Nitrogen enrichment decrease green roof multifunctionality

Nitrogen (N) enrichment changes multiple ecosystem functions and their trade-offs in natural ecosystems. However, whether N enrichment affects these processes in green roofs remains unclear. Here we conducted a 3-month green roof monocultures experiment, aiming to investigate the effects of N enrichment on eight ecosystem functions (and multifunctionality) and their trade-offs, and test the roles of functional traits in regulating ecosystem functions. We found that high N enrichment decreased green roof multifunctionality, especially decreasing substrate cooling, organic carbon storage, phosphate removal and nitrate removal but increasing stormwater capture potential over a short time. N enrichment changed the trade-off relationships between ecosystem functions, and high N enrichment increased the trade-offs between ecosystem functions. In addition, we found that resource conservation traits (e.g., high leaf thickness and low specific root length) have greater green roof multifunctionality. Overall, our findings indicate that high N enrichment is not conducive to the ecosystem services of green roofs. We emphasized that the improvement of green roof multifunctionality should be paid attention to plant design (e.g., selecting for resource conservation traits or increasing species and/or trait diversity) in the context of future high N enrichment.