Climax community
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The term climax community, also described as a climatic climax community is an obsolete ecological term for a biological community of plants and animals which, through the process of succession, has reached an equilibrium or steady state. The term is sometimes also applied in soil development. The idea of a single climatic climax, where the final steady state depends only on regional climate, originates with Frederic Clements in the early 1900s. Clements saw the ecological community as an organic superorganism in which the successional development is analogous with the ontogenetic development of an organism. Clement's "monoclimax" theory was modified in Arthur Tansley's idea of the "polyclimax" which allowed for multiple steady-state end-points, determined by edaphic factors, in a given climatic zone. Henry Gleason's early challenges to basic premises of climax theory were largely disregarded for several decades until substantially vindicated by research in the 1950s and 1960s (below). Meanwhile, climax theory was deeply incorporated in both theoretical ecology and in vegetation management. Terms such as pre-climax, post-climax, plagioclimax and disclimax were coined to account for the many communities that persisted in states that diverged from what was expected to occur on the basis of climate.
Later developments in the field of ecology led to a decline in the influence of climax theory. Whittaker's work undermined the superorganism idea since it could be shown that plant species distributed themselves along nutrient and other environmental gradients. In addition, the maturation of evolutionary theory discredited the level of interspecies "altruism" required by Clements' theories. More recently, palynological studies have shown that modern species assemblages are ephemeral entities - vegetation in eastern North America since the last glacial maximum has consisted of several different species assemblages, many of which have no analogues in modern "climax" communities. Ultimately, even if succession tends towards a steady state, the time required to achieve this state is unrealistically long; in most cases, external disturbances and environmental change occur too frequently for the realization of a climax community. Long-term vegetation dynamics are strongly shaped by stochastic factors.
Despite the fact that it is based on disproven assumptions, many authors continue to use the term climax in a diluted form to refer to what might otherwise be called mature or old-growth communities.