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On Certain Unifying Principles in Ecology

R. Margalef
The American Naturalist
Vol. 97, No. 897 (Nov. - Dec., 1963), pp. 357-374
Stable URL: http://www.jstor.org/stable/2459227
Page Count: 18
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On Certain Unifying Principles in Ecology
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Abstract

An attempt is made to provide some unifying principles in ecology. The structure of ecosystems is considered in relation to various components, with emphasis on the characteristics of maturity as measured by diversity data and other determinable features, including primary production (P) and biomass (B). Ecosystems with complex structure and containing a high amount of information can be maintained with a relatively lower expenditure of energy. Oscillations, introduced for example by environmental changes or outside exploration, tend to retain an ecosystem in a state of lower maturity. Where succession is occurring, involving exchange of an excess of available energy for a future increase in biomass, the relations encountered may be applied not only to successive states in the same system; but to adjoining or coupled subsystems. Steepness of the gradient between subsystems is shown to depend on several factors subject to quantitative determination and the relation between these subsystems can be imitated by simple experiment. When ecosystems contract or expand there are corresponding increase or decreases of maturity. Factors affecting the maturity of ecosystems and of special interest are the movement of species. These suggest a spatial correspondence between the juvenile or immature portion of an unspecific population and the less mature parts of ecosystems available for habitation. Maturity is related to evolution in a way that permits generalization concerning the type of organisms to be found in ecosystems of more or less maturity and stability. As evolution proceeds, there is a trend toward adjustment to maturity. The concepts that emerge may be applied to human social systems. Two principles become evident: The energy required to maintain an ecosystem is inversely related to complexity, with the natural trend toward decreasing flow of energy per unit biomass; that is, increased maturity. Secondly, in adjacent systems there is a flow of energy toward the more mature system and an opposite movement in the boundary or surface of equal maturity.

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