Vegetation Patterns and Dynamics of Renosterveld at Agter-Groeneberg Conservancy, Western Cape, South Africa By Benjamin Alan Walton Thesis presented in partial fulfillment of the requirements for the degree of Master of Science at the Stellenbosch University Supervisor Professor Sue J Milton (Department of Conservation Ecology) Co-supervisors A le Roux (CapeNature) Professor L Mucina (Department of Botany and Zoology) April 2006 i Φ Poem “Colour awash over forelands of fertile clay” “When the winters’ cold and grim the Oxalis’s start to brim - they open up. The first feast for bees, in the shrubland short of trees not breeze. Sun’s rays soon last longer in the days: Babianas, Chlorophytums, Geissorhizas, Gladiolius’s, Hesperanthas, Lachenalias, Moraeas and Trachyandras spread their cheerful gaze. Accompanied by annual daisies and bright gladioli filling the air with strong scents of honey - monkey beetles waste no time as they perch upon delicate flowers, lest they are caught in the season’s showers. As if to suggest this is the best nature sends small midge flies to pollinate in jest, and surround mammals to tease their bloody channels. Another month has come and gone - not long now for the raaptol and Micranthus which provide nectar for brown butterflies and painted ladies. Then is the last sequence of bulbs - the fine white-filled fields of chinkerinchees. Grasses’ hour is now soaking up the sun displaying beautifully crafted silhouettes till summers end. As if heaven sent delicate geophytes are still producing their charm, when botanists avoid the midday sun. A brief lapse in displays until the autumn reds begin the seasonal cycles.” Figure a: From left to right: Moraea villosa (Ker Gawl.) Ker Gawl. subsp. villosa, Gladiolus watsonius Thunb. and Lampranthus elegans (Jacq.) Schwantes ii 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…………………………. Dedicated to my daughter June Protea Walton For those who cherish wild landscapes filled with wild plants and animals iii Table of Contents Vegetation Patterns and Dynamics of Renosterveld at Agter-Groeneberg Conservancy, Western Cape, South Africa ............................................................................................................... Φ Poem.................................................................................................................................................i Declaration..........................................................................................................................................ii Table of Contents ..............................................................................................................................iii List of Figures.....................................................................................................................................v List of Tables ...................................................................................................................................viii Preface................................................................................................................................................ix Abstract...............................................................................................................................................x Acknowledgements ..........................................................................................................................xii Chapter 1: Renosterveld: Concept, Ecology and Variability ........................................................1 1.1. Introduction...................................................................................................................................2 1.2. Concept of Renosterveld...............................................................................................................5 1.3. Patterns of Functional Types.........................................................................................................8 1.4. Geology and Soils .......................................................................................................................10 1.5. Climate........................................................................................................................................11 1.6. Disturbance and Vegetation Dynamics.......................................................................................12 1.6.1. Fire .......................................................................................................................................13 1.6.2. Biotic Influence....................................................................................................................18 1.6.3. Succession............................................................................................................................22 1.7. Distribution, Typology and Floristics of Renosterveld...............................................................27 1.8. Conservation Implications ..........................................................................................................29 1.9. References...................................................................................................................................32 Chapter 2: Agter-Groeneberg Conservancy: Description of the Study Area ............................46 2.1. The Study Area ...........................................................................................................................47 2.2. Major Vegetation Patterns ..........................................................................................................48 2.3. Rainfall and Temperature Patterns..............................................................................................51 2.4. Geology and Soils .......................................................................................................................52 2.5. Disturbance .................................................................................................................................55 2.5.1. Fire History ..........................................................................................................................55 2.5.2. Grazing Intensity..................................................................................................................56 2.5.3. Ploughing .............................................................................................................................57 2.5.4. Invasive Alien Plant Species................................................................................................58 2.6. References...................................................................................................................................59 Chapter 3: Vegetation Community Patterns in Renosterveld and Old-fields at Agter- Groeneberg Conservancy near Wellington, Western Cape, South Africa .................................62 3.1. Introduction.................................................................................................................................63 3.2. Materials and Methods................................................................................................................65 3.2.1. Vegetation Data....................................................................................................................65 3.2.2. Environmental Data .............................................................................................................67 3.2.3. Soil Sampling and Analysis .................................................................................................69 iv 3.2.4. Methods of Vegetation Classification..................................................................................71 3.2.5. Nomenclature of Plants and Plant Communities .................................................................72 3.2.6. Multivariate Analyses ..........................................................................................................72 3.3. Results.........................................................................................................................................73 3.3.1. Classification of Vegetation.................................................................................................73 3.3.2. Ordination ............................................................................................................................78 3.4. Discussion ...................................................................................................................................90 3.4.1. Vegetation Community Patterns ..........................................................................................90 3.4.2. Gradient Analyses................................................................................................................92 3.5. References...................................................................................................................................94 Chapter 4: Vegetation Dynamics of Renosterveld at Agter-Groeneberg Conservancy, Western Cape, South Africa.........................................................................................................................100 4.1. Introduction...............................................................................................................................101