Trees Take the Streets: Urban Tree Growth and Hazard Potential.

Urban forestry is the science and technology of managing trees and forest resources in and around urban community ecosystems for the physiological, sociological, economic, and aesthetic benefits trees provide society. As urbanization rapidly increases, so does urban forestry. Although increasing the number of trees in urban environments can be beneficial to human residents, trees in urban environments can also become hazardous if improperly trimmed, located, and cared for. For example, human-induced pruning via side trimming compromises tree branch structural integrity. This study investigates whether the phenomenon of side pruning can be brought about naturally by specific combinations of tree aspect relative to the tree’s nearest building and nearest building height. Measuring trees in a predominantly commercial neighborhood in the Northern hemisphere, we found that trees on the south side of buildings (those which receive the most sunlight) have a greater proportion of branch diameter comprised of far branches and naturally mimic a possibly dangerous side-pruned shape. Nearest building height did not impact branch growth patterns. Therefore, trees planted on the south side of buildings have a higher potential to become hazardous, due to naturally induced asymmetrical branch growth, and thus should be monitored more closely for hazard potential