ROOT SPACE UNDERNEATH TRAFFIC LANES

Abstract

Summary Tree roots need certain essential conditions for optimal growth. These include, for instance: enough space, enough ground air ventilation and moisture, sufficient amounts of macro- and micro-nutrients, as well as the existence of symbionts. However, these conditions are not always found at potential rooting zones for urban street trees. Rooting zones often lack space and the soil is often too compacted. Furthermore, the surface is sealed off with materials impermeable to water and air, thereby causing additional problems for growth. Additional problems arise if street trees are planted in narrow central strips between traffic lanes. The tree roots are stuck between the concrete kerbstones of the lanes on both sides and in such cases the soil often consists of highly-compressed building material through which tree roots cannot grow. These are some of the reasons why many trees that are planted in such places are in a very poor condition. Similar poor development of trees is observed when trees are planted in small planting pits in highly-compacted road beds or in poor soil. In the city of Osnabrück (Germany), officers responsible for trees and arboriculture and for road construction worked together to find solutions to these problems by using novel methods for the creation of additional rooting zones for trees. The structures underneath traffic lanes are referred to as Wurzelkanäle (Root Ducts) and Wurzelkammern (Root Chambers).