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Conservation of Social Broadleaves genetic resources in Switzerland
Patrick Bonfils
Swiss Federal Institute for Forest, Snow and Landscape Research, Birmensdorf, Switzerland
Occurrence and origin of beech and oaks in Switzerland
Switzerland is commonly divided into five different geographic regions: the Jura Mountains,
the Central Plateau, the Lower Alps, the Alps and the Southern Alps (Fig. 1). These regions
are characterized by specific ecological conditions. Overall, a great variety of different site
types can be found, ranging from basic to acidsoils and from atlantic to continental climates.
Fig. 1. The five geographic regions of Switzerland: Jura Mountains, Central Plateau, Lower Alps, Alps
and Southern Alps.
Beech
Fagus sylvatica is mainly found in the Jura Mountains and the Central Plateau. It is not
present in the dry and continental climates of the Alpine region (Fig. 2). In the subatlantic
climate regions of Switzerland, beech forests form a broad vegetation belt between the
subalpine vegetation zone dominated by Norway spruce and the lowland vegetation zone
which is characterized by mixed deciduous forests. Beech occurs in almost all forest
communities except those from subalpine mountain forests (Leibundgut 1984). Beech
appears commonly as a species of mixed forests and only in 20% of the stands is its
abundance higher than 66%. It is often associated with Norway spruce and silver fir, but
also with sycamore maple, ash, oak and Scots pine (Brandli 1996). Fresh deep fertile soils,
high humidity and high precipitation (>750 mm/year) are beneficial to beech (ETH-Zurich
1993). Beech requires a cooler climate than oak but a slightly warmer one than silver fir
(Leibundgut 1984).
In the past, forest stands were considerably affected by human activities. Destruction of
beech forests started in Roman times and continued throughout the Middle Ages. A
significant proportion of beech stands disappeared as a result of clearing. Large areas were