Semidesert Shallow Loam (Wyoming Big Sagebrush) North

Description

The Reference State describes the various biotic communities that are expected to be found on this ecological site under natural conditions. This reference state has a well developed shrub layer with Wyoming big sagebrush dominating. Nevada ephedra, winterfat, and shadscale are other common shrub species. Bluebunch wheatgrass and Indian ricegrass are the most dominant herbaceous species with needle-and-thread, western wheatgrass and James' galleta commonly occurring. The percentage of warm season species including James' galleta and blue grama found in the communities in this state will increase as one travels from north to south. Other native grasses, forbs, and shrubs will often produce a significant portion of vegetative composition in the plant community.

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 livestock grazing and 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 Wyoming big sagebrush and bluebunch wheatgrass. The density of the 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 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 State 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 well developed shrub layer with Wyoming big sagebrush often dominating. Nevada ephedra and shadscale are other common shrub species. Bluebunch wheatgrass and Indian ricegrass are the dominant herbaceous species. Other perennial grasses and forbs are also commonly found in abundance. These other native grasses, forbs, and shrubs may produce significant composition in the plant community. Cheatgrass, Halogeton, alyssum, 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 Wyoming big sagebrush and bluebunch wheatgrass. The density of the shrub canopy 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

The Seeded State describes plant community phases that have been mechanically treated to remove Wyoming big sagebrush. Common treatment methods include brush beating, heavy disking, and occasionally, chaining. These treated pastures are then typically seeded to introduced forage species such as intermediate or crested wheatgrass, or managed to allow native perennial grasses to recover. Invasive weedy species, including cheatgrass, Halogeton, alyssum, various mustard species and other non-native species, are present and, in some cares, may visually dominate the sites herbaceous layer. On pastures where seedings fail or native species do not respond to management, the site is often covered with annuals which can prevent site recovery and may periodically burn and re-burn.

The primary disturbance mechanisms include; the amount of of invasive herbaceous species present; weather fluctuations, and fire patterns. This state may have lost its resistance to change due to the impact of these disturbances and has less resilience following those disturbances.

Definitions:

Seeded State: Plant communities that have been manipulated to remove Wyoming big sagebrush; long term weather fluctuations; and periodic fire.

Indicators: The composition of the herbaceous community determines any additional treatment needs including range seeding and/or proper grazing management to allow native and introduced grasses and forbs to recover.

Feedbacks: Natural fluctuations in weather patterns that impact herbaceous communities. Prolonged drought, less frequent fire, 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