High Mountain Gravelly Loam (mountain big sagebrush)

Description

This state describes the biotic communities that may become established on this ecological site if all successional sequences are completed under natural disturbance conditions. Species composition is generally dominated by mountain big sagebrush and mountain snowberry. Other important shrubs include Utah serviceberry and bitterbrush. Perennial herbaceous species occurrence is directly related to canopy density with bluebunch wheatgrass, Letterman needlegrass and geyer sedge being the most common species. Sites located at higher elevations may contain species such as spike trisetum and a few aspen.

The primary disturbance mechanisms are shrub canopy density, weather fluctuations, and fire or lack of fire. The reference state is self-sustaining and resistant to change due to a high resistance to natural disturbances and a high resilience following those disturbances. When natural disturbances occur, the rate of recovery can be quite variable.

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

Indicators: A community dominated by mountain big sagebrush and mountain snowberry. The density of the shrub canopy determines the amount and composition of the other native perennial grasses, grasslikes and forbs that may be present.

Feedbacks: Natural fluctuations in weather patterns that allow for a self sustaining shrub and native grass and grasslike community. Insect herbivory, more frequent fires, or other disturbances that may allow for the establishment 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 establish.

Trigger: The establishment of invasive plant species

Submodel

Description

The current potential state is similar to the reference state, however minor amounts of invasive species may now present in all community phases. This state describes the biotic communities that may become established on this ecological site if all successional sequences are completed under natural disturbance conditions.

The current potential state is generally dominated by mountain big sagebrush and mountain snowberry. Other important shrubs include Utah serviceberry and bitterbrush. Perennial herbaceous species occurrence is reduced with bluebunch wheatgrass, Letterman needlegrass and geyer sedge still being the most common species. Cheatgrass and non-native annual forbs could potentially be present in both community phases but this occurrence has not yet been well documented. Areas disturbed by road building an/or mining are most likely to allow this invasion to occur.

The primary disturbance mechanisms are shrub canopy density, weather fluctuations and fire or lack of fire. The current potential state is still self-sustaining but has a lower resistant to change due to a reduced resistance to disturbances. When disturbances do occur, the rate of recovery can be highly variable.

Current Potential State: Plant communities influenced by shrub canopy density, long term weather fluctuations, and periodic fire.

Indicators: A community dominated by mountain big sagebrush and mountain snowberry. The density of the overstory canopy determines the amount and composition of the other native and non-native grasses, grasslikes and forbs that may be present.

Feedbacks: Natural fluctuations in weather patterns that allow for a self sustaining shrub and native grass and grasslike community. Insect herbivory, more frequent fires, or other disturbances that may allow for the development 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: The increase of invasive plant species.

Submodel