Faculty of Agriculture Department of Geology and Mechanical Engineering, Bioengineering and Hydraulics for the Territory (GEMINI) PhD Course in Horticulture XXIII Cycle PLANT AGRONOMIC PERFORMANCE AND SELECTION FOR GREEN ROOFS UNDER MEDITERRANEAN AND MARITIME CLIMATE CONDITIONS SSD AGR/04 Coordinator: Prof. Alberto Graifenberg Tutor: Dr. Giuseppe Colla Co-tutor: Dr. Nigel Dunnett PhD student: Maria Elena Provenzano A tutti coloro che in questi anni hanno creduto in me, offrendomi e mostrandomi sinceramente il loro amore, la loro stima ed il loro supporto; che hanno saputo gioire, vivere e codividere con me questo percorso professionale e di vita 'What is essential is invisible to the eye’ [...] ‘ It is the time you have wasted on your rose that makes your rose so important.' "The Little Prince" by Antoine de Saint-Exupéry CONTENTS 1 GENERAL INTRODUCTION ......................................................................................................................... 2 1.1 RESEARCH OBJECTIVES ...................................................................................................................... 3 1.2 THESIS OUTLINE ................................................................................................................................. 5 1.3 OVERVIEW OF GREEN ROOFS ............................................................................................................ 6 1.3.1 Benefits of green roofing ............................................................................................................... 6 Promotion of Biodiversity and Habitat Preservation ................................................................................ 6 Energy Savings and thermal benefits ........................................................................................................ 7 Air Quality and Carbon Sequestration ....................................................................................................... 8 Reducing the Urban Heat Island Effect ..................................................................................................... 8 Enhanced Stormwater Management and Runoff Quality ......................................................................... 9 A Raw Benefits/Costs Comparison .......................................................................................................... 10 1.3.2 From the traditional roof gardens to the contemporary types of green roofs ........................... 11 A brief history of green roofs .................................................................................................................. 11 Types of green roofs ................................................................................................................................ 11 2 STUDIES ON PLANT SELECTION AND PERFORMANCE FOR EXTENSIVE AND SIMPLE-INTENSIVE GREEN ROOFS IN A MEDITERRANEAN CLIMATE ......................................................................................................... 13 2.1 BACKGROUND ................................................................................................................................. 13 2.2 EXPERIMENT 1 ................................................................................................................................. 20 2.2.1 Greenhouse screening of green roofs potential perennial groundcovers for drought tolerance under Mediterranean climate conditions ............................................................................... 20 ABSTRACT ................................................................................................................................................ 20 2.2.2 INTRODUCTION ....................................................................................................................... 20 2.2.3 MATERIALS AND METHODS ..................................................................................................... 24 Study site ................................................................................................................................................. 24 Plant material and growth conditions ..................................................................................................... 24 Experimental design ................................................................................................................................ 25 Measurements ......................................................................................................................................... 25 Statistical analyses ................................................................................................................................... 27 2.2.4 RESULTS AND DISCUSSION ...................................................................................................... 32 Pests and Diseases ................................................................................................................................... 32 Plant Water Consumption and Growth relations .................................................................................... 32 Plant Growth ............................................................................................................................................ 34 Leaf Relative Water Content and Temperature ...................................................................................... 39 Correlation analysis ................................................................................................................................. 43 Chlorophylls and carotenoids content .................................................................................................... 44 Overall considerations on taxa response to the imposed drought conditions ....................................... 47 2.2.5 CONCLUSIONS.......................................................................................................................... 49 2.3 EXPERIMENT 2 ................................................................................................................................. 52 2.3.1 Evaluation of potential perennials in a Mediterranean climate in roof top conditions .......... 52 2.3.2 INTRODUCTION ....................................................................................................................... 52 Identification of plant species ................................................................................................................. 55 Experimental Site ..................................................................................................................................... 55 Plant materials ......................................................................................................................................... 57 Climatic conditions and irrigation management ..................................................................................... 62 DATA COLLECTION AND MEASUREMENTS .............................................................................................. 64 Plant growth ............................................................................................................................................ 64 Statistical analyses ................................................................................................................................... 64 2.3.3 RESULTS AND DISCUSSION ...................................................................................................... 65 Plant Growth ............................................................................................................................................ 65 Bars with the same superscript do not differ significantly from each other. Flowering Dynamics ........ 72 Colonizing species .................................................................................................................................... 77 2.3.4 CONCLUSIONS.......................................................................................................................... 80 3 EXTENSIVE AND SIMPLE-INTENSIVE GREEN ROOFS’ THERMAL EFFECT IN A MEDITERRANEAN CLIMATE 83 3.1.1 INTRODUCTION ....................................................................................................................... 83 3.1.2 MATERIALS AND METHODS ..................................................................................................... 84 Study site ................................................................................................................................................. 84 Plots characteristics and layout ............................................................................................................... 84 Temperature, Moisture and Meteorological Measurement .................................................................. 85 Statistical analysis .................................................................................................................................... 86 3.1.3 RESULTS AND DISCUSSION ...................................................................................................... 87 3.1.4 CONCLUSIONS.......................................................................................................................... 91 4 STUDIES ON PLANT SELECTION, PERFORMANCE AND DYNAMICS ON GREEN ROOFS IN A MARITIME CLIMATE ..........................................................................................................................................................