Green Roof Plant Traits: Influence of Functional Diversity on Ecosystem Services and Coexistence

Abstract

Green roofs are a novel ecosystem incorporated into the urban landscape to increase green space and provide ecosystem services. Different plant traits excel at providing different green roof ecosystem services, leading to a growing demand for biodiverse green roofs. Research is needed to understand how plant biodiversity can be maintained over time on green roofs, and to determine which species combinations might maximize a given ecosystem service. In this three-year green roof experiment, we use 11 species incorporated into 7 species combinations to create treatments that vary in functional diversity, with treatments including species that are functionally similar, dissimilar, or of intermediate similarity. The selected species combinations were used to determine how trait diversity influences the key ecosystem services of stormwater retention, reduced substrate temperature, pollinator appeal (flower quantity), and the production of aboveground biomass. Additionally, we examine the likelihood of species survival and facilitation within each combination. Here, high functional diversity in leaf thickness and low functional diversity in height and leaf dry matter content was associated with increased biomass, while higher functional diversity in leaf thickness and root length density was associated with decreased substrate temperatures.