The Effects of Pruning on Wind Resistance of Shade Trees

Three tree species, Freeman maple (Acer x. freemanii), swamp white oak (Quercus bicolor (Willd.)) and shingle oak (Quercus imbricaria (Michx.)) were tested before and after pruning to determine the effectiveness of pruning on reducing drag and bending moment. Pruning methods were thin, reduce and raise and meet the requirements set by the American National Standard Institute A300 standards for Tree Care Operations Trees, Shrub, and Other Woody Plant Maintenance - Standard Practices (Pruning). Trees were tested up to speeds of 22.4m*s-1 over 1.6km by driving them in the bed of a truck. Drag, based on a centroid of the crown, and a bending moment was calculated. Drag and bending moment were also normalized by tree mass and crown area. Reduction pruning worked more effectively for Freeman maple and raise pruning for swamp white oak at reducing drag. Simple to measure tree characteristics were analyzed to determine the best predictors of drag and bending moment in the field. Tree mass frequently was the best predictor of drag and bending moment. Information should be used with caution due to the fact that the trees tested were small stature and a limited number of trees were tested.