The enhancement of Mediterranean species to increase the functionality and biodiversity of extensive green roofs (EGRs)

The enhancement of Mediterranean species to increase the functionality and biodiversity of extensive green roofs (EGRs).This doctoral project, developed in line with the objectives of the National Strategy for Sustainable Development in the National Recovery and Resilience Plan (PNRR) and in collaboration with the company Bindi Secondo s.r.l., explores the potential of Mediterranean plant species to improve the functionality and biodiversity of extensive green roofs (EGR). The study was structured in distinct theoretical and experimental phases, whose results led to scientific publications of international relevance. The first phase involved a systematic analysis of global literature on EGRs and research trends, applying the "Five Ws" method (Where, When, Who, Why, Which) to outline the temporal and geographical evolution of this technology, identify the main themes and professional skills involved, with particular attention to the selection criteria for plant species. The second phase, experimental in nature, evaluated the performance of cultivated and spontaneous plant species on the green roof of the Keplero scientific high school (Rome). Following a previously initiated experiment, the behavior of six native Mediterranean perennial species was evaluated under different water regimes, assessing their survival and contribution to water efficiency. Subsequently, the effects of the roof left without irrigation and maintenance were studied to derive natural colonization models and ecological succession, acquiring crucial information on the adaptive strategies of species in an extreme environment such as a green roof in a Mediterranean climate. Finally, in a new experiment set up ad hoc, four additional native Mediterranean species were studied, comparing them with Sedum album – a species commonly used in green roofs regardless of climatic conditions – evaluating parameters such as vegetative state, degree of coverage, and their contribution to thermal insulation. The overall results of this project have contributed to filling significant knowledge gaps on the implementation of biodiversity in green roofs in Mediterranean climate regions, where long, arid summers represent critical challenges for the survival and efficiency of vegetation. They have also contributed to studies on urban sustainability and the role of plants in providing various ecosystem services, addressing the specific challenges of Mediterranean regions and expanding the range of plant species suitable for green roofs. The integration between theoretical elaboration and practical experimentation has provided a solid basis for the design and implementation of green roofs in Mediterranean bioclimatic or geographical regions.