Phytocoenosis

(also plant community), the aggregate of vegetable organisms within a relatively homogeneous area. The plants of a phytocoenosis display complex interrelations with other plants, with animals, and with the environment. Each phytocoenosis is a system with a definite composition (consisting as a rule of many ecologically and biologically different species) and a definite structure. The composition and structure of phytocoenoses evolve as a result of the natural selection of plant species capable of coexisting with each other and with animals in certain environmental conditions, and in many instances as a result of the influence of man.

The plants that constitute a phytocoenosis alter their environment in the process of their vital activity, although different groups of plant species (phytocoenotypes) play varying roles. After consuming necessary resources, such as light, water, and minerals, they secrete metabolic wastes into the external environment and leave dead organs in or on the soil, thus leading to the formation of a special phytoclimate. Each phytocoenosis is characterized by specific environmental factors.

The phytocoenosis is the most active part of a biocoenosis and biogeocoenosis (ecosystem). It accomplishes photosynthesis (as a result of the vital activity of photosynthesizing organisms) and nitrogen fixation (by nitrogen-fixing microorganisms) and, together with animals, plays an important part in energy conversion and the cycle of matter on earth. Thus, the phytocoenosis is the major producer of organic substances, which it supplies to heterotrophic organisms, including man. A phytocoenosis is a dynamic system that changes from season to season and year to year. Every phytocoenosis is eventually superseded by another; this process is called succession. The study of phytocoenoses is called phytocoenology.