Changes in Mountain Big Sagebrush Habitat Types following Spray Release

Abstract

Three habitats dominated by mountain big sagebrush were sprayed with 2,4-D butyl ester. Shrub cover in sprayed mountain big sagebrush communities was significantly less than unsprayed. Perennial grass production and density were twice as high across sprayed stands as compared with nonsprayed stands. Across the three habitat types bluebunch wheatgrass productivity was more responsive on the sprayed stands than Idaho fescue. Production and density of tailcup lupine, the most abundant forb across the three sites, was significantly less in sprayed communities, causing total forb production to be lower. Other forbs either showed little or no difference in production and density between the sprayed and nonsprayed communities. Intensive management of our resources requires accurate biological information. The need for plant response data in chemical control programs on rangelands has intensified due to an increase in users of this resource. Land managers must be able to predict accurately the outcome of brush control programs. Researchers have reported numerous examples of increases in forage production and beef production following chemical control of sagebrush (Artemisia tridentata) (Hyder and Sneva 1956; Hedrick et al. 1966; Laycock and Phillips 1968; Sneva 1972; Schumaker and Hanson 1977; and Sturges 1977). Information is also available on changes in plant composition following brush control with 2,4-D (2,4-dichlorophenoxy acetic acid) (Hurd 1955; Blaisdell and Mueggler 1956; Findley 1974; Sturges 1977; and Tomkins and Grant 1977). Although numerous publications have dealt with the effects of spraying big sagebrush, the specific subspecies being evaluated was rarely identified. Taxa of Artemisia tridentata not only vary morphologically and phenologitally but also have distinct ecologic and hydrologic requirements (Beetle 1960; Beetle and Young 1965; Winward 1970; Winward and Tisdale 1977; West et al. 1978). Sturges (1977) reported parameters relating to available moisture which affect the distribution of sagebrush subspecies also influence soil moisture response following sagebrush control. Predictions of plant community response to chemical brush control may be more accurate in sagebrush communities if data were evaluated by sagebrush subspecies. The purpose of this study was to document changes in forage production and plant species abundance following application of 2,4-D in three mountain big sagebrush (Artemisia tridentata subsp. vaseyana) habitat types. Habitat Authors are assistant professor, Rangeland Resources Program, Oregon State University, Corvallis; instructor, Department of Agriculture, Treasure Valley Community College, Ontario, Oregon; and range conservationist, Bureau of Land Management, Vale, Oregon, respectively. This report was submitted as Technical Paper No. 5054. Oregon Agricultural Experiment Station, Corvallis 9733 1. Manuscript received January 8, 1979. types studied were: mountain big sagebrush/ Idaho fescue (Artemisia tridentata subsp. vaseyanal Festuca idahoensis) and mountain big sagebrush/ bluebunch wheatgrass (Artemisia tridentata subsp. vaseyanal Agropyron spicatum) (Winward 1970). The third community, mountain big sagebrush/ Idaho fescue-bluebunch wheatgrass (Artemisia tridentata subsp. vaseyana / Festuca idahoensis-Agropyron spicatum), recognized as a distinctly different site by Sheehy (1975), will be called a habitat type in the following discuso Strickler and Stearns 1962). A plant was counted inside the plot if the main stem or stems were rooted inside the plot if the main stem 278 JOURNAL OF RANGE MANAGEMENT 33(4), July 1980