Urban Forest Quality Corresponds with Soil Microbial Community Composition and Arbuscular Fungi Root Colonization

Fairfax County government in Virginia, USA, conducted an extensive survey of urban forests that included assessing tree health, quantifying invasive species, and determining impervious surface. These measurements were used to calculate a quality index using the iTree tool kit. Building on survey results, our research team sampled soils and tree roots in a subset of sites representing a range of forest quality index values. Soil bacterial/archaeal and fungal communities were quantified and characterized using qPCR and amplicon sequencing to understand how soil biology relates to aboveground forest health. We observed differences in community composition and putative functional assignments indicated a decrease in ectomycorrhizal fungi with declining quality. Arbuscular mycorrhizal fungal root colonization also decreased with forest quality. This study demonstrates the crucial above- and belowground connections within urban forests and highlights the need for urban managers to consider soil biology when assessing urban ecosystem health.