Tree species composition
The forest is extremely important for biological diversity in Switzerland: Nearly half of native plant and animal species depend on it. With its heterogeneous topography and large differences in altitude, Switzerland has a great diversity of site conditions, which is reflected in a species-rich flora, including in the forest. Changes in the tree species composition of forest stands in Switzerland have various reasons: natural succession, changing climatic conditions, pest organisms, disturbance events, and forest management. The adaptability and resilience of a forest are also increased when multiple tree species are present.
good
impossible to evaluate
- Database
- National forest inventory NFI
Three tree species dominate in Swiss forests and together account for over two-thirds of the growing stock: spruce, beech, and fir. However, the tree species composition varies considerably depending on altitude and region. For example, chestnut is also very common on the southern side of the Alps.
Because spruce is by far the most common tree species in Switzerland, its decline contributes most to the change. But ash trees are also retreating nationwide due to ash dieback (fungal infection).
In view of climate change, a diverse mixture of tree species is advantageous because it distributes the risk of stress intolerance across several species. It is not possible to define an ideal composition of tree species in forests. Therefore, a targeted trend cannot be defined for each species. For this reason, the indicator is not evaluated at the trend level.
The indicator is used in the context of the Ministerial Conference for the Protection of Forests in Europe (Forest Europe) and is therefore comparable throughout Europe. However, when making a comparison, the most diverse site conditions between countries should be taken into account.
Data based on the list from the ETH project on promoting rare tree species in the Northern Alps (SEBA). According to the SEBA list, data are lacking on Sorbus domestica (service tree), Ulmus laevis (European white elm) and Pyrus pyraster (European wild pear tree). Due to the rareness of these tree species, the data should be interpreted with caution and take into account the standard error (see original NFI data).
The tree species composition is surveyed using samples taken in the forest, modelled and calculated for the entire forest area and the producing regions. Evaluation unit: accessible forest without brushwood. Network: 1.4 km network (in NFI5: 1.4 km network, sub-networks 1-5).
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