What Happens to Plant Cover and Species Diversity When an Extensive Green Roof System Is Tilted? A Case Study on Green Roof Design, Old Mission Peninsula, Michigan

Abstract

ABSTRACT This paper describes plant species composition and coverage changes that occurred on an extensive (shallow) green roof system exposed to direct solar exposure and steep roof conditions over time. The green roof system, installed in August, 2005, involved a pre-seeded, manufactured mat product that initially was vegetated with twelve plant species. During the interim between installation and data collection for this paper, no maintenance, fertilizer, or irrigation was applied, despite the fact that observable differences in plant coverage were noted. In April, 2009, undergraduate student researchers revisited the green roof system and examined the green roof for species composition and absolute plant cover. These data were compared to a control area where solar incidence and slope were comparable to the conditions found on a flat roof system. This paper reports on the findings of this study, and offers insight to the types of modifications in extensive green roof technology that may be necessary if extensive green roof application is to be useful for steep roof conditions in cold climate environments.