Plant and macrofauna communities dynamics in constructed Technosols over 10 years of experimentation

Greater progress in the circular economy is expected to enable large cities to benefit more from ecosystem services. Reusing urban wastes can help reshape the urban environment and make the ecosystem more suitable for human use. Excavated material from building sites is one of the most abundant waste resources in megacities around the world, and some of this mineral waste can be used to create substrates, known as constructed Technosols, for the development of new green spaces. However, long-term studies are needed to determine the influence of the parent materials used in Technosol formulations on the community dynamics and trajectory of these new ecosystems. In this study, we assessed the impact of organic amendment on the evolution of constructed Technosols and the diversity of plant and soil macrofauna. A large-scale experiment was set up in 2013 in the suburban region of Paris, France, using excavated mineral materials with or without green waste compost (10%, v/v). Flora and macrofauna inventories were carried out over 10 years, as well as the physico-chemical properties of both Technosols. Plant biomass was consistently higher in the Technosols amended with compost, while plant diversity converged towards the same level. Soil macrofaunal diversity was negatively affected by the organic amendment initially, but after 10 years it was similar between the two soils and the neighboring soil used as reference. Macroorganisms abundance increased linearly during the first 4 years, especially for earthworms in Technosols with compost, but after 10 years it also decreased to a lower level compared to the neighboring reference soils. This study showed that Technosols constructed with mineral waste is a promising alternative to natural topsoils for green spaces. The addition of compost promoted plant growth throughout the experiment and had no impact on the diversity of plants and soil macrofauna in the long term.