A biocenosis or biocoenosis ( ancient Greek βίος bios , German 'life' and κοινός koinós 'common') is a community of organisms of different species in a definable habitat ( biotope ) or location . Biocenosis and biotope together form the ecosystem .
The living beings of such a community are in numerous interrelationships, are influenced by abiotic environmental factors and have an effect on them. Because of this interrelation, they are in an interdependent relationship ( biocenotic connex ). A biological or ecological balance is created . These relationships are examined in biocenology (or biocenotics ), a sub-discipline of ecology . One also speaks of synecology - in contrast to autecology , in which the ecological relationships of individual species are considered.
The nature conservation terms species inventory or species spectrum refer to the composition of the biocenoses of certain ecosystems.
The term Biocönose was coined in 1877 by Karl August Möbius , who saw the organisms living on an oyster bank as a community.
Characterization of biocenoses
Depending on the focus of typing, biocenoses can be characterized using different taxa :
- A phytocoenosis (plant community) is formed by plants of different species living together in a biotope. In plant sociology, plant communities are described for the characterization of phytocoenoses , each of which is characterized by character species with similar or identical demands on their location. Example: The rock debris community of the high mountains with the round-leaved pocketwort ( Thlaspi rotundifolium ) is defined as the plant community Thlaspietea rotundifolii .
- A zoo zoenosis (animal community) is formed by animals of different species living together in a biotope (example: the animal community of the Ngorongoro Crater). Although typical zoo communities occur in certain biotope types , which, like plant communities, can be described as characteristic combinations of species, a similar formalized system is not used in zoology.
- A microbiocenosis (microbial society) represents the entirety of the microorganisms occurring in a microhabitat . The demands and metabolic pathways of the individual species can be very different, since the metabolic end product of one microorganism can be the substrate for another microorganism.
Coenosis can stand as a generic term for phytocoenosis and zoo community. Delimited partial communities of a certain systematic order are generally called taxozoenoses (example: beetles in a beech forest, mosses in flowing waters, birds in an agricultural landscape). The designation according to the respective group treated, for example avizoenosis for the bird world, is possible but not very common. If organisms of different systematic rank are grouped together in partial habitats (e.g. all organisms in decomposing wood, all coprophages on faeces of ungulates, all inhabitants of the crown layer in the tropical rainforest ) one speaks more of synusia .
The types of biological communities occupy according to the niche theory different ecological niches . Species of a similar way of life (example: all seed eaters ) that exploit the same resource in a similar way are grouped together as guilds .
Interactions between living things
A distinction is made between interactions between the members of a species ( intraspecific interrelationships ) and interactions between members of different species ( interspecific interrelationships ).
These interactions can influence the survival and reproductive ability of the individual ( fitness ) and thus also the development of the population density of a species in an ecosystem (see population ecology ).
Relationships include food , transport , and shelter relationships .
Possible effects of the interactions between two species on population density:
- The trivial case that two species in the same habitat do not influence each other is very difficult to prove due to the complexity of ecosystems. It may be the case if, for example, migratory birds with different ecological demands congregate at a resting place overnight on their migration.
- One type benefits from the relationship, the other is not affected. Depending on the degree of dependency, a distinction is made between pro, para- and metabiosis . Examples: Karpose , commensalism .
- Symbiosis : Both types benefit from the relationship (symbiosis in the narrower sense, see mutualism ).
- One species is harmed without the other species having any advantage or disadvantage. Example: If heavy ungulates often go the same route, they destroy the vegetation as they move ( amensalism ).
- Both types are disadvantaged by the relationships ( competition ).
- One species benefits from the relationship, but at the same time damages the other species. Examples: predation , parasitism .
Biocenoses are a dynamic system that is constantly changing. The dynamics and structure of the community are determined by the trophic structure. If the number of individuals and species remains constant over a longer period of time, the ecosystem is in equilibrium . However, changes in environmental conditions or the composition of species can quickly change a biocenosis. According to a widespread hypothesis, species-rich ecosystems can compensate for changes better than species-poor, they are more stable. The connection between biodiversity and stability is, however, controversial in ecological research. B. because there are counterexamples - very species-poor, but stable communities.
If different biocenoses occur one after the other in an ecosystem, one speaks of succession .
A species can - especially if it migrates - be members of different biocenoses. Young river eels in the sea belong to the plankton as willow leaf larvae , later as glass eels to the necton and finally to the necton of a river or lake. Belonging to a biocenosis can therefore also change in the course of the various stages of development. For example, most cancers as Nauplius - or Zoea larvae part of the plankton, live as adults but on or in the water bottom and thus belong to the benthos . The situation is similar with many mussels and bristle worms .
Basic biocenotic principles
- The more diverse the ecological niches of a biotope, the more species-rich the biocenosis (see tropical forests ).
- The reverse is also true: the more species, the more niches. For example, in a biocenosis with many plant species, there are usually many niches for phytophages . It is not easy to formulate ecological conditions for niche-rich systems. It seems to be important that the interspecific competition does not dominate the community.
- The more the abiotic factors of a biotope diverge from the physiological optimum of most species, the fewer species, but also the more individual the biocenosis, the organisms of these communities are mostly highly specialized. ( Salt lakes , heavy metal lawns ).
- The slower and more continuously the living conditions in a biotope have changed, the more species-rich its biocenosis is. ( Coral reefs ).
The intensive interrelationships, especially the food relationships, promote evolution and thus the adaptation of species to the biotic and abiotic factors of an ecosystem. Of co-evolution occurs when a mutual adjustment takes place together with two types (eg System pollinators -. Flowering). Coevolution promotes the specialization of species and thus tends to increase the species richness of biocenoses.
In a thanatocoenosis ("grave community"), the remains of organisms of a biocenosis are stored and fossilized .
- Eugene P. Odum : Ecology . Georg Thieme Verlag, Stuttgart 1999, ISBN 3-13-382303-5 .
- Carl Beierkuhnlein: Biogeography . UTB, Stuttgart 2007, ISBN 978-3-8252-8341-4 .
- Hartmut readers: landscape ecology . UTB, Stuttgart 1997, ISBN 3-8252-0521-5 .
- ↑ Karl Möbius: The oyster and the oyster economy . Verlag von Wiegandt, Hemple & Parey, Berlin 1877. Chapter 10: “An oyster bank is a biocoenosis or community”.