Climax: Culmination stage of plant succession for a given environment. If succession is allowed to progress without disturbance, a stage is reached when no more improvement is possible in the soil and the vegetation. At that stage the vegetation is in equilibrium with the environment, and stays unchanged indefinitely by reproducing itself.

Mono-climax theory developed by Clements, who believed that in a general climate of a region, could be only one climax and these variations ultimately progress, even though slowly, towards that climatic climax. Mono-climax theory is assumed to occur only in one climatic climax. As this is not possible, soil conditions differ even in a uniform area excluding climatic factors.

Thus, there can be more than one climax communities in one given climate, that is called poly-climax theory. Presently, the poly-climax theory has been more popular than the mono-climax theory.

Characteristics of climax

• The vegetation is tolerant of environmental conditions.
• It has a wide diversity of species, a well-drained spatial structure, and complex food chains.
• 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 litterfall to the soil.
• Individuals in the climax stage are replaced by others of the same kind. Thus the species composition maintains equilibrium.
• It is an index of the climate of the area. The life or growth forms indicate the climatic type.

Classification of Climax

Even though the concept of climax is still developing, it can be classified as follows:

1. Climatic climax: It is the climax which owes its distinctive characters to climatic factors in conjunction with only such biotic influence as plants and animals naturally occurring in the area. Thought Clements considered climate as the dominant community – forming factor, he recognized the importance of soil, topography, relief and biotic factors as being additional dimensions to the main factor which delayed the progress of vegetation to a climatic climax.
2. Edaphic climax: A community which differs from the climatic climax of the area owing to the influence of special soil factors. Succession ends in an edaphic climax where topography, soil, water, fire, or other disturbances are such that a climatic climax cannot develop.
3. Pre-climax : The plant community immediately preceding in seral development of the climatic climax of the region and found under conditions drier than are usual in the climate of the region.
4. Post climax: A plant community more exacting than the climatic climax of a given and found exceptionally favorable site conditions within that region. It actually occurs on sites very much moister than the normal sites in that climatic region.
5. Biotic climax or sub-climax: A climax which differs from the climatic climax of the area owing to the action of biotic factors.
6. Catastrophic Climax: Climax vegetation vulnerable to a catastrophic event such as a wildfire. For example, in California, Chaparral vegetation is the final vegetation. The wildfire removes the mature vegetation and decomposers. A rapid development of herbaceous vegetation follows until the shrub dominance is re-established. This is known as catastrophic climax.
7. Disclimax: When a stable community, which is not the climatic or edaphic climax for the given site, is maintained by man or his domestic animals, it is designated as Disclimax (disturbance climax) or anthropogenic subclimax (man-generated). For example, overgrazing by stock may produce a desert community of bushes and cacti where the local climate actually would allow grassland to maintain itself.