Plant Identity Shapes Core Microbiomes on Green Roofs

Extensive green roof substrates support plant-microbe interactions that may contribute to ecosystem functioning. Yet the role of plant identity in shaping substrate-associated microbiomes remains insufficiently resolved beyond Sedum-dominated systems. We examined bacterial and fungal communities associated with three plant species representing contrasting functional groups in sterilized and non-sterilized green roof substrates, integrating taxonomic differentiation with plant functional traits and predicted metabolic pathways. Plant identity was associated with distinct microbial community patterns in sterilized and non-sterilized substrates, and these associations varied with the substrate's initial microbial state. LEfSe identified 13 discriminant fungal genera in ITS data and 65 bacterial genera in V4 data; strong discriminant taxa included Mortierella, Schizothecium, and Serendipita in fungal communities, and Sphingomonas, Brevundimonas, and Tumebacillus in bacterial communities. Lotus corniculatus showed particularly distinct plant-associated microbial patterns, while differences in predicted metabolic pathways provided a complementary functional perspective on taxonomic differentiation. Integrating plant functional traits with bacterial and fungal community analyses provided an ecological framework for interpreting plant-associated microbiome differentiation in extensive green roof substrates. Integrating plant functional traits with microbial community analyses provides an ecological framework for interpreting plant-associated microbiome differentiation in extensive green roof substrates.