Ecological buffer capacity

A new concept — the ecological buffer capacity — has been introduced to express the response of an ecosystem to changes in the loading. Either the relative or absolute stability gives this sort of information. By means of this concept, it has been attempted to show how complicated a model must be to give an acceptable description of the response to changes in the phosphorus loadings. It was found that the ecological buffer capacity increases with increasing model diversity, either expressed by means of the Shannon index or the number of state variables, but since it is of importance to include the most essential mass flows, the exergy is more suitably related to the buffer capacity than the diversity. Consequently, the exergy can be used as an expression for the buffer capacity, that is, as an expression for the response of an ecosystem to changes in the driving functions. Both the buffer capacity and the exergy can be used to select the required state variables for a model. Interchanging Pjeq (= phosphorus concentration in box j at thermodynamic equilibrium) with Pj0 (= phosphorus concentration in box j at steady state) in the exergy expression, seems to give a useful Liapunov function for the considered set of models.