Coastal Arborist Association
The effects of pruning on drag & bending moment. A better way to prune
Michael W. Pavlis, Owner of Ossabaw Consulting, LLC & President of CAA
About: 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.
Please note: Directly following the CAA Meeting, there will also be a Coastal Consulting Arborists meeting from 1 to 2 pm at Savannah Coffee Roasters about the division of labor between UGA ANR Agents and the Arboricultural Consulting community.
Location: Savannah Coffee Roasters, 215 W Liberty St., Savannah, GA 31401
Parking: There is no designated parking for Savannah Coffee Roasters. Parking is available at metered locations on the street, at the Liberty Street Parking Garage, or at the Liberty Parking Deck.
Cost: There will be a $10 charge at the door for CAA members and a $20 charge for non-members. Cash or check only please.
Lunch: A sandwich or wrap of your choice, plus a bag of chips and choice of water or sweet tea. A veggie wrap option is available for guests with dietary restrictions.
Questions? Contact Holly Elliott, CAA Administrator at 904-608-9539 or at firstname.lastname@example.org.