Improving the Biodiversity of Green Roofs

Using living organisms such as bacteria or fungi, as an alternative to chemical fertilisers, can improve the soil biodiversity of green roofs, according to new research from the University of Portsmouth.

Green roofs are covered with plants and vegetation and are increasingly used in cities to make buildings more energy efficient and environmentally friendly. However, high winds, prolonged UV exposure and unpredictable water availability mean that many green roofs lack nutrients, which can limit plant growth and the biodiversity of soil organisms, which are responsible for the quality of nutrients in the soil.

This could have implications for the environmental and economic benefits of green roofs.

The study, published in the journal Ecological Engineering, found that the addition of certain types of microbial inoculants (plant growth-promoting bacteria and fungi used as an alternative to chemical fertlisers), in particular a fungi called Trichoderma , produced higher populations of tiny insects called springtails (which range from 0.25 to 6mm in size). While these changes improved the abundance of springtails, they did not result in a positive effect on plant growth.

Lead author Dr Heather Rumble, Senior Lecturer in Environmental Geography at the University of Portsmouth, said: “Few studies have investigated whether green roofs are a good urban habitat, particularly for soil organisms. We think that mature extensive green roofs have an established microbial community that may limit the success of commercial inoculants.

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