Cost of Controlling Maturing Western Juniper Trees

Abstract

A cost evaluation was conducted of four alternatives for improvements on maturing western juniper (Juniperus occidentulis) woodlands. The alternatives were: (a) the use of picloram (4-amino-3,5,6-trichloropicolinic acid) to kill the trees with no further treatment, with a total cost of %78/ha (%3l/acre); (b) picloram with sufficient limbing and/or removal of trees to allow passage of a rangeland drill for seeding at a cost of %448/ha ($179/acre); (c) mechanical clearing and burning of the trees at a cost of %595/ha (%237/acre); and (d) wood harvesting and slash disposal at a cost of %2,08O/ha ($832/acre). The picloram and limb, mechanical, and wood-harvesting treatments provide mechanically seedable sites, but of considerably different quality in terms of ease of seeding and chances of seedling establishment. The mechanical treatment requires a large capital investment, while the wood-harvesting treatment requires a large amount of labor. Based on equivalent energy values, the wood-harvesting operation would produce a profit for the landowner who could afford to invest the labor. For a specific woodland, a combination of treatments would be most cost effective. During the late 19th and early 20th centuries, range sites that formerly supported big sagebrush (Artemisia tridentam)/ bunchgrass communities were suddenly invaded by western juniper (Juniperus occidentalis subsp occidentalis) trees (Burkhardt and Tisdale 1969, 1976; Young and Evans 1980). These stands are now in a successional stage where the trees completely dominate the site and have largely depleted the understory of competing grass and browse species. Juniper roots occupy the soil profile to the extent that the site is effectively closed for seedling establishment of desirable forage or browse species. In many stands the junipers are approaching maturity, with 150 trees/ ha (60/acre); individual trees are 9.2 m (30 ft) tall and 0.5 m (20 inches) in diameter at the base (Young and Evans 1981). The tree canopies are not closed, and projected crown covers range from 36 to 45% in the stands. The density of trees on invasion sites is relatively constant, apparently reflecting an equilibrium with available environmental potential. The purpose of this study is to evaluate alternatives for the improvement and utilization of these stands by ranchers. In other studies, either published or in progress, we have reported on why these invasion stands exist and how to prevent their occurrence. This study concerns the ranch manager’s options given the existing woodlands. The study was designed for western juniper woodlands that are owned by ranchers who are interested in enhancing forage production for livestock. Because of the power units available and the biological conditions of the stands, we did not consider chaining as a treatment. Within these constraints, the treatments evaluThe authors are range scientists, U.S. Dep. Agr., Agr. Res. Serv., Reno. Nev. 89512; assistant professor of forestry; and formerly research associate, agricultural and