebrush Super-dominance State to Managed Herbaceous State
Depending on the desired outcome and provided adequate native perennial species are still present, a the establishment of a native herbaceous community is possible through brush removal using either chemical means (i.e. 2,4-D) or prescribed fire, followed by a period of grazing deferment for at least one year, and moderate grazing thereafter.
Mechanism
T3b: from State 3 to State 5 (Snowfield Sagebrush Super-dominance State to Introduced Grassland State
On sites with lowered productivity and reduced native species, some have opted to till and re-seed with an introduced species such as orchardgrass (Dactylis glomerata), or Kentucky bluegrass (Poa pratensis) to increase forage production potential. Smooth brome (Bromus inermis) may have also been seeded to control soil erosion.
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