Inventory process-type approach

The accumulation of carbon in the organic layer after fire points at a basic problem of the simplified flux scheme of Schulze and Heimann (1998), namely, that intermediate pools exist at each level with different mean residence time, and depending on the level of spatial integration these pools may or may not average out. The problem is illustrated in Figure 7, where an inventory-process type approach (in contrast to eddy covariance flux measurements) was chosen to calculate the carbon sink capacity of European forest ecosystems. If NPP was plotted against C-mineralization, then NPP minus C-mineral-ization would represent NEP at the plot scale (Schulze et al.,... 

Remark. A different type of approach to study forecasting issues in inventory management is that taken, e.g., by Chen et al. (1999). In their models they assume that the decision-makers are not aware of the exact characteristics of the demand process, and hence they resort to popular forecasting mechanisms such as the moving-average technique when making replenishment decisions. Chen et al. also propose heuristic policies that are very similar in their nature to those proposed in this paper. 

A natural and obvious way to calculate a periodic state of a cyclic process is to simply simulate the dynamic behaviour of the process. The simulation will approach, as does the physical system, a periodic state. The disadvantage of this strategy is that the initial transient phase may be very long, in particular in the presence of large capacity terms and slow kinetic terms. All extunple reactor types given above are based on packed beds, where a column is filled with a solid sorbent and/or catalyst. Typically the solids inventory is very high and so is the buffer capacity in terms of the adsorption capacity or heat capacity. For such systems the dynamic simulation of the process may need tens of thousands of cycles in order to converge to a periodic state. 

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