Plant establishment on a green roof under extreme hot and dry conditions: The importance of leaf succulence in plant selection |
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| Institution: | 1. Terrestrial Ecosystems and Climate Change, College of Marine and Environmental Sciences, James Cook University, Townsville 4811, Queensland, Australia;2. Smithsonian Tropical Research Institute, PO Box 0843-03092, Balboa, Ancón, Panama;3. Department of Ecology and Evolutionary Biology, Brown University, Box G-W, Providence, RI 02912, USA;4. Research School of Biology, Australian National University, Canberra 2601, ACT, Australia;5. Australian Tropical Herbarium, James Cook University, PO Box 6811, Cairns 4870, Queensland, Australia;6. Department of Ecology and Evolutionary Biology, University of Toronto, Canada;1. Key Laboratory of Biodiversity Dynamics and Conservation of Guangdong Higher Education Institutes, School of Life Sciences, Sun Yat-sen University, Guangzhou 510275, China;2. College of Natural Resources, University of California, Berkeley, CA 94720, USA |
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| Abstract: | Plant selection for extensive green roofs has largely been based on cool, temperate climate research. However, as green roof implementation in hotter and drier climates increases, there is a need to evaluate plant performance under these climatic conditions. Succulents have been shown to be successful in hot and dry green roofs, although survival differs between species and the role of leaf succulence in survival has not been fully explored. For non-succulent plants, habitats with conditions similar to green roofs (‘habitat templates’) have been used to select plants, although few studies have discussed the performance of these selections under green roof conditions. Therefore, we evaluated establishment of 32 plant species on an unirrigated extensive (125 mm deep) green roof in Melbourne, Australia over a 42 week period (from winter through summer into autumn). Plants were selected on the basis of life-form, succulence, appropriate habitat templates and/or successful use on green roofs internationally. Climatic conditions during the experiment were often extreme, with evaporation regularly exceeding rainfall and a hot and dry summer (mean maximum air temperature 35 °C and 80.6 mm total rainfall), leading to roof temperatures of 65 °C. After 42 weeks, only succulent plants remained alive and only three of the succulent species had 100% survival. Survival was positively related to the degree of leaf succulence (g H2O leaf area cm−1) making this a useful trait for plant selection for unirrigated green roofs in hot, dry climates. The failure of most species, despite being chosen from appropriate habitats, demonstrates the need to evaluate potential plants on green roofs under extreme climatic conditions. Supplementary irrigation may be essential to sustain non-succulent species during extreme weather in hot and dry climates. |
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