The effects of Chromolaena odorata on tree growth dynamics at Buffelsdraai Landfill site by Rerani Ramaano Thesis is submitted in fulfilment of the academic requirements for the degree of Master of Science in the Discipline of Ecology, School of Life Sciences College of Agriculture, Engineering and Science University of KwaZulu-Natal Pietermaritzburg South Africa 2019 i Table of Contents List of tables ............................................................................................................................................ v List of figures ......................................................................................................................................... vi List of appendices ................................................................................................................................. vii Preface…….......................................................................................................................................... viii Declaration 1: Plagiarism ....................................................................................................................... ix Dedication .............................................................................................................................................. xi Abstract… ............................................................................................................................................. xii Chapter One: Introduction ...................................................................................................................... 1 1.1. Background ............................................................................................................................. 1 1.2. Restoration and rehabilitation of ecosystems .......................................................................... 1 1.2.1. Restoration and rehabilitation definitions .............................................................................. 1 1.3. Ecological restoration ............................................................................................................. 2 1.4. Restoration and global climate change ................................................................................... 4 1.5. Invasive alien plants ................................................................................................................ 4 1.5.1. Invasive alien plants in South Africa ...................................................................................... 5 1.5.2. Chromolaena odorata ............................................................................................................. 5 1.6. Effects of alien plant invasion ................................................................................................. 6 1.7. Costs of invasive alien plants control ..................................................................................... 7 1.8. Management of Chromolaena odorata ................................................................................... 8 1.8.1. Biological control of Chromolaena odorata ........................................................................... 8 1.8.2. Chemical control of Chromolaena odorata ............................................................................ 8 1.8.3. Mechanical control of Chromolaena odorata in South Africa ............................................... 9 1.9. Tree-grass competition in savannas ...................................................................................... 10 1.10. Resprouting and reseeding strategies in plants ..................................................................... 12 1.11. Recovery from disturbance-induced damage ........................................................................ 13 1.12. Invasion of the buffer zone of Buffelsdraai Landfill Site ..................................................... 13 1.13. Aims and Objectives ............................................................................................................. 14 1.14. Outline of thesis .................................................................................................................... 14 1.15. References ............................................................................................................................. 15 ii Chapter 2: The influence of understory plants on the growth of established tree saplings in a community restoration initiative ........................................................................................................... 23 2.1. Abstract ................................................................................................................................. 23 2.2. Introduction ........................................................................................................................... 24 2.3. Methods................................................................................................................................. 26 2.3.1. Study area ............................................................................................................................. 26 2.3.2. Study species ......................................................................................................................... 27 2.3.3. Experimental design .............................................................................................................. 28 2.3.4. Sampling ............................................................................................................................... 29 2.3.5. Data analyses ........................................................................................................................ 29 2.4. Results ................................................................................................................................... 30 2.4.1. Height growth ....................................................................................................................... 30 2.4.2. Canopy diameter ................................................................................................................... 30 2.4.3. Trunk diameter ...................................................................................................................... 30 2.4.4. Stem length ............................................................................................................................ 31 2.5. Discussion and conclusion .................................................................................................... 34 2.6. References ............................................................................................................................. 36 Chapter 3: The responses of an alien invasive weed, Chromolaena odorata, to repeated cutting ....... 42 3.1. Abstract ................................................................................................................................. 42 3.3. Methods................................................................................................................................. 45 3.3.1. Study area ............................................................................................................................. 45 3.3.2. Study species ......................................................................................................................... 45 3.3.3. Sampling ............................................................................................................................... 46 3.3.4. Data analysis ........................................................................................................................ 47 3.4. Results ................................................................................................................................... 47 3.4.1. Effect of cutting frequency and height on number of resprouting shoots ............................. 47 3.4.2. Shoot length .......................................................................................................................... 48 3.4.3. Shoot diameter ...................................................................................................................... 48 3.4.4. Shoot production ................................................................................................................... 48 3.4.5. Total shoot basal area:stump basal area ratio ..................................................................... 48 iii 3.4.6. Shoot taper function .............................................................................................................. 49 3.5. Discussion ............................................................................................................................. 56 3.6. References ............................................................................................................................. 58 Chapter 4: Summary and Recommendations ........................................................................................ 63 4.1. Summary ............................................................................................................................... 63 4.2. Recommendations ................................................................................................................. 65 4.3. References ............................................................................................................................. 66 iv