DESIGNING THE FUNGAL CITY: A framework for connecting mycorrhizal networks in the built environment

Abstract

Urban infrastructure has replaced what once was biologically rich soil with compacted, sterile substrates severing the underground networks that facilitate mutualistic relationships between plants and mycorrhizal fungi. This dissertation argues that one way of reintegrating mycorrhizal networks – and thereby restoring the health and resilience of the urban biota—is by redesigning underground environments. An extensive literature review was first undertaken to develop a comprehensive understanding of current research across the fields of landscape architecture, microbiology and ecology. The review revealed a lack of cross disciplinary collaboration and highlighted the need for a more integrative approach to studying and designing urban environments. Central to this dissertation is the design, development and testing of the soil conduit—a new form of green infrastructure designed to connect trees physically in order to help foster the growth of fungal networks in urban conditions. By creating a connected rhizosphere, the soil conduit enables trees to exchange nutrients, which encourages health and resilience through cooperative dynamics. To demonstrate the feasibility and impact of the soil conduit, this research employed two proof of concepts at different scales. At the micro scale, a controlled experiment was conducted in a greenhouse with 53 oak saplings to evaluate the effects of the soil conduit on tree health and fungal communities. Over the course of the study, samples were collected from the soil and the root zones, to be analysed using molecular and microscopic techniques. The results confirmed the presence of ectomycorrhizal fungi in the soil conduit, in addition to improved tree health-scores and growth measurements in connected treatments. These findings suggest that the conduit is effective in promoting underground connectivity and ecological resilience in urban landscapes. At the macro scale, a mapping exercise was undertaken to analyse the spatial and infrastructural conditions that support soil connectivity and tree health. A study explored trees growing in parks and sidewalks to determine the effects of fragmentation in an urban context on the structure of the soil as well as the health score and growth measurements of trees. Here mapping is also suggested as a tool to begin speculating about potential underground fungal networks in the built environment and how a soil conduit might enhance this connectivity, thereby enhancing the resilience of the urban forest. This research demonstrates the soil conduit’s potential to transform how we design for urban ecosystems, reimagining the underground landscapes as a site of connection rather than isolation by offering a scalable and design-oriented framework for reintegrating mycorrhizal fungi—and the vital ecological functions they support—into the urban fabric.