78 Gilman and Grabosky: Branch Union Morphology Affects Decay Following Pruning small-diameter branches. Removing larger branches created a greater volume of dysfunctional wood. Therefore, urban trees should be managed to minimize the diameter of branches that will eventually require removal as they age. The diameter of the cut branch may affect the development of discolored and decayed wood after branch removal, par- ticularly in large branches that contain heartwood (Shigo 1986). The results from our study are most relevant for young tree (small branch) pruning; further study is necessary to test the relation between the aspect ratio and long-term trunk discoloration for branches in excess of 2.5 cm (1 in) in di- ameter. Acknowledgments. The authors thank the TREE Fund and the GreatSouthern- TreeConference.org for partial funding of this project. LITERATURE CITED Biggs, A.R. 1989. Effect of pruning techniques on Leucos- toma infection and callus formation over wounds in peach trees. Plant Disease 73:771–773. Eisner, N., E.F. Gilman, J. Grabosky, and R.C. Beeson. 2002a. Branch morphology affects compartmentalization of pruning wounds. Journal of Arboriculture 28:99–105. ———. 2002b. Branch junction characteristics affect hy- draulic segmentation in red maple. Journal of Arboricul- ture 28:245–251. Ewers, E.W., and M.H. Zimmermann. 1984. The hydraulic architecture of balsam fir. Physiologia Plantarum 60: 453–458. Green, D.J., W.C. Shortle, and A.L. Shigo. 1981. Compart- mentalization of discolored and decayed wood in red maple branch stubs. Forest Science 27:519–522. Neely, D. 1988. Closure of branch pruning wounds with con- ventional and ‘Shigo’ cuts. Journal of Arboriculture 14: 261–264. Pearce, R.B. 2000. Decay development and its restriction in trees. Journal of Arboriculture 26:1–10. Pearce, R.B., and S. Woodward. 1986. Compartmentalization and reaction zone barriers at the margin of decayed sap- wood in Acer saccharinum L. Physiological and Molecu- lar Plant Pathology 29:197–216. Shigo, A.L. 1985. How tree branches are attached to trunks. Canadian Journal of Botany 63:1391–1401. ———. 1986. A New Tree Biology. Shigo and Trees, As- sociates, Durham, NH. 595 pp. Toole, E.R. 1961. Rot entrance through dead branches of southern hardwoods. Forest Science 7:219–226. Von Aufsess, H. 1975. The formation of a protective zone at the base of branches of broad-leaved and coniferous trees ©2006 International Society of Arboriculture and its effectiveness in preventing fungi from penetrating into the heartwood of living trees. Forstwiss Centralblatt 94:140–152. ———. 1984. Some examples of wood discolourations re- lated to mechanisms for potential protection of living trees against fungal attack. IAWA Bulletin 5:133–138. Zimmermann, M.H. 1978. Hydraulic architecture of some diffuse porous trees. Canadian Journal of Botany 56: 2286–2295. ———. 1983. Xylem structure and ascent of sap. In: Tim- mel, T.E. (Ed.). Springer Series in Wood Science. Springer Verlag, Berlin, Germany. 143 pp. Edward F. Gilman (corresponding author) Professor Environmental Horticulture Department 1549 Fifield Hall University of Florida Gainesville, FL 32611, U.S.
[email protected] Jason C. Grabosky Assistant Professor Department of Ecology, Evolution and Natural Resources Rutgers University New Brunswick, NJ 08901, U.S. Résume. Le diamètre de la branche par rapport à celui du tronc affecte l’étendu du bois décoloré et carié dans le tronc de semis d’érable rouge (Acer rubrum L.) après la coupe de la branche. Plus de décoloration résulte de la coupe de branches codominantes que de la coupe de branches plus petites que le tronc. La coupe de branches qui proviennent de bourgeons latéraux produit la même quantité de décoloration et de carie que la coupe de branches qui étaient autre- fois des branches terminales. Ce résultat fournit une preuve indirecte que la coupe d’une petite branche codominante faite à l’aide de techniques d’élagage pour ralentir son taux de croissance peut produire une zone de protection au niveau du point de jonction. Il n’y a aucune relation entre la présence d’écorce incluse et la carie quatre ans aprèslaréalisation des coupes. Zusammenfassung. Der Astdurchmesser in Relation zum Stam- mdurchmesser beeinflußt nach der Astentfernung die Ausdehnung von verfärbtem und faulem Holz im Stamm von aus Sämlingen gezogenen Rotahornen. Weitere Verfärbungen resultierten eher von der Entfernung codominanter Stämmlinge als von der Entfernung kleinerer Äste. Die Entfernung von Baumteilen, die aus lateralen Knospen entsprangen führte zu ähnlichen Verfärbungen und Fäulnis als die Entfernung unterdrückter, früherer Leittriebe. Diese Ergeb- nisse liefern indirekt Beweis dafür, dass ein kleiner codominanter Stamm, der durch Schnitttechniken im Wachstum behindert wird, eine Schutzzone an der Verbindungsstelle zum Stamm schaffen
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