SR Juniper Tableland 12-16 PZ

Description

The Reference State is representative of the natural range of variability for the site under pristine conditions. The reference state is a low productivity, bunchgrass shrubland. 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 are maintained by ecosystem processes and structural elements such as the presence of all structural and functional plant groups, the retention of organic matter and the maintenance of plant community cover. Plant community phase changes are primarily driven by infrequent fire and/or periodic drought.

Submodel

Description

This state is similar to the Reference State. Ecological function has not changed fundamentally, however the resiliency of the site has been reduced by the presence of invasive plants. Additionally, livestock herbivory may be present as a disturbance process and changes in climate may be altering ecological dynamics. Non-native plant species may increase in abundance but will not become dominant or control ecological processes within this state. These species 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 are maintained by ecosystem processes and structural elements such as the presence of all structural and functional groups, and retention of organic matter and nutrients. Positive feedbacks driven by plant community invasion decrease ecosystem resilience and stability of the state. These include exotic plant species' high seed output, persistent seed bank, rapid growth rate, ability to cross pollinate, and adaptations for seed dispersal. Plant community phase changes are primarily driven by infrequent fire, periodic drought and ungulate herbivory.

Current potential plant communities also mirror those of the above Historical Reference (State 1) yet with the addition of a low level of invasive exotic plant invasion and influences of livestock herbivory. Livestock herbivory may result in decreases in deep rooted perennial grasses, and related increases in shallow-rooted perennial grasses (such as Sandberg bluegrass), unpalatable forbs and shrubs.

Description

Within this state, site resources are primarily controlled by exotic annual herbaceous species. Native perennial grass and forb composition has been greatly diminished. Fire frequency may be increased by higher fine fuel loads, potentially having significant ecological consequences for this otherwise fuel limited site. Rehabilitation of this state will be extremely difficult due to thin soils, high potential for invasive annual grass encroachment, susceptibility of soils to erosion and damaging frost heaving, and mechanical limitations due to areas of rock outcrop.

Multiple plant communities are possible within this state, all of which are dominated by invasive annual grasses such as cheatgrass, ventenata and medusahead and potentially invasive annual and perennial forbs. Scabland sagebrush and old growth western juniper may also be present, and young juniper may be increase. Overtime, with increasing annual plant invasion, soil stabilizing perennial root biomass will be decreased. Bare ground will increase, potentially increasing erosion of these thin soils and risking a transition to an eroded state.

Description

Within this state, site resources are primarily controlled by western juniper and rigid sagebrush. While this site historically supported old growth juniper, significant infill of young juniper has increased the presence of juniper beyond the natural range of variability for the site. Shallow and deep rooted native perennial grass composition has been reduced considerably and native forbs composition has been diminished. Exotic herbaceous species are often present. Juniper encroachment can decrease cover of grasses and shrubs by reducing light availability and altering site hydrology through increased interception of precipitation, reduced infiltration and increased erosion. Bare ground will increase and erosion may be increased rendering the site at risk of transitioning to an eroded state (State 5).

Multiple plant community phases are likely within this state, influenced by livestock herbivory and time since fire. Rigid sagebrush may be outcompeted by western juniper overtime as canopy closure and moisture competition progresses. Invasive annual grasses such as cheatgrass, ventenata and medusahead are likely in all communities.

Description

This state is characterized by significant soil loss through wind and water erosion. Most herbaceous cover has been lost and soil stabilizing microbiotic soil crusts are degraded. Loss of these components reduces soil stability and renders the soil surface vulnerable to raindrop impacts, runoff and transport of soil by water and entrainment of soil particles by wind. Extensive areas of erosion pavement are common. Rill and gully formation may occur, especially toward the higher slope range of this site. Positive feedbacks develop as low vegetative cover leads to decreased litter and organic matter production, higher soil temperature variability, and decreased nutrient cycling, further destabilizing soil and decreasing potential plant establishment. Old growth juniper is likely present and infill of young juniper may be significant. Grass, shrub and forb vegetative cover is low yet invasive annual plants are likely. Potential for rehabilitation of this state is unknown but would likely pose significant challenges due to degradation of abiotic function of the site, the susceptibility of soils to erosion and damaging frost heaving, and mechanical limitations due to areas of rock outcrop.