Journal of Arboriculture 31(5): September 2005 263 INTEGRATED VEGETATION MANAGEMENT ON AN ELECTRIC TRANSMISSION RIGHT-OF-WAY IN SOUTHEASTERN PENNSYLVANIA, U.S. By Richard H. Yahner1 and Russell J. Hutnik2 Abstract. Integrated Vegetation Management (IVM) via the wire– border zone method has been used for the maintenance of vegetation along an electric utility transmission right-of-way (ROW) at the Green Lane Research and Demonstration Area, Montgomery County, Pennsylvania, U.S., since 1987. The wire– border zone method creates a forb–grass–short shrub cover type in wire zones and a tall shrub cover type in border zones. The Green Lane Research and Demonstration Area has been studied annually since 1987, which makes this 18-year-old project one of the longest continuous studies documenting the effects of mechanical and herbicidal maintenance on flora and fauna along an electric transmission ROW. In this paper, our objective is to present target (undesirable) tree density and cover-type development in response to IVM prior to the most recent treatment (June 1999) and 4 to 5 years after treatment. Excellent control of target trees was noted in 1999 in wire zones of mowing plus herbicide units; in contrast, tree control was poor in wire zones of mechanical units (mowing and handcut). Maximum tree height averaged 4.3 m (14 ft) and 4.9 m (16 ft) in wire and border zones, respectively. Immediately prior to the 1999 treatment of the Green Lane ROW, cover types in wire zones of herbicidal units (mowing plus herbicide, stem–foliage spray, and foliage spray) were classified as shrub–forb–grass–tree, whereas types in border zones of these units were tree–shrub–forb. Both wire and border zones of mechanical units were considered tree–shrub–forb cover type. The overall density of target trees increased 7.3% and 26.4% in wire zones and border zones, respectively, in 2004 compared to 2003. From 1999–2004, the most common target tree species on the Green Lane ROW was white ash (Fraxinus americana). In both 2003 and 2004, shrubs and forbs were the most important cover types in wire zones of all treatment units; grass cover type, however, was important in wire zones of five of the ten units. IVM of a ROW is a “tree resistant” but not a “tree proof ” means of reducing tree invasion. Competition with existing plants and wildlife predation on tree seeds on a ROW managed via the wire–border zone method keeps tree invasion to a minimum. Thus, over the years since 1987, IVM and the wire– border zone method of ROW maintenance have increased the time between treatment cycles, thereby reducing labor and chemical costs for ROW maintenance. Key words. Cover type; herbicide; Integrated Vegetation Management; right-of-way; tree control; vegetation, wire– border zone method. Integrated Vegetation Management (IVM) via the wire–border zone method has been used for vegetative maintenance along an electric utility transmission right-of-way (ROW) at the Green Lane Research and Demonstration Area, Montgomery County, Pennsylvania, U.S., since 1987 (Bramble and Brynes 1996; Yahner and Hutnik 2004a). IVM comprises two treatment phases: (1) use of herbicidal sprays or mechanical treatments to eliminate target (undesirable) tree species (i.e., those that have the potential of growing to a height that is not compatible with safe ROW maintenance), and (2) development of tree-resistant plant cover types to reduce invasion of the ROW by target tree species (Bramble and Byrnes 1996; Yahner and Hutnik 2004b). The wire–border zone method was implemented on the ROW in 1987 (Figure 1) (Yahner and Hutnik 2004a; see also Yahner and Hutnik 2004b). This method creates forb– grass–short shrub cover type in wire zones and shrub cover type in border zones (Bramble et al. 1991), thereby produc- ing a ROW with economic, aesthetic, and wildlife benefits (Yahner 2004). Recently, electric utility companies have recommended the use of the wire–border zone method and IVM for maintenance of vegetation along transmission ROW (Burns 2004). In this paper, our objective was to present target tree density and cover-type development on the ROW at the Green Lane Research and Demonstration Area in response to IVM prior to the most recent treatment (1999) and 4 to 5 years after treatment. STUDY AREA AND TREATMENT METHODS The Green Lane Research and Demonstration Area is located along a 500-kV transmission ROW of PECO in the Piedmont Region of southeastern Pennsylvania (Yahner and Figure 1. Diagram of a 500-kV electric transmission line, showing wire and border zones. A combination of a low-growing forb–grass–shrub cover type develops in wire zones, and a tall shrub cover type occurs in border zones. Adjacent to the border zone is mature forest. ©2005 International Society of Arboriculture
September 2005
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