Upland Very Steep Stony Loam (pinyon-Utah juniper)

Description

The Reference state has been determined by study of rangeland relic areas, areas protected from excessive disturbance, and areas under influences such as grazing and recreational uses. Through literature review, historical accounts and observations of trends in plant community dynamics under a variety of uses have been considered.
Community phases, community pathways, states, transitions, and thresholds, have been determined through similar studies and experience.

This state represents the natural range of variability that historically dominated the dynamics of this ecological site. This state includes the biotic communities that would have been expressed on the ecological site if all successional sequences were completed without interferences by man under the present environmental conditions; natural disturbances are inherent in its development. This state is dominated by Pinyon and Utah juniper with a well developed understory of native shrubs, perennial grasses and perennial and annual forbs. The primary disturbance mechanisms for this site in reference condition include drought and insects.

Reference state: Community phases maintained by drought and insect pathogen cycles
Indicators: A well developed shrub and grass understory co-existing with a canopy of Pinyon and Utah juniper.

Feedbacks: Infrequent, but regular droughts to reduce tree cover, and allow for a subsequent increase in the shrub, grass, and forb understory.

At-risk Community Phase: All communities are at risk when native plants in the understory are stressed, and nutrients become available for non-natives to establish.

Trigger: The introduction of non-native plants into the understory.

Submodel

Description

This state is very similar to the reference state, except that non-native grasses and/or forbs are now present in all phases. The current potential state may include naturalized or invasive nonnative species. The primary disturbance mechanisms for this state include natural and human caused disturbances. Drought and insects still influence the community shifts; however, due to steep slopes there are very little man induced disturbances. Trailing of livestock to water and some minor recreational activities (i.e. hiking) are the most common and have very little impact on the site other than introduction of these non-native grasses and forbs. The shift in species composition could affect nutrient cycling, hydrology and soil stability. At this time there is no known way to effectively remove the non-native plants from the site once they have become established. Therefore, this site is often irreversibly altered from the reference state

Current Potential state: Community phases maintained by drought and insect herbivory cycles

Indicators: A well developed shrub and grass understory co-existing with a canopy of Pinyon and Utah juniper.

Feedbacks: Infrequent, but regular droughts to reduce tree cover, and allow for a subsequent increase in the shrub, grass, and forb understory. Establishment of non-native plant species, such as cheatgrass.

At-risk Community Phase: All communities are at risk when native plants become stressed and non-native invasive species are allowed to flourish.

Submodel