Long-term monitoring of vegetation dynamics in the Goegap Nature Reserve, Namaqualand, South Africa by NADINE LIDA BROODRYK Submitted in partial fulfilment of the requirements for the degree MAGISTER SCIENTIAE Department of Plant Science School of Biological Sciences In the Faculty Natural and Agricultural Sciences University of Pretoria Pretoria Supervisor: Prof. M. W. van Rooyen April 2010 © University of Pretoria I declare that the thesis/dissertation, which I hereby submit for the degree Magister Scientiae at the University of Pretoria, is my own work and has not previously been submitted by me for a degree at this or any other tertiary institution. SIGNATURE: ……………………………….. DATE: ………April 2010………………….… TABLE OF CONTENTS ABSTRACT ............................................................................................vi ACKNOWLEDGEMENTS......................................................................... vii CHAPTER 1 INTRODUCTION .......................................................... 1 CHAPTER 2 LITERATURE REVIEW.................................................. 4 2.1 Introduction ..................................................................................... 4 2.2 Long-term monitoring ......................................................................... 4 2.2.1 Introduction ............................................................................. 4 2.2.2 Defining long-term ecological monitoring/research ................................... 5 2.2.3 The importance of long-term studies in environmental science...................... 5 2.2.4 Systematic approaches to long-term studies (LTS) .................................. 7 2.2.5 Long-term study requirement .......................................................... 7 2.2.6 Phenomena addressed by long-term studies (LTS) .................................. 9 2.2.7 Advantages of long-term studies (LTS) ..............................................11 2.2.8 Alternative approaches to long-term studies (LTS) ..................................12 2.2.9 Concluding remarks on long-term monitoring ........................................13 2.3 Vegetation dynamics ......................................................................... 13 2.3.1 Introduction ............................................................................ 13 2.3.2 The traditional concept of succession ................................................14 2.3.3 Terminology............................................................................ 16 2.3.4 Documenting succession..............................................................17 2.3.5 Modelling and succession.............................................................17 2.3.6 Vegetation dynamics and plant community management...........................18 2.3.7 Implications of vegetation change for range or veld management in arid and semi-arid rangelands................................................................18 2.3.8 Sustainability and productivity modeling .............................................22 2.3.9 Concluding remarks on vegetation dynamics ........................................22 i 2.4 Veld management ............................................................................. 23 2.4.1 Introduction ............................................................................ 23 2.4.2 Carrying capacity and succession ....................................................23 2.4.3 Ecological carrying capacity versus economic carrying capacity ...................24 2.4.4 Veld condition assessment............................................................25 2.4.5 Comparison of the ecological index method (EIM) and the degradation gradient method (DGM).............................................................29 2.4.6 Concluding remarks on veld condition................................................31 2.5 Mechanism of plant species survival .......................................................31 2.5.1 Life form classification.................................................................31 2.5.2 The annual species – evasion ........................................................32 2.5.3 The succulent species – tolerance ...................................................34 2.5.4 Concluding remarks on plant life history strategies..................................35 CHAPTER 3 STUDY AREA.............................................................36 3.1 Introduction .................................................................................... 36 3.2 Goegap Nature Reserve ...................................................................... 38 3.3 Background .................................................................................... 38 3.4 Climate.......................................................................................... 39 3.5 Wildlife.......................................................................................... 40 3.6 Vegetation...................................................................................... 41 3.7 Geology and soils ............................................................................. 42 3.8 Management units............................................................................. 46 3.9 The line transects ............................................................................. 47 ii CHAPTER 4 METHODS .................................................................50 4.1 Field methodology ............................................................................ 50 4.2 Data analyses .................................................................................. 55 4.2.1 Vegetation cover and diversity........................................................55 4.2.2 Life forms............................................................................... 55 4.2.3 Range condition and carrying capacity...............................................57 4.2.4 Ordination .............................................................................. 57 CHAPTER 5 RESULTS AND DISCUSSION .......................................59 5.1 Bleshoek Plains ............................................................................... 59 5.1.1 Rainfall ................................................................................. 59 5.1.2 Frequency of occurrence of annual and perennial species .........................59 5.1.3 Species and life form diversity ........................................................60 5.1.4 Species composition ..................................................................65 5.1.5 Grazing capacity....................................................................... 71 5.2 Bluemine Mountain ........................................................................... 72 5.2.1 Rainfall ................................................................................. 72 5.2.2 Frequency of occurrence of annual and perennial species .........................72 5.2.3 Species and life form diversity ........................................................74 5.2.4 Species composition ..................................................................76 5.2.5 Grazing capacity....................................................................... 83 5.3 Goegap Plains ................................................................................. 84 5.3.1 Rainfall ................................................................................. 84 5.3.2 Frequency of occurrence of annual and perennial species .........................84 5.3.3 Species and life form diversity ........................................................86 5.3.4 Species composition ..................................................................88 5.3.5 Grazing capacity....................................................................... 96 iii 5.4 Jaleeg Plains................................................................................... 97 5.4.1 Rainfall ................................................................................. 97 5.4.2 Frequency of occurrence of annual and perennial species .........................97 5.4.3 Species and life form diversity ........................................................99 5.4.4 Species composition ................................................................ 101 5.4.5 Grazing capacity..................................................................... 108 5.5 Koperberg Plains............................................................................ 109 5.5.1 Rainfall ............................................................................... 109 5.5.2 Frequency of occurrence of annual and perennial species ....................... 109 5.5.3 Species and life form diversity ...................................................... 111 5.5.4 Species composition ................................................................ 114 5.5.5 Grazing capacity..................................................................... 120 5.6 T’ganagas Plains ............................................................................ 121 5.6.1 Rainfall ............................................................................... 121 5.6.2 Frequency of occurrence of annual and perennial species ....................... 121 5.6.3 Species and life form diversity ...................................................... 122 5.6.4 Species composition ................................................................ 124 5.6.5 Grazing capacity....................................................................