Upland Shallow Loam (Utah Juniper - Singleleaf Pinyon)

Description

The Reference State describes the various biotic communities that are expected to be found on this ecological site under natural conditions. The Reference State has an overstory canopy of Utah juniper with lesser amounts of singleleaf and/or two-needle pinyon. The shrub layer is typically dominated by black sagebrush. A mixture of other shrubs including big sagebrush, antelope bitterbrush, and alderleaf mountain mahogany are commonly found. Bluebunch wheatgrass is the dominant herbaceous species with Nevada bluegrass and Indian ricegrass commonly occurring. Other native grasses, forbs, and shrubs will often produce a significant portion of vegetative composition in the plant community.

The Reference State is self-sustaining and resistant to change due to a good natural resilience to its natural disturbances. The primary natural disturbance mechanisms are wildlife population densities which can affect the shrub layer composition, weather fluctuations, and fire period.

Definitions:

Reference State: Natural plant communities as influenced by tree and shrub canopy densities, long term weather fluctuations, and periodic fire.

Indicators: These communities are dominated by Utah juniper, black sagebrush, and bluebunch wheatgrass. The density of the tree and shrub canopies determines the amount and composition of the other native species present in the community. The composition by air-dry weight is approximately 15 percent trees, 35 percent perennial grasses, 10 percent forbs, and 40 percent shrubs.

Feedbacks: Natural fluctuations in weather patterns that allow for a self-sustaining tree, shrub and native grass community. Prolonged drought, an increase in fire frequency, or other disturbances may allow for the establishment of invasive species.

At-risk Community Phase: All communities are at risk when native plants are stressed and conditions are created that may allow invasive plants to establish.

Trigger: The establishment of invasive plant species.

Characteristics and indicators

This state will have only native species in the plant communities.

Submodel

Description

The Current Potential State is similar to the Reference Sate except that non-native species are now present. Ecological function has not changed; however the resiliency of the state has been reduced by the presence of non-native species. These non-natives, particularly cheatgrass, can be highly flammable and promote fire where historically fire had been infrequent. Negative feedbacks enhance ecosystem resilience and contribute to the stability of the state. These include the presence of all structural and functional groups, low fine fuel loads and retention of organic matter and nutrients. Positive feedbacks decrease ecosystem resilience and stability of the state. These include the nonnatives’ high seed output, persistent seed bank, rapid growth rate, ability to cross pollinate, and adaptations for seed dispersal. Fires within this community with the small amount of non-native annual species present are likely still small and patchy due to low fuel loads. This fire type will create a plant community mosaic that will include all/most of the following community phases within this state. The Current Potential State describes the plant communities that may or have become established on this ecological site under various successional sequences and disturbance conditions. This state typically has a well developed overstory canopy composed of Utah juniper with lesser amounts of singleleaf and/or two-needle pinyon. Black sagebrush often dominates the shrub layer. Wyoming big sagebrush, antelope bitterbrush, and alderleaf mountain mahogany are common shrub species. Bluebunch wheatgrass is the dominant herbaceous species with Indian ricegrass, Nevada bluegrass and other perennial grasses and forbs also commonly found in abundance. Cheatgrass, alyssum, various mustard species and other non-native species are present on the site and, under certain circumstances, may visually dominate the sites aspect.

The primary disturbance mechanisms are the tree and shrub layer densities; the amount and kinds of invasive species present; weather fluctuations; and fire. The Current Potential State is still self-sustaining but may be losing its resistance to change due to the impact of disturbances with less resilience following those disturbances.

Definitions:

Current Potential State: Plant communities influenced by tree and shrub canopy density, long term weather fluctuations, and periodic fire. Invasive species are present in various amounts.

Indicators: A community dominated by Utah juniper, black sagebrush and bluebunch wheatgrass. The density of the tree and shrub canopies determines the amount and composition of the other native and introduced grasses and forbs that may be present.

Feedbacks: Natural fluctuations in weather patterns that allow for a self sustaining shrub and native grass community. Prolonged drought, more frequent fires, and/or other disturbances that may allow for the increase 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: A reduction of perennial grass and forb species combined with an increase of invasive plant species.

Characteristics and indicators

This state will have non-native species in the plant community.

Submodel

Description

The Infilled Tree State has one community phase that is characterized by the dominance of Utah juniper and singleleaf pinyon in the overstory. This state is identifiable by 30 to over 50 percent cover of Utah juniper and singleleaf pinyon. This stand exhibits a mixed age class. Older trees are at maximal height and upper crowns may be flat-topped or rounded. Younger trees are typically cone- or pyramidal shaped. Understory vegetation is sparse due to increasing shade and competition from trees.

Submodel

Description

The Annual State occurs when a recent crown fire has removed most of the Utah juniper and any pinyon trees present from the site. Black sagebrush and other fire sensitive species have also been removed or significantly reduced. The site has a herbaceous aspect with both native and non-native grass and forb species present. Fire resistant shrubs are typically recovering and are increasing in the communities associated with this state. The herbaceous vegetation communities associated with this state can be highly variable depending on the before fire conditions. Typically however, bluebunch wheatgrass is the dominant herbaceous species with Indian ricegrass, Nevada bluegrass, and other perennial grasses and forbs commonly found. Cheatgrass, alyssum, various mustard species, and other non-native species are often present on the site and, under certain circumstances, may visually dominate the sites aspect.

The primary disturbance mechanisms intensity of the fire; the amount and kinds of native and non-native species present; weather fluctuations; and time since the fire occurred. This state may be losing self-sustainability or may be increasing its resistance to degradation due to the impact of fire and the before fire conditions.

Definitions:

Annual: Plant communities influenced by recent crown fire and its impact on the tree and shrub canopy density, long term weather fluctuations, time since the fire occurred. Invasive species are present in various amounts.

Indicators: A community dominated by herbaceous species. The kind and amounts of native and introduced grasses and forbs that may be present.

Feedbacks: Natural fluctuations in weather patterns that allow for a self sustaining shrub and native grass community to develop. Prolonged drought, more frequent fires, and/or other disturbances that may allow for the increase 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. Annual grasses and forbs that may shorten the sites fire period.

Trigger: A reduction of perennial grass and forb species combined with an increase of invasive plant species.

Submodel