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Arboriculture & Urban Forestry Online
Volume 31, Issue 5 — September 2005


Richard H. Yahner and Russell J. Hutnik

Abstract: Integrated Vegetation Management (IVM) via the wire­border 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 wire­border zone method creates a forb­grass­short 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, stem­foliage spray, and foliage spray) were classified as shrub­forb­grass­tree, whereas types in border zones of these units were tree­shrub­forb. Both wire and border zones of mechanical units were considered tree­shrub­forb 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 1999­2004, 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 wire­border zone method keeps tree invasion to a minimum. Thus, over the years since 1987, IVM and the wire­border zone method of ROW maintenance have increased the time between treatment cycles, thereby reducing labor and chemical costs for ROW maintenance.

Keywords: Cover type; herbicide; Integrated Vegetation Management; right-of-way; tree control; vegetation, wireborder zone method.

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