Assistant Professor Elmhurst University Elmhurst, Illinois, United States
In the absence of high-maintenance practices, self-sustaining plant communities are necessary to provide the ecosystem services for which green roofs are designed. Plants growing on green roofs likely depend heavily ecosystem processes provided by a healthy soil community to aid in their survival. However, soil microbiomes on green roofs may vary considerably from the natural habitats in which many plant species are typically found because green roofs are usually constructed using sterile engineered soil. Beneficial microbes, such as arbuscular mycorrhizal (AM) fungi can be added to green roof soil during installation, but little is known about how AM communities change over time or contribute to long-term persistence of plant communities in this environment. In addition to what may be added to green roof soil through active management practices, AM fungal propagules as well as pathogenic fungi, bacteria, and viruses can disperse passively into green roof soils through vectors like wind or animals, setting up a dynamic soil community that can affect plant fitness and overall green roof performance. Our research investigates changes in the plant and microbiome communities in extensive green roof trays over an eight-year period. We demonstrate that: 1) Both active and passive addition of AM fungal propagules contribute to the soil microbiome and change the community over time, with active addition contributing to a more diverse community; and 2) Soil microbes with potentially pathogenic properties, such as plasmodiophorids, may accumulate in the soil over time and prohibit establishment of subsequent plant communities. These results support the need for further long-term investigations into both the above- and below-ground communities to inform future green roof designs that support overall ecosystem functioning.
