Major changes in forest floor vegetation were identified on the basis of three nationwide surveys conducted as part of national forest inventories in 1951–1953, 1985–1986 and 1995. These surveys provided objectively selected, statistically representative samples of all forested land in Finland. The 1951–1953 data consist of over 10000 sample plots, while the later surveys were conducted on ca. 3000 permanent plots.
Changes in relative abundance of dominant species (i.e. in the proportions of species of the total cover of forest floor vegetation) were analysed across biogeographical provinces. Spatial correlation, systematic sampling, partial re-measurement and multiple testing were taken into account in assessment of the statistical significance of the observed changes.
The most notable changes in forest floor vegetation were a decrease in the relative abundance of Hylocomium splendens and an increase in Dicranum polysetum. In N Finland, where forests are grazed by semi-domestic reindeer, we observed a decline in the abundance of Cladina lichens and an increase in Dicranum mosses. Peltigera aphthosa declined throughout the country. Polytrichum juniperinum, Pohlia nutans, and Brachythecium species, which occupy disturbed sites or grow on litter, increased in abundance. The relative abundance of Sphagnum species decreased, particularly in W Finland, where Pleurozium schreberi was favoured. A major decline in S. fuscum was also recorded in C and E Finland.
Many of the changes detected in this study are apparently related to intensified forest management; but solely on the basis of this study, its effects cannot be distinguished from those of other large-scale environmental changes.