MEDICAL BOTANY - A.G. Serbin - 2003

SECTION 4. ECOLOGY, PHYTOCENOLOGY, PHYTOGEOGRAPHY

CLASSIFICATION OF PHYTOCENOSES

A vast diversity of phytocenoses exists in nature, showing varying degrees of similarity to one another. The currently accepted Classification of phytocenoses identifies seven subordinate systematic units: 1) association; 2) association group; 3) association Class; 4) formation; 5) formation group; 6) formation class; 7) vegetation type.

Association. This is the primary and lowest systematic geobotanical unit, representing a collection of phytocenoses that share a complex of similar features. All phytocenoses belonging to the same association share common physiognomy, vertical stratification (canopy layers), species composition, quantitative ratios of species, and similar habitat conditions. Each association is characterized by a specific plant species composition, Structure (stratification), sequential development of its constituent plants, and a successive change of phenological aspects (i.e., external appearance). Every plant association is linked to specific environmental conditions, including climate, soil, and biotic factors. An association is named after its dominant species with the suffix -etum and its subdominant species with the suffix -osum. For example, a pine forest association with Scots pine (Pinus) as the dominant and cowberry (Vaccinium) as the subdominant is designated as Pinetum vacciniosum.

Association group unites those associations that share the same dominant species. For instance, a Norway spruce forest mixed with broadleaved trees and shrubs.

Formation. This is a major systematic unit that groups together plant associations in which the dominant plants belong to the same botanical species. For example, all associations of spruce forests formed by Norway spruce belong to a single formation—Norway spruce forest; likewise, all pine forest associations consisting of Scots pine also belong to a single formation. Plant formations are grouped into larger units, namely formation groups and formation classes. A formation group comprises plant formations whose dominants belong to the same botanical genus (e.g., spruce forests, pine forests, oak forests). Examples of formation classes include coniferous forests and deciduous forests.

Vegetation type is the highest taxonomic rank in the classification of phytocenoses. It unites plant communities that share common biological and ecological plant traits. Vegetation types differ sharply from one another in their physiognomy. Four main vegetation types are commonly distinguished globally: 1) arboreal, or tree-shrub; 2) herbaceous; 3) desert; 4) aquatic (floating/submerged). The first three types comprise plants anchored to the soil, whereas the fourth includes aquatic plants.

Agrophytocenoses are artificially created phytocenoses managed by humans. Cultural phytocenology is the scientific discipline dedicated to studying cultivated vegetation. Agrophytocenoses vary depending on climatic and agronomic conditions. When establishing agrophytocenoses, the Selection of components involves carefully choosing crop varieties and species suited to the specific conditions of the region. Even when establishing a simple two-component agrophytocenosis (clover + timothy grass) to achieve higher yields, it is essential to select appropriate varieties (early-ripening, winter-hardy, disease-resistant, etc.). Simple agrophytocenoses consist of 2–3 components (oats + field pea; red clover + meadow timothy + meadow fescue), while complex ones comprise 4–6 or more components. Understanding the regularities of plant-to-plant interactions, as well as the interplay between the entire cultivated phytocenosis and its growing environment, helps in creating highly productive and stable agrophytocenoses.

The Earth's surface has already ceased to be solely a natural formation. Through human activity, a new artificial shell of the Earth is being created—the noosphere. In terms of its scale, human impact is The most significant among all known natural factors.