Tall trees that are not in a forest are out of place, probably because of human interference. It is a complete waste of effort to grow tall if you are the only tree around. It is much better to spread out sideways like grasses because that way you trap more photons per unit of effort put into growing. As for forests, it is no accident that they are so dark. Every photon that makes it to the ground represents failure on the part of the leaves above.
