Developing resilient green roofs in a dry climate

• Published in: The Science of the total environment Vol. 490; pp. 579 - 589
• Main Authors: Razzaghmanesh, M., Beecham, S., Brien, C.J.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier B.V 15-08-2014; Elsevier
• Subjects: Agricultural and forest climatology and meteorology. Irrigation. Drainage; Agricultural and forest meteorology; Agronomy. Soil science and plant productions; Applied sciences; Biological and medical sciences; Buildings; Buildings. Public works; Climate; Climate Change; Climatic adaptation. Acclimatization; Conservation of Natural Resources - methods; Disphyma; Drying; Environment; Exact sciences and technology; External envelopes; Facility Design and Construction - methods; Fundamental and applied biological sciences. Psychology; General agronomy. Plant production; Green roof; Media; Plant Development; Plant growth index; Plants; Plants (organisms); Platforms; Resilient cities; Roof; Roofs; Roots; Slopes; Stormwater; Water sensitive urban design; Green roof; Plant growth index; Resilient cities; Stormwater; Water sensitive urban design; Growth; Urban area; Runoff water; Compositae; Design; Dry climate; Dicotyledones; Angiospermae; Rain water; Spermatophyta; Storm water
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2014.05.040

Living roofs are an emerging green infrastructure technology that can potentially be used to ameliorate both climate change and urban heat island effects. There is not much information regarding the design of green roofs for dry climates and so the aim of this study was to develop low maintenance and unfertilized green roofs for a dry climate. This paper describes the effects of four important elements of green roofs namely slope, depth, growing media and plant species and their possible interactions in terms of plant growth responses in a dry climate. Sixteen medium-scale green roofs were set up and monitored during a one year period. This experiment consisted of twelve vegetated platforms and four non-vegetated platforms as controls. The design for the experiment was a split–split-plot design in which the factors Slope (1° and 25°) and Depth (100mm, 300mm) were randomized to the platforms (main plots). Root depth and volume, average height of plants, final dry biomass and ground cover, relative growth rate, final dry shoot–root ratio, water use efficiency and leaf succulence were studied during a twelve month period. The results showed little growth of the plants in media type A, whilst the growth was significant in both media types B and C. On average, a 90% survival rate of plants was observed. Also the growth indices indicated that some plants can grow efficiently in the harsh environment created by green roofs in a dry climate. The root growth pattern showed that retained water in the drainage layer is an alternative source of water for plants. It was also shown that stormwater can be used as a source of irrigation water for green roofs during six months of the year at the study site. In summary, mild sloping intensive systems containing media type C and planted with either Chrysocephalum apiculatum or Disphyma crassifolium showed the best performance.
•Intensive beds with media type B or C and a mild or steep slope performed best.•C. apiculatum and D crassifolium performed better than B multifida.•D crassifolium gave more cover and C. apiculatum taller, better surviving plants.•Plants did not grow in media type A.•Media type C showed superior water use efficiency.