Wildflower green roofs for urban landscaping, ecological sustainability and biodiversity

Abstract

The aim of this trial was to test a wildflower roof in order to show how a country landscape fits in an urban environment. The bio-agronomic performance, the biodiversity dynamics during the two-years experiment, and the pollinating fauna, were analysed.Each plant group was able to efficiently colonize the surface of the roof though in different periods and with various modalities. Thermal insulation of green roof was connected to different development dynamics of leaf canopies. In particular, this cooling effect took place during the peak of the vegetation's growth pattern. As expected, each plant group had differing flowering periods, during which were observed coincided highest rate of pollinator’ visits (domestic and solitary bees, bumblebees, lepidoptera, diptera both syrphidae and bombyliidae). The agronomic management, consisting in senescent vegetation mowing, was of crucial importance to ensure the plant equilibrium of spring and summer flowering species. The lack of a prevailing species was highlighted by several biodiversity indexes. On the contrary, early and late flowering species (geophytes) did not require any vegetation management. In conclusion, even if wildflowers exhibit critical aspects in terms of covering dynamics, due to the periodic senescence of vegetation, they represent a valid instrument to improve the biodiversity and the landscape of the Mediterranean urban ecosystem.