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AUSTRALIAN PLANTS FOR EXTENSIVE GREEN ROOFS

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					Australian Plants for Extensive Green Roofs: a Sub-tropical Perspective
- Dr Melinda Perkins, Postdoctoral Research Fellow, Centre for Native Floriculture, The University of Queensland




                                     AUSTRALIAN PLANTS FOR EXTENSIVE
                                              GREEN ROOFS

                                                     A SUBTROPICAL PERSPECTIVE


                                                      Dr Melinda Perkins and Prof. Daryl Joyce
                                           Centre for Native Floriculture, School of Land, Crop and Food
                                            Sciences, The University of Queensland, Gatton Campus


                                           Green Roofs Conference 2010, Adelaide Zoo, 20-23 October




                                                                             Australian plants for extensive green roofs: a subtropical perspective




                                    OVERVIEW




                                    Background
                                    Benefits and drawbacks of a subtropical climate
                                    Current status of extensive green roof research in the subtropics
                                    The need for climate-specific research
                                    The Centre for Native Floriculture


                                    Research Approach
                                    Objectives
                                    Selection of plant species
                                    The trial site
                                    Data collection


                                    Future research


                                                                             Australian plants for extensive green roofs: a subtropical perspective




Green Roofs Conference 2010                                                                                                                           1
Australian Plants for Extensive Green Roofs: a Sub-tropical Perspective
- Dr Melinda Perkins, Postdoctoral Research Fellow, Centre for Native Floriculture, The University of Queensland




                                    BACKGROUND
                                    Benefits and drawbacks of Australia’s subtropical climate




                                    Brisbane’s climate is characterised by:
                                    • Mean daily min/max temperatures of 9/22°C in winter and 20/30°C in summer
                                    •   Summer dominant rainfall pattern
                                    •   977 mm mean annual rainfall

                                    Benefits:
                                    • Abundant sunshine
                                    • Mild winter temperatures
                                    • Year round plant growth


                                    Drawbacks:
                                    • Extended periods of drought  supplementary irrigation
                                    • High intensity rainfall events  substrate erosion, nutrient leaching
                                    • High light intensity during winter  photoinibition?

                                                                            Australian plants for extensive green roofs: a subtropical perspective




                                    BACKGROUND
                                    Current status of extensive green roof research in the subtropics




                                                       Substrate
                                    Location                          Area (m2)            Plant species                              Irrigation
                                                       depth (cm)

                                    University of                                          Native perennial forbs
                                                            10             61                                                                
                                    Texas1                                                 and grasses


                                                                                           Sedum kamtschaticum
                                    Texas A&M
                                                            7              4.5             Delosperma cooperi                                
                                    University2
                                                                                           Talinum calycinum


                                    Fort Myers,                                            Sedum spp. (initially)
                                                            ?              223                                                            /
                                    Florida3                                               Primarily native species


                                    University of
                                                          15-20            153             Primarily native species                          
                                    Central Florida4



                                                                            Australian plants for extensive green roofs: a subtropical perspective




Green Roofs Conference 2010                                                                                                                          2
Australian Plants for Extensive Green Roofs: a Sub-tropical Perspective
- Dr Melinda Perkins, Postdoctoral Research Fellow, Centre for Native Floriculture, The University of Queensland




                                    BACKGROUND
                                    The need for climate-specific research




                                    Sedums are not the universal solution:
                                    • Half of Sedum kamtschaticum plants on an extensive green roof in southern
                                      Texas died during summer2
                                    • 10 Sedum spp. on an extensive green roof in Florida were unable to withstand
                                      the humid, high moisture summer conditions3


                                    Wrong plant selection can lead to:
                                    • Pest/disease problems
                                    • Plant losses
                                    • Excessive growth
                                    • Higher maintenance $
                                    • Unattractive structures
                                    • Poor public perception
                                    • Inability to provide benefits

                                                                         Australian plants for extensive green roofs: a subtropical perspective




                                    BACKGROUND
                                    The need for climate-specific research




                                    Sedums are not the universal solution:
                                    • Half of Sedum kamtschaticum plants on an extensive green roof in southern
                                      Texas died during summer2
                                    • 10 Sedum spp. on an extensive green roof in Florida were unable to withstand
                                      the humid, high moisture summer conditions3


                                    Wrong plant selection can lead to:
                                    • Pest/disease problems
                                    • Plant losses                            What species are suitable for
                                                                               the Australian subtropics?
                                    • Excessive growth
                                    • Higher maintenance $
                                    • Unattractive structures
                                    • Poor public perception
                                    • Inability to provide benefits

                                                                         Australian plants for extensive green roofs: a subtropical perspective




Green Roofs Conference 2010                                                                                                                       3
Australian Plants for Extensive Green Roofs: a Sub-tropical Perspective
- Dr Melinda Perkins, Postdoctoral Research Fellow, Centre for Native Floriculture, The University of Queensland




                                    BACKGROUND
                                    The Centre for Native Floriculture




                                    Who are we?
                                    • A research centre within the School of Land, Crop and Food
                                      Sciences, The University of Queensland
                                    • Established in 2003 with the vision to ‘help create internationally
                                      competitive and environmentally sustainable native floriculture
                                      industries that provide significant employment opportunities in
                                      Queensland’.
                                    • Development of new plant varieties has been a major focus.




                                                                         Australian plants for extensive green roofs: a subtropical perspective




                                    BACKGROUND
                                    The Centre for Native Floriculture




                                                                         Australian plants for extensive green roofs: a subtropical perspective




Green Roofs Conference 2010                                                                                                                       4
Australian Plants for Extensive Green Roofs: a Sub-tropical Perspective
- Dr Melinda Perkins, Postdoctoral Research Fellow, Centre for Native Floriculture, The University of Queensland




                                    RESEARCH APPROACH
                                    Objectives




                                      1. Review existing knowledge of plant selection and performance for
                                         extensive green roofs
                                      2. Prepare a climate-specific plant selection matrix and generate list of
                                         potential extensive green roof species
                                      3. Establish and evaluate plants using pilot-scale extensive green roof
                                         modules
                                      4. Establish a demonstration extensive green roof to provide “real
                                         world” data on plant performance and thermal benefits
                                      5. Communicate outcomes to key stakeholders via workshops,
                                         conferences, research publications, popular press
                                      6. Develop linkages with government and industry




                                                                           Australian plants for extensive green roofs: a subtropical perspective




                                    RESEARCH APPROACH
                                    Selection of plant species




                                      Plant selection criteria for subtropical extensive green roofs:

                                       • Low-growing                               • Easily propagated
                                       • Shallow root system                       • Rapid establishment
                                       • Dense foliage                             • Minimal maintenance requirements
                                       • Well anchored, strong structure           • Minimal weed potential
                                       • Few pest/disease problems                 • Minimal fire risk
                                       • Ability to withstand:                     • Longevity (perennial vs annual)
                                         – High temperature/humidity               • Aesthetic appeal
                                         – High light intensity
                                         – Mechanical damage (wind/rain)




                                                                           Australian plants for extensive green roofs: a subtropical perspective




Green Roofs Conference 2010                                                                                                                         5
Australian Plants for Extensive Green Roofs: a Sub-tropical Perspective
- Dr Melinda Perkins, Postdoctoral Research Fellow, Centre for Native Floriculture, The University of Queensland




                                    RESEARCH APPROACH
                                    Selection of plant species




                                      Some potentially suitable Australian native species:

                                       • Bulbine vagans                                           C. balonensis
                                       • Calandrinia balonensis
                                       • Calandrinia eremea
                                       • Calandrinia schistorhiza
                                       • Eremophila debilis                                                                          B. vagans

                                       • Enchylaena tomentosa
                                       • Myoporum parvifolium




                                                                             Australian plants for extensive green roofs: a subtropical perspective




                                    RESEARCH APPROACH
                                    The trial site




                                      Extensive green roof modules at UQ Gatton Campus:
                                      • Fully enclosed steel structure
                                      • Roof area of ~3 m2 with a 3° pitch
                                      • Load bearing capacity of 200 kg/m2
                                      • Northerly aspect
                                      • Elmich green roof system to be installed




                                                                             Australian plants for extensive green roofs: a subtropical perspective




Green Roofs Conference 2010                                                                                                                           6
Australian Plants for Extensive Green Roofs: a Sub-tropical Perspective
- Dr Melinda Perkins, Postdoctoral Research Fellow, Centre for Native Floriculture, The University of Queensland




                                    RESEARCH APPROACH
                                    Data collection




                                       Plant growth (height, width, canopy area)
                                       Plant survival rate
                                       Pest/disease symptoms
                                       Flowering
                                       Canopy temperature
                                       Stomatal conductance
                                       Chlorophyll fluorescence
                                       Environmental conditions (ambient temperature, humidity, light intensity)




                                                                          Australian plants for extensive green roofs: a subtropical perspective




                                    RESEARCH APPROACH
                                    Data collection




                                                                    Photoinhibition
                                Absorbed
                                solar radiation




                                                                                                                        Excess energy
                                                                                                                        dissipated as
                                                                                                                        heat
                                                                   PSII




                                                                                 Energy for carbohydrate production
                                                                                           = biomass gain

                                                                          Australian plants for extensive green roofs: a subtropical perspective




Green Roofs Conference 2010                                                                                                                        7
Australian Plants for Extensive Green Roofs: a Sub-tropical Perspective
- Dr Melinda Perkins, Postdoctoral Research Fellow, Centre for Native Floriculture, The University of Queensland




                                    RESEARCH APPROACH
                                    Data collection




                                                                     Photoinhibition
                                Absorbed
                                solar radiation




                                                                                                                         Not all excess
                                                                                                                         energy can be
                                                                                                                         dissipated as
                                                                    PSII                                                 heat



                                                                                   Less efficient carbohydrate production
                                                                                            = lower biomass gain

                                                                           Australian plants for extensive green roofs: a subtropical perspective




                                    FUTURE RESEARCH




                                          Key questions that need to be investigated include:

                                          • What level of irrigation will be required to maintain an extensive
                                            green roof in Brisbane?

                                          • What substrate formulation provides the best growing environment
                                            for plants over a long period?

                                          • What are the thermal benefits of an extensive green roof in
                                            Brisbane? (How much money can be saved on building cooling
                                            costs?)




                                                                           Australian plants for extensive green roofs: a subtropical perspective




Green Roofs Conference 2010                                                                                                                         8
Australian Plants for Extensive Green Roofs: a Sub-tropical Perspective
- Dr Melinda Perkins, Postdoctoral Research Fellow, Centre for Native Floriculture, The University of Queensland




                                    FUTURE RESEARCH




                                         Key questions that need to be investigated include:

                                         • What level of irrigation will be required to maintain an extensive
                                           green roof in Brisbane?

                                         • What substrate formulation provides the best growing environment
                                           for plants over a long period?

                                         • What are the thermal benefits of an extensive green roof in
                                           Brisbane? (How much money can be saved on building cooling
                                           costs?)




                                         Collaboration with industry and government is essential!!

                                                                       Australian plants for extensive green roofs: a subtropical perspective




                                    ACKNOWLEDGMENTS




                                      Rural Industries Research and Development Corporation
                                      Green Infrastructure Network Australia
                                      Elmich Queensland (Brad Walker Agencies)
                                      Tuff-Span Lockyer
                                      Aussie Colours




                                                                       Australian plants for extensive green roofs: a subtropical perspective




Green Roofs Conference 2010                                                                                                                     9
Australian Plants for Extensive Green Roofs: a Sub-tropical Perspective
- Dr Melinda Perkins, Postdoctoral Research Fellow, Centre for Native Floriculture, The University of Queensland




                                    REFERENCES




                                      1.   Simmons MT, Gardiner B, Windhager S and Tinsley J (2008), Green roofs are not created
                                           equal: the hydrologic and thermal performance of six different extensive green roofs and
                                           reflective and non-reflective roofs in a sub-tropical climate. Urban Ecocsys 11:339-348.
                                      2.   Aitkenhead-Peterson JA, Dvorak BD, Volder A and Stanley NC (in press), Chemistry of
                                           growth medium and leachate from green roof systems in south-central Texas. Urban Ecosys
                                           (DOI 10.1007/s11252-010-0137-4).
                                      3.   Denison T, Fikoski K, Livingston E, Lohr ML and Miller C (2008) Green roof evaluation at
                                           Shadow Wood Preserve. Retrieved 23 August 2010.
                                           http://www.eifg.org/portal/portal/item_abstract.aspx?item_id=384&params=P21lbnVfdHlwZT
                                           1jYXRlZ29yeSZpZGVudGlmaWVyPTEy.
                                      4.   Sonne J and Parker D, "Energy Performance Aspects of A Florida Green Roof, Part 2",
                                           Sixteenth Symposium on Improving Building Systems in Hot and Humid Climates, December
                                           15-17, 2008, in Dallas, TX.




                                                                                Australian plants for extensive green roofs: a subtropical perspective




Green Roofs Conference 2010                                                                                                                              10

				
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