- Pollen analysis and the vegetational history of Barra and South Uist in the Outer Hebrides, Scotland Volume 2 Barbara A Brayshay For the degree of Doctor of Philosophy University of Sheffield June 1992 Contents Volume 2 The Past Chapter 8. Holocene history vegetation 220 - 239 at Loch Hellisdale, South Uist. Chapter 9 Holocene vegetationhistory 240 - 259 at Kildonan Glen South Uist Chapter 10 The historical loch ecology of island 260 - 289 woods, Loch Druidibeg, South Uist. Chapter 11 Holocene history vegetation 290 - 312 at Port Caul, Barra. Chapter 12 Holocene history vegetation 313 - 341 at Lochan na Cartach,Barra. Chapter 13 Borve Valley sub-peat stone 342 - 352 setting, Barra. Chapter 14 Conclusions. 353 - 362 LIST OF FIGURES Volume 1 Figure 1. Location map of study area. Figure 2. Satellite photograph of South Uist study transect Figure 3. Major landscape units : South Uist and Barra. Figure 4. Location map showing Tao Galson. Figure 5. Previous palynological study sites. Figure 6. Inter-tidal and sub-tidal peat deposits. Figure 7. Potential vegetation zones for 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 & ercus Figure 9c. Holocene tree migration patterns : Alnus & Pinus Figure 10. The relationship between site size and pollen source area. Figure 11. The South Uist Environmental Transect Figure 12. Location map of vegetation quadrats on the South Uist transect. Figure 13. Palynological study sites : this study. Figure 14. Pollen preparation method. Figure 15. A simplified geological map of the Outer Hebrides. Figure 16. Reconstructed extent of ice-sheets (13,000 B. P. ) Figure 17. Reconstructed extent 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. CANOCObiplot of characterising species / environmental variables. Figure 23. CANOCObiplot of IWINSPAN groups and environmental variables. Figure 24. South Uist transect surface sample pollen percentage diagram. ' Volume2 Figure 25. Location map, Loch Hellisdale, South Uist. Figure 26. Loch Hellisdale, South Uist. Figure 27. Pollen percentage diagram from Loch Hellisdale, South Uist. _'_ Figure 28. Pollen concentration diagram from Loch Hellisdale, South Uist., Figure 29. Abandoned croft, Glen Hellisdale. Figure 30. Location map, Kildonan Glen, South Uist. Figure 31. Kildonan Glen, South Uist. Figure 32. Pollen percentage diagram from Kildonan Glen, South Uist. ' Figure 33. Pollen concentration diagram from Kildonan Glen South Uist. Figure 34. Location map, Loch Druidibeg, South Uist. Figure 35. Wooded islands at Loch Druidibeg, South Uist. Figure 36. Pollen percentage diagram Taxus - Sorbus stand, Loch Druidibeg, South Uist. ',. Figure 37. Pollen concentration diagram Taxus - Sorbus stand, Loch Druidibeg, South Uist. - Figure 38. Pollen percentage diagram Salix stand, Loch Druidibeg, South Uist. * Figure 39. Pollen concentration diagram Salix stand, Loch Druidibeg, South Uist. -; Figure 40. Model of recent woodland succession in Ireland. Figure 41. Port Caol, Barra, sub-tidal peat site. Figure 42. Location map of Port Caol, Barra. Figure 43. Coastal sedimentary sequences, Port Caol, Barra. Figure 44. Pollen percentage diagram, Port Caol, Barra.;: Figure 45. Pollen concentration diagram, Port Caol, Barra. * Figure 46. Location map showing Lochan na Cartach, Barra. Figure 47. Lochan na Cartach, Barra. Figure 48. Pollen percentage diagram, Lochan na Cartach, Barra.. Figure 49. Pollen concentration diagram, Lochan na Cartach, Barra. -,'.- Figure 50. Sediment accumulation at Lochan na Cartach, Barra. Figure 51. Location map showing sub-peat stone setting, Borve Valley, Barra. Figure 52. Ditch section, Borve Valley, Barra. Figure 53. Pollen percentage diagram, Borve Valley, Barra. * Figure 54. Pollen percentage diagram 2, Borve Valley, Barra. * see Appendix 1. Appendix 1 Figure 24. South Uist transect surface sample pollen percentage diagram. Figure 27. Pollen percentage diagram from Loch Hellisdale, South Uist. Figure 28. Pollen concentration diagram from Loch Hellisdale, South Uist. Figure 32. Pollen percentage diagram from Kildonan Glen, South Uist. Figure 33. Pollen concentration diagram from Kildonan Glen South Uist. Figure 36. Pollen percentage diagram Taxus - Sorbus stand, Loch Druidibeg, South Uist. Figure 37. Pollen concentration diagram Taxus - Sorbus stand, Loch Druidibeg, South Uist. Figure 38. Pollen percentage diagram Salix stand, Loch Druidibeg, South Uist. Figure 39. Pollen concentration diagram Salix stand, Loch Druidibeg, South Uist. Figure 44. Pollen percentage diagram, Port Caol, Barra. Figure 45. Pollen concentration diagram, Port Caol, Barra. Figure 48. Pollen percentage diagram, Lochan na Cartach, Barra. Figure 49. Pollen concentration diagram, Lochan na Cartach, Barra. Figure 53. Pollen percentage diagram, Borve Valley, Barra. Figure 54. Pollen percentage diagram 2, Borve Valley, Barra. LIST OF TABLES Volume 1. Table 1. Selected climatic variables, Benbecula, outer Hebrides. Table 2. Scottish island plant species numbers, island area, 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 of the South Uist transect. Table 7. South Uist environmental transect data. Table 8. Matrix of Pearson product moment correlation between ordination axes and environmental factors along the South Uist transect. Table 9. Pollen representation categories Table 10. Pollen representation classes. Table 11. Plant abundance and pollen representation, (Festuca (Group rubra - Galium verum - dune machair community H). Table 12. Plant abundance and pollen representation, Festuca rubra Potentilla anserina - Trifolium repens - Agrostis stolonifera inland grassland community (Group I). Table 13. Plant abundance and pollen representation, Iris pseudacorus inner machair community (Group G). Table 14. Plant abundance and pollen representation, Iris psuedacorus inner machair community (Group N). Table 15. Plant abundance and pollen representation, Phragmites australis machair swamp community (Group 0). Table 16. Plant abundance and pollen representation, Eleocharis palustris lake margin community (Group M). Table 17. Plant abundance and pollen representation, Potentilla anserina - Carex nigra - Vicia cracca inner machair community (Group Q. Table 18. Plant abundance and pollen representation, Agrostis (Group capillaris - Festuca ovina grasslands E2). Table 19. Plant abundance and pollen representation, Agrostis (Group capillaris - Festuca ovina grasslands El). Table 20. Plant abundance and pollen representation, Pteridium aquilinum - Potentilla erecta - Anthoxanthum odoratum bracken infested grasslands (Group F). Table 21. Plant abundance and pollen representation, Eriophorum angustifolium bog pool community (Group B). Table 22. Plant abundance and pollen representation, Molinia caerulea - Scirpus cespitosus - Erica tetralix wet heath (Group C). Table 23. Plant abundance and pollen representation, Calluna vulgaris heath community (Group D). Table 24. Plant abundance and 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 loch island vegetation survey (1). Table 27. Loch Druidibeg loch island vegetation survey (2). Table 28. Loch Druidibeg loch island vegetation survey (3). Table 29. Loch Druidibeg loch island vegetation survey (4). Table 30. Loch Druidibeg loch island vegetation survey (5). Table 31. Pollen percentage values indicative of the local presence of trees. s 4 Chapter 8. Holocene Vegetation History at Loch Hellisdale, South Uist. '- ý- Holocene vegetation history at Loch Hellisdale ; South Uist. Site description Loch Hellisdale (NF828310) isýan upland loch situated in a remote glacial trough, Glen Hellisdale, on the mountainous east coast of South Uist (Figure 25). The loch represents the eastern most pollen site sampled on the South Uist transect. The loch has an inflow stream which is draining into the loch from the slopes of Beinn Mhor (620m O. D) and Cas fo Dheos (1723m O. D. ) which rises steeply from the north shore of the loch. An outflow stream flows into the lower valley. The loch was selected for analysis because of its low organic productivity, long sediment sequence (extending potentially into the Devensian Late-glacial), its relative protection from strong winds which could disturb lake sedimentation and its potential as a trap for the airfall recruitment of pollen and tephra. This relatively shallow loch is typically 1-5m deep and lies at approximately 75m O. D. in the eastern end of Glen Hellisdale, itself an isolated, short, glacially-eroded, steep sided trough-like valley which opens eastward from its head at the flanks of Beinn Mhor towards the Sea of the Minches (Figure 26). Geology and soils The solid geology of the valley is predominantly Lewisian granitic gneiss, with hornblende lenses. The impact of the Outer Hebrides thrust zone is thought to have produced the myolinites and crushed gneisses found along this eastern coast of the Outer Hebrides. (Figure 15). Drift deposits consist of a thin covering