Urban forest quality corresponds with soil microbial community composition and arbuscular mycorrhizal fungi root colonization

Abstract Fairfax County government (Virginia, USA) conducted an extensive survey of urban/suburban forests. Measurements such as tree health, impervious surface, and invasive species was used to calculate a quality index with the iTree tool kit. Building on survey results, our team sampled soils and tree roots in a subset of sites representing a range of forest quality index values. Our goal was to determine if aboveground forest quality correlated to belowground soil biomass, microbial community composition, and mycorrhizal fungal abundance. Soil bacterial/archaeal and fungal communities were quantified (qPCR) and characterized (amplicon sequencing). We observed differences in community composition, but not quantity. Putative functional assignments indicated a decrease in ectomycorrhizal fungi with declining quality and arbuscular mycorrhizal fungal root colonization also decreased. This study demonstrates the crucial above- and belowground connections within urban forests and highlights the need for managers to consider soil biology when assessing ecosystem health.