Biogeochemistry of Green Roof Systems

Green roof ecosystems are increasingly used to compensate for the loss of green space and biodiversity in many cities. Their ecosystem services and the performance of the aboveground biota have been extensively studied, e.g. pollinators and plant community composition (see page by Kzasiak). However, the functioning in the largest and most indispensable component of green roofs, namely the soil substrate, has long been overlooked. We are examining the effects of plant species and functional group on nutrient cycling, carbon sequestration, and how common green roof plant species and the soil microbes respond to nitrogen pollution.
Our results to date show that green roofs are possibly less effective than restored prairies for carbon sequestration because there are fewer aggregates (or crumbs) for carbon storage, and soil microbes appeared to rapidly breakdown any available carbon. In addition, we have detected significant differences in water and nitrogen use by different plant species. Overall, plant communities on green roofs seem to show strongly altered carbon and nitrogen cycles.