Utah Juniper/Big Sagebrush

(4) Utah Juniper/Big Sagebrush Plant Community
(Juniperus osteosperma/Artemisia tridentata)

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PLANT LIST for Utah Juniper/Big Sagebrush Plant Community»

Utah Juniper is the dominant tree on the south side of the Pryors, which is also the northern limit of its range. They occur along a large portion of Crooked Creek Road. The plant community occurs on limestone or calcareous sandstone soils in the valley and montane zone. At higher elevations in the Pryors Utah Juniper is replaced by Rocky Mountain Juniper (Juniperus scopulorum). Utah Juniper is an erect shrub or small tree that often appears in a more rounded form than the more conical crown shape of Rocky Mountain Juniper. The bark of Utah Juniper is gray-brown and stringy and the branches tend to become ribbon-like with age and sprawl horizontally. This species produces a taproot that can use water at depth as well as shallow surface roots that take advantage of brief rainfall events. The trees are capable of living up to 650 years old. Utah Juniper populations are abundant in the semi-arid areas in the Great Basin and since the end of the Wisconsin ice age 11,500 years ago, the species has migrated north to southern Montana and adjacent Wyoming.

In the Pryor Mountains, the Utah Juniper/Big Sage community type occurs along Crooked Creek Road near Demijohn Flats flowing along the landscape like a sea of green. Utah Juniper also occurs at higher elevation in the Pryors with mountain mahogany (Cercocarpus ledifolius) as the dominant shrub.

There are stages in the juniper life history that make it vulnerable to disturbances such as herbivory, invasion from exotic species, and impacts that may change soil characteristics. Utah Junipers generally don’t begin bearing fruit until they are 10-20 years old. It takes two growing seasons for the juniper fruit to mature on this monoecious tree (male and female cones are produced on the same tree). The ripe female fruits (modified cones) may remain on the tree for 2-3 years. There is extensive loss of potential seed production and seed maturation because many fruits fail to fill because of genetic or climatic factors, or predation by insects and herbivores. Seed-caching rabbits and rodents are thought to be the primary seed dispersers of Utah Juniper.

In our study area along Crooked Creek the only observed disturbance on the vegetation community are tracks from motorized use. All twenty-three species we recorded in our plots are plants native to Montana, indicating that the Utah Juniper plant community is in excellent condition at this time.

Potential negative impacts to the health of the Utah Juniper woodlands could result from loss of seed dispersers, a change in the level of insect damage and unusual impacts from other herbivore predators or an invasion by exotic plant species. Studies in the Great Basin show that invasion by annual cheat grass species, particularly Bromus tectorum, impact Utah Juniper communities by competing for surface water that the shallow root systems of Utah Juniper rely upon or by creating dangerous wild fire conditions. So far the Pryor Mountain Utah Juniper plant communities show little evidence of cheat grass invasion but ongoing monitoring is important for identifying changes and preventing habitat degradation.

Return to the main Botanical Guide to Special Places in the Pryors.