Durham E-Theses Phytosociological studies in the southern Isles of Shetland Hilliam, Judith How to cite: Hilliam, Judith (1977) Phytosociological studies in the southern Isles of Shetland, Durham theses, Durham University. Available at Durham E-Theses Online: http://etheses.dur.ac.uk/9637/ Use policy The full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that: • a full bibliographic reference is made to the original source • a link is made to the metadata record in Durham E-Theses • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders. Please consult the full Durham E-Theses policy for further details. Academic Support Oce, Durham University, University Oce, Old Elvet, Durham DH1 3HP e-mail: [email protected] Tel: +44 0191 334 6107 http://etheses.dur.ac.uk Phytosociological Studies in the Southern Isles of Shetland By Judith Hilliam (B.Sc. Dunelm) A Thesis submitted for the Degree of Doctor of Philosophy in the University of Durham Department of Botany March 1977 The copyright of this thesis rests with the author. No quotation from it should be published without his prior written consent and information derived /S^^^^f^^?^"*''^ from it should be acknowledged. ( 1 2 APR 1978 j The fieldwork for this project was carried out with Anne M.Lewis, who was studying the vegetation of the Northern Islands of Shetland, but the content of this thesis is entirely my own work, except for the text references to publications. It has not previously been submitted for any degree or diploma. Judith Hilliam. March 1977. CONTENTS Volume 1 Page No. Abstract Acknowledgemen t s Chapter 1: Introduction 1.1: The Shetland Isles 1 1.2: Background to the project 1 1.3: Identification 3 1.4: Coventions and terms 3 Chapter 2: The Shetland Isles 2.1: Physical 5 2.2: Climate 15 2.3: Soils and land use 24 2.4: Previous work on Shetland vegetation 27 Chapter 3: Methods 32 .3.1: Potential methods in phytosociological survey 33 3.2: Summary and definition of terms used 41 3.3: Methods used 43 Chapter 4: Syntaxonomic categories used in the classification of vegetation of vegetation from the Southern Isles. 4.1 Cakiletea maritimae 52 4.2 Agropyretea pungentis 53 4.3 Ammophiletea 55 4.4 Plantaginetea major!s 57 4.5 Phragmitetea 58 4.6 Koelerio-Corynephoretea 60 4.7 Festuco-Brometea 62 64 4.8 Saginetea maritimae 65 4.9 Asteretea tripolii 68 4.10 Molinio-Arrhenatheretea Page No. 4.11; Montio-Car daminetea 71 4.12: Parvocaricetea 72 4.13; Scheuchzerietea 76 4.14: Oxycocco-Sphagnetea 77 4.15: Nardo-Callunetea 80 4.16; Caricetea curvulae 83 Chapter 5: The Plant Communities of the Southern Isles 85 5.1: Shingle 86 5.2: Sand-dunes 95 5.3: Saltmarsh 112 5.4: Grassland 125 5.5: Wet meadows 149 5.6: Blanket bog 167 5.7: Bog pools 183 5.8: Heath 187 Chapter 6: Discussion 6.1; A brief synopsis of the vegetation type of each of the Southern Isles. 216 6.2: General Discussion 224 6.3: Conclusions 234 6.4; Conspectus of Associations and other main units 236 References; 240 Volume 2 Phytosociological tables, Sites lists List of syntaxa. LIST OF FIGURES Page No. Figure 2 1.1.1. Map to show position of the Shetland Isles. 6 2.1.1. Geographical areas of the Southern Isles. 7 2.1.2. Simplified geological map of the Southern Isles. 26 2.3.1. Main settlements of the Southern Isles. 48 3.3.1. Distribution of sites sampled with Southern Isles. 3.3.2. Minimal area curves. 49 50 3.3.3. Completed field record card. Summaries of vegetation groups in the Southern Isles. 95 5.1. Shingle. 110 5.2 . Sand-dune. 124 5.3. Saltmarsh. 148 5.4. Grassland. 166 5.5. Wet meadow. 182 5.6. Blanket bog. 186 5.7. Bog pools. 215 5.8 u Heath. TABLES IN.VOLUME 1 Table Page No. 2.2.1. Potential water deficit divisions, (Birse and Dry, 1970). 16 2.2.2. Comparison of temperatures at sites in Shetland, Scotland and Faroe. 17 2.2.3. Accumulated temperature divisions, (Birse and Dry, 1970). 19 2.2.4. Accumulated frost divisions, (Birse and Robertson, 1970). 23 2.3.1. Land-use in Shetland, 1974. 24 2.3.2. Acreage of grassland and crops,1974. 25 2.3.3. Populations of inhabited islands, 1971. 26 ABSTRACT Over 500 samples were collected from as wide a variety of vegetation types as possible. The principles of the Zurich- Mbntpellier School of phytosociology were followed to form the data into a species-releve matrix for each vegetation type. The CLUSTAN package of computer programs was utilised, using Ward's Error Sum of Squares as a sorting routine, to produce differentiated data tables. 72 groups were identified, and described and compared with units recognised in Britain and North-West Europe. 38 groups were assigned to 21 Associations and the remainder were left as noda of doubtful status within alliances and orders. All communities were classified into higher syntaxa fdllowing, with only a few exceptions, the scheme of Westhoff and Den Held (1969). The Classes and Alliancies used to.contain the communities are as follows: Cakiletea maritimae Atriplicion littoralis Open communities (of mainly annual species) of shingle beaches and strandlines Agropyretea_gungentis Honkenyo-Crambi on ma ri timae Open, unstable, halonitrophile communities of biennials and perennials, of shingle beaches and strandlines. Agropyrion pungentis Stable communities in maritime areas subject to disturbance. Ammophiletea Agropyrion boreoatlanticum Unstable^ pioneer communties on sand. Ammophilion borealis Mobile dune communities. ?l§0*§SiD§*§§_5S!ii9Eis Agropyro-Rumicion crispi Disturbance communities of transitional and relatively unstable habitats. Phragmitetea Magnocaricion Large sedge communities. Galio-Koelerion Dry grasslands on acidic soils in the atlantic sector Fes tuco-Brome tisa Mesobromion erecti Semi-dry calcareous grasslands. Saginion maritimae Closed maritime grasslands on sandy soils in the upper saltmarsh regions. Asteretea tripolii Puccinellion maritimae Halophyte communities of lower saltmarshes. Armerion maritimae Halophyte communities of upper saltmarshes. Elecharion uniglumis Communal sedge communities of saltmarsh boundaries. Puccinellio-Spergularion salinae Distrubed maritime communities on sand and gravel. Molini o-Arrhena the re tea Calthion palustris Fen meadow vegetation. Cynosurion cristati Communities of grazed, lowland pastures and similar habitats. Montio-Cardaminetea Cratoneurion Chalk and limestone spring communities. Parvocaricetea Caricion curto-nigrae Small sedge communities in . habitats near springs. Caricion davallianae Small sedge vegetation of base-rich habitats. Scheuchzerietea Rhyncospprion albae Species poor vegetation in pools in poor fens and mires. Caricion lasiocarpae Communities of pools in moderately rich fois and mires. Oxycocco^Sghagnetea Ericion tetralicis Wet heath communities on shallow peat. Erico-Sphagnion Bog communities. Na rdo-Ca11une tea Violion caninae Rough grasslands. Ulicion nanae Oceanic heaths. Caricetea curvulae Arctostaphyleto-Cetrarion nivalis Chionophobous montane grass and dwarf-shrub heath communities. The occurrence and inter-relationships of the plant communities of the Southern Isles are discussed, and the potential pressures on Shetland vegetation are examined. ACKNOWLEDGEMENTS I should like to thank all the people in Shetland who showed great kindness during my visits there. They are too numerous to mention individually, but all made life in the Islands a most enjoyable experience. Special thanks are due to Mr.Se Mrs.R.Tulloch of Mid Yell for their help and hospitality over a number of years. In Durham, the enthusiasm and support of Dr.D.J.Bellamy has been greatly appreciated, as has the advice of Dr.B.D.Wheeler on matters phytosociological. I should also like to thank Professor D.Boulter for use of facilities in The Botany Department, University of Durham; the staff of the Univerisity Science Library who have always been extremely helpful; and Mrs.C.Rowes for typing the text of this work. A number of people have helped with the identification of specimens, and in this respect thanks are especially due to Dr.M.Roberts, Rev.G.G.Graliam and J.Skinner in Durham, and Dr.P.Yeo, Cambridge. The study was supported by a Durham Research Studentship, with help with travelling expenses from B.P.Oil Limited and a Swire-Smith Travel Scholarship. Finally, I should like to thank my parents for their interest and encouragement; and many kind and tolerant friends who have helped In many ways. In particular, special thanks are due to Anne Lewis for days of happy and enjoyable fieldwork in Shetland, and of stimulating discussion and encouragement in Durham. CHAPTER 1 INTRODUCTION -1- 1.1 THE SHETLAND ISLES The Shetland Islands lie across latitude 60°N, about 241 km north of Duncansby Head, Scotland, and 322 km west of Bergen in Norway. There are over 100 islands, ranging in size from the Mainland which is 88 km long and, at its broadest, 32 km wide, to countless stacks and holms barely as large as an acre. Fig.1.1.1 shows the position of the Shetland Isles. Until recently the Islands' economy rested on crofting, fishing, knitwear and tourism, but the discovery of oil beneath the North Sea has brought new wealth, new ideas and new people to this isolated archipelago. This study is particularly concerned with the Southern Isles, that is, south of an imaginary line drawn through the Yell Sound (see Fig.2.1.1) but is intended to complement a similar survey of the Northern Isles by Lewis (1976). 1.2 BACKGROUND TO THE PROJECT Since the "phytosociological revolution" brought about by Braun- Blanquet and his followers in Europe, British ecologists have described parts of the United Kingdom according to his methods.