Coastal Vegetated Shingle Structures of Great Britain: Appendix 1
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Coastal vegetated shingle structures of Great Britain: Appendix 1. Shingle sites in Wales P. Sneddon & R.E. Randall Girton College Cambridge March 1993 © JNCC 1993 ISBN 1 873701 30 6 Full set ISBN 1 873701 15 2 Main report ISBN 1 873701 16 0 Appendix 1. Wales ISBN 1 873701 17 9 Appendix 2. Scotland ISBN 1 873701 18 7 Appendix 3. England Design: Nick Davidson, JNCC Cover design: Nature Conservation Bureau Ltd. Originally printed by: Lake-Shore Graphics, Nottingham. Converted to digital format from the original by GeoData Institute, University of Southampton: 2009 2 Contents Page No. Preface - JNCC's coastal survey programme 5 Background 6 Acknowledgements 7 Introduction 8 Methods 9 Introduction to Welsh shingle sites 12 Site reports 14 17 Llanddulas 19 Gronant 20 Red Wharf Bay 21 Traeth Dulas 24 Cemlyn Bay 26 Dinas Dinle 29 Pontlyfni 30 Aberdesach 31 Afon Dwyfor 33 Pen-y-chain 36 Criccieth 39 Aber Dysynni 43 Traeth Tanybwlch 46 Crabhall Saltings 48 Pennard Burrows 51 Pwll du 54 East Aberthaw Porthkerry References 56 3 4 Preface - JNCC's coastal survey programme The work reported here was originally Branch of the Joint Nature Conservation commissioned by the Coastal Ecology Committee's support unit and the results Branch of the Nature Conservancy are being published as part of the Council's Chief Scientist Directorate in Branch's publication programme. 1987. The survey forms part of an attempt to describe the size, location and This report provides a classification of quality of the main coastal habitats in the main shingle plant communities found Great Britain (saltmarshes, sand dunes, on stable or semi-stable shingle structures vegetated shingle, sea cliffs, strandlines, in Great Britain. It does not attempt to 'reclaimed1 land and maritime islands). provide an assessment of the comparative nature conservation values of the sites The collection of basic data on the main surveyed. The more detailed descriptions coastal habitats is an important first step presented as appendices to the main in identifying the most important sites, report can be used to provide a first establishing a basis for monitoring and indication of importance in relation to the understanding the impact of management size of site and the number and operations and major development representation of the plant communities. projects on them. Further information can be obtained A survey of saltmarshes in Great Britain from: was completed in 1991 and surveys of the majority of sand dune sites in Dr J.P. Doody. Coastal Conservation England and Wales, and a selection of Branch, Joint Nature Conservation the most important in Scotland, have Committee, Monkstone House, City been completed. Responsibility for Road, Peterborough, PE1 1JY, UK. completing the existing round of survey passed to the Coastal Conservation 5 Background A survey of shingle structures in Great conducted within the framework of the Britain was initiated in 1987 under National Vegetation Classification (NVC) contract to Girton College, Cambridge in order to assess the applicability of from the Nature Conservancy Council. existing NVC categories to the shingle communities and, where appropriate, to This research project provides: extend the NVC by highlighting any new communities identified. At the start of a. an overall report which combines all the project only one community was data in order to determine which plant specifically attributed to the shingle communities are found on shingle at a substrate - SD1, within which two sub- national level, and how these relate to communities had been recognised. This existing NVC categories; and reflected the limited data supply for the shingle substrate at that time. b. written descriptions and maps of the major plant communities at each site The main report provides a summary surveyed, which are collated into classification which is discussed more regional reports for Wales, Scotland fully in the detailed account of Sneddon and England; (1992). This report on the sites in Wales forms Appendix 1 to the main report This report gives a preliminary (Sneddon & Randall 1993). Further description of the results of site surveys reports are Appendices giving site conducted in Wales. It forms part of the descriptions for Scotland and Wales. wider study of the vegetation of shingle structures in Britain. This work has been Acknowledgements The production of this report would have Cemlyn Bar Nature Reserve during the been impossible without the cooperation site visit. of all regional staff in North Wales, Dyfed/Powys, and South Wales regions. Finally, many thanks to Ian Agnew and In each case help was given in the the Cambridge Geography Department identification of sites and in obtaining Drawing Office who produced the base permission for access to those sites for maps for this report. fieldwork. Thanks should also be offered to The P. Sneddon North Wales Naturalists' Trust who R.E. Randall allowed access to restricted areas of 6 Introduction The term shingle may be applied to any beaches. The first has been mentioned sediment which has a mean grain size of earlier, the mobility of the beach. between 2 and 200 mm. Sediments below Clearly, if a beach is highly mobile then that size are termed sand, silt or clay, a seed is likely to be washed away before according to mean grain size, while it is able to germinate and so the particles of a diameter greater than 200 mm frequency of inundation of a site will are termed boulders. This empirical have an important influence on the distinction reflects a biological distinction vegetation of that site. Indeed, this factor based on environmental factors such as was recognised by Scott (1963) in his moisture content which lead to differing classification of vegetation on shingle habitats associated with each sediment. which divides shingle vegetation into five categories according to the stability of Shingle may occur as a riverine sediment sites. but in the UK it is most commonly found in marine environments around the coast. A second factor determining the Indeed, approximately one third of the establishment of vegetation on shingle is coastline of England and Wales is bordered the presence of a fine matrix in the by shingle. This marine sediment may have shingle (Fuller 1987). The nature of the been derived from three major sources: fine matrix has been shown to influence the type of vegetation with four types of a. by rivers transporting shingle to the shingle substrate identified by Scott coast; (1963); pure shingle, shingle with a sand admixture, shingle with silt and, finally, b. as glacial sediments deposited offshore shingle with wrack (rotting seaweed). which have been reworked with rising sea levels to be deposited along the The final factor influencing the presence coast; and finally, of vegetation on a shingle beach is the hydrological properties of the shingle. c. shingle may result from active erosion Clearly, shingle has a high porosity and of existing coastal cliffs such as the low water retention. However, this is flint shingle derived from chalk cliffs overcome to some extent by the presence found along much of the south coast. of a fine matrix which serves as a reservoir of water, which is critical at the Five types of shingle beach have been germination stage of seed development. recognised (Sparks 1972, Chapman Once established, the vegetation relies on 1976): adaptations to drought conditions in the form of thick leaf cuticles and the a. fringing beaches; mulching effect of wetter shingle by dry b. spits; shingle layers above to provide an c. bars; adequate water supply (Fuller 1987). d. apposition beaches/cuspate forelands; e. barrier islands. To sum up, the establishment and maintenance of a permanent flora on These categories vary according to their shingle beaches is dependent upon the mobility and oceanicity and they, mobility, matrix characteristics and therefore, offer different habitats. moisture conditions of that beach. It has been shown by Randall (1977) that For a more detailed introduction see the three key factors are required to enable final report (Sneddon & Randall 1993). the establishment of vegetation on shingle 7 Methods Each site was surveyed within the biological, which may provide a useful framework of the National Vegetation supplement to the quadrat data collected Classification (NVC). The field in terms of the analysis of community techniques were based, therefore, on types. those outlined in the NVC field manual. Site data, such as land use and any Individual sites were identified from forms of disturbance, were collected at habitat maps held by the Nature each site, while additional site Conservancy Council (NCC), through information such as % SSSI coverage consultation with the then Chief and past land use were recorded, based Scientist Directorate of NCC, and, at a on information collected prior to local level, with the NCC regional fieldwork. staff. Clearly, not all shingle sites fall into the category of shingle structures. The quadrat data were entered onto a Equally, not all shingle sites are computer which organised them into vegetated, e.g. Hell's Mouth. Some classificatory units to be used for sites have, therefore, not been included mapping. The programmes used were in this survey. In addition, time TWINSPAN and TWINTAB as constraints led to concentrating on the specified by the NVC. These packages survey of the vegetation of larger sites. combine quadrats of similar floristic composition into groups and these Sites were firstly surveyed by eye to groupings were then compared with identify stands of homogeneous those already identified by the NVC vegetation to be used as mappable keys and tables. These units were then units. Within these stands, vegetation used for mapping. was sampled using a 4x2 m quadrat, found to be the most appropriate size Two methodologies for mapping in the for the vegetation types encountered, field were employed according to the and consistent with the quadrat size availability of aerial photographs.