Age Structure and Expansion of Piñon-Juniper Woodlands: A Regional Perspective in the Intermountain West

You may order additional copies of this publication by sending your mailing information in label form through one of the following media. Please specify the publication title and series number. Numerous studies have documented the expansion of woodlands in the Intermountain West; however, few have compared the chronology of expansion for woodlands across different geographic regions or determined the mix and extent of presettlement stands. We evaluated tree age structure and establishment for six woodlands in four ecological provinces in the central and northern Great Basin. Since 1860, the area occupied by piñon and or juniper has increased 125 to 625 percent. The increase of trees was a result of infill into shrub-steppe communities with relatively open low density stands of trees and expansion of piñon and juniper into sagebrush-steppe communities that previously did not support trees. Woodland expansion in Oregon, Utah, and Nevada were similar, but began two to three decades earlier in Idaho. The majority of woodlands are still in the early to mid phases of stand closure, which means they often support an understory of shrubs and herbaceous vegetation. This has implications for future changes that will occur within these woodlands in the next 30 to 50 years. In the absence of disturbance or management, the majority of these landscapes will become closed woodlands resulting in the loss of understory plant species and greater costs for restoration. Richard Miller is a professor with the Eastern Oregon Agricultural Research Station, Oregon State University in Corvallis, OR. He completed a B.S. in range management at Humboldt State University, an M.S. in range ecology and management at Oregon State University, and a Ph.D. in range ecology and plant physiology at New Mexico State University. Abstract Authors University Agricultural Experiment Station. We wish to thank reviewers Jon Bates, Range Scientist for the USDA-ARS, and Richard Stevens, retired research leader for the Utah Division of Wildlife, for their thoughtful and constructive review of this manuscript.