Arboriculture & Urban Forestry 32(6): November 2006 263 LITERATURE CITED American National Standards Institute. 2001. American Na- tional Standards for Tree Care Operations-Tree, Shrub, and Other Woody Plant Maintenance—Standard Practices (Punning) (A300, Part 1). Tree Care Industry Association, Manchester, NH. Browning, D.M., and J.V. Wiant. 1997. The economic im- pacts of deferring electric utility tree maintenance. Journal of Arboriculture 23:106–111. Costello, L.R., E.J. Perry, N.P. Matheny, J.M. Henry, and P.M. Geisel. 2003. Abiotic Disorders of Landscape Plants: A Diagnostic Guide. University of California Ag- riculture and Natural Resources. Oakland, CA. 242 pp. Figure 3. Regression relationship and 95% prediction in- terval for the square root of percent volume loss resulting from decay of leaders and length of external decay (X1 in centimeters at diameter decay at heading cut (X5 ) ) of 4 cm (1.6 in) in silver maple trees converted from roun- dover to V-trims during electrical line clearance opera- tion. R2 for the regression model was 0.57. Indeed, Giles (2001) lists silver maple heartwood as having a low resistance to decay. The predicted volume of decay also increased with the length of external decay and diameter of the two ends of the leader (Figure 2). Percentage of volume loss was found to be three times greater in leaders in which internal decay began at the heading cut and increased as the length of external decay and diameter of decay the heading cut increased (Figure 3). Because nearly half the leaders had decay at the tip, it seems reasonable to suggest that heading cuts are likely to create sizable decay columns, which may cause the leaders to be- come susceptible to failure. Although no direct relationship to strength loss can be inferred from the regressions presented here, utility arborists may want to use the equations to estimate the extent of in- ternal decay columns in silver maple trees. Estimating inter- nal decay from the presence of external decay can be a useful tool when deciding on failure risk levels in trees converted from roundovers to V-trims. A better understanding of the amount of decay present in the leaders will help arborists determine wheth- er the risk of failure is high enough to warrant the removal of a leader or the whole tree. Future research should investigate if the patterns of decay are similar in other tree species. Acknowledgments. The authors thank Purdue University, the Department of Forestry and Natural Resources, and the TREE Fund for financial support. PSI Cinergy and Tipmont REMC donated tree crew time. Finally, the authors appre- ciate the suggestions provided by the anonymous reviewers; the manuscript is stronger with their help. Dahle, G.A., H.A. Holt, W.R. Chaney, T.M. Whalen, D.L. Cas- sens, R. Gazo, and R.L. McKenzie. 2006a. Implications of branch strength loss in silver maple trees converted from round-over to V-trims during electrical line clearance opera- tions. Proc. Environmental Concerns in Rights-of-Way Management Eighth International Symposium (In press). ———. 2006b. Branch strength loss implications for silver maple (Acer saccharinum) converted from round-over to V-trim. Arboriculture & Urban Forestry 32(4):148–154. Fazio, J.R., and E.E. Krumpe. 1999. Underlying beliefs and attitudes about topping trees. Journal of Arboriculture 25: 193–199. Giles, R.J. 2001. A total forest management plan and wild- land management decision support system. Virginia Poly- technic Institute and State University, Blacksburg, VA. http://fwie.fw.vt.edu/rhgiles/Trevey/forSnags.htm (ac- cessed 9/27/06). Gilman, E.F. 2002. An Illustrated Guide to Pruning. Delmar, Albany, NY. 330 pp. Johnstone, R.A. 1983. Management techniques for utility tree maintenance. Journal of Arboriculture 9:17–20. Kaiser, C.A., M.L. Witt, J.R. Hartman, R.E. McNeil, and W.C. Dunwell. 1986. Warning: Topping is hazardous to your trees health. Journal of Arboriculture 12:50–52. SAS Institute Inc. 1999. SAS/STAT User’s Guide, Version 8. SAS Institute Inc., Cary, NC 3884 pp. Gregory A. Dahle (corresponding author) Research Assistant 14 College Farm Road Department of Ecology, Evolution & Natural Resources Rutgers University New Brunswick, NJ 08901-8551, U.S.
[email protected] Harvey H. Holt Professor of Forestry 195 Marsteller Street Department of Forestry & Natural Resources Purdue University West Lafayette, IN 47907-2033, U.S. ©2006 International Society of Arboriculture
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