Phytosociological studies on rich fen systems in England and Wales

Abstract

The thesis presents an attempt to detect, define and characterise, on the basis of their floristic composition, the principal types of rich fen vegetation in lowland England and Wales. Some 1,000 samples were taken from a wide variety of rich fen systems throughout England and Wales and from one area in S. Scotland, by a subjective procedure based upon stand selection. A computer-based system was developed to handle these data combining both numerical and traditional (Zurich-Montpellier) methods of analysis. The dataware processed by normal and inverse Information Analysis in. conjunction with a computer-assisted hand-sorting routine leading to the production of structured species-sample tables. One hundred and eight noda were identified and described and compared with related units recognised from Britain and N.W. Europe. Sixty eight were arranged into 11 Associations of which 4 represent new syntaxa. The remainder were placed into sociations or left as noda of uncertain status. The communities were all classified into higher syntaxa essentially following the scheme advocated by WESTHOFF & DEN HELD (1969). The Classes and Alliances used to contain the communities are: Phragmitetea Phragmition reedswamp communities Magnocaricion tall growing sedge and reed fen vegetation of topogenous mire Parvocaricetea Caricion davallianae low-growing sedge vegetation of calcareous mire Molinio-Arrhenatheretea Calthion palustric fen meadow vegetation Molinion caerulea Molinia-dominated fen grassland Filipendulion species-poor, tall herbaceous vegetation of eutrophic mires Franguletea Salicion cinereae fen scrub communities Alnetea glutinosae Alnion glutinosae alder carr vegetation The new associations described are the Peucedano- Calamagrostietum canescentis of the Magnocaricion; the Schoeneto-Juncetum subnodulosi of the Caricion davallianae; and the Cropido-Salicetum pentandrae and the Betulo-Dryopteridetum cristatae, both of the Franguletea. A short account of the occurance of rich fen systems in lowland England and Wales is given. A brief discussion of the rich fen cirlce of vegetation in lowland England and Wales is also given.