Semidesert Very Shallow Gravelly Loam (Utah Juniper)

Description

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 blackbrush, Utah juniper, and twoneedle pinyon, however depending on disturbance history, native grasses, forbs, or other shrubs may occupy significant composition in the plant community. The primary disturbance mechanism is climate fluctuation. During long periods of drought, this site may lose the two-needle pinyon (phase 1.2). The reference state is self sustaining and resistant to change due to high resistance to natural disturbances and high resilience following natural disturbances. When natural disturbances occur, the rate of recovery is variable. Typically, in the reference state this site will fluctuate between community phases 1.1 and 1.2; however once invasive plants establish, return to these community phases may not be possible.

Reference State: Plant communities influenced by insect herbivory, and climate fluctuations.

Indicators: A community dominated by Utah juniper and blackbrush where twoneedle pinyon and native perennial grasses and forbs may or may not be present.

Feedbacks: Natural fluctuations in climate that allow for a self sustaining juniper-blackbrush and native grass community. Insect herbivory, more frequent fire, 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 invasive species are present in all community phases. This state is generally dominated by Utah juniper, twoneedle pinyon, and blackbrush, however depending on disturbance history, native grasses, forbs, or other shrubs may dominate the site. Primary disturbance mechanisms include climate fluctuations, insect herbivory, 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 documented 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. Typically in the current potential state this site will fluctuate between community phases 2.1 and 2.2.

Current Potential State: Plant communities influenced by insect herbivory, climate fluctuations, and surface disturbances.

Indicators: A community dominated by Utah juniper and blackbrush where twoneedle pinyon and 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 juniper-blackbrush and grass community.

Submodel