From Big Medical Encyclopedia

BIOCENOSIS (grech, bios life + koinos the general) — set of animals (zoocoenosis), plants (phytocenosis) and the microorganisms (microbiocenosis) inhabiting the site of the biosphere with more or less homogeneous conditions (biotope). B. it is characterized by a certain relationship, in particular a certain type of a metabolism and energy between various organisms, and also between organisms and the habitat. B. together with biotope (see) form biogeocenosis (see). In B. allocate several levels (groups of the organisms) connected among themselves by the trophic relations. So, producers — chlorophyll-bearing plants and chemosynthetic bacteriums — build organic matter by means of energy of sunshine or the energy emitted at oxidation-reduction processes with use of carbonic acid (see. biological oxidation , Photosynthesis ). Konsumenta — animal and nongreen plants — use this organic matter, quite often transferring it to other forms. Distinguish several types (orders) of konsument: first order (herbivorous animals, parasitic fungi, bacteria etc.), second order (predators and parasites of herbivorous organisms) etc. Activity of konsument promotes transformations and movements of organic matters to B., their partial mineralization. At last, reducers (generally bacteria) decompose organic matter before the mineral connections available to the direct use by plants and other organisms. Thanks to interaction of the organisms relating to various trophic levels to B. there is a continuous circulation of substance and energy — so-called small biol, circulation. Plants at the same time carry out vertical transfer of substance and energy (from the soil on a surface), and the animals connected, as a rule, from several B — horizontal.

B. sharply differ by amount of the biomass formed in them. So, primary production of mountain rainforests reaches 3275 c on 1 hectare of their area a year, and some deserts — only 5 c. The different types of animals, plants and microorganisms forming B. have unequal number. Distinguish dominants — the dominating types, sodominant — codominant types, types minor etc. The dominants defining features of the environment B. (usually it plants), call edificator plants. So, in a spruce forest the edificator plant is the fir-tree, and on peat peat moss bogs — a moss a sphagnum.

The structural basis of B. is formed by tiers, i.e. groups of organisms distributed down. In land B. they are formed by plants, animals also participate in some benthonic B. of reservoirs in their education. Existence of storeyed structire allows to be placed on the same square to bigger number of species of plants and animals.

Some organisms (plants, microorganisms, some animals) carry out all life in one B., others pass from one B. into another.

Organisms, and first of all plants, create the internal environment of B. which is characterized by a certain temperature schedule, air humidity and soils, an amount of precipitation, level of subsoil waters and so forth.

Though B. develops on more or less homogeneous sites, however activity of the organisms forming it creates distinctions in living conditions in its different sites (microcoenosis), napr, hummocks and spaces between them on swamps.

Within B. distinguish mains circuits, konsortion and synusias. The organisms eating each other, napr enter a mains circuit, the plant eating it a herbivorous animal, the predator eating this animal etc.

of Konsortion is a set of an autotrophic plant and all organisms, dependent on it (lianas, epiphytes, parasites, consumers of vegetable weight, carriers of seeds, pollen etc.), napr, a fir-tree with all organisms, related directly. One look can be a part of several konsortion. A synusia call the structural part B. formed by ecologically homogeneous organisms (e.g., set of epiphytes, set of zemleroyushchy rodents etc.).

Biocenoses are dynamic. They develop in time, and one B. can be replaced by another, and these shifts happen the nondirectional (reversible) and directed (they are called successions). Short-term (private) successions cover insignificant territories and separate B.; the general (or century) — all biocenoses of extensive regions. Short-term successions are subdivided on endodynamic (B. caused by internal development) and exodynamic (caused by factors, external in relation to B.). Changes of biocenoses on cuttings down, big fires, the opened sites, to number endodynamic — bogging of the woods as a result of development of their ground cover etc. are among exodynamic changes. In development biocenoses gradually come to a condition of relative compliance to environmental conditions, and their development is sharply slowed down in this connection them call the climax.

The special category B. is represented by agrobiocenoses in which separate components B. are consciously regulated by the person.

Existence of carriers and carriers of diseases is defined by B.'s features and biocenotic bonds. Quite often the carrier passes one phases of development in one B., and others — in others. So, the larva of a malarial mosquito develops in reservoirs, and adult individuals live in land biocenoses. The natural centers of diseases are connected with a combination defined B. Tak, e.g., with B. of the southern part of a forest zone the centers of a tick-borne encephalitis, are connected with B. of deserts — the centers of a tick-borne spirochetosis etc. B.'s changes under the influence of the person cause changes of living conditions of carriers and carriers of diseases (development of an irrigation system and creation of the new centers of a tularemia, plowing of forest spaces and disappearance of the centers of a tick-borne encephalitis etc.).

Biocenoses are a subject of studying of a biocoenology.

See also Biosphere , Ecology .

Bibliography: Arnoldi K. V. and Arnoldi L. V. O biocenosis as one of the basic concepts, its structure and volume, Zool. zhurn., t. 42, century 2, page 161, 1963; Ravens A. G. Rol of the animal population in formation of structures of biocenoses, Bulletin Mosk. islands ispyt. nature, otd. biol., t. 73, century 1, page 85, 1968; Vtorov P. P. Problems of studying of land ecosystems and their animal components, Frunze, 1971, bibliogr.; Bases of a forest biogeocenology, under the editorship of V. N. Sukachyov and N. V. Dylis, M., 1964; Odum E. P. Fundamentals of ecology, Philadelphia a. o.t 1971, bibliogr.

A. G. Voronov.