An assessment of greenroofs as urban invertebrate habitat
Results/Conclusions: Data analysis is ongoing, but for spring samples no significant difference in beetle abundance or richness was measured between ground and roof sites. Still on average, beetle abundance was higher on the ground at 84.2(±21) compared to an average abundance of 30.2(±10) on greenroofs. At 12.8(±2.5), average beetle species richness was also higher on the ground compared to 8.4(±1.4) on greenroofs. Patterns of spider abundance for the whole 2014 field season are the opposite of those for beetles, with the greenroofs supporting a greater spider abundance compared to ground sites. Spider abundance was also much higher (>1500 individuals for the season on one roof) on the greenroofs planted with herbaceous species compared to those planted in Sedum. Spider identification is ongoing, but samples are dominated by members of the Thomisidae and Lycosidae families. Ongoing work will integrate these findings to characterize the greenroof foodweb. The abundance of predatory spiders raises questions about the availability of prey, for example. The beetle species found on the most greenroofs, the introduced Xantholinus linearis, is a detrivore, which raises questions about energy requirements as well as about whether these organisms are using the greenroof as their primary habitat.