Oak trees require plenty of light; maples or beeches thrive on little light.
The seed of trees requiring little light may be scattered in a dense forest together with that of trees which need plenty of daylight in order to make normal growth.

The seedlings that like shade will develop under such conditions while those that need light will pine away and die.

Gradually the shade-loving trees will replace the light-loving trees in such a forest stand.

Even the different trees of the same family often strive with one another for light and moisture.

Each tree differs from every other one in shape and size.