Phytosociological and geographical survey of Mesohromion communities in Western Europe

A survey is given of the floristic composition and geographical distribution of limestone grasslands assigned to the Mesobromion ereeti, in Western Europe.This survey is based upon 800 vegetation relevés from various investigators throughout the area. Relevant tables have been summarized into a synoptic table with 30 columns. Each column represents a community described as an association or a subassociation.The synoptic table shows a division into a NW European group (Ireland, England, Denmark, and South Sweden) and a Central-W European group (Germany, The Netherlands, Belgium, France, and Switzerland). Associations belonging to the former have, as a rule, a smaller distribution area than the latter.In the latter group only two associations can be distinguished: Mesobrometum erecti and Antherico-Brometum ass. nov. The Mesobrometum is widespread and includes many subassociations. The Antherico-Brometum shows a transition towards the Xerobromion erecti.According to Barkman et al., (1976) the often used name Gentiano-Koelerietum has to be seen as a not-correct synonym for the Mesobrometum erecti.The Mesobromion grasslands can, in general, not be divided based upon their agricultural management system.An attempt is made to interpret the gradual transition in floristic composition of the limestone grasslands from NW to SE, with climatological data.Plant nomenclature follows Heukels & Van Ooststroom (1975) or, else, Clapham et al. (1968) for phanerogams and Vander Wijk et al. (1969) for bryophytes.I am much indebted to Prof. Dr. J. J. Barkman, who encouraged me to tackle the present study and stimulated me throughout its duration.