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plants that are closely associated with particular ecological conditions, which can be qualitatively or quantitatively interpreted based on the presence of these plants. They include species as well as intraspecies units, various anomalous forms that regularly and constantly occur under the influence of certain external factors, and even plant communities. The developmental rhythm of plants and the times of onset of various phenological phases also have indicator significance. Soils, certain rocks, groundwater and the presence of certain elements may be the objects of indication. Some indicator plants—direct indicators—are directly associated with the object of indication (they usually retain their indicator value within the entire area of distribution); others—indirect indicators—are associated with certain factors that are correlatively dependent on objects of indication (they are most often regional or narrowly localized).
Indicator plants are used in evaluating the mechanical composition and salinization of soils, in the search for fresh water in deserts, and in mapping soil-forming source rocks and certain types of minerals. Recognizing plant (and community) indicators is one of the means of interpreting aerial photographs in soil and geological surveying. Widely practiced is the creation of botanical indicator maps and of indicator manuals for use in field research. Indicator plants are the subject of study of indicator geobotany.
S. V. VIKTOROV