Factors influencing vegetation and arthropod community composition along a green roof chronosequence
In many cities throughout the world green roofs are becoming a widely used technology to mitigate negative effects of climate change and urbanization. Understanding how dynamic community relationships change over time in these habitats is necessary to predict their potential future contributions to urban ecology. In North America, where most green roofs have been installed within the last decade, it is difficult to study the long-term trajectory of community succession in these novel habitats. In this study, we tested the hypothesis that plant diversity increases over time and is a significant predictor of arthropod diversity on green roofs using a chronosequence of green roofs. Vegetation, arthropod, substrate, and roof property data were collected from study sites located in northeastern Germany, which ranged in time since construction from 1 to 93 years and therefore represented this habitat type throughout its various successional stages.
We found that vegetation community composition varied with successional stage. Site age itself was not a significant predictor of overall arthropod community richness or abundance although patterns were observed for certain insect guilds. Surrounding green space and substrate depth, particle size and nutrient composition varied by site and may be important predictors of community assembly and succession on green roofs. These results contribute to the growing body of literature demonstrating that green roofs are dynamic habitats that provide a variety of resources to many urban plants and animals during all stages of ecological succession.