Soil volume restrictions and urban soil design for trees in confined planting sites

Urban trees often suffer from poor soil conditions, compromising their health and safety and raising management issues. In compact development areas, planting sites are beset by critical physical soil constraints, especially confined soil volume on narrow roadsides. These include internal (micro-scale) restrictions due to compaction and excessive coarse fractions such as gravels, and external (macro-scale) restrictions due to limited soil depth and width. Soil area provision (SAP) is assessed based on the moisture need of trees. A creative soil design scheme is proposed to expand soil volume, based on the principle of soil volume sharing, subsurface soil conduits, and subsurface soil corridors supplementing the routine open soil corridor. SAP could extend from the narrow footpath to the adjoining carriageway as a soil peninsula and green space as offset soil volume. The study aimed at knowledge exchange among science, policies, and practices, with implications for the sustainable management of many roadside trees in cities. Copyright © 2019 Informa UK Limited.