The Tripping Point–Minimum Planting Widths for Small-Stature Trees in Dense Urban Developments

Andrew K Koeser,Allyson B Salisbury,Hunter Thorn,Richard J Hauer,Robert J Northrop,Drew C Mclean,Deborah R Hilbert

doi:10.3390/su14063283

Andrew K Koeser, Allyson B Salisbury + Show 5 more

Open Access

https://doi.org/10.3390/su14063283

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Abstract

As urban development increases in density, the space to grow urban trees becomes more constrained. In heavily developed areas, small stature trees can be planted to reduce both above- and below-ground conflicts with infrastructure elements. However, even these species can interfere with pavement when placed in extremely confining conditions. In this study, we build on past work to determine the minimum planting space widths of small stature urban trees. Species, stem diameter, and the height at which stem diameter measurements occurred were all strong predictors of trunk flare (i.e., the interface region between large structural roots and the trunk) diameter (adjusted R2 of 0.843). Additionally, we modelled the relationship between planting space and the presence or absence of pavement conflicts using the predictions derived from this effort to project the potential cost savings in two United States cities. Study results provide a guideline to create sufficient space for urban trees and minimize infrastructure damage and associated cost savings.

Highlights

Urban trees are often integrated into urban planning and design efforts to increase the walkability of neighborhoods [1], calm traffic [2], and shade parking areas [3,4]
We worked with local urban foresters to locate and measure small stature urban trees We worked with local urban foresters to locate and measure small stature urban in Lakeland
Dx, and Hx were all significant predictors of trunk flare diameter (TFD) (Table 1)

Summary

Introduction

Urban trees are often integrated into urban planning and design efforts to increase the walkability of neighborhoods [1], calm traffic [2], and shade parking areas [3,4] Their ability to cool localized environments through the absorption of the sun’s light energy and the transpiration of soil moisture has been used to mitigate the impacts of urban heat island buildup [5], as well as to extend the life of some paving materials [6]. This noted, conflicts between tree roots and the paved surfaces that facilitate pedestrian and vehicular traffic are a common ecosystem disservice [7] as tripping hazards can arise and replacements are a major municipal expense [8,9]. In more recent conversations with local transportation engineers, tree and sidewalk conflicts are still seen as the primary cause necessitating sidewalk replacement [10]

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