Semidesert Sand (Dune)

Description

The reference state represents the plant community and ecological dynamics of the Semidesert Sand Dune site. This state includes the biotic communities that become established on the ecological site if all successional sequences are completed under the natural disturbance regimes. The reference state is generally dominated by a shrub species. Primary disturbance mechanisms include climate fluctuations and events that result in soil stability changes. The process of changing from the dune phase to the stabilized phase is driven by plant succession. Typically, shrubs such as sand sagebrush and Cutler's jointfir establish on a site and begin to stabilize the soil. Then, more grasses begin to become established until the soil is stabilized and the site is no longer actively eroding and depositing in the form of dunes. Changing from a stabilized phase to a dune phase occurs as plant cover is reduced and wind erosion causes active dunes to form. The reference state is self sustaining and resistant to change due to high resistance to natural disturbances and high resilience following natural disturbances. Once invasive plants establish, return to the reference state may not be possible. Both community phases 1.1 ans 1.2 occur naturally and are a reflection of natural environmental variation.

Reference State: Plant community resistant to fluctuations in climate.

Indicators: A community dominated by shrub species where native perennial grasses and forbs may or may not be present.

Feedbacks: Natural fluctuations in climate that allow for a self sustaining shrub and grass community. Any disturbance that allows for the establishment of invasive species.

At-risk Community Phase: This community is at risk when 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 invasive species are present. This state is generally dominated by shrub species. Disturbance mechanisms that may occur include climate fluctuations and events that result in soil stability changes. The process of changing from the dune phase to the stabilized phase is driven by plant succession. Typically shrubs such as sand sagebrush establish on a site and begin to stabilize the soil. Then more grasses begin to establish until the soil is stabilized and no longer actively eroding and depositing in the form of dunes. Changing from a stabilized phase to a dune phase occurs as plant cover is reduced and wind erosion causes active dunes to form. Other disturbances include domestic livestock grazing, and surface disturbances such as road and pipeline development and off road vehicle (OHV) use. Due to lack of disturbed areas, the community responses to such disturbances are not well understood, and are not currently included in the state and transition model. The current potential state is still self sustaining; but is losing resistance to change due to lower resistance to disturbances and lower resilience following disturbances, and new drastic disturbances such as fire being more likely to occur.

Current Potential State: Plant communities resistant to climate fluctuations, herbivore grazing, and surface disturbance.

Indicators: A community dominated by shrub species where native perennial grasses and forbs may or may not be present. Invasive grasses and forbs are present.

Feedbacks: Natural fluctuations in climate that allow for a self sustaining shrub and grass community.

Submodel