What explains the layered structure of the phytocenosis?

A phytocenosis (plant community) is a collection of plant organisms within a relatively homogeneous area. In plants, the phytocenosis displays complex relationships with other plants, with animals, and with the environment. Each phytocenosis is a system with a more specific composition (consisting, as a rule, of many ecologically and biologically different species) and a specific structure. The composition and structure of phytocenoses develop as a result of natural selection of plant species capable of coexisting with each other and with animals under certain environmental conditions, and in many cases as a result of human influences.