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Forests more diversely structured The forest habitat – more biological diversity in the forests

Forests more diversely structured

A forest’s horizontal and vertical structure, i.e. its tree species mixture and its stratification in the canopy, are important indicators of its structural diversity.

Mixture. Source: BMEL

A forest in which a variety of different tree species stand next to one another and the crown canopies of a multiple tree layers rise above one another offers diversified habitats for animals and plants. Due to its structural diversity, it can also better react to environmental impacts.

Tree species composition is also a key element of the forest’s horizontal structure. German forests are dominated by mixed forests, with 76 % of the area percentage. Pine forests, with an area percentage of 57% admixture or spruce forests with 71 % are relatively less mixed. All other forest cover types are more mixed.

Over the past ten years, the tree species composition has intensified somewhat. The area of mixed forest cover rose by 5 %.

With 85 % of the area percentage of young forest cover, natural regeneration is the dominant form of regeneration in the German forests. Plantings only make up 13 % and are primarily found among Douglas fir forest cover (73% of Douglas fir forest cover) and in oak forest cover (44 % of oak forest cover). The remaining area (seed, coppice shoots, unclassified) makes up a mere 2 %.

What is a mixed forest?

Canopy layers. Source: BMEL

The vertical structure of a forest is described by its stratification. 68% of our forests are two or multi-layered. That is 28% more than in the year 2002. Young forest cover is found on approximately one fourth of all timberland. It is therefore an important element of the vertical structure of the forest.

In addition, there are approximately 30 million holdover trees. Holdover trees are particularly old trees that remain in the forest for a second rotation or cutting interval and therefore whose crowns frequently rise above the others. They are important elements for the forest structure and biological diversity. On average, we find three holdover trees per hectare.

The most frequent structures are two and multi-layered structures among fir (84%), beech (80%), oak (78%) and ash forests (78%).

Structural diversity of the forests
Structural diversity of the forests. Source: BMEL

Two and multi-layered structures are less common among Douglas fir (53 %) and spruce forests (58 %).

Forests in which trees of various species and sizes occur together offer the greatest structural diversity. These are often beech forests or oak forests. Even the rare fir forests often exhibit structures with multiple tree species and layers in the canopy. Mixed and stratified structures are less common in spruce and pine forests.