Hammond, M. E. R. 2001. the Experimental Control of Spartina
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THE EXPERIMENTAL CONTROL OF SPARTINA ANGLICA AND SPARTINA X TOWNSENDII IN ESTUARINE SALT MARSH MARK E. R. HAMMOND B.Sc. (Hons), M.Res. FACULTY OF SCIENCE ENVIRONMENTAL STUDIES UNIVERSITY OF ULSTER COLERAINE BT52 1SA NORTHERN IRELAND THESIS SUBMITTED FOR THE DEGREE OF DOCTOR OF PHILOSOPHY 2001 Contents Acknowledgements i Declaration on access to contents ii Abstract iii 1. Introduction 1 1.1. Spartina anglica and Spartina x townsendii origin, spread and growth 1 1.2 . The advantages and disadvantages of S. anglica agg. invasion 4 1.2.1. Physical effects of S. anglica agg. invasion 4 1.2.2. Effects of S. anglica agg. invasion on flora 5 1.2.3. Effects of S. anglica agg. invasion on fauna (excluding birds) 5 1.2.4. Effects of S. anglica agg. invasion on birds 6 1.2.5. Economic impacts of S. anglica agg. invasion 7 1.3. Spartina spp. control / eradication treatments 8 1.3.1. Cutting, trampling and burning 8 1.3.1.1. Cutting / grazing 9 1.3.1.2. Trampling / crushing 9 1.3.1.3. Burning / steam treatment 9 1.3.1.4. Digging / bulldozing 10 1.3.2. Smothering, burying, herbicides 10 1.3.2.1. Smothering 10 1.3.2.2. Burying 11 1.3.2.3. Herbicides 11 1.3.2.3.1. Method of herbicide application 13 1.3.2.3.2. Environmental conditions at time of spray 13 1.3.3. Other possible methods for Spartina spp. control 13 1.3.3.1. Biological control 14 1.3.3.2. Coastal engineering 14 1.3.3.3. Other methods 15 1.3.4. Self control by S. anglica agg. / Die-back 15 1.4. Spartina anglica agg. In Northern Ireland 15 1.4.1. Lough Foyle 16 1.4.2. Strangford Lough 16 1.4.3. Northern Ireland concerns about S. anglica agg. spread 20 1.5. Objectives 21 2. Methods 22 2.1. Study area 22 2.2. Experimental lay-out 25 2.2.1. Plot design 26 2.2.3. Treatments 26 2.3.1. Herbicidal treatments 26 2.3.1.1. Herbicide formulation 28 2.3.1.2. Herbicide application 28 2.3.2. Mowing treatments 28 2.3.3. Plastic sheeting 29 2.4. Experimental records 29 2.4.1. Vegetation recording 30 2.4.1.1. Quadrat sampling for stem height, stem density and Domin values30 2.4.1.2. Stem height measurements 30 2.4.1.2.1. Sacrificial pseudoreplication 30 2.4.1.3. Stem density recording 31 2.4.1.4. Domin values 31 2.4.1.5. Dry weight of roots and rhizomes 31 2.4.2. Macro-invertebrate analysis 32 2.5. Statistical analysis 33 2.5.1. Analysis of Variance (ANOVA, F-test) 34 2.5.1.1. Tukey test 34 2.5.1.2. ANOVA assumptions 35 2.5.1.3. Transformations 35 2.5.2. Kruskal-Wallis test 36 3. Results 39 3.1. Live S. anglica agg. stem density 39 3.2. S. anglica agg. stem height 40 3.3. Root dry weight 42 3.4. Puccinellia maritima abundance 42 3.5. Other plant species 43 3.6. Invertebrate abundance 44 4. Discussion 66 4.1. Effects of control treatments on S. anglica agg. 66 4.2. Effects of control treatments on other salt marsh species 70 4.3. Effects of S. anglica agg. control on benthic fauna 75 4.4. Effects of S. anglica agg. control on sediments 82 4.5. Conclusions 84 5. Spartina anglica agg. management strategy 87 5.1. General strategy 87 5.2. Economic and practical restraints 89 5.3. Legal restraints 91 5.4. Alternative Spartina anglica agg. control in areas where legal 92 and economic restraints make eradication improbable 5.5. Other management considerations 93 6. References 87 7. Appendix – Raw data 127 Acknowledgments This project was funded through a Department of Environment & Heritage Service, Northern Ireland and Department of Education, Northern Ireland, Co-operative Assisted Science and Technology (CAST) award. I would like to thank Dr. Alan Cooper for his help and guidance during my research; Sam, Robert, Anja, Belinda, Gareth, Julia, George and Paul Hackney for assistance in the field and plant identification; Euan for computer assistance; Tommy for statistical advice; Nigel for photography; Shirley for financial issues; members of the ‘Spartina control group’ especially the late Davey Andrews for assistance given during this study; fellow Spartina researchers, Paul Hedge, Kim Patton, Andrew Bishop, Lisa Lantz, Janie Civille, Mark McCorry, Phil Davey, Alasdair Wells, Willie Shaw, and Paul Gillespie who have given me advice and information during this study; and Pierre for sharing his valuable knowledge and contacts within the field of invasive species. Thanks also goes to all the friends who have made my three years study a very enjoyable and humorous time. Unfortunately they are too many to mention, but they know who they are. Special thanks go to my family and to the hummingbird for shared wisdom. Declaration on access to contents “I hereby declare that with effect from the date on which the thesis is deposited in the library of the University of Ulster, I permit the Librarian of the University to allow the thesis to be copied in whole or in part without reference to me on the understanding that such authority applies to the provision of single copies made for study purposes or for inclusion within the stock of another library. This restriction does not apply to the British Library Thesis Service (which is permitted to copy the thesis on demand for loan or sale under the terms of a separate agreement) nor to the copying or publication of the title and abstract of the thesis. IT IS A CONDITION OF USE OF THIS THESIS THAT ANYONE WHO CONSULTS IT MUST RECOGNIZE THAT THE COPYRIGHT RESTS WITH THE AUTHOR AND THAT NO QUOTATION FROM THE THESIS AND NO INFORMATION DERIVED FROM IT MAY BE PUBLISHED UNLESS THE SOURCE IS PROPERLY ACKNOWLEDGED” _________________ Mark Hammond Abstract Spartina anglica and Spartina x townsendii were introduced into estuarine habitats in Northern Ireland between the 1930s and 1950s. They were planted largely into inter-tidal sediment and have subsequently spread to develop mono-dominant swards at several locations. Sward development reduces the feeding habitat for wildfowl and waders by excluding salt marsh species such as Zostera spp. and physically preventing access to benthic invertebrates. Spartina anglica and Spartina x townsendii are therefore considered to be a pest species requiring control. This thesis investigates methods used for controlling Spartina anglica and Spartina x townsendii by field experiment. Experiments were initiated to study the effectiveness of control methods at two sites, one a S. anglica sward, the other a S. x townsendii sward. The treatments studied included, smothering with black plastic sheeting, applying the herbicides dalapon and glyphosate, and cutting followed by herbicide application. The effects of the control treatments on live S. anglica and S. x townsendii stem density, stem height, dry root weight, and associated flora and benthic fauna was examined. Dalapon applied at a rate of 57kg ha-1 and smothering were the most effective control methods, reducing live S. anglica and S. x townsendii stem density by over 95 %. Glyphosate was relatively ineffective. S. anglica and S. x townsendii re-established via re-growth or seedling colonization in all treatments over the two years following treatment applications, indicating that S. anglica and S. x townsendii eradication would require re-application of control treatments. Cutting treatments increased the abundance of Puccinellia maritima in the S. x townsendii sward one year after stem removal. This suggests that S. anglica and S. x townsendii control treatments may facilitate the growth of other salt marsh species. There were no differences in invertebrate numbers prior to and one year after treatment application. S. anglica and S. x townsendii eradication management strategies should initially focus on eradication of small foci (seedlings – clumps). Monitoring is required to prevent S. anglica or S. x townsendii re-colonization. It is suggested that swards are eradicated in the next phase of the management strategy. It is advisable to use herbicides for eradication when possible due to cost effectiveness and practicality. If herbicide use is prohibited non- herbicidal methods should be used to eradicate small foci. At present it is not practical or cost-effective to remove sward areas with non-herbicidal methods. In such cases it may be possible to covert Spartina spp. sward areas into mixed saltmarsh by using control techniques that facilitate the spread of other saltmarsh species within the sward. 1 1. Introduction Invasion by non-native introduced species has been recognised as a major threat to conservation of the marine and coastal environment (Carlton 1989, 1996). Fourteen species of marine algae, five diatoms, one angiosperm and thirty invertebrates have been identified as non-native to British marine waters (Eno et al. 1997). These introductions have included species that adversely affect native species and habitats. Control methods have been applied to these detrimental species but, to-date, no non- native marine species has been successfully eradicated from British waters (Eno et al. 1997). Spartina anglica C. E. Hubbard, is an example of an introduced non-native species that has caused changes to native habitats and species. In many areas its invasion is seen as a threat to the conservation (e.g. through loss of bird feeding habitat), and amenity interests of the area. S. anglica has therefore been subject to direct control attempts. 1.1. Spartina anglica and Spartina townsendii origin, spread and growth Spartina anglica and Spartina x townsendii H.