1 - A sharp treeline formed by Nothofagus sp. near Therma caliente, Chile, 1800 m

2 - The Nothofagus menziesii treeline near Haast Pass, South Island, New Zealand at 1200 m. This treeline does not represent the life form's upper climatic limit: planted Pinus contorta grows well up to 1600 m elevation.

There is an upper elevational limit for any organism on the globe. For some this is 300 m above the tropical sea level (coconut "treeline"), for others it is the peak of Mt. Everest (some bacteria). Different species reach different elevations in different parts of the world, some tree species reach the upper climatic limit of the life form tree. We call these treeline forming tree species. In some parts of the world such species are missing (e.g. in Hawaii, New Zealand), hence, there is no climatic "tree"-line (but still an upper climate driven limit of the locally available tree species).

In other parts of the world "treeline species" are available, but trees are absent because of

• shortage of moisture (arid regions)
• loose substrate (e.g. on volcanoes)
• fire or other disturbance (human land use)

Since these influences are not restricted to mountains, but can operate anywhere, they are not of interest here.

3 - A gradual treeline in the Alps, here on Mount Patscherkofel, Tyrol at 2000 m with Pinus cembra.

4 - Not too high for trees! This mountain semi-desert in Tenerife at 2600 m (Canary Islands) is too dry for forest growth.

29 August 2011
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