Green roofs as urban habitat for native plant seedlings and wild bees

Abstract

Though green roofs offer an integrated response to urban issues, no designs that promote seedling survival and diversity have been investigated, and few studies have quantified the relationship between green roof resources and invertebrate visitors. Research presented here has two objectives: to determine the effect of designed heterogeneity on substrate conditions and seedling dynamics of green roofs, and to compare the composition and pollen collecting habits of bee communities visiting green roof, urban, and coastal barrens habitat. Several features cooled substrate, retained substrate moisture, increased seedling survival, and delayed species loss in periods of drought. Relative to ground level habitats, green roof wild bee communities were less abundant and species rich but shared species with all habitat types. Pollen collection of bumblebees on green roofs was similar to that observed in urban and barrens habitat. These results suggest that green roofs may offer harmonized solutions to multiple urban problems.