Ammophila Arenaria (L.) Link (Marram Grass) in South Africa and Its Potential Invasiveness
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AMMOPHILA ARENARIA (L.) LINK (MARRAM GRASS) IN SOUTH AFRICA AND ITS POTENTIAL INVASIVENESS THESIS Submitted in fulfilment of the requirements for the Degree of DOCTOR OF PHILOSOPHY of Rhodes University by URSULA MARGRET HERTLING Department of Botany Rhodes University December 1997 TABLE OF CONTENTS ACKNOWLEDGEMENTS Vlll ABSTRACT X CHAPTER SUMMARIES XI LIST OF FIGURES xviii LIST OF TABLES XXI LIST OF PLATES XXIV LIST OF APPENDICES xxv CHAPTER ONE: Introduction 1 1.1 Rationale 1 1.2 A. arenaria - The plant and its communities 2 1.3 The use of A. arenaria for dune stabilisation and management implications 6 1.4 Research objectives 8 1.5 Outline of the thesis 9 CHAPTER TWO: Biological invasions and A mmoph ila arenaria 11 2.1 Theories and definitions 11 2.2 Human beings as vectors of plant distribution 13 2.3 Prerequisites of invasion 14 2.4 The case of A. arenaria in South Africa - A possible invader? 16 2.4.1 Potential invasive attributes of A. arenaria 18 I Attributes related to ecology and physiology 18 II Attributes related to demography 21 III Attributes related to genetics 22 2.4.2 Potential attributes of South African Cape coastal dunes favourable for invasion 24 I Habitat attributes 24 ii II Biotic attributes 25 2.5 The A. arenaria problem in North America 26 2.5.1 Introduction and spread 26 2.5.2 Invasive properties of A. arenaria in North America 27 2.5.3 Concern about A. arenaria in North America 28 2.5.3.1 Impact on dune geomorphology 29 2.5.3.2 Impact on dune biota 30 2.5.4 Control programmes 31 2.6 A. arenaria in other parts of the world 32 2.6.1 Australia 32 2.6.2 New Zealand 33 2.6.3 Other countries 35 2.7 Conclusions 35 CHAPTER THREE: Ammophila arenaria in South Africa 37 3.1 Introduction of A. arenaria to South Africa 37 3.l.1 The need for dune stabilisation 37 3.1.2 A. arenaria - A solution for the driftsand problem 39 3.2 Use of A. arenaria for dune stabilisation in South Africa in past and present 42 3.3. Present distribution of A. arenaria in South Africa 47 3.4 The controversy over A. arenaria in South Africa 55 3.4.1 A. arenaria as "non-invasive" alien 55 3.4.2 Concern about its further use 56 3.5 Stabilisation sites in the opinion of South Africans - A questionnaire 62 3.5.1 Introduction 62 3.5.2 Results 63 3.6 Conclusions 66 iii CHAPTER FOUR: Ammophila arenaria communities - A comparative vegetation analysis 69 4.1 Introduction 69 4.2 A. arenaria communities and indigenous dune plant communities in South Africa 72 4.2.1 Introduction 72 4.2.2 Study area 73 4.2.3 Methods 74 4.2.4 Results 78 Species richness and species diversity 78 Importance values and life-forms 80 Species associations 85 Classification and ordination ofstands 89 Edaphic and other environmental factors 94 Dune profiles 99 4.2.5 Discussion 101 4.3 A. arenaria communities in South Africa and Europe 109 4.3.1 Introduction 109 4.3.2 Study area 110 4.3.3 Methods 113 4.3.4 Results 114 Species richness and species diversity 114 Importance values and life-forms 114 Species associations 118 Classification and ordination ofstands 118 Edaphic and other environmental factors 122 Dune profiles 125 4.3.5 Discussion 126 4.4. Conclusions 129 IV CHAPTER FIVE: Succession of A mmophila arenaria communities in South Africa 137 5.1 Introduction 137 5.2 Succession of a large-scale stabilisation site at De Mond Nature Reserve, southwestern Cape 138 5.2.1 Introduction 138 5.2.2 Study area 141 5.2.2.1 Physiography and climate 141 5.2.2.2 History of the area 142 5.2.2.3 Methods of stabilisation at De Mond Nature Reserve 148 5.2.3 Methods 151 5.2.4 Results 152 Evidence ofsuccession 152 Vegetation of the different successional stages 161 Edaphic and other environmental factors 166 5.2.5 Discussion 168 5.3 The involvement of nematodes in the die-back of A. arenaria in South Africa - A preliminary study 174 5.3.1 Introduction 174 5.3.2 Methods 175 5.3.3 Results 176 Nematodes in differently aged stands ofA. arenaria 176 Identification of nematodes 178 Nematodes in stands of indigenous dune plants 178 5.3.4 Discussion 178 5.4 Conclusions 180 y CHAPTER SIX: Ammophila arenaria in South Africa - Short-term changes 183 6.1 Introduction 183 6.2 Floristic changes in A. arenaria and indigenous dune plant communities at K1einemonde, Eastern Cape 185 6.2.1 Introduction 185 6.2.2 Study area 185 6.2.3 Methods 188 6.2.4 Results 189 Change ofspecies richness and species diversity 189 Change of abundance ofspecies 190 6.3 Floristic and demographic changes in a driftline community of A. arenaria and various indigenous dune plants at K1einemonde, Eastern Cape 197 6.3.1 Introduction 197 6.3.2 Study area 199 6.3.3 Methods 199 6.3.4 Results 200 Importance values 200 Life history stages 201 6.4 The demography of leaves and tillers of A. arenaria and indigenous dune plants at Port Alfred, Eastern Cape 207 6.4.1 Introduction 207 6.4.2 Study area 207 6.4.3 Methods 208 6.4.4 Results 209 Gain and loss of tillers 209 Leaf/tiller-ratios and leaf lengths 211 6.5 Clonal spread of A. arenaria and indigenous dune plants at Port Alfred, Eastern Cape 214 6.5.1 Introduction 214 6.5.2 Study area 215 6.5.3 Methods 215 vi 6.5.4 Results 216 Growth 216 Orientation ofrhizomatous growth 218 Biomass allocation 220 6.6 Discussion 222 6.7 Conclusions 225 CHAPTER SEVEN: Reproduction biology of A mmophila arenaria in South Africa 227 7.1 Introduction 227 7.2 Study area 229 7.3 Methods 229 7.4 Results 233 Flowering and seed production 233 Germination and seedling establishment 238 Vegetative reproduction 252 7.5 Discussion 253 7.6 Conclusions 259 CHAPTER EIGHT: Conclusions 260 REFERENCES 264 Vll ACKNOWLEDGEMENTS • This research was made possible with financial assistance from Deutscher Akademischer Austauschdienst (DAAD), the Ian Mackenzie Scholarship for Environmental Studies, the Foundation for Research Development, Rhodes University Council Research Grants and a Rhodes University Travel Bursary. • A very special word of thanks to my supervisors Professor R.A. Lubke and Dr. A.M. Avis who initiated this research and gave many helpful instructions and comments. Roy Lubke in particular is thanked for assistance in the field and the encouragement to present excerpts of this thesis at conferences and meetings. • I am grateful to Simon Walsh for the time he set aside to assist with searching for marram grass, digging up rhizomes and interviewing people. • A sincere thank you to Rolf Hertling who helped with the comparative studies on Sylt Island in the North Sea and worked long hours on cold and windy beaches. • Many thanks to Gavin Hellstrom of Cape Nature Conservation, George, and Cathy Avierinos for their encouragement and interest in this project and their hospitality. • Dr. W.M. van der Putten of the Centre for Terrestrial Ecology at Heteren in the Netherlands is thanked for much useful information about marram grass and the examination of soil samples for nematode presence. • Thank you to the staff of the De Mond Nature Reserve (Cape Nature Conservation) for their help and interest in our work at this most beautiful reserve. • Dr. Joachim Jahnke of the Institut fur Botanik J, Rheinisch-Westfalische Technische Hochschule Aachen, Germany, is thanked for the friendly offer of laboratory space and equipment to examine soil samples from Sylt Island. • Mike Bums and Peter Raal of the Council of Scientific and Industrial Research (CSIR) in Stellenbosch are thanked for their information on the current use of marram grass for dune stabilisation in South Africa. • Thanks are due to Dr. P.G. Reyneke of the Department of Water and Forestry in Nelspruit, who provided a lot of data on the planting of marram grass by government foresters in the past. • Many thanks to Drs Linda Miller and Andrea Pickart (Lanphere Christensen Dunes Preserve, Arcata, California), to Ruth Pratt (U.S. Fish and Wildlife Service, Sacramento, California) and to Dr. Alfred Wiedemann (The Evergreeen State College, Olympia, VllI Washington) for the abundance of literature on the ecological impact of marram grass along the North American west coast. • Thanks also to Garry Druett of the Department of Land and Water Conservation at Nowra, New South Wales, for the information and material on the use of marram grass in Australia. • Many more people have contributed to this thesis and are mentioned alphabetically. Thank you to Janet Allsopp, Professor C.E.J. Botha, Debi Brody, Estelle Brink, Andrew Cook, the Denis family, Toni Dold, Jacques Gerber, Claire Jarman, John Keulder, Rowan Lubke, Tobias Nischalke, Fred Orban, the Opperman family, Brad Ripley, Bernd Sonnenberg, Eric Tasmer, Ruth von Maltzahn, Martin Villet, Sheila Villet, Undine Weber and Susan Ziehl. • Finally, a sincere and warm thank you to my parents, who supported me in many ways during this period. IX ABSTRACT Ammophila arenaria (L.) Link is a European sand binding plant which was introduced to South Africa in the 1870's for the purpose of dune stabilisation. Because of its known invasiveness along the west coast of North America, and the problems South African ecosystems experience with alien invader plants, it was deemed necessary to study the biology and ecology of this species in South Africa.