Management Issues: Juniper
Western juniper (Juniperus occidentalis) occupies 9 million acres in central and eastern Oregon, northeastern California, southwestern Idaho, and northwestern Nevada, and occurs in a few outlying stands in southern Washington (Gedney et al. 1999, Miller and Tausch 2001, Azuma et al. 2004). It grows in mesic and arid environments and occupies elevations ranging from 600 to 8,000 ft (Sowder and Mowat 1958, Miller and Rose 1995, Gedney et al. 1999, Miller et al. 2000). During the past 130 years, western juniper has been expanding into neighboring vegetative communities at unprecedented rates compared to any other time period (Miller and Wigand 1994, Miller and Tausch 2001). The start of this expansion coincided with a change in climatic patterns to warmer and wetter weather, introduction and overstocking of livestock and the reduced role of fire in the late 1800s (Oliphant 1968, Miller et al. 1994, 1999a). Natural wildfires historically limited the range of this species because juniper is not resilient to fire and does not sprout from roots. Juniper encroachment has now become a priority management issue.
Although juniper woodlands are ecologically important for many wildlife species, the rapid expansion of their range has caused considerable concern because of increased soil erosion, potential reduced stream flows, reduced forage production, altered wildlife habitat, changes in plant community composition, structure and biodiversity, and the replacement of mesic and semi-arid plant communities, such as sagebrush, with woodlands (Miller et al. 2005). Low levels of western juniper can be beneficial for many wildlife species but increasing dominance at both the community and landscape levels generally results in a decline in floristic diversity, resulting in a decline of wildlife abundance and diversity (Miller et al. 2005). Sage-grouse (Centrocercus urophasianus), a sagebrush obligate species, are known to avoid western juniper communities for nesting and winter use (BLM 1994). Current control of western juniper mostly focuses on cutting and prescribed fire and may incorporate reseeding of the desired species after juniper removal.
References
Azuma, K.L., B.A. Hiserote, and P. A. Dunham. 2004. The western juniper resource of eastern Oregon. USFS GTR (in progress).
BLM. 1994. Sage-grouse in the high desert of central Oregon. USDI, Bureau of Land Management, Prineville District, OR.
Gedney, D.R., D.L. Azuma, C.L. Bolsinger, and N. McKay. 1999. Western juniper in eastern Oregon. U.S. Forest Service General Technical Report NW-GTR-464.
Miller, R.F., J.D. Bates, T.J. Svejcar, F.B. Pierson, and L.E. Eddleman. 2005. Biology, ecology and management of western juniper (Juniperus occidentalis). Oregon State University Agricultural Experiment Station Technical Bulletin 152, 82 pp.
Miller, R.F., and J.A. Rose. 1995. Historic expansion of Juniperus occidentalis (western juniper) in southeastern Oregon. Great Basin Naturalist 55:37–45.
Miller, R.F., T.J. Svejcar, and J.A. Rose. 2000. Impacts of western juniper on plant community composition and structure. Journal of Range Management 53:574–585.
Miller, R.F., T.J. Svejcar, and N.E. West. 1994. Implications of livestock grazing in the Intermountain sagebrush region: plant composition. Pages 101–146. In M. Vavra, W.A. Laycock, and R.D. Piper (editors). Ecological Implications of Livestock Herbivory in the West. Society for Range Management, Denver, CO.
Miller, R.F. and R.J. Tausch. 2001. The role of fire in piñon and juniper woodlands: a descriptive analysis. Pages 15–30. In K.E.M. Galley and T.P. Wilson (editors). Proceedings of the Invasive Species: the Role of Fire in the Control and Spread of Invasive Species. Miscellaneous Publication No. 11, Tall Timbers Research Station, Tallahassee, FL.
Miller, R.F, R.J. Tausch, and W. Waichler. 1999. Old growth juniper and piñon woodlands. Pages 375–384. In S.B. Monsen, R. Stevens, R.J. Tausch, and R.F. Miller (compilers). Proceedings: Ecology and Management of Piñon-juniper Communities within the Interior West. USDA Forest Service Proceedings RMRS-P-9.
Miller, R.F., and P.E. Wigand. 1994. Holocene changes in semiarid piñon-juniper woodlands: response to climate, fire and human activities in the U.S. Great Basin. BioScience 44:465–474.
Oliphant, J.O. 1968. On the cattle ranges of the Oregon country. University of Washington Press, Seattle, WA.
Sowder, J.E., and E.L. Mowat. 1958. Sivical characteristics of western juniper. USDA Forest Service PNW Sivical Series 12.
