Urban land use influences microbial functional traits along a management intensity gradient

Introduction: Urbanization alters soil conditions and may strongly affect microbial communities, yet the functional consequences of these changes remain poorly understood. We investigated how urban land use and management intensity shape microbial diversity, functional traits, and interaction patterns in urban soils. Methods: We sampled 135 soils across eight land-use types in Blois (France), each assigned a management intensity level from 1 (low) to 4 (high). Bacterial and fungal communities were characterized using Illumina sequencing, fungal guilds were identified using FungalTraits, bacterial taxa were classified by life strategies, enzymatic activities were measured, and co-occurrence networks were constructed. Results: Land-use type and management intensity strongly influenced microbial composition, diversity, and functioning. Highly managed sites (Gardens, Sports fields) showed lower fungal 18S rRNA gene abundance, higher bacterial 16S rRNA gene copy numbers, reduced diversity, and lower nitrogen-related enzyme activities compared to less managed sites (Unused areas). These sites also exhibited more oligotroph-dominated and interconnected communities. Co-occurrence networks were less connected than those reported in semi-natural ecosystems, indicating more fragmented microbial associations in urban soils. Discussion: Our findings reveal that management intensity acts as a strong ecological filter shaping microbial functional traits and interaction patterns in urban soils. The reduced connectivity and functional shifts observed in intensively managed sites highlight the need to integrate microbial indicators into urban green-space planning and management.