The spectrum of forest species occurring in Germany is comparatively narrow. Only about 80 tree species are native to the temperate zone of Europe. In other regions, for example in the east of the USA, there are about 250 species.
The ice ages were the determining factor for this relative poverty of species. The barrier effect of the Alps as "crossbars" led to species impoverishment during the recolonisation in the interglacial periods. The current distribution of tree species in Germany, but also their genetic diversity, was largely determined by the return migration, above all by circumventing the Alps in the East.
However, the forest vegetation in Germany is mainly determined by the four tree species Norway spruce, Scots pine (pine), common beech and oak (Sessile and English oak). These take up 78% of the forest area.
The potential natural forest vegetation, i.e. without human influence, would result in a deciduous forest share of about 90 % in Germany, determined by common beech and oak forests.
With the beginning of controlled forestry about 250 years ago, often fast-growing conifers were chosen for establishing forests (spruce as the "bread [high yield] tree of forestry"). This is still visible today by the high proportion of the two coniferous species Norway spruce and Scots pine, accounting for more than 50 % of the forest area.
In addition to the native forest tree species, numerous foreign tree species are successfully cultivated and used in forestry in Germany. Some of these are neophytes, especially if they are competitive and rejuvenate naturally. Examples are Douglas fir, Red oak, Robinia and Chestnut.
*) Schmidt, M.; Ewald, J.; Fischer, A.; Oheimb, G. V.; Kriebitzsch, W.-U.; Ellenberg, H.; Schmidt, W. (2003): Liste der Waldgefäßpflanzen Deutschlands - In: Mitteilungen der Bundesforschungsanstalt für Forst- und Holzwirtschaft - v. 212, 35 p.