With the majority of people living in cities, innovative solutions for greening the urban environment are necessary to provide ecosystem services such as urban cooling and remediating habitat loss. Green roofs are one potential solution within green infrastructure. Few studies have investigated whether green roofs are a good urban habitat, particularly for soil organisms. The soil food web is vital to above-ground ecosystem processes as it regulates nutrients and can alleviate drought stress, so could be an important but overlooked factor in green roof design. This is the first multi-season study to examine green roof soil organisms in detail, whilst tracking abiotic factors and plant cover. The first part of this thesis characterises the microarthropod and microbial community present on two green roofs in Greater london. It was found that the mite population was dominated by a xerophilic family (Scutoverticidae) and that collembola suffered population crashes in summer. Soil bacteria and fungi were low in abundance, but were more prevalent in dry weather. In general the soil community was impoverished and influenced by drought. The second part of this thesis explores the, use of microbial inoculants to improve the soil community. Bacteria, mycorrhiza and Trichoderma were added to a new and mature roof. On the mature roof, plant growth was not affected by treatments, but collembola populations were higher when Trichoderma were added. On the new roof, inoculants negatively affected plant growth and mite populations, but benefitted collembola. Soi l organisms on the new roof colonised independently and from the Sedum plugs. One species of rarely recorded collembola (Sminthurinu5 trinotatus) colonised early after construction. Planting with Sedum was found to improve the soil community compared to leaving the substrate bare. The results presented here highlight that C.ll rrent green roof designs do not support a functional soil community but that microbial inoculants have the potential to improve them.
|Date of Award||10 Dec 2013|
|Sponsors||Symbio Ltd & Laverstoke Park Farm|
|Supervisor||Alan Gange (Supervisor)|