Ecological dynamics
The Upland Claypan (Low Sagebrush) site is found in the Great Salt Lake Area of the Basin and Range Ecological Provence. It developed under the natural ecological conditions found there, including the normal influences of native wildlife herbivory, fire, and climate.
Low sagebrush is the dominant shrub with bluebunch wheatgrass as the dominant herbaceous plant in this ecological site. Low sagebrush is typically found in soil that has a clay pan or a rocky layer within 8 to 13 inches of the soil surface (Steinberg 2002). Soils with claypans may develop a perched water table or higher soil moisture in the spring and winter, which will exclude other sagebrush types.
Low sagebrush communities are often low productivity sites compared to big sagebrush sites. This is thought to be due to the high clay in subsurface horizons that may restrict root growth.
As vegetative communities respond to changes caused by natural or human caused events that cause them to cross ecological thresholds, a return to previous states may not be possible. The amount of effort needed to affect desired vegetative shifts depends on the present biotic and abiotic features and the desired results.
Fire Ecology:
Low sagebrush is not tolerant of fire and will not sprout (Steinberg 2002).
Livestock/Wildlife Grazing Interpretations:
Low sagebrush can tolerate and increase with disturbance by grazing (Steinberg 2002). Low sagebrush is considered a good browse plant during the spring, fall, and winter months (Monsen and Shaw 1986) if not covered with snow.
Three possible alternative stable states have been hypothesized for this ecological site. This site is similar to 028AY125NV developed in Nevada. The state and transition model and narratives used from site 0125NV and applied to Upland Claypan (Low Sagebrush) (Stringham et al. 2015). The Reference State contains three community phases, shrub/grass dominated, shrub dominated, grass dominated, and a fire tolerant phase. The primary drivers in this state are fire, drought, and/or insect of disease. The Current Potential State is like the Reference State; however, non-native species have been introduced in the system which alters the resilience and resistance of the state. The Shrub State occurs when shrubs become much more dominant in the plant community, out-competing grasses in the understory. Specific community phases and transitions will be described in the narratives below.
State 1
Reference State
The Reference State 1 is a representative of the natural range of variability under reference conditions. The Reference State has 3 community phases; a shrub/grass dominant phase, a perennial grass dominant phase and a shrub dominant phase. State dynamics are maintained by interactions between climatic patterns and disturbance regimes. Negative feedbacks enhance ecosystem resilience and contribute to the stability of the state. These include the presence of all structural and functional groups, low fine fuel loads, and retention of organic matter and nutrients. Plant community phase changes are primarily driven by fire, periodic drought and/or insect or disease attack.
Community 1.1
Low sagebrush/bluebunch wheatgrass
This community is dominated by low sagebrush and bluebunch wheatgrass. Forbs and other grasses make up smaller components. Antelope bitterbrush, Utah juniper, and singleleaf pinyon are described in the site concept and may or may not be present in low densities.
Community 1.2
Bluebunch wheatgrass/sprouting shrubs
This community phase is characteristic of a post-disturbance, early/mid-seral community. Bluebunch wheatgrass and other perennial bunchgrasses dominate. Depending on fire severity patches of intact sagebrush may remain. Rabbitbrush and other sprouting shrubs may be sprouting. Perennial forbs may be a significant component for a number of years following fire.
Community 1.3
Low sagebrush (increase)/perennial bunchgrasses (decrease)
Sagebrush increases in the absence of disturbance. Decadent sagebrush dominates the overstory and the deep-rooted perennial bunchgrasses in the understory are reduced either from competition with shrubs and/or from herbivory.
Pathway 1.1a
Community 1.1 to 1.2
Fire will decrease or eliminate the overstory of sagebrush and allow for the perennial bunchgrasses to dominate the site. Fires will typically be low severity resulting in a mosaic pattern due to low fuel loads. A fire following an unusually wet spring may be more severe and reduce sagebrush cover to trace amounts.
Pathway 1.1b
Community 1.1 to 1.3
Time and lack of disturbance such as fire allows for sagebrush to increase and become decadent. Chronic drought, herbivory, or combinations of these will cause a decline in perennial bunchgrasses and fine fuels leading to a reduced fire frequency and allowing sagebrush to dominate the site.
Pathway 1.2a
Community 1.2 to 1.1
Time and lack of disturbance will allow sagebrush to increase.
Pathway 1.3a
Community 1.3 to 1.1
A low severity fire, herbivory or combinations will reduce the sagebrush overstory and create a sagebrush/grass mosaic.
Pathway 1.3b
Community 1.3 to 1.2
Fire will decrease or eliminate the overstory of sagebrush and allow for the perennial bunchgrasses to dominate the site. Fires may be high severity in this community phase due to the dominance of sagebrush resulting in removal of overstory shrub community.
State 2
Current Potential State
The Current Potential State is similar to the Reference State 1 with three similar community phases. Ecological function has not changed; however the resiliency of the state has been reduced by the presence of invasive weeds. Non-natives may increase in abundance but will not become dominant within this state. These non-natives can be highly flammable and can promote fire where historically fire had been infrequent. Negative feedbacks enhance ecosystem resilience and contribute to the stability of the state. These feedbacks include the presence of all structural and functional groups, low fine fuel loads, and retention of organic matter and nutrients. Positive feedbacks decrease ecosystem resilience and stability of the state. These include the non-natives’ high seed output, persistent seed bank, rapid growth rate, ability to cross pollinate, and adaptations for seed dispersal.
Community 2.1
Low sagebrush/bluebunch wheatgrass/non-native species
This community phase is similar to the Reference State Community Phase 1.1, with the presence of non-native species in trace amounts. Sagebrush, bluebunch wheatgrass dominate the site. Forbs and other shrubs and grasses make up smaller components of this site.
Community 2.2
Bluebunch wheatgrass/sprouting shrubs/ non-native species
This community phase is characteristic of a post-disturbance, early to mid-seral community where annual non-native species are present. Sagebrush is present in trace amounts; perennial bunchgrasses dominate the site. Depending on fire severity patches of intact sagebrush may remain. Rabbitbrush may be sprouting or dominant in the community. Perennial forbs may be a significant component for a number of years following fire. Annual non-native species are stable or increasing within the community.
Community 2.3
Low sagebrush (increase)/perennial bunchgrasses (decrease)/non-native species (At-risk)
This community is at risk of crossing a threshold to another state. Sagebrush dominates the overstory and perennial bunchgrasses in the understory are reduced, either from competition with shrubs or from inappropriate grazing, or from both. Rabbitbrush may be a significant component. Sandberg bluegrass may increase and become co-dominate with deep rooted bunchgrasses. Annual non-natives species may be stable or increasing due to lack of competition with perennial bunchgrasses. This site is susceptible to further degradation from grazing, drought, and fire.
Pathway 2.1a
Community 2.1 to 2.2
Fire reduces the shrub overstory and allows for perennial bunchgrasses to dominate the site. Fires are typically low severity resulting in a mosaic pattern due to low fuel loads. A fire following an unusually wet spring or a change in management favoring an increase in fine fuels may be more severe and reduce sagebrush cover to trace amounts. Annual non-native species are likely to increase after fire.
Pathway 2.1b
Community 2.1 to 2.3
Time and lack of disturbance allows for sagebrush to increase and become decadent. Chronic drought reduces fine fuels and leads to a reduced fire frequency, allowing big sagebrush to dominate the site. Inappropriate grazing management reduces the perennial bunchgrass understory; conversely Sandberg bluegrass and muttongrass may increase in the understory depending on grazing management.
Pathway 2.2a
Community 2.2 to 2.1
Time and lack of disturbance and/or grazing management that favors the establishment and growth of sagebrush allows the shrub component to recover. The establishment of low sagebrush can take many years.
Pathway 2.3a
Community 2.3 to 2.1
A change in grazing management that reduces shrubs will allow for the perennial bunchgrasses in the understory to increase. Heavy late-fall or winter grazing may cause mechanical damage and subsequent death to sagebrush, facilitating an increase in the herbaceous understory. Brush treatments with minimal soil disturbance will also decrease sagebrush and release the perennial understory. A low severity fire would decrease the overstory of sagebrush and low for the understory perennial grasses to increase. Due to low fuel loads in this State, fires will likely be small creating a mosaic pattern. Annual non-native species are present and may increase in the community.
Pathway 2.3b
Community 2.3 to 2.2
Fire eliminates/reduces the overstory of sagebrush and allows for the understory perennial grasses to increase. Fires may be high severity in this community phase due to the dominance of sagebrush resulting in removal of overstory shrub community. Annual non-native species respond well to fire and may increase post burn.
State 3
Shrub State
This state is a product of many years of heavy grazing during time periods harmful to perennial bunchgrasses. Sandberg bluegrass and muttongrass will increase with a reduction in deep rooted perennial bunchgrass competition and become the dominant grasses. Sagebrush dominates the overstory and rabbitbrush may be a significant component. Sagebrush cover exceeds site concept and may be decadent, reflecting stand maturity and lack of seedling establishment due to competition with mature plants. The shrub overstory and bluegrass understory dominate site resources such that soil water, nutrient capture, nutrient cycling and soil organic matter are temporally and spatially redistributed.
Community 3.1
Low sagebrush/other shrubs/muttongrass or Sandberg's bluegrass/ non-native species
Decadent sagebrush dominates the overstory. Rabbitbrush may be a significant component. Deep-rooted perennial bunchgrasses may be present in trace amounts or absent from the community. Sandberg bluegrass, muttongrass and annual non-native species increase. Bare ground is significant.
Transition T1A
State 1 to 2
Trigger: This transition is caused by the introduction of non-native annual plants, such as cheatgrass, mustards, and bur buttercup.
Slow variables: Over time the annual non-native species will increase within the community.
Threshold: Any amount of introduced non-native species causes an immediate decrease in the resilience of the site. Annual non-native species cannot be easily removed from the system and have the potential to significantly alter disturbance regimes from their historic range of variation.
Transition T2A
State 2 to 3
Trigger: To Community Phase 3.1: Inappropriate grazing will decrease or eliminate deep rooted perennial bunchgrasses, increase Sandberg bluegrass, and muttongrass and favor shrub growth and establishment.
Threshold: Loss of deep-rooted perennial bunchgrasses changes nutrient cycling, nutrient redistribution, and reduces soil organic matter.
