The provision of vegetation, or green space, in urban areas is known to impact the well-being of residents. One potential mechanism for this relationship is that vegetation influences the microbial composition of the environments in which we live, work, and play. However, little is known about how fine-scale variation in urban vegetation affects microbial communities in our neighborhoods. To explore this, we sequenced the bacterial 16S rRNA gene on the Illumina NextSeq platform for 50 sites in Eugene, Oregon, over an eight-week period (August-September). The sampling locations were representative of parking lots, grass fields, and urban forests. ArcGIS, FUSION, and R were used to measure vegetation amount and structural diversity from 4-band aerial orthoimagery and LiDAR data; we performed field sampling to assess vegetation species diversity.
Vegetation structure was the most important factor structuring the composition of airborne bacteria in this study. We found that the amount of vegetation within 50 meters has a significant effect but, more importantly, that more structurally diverse sites (i.e. forests) show evidence of greater local differentiation of microbial communities than grass and paved sites. We also found that certain low-abundance bacterial lineages are stable over time for certain sites, suggesting these taxa are emitted from a nearby source. The top most abundant taxa changed over the course of the sampling campaign and we hypothesize that this turnover is related to compositional changes in regional and long-distance air masses. Our results from this work represent continued progress in understanding how urban vegetation patterns impact the microbial communities occupying our cities and buildings. In the long-term, this information can help urban designers and landscape architects to create healthier environments for future urban residents.