a group of plant species important for various reasons in determining the character of phytocoenoses (plant communities). At first, two basic species groups were distinguished: organizing species (“components”), which predominate in the phytocoenosis and essentially determine its character, and random species (“ingredients”), which play a secondary role in the phytocoenosis.
In 1928, V. N. Sukachev distinguished two types of plant species: edificators and assectators. Edificators, the creators or builders of phytocoenoses, include autochthonous species, which influence phytocoenoses without human involvement, and digressive species, which determine the character of phytocoenoses mainly after interference by man or animals. Assectators are involved in the formation of phytocoenoses but have little influence on the creation of the plant environment; they are subdivided into autochthonous species and adventitious species, which occur randomly in the community.
L. G. Ramenskii devised his own classification, which took into account the different ways in which plants adapt to coexistence in a phytocoenosis. Subsequently, more detailed classifications led to the establishment of two approaches to the study of coenotypes—one based on the position occupied by the species in actual phytocoenoses, and the other on the ability of the species as a whole to contribute to the formation of phytocoenoses. In the latter instance, phytocoenotypes are defined as groups of plant species whose significance in the phytocoenosis changes to similar degrees, depending on growth conditions and the peculiarities of their life cycle.
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T. A. RABOTNOV