High water users can be drought tolerant: using physiological traits for green roof plant selection
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High water users can be drought tolerant: using physiological traits for green roof plant selection Claire Farrell & Christopher Szota & Nicholas S. G. Williams & Stefan K. Arndt
Received: 3 February 2013 / Accepted: 9 April 2013 # Springer Science+Business Media Dordrecht 2013
Abstract Background and aims Green roofs are often installed to reduce urban stormwater runoff. To optimally achieve this, green roof plants need to use water when available, but reduce transpiration when limited to ensure survival. Succulent species commonly planted on green roofs do not achieve this. Water availability on green roofs is analogous to natural shallow-soil habitats including rock outcrops. We aimed to determine whether granite outcrop species could improve green roof performance by evaluating water use strategies under contrasting water availability. Methods Physiological and morphological responses of 12 granite outcrop species with different life-forms (monocots, herbs and shrubs) and a common green roof succulent were compared in well watered (WW) and water deficit (WD) treatments.
Key results Granite outcrop species showed a variety of water-use strategies. Unlike the green roof succulent all of the granite outcrop species showed plasticity in water use. Monocot and herb species showed high water use under WW but also high water status under WD. This was achieved by large reductions in transpiration under WD. Maintenance of water status was also related to high root mass fraction. Conclusions By developing a conceptual model using physiological traits we were able to select species suitable for green roofs. The ideal species for green roofs were high water users which were also drought tolerant. Keywords Granite outcrop . Shallow soil . Geophyte . Water relations . Trait . Sedum
Introduction Responsible Editor: Michael Denis Cramer. C. Farrell (*) : C. Szota : N. S. G. Williams Department of Resource Management and Geography, The University of Melbourne, 500 Yarra Boulevard, Richmond, Victoria 3121, Australia e-mail: [email protected] S. K. Arndt Department of Forest and Ecosystem Science, The University of Melbourne, 500 Yarra Boulevard, Richmond, Victoria 3121, Australia
Green or vegetated roofs have great potential to restore ecosystem services to cities by reducing stormwater runoff (Carter and Jackson 2007; VanWoert et al. 2005), mitigating the urban heat island effect (Bass and Baskaran 2003) and increasing biodiversity (Brenneisen 2006). Although reduced stormwater runoff is only one of the benefits of green roofs, it is the driver of green roof implementation, with cities internationally legislating or incentivising green roofs for stormwater retention runoff reduction (Getter and Rowe 2006). Restoration of ecosystem services at a
Plant Soil
city-scale requires establishment of green roofs on existing buildings, which may not have the structural capacity to support heavy loads. Consequently, substrate (growing media) depths are generally shallow (
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