Economic and Biophysical Implications of Alternative Street-tree Spacings in Halifax, Canada

Abstract

Municipalities establish, maintain, and administer trees on the rights of way along streets. In spite of the many benefits trees provide, they are often planted far apart. The overall objective of this study was to explore the optimal spacing of street trees in Halifax. Altogether 2,162 trees were measured with an average spacing of 15.4 metres (m) and standard deviation (SD) of 10.5 m. Regression equations were developed for three-dominant species to predict crown diameter from diameter at breast height (DBH) and used in the simulation to calculate crown coverage over 60 years, at spacings from 5 to 20 m in a 1 hectare (ha) area. A row of street trees at close spacing delivers a greater canopy coverage per unit area. I recommend street-tree spacing between 5 and 10 m. It is important to find an affordable way to plant trees closer together in streets to maximise ecosystem services.