The article contains tree lectures given in the meeting of the Geographical Society in Finland on February 25th 1921. The titles of the lectures are I Forest types in general, II Forest types as a basis for new growth and yield tables in Finland, and III Other research on forest types.
The first lecture is a follow-up of the Cajander’s 1909 published article on forest types. It deepens the theory on forest types. The classification into forest types represents primarily different plant communities of ground cover. The types are named after the characteristic plant species, indicator plants, however, many other species appear in different abundance.
The second lecture represents the research proceedings of mensuration of forest stands of different types to compile yield tables for pine. The forest types differ from each other distinctly on their growing preconditions, but inside one class the variation of the growing conditions is so small, that the classification can be used for yield tables, determining the basis of taxation and for classification of forest based on height over age.
The third lecture is a summary of other studies about forest type classification. They confirm the results presented in earlier lectures.