Effects of treatment on Lantana camara (L.) and the restoration potential of riparian seed banks in cleared areas of the Victoria Falls World Heritage Site, Livingstone, Zambia Michael Nang’alelwa Thesis presented in fulfilment of the requirements for the degree of Master of Science, Botany Department Rhodes University Project Supervisor: Dr. S. Vetter December 2010 1 Declaration I, the undersigned, hereby declare that the work contained in this thesis is my own original work and that I have not previously in its entirety or in part submitted it at any university for a degree Signature…………………………... Date………………………… i Table of Contents Declaration ....................................................................................................................................... i List of tables ..................................................................................................................................... i List of appendices ............................................................................................................................ i List of figures .................................................................................................................................... i Acknowledgements .......................................................................................................................... i Summary ..........................................................................................................................................ii CHAPTER 1 ...................................................................................................................................... 5 Biological invasions and their impacts ......................................................................................... 5 Biological invasions and riparian areas ........................................................................................ 7 Clearing invasive alien species in riparian areas .......................................................................... 9 Recovery of riparian ecosystems after clearing invasive aliens ................................................ 10 Seed bank ecology of riparian areas .......................................................................................... 12 The Lantana camara invasion in the Victoria Falls riparian area ............................................... 16 History of lantana invasion and control in the Victoria Falls World Heritage Site .................... 19 Aims of the study ....................................................................................................................... 22 CHAPTER 2 .................................................................................................................................... 25 Study Area .................................................................................................................................. 25 The Study Species ...................................................................................................................... 27 i Experimental Sites ..................................................................................................................... 30 Experimental Design .................................................................................................................. 34 CHAPTER 3: ................................................................................................................................... 35 Introduction ............................................................................................................................... 35 Aims 40 Description of herbicides used in this study .............................................................................. 41 Glyphosate ............................................................................................................................ 41 Imazapyr ................................................................................................................................ 41 Metsulfron ............................................................................................................................ 42 Adjuvants .............................................................................................................................. 43 Methods ..................................................................................................................................... 44 Data collection ...................................................................................................................... 50 Data analysis ......................................................................................................................... 50 Results ........................................................................................................................................ 52 Effect of treatments on lantana ............................................................................................ 52 Cost of treatments used for lantana management .............................................................. 55 Cost of chemicals .................................................................................................................. 56 Labour ................................................................................................................................... 57 Discussion................................................................................................................................... 59 Mortality of lantana .............................................................................................................. 59 ii Lantana seedling density ...................................................................................................... 62 Cost of treatments ................................................................................................................ 63 Costs of labour ...................................................................................................................... 64 Conclusion .................................................................................................................................. 65 CHAPTER 4 .................................................................................................................................... 68 THE EFFECTS OF CHEMICAL AND PHYSICAL CONTROL TREATMENTS ON VEGETATION COMPOSITION AFTER CLEARING LANTANA CAMARA IN INVADED AREAS .................................. 68 Introduction ............................................................................................................................... 68 Methods ..................................................................................................................................... 72 Experimental design ............................................................................................................. 72 Data analysis ......................................................................................................................... 74 Results ...................................................................................................................................... 75 Understorey response to clearing in lantana invaded areas ................................................ 75 Species richness .................................................................................................................... 75 Seedling density .................................................................................................................... 76 Species diversity .................................................................................................................... 77 Effects of lantana invasion on vegetation composition at baseline ..................................... 79 Effects of treatments on non‐target species in the short and medium‐term ...................... 79 Discussion ................................................................................................................................ 81 Effects of lantana on species richness, diversity and density at baseline ............................ 81 Effect of treatments on vegetation composition in the short and medium‐term ............... 82 iii Conclusions .............................................................................................................................. 82 CHAPTER 5 .................................................................................................................................... 92 Introduction ............................................................................................................................... 92 Seed banks ............................................................................................................................ 93 Seed rain ............................................................................................................................... 96 Aims of this study .................................................................................................................. 99 Methods ................................................................................................................................... 101 Sampling of seedlings, herbaceous species, small woody plants and woody vegetation.. 101 Sampling methods for seed bank ....................................................................................... 101 Sampling methods