Arboriculture & Urban Forestry 34(4): July 2008 Table 1. Total number of plant species in wire zones, in border zones, and in either zone of ten treatment units at the Green Lane Research and Demonstration Area from late May through mid-August 2005 to 2006.z Treatment Mowing Replicate unit M-1 M-2y Zone Wire Border Either 52 (18, 0.36) 35 (10, 0.24) 56 (19, 0.60) 35 (10, 0.23) 26 (7, 0.15) 41 (12, 0.38) Average 44 (14, 0.30) 31 (9, 0.20) 49 (16, 0.49) Mowing plus MH-1 33 (14, 0.19) 36 (6, 0.13) 52 (17, 0.32) herbicide MH-2 34 (10, 0.60) 28 (9, 0.40) 48 (15, 1.00) Average 34 (12, 0.40) 32 (8, 0.27) 50 (16, 0.66) 39 (10, 0.37) 30 (6, 0.25) 47 (11, 0.62) 60 (20, 0.41) 34 (9, 0.28) 66 (22, 0.69) Stem–foliage SF-1y spray SF-2 Foliage spray Handcut Total area sampled (ha) Average 50 (15, 0.39) 32 (8, 0.27) 57 (17, 0.66) F-1 F-2 Average 41 (10, 0.29) 36 (8, 0.20) 50 (12, 0.49) HC-1 HC-2 Average 40 (11, 0.25) 26 (6, 0.17) 46 (11, 0.42) 3.24 2.19 5.43 zNumber of exotic species and total area (ha) are given in parentheses. yUnit adjacent to a secondary road (Upper Ridge Road). 33), but the SGL 33 ROW consisted of 15 units (Yahner and Hutnik 2005). Total number of species per unit at the Green Lane Research and Demonstration ROW ranged from 46 (40%) in handcut units to 57 (50%) in stem–foliage units (Table 1; Appendix). Only 27 (24%) of the total number of species were considered wide- spread (e.g., those found in 80% or more of the units), and seven of these (26%) were exotic. In comparison, 35 (31%) of the total number of species were exotic. This percentage of exotic species is considerably higher than that noted on the SGL 33 ROW (23%), which traverses a relatively pristine forested landscape (Yahner and Hutnik 2005), or that found in unfragmented forest stands in Wisconsin (20%) (Rooney et al. 2004). The Green Lane ROW traverses residential areas that have been human- impacted for decades; thus, the number of exotic species was expected to be high on the Green Lane ROW, like in a sector of Valley Forge National Historical Park (34%) in southeastern Pennsylvania (Cypher et al. 1986; see also Lundgren et al. 2004). Of the total number of species, 103 (90%) and 81 (71%) were in wire and border zones, respectively (Appendix). In wire zones, number of species ranged from 34 (30%) in mowing plus herbicide units to 50 (44%) in stem–foliage units (Table 1). In border zones, number of species varied from 26 (23%) in hand- cut units to 36 (32%) in foliage–stem units. The number of exotic species ranged from 33 (29%) in wire zones to 22 (19%) in border zones (Appendix). The total number of species or number of exotic species were not correlated with size of units (r0.19 and 0.08, respectively; P > 0.90). Also, because exotic species were found throughout the ROW, the proximity to a road was not a factor in determining the current distribution of exotic species (Brothers and Spingarn 1992; Watkins et al. 2003; Yahner and Hutnik 2005). Acknowledgments. Cooperators were Asplundh Expert Tree Company, Dow AgroSciences, and Philadelphia Electric Company. 48 (15, 0.23) 43 (10, 0.16) 59 (16, 0.39) 34 (5, 0.35) 28 (5, 0.24) 41 (7, 0.59) 36 (12, 0.09) 24 (7, 0.06) 43 (13, 0.15) 43 (9, 0.41) 28 (4, 0.28) 48 (9, 0.69) LITERATURE CITED Ballard, B.D., K.T. McLoughlin, and C.A. Nowak. 2007. New diagrams and applications for the wire zone–border zone approach to vegeta- tion management on electric transmission rights-of-way. Arboricul- ture and Urban Forestry 33:435–439. Bramble, W.C., and W.R. Byrnes. 1996. Integrated vegetation manage- ment of an electric utility right-of-way ecosystem. Down to Earth 51:29–34. Brothers, T.S., and A. Spingarn. 1992. Forest fragmentation and alien plant invasion of central Indiana old-growth forests. Conservation Biology 6:91–100. Cypher, E.A., R.H. Yahner, G.L. Storm, and B.L. Cypher. 1986. Flora and fauna survey in a proposed recreational area of Valley Forge National Historical Park. Proceedings of the Pennsylvania Academy of Sciences 60:47–50. Lundgren, M.R., C.J. Small, and G.D. Dreyer. 2004. Influence of land use and site characteristics on invasive plant abundance in the Quine- baug Highlands of southern New England. Northeastern Naturalist 11:313–322. Rhoades, A.F., and W.M. Klein Jr. 1993. The Vascular Flora of Penn- sylvania: Annotated Checklist and Atlas. American Philosophical So- ciety, Philadelphia, PA. 636 pp. Rooney, T.P., S.M. Wiegmann, D.A. Rogers, and D.M. Waller. 2004. Biotic impoverishment and homogenization in unfragmented forest understory communities. Conservation Biology 18:787–798. Sokal, R.R., and F.J. Rohlf. 1995. Biometry: Principles and Practice of Statistics in Biological Research. 3rd Ed. W.H. Freeman and Com- pany, New York, NY. 887 pp. Watkins, R.Z., J. Chen, J. Pickens, and K.D. Brosofske. 2003. Effects of forest roads on understory plants in a managed forested landscape. Conservation Biology 17:411–419. Yahner, R.H. 2000. Eastern Deciduous Forest: Ecology and Wildlife Conservation. 2nd Ed. University of Minnesota Press, Minneapolis, MN. 295 pp. ———. 2006. Green Lane Research and Demonstration Project: 20 Years of Continuous Study. Annual Report to Cooperators. 36 pp. Yahner, R.H., and R.J. Hutnik. 2004a. Integrated vegetation manage- ment on an electric transmission right-of-way in Pennsylvania, U.S. Journal of Arboriculture 30:295–300. ———. 2004b. State Game Lands 33 Research and Demonstration Project—52 Years of Continuous Study. Annual Report to Coopera- tors. 33 pp. ———. 2005. Plant species richness on an electric transmission right- of-way using integrated vegetation management. Journal of Arbori- culture 33:124–130. Richard H. Yahner (corresponding author) School of Forest Resources The Pennsylvania State University University Park, PA 16802, U.S.
[email protected] Richard T. Yahner 202 Amblewood Way State College, PA 16803, U.S. Bradley D. Ross 734 Partridge Lane State College, PA 16801, U.S. ©2008 International Society of Arboriculture 239
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