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Contact: [email protected] The Environmental Impact of Crassula helmsii by Tim Smith Canterbury Christ Church University Thesis submitted for the Degree of Doctor of Philosophy 2015 Abstract The aquatic macrophyte Crassula helmsii is a non-native species and classed as ‘invasive’ in the UK. This study was carried out in an attempt to provide empirical evidence as to whether the establishment and growth of Crassula helmsii has a measurable impact on the ecology of invaded sites. Dispersal and distribution patterns across England were explored using databases and GIS interpretation. Ecological impact was measured by comparing invaded sites with uninvaded control sites on a range of habitats and waterbody types across Kent and East Sussex. The analysis of spread patterns provided evidence that the plant is likely to have been dispersed due to the horticultural trade, as well as natural vectors into neighbouring habitats. Macrophyte analysis showed that species losses did not occur when C. helmsii was present. Changes to species composition did occur, with rarer plant species being associated with the presence of C. helmsii. Freshwater macroinvertebrates showed no change in either species number or species rarity. The seed banks of invaded and control sites showed no difference, but active management was shown to reduce the total number of seeds in the soil significantly. The water chemistry of invaded and uninvaded sites showed a relationship between the presence of C. helmsii and reduced total organic nitrogen. The results of this study show that the expected species loss associated with non-native species may not be occurring with C. helmsii. Active management may be impacting the ability of native species to recolonise. Further work on other habitats and waterbodies across a wider geographic range are required to explore whether this is a localised effect. i Tim Smith The Environmental Impact of Crassula helmsii Acknowledgements The majority of the funding for this research project came from the staff development fund (in the form of a fee waiver) from Canterbury Christ Church University, to which I am very grateful. A research grant was also received from the Botanical Society for the British Isles, to help with equipment and travel costs, which helped enormously and was gratefully received. I thank all of the organisations who helped with organising site access, warden time and the provision of data and general advice and guidance. These organisations included; Kent Wildlife Trust, The Royal Society for the Protection of Birds, Natural England, Kent County Council, Fowlmead Country Park, Eastry Parish Council, Southern Water and the BSBI. I also thank my research panel of Dave Ponsonby and Georges Dussart for their guidance and initial recommendations to escape the lab and get out in the field. I would especially like to thank my supervisor Phil Buckley, for his dedicated patience in rediscovering a scientific method through numerous edits and guidance. Finally I thank my research assistant and partner Laura Edey, who tolerated a range of weather conditions and expeditions across reserves with only minimal moaning, allowed the fridge, freezer and house in general to be commandeered by samples and tolerated continual rants about non-native species getting unfair treatment. ii Tim Smith The Environmental Impact of Crassula helmsii Table of Contents Abstract i Acknowledgements ii Table of Contents iii List of Figures xiii List of Tables xviii Chapter 1 – An Introduction to Crassula helmsii Page 1 Origins Page 1 Introduction to the UK Page 2 Morphology Page 3 Flowers Page 5 Seeds Page 6 Growth Forms Page 7 Habitats Page 10 CAM Metabolism Page 11 Nutrient Requirements Page 13 Metal Accumulation Page 15 Genetic Diversity Page 16 Growth Regulator Interactions Page 16 iii Tim Smith The Environmental Impact of Crassula helmsii Asexual reproduction Page 17 Dispersal Mechanisms Page 18 Environmental Impacts Page 20 Control Attempts Page 21 Herbicides Page 22 Hydrogen Peroxide Page 25 Liquid Nitrogen Page 25 Hot Foam Page 25 Flame Throwers Page 26 Physical Removal Page 26 Shading Page 27 Salt Water Page 28 Other Control Methods Page 30 Biological Control Page 32 Literature Overview Page 33 Chapter 2 – The Spread of Crassula helmsii in the UK and Kent Page 35 Introduction Page 35 Short Distance and Long Distance Dispersal Page 35 iv Tim Smith The Environmental Impact of Crassula helmsii Modelling Species Spread Page 37 Management Informed Models Page 40 Vectors Page 43 Use of Geographic Information Systems Page 43 Aims Page 44 Method Page 44 Data Sources Page 44 Distribution Method – SDD vs. LDD using UK Data Page 45 Designated Sites using UK Data Page 46 County Level Analysis using Kent Data Page 49 Results Page 51 Records Overview of UK Data Page 51 Distribution Method Using UK Data Page 53 Designated Sites Using UK Data Page 55 County Level Analysis Using UK Data Page 57 Discussion Page 57 Records Overview Using UK Data Page 57 Distribution Method Using UK Data Page 58 Designated Sites Using UK Data Page 59 v Tim Smith The Environmental Impact of Crassula helmsii County Level Analysis Using Kent Data Page 61 Limitations Page 62 Conclusion Page 63 Chapter 3 – Surveying Strategy and Methodology Page 65 Introduction Page 65 Locating Sites Page 66 Timings Page 66 Bio-Security Page 67 Sampling Locations Page 67 Site Descriptions Page 70 Fowlmead Country Park Page 70 Eastry Village Pond Page 72 Stodmarsh NNR Page 73 Blean Woods NNR Page 74 Perry Woods LNR Page 75 Hothfield Heathlands SSSI Page 76 Shorne Woods Country Park Page 78 Oare Gunpowder Works Country Park Page 79 vi Tim Smith The Environmental Impact of Crassula helmsii Oare Marshes SSSI Page 80 Rye Street Reserve Page 81 Bough Beech Local Wildlife Site Page 82 Sevenoaks Reserve SSSI Page 84 Beacon Wood Country Park Page 85 Romney Marsh Country Park Page 86 Dungeness RSPB Reserve Page 87 Rye Harbour SSSI Page 88 Orlestone Forest SSSI Page 89 Bewl Water Page 90 Sampling Analysis Page 91 Plant Sampling Page 91 Invertebrate Sampling Page 92 Seed Bank Sampling Page 93 Water Sampling Page 95 Chapter 4 – The Effects of Crassula helmsii on Native Macrophyte Assemblages Page 97 Introduction Page 97 Aims Page 99 vii Tim Smith The Environmental Impact of Crassula helmsii Method Page 99 Results Page 103 Waterbody Comparison Page 103 Direct Comparison Page 106 Habitat Comparison Page 106 Management Comparison Page 108 MAVIS Analysis Page 108 Discussion Page 109 Waterbody Comparison Page 109 Direct Comparison Page 110 Habitat Comparison Page 112 Management Comparison Page 114 MAVIS Analysis Page 114 Conclusion Page 116 Chapter 5 – The Effects of Crassula helmsii on Freshwater Macroinvertebrates Page 117 Introduction Page 117 Aims Page 118 Method Page 119 viii Tim Smith The Environmental Impact of Crassula helmsii Revised Scoring System Page 120 Macrophyte and Macroinvertebrate Correlation Page 122 Results Page 122 Comparison between C.helmsii invaded sites and control sites .. Page 122 Habitat Division Page 122 Management Division Page 123 Revised Scoring System Page 123 Macroinvertebrate and Macrophyte Correlation Page 123 Discussion Page 124 Comparison between C.helmsii invaded sites and control sites .. Page 124 Habitat Division Page 125 Management Division Page 126 Revised Scoring System Page 126 Macroinvertebrate and Macrophyte Correlation Page 127 Conclusion Page 128 Chapter 6 – The Effects of Crassula helmsii on Soil Seed Banks Page 131 ix Tim Smith The Environmental Impact of Crassula helmsii Introduction Page 131 Aims Page 133 Methods Page 134 Results Page 138 Comparison between C.helmsii invaded sites and control sites .. Page 138 Management Division Page 138 Correlation between seed banks and macrophyte assemblages Page 139 Comparison of seed banks against duration of presence Page 141 Discussion Page 142 Comparison between C.helmsii invaded sites and control sites .. Page 142 Management Division Page 143 Correlation between seed banks and macrophyte assemblages Page 145 Comparison of seed banks against duration of presence Page 146 Conclusion Page 148 x Tim Smith The Environmental Impact of Crassula helmsii Chapter 7 – The Effects of Crassula helmsii on Water Chemistry Page 149 Introduction Page 149 Aims Page 151 Methods Page 151 Results Page 154 Single Variable Analysis Page 154 Binary Logistic Regression – Single Variable Page 155 Binary Logistic Regression – Two Variables Page 156 Discussion Page 157 Single Variable Analysis Page 158 Binary Logistic Regression – Single Variable Page 159 Binary Logistic Regression – Two Variables Page 162 Conclusion Page 164 Chapter 8 – Study Conclusion Page 165 Overview of Findings Page 165 Spread Patterns Page 165 Macrophytes Page 166 Macroinvertebrates Page 167 xi Tim Smith The Environmental Impact of Crassula helmsii Seed Banks Page 167 Water Chemistry Page 167 Implications of the study Page 168 Limitations of the study and future work Page 170 Conclusion Page 173 References Page 174 Appendices Page 208 Appendix 1 – Site Classifications Page 208 Appendix 2 – Sampling Locations Page 211 Appendix 3 – Species Spread and Designated Sites Data Page 214 Appendix 4 – Plant Naming Authorities for Species Recorded Page 216 Appendix 5 – Plant Species Lists by Sampling Location Page 218 xii Tim Smith The Environmental Impact of Crassula helmsii List of Figures Figure 1.1 C.