Semidesert Shallow Loam (Black Sagebrush/Indian Ricegrass)

Description

This state describes the various biotic communities that are expected to be found on this ecological site under natural conditions. This reference state has an overstory of scattered Utah juniper with a few two-needle pinyon present. There is a well developed shrub layer with black sagebrush dominating. Mexican cliffrose and Nevada jointfir are other common shrub species. Indian ricegrass is the dominant herbaceous species with James galleta and blue grama commonly occurring. Other native grasses, forbs, and shrubs will often produce a significant portion of vegetative composition in the plant community.

This site occurs on 2 to 30% slopes (occasionally 60%) on all aspects. It is usually found on more cuestas and structural benches. Its soils are shallow to very shallow, well drained and typically gravelly loams in texture.

The reference state is self-sustaining and resistant to change due to a good natural resilience to its natural disturbances. The primary natural disturbance mechanisms are wildlife population densities which can affect the shrub layer composition, weather fluctuations, and fire period.

Definitions:

Reference State: Natural plant communities as influenced by shrub canopy density, long term weather fluctuations, and periodic fire.

Indicators: These communities are dominated by Utah juniper, black sagebrush and Indian ricegrass. The density of the tree and shrub canopy determines the amount and composition of the other native species present in the community.

Feedbacks: Natural fluctuations in weather patterns that allow for a self-sustaining tree and shrub and native grass community. Prolonged drought, an increase in fire frequency, or other disturbances may allow for the establishment of invasive species.

At-risk Community Phase: All communities are at risk when native plants are stressed and conditions are created that may allow invasive plants to establish.

Trigger: The establishment of invasive plant species.

Submodel

Description

The Current Potential State is similar to the Reference Sate except that non-native species are now present. This state describes the plant communities that may or have become established on this ecological site under various successional sequences and disturbance conditions. This state typically has a scattered overstory of Utah juniper with a few two-needle pinyon also present. Black sagebrush dominates the shrub layer. Mexican cliffrose and Nevada and/or Utah jointfir are other common shrub species. Indian ricegrass is the dominant herbaceous species with James galleta and other perennial grasses and forbs commonly found in abundance also. These other native grasses, forbs, and shrubs may produce significant composition in the plant community. Cheatgrass, Russian thistle, redstem storksbill, various mustard species and other non-native species are present on the site and under certain circumstances, may visually dominate the sites aspect.

The primary disturbance mechanisms are the shrub layer density; the amount of invasive species present; weather fluctuations; and fire. The current potential state is still self-sustaining but may be losing its resistance to change due to the impact of disturbances with less resilience following those disturbances.

Definitions:

Current Potential State: Plant communities influenced by shrub canopy density, long term weather fluctuations, and periodic fire. Invasive species are present in various amounts.

Indicators: A community dominated by Utah juniper, black sagebrush and Indian ricegrass. The density of the tree and shrub canopies determines the amount and composition of the other native and introduced grasses and forbs that may be present.

Feedbacks: Natural fluctuations in weather patterns that allow for a self sustaining shrub and native grass community. Prolonged drought, more frequent fires, and/or other disturbances that may allow for the increase of invasive species.

At-risk Community Phase: All communities are at risk when native plants are stressed and nutrients become available for invasive plants to increase.

Trigger: A reduction of perennial grass and forb species combined with an increase of invasive plant species.

Submodel

Description

Natural or prescribed fire (rarely chaining)has removed the sites overstory Utah juniper and much the sites shrub layer. This state is now dominated by native and/or introduced herbaceous species for grass and/or forbs. Indian ricegrass and other native perennial grass species range from abundant to nearly missing depending on the site pre-fire condition. A wide array of native and/or invasive forbs may also be present. Invasive weedy species may include cheatgrass, Russian thistle, red-stem storksbill, various mustard species.

The primary disturbance mechanisms include fire which removes or reduces the overstory Utah juniper and black sagebrush; amounts of invasive herbaceous species present; weather fluctuations, and fire patterns. This state is losing its resistance to change due to the impact of these disturbances and has less resilience following those disturbances.

Definitions:

Natural or prescribed fire state: Plant communities dominated by herbaceous grass and/or grass or forbs; long term weather fluctuations; and periodic fire timeframes.

Indicators: The post-fire density of the tree and shrub canopies determines the amount and composition of the other native and introduced grasses and forbs that may be present.

Feedbacks: Natural fluctuations in weather patterns that allow Utah juniper and black sagebrush to become reestablished and their impact the native or introduced herbaceous communities. Prolonged drought, more frequent reburns, and/or other disturbances that allow for the increase of all invasive species.

At-risk Community Phase: All communities are at risk when native plants are stressed and nutrients become available for invasive plants to increase.

Trigger: A reduction of perennial grass and forb species combined with an increase of invasive plant species.

Submodel