Résumé
Rapid urbanization is leading to massive soil sealing, limiting biophysical exchanges between underground and surface layers. This phenomenon disrupts soil ecological functions and negatively impacts biodiversity. To address this issue, soil unsealing has emerged as a key solution, promoting the return of permeable and vegetated surfaces. However, as these practices are relatively recent, their effects on urban soil biodiversity remain poorly documented.This thesis investigates the impact of soil unsealing on urban soil biodiversity by focusing on three bioindicator groups with key ecological roles and varying dispersal abilities: microorganisms (bacteria and fungi), earthworms, and ants. The study aims to (i) identify the communities capable of colonizing these newly created urban habitats and (ii) analyze their spatio-temporal dynamics in response to these transformations.The research is based on unsealed sites in a Mediterranean context, a global biodiversity hotspot for the studied groups. The main study sites include unsealed schoolyards and micro-greened urban spaces. A quasi-non-lethal approach was adopted, combining environmental DNA (eDNA) metabarcoding analyses for microorganisms and earthworms, along with ecological monitoring of ants using baiting methods. The study also considers the spatio-temporal effects on biological communities through landscape and physico-chemical analyses.The manuscript is structured into several sections. The first, dedicated to materials and methods, describes and justifies the selection of study sites, models, and methodological protocols. The following three chapters analyze the response of each studied taxon to unsealing operations. A fourth, transdisciplinary chapter explores the social significance of these spaces and their potential as habitats for soil biodiversity. Finally, the general discussion contextualizes these findings through a multi-taxon and multi-scale approach, highlighting ecological challenges and urban planning perspectives.The results reveal that unsealed spaces can rapidly host abundant soil biodiversity, regardless of the studied organism group. However, colonization appears to be primarily influenced by local factors, particularly the type of ground cover following unsealing, which plays a crucial role in habitat quality. This thesis provides new insights into the interactions between biodiversity and urban soil restoration, contributing to a better integration of living organisms into urban planning policies for more resilient and ecologically sustainable cities.