Effects of diverse vegetation assemblages on the thermal behavior of extensive vegetated roofs

Extensive vegetated roofs (EVRs) offer effective nature-based solutions to cities, mitigating thermal extremes induced by urbanization and climate change. A field experiment monitored EVR's thermal regulation in summer and winter. Two sites with contrasting microclimatic conditions in Córdoba city, Argentina, were compared: city center (Core of the urban heat island, UHI) and city periphery (Fringe of the UHI). Diverse plant assemblages constituted five treatments to evaluate plant and thermal performance. A Random Forest model analyzed the contributions of various factors to thermal benefits. All treatments showed > 60 % plant survival rates, and four treatments achieved > 90 % coverage. In winter, the assemblages, including succulents, herbs, and graminoids, offer effective thermal regulation. In summer, thermal performance differed between the two sites. At the Fringe, the native flora (herbaceous and graminoids) + herbaceous + succulents, and succulents + graminoids furnished outstanding thermal regulation. Conversely, at the Core, succulents outperformed. The coverage was the dominant variable for predicting thermal performance, followed by season and location. The findings provide the basis for designing EVRs to optimize thermal benefits.