Changes in herb layer heterogeneity of Scots pine forests along the North-South transect

The purposes of the present paper are: a) to show the synusial structure of the herb layer often sites, located in Norway, Finland, Estonia, Latvia, Lithuania and Poland along the transect stretching between 50°28′ and 70°09′ N, and b) to characterise the species-area curves for all the sites studied. The number of types of synusiae on the particular sites ranges from three to ten, though only one or two have the dominating character, that is, occupy at least 20% of surface. From the point of view of synusial differentiation three geographical groups of sites could be established: the most distinctly different are the northern sites. The second subset of sites, though featuring relatively weak internal mutual similarities, encompasses the sites located in the middle part of the transect. The third subset of sites, represents a more southern character. For each of the sites separately the dependence between the number of vascular species of the herb layer and the area of the site considered (the species-area relationship) is described by the formula y = axb. Correlation coefficients between the model and the actual number of species are very high, from 0.902 to 0.998.