Soil microarthropod community dynamics in extensive green roofs

Heather Rumble,Alan C Gange

doi:10.1016/j.ecoleng.2013.04.012

Abstract

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.

Highlights

Green roofs, i.e. intentionally vegetated roofs, are attracting the attention of ecologists as a novel urban habitat (Oberndorfer et al, 2007)
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 the success of the roof as an urban habitat
We present the first study to examine changes over an annual cycle of microarthropods in extensive green roof soils and determine what organisms constitute the green roof community and what challenges they face

Summary

Introduction

I.e. intentionally vegetated roofs, are attracting the attention of ecologists as a novel urban habitat (Oberndorfer et al, 2007) They were developed to provide a range of environmental and economic benefits, from improving the energy efficiency of buildings (Jaffal et al, 2012) to carbon sequestration (Getter et al, 2009). The majority of UK green roofs are extensive, with a crushed red brick substrate and hardy plants of the genus Sedum (Grant, 2006) They are designed to be cost effective and low maintenance, but are a challenging environment for non-drought adapted plants (Dunnett and Kingsbury, 2004). Little work has been done on below-ground communities, despite abundant evidence to suggest that these are inextricably linked to above-ground processes (Wardle et al., 2004)

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Conclusion