Biology, ecology, and management of western juniper (Juniperus occidentalis)

Abstract

T he rapid expansion of western juniper into neighboring plant communities during the past 130 years has caused considerable concern because of increased soil erosion, 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 with woodlands. However, the impacts of postsettlement woodland expansion are not always clear or consistent across sites and have led to debate and legal challenges over control projects and management plans for western juniper. This publication represents a synthesis of what is known about the history, biology, ecology, and management of western juniper. Western juniper 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. Presettlement changes in woodland abundance and distribution are largely attributed to long-term changes in temperature, amounts and distribution of precipitation, and the extent and return intervals of fire. Evidence supporting rapid post-settlement expansion is derived from old surveys, photographs, the distribution of relict presettlement woodlands, and tree-ring chronologies.