INTEGRATED VEGETATION MANAGEMENT ON AN ELECTRIC TRANSMISSION RIGHT-OF-WAY IN PENNSYLVANIA, U.S.

Journal of Arboriculture, Sep 2004 by Yahner, Richard H, Hutnik, Russell J

Abstract. Integrated vegetation management (IVM) has been used for the maintenance of vegetation along an electric utility transmission right-of-way (ROW) at the State Game Lands (SGL 33) Research and Demonstration Area, Centre County, Pennsylvania, U.S., since 1987. In addition, the wire-border zone method was implemented on the ROW in 1987. The wire-border zone method results in forb-grass-shrub cover types in wire zones and shrub cover types in border zones. The SGL 33 Research and Demonstration Area has been studied since 1953, which makes this 51-year-old project the longest continuous study 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 (2000) and 2 to 3 years after treatment. Results were compared to those obtained from the late 1980s and 1990s. For all units combined (except handcut) in 1999, average target tree densities prior to treatment were 288 trees/ha (117 trees/ac) in wire zones and 759 trees/ha (307 trees/ac) in border zones. Excellent control of target tree density [62 to 124 trees/ha (25 to 50 trees/ac)] was noted in wire zones of mowing plus herbicide, stem-foliage spray, and foliage spray units; moderate control [371 to 680 trees/ha (150 to 275 lrees/ac)] was observed in low-volume basal spray, high-volume basal spray units, and mowing units; and poor control (4,818 trees/ha [1,951 trees/ac]) was found in the handcut unit. In 2003, the density of target trees in all treatment units combined was 1,544 trees/ha (625 tree/ac) in wire zones and 1,594 trees/ha (645 trees/ac) m border zones. If the handcut unit was omitted from the calculations, then only 340 target trees/ha (138 trees/ac) in wire zones and 501 trees/ha (203 trees/ac) in border zones were present. IVM of a ROW is not a "tree-proof but rather a "tree-resistant" 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 minimized but did not eliminate tree invasion. Since 1987, IVM and the wire-border zone method of ROW maintenance has increased the time between treatment cycles, thereby reducing labor and chemical costs at the SGL 33 Research and Demonstration Area.

Key Words. Cover types; herbicides; integrated vegetation management; rights-of-way; tree control; vegetation.

Integrated vegetation management (IVM) has been used for the maintenance of vegetation along an electric utility transmission right-of-way (ROW) at the State Game Lands (SGL 33) Research and Demonstration Area, Centre County, Pennsylvania, U.S., since 1987 (Bramble and Byrnes 1996; Yahner et al. 2003). IVM involves two treatment phases: (1) use of a herbicidal spray or mechanical treatment to initially control the density of target (undesirable) tree species, i.e., those that have the potential of growing to a height that is not compatible safe ROW maintenance, and (2) development of tree-resistant plant cover types to reduce invasion of the ROW by target trees.

In addition to IVM, the wire-border zone method was implemented on the ROW in 1987 (Figure 1) (Bramble et al. 1992). The wire-border zone method results in forb-grass-shrub cover types in wire zones and shrub cover types in border zones (Bramble et al. 1990), thereby producing a ROW with economic, aesthetic, and wildlife benefits (Yahner 2003, Yahner et al. 2003).

The SGL 33 Research and Demonstration Area has been studied since 1953, which makes this 51-year-old project the longest continuous study documenting the effects of mechanical and herbicidal maintenance on flora and fauna along an electric transmission ROW This project is invaluable from management and ecological perspectives by providing an understanding of the response of plant and animal communities within the ROW to the maintenance practices.

In this paper, our objective was to present target tree density and cover-type development on the ROW at the SGL 33 Research and Demonstration Area in response to integrated vegetation management prior to the most recent treatment and 2 to 3 years after treatment. Results then were compared to those obtained on the ROW irom the late 1980s and 1990s.

STUDY AREA AND TREATMENT METHODS

The State Game Lands 33 Research and Demonstration Area, which is located along a 230-kV transmission right-of-way (ROW) of FirstEnergy (Penelec), is in the Allegheny Mountain Region of central Pennsylvania (Yahner et al. 2003). Treatment units on the ROW are rectangular in shape, 0.8 to 1.75 ha (2 to 4.3 ac) each, and span the entire width of the ROW

In 1987, seven treatments were applied: handcut, mowing, mowing plus herbicide, high-volume basal spray, low-volume basal spray, foliage spray, and stem-foliage spray (Bramble et al. 1991). In the handcut unit, woody vegetation was cut to a 10 cm (2.5 in.) height in wire zones, and undesirable trees were cut in border zones. In mowing units, vegetation was mowed in the entire wire zone, and a low-volume selective basal spray was applied to target trees using undiluted Weedone CB in border zones. In mowing plus herbicide units, vegetation was mowed in the entire wire zone, and a broadcast spray was applied immediately using a mix of Tordon K (0.75%), Garion 3A (0.75%), water, and blue dye (Bullseye; 0.16% in water); a low-volume selective basal spray was applied to target trees using undiluted Weedone CB in border zones. In high-volume basal spray units, a mix of Access (Picloram Tricolpyr; 1.5%) in fuel oil was applied to all trees and tall shrubs in wire zones, and the same spray was applied to target trees in border zones. In low-volume basal spray units, Access (12.5%) and Garlon 4 (12.5%) in Arborchem basal oil was applied to all trees and tall shrubs in wire zones and to target trees in border zones. In stem-foliage spray units, a selective stem-foliage spray of Tordon K (0.2%), Garlon 3A (0.5%), and water was applied to all trees, tall shrubs, and blackberry in wire zones, using an undiluted mix of Weedone CB (87.5%) and Garlon 4 (12.5%). Weedone CB and Garlon 4 also were applied to target trees in border zones. In foliage spray units, Accord in water was applied to the foliage of all trees and tall shrubs in wire zones, and a mix of Weedone CB and Garlon 4 was applied to target trees in border zones.