FO9 Tree species composition

>> Background information

Development

The dominating tree species is generally defined in young and mature forest stands as the species, which takes up the greatest share of the volume of the growing stock present in the stand. In seedling stands the dominating tree species is defined as the species that is being promoted by forestry operations.

The preference of Scots pine over other species in artificial regeneration forests started in the 1960s and lasted until the beginning of the 1980s. The pine-dominated forests have become more abundant also because of mire draining, as these areas are usually naturally suitable for Scots pine. During the latest 20 years the use of spruce has increased a great deal in forest cultivation. Nevertheless, the share of spruce-dominated forests has fallen by 11% since 1950s. At the same time, the share of pine-dominated forests has increased by 17 %. In terms of deciduous trees the development has been less linear. Deciduous forests continued to decline until the 1960s as a result of the disappearance of old slash-and-burn forests, but have slowly begun to become more common again during the past decades.

The volume of Common Aspen has more than doubled in southern Finland since the 1950s. This has not been matched by the development in northern Finland where Common Aspen volumes have remained almost at the same level. The increase of Common Aspen in the southern part of the country tracks the growth of the total volume of trees and therefore the share of Common Aspen of the total growing stock has increased only by 0.4 percentage point.

Impact on biodiversity

Finnish forests are composed of relatively few tree species in general, but their number is nevertheless significant for biodiversity. Tree species vary in their structural characteristics and therefore host different species. For example herbivores are often able to feed on only a few species or plant parts. Different tree species also provide a habitat for different epiphytic lichen species and are eventually decomposed by specialized organisms.