Climax Community - Frederic Clements's Use of "climax"

Frederic Clements's Use of "climax"

Clements described the successional development of an ecological communities comparable to the ontogenetic development of individual organisms. Clements suggested only comparisons to very simple organisms. Later ecologists developed this idea that the ecological community is a "superorganism" and even sometimes claimed that communities could be homologous to complex organisms.

Clements's theory sought to define a single climax-type for each area. Arthur Tansley developed this idea with the "polyclimax" -- multiple steady-state end-points, determined by edaphic factors, in a given climatic zone. Clements had called these end-points other terms, not climaxes, and had thought they were not stable, because by definition climax vegetation is best-adapted to the climate of a given area. Henry Gleason's early challenges to Clements's organism simile, and other of his strategies for describing vegetation, 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. Clements's terms such as pre-climax, post-climax, plagioclimax and disclimax continued to be used to describe the many communities which persist in states that diverge from the climax ideal for a particular area.

Though the views are sometimes attributed to him, Clements never argued that climax communities must always occur, or that the dominant cause of vegetation is climate, or that the different species in an ecological community are tightly integrated physiologically, or that plant communities have sharp boundaries in time or space. Rather, he employed the idea of a climax community--of the form of vegetation best adapted to some idealized set of environmental conditions--as a conceptual starting point for describing the vegetation in a given area. There are good reasons to believe that the species best adapted to some conditions might appear there, when those conditions occur. But much of Clements's work was devoted to characterizing what happens when those ideal conditions do not occur. In those circumstances, vegetation other than the ideal climax will often occur instead. But those different kinds of vegetation can still be described as deviations from the climax ideal. Therefore Clements developed a very large vocabulary of theoretical terms describing the various possible causes of vegetation, and various non-climax states vegetation adopts as a consequence. His method of dealing with ecological complexity was to define an ideal form of vegetation--the climax community--and describe other forms of vegetation as deviations from that ideal.