Impacts and control of alien Proteaceae invasion in the Western Cape Province, South Africa by Laimi Nelago Koskima Erckie Dissertation submitted in fulfilment of the requirements for the degree MAGISTER SCIENTIAE in BIODIVERSITY AND CONSERVATION BIOLOGY in the FACULTY OF NATURAL SCIENCES at the University of the Western Cape Supervisor: Prof. JS Boatwright Co-supervisor: Dr. E. van Wyk Co-supervisor: Dr. S. Geerts November 2017 University of the Western Cape Private Bag X17, Bellville 7535, South Africa Telephone: ++27-21- 959 2255/959 2762 Fax: ++27-21- 959 1268/2266 Email: [email protected] FACULTY OF NATURAL SCIENCE DECLARATION PLAGIARISM DECLARATION TO BE INCLUDED IN ALL ASSIGNMENTS, THESIS PROPOSALS ETC, BE IT FOR MARKS OR NOT: I……..Laimi Nelago Koskima Erckie………………………………………………………… Student number….......3418027……………………….declare that the attached thesis entitled ……Impacts and control of alien Proteaceae invasion in the Western Cape Province, South Africa………………………………………………………………………………….. is my own work and that all the sources I have quoted have been indicated and acknowledged by means of complete references. Signed this day……20…… of ……November…….. 2017……. at ..........Bellville………… _____________________________ Signature i http://etd.uwc.ac.za/ ABSTRACT Research focused on ecological impacts and control of invasive alien species (IAS) is gaining attention worldwide. The eradication and control of invasive alien plants (IAP) is essential for the restoration of native plant communities. Understanding ecological impacts and potential invasive risks of IAP is important for their effective management, particularly for prioritisation. Most studies concerning impacts on vegetation structure and plant-pollinator interactions have measured few ecological metrics, resulting in a superficial understanding of plant species invasion. Additionally, most studies related to the control of IAP have focused on major invaders which have demonstrated severe impacts, with less focus on emerging invaders. This study assessed ecological impacts, invasive risks and chemical control options for alien Hakea drupacea and Banksia species in the Western Cape Province, South Africa. Multiple ecological metrics data on vegetation, soil and plant-pollinator parameters were measured and compared between invaded and uninvaded sites. The invasion risk of fourteen Banksia species which have been introduced to South Africa was evaluated by conducting a weed risk assessment (WRA). The herbicide efficacy of resprouting Banksia integrifolia and Banksia serrata was determined by rating plants response to different treatments, with percentage, height and resprout vigour as measures. Results revealed significant negative impacts of alien H. drupacea and Banksia speciosa invasion on native plant species richness and diversity and on the abundance of native pollinators. The study demonstrated that 79% of Banksia species have a high risk of invading the Fynbos Biome. Chemical control with triclopyr+picloram mix provided effective means of controlling resprouting Banksia species. The high invasive risk of Banksia species and competitive effects of invasive alien B. speciosa and H. drupacea with native plant species for biotic and abiotic resources represents a major threat to biodiversity conservation in the Fynbos Biome. The removal of both naturalised and invasive alien H. drupacea and Banksia populations is recommended in order to conserve native plant communities in the Fynbos Biome. ii http://etd.uwc.ac.za/ ACKNOWLEDGEMENTS First, I would like to thank the Almighty God for blessing me with intelligence and determination. Thank you Lord for giving me the strength and for guiding me throughout this study. Thanks to my wonderful supervisors, Prof. Stephen Boatwright, Dr. Ernita van Wyk and Dr. Sjirk Geerts for their advice, useful comments and proper guidance provided throughout the entire research process. Special appreciation is extended to Dr. Ernita van Wyk for her involvement in data collection and for providing assistance and support during field work. This work was supported by the South African National Department of Environmental Affairs through its funding of the South African National Biodiversity Institute Invasive Species Programme (SANBI-ISP). The National Commission on Research Science and Technology (NCRST) has provided partial funding. I gratefully acknowledge the Namibian Ministry of Environment and Tourism for granting me special study leave. Thanks to the Western Cape Department of Agriculture, Elsenburg Laboratory for efficiently analysing my soil samples. I would like to extend thanks to the South African National Parks (SANParks) for permission to work on their premises in the Agulhas National Park. Thanks are also due to various farm owners for permission to access study sites in their properties. I am grateful to Virgil Jacobs for his permission to use data for the herbicide trial experiment. Thanks to Liada Musandiwa and Nolwethu Jubase for their great assistance with field work. Pieter Winter and Joy Tobin from Compton Herbarium are thanked for assisting in mantaining and storing plant specimens. Thanks to Nick Helme for plant species identification. Finally, I want to express my gratitude to my parents, my wonderful husband and two daughters, who provided immense support and encouragement. This work would have never been completed without their patience and understanding. iii http://etd.uwc.ac.za/ TABLE OF CONTENT DECLARATION.................................................................................................................................... i ABSTRACT ........................................................................................................................................... ii ACKNOWLEDGEMENTS ................................................................................................................ iii TABLE OF CONTENT ....................................................................................................................... iv LIST OF TABLES ............................................................................................................................. viii LIST OF FIGURES ............................................................................................................................. ix Chapter 1: General Introduction ............................................................................................................. 1 1 BIOLOGICAL INVASIONS .......................................................................................................... 1 1.1 INVASIVE ALIEN PLANTS ................................................................................................ 1 1.2 INVASIVE ALIEN PLANTS IN SOUTH AFRICA ............................................................. 2 1.3 IMPACTS OF INVASIVE ALIEN PLANTS ........................................................................ 2 1.3.1 Impacts of invasive alien plants on community structure ............................................... 3 1.3.2 Impacts of invasive alien plants on plant-pollinator interactions .................................... 4 1.4 CONTROL OF INVASIVE ALIEN PLANTS ....................................................................... 5 1.4.1 Mechanical control .......................................................................................................... 6 1.4.2 Chemical control ............................................................................................................. 6 1.4.3 Biological control ............................................................................................................ 7 1.4.4 Integrated weed management .......................................................................................... 7 1.5 THE FAMILY PROTEACEAE .............................................................................................. 8 1.6 AIM AND OBJECTIVES ..................................................................................................... 10 1.7 RESEARCH QUESTIONS................................................................................................... 10 1.8 THESIS CHAPTERS ............................................................................................................ 10 Chapter 2: Impacts of an invasive alien Hakea drupacea on the vegetation structure and soil properties .............................................................................................................................................. 12 Abstract ................................................................................................................................................. 12 2 INTRODUCTION ........................................................................................................................ 13 2.1 MATERIALS AND METHODS .......................................................................................... 15 2.1.1 Study species ................................................................................................................. 15 2.1.2 Study area ...................................................................................................................... 16 2.1.3 Experimental design ...................................................................................................... 16 2.1.4 Data collection .............................................................................................................. 17 2.1.4.1 Vegetation survey