Aspects of the Ecology of Desmoschoenus Spiralis (A. Rich.) Hook. F
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ASPECTS OF THE ECOLOGY OF DESMOSCHOENUS SPIRALIS (A. Rich.) Hook. f. A thesis submitted in partial fulfilment of the requirements for the Degree of Master of Science in Botany in the University of Canterbury by Shannel P. Courtney .,;:::c University of Canterbury 1983 i ka tipu whakarunga, ka tipu whakararo, te pingao hei here i te kirikiri ii CONTENTS PAGE CONTENTS ii LIST OF FIGURES v LIST OF TABLES ix ABSTRACT ix CHAPTER I INTRODUCTION 1 II TAXONOMY AND DESCRIPTION 4 2.1 Taxonomy 4 2.2 Description 8 2.2.1 General Description 8 2.2.2 Habit 8 2.2.3 The Rhizome 13 2.2.4 The Leaves 15 2.2.5 The Roots 18 2,.2.6 The Inflorescence 18 III DISTRIBUTION 23 3.1 Past Distribution 23 3.2 Present Distribution 24 3.2.1 Methods 24 3.2.2 Results and Discussion 26 3.2.3 Limitations 32 3.3 North Canterbury Coast Survey 34 3.3.1 History of Pegasus Bay Dunes 34 3.3.2 Results and Discussion 35 IV BACKGROUND - KAITORETE SPIT 44 4.1 Introduction 44 4.2 Geomorphology 44 46 4.3 The Dune System 4.4 The Physical Environment of the Dunes 50 4.4.1 Sand and Soils 51 4.4.2 Water Relations 51 4.4.3 Temperature 53 4.4.4 Wind 53 4.4.5 Comparison of the Climate During the Period of Fieldwork with the Climate of Previous Seasons 54 4.5 The Study Area 59 4.5.1 The Sites 59 4.5.2 The Investigations 61 iii CHAPTER PAGE v FRUIT, SEED AND SEEDLING ECOLOGY 63 5.1 Introduction 63 5.2 Dispersal 63 5.2.1 Adaptations for Wind Dispersal 63 (Anemochory) 5.2.2 Adaptation for Dispersal by Sea (Hydrochory) 65 5.3 Seed Predation 70 5.4 Seed Germination and Viability 71 5.4.1 Introduction 71 5.4.2 Method and Materials 74 5.4.3 Results and Discussion 79 5.5 Seedling Ecology 82 5.5.1 Method and Materials 83 5.5.2 Results and Discussion 83 VI COMPARATIVE ANALYSIS 91 6.1 Introduction 91 6.2 Quantitative Analysis 92 6.2.1 Introduction 92 6.2.2 Tuft Dispersion 94 6.2.3 Percentage Cover 96 6~2.4 Habit 99 6.2.5 Quantitative Measurements 102 6.2.6 Estimate of Biomass 110 6.3 Growth Analysis 114 6.3.1 Introduction 114 6.3.2 Methods and Materials 114 6.3.3 Results and Discussion 116 6.4 Environmental Factors 144 6.4 • .1 Introduction 144 6.4.2 Soil Water Content 144 6.4.3 Salt Content 150 6.4.4 Sand Movement 151 6.4.5 Burial by Sand 158 6.4.6 plant Interactions 161 6.4.7 Animal.Interactions 164 6.4.8 Storm Surges and High Tides 167 VII FINAL DISCUSSION 170 APPENDIX I PRESENT AND PAST DESMOSCHOENUS SPIRALIS DISTRIBUTION RECORDS IN NEW ZEALAND 175 II SURVEY OF DESMOSCHOENUS SPIRALIS DISTRIBUTION IN NORTH CANTERBURY 195 lV APPENDIX PAGE III MISCELLANEOUS 202 IV MANAGEMENT OF KAITORETE SPIT SCIENTIFIC RESERVE AND ENVIRONS 214 ACKNOWLEDGEMENTS 226 REFERENCES 228 v LIST OF FIGURES Figure Page Frontispiece. Desmoschoenus spiralis on Kokota Spit, Parengarenga Harbour, Northland. i 1 Desmoschoenus spiralis 9 2 Erect and leader habits of Desmoschoenus spiralis 3 Erect habit of pingao .12 4 Leader habit of pingao 5 Stunted-leader habit of pingao 14 6 Persistant rhizome of a dead pingao plant with leader habit 14 7 Rhizome excavation to show rhizome and root patterns 16 8 Rhizome patterns of pingao 17 9 Cross-section of a tuft of pingao showing the position of consecutive leaves 16 10 Detail of an inflorescence of pingao showing spirally arranged bracts subtending clusters of spikelets with exserted stamens and stigmas 20 11 Longitudinal section of the embryo of D~smoschoenus spiralis, (x200) 20 12 Distribution of Desmoschoenus spiralis in the North Island and offshore islands 27 13 Distribution of Desmoschoenus spiralis in the South Island, Stewart Island, and Chatham Island 28 14 Distribution of Desmoschoeims spiralis in North Canterbury, (Map 1) 36 15 Distribution of Desmoschoenus spiralis in North Canterbury, (Map 2) 37 16 Distribution of Desmoschoenus spiralis in North Canterbury, (I-1ap 3) 38 17 Distribution of Desmoschoenus spiralis in North Canterbury, (Map 4) 39 18 Desmoschoenus- dominant dune at Southshore, New Brighton. Marram and senecio elegans also present 40 vi Figure Page 19 Location Hap 45 20 Foredune, Kaitorete Spit dunes, looking east 48 21 Blowout and eroding transverse dune, Kaitorete Spit dunes, looking south-east 48 22 Reardunes and blowout, Kaitorete Spit dunes, looking east 49 23 Grassland and remnant dunes in the distance, Kaitorete Spit dunes, looking north-west 49 24 Monthly mean wind run and average monthly mean wind run, Lincoln 56 25 Monthly rainfall and average monthly rainfall, Lincoln 56 26 Monthly mean temperature and average monthly mean temperature, Lincoln 57 27 Monthly potential evaporation and average monthly potential evaporation, Lincoln 57 28 The study area 60 29 Average number of fruit sunk over 50 days in freshwater and seawater 67 30 Duration of fruit floatation expressed as a percentage 68 31 Incubation of pingao fruit 75 32 Slit pericarp and nicked p~ricarp 75 33 A seedling with all its tufts browsed, site H 88 34 Four month old seedling;:, The single tuft and thin laminae make it inconspicuous 88 35 Site H on the grassland 93 36 An example of a 10 m x 10 m plot, (set up at site F on the reardunes) 93 37 Percentage cover and approximate ratio of live pingao, dead pingao, for sites A to H 98 38 Percentage habit types of pingao for sites A to I 98 39 Lamina length and width and inflorescence length of Desmoschoenus at sites A-D, E-H, l07 Is and I ns vii Figure Page 40 Inflorescence width, lowest bract length, and bracts per inflorescence of Desmoschoenus at sites A-D, E-H, Is and Ins 108 41 Spikelets per inflorescence, flowers per spikelet and fruit per spikelet of Desmoschoenus at sites A-D, E-H, Is and Ins 109 42 New tufts arising from monitored tufts 117 43 Average increase in the length of developing culms-peduncles 117 44 Average rhizome growth of monitored plants 117 45 Number of leaves produced per average tuft per month at sites A, C, E, G & H 119 46 Average lamina die-back per month at sites A, C, E, G and H. 122 47-59 Examples of graphs representing dynamics of tuft growth and die-back 125-.137 60 Estimate of biomass produced per square metre per year 142 61 A gypsum block being buried adjacent to the rooting zone of pingao 146 62 Soil moisture content calibration curve for Hanford sand 146 ·63 Graduated stake positioned within a plant to monitor the amount of sand movement 152 64 Transverse dune showing slowly eroding windward slope resulting in the undermining of pingao on the crest. 152 65 Site I on the grassland with subsite I on s the left and subsite I on the right. Note the differences betweeHStufts of the two subsites as a result of sand deposition on the tufts of Is 157 66 Leeside of the eroding transverse dune, looking north-west 157 67 Lengths of successive laminae, sheaths, and internodes of a non-buried tuft and a buried tuft 159 68 Buried tufts just before harvesting with new emergent growth 160 69 A sward of self-sown mar ram expanding at the expense of pingao 163 viii Figure Page 70 Marram competition. An emergent tiller from a rhizome which has travelled under pingao from the main sward 163 71 Pingao plant damaged by sheep browsing 165 72 Tufts of pingao browsed by hares or rabbits 165 73 Pingao uprooted by the passage of cattle 168 74 North Raipara Head, Northland 177 75 Waikato River Mouth 177 76 Kokota Spit, Parengarenga Harbour, Northland 180 77 Saltwater Beach, South Westland 185 78 Sandhill Point, waitutu, Southland 185 79 New Brighton Beach, Canterbury 189 80 Tautuku Beach, Catlins, Southland 189 81 Mason Bay, Stewart Island 192 82 Waitangi West Beach, Chatham Island 192 LIST OF TABLES Table Page 1 Sites of investigations 62 2 Stake posi tion~. 62 3 The effect of various treatments on the germination of pingao seed 80 4 Seedling growth and death in relation to browsing, site M. 85 5 Old and new tufts in relation to browsing frequency, site M. 85 6 Leaf production and mortality of newly germinated seedlings, site M. 90 7 Detection of non-randomness 95 8 Comparison of percentage cover between sites A-D and E-H 97 9 Percentage habit types and habit index of sites A to I 101 10 Means of the characteristics of Desmoschoenus at sites A to I 104 11 Means of the characteristics of Desmoschoenus at fore dune sites (A-D), reardune-grassland sites (E-H), and subsites I and I 106 s ns 12 Comparison of the characteristic means of Desmoschoenu£i between foredune sites (A-D), reardune-grassland. sites (E-H), subsite I s and subsite Ins 106 13 Mean biomass (g) and Biomass,m-2 of tufts at sites A to I 112 14 Mean biomass (g) of tufts of different habits 112 15 Number of leaves produced per average tuft per month at sites A, C, E, G and H. 120 16 Average lamina die-back (cm) per month at sites A, C, E, G and H. 123 17 Average leaf longevity of tufts at sites A, C, E, G and H.