Essay on Theoretical Approaches towards The Concept of Climax Community !
The concept of climax long was a subject of much controversy and discussion. There are following three theoretical approaches to the climax:
1. Monoclimax theory:
This theory is developed largely by Frederick Clements. This theory recognizes only one climax, determined solely by climate, no matter how great the variety of environmental conditions is at the start. All seral communities in a given region, if allowed sufficient time, would ultimately converge to a single climax.
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The whole landscape would be clothed with a uniform plant and animal community. All other communities than the climax are related to the climax by successional development and are recognized as sub climax, disclimax, preclimax, post-climax and so on.
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A subclimax is a stage in succession of forests just preceding the climate climax community. The disclimax is the particular type of vegetation maintained in an area as a result of recurrent disturbance, chiefly the biotic, thus preventing a successful establishment of climate climax community. The preclimax is a vegetation of lower-life forms than the one adjacent to it and results from different edaphic conditions.
The post climax is a strip of vegetation of higher life-forms occurring within a climate climax, for example, a forest along a stream in a grassland community constitutes post climax community. Later on numerous other terms such as coclimax, super climax, quasiclimax, anticlimax, pseudo climax, etc., were coined by some post-Clements ecologists to describe specific situations.
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The monoclimax theory is supported by Cowles, Ranganathan, and Puri, but strongly objected by Daubenmire (1968).
2. Polyclimax theory:
This theory was developed by Tansley. This theory considers that the climax vegetation of region consists not just one type but a mosaic of vegetation climaxes controlled by soil moisture, soil nutrients, topography, slope exposure and animal activity.
The advocates of polyclimax theory preyed to call each stable community as a climax and described with a prefix as edaphic climax, topographic climax, biotic grazing or anthropogenic) climax and fire climax. For example grassland communities of central India, Sri Lanka and Parts of California have developed under the influence of fire, factors and so have been considered as climaxes by Misra, Pandeya and Holmes.
3. Climax pattern hypothesis:
This theory was developed by Whittaker, Macintosh and Sellack. According to this theory, the composition, species structure and balance of climax community are determined by the total environment of the ecosystem and not by one aspect, such as climate alone.
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Involved are the characteristics of each species population, their biotic interrelationships, availability of flora and fauna to colonize the area, the chance dispersal of seeds and animals, and the soils and climate. The pattern of climax vegetation will change as the environment changes.
Thus the climax community presents a pattern of populations that corresponds with and changes with the pattern of environmental gradients, intergrading to form ecoclines the central and most widespread community in the pattern is the prevailing or climatic climax. It is the community that most dearly expresses the climate of the area.
4. Information theory:
This theory is proposed by Leith, Odum and Golley. It considered succession and climax in terms of ecosystem development. In autotrophic succession (ecosystem development), diversity of species tends to increase with an increase in organic matter content and biomass supported by the available energy.
Thus, in a climax community, the available energy and biomass, this is called information content, increase. In contrast to it, in a heterotrophic succession occurs a gradual depletion of energy, because the rates of respiration always exceed production rates. However, in an ecosystem, both the autotrophic and heterotrophic successions operate in a co-ordinate manner.
The autotrophic individuals drives mineral elements from the soil and atmosphere, while the heterotrophic individuals carry on the return of the nutrients to soil and atmosphere, through decomposition of complex dead organic matter.
Thus, succession reaches a stage, the climax stage, when the amount of energy and nutrients received from the environment by the plants is again returned in more or less similar amount to the environment by decomposition through heterotrophs.