Ecological Gradients as Causes and Effects of Ecosystem Organization
In the course of ecosystem evolution gradients emerge as fundamental features of self-organization processes under the influence of neighbouring geo- and ecosystems (Müller 1998). Thus, analysing ecological heterogeneities (e.g. Kolasa and Picket 1991; Breede 2000; Reiche et al. 2001), ecotones (e.g. Gosz 1992; Fränzle and Kluge 1997; Kluge et al. 2003) or patch dynamics (e.g. Shugart and Urban 1988), implicitly means investigating ecological gradients. In this context two theoretical concepts are fundamental:
The thermodynamic non-equilibrium principle of Schneider and Kay (1994a, b) is related to the flow and storage of exergy which is a measure of the maximum capacity of the energy content of a system to perform constructive work (see also Jørgensen 2000; Kay 2000).
While Schneider and Kay stress the system’s degradation capacity, Jørgensen’s exergy optimization principle puts emphasis on the development of gradients and structures: “If a system receives a throughflow of exergy, the system will utilize this exergy to move away from thermodynamic equilibrium. If the system is offered more than one pathway to move away from thermodynamic equilibrium, the one yielding most stored exergy, i.e. with the most ordered structure or the longest distance from thermodynamic equilibrium by the prevailing conditions, will have a propensity to be selected” (Jørgensen 2000, p. 166).
KeywordsBeech Forest Ground Beetle Structural Gradient Ecological Gradient Functional Gradient
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