Phytosociological studies at malham tarn moss and fen, Yorkshire, England

During a field course the vegetation of the extensive mire complex on the west side of Malham Tarn was examined. 84 relevés were collected, with 210 taxa in total. This data set has been 'structured' by classical phytosociological techniques. It is suggested that it approaches the maximum size of data-set which can be handled in this way, especially if the data are not all collected by one person. Ordination of the quadrats was carried out but gave little insight into the data despite the use of non-centred as well as centred principal components analysis. Numerical classification of the quadrats using minimumvariance cluster analysis was shown to produce a structure interpretable in ecological terms. A classification of the taxa was carried out by the same method and a 'rearranged' table was drawn up using the results of the two classifications. A relocation technique was applied at an appropriate cluster level but little was felt to be gained from this. The use of 'two-way' minimum-variance cluster analysis for the rapid production of re-arranged tables is recommended for large data-sets. In addition the vegetational units recognised in the data are described and discussed.