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THE POPULATION DYNAMICS OF ACACIA NILOTICA SUBSP. KRAUSSIANA IN NORTHERN KWAZULU-NATAL By JANET MARY TAYLOR Submitted in fulfilment of the requirements for the degree MAGISTER SCIENTIAE In the faculty of Natural & Agricultural Sciences Department of Animal, Wildlife and Grassland Sciences University of the Free State Bloemfontein South Africa Supervisor: Prof. G.N. Smit Department of Animal, Wildlife and Grassland Sciences, UFS, Bloemfontein January 2014 i DECLARATION I declare that the thesis hereby handed in for the qualification, Master of Science, Grassland Science, at the University of the Free State, is my own independent work and that I have not previously submitted the same work for a qualification at/in another University/faculty. Signed:………………………….. Date:…………………........... ii Acacia nilotica, the plant of study, within uMkhuze Game Reserve. iii ACKNOWLEDGEMENTS I wish to express my sincere thanks to all whose guidance and assistance was sought during the course of this study. I am very grateful to my supervisor, Prof. Nico Smit for his knowledge shared, encouragement, support and guidance throughout my study. Your patience with me while I was undertaking this study as well as attending to my full-time work commitments is greatly appreciated. This study was undertaken while employed by the Department of Agriculture and Environmental Affairs (DAEA). The Department is thanked for allowing me to undertake this work as part of my official duties, and allowing me to use the Departmental equipment and resources. The Department is also thanked for assisting me financially by providing me with a bursary to study over a period of two years. I would like to express my gratitude to Felicity Mitchell (Scientific Manager, Natural Resources Section), as my work place supervisor, for being so supportive, understanding and facilitative towards me and this study. A huge thank you too, to Cobus Botha, Michelle Keith and Clement Adjorlolo (DAEA-Natural Resource Section field scientists) for their integral in-field support during this project as well as for their tolerance towards me during the writing up stage of this study. Thank you to Jeremiah Gumbi (Ezemvelo KZN Wildlife) for being a meticulous scribe, sharing his valuable knowledge of the history of the reserve, assisting with site location and having a wonderful sense of humour while being so patient with me during my many tree measurements. A huge thank you to my Mom, Dad and brother, Robert for being so supportive to me throughout my study, for their unfailing patience, encouragement and guidance and for their motivation during this study. Finally, a big thank you to the following that provided valuable assistance to me during the study: Dave Robertson, Park manager - uMkhuze Game reserve - and his staff for being so supportive of the project and for facilitation and help during the study period. Debbie Jewitt (Ezemvelo KZN Wildlife) for her patience and assistance in guiding me through the Maxent modelling program. Craig Morris (Agricultural Research Council - University of KwaZulu-Natal) for his time spent assisting me with statistical advice. Beanelri Janecke (University of the Free State) for advice on analysis of phenology data. iv All the staff of the Natural Resources Section, Department of Agriculture and Environmental Affairs (DAEA) for all their support, patience and encouragement throughout the study. Thandakwazi Nkhosi and the uMhkuze Field Rangers (Ezemvelo KZN Wildlife) who assisted with scribing and for providing a second pair of eyes and ears in the bush! Caroline Fox, S’bu Mfeka, Thandakwazi Nkhosi and Jeremiah Gumbi (KZN Wildlife St Lucia Research staff) for assisting me with BECVOL tree transect measurements. Craig Mulqueeny and Tarik Bodasing- (Ezemvelo KZN Wildlife) giving me assistance and useful knowledge of the reserve. Rikki Abbott for her assistance with the editing of this document. The Botanical education trust for their financial support during the study period. Ezemvelo KZN Wildlife and iSimangaliso Authority for permission to work in the reserve and Ezemvelo KZN Wildlife for access to uMkhuze Game Reserve records and data to assist me with my research as well as providing me with the ability to build on the research done by Pete Goodman. ------------------------------------------------------------------------------------------------------------------ v TABLE OF CONTENTS DECLARATION ..................................................................................................................................... i ACKNOWLEDGEMENTS ................................................................................................................... iii LIST OF FIGURES ............................................................................................................................. viii LIST OF TABLES ................................................................................................................................ xii LIST OF APPENDICES ...................................................................................................................... xiii CHAPTER 1: INTRODUCTION ........................................................................................................... 1 1.1 Background ................................................................................................................................. 1 1.2 Causes of woody plant thickening .............................................................................................. 2 1.3 Acacia nilotica encroachment/ thickening .................................................................................. 4 CHAPTER 2: STUDY AREA ................................................................................................................ 8 2.1 Selection of study area ................................................................................................................ 8 2.2 Geographical location ................................................................................................................. 8 2.3 History of uMkhuze Game Reserve ............................................................................................ 9 2.4 Topography and geology ............................................................................................................ 9 2.5 Climate ...................................................................................................................................... 12 2.6 Vegetation and soil ................................................................................................................... 13 2.7 Fauna ......................................................................................................................................... 15 2.8 Management .............................................................................................................................. 18 2.8.1 Fire .................................................................................................................................... 18 2.8.2 Animal offtakes ................................................................................................................. 18 2.9 Study plant species .................................................................................................................... 18 2.9.1 Flowering and seeds .......................................................................................................... 19 2.9.2 Seedlings ........................................................................................................................... 20 2.9.3 Mature Plants .................................................................................................................... 20 CHAPTER 3: PREDICTING THE DISTRIBUTION OF ACACIA NILOTICA IN KWAZULU- NATAL ................................................................................................................................................. 22 3.1 Introduction ............................................................................................................................... 22 3.2 Methods..................................................................................................................................... 25 3.3 Results ....................................................................................................................................... 28 3.4 Discussion ................................................................................................................................. 33 3.5 Conclusion ................................................................................................................................ 35 vi CHAPTER 4: HISTORICAL AND CURRENT VEGETATION TRENDS IN UMKHUZE GAME RESERVE ............................................................................................................................................. 36 4.1 Introduction ............................................................................................................................... 36 4.2 Methods..................................................................................................................................... 39 4.2.1 Vegetation community map .............................................................................................. 39 4.2.2 Description of the vegetation communities ....................................................................... 39 4.2.3 Calculation