Naturalness of the tree species composition is somewhat improved
The growth and vitality of a forest are determined by the competition among trees. The most vital trees are those on sites that optimally fulfil their species-specific demands for water, nutrients, light, warmth, etc. Other tree species can hardly compete on such sites without human assistance. Hence, natural selection gives rise to the typical tree species composition, also called the “present potential natural vegetation.” This is the vegetation that would occur at the end of all development stages under the present site conditions without human interference.
If trees are planted on sites that are less suitable for them, their vitality suffers and they become susceptible to damages from pests, drought, storms and other stress factors. The ability of such forest stands to react to additional or new stress factors like air pollutants or climate change is reduced and their stability is impaired.
The parameter “naturalness of the tree species composition” describes the extent to which the tree species composition of our forests corresponds to the present potential natural vegetation. This is an indicator for forestry policy and ecologically compatible forest management.
The forest is an element of the cultural landscape influenced by humans. By nature, Germany is beech country and if left to nature, today’s forest area would be made up of 75% beech forests and 17% oak forests. Where beech forests would naturally grow, today only 21% beech forests stand; 34% are spruce forests and 17% are pine forests. On the area of natural oak forest communities, today only 14% oak forests grow; 55% are pine forests.
The naturalness of the tree species composition in the main forest cover changed only slightly compared with the last inventory. A bit less of it is conditioned by culture and thus somewhat more are semi-natural forests. 15% of the forests have a very semi-natural composition and another 21% a semi-natural composition of tree species. The share of these two stages of naturalness is particularly high among beech forests (84%) and fir forests (68%). It is especially low among pine forests at 15%.
The investments made in the semi-natural transformation of forest stands are apparent, however, among the young forest cover (trees up to 4 metres in height) where the share of very semi-natural and semi-natural tree species composition is approximately 51%. Only 5% of young forest cover is accentuated by culture and 13% is conditioned by culture.
Semi-natural and very semi-natural tree species compositions are very high in the state forests (43%) and in the communal forests (41%) where the transformation of forest stands has advanced the farthest.