Why don’t trees grow above the tree line?

Answer

Hello Willy,

The presence or absence of trees is determined by a combination of environmental variables. Usually, temperature and moisture are the main factors that determine whether trees can exist at a certain height. From a certain height it gets too cold and there is snow for too long a period of time to allow tree growth. It is also usually drier at high altitudes, or the amount of moisture fluctuates too much between the seasons (for example, a lot of meltwater in the spring vs. a dry summer). The height at which a tree line can be found can differ between mountain ranges and is therefore related to environmental factors: temperature, moisture and possibly also strong wind and the salinity of the soil.

The tree species also change as you ascend in a mountain range: on lower parts you will find mainly deciduous tree species by nature, while the amount of coniferous trees increases on higher parts. This is no coincidence, because coniferous trees are better adapted to the less favorable conditions at high altitude. For example, they lose much less moisture through their needles than deciduous trees through their leaves and the fact that they keep their needles all year round ensures that they can photosynthesize all year round.

Kind regards,

Tanja