Biocenosis is a historically established group of plants, animals, fungi and microorganisms that inhabit one area (a land or water site). Biocenoses are formed either on their own, or under the influence of a person.
Biocenosis, as a term, was proposed by Karl Mobius in the 19th century. The existence of a biocenosis can be determined by both biological and physical-geographical features. The composition, structure of the biocenosis, its characteristics depend on various factors, ranging from climatic conditions and ending with the composition of the soil. In different zones, the composition and characteristics of biocenoses differ.
Any biocenosis is a combination of natural components that have their own species composition. So, let's say, the biocenosis of the tropical moist forest will be very different from the desert, that is, the number of species of the tropic biocenosis will be much larger than in the desert. The formation of the species composition of biocenoses is also influenced by historical factors. For example, older communities have more species than younger ones.
Layering (spatial structure of biocenosis) is the vertical arrangement of the phytocenosis in the underground and ground parts. The structure of the biocenosis has a ground component and an underground one. All tiers of the biocenosis are characterized by various characteristics: ecological, floristic, morphological, etc. The tiering is well expressed in forests where it is represented:
- tree layer;
- shrubby;
- shrubby-grassy;
- tier of mosses and lichens.
By the number of tiers, biocenoses are:
Biocenosis is a complex of living organisms in which there are constant connections called food or trophic. Based on them, power circuits are formed . The trophic structure of the biocenosis suggests the occurrence of food ties in those cases when the organisms of one species or another feed on the organisms of another species themselves or their metabolic products. Such relationships are called direct or indirect. Direct connections are formed due to the absorption by organisms of one species of representatives of another. Indirect connections are formed due to the competition of two different species of organisms for food.
Biocenosis is a variable structure. It can undergo long-term changes in one direction, which lead to a restructuring of its features, and can also cause the replacement of one biocenosis with another. This process is called succession. Successions are divided into primary and secondary. Primary successions occur in a territory not previously inhabited by any biocenosis. Secondary successions occur at the site of extinct or destroyed biocenoses. The final stage of the life of the phytocenosis is called menopause. Successions are usually divided into the following types:
- syngenesis (changes caused by the mutual influence of plants);
- endoecogenesis (changes that occur as a result of the vital activity of the phytocenosis itself);
- exoecogenesis (changes caused by the actions of natural factors external to the phytocenosis).
These types, in turn, are divided into:
- climatogenic;
- edaphogenic;
- zoogenic;
- man-made.
Under the influence of successions, a stable phytocenosis can be restored or formed, or, conversely, regress.
The dominant environmental factors are determined by the division of zones according to the distribution of ambient temperatures and the amount of precipitation. With increasing distance from the equator, a change in natural zones occurs. Within natural zones , impacts called extrazonal and intrazonal arise, which are determined by the influence of topography, hydrological objects, and other factors.
Some authors insist that there are clear boundaries between plant groups. But there is also an opinion that the vegetation cover has some continuity.