Beech forest communities in the Nordic countries - a multivariate analysis

In this study we present the first comprehensive multivariate analysis of b eech (Fagus sylvatica) forest communities in the Nordic countries. The hist ory of beech and beech forests in Scandinavia are described. In the north, the species is climatically restrained and, at present, restricted to Denma rk and the southern parts of Sweden and Norway. More than 2000 sample plots were compiled, partly from literature, partly f rom new and unpublished data. The material included more than 20 studies of beech forests, often recorded by different non-standardised sampling desig ns. Therefore, prior to data analysis, a large number of plots had to be ex cluded to reduce the heterogeneity of the data. Only such sample plots were considered that showed a predominance of Fagus sylvatica in the canopy, th at had a size within the interval of 16-100 m(2), and that could be located by geographical coordinates. All species abundance values were transformed into simple species presences, and data from different vegetation layers w ere merged into one. A TWINSPAN cluster analysis resulted in 15 types. Three main communities wi th several sub-communities and varieties can be distinguished: (1) the Fagu s sylvatica-Fraxinus excelsior-Stachys sylvatica community on the most basi c and fertile soils, (2) the Fagus sylvatica-Corylus avellana-Galium odorat um community on moderately fertile and acid soils, and (3) the Fagus sylvat ica-Sorbus aucuparia-Deschampsia flexuosa community on very acid and oligot rophic soils. Synonyms in the recent literature on Nordic beech forests to these communities are given. An ordination with the program DECORANA confir med the primary significance of soil acidity and nutrient status for commun ity differentiation.