The phytosociology of calcareous grasslands in the British Isles

Abstract

The thesis attempts a broad overall survey and classification according to the Zurich-Montpellier system ofplant sociology, of limestone grassland vegetation in the British Isles The classification is based on some 535 grassland Aufnahmen and 75 Aufnahmen of contact communities. In all, some 13 grassland Associations are recognised, whilst the zonal and successional communities are classified in 16 Associations. The Associations are classified in the system of classification advocated by Lohmeyer et al. (1962), and the phytogeographical relationships of the related Association-groups or Alliances are considered in detail. The limestone grassland communities of the British Isles have been found to be representative of four Classes: - (a) Festuco-Brometea - thermophilous dry grassland communities of the sub-mediterranean and sub - atlantic regions of Europe; (b) Elyno-Seslerietea - dry sub-montane, sub-alpine grass heaths of the low alpine region of central Europe and Scandinavia; ( c ) Molinio-Arrhenatheretea - mesophilous, grazed or mown hay meadows and pastures of the lowland zone of western Europe; (d) Violetea calaminariae - open grassland communities IV of heavy metal - rich strata and spoil banks. The thesis is divided into 5 parts : - Part 1 reviews the methods available for a vegetation survey and phytosociological technique in general; outlines the history and status of limestone grasslands; and summarises the methods used for previous description of British vegetation; Part 2 presents the results of the grassland survey and relates the change in overall floristic composition and grassland type to climatic factors using the climate diagrams of Walter & Lieth (1967); Part 3 considers the successional and zonal relationships of these grassland communities, whilst Part 4 discusses the validity of the methods used for the survey and suggests some of the logical extensions of t h is work with reference to the conservation and management of an area limestone grassland on the Magnesian Limestone of Co. Durham. Part 5 comprises 36 Association Tables and an Aufnahmen locality Appendix, and is to be found in the folio volume. References LOHMEYER, W. et a l . (1962). Contribution a 1 ' unification du systeme phytosociologique pour 1'Europe moyenne et nord-occidentale. Melhoramento, 15, 137-151. Walter, H. & Leith, H. (1967). Klimadiagramm Weltatlas. Jena.