Systematische ordnung und floristische zusammensetzung Niederländischer wald- und gebüschgesellschaften

Classification and floristical composition of woodland and shrub communities of the Netherlands Since the study of Meijer Drees (1936) no exhaustive and well documented review has been published on the subject of woodland vegetation of regions of any importance in the Netherlands. Many data collected meanwhile, numerous published reviews of forest classification of various European countries, and altered opinions regarding principles of classification made it highly desirable to compose a complete revision of this subject. The necessary detailed studies being available, science and practice being in want of a compilation of all these data and confusion on classification increasing constantly, the moment had come for a survey of the classification and floristical composition of woodland and shrub communities of the Netherlands as a whole. The principles of the Braun-Blanquet system of classification in general have been accepted by the author; there exists no other choice in usable and sufficiently detailed classification of Western European woodlands. However the disadvantages of this system have been avoided as much as possible. In this connection all species ocurring in the communities were arranged in a set of 70 “sociological groups”, viz. groups of species, connected by mutual sociological affinities (chapter 2). The system presented here has evolved from the arrangement of these groups, the use of separate characteristic and differential species having been avoided as much as possible. For all groups, and for all species within the groups, a certain sequence was adopted, enabling the comparison of all tables of associations and sub-alliances. The frequent, but unsatisfactory use (or misuse) of characteristic species of a class, an order, an alliance and an association, “companion”, “casual” and “transgredient” species etc. could be abandoned in this manner. In addition to the floristical composition other criteria have been used for classifications, such as structure and dynamics of the community and nature of adjacent and substituting communities. The tables of releves on which the classification adopted here has been based will be published separately. The principles used, have been playing an increasing role in most of the proposed new classification-systems within the Braun-Blanquet school during the past 10 years, sometimes perhaps unconsciously so. In the authors opinion they indicate an internal evolution of methodology rather than abandoning the “school”. Chiefly on account of structural characteristics (dominance of tree or shrub species), woodland and shrub communities are separated from each other and brought into two “chief formations” (an additional unit in the Braun-Blanquet system, proposed at an earlier date by the author). This enables the introduction of a considerable simplification of the classification of the woodlands and satisfactory arrangement of a number of shrub communities (e.g. communities of Hippophaë, Sambucus, Sarothamnus, Ulex, Rubus and Salix species), whose position as far had been still uncertain. Moreover the proposed classification is more in line with several systems, used in other parts of the world. In chapter 3 the propositions of the author are discussed. Observations made in the Netherlands and in several other European countries are brought into account here. New units, distinguished in this study (mainly already mentioned in preliminary publications) are the classes: Sambucetea and Franguletea. the orders: Salicetalia auritae, Pteridio-Rubetalia and Alno-Salicetalia cinereae, the alliances: Arctio-Sambucion nigrae, Oenothero-Hippophaeion maritimi and Salicion auritae, the sub-alliances: Violo-Quercion, Vaccinio-Quercion, Carpino-Rubion, Sambuco- Rubion, Carpino-Berberidion and Sambuco-Berberidion, the associations; Carici remotae-Populetum nigrae, Anthrisco-Fraxinetum, Stachyo-Quercetum roboris, Convallario-Quercetum roboris, Sambuco-Prunetum spinosae, Orchido-Cornetum, Ulmo-Clematidetum, Polygonato odoratae-Euonymetum, Polypodio-Ligustretum, Aegopodio-Sambucetum nigrae, Hippophao-Sambucetum, Oenothero-Hippophaetum and Salicetum arenario-purpureae, and the sub-associations; Salicetum triandroviminalis cardaminetosum, Fraxino-Ulmetum ulmetosum glabrae and cynoglossetosum, Myricetum gale salicetosum arenariae. In addition, new units for the Netherlands are (as far as concerning complete descriptions) the class Salicetea purpureae, the orders: Populetalia, Betulo- Vaccinetalia uliginosi, Prunetalia, Sambucetalia and Salicetalia purpureae, the alliances: Alno-Ulmion, Pruno-Rubion subatlanticum, Berberidion, Ulici-Sarothamnion, Alno-Salicion cinereae and Salicion triandrae, the sub-alliances: Circaeo- Alnion and Ulmion carpinifoliae and the associations: Fraxino-Ulmetum, Violo- Quercetum roboris, Carpino-Prunetum spinosae and Alno-Salicetum cinereae. New, respectively partly altered, names for existing units are those of the orders: Populetalia and Prunetalia, the alliances: Sphagno-Betulion pubescentis, Pruno- Rubion subatlanticum, Ulici-Sarothamnion and Alno-Salicion cinereae, the suballiances: Circaeo-Alnion and Ulmion carpinifoliae, and the associations: Violoodoratae-Ulmetum, Solidagino-Quercetum petraeae, Irido-Alnetum and Frangulo- Salicetum auritae. Finally the concept of the following units as been understood here is at variance with other authors, partially without altering names; classes Querco-Fagetea (Prunetalia and Quercetalia pubescentis no longer incorporated, no more than Luzulo-Fagion), Alnetea glutinosae (“Salicion cinereae" sensu Muller & Gors no longer incorporated) and Salicetea purpureae (Salicion albae no longer incorporated, in contrast with Alno-Salicion cinereae), orders Fagetalia (Alno- Ulmion and Luzulo-Fagion not incorporated), Quercetalia robori-petraeae (Luzulo- Fagion incorporated), Prunetalia (“Salicion arenariae” not incorporated) and Sambucetalia (two new alliances distinguished within this order), alliances Ulici- Sarothamnion (also Ulex europaeus and different Rubus shrub communities placed here) and Alno-Salicion cinereae (the Salicion auritae not incorporated) and the associations Sphagna-Alnetum and Irido-Alnetum (both conceived much more broadly in a geographical and ecological sense, more narrowly in a physiognomical sense, compared with the associations, usually being distinguished within the Alnion glutinosae), Carpino-Prunetum spinosae (Sambuco-Prunetum spinosae not incorporated) and Alno-Salicetum cinereae (not united with the Frangulo-Salicetum auritae). The new division of the “Salicetum albae” sensu Zonneveld (including the new association Salicetum arenario-purpureae) is not based on new data, but on general considerations only. For each association (chapter 4) was composed a review of its habitat, area, geomorphological and dynamic position, importance for nature conservancy, landscape architecture and forestry, its structure, floristical composition, subdivision (sub-associations, geographical variations within the Netherlands) and seasonal aspects. Owing to the present lack of knowledge of these species among our phytosociologists, the review remained incomplete with respect to communities in which Rubus-species play an important role. The list of references is more or less complete as regards literature on Dutch woodland and shrub communities (for a considerable part consisting of unpublished reports, descriptions etc.); recent continental literature with propositions regarding classification of these communities and some general literature on phytosociology and auxiliary sciences, having been consulted for the composition of this study, was added.