Soil microarthropod community dynamics in extensive green roofs

Green roofs are of increasing interest to ecologists, engineers and architects, as cities grow and aim to become more sustainable. They could be exploited to improve urban biodiversity and ecosystem services, yet almost nothing is known about them from a soil community ecology perspective, despite how critical soil food webs are to ecosystem functioning. This paper provides the first comprehensive study incorporating the annual cycle of green roof soil microarthropods.

Microarthropod communities were monitored over 14 months on two extensive green roofs. Abiotic factors, including substrate moisture, were recorded, as were biotic factors such as plant and mycorrhizal colonisation. Microarthropod interactions with these variables were then examined.

Microarthropod diversity was low overall, with a few dominant species peaking seasonally. On occasion, total abundance was comparable to other early successional soils. The majority of species present were drought tolerant collembola and xerophillic mites, suggesting that moisture levels on green roofs are a major limiting factor for soil microarthropods.

Our results suggest that the microarthropod community present in extensive green roof soils is impoverished, limiting the success of above-ground flora and fauna and ultimately the success of the roof as an urban habitat. We conclude that green roof building guidelines should incorporate soil communities in their design and should aim to be heterogeneous at the roof and landscape level, for the purpose of supporting soil biodiversity and creating sustainable habitats.