Upland Shallow Loam (Pinyon-Utah Juniper) AWC >3

Description

The reference state was determined by literature review, historical accounts, reports, and observations of trends in plant community dynamics.

The reference state represents the plant communities and ecological dynamics of this ecological site under pre-settlement conditions and a natural disturbance regime. The plant communities of the reference state were similar to those of the current potential state (State 2), with a climax community of relatively productive woodland, dominated by twoneedle pinyon (Pinus edulis) and Utah juniper (Juniperus osteosperma), and understory that typically includes an open shrub layer of Gambel’s oak (Quercus gambelii) and mountain big sagebrush (Artemisia tridentata subsp. vaseyana), and a perennial grass layer dominated by muttongrass (Poa fendleriana). Tree density and cover may have been slightly lower in the historic state, and herbaceous cover higher. Non-native species were not present in the reference state. The primary disturbances included infrequent fire, fluctuations in precipitation, and native ungulate browsing. Plant communities will naturally shift among the four phases with infrequent fire and climatic fluctuations, and interactions with pathogens and browse pressure.

Reference State: Plant communities influenced by fire, browse, and climate fluctuations between wet and dry periods.

Indicators: Productive woodland dominated by twoneedle pinyon and Utah juniper with a diverse and highly variable understory. Gambel’ oak and mountain big sagebrush typically present, and a productive perennial grass component dominated by muttongrass. Perennial forbs are significant, and abundant species include rock goldenrod and dwarf lousewort.

Feedbacks: Infrequent stand-clearing fire and light browse pressure allows for a self-sustaining woodland with herbaceous and shrub successional phases.

At-risk Community Phase: All community phases are susceptible to severe impacts to BSC and soils from livestock grazing. Community phases 1.2 and 1.5 are particularly susceptible to invasion due to soil disturbance, increased bare soil and reduced competition. All phases are susceptible to invasion, especially with heavy grazing, browse or other disturbances that remove vegetative cover and disturb soils.

Trigger: Improper livestock grazing and introduction of invasive species.

Submodel

Description

This state represents the current potential of this ecological site, and in addition to infrequent fire and climate fluctuations, the dynamics include disturbance by livestock and forest thinning management. The current potential state will naturally fluctuate between community phases 2.1-2.4, and will shift to community phase 2.5 with fuel reduction treatment and seeding. Community phase 2.3 may also be reached through forest treatment.

Current Potential State: Plant communities influenced by infrequent fire, climate fluctuations between wet and dry periods, livestock grazing, and fuel reduction management.

Indicators: Productive woodland dominated by twoneedle pinyon and Utah juniper with a diverse and highly variable understory. Gambel’s oak and mountain big sagebrush typically present, and a productive perennial grass component dominated by muttongrass. Perennial forbs are significant, and abundant species include rock goldenrod and dwarf lousewort. Non-native species including cheatgrass, western wheatgrass, tall tumblemustard (Sisymbrium altissimum), and Russian thistle (Salsola spp) may be present, especially in more disturbed community phases.

Feedbacks: Infrequent stand-clearing fire and light browse and grazing pressure allow for a self-sustaining woodland with herbaceous and shrub successional phases. Non-native species are naturalized across the landscape.

At-risk Community Phase: Communities 2.1 and 2.5 are especially at risk of invasion and dominance by invasive species, although cheatgrass may become established and abundant in any community phase with high winter precipitation.

Submodel