This relationship is obligatory in one direction only.
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The trees in a forest community can live just as good as without shrubs and herbs which grow under them. The relationships, between coexisting species may be obligatory in one direction or in both. The coexisting populations are interrelated and they show some sorts of interaction. Species occurring in the particular habitat do not live in complete isolation as pure cultures, but they coexist in mutual adjustment. The nature of community of a particular habitat is determined by the species contents, ecological amplitudes of the species and physical and biotic influences prevailing in the locale of community. The range of environment a species can tolerate is called its ecological amplitude. A clearly distinguished area or a type of area with uniform habitat conditions and supporting characteristic type of vegetation is termed “biotope”.Įach species of community has got definite range of tolerance towards the physical and biological environmental conditions of the habitat. Some community areas have limits but more often the community boundaries are hard to define. Vegetation therefore, is reflection of a climate and, in general, widely separated areas having similar climate have similar aspects of landscape. Because in any particular habitat there is no considerable variation in environmental conditions, the plants growing together in a community show unique uniformity in their behaviour. Species diversity is high in natural community and low in managed ecosystem such as croplands. The ratios between the number of species, their biomass and productivity provide valuable information about community and are called species diversity indices. The common abundant species are called dominants whereas rare species determine species diversity. Of the total number of species in a biotic community a few species are abundant while a large percentage is rare. Various species of plants and animals living in a community exhibit species diversity. Actually it is a part of a larger whole ecosystem in which living and non-living components interact and bring about circulation, transformation and accumulation of energy and matter. The biotic community is a natural assemblage of a large number of plant and animal species in an area. The following points characterize the community: (1) Species diversity: According to them, the climatic climax community is in, complete equilibrium not only with climate but also with the whole complex of environment. Misra and Pun (1954) are of the opinion that Clements’ original concept which defined “community as any unit of vegetation whether developmental or climax in status”, should be accepted as such and they used the term association for climatic climax. Pondeyar (1960, 1961) has discussed this subject and suggested that an association is a temporary phenomenon which is continuous in space and with slight irregularities, all of which blend into an entirety of apparent abstract homogeneity.Īccording to him the association is not a final vegetation but an assemblage of plants of any status. It is uniform either in space or in time and possesses definite limits of area only to a reasonable extent. Earlier Gleason (1939) in his individualistic concept of plant association suggested that an association is a complex of slight irregularities, all of which blend into an entirety of apparent homogeneity. Costing defines community as “an aggregation of living organisms having mutual relationship among themselves and to the environment.” In modem books of ecology, plant community is defined as uniform flonstic composition.
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Thus a population is a part of community and populations of different species may be intermingled in a community. A group of individuals of the same species is commonly known as population. In a community, each plant species is represented by innumerable individuals. The species living together in groups exhibit various degrees of adjustment among themselves and with their physical habitats as well.Įach community consists of a set of many different species which persist year after year. The communities are not the random mixtures of species. The basic unit of vegetation is called plant community or a plant association. The study of the relationships of plants and animals making up a natural community is termed as community ecology or synecology. In view of these facts, modem biologists prefer use of biotic community to plant community or animal community.