A Plant Sociological Procedure for the Ecological Design and Enhancement of Urban Green Infrastructure

Urban green infrastructure could represent an important mean for environmental mitigation, if designed according to the principles of restoration ecology. Moreover, if suitably executed, managed and sized, they may be assimilated to meta-populations of natural habitats, deserving to be included in the biodiversity monitoring networks. In this chapter, we combined automatised and expert opinion-based procedures in order to select the vascular plant assemblages to populate different microhabitats (differing in terms of light and moisture) co-occurring on an existing green roof in Zurich (Switzerland). Our results lead to identify three main plant species groups, which prove to be the most suitable for the target roof. These guilds belong to mesoxeric perennial grasslands (Festuco-Brometea), nitrophilous ephemeral communities (Stellarietea mediae) and drought-tolerant pioneer species linked to nutrient-poor soils (Koelerio-Corynephoretea). Some ruderal and stress-tolerant species referred to the class Artemisietea vulgaris appear to fit well with local roof characteristics, too. Inspired by plant sociology, this method also considers conservation issues, analysing whether the plants selected through our procedure were characteristic of habitats of conservation interest according to Swiss and European laws and directives. Selecting plant species with different life cycles and life traits may lead to higher plant species richness, which in turn may improve the functional complexity and the ecosystem services provided by green roofs and green infrastructure in general.