Vancouver Urban Meadow Project. Naturalization causes shifts in fungal community composition, but not bacterial community composition, in urban meadows

Urban centers are shifting their land management toward more green space, such as naturalized meadows once maintained as turfgrass. Although more green space is known to affect animal and plant diversity, there is limited data on how these land management shifts affect soil health. Soil health is the ability of the soil to support and maintain plant and animal life and its capacity to function sustainably through time. We examined the microbial diversity and function of the City of Vancouver parks that have been naturalized as part of a multi-year naturalization project. We aimed to determine whether naturalization affects bacterial and fungal diversity. Paired soil samples were collected from naturalized meadows and adjacent turfgrass in 10 parks, established two or five-plus years before sampling. Using Illumina amplicon sequencing, we analyzed soil bacterial (16S) and fungal (ITS2) compositions. Bacterial composition (beta diversity) differed between different aged locations. In contrast, fungal community composition differed between turfgrass and naturalized meadows, and different aged locations. We observed no significant differences in bacterial and fungal alpha diversity. In addition, we identified bacteria and fungi that are indicators of newly formed meadows, namely the fungi Cladosporium, which decreases in meadows and is a common mold that functions as a plant pathogen and can exacerbate allergy and asthma symptoms in humans. Our findings support the notion that, through time, the naturalization of meadows changes microbial biodiversity, particularly fungal Cladosporium and Gibellulopsis communities.