Pollen Analysis and the Vegetational History of Barra and South Uist in the Outer Hebrides, Scotland
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IX, Pollen analysis and the vegetational history of Barra and South Uist in the Outer Hebrides, Scotland - Volume 1 Barbara A Brayshay For the degree of Doctor of Philosophy University of Sheffield June 1992 CONTAINS PULLOUT Contents Volume 1 The Problem. Chapter 1 Introduction 1-27 Chapter 2 Literature Review 28 - 59 Chapter 3 ResearchDesign 60 - 73 Chapter 4 Methods 74 - 84 The Present. Chapter 5 The geographicalsetting 85 - 106 Chapter 6 Vegetation and environmental 107 - 129 survey. Chapter 7 Pollen in taphonomy relation 130 - 219 to local vegetation. List of Figures. Volume 1. Figure 1. Location map of the study area. Figure 2. Satellite photographof the South Uist study transect. Figure 3. Major landscapeunits : South Uist and Barra. Figure 4. Location map, Tao Galson. Figure 5. Previouspalynological study sites. Figure 6. Inter-tidal and sub-tidal peat deposits. Figure 7. Potential vegetation zonesfor Scotland. Figure 8. Distribution of existing woodland in the Inner Hebrides. Figure 9a. Holocene tree migration patterns : Betula & Corylus. Figure 9b. Holocene tree migration patterns : Ulmus & Quercus. Figure 9c. Holocene tree migration patterns : Alnus & Pinus. Figure 10. The relationship betweensite size and pollen sourcearea. Figure 11. The South Uist environmental transect. Figure 12. Location map showing vegetation quadratson the South Uist transect. Figure 13. Palynological study sites : this study. Figure 14. Pollen preparationmethod. Figure 15. A simplified geology map of the Outer Hebrides Figure 16. Reconstructedextent of ice sheets(13,000 B. P.) Figure 17. Reconstructedextent of ice sheets(11,000 - 10,000 B. P.) Figure 18. Soil map units - South Uist. Figure 19. Soil map units - Barra. Figure 20. Annual rainfall - Outer Hebrides. Figure 21. Location of plant communities on the South Uist transect. Figure 22. CANOCO biplot of characterising species / environmental variables. Figure 23. CANOCO biplot of TWINSPAN groups and environmental variables. Figure 24. South Uist transect,surface samplepollen percentagediagram Volume 2 Figure 25. Location map, Loch Hellisdale, South Uist. Figure 26. Loch Hellisdale, South Uist. Figure 27. Pollen percentage diagram, Loch Hellisdale, South Uist. * Figure 28. Pollen concentrationdiagram, Loch Hellisdale, South Uist. * Figure 29. Abandonedcroft, Glen Hellisdale. Figure 30. Location map, Kildonan Glen, South Uist. Figure 31. Kildonan Glen, South Uist. Figure 32. Pollen percentagediagram : Kildonan Glen, South Uist. * Figure 33. Pollen concentrationdiagram : Kildonan Glen, South Uist. * Figure 34. Location map, Loch Druidibeg, South Uist. Figure 35. Wooded islands, Loch Druidibeg, South Uist. Figure 36. Pollen percentagediagram : Taxus - Sorbus stand,Loch Druidibeg, South Uist. * Figure 37. Pollen concentrationdiagram : Taxus - Sorbus stand,Loch Druidibeg, South Uist. Figure 38. Pollen percentagediagram : Salix stand : Loch Druidibeg, South Uist. * Figure 39. Pollen concentrationdiagram : Salix stand,Loch Druidibeg, South Uist. * Figure 40. Model of recent woodland successionin Ireland. Figure 41. Port Caol, Barra, sub - tidal peat site. Figure 42. Location map, Port Caol, Barra. Figure 43. Coastal sedimentarysequences, Port Caol, Barra. Figure 44. Pollen percentagediagram, Port Caol, Barra.* Figure 45. Pollen concentrationdiagram, Port Caol, Barra.* Figure 46. Location map : Lochan na Cartach,Barran. Figure 47. Lochan na Cartach,Barra. Figure 48. Pollen percentagediagram : Lochan na Cartach,Barra. * Figure 49. Pollen concentrationdiagram : Lochan na Cartach,Barra. * Figure 50. Sedimentaccumulation curve, Lochan na Cartach,Barra. Figure 51. Location map : sub=peatstone setting, Borve Valley, Barra. Figure 52. Ditch section : Borve Valley, Barra. Figure 53. Pollen percentagediagram : Borve Valley, Barra.* Figure 54. Pollen percentagediagram 2: Borve Valley, Barra.* * see Appen dix 1 Appendix 1 Figure 24. South Uist Transect : surface sample pollen percentage diagram Figure 27. Pollen percentagediagram : Loch Hellisdale, South Uist Figure 28. Pollen concentrationdiagram : Loch Helisdale, South Uist. Figure 32. Pollen percentagediagram : Kildonan Glen, South Uist. Figure 33. Pollen concentration diagram : Kildonan Glen, South Uist. Figure 36. Pollen percentagediagram : Taxus - Sorbus stand,Loch Druidibeg, South Uist. Figure 37. Pollen concentrationdiagram : Taxus - Sorbus stand,Loch Druidibeg, South Uist. Figure 38. Pollen percentagediagram : Salix stand,Loch Druidibeg, South Uist. Figure 39. Pollen concentrationdiagram : Salix stand,Loch Druidibeg, South Uist. Figure 44. Pollen percentagediagram : Port Caol,.Barra. Figure 45. Pollen concentrationdiagram : Port Caol, Barra. Figure 48. Pollen percentagediagram : Lochan na Cartach,Barra. Figure 49. Pollen concentrationdiagram : Lochan na Cartach,Barra. Figure 53. Pollen percentagediagram : Borve Valley, Barra. Figure 54. Pollen percentagediagram 2: Borve Valley, Barra. List of tables Volume 1 Table 1. Selected climatic variables : Benbecula, Outer Hebrides. Table 2. Scottish island area,plant speciesnumbers, soils and distance from the mainland. Table 3. 95% confidence intervals for percentages of increasing total pollen counts. Table 4. Summary of Pleistocene history, Outer Hebrides. Table 5. Soil map legend. Table 6. Plant communities on the South Uist transect. Table 7. South Uist environmentaltransect data. Table 8. Matrix of Pearsonproduct moment correlation between ordination axesand environmentalfactors along the South Uist transect. Table 9. Pollen representationcategories. Table 10. Pollen representationclasses. Table 11. Plant abundance/ Pollen representation: Festuca rubra - Galium verum dune machair community (Group H) Table 12. Plant abundance/ Pollen representation: Festuca rubra - Potentilla anserina - Trifolium repens - Agrostis stolonifera inland grasslandcommunity (Group I). Table 13. Plant abundance/ Pollen representation: Iris psuedacorus inner machair community (Group G). Table 14. Plant abundance/ Pollen representation: Iris psuedacorus inner machair community (Group N). Table 15. Plant abundance/ Pollen representation: Phragmites australis machair swamp community (Group 0). Table 16. Plant abundance / Pollen representation : Eleocharis palustris lake margin community. Table 17. Plant abundance/ Pollen representation: Potentilla anserina - Carex nigra - Vicia cracca inner machair community (Group L). Table 18. Plant abundance/ Pollen representation: Agrostis capillaris - Festuca ovina grasslands(Group E2). Table 19. Plant abundance/ Pollen representation Agrostis capillaris - Festuca ovina grasslands(Group El). Table 20. Plant abundance/ Pollen representation: Pteridium aquilinum - Potentilla erecta - Anthoxanthum odoratum braken infested grassland(Group F). Table 21. Plant abundance/ Pollen representation: Eriophorum angustifolium bog pool community (Group B). Table 22. Plant abundance/ Pollen representationMolinia caerulea - Scirpus cespitosus- Etrica tetralix wet heath (Group C) Table 23. Plant abundance/ Pollen representation: Calluna vulgaris dry heath community (Group D) Table 24. Plant abundance / Pollen representation : Festuca rubra - Armeria maritima - Plantago coronopus maritime grassland community (Group A). Table 25. 'Out-community' pollen representation. Volume 2 Table 26. Loch Druidibeg island vegetation (1) Table 27. Loch Druidibeg island vegetation (2) Table 28. Loch Druidibeg island vegetation (3) Table 29. Loch Druidibeg island vegetation (4) Table 30. Loch Druidibeg island vegetation (5) Table 31. Pollen percentagevalues indicative of the local presenceof trees. Acknowledgements. So many people have given me friendship, help, support and encouragement during the course of this project that it is difficult to extenja big enough thank you to them all. However some have been outstandingly patient, most notably Professor D. D. Gilbertson who supervised the project. Special thanks also to Dr. M. Kent, Dr. R. Weaver and Dr. P. Wathern, Dr. A Dugmore, Dr. P. Buckland and Dr. B. Pyatt who all shared their expertise with me, and got me to accomplish seemingly impossible feats of endurance (such as eating 'Beanfeasts' in the rain! ) and Pete Campell and Richard Morn who assisted on the first trip to Barra. I am especially grateful to all those who provided me with lodgings and refuges in which to write this thesis,particularly Helen Smith, Dr. Cathy Couttes,Sylvie and SammySpears, Chris and Carol Rodgers and Albert and Yvonne Jackson. Special thanks to Jaqui Mulville for being a great unstinting friend and to Caroline Newman, Margaret Anderson and Francis MacDonald for their help everyday with Cai Brayshay (aged 3 at the start) and for the hours of listening they all put in. Finally I would like to thank myfamily for changing their lives around me. Abstract This study examinescontemporary vegetation, pollen taphonomyand Holocene vegetationhistory acrosseast-west trending environmental transects in the southernOuter Hebrideanislands of South Uist and Barra. The pollen depositionalcharacteristics of sixteenplant communities are describedand modernpollen deposition is found to reflect the distribution of major vegetationtypes on the islands. The history of Holocene vegetationis investigatedat a number of sites which include exposedwest coastinter-tidal peat deposits,wooded loch islands and pre-peat soils associatedwith archaeologicalfeatures. These studies indicate that Holocene vegetation development followed a pattern typical for the region at similar latitudes. The early post-glacial vegetation