Tree Line

Why the Trees do not Reach to the Sky
The Alpine Garden lies in the highest regions of the pine wood which on the Patscherkofel rises to 2000 metres. The upper border of the mountain forest called the tree line is one of the most conspicuous limits to vegetation that can be found. In undisturbed primeval forest regions this border is clear-cut; in the alpine region it is frequently interrupted by alpine pastures.

The tree line is essentially a climatic border - on average a tree needs at least 100 warm days with an average temperature of more than 5 degrees to achieve a positive metabolic balance and thus for growth. For their nourishment, forest trees are also dependent upon mykorrhiza. Near the tree line many dangers lurk for trees: the strong ultraviolet radiation can damage the chlorophyll sheath; snow fungus can affect young growth; but in particular it is the winter wind that deprives the needles of water through high levels of evaporation. As the ground is frozen dry, damage occurs despite sufficient resistance to frost, winter desiccation. During photosynthesis the green plant factory creates organic compounds out of dissolved anorganic material and the CO2 contained in the air. When this material gain is no longer sufficient to compensate for the consumption resulting from breathing the balance turns negative. Growth is rendered impossible. The limit to life has been reached: we have reached the tree line.

Tree Line