Forests are also the dominant form of vegetation in the mountains. With increasing altitude, the climate becomes correspondingly colder and harsher. The timberline forms where trees are unable to grow for at least three months a year. The most suitable growing conditions for spruce are between 1,000 and 1,600 metres above sea level.
The highest growth limit for spruce is 2,000 m, while for larch and Swiss stone pine it is up to 2,400 m.
The warming of the climate will lead to a shift in the timberline upwards by several hundred metres.