In this article we will discuss about the study of community structure.
A “vegetation is the sum total of plants covering an area” (Weaver and Clements, 1966) which generally consists of a number of communities. According to Benton and Werner (1974) “a biological community consists of all the organisms living together in an interrelated fashion in a given environment”. Biological communities are independent in functioning though greatly influenced by adjacent communities.
Each community consists of a set of many different species which persist year after year and each species is represented by innumerable individuals or strands. Individuals of the same community are together termed population (e.g. the population of Cassia tora, etc.). Such populations of a number of species generally intermingle in a community and form an apparently homogeneous structure.
So, in response to the climatic complex, the entire vegetation responds by its distribution into groups, each of which is near equilibrium.
The following groups are generally used for the detailed description of vegetation:
1. The Formation:
It is the natural climax community of an area and is the major unit of vegetation. As the different species in a formation have been naturally selected against the same climatic complex over the entire area they generally express uniformity in their behaviour.
2. The Association:
Every climax formation consists of two or more subdivisions known as associations which are units of climax communities in which a few species are dominant. An association is generally named after two or three of its dominant species.
3. The Consociation:
There are a number of dominants in an association but each dominant species does not occur uniformly in it. A dominant species may be sparingly present in some areas and form a consociation. Consociation over a considerable area is mainly due to the fluctuation of available water in the soil within the limits set by the requirement of a dominant.
4. The Variation:
This is also a subdivision of the association characterized not by pure dominance but by grouping of dominant or controlling species. The entire area of the association is generally composed of its various faciations. Each faciation corresponds to a particular regional climate of real but small differences in precipitation, evaporation and temperature.
5. The Society:
Within the consociation and faciation some subdominant species might have some control over the local community. These subdominants strongly influence and largely determine the other species growing in the association. These local communities are called Societies.
In each society may be found two or more smaller climax units. These are called clans. Each clan is a small aggregation of a single but locally dominant species. The same type of communities or formations are also found in successional seres.
The seral communities are progressively dynamic with their changing species, diversity, dominants and co-dominants. Here these vegetational groups are named Associes, Consocies, Fades, Socies, Families, etc. While studying any vegetation or plant community one must try to realise the structure, the cause and the influences of these vegetational groups over the entire community.