Transformation of Cover-Abundance Values in Phytosociology and its Effects on Community Similarity

TLDR: In this article, the authors proposed a pseudo-qualitative basis for various calculations by means of a "coupure" that deletes lower values, usually according to a fixed criterion, e.g. the number of occurrences in a phytosociological table to be remained should be as close as possible to 50%.

Abstract: The numerical treatment of phytosociological data is often based on estimates of cover and/or abundance according to the Braun-Blanquet and Domin scales. Since Schwickerath (1931, 1938, 1940) and Tuxen & Ellenberg (1937) published their transformations there has been discussion on the way the scale values should be used in calculations Qualitative approaches, i.e. based on presence and absence have also been favoured (e.g. Williams & Lambert 1959, van der Maarel 1966) Dagnelie (I960) proposed a pseudoqualitative basis for various calculations by means of a ‘coupure’. A coupure includes the deletion of lower values, usually according to a fixed criterion, e.g. the number of occurrences in a phytosociological table to be remained should be as close as possible to 50%. Dagnelie’s approach remained largely unknown and apparently it has never been tested.