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The Effects of Pruning on Drag and Bending Moments of Shade Trees
Arboriculture & Urban Forestry (2008)
  • Michael Pavlis, Virginia Polytechnic Institute and State University
  • Brian C.P. Kane, University of Massachusetts - Amherst
  • J Roger Harris, Virginia Polytechnic Institute and State University
  • John R Seller, Virginia Polytechnic Institute and State University

Arborists assume that pruning can help reduce the risk of tree failure by reducing the pressure exerted on trunks by wind (drag-induced bending moment), but there are few studies that quantify this effect. We simulated wind by driving trees in the back of a pickup truck from 0 to 24.5 m/s (0 to 55 mph) and measured drag-induced bending moment as well as tree morphometric data for Freeman maple (Acer × freemanii), swamp white oak (Quercus bicolor Willd.), and shingle oak (Quercus imbricaria Michx.). Measurements were taken before and after application of one of three American National Standards Institute A300 pruning types (raising, reduction pruning, thinning). Reduction of drag-induced bending moment differed by pruning type, largely in accordance with the mass of foliage and twigs removed. The effectiveness of pruning types was also species-dependent because crown architecture affected how much mass each pruning type removed. In general, per unit of mass removed, reduction pruning more effectively reduced the drag-induced bending moment than thinning or raising. Reduction pruning reduced the center of pressure height and, presumably, increased crown porosity after pruning. Prediction of the reduction of drag-induced bending moment was not reliable based on reduction in crown area after pruning. We discuss the practical applications of our findings.

  • Bending moment,
  • drag,
  • pruning
Publication Date
Citation Information
Michael Pavlis, Brian C.P. Kane, J Roger Harris and John R Seller. "The Effects of Pruning on Drag and Bending Moments of Shade Trees" Arboriculture & Urban Forestry Vol. 34 Iss. 4 (2008)
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