Plant diversity patterns of domestic gardens in five settlements of South Africa E Davoren 13087452 Thesis submitted for the degree Philosophiae Doctor in Environmental Sciences at the Potchefstroom Campus of the North-West University Promoter: Prof SS Cilliers Co-promoter: Prof SJ Siebert May 2017 Abstract As urbanisation increases globally, domestic gardens are becoming increasingly important in terms of ecosystem service provisioning, biodiversity conservation and human health and well- being. Individually gardens are small, but collectively they comprise substantial proportions of both rural and urban areas and consequently they provide green corridors for the movement of wildlife through the urban matrix. The aim of this thesis was to collect and compare information on the flora present in the domestic gardens of five different settlements across South Africa (Tlhakgameng, Ganyesa, Ikageng, Potchefstroom and Roodepoort) and to determine if the garden management practices and socioeconomic status of householders influences the plant species richness and diversity of these domestic gardens. Additionally, the plant diversity patterns of different land-use types were compared with those of the sampled domestic gardens within each settlement. In comparison with other land-use types, domestic gardens contribute greatly to the overall species richness of both urban and rural settlements. A total of 1424 species were recorded in 598 sample sites for all five settlements and 1524 species were recorded in 256 domestic gardens. The majority of species recorded in the domestic gardens were alien cultivated, while the natural areas contained mostly indigenous species in all five settlements. However, despite the fact domestic gardens provide habitats for biodiversity conservation and support the livelihoods of householders, by introducing and spreading alien species, gardens could threaten natural ecosystems and their services. Nevertheless, domestic gardens have the potential to provide numerous ecosystem services, but this greatly depends on the management decisions, socioeconomic status and personal preferences of the householder. The results of this study showed that the species composition and richness in domestic gardens was influenced by the management activities and socioeconomic status of the householders. In most of the settlements, the floristic diversity increased as the frequency and intensity of management practices increased. Furthermore, the species richness of domestic gardens increased from a low to high SES. This study contributes to our knowledge of the different types of green infrastructure (represented by various land-use types) present in five different settlements in South Africa, their species composition and diversity. This type of research is especially important when considering the rate of urbanisation in South Africa. By understanding the contribution that different land-use types, especially domestic gardens, make to the overall diversity of an urban or rural settlement will aid policy makers and municipal governments in properly managing these areas and ensuring the provisioning of ecosystem services in an urbanising South Africa. Future domestic garden studies in South Africa should attempt to identify the motivations behind gardening in SA, the influences of culture on gardening, promote environmentally-friendly gardening practices, limit the spread of invasive species, promote the cultivation of indigenous species and encourage people to protect ii biodiversity in cities and towns. If the current rate of urbanisation continues, gardens may become the only source of interaction with nature that some people will have on a daily basis. Keyword: Plant diversity patterns, domestic gardens, garden management, socio-economic status iii Acknowledgements First of all, I would like to thank God for blessing me with the opportunity to do this study and for guiding me through it. I would like to acknowledge the following persons for their assistance and valuable contributions during the completion of this thesis: I would like to thank my parents, William and Suset Davoren, for their love, support and understanding. Without them this would not have been possible. To my sisters and best friends, Elmarie Davoren, Sanel Davoren-Botha, Carien Mulder and Marié du Toit, my brother in-law Juan Botha and my nephew Du Bruyn Botha, your support and motivation did not go unnoticed. I especially would like to thank my supervisors Prof. Sarel Cilliers and Prof. Stefan Siebert, for all their patience, guidance, time, help and support during the completion of this study. Every homeowner who permitted access to their gardens, without your willingness to participate, this study would not have been possible. My mother Suset Davoren, Mr. Leon Hefer, Prof. Sarel Cilliers, Prof. Stefan Siebert and Mr. Albie Götze for their assistance with field work. Dr Madeleen Struwig, Dennis Komape and Prof Stefan Siebert of the AP Goossens Herbarium, NWU, Mr. Chris van Niekerk of the botanical garden of the NWU and Mr. Leon Hefer for their assistance with plant identification. Dr. Marié du Toit for assistance with maps, providing technical support and for being a great friend. I want to thank Dr Suria Ellis and Prof. Faans Steyn, of the Statistical Consultation Services, NWU, for helping with all the statistical analyses of this study and answering so many questions. Dr. Jean du Toit for technical assistance and for being a great friend. I would also like to thank the Panic Monster for chasing away the Instant Gratification Monkey and allowing the Rational Decision-Maker to finish this thesis. The National Research Foundation (NRF) for awarding me a PhD Freestanding Scholarship. iv Table of Contents Abstract ......................................................................................................................................... ii Acknowledgements ...................................................................................................................... iv Table of Contents .......................................................................................................................... v List of Figures ................................................................................................................................ x List of Tables .............................................................................................................................. xvi List of Abbreviations ................................................................................................................. xxiii Chapter 1 - Introduction ........................................................................................................... 1 1.1 General introduction ....................................................................................................... 1 1.2 Motivation ....................................................................................................................... 2 1.3 Aims of the thesis ........................................................................................................... 3 1.3.1 General objective: ........................................................................................................ 3 1.3.2 Specific objectives: ...................................................................................................... 3 1.4 Thesis structure and content .......................................................................................... 4 Chapter 2 - Literature review ................................................................................................... 7 2.1 Introduction .................................................................................................................... 7 2.2 Urbanisation ................................................................................................................... 8 2.3 Urban ecology ................................................................................................................ 8 2.4 Urban ecosystems ....................................................................................................... 10 2.4.1 Climate ....................................................................................................................... 11 2.4.2 Hydrology ................................................................................................................... 14 2.4.3 Biogeochemical cycles .............................................................................................. 15 2.4.4 Biodiversity ................................................................................................................ 16 2.5 Urban green infrastructure ........................................................................................... 17 2.6 Gardens as green spaces ............................................................................................ 18 2.6.1 The history of gardening ............................................................................................ 19 2.6.2 What is a garden? ...................................................................................................... 20 2.6.3 What are gardens used for? ...................................................................................... 21 2.6.4 Why do people garden? ............................................................................................. 21 2.6.5 Garden management practices ................................................................................