Most of the defining criteria are related to site-specific factors (mostly nutrients, partly climate), whereas others are mainly defined by the forest state (by forest age or disturbance agent), and in most cases dominant tree species are included as an important criterion. Nevertheless, the DN forest types appear to be easier to associate with a few underlying environmental gradients (climate, site quality), supplemented by information on forest age and tree species composition, to provide a link to data from forest inventories and thus the possibility of assessing tree biomass, carbon stocks and even carbon uptake or loss for the various forest types. Forest types of the EU Habitat Directive, Annex I, in Denmark, Finland, and Sweden.