Oak-hornbeam forests of central Europe

Abstract

Oak-hornbeam forests (order Carpinetalia) are a widespread vegetation type in central Europe. As vegetation ecologists focused on them since the pioneering times of vegetation research, many syntaxonomic units are described. However, classification systems used in various central European countries suffer from inconsistencies and overlaps of the concepts of particular associations. Currently there is no consistent syntaxonomic system based on numerical analysis of vegetation plots that would be valid for the whole of central Europe. Therefore, the main goal of this study is to provide a revised syntaxonomic system of oak-hornbeam forests across central Europe, develop formal definitions of the associations and include these definitions in a classification expert system. We recognized 13 associations, 9 from the alliance Carpinion betuli (central European oak-hornbeam forests) and 4 from the alliance Erythronio-Carpinion (Illyrian and northern Italian oak-hornbeam forests). We prepared an expert system that classified 55% of the releves in a central European oak-hornbeam forest dataset (n = 6212) at the association level. To stabilize the Carpinion betuli association names, we selected nomenclatural type releves for associations that have not been typified so far. In addition, two association names (Poo chaixii-Carpinetum and Pseudostellario-Carpinetum) were validated. Ordination revealed the main drivers of species diversity in these forests, including a complex gradient of soil moisture, nutrient availability and geographical position (mainly latitude). Among the climate variables, annual temperature amplitude and mean annual temperature were most closely correlated with species composition.