Arboriculture & Urban Forestry 34(4): July 2008 263 Esau, K. 1960. Anatomy of Seed Plants. Wiley, New York, NY. 376 pp. Fraedrich, B.R., and E. Thomas Smiley. 2002. Assessing the failure potential of tree roots, pp. 159–163. In: Smiley, E.T., and K.D. Coder (Eds.). Tree Structure and Mechanics Conference Proceedings: How Trees Stand Up and Fall Down. International Society of Arboricul- ture, Champaign, IL. Garboletto, M., G. Slaughter, T. Popenuck, F.W. Cobb, and T.D. Bruns. 1997. Secondary spread of Heterobasidion annosum in white fir root- disease centers. Canadian Journal of Forest Research 27:766–773. Hartman, J.R., T.P. Pirone, and M.A. Sall. 2000. Pirone’s Tree Main- tenance. Oxford University Press, New York, NY. 545 pp. James, R.L., F.W. Cobb Jr., P.R. Miller, and J.R. Parmeter Jr. 1980. Effects of oxidant air pollution on susceptibility of pine roots to Fomes annosus. Phytopathology 70:560–563. Lindberg, M., and M. Johansson. 1992. Resistance of Picea abies seed- lings to infection by Heterobasition annosum in relation to drought stress. European Journal of Forest Pathology 22:115–124. Morrison, D.J., and D.B. Redfern. 1994. Long-term development of Heterobasition annosum in basidiospore-infected Sitka spruce stumps. Plant Pathology 43:897–906. Nowak, D.J., M. Kuroda, and D.E. Crane. 2004. Tree mortality rates and tree population projections in Baltimore, Maryland, USA. Urban For- estry and Urban Greening 2:139–148. Figure 2. Example of discoloration and decay pattern from root flare cut. Discoloration in trunk wood was never more than a small streak. CONCLUSIONS Roots are good compartmentalizers. Severed roots of all sizes, located throughout the root system, showed only minimal dis- coloration and decay defects after 5 years. In these four species, there is minimal risk of introducing serious decay through injury of tree roots. Unlike branches, in which leaving a stub can lead to more extensive decay, “leaving a root stub” did not result in substantial decay and deterioration of the roots. A 5-year study may not be entirely conclusive but does give a strong indication that root injury does not typically lead to ex- tensive basal decay in trees. Based on the rate of decay observed in the first 5 years after severing the roots, extensive decay is not likely to develop in urban trees with a lifespan estimated at 5 to 45 years (Nowak et al. 2004). A long-term study of branch wounds showed that there was little difference in the area of discoloration between the first and ninth year after wounding (Dujesiefken and Stobbe 2002). If the same is true of roots, decay may have essentially stopped by the fifth year sampling date and pose no threat at all to the long-term health and stability of the trees. Acknowledgments. Partial funding for this project was received from the The Care of Trees, Wheeling, Illinois. LITERATURE CITED Balder, V.H., D. Dujesiefken, T. Kowol, and E. Schmitz-Felten. 1995. Aspects of wound treatments of oak and basswood roots. Nachrich- tenblatt des Deutschen Pflanzenschutzdienstes 47:28–35. Costello, L.R., and S.L. Quarles. 1999. Detection of wood decay in blue gum and elm: And evaluation of the Resistograph and the portable drill. Journal of Arboriculture 25:311–318. Desprez-Loustau, M.-L., B. Marcais, L.-M. Nageleisen, D. Piou, and A. Vannini. 2006. Interactive effects of drought and pathogens in forest trees. Annals of Science 63:597–612. Dujesiefken, D., and H. Stobbe. 2002. The Hamburg tree pruning sys- tem—A framework for pruning of individual trees. Urban Forestry and Urban Greening 1:75–82. Piri, T. 1998. Effects of vitality fertilization on the growth or Hetero- basidion annosum in Norway spruce roots. European Journal of For- est Pathology 28:391–397. Platt, W.D., E.B. Cowling, and C.S. Hodges. 1965. Comparative resis- tance of coniferous root wood and stem wood to decay by isolates of Fomes annosus. Phytopathology 55:1347–1353. Redmond, D.R. 1957. Infection courts of butt-rotting fungi in balsam fir. Forest Science 3:15–21. Robinson, R.M., and D.J. Morrison. 2001. Lesion formation and host response to infection by Armilaria ostoyae in the roots of western larch and Douglas-fir. Forest Pathology 31:371–385. Santamour, F.S. Jr. 1985. Trunk wood discoloration and decay follow- ing root wounding. Journal of Arboriculture 11:257–262. Shigo, A.L. 1967. Successions of organisms in discoloration and decay of wood. International Review of Forestry Research 2:237–299. ———. 1972. Successions of microorganisms and patters of discolor- ation and decay after wounding in red oak and white oak. Phytopa- thology 62:256–259. ———. 1977. Compartmentalization of Decay in Trees. USDA Forest Service Agriculture Information Bulletin Number 405. 70 pp. ———. 1979a. Tree Decay: An Expanded Concept. USDA Forest Ser- vice Agriculture Information Bulletin Number 419. 72 pp. ———. 1979b. Compartmentalization of decay associated with Hetero- basidion annosum in roots of Pinus resinosa. European Journal of Forest Pathology 9:341–347. ———. 1986. A New Tree Biology Dictionary. Shigo and Trees, As- sociates, Durham, NH. 132 pp. ———. 1991. Modern Arboriculture. Shigo and Trees, Associates, Durham, NH. 424 pp. Shigo, A.L., and W.E. Hillis. 1973. Heartwood, discolored wood, and microorganisms in living trees. Annual Review of Phytopathology 11:197–222. Singh, P. 1983. Armillaria root rot: Influence of soil nutrients and pH on the susceptibility of conifer species to the disease. European Journal of Forest Pathology 13:92–101. Stone, E.L. 1977. Abrasion of tree roots by rock during wind stress. Forest Science 23:333–336. Tian, S., and W.D. Ostrofsky. 2007. Butt and root decay in precommer- cially thinned spruce-fir stands. Northern Journal of Applied Forestry 24:129–133. Tippett, J.T., and A.L. Shigo. 1981. Barriers to decay in conifer roots. European Journal of Forest Pathology 11:51–59. ©2008 International Society of Arboriculture
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