Carbon reservoirs, main exchanging

The cycles of carbon and the other main plant nutrients are coupled in a fundamental way by the involvement of these elements in photosynthetic assimilation and plant growth. Redfield (1934) and several others have shown that there are approximately constant proportions of C, N, S, and P in marine plankton and land plants ("Redfield ratios") see Chapter 10. This implies that the exchange flux of one of these elements between the biota reservoir and the atmosphere - or ocean - must be strongly influenced by the flux of the others. 

Fig. 6.1 Simplified summary of the preindustrial global carbon cycle, showing approximate sizes of the main reservoirs (variously shaped boxes) and annual fluxes (arrows) in Gt (1015g) of carbon (after several sources, including Bolin et al. 1979, 1983 Kempe 1979 Mopper Degens 1979 DeVooys 1979 Siegenthaler Sarmiento 1993 Sundquist 1993 Arthur 2000 Falkowski et al. 2000). Reactive sediments are capable of exchanging material with the water column.

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