According to classical ecological theory, succession stops when the sere has arrived at an equilibrium or steady state with the physical and biotic environment. At this point the community is stable and self replication. Barring major disturbances, it will persist indefinitely. This end point of succession is called climax.
Characteristics of climax
â€¢ The vegetation is tolerant of environmental conditions.
â€¢ It has a wide diversity of species a well drained spatial structure and complex food chains.
â€¢ The climax ecosystem is balanced. There is equilibrium between gross primary production and total respiration, between energy used from sunlight and energy released by decomposition, between uptake of nutrients from the soil and the return of nutrient by litter fall to the soil.
â€¢ Individuals in the climax stage are replaced by others of the same kind. Thus the species composition maintains equilibrium.
â€¢ It is an index of the climate of the area. The life or growth forms indicate the climatic type.
Theories Regarding Nature of Climax
There are three schools of interpretations explaining the climax concepts. They are as follows.
Monoclimax or Climatic Climax Theory
This theory was advanced by Clements in 1916 and recognized only one climax whose characteristics are determined solely by climate meaning climatic climax. The processes of succession and modification of environment overcome the effects of differences in topography, parent material of the soil and other factors. The whole area would be covered with uniform plant community. Communities other than the climax and related to it are recognized as sub climax post climax and disclimax.
This theory was advanced by Tansley in 1935. It proposes that the climax vegetation of a region consists of more than one vegetation climaxes controlled by soil moisture, soil nutrients, topography, slope exposure, fire and animal activity.
Climax Pattern Theory
This theory was proposed by Whittaker in 1953. The climax pattern theory recognizes a variety of climaxes governed by responses of species populations to biotic and abiotic conditions. According to this theory the total environment of the ecosystem determines the composition, species structure and balance of a climax community. The environment includes the species responses to moisture, temperature, and nutrients and their biotic relationships. Availability of flora and fauna to colonized the area, chance dispersal of seeds and animals, soils, climate and disturbance such as fir and wind. The nature of climax vegetation will change as an environment change. The climax community represents a pattern of populations that corresponds to a change with the pattern of environment. The central and most widespread community is the climatic climax.
Types of Climax
If there is only a single climax and the development of climax community is controlled by the climate of the region, it is termed as climatic climax. For example, development of maple beech climax community over the moist soil. Climatic climax is theoretical and develops where physical conditions of the substrates are not show extreme as to modify the effects of the prevailing regional climate.
When there is more than one climax community in the region, modified by local conditions of the substrates such as soil moisture, soil nutrients, topography, slope exposure, fire and animal activity it is called edaphic climax. Succession ends in edaphic climates where topography, soil, water, fire and other disturbances are such that a climatic climax cannot develop.
Climax vegetation vulnerable to a catastrophic event such as a wild fire. For example, in California chaparral vegetation is the final vegetation. The wild fire removes the mature vegetation and decomposes. A rapid development of herbaceous vegetation follows until the shrub dominance is reestablished. This is known as catastrophic climax.
When the stable community which is not the climatic or edaphic climax for the given site is maintained by man or hid domestic animals, it is designated as disclimax or disturbance climax or anthropogenic sub climax meaning man generated. For example overgrazing by stock may produce a desert community of bushes and cacti where the local climate actually would allow grass land to maintain itself.
Preclimax and Post climax
In certain areas different climax communities developed under similar climatic conditions. If the community has life forms lower than those in the expected climatic climax, it is called preclimax. A community that has life forms higher than those in the expected climatic climax is post climax. Preclimax strips develop in less moist and hotter areas. Whereas post climax strips develops in more moist and cooler areas than the surrounding climate.
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