Urban greenspace aerobiomes are shaped by soil conditions and land cover type

Growing evidence suggests that exposure to microbial biodiversity is important for human immunoregulation and health. Urban greenspaces harbour airborne bacterial communities (aerobiomes) with the potential to transfer beneficial bacteria to humans. However, limited studies have examined the ecological influences of soil, vegetation, and rainfall on aerobiomes in urban greenspaces. Here, we utilised 16S rRNA amplicon sequence data to analyse the effects of land cover, soil abiotic characteristics, surrounding vegetation diversity, and rainfall on aerobiome diversity and composition from 33 urban greenspace sites in Adelaide, South Australia. We sampled air and soil from two urban greenspace land cover types: highly-managed sports fields (n = 11) and minimally-managed nature parks (n = 22). Sports field aerobiomes had a distinct aerobiome community composition and higher alpha diversity than nature parks. Aerobiome alpha diversity was shaped more by soil abiotic characteristics, particularly soil pH and iron levels, than woody plant species diversity. Rainfall prior to sampling also had strong effects on the aerobiome community composition and associated with decreased alpha diversity. These findings point toward soil iron and pH management as pathways to increase aerobiome bacterial diversity. Our study shows that, with additional research, there is potential for greenspace managers and urban planners to target specific soil abiotic characteristics in urban greenspaces to improve microbiome-mediated urban health.