Biodiversity of collembola on green roofs: A case study of three cities in Belgium

Abstract

Green roofs are often promoted as a mean to counter the negative environmental effects of urbanization on nature and to increase the amount of green space in cities. Green roofs often enhance aboveground biodiversity, especially herbivores and pollinators. However, if and in what way they support belowground biodiversity, and more specifically soil fauna, is rarely studied. Therefore, we evaluated the diversity of a dominant group of soil fauna, Collembola (springtails), on twelve extensive green roofs in three cities in Belgium (Antwerp, Ghent and Hasselt), over a one year period. The roofs differed in height above the ground, surface area, vegetation type, and age, i.e. time since construction. We analysed if these roof characteristics influenced species richness, abundance or diversity of Collembola. In total we found ten species of Collembola. Species richness was not higher on roofs that were larger (habitat area) or closer to the ground (isolation to surrounding soil), indicating that island-biogeographic theory is not applicable to species richness in our study system. However, significant differences in the mean number of individuals (abundance) were found between different months. Collembola taxonomical composition also varied between the roofs, but this variation could not be related to any of the measured roof variables. Roof communities were characterised by hemiedaphic life forms, preferring neutral to semi-moist conditions. Apart from the age of the roof that showed a positive significant impact on the abundance of Collembola present, our results suggested that the collembolan fauna showed no significant differences in abundance, species richness or diversity between roofs with different characteristics. However, we suggest that future studies are needed to investigate whether our findings are applicable to other groups of soil-living arthropods.