Spatial and temporal variation of the airborne microbial community across New York City green roofs

Background/Question/Methods

In urban environments, green roofs provide a number of potential benefits, including decreases in urban heat island effects and reduced energy costs for buildings. Moreover, green roofs may serve as biological habitats for organisms moving across the urban environment. Although most studies on green roofs have focused on the engineering aspects and benefits of energy savings, little is known about their ecological function of maintaining urban biodiversity. One aspect of urban biodiversity that has been poorly studied is that of soil microbial communities, which facilitate the growth and survival of plants. For the current study, our objectives were to evaluate (1) whether or not green roofs and city parks function as suitable habitats for soil microbial communities, (2) how the community composition of green roof microbes is assembled and maintained in the urban environment, and (3) how the microbial communities vary over time and space across green roofs and city parks. To accomplish these objectives, soil cores were collected from parks and nearby rooftop plots composed of the same native plant communities and substrate. After collection, microbial community composition was assessed using phospholipid fatty acid analysis and DNA sequencing of the fungal ITS region using the Illumina HiSeq platform.

Results/Conclusions

Based on the phospholipid fatty acid and sequencing results, it was determined that microbial communities did not cluster by roofs, and that green roof microbial communities were distinct from soil microbes collected from parks. Although the microbial communities on green roofs were distinct, these communities overlapped with parks, and the total microbial biomass was not significantly different in parks compared to roofs. Furthermore, microbial communities were distinct across city parks, possibly due to substrate differences or due to time since planting. Since the green roofs are younger than the city parks, they may not have had sufficient time to differentiate. Based on these results, it can be concluded that both parks and green roofs serve as suitable habitats for microbes traveling across an urban matrix.