Cyclic structure is typical for living systems of all levels of organization. On the top levels (the levels of ecosystems and the biosphere as a whole) the main cyclic process is a turnover of the matter (a composition of chemical elements) through different components of ecosystems. The matter turnover is peculiar to the Earth life from the first steps of its development; and it is quite probable that the elemental cycling is initial and forming core of the life origin process (see Phenomenon of Life: General Aspects).
The cyclic character of stable natural systems can be explained by a number of considerations from philosophy, systems theory, chemistry, etc. Thus, it is logically evident that any long-term dynamics in bounded environment should have a periodical character. It is understandable that in stable chemical processes a dynamic balance between synthesis and destruction has to be observed. In accordance with cybernetic principles, formulated by N. Wiener in 1948, for stability of systems, their structure should include feedback loops (extreme importance of this principle for biological systems was grounded by L. von Bertalanfy in 1964). It is demonstrative that the wheel is a symbol of the World in many philosophical and religious systems. The list of theoretical reasons, pointing to the importance of cyclic processes, can be expanded.
Let us consider peculiarities of the natural matter cycling. We shall start from the consideration of global geochemical cycles, which are the basis of biogeochemical ones. In the next two sections, pure biological effects and the structure of global cycling (including cycling of separate biogenic elements) will be analyzed. Finally, the questions about driving forces, main dynamical properties and evolution of biogeochemical cycling, will be discussed.
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