Rare bacterial genera dominate differences in urban green space soil communities in three cities across the world.. International_soils

Microbial diversity is critical to every biome on earth, from biogeochemical processes to host health outcomes. As such, conserving and restoring microbial diversity is key for our current global climate, biodiversity, and health crises. Restoring urban areas to green spaces can be a unique source of biodiversity conservation, including microbial diversity, given their proximity to societies that ensure resources and care. However, there is little knowledge on the types or designs of urban green spaces that promote ecological conservation and biological restoration efforts. Here, we investigated the influence of vegetation complexity (i.e., diversity and structure) on soil bacterial communities in urban green spaces around the world. By sequencing the 16S rRNA V4 gene region, we assessed the bacterial diversity of urban green space soils in Bournemouth, UK; Haikou, China; and the City of Playford, Australia. We characterized these urban green spaces as having ‘high’ or ‘low’ vegetation complexity. We then explored whether urban green spaces of these two broad categories around the world contained similar bacterial taxonomy or levels of diversity. Soil bacterial genera were significantly different between cities, however; within cities soil bacterial genera were significantly different in alpha and beta diversity between vegetation complexities. Furthermore, rare genera (those < 1 % relative abundance) were most likely to be significantly different in abundance between vegetation complexities and thus drove many of the community differences. Overall, general trends exist between cities in our study. However, given the uniqueness of a particular cities climate, geography, and existing design, embedded experiments within new green space designs will be required to provide local adaptation to conserving and restoring microbial diversity within each city.