In light of the risk of litigation following damage related to tree failure in urban and suburban settings, more empirical data related to tree risk assessment are needed. We measured drag and drag-induced bending moment (M) and calculated drag coefficient ([C.sub.D]) and trunk stress ([sigma]) for three deciduous trees at wind speeds up to 22.4 m/s. We measured the modulus of rupture (MOR) of wood samples from trunks and calculated the factor of safety (SF = MOR/[sigma]) for each tree. We also investigated which tree morphometric variables best predicted drag and M and whether simple two- and three-dimensional shapes accurately represented actual tree crowns. Drag, [C.sub.D], M, [sigma], and SF differed among species in accordance with physical parameters. More massive trees experienced greater drag and M, but [sigma] was greater for trees with smaller trunk diameters. Tree mass reliably predicted drag and M; crown dimensions, including crown area, were less reliable predictors. Crown reconfiguration varied only slightly among species, and [C.sub.D] values were similar to previously reported values for trees of similar size. Our study has important applications for practitioners who manage tree risk, particularly the critical wind speeds and percentage of trunk cross-sectional area that could be decayed before trunk failure.
Available at: http://works.bepress.com/brian_kane/12/