In modern books of ecology, plant community is defined as “uniform floristic composition”. Each community is unique with a set of features. Here we will see the various characteristics of community ecology.
Plants usually do not live singly in nature. In any habitable area, many plants belonging to one species live together forming small and large groups. An assemblage of plants of one kind is called a population. Quite commonly several plant populations link together and such an aggregation of plants having mutual relationships among themselves is called a plant community.
Several tree species growing together in a forest with the associated ground flora form a community. Lichen and mosses growing on a rock, and a mat of alga on a pond or a lake are all examples of plant communities of different types.
The basic unit of vegetation is called a plant community or association. Instead of a random mix of species, each community has species living together in groups exhibiting various degrees of adjustment among themselves and with their physical habitat as well.
Characteristics of Community Ecology
Each community consists of a set of many different species which persist year after year. A group of individuals of the same species is commonly known as a population. Thus a community has an intermingled population of different species.
Plant Association
A fully developed plant community within a climatic region is called plant formation. Plant associations are the major subdivisions of formation. Every formation consists of two or more associations. The number of associations is determined by the number of subclimates within the general climate of formation.
The different associations in a formation have the same physiognomy or growth form but may differ from one another in their floristic composition, especially in the dominant species. Each association has two or more dominant forms.
It may be emphasized again that a dominant is characterized not only by physiognomy (the general outward appearance or growth form) but also by its almost uniform floristic composition, at least in the dominant species.
Species Diversity in Communities
In nature, organisms grow in association with each other. A group of several species (plants or animals) living together with mutual tolerance (adjustment) and beneficial interaction in a natural area is called a community.
Thus, in a community, organisms share the same habitat in a uniform environment. So a forest, grassland, a desert, or a pond are natural communities.
A community shows species diversity. It has a highly complex structure because of the relations and interactions of its constituent populations. In a community, plants of one or more species are more prominent than the others because they are tallest and largest and are represented in considerable numbers.
They largely control the environment and determine what other species may grow in the community. These are dominant species that exert a controlling effect over the occurrence of other species.
The various kinds of plants in a community interact with one another in several ways.
Competition
There is competition in soil for water and other essential soil minerals, air, light, etc. The competition is more intense among the members of the same species (interspecific) than that is between members of different species.
As a result, more vigorous and better-adapted plants become dominant, and other less vigorous ones are suppressed to a greater or lesser degree or altogether eliminated.
Stratification
In a plant community, the plants that have some sort of relationship among themselves may be trees, shrubs, herbs, mosses, lichens, and thallophytes. These plants form more or less distinct strata or layers or stories on vertical as well as horizontal plains. This is characteristically known as stratification.
The individuals of different layers represent different life forms. Each layer of community may include individuals of different morphological classes. For eg, The top layer or canopy of the forest may be formed by the tallest trees and lianas (wood climbers). The middle strata consists of shrubs and the lowest strata may be made up of mosses, lichens, and sometimes algae.
Dependencies
Some members of a community are dependent on others for their survival. Most of the thallophytes, liverworts, mosses, ferns, etc live as dependent on the trees. Removal of the dominant trees results in the disappearance of such dependents as well.
Co-existence
Species that occur in their particular habitat do not live in complete isolation or pure culture but they coexist in mutual adjustment. The co-existing populations are interrelated and they show some sort of interactions.
The relationship between pre-existing species may be obligatory in one direction or both. The trees in a forest community can live just as well without shrubs and herbs that grow under them. This relationship is obligatory only in one direction.
Such interactions between two coexisting species may fall into the following types.
- Exploitation is where one species lives at the expense of another.
- Mutualism has two or more coexisting populations benefit from the relationship but no one suffers.
- Competition is where different species compete for the same resources or habitat.
- Neutralism is where two populations are independent and neither affects the other.
References
- Shukla, R.S. and Chandel, P.S. (2001) Plant Ecology. S. Chand and Company Ltd., New Delhi.
- Verma, P.S., Agarwal, V.K. (1999). Cell biology genetics molecular biology evolution and ecology. New Delhi: S.Chand Co.(Pvt) Ltd.
- Community Ecology
