Green roofs are vegetated rooftops installed to absorb stormwater, insulate buildings, cool surrounding neighborhoods, and support biodiversity in urban ecosystems. They both mitigate and provide adaptations to climate change in cities. Significant challenges still exist for developing green roofs that support native plants in a self-sustaining manner. Arbuscular mycorrhizal (AM) fungi associate with most herbaceous plants, delivering scarce soil resources to plants in exchange for photosynthetically derived carbon. Green roofs are generally planted in gravelly, porous, sterile soils that lack these beneficial fungi. Previous work has demonstrated that AM fungal propagules can build up in green roof soils over time, but the composition of these passively-established communities is unknown. Furthermore, the benefit to plants and influence on green roof function will likely vary depending on the particular AM fungal species present. In a multi-year green roof field experiment at two urban sites, we tested the influence of different green roof plant communities, inoculation with native prairie AM fungi, and their interaction on AM fungal community establishment. We asked: 1) How do different green roof plant communities influence AM fungal community structure? 2) How does inoculation with native AM fungi affect the establishment of AM fungal communities in green roofs?
Results/Conclusions
Preliminary analyses show that soil DNA concentration is greater in vegetated green roofs trays, and highest in trays that were inoculated with AM fungi. Sequencing of AM fungal DNA from the small subunit ribosomal RNA (SSU rRNA) determined 80 fungal communities from 40 plots at two sites. Virtual AM fungal taxa are identified in plots both five months and two years after the initiation of the experiment. Community analyses determine the relative abundance and accumulation of AM fungal virtual taxa, including the taxa that were added intentionally and taxa that passively established without active inoculation. Specific AM fungal virtual taxa will also be related to plant community, soil temperature, and evapotranspiration data to assess AM fungal contributions to green roof ecosystem services. To our knowledge, this is the first study to assess the efficacy of AM fungal inoculation on green roofs, as well as the effect of inoculation on green roof plant communities and functions. Furthermore, this study will shed light on how AM fungi may help green roof plants cope with urban stressors and inform best practices for promoting urban sustainability.