Upland Shallow Loam (Two-Needle Pinyon / Utah Juniper)

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. The reference state is generally dominated by an overstory canopy of two-needle pinyon with lesser amounts of Utah juniper. Alderleaf mountain mahogany and Black sagebrush are the dominate shrubs. Indian ricegrass and Salina wildrye are the most common grasses. Other native grasses, forbs, and shrubs may produce significant composition in the plant community.

The primary disturbance mechanisms are overstory canopy density, weather fluctuation, and 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. Typically in the reference state, this ecological site will fluctuate between community phases 1.1 and 1.2.

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

Indicators: A community dominated by two-needle pinyon, Utah juniper and alderleaf mountain mahogany. The density of the overstory canopy determines the amount and composition of the other native perennial grasses and forbs that may be present.

Feedbacks: Natural fluctuations in weather patterns that allow for a self-sustaining two-needle pinyon, Utah juniper, alderleaf mountain mahogany and native grass 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 invasive species are now present in all community phases. This state is generally dominated by two-needle pinyon, with lesser amounts of Utah juniper present. Alderleaf mountain mahogany and black sage are the most common shrubs. Depending on the sites disturbance history, native perennial grasses, forbs, or other shrubs may be common in the sites understory. Primary disturbance mechanisms are thought to include long-term weather fluctuations, insect herbivory, improper livestock grazing, fire interval and surface disturbances such as road and pipeline development and off road vehicle (OHV) use. Few disturbed sites have been located to date and so little data exists regarding them. The current potential state is still self sustaining but has less resistance to change due to lower resistance to disturbances and lower resilience following disturbances. This state will typically fluctuate between community phases 2.1 and 2.2.

Current Potential State: Plant communities influenced by livestock grazing, wildlife browsing, insect herbivory, weather fluctuations, fire periods and surface disturbances.

Indicators: A community dominated by two-needle pinyon and alderleaf mountain mahogany where other shrubs and native perennial grasses and forbs may also be present. Invasive grasses and forbs are present.

Feedbacks: Natural fluctuations in weather that allow for a self sustaining two-needle pinyon, alderleaf mountain mahogany and grass community.

Submodel